EP4633956A1

EP4633956A1 - Printer and associated method

Info

Publication number: EP4633956A1
Application number: EP23828449.1A
Authority: EP
Inventors: Carl Mann; Samuel LORENZ; Michael Jeffrey Stamp; Robert Squires; Bartosz Marcin OPRZADEK; David DOSWELL; Ben Tuncay ARSLAN; David Andrew Horsnell
Original assignee: Videojet Technologies Inc
Current assignee: Videojet Technologies Inc
Priority date: 2022-12-15
Filing date: 2023-12-14
Publication date: 2025-10-22
Also published as: CN120322330A; WO2024127027A1

Abstract

A self-cleaning print head for a continuous inkjet printer is disclosed. The print head comprises a cleaning chamber, a nozzle, at least one electrode and a gutter. The cleaning chamber is selectively sealable by a sealing mechanism. The nozzle is for generating and ejecting a stream of ink droplets for printing. The at least one electrode is for guiding the stream of ink droplets. The gutter is for receiving droplets of ink which are not used for printing. The cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber. The first and second ports are diametrically opposed from one another.

Description

Printer and Associated Method

The present invention relates to a self-cleaning print head for a continuous inkjet printer, a continuous inkjet printer, a connector block, a connector block assembly, a method of cleaning a self-cleaning print head, and various other associated methods.

In inkjet printing systems, the print is made up of individual droplets of ink generated at a nozzle and propelled towards a substrate. There are two principal systems: droplet on demand, where ink droplets for printing are generated as and when required; and continuous inkjet (Cl J) printing, in which droplets are continuously produced and only selected ones are directed towards the substrate, the others being recirculated to an ink system.

CIJ printers supply pressurised ink to a print head droplet generator where a continuous stream of ink emanating from a nozzle is broken up into individual regular droplets by, for example, an oscillating piezoelectric element. The droplets are directed past a charge electrode, where they are selectively and separately given a predetermined charge, before passing through a transverse electric field provided across a pair of deflection plates, the pair comprising a high voltage (or extra high tension (EHT)) plate and a zero or negative voltage plate (the ‘ground’ plate). Each charged droplet is deflected by the field by an amount that is dependent on its charge magnitude before impinging on the substrate, whereas the uncharged droplets proceed without deflection and are collected at a gutter from where they are recirculated to the ink system. The charged droplets bypass the gutter and hit the substrate at a position determined by the charge on the droplet and the position of the substrate relative to the print head. Typically the substrate is moved relative to the print head in one direction and the droplets are deflected in a direction generally perpendicular thereto, although the deflection plates may be oriented at an inclination to the perpendicular to compensate for the speed of the substrate (the movement of the substrate relative to the print head between droplets arriving means that a line of droplets would otherwise not quite extend perpendicularly to the direction of movement of the substrate). The various components of the print head are typically contained within a cover tube or print head casing. In CIJ printing, a character is printed from a matrix comprising a regular array of potential droplet positions. Each matrix comprises a plurality of columns (strokes), each being defined by a line comprising a plurality of potential droplet positions (e.g. seven) determined by the charge applied to the droplets. Thus, each usable droplet is charged according to its intended position in the stroke. If a particular droplet is not to be used then the droplet is not charged and it is captured at the gutter for recirculation. This cycle repeats for all strokes in a matrix and then starts again for the next character matrix.

Ink is delivered under pressure to the print head by an ink system that is generally housed within a sealed compartment of a cabinet that includes a separate compartment for control circuitry and a user interface panel. The ink system includes a main pump that draws the ink from a reservoir or tank (often referred to as a mixing tank) via a filter and delivers it under pressure to the print head. As ink is consumed, the reservoir is refilled as necessary from a replaceable ink cartridge that is releasably connected to the reservoir by a supply conduit. The ink is fed from the reservoir via a flexible delivery conduit to the print head. The unused ink droplets captured by the gutter are recirculated to the reservoir via a return conduit by a pump. The flow of ink in each of the conduits is generally controlled by solenoid valves and/or other like components.

As the ink circulates through the system, there is a tendency for it to thicken because of solvent evaporation, particularly in relation to the recirculated ink that has been exposed to air in its passage between the nozzle and the gutter. In order to compensate for this, “make-up” solvent is added to the ink as required from a replaceable solvent cartridge to maintain the ink viscosity within desired limits. The ink and solvent cartridges are filled with a predetermined quantity of fluid and generally releasably connected to the reservoir, or mixing tank, of the ink supply system so that the reservoir can be intermittently topped-up by drawing ink and/or solvent from the cartridges as required.

CIJ printers generally operate in high throughput environments for which the printers, and inks, need to be able to keep up with high production line speeds, fast drying time requirements and virtually non-stop production. A problem faced by operators of existing continuous inkjet printers is that of undesirable build-up of deposits within, and around, the print head. Deposits include ink ‘fur’, created by ink pigment which remains after the fluid component of the ink (and solvent mixture) has evaporated. Such deposits risk the accuracy of printing, the operation of the print head, and, in extreme circumstances, may result in the blocking of an ink ejection aperture of the print head (e.g. rendering the print head non- operational for at least a period of time). Presently, the print head must manually cleaned, sometimes requiring at least partial disassembly of the print head, to remove the aforementioned deposits. This is undesirable for reasons of complexity, operator intervention, print head downtime and the quality of the cleaning.

There exists a need to provide an alternative continuous inkjet (CM) printer that overcomes one or more of the disadvantages of known systems, whether mentioned in this document or otherwise.

According to a first aspect of the invention there is provided a self-cleaning print head for a continuous inkjet printer, comprising: a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; and wherein the first and second ports are diametrically opposed from one another.

Self-cleaning print head is intended to encompass a print head which can be cleaned without the need to remove the print head from a production line or place the print head at a cleaning or waste station or similar. Self-cleaning print head therefore encompass a print head which can undergo a cleaning, and optionally a drying, cycle in-situ in an automated manner. Self-cleaning print head encompasses a print head which can be cleaned without the print head moving, or being moved, from a printing position. Described another way, there may be no movement (e.g. repositioning and/or change of configuration) of an outer geometry of the print head between the print head being used for printing (e.g. in a printing configuration, whereby the chamber is not sealed by the sealing mechanism) and the print head being cleaned (e.g. when the chamber is sealed by the sealing mechanism).

The continuous inkjet printer may be for printing onto a substrate that moves past the printer. The substrate may be described as an external substrate. The continuous inkjet printer may be configured to print on a series of discrete products that move past the printer on a processing line (e.g. a production or packaging line).

The cleaning chamber may be a fixed geometry cleaning chamber. The chamber may be defined by a chamber housing. The chamber may be entirely defined by a chamber housing. The chamber may be defined by a combination of a chamber housing and a casing of the sealing mechanism. A rotatable body of the sealing mechanism may define a downstream (e.g. second) end of the chamber. The cleaning chamber may be referred to as a chamber.

The sealing mechanism may comprise a rotatable body which is rotatable about an axis within a casing. The sealing mechanism may comprise a rotatable end cap. The sealing mechanism may comprise a number of other arrangements where the chamber can be selectively provided in communication with atmosphere via an ink capture in a first, printing, configuration, and where the chamber can be selectively sealed in a second, sealing, configuration. Fixed geometry cleaning chamber is intended to mean that the majority of the volume of the chamber does not change in operation. Instead, a comparatively fixed geometry chamber is opened or closed by the sealing mechanism. The nozzle may be disposed proximate an upstream end of the chamber. The chamber may be described as interposing the nozzle and the rotatable body. The nozzle may be disposed proximate a first end of the chamber. The rotatable body may be disposed proximate a second end of the chamber. The first end of the chamber may oppose the second end of the chamber. The nozzle may be described as in fluid communication with the chamber. The nozzle may be described as in fluid communication with the chamber independent of the configuration of the sealing mechanism body. Put another way, the sealing mechanism does not affect a fluid communication path between the chamber and the nozzle. Described a further different way, the nozzle may always be open to the chamber (e.g. permanently open to, or in fluid communication with, the chamber). The chamber may be described as being disposed downstream of the nozzle, and downstream of the charge electrode. The sealing mechanism may define an ink aperture. The ink aperture may be described as being downstream of the at least one (e.g. deflection) electrode.

The nozzle is preferably fixed in position (e.g. not movable). The gutter is preferably fixed in position (e.g. not movable). The nozzle and gutter are preferably separate components to ports of the chamber. Put another way, the nozzle and gutter are preferably not ports of the chamber (e.g. are not used for providing, or draining, cleaning fluid from the chamber). That said, it may be advantageous to drain at least some of the cleaning fluid through the gutter to clear ink from the gutter line. Otherwise, ink may diffuse into the cleaning fluid.

The chamber may be described as containing one or more components. Put another way, one or more components may be disposed in the cleaning chamber. The cleaning chamber may be described as containing one or more of a pair of deflection electrodes (e.g. a high voltage electrode and/or a low voltage electrode). Put another way, one or more of a pair of deflection electrodes (e.g. a high voltage electrode and/or a low voltage electrode) may be disposed in the cleaning chamber. A charge electrode and nozzle may be described as being in fluid communication with the cleaning chamber. The charge electrode and nozzle may be described as being in fluid communication with the chamber via a channel.

The nozzle may otherwise be described as an aperture of a droplet generator, or a jewel. At least some of the ink droplets of the stream of ink droplets may be deflected in operation to apply a printed pattern to an external substrate. The stream of ink droplets generated by the nozzle may be generated by breaking up a continuous stream of ink using, for example, an oscillating piezoelectric element. Droplets may then be directed past a charge electrode where they are given an electric charge, and subsequently guided by a further electrode to direct the now-charged droplet as needed. The at least one electrode for guiding the stream of ink droplets may comprise a zero or negative voltage plate (e.g. the ground plate) and a high voltage (extra high tension (EHT)) plate. The EHT plate may be described as a deflection electrode. A (transverse) electric field is generated across the plates and a charged droplet is deflected by the field by an amount dependent upon the charge and the electric field. The at least one electrode for guiding the stream of ink droplets may be disposed in the chamber. At least part of a charge electrode may also be disposed in the chamber. Any component disposed in the chamber may be cleaned as part of a cleaning cycle when the chamber is sealed by the sealing mechanism.

The gutter may comprise an aperture, referred to as a gutter aperture. It may specifically be the gutter aperture which receive droplets of ink which are not used for printing. The gutter may be defined by way of a gutter block, a separate component which is coupled within the chamber. In some embodiments the gutter may be integral with the sealing mechanism in that, for example, a rotatable body of the sealing mechanism may comprise an integral gutter. In other embodiments, the gutter may be fixed in position (e.g. not movable).

Ends of the cleaning chamber may be defined across a major dimension of the cleaning chamber. For example, where the cleaning chamber is generally cuboidal, the ends of the cleaning chamber are preferably defined by the faces which oppose each other across a major dimension of the cuboid. First and second ends of the chamber is intended to encompass first and second outermost ends of the chamber (e.g. the outermost limits of the chamber). Ports being disposed proximate ends of the cleaning chamber may encompass ports being disposed in a region of the cleaning chamber corresponding to a first or last quarter of a major dimension of the cleaning chamber. For example, where the cleaning chamber has a major dimension of 100 mm, the port being disposed proximate the first end of the cleaning chamber may comprise the port being disposed within a first 25 mm of the chamber. Similarly, a second port being disposed proximate a second, opposing end of the clean chamber may comprise a second port being disposed at a position between 75 mm to 100 mm in the chamber.

A port may comprise an aperture. A port maybe described as being in fluid communication with a corresponding conduit. The port may define a single port, or the port may comprise a plurality of subports (e.g. similar to a sink or shower drain). One or more of the first and second ports is preferably disposed at a junction of one or more walls within the cleaning chamber so that fluid is still directed towards one of the ports when the print head is in a range of orientations. In preferred embodiments the first port is referred to as an upstream port, proximate the nozzle. In preferred embodiments the second port is referred to as a downstream port, proximate the gutter or an ink capture through which ink droplets used for printing are rejected from the print head towards a substrate.

The first and second ports being diametrically opposed from one another is intended to encompass the first and second ports being disposed in a range of different locations. For example, where the cleaning chamber is generally cuboidal, and where outermost ends of the chamber are square in cross-section, diametrically opposed ports is intended to encompass the first and second ports being provided on diagonally opposing corners relative to one another. Diametrically opposed also encompasses the first and second ports being provided part-way along edges of the outermost ends (e.g. at a midpoint) but still diagonally opposing one another to the extent possible. For example, the first port may be disposed at a midpoint of an upper edge of a first end, and the second port may be disposed at a midpoint of a lower edge at the other end.

Advantageously, providing first and second ports diametrically opposed from one another, and proximate first and second opposing ends of the cleaning chamber, means that the first and second ports can be used to drain the cleaning chamber, during or following a cleaning cycle, with the chamber, and print head more generally, in a wider range of orientations. Providing the ports in these positions avoids an undesirable situation where significant pockets of cleaning fluid remain present in the chamber, owing to the orientation of the chamber, following a cleaning cycle. Providing the ports in these positions therefore means the print head can be provided in a greater range of orientations whilst an automatic cleaning process could still be carried out without leaving significant pooling of cleaning fluid in the chamber following a cleaning cycle.

The cleaning chamber can therefore be used as part of a self-cleaning print head in which the build-up of ink fur and other debris can be intermittently removed by operation of a cleaning and drying cycle. Furthermore, this can be achieved without needing to remove the print head from a printing or production line, and without having to place the print head in a cleaning station. The invention therefore overcomes the disadvantages associated with known cleaning methods including: production downtime, required operator skill and training, the cost of handling hazardous fluids, the cost of safety precautions and time to prepare the necessary personal protective equipment, the cost of any cleaning fluids used which are not recycled and are discarded, and the cost of hazardous waste disposal. The invention thus: reduces downtime, avoids the need for the print head to be removed from a printing or production line, does not require a skilled operator, provides consistent and repeatable results, avoids the need to handle any hazardous waste owing to the washing fluids being recycled back into the ink system, and reduces environmental impact and running costs.

The first and second ports may be multifunction fill/drain ports.

The first and second ports being multifunction fill/drain ports is intended to mean that the first and second ports can be used to fill the cleaning chamber with cleaning fluid and, separately, they can also be used to drain the cleaning fluid from the chamber. Described another way, the ports may be described as bidirectional.

Advantageously, by being able to use the first and second ports as multifunction fill/drain ports, the chamber can be drained of cleaning fluid in a wider variety of orientations. Furthermore, a single design of self-cleaning print head can be used and incorporated in a range of different orientations whilst still providing a cleaning functionality.

In preferred embodiments the first and/or second ports are multifunction fill/drain/drying ports. That is to say, as well as filling and draining the chamber with/of cleaning fluid, air can also be pumped through the first and/or second ports to facilitate drying of the chamber.

The first port may be in fluid communication with a first conduit.

The first conduit may also be in fluid communication with a third port.

The first conduit also being in fluid communication with the third port may otherwise be described as the first conduit being in fluid communication with a plurality of ports. The third port may be in communication with a third conduit, and the third conduit effectively branch off the first conduit. Advantageously, providing the first conduit in fluid communication with the first and third ports means that there is a greater flexibility of where cleaning fluid fills the chamber and where cleaning fluid is drained from the cleaning chamber.

The third port may be defined by a nozzle body which defines the nozzle.

The third port may be defined in a face of the nozzle body.

Advantageously the third port being defined by the nozzle body means that the third port can be used to drain cleaning fluid, at least when the print head is in a vertically upright position, from any position which may be vertically beneath the first port and so which otherwise may not be drained. This may include any cleaning fluid which remains in the charge electrode and in any channel which connects the charge electrode to the chamber. Providing the third port in the nozzle body, but separate to the nozzle, is also desirable for the reason that when cleaning fluid is drained from the chamber by the third port, debris is not drawn towards the comparatively small aperture nozzle (which may otherwise risk blockage of the nozzle).

The second port may be in fluid communication with a second conduit.

The second conduit may only be in fluid communication with the second port. Described another way, the second conduit may not be a branched conduit.

The cleaning chamber may comprise no undercut features.

No undercut features is intended to mean no recesses or other features, in which cleaning fluid could be retained in the chamber after draining, are present.

Advantageously, the cleaning chamber comprising no undercut features reduces the risk that pockets of cleaning fluid remain in the chamber following a cleaning and draining cycle (i.e. pockets which may not be drainable by the ports).

The cleaning chamber may comprise no vertices.

No vertices is intended to mean no sharp corners. Advantageously, avoiding incorporation of sharp corners means that cleaning fluid is generally guided towards one or more of the first and second ports. Furthermore, the risk of vertices defining undercut pockets where cleaning fluid may remain, after a cleaning cycle, is reduced. Advantageously, the chamber is therefore more fully drained of cleaning fluid following a cleaning cycle.

The cleaning chamber may be defined by a pair of parallel sides.

The cleaning chamber being defined by a pair of parallel sides is intended to encompass the cleaning chamber being defined by two sides that are at least partially parallel.

Advantageously the use of parallel sides may provide a more readily manufacturable chamber.

Surfaces that define the cleaning chamber may be contoured for guiding fluid towards the first or second ports.

The surfaces that define the chamber being contoured for guiding fluid towards the first and second ports encompasses at least some of the surfaces being cambered (e.g. arcuate) to direct fluid towards the first and second ports.

Advantageously, this reduces the risk that cleaning fluid puddles within the chamber such that it is not drained following a cleaning cycle.

A deflection electrode of the at least one electrode may be disposed in the cleaning chamber by one or more supports which sealingly engage a periphery of the cleaning chamber.

The one or more supports may otherwise be described as posts or legs. The one or more supports may be integral with the deflection electrode. The deflection electrode may be described as suspended within the chamber by the one or more supports. The one or more supports may sealingly engage a periphery of the cleaning chamber, which may otherwise be described as a surface, by sandwiching seals (such as O-rings or other gaskets) between the deflection electrode and the periphery. In other embodiments, the deflection electrode may be press-fitted in position or secured in position by adhesive.

Advantageously, the one or more supports of the deflection electrode means that the deflection electrode can be disposed within the cleaning chamber whilst the cleaning chamber is still sealable such that a cleaning process can be carried out without undue leakage of cleaning fluid.

A low voltage electrode of the at least one electrode may define at least part of the cleaning chamber.

The low voltage electrode may be said to define at least part of a lower surface of the cleaning chamber in one orientation. Described another way, one surface of the cleaning chamber may have an aperture in which the low voltage electrode is receivable.

Advantageously, the low voltage electrode defining at least part of the chamber means that the low voltage electrode is disposed in the chamber and is therefore cleaned as part of the cleaning cycle when the cleaning chamber is filled with cleaning fluid. The low voltage electrode can also be disposed generally opposite the deflection electrode to form the deflection field therebetween.

The cleaning chamber may be defined by a chamber housing and the sealing mechanism, the sealing mechanism sealingly engaging the chamber housing.

The cleaning chamber may specifically be defined by a combination of the chamber housing and a casing of the sealing mechanism. The sealing mechanism may sealingly engage the chamber housing by way of a seal, such as an O-ring. It may specifically be a casing of the sealing mechanism that sealingly engages the chamber housing.

Advantageously, the chamber being defined by both the chamber housing and the sealing mechanism provides a print head in which the chamber can be readily manufactured. The second port may be defined by the gutter.

Described another way, the gutter (aperture) is the second port. Using the gutter as the second port is desirable for the reason that the gutter is already present as part of the print head geometry. Furthermore, the gutter may be integrally formed with a rotatable body of the sealing mechanism such that the gutter is rotatably coupled thereto.

The gutter may define a separate port to the first and second ports.

The gutter may be defined by a gutter block. The gutter block may separately (also) define the second port. The first and second ports (and third port, if present) may also define separate ports to the nozzle. Put another way, in preferred embodiments the nozzle and gutter are separate to the first and second (and third, if appropriate) ports of the chamber.

One or more of the first port and the second port may comprises a plurality of subports.

Described another way, the first and/or second ports may form part of an array of ports extending around the cleaning chamber.

The subports may be said to define an array of apertures. The plurality of subports preferably extend circumferentially around the cleaning chamber.

Advantageously, by incorporating a plurality of subports cleaning fluid can be drained from the chamber from a wider variety of orientations. Described another way, the likelihood that the first port or second port is in communication with cleaning fluid is increased by virtue of the port effectively having a distribution of ports around the chamber. The plurality of subports may be described as a sink or drain-like arrangement.

The first port may define a first port axis, and the first port axis may be substantially parallel with a nozzle axis defined by the nozzle. The first port axis being substantially parallel with the nozzle axis is intended to encompass the first port axis and nozzle axis not intersecting within an extent of the cleaning chamber. The first port axis being substantially parallel with the nozzle axis is also intended to encompass a positive flow of air exerted through the first port axis not interfering with the stream of ink droplets ejected along the nozzle axis.

Advantageously, as mentioned above a positive flow of air can be pumped through the first port axis without interfering with the stream of ink droplets ejected along the nozzle axis when the port access is substantially parallel to the nozzle axis.

The self-cleaning print head may further comprise an orientation sensor configured to detect the orientation of the self-cleaning print head.

The orientation sensor may be an accelerometer or any other variety of orientation sensor. The orientation sensor may be configured to output an orientation signal to a controller which is indicative of the orientation of the print head. The orientation sensor may specifically indicate the orientation of the cleaning chamber, although it will be appreciated that the orientation of the cleaning chamber is discernible if the orientation of the overall print head is known. The orientation sensor may be mounted within/to the print head. The orientation sensor may be mounted to a PCB within the print head.

Advantageously, the orientation sensor can be used to detect the orientation of the print head and so cleaning chamber. The orientation of the cleaning chamber can be used to determined which of the first and second ports (or other ports, if applicable) is used as a fill or drain port respectively based upon the orientation of the print head. The orientation sensor can therefore form part of a feedback loop in which an orientation of the print head is detected and a subsequent processing step decides which of the first and second port is to be used as a fill or drain port.

According to a second aspect of the invention there is provided a continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller; the self-cleaning print head comprising: a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; wherein the first and second ports are diametrically opposed from one another; and wherein the first port is in fluid communication with a first conduit, and the second port is in fluid communication with a second conduit.

The nozzle may otherwise be described as an aperture of a droplet generator, or a jewel. At least some of the ink droplets of a stream of ink droplets may be deflected in operation to apply a printed pattern to the external substrate. The stream of ink droplets generated by the nozzle may be generated by breaking up a continuous stream of ink using, for example, an oscillating piezoelectric element. Droplets may then be directed past a charge electrode where they are given an electric charge, and subsequently guided by a further electrode to direct the now-charged droplet as needed. The at least one electrode for guiding the stream of ink droplets may comprise a zero or negative voltage plate (e.g. the ground plate) and a high voltage (extra high tension (EHT)) plate. The EHT plate may be described as a deflection electrode. A (transverse) electric field is generated across the plates and a charged droplet is deflected by the field by an amount dependent upon the charge and the electric field.

The ink system may comprise a number of components including, but not limited to, a mixing tank, a plurality of pumps, a cartridge, a plurality of filters and a plurality of valves. The ink system may be described as being a closed system in which ink and solvent are received by way of a cartridge, and an appropriate mixture is prepared in the mixing tank ready for printing. Ink is supplied from the mixing tank to the print head.

The first conduit and/or second conduit may be at least partly defined by a chamber housing which also defines at least part of the cleaning chamber. Cleaning fluid may be pumped through, or drained via, the first and second conduits.

The self-cleaning print head may comprise an orientation sensor configured to detect the orientation of the self-cleaning print head, and the orientation sensor may be configured to output an orientation signal, to the controller, indicative of the orientation of the self-cleaning print head.

The orientation sensor may be described as being in operative communication with the controller. The orientation sensor may be an accelerometer or any other variety of orientation sensor. The orientation sensor may be configured to output an orientation signal to a controller which is indicative of the orientation of the print head. The orientation sensor may specifically indicate the orientation of the cleaning chamber, although it will be appreciated that the orientation of the cleaning chamber is discernible if the orientation of the overall print head is known.

A plurality of valves may be operable to control a flow of cleaning fluid into and/or out of the cleaning chamber.

The plurality of valves may be operable to control a direction of the flow of cleaning fluid flow into and/or out of the cleaning chamber. The plurality of valves may be operable to control a direction of the flow of cleaning fluid flow through the first and second conduits. The plurality of valves may be operable to control the flow of cleaning fluid through the cleaning chamber.

Described another way, operation of the plurality of valves may determine whether the first or second port is a fill port, and whether the first or second port is a drain port. The port which is used for filling the cleaning chamber with cleaning fluid, and the port which is used for draining the cleaning chamber of the cleaning fluid, may be controlled by actuation of the plurality of valves.

The plurality of valves may form part of a H-bridge arrangement. The H-bridge arrangement may be operative to control a direction of cleaning fluid flow through the first and second conduits.

Advantageously, the plurality of valves being operable to control a flow of cleaning fluid into and/or out of the cleaning chamber means that the cleaning chamber can be cleaned in a manner which is best suited to the current orientation of the print head and chamber. For example, in an orientation where the print head is oriented vertically upwards, it is desirable that the (vertically lower) first port is a fill and drain port. If the (vertically higher) second port were the fill and drain port, as solvent was filled through the second port it would drain from the chamber (without providing a desired cleaning action) through the first port. The first port would be open to allow air to be displaced from within the chamber as the chamber is filled with solvent. By filling and draining via the first port, air can be displaced from the (vertically higher) second port as solvent is added (through the first port) without the solvent leaving the chamber. In contrast, where the print head is in a vertically downward orientation, it is desirable that the (vertically lower) second port be the fill and drain port. Put another way, it is desirable that the vertically lowest port be selected as the fill and drain port such that: i) solvent does not drain from the chamber prematurely; and ii) the greatest amount of cleaning fluid can be drained from the cleaning chamber when desired. Put another way, it is desirable that the fill and drain port be selected such that the port is the vertically lowest of the ports in the chamber. Cleaning fluid will also pool, collect or gather at the vertically lowest point under gravity, so having the vertically lower port be the drain port means the greatest possible volume of cleaning fluid can be drained from the chamber after a cleaning cycle (e.g. reducing the time taken for the chamber to dry, thereby reducing the cleaning cycle time). Also advantageously, by using the plurality of valves to control the flow of cleaning fluid through the chamber, a one-directional pump can be used (e.g. a diaphragm pump). For example, an existing (single) gutter pump, which is a diaphragm pump, can be used to draw cleaning fluid into the chamber by either port, as determined by the plurality of valves, and also draw cleaning fluid back out of the chamber (by the other of either port).

Advantageously the plurality of valves operate to substantially prevent the leakage of undesirable cleaning fluid through the cleaning chamber other than during a cleaning cycle. To facilitate this, the unpowered state (e.g. de-energised state) of the plurality of valves connects the first and second ports to the air line only (e.g. not to the cleaning fluid supply or gutter line).

The controller may be configured to receive the orientation signal, process the orientation signal, and output a valve control signal, to the plurality of valves, to control the flow of cleaning fluid into and/or out of the cleaning chamber based upon the orientation of the self-cleaning print head.

Where the plurality of valves form part of a H-bridge arrangement, the valve control signal may be outputted to the H-bridge arrangement.

The plurality of valves may control the direction of cleaning fluid flow into and/or out of the cleaning chamber. The plurality of valves may control the direction of cleaning fluid flow through the first and second conduits.

By using the orientation sensor of the print head to determine the orientation, and subsequently send a valve control signal to control the flow of cleaning fluid through the plurality of valves in a manner which is best suited for that orientation, the selection of the fill and/or drain port can occur automatically and in a manner which is optimised for the current orientation of print head.

The plurality of valves may comprise: a first flow valve configured to selectively place the first conduit in fluid communication with a gutter line or a first feed valve, wherein the first feed valve is selectively connectable to a cleaning fluid, or air, supply; and a second flow valve configured to selectively place the second conduit in fluid communication with the gutter line or a second feed valve, wherein the second feed valve is selectively connectable to the cleaning fluid, or air, supply.

The plurality of valves may be referred to as plurality of control valves. The plurality of valves may form part of a cleaning module. The cleaning module may be described as forming part of the overall ink system.

The first flow valve may otherwise be described as a first fill/drain valve. The first flow valve may otherwise be described as a second control valve. The first flow valve may be described as being connected to each of the first conduit, a draw line and a first feed valve. The first flow valve may be directly connected to the gutter line, or the first flow valve may be connected to the gutter line by the intermediate draw line. Placing the first conduit in fluid communication with the gutter line means that suction will be applied, when the gutter pump is activated, through the first conduit. The fluid within the cleaning chamber will thus be drawn out of the chamber via the first conduit and corresponding first port. Similarly, if the gutter pump is activated before the cleaning chamber has been filled with cleaning fluid, suction through the first conduit will draw cleaning fluid through the second conduit, depending upon the valve configuration, into the chamber in that manner.

The first feed valve may be connectable to a solvent supply by way of an inlet line which is, in turn, connected to a solvent tank. The first feed valve may be selectively connectable to an air supply by way of being connected to an air line. An air pump may be disposed in the air line. The air pump may be activated to draw in air from an external vent to be pumped through the air line. By being connectable to the air supply, air can be pumped into the chamber, via the first conduit, to dry the chamber as part of a cleaning cycle.

The second flow valve may otherwise be described as a second fill/drain valve. The second flow valve may otherwise be described as a third control valve. The second flow valve may be described as being connected to each of the second conduit, the draw line and a second feed valve. The second flow valve may be directly connected to the gutter line, or the second flow valve may be connected to the gutter line by the intermediate draw line. Placing the second conduit in fluid communication with the gutter line means that suction will be applied, when the gutter pump is activated, through the second conduit. The fluid within the cleaning chamber will thus be drawn out of the chamber via the second conduit and corresponding second port. Similarly, if the gutter pump is activated before the cleaning chamber has been filled with cleaning fluid, suction through the second conduit will draw cleaning fluid through the first conduit, depending upon the valve configuration, into the chamber in that manner.

The second feed valve may be connectable to the solvent supply by way of an inlet line which is, in turn, connected to a solvent tank. The second feed valve may be selectively connectable to the air supply by way of being connected to the air line. By being connectable to the air supply, air can be pumped into the chamber, by the second conduit, to dry the chamber as part of a cleaning cycle.

Advantageously, the above-described valve configuration allows cleaning fluid to be drawn into the cleaning chamber by either of the first and second conduits (and so either of the first and second ports). The valve configuration can also be used to select whether solvent or air is provided, and through which of the first and second conduits.

A gutter pump, disposed in the gutter line, may be configured to draw cleaning fluid from the cleaning fluid supply into the cleaning chamber.

In preferred embodiments, the gutter pump is the only component which actively draws the cleaning fluid from the cleaning fluid supply into the cleaning chamber. Described another way, the cleaning fluid is preferably not pumped into the chamber, but is instead drawn through the chamber. Put another way, the cleaning chamber can be considered to form part of the fluid circuit between the cleaning fluid supply and the gutter pump.

Advantageously, drawing the cleaning fluid into the cleaning chamber provides a failsafe functionality in that a significant leak in the cleaning chamber will simply lead to no cleaning fluid being drawn therethrough. For example, if the sealing mechanism were to fail open, such that the cleaning chamber was open to atmosphere, it will not be possible to generate a sufficiently low pressure in the cleaning chamber to draw the cleaning fluid into the cleaning chamber. This is desirable because, in instances where the cleaning fluid were pumped into the cleaning chamber, failure of the sealing mechanism would otherwise result in cleaning fluid being ejected out of the cleaning chamber and risk contamination of any products on the printing line (e.g. foodstuffs).

Responsive to the output of a first orientation signal by the orientation sensor to the controller, indicative of the self-cleaning print head being in a first orientation, the controller may be configured to output a first valve control signal, to the plurality of valves, in which: the first flow valve is configured to place the first conduit in fluid communication the first feed valve, wherein the first feed valve is connected to the cleaning fluid supply; and the second flow valve is configured to place the second conduit in fluid communication with the gutter line.

The self-cleaning print head being in a first orientation may otherwise be described as the self-cleaning print head in a vertically upright position. The first flow valve being configured to place the first conduit in fluid communication with the first feed valve, and the first feed valve being connected to the cleaning fluid supply, means that cleaning fluid will be drawn through the first conduit into the cleaning chamber. In the vertically upright position, drawing cleaning fluid through the first conduit is desirable because the first port is the vertically lower port. Air can thus be vented from within the cleaning chamber via the second conduit, without also drawing solvent out of the cleaning chamber undesirably (i.e. as would be the case if the first conduit were open for air to be vented therethrough).

The second flow valve being configured to place the second conduit in fluid communication with the gutter line means that suction will be applied through the second conduit. Given that the first conduit is connected to the cleaning fluid supply, via the first feed valve, cleaning fluid will be drawn via the cleaning chamber and via the first conduit owing to the suction applied through the second conduit.

Responsive to the output of a second orientation signal by the orientation sensor to the controller, indicative of the self-cleaning print head being in a second orientation, the controller may be configured to output a second valve control signal, to the plurality of valves, in which: the first flow valve is configured to place the first conduit in fluid communication with the gutter line; and the second flow valve is configured to place the second conduit in fluid communication with the second feed valve, wherein the second feed valve is connected to the cleaning fluid supply.

The self-cleaning print head being in a second orientation may otherwise be described as the self-cleaning print head in a vertically downwards position. The first flow valve being configured to place the first conduit in fluid communication with the gutter line means that suction will be applied through the first conduit. Given that the second conduit is connected to the cleaning fluid supply, via the second feed valve, cleaning fluid will be drawn via the cleaning chamber and via the second conduit owing to the suction applied through the first conduit.

The second feed valve being connected to the cleaning fluid supply means that cleaning fluid will be drawn through the second conduit into the cleaning chamber. In the vertically downwards position, drawing cleaning fluid through the second conduit is desirable because the second port is the vertically lower port. Air can thus be vented from within the cleaning chamber via the first conduit, without also drawing solvent out of the cleaning chamber undesirably (i.e. as would be the case if the second conduit were open for air to be vented therethrough).

The plurality of valves may be disposed outside of the self-cleaning print head.

The plurality of valves may be disposed in the printer body (e.g. cabinet). The plurality of valves may form part of the ink system. The plurality of valves may be disposed within a cleaning fluid circuit, which may form part of the ink system.

Providing a plurality of valves outside of the self-cleaning print head is advantageous for at least the reason that the size of the print head can be kept smaller than if the plurality of valves were incorporated in the print head. Furthermore, providing the plurality of valves outside of the self-cleaning print head may reduce the number of fluid and/or electrical conduits which need to extend through the umbilical to provide communication between the ink system and the print head. According to a third aspect of the invention there is provided a method of cleaning a self-cleaning print head of a continuous inkjet printer, comprising: sealing a cleaning chamber of the print head by actuating a sealing mechanism, and selecting a port of the cleaning chamber as a fill port, and a port of the cleaning chamber as a drain port, based upon the orientation of the self-cleaning print head; directing a flow of cleaning fluid through the fill port, into the cleaning chamber, to clean the cleaning chamber; and draining the cleaning fluid from the cleaning chamber, through the drain port, to drain the cleaning chamber.

The method for cleaning a self-cleaning print head may specifically be described as a method of cleaning a cleaning chamber of a self-cleaning print head. It will be appreciated that by cleaning the cleaning chamber, any components disposed in the cleaning chamber (e.g. one or more electrodes) will also be cleaned.

Sealing the cleaning chamber of the print head by actuating the sealing mechanism may comprise rotating a rotatable body of the sealing mechanism to close an ink aperture. Actuating the sealing mechanism may otherwise comprise rotating an end cap to close an ink aperture.

The cleaning chamber may comprise a first port proximate a first end of the chamber, and a second port proximate a second end of the chamber. Selecting a port of the cleaning chamber as a fill port may comprise selecting the first or second port as a fill port. Selecting a port of the cleaning chamber as a drain port may comprise selecting one of the first and second ports as a drain port. The selection of the ports being based upon the orientation of the self-cleaning print head may comprise a controller receiving an orientation signal from an orientation sensor, processing that signal and outputting a valve control signal to a plurality of valves.

Directing cleaning fluid through the fill port may comprise pumping cleaning fluid through the fill port (e.g. under a positive pressure). Directing cleaning fluid through the fill port may comprise drawing cleaning fluid through the fill port (e.g. under a negative pressure). Directing cleaning fluid through the fill port and draining the cleaning fluid from the cleaning chamber may occur simultaneously. Alternatively, the cleaning chamber may be filled with cleaning fluid and then subsequently drained of cleaning fluid (e.g. the cleaning fluid be drawn out of or pumped out of the chamber). In some embodiments a single port may define the fill port and the drain port. For example, where the print head is in a vertically upward orientation, the vertically lowest first port may define both the fill port and the drain port in a method which comprises first filling the cleaning chamber with cleaning fluid through the first port, waiting for a period of time, and then subsequently draining the cleaning fluid through the first port. The cleaning fluid may be a blend of solvents.

Directing a flow of cleaning fluid through the fill port into the cleaning chamber may comprise at least partially filling the cleaning chamber. The cleaning chamber may be described as a selectively sealable volume. Cleaning the cleaning chamber may clean other components disposed in the cleaning chamber (e.g. deflection electrode, other surfaces etc.).

Advantageously, the method of cleaning a self-cleaning print head reduces the cleaning time required to clean the print head, it does not require skilled operator intervention, provides consistent and repeatable results, avoids the need to handle hazardous waste and therefore reduces the environmental impact and running costs associated with the printer. Furthermore, all of the above can be carried out in an automated manner which does not require that the print head be moved from the printing line.

Directing the cleaning fluid into the chamber may comprise sucking cleaning fluid into the chamber Cleaning fluid may subsequently be drawn out of the chamber, again under a negative pressure. Advantageously, the gutter pump can be used to draw the cleaning fluid in this manner. Drawing cleaning fluid under a negative pressure is advantageously failsafe insofar as if the sealing mechanism were to fail, no cleaning fluid would be drawn into the chamber owing to the negative pressure drawing in only air via the open sealing mechanism. Such an arrangement is therefore inherently failsafe in mitigating the risk that pressurised cleaning fluid be inadvertently ejected from the print head onto a printing line.

The cleaning fluid may be directed into the chamber from a solvent tank. The solvent tank may contain solvent which has previously been used in the ink system. Such ‘used’ cleaning fluid may advantageously be warmer than ‘fresh’ solvent from the solvent cartridge. The cleaning fluid may be directed into the chamber from a solvent cartridge. The solvent cartridge may contain fresh, or virgin, solvent. A cleaning cycle may first be carried out using cleaning fluid from the solvent reservoir. The cleaning cycle may then be carried out using fresh cleaning fluid from the solvent cartridge. This may be described as pre-cleaning, or a prewash, with dirty solvent, and finishing the cleaning cycle with a virgin solvent rinse. Cleaning the chamber may comprise agitating the cleaning fluid, in the chamber, by directing a flow of air through the chamber. This may be described as bubbling air through the chamber to agitate the cleaning fluid in the chamber.

The method may further comprise using an orientation sensor of the self-cleaning print head to determine the orientation of the self-cleaning print head.

Determining the orientation of the self-cleaning print head using the orientation sensor may comprise the orientation sensor outputting an orientation signal corresponding to an orientation of the print head. For example, where the print head is in a first orientation, the orientation sensor may output a first orientation signal. Where the print head is in a second orientation, the orientation sensor may output a second orientation signal. The orientation signal may be received by a controller. The controller may process the orientation signal. The controller may subsequently output a valve control signal (e.g. a first or second valve control signal) to a plurality of valves to control the configuration of a cleaning fluid circuit. The configuration of the cleaning fluid circuit may determine which of the first and second ports is the fill port, and which of the first and second ports is the drain port.

Selecting a port of the cleaning chamber as a fill port, and a port of the cleaning chamber as a drain port, based upon the orientation of the self-cleaning print head, may comprises selecting one of a first port and a second port of the cleaning chamber as the fill port and the drain port.

Selecting one of the first port and the second port of the cleaning chamber as both the fill port and the drain port is advantageous because a lowermost port can be used as a fill port to draw cleaning fluid into the cleaning chamber whilst air within the cleaning chamber is vented through the other, vertically upper port. Air can therefore be displaced from the cleaning chamber without solvent undesirable leaking through that same port.

Selecting one of the first port and the second port of the cleaning chamber as the fill port and the drain port may comprise determining, using the orientation sensor, which of the first and second ports is the vertically lower port.

Selecting the fill port and the drain port may comprise operating a plurality of valves to place a cleaning fluid circuit in a first configuration, the first configuration corresponding to the self-cleaning print head being in a first orientation.

The cleaning fluid circuit may be described as a cleaning module. The cleaning fluid circuit may comprise the plurality of valves. Placing the cleaning fluid circuit in a first configuration may otherwise be described as providing one of the first and second ports in fluid communication with a gutter line, and providing the other of the first and second ports in fluid communication with a solvent supply. Alternatively or in combination, the cleaning fluid circuit may be placed in a different configuration by virtue of a direction of a pump being reversed.

The controller may ascertain the orientation of the print head, optionally by way of an orientation sensor. The controller may then commit to a specific valve sequence, for operating the plurality of valves, determined by the orientation of the print head. Described another way, the valve sequence may be specific to the orientation of print head.

The method may further comprise: adjusting the orientation of the self-cleaning print head from the first orientation to a different, second orientation; sealing the cleaning chamber by actuating the sealing mechanism, and selecting a different fill port and/or drain port, based upon the orientation of the selfcleaning print head; directing a flow of cleaning fluid through the fill port, into the cleaning chamber to clean the cleaning chamber; and draining the cleaning fluid from the cleaning chamber, through the drain port, to drain the cleaning chamber. Described another way, the change in the orientation of the self-cleaning print head may result in a different one of the first and second port being selected as the fill and/or drain port. This may be owing to a different port being better suited as the fill and/or drain port (e.g. a different port becoming the vertically lowermost port in that print head orientation).

Advantageously, this means that the selection of the fill and drain ports is based upon the orientation of the print head, even if the print head orientation has changed since a previous cycle and/or installation.

Selecting the different fill port and/or drain port may comprise operating the plurality of valves to place the cleaning fluid circuit in a second configuration, the second configuration corresponding to the self-cleaning print head being in the second orientation

Placing the cleaning fluid circuit in a second configuration may otherwise be described as providing a different one of the first and second ports in fluid communication with a gutter line, and providing the other of the different one of the first and second ports in fluid communication with the solvent supply. Cleaning fluid may thus be directed into the chamber via a different port. Cleaning fluid may be drained from the chamber via a different port. Alternatively or in combination, the cleaning fluid circuit may be placed in a different configuration by virtue of a direction of a pump being reversed.

The method may further comprise holding the cleaning fluid within the cleaning chamber, for a period of time, before draining the cleaning fluid from the cleaning chamber.

Holding the cleaning fluid within the cleaning chamber for a period of time may otherwise be referred to as a dwell period of a cleaning cycle. An example of the period time for which cleaning fluid may be held within the cleaning chamber is around 5 seconds.

Holding cleaning fluid within the cleaning chamber for a period of time has been found to advantageously improve the cleaning process. The method may further comprise percolating air through the cleaning fluid held within the cleaning chamber.

Percolating air through the cleaning fluid may otherwise be described as providing a supply of air through the cleaning fluid. Percolating air through the cleaning fluid may otherwise be described as air bubbles agitating the cleaning fluid held within the cleaning chamber.

Advantageously, percolating air through the cleaning fluid has been found to improve the quality of the clean and assist with dislodging ink sediment and other debris within the cleaning chamber.

Directing the flow of cleaning fluid through the fill port, into the cleaning chamber to clean the cleaning chamber, may comprise drawing cleaning fluid into the chamber using a gutter pump.

Drawing cleaning fluid into the chamber may otherwise be described as a cleaning fluid being sucked into the chamber downstream pump. Advantageously, using the gutter pump means that the same pump can be repurposed and used to draw cleaning fluid trough the cleaning chamber. Furthermore, drawing cleaning fluid under action of the gutter pump provides a fair safe functionality in that should the sealing mechanism of the cleaning chamber fail open, a pressure sufficiently low to draw cleaning fluid into the cleaning chamber will not be reached and so the cleaning process will simply not occur. This is desirable over instances where pressurized cleaning fluid be pumped into the cleaning chamber where, should the sealing mechanism fail open, cleaning fluid will be undesirably ejected out of the print head onto a printing line risking contamination of goods to be printed (e.g. foodstuffs).

According to a fourth aspect of the invention there is provided a self-cleaning print head module kit of parts for a continuous inkjet printer, comprising: a self-cleaning print head and a cleaning fluid circuit; the self-cleaning print head comprises: a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; a gutter for receiving droplets of ink which are not used for printing; and an orientation sensor configured to detect the orientation of the selfcleaning print head and output a corresponding orientation signal; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; and wherein the first and second ports are diametrically opposed from one another; and the cleaning fluid circuit comprises first and second conduits, connectable to the first and second ports respectively, and a plurality of valves operable to control the flow of cleaning fluid into and/or out of the cleaning chamber based upon the orientation signal.

The plurality of valves may be operable to place the cleaning fluid circuit in a first configuration or a second configuration, optionally based upon the orientation of the print head. In the first configuration the first port may be a fill port for filling the cleaning chamber with cleaning fluid. In the first configuration the second port may be a drain port for draining cleaning fluid from the cleaning chamber. In the second configuration the second port may be a fill port for filling the cleaning chamber with cleaning fluid. In the second configuration the first port may be a drain port for draining cleaning fluid from the cleaning chamber. The cleaning fluid circuit may be placeable in the first configuration responsive to the orientation sensor outputting a first orientation signal indicative of the print head being in a first orientation. The cleaning fluid circuit may be placeable in the second configuration responsive to the orientation sensor outputting a second orientation signal indicative of the print head being in a second orientation.

Advantageously, the self-cleaning print head module kit of parts can be used to retrofit an existing system with self-cleaning print head capability.

According to a fifth aspect of the invention there is provided a continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller; and a cleaning fluid circuit for supplying cleaning fluid to the self-cleaning print head, the cleaning fluid circuit comprising first and second conduits and a plurality of valves for controlling a flow of cleaning fluid into and/or out of a cleaning chamber; the self-cleaning print head comprising: the cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; a gutter for receiving droplets of ink which are not used for printing; an orientation sensor configured to detect the orientation of the selfcleaning print head and output an orientation signal, to the controller, indicative of the orientation of the self-cleaning print head; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; wherein the first port is in fluid communication with the first conduit, and the second port is in fluid communication with the second conduit; and wherein the controller is configured to receive the orientation signal, process the orientation signal, and output a valve control signal, to the plurality of valves, to control the flow of cleaning fluid into and/or out of the cleaning chamber based upon the orientation of the self-cleaning print head.

The cleaning fluid circuit may form part of the ink system. Controlling the flow of cleaning fluid into and/or out of the cleaning chamber may comprise selecting one of the first and second ports as a fill port, and one of the first and second ports as a drain port. Controlling the flow of cleaning fluid into and/or out of the cleaning chamber may comprise controlling the flow direction of cleaning fluid into and/or out of the cleaning chamber. Controlling the flow of cleaning fluid into and/or out of the cleaning chamber may comprise controlling the flow of cleaning fluid through the cleaning chamber.

According to a sixth aspect of the invention there is provided a method of cleaning a self-cleaning print head of a continuous inkjet printer, comprising: sealing a cleaning chamber of the print head by actuating a sealing mechanism; connecting a first port of the cleaning chamber to a cleaning fluid supply, and connecting a second port of the cleaning chamber to a suction source; and activating the suction source to draw cleaning fluid through the first port, into the cleaning chamber, to at least partially fill the cleaning chamber with cleaning fluid. The suction source is preferably the only component which actively draws the cleaning fluid from the cleaning fluid supply into the cleaning chamber. Described another way, the cleaning fluid is preferably not pumped into the chamber, but is instead drawn into/through the chamber. Put another way, the cleaning chamber can be considered to form part of the fluid circuit between the cleaning fluid supply and the suction source. The suction source may be a gutter pump or a Venturi.

Advantageously, drawing the cleaning fluid into the cleaning chamber provides a failsafe functionality in that a significant leak in the cleaning chamber will simply lead to no cleaning fluid being drawn therethrough. For example, if the sealing mechanism were to fail open, such that the cleaning chamber was open to atmosphere, it will not be possible to generate a sufficiently low pressure in the cleaning chamber to draw the cleaning fluid into the cleaning chamber. This is desirable because, in instances where the cleaning fluid were pumped into the cleaning chamber (e.g. under action of an upstream pump, and by positive pressure), failure of the sealing mechanism would otherwise result in cleaning fluid being ejected out of the cleaning chamber and risk contamination of any products on the printing line (e.g. foodstuffs).

The suction source may comprise a gutter pump, and activating the suction source comprises activating the gutter pump.

Advantageously, using the gutter pump as the suction source means that the existing gutter pump can also be used to draw cleaning fluid into the cleaning chamber.

Connecting the second port of the cleaning chamber to the suction source may comprise placing the second port in fluid communication with a solvent reservoir, with the suction source interposing the second port and the solvent reservoir.

The solvent reservoir may be a solvent tank. The solvent reservoir may contain solvent which has previously been used in the ink system. Such ‘used’ cleaning fluid may advantageously be warmer than ‘fresh’ solvent from the solvent cartridge. Advantageously, using used cleaning fluid from the solvent reservoir means used cleaning fluid can be recycled. The method may further comprise holding the cleaning fluid in the cleaning chamber for a soaking period.

Holding the cleaning fluid may otherwise be described as a dwell, a soak, or a pause. The soaking period may be at least 1 second. The soaking period may be at least around 5 seconds. The soaking period may be up to around 10 seconds, or up to around 30 seconds.

Advantageously, holding the cleaning fluid in the cleaning chamber for a soaking period has been found to improve the quality of the clean.

The method may further comprise draining the cleaning fluid from the cleaning chamber through the first port.

Draining cleaning fluid from the chamber through the first port, as well as filling the chamber via the first port, is advantageous in that the fluid can be readily retained in the chamber for a soaking period. Furthermore, where the first port is selected as being the vertically lowest port, air displaced from the chamber by the cleaning fluid can be vented from vertically higher port (e.g. the second port) without cleaning fluid leaking therethrough.

According to a seventh aspect of the invention there is provided a continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller and a suction source disposed along a gutter line; and a cleaning fluid circuit for supplying cleaning fluid to the self-cleaning print head, the cleaning fluid circuit comprising first and second conduits connectable to a cleaning fluid supply or the suction source by a plurality of valves, wherein the plurality of valves are for controlling a flow of cleaning fluid into and/or out of a cleaning chamber; the self-cleaning print head comprising: the cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; a gutter for receiving droplets of ink which are not used for printing, wherein the gutter is in fluid communication with the suction source via the gutter line; wherein the cleaning chamber comprises a first port and a second port; wherein the first port is in fluid communication with the first conduit, and the second port is in fluid communication with the second conduit; and wherein the suction source is configured to draw cleaning fluid, from the cleaning fluid supply, into the cleaning chamber via the first port or the second port.

The suction source is preferably the only component which actively draws the cleaning fluid from the cleaning fluid supply into the cleaning chamber. Described another way, the cleaning fluid is preferably not pumped into the chamber, but is instead drawn into/through the chamber. Put another way, the cleaning chamber can be considered to form part of the fluid circuit between the cleaning fluid supply and the suction source. The suction source may be a gutter pump or a Venturi.

According to an eighth aspect of the invention there is provided a method of cleaning a self-cleaning print head of a continuous inkjet printer, comprising: sealing a cleaning chamber of the print head by actuating a sealing mechanism; at least partially filling the cleaning chamber with used cleaning fluid; draining the used cleaning fluid from the cleaning chamber; at least partially filling the cleaning chamber with virgin cleaning fluid; and draining the virgin cleaning fluid from the cleaning chamber. Advantageously, comparatively warmer used cleaning fluid can be used to perform an initial rinse. This desirably removes the worst of the debris from the cleaning chamber. A subsequent rinse, with virgin (e.g. fresh) cleaning fluid can then be used to perform a final rinse. A desirable balance between cleaning quality and usage of virgin cleaning fluid can therefore be achieved. The volume of virgin cleaning fluid used is also desirably reduced.

Virgin cleaning fluid may otherwise be described as fresh cleaning fluid (e.g. from a solvent cartridge).

Using at least some virgin cleaning fluid to clean the self-cleaning print head advantageously reduces the risk that a conductive residue (e.g. due to dyes/salts in the ink used for printing) remain in the chamber or on the deflection electrode, for example, when the printer is next used for printing operations.

Used cleaning fluid may be circulated through the system (e.g. for around 30 minutes) to dislodge debris within the chamber.

At least partially filling the cleaning chamber with used cleaning fluid may comprise connecting a fill port of the cleaning chamber to a solvent reservoir.

The solvent reservoir may be a solvent tank.

At least partially filling the cleaning fluid with virgin cleaning fluid may comprise connecting a fill port of the cleaning chamber to a solvent cartridge.

The method may further comprise activating an air pump to pump air into the cleaning chamber to at least partially dry the cleaning chamber

According to a ninth aspect of the invention there is provided a method of using a selfcleaning print head of a continuous inkjet printer, comprising: during a printing operation: using a gutter pump to draw droplets of ink, which are not used for printing, through a gutter into a mixer tank; using an air pump to pump air into the print head; and during cleaning; sealing the cleaning chamber of the print head by actuating a sealing mechanism; at least partially filling the cleaning chamber with cleaning fluid; draining the cleaning fluid from the cleaning chamber; and using the air pump to pump air into the cleaning chamber to at least partially dry the cleaning chamber.

Advantageously, using the air pump to pump air into the print head (e.g. into the cleaning chamber) can replenish the air removed from the chamber under action of the gutter (e.g. during printing operations). This advantageously reduces the risk that the pressure within the print head reduces to such a level that debris is drawn into the print head from outside the print head. This may be described as a positive air pump. When coupled with an air dryer, the moisture level of the air, pumped into the chamber by the positive air pump, can also be advantageously reduced. The likelihood of water entering the ink system, through excess ingestion of atmospheric air, which may have a relatively high humidity, is therefore also advantageously reduced.

Using the same air pump for both positive air replenishment during printing operations, and for drying the cleaning chamber as part of a cleaning cycle, advantageously reduces the component count within the print head.

The printing cycle may conclude by deactivating the gutter pump and the air pump.

The air pump is preferably a variable speed air pump. Advantageously, the flow rate of air pumped into the print head, optionally the chamber, during printing operation can be comparatively lower than the flow rate of air pumped into the cleaning chamber during cleaning. This provides a swift cleaning time without unduly disrupting the ink droplets ejected by the nozzle during printing operations. Put another way, the flow rate of the positive air pump can be reduced to reduce the risk of disturbing the stream of ink droplets in flight due to excess turbulence.

Activating the air pump to pump air may comprise activating the air pump to pump air from an air supply. Activating the air pump to pump air into the print head may comprise connecting one or more ports of the cleaning chamber to the air pump and pumping air through the one or more ports into the cleaning chamber.

Activating the air pump to pump air into the cleaning chamber to at least partially dry the cleaning chamber may comprise connecting the one or more ports of the cleaning chamber to the air pump and pumping air through the one or more ports to at least partially dry the cleaning chamber.

According to a tenth aspect of the invention there is provided a continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller; and a cleaning fluid circuit for supplying cleaning fluid to the self-cleaning print head, the cleaning fluid circuit comprising first and second conduits connectable to an air supply by a plurality of valves, the first and second conduits being connectable to the air supply by an air line and an air pump disposed along the air line; the self-cleaning print head comprising: the cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises a first port and a second port; wherein the first port is in fluid communication with the first conduit, and the second port is in fluid communication with the second conduit; and wherein the air pump is configured to pump air into the cleaning chamber via the first port and/or the second port during printing operations; and wherein the air pump is configured to pump air into the cleaning chamber to at least partially dry the cleaning chamber during a cleaning cycle.

Advantageously, using the air pump to pump air into the print head (e.g. into the cleaning chamber) can replenish the air removed from the chamber under action of the gutter (e.g. during printing operations). This advantageously reduces the risk that the pressure within the print head reduces to such a level that debris is drawn into the print head from outside the print head. Using the same air pump for both positive air replenishment during printing operations, and for drying the cleaning chamber as part of a cleaning cycle, advantageously reduces the component count within the print head.

According to an eleventh aspect of the invention, a continuous inkjet printer configured to carry out the method according to the sixth, eighth or ninth aspects set out above, comprising: an ink system for storing ink and supplying ink to the self-cleaning print head, the ink system comprising a controller; the self-cleaning print head comprising: the cleaning chamber selectively sealable by the sealing mechanism, the cleaning chamber comprising one or more ports; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the at least one electrode is disposed in the cleaning chamber; and wherein the one or more ports are in fluid communication with a respective conduit.

The cleaning chamber may comprise a first port and a second port. The first port may be in fluid communication with a first conduit. The second port may be in fluid communication with a second conduit.

The sealing mechanism may comprise a rotatable body rotatable about an axis of rotation between a first configuration and a second configuration

The self-cleaning print head may further comprise a casing defining an ink aperture, the casing at least partly defining the cleaning chamber.

In a first configuration, an ink path for the stream of droplets for printing may be defined through the chamber, across the rotatable body and through the ink aperture such that the chamber is in communication with atmosphere via at least the ink aperture; and in a second configuration the rotatable body may close the ink aperture such that the chamber is sealed by the rotatable body.

A motor may be in power communication with the rotatable body via a worm gear.

The one or more ports may comprise a plurality of ports.

The plurality of ports may comprise: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber.

The first and second ports may be diametrically opposed from one another.

The self-cleaning print head may comprise an orientation sensor configured to detect the orientation of the self-cleaning print head, and wherein the orientation sensor may be configured to output an orientation signal, to the controller, indicative of the orientation of the self-cleaning print head.

A plurality of valves may be operable to control a flow of cleaning fluid flow into and/or out of the cleaning chamber.

According to a twelfth aspect of the invention there is provided a method of automatically backflushing a nozzle of a print head of a continuous inkjet printer, comprising: drawing a flow of cleaning fluid through a fill port towards a first side of the nozzle; and activating a pump, provided in fluid communication with a second side of the nozzle via a line, and drawing a proportion of the cleaning fluid through the nozzle, from the first side towards the second side, and into a nozzle body. The print head may be a self-cleaning print head.

The pump may be a gutter pump. The line may be a purge line. The fill port may be a third port, the third port disposed proximate the nozzle. The third port may be defined in a front face of the nozzle body. The cleaning fluid may be virgin cleaning fluid.

The method may further comprise providing a distribution of cleaning fluid around the first side of the nozzle by a plurality of channels.

The method may further comprise sealing a chamber of the print head by actuating a sealing mechanism before drawing the flow of cleaning fluid through the fill port.

According to a thirteenth aspect of the invention there is provided a print head for a continuous inkjet printer, comprising: a nozzle for generating and ejecting a stream of ink droplets for printing, the nozzle being mounted to a nozzle body; a fill port, proximate a first side of the nozzle, for drawing a flow of cleaning fluid to the first side of the nozzle; and a pump provided in fluid communication with a second side of the nozzle via a line, the pump being configured to draw a proportion of the cleaning fluid through the nozzle, from the first side towards the second side, into the nozzle body.

The print head may be a self-cleaning print head.

According to a fourteenth aspect of the invention there is provided a connector block for a print head of a continuous inkjet printer, comprising: a barb for engagement with a conduit; an internal channel that extends through the connector block; an aperture defined in an engagement face of the connector block; wherein the internal channel extends between the barb and the aperture to define a fluid pathway across the connector block.

The connector block may further comprise: a plurality of barbs, a plurality of internal channels, a plurality of apertures, wherein the internal channels extend between a respective barb and aperture to define a fluid pathway across the connector block, the plurality of internal channels defining a plurality of fluid pathways across the connector block.

According to a fifteenth aspect of the invention there is provided a connector block assembly for a print head of a continuous inkjet printer, comprising: the connector block according to the fourteenth aspect of the invention; a conduit engaged with the barb; and a component, the connector block coupled to the component at the engagement face; wherein the connector block is coupled to the component by a fastener; and wherein the fluid pathway extends from the conduit, across the connector block, and across an interface defined between the engagement face of the connector block and the component.

According to a sixteenth aspect of the invention there is provided a method of decoupling the connector block assembly of the fifteenth aspect of the invention, comprising: loosening the fastener; separating the connector block from the component such that the fluid pathway extending from the conduit terminates at the aperture in the engagement face.

According to a seventeenth aspect of the invention there is provided a self-cleaning print head for a continuous inkjet printer, comprising: a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; and wherein one or more of the first port and the second port comprises a plurality of subports.

The plurality of subports may be distributed annularly. The self-cleaning print head may further comprise a third port, disposed proximate the nozzle.

The third port may be in fluid communication with the cleaning chamber via a cavity defined by a charge electrode. The third port may be in fluid communication with the cavity by a plurality of channels. The plurality of channels may be distributed annularly. The plurality of channels may extend between an annular channel and the cavity defined by the charge electrode. The third port may be in fluid communication with the nozzle via the plurality of channels.

According to an eighteenth aspect of the invention there is provided a continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a print head; the print head comprising the print head according to the tenth or seventeenth aspects of the invention.

Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional and/or preferred features for each aspect of the invention set out herein are also applicable to any other aspects of the invention, where appropriate. For example, it will be appreciated that each of the twelfth, thirteenth, fourteenth, fifteenth, sixteenth and seventeenth aspects of the invention may be combined with one another. Similarly, optional or preferred features of each of the twelfth, thirteenth, fourteenth, fifteenth, sixteenth and seventeenth aspects of the invention may be applicable to one another.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic illustration of a continuous inkjet (Cl J) printer according to an embodiment of the invention;

Figure 2 is a perspective view of a print head, of the printer shown in Figure 1 , in isolation;

Figure 3 is an alternative perspective view of the print head of Figure 2 with an outer casing omitted;

Figure 4 is an alternative perspective view of the print head of Figure 3; Figure 5 is a magnified view of part of the print head shown in Figures 4 and 5 with a chamber housing omitted;

Figure 6 is a perspective view of a subassembly of the print head of Figures 2 to 5;

Figure 7 is a cross-section side view of the subassembly of Figure 6;

Figure 8 is an alternative cross-section view of the subassembly of Figures 6 and 7;

Figure 9 is a perspective cross-section view of part of the subassembly of Figure 6;

Figure 10 is a simplified schematic diagram of a fluid system for the printer of Figure 1, incorporating the print head shown in Figures 2 to 8,

Figure 11 is a flow chart showing a method for a print head in a first orientation;

Figures 12 and 13 are simplified schematic fluid circuit diagrams which show parts of the overall fluid system shown in Figure 10;

Figure 14 is a flow chart showing a method for a print head in a second orientation;

Figures 15 and 16 are simplified schematic fluid circuit diagrams which show parts of the overall fluid system shown in Figure 14;

Figure 17 is a perspective view of a sealing mechanism of the print head of Figures 2 to 8 with a rotatable body shown in a second configuration;

Figure 18 shows the sealing mechanism of Figure 17 with the rotatable body in a first configuration and with some components omitted;

Figure 19 is a magnified cross-section view of part of the print head of the preceding Figures;

Figure 20 is a perspective view of a different part of the print head to that shown in Figure 19;

Figures 21 and 22 are perspective views of the nozzle body, forming part of the print head of the preceding Figures, with various conduits/ports visible;

Figure 23 is a schematic illustration showing the locations of the ports and conduits within the print head;

Figure 24 is a perspective view of a sealing mechanism according to another embodiment, with the rotatable body incorporating an integrated gutter and shown in a first configuration;

Figure 25 shows the sealing mechanism of Figure 24 with the rotatable body in a second configuration; Figures 26a-c are schematic illustrations of a chamber arrangement in a first orientation;

Figures 27a-c are schematic illustrations of a chamber arrangement in a different orientation;

Figures 28a-c are schematic illustrations of a chamber arrangement in a further different orientation;

Figure 29a is a perspective view of a schematic illustration of an alternative embodiment of housing;

Figure 29b shows a cross-section side view of the housing of Figure 29a; and

Figure 30 is a perspective view of part of a housing according to another embodiment;

Figure 31 is a perspective view of a print head according to another embodiment;

Figure 32 is a perspective view of the print head of Figure 31 with an outer shell omitted;

Figure 33 is an alternative perspective view of the print head of Figures 31 and 32, with a chamber housing (and outer shell) omitted;

Figure 34 is an alternative perspective view of part of the print head shown in Figure 33;

Figure 35 is a cross-section side view of the print head of Figures 31 to 34 with an outer shell omitted; and

Figure 36 is a perspective view of the sealing mechanism of the print head of Figures 31 to 35 in isolation;

Figure 37 is a cross-section perspective view of a region of interest around the first port of the print head of Figures 31 to 35;

Figure 38 is an alternative cross-section view to that shown in Figure 37;

Figure 39 is a perspective view of the socket plate, of the print head of Figures 31 to 35, in isolation;

Figure 40 is a magnified cross-section side view of part of the print head;

Figure 41 is a perspective cross-section view of the features shown in Figure 40;

Figure 42 is a perspective cross-section side view of the charge electrode mount in isolation;

Figures 43 to 46 are magnified perspective cross-section views of the print head at different axial positions; Figure 47 is a perspective view of the connector block of the print head;

Figure 48 is a perspective view generally showing an underside of the connector block of Figure 48; and

Figure 49 is a perspective cross-section side view of the connector block about a plane schematically indicated in Figure 48.

Figure 1 schematically illustrates a continuous inkjet (CM) printer 1 according to an embodiment of the invention. The printer 1 comprises a printer body 2 (which may be referred to as a cabinet) connected to a print head 3 by an umbilical cable 4. The printer body 2 houses an ink system 5 and a printer controller 6. The printer body 2 also has an interface 7 (e.g. a display, keypad, and/or touch screen) for use by an operator. The print head 3 comprises an orientation sensor 3a. The orientation sensor is configured to detect the orientation of the print head 3. The orientation sensor 3a is in operative communication with the printer controller 6.

The print head 3 is arranged to print on a substrate provided adjacent to the print head 3. The printer 1 typically comprises two cartridge connections for engagement with respective fluid cartridges. In particular, the printer 1 comprises an ink cartridge connection for engagement with an ink cartridge 8 and a (separate) solvent cartridge connection for engagement with a solvent cartridge 10. The cartridge connections typically each comprise a fluid port arranged to connect to a fluid pathway within the printer 1 to allow fluid to flow between the cartridges 8, 10 and other parts of the inkjet printer 1, such as the ink system 5 and the print head 3 (via the umbilical 4). The solvent cartridge 10 comprises fresh (i.e. virgin, not used) solvent.

In operation, ink from the ink cartridge 8 and solvent from the solvent cartridge 10 can be mixed within the ink system 5 to generate printing ink of a desired viscosity that is suitable for use in printing. This ink is supplied to the print head 3 and unused ink is returned from the print head 3 to the ink system 5 (via the umbilical 4). When unused ink is returned to the ink system 5 from the print head 3, air may be drawn in with ink from a gutter of the print head 3. The air may then become saturated with solvent in the gutter line.

In operation, ink is delivered under pressure from the ink system 5 to the print head 3 and recycled back via flexible tubes which are bundled together with other fluid tubes and electrical wires (not shown) into the umbilical cable 4. In order to maintain correct consistency of the ink, the ink system 5 may be operable to mix ink removed from the cartridge 8 with solvent removed from the cartridge 10 and to mix them together to obtain an ink having the correct viscosity and/or density for a particular printing application.

Of particular relevance to the present application, the print head 3 is a self-cleaning print head. Without operator intervention, the print head 3 can be sealed, and a cleaning fluid (e.g. fresh and/or used solvent, or a fresh and/or used blend of solvents) be flushed through at least part of the print head 3, in order to clean the print head 3. As will be described below in more detail, the cleaning fluid can be drained from the print head 3 in a range of different print head orientations. That is to say, a cleaning cycle can be carried out with the print head 3 in a number of different orientations.

Turning to Figure 2, a perspective view of the print head 3 in isolation is provided.

The print head 3 comprises a first end 100 by which the print head 3 is connectable to an umbilical 4 as shown in Figure 1. The first end 100 may therefore comprise a connector (e.g. a threaded connector in the illustrated embodiment). At an opposing end, the print head 3 comprises a second end 102. Provided at the second end 102 is an end cap 104. The end cap 104 defines an outermost part of the print head 3. The end cap 104 comprises an ink aperture 106, which may be referred to as an ink slot. It is through the ink aperture 106 that deflected ink, in operation, is ejected from the print head 3 onto a substrate (e.g. an external substrate which moves past the print head 3). The print head 3 comprises a single ink aperture 106. In other embodiments the print head 3 may comprise two ink apertures. Extending generally between the first and second ends 100, 102 is an outer shell 108. The outer shell 108 is generally cylindrical in the illustrated embodiment and provides a protective cover for the components which make up the print head 3. In order to expose the components, such as for maintenance, the outer shell 108 is removable. The combination of the end cap 104 and the outer shell 108 may be described as an outer cover 110 of the print head 3.

When the print head 3 is to be cleaned (e.g. by way of the self-cleaning capability of the print head 3), the ink aperture 106 can effectively be closed, and sealed, by a sealing mechanism within the print head 3. That is to say, when cleaning fluid is flushed through a chamber of the print head 3 (which will be described below), cleaning fluid cannot escape from the print head 3 through the ink aperture 106. For the purposes of this application, the closing of the ink aperture 106 may not infer a change in the geometry of the ink aperture 106 geometry itself. That is to say, the ink aperture 106 remains as shown in Figure 2 regardless of whether it is opened or closed (by operation of the sealing mechanism). However, at least in the illustrated embodiment, the ink aperture 106 can be obscured (e.g. covered, internally) by an upstream rotatable body to define the sealed chamber. This will be described in detail later in this document.

Turning to Figure 3, a perspective view of the print head 3 is provided with the outer shell 108 omitted. Various components which make up the print head 3 are therefore visible, and a number of components are also shown in a partially cutaway view to improve visibility.

Figure 3 shows a connector 112, by which the print head 3 is connectable to an umbilical, provided at the first end 100 of the print head. The connector 112 is integral with a chassis 114. The chassis 114 defines a platform of sorts to which various other components are mounted. For example, a motor 116 and high voltage resistor 118 are mounted to the chassis 114 in the illustrated embodiment. The high voltage resistor 118 limits the current and spark energy available to the electrodes (described below). In other embodiments the high voltage resistor 118 may be mounted closer to a deflection electrode 168 to reduce a cable length therebetween. The high voltage resistor 118 may therefore be mounted to a chamber housing 162 or PCB 167, for example. A solenoid valve 120 is also mounted to the chassis 114. In the illustrated embodiment the solenoid valve 120 is mounted to the chassis 114 via a valve manifold. The motor 116 is a stepper motor in the illustrated embodiment, but other varieties of motor may otherwise be used (e.g. a brushless DC motor, a linear motor, a solenoid or other suitable actuator).

A shaft of the motor 116 rotates about an axis of rotation 117, which may be referred to as a motor axis. The motor 116 is provided in power communication with a rotatable body 122 which forms part of a sealing mechanism 124. The sealing mechanism 124 is located at the second end 102 of the print head 3. Briefly, the rotatable body 122 is rotatable about an axis of rotation 126. The rotatable body 122 is rotatable between a first configuration, in which an ink path is defined across the rotatable body 122 and through the ink aperture 106, and a second configuration (as shown in Figure 3) in which the rotatable body 122 closes the ink aperture 106. In the second configuration the sealing mechanism 124, specifically the rotatable body 122 thereof, seals part of the print head 3 (i.e. a chamber) to allow that part to be flushed with cleaning fluid to clean the print head 3.

As previously mentioned, the motor 116 is in power communication with the rotatable body 122 to drive rotation of the rotatable body 122. The motor 116 is in power communication with the rotatable body 122 via a shaft 128. The shaft 128 is disposed outside of a chamber which is selectively sealed by the rotatable body 122 (e.g. see chamber 164 in Figure 7). The shaft 128 extends along an extent of the chamber. The shaft 128 is in power communication with the rotatable body 122 via a worm gear 130 comprising a worm 132 and a gear 134. The worm 132 is coupled to an end of the shaft 128 (e.g. which is proximate the second end 102 of the print head 3). The gear 134 is rotatably coupled to the rotatable body 122. The worm gear 130 changes the direction of rotation of the shaft 128 from the axis of rotation 129 to the axis of rotation 126. Although not visible in Figure 3 a further worm gear is used to change a direction of rotation of the motor 116 at an obscured end of the shaft 128 (e.g. located towards the first end 100 of the print head 3). As mentioned above, the shaft 128 rotates about the axis of rotation 129. The axis of rotation 129 extends in a longitudinal direction along the print head 3, and the print head 3 may be described as generally extending in the same longitudinal direction.

The use of the drive assembly including the shaft 128 and the worm gear 130 is advantageous for a number of reasons. Firstly, incorporation of the shaft 128 means that the motor 116 can be disposed in a different part of the print head 3 to that of the rest of sealing mechanism 124. This is desirable for reasons of not increasing the longitudinal extent of the print head 3 at the second end 102 by any more than is needed (e.g. to accommodate the volume of the motor). Increasing the longitudinal extent of the print head 3 at the second end 102 risks reducing a throw distance by which the print head 3 must be offset from a substrate to be printed. The use of the worm gear 130 is also advantageous for at least the reason that the gearing can effectively increase the torque output transmitted by the motor 116 to the rotatable body 122. This is particularly desirable where the rotatable body 122 may be partially stuck in position (e.g. stiction) following a cleaning process and a subsequent drying process. Described another way, the use of the worm gear 130 reduces the risk that the rotatable body 122 is stuck in position such that the drive assembly is unable to rotate the rotatable body 122 about the axis of rotation 126.

Returning to describe other components of the print head 3, coupled to the chassis 114 is a manifold 136. Various fluid and electrical connections extend through the manifold 136.

A nozzle housing 138 (shown in a partially cutaway view in Figure 3) is coupled to the manifold 136 and houses a nozzle assembly 140. The nozzle housing 138 may otherwise be described as a body forming part of a housing. The nozzle assembly 140 comprises, among other components, a nozzle cradle 142 and a nozzle body 143. The nozzle body 143 defines a nozzle (not visible in Figure 3) for generating and ejecting a stream of ink droplets for printing. The print head 3 comprises a single nozzle body 143, which defines a single nozzle.

A charge electrode assembly 146 is coupled to the nozzle assembly 140. The charge electrode assembly 146 comprises a charge electrode 148 and a guide 150 to which the charge electrode 148 is coupled. As a stream of ink droplets is directed past the charge electrode 148 in use, they are selectively and separately given a predetermined level of charge by the charge electrode 148. In order to aid the alignment of the charge electrode 148 with respect to the stream of droplets emanating from the nozzle of the nozzle body 143, the charge electrode 148 is rotatably adjustable about axis of rotation 152 (which, for completeness, also generally corresponds to a path of the stream of ink droplets). The adjustment is achieved by loosening fasteners 154, 156, which secure the charge electrode assembly 146 with respect to the nozzle assembly 140, and rotating the charge electrode assembly 146. Movement of the charge electrode assembly 146 is constrained by the passage of the fasteners 154, 156 within tracks 158, 160 (track 160 not being visible in Figure 3) defined in the guide 150. A grommet 151 is also shown in Figure 3. As will be appreciated from Figure 3, in the illustrated embodiment the grommet 151 is sandwiched between the charge electrode 148 and a chamber housing 162. The grommet 151 allows the charge electrode 148 to remain sealingly engaged with the chamber housing 162 (see also Figures 7/8) whilst the charge electrode 148 is adjusted. An O-ring, or other variety of gasket, could otherwise be used, but a grommet has been found to provide for a comparatively larger degree of movement of the charge electrode 148 whilst maintaining the seal. A face seal or piston seal may be used, or elements of the grommet may engage corresponding elements (e.g. grooves) in a component to be sealed.

Returning to Figure 3, coupled to the nozzle housing 138 is a chamber housing 162 (also shown partially cutaway in Figure 3). The chamber housing 162 defines a chamber 164. The chamber 164 may otherwise be described as a washing cavity or a cleaning chamber. Although further information in connection with the chamber 164 will be provided in the following Figures (the chamber 164 being visible in Figures 7 and 8 in particular), when the rotatable body 122 is in a second configuration in which the ink aperture 106 is closed, the chamber 164 is sealed for cleaning. Directing, or flushing a cleaning fluid into and through the chamber 164 when sealed thus cleans the chamber 164 and the associated components of the print head 3 which are provided in the chamber 164. Directing a cleaning fluid into the chamber 164 may comprise pumping the cleaning fluid (e.g. by action of an upstream pump, and under a positive pressure) and/or drawing the cleaning fluid (e.g. by action of a downstream pump, and under a negative pressure).

Coupled to the chamber housing 162, and mounted within the chamber 164, is a low voltage (e.g. grounded, or negative potential) electrode 166 and a deflection (e.g. high voltage) electrode 168. The electrodes 166, 168 may collectively be referred to as a pair of deflection electrodes. The low voltage electrode 166 may further comprise a phase detector which detects the phase of the charged particles in operation. The low voltage electrode 166 may be coupled to the chamber housing 162 by adhesive. In other embodiments the low voltage electrode 166 may be coupled to the chamber housing 162 by a gasket. The deflection electrode 168 is for guiding the stream of ink droplets, which are ejected by the nozzle and charged by the charge electrode 148, away from a gutter and towards the ink aperture 106 for printing onto a substrate in use. The deflection electrode 168 is disposed within the chamber 164 and can therefore be cleaned when the chamber 164 is sealed and the cleaning process is carried out.

The print head 3 further comprises a casing 170. The casing 170 forms part of the sealing mechanism 124. The casing 170 is coupled to the chamber housing 162. The casing 170 sealingly engages the chamber housing 162 by way of a gasket 173 which interposes the chamber housing 162 and the casing 170. The casing 170 may otherwise be described as a rotatable body mount, or housing. As will be described in detail later in this document, the rotatable body 122 is rotatably mounted within the casing 170 to selectively open and close the ink aperture 106. The casing 170 further comprises a cap 172 which is selectively detachable from the rest of the casing 170 to aid the installation and maintenance of the moving parts of the sealing mechanism 124 (e.g. the rotatable body 122). The casing 170 further comprises the end cap 104, which defines the ink aperture 106. The casing 170 may therefore be said to define the ink aperture 106. Although the ink aperture 106 is specifically defined by end cap 104 in the illustrated embodiment, in other embodiments the end cap 104 may be omitted. The casing 170 may therefore define the ink aperture even in the absence of an end cap. Also of note, the ink aperture 106 is downstream of the rotatable body 122 in the illustrated embodiment. That is to say, a stream of ink droplets first passes across the rotatable body 122 and then passes through the ink aperture 106. In other embodiments the rotatable body may define a downstream-most point of the ink path, such that there is no end cap positioned downstream of the rotatable body. In such embodiments the surrounding casing may be considered to define an ink aperture across the rotatable body.

For the avoidance of doubt, in the illustrated embodiment the end cap 104 is coupled to the chamber housing 162 and does not move in operation. That is to say, the end cap 104 is fixed in position. However, in other embodiments the end cap may define at least part of the rotatable body of the sealing mechanism. For example, the end cap may rotate, about an axis generally parallel to axis 129. The rotational position of the end cap may determine an extent to which an ink aperture of the end cap overlaps an ink aperture of an adjacent casing to ‘open’ the ink aperture of the adjacent casing. Where the ink apertures overlap at least partly, or entirely, the rotatable body (e.g. end cap) may be said to be in a first configuration in which an ink path is defined across the end cap. Where the ink aperture of the end cap does not overlap the ink aperture of the adjacent casing, the rotatable body (e.g. end cap) may said to be in a second configuration in which the ink aperture of the casing is closed. Although shown in Figure 3, various fasteners used to couple the chassis 114, the manifold 136, the nozzle housing 138, the chamber housing 162 and the casing 170 together are not annotated or described here in detail for brevity.

As will be appreciated from Figure 7, the chamber 164 is defined by a combination of the chamber housing 162 and the casing 170. The chamber 164 has a first (lower) surface 164a defined by a combination of the low voltage electrode 166 (e.g. by surface 166a) and the surrounding chamber housing 162 (e.g. surface 162a), a second (upper) surface 164b which extends above the deflection electrode 168 (i.e. such that the deflection electrode 168 is disposed in the chamber 164) and is at least wide enough to contain the deflection electrode 168. Third and fourth surfaces 164c, 164d (which may be referred to as side surfaces) of the chamber 164 extend between the first and second surfaces 164a, 164b to define a perimeter of the chamber 164. The fourth surface 164d is not visible in Figure 7.

With reference to Figure 3, the print head 3 further comprises a PCB 167 which is mounted within the chamber housing 164. However, as indicated in Figure 7, the PCB is not disposed within the chamber 164.

Turning to Figure 4, an alternative perspective view of the print head 3 is provided. Owing to the different perspective, a number of components not visible, or only partially visible, in Figure 3 are visible in Figure 4.

Beginning from the first end 100 of the print head 3, the connector 112 and integral chassis 114 are shown. The solenoid valve 120 is shown mounted to the chassis 114, along with a valve block 174 . Also visible in Figure 4 is a worm gear 176 comprising a worm 178 and a gear 180. The worm 178 is rotatably coupled to the motor 116 which is just visible at the opposing side of the chassis 114 as shown in Figure 4 (and is more clearly visible in Figure 3). The worm 178 is driven to rotate about the axis of rotation 117. The worm 178 is provided in driving communication with the gear 180, the gear 180 being rotatably coupled to the shaft 128. The gear 180 and shaft 128 are thus driven to rotate about the axis of rotation 129, which may be referred to as a shaft axis. It will be appreciated that by use of the worm gear 176, the direction of rotation as driven by the motor 116 is effectively translated through 90° which is advantageous for reasons of space constraints within the print head 3. The shaft 128 is shown extending across an entire extent of each of the manifold 136, nozzle housing 138, chamber housing 162 and partially through the casing 170.

As described in connection with Figure 3, also coupled to the chassis 114 are manifold 136, nozzle housing 138, chamber housing 162 and casing 170. The PCB 167 is also visible in Figure 4. The nozzle assembly 140, coupled to the nozzle housing 138, and the charge electrode assembly 146 are also partially visible in Figure 4.

Turning briefly to the sealing mechanism 124 at the second end 102 of the print head 3, as previously described the sealing mechanism 124 comprises the casing 170 (which comprises cap 172 and end cap 104) and the rotatable body 122. The ink aperture 106, defined by the casing 170, is also visible.

Of note, a component that has not yet been described in detail in connection with the print head 3 is that of a gutter. The print head 3 does incorporate a gutter which, in the illustrated embodiment, is a fixed gutter coupled to the casing 170. Details of the gutter will be provided in connection with Figure 6 onwards.

Turning to Figure 5, a magnified perspective view of part of the print head 3 is provided. As will be appreciated from Figure 5, the motor 116 is partially visible, as is the chassis 114, but any components further towards the first/connector end of the print head 3 are not visible. Similarly, the chamber housing 162 as shown in Figures 3 and 4 is not shown in Figure 5 to aid visibility of the components housed therein.

Figure 5 shows the geometry of the deflection electrode 168 which is used to guide a stream of ink droplets towards a substrate to be printed.

Figure 6 is a perspective view of a subassembly of the print head 3. Figure 6 shows the chamber housing 162 with the nozzle assembly 140 and sealing mechanism 124 coupled thereto.

As previously described, various components of the sealing mechanism 124 are visible including the rotatable body 122, the casing 170, including the cap 172, and the worm 132 and gear 134. Also visible in Figure 6 is gutter block 182. The gutter block 182 will be described in greater detail in connection with later Figures, but briefly the gutter block 182 comprises a gutter aperture (not visible in Figure 6) through which droplets of ink which are not used for printing are received and subsequently recirculated back to a mixer tank of the ink system (as will be described in detail in connection with Figure 10). In the illustrated embodiment the gutter block 182 is a separate embodiment to that of the surrounding casing 170 and other components. However, in some embodiments the gutter may be integral with the rotatable body (e.g. see Figures 16, 17).

The gutter block 182 further comprises a recess 200 defined in an effective underside of the gutter block 182. The recess 200 leads into a port 202. The port 202 may be described as a second port of the chamber 164. The port 202, in turn, defines a second conduit (e.g. 214 as shown in Figure 10). Owing to the presence of the recess 200, the second conduit is still provided in fluid communication with the chamber 164 even when the rotatable body 122 is in the second, closed configuration as shown in Figure 6. Cleaning fluid can therefore be pumped or drawn into the chamber via the second conduit, or used (e.g. dirty) cleaning fluid be pumped or drawn out of the chamber via the second conduit. Further detail in this regard will be provided below.

The second port 202 is disposed proximate the second end 169 of the chamber 164 (e.g. proximate the sealing mechanism 124).

Also schematically indicated on Figure 6 are first and second cross-sectional markers 184, 186. 184 is a vertical cross-section and 186 is a horizontal cross-section. The markers 184, 186 correspond to the cross-section views provided in Figures 7 and 8 respectively.

Turning to Figure 7, a cross-section side view of the subassembly shown in Figure 6 is provided as indicated by annotation 184 in Figure 6. Figure 7 shows the chamber 164 which can be selectively sealed by the sealing mechanism 124.

Beginning from the right hand end of Figure 7, only part of the nozzle body 143 of the nozzle assembly 140 is visible. Nozzle body 143 defines the nozzle 144 that generates and ejects a stream of ink droplets 188 for printing. Downstream of the nozzle 144 is the charge electrode 148. The charge electrode 148 is rotatably coupled to the guide 150. In the illustrated embodiment the charge electrode 148 is rotatably coupled to the guide 150 by fasteners 147, 149, which are self-tapping screws. The guide 150 (and so the charge electrode 148) is rotatably adjustable with respect to the nozzle body 143. The charge electrode 148 abuts the grommet 151 such that the grommet 151 is sandwiched between the charge electrode 148 and the chamber housing 162. The grommet 151 also facilitates adjustment of the charge electrode 148 with respect to the chamber housing 162 by allowing a degree of movement of the charge electrode 148 with respect to the chamber housing 162.

The charge electrode 148 is provided in communication with the chamber 164 by a channel 189. In use, as indicated in Figure 7, a stream of ink droplets 188 is generated and ejected by the nozzle 144 and travel through the chamber 164 via the charge electrode 148 and the first channel 189. Having passed through the charge electrode 148 the stream of ink droplets 188 has a charge applied to them. The selectively charged stream of ink droplets 188 can be selectively deflected by the deflection electrode 168 for printing. A stream of ink droplets which has been deflected for printing by the deflection electrode 168 is labelled 190 in Figure 7. A stream of ink droplets which are not used for printing, and which have therefore not been deflected by the deflection electrode 168, is labelled 194. The stream of ink droplets 194 not used for printing are received by a gutter aperture 183 of the gutter block 182. Part of a gutter conduit 196, defined by the gutter aperture 183, is also visible in Figure 7. This is the conduit through which the droplets of ink 194 which are not used for printing, and which are received by the gutter aperture 183, travel.

For completeness, in Figure 7 the rotatable body 122 of the sealing mechanism 124 is shown in the second, closed configuration. As such, none of the streams of ink droplets 188, 190, 194 would be present when the sealing mechanism 124 is in the configuration shown in Figure 7. Figure 7 indicates that the gutter block 182 is at least partially received by the casing 170 and, although not visible in Figure 7, the chamber 164 also extends behind the gutter block 182 as shown in Figure 7 (e.g. into the plane of the page). This is, however, visible in Figure 8 and will be described in connection with the same.

Returning to Figure 7, the sealing mechanism 124 comprising the rotatable body 122 rotatably coupled to the gear 134 is also shown. A shaft 198 of the rotatable body 122 is also visible. It is about the shaft 198 that the rotatable body 122 rotates about the axis of rotation 126 in use. The shaft 198 is received by a recess 199 of the cap 172 to constrain and locate the rotatable body 122.

An ink aperture 171 defined by the casing 170 is also visible in Figure 7. The rotatable body 122 effectively closes the ink aperture 171 in the configuration shown in Figure 7. In a first, open configuration, in which the rotatable body 122 is rotated relative to the position shown in Figure 7, the ink aperture 171 is effectively opened such that the stream of ink droplets 190 can pass across the rotatable body 122, through the ink aperture 171 , via an ink path 190. As the stream of ink droplets 188 passes across the chamber 164, the phase detector forming part of the low voltage electrode 166 also operates to detect the phase of the ink particles. Of note, as shown in Figure 2 the end cap 104 defines the ink aperture 106. The ink aperture 171 shown in Figure 7 overlaps the ink aperture 106 defined by the end cap 104, and the ink aperture 106 can therefore also be considered to be opened/closed by the rotatable body 104 (at least by virtue of being downstream of the ink aperture 171).

Also shown in Figure 7 is the recess 200 defined in the gutter block 182. As described in connection with Figure 6, the recess 200 partly defines the (second) port 202 which is used for cleaning and draining. As mentioned above, the second port 202 is disposed proximate the second end 169 of the chamber 164. The second port 202 is disposed proximate a filleted junction (e.g. a smoothed corner) of the second (upper) surface 164b, the third surface 164c and a second end surface 164f of the chamber 164. The second port 202 is therefore disposed proximate one diagonally outermost position of the chamber 164. For reasons which will be described in detail below, the locations of the ports (such as the second port 202) of the chamber 164 can advantageously facilitate cleaning of the chamber 164 when the chamber 164, and print head 3 more generally, are provided in a range of different orientations.

For completeness, as mentioned previously the chamber 164 is bound by the first (lower) surface 164a, the second (upper) surface 164b, and third and fourth surfaces 164c, 164d (164 not being visible in Figure 7) to define a perimeter of the chamber 164. Ends of the chamber 164 are defined by fifth and sixth surfaces (which may be described as first and second end surfaces) 164e, 164f. The fifth and sixth surfaces 164e, 164f thus define first and second ends 165, 169 of the chamber 164. From Figure 7 it will be appreciated that the rotatable body 122, and sealing mechanism 124 more generally, does not affect a fluid communication pathway between the nozzle 144 and the chamber 164. Put another way, the nozzle 144 remains in fluid communication with the chamber 164 independent of the configuration of the rotatable body 122.

Turning to Figure 8, an alternative cross-section view to that shown in Figure 7 is provided. In Figure 8 the subassembly of Figures 6 and 7 is shown by way of a crosssection view as indicated by the annotations 186 in Figure 6. Figure 8 may therefore be described as a cross-section plan view of the subassembly.

As described in connection with Figure 7, Figure 8 also shows the nozzle body 143, guide 150, charge electrode 148 and grommet 151. Figure 8 also shows the low voltage electrode 166 being located within the chamber 164. Also visible in Figure 8 is a phase detector electrode 166b and a velocity detector electrode 166c. The electrodes 166b, 166c (and low voltage electrode 166) are etched into the PCB (e.g. a rear of the PCB, in the illustrated embodiment) which defines the low voltage electrode 166. The combination of the electrodes 166, 166b, 166c may be referred to as a phase detector assembly. The phase detector electrode 166b is configured to determine a magnitude of charge applied to the droplets of ink as they move past the phase detector electrode 166b. Measurements from the phase detector electrode 166b are used to determine when to apply a voltage to the charge electrode 148. The velocity detector electrode 166c is configured to determine the velocity of the droplets of ink as they move past the electrode 166b. The velocity is determined by measuring the time between the charge ‘pulse’ being detected by the phase detector electrode 166b and subsequently by the velocity detector electrode 166c, and dividing the distance between the electrodes 166b, 166c by that time. The low voltage electrode 166 takes the form of an Electroless Nickel Immersion Gold (ENIG) coated copper ground plate in the illustrated embodiment. The low voltage electrode 166 acts as the 0V plate for the deflection electrode, which establishes the EHT field that deflects the stream of ink droplets in use. The phase detector electrode 166b and velocity detector electrode 166c are covered by an insulator (e.g. a solder resist in the illustrated embodiment). This prevents ink and/or solvent shorting the electrodes 166b, 166c to the low voltage electrode 166. Owing to each of the: phase detector electrode 166b, velocity detector electrode 166c, low voltage electrode 166 and deflection electrode 168 (not shown in Figure 8) being disposed in the chamber 164, all of these components can be cleaned during a cleaning cycle. Similarly, the charge electrode 148, although located outside of the chamber 164, can also be cleaned in a cleaning cycle by virtue of a third port (not visible in Figure 8, but will be described in detail below).

Figure 8 does show that in the illustrated embodiment the chamber 164 comprises first and second chamber portions 164g, 164h. The first chamber portion 164g is defined by the chamber housing 162. The second chamber portion 164h is defined by the casing 170. As such, the chamber 164 may be said to be at least partially defined by the casing 170 in the illustrated embodiment. In other embodiments it will be appreciated that the chamber housing 162 could be integral with the casing 170 such that the chamber 164 be defined entirely by the casing 170.

Figure 8 also shows the third and fourth surfaces (e.g. side surfaces) 164c, 164d of the chamber 164. As will be appreciated from Figure 8, the third and fourth surfaces 164c, 164d are parallel to one another, and may therefore be described as a pair of parallel sides. It will also be appreciated that the chamber 164 may be a variety of different shapes. The chamber could be generally cube shaped, for example. The generally parallel third and fourth surfaces 164e-c, 164d (shown in Figure 8) may be cambered. It may be desirable to provide third and fourth surfaces (e.g. side surfaces) 164c, 164d of the chamber 164 with a draft angle to facilitate manufacture (e.g. injection moulding).

Figure 8 also shows the chamber housing 162 comprises a (first) conduit 204 which extends partly through the chamber housing 162 and is in communication with the chamber 164 via a port 206. The port 206 may be described as a first port of the chamber 164. The port 206 may be said to at least partly define the chamber 164. The port 206, and conduit 204, is multipurpose in that it can be used to either supply the chamber 164 with cleaning fluid or to drain used cleaning fluid from the chamber 164. The conduit 204 may therefore be described as a chamber cleaning and draining channel. The conduit 204 may specifically be described as an upstream chamber cleaning/draining channel, owing to it being disposed proximate the channel 189 through which ink droplets are ejected into the chamber 164. The port 206 may be described as a multifunction fill/drain port. The port 206 may be described as a multifunction fill/drain/drying port, as air can be pumped through the port 206 to dry the chamber 164. Also of note, the port 206 is disposed proximate the first end 165 of the chamber 164. The port 206 is disposed proximate a filleted junction (e.g. smoothed corner) of the first surface 164a, the fourth surface 164d and the fifth surface 164e.

The port 206, in combination with the conduit 204, defines a first port axis 206a. The first port axis 206a makes an angle 206b of around 90° with the stream of ink droplets 190 in use. The first port 206 may therefore be said to be perpendicular to the stream of ink droplets 190. Given that the trajectory of the stream of ink droplets 190 is determined by the nozzle 144, the stream of ink droplets 190 direction may be described as being defined by a nozzle axis, or a jet axis, defined by the nozzle 144. The port axis 206a may therefore be described as also being perpendicular to the nozzle axis or jet axis. In some embodiments a flow of air may be directed through the first port 206 into the chamber 164 in use. This advantageously reduces the risk that the pressure in the chamber 164 reduce to such a level that debris is drawn into the print head (and chamber 164) from outside. Described another way, air may be directed into the chamber 164, via the port 206, to replenish air drawn out of the chamber 164 via gutter suction. The same may apply to the second port 202. Advantageously, pumping air into the chamber 164 via all ports (e.g. first and second ports 206, 202, optionally the third port 217) means air can be provided through the first port 206, proximate the stream of ink droplets, at a lower velocity. The risk of disturbing the stream of ink droplets (e.g. droplets in flight) is reduced as a result.

The first port axis may be substantially parallel to the stream of ink droplets 190 or the nozzle axis in some embodiments. Where a flow of air is directed through the first port, into the chamber, providing the first port axis substantially parallel to the stream of ink droplets 190 or nozzle axis advantageously reduces the risk of the flow of air disrupting the stream of ink droplets 190 (e.g. the trajectory thereof).

Returning briefly to Figure 6, although the port 206 is not visible, the (first) port 206 is located proximate a lower, far corner of the chamber 164. In contrast, the second port 202 is disposed proximate an upper, near corner of the chamber 164. The first and second ports 206, 202 are therefore diametrically opposed from one another within the chamber 164. With reference to Figure 8, the first port 206 is disposed proximate the first end 165 of the chamber. The first port 206 is also disposed at an upper, left-hand corner of the chamber 164 in the Figure 8 orientation. In contrast, with reference to Figure 7, the recess 200, which defines the second port 202, is disposed proximate the second end 169 of the chamber 164. With reference to Figure 8, the second port 202 (although not visible in Figure 8 due to the cross-section view) is disposed at a lower, right-hand corner of the chamber 164.

Although the first port 206 and the second port 202 are generally disposed at diagonally opposite corners of the chamber 164, in other embodiments this may not be the case. For example, the first and second ports 206, 202 are still considered to be diametrically opposite one another if the first port 206 was not located proximate a corner but was instead located at a midpoint of an upper edge of the chamber 164 proximate the first end 165 (e.g. towards, or at, the top right-hand side of the chamber 164 as shown in Figure 7). In such embodiment, the second port 202 could be defined by the gutter aperture 183 in that the gutter aperture 183 provides both a gutter and second port 202 functionality. The gutter aperture 183 and second port would thereby be disposed at a midpoint of a lower edge of the chamber 164 proximate the second end 169 (e.g. towards, or at, the lower left-hand side of the chamber 164 as shown in Figure 7).

Advantageously, providing the first and second port 206, 202 proximate the first and second ends 165, 169 of the chamber 164 respectively, and diametrically opposed from one another, means that the chamber 164 can be cleaned with the chamber 164, and print head 3 more generally, in a variety of different orientations. For example, with reference to Figure 7, if both first and second ports 206, 202 were disposed proximate the second, upper surface 164b, when the print head 3 is in the orientation as shown in Figure 7 it would be comparatively challenging to drain the cleaning fluid from the chamber 164 during, or following, a cleaning cycle. This is owing to the fact that the cleaning fluid may remain within the chamber 164 and, once the fluid level has dropped to a level where the fluid is no longer drawn out of the corresponding port(s), there may nowhere for the fluid to drain. Fluid may no longer be drawn out of the corresponding port(s) once the fluid level drops to vertically below the lowest drain port.

In another example, both first and second ports 206, 202 could be provided proximate the first end 165 of the chamber 164, but one being provided proximate the first, lower surface 164a, and the other being provided proximate the second, upper surface 164b. Although this arrangement may overcome the issue of not being able to drain the chamber 164 in the orientation shown in Figure 7, draining the chamber 164 if the chamber 164 were to be rotated 90 degrees anti-clockwise from the Figure 7 view (e.g. such that the ink aperture 171 be facing downwards) would still present a problem for drainage.

In order to provide greater flexibility of the orientation of the print head 3, and chamber 164 by association, providing first and second ports 206, 202 proximate different ends of the chamber 164 and diametrically opposed from one another means that the chamber 164 can be readily filled with cleaning fluid, and subsequently drained, in a greater range of orientations.

In a particularly advantageous aspect of the invention, the first and second ports 206, 202 are multifunction fill/drain ports. Each of the first and second ports 206, 202, and associated first and second conduits 204, 214, can therefore be used to either supply cleaning fluid to the chamber 164 or to drain used cleaning fluid from the chamber 164. Furthermore, it is envisaged that the same port (e.g. only one of the first and second ports 206, 202) could be used to initially fill, and then subsequently drain, the chamber 164 in some embodiments.

As will also be appreciated from comparing Figures 7 and 8, the chamber 164 comprises no undercut features. Described another way, there are no localised recesses or other features in which cleaning fluid may pool excessively during a cleaning cycle. This is partly attributable to the fact that the chamber 164 comprises no vertices, where vertices is intended to refer to a sharp corner. Described another way, the chamber 164 comprises a plurality of filleted edges and corners, these features being for guiding cleaning fluid towards the first or second ports 206, 202. The chamber 164 can therefore be described as being contoured for guiding fluid towards the ports.

With reference to Figure 7, it will also be appreciated that the deflection electrode 168 is disposed within the chamber 164 by a plurality of supports 168a, 168b. The plurality of supports 164a, 164b sealingly engage a periphery of the chamber 164, the second, upper surface 164b of the chamber 164, by seals 168c, 168d. Figure 8 also shows more features of the gutter block 182. As mentioned in connection with Figure 7, the gutter block 182 comprises the gutter aperture 183 through which ink droplets which are not to be used for printing are received/collected. The gutter aperture 183 defines an upstream end of the gutter conduit 196 which extends through the gutter block 182. At a point downstream, the gutter conduit 196 appears to branch off to a recess 210. The recess 210 is sealed in use, and is only to facilitate manufacture of the gutter conduit 196 through the gutter block 182. Further downstream of the gutter conduit 196 is a return conduit 212 defined at least partly by the chamber housing 162. The return conduit 212 is provided in fluid communication with the gutter conduit 196, and so the gutter aperture 183. Ink droplets which are not used for printing are thus received by the gutter aperture 183 and are drawn through the gutter conduit 196 and the return conduit 212 by suction. The unused ink droplets are then returned to the mixer tank. For completeness, the gutter block 182 is sealed against the chamber housing 162 by seal 213.

In the illustrated embodiment the gutter block 182 forms a separate component which is fixedly coupled to the casing 170. In other embodiments (e.g. Figures 16, 17), at least part of the gutter may rotatably coupled to the rotatable body 122, and may be integral with the rotatable body 122. Partially shown in Figure 8 is a recess 123 of the rotatable body 122.

When the rotatable body 122 is in the second configuration as shown in Figure 8, in which the rotatable body 122 closes the ink aperture 171, the gutter block 182 is partially received by a recess 123 of the rotatable body 122. When the rotatable body 122 is in a first configuration, in which an ink path is defined across the rotatable body 122 and through the ink aperture 171, the rotatable body 122 is effectively rotated counter clockwise by around 90° such that the gutter block 182 is still partially received by the recess 123 but in a different orientation. This will be described in greater detail in connection with Figures 11 and 12.

Turning to Figure 9, a perspective cross-section view similar to that shown in Figure 7, but with various components omitted, is provided.

Figure 9 shows the chamber housing 162 with the low voltage electrode 166 and the deflection electrode 168 in isolation. As such, various surrounding components shown in Figure 7 are not visible in Figure 9. Of note, Figure 9 is also taken from the other perspective to that shown in Figure 7 (i.e. the opposite view than the annotated markers 184 of Figure 6). As such, Figure 9 shows the first port 206 of the chamber 164, the first port 206 being disposed proximate the first end 165 of the chamber 164. As previously described, the first port 206 is a multifunction fill/drain port which can either fill the chamber 164 with cleaning fluid or drain used cleaning fluid from the chamber 164. The first port 206 is disposed proximate the channel 190 through which a stream of ink droplets (not shown in Figure 9) travels from a nozzle (also not shown) into the chamber 164. Figure 9 also shows an upstream recess 191 in communication with the channel 189. It is in the recess 191 that the charge electrode (e.g. 148 in Figures 7 and 8) is partially received, when assembled.

By comparing Figure 9 and Figure 8, it will be appreciated that only part of the chamber 164 is actually shown in Figure 9. Specifically, only a first chamber portion 164g (i.e. as defined by the chamber housing 162) is shown. The second chamber portion 164h as shown in Figure 8, defined by the sealing mechanism 124, is thus omitted in Figure 9. However, despite this, Figure 9 still shows that at least the first chamber portion 164g comprises no undercut features or vertices and that at least the first chamber portion 164g is instead defined by a contoured geometry that incorporates filleted edges and smooth corners.

Figure 9 also illustrates that the first port 206 is located at a filleted junction of the first (lower) surface 164a, the fourth (side) surface 164d and the fifth (end) surface 164e of the chamber 164. When the print head is rotated 180 degrees about the angle shown in Figure 9 (e.g. so that the first end 165 points downwards), the first port 206 can be used as a drain port to drain the cleaning fluid from within the chamber 164. Furthermore, this can be achieved with the print head in a range of different orientations and not just limited to the print head being vertically upwards. For example, the print head could be oriented anywhere up to around 45 degrees off centre (e.g. in a conical manner) and the first port 206 still serve as a drain port to drain cleaning fluid from the chamber 164.

Figure 9 also shows that the first and second surfaces 164a, 164b (e.g. the lower and upper surfaces) of the chamber 164 are not entirely parallel. Described another way, the first and second surfaces 164a and 164b are parallel for part of an extent of the chamber 164, but taper outwardly towards the second end 169 of the chamber 164. Again, it will be appreciated that in this embodiment the second end 165 is actually defined by the omitted sealing mechanism). As such, an extent 193a of the chamber 164 between the first and second surfaces 164a and 164b is smaller at the position 193a than the extent 193b towards the second end 169 of the chamber 164. As will be appreciated from Figure 9, the second surface 164b at least partially follows the geometry of the deflection electrode 168 as the geometry of the deflection electrode 168 flicks outwardly towards the second end 169 of the chamber 164. The extent 193b therefore provides a greater cross-section, along the chamber 164, through which deflected droplets can pass in use.

Referring now to Figure 10, a schematic diagram of a fluid system for the printer of Figure 1 , incorporating the print head 3, is shown. The ink jet printer 1 comprises the ink system 5 which is contained within the main printer body 2. The ink system 5 comprises at least the components that form part of a main ink block 11. The ink system may further comprise a cartridge module 12 and a cleaning module 13 (which may be referred to as a cleaning fluid circuit). Components of the print head are schematically indicated 3. In some embodiments the cleaning module may be a generally separate module to the rest of the ink system. The cleaning module may therefore be connected to the ink system of a printer at the point of assembly. The cleaning module 13 can thus be factory fitted to printers. Alternatively, the cleaning module may be integral with the ink system to reduce component count.

Beginning with the main ink block 11 , the main ink block 11 comprises a mixer tank 17 (which may also be referred to as an ink feed, or ink supply, tank) configured to supply ink along a main supply line 19. The ink is drawn from the mixer tank 17 by an ink pump 21. Ink also passes through a first filter 23, downstream of the ink pump 21 , disposed along the main supply line 19. The first filter 23 removes any particles (e.g. sediment) contained within the mixer tank 17. The first filter 23 is a 100 micron filter in the illustrated embodiment, but it will be appreciated other sizes of filter could otherwise be used. A Venturi line 24 is connected to the main supply line 19 downstream of the first filter 23. Provided along the Venturi line 24 is a Venturi 24a (e.g. a restriction). In operation, fluid (e.g. an ink mixture) is continuously circulated from the mixer tank 17, through the main supply line 19, through the Venturi line 24, and so through the Venturi 24a, before being returned to the mixer tank 17. This continuous circulation, combined with the Venturi 24a, creates suction to draw fluids into the mixer tank 17 via a refill line 25, which extends between the cartridge module 12 and the Venturi 24a. Fluids are drawn into the mixer tank 17 through the Venturi 24a and a downstream portion 24b of the Venturi line 24.

The ink pump 21 may be operated as a pressure controlled pump, meaning that the ink flow rate through the pump 21 will be adapted as necessary to maintain a target pressure downstream of the ink pump 21 (e.g. as monitored by a pressure sensor 33). The ink pump 21 may be configured to supply ink to the print head 3 at a predetermined system operating pressure, which may be determined based upon the printer configuration (e.g. nozzle geometry). For example, a nozzle having a diameter of 75 pm may require a lower operating pressure than a nozzle having a diameter of 62 pm to achieve a similar jetting performance (e.g. ink droplet breakup location, or flight time to breakup). The system operating pressure may also be varied in dependence upon other system parameters (e.g. ink type, viscosity).

A second filter 26, having a filtration size of 5 microns, is provided downstream of the first filter 23 along the main supply line 19. A damper 27 is provided downstream of the ink pump 21, and downstream of the second filter 26, to reduce fluctuations in ink pressure within the ink supply. Downstream of the damper 27, a load line 28 branches off the main supply line 19. The load line 28 comprises a restriction 29. The load line 28 is configured to maintain a near-constant load on the main supply line 19, avoiding pressure spikes in the print head 3 due to load spikes of the ink pump 21 (e.g. due to activation of the ink pump 21). A viscometer valve 30 is disposed along the load line 28. The viscometer valve 30 can selectively place the load line 28 in fluid communication with either the mixer tank 17, via a tank line 31 , or a viscometer 32. The viscometer valve’s 30 default configuration is to place the load line 28 in fluid communication with the mixer tank 17. This creates a circular fluid flow path. When it is desired to ascertain the viscosity of the ink mixture in the main supply line 19, and so the load line 28, the viscometer valve 30 is energised to direct the flow into the viscometer 32. Initially the viscometer 32 is empty. By monitoring the time taken to fill and/or empty the viscometer 32, and based upon a known volume of fluid in the viscometer 32, the viscosity of the ink mixture can be ascertained. Downstream of the damper 27 and the load line 28, a pressure sensor 33 is connected to the main supply line 19 and is configured to monitor the pressure downstream of the ink pump 21. The ink pump 21 may be operated as a constant pressure pump (i.e. the pump is controlled to maintain a constant output pressure). A third filter 34, having a filtration size of 15 microns, is provided downstream of the pressure sensor 33.

The main supply line 19 is configured to carry ink from the ink mixer tank 17, along the umbilical 4, to the print head 3. The main supply line 19 is connected to the print head 3 via a feed valve 35. The feed valve 35 is configured to control the ink supply to the print head 3. Downstream of the feed valve 35 a heater 36 is provided. The heater 36 is used to control the temperature of the ink mixture. Controlling the temperature of the ink mixture reduces the effect that temperature fluctuations could otherwise have on the viscosity of the ink mixture. For example, activation of the heater 36 provides a heating effect which reduces the viscosity of the ink mixture. A temperature sensor 37 is provided downstream of the heater 36. The heater 36 is provided in fluid communication with the nozzle body 143, and so nozzle 144, via a nozzle line 38. The heater 36 preferably maintains the ink mixture at a temperature of at least around 308° K (e.g. -35° C).

As described above, ink is fed along the main supply line 19 to the print head 3 via the umbilical 4. Within the print head 3 the ink is provided to the nozzle 144. The ink is provided to the nozzle 144 under pressure (under the influence of the ink pump 21) and forms an ink jet. The ink jet begins as a constant stream of ink and, under the influence of surface tension and vibrations applied in the nozzle body 143 (e.g. by a piezoelectric oscillator), gradually separates into a series of ink droplets 188 which continue to travel in the direction of the inkjet 57.

Shortly after emerging from the nozzle 144 of the nozzle body 143, the inkjet is passed through a charge electrode (not shown in Figure 10, but labelled 148 in Figure 3). The point at which the continuous ink jet separates into droplets 188 is arranged to occur within the charge electrode. The ink is an electrically conductive liquid, and the nozzle body 143 is conventionally held at a fixed (e.g. ground) potential. A variable voltage is applied to the charge electrode (not shown in Figure 10, but labelled 148 in Figure 3) causing charge to be induced on the continuous stream of ink droplets extending from the nozzle body 143 towards the charge electrode. As the continuous stream of ink (i.e. ink jet) separates into droplets 188, any charge induced on the ink within the droplet becomes trapped at the moment the individual droplet “snaps” off from the main stream of ink. In this way, a variable charge can be applied to each of the ink droplets within in the stream of ink droplets 188.

The stream of ink droplets 188 then continues to pass from the charge electrode between further electrodes (not shown in Figure 10, but labelled 166, 168 in Figure 3). A first electrode (e.g. a low voltage electrode) is held at a first voltage, whereas the second electrode (e.g. deflection electrode) is held at second voltage, with a large potential difference (e.g. 8-10 kilovolts) established between the electrodes. In some systems, one electrode may be maintained at a ground potential while the other electrode is held at a high (positive or negative) voltage (with respect to ground). In other systems, one electrode is held at a negative voltage (with respect to ground) and the other electrode is held at a positive voltage (with respect to ground). The electric field established between the electrodes causes any charged droplets (i.e. those that have been charged by the charge electrode) to be deflected. In this way, based upon the variable charge applied by charge electrode, the droplets 188 can be selectively (and variably) steered from the path along which they are emitted from the nozzle 144.

Droplets which pass through the deflection field and which are deflected by the electrodes are not shown in Figure 10, but are labelled 190 in Figure 7. The stream of droplets 190 are used for printing. The stream of ink droplets 190 may be described as defining an ink path across the rotatable body (of the sealing mechanism) and through the ink aperture.

Returning to Figure 10, droplets which pass through the deflection field without being deflected (i.e. droplets which are not used for printing) travel to a gutter 40 (e.g. the gutter block 182 of the earlier Figures). The gutter 40 comprises an orifice 183 (e.g. gutter aperture 183 of the earlier Figures) into which the droplets enter. The gutter 40 is connected to a gutter line 42 which extends from the gutter 40 back to the main ink block 11 (e.g. the gutter line 42 extends between at least the gutter 40 and the gutter pump 46). A gutter valve 44 is optionally provided within the gutter line 42 enabling the gutter line 42 to be opened and closed. A suction force is applied to the gutter line 42 by a gutter pump 46 to draw ink along the line from the gutter 40 back towards the main ink block 11. In other embodiments the suction may be provided by a Venturi in communication with the ink pump 21. The gutter pump 46 and Venturi are examples of a suction source.

Downstream of the gutter pump 46 a tank valve 48 is provided. The tank valve 48 selectively places the gutter pump 46 in fluid communication with either the mixer tank 17 or a solvent tank 50. The solvent tank 50 may be described as a ‘used’ solvent reservoir insofar as it contains solvent which is not fresh. In the illustrated embodiment, the solvent tank 50 is provided adjacent the mixer tank 17. The solvent tank 40 and mixer tank 17 are shown as different compartments within an overall tank in the illustrated embodiment, but in other embodiments the mixer and solvent tanks 17, 40 could be physically separate tanks. During printing operations, the tank valve 48 places the gutter pump 46 in fluid communication with the mixer tank 17. The ink mixture (e.g. the stream of ink droplets 188) received by the gutter 40 is thus returned to the mixer tank 17 and can be recirculated/reused at a later time. During non-printing operations (e.g. such as priming, cleaning operations etc.), the tank valve 48 may place the gutter pump 46 in fluid communication with the solvent tank 50. This is to avoid cleaning fluid, such as ‘used’ solvent, undesirably contaminating (e.g. altering the viscosity of) the ink mixture in the mixer tank 17.

In addition to unprinted droplets of ink being recirculated via the gutter 40, any air which is sucked into the gutter 40 will also be delivered to the mixer tank 17 or solvent tank 50. The mixer tank 17 and solvent tank 50 are in communication with one another via a condenser 52 (which also acts as a vent). Solvent in the ink mixture in the mixer tank 17 tends to evaporate as solvent vapour in the mixer tank 17. Saturated solvent vapour is therefore present in the mixer tank 17 during use. As said vapour passes over the condenser 52, the comparatively cool surfaces of the condenser 52 result in the solvent, contained in the vapour, condensing. The solvent vapour thus returns to liquid, and is deposited back into the solvent tank 50. This advantageously avoids undue loss of solvent from within the system (which would otherwise occur if both tanks were vented directly to atmosphere). Furthermore, the mixer tank 17 is effectively vented by the condenser 52, preventing excess pressure building up within the mixer tank 17. Gases vented from the mixer tank 17 thus travel into the solvent tank 50. In turn, the solvent tank 50 is vented by a solvent tank vent line 54 provided in fluid communication with the solvent tank 50. Through solvent tank vent line 54 gases can be vented, preferably to outside of the printer cabinet (in which the ink system is contained).

The ink system, specifically the cartridge module 12 thereof, comprises an ink cartridge connection 56 which may be connected to the associated ink cartridge 8 and a solvent cartridge connection 58 which may be connected to the associated solvent cartridge 10. The ink cartridge 56 and ink cartridge connection 58 are connected to the refill line 25, allowing ink or solvent to be drawn, by the Venturi line 24, into the mixer tank 17. In other embodiments, a dedicated transfer pump may be used instead of the Venturi line 24.

By using a Venturi in this way (i.e. as a jet pump), a system can be designed in which the main system ink pump 21 can generate both positive pressures (e.g. to supply ink to the print head 3) and negative vacuum pressure (e.g. to draw ink or solvent into the mixer tank 17 via the refill line 25).

The feed valve 35, provided along main supply line 19, is configured to prevent the main supply line 19 from being continuously open. However, since the feed valve 35 is provided downstream of the Venturi line 24, even when the feed valve 35 is closed, when the ink pump 21 is operating, a flow of ink will flow along Venturi line 24 through the Venturi 24a, resulting in suction being applied to the refill line 25. In this way, the suction can be applied even when ink is not being supplied to the print head 3. Of course, a second valve 61 may also be operated to block the refill line 25, meaning that the refill line suction can be controlled independently of the Venturi 24a.

It will be appreciated that by selectively activating one or more of four cartridge valves 60, 61 , 62, 63, the ink cartridge 56 can be placed in fluid communication with the refill line 25. For example, opening only first and second valves 60, 61 (and closing third and fourth valves 62, 63) places the ink cartridge 8 in fluid communication with the refill line 25 via an ink refill line 59. Ink can thus be drawn into the mixer tank 17, via the ink refill line 59 and refill line 25, to add ink to the mixer tank 17.

Solvent can be directed to the solvent tank 50, directly from the solvent cartridge 58, by the solvent refill line 64 and a solvent tank line 65. Closing the first and second valves 60, 61 , and opening third and fourth valves 62, 63, places the solvent cartridge 10 in fluid communication with the solvent tank 50 via the solvent tank line 65 and the solvent refill line 64. Solvent can also be drawn from the solvent tank 50, through the solvent tank line 65 and into the cleaning module inlet line 72 (which will be described below). A solvent tank refill line filter 66 is provided along the solvent tank refill line 64. The solvent tank 50 and the solvent cartridge 10 are examples of a cleaning fluid supply. The cleaning fluid may be fresh cleaning fluid (e.g. solvent which has not been used before, from the solvent cartridge 10) or used cleaning fluid (e.g. solvent which has been used before, from the solvent tank 50).

A solvent pump 67 is provided downstream of the solvent cartridge 10 along the solvent refill line 64. Activation of the solvent pump 67 can be used to pump solvent from the solvent cartridge 10 into the solvent tank 50. Advantageously, the amount of solvent added to the solvent tank 50 can be measured by determining the fluid level within the solvent tank 50. This volume can then be subtracted from a remaining solvent cartridge volume held on a smart chip on the solvent cartridge 10. The remaining volume of solvent in the solvent cartridge 10 can thus be ascertained. This has been found to be more accurate than measuring the volume of solvent drawn out of the solvent cartridge 10 under a negative pressure (owing to the vacuum level within a cartridge generally changing as the cartridge is evacuated of fluid). In the illustrated embodiment, solvent is pumped out of the solvent cartridge 10 under action of the solvent pump 67. In embodiments where solvent is drawn directly from the solvent cartridge 10 (e.g. for cleaning), the above-described method can also be used to ascertain the remaining volume of solvent in the solvent cartridge 10 with the difference that the solvent take a different fluid path. For example, rather than being drawn into the solvent tank 50 via a solvent tank line 65, solvent is drawn into the solvent tank 50 via the print head 3 (e.g. via a flush line 70, cleaning module inlet line 72, first or second conduits 204, 214, the chamber 164, the gutter line 42 or purge line 74).

When it is desired to add solvent to the mixer tank 17, second and fourth valves 61 , 63 are opened, and first and third valves 60, 62 closed. Solvent is then drawn from the solvent reservoir 50, via solvent tank line 65 and refill line 25, by Venturi 24a, into the mixer tank 17.

Activation of the solvent pump 67 can also be used to pump solvent from the solvent cartridge 10, along the solvent refill line 64, for some non-printing operations, such as priming the fluid circuit. This will be described below. The solvent pump 67 is not used to actively pump pressurised cleaning fluid (e.g. solvent) into the chamber 164, via the cleaning module inlet line 72, for cleaning in the illustrated embodiment. Instead, cleaning fluid is preferably (solely) drawn into the chamber 164 (e.g. under vacuum) for cleaning. This provides failsafe operation, should the sealing mechanism fail, in that the cleaning fluid will just not be drawn into the chamber 164. Were the cleaning fluid pumped into the chamber 164 under pressure (e.g. under action of an upstream pump), failure of the sealing mechanism risks cleaning fluid being ejected from the print head 3 (e.g. via the ink aperture) onto the printing line. This risks undesirable contamination. That said, cleaning fluid could equally be pumped into the chamber in some embodiments. It will be appreciated that the concept of drawing cleaning fluid into a chamber is applicable to a wide range of embodiments of self-cleaning print head (e.g. a self-cleaning print head not necessarily having diametrically opposed ports, and not necessarily having an orientation sensor, to name two examples).

A non-return valve 68 is provided downstream of the solvent pump 66, along the solvent refill line 64, to prevent fluid travelling past the non-return valve 68 towards the solvent pump 66. A further non-return valve 69 is provided in a branch line which extends around the solvent pump 67. The non-return valve 69 is an overpressure valve for the solvent pump 67. The non-return valve 69 is a pressure relief valve which determines a maximum solvent pressure from the solvent pump 67. For completeness, the cartridge valves 60-63 can also be selectively activated to provide other configurations for, for example, priming of the fluid system and for draining the mixer tank 17 and/or solvent tank 50 (e.g. during maintenance).

A flush line 70 is connected between the third valve 62 and the non-return valve 68. The flush line 70 directly connects the cartridge module 12 to the print head 3 via the umbilical 4. A flush filter 71 is provided along the flush line 70, upstream of a cleaning module inlet line 72 which branches off the flush line 70. The flush line 70 extends to the print head 3 via a flush valve 73 disposed along the flush line 70. The flush line 70 is used to route solvent from the solvent cartridge 58 into the nozzle body 143. Solvent can thus be forced through the nozzle 144 to clean the nozzle. This is by way of activating the solvent pump 67, which provides pressurised solvent to the nozzle 144 for nozzle cleaning. The flush valve 73 is closed by default (e.g. during printing operations) and is only opened during non-printing operations (e.g. priming). Solvent can be prevented from being pumped into the chamber 164 via the cleaning module inlet line 72 by selective activation of valves in the cleaning module 13. Put another way, the cleaning module inlet line 72 can effectively be closed, so that solvent flows through the flush line 70 to the flush valve 73, by selective activation of valves in the cleaning module 13. In other embodiments the cleaning module inlet line 72 may branch off of the solvent refill line 64 (e.g. between the solvent cartridge 10 and the solvent pump 67). In such embodiments, the non-return valve 68 may be omitted.

A purge line 74 is connected to the nozzle body 143. The purge line 74 is connected to a purge port 74a of the nozzle body 143. The nozzle body 143 may be provided as part of a nozzle assembly, which includes the nozzle body 143 having known acoustic properties, and a piezoelectric oscillator. The purge port may be provided by the body, or by a separate part connected to the body. The purge line 74 allows ink (and/or air and/or debris) to flow (or pass) out of the nozzle body 143 via a purge aperture 74a (e.g. a purge port) without passing through the nozzle 144, and allows the nozzle body 143 to be cleaned. The purge line 74 extends from the nozzle body 143, along the umbilical 4, and returns ink (or solvent), depending upon the phase of operation, to the mixer tank 17. The purge line 74 is provided in selective fluid communication with the gutter pump 46, via purge valve 75. Fluid is drawn through the purge line 74 by suction of the downstream gutter pump 46. A purge valve 75 is provided along the purge line 74. It will be understood that the purge line is not essential, and may be omitted in some printers. The incorporation of the purge line 74 is advantageous for a number of reasons. The purge line 74 can be used to remove air from the nozzle body 143 (e.g. from within a chamber of the nozzle body 143). Removal of air from the nozzle body 143 is desirable because the presence of air can negatively impact the acoustic performance of the nozzle body 143. The purge line 74 can also be used to remove debris that may become trapped in the nozzle chamber when a backflush is carried out. A backflush refers to a process in which solvent is applied to a front face of the nozzle 144 whilst a vacuum is generated in the nozzle body. The purge line 74 also allows ink to be removed/drained from the interior of the nozzle body 144, and the interior of the nozzle body 144 washed, more effectively.

The main supply line 19, purge line 74, gutter line 42, and flush line 70 thus connect the ink system (e.g. the main ink block 11 and cartridge block 12) to the print head 3. Additional fluid connections housed within the umbilical 4 may connect the ink system 5 to the print head 3. For example, an air recirculation line may be provided to provide solvent saturated air to the gutter line 42 close to the gutter entrance.

The chamber 164 is also schematically indicated in Figure 10. As indicated in Figure 10, the gutter 40 is disposed in the chamber 164 in the illustrated embodiment. The nozzle body 143 is outside of the chamber 164 in the illustrated embodiment. Two conduits 204, 214 are shown connected to the chamber 164. The first conduit 204 is also shown in Figure 8. The first conduit 204 is in fluid communication with the chamber 164 via the first port 206. The first port 206 is disposed proximate the charge electrode and nozzle body 144(e.g. at an upstream location within the chamber 164). The second conduit 214 is in fluid communication with the chamber 164 via the second port 202. The second port 202 is disposed proximate the gutter 40 (e.g. the gutter block 183 in Figure 6). The second port 202 is disposed at a downstream location within the chamber 164. The first and second conduits 204, 214, and so first and second ports 206, 202, can be used to supply the chamber 164 with cleaning fluid or to drain used cleaning fluid from the chamber 164. The first and second conduits 204, 214, and so first and second ports 206, 202, can be used to supply the chamber 164 with air (e.g. for drying the chamber or for pressure balancing during printing. Of note, the pressure balancing mentioned above also encompasses supplying air at a higher flowrate (e.g. >1 litre/min) than the gutter consumes (-200 cc/min). As described elsewhere, this reduces the risk of dust/contamination ingress into the print head when located in situ on a production line. Each of the first and second conduits 204, 214 can be selectively opened/closed by action of corresponding valves of the cleaning module 13.

Also shown in Figure 10 is a third conduit 216 which extends from the first conduit 204 to, and partway through, the nozzle body 143. The third conduit 216 may therefore be described as a branch of the first conduit 204. The third conduit 216 terminates at a third port 217. The third port 217 is defined in a front face of the nozzle body 143. The third conduit 216 and third port 217 are optional features of the illustrated embodiment, and may be omitted in other embodiments. The third conduit 216, and corresponding third port 217, is used to supply at least part of the charge electrode, and so downstream chamber, with cleaning fluid or to drain used cleaning fluid from the at least part of the charge electrode and chamber 164 (or provide a supply of air). By virtue of being a branch of the first conduit 204, the third conduit 216 is not independently controllable of the first conduit 204 in the illustrated embodiment. Described another way, in the illustrated embodiment, when cleaning fluid is supplied through the first conduit 204, cleaning fluid is ejected from both the first port 206 (into the chamber 164) and the third port 217 (into at least part of the charge electrode). Similarly, where used cleaning fluid is drained through the first conduit 204, cleaning fluid is drained from the chamber 164 (through the first port 206) and from at least part of the charge electrode (via the third port 217). In some orientations (e.g. vertically upwards) of the print head 3, and so chamber 164, used cleaning fluid can be drained through both the first and third ports 206, 217. Advantageously, the first port 206 drains fluid from the chamber 164, whilst the third port 217 drains fluid from the charge electrode. Incorporation of the third port 217 thus avoids an accumulation of used cleaning fluid outside of the chamber 164 which could otherwise undesirably increase the drying time of the print head 3 following cleaning. However, in other embodiments one or more valves may be incorporated along the first and/or third conduits 204, 216 to provide independent control.

Turning to describe components of the cleaning module 13, first to fourth control valves 80, 81 , 82, 83 are provided. Also extending at least partway through the cleaning module 13 is an air line 84, with an air pump 85 provided along the air line 84. The air line 84 is connected to atmosphere in the illustrated embodiment. The air line is therefore an example of an air supply. A pressure release valve 86 is also provided downstream of the air pump 85. The air line 84 is connected to atmosphere and can be used to selectively supply the chamber 164 with air. This can be used for either positive pressure drying of the chamber 164 (e.g. after cleaning) or to provide a supply of air to within the chamber 164 during printing. This is to avoid an excessive negative pressure being generated within the chamber 164 due to the suction of the gutter pump 46 via the gutter 40, which could otherwise result in debris being drawn into the print head 3 from the printing line. Advantageously the single air pump 85 provides both functionalities. It will be appreciated that the concept of the air pump providing both positive pressure air into a chamber during printing, as well as during a cleaning cycle for drying the chamber, is applicable to a wide range of embodiments of self-cleaning print head (e.g. a self-cleaning print head not necessarily having diametrically opposed ports, and not necessarily having an orientation sensor, to name two examples).

A downstream portion of the cleaning module inlet line 72, which may be referred to as an inlet line 72 for brevity, is also shown. The break in the inlet line 72 between the left hand side of the Figure (i.e. above the filter 71) and the right hand side of the Figure (i.e. above the air pump 85) is simply included to improve the clarity of the Figure, and to avoid the line extending across the various other components of the fluid circuit. A draw line 87 is also shown. The draw line 87 extends to the gutter pump 46 via part of the gutter line 42. Fluid can therefore be drawn through the draw line 87 by operation of the gutter pump 46. For completeness, the tank valve 48 also forms part of the cleaning module 13 in the illustrated embodiment. However, in other embodiments the gutter valve 48 could form part of the main ink block 11.

The first control valve 80 can selectively place the first conduit 204 (via a second control valve 81) in fluid communication with the inlet line 72 or the air line 84. The other of the inlet line 72 and the air line 84 can be selectively closed by the first control valve 80.

The second control valve 81 can selectively place the first conduit 204 in fluid communication with the draw line 87 or the inlet line 72 (via the first control valve 80) or the air line 84 (via the first control valve 80). In the configuration shown in Figure 10, the second control valve 81 places the first conduit 204 in fluid communication with the draw line 87. Activation of the gutter pump 46 thus applies suction through the draw line 87 and through the first conduit 204. In this configuration, fluid would be drawn from the chamber 164 through the first conduit 204 and draw line 87. In the configuration shown in Figure 10, the first conduit 204 is not provided in fluid communication with either of the inlet line 72 and the air line 84.

The third control valve 82 can selectively place the second conduit 214 in fluid communication with the draw line 87 or the inlet line 72 (via the fourth control valve 83) or the air line 84 (via the fourth control valve 83). In the configuration shown in Figure 10, the third control valve 82 places the second conduit 214 in fluid communication with the draw line 87. Activation of the gutter pump 46 thus applies suction through the draw line 87 and through the second conduit 214. In this configuration, fluid would be drawn from the chamber 164 through the second conduit 214 and draw line 87. In the configuration shown in Figure 10, the second conduit 214 is not provided in fluid communication with either of the inlet line 72 and the air line 84. The fourth control valve 83 can selectively place the second conduit 214 (via the third control valve 82) in fluid communication with the inlet line 72 or the air line 84. The other of the inlet line 72 and the air line 84 can be selectively closed by the fourth control valve 83.

By selective operation of the control valves 80-83, different conduits/ports can be placed in fluid communication with the inlet line 72, air line 84 and draw line 87. When connected to the inlet line 72, cleaning fluid can be directed through the conduits/ports into the chamber 164. When connected to the air line 84, air can be pumped through the conduits/ports, by the air pump 85, into the chamber 164. When connected to the draw line 87, fluid (e.g. used cleaning fluid) can be drawn from the chamber 164, through the conduits/ports, through the draw line 87 by gutter pump 46. The air line 84 can be used to pump air into the chamber 164 to dry the chamber 164 after cleaning fluid has been drawn into, and drawn out of, the chamber 164. The air line 84 can also be used to pump air into the print head 3 (e.g. into the chamber 164) to replenish the air removed from the chamber 164 under action of the gutter 40 (e.g. during printing operations). This advantageously reduces the risk that the pressure within the print head 3 reduces to such a level that debris is drawn into the print head 3 from outside the print head 3.

In preferred embodiments, one of the first and second conduits 204, 214 is placed in fluid communication with the inlet line 72, and the other of the first and second conduits 204, 214 is placed in fluid communication with the draw line 87. Activation of the gutter pump 46 then draws cleaning fluid through the inlet line 72, into the chamber 164 via the conduit connected to the inlet line 72. The cleaning fluid is then drawn back out of the chamber 164, via the other conduit (e.g. whichever of the first or second conduits 204, 214 is not connected to the inlet line 72), under suction of the gutter pump 46 via the draw line 87. The cleaning fluid is preferably drawn back out of the chamber 164, via the same conduit (e.g. whichever of the first or second conduits 204, 214 was connected to the inlet line 72), under suction of the gutter pump 46 via the draw line 87. The selection of which port is a fill port, and which port is a drain port, can be based upon the orientation of the print head 3, and so chamber 164.

Selecting the first port 206 as the fill port and the drain port may comprise operating the plurality of valves 80-83 to place the cleaning module 13 in a first configuration. The first configuration may correspond to the print head 3 being in a first orientation (e.g. where the first port 206 is vertically lower than the second port 202). Selecting the second port 202 as the fill port and the drain port may comprise operating the plurality of valves 80-83 to place the cleaning module 13 in a second configuration. The second configuration may correspond to the print head 3 being in a second orientation (e.g. where the second port 202 is vertically lower than the first port 206).

In preferred embodiments cleaning fluid is left in/resides in the chamber 164 for a dwell time before subsequently being drawn out/drained. Air may be bubbled through the chamber 164, whilst it is at least partly filled with cleaning fluid, to agitate the cleaning fluid and dislodge debris within the chamber 164. The chamber 164 may be only partially filled with cleaning fluid (e.g. around half full). The chamber 164 may be majority filled with cleaning fluid (e.g. at least around 80% of the chamber 164 volume filled with cleaning fluid). The chamber 164 may be partly filled with cleaning fluid in combination with, or in isolation of, air being bubbled through the chamber 164.

Turning to Figure 11 , a flow chart 300 setting out the various steps of a cleaning cycle of the print head 3 is provided. The flow chart 300 sets out the method for a print head in a first orientation, as will be described in detail below. The flow chart 300 sets out a method which may be described as a first valve sequence. The first valve sequence may be carried out by the controller, operatively connected to the plurality of control valves 80-83, responsive to the print head 3 being detected as being in the first orientation (e.g. where the second port 202 is vertically lower than the first port 206).

As illustrated, the cleaning cycle 300 comprises various steps which fit broadly into four different stages: a first, filling stage 301; a second, soak stage 302; a third, drain stage 303; and a fourth, drying stage 304. Save for the second, soaking stage 302, each of the other stages comprises multiple steps. The various steps forming part of the method 300 refer to components shown in the diagrams of Figures 12 and 13 copied adjacent.

Figures 12 and 13 are simplified schematic fluid circuit diagrams which show parts of the overall fluid system shown in Figure 10. For example, Figure 12 shows the tank valve 48 connected to gutter line 42, with the gutter pump 46 disposed along the gutter line 42. The lower region of Figure 12 shows the air line 84 with the air pump 85 disposed along the air line 84, along with pressure release valve 86.

Turning to Figure 13, Figure 13 shows the four control valves 80-83 which form part of the cleaning module 13 shown in Figure 10. The various connections of the four control valves 80-83 will not be repeated here in detail, as a previous explanation has been provided in this regard. However, for completeness here, the second control valve 81 may be described as a first flow valve, and the third control valve 82 may be described as a second flow valve. The second control valve 81 is connected to the first conduit 204. The third control valve 82 is connected to the second conduit 214. The first and second conduits 204, 214 are connected to chamber 164 at first and second ports 206, 202 respectively.

The unpowered state (e.g. de-energised state) of the plurality of valves 80-83 connects the first and second ports 206, 202 to the air line 84 only (e.g. not to the cleaning fluid supply or gutter line 88). This mitigates the risk of liquid leakage into the chamber 164 in the event of valve failure.

It is the first and second flow valves 81, 82 that determine the direction of fluid flow into, and out of, the chamber 164. Similarly, for completeness here, the first control valve 80 may be referred to as a first feed valve (selectively connectable to a cleaning fluid, or air, supply). The fourth control valve 83 may be described a second feed valve (selectively connectable to the cleaning fluid, or air, supply). The feed valves are so called because they determine what fluid (e.g. air or cleaning fluid) flows through the conduits 204, 214 into the chamber 164.

Returning to Figure 11 to describe the various method steps, as previously described the four sequential stages of the overall cleaning cycle for the method 300 include fill stage 301, soak stage 302, drain stage 303 and dry stage 304. The steps which make up each stage will now be described.

Beginning with the filling stage 301 , in a first step 305 the tank valve 48 is energised to place the solvent tank 50 (see Figure 10) in communication with the gutter pump 46. Used cleaning fluid from the chamber 164 can therefore be diverted to the solvent tank 50, as opposed to the mixer tank 17, and therefore be stored separately. This avoids issues with contamination of the ink mixture in the mixer tank 17, although the used cleaning fluid may be diverted there at a later time.

At a second step 306, second feed valve 83 is energised to place the second flow valve 82 in fluid communication with a cleaning fluid supply by way of the inlet line 72. The chamber 164 is thus connected to the inlet line 72 (e.g. cleaning fluid supply) via the valves 82, 83. The chamber 164 is connected to the inlet line 72 by the second conduit 214 and second port 202. The chamber 164 is thus placed in fluid communication with either the solvent tank 50 (i.e. containing used cleaning fluid) or the solvent cartridge 10 (i.e. containing fresh, or virgin cleaning fluid). The chamber 164 may be placed in fluid communication with only the solvent tank 50 or only the solvent cartridge 10.

At a third step 307 the first flow valve 81 is energised to connect the chamber 164 to the gutter line 42 (via a draw line 87). Chamber 164 is thus in fluid communication with the gutter pump 46 via the first conduit 204 and first port 206.

In a fourth step 308, the gutter pump 46 is activated which creates suction through the gutter line 42. Fluid is thus drawn through the chamber 164, via the first conduit 204 and first port 206, by gutter pump 46. Owing to the chamber 164 being connected to the cleaning fluid supply by second port 202, cleaning fluid is drawn into the chamber 164, through the second conduit 214, under action of the suction of the gutter pump 46 applied to the chamber 164 via the first conduit 204. Put another way, the chamber 164 begins to fill with cleaning fluid. No cleaning fluid is (intentionally) drawn out of the chamber 164 by the first conduit 204, though.

In a fifth step 309 there is a short pause, of 15 seconds in the illustrated embodiment, to allow time for the chamber 164 to at least partially fill with cleaning fluid. For completeness, the cleaning fluid is drawn into the chamber 164 and cleaning fluid flows from the inlet line 72, through valves 82 and 83, and via the second conduit 214 and second port 202. As previously mentioned, should the sealing mechanism fail at any stage, the cleaning fluid will not be drawn into the chamber 174 via the gutter pump 46. Instead, air is drawn into the chamber 164 via the leakage path. The chamber 164 is at least partially filled with cleaning fluid. The cleaning chamber 164 may be around halffilled with cleaning fluid. The chamber 164 may be completely filled with cleaning fluid. The chamber 164 may be overfilled with cleaning fluid (e.g. the cleaning chamber may be filled with a volume of cleaning fluid which is greater than the chamber 164). Filling or overfilling the chamber 164 advantageously reduces the risk that any component within the chamber 164, and the chamber 164 itself, is not ‘fully’ reached by (or submerged in) the cleaning fluid. It will be appreciated that the 15 second time pause time may be varied in other embodiments. The pause time may be influenced by one or more of a conduit/line length (e.g. giving rise to a transport delay), temperature and the type of ink (which affects solubility). Similarly, the pause time for any pause step (e.g. 313, 316, 318 etc.) may be varied in other embodiments.

At a sixth step 310, the gutter pump 46 is deactivated. Suction thus ceases to be applied to the chamber 164 by the gutter line 42.

In a seventh step 311, the second feed valve 83 is de-energised. In an eighth step 312, the second control valve 81 is also de-energised. The fluid circuit configuration thus returns to that shown in Figure 13. This concludes the fill stage 301 of the cleaning cycle.

The soaking stage 302 consists of a single step 313 in which a five second dwell period, in which the cleaning fluid is held within the chamber 164, is provided (in the illustrated embodiment). This is to improve the quality of the clean. This concludes the soaking stage 302.

The next stage is the draining stage 303. In a first step 314 the second flow valve 82 is energised to connect the chamber 164 to the gutter pump 46 via the second conduit 214 and corresponding second port 202.

In a second step 315 of the drain stage 303, the gutter pump 46 is activated. Cleaning fluid is thus drawn back out of the chamber 164, via the second conduit 214 and second port 202, towards the gutter pump 46. Owing to the position of the tank valve 48, used cleaning fluid is directed towards the solvent tank 50 as opposed to the mixer tank 17.

In the third and final step of the draining stage 303, step 316, a 10 second delay is provided (in the illustrated embodiment). This provides time for the gutter pump 46 to drain the used cleaning fluid out of the chamber 164. This is preferably a long enough delay to entirely empty the cleaning chamber 164 of cleaning fluid. This concludes the draining stage 303.

Turning to the next and final stage of the method 300, the drying stage 304 occurs. In a first step 317 the air pump 85 is activated. Air is therefore pumped into the chamber 164 through the first conduit 204 and first port 206. As air is pumped into the chamber 164 via the first conduit 204 and first port 206, air is drawn out of the chamber via the second conduit 214 and the second port 202 by the gutter pump 46. Air is thus simultaneously pumped into, and drawn out of, the chamber 164. This may be described as air being pumped through the chamber 164. Advantageously, the chamber 164 is dried more swiftly, by pumping the air into the chamber 164 under action of the air pump 85, than if air were merely drawn into the chamber 164 by the gutter pump 46.

At the next step 318, a 60 second delay is provided (in the illustrated embodiment). This allows time for the chamber 164 to be more thoroughly dried by the air supply pumped in by air pump 85. In the illustrated embodiment the air supply is by way of air line 84 (connected to atmosphere).

In a subsequent step 319 the air pump 85 is deactivated. In a subsequent step 320 the gutter pump 46 is deactivated.

In the final step 321 of the drying stage 304, and the overall method 300, all valves are de-energised.

The method 300 as described above is applied for a print head 3 having a cleaning chamber 164 in the orientation roughly as indicated in Figure 13. That is to say, where it is the second conduit 214 and the second port 202 that are the vertically lowest of the chamber ports, it is through the second conduit 214 and the second port 202 that cleaning fluid is directed into the chamber 164 and, after a dwell period, subsequently drained back out of the chamber 164. Put another way, no cleaning fluid actually flows through the first conduit 204 and the corresponding first port 206 where the port 206 is located vertically above the second port 202. The flow chart 322 sets out a method which may be described as a second valve sequence. The second valve sequence may be carried out by the controller, operatively connected to the plurality of control valves 80-83, responsive to the print head 3 being detected as being in a second orientation (e.g. where the first port 206 is vertically lower than the second port 202).

The method 300 may be completed in a total time period of around 60 seconds (e.g. for a ‘simple’ cleaning cycle). The method 300 may be completed in a total time period of up to around 300 seconds (e.g. for a ‘deep’ cleaning cycle). The deep cleaning cycle is particularly desirable if the cleaning process has not been carried out for a given period (e.g. in the preceding 24 or 48 hours) and/or if the print head 3 was not shut down in a controller manner (e.g. if the last operator disconnected a power supply to the printer rather than shutting down properly).

Although the method 300 shows a sequential cleaning cycle in which the fill stage 301 is followed by the soak stage 302 which is followed by the drain stage 303 which is followed by the drying stage 304, the cleaning cycle may comprise a plurality of one or more of these steps by way of a loop. For example, whereas the method 300 teaches (a single) filling, (a single) soaking, (a single) draining and (a single) drying stage, in other embodiments the method may comprise a plurality of fill, soak and drain stages. For example, after the (first) drain stage 302, the method 300 may return/loop back to the fill stage 301 and at least partially refill the chamber 164 (followed by subsequently soaking, and subsequently draining, the refilled chamber). This may otherwise be described as cycling a plurality of washes (e.g. half-filled washes). The cycling may occur a plurality of times (e.g. two, three, four or more times). Cycling the stages has been found to provide a more effective cleaning cycle.

Turning to Figures 14-16, a corresponding method 322 of cleaning is provided for the chamber 164 being provided in a different orientation. As indicated in Figure 16, the chamber 164 is oriented so that the second port 206 is vertically lower than the first port 202. This is the opposite orientation to that shown in Figure 13. This difference of orientation means that the method 322 differs from the method 300 insofar as different valves are activated to direct cleaning fluid into the chamber 164 via the second conduit 204 and second port 206, as opposed to via the first conduit 214 and first port 202 as was described in connection with Figures 11-13. The difference of orientation is preferably detected an orientation sensor mounted to the print head 3 and in operative communication with the controller.

Save for the difference of orientation of the chamber 164 in Figure 16, Figure 16 is identical to Figure 13. Similarly, there are a number of similarities between the methods 300, 322. Only the differences will be described below.

Like the method 300, the method 322 comprises four stages: a fill stage 323, a soak stage 324, a drain stage 325 and a dry stage 326.

At a second step 328, first feed valve 80 is energised to place the first flow valve 81 in fluid communication with a cleaning fluid supply by way of the inlet line 72. The chamber 164 is thus connected to the inlet line 72 (e.g. cleaning fluid supply) via the valves 81 , 82. The chamber 164 is connected to the inlet line 72 by the first conduit 204 and first port 202. The chamber 164 is thus placed in fluid communication with either the solvent tank 50 (i.e. containing used cleaning fluid) or the solvent cartridge 10 (i.e. containing fresh, or virgin cleaning fluid). The chamber 164 may be placed in fluid communication with only the solvent tank 50 or only the solvent cartridge 10.

At a third step 329 the second flow valve 82 is energised to connect the chamber 164 to the gutter line 42 (via a draw line 87). Chamber 164 is thus in fluid communication with the gutter pump 46 via the second conduit 214 and second port 202.

In a fourth step 330, the gutter pump 46 is activated which creates suction through the gutter line 42. Fluid is thus drawn through the chamber 164, via the second conduit 214 and second port 202, by gutter pump 46. Owing to the chamber 164 being connected to the cleaning fluid supply by first port 206, cleaning fluid is drawn into the chamber 164, through the first conduit 204, under action of the suction of the gutter pump 46 applied to the chamber 164 via the second conduit 214. Put another way, the chamber 164 begins to fill with cleaning fluid. No cleaning fluid is (intentionally) drawn out of the chamber 164 by the second conduit 214, though.

In a fifth step 331 there is a short pause, of 15 seconds in the illustrated embodiment, to allow time for the chamber 164 to at least partially fill with cleaning fluid. For completeness, the cleaning fluid is drawn into the chamber 164 and cleaning fluid flows from the inlet line 72, through valves 80 and 81 , and via the first conduit 204 and first port 206. As previously mentioned, should the sealing mechanism fail at any stage, the cleaning fluid will not be drawn into the chamber 174 via the gutter pump 46. Instead, air is drawn into the chamber 164 via the leakage path. The chamber 164 is at least partially filled with cleaning fluid. The cleaning chamber 164 may be around half-filled with cleaning fluid. The chamber 164 may be completely filled with cleaning fluid. The chamber 164 may be overfilled with cleaning fluid (e.g. the cleaning chamber may be filled with a volume of cleaning fluid which is greater than the chamber 164). Filling or overfilling the chamber 164 advantageously reduces the risk that any component within the chamber 164, and the chamber 164 itself, is not ‘fully’ reached by (or submerged in) the cleaning fluid. It will be appreciated that the 15 second time pause time may be varied in other embodiments. The pause time may be influenced by one or more of a conduit/line length (e.g. giving rise to a transport delay), temperature and the type of ink (which affects solubility). Similarly, the pause time for any pause step (e.g. 335, 339, 341 etc.) may be varied in other embodiments.

In a seventh step 333, the first feed valve 81 is de-energised. In an eighth step 334, the first control valve 82 is also de-energised. The fluid circuit configuration thus returns to that shown in Figure 16. This concludes the fill stage 323 of the cleaning cycle.

The soaking stage 335 is identical to the soaking stage 302 described in connection with Figure 11.

The next stage is the draining stage 325. In a first step 336 the first flow valve 81 is energised to connect the chamber 164 to the gutter pump 46 via the first conduit 204 and corresponding first port 206.

In a second step 338 of the drain stage 325, the gutter pump 46 is activated. Cleaning fluid is thus drawn back out of the chamber 164, via the first conduit 204 and first port 206, towards the gutter pump 46. Owing to the position of the tank valve 48, used cleaning fluid is directed towards the solvent tank 50 as opposed to the mixer tank 17.

In the third and final step of the draining stage 325, step 338, a 10 second delay is provided (in the illustrated embodiment). This provides time for the gutter pump 46 to drain the used cleaning fluid out of the chamber 164. This is preferably a long enough delay to entirely empty the cleaning chamber 164 of cleaning fluid. This concludes the draining stage 325.

Turning to the next and final stage of the method 322, the drying stage 326 occurs. In a first step 339 the air pump 85 is activated. Air is therefore pumped into the chamber 164 through the second conduit 214 and second port 202. As air is pumped into the chamber 164 via the second conduit 214 and second port 202, air is drawn out of the chamber via the first conduit 204 and first port 206 by the gutter pump 46. Air is thus simultaneously pumped into, and drawn out of, the chamber 164. This may be described as air being pumped through the chamber 164. Advantageously, the chamber 164 is dried more swiftly, by pumping the air into the chamber 164 under action of the air pump 85, than if air were merely drawn into the chamber 164 by the gutter pump 46.

At the next step 340, a 60 second delay is provided. This allows time for the chamber 164 to be more thoroughly dried by the air supply pumped in by air pump 85. In a subsequent step 341 the air pump 85 is deactivated. In a subsequent step 342 the gutter pump 46 is deactivated. In the final steps 343, 344 of the drying stage 326, and the overall method 322, the first control valve 81 and the tank valve 48 are deenergised (e.g. all valves are de-energised).

For completeness, any steps of the method 322 not mentioned above (e.g. 327, 332, 337) are identical to the counterpart steps shown in connection with the method 300 in Figure 11. That said, at least during step 337, and optionally during steps before and/or after, a positive cleaning fluid pressure (e.g. a supply of cleaning fluid) may be provided to a rear of the nozzle (e.g. proximate the interior of the nozzle body). By providing a positive cleaning fluid pressure across the nozzle, the risk of ‘dirty’ cleaning fluid entering the nozzle, during the drainage stage 325, is reduced. This is particularly advantageous when the print head is in an upward orientation (e.g. vertically upwards) and the nozzle is disposed proximate a lower end of the chamber (e.g. as is the case for the orientation of chamber 164 shown in Figure 16). This may be omitted for other orientations of print head (e.g. in a generally downward orientation, such as shown in Figure 13). The method 322 may be completed in a total time period of around 60 seconds (e.g. for a ‘simple’ cleaning cycle). The method 322 may be completed in a total time period of up to around 300 seconds (e.g. for a ‘deep’ cleaning cycle). The deep cleaning cycle is particularly desirable if the cleaning process has not been carried out for a given period (e.g. in the preceding 24 or 48 hours) and/or if the print head 3 was not shut down in a controller manner (e.g. if the last operator disconnected a power supply to the printer rather than shutting down properly).

Although the method 322 shows a sequential cleaning cycle in which the fill stage 323 is followed by the soak stage 234 which is followed by the drain stage 235 which is followed by the drying stage 326, the cleaning cycle may comprise a plurality of one or more of these steps by way of a loop. For example, whereas the method 322 teaches (a single) filling, (a single) soaking, (a single) draining and (a single) drying stage, in other embodiments the method may comprise a plurality of fill, soak and drain stages. For example, after the (first) drain stage 325, the method 322 may return/loop back to the fill stage 323 and at least partially refill the chamber 164 (followed by subsequently soaking, and subsequently draining, the refilled chamber). This may otherwise be described as cycling a plurality of washes (e.g. half-filled washes). The cycling may occur a plurality of times (e.g. two, three, four or more times). Cycling the stages has been found to provide a more effective cleaning cycle.

For either of the methods 300, 322, an initial subsequence of filling, soaking and draining using used cleaning fluid (e.g. from the solvent tank 50 shown in Figure 10), may first be carried out. A subsequent subsequence of filling, soaking and draining using virgin cleaning fluid (e.g. fresh cleaning fluid from the solvent cartridge 10 shown in Figure 10) may be carried out afterwards (followed by an ‘overall’ drying sequence).

In preferred embodiments the cleaning fluid supply consists of the solvent cartridge 10 and virgin cleaning fluid contained therein. It will be appreciated that the concept of an initial used cleaning fluid rinse, followed by a virgin cleaning fluid rinse, is applicable to a wide range of embodiments of self-cleaning print head (e.g. a self-cleaning print head not necessarily having diametrically opposed ports, and not necessarily having an orientation sensor, to name two examples). The methods 300, 322 have been found to provide a desirable balance of cleaning of the chamber 164, and the components disposed therein, without taking an unduly long time to complete a cleaning cycle. In particular, the methods facilitate the swift drying of the chamber 164 so that the print head 3 can return to printing operations.

For completeness, in connection with methods 300, 322, given the connections of the first and third conduits 204, 216, from the layout shown in Figure 23 it will be appreciated that the directionality of fluid through the third conduit 216 (for embodiments which incorporate a third conduit 216 and corresponding third port 217) is driven by, and mirrors, the directionality of the first conduit 204. Described another way, when cleaning fluid (for example) is pumped through the first conduit 204, fluid will also be pumped through the third conduit 216 and so cleaning fluid will be pumped through the first and third ports 206, 217. The first conduit 204 thus serves two ports.

Turning to Figure 17, a perspective view of the sealing mechanism 124 with the rotatable body in the second, closed configuration is provided.

Figure 17 shows the rotatable body 122 rotatably mounted within the casing 170 and rotatable about the axis of rotation 126. As mentioned, in Figure 17 the rotatable body 122 is shown in the second, sealed configuration. In the second configuration the rotatable body 122 closes the ink aperture 171 of the casing 170. Rotation of the rotatable body 122 is driven by the motor (not shown in Figure 11) via the worm gear 130 comprising the worm 132 coupled to the shaft (not shown in Figure 10) and the gear 134 rotatably coupled to the rotatable body 122. Figure 17 also shows a shaft adapter 218 which is rotatably coupled to the worm 132 at one end and is coupled to the shaft (again, not shown in Figure 17) at the other end. The worm 132 and shaft adapter 128 are rotatable about the axis of rotation 129.

Figure 17 also shows the cap 172 which is coupled to, and forms part of, the casing 170, with the rotatable body 122 and gear 134 in situ, to axially constrain the rotatable body 122 and gear 134 about the axis 126.

Figure 17 also shows the gutter block 182. As previously described, the gutter block 182 is fixedly attached to the chamber housing 162 (not shown in Figure 17) and does not rotate with the rotatable body 122. The sealing mechanism 124 can be removed from the overall print head assembly whilst the gutter block 182 remains in situ, coupled to the chamber housing. The relationship (e.g. alignment) between the gutter block 182 (e.g. aperture 183), the nozzle 144 and the stream of ink droplets can thus be maintained despite removal of the sealing mechanism 124 (e.g. despite disassembly and subsequent reassembly). The gutter block 182 comprises the gutter aperture 183. The gutter aperture 183 is defined on a gutter arm 185. The gutter arm 185 projects from a main body of the gutter block 182. By providing the gutter aperture 183 on the gutter arm 185, a bulk of the gutter block 182 can be positioned away from the rotatable body 122 whilst the gutter aperture 183 (by virtue of the gutter arm 185) is still disposed within the recess 123 of the rotatable body 122. This means that when the rotatable body 122 is in the open configuration, an ink path can still be defined across the rotatable body 122 in a region which is not obscured by the gutter arm 185. Owing to the geometry of the recess 123, and rotatable body 122 more generally, the rotatable body 122 may be described as a half-shaft. The rotatable body 122 may be said to swing under a transverse gutter (e.g. specifically under gutter arm 185). Dowels 187a, 187b are received in corresponding recesses of the gutter block 182 to facilitate locating the gutter block 182 with respect to the casing 170. The dowels 187a, 187b also assist with aligning the gutter aperture 183 with the stream of ink droplets (which are not used for printing) in use.

Seals 213, 220 (which take the form of O-rings in the illustrated embodiment) are seated within recesses in the gutter block 182. The seal 213 corresponds to that shown in Figure 8 and seals a connection between the gutter conduit 196 defined in the gutter block 182 and the return conduit 212 defined in the chamber housing 162. Returning to Figure 17, the seal 220 surrounds an aperture 222 which is configured to receive a fastener to couple the gutter block 182 to the chamber housing. Figure 17 also shows part of the recess 200 defined in an effective underside of the gutter block 182 as oriented in Figure 17. As partly described in connection with Figure 6, the recess 200 leads into the (second) port 202 (not shown in Figure 17) which, in turn, defines the second conduit 214 shown in Figure 10. It will be appreciated that, owing to the presence of the recess 200, the second conduit 214 is still provided in fluid communication with the chamber even when the rotatable body 122 is in the second, closed configuration as shown in Figure 17. Cleaning fluid can therefore be pumped or drawn into the chamber via the second conduit 214, or used (e.g. dirty) cleaning fluid be pumped or drawn out of the chamber via the second conduit 214. Described another way, the second conduit 214 defines part of a pathway for supplying cleaning fluid or draining used cleaning fluid from the chamber. The casing 170 of Figures 17 and 18 is shown in a partially cutaway view in that various components (e.g. the ink aperture 171 and gear 134) which would normally be obscured in these views are visible.

Turning to Figure 18, a perspective view of some components of the sealing mechanism 124 shown in Figure 17 is provided with the rotatable body 122 in a first configuration. Some components shown in Figure 17 (e.g. dowels 187a, 187b) are omitted in Figure 18. In Figure 18only the casing 170, rotatable body 200 and gutter block 182 are visible. In contrast to the position of the rotatable body 122 in Figure 17, in Figure 18the rotatable body 122 is rotated by around 90° about the axis of rotation 126 in a generally anti-clockwise direction from the Figure 18perspective. As such, an abutment surface 123a of the rotatable body 122 is disposed along an extent of the gutter arm 183 in Figure 18. Given this rotational position of the rotatable body 122, an ink path is defined across the rotatable body 122 and through the ink aperture 171. Described another way, the chamber is provided in communication with atmosphere via the ink aperture 171. A stream of ink droplets for printing can therefore be ejected from the print head 3 and applied to a substrate moving past the print head 3. This is in contrast to the Figure 17 configuration in which the chamber is sealed so that cleaning fluid can be pumped or drawn through the chamber to clean it.

Using the sealing mechanism 124 of Figures 17 and 18, the chamber can be selectively sealed to carry out methods associated with the print head 3 and printer 1 more generally.

A method of sealing the print head 3 comprises rotating the rotatable body 122 from a first configuration (e.g. as shown in Figure 18), in which the chamber is in communication with atmosphere via at least the ink aperture 171, to a second configuration in which the chamber is sealed by the rotatable body 122 (e.g. as shown in Figure 17). Even when sealed, with reference to Figure 10, the chamber 164 may be in communication with conduits such as the first and second conduits 204, 214.

A method of cleaning the print head 3 comprises sealing the chamber 164 of the print head 3 by actuating the sealing mechanism. Actuating the sealing mechanism may comprise the method of sealing the print head as set out above (e.g. in connection with sealing mechanism 124). Alternatively, another sealing mechanism and/or another form of actuation may otherwise be used. A port of the chamber 164 is then selected as a fill port. A port of the chamber 164 is also selected as a drain port. The second port 206 may be selected as either or both of the fill port and the drain port. The first port 206 and, if appropriate, the third port 217, may be selected as either or both of the fill port and the drain port. In preferred embodiments, the second port 202 is selected as either the fill port or the drain port, and the first port 206, and optionally the third port 217, selected as the other of the fill port and the drain port. In such embodiments, the ports thus define a flowpath through the chamber 164 insofar as cleaning fluid enters the chamber 164 in one region, and exits the chamber 164 in a different region. The selection of the fill and drain ports is preferably based upon the orientation of the print head 3.

The method further comprises directing (e.g. pumping or drawing) a cleaning fluid through the fill port, into the cleaning chamber to clean the cleaning chamber. The method further comprises draining the cleaning fluid from the cleaning chamber, through the drain port, to drain the cleaning chamber.

The cleaning fluid may be solvent. Cleaning fluid is preferably drawn into the chamber 164 via the first or second conduits 204, 214. Used cleaning fluid is preferably drained from the chamber 164 via the same one of the first and second conduits 204, 214, preferably after a short dwell period (e.g. 5 seconds). Cleaning fluid may be actively pumped through the chamber 164 (e.g. simultaneous, or contemporaneous, filling and draining), or cleaning fluid may be retained in the chamber 164, in a stagnant manner, for a period of time. Each of first and second conduits 204, 214 is preferably bidirectional insofar as cleaning fluid can be pumped or drawn through them, into the chamber 164, and/or used cleaning fluid can be drained from the chamber 164 through the conduits 204, 214. In other embodiments cleaning fluid may be drained from the chamber 164 via multiple conduits. It is desirable that air be fed into the chamber 164 as fluid/air is removed/drained from the chamber 164.

By filing the chamber 164 with cleaning fluid, ink particles and other debris, which otherwise risk clogging the chamber 164 and associated components, are removed and transported out of the chamber 164 upon draining. The chamber 164 is thus cleaned, along with any components of the print head which reside within the chamber 164. Such components include the electrodes 166, 168. The chamber 164 may only be part-filled with cleaning fluid.

With reference to Figure 10, cleaning fluid drained from the chamber 164 is returned to the solvent tank 50. The used cleaning fluid is therefore kept separate from the mixer tank 17 until such a time that the cleaning fluid is used to adjust the viscosity of the ink mixture in the mixer tank 17.

As mentioned above, selection of the fill and drain ports is preferably based upon the orientation of the print head 3. In preferred embodiments this is by way of the print head 3 comprising an orientation sensor configured to determine the orientation of the print head 3. The orientation sensor may be an accelerometer or other sensor. In preferred embodiments, the method comprises the orientation sensor outputting an orientation signal, corresponding to the orientation of the print head 3, to the controller. The controller then processes the orientation signal. The controller subsequently outputs a valve control signal which determines which of the ports are selected as the fill and drain ports.

Turning to Figure 19, a magnified cross-section view of part of the print head is provided. In Figure 19the chamber housing is omitted. Furthermore, as will be appreciated by comparing Figure 19with Figure 3, Figure 19is taken looking roughly into the plane of the page from the view shown in Figure 3 (e.g. such that the grommet 151 obscures part of the PCB 167 behind it). Figure 19thus shows part of the nozzle body 143 and almost all of the charge electrode assembly 146. Again comparing Figure 19with Figure 3, one of the fasteners 156 which secures the charge electrode assembly 146 to the nozzle body 143 is visible.

Figure 19 also shows the nozzle 144 defined by the nozzle body 143. Fasteners 236, 238 which couple the charge electrode 148 to the guide 150 are also visible. Multiple seals are also shown in Figure 19. A first seal 240 is disposed between the guide 150 and the nozzle body 143. The seal 240 takes the form of an O-ring in the illustrated embodiment, but it will be appreciated that other seals may otherwise be used. A further seal 242 is also shown and is disposed between the guide 150 and the charge electrode 148 as part of the charge electrode assembly 146. Again, the further seal 242 takes a form of an O-ring in the illustrated embodiment, but other seals could otherwise be used.

As has previously been described, in use ink is pumped through the nozzle 144 and into the charge electrode 148. The jet of ink breaks up within the charge electrode 148 where a charge is also selectively applied to the stream of ink droplets.

As introduced in connection with Figure 10, the third port 217 and corresponding third conduit 216 are also shown in Figure 19. The third port 217 and third conduit 216 provide another path through which cleaning fluid may be pumped into the chamber, or used cleaning fluid be pumped out of the chamber, (albeit indirectly) in use. The third port 217 is defined in an outer face 143a of the nozzle body 143. A schematic indication of the flow path of (cleaning) fluid through the third conduit 216 is labelled 244 in Figure 19. The flow path 244 is indicative of fluid travelling towards the third port 217, or away from the third port 217, through the third conduit 216. Also schematically indicated on Figure 19is a further fluid flow path 246 of (cleaning) fluid towards, or away from, the third port 217 but through the charge electrode 148. As will be appreciated from the combination of the fluid flow paths 244, 246, fluid can be pumped through the third conduit 216, through the charge electrode 148, and into the chamber, or can be pumped from the chamber out of the third port 217 via the charge electrode 148. The arrangement of first and second seals 240, 242 facilitates fluid being able to travel between the sealed components. Furthermore, the seals 240, 242 prevent the fluid from being able to travel between the components through the seals, save for the fluid flow path 246 (which may be achieved by way of a gap in the seal 240 or other fluid passageway).

The incorporation of the third port 217 and the third conduit 216 is advantageous for a number of reasons. However, in particular, if Figure 19is compared with Figure 8, it will be appreciated that the first port 206, and corresponding first conduit 204, may not be able to drain cleaning fluid from the chamber 164 if the print head points vertically upwards (e.g. if Figure 8 is rotated by around 90° in the anticlockwise direction). Any cleaning fluid, in this orientation, which resides in the channel 189 and in the charge electrode 148 may therefore not be drained following a cleaning cycle. This could undesirably lead to cleaning fluid still being present when the printer is reactivated following a cleaning cycle. Advantageously, by incorporating the third port 217 and third conduit 216, even when the print head is in an orientation as shown in Figure 19 (e.g. pointing vertically upwards) any fluid residing within the channel and charge electrode 148 can still be drained via the third port 217 and third conduit 216. This advantageously means that the chamber should also be largely free of cleaning fluid following a cleaning cycle. Although cleaning fluid could be drained via the nozzle 144, and indeed pumped through the nozzle 144 in use, the nozzle 144 has a very small aperture and the achievable flow rates are therefore comparatively much lower than if a separate port (e.g. the third port 217) is used. Furthermore, it is undesirable to drain the cleaning fluid using the nozzle 144 owing to the risk of debris building up in the small aperture of the nozzle 144. The incorporation of the third port 217 and third conduit 216 thus defines a lowermost drainage point when the print head is in a vertically upright position as shown in Figure 19. As described in connection with Figure 10, the third conduit 216 is in communication with the second conduit 204 such that fluid is pumped through, or drained through, the first and third ports 206, 217 simultaneously.

Finally, Figure 19also shows part of the shaft 128 that is used to rotate the rotatable body of the sealing mechanism (not shown in Figure 19).

Turning to Figure 20, a perspective view of part of the print head is shown. In Figure

20 many components are omitted and so Figure 20 only shows the nozzle body 143 with part of the charge electrode assembly 146 coupled thereto. Furthermore, the guide 150 and charge electrode 148 are shown in a partially cutaway view. The first and second seals 240, 242 are also visible. Figure 20 shows the third port 217 defined in the front face 143a of the nozzle body 143. The third port 217 is thus provided in communication with an interior of the charge electrode 148 such that the interior of the charge electrode 148 can also be cleaned during a cleaning cycle.

Figures 21 and 22 are perspective views of the nozzle body 143 with various conduits/ports visible. Nozzle line 38 (which may be referred to as an ink line) is visible, with a corresponding ink port labelled 38a. Purge line 74 is visible, along with purge port 74a. Lastly, part of the third conduit 216, and third port 217, are also shown. Figure

21 shows part of the grommet 151 , and an outer geometry of a nozzle chamber 143b is highlighted in Figure 22. An exit 143c of the nozzle chamber 143b, which defines the nozzle, is also schematically indicated in Figure 22. In the illustrated embodiment the nozzle is defined by an industrial sapphire comprising an aperture, which is held in place by the grommet 151. The ink port 38a and purge port 74a are in communication with the nozzle via the chamber 143b. The third port 217 extends through the nozzle body 143 but not into the chamber 143b.

Turning to Figure 23, a schematic illustration showing the locations of the ports and conduits within the print head is provided.

Figure 23 schematically shows the nozzle body 143, which defines the nozzle 144, the charge electrode 148 and the chamber 164. Also schematically indicated is a stream of ink droplets 190 extending from the nozzle 144 through the charge electrode 148 and the chamber 164. First and second ends 165, 169 of the chamber 164 respectively are also indicated.

As briefly described in connection with the earlier Figures, the first port 206 is provided proximate the first end 165 of the chamber 164. The first port 206 is in fluid communication with the first conduit 204. The second port 202 is disposed proximate the second end 169 of the chamber 164. The second port 202 is in fluid communication with the second conduit 214. Figure 23 also shows the third conduit 216 branching off the first conduit 204 and connecting to nozzle body 143 via port 217. For completeness, from Figure 19it will be recalled that the third conduit 216 travels partway through the nozzle body 143 and actually exits the nozzle body 143 via the third port 217.

Figure 23 schematically indicates that the first and second ports 206, 202 are diametrically opposed from one another in the chamber 164 and are disposed proximate the first and second ends 165, 169 of the chamber 164 respectively. As indicated by arrows 248, cleaning fluid can be pumped in through the first and second conduits 204, 214 in either direction. That is to say, cleaning fluid may be pumped into the chamber 165 via the first or second conduit 204, 214 and may be drained from the cleaning chamber 164 via the first or second conduits 204, 214. Given the connections of the first and third conduits 204, 216, from the layout shown in Figure 23 it will be appreciated that the directionality of fluid through the third conduit 216 is driven by, and mirrors, the directionality of the first conduit 204. Described another way, when cleaning fluid is pumped through the first conduit 204, fluid will also be pumped through the third conduit 216 and so cleaning fluid will be pumped through the first and third ports 206, 217. The first conduit 204 thus serves two ports. In contrast, in the illustrated embodiment the second conduit 214 serves only a single port: the second port 202. It will also be recalled that the first and second ports 206, 202 are directly disposed in the chamber 164 in the illustrated embodiment. In contrast, the third port 217 is not disposed directly in the chamber 164 per se but is still provided in fluid communication with the chamber 164 via the charge electrode 148.

As has been described previously, by providing this arrangement of ports the chamber 164 can advantageously be drained with the print head in a wider variety of orientations as opposed to, for example, if only a single port were present. Furthermore, in preferred embodiments the selection of which of the ports is used as a fill port, and which is used as a drain port, is preferably driven by an orientation sensor which forms part of the print head. The directionality of the first and second conduits 204, 214 is preferably controlled by a plurality of valves (e.g. control valves 80-83 shown in Figure 10). The plurality of valves is preferably operated to control the direction of fluid through the first and second conduits 204, 214.

For completeness, it will be appreciated that in some embodiments it may be possible to clean the chamber 164 without using both the first and second conduits 204, 214. For example, as shown in Figure 23 in the orientation where the print head faces vertically downwards, the chamber 164 can be filled via the second port 202 only, and then subsequently drained of cleaning fluid, again by the second port 202, without the need for the first conduit 204. However, for the majority of different orientations of the print head, it is anticipated that the use of both the first and second conduits 204, 214 (e.g. in tandem, or in cooperation with one another) will provide advantageous results.

It will also be appreciated that the concept described above may be incorporated in a printer by way of a self-cleaning print head module kit of parts. That is to say, the advantages associated with the multiport chamber can be incorporated in an existing printer by way of a retrofit module. Said kit of parts may comprise a self-cleaning print head with a chamber, nozzle, at least one electrode, a gutter and an orientation sensor. The kit of parts may further comprise a cleaning fluid circuit comprising the first and second conduits and a plurality of valves operable to control the flow of cleaning fluid through the chamber based upon an orientation signal outputted by the orientation sensor.

Turning to Figure 24, a perspective view of a sealing mechanism 400 according to another embodiment is provided. The sealing mechanism 400 shares a number of features in common with the sealing mechanism 124 described earlier in this document, and only the differences will be described in detail.

The sealing mechanism 400 comprises a casing 402 and a rotatable body 404. The rotatable body 404 is rotatable about the axis of rotation 406 between a first and second configuration. In Figure 24 the rotatable body 404 is shown in a first configuration in which an ink path is defined across the rotatable body 404 through an ink aperture 408 defined in the casing 402. The casing 402 thus defines the ink aperture 408, selectively sealable by the rotatable body 404, and an ink channel 409 upstream of the rotatable body 404.

A notable difference of the sealing mechanism 400 is that the rotatable body 404 comprises an integral gutter 410. The integral gutter 410 comprises a gutter aperture 412 which is defined in the rotatable body 404 itself. The gutter aperture 412 is recessed with respect to the surrounding surface of the rotatable body 404. This is to protect the gutter 410 from damage as the rotatable body 404 is rotated in use. The recessed nature of the gutter aperture 412 also means that a gap is defined through which fluids can pass (e.g. cleaning fluids or dirty cleaning fluids) such that the gutter aperture 412 can be used as a conduit to drain the chamber or fill the chamber with cleaning fluid during a cleaning cycle. The gutter aperture 412 can thus function as a drain/filling port for the chamber. The gutter aperture 412 can thus replace the (second) port 202 (see Figure 23) defined in the chamber. Advantageously, the number of conduits within the umbilical can thus be reduced. Alternatively, the gutter aperture 412 could provide an additional drain/filling port, for the chamber, in addition to the second port 202. Where the gutter aperture 412 provides an additional drain/filing port, the second port 202 is preferably provided in a different location to the gutter aperture 412. For example, if the gutter aperture 412 were provided proximate a lower side of the chamber 162 shown in Figure 7, the second port 202 may be provided proximate an upper side of the chamber 162 (but still at the same end of the chamber 162). It will be appreciated that it may be necessary to selectively place the gutter aperture 412 in fluid communication with the solvent tank 50 to avoid the used cleaning fluid being returned to the mixer tank 17.

The rotatable body 404 further comprises an engagement feature 416. In the illustrated embodiment the engagement feature 416 takes the form of a slot. The engagement feature can advantageously be used to unstick the rotatable body 404 if it becomes stuck in use. In other embodiments an alternative engagement feature to the slot, such as a hexalobular slot or a hexagonal recess, could otherwise be used. Alternatively, the engagement feature 416 may be omitted. It will also be appreciated that an engagement feature as described above may be incorporated in any of the sealing mechanism embodiments described in this document.

The rotatable body 404 further comprises a domed end 418. Domed end 418 opposes the engagement feature 416 in the illustrated embodiment. The domed end 418 tapers into the rest of the rotatable body 404. That is to say, the end of the rotatable body 404 may be described as being defined by a combination of a taper and a dome. Although not visible in Figure 24, a gutter conduit extends from the gutter aperture 412 through the rotatable body 404 and through the domed end 418, terminating at an aperture defined in the domed end 418. This defines a fluid pathway by which the gutter aperture 412 can be selectively provided in fluid communication with the rest of the ink system, whether for printing in normal use (e.g. for transporting ink droplets not used for printing back to the mixer tank) or for cleaning or draining. The domed end 418 can advantageously be used to define a sealing interface with a corresponding cooperating surface in, for example, a cap of the casing 402.

Turning to Figure 25, the sealing mechanism 400 is shown with the rotatable body 404 in a second, closed configuration. In the second configuration shown in Figure 25 the rotatable body 404 thus closes the ink aperture 408 of the casing 402. Figure 25 shows the rotatable body 404 further comprises a utility slot 420. The utility slot 420 is in communication with the ink slot 414, the ink slot 414 extending through an entirety of the rotatable body 404. Unlike the ink slot 414, the utility slot 420 does not extend through the entirety of the rotatable body 404. Instead, the utility slot 420 extends only partway through. As indicated by the arrows 422, 424, the combination of the ink slot 414 and the utility slot 420 defines a fluid pathway through which cleaning fluid can be pumped or drawn into the chamber or used cleaning fluid be pumped or drawn out of the chamber via the gutter aperture 412. The utility slot 420 thus allows the gutter 410 to be used as a lowest cleaning/draining port. The gutter 410 can thus also serve as a drain port, draining the chamber through the utility slot 420 even when the rotatable body 404 is in the second configuration. Owing to the gutter aperture 412 being recessed relative to the surrounding surface of the rotatable body 404, the rotatable body 404 can still seal the ink aperture 408 of the casing 402, such that cleaning fluid does not escape from the casing 402 (e.g. around the rotatable body 404) but can still travel through the rotatable body 402.

In some embodiments, the gutter aperture 412 may define an effective second port of the cleaning chamber (e.g. second port 202 as shown in Figure 10). That is to say, the second port may be defined by the gutter. However, as initially described, in some embodiments the first, second and (optionally) third ports of the chamber are separate to that of the gutter.

Turning to Figure 26a, a schematic illustration of a chamber arrangement 426 is provided. The chamber arrangement 426 comprises a chamber 427. First and second conduits 428, 429 are connected to the chamber 427 via respective first and second ports 428a, 429a. The chamber 427, conduits 428, 429 and ports 428a, 429a are indicative of the chamber, conduits and ports described elsewhere in this document. A volume of fluid 430 is also illustrated as being contained within the chamber 427, indicative of cleaning fluid during a cleaning cycle.

The chamber 427 is generally cuboidal. The first port 428a is disposed on a first (lower) surface 427a of the chamber 427. The first conduit 428 extends generally perpendicularly from the first surface 427a. The second port 429a is disposed on an second (upper) surface 427b of the chamber 427. The second conduit 429 extends generally perpendicularly from the second surface 427. The first port 428a is disposed proximate a first end 431 of the chamber 427. The second port 429a is disposed proximate a second end 432 of the chamber 427. The first and second ends 431, 432 of the chamber 427 oppose one another. The first and second ports 428a, 429a are diametrically opposed from one another as they are disposed on opposing surfaces 427a, 427b of the chamber 427 and proximate diagonally opposing corners 433, 433 of the chamber 427. As will be appreciated from Figure 26a, draining the fluid 430 through the first port 428a and first conduit 428 would fully drain the chamber 427 in the illustrated orientation. This is owing to the first port 428a being the vertically lowest port, and because the chamber 427 is in a flat orientation resting on the first (lower) surface 427a. For reasons mentioned elsewhere in this document, it is also desirable to fill the chamber 427 with fluid via the first port 428a and vent air from within the chamber 427 via the second port 429a.

Figures 26b and 26c show the chamber arrangement 426 from the side and end, and show the first and second conduits 428, 429 extending normal to the lower and upper surfaces 427a, 427b respectively.

Turning to Figure 27a, the chamber arrangement 426 is shown in a different orientation. In Figure 27a, the chamber arrangement 426 is shown resting on a fourth (lower) surface 427d. For completeness, a third (upper) surface 427d is also labelled. Owing to the different orientation, the first port 428a, and first conduit 428, are no longer in fluid communication with the volume 430 of fluid. Draining fluid through the second port 429a, and second conduit 429, is therefore desirable in the illustrated orientation. Again, this is owing to the second port 429a being vertically lower than the first port 428a. Again, it is also desirable to fill the chamber 427 with fluid using the second port 429a and venting air from within the chamber 427 via the first port 428a.

Figures 27b and 27c show the chamber arrangement 426 from the side and end, and show the first and second conduits 428, 429 extending normal to the lower and upper surfaces 427a, 427b respectively.

Turning to Figure 28a, the chamber arrangement 426 is shown in a different orientation again. In Figure 28a, the chamber arrangement 426 is shown resting on a fifth (end) surface 427e generally corresponding to the first end 431. For completeness, a sixth (end) surface 427f is also labelled. Owing to the different orientation, the first port 428a, and first conduit 428, are once again provided in fluid communication with the volume 430 of fluid. Draining fluid through the first port 428a, and first conduit 428, is therefore desirable in the illustrated orientation. Again, this is owing to the first port 428a being vertically lower than the second port 429a. Again, it is also desirable to fill the chamber 427 with fluid using the first port 428a and venting air from within the chamber 427 via the second port 429a.

Figures 28b and 28c show the chamber arrangement 426 from two different sides, and show the first and second conduits 428, 429 extending normal to the lower and upper surfaces 427a, 427b respectively.

Turning to Figure 29a, a perspective view of a schematic illustration of an alternative housing 500 is provided. The housing 500 is shown in a partially transparent view to aid understanding. Figure 29b shows a cross-section side view of the housing 500.

The housing 500 defines a chamber 502, which may be referred to as a cleaning chamber. The chamber 502 is defined in a central region of the housing 500. Both the chamber 502, and housing 500 more generally, are generally cylindrical. The chamber 502 has a first end 504 and a second end 506. Disposed proximate the first end 504 is a first port 508 which comprises a plurality of subports 508a, 508b etc. Similarly, disposed proximate the second end 506 of the chamber 502 is a second port 510 which comprises a plurality of subports 510a, 510b etc. The pluralities of subports may otherwise be described as an array of ports. Each of the first and second pluralities of subports 508a, 508b, 510a, 510b extend around the chamber 502 in a circumferential manner.

The housing 500 further comprises a first conduit 512 which is in fluid communication with the first port 508 (e.g. and so each of the associated plurality of subports 508a, 508b etc.). The housing 500 further comprises a second conduit 514 which is in fluid communication with the second port 510 (e.g. and so each of the associated plurality of subports 510a, 510b etc.). The pluralities of subports 508a, 508b, 510a, 510b provide a similar functionality to the diametrically opposed ports described in connection with earlier embodiments insofar as there are individual subports within the pluralities which are diametrically opposed to one another. Fluid can thus be drained from the chamber 502 with the overall print head provided in a wider variety of orientations than if a single port (e.g. single aperture) were incorporated. Figures 29a and 29b also show first and second channels 516, 518 which are in communication with the first and second arrays of ports 508, 510 respectively. The first and second channels 516, 518 interpose the first and second conduits 512, 514 and the respective ports 508, 510 to provide fluid communication therebetween.

Turning to Figure 30, a perspective view of part of a housing 600 according to another embodiment is provided. The housing 600 defines a first conduit 502 in a bulkhead 503. The housing 600 defines a chamber (only part of which is shown in Figure 30) and a first subport 504 is in communication with that chamber. A corresponding, opposing subport is provided in the other side of the bulkhead 503 but is not visible in Figure 30. The subports 504 are also in communication with the first conduit 502 via a corresponding subport conduit 506. A combination of the two subports 504 provided at each side of the bulkhead 503 facilitates the draining of cleaning fluid from either side of the bulkhead 503. Described another way, the risk of cleaning fluid not being drained, owing to it residing in a pocket or similar that is not in communication with the first conduit 502, is reduced. Fluid can be drained from a greater variety of regions within the chamber. The combination of the first and second subports 504 may thus form one of the ports shown in the fluid layout of Figure 23, for example.

Turning to Figure 31, a perspective view of a print head 800 according to another embodiment is provided. For completeness, the print head 800 shares various features in common with the print head 3 shown in Figures 2 to 8, and only the differences relative to the print head 3 will be described in detail. The print head 800 can also be used in the printer 1 of Figure 1 and in the fluid system shown in Figure 10 (albeit with a change of location of the heater 36, as will be described below). Equally, the description provided in connection with Figures 10 to 30 (e.g. including the flow chart 300 and associated method) also applies, where appropriate, to the print head 800. The print head 800 is thus also a self-cleaning print head.

At a first end 802 the print head 800 comprises a connector 804 by which the print head 800 is connectable to the umbilical. At a second end 806 of the print head 800 an end cap 808 is provided. There are a number of differences between the end cap 808 of the print head 800 and the earlier embodiment, which will be described in detail below. However, an ink aperture 810, through which deflected ink is ejected in operation, is still defined through the end cap 808. An outer shell 812 is generally cylindrical and extends along a majority of the print head 800. A sealing cover 814 extends adjacent the outer shell 812, proximate the second end 806 of the print head, and extends around, and slightly beyond, the end cap 808. The combination of the outer shell 812 and sealing cover 814 define an outer cover of the print head 800, the outer cover being removable for maintenance.

Turning to Figure 32, a perspective view of the print head 800 is provided with the outer shell 812 omitted. As will be appreciated by comparing Figure 32 with Figure 3, there are various similarities between the print head 800 and print head 3. Again, only the differences will be described in detail.

Briefly, the print head 800 comprises a chassis 816 to which various other components are mounted. A motor 817, a brushless DC motor in this embodiment, is also mounted to the chassis 816 and drives rotation of a rotatable body as will be described in detail below. In other embodiments an actuator that drives rotation of the rotatable body may otherwise comprise a stepper motor, a linear motor, a solenoid or other suitable actuator. A solenoid valve 818 and valve block 820 are also mounted to the chassis 816. A chamber housing 822 is connected to the chassis 816 and, at the other end, is coupled to a sealing mechanism 824. The sealing mechanism 824 may be described as an example of a cap assembly. Other examples of cap assemblies may not be sealing mechanisms. For example, a non-self-cleaning print head may comprise a cap assembly, but not use a sealing mechanism.

One difference between the print head 800 and the print head 3 can be observed by comparing Figure 32 with Figure 5. Unlike the print head 3, in the print head 800 the chamber housing 822 is connected to the chassis 816 and the sealing mechanism 824. That is to say, multiple housing components are eliminated by using the single chamber housing 822. Furthermore, the chamber housing 822 can be detached from the chassis 816, and moved away therefrom, by removing four fasteners, two of which are visible in Figure 32 and labelled 826, 828 respectively. This is advantageous for at least the reason that various components for which servicing may be of interest (e.g. parts of the sealing mechanism 824) are mounted to the chamber housing 822. These components can also be readily detached from the chassis 816 to facilitate servicing.

Turning to Figure 33, an alternative perspective view of the print head 800 is provided with the chamber housing 822 also omitted. Various components already described are visible in Figure 33, along with some further components. A nozzle cradle 830, to which a nozzle body 832 is coupled, is visible in Figure 33. The nozzle cradle 830 and nozzle body 832 form part of a nozzle assembly 834 (which further comprises a nozzle, not visible in Figure 33). Part of a charge electrode 860 is also visible in Figure 33. As will be described in connection with Figure 35, the charge electrode 860 is coupled to the nozzle assembly 834 (specifically the nozzle body 832 thereof). For reasons which will be described below, in some embodiments the nozzle cradle 830 may be omitted.

The print head 800 further comprises a socket plate 836. The socket plate 836 is coupled to the chamber housing 822, and defines part of a ball joint by which a combined charge electrode and nozzle assembly can be adjusted to align an ink jet with a gutter (the gutter not being visible in Figure 33, but shown labelled 844 in Figure 34). The adjustment takes place by way of the nozzle body 832 being adjusted with respect to the (fixed) nozzle cradle 830 (the nozzle cradle 830 being coupled to the chamber housing 822). One such cam fastener is shown in Figure 34 labelled 833. A second cam fastener is obscured from view in Figure 34 but is generally located in the underside of the nozzle cradle 830. The combination of the two cam fasteners provides X-Y adjustment of the nozzle body 832, and any coupled components (e.g. the charge electrode), with respect to the nozzle cradle 830. The combined charge electrode and nozzle assembly is also constrained by the ball joint defined by the socket plate 836 (and the charge electrode 860 - see Figure 35).

Returning to Figure 33, the socket plate 836 also effectively caps one end of a (cleaning) chamber defined by the chamber housing (visible in Figure 35). Although the socket plate 836 is coupled to the chamber housing 822 by fasteners in the illustrated embodiment, it could otherwise be coupled to the chamber housing 822 using an alternative coupling, such as by ultrasonic welding. In further alternative embodiments, the socket plate 836 may effectively be merged with the chamber housing 822 (e.g. by way of a single-piece moulding). In such embodiments, a combined charge electrode and nozzle assembly is coupled directly to the chamber housing.

Although an adjustment mechanism is shown in the illustrated embodiment, in other embodiments the adjustment mechanism (e.g. the ball joint, the cam fasteners, nozzle cradle etc.) may be omitted. Instead, the alignment of the nozzle, with respect to the gutter, may be set in-factory (e.g. using a jig) and then (permanently) fixed in place (e.g. permanently aligned). This advantageously eliminates the need for the adjustment mechanism whilst still permanently providing alignment of the nozzle (and so jet) and gutter.

Turning to Figure 34, an alternative perspective view of (part of) the print head 800, in the configuration shown in Figure 33 (i.e. with some components omitted) is provided. Figure 34 shows the components located between the socket plate 836 and the sealing mechanism 824 in more detail.

Briefly, Figure 34 shows a nozzle heater assembly 838 which is coupled to the nozzle body 832. The nozzle body assembly 838 comprises a PCB, thermal fuse and a resistive heater. Advantageously, the nozzle heater assembly 838 can selectively heat ink in the nozzle body 832 (which may be described as a close coupled nozzle heater). Put another way, ink in the nozzle body 832 can be directly heated, in contrast to heating the ink further upstream of the nozzle body 832. This is primarily to improve the control of the viscosity of the ink ejected from the nozzle. Ink viscosity reduces with temperature, so if the ink in the nozzle is colder than expected, it is also thicker than expected. An incorrect viscosity corrective action may be applied (e.g. heating the ink) if the system detects the viscosity is lower than expected. Heating ink in the nozzle body 832 reduces the risk, as has been observed in other implementations, that the ink temperature decreases, between a point of heating and the point of ejection by the nozzle, in certain ambient conditions (owing to the ink being heated at a point further away from the nozzle itself). Improved control of the ink temperature thus results.

The nozzle heater assembly 838, specifically the heater thereof, replaces the heater 36 shown in the fluid circuit of Figure 10. As such, in contrast to the fluid circuit shown in Figure 10, for the fluid circuit of the print head of the present embodiment there is no nozzle line between the heater and the nozzle body. Instead, the heater is directly mounted to the nozzle body itself.

Figure 34 shows a deflection electrode 840 (e.g. a high voltage electrode) and a corresponding low voltage electrode 842 (e.g. a grounded electrode). A combination of the electrodes 840, 842 may be referred to as a pair of deflection electrodes. The gutter 844 is also visible in Figure 34, the gutter 844 being provided downstream of the pair of deflection electrodes. Of note, the gutter 844 is not coupled to the sealing mechanism 824. As such, the sealing mechanism 824 can be removed whilst leaving the gutter 844 in position.

Also partly visible in Figure 34 is shaft 846. Shaft 846 is driven by the motor 817, albeit by a gearing arrangement (not visible in Figure 34). An end of the shaft 846 proximate sealing mechanism 824 comprises a domed tip (e.g. a hex-ball style arrangement in the illustrated embodiment). The domed tip is received by a corresponding socket 850 which forms part of the sealing mechanism 824. The socket 850, in turn, drives a rotatable body to selectively open and close an ink aperture defined by the sealing mechanism 824. Advantageously, the incorporation of the domed tip of the shaft 846 provides a greater alignment tolerance between the sealing mechanism 824 and the shaft 846. This is of particular benefit where the sealing mechanism 824 is detached for servicing, and is then reattached to the rest of the print head 800 following servicing.

Also visible in Figure 34 is connector block 852. The connector block 852 is coupled to the nozzle body 832 by a fastener 854. The connector block 852 comprises three barbs (one of which is labelled 853). Each barb is connectable to a different fluid line (although in Figure 34 the barbs are shown without a fluid line connected thereto, for ease of visibility) and provides a different functionality. One barb provides an ink supply to the nozzle body 832, another barb provides a connection to a purge port in the nozzle body 832, and a third barb provides further communication to a third port. The third port is in fluid communication with the chamber, and is incorporated to facilitate draining cleaning fluid from, supplying cleaning fluid to, and providing air to, an internal chamber of the charge electrode. The connector block 852 defines a plurality of channels internally (e.g. one for each barb). Advantageously, by removal of the fastener 854, the connector block 852, with barbs and fluid lines attached, can be decoupled from the nozzle body 832. This is advantageous for reasons of being able to more readily service components of the print head 800 without having to destructibly detach the barbs and fluid lines. Instead, the connector block 852, and connected fluid lines, can be detached from the nozzle body 832 and then re-attached thereto (e.g. in a non-destructible [i.e. modular] manner).

Turning to Figure 35, a cross-section side view of the print head 800 in the configuration shown in Figure 32 (i.e. with the outer shell admitted) is provided. The cross-section is taken about the plane 859 schematically indicated in Figure 32. Figure 35 shows a (cleaning) chamber 856 within the print head 800.

Beginning from the right hand side of Figure 35, the nozzle body 832 is shown, as is the nozzle cradle 830. A nozzle 858 is also labelled, the nozzle 858 being defined by a nozzle plate 835. The nozzle plate 835 is, in turn, coupled to the nozzle body 832 by a retaining ring 839. The charge electrode 860 is also visible, the charge electrode 860 being received by a charge electrode mount 862. The charge electrode mount 862 is coupled to the nozzle body 832 by locking ring 864. By virtue of the locking ring 864, the nozzle body 832 and charge electrode 860 are (adjustably) coupled to one another (via the charge electrode mount 862). The coupled charge electrode and nozzle assembly is then received by the socket plate 836. As labelled 866, a ball joint is defined between the charge electrode 860 and the socket plate 836. This provides a degree of adjustment of the (combined) charge electrode and nozzle assembly with respect to the socket plate 836 (to facilitate alignment of the ink jet with gutter 844). For completeness, part of an ink jet is schematically indicated in Figure 35 and labelled 837.

Of note, a particular advantage is that the nozzle 858 and gutter 844 are both coupled to the chamber housing 822. Put another way, the nozzle 858 and gutter 848 are fixed to the same substructure within the overall print head (the nozzle 858 via the nozzle body 832). The alignment of the nozzle 858 with respect to the gutter 844 can therefore be adjusted (e.g. to align the jet produced by the nozzle 858 with the gutter 844) and these components then fixed in place, without needing further adjustment in the future. Put another way, a single adjustment to align the nozzle 858 with the gutter 848 provides a permanent alignment therebetween. This could be factory-set, whilst still allowing servicing of other components (e.g. the sealing mechanism 824) around the nozzle 858 and gutter 844). As mentioned above, the ball joint 866 defined between the charge electrode 860 and the socket plate 836 provides the aforementioned adjustment of the (combined) charge electrode and nozzle assembly with respect to the gutter 844.

Turning to discuss the chamber 856, like in the previous embodiment the electrodes 840, 842 are disposed in the chamber 856. By virtue of sealing the chamber 856, and at least partially filling the chamber 856 with cleaning fluid, these components can thus be cleaned. Other components which may be cleaned as part of a cleaning cycle include the gutter 844 and rotatable body 844. The chamber 856 may be referred to as a cleaning chamber.

A first portion 856a of the chamber 856 is defined by the chamber housing 822. A second portion 856b of the housing 856 is defined by a casing 870. The casing 870 forms part of the sealing mechanism 824. It is with respect to the casing 870 that the rotatable body 864 can rotate to selectively seal the chamber 856 (e.g. by closing an ink aperture defined by the casing 870). The endcap 808 is shown disposed over the casing 870. This will be described in detail in connection with the later figures. The rotatable body 868 is actuated, by shaft 846, via a gearing arrangement generally labelled 872. Again, this will be described in further detail below.

Turning briefly to describe the ports of the chamber 856: the chamber 856 comprises a first port 876 and a second port 874.

The second port 874 is defined by the casing 870. As shown in Figure 29 the second port 874 is provided in a top left-hand corner of the chamber 856. Part of the first port

876 of the chamber 876 is visible in Figure 35. The first port 876 comprises a plurality of subports (e.g. 876a, 876b etc.) and is defined by a combination of the chamber housing 822 and the socket plate 836. Specifically, the subports which form the first port 876 (and so the first port 876 more generally) are partly defined by castellations on the socket plate 836. Castellations is intended to mean recesses, or grooves, disposed about a perimeter (e.g. circumferential rim 878). A combination of the castellations, and a frustoconical surface 823 of the chamber housing 822, define the first port 876 (or, put another way, define the plurality of subports). The subports extend in a circular manner (e.g. generally around the nozzle 858, and so ink jet ejected therefrom). The subports are in fluid communication with an annular channel 877. The annular channel

877 is effectively disposed behind the subports in the orientation shown in Figure 29 (e.g. towards the nozzle 858). The annular channel 877 is also defined by a combination of the socket plate 836 and the chamber housing 822 (specifically the frustoconical surface 823 thereof). The annular channel 877 is, in turn, in fluid communication with a conduit 879 (e.g. corresponding to the first conduit 204 in Figure 10). The subports advantageously provide multi-directional drainage and filling of the chamber 856 (e.g. cleaning fluid can be drained from the chamber 856, via the first port 876, with the print head 800 in a wider variety of orientations). A further advantage is that when air is pumped into the print head 800 during operation, to balance a pressure reduction due to the gutter 844 drawing air from within the chamber 856, the annular arrangement of subports reduces disruption to the ink jet by virtue of diffusing air around the jet. This is in contrast to the first port consisting of a single aperture. As will be appreciated from Figure 35, the first port 876 is (partly) provided at a lower righthand corner of the chamber 856. The first and second ports 876, 874 are thus diagonally opposed with respect to one another, by virtue of at least one of the subports of the second port 874 diagonally opposing the second port 874. This advantageously provides desirable draining capability, irrespective of the orientation of the print head 800. That said, owing to the first port 876 defining the plurality of subports 876a, 876b etc., providing a wider range of drainage directionality, in some embodiments the first and second ports 876, 874 may not be diametrically opposed with respect to one another.

Like in the print head 3 of the earlier embodiment, a third port is also provided, in fluid communication with the chamber 856 but not in the chamber per se, between the nozzle body 832 and the charge electrode 860. Although not visible in Figure 35, the third port is defined in an outer face 880 of the nozzle body 832. The third port allows cleaning fluid to drain from within the charge electrode 860 when the print head 800 is in a generally upwards orientation. Fluid within a cavity generally defined between the charge electrode 860 and nozzle body 832 would otherwise remain, owing to the fluid level being vertically beneath the first port 870 (e.g. said fluid could not be drained via the first port 870). That said, like the first embodiment, incorporation of the third port is optional. Also like the first embodiment, the third port is preferably provided in fluid communication with the first port 870 such that the third port drainage/filling functionality mirrors that of the first port 870. Put another way, the first port 870 and third port are preferably provided in fluid communication with a (common) first conduit such that cleaning fluid is contemporaneously filled through, or drained via, the first port 870 and third port. However, again, this is an optional feature and the first and third ports may be independently controllable (e.g. by virtue of connection to separate conduits). The third port is provided in fluid communication with the charge electrode 860, specifically cavity 861 thereof, via a plurality of castellations 882 defined by the charge electrode mount 862. Only one castellation is labelled 882 in Figure 35, but the castellations extend in an annular manner around the nozzle 858. The combination of the castellations 882 and the charge electrode mount 862 define a plurality of channels, which generally extend in an axial direction and are distributed in an annular manner. Two such channels are labelled 877a, 877b. These castellations 882, and corresponding plurality of channels 877a, 877b, provide similar advantages to the subports defined by the first port 876, as well as further advantages. For example, solvent exits the plurality of channels generally perpendicularly to the ink jet and can therefore wash the front face of the nozzle 858. Because solvent can be provided to the front face of the nozzle 858, the nozzle 858 can be back flushed to remove debris if a blockage occurs (e.g. solvent drawn from the front face of the nozzle 858 towards, and into, the nozzle body 832). Where air is provided through the third port (e.g. positive air, during printing), the air is diffused through the (downstream) plurality of channels at a lower velocity than it would be through a single port. The air is therefore less likely to influence the inkjet provided by the nozzle 858, and so less likely to affect drop position/print quality (which could otherwise result from undesirable interference with the ink jet). The plurality of channels improve the ability to drain solvent from a wider range of print head orientations/angles (e.g. in comparison to a single port location).

Turning to Figure 36, a perspective view of the sealing mechanism 824 shown in Figure 30 is provided in isolation. Figure 36 is generally from a chamber-side of the sealing mechanism 824.

Briefly, Figure 36 shows the socket 850 which receives the shaft (specifically the domed tip thereof) to drive the rotatable body 868. Part of a housing 888 of a gearbox is also visible, and received by the casing 870. A cavity 890, which defines a second portion of the chamber 856, is also labelled. The second port 874 is shown in fluid communication with the cavity 890. Similarly, an aperture 892, in fluid communication with the second port 874 via an internal conduit, is also defined by the casing 870. Dowels which are used to align the casing 870 with respect to the chamber housing, and apertures through which fasteners are received to secure the casing 870 to the chamber housing, are also visible in Figure 36. Turning to Figure 37, a cross-section perspective view of a region of interest around the first port 876 is provided. Various features already described in connection with Figure 34 are visible, and associated description will not be repeated here. However, added for ease of reference is a schematic marker 980 which indicates the possible directions of fluid travel across the first port 876. That said, it will be appreciated that the marker 980 is only indicative of fluid travel through one of the various sub ports defined by the first port 876. A first conduit 982 defined through the chamber housing 822 and provided in fluid communication with the annular channel 877 is also shown. The first conduit 982 generally corresponds to the first conduit 204 as labelled in the top right hand region of Figure 10.

Turning to Figure 38, an alternative cross-section view is provided. The Figure 38 view is taken about a plane normal to a longitudinal axis of the print head, at a point between where the socket plate 836 meets the chamber housing 822.

Figure 38 shows the annular arrangement of castellations distributed around the socket plate 836 (specifically around circumferential rim 878). Two of the plurality of subports, 876a, 876b, defined by (two of) the castellations are labelled. Like Figure 37, schematic marker 980 shows the possible fluid directionalities along the first conduit 982, through the first port 876. Although not schematically indicated in either Figure 37 or 38, it will be appreciated that the fluid 980 may also travel in an annular direction, through the annular channel 877 (see Figure 37) to exit via subports located further away from the first conduit 982. Similarly, and has been previously described, as well as being filled through the first port 876, and associated subports 876a, 876b (among others), fluid can also be drained through these features. Furthermore, as well as cleaning fluid (e.g. solvent) being passed through the first port 876, air can also be passed through the first port 876 to facilitate drying the chamber (or to provide pressure balancing, within the print head, during operation of the gutter).

Briefly, Figure 38 also shows the first conduit 982 being partly defined by a first port connector block 984. The first port connector block 984 shares various features in common with the connector block 852 labelled in connection with Figure 34, albeit with fewer barbs (the first port connector block 984 comprising only a single barb, and corresponding internal channel). For completeness, the first port 876 generally corresponds to either of the first port 508 and the second port 510 shown and described in connection with Figures 29a and 29b.

Turning to Figure 39, a perspective view of the socket plate 836 in isolation is provided. Figure 39 shows the socket plate comprising a plate 986 and a socket 988 which projects therefrom. It is the socket 988 which comprises the (intermittent) circumferential rim 878 on which castellations, which are distributed in an annular manner, are disposed. Two of the subports defined by the castellations 878, forming part of the first port, are labelled 876a, 876b.

Turning to Figure 40, a magnified cross-section side view of part of the print head is provided. Figure 40 focuses on the combined charge electrode and nozzle assembly. As previously described, the charge electrode 860 is coupled to the nozzle body 832 by a charge electrode mount 862 which is, in turn, coupled to the nozzle body 830 by locking ring 864. The charge electrode 860 is coupled to the charge electrode mount 862 by way of an engagement (e.g. a snap-fit, or interference fit). However, in other embodiments an equivalent charge electrode mount could be moulded over the charge electrode. The charge electrode 860 could comprise a conductive plastic bore, or could be a sputtered glass tube (e.g. an Indium Tin Oxide [ITO] sputtered glass tube). Before the locking ring 864 is secured, the charge electrode 860 and charge electrode mount 862 (subassembly) can be rotated with respect to the nozzle body 832 (and so nozzle 858 and inkjet).

Figure 40 also shows a repeating array of castellations 882 which are defined by the charge electrode mount 862. The castellations 882 are somewhat similar to the castellations described in connection with the socket plate 836 (and rim 878). Defined by the castellations 882 of the charge electrode mount 882, in combination with a projecting portion 833 of the nozzle body 832, are a plurality of channels, four of which are labelled 877a-d. The channels 877a-d provide fluid communication between the front face 832 of the nozzle body 832 and the cavity 861 defined by the charge electrode 860. For ease of reference, a cross-section view of the charge electrode mount 862 in isolation is shown in Figure 42. An annular channel 992 extends around the front face 880 of the nozzle body 832. The annular channel 992 may be described as interposing the third port, defined in the front face 880, and the channels 877a-d. Turning to Figure 41 , a perspective cross-section view of the features shown in Figure 40 is provided.

Figure 41 shows the annular channel 992 which interposes a third port 998 and the channels 877a-d. A schematic marker 993 shows possible directionality of fluid travel between the third port 998 (specifically the annular channel 992) and the cavity 861 defined by the charge electrode 860 (via the channel 877d). It will be appreciated that corresponding fluid paths, between the cavity 861 and annular channel 992 (and so third port 998) exist through each of the other channels (e.g. 887a, 887b etc.).

Turning to Figure 42, a perspective cross-section side view of the charge electrode mount 862 in isolation is provided. Charge electrode mount 862 comprises a cavity 994 which is configured to receive the charge electrode 860 (not shown in Figure 42 but shown and labelled in Figure 41). Annular channels 877a-d are labelled in Figure 42, and are shown axially extending through part of the charge electrode mount 862. As previously described, the channels 877a-d are at least partly defined by castellations (e.g. the castellation 882 defining the channel 887a, castellation 996 defining channel 887b etc.). Faces defined by (e.g. between) the castellations (e.g. see face 882a defined between castellations 882, 996) define an intermittent annular surface by which the charge electrode mount 862 can be placed over the projecting part (e.g. 833 in Figure 41) of the nozzle body 832 to locate it therewith. The presence of the channels 877a-d means that fluid can still effectively travel across this alignment boundary to, or from, the third port. An intermittent annular rim is defined between adjacent castellations, with two portions of the rim labelled 997, 999.

Turning to Figure 43, a magnified perspective cross-section view of the print head is provided at a plane which generally corresponds to the front face 880 of the nozzle body 832. Figure 43 shows the third port 998 defined in the front face 880 of the nozzle body 832. Chamber housing 822, shaft 846, nozzle cradle 830 and nozzle heater assembly 838 are also visible, as is the connector block 852. The annular channel 992, generally defined between the projection portion 833 of the nozzle body 832 and a gasket 995, is also indicated in Figure 43.

Turning to Figure 44, a further perspective cross-section view like that shown in Figure 43 is provided but taken at a plane further away from the nozzle body 832. Figure 44 thus shows a section through parts of the locking ring 864, the charge electrode mount 862 and the projecting portion 833 of the nozzle body 832. Channels 877a-d defined by the charge electrode mount 862 are also visible, the channels being defined between the charge electrode mount 862 and the projecting portion 833 of the nozzle body 832.

Turning to Figure 45, a perspective cross-section view is again provided, but at a position further away from the nozzle body 832 (e.g. towards the gutter). Figure 45 thus shows (distal ends of) the channels 877a-d (i.e. located furthest away from the nozzle body 832). Figure 45 shows a point on a longitudinal extent of the print head where the channels 877a-d are in communication with one another and in communication with the cavity defined by the charge electrode (not visible in Figure 45 but shown in Figure 46 - cavity labelled 861).

Turning to Figure 46, a perspective cross-section view is provided at a further position, further away from the nozzle body 832. Figure 46 thus shows the charge electrode 860 received by the corresponding cavity in the charge electrode mount 862. The cavity defined by the charge electrode 860 is also labelled 861. None of the plurality of channels are visible in Figure 46 owing to them being obscured by the charge electrode 860 and charge electrode mount 862.

Returning briefly to Figure 41, as has previously been described the presence of the third port 998 advantageously means that fluid can be drained from the cavity 861 defined by the charge electrode 861 when the print head is in certain orientations (in which the fluid would otherwise remain due to the relative position of the first port). It will be recalled that marker 993 indicates the possible fluid path (for draining, the fluid would pass from the cavity 861 towards the third port 998). However, a further advantage of the third port 998 is that an automatic backflush of the nozzle 858 is facilitated. As is known, in use ink is ejected through the nozzle 858 under pressure. Particulates in the ink mixture, such as ink sediment, can sometimes undesirably build up behind, and block, the nozzle 858. It is therefore desirable to be able to perform a backflush process in which solvent is received from the charge electrode 860 side (e.g. front) of the nozzle 858, across the nozzle 858 and into the nozzle body 832 (e.g. to the rear of the nozzle) to dislodge, and transport, any such particulates. This is typically carried out with the nozzle 858 under vacuum. With reference to Figure 10, the gutter pump 46 is activated when purge valve 75, and so purge line 74, are open. In other words, a vacuum is applied to the back of the nozzle 858 (e.g. inside the nozzle body 832).

A problem encountered with existing solutions is that an operator has to manually inject (e.g. ‘squirt’) solvent into the nozzle (e.g. from the gutter side) to be able to provide solvent from that direction (e.g. from a front face of the nozzle, towards the nozzle body). However, by incorporation of the third port 998 proximate the nozzle 858, when cleaning fluid is pumped through the third port 998, and through the channels 887a-d, where the nozzle 858 is under vacuum a proportion of the cleaning fluid is drawn back across the nozzle 858 (e.g. into the nozzle body 832) without the need for manual intervention. Put another way, the third port 998 means that cleaning fluid can be supplied to a downstream end of the nozzle 858 without the need or an operator to manually inject solvent into the nozzle. This is desirable for reasons of being able to automate a backflush operation, avoiding otherwise necessary disassembly of components of the print head. Furthermore, this operation can occur without the physical movement of any of the components surrounding the nozzle 858, with the only actuation being the valves and pumps of the fluid circuit, and (optional) closure of the rotatable body of the sealing mechanism (e.g. to seal the chamber). The cleaning fluid supplied for an automatic backflush process is preferably virgin (e.g. unused) solvent. This reduces the risk of contaminants entering the nozzle 858. In some embodiments, the incorporation of the plurality of channels 887a-d, distributed in an annular manner, provides a distribution of cleaning fluid around the front of the nozzle 858 during an automatic backflush process. The annular distribution of the plurality of channels 887a- d is advantageous for draining, drying and providing a positive air supply during printing (e.g. pressure balancing). However, the plurality of channels 887a-d are not essential for the automatic backflush process.

During the automatic backflush process, cleaning fluid may be pulsed over, and into, the nozzle 858. That is to say, cleaning fluid may be supplied in a plurality of bursts (e.g. time intervals). This has been found to increase airflow and improve the efficacy of the nozzle clean.

Drawing cleaning fluid through the third port 998 may be described as directing a flow of cleaning fluid through the third port 998. Where cleaning fluid is supplied through the third port 998 towards the nozzle 858 (e.g. by way of drawing), the third port 998 may be described as a fill port. A front of the nozzle 858 (e.g. a side proximate the charge electrode 861) may be described as a first side of the nozzle. A rear of the nozzle 858 (e.g. a side proximate an interior of the nozzle body 832) may be described as a second side of the nozzle. During a backflush process, cleaning fluid passes from the front of the nozzle 858 (e.g. from the first side) to the rear of the nozzle 858 (e.g. to the second side). Put another way, cleaning fluid passes ‘backwards’, or in an ‘upstream direction’, across the nozzle 858. The supply of cleaning fluid through the third port is by way of drawing (e.g. under a negative pressure) in this embodiment.

When the print head is in an orientation pointing generally upwards (e.g. such that the nozzle 858 is generally located at a bottom of the cleaning chamber), a positive cleaning fluid pressure (e.g. a supply of cleaning fluid) may also be provided to a rear of the nozzle 858 (e.g. proximate the interior of the nozzle body 832) during a cleaning chamber cleaning cycle. By providing a positive cleaning fluid pressure across the nozzle 858 the risk of ‘dirty’ cleaning fluid, having been drawn or pumped into the chamber, entering the nozzle 858 is reduced.

For completeness, the automatic backflush process described above may be carried out as a separate process to the methods 300, 322 described in connection with Figures 11 to 16. Alternatively, the automatic backflush process may be incorporated in the methods 300, 322. Furthermore, whilst the automatic nozzle backflush is described in connection with a self-cleaning print head, it will be appreciated that the automatic nozzle backflush may otherwise be incorporated in a print head which is not selfcleaning (e.g. does not include a chamber selectively sealable by a sealing mechanism etc.).

Turning to Figure 47, a perspective view of the connector block 852 is provided. It will be recalled the connector block 852 was briefly introduced in connection with, and is shown in-situ in, Figure 34.

The connector block 852 is coupled to the nozzle body by the fastener 854. The connector block 852 comprises three barbs 853, 1000, 1002. Each barb 853, 1000, 1002 is connectable to a different fluid line (although in Figure 47 the barbs are shown without a fluid line connected thereto, for ease of visibility) and provides a different functionality. The first barb 853 provides a connection to a purge port in the nozzle body 832 (e.g. purge port 74a in Figure 10). The second barb 1000 provides an ink supply to the nozzle body 832. The third barb 1002 provides a connection to the third port defined in the nozzle body 832 (e.g. 998 in Figure 43). When connected to the barbs 853, 1000, 1002, corresponding fluid lines are typically plastically deformed over the barb 853, 1000, 1002. As such, it is difficult, if possible at all, to replaceable remove the fluid line from the barb 853, 1000, 1002. Instead, fluid lines are typically cut from the barb 853, 1000, 1002.

Turning to Figure 48, a perspective view generally showing an underside of the connector block 850 is provided. An engagement face 1003 of the connector block 852 is shown. The engagement face 1003 may be described as forming a face seal with an adjacent component when the connector block 852 is installed in-situ. An interface may be described as being defined between the engagement face 1003 and a corresponding face of the adjacent component (e.g. to which the connector block 850 is coupled). Three apertures 1004, 1006, 1008 are defined in the engagement face 1004. Each aperture 1004, 1006, 1008 is associated with a different barb 853, 1000, 1002 respectively. A gasket 1010, 1012, 1014 is placed around each of the apertures 1004, 1006, 1008. When installed, the gaskets 1010, 1012, 1014 are compressed between the engagement face 1003 of the connector block 852 and a further surface (e.g. the nozzle body, for the connector block 852). An underside of the fastener 854, by which the connector block 852 is coupled to an adjacent component, is also visible.

Turning to Figure 49, a perspective cross-section view of the connector block 852 is provided about a plane schematically indicated 1016 in Figure 48.

As previously mentioned, the connector block 852 defines a plurality of channels internally (e.g. one for each barb 853, 1000, 1002). Only second and third channels 1018, 1020 are visible in Figure 49, but a corresponding first channel is provided for the first barb 853.

Taking the second channel 1018 as an example, the second channel places the second aperture 1006 in fluid communication with the second barb 1000 (and, when installed, associated fluid line). In use, fluid can travel through the barb 1000, through the second channel 1018 and the aperture 1006 (and in the other direction, too). When the connector block 852 is installed, with the fastener coupling the connector block 852 to an adjacent component (e.g. the nozzle body), a fluid pathway is also defined between the aperture 1006 and a port of the adjacent component as limited (e.g. bound) by the gasket 1012. The same also applies for the other barbs 853, 1002, corresponding channels, apertures and gaskets.

From Figure 49 it will be appreciated that the internal channel 1018 also incorporates a change of direction (e.g. of approximately 90°). The internal channels can therefore advantageously be used to avoid sharp bends, or ‘kinks’, in the fluid lines, which could otherwise risk damage to the fluid lines and/or blockage of fluid flow therethrough.

When the connector block 852 is coupled to an adjacent component, the two parts form part of a connector block assembly. In such assemblies, the fluid pathway(s) described above, defined by the connector block 852, can also be considered to extend across the interface defined between the engagement face 1003 of the connector block 852 and the component (e.g. as bound by a corresponding gasket 1012, which also defined part of the fluid pathway).

Advantageously, by removal of the fastener 854, the connector block 852, with barbs and fluid lines attached, can be decoupled from the adjacent component (e.g. nozzle body 832). This is advantageous for reasons of being able to more readily service components of the print head 800 without having to destructibly detach the fluid lines from the barbs 853, 1000, 1002. Instead, the connector block 852, and connected fluid lines, can be detached from the adjacent component (e.g. nozzle body 832) and then reattached thereto (e.g. in a non-destructible, modular manner). It will be appreciated that when the fastener is loosened or removed, and the connector block 852 separated from the adjacent component, the fluid pathway(s) extending across the connector block 852 and across the interface between the connector block 852 and component are separated. For a separated connector block 852, with a fluid conduit attached to the barb 1000, the fluid pathway would therefore only extend from the conduit to the aperture 1006 (e.g. would terminate at the aperture 1006).

For completeness, although the connector block 852 defines three fluid pathways across it, in other embodiments the connector block may have more, or fewer, fluid pathways (and so an associated more, or fewer, barbs, internal channels, apertures and gaskets). For example, although not described here in detail, the first port connector block 984, shown and briefly described in connection with Figure 38, is an example of a connector block defining only a single fluid pathway across it. That said, the advantages above re. being able to decouple/detach the connector block, in a replaceable manner, apply equally here.

With brief reference to Figure 32, each of the (nozzle body) connector block 852, first port connector block 984 and the gutter connector block 1022 are visible in an installed position. Each of the blocks 852, 984, 1022 are, directly or indirectly, coupled to the chamber housing 822. By decoupling each of the blocks 852, 984, 1022, the chamber housing 822, and associated components mounted thereto, can be decoupled from the chassis 816 for maintenance. Furthermore, the gutter connector block 1022, even when coupled to the chamber housing 822, facilitates removal of the sealing mechanism 824 (by virtue of the gutter connector block 1022 only being in sealing engagement with the sealing mechanism 824). It will be appreciated that the connector blocks described herein may be applicable to a range of technical fields, and that their application is not limited to the field of printers (CIJ or otherwise).

As well as the rotatable body sealing mechanism described above, other sealing mechanisms may otherwise be used. For example, the end cap may be rotatable to close an ink aperture. An inflatable balloon seal could be used to obscure an ink aperture. Slidable housing pieces, which change the volume of the chamber itself, could be used.

As well as the multiple worm gear driving arrangement described earlier in this document, other actuation mechanisms for rotating the rotatable body disclosed herein are also contemplated. Other options include a bistable solenoid, a pneumatically actuated rotatable body by way of a diaphragm, and a rotary worm gear. Any mechanism which provides desirable mechanical advantage, to drive rotation of the rotatable body, may be used. Any of the above-listed drive options may be coupled to a lever or linkage to increase the mechanical advantage to the rotatable body.

Hydraulic connections (e.g. of conduits to adjacent components) may be by way of barbs. Barbs may be press-fitted into the component. An end of the conduit may be pushed over the barb. The conduits may be tubes, such as PTFE tubes. The term ‘drawn’ encompasses fluid being sucked by a downstream pump (e.g. under a negative [gauge] pressure). References to a negative pressure throughout this document may specifically be to a negative gauge pressure. References to vacuum may not refer to an absolute vacuum per se, but a negative gauge pressure.

Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional and/or preferred features for each aspect of the invention set out herein are also applicable to any other aspects of the invention, where appropriate.

Claims

CLAIMS:

1. A self-cleaning print head for a continuous inkjet printer, comprising: a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; and wherein the first and second ports are diametrically opposed from one another.

2. The self-cleaning print head according to claim 1, wherein the first and second ports are multifunction fill/drain ports.

3. The self-cleaning print head according to either of claims 1 or 2, wherein the first port is in fluid communication with a first conduit.

4. The self-cleaning print head according to claim 3, wherein the first conduit is also in fluid communication with a third port.

5. The self-cleaning print head according to claim 4, wherein the third port is defined by a nozzle body which defines the nozzle.

6. The self-cleaning print head according to any preceding claim, wherein the second port is in fluid communication with a second conduit.

The self-cleaning print head according to any preceding claim, wherein the cleaning chamber comprises no undercut features.

8. The self-cleaning print head according to any preceding claim, wherein the cleaning chamber comprises no vertices.

9. The self-cleaning print head according to any preceding claim, wherein the cleaning chamber is defined by a pair of parallel sides.

10. The self-cleaning print head according to any one of claims 1 to 8, wherein surfaces that define the cleaning chamber are contoured for guiding fluid towards the first or second ports.

11. The self-cleaning print head according to any preceding claim, wherein a deflection electrode of the at least one electrode is disposed in the cleaning chamber by one or more supports which sealingly engage a periphery of the cleaning chamber.

12. The self-cleaning print head according to any preceding claim, wherein a low voltage electrode of the at least one electrode defines at least part of the cleaning chamber.

13. The self-cleaning print head according to any preceding claim, wherein the cleaning chamber is defined by a chamber housing and the sealing mechanism, the sealing mechanism sealingly engaging the chamber housing.

14. The self-cleaning print head according to any preceding claim, wherein the gutter defines a separate port to the first and second ports.

15. The self-cleaning print head according to any preceding claim, wherein one or more of the first port and the second port comprises a plurality of subports.

16. The self-cleaning print head according to any preceding claim, wherein the first port defines a first port axis, and wherein the first port axis is substantially parallel with a nozzle axis defined by the nozzle.

17. The self-cleaning print head according to any preceding claim, further comprising an orientation sensor configured to detect the orientation of the selfcleaning print head.

18. A continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller; the self-cleaning print head comprising: a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; wherein the first and second ports are diametrically opposed from one another; and wherein the first port is in fluid communication with a first conduit, and the second port is in fluid communication with a second conduit.

19. The continuous inkjet printer according to claim 18, wherein the self-cleaning print head comprises an orientation sensor configured to detect the orientation of the self-cleaning print head, and wherein the orientation sensor is configured to output an orientation signal, to the controller, indicative of the orientation of the self-cleaning print head.

20. The continuous inkjet printer according to claims 18 or 19, wherein a plurality of valves are operable to control a flow of cleaning fluid into and/or out of the cleaning chamber.

21. The continuous inkjet printer according to claims 19 and 20, wherein the controller is configured to receive the orientation signal, process the orientation signal, and output a valve control signal, to the plurality of valves, to control the flow of cleaning fluid into and/or out of the cleaning chamber based upon the orientation of the self-cleaning print head.

22. The continuous inkjet printer according to claims 19 to 21 , wherein the plurality of valves comprises: a first flow valve configured to selectively place the first conduit in fluid communication with a gutter line or a first feed valve, wherein the first feed valve is selectively connectable to a cleaning fluid, or air, supply; and a second flow valve configured to selectively place the second conduit in fluid communication with the gutter line or a second feed valve, wherein the second feed valve is selectively connectable to the cleaning fluid, or air, supply.

23. The continuous inkjet printer according to claim 22, wherein a gutter pump, disposed in the gutter line, is configured to draw cleaning fluid from the cleaning fluid supply into the cleaning chamber.

24. The continuous inkjet printer according to claims 22 or 23, wherein, responsive to the output of a first orientation signal by the orientation sensor to the controller, indicative of the self-cleaning print head being in a first orientation, the controller is configured to output a first valve control signal, to the plurality of valves, in which: the first flow valve is configured to place the first conduit in fluid communication the first feed valve, wherein the first feed valve is connected to the cleaning fluid supply; and the second flow valve is configured to place the second conduit in fluid communication with the gutter line.

25. The continuous inkjet printer according to any one of claims 22 to 24, wherein, responsive to the output of a second orientation signal by the orientation sensor to the controller, indicative of the self-cleaning print head being in a second orientation, the controller is configured to output a second valve control signal, to the plurality of valves, in which: the first flow valve is configured to place the first conduit in fluid communication with the gutter line; and the second flow valve is configured to place the second conduit in fluid communication with the second feed valve, wherein the second feed valve is connected to the cleaning fluid supply.

26. The continuous inkjet printer according to any one of claims 20 to 24, wherein the plurality of valves are disposed outside of the self-cleaning print head.

27. A method of cleaning a self-cleaning print head of a continuous inkjet printer, comprising: sealing a cleaning chamber of the print head by actuating a sealing mechanism, and selecting a port of the cleaning chamber as a fill port, and a port of the cleaning chamber as a drain port, based upon the orientation of the self-cleaning print head; directing a flow of cleaning fluid through the fill port, into the cleaning chamber, to clean the cleaning chamber; and draining the cleaning fluid from the cleaning chamber, through the drain port, to drain the cleaning chamber.

28. The method according to claim 27, further comprising using an orientation sensor of the self-cleaning print head to determine the orientation of the self-cleaning print head.

29. The method according to claims 27 or 28, wherein selecting a port of the cleaning chamber as a fill port, and a port of the cleaning chamber as a drain port, based upon the orientation of the self-cleaning print head, comprises selecting one of a first port and a second port of the cleaning chamber as the fill port and the drain port.

30. The method according to claim 29, wherein selecting one of the first port and the second port of the cleaning chamber as the fill port and the drain port comprises determining, using the orientation sensor, which of the first and second ports is the vertically lower port.

31. The method according to any one of claims 27 to 30, wherein selecting the fill port and the drain port comprises operating a plurality of valves to place a cleaning fluid circuit in a first configuration, the first configuration corresponding to the self-cleaning print head being in a first orientation.

32. The method according to any one of claims 27 to 31 , further comprising: adjusting the orientation of the self-cleaning print head from the first orientation to a different, second orientation; sealing the cleaning chamber by actuating the sealing mechanism, and selecting a different fill port and/or drain port, based upon the orientation of the selfcleaning print head; directing a flow of cleaning fluid through the fill port, into the cleaning chamber to clean the cleaning chamber; and draining the cleaning fluid from the cleaning chamber, through the drain port, to drain the cleaning chamber.

33. The method according to claim 32 when dependent upon claim 31 , wherein selecting the different fill port and/or drain port comprises operating the plurality of valves to place the cleaning fluid circuit in a second configuration, the second configuration corresponding to the self-cleaning print head being in the second orientation

34. The method according to any one of claims 27 to 33, further comprising holding the cleaning fluid within the cleaning chamber, for a period of time, before draining the cleaning fluid from the cleaning chamber.

35. The method according to claim 34, further comprising percolating air through the cleaning fluid held within the cleaning chamber.

36. The method according to any one of claims 27 to 35, wherein directing the flow of cleaning fluid through the fill port, into the cleaning chamber to clean the cleaning chamber, comprises drawing cleaning fluid into the chamber using a gutter pump.

37. A continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller; and a cleaning fluid circuit for supplying cleaning fluid to the self-cleaning print head, the cleaning fluid circuit comprising first and second conduits and a plurality of valves for controlling a flow of cleaning fluid into and/or out of a cleaning chamber; the self-cleaning print head comprising: the cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; a gutter for receiving droplets of ink which are not used for printing; an orientation sensor configured to detect the orientation of the selfcleaning print head and output an orientation signal, to the controller, indicative of the orientation of the self-cleaning print head; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; wherein the first port is in fluid communication with the first conduit, and the second port is in fluid communication with the second conduit; and wherein the controller is configured to receive the orientation signal, process the orientation signal, and output a valve control signal, to the plurality of valves, to control the flow of cleaning fluid into and/or out of the cleaning chamber based upon the orientation of the self-cleaning print head.

38. A method of cleaning a self-cleaning print head of a continuous inkjet printer, comprising: sealing a cleaning chamber of the print head by actuating a sealing mechanism; connecting a first port of the cleaning chamber to a cleaning fluid supply, and connecting a second port of the cleaning chamber to a suction source; and activating the suction source to draw cleaning fluid through the first port, into the cleaning chamber, to at least partially fill the cleaning chamber with cleaning fluid.

39. The method according to claim 38, wherein the suction source comprises a gutter pump, and activating the suction source comprises activating the gutter pump.

40. The method according to claims 38 or 39, wherein connecting the second port of the cleaning chamber to the suction source comprises placing the second port in fluid communication with a solvent reservoir, with the suction source interposing the second port and the solvent reservoir.

41. The method according to any one of claims 38 to 40, further comprising holding the cleaning fluid in the cleaning chamber for a soaking period.

42. The method according to any one of claims 38 to 41, further comprising draining the cleaning fluid from the cleaning chamber through the first port.

43. A continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller and a suction source disposed along a gutter line; and a cleaning fluid circuit for supplying cleaning fluid to the self-cleaning print head, the cleaning fluid circuit comprising first and second conduits connectable to a cleaning fluid supply or the suction source by a plurality of valves, wherein the plurality of valves are for controlling a flow of cleaning fluid into and/or out of a cleaning chamber; the self-cleaning print head comprising: the cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; a gutter for receiving droplets of ink which are not used for printing, wherein the gutter is in fluid communication with the suction source via the gutter line; wherein the cleaning chamber comprises a first port and a second port; wherein the first port is in fluid communication with the first conduit, and the second port is in fluid communication with the second conduit; and wherein the suction source is configured to draw cleaning fluid, from the cleaning fluid supply, into the cleaning chamber via the first port or the second port.

44. A method of cleaning a self-cleaning print head of a continuous inkjet printer, comprising: sealing a cleaning chamber of the print head by actuating a sealing mechanism; at least partially filling the cleaning chamber with used cleaning fluid; draining the used cleaning fluid from the cleaning chamber; at least partially filling the cleaning chamber with virgin cleaning fluid; and draining the virgin cleaning fluid from the cleaning chamber.

45. The method according to claim 44, wherein at least partially filling the cleaning chamber with used cleaning fluid comprises connecting a fill port of the cleaning chamber to a solvent reservoir.

46. The method according to claims 44 or 45, wherein at least partially filling the cleaning fluid with virgin cleaning fluid comprises connecting a fill port of the cleaning chamber to a solvent cartridge.

47. The method according to any one of claims 44 to 46, further comprising activating an air pump to pump air into the cleaning chamber to at least partially dry the cleaning chamber

48. A method of using a self-cleaning print head of a continuous inkjet printer, comprising: during a printing operation: using a gutter pump to draw droplets of ink, which are not used for printing, through a gutter into a mixer tank; using an air pump to pump air into the print head; and during cleaning; sealing the cleaning chamber of the print head by actuating a sealing mechanism; at least partially filling the cleaning chamber with cleaning fluid; draining the cleaning fluid from the cleaning chamber; and using the air pump to pump air into the cleaning chamber to at least partially dry the cleaning chamber.

49. The method of claim 48, wherein activating the air pump to pump air comprises activating the air pump to pump air from an air supply.

50. The method of claims 48 or 49, wherein activating the air pump to pump air into the print head comprises connecting one or more ports of the cleaning chamber to the air pump and pumping air through the one or more ports into the cleaning chamber.

51. The method of claim 50, wherein activating the air pump to pump air into the cleaning chamber to at least partially dry the cleaning chamber comprises connecting the one or more ports of the cleaning chamber to the air pump and pumping air through the one or more ports to at least partially dry the cleaning chamber.

52. A continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a self-cleaning print head, the ink system comprising a controller; and a cleaning fluid circuit for supplying cleaning fluid to the self-cleaning print head, the cleaning fluid circuit comprising first and second conduits connectable to an air supply by a plurality of valves, the first and second conduits being connectable to the air supply by an air line and an air pump disposed along the air line; the self-cleaning print head comprising: the cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises a first port and a second port; wherein the first port is in fluid communication with the first conduit, and the second port is in fluid communication with the second conduit; and wherein the air pump is configured to pump air into the cleaning chamber via the first port and/or the second port during printing operations; and wherein the air pump is configured to pump air into the cleaning chamber to at least partially dry the cleaning chamber during a cleaning cycle.

53. A continuous inkjet printer configured to carry out the method of any of claims 38 to 42, and 44 to 51 , comprising: an ink system for storing ink and supplying ink to the self-cleaning print head, the ink system comprising a controller; the self-cleaning print head comprising: the cleaning chamber selectively sealable by the sealing mechanism, the cleaning chamber comprising one or more ports; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the at least one electrode is disposed in the cleaning chamber; and wherein the one or more ports are in fluid communication with a respective conduit.

54. A method of automatically backflushing a nozzle of a print head of a continuous inkjet printer, comprising: drawing a flow of cleaning fluid through a fill port towards a first side of the nozzle; and activating a pump, provided in fluid communication with a second side of the nozzle via a line, and drawing a proportion of the cleaning fluid through the nozzle, from the first side towards the second side, and into a nozzle body.

55. The method according to claim 54, wherein the pump is a gutter pump.

56. The method according to claims 54 or 55, wherein the line is a purge line.

57. The method according to any one of claims 54 to 56, wherein the fill port is a third port, the third port disposed proximate the nozzle.

58. The method according to claim 57, wherein the third port is defined in a front face of the nozzle body.

59. The method according to any one of claims 54 to 58, wherein the cleaning fluid is virgin cleaning fluid.

60. The method according to any one of claims 54 to 59, further comprising providing a distribution of cleaning fluid around the first side of the nozzle by a plurality of channels.

61. The method according to any one of claims 54 to 60, further comprising sealing a chamber of the print head by actuating a sealing mechanism before drawing the flow of cleaning fluid through the fill port.

62. A print head for a continuous inkjet printer, comprising: a nozzle for generating and ejecting a stream of ink droplets for printing, the nozzle being mounted to a nozzle body; a fill port, proximate a first side of the nozzle, for drawing a flow of cleaning fluid to the first side of the nozzle; and a pump provided in fluid communication with a second side of the nozzle via a line, the pump being configured to draw a proportion of the cleaning fluid through the nozzle, from the first side towards the second side, into the nozzle body.

63. A connector block for a print head of a continuous inkjet printer, comprising: a barb for engagement with a conduit; an internal channel that extends through the connector block; an aperture defined in an engagement face of the connector block; wherein the internal channel extends between the barb and the aperture to define a fluid pathway across the connector block.

64. The connector block according to claim 63, further comprising: a plurality of barbs, a plurality of internal channels, a plurality of apertures, wherein the internal channels extend between a respective barb and aperture to define a fluid pathway across the connector block, the plurality of internal channels defining a plurality of fluid pathways across the connector block.

65. A connector block assembly for a print head of a continuous inkjet printer, comprising: the connector block according to claims 63 or 64; a conduit engaged with the barb; and a component, the connector block coupled to the component at the engagement face; wherein the connector block is coupled to the component by a fastener; and wherein the fluid pathway extends from the conduit, across the connector block, and across an interface defined between the engagement face of the connector block and the component.

66. A method of decoupling the connector block assembly of claim 65, comprising: loosening the fastener; separating the connector block from the component such that the fluid pathway extending from the conduit terminates at the aperture in the engagement face.

67. A self-cleaning print head for a continuous inkjet printer, comprising: a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; at least one electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein the cleaning chamber comprises: a first port disposed proximate a first end of the cleaning chamber, and a second port disposed proximate a second, opposing end of the cleaning chamber; and wherein one or more of the first port and the second port comprises a plurality of subports.

68. The self-cleaning print head according to claim 67, wherein the plurality of subports are distributed annularly.

69. The self-cleaning print head according to either of claims 67 or 68, further comprising a third port, disposed proximate the nozzle.

70. The self-cleaning print head according to claim 69, wherein the third port is in fluid communication with the cleaning chamber via a cavity defined by a charge electrode.

71. The self-cleaning print head according to claim 70, wherein the third port is in fluid communication with the cavity by a plurality of channels.

72. The self-cleaning print head according to claim 71 , wherein the plurality of channels are distributed annularly.

73. The self-cleaning print head according to claims 71 or 72, wherein the plurality of channels extend between an annular channel and the cavity defined by the charge electrode.

74. The self-cleaning print head according to any one of claims 71 to 73, wherein the third port is in fluid communication with the nozzle via the plurality of channels.

75. A continuous inkjet printer comprising: an ink system for storing ink and supplying ink to a print head; the print head comprising the print head according to claims 62 or 67 to 74.