WO2025257569A1

WO2025257569A1 - Printer and associated method

Info

Publication number: WO2025257569A1
Application number: PCT/GB2025/051305
Authority: WO
Inventors: David Andrew Horsnell; Bartosz Marcin OPRZADEK; David DOSWELL
Original assignee: Videojet Technologies Ltd; Videojet Technologies Inc
Current assignee: Videojet Technologies Ltd; Videojet Technologies Inc
Priority date: 2024-06-14
Filing date: 2025-06-13
Publication date: 2025-12-18
Anticipated expiration: 2026-12-14
Also published as: GB202408558D0

Abstract

There is disclosed a continuous inkjet printer. The printer comprises a printer body, an umbilical, a controller and a self-cleaning print head. The printer body comprises an ink system for storing ink and supplying ink to a self-cleaning print head. The umbilical couples the self-cleaning print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires. The controller is in electrical communication with the self-cleaning print head. The self-cleaning print head comprises a cleaning chamber, a nozzle, a charge electrode, a low voltage electrode, a deflection 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 charge electrode is for selectively charging the stream of ink droplets. The low voltage electrode and deflection electrode are for guiding the stream of ink droplets. The gutter is for receiving droplets of ink which are not used for printing. One or more of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter are disposed in the cleaning chamber. The controller is configured to: initiate a fill stage, comprising at least partially filling the cleaning chamber with cleaning fluid and/or ink; and determine an electrical response of one or more components disposed in the cleaning chamber to determine a parameter of the self-cleaning print head.

Description

Printer and method The present invention relates to a continuous inkjet printer and various 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 (CIJ) 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) 69726571-1 determined by the charge applied to the 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 non-volatile ink components which remain 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 69726571-1 for at least a period of time). Deposits exist internally within the print head, but also externally. For example, an (external) end face of the print head (e.g. in which the ink aperture is located) may also be liable to the build-up of deposits due to ink ‘splash-back’ during printing. There exists a need to provide an alternative continuous inkjet (CIJ) 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 continuous inkjet printer comprising: a printer body comprising an ink system for storing ink and supplying ink to a self- cleaning print head; an umbilical coupling the self-cleaning print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; a controller in electrical communication with the self-cleaning print head; 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; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein one or more of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter are disposed in the cleaning chamber; wherein the controller is configured to: initiate a fill stage, comprising at least partially filling the cleaning chamber with cleaning fluid and/or ink; and determine an electrical response of the one or more components disposed in the cleaning chamber to determine a parameter of the self-cleaning print head. Determining an electrical response of one or more components may be described as monitoring an electrical response of one or more components. Determining an electrical response may comprise determining a voltage drop across the one or more components. 69726571-1 Determining an electrical response of one or more components may comprise determining whether the component has shorted to ground. Determining an electrical response of one or more components may comprise determining an electrical response of all components disposed in the cleaning chamber. Alternatively, determining an electrical response of one or more components may comprise determining an electrical response of a subset of components disposed in the cleaning chamber. Each of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter may be disposed in the cleaning chamber. Alternatively, only a subset of these components may be disposed in the cleaning chamber. The one or more components _{may comprise the nozzle, charge electrode, low voltage electrode, deflection electrode} _{and gutter. Determining an electrical response of the one or more components disposed} in the cleaning chamber may comprise determining an electrical response of each of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter, or (only) a subset thereof. The fill stage may comprise filling the cleaning chamber with only cleaning fluid, only ink, or a combination of cleaning fluid and ink. _{Determining an electrical response of the one or more components disposed in the} _{cleaning chamber preferably occurs whilst the cleaning chamber is at least partially filled} _{with cleaning fluid and/or ink. Determining an electrical response of the one or more} _{components disposed in the cleaning chamber preferably occurs whilst cleaning fluid} _{and/or ink is held in the cleaning chamber for a period of time. Determining an electrical} _{response of the one or more components disposed in the cleaning chamber may occur} during a fill stage and/or may occur during a soaking stage. Advantageously, electrical connections made between the components, owing to the cleaning fluid, can be used to determine useful parameters of the self-cleaning printhead. Said parameters comprise a fill level of cleaning fluid within the cleaning chamber, and/or an orientation of the printhead. 69726571-1 The electrical response of the one or components disposed in the cleaning chamber may comprise a current draw from a voltage source. The electrical response of the one or more components disposed in the cleaning chamber may comprise a current _{sunk into one or more lower potential (e.g. grounded) components. The electrical} response of the one or more components disposed in the cleaning chamber may comprise a voltage drop. The electrical response may comprise a plurality of the aforementioned electrical responses. A current draw from a voltage source (e.g. between a voltage source and the one or more components) is indicative that the one or more components is connected to a lower potential (e.g. shorted to ground). A current sunk into one or more lower potential (e.g. _{grounded) components is indicative that the one or more components is electrically} _{connected to the one or more lower potential (e.g. grounded) components, and is also} at the lower potential (e.g. grounded). A voltage drop (e.g. where the voltage is from a high impedance source, such as the deflection electrode) is indicative that the one or more components is grounded. _{The above electrical responses may be used to determine whether or not the component} is shorted to ground. The components being shorted to ground may be indicative that the component is in electrical communication with at least one other component which is grounded. This, in turn, can be used to infer a parameter of the self-cleaning printhead. The electrical response may be used to determine that the component is connected to a lower potential component. The lower potential component may be grounded, or may be held at a potential between the component being tested/monitored and ground (e.g. an intermediate potential). That is to say, the lower potential component does not necessarily need to be grounded. Examples of grounded components include the sealing mechanism (in some embodiments), the gutter and the low voltage electrode. A plurality of: the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter may be disposed in the cleaning chamber. Advantageously, by providing a plurality of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter in the cleaning chamber, the electrical 69726571-1 response of multiple components can be This sequential comparison can be used to infer a parameter of the self-cleaning printhead. Furthermore, disposing multiple components in the self-cleaning chamber also means that the multiple components can be cleaned during the cleaning cycle. _{Determining the electrical response of the one or more components disposed in the} cleaning chamber may comprise determining an electrical response of the plurality of components disposed in the cleaning chamber. Determining an electrical response of the plurality of components disposed in the cleaning chamber may comprise determining an electrical response of all components disposed in the cleaning chamber. Advantageously, by determining an electrical response of a plurality of components, the electrical response can be compared from component to component, to provide a more accurate indication of a parameter of the printhead. Determining the electrical response of the plurality of components disposed in the cleaning chamber may comprise determining an order of the plurality of components being connected to a lower potential (e.g. shorted to ground). Determining an order of the plurality of components being connected to a lower potential _{(e.g. shorted to ground) may otherwise be described as determining an order by which} the plurality of components are provided in electrical communication with a lower _{potential (e.g. grounded) component. Put another way, it may otherwise be described} as determining an order by which the voltage level of the components is pulled low. The components being shorted to ground may be described as a current being sunk to ground. An associated trip may be described as the current draw reaching a threshold. Advantageously, the order of the plurality of components being connected to a lower _{potential (e.g. shorted to ground) can be used to determine one or more of a fill level of} cleaning fluid in the cleaning chamber and/or an orientation of the self-cleaning printhead. These are both useful parameters that can be used to inform the cleaning cycle and provide more information to an operator. 69726571-1 The controller may be configured to a cleaning cycle, the cleaning cycle comprising the fill stage. Where a cleaning cycle comprises the fill stage, the overall cleaning cycle can utilise an identified fill level of cleaning fluid in the chamber before moving onto a subsequent (optional) soaking stage, draining stage or drying stage. Alternatively, the fill stage may form part of a separate orientation testing method. That is to say, the two steps of initiating a fill stage and determining an electrical response may form part of a stand- alone method only used for an orientation of a printhead, described as an orientation test. The parameter of the self-cleaning print head may comprise a fill level of the cleaning fluid and/or ink in the cleaning chamber. The fill level of the cleaning fluid and/or ink in the cleaning chamber may otherwise be described as a maximum liquid level of cleaning fluid and/or ink within the chamber. It may be possible to determine the volume of cleaning fluid and/or ink in a chamber based upon an identified fill level. It may also be possible to determine a volume of cleaning fluid within the wider system (e.g. where the volume of cleaning fluid in a fluid conduit extending between the printer body and the printhead, for example, is known, and it can be determined that the cleaning chamber is full, the total volume [conduit volume + chamber volume] can be determined). Advantageously, knowing the fill level provides useful operational feedback. The parameter of the self-cleaning print head may comprise an orientation of the self- cleaning print head. Being able to determine the orientation of the self-cleaning printhead is a further useful parameter which can be determined based upon the electrical response of the one or more components. This can be used to confirm that an orientation indicated by an operator is correct, or could be used to automatically inform the controller of the current position of the printhead. This could, in turn, be used to modify a cleaning cycle which is at least partially dependent upon orientation of the printhead. The orientation sensing 69726571-1 may also eliminate the need for a ‘dedicated’ orientation sensor (e.g. accelerometer). According to a second aspect of the invention there is provided a method of using a self- cleaning print head of a continuous inkjet printer, comprising: initiating a fill stage, comprising at least partially filling a cleaning chamber of the self-cleaning print head with cleaning fluid and/or ink, the cleaning chamber comprising one or more components disposed therein; and determining an electrical response of the one or more components disposed in the cleaning chamber and determining a parameter of the self-cleaning print head. _{Determining an electrical response of the one or more components disposed in the} _{cleaning chamber preferably occurs whilst the cleaning chamber is at least partially filled} _{with cleaning fluid and/or ink. Determining an electrical response of the one or more} _{components disposed in the cleaning chamber preferably occurs whilst cleaning fluid} _{and/or ink is held in the cleaning chamber for a period of time. Determining an electrical} _{response of the one or more components disposed in the cleaning chamber may occur} during a fill stage and/or may occur during a soaking stage. _{The one or more components disposed in the cleaning chamber may comprise: a nozzle} for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection _{electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink} _{which are not used for printing. Determining an electrical response of the one or more} components disposed in the cleaning chamber may comprise determining an electrical response of each of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter, or (only) a subset thereof. Determining the electrical response of the one or more components may comprise determining a current draw from a voltage source. Determining the electrical response of the one or more components may comprise determining a current sunk into one or _{more lower potential (e.g. grounded) components. Determining the electrical response} of the one or more components may comprise determining a voltage drop. Determining the electrical response may comprise a plurality of the aforementioned determinations. 69726571-1 A plurality of nozzle, charge electrode, voltage electrode, deflection electrode and gutter may be disposed in the cleaning chamber. Determining the electrical response of the one or more components disposed in the cleaning chamber may comprise determining an electrical response of the plurality of components disposed in the cleaning chamber. Determining the electrical response of the plurality of components disposed in the cleaning chamber may comprise determining an order of the plurality of components being connected to a lower potential (e.g. shorted to ground). The method may comprise initiating a cleaning cycle, the cleaning cycle comprising the fill stage. Determining the parameter of the self-cleaning print head may comprise determining a fill level of the cleaning fluid and/or ink in the cleaning chamber. The method may further comprise pausing a supply of cleaning fluid and/or ink when the fill level of the cleaning fluid in the cleaning chamber reaches a predetermined level. Determining the parameter of the self-cleaning print head may comprise determining an orientation of the self-cleaning 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; at least partially filling the cleaning chamber with ink to clean the cleaning chamber; draining the ink from the cleaning chamber; at least partially filling the cleaning chamber with cleaning fluid to rinse the cleaning chamber; and draining the cleaning fluid from the cleaning chamber. The method of cleaning a self-cleaning printhead which uses a first cycle to at least partially fill the cleaning chamber with ink, drains the ink, uses a second sub-cycle to at 69726571-1 least partially fill the cleaning chamber cleaning fluid, and then drains the cleaning fluid, may be described as a twin-shot cycle. The cleaning chamber may be entirely filled with ink, or may only be partially filled. The fill level when the chamber is filled with cleaning fluid may be the same as for the ink step, or may be different. That is to say, the chamber may be only partially filled with cleaning fluid, or may be entirely filled with cleaning fluid. Between one or more of the filling and draining steps there may be an optional soaking step during which the fluid is left in the chamber for a period of time. Advantageously, providing an initial rinse of the chamber with ink reduces the solvent use during a cleaning cycle. It can also reduce the risk of solvent reducing the viscosity of ink. According to a fourth aspect of the invention there is provided a continuous inkjet printer comprising: a printer body comprising an ink system for storing ink and supplying ink to a self- cleaning print head; an umbilical coupling the self-cleaning print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; a controller in electrical communication with the self-cleaning print head; 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; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein one or more of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter are disposed in the cleaning chamber; wherein the controller is configured to: seal the cleaning chamber by actuating the sealing mechanism; at least partially fill the cleaning chamber with ink to clean the cleaning chamber; drain the ink from the cleaning chamber; 69726571-1 at least partially fill the cleaning with cleaning fluid to rinse the cleaning chamber; and drain the cleaning fluid from the cleaning chamber. _{According to a fifth 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 at least partially filling the cleaning chamber with a volume of aerated cleaning fluid or ink. The cleaning chamber may be entirely filled with a volume of aerated cleaning fluid or ink, or may only be partially filled. The volume of aerated cleaning fluid or ink may be introduced to the chamber as an aerated fluid, or cleaning liquid or ink may be aerated once the cleaning liquid or ink is delivered to the chamber. The cleaning fluid or ink may otherwise be described as a froth when it is aerated. Advantageously, at least partially filling the chamber with a volume of aerated cleaning fluid or ink has been found to improve the efficiency of cleaning, particularly in conditions generally requiring a deeper clean. The volume of aerated cleaning fluid or ink may be supplied to the cleaning chamber as a froth. Supplying the cleaning fluid or ink to the cleaning chamber as a froth is intended to mean that the cleaning fluid or ink is already aerated at the point where it arrives to the cleaning chamber. Froth refers to a multi-phase mixture of liquid and gas. The froth is preferably a stable froth in that it is able to remain in froth form for a period of time (e.g. not breaking down once formed). A surfactant may be used to facilitate the formation of a stable froth. Advantageously, supplying the aerated cleaning fluid or ink to the cleaning chamber as a froth means that the effectiveness of cleaning can be improved and the volume of cleaning fluid or ink that is used can be reduced. A further advantage is that less liquid is used than if the liquid were not aerated. This is particularly advantageous where cleaning fluid is aerated, where an otherwise greater volume of cleaning fluid could risk 69726571-1 reducing the viscosity of ink (e.g. in a tank) beyond a desired level when drained from the chamber (for example). The volume of aerated cleaning fluid or ink may be supplied to the cleaning chamber as a liquid cleaning fluid or ink and subsequently aerated in the cleaning chamber to form the aerated cleaning fluid or ink. A liquid cleaning fluid or ink being subsequently aerated in the cleaning chamber to form the aerated cleaning fluid or ink may be described as a froth forming in the cleaning chamber. This may be achieved by providing a supply of air to the chamber once the cleaning fluid or ink is in-situ. Advantageously, aerating the cleaning fluid or ink in the chamber means that the cleaning fluid or ink can be comparatively easier to deliver to the cleaning chamber than a froth. The aerated cleaning fluid or ink may be maintained in the chamber by continuous aeration of the chamber. Put another way, an air supply to the chamber may be provided to maintain the aerated cleaning fluid or ink in the aerated form. Advantageously, this reduces the risk of the aerated cleaning fluid or ink dissipating in the chamber. _{According to a sixth aspect of the invention there is provide a continuous inkjet printer} comprising: a printer body comprising an ink system for storing ink and supplying ink to a self- cleaning print head; an umbilical coupling the self-cleaning print head to the printer body, the umbilical comprising one or more fluid conduits and electrical wires; a controller in electrical communication with the self-cleaning print head; 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; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; 69726571-1 wherein one or more nozzle, charge electrode, low voltage electrode, deflection electrode and gutter are disposed in the cleaning chamber; wherein the controller is configured to: seal the cleaning chamber by actuating the sealing mechanism; at least partially fill the cleaning chamber with a volume of aerated cleaning fluid or ink. _{According to a seventh 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, the nozzle defining a nozzle axis; 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 plurality of subports arranged around the nozzle axis; and wherein the plurality of subports are connectable to an air supply. The at least one electrode is preferably disposed in the cleaning chamber. One or more of the nozzle, electrode, and gutter may be disposed in the cleaning chamber, preferably all. A plurality of subports may be described as constituent ports of a primary port. The port may, for example, take the form of a cavity or supply line which is in fluid communication _{with all of the subports simultaneously. The plurality of subports may be described as a} distribution of apertures. The plurality of subports arranged around the nozzle axis is preferably in an annular manner. The air supply may be passive air supply (e.g. being connected to atmosphere) or may be an active air supply (e.g. where a pump is used to positively pump air into the cleaning chamber). Advantageously, the plurality of subports provide more versatile draining functionality by being able to drain cleaning fluid in the cleaning chamber from a wider range of orientations (of print head). Furthermore, the plurality of subports can be used for 69726571-1 pressure balancing purposes whilst disruption to the jet. Described another way, owing to there being a plurality of subports distributed about the nozzle axis, an air flow can be gently introduced around the jets (e.g. diffused) without affecting the jet. _{According to an eighth aspect of the invention there is provided a method of using a self-} cleaning print head of a continuous inkjet printer, comprising: initiating a printing mode comprising: generating and ejecting a stream of ink droplets for printing, via a nozzle, the nozzle defining a nozzle axis, and activating a gutter pump to draw ink droplets, not used for printing, through a gutter; and providing a supply of air around the stream of ink droplets via a plurality of subports arranged around the nozzle axis; terminating the printing mode, and initiating a cleaning cycle comprising: sealing a 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 via one or more of the plurality of subports; and drying the cleaning chamber by providing a supply of air via one or more of the plurality of subports. Drying the cleaning chamber by providing a supply of air via one or more of the plurality of subports comprises pumping air through the one or more of the plurality of subports. Drying the cleaning chamber by providing a supply of air via one or more of the plurality of subports may comprise connecting the one or more of the plurality of subports to atmosphere and providing a passive supply of air. 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, the second, third fifth and eighth aspect of the invention may be combined with one another. The first, fourth, sixth and seventh aspects of the invention may be combined with one another. The second aspect of the 69726571-1 invention may be carried out using the aspect of the invention. The third aspect of the invention may be carried out using the fourth aspect of the invention. The fifth aspect of the invention may be carried out using sixth aspect of the invention. The eighth aspect of the invention may be carried out using the seventh aspect of the invention. 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 (CIJ) printer, comprising a self-cleaning print head, according to an embodiment of the invention; F_{igure 2 is a schematic cross-section side view through part of the self-cleaning} print head of the printer of Figure 1; F_{igure 3 is a flowchart showing steps of a method of cleaning the self-cleaning} print head of Figure 2; Figures 4 to 6 show the self-cleaning print head of Figure 3 in a horizontal orientation and with three different fill levels of cleaning fluid within the chamber, exemplifying a method in accordance with an embodiment of the invention; Figures 7 to 9 show the self-cleaning print head of Figure 3 in a vertical, downward-facing orientation with three different fill levels of cleaning fluid within the chamber; Figure 10 is a flow chart showing the steps of a method of using the self-cleaning print head in accordance with an embodiment of the invention; F_{igure 11 is a flow chart showing the steps of another method according to} another embodiment of the invention; Figure 12 is a flow chart showing the steps of another method according to another embodiment of the invention; Figure 13 is a schematic illustration of a cross-section side view of a self-cleaning print head according to an embodiment of the invention; and Figure 14 is a schematic illustration of an axial cross-section view of the print head of Figure 13 is taken about a construction line shown in Figure 13. Figure 1 schematically illustrates a continuous inkjet (CIJ) 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. Although 69726571-1 the controller 6 is disposed in the printer 2 in the illustrated embodiment, in other embodiments the controller 6 may be disposed in the print head 3. In either case, the _{controller 6 is provided in electrical communication with the print head 3, and preferably} also the printer body 2. 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 unused 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 (e.g. conduits) 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. In accordance with the invention, the print head 3 can be cleaned. In the illustrated example, 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, 69726571-1 in order to clean the print head 3. The fluid circulates through the printer 1 from the printer body 2 to the print head 3, and then returns to the printer body 2 after. Self- cleaning print heads are advantageous for a number of reasons including, but not limited to: repeatable cleaning cycles, in-situ cleaning, and not needing operator intervention. The ink system 5 is also operable to store cleaning fluid and supply cleaning fluid to the _{print head 3 (e.g. in isolation of ink). This is particularly advantageous for a self-cleaning} print head 3, in which cleaning fluid is circulated through the printer 1 to clean the printer 1 (e.g. specifically a chamber, and associated components, within the print head 3). Alternatively, a continuous inkjet printer may comprise an ink system for storing ink and _{supplying ink to the print head, and a separate system (e.g. cleaning fluid system) for} storing cleaning fluid and supplying cleaning fluid to the print head. Turning to Figure 2, a schematic cross-section side view through part of the self-cleaning _{print head 3, as shown in Figure 1, is provided. Figure 2 shows the print head 3} comprising a nozzle body 20, charge electrode 24, chamber 26, low voltage electrode 28, deflection electrode 30, gutter 32 and sealing mechanism 34. An ink jet 36 (e.g. a stream of ink droplets), not deflected by deflection electrode 30, is also schematically indicated in Figure 3. Briefly stepping through each of the aforementioned components in turn: the nozzle body 20, as mentioned, defines the nozzle 22. The nozzle 22 is for generating and ejecting a _{stream of ink droplets for printing. The ink jet 36 is shown being expelled by the nozzle} 22, although these ink droplets would not be used for printing because they pass straight into the gutter 32. Downstream of the nozzle and nozzle body 20, 22, the charge electrode 24 is provided. As the stream of ink droplets 36 is directed past the charge electrode 24, they are selectively and separately given a pre-determined level of charge by the charge electrode 24. Downstream of the charge electrode 24, low voltage and deflection electrodes 28, 30 are provided. The low voltage electrode 28 may otherwise be described as a grounded, or negative potential, electrode. The deflection electrode 30 may be described as a high voltage electrode. The electrodes 28, 30 may collectively be described as a pair of 69726571-1 electrodes. An electric field is generated between the low voltage and deflection electrodes 28, 30 for guiding the stream of ink droplets 36 away from the gutter 32 and towards an ink aperture for printing onto a substrate in use. The ink aperture is labelled 38. The ink aperture 38 may be described as being selectively opened and closed by the sealing mechanism 34. Downstream of the electrodes 28, 30, the gutter 32 is provided. The gutter 32 comprises a gutter aperture through which droplets of ink not used for printing (e.g. of ink jet 36) are received and subsequently recirculated back into the ink system. _{Also shown in Figure 2 is a sealing mechanism 34. The purpose of the sealing} mechanism 34 is to selectively seal the chamber 26 within the print head 3. The chamber 26 is thus a selectively sealable volume which can be at least partly filled with cleaning fluid, and subsequently drained, in order to clean one or more components disposed within the chamber 26. As indicated in Figure 2, components disposed within the _{chamber 26 include the gutter 32, electrodes 28, 30, the charge electrode 24 and the} nozzle 22. Fluid within the chamber 26 can thus contact any one of these components. The charge electrode 24 can thus also be cleaned by filling the chamber 26 with cleaning _{fluid. A cavity defined by the charge electrode 24 may be described as forming part of} the chamber 26. The chamber 26 may be described as a cleaning chamber, or a cleaning _{volume (e.g. an internal cleaning chamber).} The sealing mechanism 34 may otherwise be described as a closure. The sealing mechanism 24 may take one of a number of different forms. The sealing mechanism 34 may comprise: a rotatable sealing mechanism (e.g. a rotatable body that rotates about an axis to selectively open/seal chamber 26), a slidable sealing mechanism which selectively opens/seals the chamber 26, an inflatable balloon seal that selectively opens/seals the chamber 26, or slidable housing pieces which selectively change the volume of the chamber. The chamber 26, in the case of a self-cleaning print head, is a sealable internal volume. Although not illustrated in Figure 2, one or more ports, preferably a plurality of ports, may be disposed in fluid communication with the chamber 26. These ports may provide one or more of: a supply of cleaning fluid for cleaning the chamber, a supply of air for pressure balancing (e.g. during printing, to replenish fluid drawn out of the chamber by the gutter), 69726571-1 drainage of used cleaning fluid from and a supply of air for drying the chamber. One or more of the gutter 32 and the nozzle 22 may also provide the aforementioned port functionalities, although in preferred embodiments the gutter 32 and nozzle 22 are not used to provide the chamber with such filling, draining or drying functionalities (the chamber 26 instead comprising one or more ‘dedicated’ multifunction fill/drain/dry ports). Turning to Figure 3, steps of a method 50 are shown illustrating a cleaning cycle for the self-cleaning print head 3. The method 50 comprises a fill stage 52, soak stage 54, drain stage 56 and a dry stage 58. During the fill stage 52, the chamber 26 is at least partly filled with cleaning fluid. By virtue of the chamber 26 being partly filled with cleaning fluid, components within the chamber 26 which are reached by the liquid level of the cleaning fluid are contacted by the cleaning fluid. In the soaking stage 54, the cleaning fluid is held in the chamber. As suggested by the name, the soaking stage 54 provides a dwell period, (e.g. a period of time) in which the cleaning fluid acts to remove deposits/build-up from the components and the chamber 26 itself. The soaking stage 54 may comprise percolating air or otherwise disturbing the cleaning fluid in the chamber 26 to improve the clean. In the draining stage 56, the used cleaning fluid from within the chamber 26 is drained. The chamber 26 is thus emptied of used cleaning fluid (and any deposit/build-up entrained within the used cleaning fluid). In the drying stage 58, the chamber 26, and any components provided in fluid communication with the chamber 26, are dried. Although there are a number of different ways in which the drying can take place, one such example is that a supply of air be provided through one or more ports in communication with the chamber 26. It will be appreciated that the method 50 may be modified in various different ways, and may be repeated in multiple cycles to provide a deeper clean. For example, the method _{50 may run multiple times in succession for a deeper clean of the print head 3a. It will} 69726571-1 also be appreciated that a sealing which the sealing mechanism sealing the chamber, precedes the fill stage 52. _{Turning now to Figures 4 to 6, a method of using the self-cleaning print head 3 shown in} Figure 2 will be described. Specifically, Figures 4 to 6 show a varying fill level of a _{cleaning fluid for the self-cleaning print head 3 in a horizontal orientation. Figures 7 to 9} _{show varying fill levels of cleaning fluid for the self-cleaning print head 3 in a downward-} _{facing vertical orientation. Whilst the following description refers to a fill level of cleaning} fluid, the method could also be used with a chamber at least part-filled with ink, or a combination of cleaning fluid and ink. With brief reference to Figure 3, during the fill step 52, there are a number of different _{parameters of the self-cleaning print head 3 which can be determined by determining, or} monitoring, an electrical response of components disposed in the cleaning chamber 26. These parameters include a fill level of the cleaning fluid in the chamber 26, and an _{orientation of the print head 3.} With initial reference to Figure 4, it will be recalled that each of the nozzle 22, charge electrode 24, low voltage electrode 28, deflection electrode 30 and gutter 32 are disposed in the chamber 26. In other embodiments, one or more of these components may not be disposed in the chamber 26. In normal operation, low voltage electrode 28 and gutter 32, specifically a gutter build- up sensor thereof, are grounded. That is to say, these components are held at zero potential. In some embodiments, the sealing mechanism 34 may also be grounded. Any one of the low voltage electrode 28, gutter 32 and sealing mechanism 34 may therefore act as a pick-up point that can be used to send or receive ground signals. In contrast, the charge electrode 24 is selectively provided with a non-zero (e.g. supply) voltage for selectively charging ink droplets. Similarly, the deflection electrode 30 is selectively provided with a supply voltage for creating an electric field between the deflection electrode 30 and low voltage electrode 28. The charge electrode 24 slews rapidly between a typical 0 V. The charge electrode 24 may be held at up to around -20 V during phasing (e.g. start-up), up to around +300 V during printing. The deflection electrode is _{typically supplied with between around 6 kV to around 8 kV.} 69726571-1 Whilst the low voltage electrode 28, 32, and (optionally) sealing mechanism 34 are grounded in the illustrated embodiment, in other embodiments one or more of these components may be provided at a non-ground (e.g. non-zero) potential. Provided the potential of these components is lower than that of a component being tested, or monitored, an electrical connection between the component and the lower potential component can still be detected, and the method still carried out. When the sealing mechanism 34 is closed, so as to seal the chamber 26, when the fill stage is initiated chamber 26 starts to fill with cleaning fluid. As previously described, in the illustrated embodiment the fill ports of the chamber 26 are not shown. However, the fill ports could be located at any position in fluid communication with the chamber 26. Furthermore, only a single port could be provided if needed. Nozzle 22 could also provide the fill port functionality. When the chamber 26 comprises no cleaning fluid, such as shown in Figure 2, each of the components disposed in the chamber 26 is electrically isolated from one another. That is to say, there is no conductive path between the components. However, returning to Figure 4, when the chamber 26 begins to fill with _{cleaning fluid, which is indicated by hashed box 40, the cleaning fluid can provide a} conductive path which electrically connects these components. This conductive path between the components changes an electrical response of the one or more _{components, and it is this electrical response which can be determined, or monitored,} _{and subsequently processed to infer one or more parameters of the print head. For} completeness, it will be appreciated that components which are contacted by the cleaning fluid (e.g. components at least partly positioned at, or below, a fill level of the chamber 26) which are electrically connected to one another. As ink residue in the chamber 26, for example, dissolves in the cleaning fluid, the conductivity of the cleaning fluid increases. This provides for a more reliable, and stronger, conductive pathway between components in the chamber 26. In some _{embodiments, ink may be intentionally added to the chamber 26 (e.g. the chamber 26 at} least partially filled with ink) before the cleaning fluid is provided. The ink then dissolves in the cleaning fluid, increasing the conductivity of the cleaning fluid. That is to say, ink may be added to the chamber 26, either before or as part of a fill stage, to increase the _{conductivity of the cleaning fluid. Alternatively, and as described above, the fill stage may} comprise at least partially filling the chamber 26 with ink (e.g. in the absence of cleaning 69726571-1 fluid). Ink is sufficiently conductive that connections can be made, between components, via the ink. _{With continued reference to Figure 4, Figure 4 shows a self-cleaning print head 3 during} _{a fill stage, partially filled with cleaning fluid 40 at a first fill level. In the horizontal} orientation shown, at the illustrated fill level, the cleaning fluid 40 provides a conductive path between the low voltage electrode 28 and the charge electrode 24. Accordingly, the voltage drop across the charge electrode 24 is equal to the supply voltage provided to the charge electrode 24. This is owing to the charge electrode 24 effectively being _{shorted to ground by virtue of the electrical connection to the low voltage electrode 28,} which is in turn grounded. For completeness, if the sealing mechanism 34 is also grounded, as shown in Figure 4 each of the sealing mechanism 34, gutter 32, low voltage electrode 28 and charge electrode 24 are connected to one another by virtue of the cleaning fluid 40. _{So, by determining an electrical response of the charge electrode 24 (for example), it} _{can be determined that charge electrode 24 has shorted to ground. It can thus be} determined that the fill level of cleaning fluid 40 is as shown in Figure 4. A further _{parameter which can be determined is that an orientation of the self-cleaning print head} _{3 is generally horizontal, as shown in Figure 4. Where the print head 3 is provided in a} _{vertical upward facing orientation (e.g. ink aperture 38 facing upwards), the nozzle 22,} _{and possibly a nozzle body 20 thereof, are shorted before the charge electrode 24.} _{Determining the electrical response of the component may comprise sensing a current} draw from the voltage source (e.g. like for a charge electrode). Determining the electrical response of the component may comprise sensing a current sunk into lower potential _{(e.g. grounded) components. Determining the electrical response of the component may} comprise sensing a voltage drop, particularly if the voltage is from a high impedance source (e.g. such as the deflection electrode 30). _{Figure 5 shows the self-cleaning print head 3 with the chamber 26 partially filled with} cleaning fluid 42 at a second fill level. The second fill level is higher than the first fill level _{shown in Figure 4. At the second fill level, as well as the charge electrode 24 being} _{shorted to ground via the lower voltage electrode 28, owing to the cleaning fluid 42,} _{nozzle 22 and gutter 32 are also shorted to ground due to the fill level.} 69726571-1 Turning to Figure 6, the cleaning fluid is provided at a third fill level greater than both the first and second fill levels of Figures 4 and 5. At this third fill level, the deflection electrode _{30 is also shorted to ground by virtue of being electrically connected to the low voltage} electrode 28 by the cleaning fluid 44. _{From Figures 4 to 6, and corresponding description, it will be appreciated that monitoring,} or determining, an electrical response of one or more components disposed within the cleaning chamber 26 can be used to determine a fill level and/or orientation of the print _{head. This provides useful information during operation of the print head which could be} fed back into a cleaning method to determine one or more associated parameters (e.g. forming a feedback loop). Turning to Figure 7, Figures 7 to 9 show three varying fill levels of cleaning fluid within _{the chamber 26 of the self-cleaning print head 3 with the print head 3 in a vertical,} _{downward-facing orientation (e.g. the ink aperture 38 faces downwards). Figures 7 to 9} _{are used to describe how the order of shorting of components disposed within the} _{cleaning chamber 26 varies with a different orientation of print head 3.} _{Beginning with Figure 7, as mentioned Figure 7 shows the self-cleaning print head 3 in} _{a downward facing vertical orientation with a first fill level of cleaning fluid 46. Figure 7} illustrates how even at this first comparatively low fill level 46, each of the gutter 32, deflection electrode 30 and low voltage electrode 28 are connected to one another by _{virtue of the cleaning fluid 46. Accordingly, the deflection electrode 30 is shorted to} ground (i.e. voltage pulled low). Accordingly, where the deflection electrode 30 is shorted to ground before the charge electrode 24, for example, it can be determined that the print _{head 3 is not in the horizontal orientation shown in Figure 4. For completeness, if the} sealing mechanism 34 is also grounded, as shown in Figure 7 each of the sealing mechanism 34, gutter 32, deflection electrode 30 and low voltage electrode 28 are connected to one another by virtue of the cleaning fluid 46. _{Turning to Figure 8, the self-cleaning print head 3 is shown in the same orientation as in} _{Figure 7 but with a second, high fill level of cleaning fluid 48. In Figure 8 a majority of} the volume of the cleaning chamber 26 is filled with cleaning fluid 48, and just a volume defined by the charge electrode 24 is absent cleaning fluid. In the Figure 8 scenario 69726571-1 each of the deflection electrode 30 and electrode 24 would be shorted to ground, by virtue of connection to the low voltage electrode 28, but the nozzle 22 is not. It can therefore be determined that the fill level is as shown in Figure 8, and that the orientation is as shown in Figure 8. _{Turning to Figure 9, the self-cleaning print head 3 is shown with a third fill level of cleaning} fluid 49, higher than both the first and second fill levels of Figures 7 and 8. In Figure 9 the third fill level corresponds to a completely filled cleaning chamber 26, including the volume defined by the charge electrode 24. In this scenario all of the components are connected to one another and would therefore be shorted to ground by virtue of the fill level. The third fill level could therefore be determined, along with an order of shorting _{of components being used to infer the orientation of the print head 3.} Turning to Figure 10, a flow chart showing the steps of a method 70 of using the self- _{cleaning print head 3, linked to the varying fill levels shown in Figures 4 to 9, is provided.} In a first step 72 the fill stage is initiated. The fill stage 72 may form part of a cleaning method. Alternatively, the initiate fill stage 72 may form part of an orientation testing method. _{Following, or during, the initiation of the fill stage 72, the chamber is at least partially filled} with cleaning fluid and/or ink 74. In following step 76 the electrical response of one or more components disposed in the chamber is determined. This may be described as monitoring the electrical response of one or more components disposed in the chamber. Specifically, step 76 may comprise determining the electrical response of one or more of: the nozzle 22 (optionally a nozzle body 20 defining the nozzle 22), the charge electrode 24, low voltage electrode 28, deflection electrode 30, and gutter 32 (optionally an associated gutter build-up sensor of the gutter 32). Determining the electrical response may comprise determining a voltage drop, or a voltage level, of the one or _{more components disposed in the chamber. Put another way, determining the electrical} response of the one or more components may comprise determining whether the component has been connected to a lower potential component (e.g. shorted to ground). _{As described in connection with Figures 4 to 9, this occurs by virtue of the varying fill} level of cleaning fluid (and/or ink) providing electrical connections between the _{components disposed in the cleaning chamber. Determining the electrical response of} 69726571-1 the component may comprise one or of: sensing a current draw from a voltage _{source, sensing a current sunk into a lower potential (e.g. grounded) components, and} sensing a voltage drop. Determining the electrical response of components in the chamber 76 may comprise determining an order of the plurality of components being connected to a lower potential (e.g. shorted to ground). Put another way, where step 76 comprises determining an electrical response of a plurality of components in the chamber, the order in which these _{components are connected to a lower potential (e.g. shorted to ground [i.e. the voltage} level reduced to zero]) is preferably determined. Following step 76, a parameter of the print head is determined at step 78. As previously mentioned, the parameter may comprise a fill level of cleaning fluid (and/or ink) within the cleaning chamber. That is to say, based upon the electrical response of one or more _{components in the chamber, it is possible to determine a liquid level of fluid within the} _{chamber. Alternatively, the parameter of the print head may comprise an orientation of} _{the self-cleaning print head. Again, as described and illustrated in connection with} _{Figures 4 to 6, in comparison to Figures 7 to 9, different orientations of print head result} in an effective different order of the components disposed within the chamber being _{connected to one another. Determining the order of components shorting to ground, or} grounding, or their voltage level reducing, can therefore also be used to infer an _{orientation of the print head. The method then terminates at step 80. A drainage or} soaking step preferably follows. It will be appreciated that the method 70 may form part of a cleaning method (e.g. where it is desired to determine the fill level during the fill stage 52 of the method 50 shown in _{Figure 3). Alternatively, the method 70 may be a standalone method of determining a} _{print head orientation. It will also be appreciate that before the method 70 ends at step} _{80, in response to determining the parameter of the print head 78 one or more action} _{steps may occur. For example, if it is determined that a fill level of the print head is either} _{too high or too low, a parameter of the method may be adjusted accordingly to drain} some cleaning fluid from the chamber or potentially to fill the chamber with further _{cleaning fluid to achieve a desired fill level (respectively).} 69726571-1 In some embodiments, where it is determine a fill level, an orientation of the print head may first be determined. The orientation of the print head may be determined by an orientation sensor (e.g. accelerometer) or manually input by an operator. Put another way, the orientation may be determined in a manner which is not related to the fill level. Knowing the orientation of the print head may provide a more reliable determination of the fill level. Before at least partly filling the chamber with cleaning fluid, in step 74, an electrical response control code mode may be initiated. The electrical response control code mode refers to a different mode of operation of the deflection electrode, specifically a trip functionality thereof in normal operations. Trip is another way of describing an _{unexpected ‘grounding’, or ‘shorting’, of the deflection electrode. A trip may be detected} by a current detection and/or voltage reduction. In particular, a trip may be indicative of a current draw rising above a threshold level. Typically, when a trip event is detected, indicative of a fault, the printer is shut down. In accordance with the invention, upon initiation of the electrical response control code mode, the trip functionality is shut down (e.g. the typical printer response to shut down the printer, upon detection of a trip event, is prevented). The electrical response control code mode instead utilises the response of the deflection electrode to determine a parameter of the print head (e.g. fill level or orientation). It may also be possible to determine a volume of cleaning fluid within the wider system by determining the fill level within the chamber. For example, if the volume of a fluid conduit extending between the printer body and the print head is known (e.g.6 cc’s), and the chamber 26 volume is known (e.g.3 cc’s), a ‘full’ fill level can be taken to mean there are 9 cc’s of cleaning fluid in the system (conduit volume + chamber volume). This is useful for a number of reasons, including being able to monitor and/or predict solvent usage/the need to replace a solvent cartridge in use. It is also envisaged that cleaning fluid be drawn into the fluid conduit only until the chamber is determined to be full, reducing the amount of cleaning fluid otherwise present in the fluid conduit(s). Put another way, drawing excess cleaning fluid from elsewhere in the system may be avoided. 69726571-1 Turning to Figure 11, a method 100 to another embodiment of the invention is illustrated by way of a flow chart. The method 100 may be carried out in connection with _{the print head 3 described earlier in this document.} _{It will be recalled, from the method 50 shown in Figure 3, that a cleaning method 50} comprises fill, soak, drain and drying stages. The fill stage 52 comprises at least partially filling the cleaning chamber with cleaning fluid, such as solvent. With reference to Figure 11, Figure 11 shows a flow chart for a method 100 in which the _{chamber is at least partially filled with ink to clean the chamber, the ink then being} _{subsequently drained. In a subsequent fill cycle, the chamber is at least partially filled} _{with cleaning fluid (e.g. solvent), and the cleaning fluid then subsequently drained. This} may be described as a twin-shot cleaning cycle, or a twin-shot fill cycle. Advantageously, this reduces the solvent use in contrast to if the twin-shot cycle were to occur with solvent _{in both phases (for example), whilst still providing a cleaning effect by virtue of the ink} _{loosening ink residue or other build-up on/in the cleaning chamber and associated} components. In a first stage of the method 100 a fill stage is initiated 102. The cleaning chamber is _{sealed 104, otherwise described as activation or closure of a sealing mechanism. At} _{subsequent step 106, the chamber is at least partially filled with ink. The chamber may} _{be entirely filled, or just partly filled, with ink. In subsequent step 108 the ink is drained} _{from the cleaning chamber, along with any ink residue or other deposits removed by the} liquid ink. At subsequent step 110 the chamber is at least partially filled with cleaning fluid, preferably in the form of solvent. Step 110 thus provides an effective rinse of the _{chamber for any ink liquid which may remain after steps 106, 108. At step 112 the} _{cleaning fluid is drained from the cleaning chamber, along with any ink residue or} _{remaining ink liquid. The method terminates at step 114.} It will be appreciated that the method 100 may be carried out by a controller forming part of a continuous inkjet printer. Turning to Figure 12, a flow chart is provided illustrating the steps of a method 120 according to another embodiment of the invention. The method 120 is one example of at least the fill stage 52 shown in the method 50 of Figure 3, with an optional soaking 69726571-1 _{step 128 corresponding to a soak step the method 50 in Figure 3, and a drainage} step 130 corresponding to the drain step 56 in Figure 3. The method 120 can be carried _{out on the self-cleaning print head 3.} _{Figure 12 shows exemplified fill, soak and drain steps in which an aerated cleaning fluid} (or ink) is used to at least partially fill the cleaning chamber. Another way of describing _{the aerated cleaning fluid (or ink) is a froth. Aerated fluid has a greater volume than if} _{the fluid were entirely in liquid form. The aerated fluid is therefore advantageous in being} able to reach, and clean, some difficult-to-reach areas of the cleaning chamber, _{particularly when the cleaning chamber is not entirely filled with fluid. The use of aerated} _{fluid is also advantageous in that less liquid (e.g. cleaning fluid or ink) is used. That is to} say, less cleaning fluid liquid or ink is needed when it is aerated. Considering each of the steps in turn: an initiate fill stage is labelled 122. At step 124 a cleaning chamber is sealed, preferably by a sealing mechanism. In subsequent step _{126 the cleaning chamber is at least partially filled with aerated cleaning fluid or ink. In} _{one embodiment this comprises supplying a volume of aerated cleaning fluid (or ink) to} the chamber as a froth. That is to say, the cleaning fluid (or ink) enters the chamber as _{an aerated cleaning fluid (or ink). In other embodiments, the cleaning fluid (or ink) enters} _{the chamber as a liquid, and is subsequently aerated in the chamber to form an aerated} _{cleaning fluid (or ink). This is more vigorous than merely percolating, or bubbling, air} _{through a partly filled chamber, and instead refers to a stable aerated cleaning fluid (or} _{ink) being generated in the cleaning chamber, incorporating a mixture of liquid and gas} _{phases. Where the aerated cleaning fluid (or ink) is supplied as a froth to the chamber,} the froth may be generated by drawing in cleaning fluid (or ink) from a solvent source or ink source using a venturi (e.g. a jet pump). The action of drawing the solvent or ink through the venturi acts to create a froth, which can subsequently be provided to the print _{head in the chamber. It will be appreciated that either a cleaning fluid (e.g. solvent, such} as used or virgin solvent) or ink can be aerated in accordance with this embodiment. In subsequent step 128 an optional soaking step is provided. As will be appreciated from the dashed lines, in some embodiments the soak step 128 may be omitted. However, it is anticipated that during the soak stage the method pauses for a period of time to allow _{the aerated cleaning fluid (or ink) to act on the ink residue/deposits in the chamber, and} _{associated components, so as to clean them and loosen them. The soak step may last} 69726571-1 for, for example, around 10 seconds, 30 seconds, or around 60 seconds. The soaking step may last for a longer period of time for a deep clean cycle. _{In step 130 the aerated cleaning fluid (or ink) is drained from the cleaning chamber. The} _{cleaning chamber is preferably entirely drained of the aerated cleaning fluid (or ink). In} subsequent step 132 the method 120 ends. Step 132 may be followed by a drying stage. One or more surfactants may be introduced into the cleaning fluid (or ink) to facilitate the formation of a stable foam. Turning to Figure 13, a schematic illustration of a cross-section side view of a self- _{cleaning print head 150 according to an embodiment of the invention is provided. The} _{print head 150 shares many features in common with the print head 3 shown in Figure} _{2, like features are provided with like reference numerals. A distinction of the self-} _{cleaning print head 150 is that the cleaning chamber 26 comprises a plurality of subports,} _{two of which are labelled, 152a and 152g (all subports being generally referred to by} numeral 152), in the cross-section view of Figure 13. _{The plurality of subports 52 provide openings, or fluid communications, into the cleaning} chamber 26 through which cleaning fluid may be supplied or drained, and by which air may be received in the chamber 26. The air being received may occur during a drying _{stage of a cleaning method or, alternatively, during pressure balancing in use when the} _{ink jet 36 is being produced (e.g. during printing). Pressure balancing refers to the} _{provision of air into the print head 150 to avoid the pressure within the print head 150} reducing, owing to the operation of the gutter 32 and associated gutter pump reducing _{the pressure within the print head (e.g. in the sealed chamber 26). Maintaining a near} _{atmospheric, or positive, pressure is desirable to avoid dust and other debris being drawn} _{into the print head 150 from the factory setting in which the print head 150 is used.} _{The plurality of subports 152a, 152g are so called because they define multiple apertures} _{of what may be considered to be a single port. Both subports 152a, 152g (and, indeed,} _{all subports 152) are provided in fluid communication with a cavity 154 disposed between} _{the subports 152 and the nozzle 22. The cavity 154 is, in turn, provided in fluid} communication with a supply conduit 156. Supply conduit 156 may be connected or connectable to a cleaning fluid supply or an air supply. 69726571-1 _{Turning now to Figure 14, an axial cross-section view of the print head 150 of Figure 13} _{is taken about construction line 158 shown in Figure 13. Figure 14 is taken between the} _{deflection electrode 30 and the charge electrode 24, facing towards the nozzle 22.} _{Figure 14 shows the plurality of subports 152 comprising a total of 12 ports labelled 152a} _{to k respectively. In the illustrated embodiment these are all circular apertures, but other} _{geometries could otherwise be used. The plurality of subports 152 are provided in fluid} communication with the cavity 154 shown in Figure 13. Also visible in Figure 14 is an _{outer perimeter of the print head 150, the nozzle body 20 and the nozzle 22 defined by} the nozzle body 20, and a boundary of the cleaning chamber 26. _{The plurality of subports are arranged around the nozzle 22, specifically around a nozzle} axis defined by the nozzle 22. From Figure 13 it will be appreciated that the ink jet 36 is _{indicative of an axis defined by the nozzle 22 (e.g. a nozzle axis).} _{Incorporation of the plurality of the subports 152 is advantageous for a number of} reasons. Firstly, when it is desired to drain the cleaning chamber 26 of cleaning fluid, _{provision of a plurality of subports 152, in communication with the supply conduit 156 via} _{the cavity 154 (for example), means that the cleaning fluid can be drained with the print} _{head 150 in a range of different orientations. Put another way, the drainage is not limited} to a single aperture in the chamber 26, and can occur from any one of the plurality of _{subports. This can occur from the wider range of orientations. A further advantage} _{provided by the plurality of subports is during air supply. When the inkjet 36 is running,} the gutter 32 is also activated. As previously described, it is desirable to provide pressure _{balancing of the print head 150 when in operation (e.g. in a printing mode). Providing} _{the plurality of subports 152, particularly distributed around the nozzle axis, means that} balancing air can be provided whilst reducing any distribution to the ink jet 36. The _{plurality of subports can also be used to dry the cleaning chamber during the drying stage} _{of the cleaning cycle (e.g. by way of introduction of air or another drying fluid).} _{For pressure balancing, during the printing mode, the plurality of subports 152 can be} _{connected to an air supply. The air supply may be an atmospheric air supply (e.g. a} passive supply of air). Alternatively, the air supply may be provided with an in-line air _{pump, for example, so as to positively, or actively, pump air into the print head 150.} _{Provision of a passive air supply is desirable during printing because it removes the need} 69726571-1 _{to operate an air pump. Wear on the is thus at least reduced. The provision of a} passive supply of air, during the operation of the inkjet 36, may be described as allowing _{the jet to breathe. This may otherwise be described as the plurality of subports diffusing} _{air around the jet. From the above it will be appreciated that the plurality of subports 152} _{can be used to provide pressure balancing during a printing mode, and can also provide} drying during a cleaning cycle. For any embodiment described herein, the print head may be a self-cleaning print head. The print head may comprise a cleaning chamber, optionally selectively sealable by a sealing mechanism. The at least one electrode may be disposed in the chamber. Preferably one or more of a nozzle, charge electrode, low voltage electrode, deflection electrode and gutter are also disposed in the chamber. Any one of the methods described herein may be implemented by a controller. The controller is preferably in electrical communication with the printer body and print head. The controller is preferably disposed in the printer body, but may otherwise be disposed in the print head. Unused solvent may otherwise be described as fresh, or virgin, solvent. 69726571-1

Claims

CLAIMS: _{1. A continuous inkjet printer comprising:} a printer body comprising an ink system for storing ink and supplying ink to a self- cleaning print head; an umbilical coupling the self-cleaning print head to the printer body, the umbilical _{comprising one or more fluid conduits and electrical wires;} _{a controller in electrical communication with the self-cleaning print head;} 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; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; w_{herein one or more of the nozzle, charge electrode, low voltage} electrode, deflection electrode and gutter are disposed in the cleaning chamber; wherein the controller is configured to: initiate a fill stage, comprising at least partially filling the cleaning chamber with _{cleaning fluid and/or ink; and} _{determine an electrical response of the one or more components disposed in the} cleaning chamber to determine a parameter of the self-cleaning print head. _{2. The printer according to claim 1, wherein the electrical response of the one or} _{more components disposed in the cleaning chamber comprises one or more of: a current} _{draw from a voltage source, a current sunk into one or more lower potential components,} and a voltage drop. _{3. The printer according to claims 1 or 2, wherein a plurality of: the nozzle, charge} electrode, low voltage electrode, deflection electrode and gutter are disposed in the cleaning chamber. _{4. The printer according to claim 3, wherein determining the electrical response of} the one or more components disposed in the cleaning chamber comprises determining an electrical response of the plurality of components disposed in the cleaning chamber. 69726571-1

_{5. The printer according to claim 4, determining the electrical response of} the plurality of components disposed in the cleaning chamber comprises determining an _{order of the plurality of components being connected to a lower potential.} _{6. The printer according to any preceding claim, wherein the controller is configured} to initiate a cleaning cycle, the cleaning cycle comprising the fill stage. _{7. The printer according to any preceding claim, wherein the parameter of the self-} cleaning print head comprises a fill level of the cleaning fluid and/or ink in the cleaning chamber. _{8. The printer according to any preceding claim, wherein the parameter of the self-} cleaning print head comprises an orientation of the self-cleaning print head. _{9. A method of using a self-cleaning print head of a continuous inkjet printer,} comprising: initiating a fill stage, comprising at least partially filling a cleaning chamber of the _{self-cleaning print head with cleaning fluid and/or ink, the cleaning chamber comprising} one or more components disposed therein; and determining an electrical response of the one or more components disposed in _{the cleaning chamber and determining a parameter of the self-cleaning print head.} _{10. The method according to claim 9, wherein determining the electrical response of} the one or more components comprises determining one or more of: a current draw from _{a voltage source, a current sunk into one or more lower potential components, and a} voltage drop. _{11. The method according to claims 9 or 10, wherein a plurality of nozzle, charge} electrode, low voltage electrode, deflection electrode and gutter are disposed in the cleaning chamber. _{12. The method according to claim 11, wherein determining the electrical response} of the one or more components disposed in the cleaning chamber comprises determining an electrical response of the plurality of components disposed in the cleaning chamber. 69726571-1

_{13. The method according to claim wherein determining the electrical response} of the plurality of components disposed in the cleaning chamber comprises determining _{an order of the plurality of components being connected to a lower potential.} _{14. The method according to any one of claims 9 to 13, wherein the method} comprises initiating a cleaning cycle, the cleaning cycle comprising the fill stage. _{15. The method according to any one of claims 9 to 14, wherein determining the} parameter of the self-cleaning print head comprises determining a fill level of the cleaning fluid and/or ink in the cleaning chamber. _{16. The method according to claim 15, wherein the method further comprises} pausing a supply of cleaning fluid and/or ink when the fill level of the cleaning fluid in the cleaning chamber reaches a predetermined level. _{17. The method according to any one of claims 9 to 16, wherein determining the} parameter of the self-cleaning print head comprises determining an orientation of the self-cleaning print head. _{18. 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; a_{t least partially filling the cleaning chamber with ink to clean the cleaning} chamber; draining the ink from the cleaning chamber; a_{t least partially filling the cleaning chamber with cleaning fluid to rinse the} cleaning chamber; and draining the cleaning fluid from the cleaning chamber. _{19. A continuous inkjet printer comprising:} a printer body comprising an ink system for storing ink and supplying ink to a self- cleaning print head; an umbilical coupling the self-cleaning print head to the printer body, the umbilical _{comprising one or more fluid conduits and electrical wires;} a controller in electrical communication with the self-cleaning print head; 69726571-1 the self-cleaning print head a cleaning chamber selectively sealable by a sealing mechanism; a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; wherein one or more of the nozzle, charge electrode, low voltage electrode, deflection electrode and gutter are disposed in the cleaning chamber; wherein the controller is configured to: seal the cleaning chamber by actuating the sealing mechanism; at least partially fill the cleaning chamber with ink to clean the cleaning chamber; drain the ink from the cleaning chamber; at least partially fill the cleaning chamber with cleaning fluid to rinse the cleaning chamber; and drain the cleaning fluid from the cleaning chamber. _{20. 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 a_{t least partially filling the cleaning chamber with a volume of aerated cleaning} _{fluid or ink.} _{21. The method of claim 20, wherein the volume of aerated cleaning fluid or ink is} supplied to the cleaning chamber as a froth. _{22. The method of claim 21, wherein the volume of aerated cleaning fluid or ink is} supplied to the cleaning chamber as a liquid cleaning fluid or ink and subsequently _{aerated in the cleaning chamber to form the aerated cleaning fluid or ink.} _{23. A continuous inkjet printer comprising:} a printer body comprising an ink system for storing ink and supplying ink to a self- cleaning print head; 69726571-1 an umbilical coupling the self- print head to the printer body, the umbilical _{comprising one or more fluid conduits and electrical wires;} a controller in electrical communication with the self-cleaning print head; 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; a charge electrode for selectively charging the stream of ink droplets; a low voltage electrode and a deflection electrode for guiding the stream of ink droplets; and a gutter for receiving droplets of ink which are not used for printing; w_{herein one or more of the nozzle, charge electrode, low voltage} electrode, deflection electrode and gutter are disposed in the cleaning chamber; wherein the controller is configured to: seal the cleaning chamber by actuating the sealing mechanism; at least partially fill the cleaning chamber with a volume of aerated cleaning fluid or ink. _{24. 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, the nozzle defining a nozzle axis; 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; w_{herein the cleaning chamber comprises a plurality of subports arranged around} _{the nozzle axis; and} wherein the plurality of subports are connectable to an air supply. _{25. A method of using a self-cleaning print head of a continuous inkjet printer,} comprising: initiating a printing mode comprising: generating and ejecting a stream of ink droplets for printing, via a nozzle, the nozzle defining a nozzle axis, and activating a gutter pump to draw ink droplets, not used for printing, through a gutter; and providing a supply of air around the stream of ink droplets via a plurality of subports arranged around the nozzle axis; 69726571-1 _{terminating the printing mode, a cleaning cycle comprising:} sealing a cleaning chamber of the print head by actuating a sealing mechanism; a_{t least partially filling the cleaning chamber with cleaning fluid;} draining the cleaning fluid from the cleaning chamber via one or more of the plurality of subports; and drying the cleaning chamber by providing a supply of air via one or more of the plurality of subports. _{26. The method according to claim 25, wherein drying the cleaning chamber by} providing a supply of air via one or more of the plurality of subports comprises pumping air through the one or more of the plurality of subports. _{27. The method according to claims 25 or 26, wherein drying the cleaning chamber} by providing a supply of air via one or more of the plurality of subports comprises connecting the one or more of the plurality of subports to atmosphere and providing a passive supply of air. 69726571-1