WO2025257570A1 - Printer and associated method - Google Patents

Abstract

There is disclosed a cleaning cap for a print head of a continuous inkjet printer. The cleaning cap comprises a sealing surface and an engagement feature. The engagement feature is coupled to the sealing surface. The engagement feature is configured to detachably couple the cleaning cap to the print head.

Description

_{Printer and associated method} Field _{The present invention relates to a cleaning cap for a print head, a print head assembly, a continuous inkjet printer, a sealing mechanism, a washing station, and various} associated methods. Background 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. 69719087-1 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 69719087-1 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 for at least a period of time). Deposits can 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. Summary According to a first aspect of the invention there is provided a cleaning cap for a print head of a continuous inkjet printer, wherein the cleaning cap comprises: a sealing surface; and an engagement feature, coupled to the sealing surface; wherein the engagement feature is configured to detachably couple the cleaning cap to the print head. Advantageously, the cleaning cap can be used to seal the print head for cleaning. _{The cleaning cap may comprise a skirt and the engagement feature may be disposed on} the skirt. The term ‘skirt’ denotes a tubular member extending away from the sealing surface. Advantageously the skirt provides a larger surface area for provision of engagement _{features, enhancing the security of the cleaning cap and print head coupling. The skirt} itself provides a large contact area between the print head and the cleaning cap. This is desirable as a large contact area can provide some degree of additional sealing and engagement. 69719087-1 The engagement feature may be disposed on or in an outer periphery of the cleaning cap. By utilising the outer periphery of the cleaning cap, the cleaning cap’s footprint can be reduced. An exterior (e.g. end cap) of the print head may also be cleaned. _{The engagement feature may comprise one or more projections or recesses.} The one or more recesses may be for a bayonet mount or a snap fit. Bayonet mounts and snap fits allow very quick coupling and detachment of the cleaning cap. Bayonet mounts and snap fits also provide repeatable location of the cleaning cap and thus repeatable sealing between the print head and the cleaning cap _{The engagement feature may comprise a threaded surface. Threaded engagement of the cap provides a very secure, but detachable, coupling} between the print head and the cleaning cap. _{The cap may comprise a fluid port.} The fluid port may be configured to allow cleaning fluid into and/or out of the print head Advantageously, the provision of a fluid port allows the cleaning cap to effect cleaning in conjunction with print heads having no integral fluid ports. _{The cap may comprise a port exposed at the sealing surface of the cap for alignment} with a port of the print head. The sealing surface may be described as an internal surface. The exposed port allows the cleaning cap to form fluid interfaces with other ports provided on the print head. _{According to a second aspect of the invention there is provided a print head assembly} comprising: a print head for a continuous inkjet printer; and 69719087-1 _{a cleaning cap according to the first aspect of the invention, coupled to the print} head; wherein the cleaning cap and print head define an enclosed cleaning chamber. Advantageously, the enclosed cleaning chamber can be flushed with cleaning fluid to clean one or more components therein. The cleaning cap may be coupled to an end face of the print head. Coupling the print head end face and the cleaning cap provides further hydraulic sealing in addition to the engagement feature, reducing the risk of leaks. The cleaning cap may be coupled to the print head around a periphery of the print head. The term periphery denotes the portions of the print head outer shell adjacent to the end face. _{The enclosed cleaning chamber may comprise a portion between the sealing surface of} the cleaning cap and the end face of the print head. Advantageously, the provision of a portion of the enclosed cleaning chamber at the end face allows undesirable build-up of ink deposits at the end face to be removed. The print head and the cleaning cap may be hingeably coupled. _{By hingeably coupling the print head and the cleaning cap, loss of the cleaning cap can} be prevented in use, whilst allowing the cleaning cap to be removed from the print head ink aperture during operation. _{The cleaning cap may comprise one or more magnetic elements. The print head may comprise a reed switch configured to detect the position of the} cleaning cap. 69719087-1 Advantageously, detection of the cleaning cap position may be used to prevent initiation of a print head cleaning cycle in the absence of a cleaning cap, rendering the arrangement safer. _{The print head may comprise one or more magnetic elements, detachably coupling the} cleaning cap to the print head. _{Magnetic elements in the cleaning cap and the print head can form a magnetic interface,} advantageously allowing rapid coupling and detachment of the cleaning cap. _{The print head may comprise one or more passive valves. Advantageously, passive valves do not require external power or control inputs,} simplifying the print head assembly. _{The cleaning chamber may comprise the one or more passive valves; wherein the} configuration of the one or more passive valves is dependent on print head orientation. _{The one or more passive valves may be actuated by buoyancy and/or weight. The} passive valves may comprise float valves. Advantageously, dependency of the passive valves on print head orientation can provide orientation-agnostic operation, reducing or avoiding the need for complex sensors and control systems. _{The print head may comprise a drain port arrangement, comprising:} a plurality of drain ports configured to drain cleaning fluid from the enclosed cleaning chamber; and a member rotatable with respect to the drain ports; wherein a subset of the plurality of drain ports are blockable by rotation of the member. The plurality of drain ports may be arranged radially about a central axis and the moveable member may be rotatable about the central axis. 69719087-1 Blocking a subset of the drain ports ensures that cleaning fluid can be effectively drained from the drain ports in fluid communication with the cleaning fluid. _{The enclosed cleaning chamber may comprise one or more corners, and the enclosed cleaning chamber may further comprise a plurality of drain ports, at least one drain port} being disposed at each corner of the enclosed cleaning chamber. _{The term corner here may be taken to denote any sudden contour change within the enclosed cleaning chamber. Corner encompasses an intersection point between a} plurality of surfaces, or faces, of the chamber. Advantageously, the provision of drain ports at each corner of the enclosed cleaning chamber ensures that the enclosed cleaning chamber can be drained effectively at any print head orientation. _{The print head may comprise a first port, exposed at the end face, and the cleaning cap} comprises a second port, wherein the first port and second port are aligned, defining a fluid conduit. Advantageously, the definition of fluid conduits across the print head and the cleaning cap can reduce the number of connections needing to be manually joined by an operator. _{According to a third aspect of the invention there is provided a continuous inkjet printer} comprising: a _{print head assembly according to the second aspect of the invention; and} an ink system for storing ink and supplying ink to the print head. _{The continuous inkjet printer may comprise a mount configured to support the print head} assembly in a plurality of orientations, wherein the print head assembly is moveable between: a printing configuration, wherein the print head assembly is supported in a first orientation; and a cleaning configuration, wherein the print head is supported in a second orientation. 69719087-1 Advantageously, the provision of the mount allows the print head to be accurately and repeatedly moved between optimal positions for printing and cleaning, respectively. The orientation of the print head may be moved between the printing and cleaning configuration by a robot arm or operator. _{According to an fourth aspect of the invention there is provided a method for cleaning a} print head of a continuous inkjet printer, wherein the method comprises: coupling a cleaning cap to the print head, defining an enclosed cleaning chamber within the print head; flushing the enclosed cleaning chamber of the print head with cleaning fluid; and decoupling the cleaning cap and print head. The cleaning fluid may be a solvent. Advantageously, coupling and decoupling the cleaning cap provides an economic and _{repeatable means to seal the print head for flushing. The cleaning fluid is thus contained} within the print head. _{The print head may comprise one or more drain ports disposed in the enclosed cleaning chamber, and the method may further comprise orienting the print head for printing, such} that the one or more drain ports are located proximate pooling regions of the enclosed cleaning chamber. The term ‘pooling locations’ denotes areas of the enclosed cleaning chamber at which (residual) cleaning liquid accumulates. Proximate pooling regions may be described as the drain ports being provided in fluid communication with areas of the chamber where cleaning fluid has a tendency to stand in that orientation of print head. Advantageously, orienting the print head to locate the one or more drain ports at pooling regions means the enclosed cleaning chamber can be drained effectively. _{The method may further comprise moving the print head between:} a printing configuration, wherein the print head is supported in a first orientation; and 69719087-1 a cleaning configuration, wherein the print head is supported in a second orientation; wherein, in the cleaning configuration the enclosed cleaning chamber of the print head is flushed with cleaning fluid. Advantageously, the moving the print head between the first and second orientations for printing and cleaning respectively allows more efficient cleaning of the print head. _{According to an fifth aspect of the invention there is provided a sealing mechanism for} sealing a print head of a continuous inkjet printer, comprising: a casing defining an ink aperture; a moveable body, held moveably captive in the casing; and an exposed engagement feature, coupled to the moveable body; wherein the moveable body is moveable by the exposed engagement feature between: a first configuration, wherein an ink path is defined through the ink aperture; and a second configuration, wherein the moveable body closes the ink aperture. The exposed engagement feature may be integral with the moveable body. Advantageously, the sealing mechanism provides a self-contained means to seal the print head for cleaning. _{According to a sixth aspect of the invention there is provided a washing station for a print} head of a continuous inkjet printer, wherein the washing station comprises: a hose, having a first end and a second end; a cleaning cap, for engagement with the print head, in fluid communication with the first end of the hose; a pump in fluid communication with the second end of the hose; and a cleaning fluid source in fluid communication with the pump. The cleaning cap may be in accordance with the first aspect of the invention, optionally incorporating one or more optional features described in connection with the first aspect of the invention. 69719087-1 Advantageously the washing station can effect cleaning in conjunction with print heads having no integral provision to pump cleaning fluid. _{The pump may be a manual pump. The manual pump may be may be a bulb-type hand} pump. Manual pumps reduce the need for an external source of power for the washing station. _{The washing station may further comprise an inspection section for visual inspection of} cleaning fluid. Advantageously, the inspection section allows the progress of cleaning and/or cleanliness of the print head to be monitored by an operator. _{According to a seventh aspect of the invention there is provided a continuous inkjet} printer system, comprising: a _{washing station according to the sixth aspect of the invention; and} a print head; wherein the cleaning cap of the washing station is engaged with the print head. _{According to an eighth aspect of the invention there is a provided a method for cleaning} a print head of a continuous inkjet printer, wherein the method comprises: engaging a cleaning cap of a washing station of the sixth aspect of the invention with the print head; pumping cleaning fluid from the cleaning fluid source into the print head; draining the cleaning fluid from the print head; and disengaging the cleaning cap and print head. _{Advantageously, engaging the cleaning cap of the washing station can facilitate cleaning} of the print head in-situ (e.g. without requiring repositioning, or movement, of the print head). _{According to a ninth aspect of the invention there is provided a print head for a continuous} inkjet printer, comprising: a cleaning chamber; 69719087-1 a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets, the at least one electrode disposed within the cleaning chamber; a gutter for receiving droplets of ink which are not used for printing; and one or more passive valves. The print head may be a self-cleaning print head. The cleaning chamber may be _{selectively sealed by a sealing mechanism (e.g. defining an enclosed cleaning chamber). The cleaning chamber may comprise the one or more passive valves. The configuration of the one or more passive valves may be dependent on print head orientation. The one} or more passive valves may be actuated by buoyancy and/or weight. The passive valves may comprise float valves. Advantageously, dependency of the passive valves on print head orientation can provide orientation-agnostic operation, reducing or avoiding the need for complex sensors and control systems. _{According to a tenth aspect of the invention there is provided a print head for a} continuous inkjet printer, comprising: a cleaning chamber; a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets, the at least one electrode disposed within the cleaning chamber; a gutter for receiving droplets of ink which are not used for printing; and a drain port arrangement, comprising: a plurality of drain ports configured to drain cleaning fluid from the enclosed cleaning chamber; and a member rotatable with respect to the drain ports; wherein a subset of the plurality of drain ports are blockable by rotation of the member. The print head may be a self-cleaning print head. The cleaning chamber may be selectively sealed by a sealing mechanism (e.g. defining an enclosed cleaning chamber). 69719087-1 The plurality of drain ports may be arranged radially about a central axis and the moveable member may be rotatable about the central axis. Blocking a subset of the drain ports ensures that cleaning fluid can be effectively drained from the drain ports in fluid communication with the cleaning fluid. _{According to a eleventh aspect of the invention there is provided a print head for a} continuous inkjet printer, comprising: a cleaning chamber; a nozzle for generating and ejecting a stream of ink droplets for printing; a charge electrode for selectively charging the stream of ink droplets; at least one electrode for guiding the stream of ink droplets, the at least one electrode disposed within the cleaning chamber; a gutter for receiving droplets of ink which are not used for printing; and a plurality of drain ports, at least one drain port being disposed at each corner of the enclosed cleaning chamber. The print head may be a self-cleaning print head. The cleaning chamber may be _{selectively sealed by a sealing mechanism (e.g. defining an enclosed cleaning chamber).} The term corner here may be taken to denote any sudden contour change within the _{enclosed cleaning chamber. Corner encompasses an intersection point between a} plurality of surfaces, or faces, of the chamber. Advantageously, the provision of drain ports at each corner of the enclosed cleaning chamber ensures that the enclosed cleaning chamber can be drained effectively at any print head orientation. According to a twelfth aspect of the invention there is provided a continuous inkjet printer, comprising: a print head; an ink system for storing ink and supplying ink to the print head; and a mount configured to support the print head assembly in a plurality of orientations, wherein the print head assembly is moveable between: a printing configuration, wherein the print head assembly is supported in a first orientation; and 69719087-1 a cleaning configuration, wherein the print head is supported in a second orientation. Advantageously, the provision of the mount allows the print head to be accurately and repeatedly moved between optimal positions for printing and cleaning, respectively. The orientation of the print head may be moved between the printing and cleaning configuration by a robot arm or operator. According to a thirteenth aspect of the invention there is provided a method for cleaning _{a print head of a continuous inkjet printer, wherein the print head comprises one or more drain ports disposed in a cleaning chamber, and the method comprises:} orienting the print head for printing, such that the one or more drain ports are located proximate pooling regions of the cleaning chamber. The print head may be a self-cleaning print head. The cleaning chamber may be selectively sealed by a sealing mechanism (e.g. defining an enclosed cleaning chamber). The term ‘pooling locations’ denotes areas of the enclosed cleaning chamber at which (residual) cleaning liquid accumulates. Proximate pooling regions may be described as the drain ports being provided in fluid communication with areas of the chamber where cleaning fluid has a tendency to stand in that orientation of print head. Advantageously, orienting the print head to locate the one or more drain ports at pooling regions means the cleaning chamber can be drained effectively. _{The method may further comprise moving the print head between:} a printing configuration, wherein the print head is supported in a first orientation; and a cleaning configuration, wherein the print head is supported in a second orientation; wherein, in the cleaning configuration the cleaning chamber of the print head is flushed with cleaning fluid. 69719087-1 According to a fourteenth aspect of the invention there is provided a method for cleaning a print head of a continuous inkjet printer wherein the print head comprises a cleaning chamber and the method comprises moving the print head between: a printing configuration, wherein the print head is supported in a first orientation; and a cleaning configuration, wherein the print head is supported in a second orientation; wherein, in the cleaning configuration the cleaning chamber of the print head is flushed with cleaning fluid. The print head may be a self-cleaning print head. The cleaning chamber may be selectively sealed by a sealing mechanism (e.g. defining an enclosed cleaning chamber). Advantageously, the moving the print head between the first and second orientations for printing and cleaning, respectively allows more efficient cleaning of the print head. 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 fourteen} aspects of the invention may be combined with one another. Similarly, optional or preferred features of each of the fourteen aspects of the invention may be applicable to one another. Brief Description of Figures 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; F_{igure 2 is a schematic cross-section of part of a print head assembly according} to an embodiment of the invention; F_{igure 3 is a schematic cross-section of a portion of a print head assembly} according to another embodiment of the invention; 69719087-1 _{Figure 4 is a schematic cross-section of a print head assembly according to} another embodiment of the invention; F_{igure 5 is a schematic cross-section of a print head assembly according to} another embodiment of the invention; F_{igure 6 is a schematic cross-section of a print head assembly according to} another embodiment of the invention; F_{igure 7 is a schematic cross-section of a print head assembly according to a} further embodiment of the invention; F_{igure 8 is schematic illustrating the steps for cleaning a print head according to} an embodiment of the invention; F_{igure 9 is schematic illustrating the steps of a cleaning cycle for a print head} according to an embodiment of the invention; F_{igure 10 is a schematic cross-section of an integral sealing mechanism for a print head assembly according to an embodiment of the invention; Figure 11 is a schematic cross-section of an integral sealing mechanism for a print head assembly according to the embodiment shown in Figure 10 in a different} configuration; F_{igure 12 is a schematic cross-section of a portion of a print head assembly,} illustrating a passive valve arrangement according to another embodiment of the invention; Figure 13 schematically illustrates a drain port arrangement according to another embodiment of the invention; F_{igure 14a is a schematic cross-section of a portion of a continuous inkjet printer} according to an embodiment of the invention; F_{igure 14b is a schematic cross-section of a portion of a continuous inkjet printer} according to the embodiment shown in Figure 10 in a different configuration; F_{igure 15 illustrates a self-cleaning print head according to an embodiment of the} invention; F_{igure 16 is a schematic illustration of a washing station, according to an embodiment of the invention, connected to a print head; and} Figure 17 schematically illustrates the steps of a method for cleaning a print head with the washing station shown Figure 16. Detailed Description 69719087-1 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 the controller 6 is disposed in the printer body 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 un 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 (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. 69719087-1 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, _{in order to clean the print head 3. The cleaning 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. In other embodiments, such as that shown in Figure 2, the print head may not be a self- cleaning print head. Instead, manual intervention by an operator may be needed to clean the print head. In other embodiments, the print head may not be a self-cleaning print head, but be cleaned using a wash station. _{Turning to Figure 2, a schematic cross-section side view through part of a print head 12, according to an embodiment of the invention, is provided. Figure 2 shows the print head} 12 comprising a nozzle body 20, charge electrode 24, chamber 26, low voltage electrode _{28, deflection electrode 30, and gutter 32. 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. 69719087-1 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 electrodes. An electric field is selectively 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 38, defined in an end face 34 of the print head 12, for} printing onto a substrate in use. _{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. _{The print head 12 uses a cleaning cap 40, detachably coupled to the print head 12, to} define/seal the chamber 26. _{The print head 12 and the cleaning cap 40 may be collectively referred to as a print head} assembly. The cleaning cap 40 covers the ink aperture 38 and the end face 34. The _{cleaning cap 40 comprises a sealing surface 42 and an engagement feature 44, coupled} to the sealing surface. The engagement feature 44 is configured to detachably couple _{the cleaning cap 40 to the print head (e.g. in a releasable manner). The cleaning cap 40} comprises a skirt 46. The skirt 46 extends along print head 12. Engagement feature 44 _{comprises a threaded surface disposed on the skirt 46, at least in the illustrated embodiment. The cleaning cap 40 is coupled to the print head 12 around a periphery of the print head by the engagement of engagement feature 44 with a complementary set of threads 45 at the print head periphery (e.g. an outer perimeter). The term periphery denotes portions of a print head outer shell 49 adjacent to the end face 34. The cleaning cap may further comprise a gasket or O-ring 48 for enhancing the hydraulic seal between the sealing surface 42 and the print head 12.} 69719087-1 _{The purpose of the cleaning cap 40 is to selectively seal the chamber 26, defining an} enclosed cleaning chamber. 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. The chamber 26 may be described as being defined by a combination of the print head 12 and the cap 40. 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 sealing surface 42 and the end face 34 are separated. As such, the enclosed cleaning chamber 26 comprises a portion between the sealing surface 42 of the cleaning cap 40 and the end face 34 of the print head. This arrangement allows undesirable build- _{up of ink deposits at the end face 34 to be removed by cleaning fluid. Put another way,} the end face 34 of the print head is enclosed by the volume. _{Although not illustrated in Figures 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), drainage of used cleaning fluid from the chamber, 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). The embodiment described with reference to Figure 2 is just one of a plurality of alternative cleaning caps. In the following discussion of selected alternative _{embodiments, reference is made to figures in which detail of the print head structure is omitted for brevity. The print head assemblies discussed below share many features in common with the print head assembly shown and described in connection with Figure 2,} and corresponding components are denoted using the same numerals. 69719087-1 _{In some embodiments, the cleaning cap 40 may comprise one or more fluid ports. Figure 3 schematically illustrates a modified cleaning cap 95 and an adjacent portion of print head 12. Cleaning cap 95 comprises a fluid port 96, which is in fluid communication with} the enclosed cleaning chamber 26. The fluid port 96 is configured to allow cleaning fluid _{into and/or out of the print head. In addition, the print head 12 comprises a first port 98,} exposed at the end face 34, and the cleaning cap 95 comprises a second port 99, _{exposed at the sealing surface 42. The first port 98 and second port 99 are aligned when the cap 95 is engaged with the print head 12. The aligned ports 98, 99 define a fluid conduit across the cleaning cap 95 and the print head 12 (e.g. across a sealing interface} thereof). The Figure 3 embodiment of cleaning cap 95 advantageously provides for the passage of fluid through the cap 95. Cleaning, such as by using a manual wash station, is therefore facilitated. _{Turning to Figure 4, a print head assembly according to an alternative embodiment is} schematically illustrated. In this case, the cleaning cap 60 comprises an engagement _{feature 54 comprising a threaded surface disposed on an outer periphery 62 of the cleaning cap. Put alternatively, the cleaning cap 60 is externally-threaded. The cleaning cap 60 is coupled to the print head 12 by the engagement of the threads of engagement feature 54 with a complementary set of (internal) threads 55 disposed on a protruding lip 64. The sealing surface 42 engages the end face 34 of the print head 12. Figure 5 shows a further alternative embodiment comprising a cleaning cap 70. Cleaning} cap 70 differs from the above-described embodiments in its engagement feature 74. The _{engagement feature 74 comprises a protrusion for a snap-fit disposed on a skirt 46 of the cleaning cap 70. The cleaning cap 70 is coupled to the print head 12 around a periphery of the print head by the engagement of engagement feature 74 with a complementary depression 75 (e.g. recess) disposed at the print head periphery. This} engagement may be described as a snap-fit arrangement. In an alternative, the snap fit protrusion and complementary depression may instead be _{disposed at the print head periphery and the cleaning cap skirt, respectively. Figure 6 shows an embodiment of the print head assembly comprising a cleaning cap 80, wherein the engagement feature 84 comprises a plurality of projections (e.g. a pair,} 69719087-1 _{in this instance) for a bayonet mount (e.g. fitting). The pair of projections of engagement} feature 84 are configured to be inserted into a complementary recess 85 defined in the print head 12. In an alternative, schematically illustrated in Figure 7, the cleaning cap 90 comprises a _{first plurality of magnetic elements 92a. In addition, the print head 12 comprises a second plurality of magnetic elements 92b. The first and second plurality of magnetic elements 92a, 92b are configured to attract each other, detachably coupling the cleaning cap 90} to the print head 12. _{Additionally, or alternatively, the print head may also comprise a reed switch configured to detect the position of the cleaning cap. In an example, the reed switch may form part of a system preventing initiation of a print head cleaning cycle in the absence of a} cleaning cap. The reed switch may be at least partly defined by one or more magnetic elements disposed in the cap or print head. _{In some embodiments, the print head and the cleaning cap are hingeably coupled. This} can prevent loss of the cleaning cap in use, whilst allowing the cleaning cap to be _{removed from the print head ink aperture during operation. Alternatively, the cleaning cap may be retained with the print head by means of a string} or chain linking the two. _{Turning to Figure 8, the steps of a method 100 for cleaning a print head 12 of a continuous inkjet printer are provided. Method 100 comprises a coupling stage 102,} flushing stage 104, and a decoupling stage 106. The method 100 may be used with the _{print head assemblies of any other of the above-described embodiments. That is to say,} any one of the cleaning caps 40, 95, 60, 70, 80, 90 may be used in connection with the method 100. At the coupling stage 102, a cleaning cap is coupled to the print head, defining an enclosed cleaning chamber. Put another way, the cleaning cap ‘caps’ the print head to define an enclosed cleaning chamber between (e.g. bound by) the cap and print head. 69719087-1 At a flushing stage 104, which follows coupling stage 102, the enclosed cleaning _{chamber 26 of the print head is flushed with a cleaning fluid. The flushing stage may also} be referred to as a cleaning stage, optionally incorporating one or more steps of the method of Figure 9. _{At a decoupling stage 106, which follows the flush stage 104, the cleaning cap and print head are decoupled from one another. Decoupling the cleaning cap and the print head leaves the ink aperture of the print head open for ink ejection. Put another way, the print} head, and printer more generally, may be returned to a printing-ready state, or configuration. Turning to Figure 9, steps of a method 110 are shown illustrating a flushing stage or _{cleaning cycle for the print head 12. The method 110 comprises a fill stage 112, soak} stage 114, drain stage 116 and a dry stage 118. During the fill stage 112, 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 114, the cleaning fluid is held in the chamber. As suggested by the _{name, the soaking stage 114 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 114 may comprise percolating air or otherwise disturbing} the cleaning fluid in the chamber 26 to improve the clean. In the draining stage 116, 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/dissolved within the used cleaning fluid). In the drying stage 118, 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. 69719087-1 _{It will be appreciated that the method 110 may be modified in various different ways, and} may be repeated in multiple cycles to provide a deeper clean. For example, the method 110 may run multiple times in succession for a more thorough clean of the print head 12. The flush stage 104 of method 100 may incorporate all, or just a subset, of the steps 112, 114, 116, 118 of the method 110 in operation. For example, the soaking stage 114 and/or drying stage 118 may be omitted. It will be appreciated that the chamber 26 may be selectively sealed by alternative means. For example, instead of a cleaning cap, the chamber may be sealed by means of an integral sealing mechanism 200, schematically illustrated in cross-section in _{Figures 10 and 11. The sealing mechanism 200 comprises a casing 202, a moveable body 204 and an exposed engagement feature 206. The casing 204 defines an ink aperture. The moveable body 204 is held moveably captive in the casing 202. In the} illustrated embodiment moveable body 204 has a cylindrical geometry. Other geometries may otherwise be used, however. Also in the illustrated embodiment, the moveable body _{204 is rotatable about an axis 210 by the exposed engagement feature 206, which is} coupled to the moveable body. The exposed engagement feature being coupled to the moveable body also encompasses the exposed engagement feature being integral with _{the moveable body. The moveable body 204 further comprises a passage 205 (e.g. a recess, or opening). The exposed engagement feature 206 can be used to move the moveable body between a first configuration, shown in Figure 10, and a second configuration, shown in Figure 11. In the first configuration, an ink path 212 is defined} through the ink aperture by the alignment of the passage 205 with the ink aperture. In _{the second configuration, the moveable body 204 closes the ink aperture.} Advantageously, the exposed engagement feature 206 can be used to adjust the configuration of the sealing mechanism 200 (e.g. specifically the moveable body 204 thereof). Specifically, the engagement feature 206 can be used to open or close the ink aperture by movement of the moveable body 204. The exposed engagement feature 206 may take one of a number of different forms. A fastener-style engagement feature may be used (e.g. a hex bolt) rotatably coupled to the moveable body. The feature may be engageable with a tool (e.g. tool 208 in Figure 11), to rotate the moveable body. In other embodiments, such as a slideable moveable body (e.g. as opposed to a rotatable moveable body), the engagement feature may take the 69719087-1 form of a leadscrew-style fastener, where rotation of the fastener is converted to linear movement of the moveable body. The engagement feature provides a manual interface _{by which an operator can manually close an integral sealing mechanism. A camera} shutter-style closure could otherwise be used. The exposed engagement feature may be used to adjust the extent to which the camera shutter is open (or closed). For one or more embodiments described herein, an internal pressure in the chamber may further improve the seal at the interface between the cap and print head. In some embodiments it may be advantageous to provide features directed to reducing _{the sensitivity of the self-cleaning print head cleaning cycle to print head orientation. In} particular, during the draining process it may be more efficient to open only those ports, _{of the chamber, which are in fluid communication with cleaning fluid. In some embodiments, the print head comprises one or more passive valves. The one} or more passive valves may be actuated in an automated manner, but without power input. For example, passive valves may be actuated by buoyancy and weight (i.e. more generally, gravitational forces). Figure 12 is a schematic illustration of a portion of a print _{head comprising an enclosed cleaning chamber 26 and a drain port arrangement. The} drain port arrangement comprises a first passive valve 250a and a second passive valve _{250b disposed within the enclosed cleaning chamber 26. The first passive valve 250a} and the second passive valve 250b are substantially similar, but oriented in opposite _{directions. The configuration (i.e. open/closed) of the first passive valve 250a and the second passive valve 250b is dependent on print head orientation. Each of the passive valves 250a, 250b comprises a conduit 252 (only labelled in} connection with first valve 250a), a moveable stopper 256 (e.g. valve element) and a valve seat 258. The conduit comprises a first portion 253 and a second portion 254. The first portion 253 of the conduit is provided in fluid communication with the ink system in _{the printer body. The valve seat 258 is provided between a first portion 253 and a second} portion 254 of the conduit 252. The second portion 254 is in fluid communication with the _{enclosed cleaning chamber 26 via openings 255. The moveable stopper 256 is held captive in the second portion 254 of the conduit 252 by a constriction (e.g. narrowing) in} the conduit 252 formed by valve seat 258. The moveable stopper 256 is configured to move under gravity between a closed position (depicted in passive valve 250b) and an 69719087-1 open position (depicted in passive vale 250a). In the closed position, the stopper 256 is seated at the valve seat 258, blocking fluid communication between the first portion 253 and the second portion 254 of the conduit 252. More importantly, in the closed position the stopped 256 blocks fluid communication between the first portion 253 and the chamber 26. In the open position, the moveable stopper 256 is separated from the valve seat 258, and the first portion 253 is provided in fluid communication with the chamber _{26. The passive valves 250a, 250b provide selective fluid communication between a} respective conduit and the chamber 26, dependent upon the orientation of the print head. It will be appreciated that the above described passive valve arrangement results in a valve which is open when the first portion 253 is lower than the second portion 254. In _{such orientation, the downward-orientated valve is passively opened. As such, the first passive valve 250a is open to flow (indicated by arrows), but the second, upwardly-} oriented passive 250b is closed. Such an arrangement allows passive, automatic _{opening of the downward-oriented valve without external intervention (e.g. by a control system or operator). This is advantageous because the downward-oriented valve 250a will be in fluid communication with the cleaning fluid 260, e.g. for draining, whilst the second valve 250b is closed. Drainage may be more readily carried out, owing to only} needing to draw liquid through one open valve. It will be appreciated that the stoppers 256 shown in Figure 12 must be sufficiently heavy _{that they do not float. That said, in other embodiments the passive valves may comprise float valves (e.g. stoppers, or valve elements, which do float). Figure 13 schematically illustrates drain port arrangement for a print head. The drain port} arrangement comprises a first drain port 302a, a second drain port 302b and a member 304. The first and second drain ports 302a, 302b are configured to drain cleaning fluid _{from the enclosed cleaning chamber. The first and second drain ports 302a, 302b may form part of, or be disposed in, the chamber. The member 304 is rotatable with respect to the first and second drain ports 302a, 302b. The first and second drain ports 302a,} 302b are arranged radially about a central axis 306. The member 304 is rotatable about _{the central axis 306. The member 304 comprises a cut-out 308. A subset of the first and} second drain ports 302a, 302b are blockable by rotation of the member 304. 69719087-1 In use, rotation of the member 304 alternately exposes the first and second drain ports _{302a, 302b whilst blocking the other drain port. In Figure 13, the cut-out 308 exposes} the first drain port 302a whilst blocking the second drain port 302b. In other embodiments, the drain port arrangement may comprise three, four, five, six or more drain ports. The geometry of the member may vary accordingly. _{By alternating between blocking first drain port 302a, and a second drain port 302b, it is cleaning fluid can be effectively drained from the drain port in fluid communication with the cleaning fluid. Put another way, suction can be applied to each drainage port (albeit} intermittently). This is desirable because when the print head is used in a range of different orientations, a fill level of cleaning fluid may only reach one of the drain ports (e.g. dependent upon orientation). By cyclically blocking/exposing the drain ports, by rotation of the member 304, drainage will be applied to both drain ports (again, _{intermittently). If not for the rotatable member, there may be a tendency for suction to} only be applied through a port not exposed to cleaning fluid (e.g. a path of least resistance, drawing gas). This is mitigated by use of a rotatable member. _{Additionally, or alternatively, the print head may comprise a plurality of drain ports, at} least one drain port being disposed at each corner of the enclosed cleaning chamber. This provides effective draining in all orientations, as corners or vertices may constitute wells in the cleaning chamber 26 in which (residual) cleaning liquid tends to accumulate. _{Figure 14a and Figure 14b illustrates a portion of a continuous inkjet printer according to another embodiment. The printer comprises a mount 352 configured to support the print head 12 (and, by extension, and where appropriate, the print head assembly) in a plurality of (predetermined) orientations. The print head assembly is moveable between a printing configuration, shown in Figure 14a and a cleaning configuration (an example of which is shown in Figure 14b).} The mount 352 comprises an axis 360, a first limit block 356a and a second limit block _{356b. The print head 12 is rotatably coupled to the mount 352 about the axis 360. The print head 12 is moveable by rotation about the axis 360.} 69719087-1 _{In the printing configuration, the print head 12 is supported in a first orientation, such that the print head is substantially horizontal and the ink aperture 38 faces a substrate 354 for printing (upon removal of the cleaning cap 40). The print head 12 is located in the first orientation by the first limit block 356a, which prevents further rotation past this} position. _{In the cleaning configuration, the print head 12 is supported in a second orientation, such that the print head is substantially vertical. In the cleaning configuration the enclosed cleaning volume of the print head is configured to be flushed with cleaning fluid. In} particular, the drain ports may be oriented such that they are located in pooling locations _{for cleaning fluid. The print head assembly is located in the second orientation by the} second limit block 356b which prevents further rotation. _{Advantageously, the provision of mount 352 allows the print head to be accurately and repeatedly moved between predetermined positions for printing and cleaning, respectively. It will be appreciated that the predetermined positions for printing and cleaning may vary with the exact configuration of the print head and the substrate position. The orientations shown in Figures 14a and 14b are for the purposes of illustration only. Ultimately, the provision of the mount 352 means that the location of} cleaning fluid, within the chamber, is more predictable because the print head 12 is in a cleaning position when cleaned. The position of drain ports can thus be mapped accordingly, reducing the risk of pooling cleaning fluid which is otherwise challenging to drain from the chamber. _{In some embodiments the orientation of the print head 12 may be moved between the} printing and cleaning configuration by a robot arm, or manually by an operator. The terms horizontal and vertical as used in relation to the embodiment of Figures 14a _{and 14b relate to the orientation of the print head 12 relative to the direction of gravity. It} will be appreciated that these are just exemplary, and that a range of different orientations could otherwise be used. Figure 15 illustrates a further embodiment of the self-cleaning print head, configured to carry out printing and cleaning operations in the same, fixed orientation. The print head _{12 comprises a first drain port 372a and a second drain port 372b disposed in the} 69719087-1 _{enclosed cleaning chamber 26. In use, the print head 12 is oriented (toward substrate 374) for printing, such that the drain ports 372a and 372b are located at pooling regions} of the enclosed cleaning chamber. The term ‘pooling locations’ denotes areas of the enclosed cleaning chamber 26 at which _{(residual) cleaning liquid 376 accumulates. Turning to Figure 16, a washing station 400 is schematically illustrated in situ with a print head 12. Print head 12 shares many features in common with the print head 12 shown} and described in connection with Figures 2-15, and corresponding components are _{denoted using the same numerals. Print head 12 is not a self-cleaning print head: operator intervention is needed to affix the cleaning cap to the print head 12 and flush the print head 12 with cleaning fluid. Washing station 400 comprises a hose 402 (e.g. a conduit), a cleaning cap 404, a pump} 406 and a cleaning fluid source 408. Hose 402 has a first end 402a and a second end _{402b. The cleaning cap 404 is fluid communication with the first end of the hose 402a. Pump 406 is in fluid communication with the second end 402b of the hose and the cleaning fluid source 408. The cleaning cap 404 fluidly couples the hose 402 and an enclosed cleaning chamber 26 of the print head 12. The cleaning fluid source 408 may} be a tank, preferably a refillable tank. _{In some embodiments the pump 406 may be a manual pump – for example, a hand pump. In other embodiments, pump 406 may be electrically-powered. The hand pump} may take the form of a bulb-style pump (e.g. similar to a priming bulb on a 2-stroke engine). _{It will be appreciated that the cleaning cap 404 may engage with the print head 12 by any of the arrangements described with respect to the cleaning caps of Figures 2-11} (e.g. by a bayonet mounting arrangement). _{The washing station 400 further comprises a drain line 409 and an inspection section 410 for visual inspection of cleaning fluid. Drain line 409 is in fluid communication with} the enclosed cleaning chamber 26. Inspection section 410 is disposed in line with the drain line 409. Inspection section 410 may comprise a transparent section of fluid conduit. Advantageously, the inspection section 410 allows an operator to inspect the 69719087-1 cleaning fluid leaving the chamber 26, which provides a visual indication of the cleanliness of the chamber. _{Although not shown in Figure 16, the drained cleaning fluid from the print head 12 may flow to a catch tank, which may be integral with, or separate from, the washing station 400. Further alternatively, the drain line 409 may be routed back through the cleaning fluid source 408 (e.g. forming a circular fluid circuit). Figure 17 schematically illustrates the steps of a method for cleaning print head 12 with the washing station 400.} During the engagement step 452, the cleaning cap 404 of the wash station 400 is engaged with the print head 12. During the pumping step 454, cleaning fluid from the cleaning fluid source 408 is pumped _{(e.g. urged) into the print head 12 by pump 406. The cleaning fluid flushes the enclosed} cleaning chamber 26 and the components within (e.g. deflection electrodes etc.), removing any ink deposits. Pumping step 454 may further comprise a soaking step wherein the cleaning fluid is held in the chamber for a period of time. _{During the draining step 456, cleaning fluid from the print head (in particular, the enclosed cleaning chamber 26) is drained, for example via drain line 409. The cleaning fluid, which may contain dissolved ink deposits, can be visually inspected by an operator} at inspection section 410 as it drains. The appearance of the cleaning fluid at inspection section 410 can inform an operator as to the progress of cleaning and/or cleanliness of the print head 12. _{During the disengaging step 458, the cleaning cap 404 and print head 12 are disengaged. At this point the print head 12 is clean, and may be ready for further} operations (e.g. printing, although an optional drying, or other step, may occur frst). In some embodiments, it may be an operator that manually engages connects the wash _{station 400 to the print head 12 at engagement step 452. Alternatively, in further variants,} the print head 12 may be automatically (e.g. by way of a robot arm) engaged with the wash station. 69719087-1 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. 69719087-1

Claims

CLAIMS: _{1. A cleaning cap for a print head of a continuous inkjet printer, wherein the cleaning} cap comprises: a sealing surface; and an engagement feature, coupled to the sealing surface; wherein the engagement feature is configured to detachably couple the cleaning cap to the print head. _{2. The cleaning cap of claim 1, wherein, the cleaning cap comprises a skirt and the} engagement feature is disposed on the skirt. 3. The cleaning cap of claim 1 or 2, wherein, the engagement feature is disposed on or in an outer periphery of the cleaning cap. 4. The cleaning cap of any of claims 1 to 3, wherein the engagement feature comprises one or more projections or recesses. 5. The cleaning cap of any of claims 1 to 4, wherein the engagement feature comprises a threaded surface. _{6. The cleaning cap of any preceding claim, wherein the cap comprises a fluid port. 7. The cleaning cap of claim 6, wherein the cap comprises a port exposed at the} sealing surface of the cap for alignment with a port of the print head. _{8. A print head assembly comprising: a print head for a continuous inkjet printer; and} a cleaning cap according to any preceding claim, coupled to the print head; w_{herein the cleaning cap and print head define an enclosed cleaning chamber. 9. The print head assembly of claim 8, wherein the cleaning cap is coupled to an} end face of the print head. 69719087-1

_{10. The print head assembly of claims 8 or 9, wherein the cleaning cap is coupled to} the print head around a periphery of the print head. _{11. The print head assembly of claim 10, wherein the enclosed cleaning chamber} comprises a portion between the sealing surface of the cleaning cap and the end face of the print head. _{12. The print head assembly of any of claims 8 to 11, wherein the print head and the} cleaning cap are hingeably coupled. _{13. The print head assembly of any of claims 8 to 12, wherein the cleaning cap} comprises one or more magnetic elements. _{14. The print head assembly of claim 13, wherein the print head comprises a reed} switch configured to detect the position of the cleaning cap. _{15. The print head assembly of claims 13 or 14, wherein the print head comprises} one or more magnetic elements, detachably coupling the cleaning cap to the print head. _{16. The print head assembly of any of claims 8 to 15, wherein the print head} comprises one or more passive valves. _{17. The print head assembly of claim 16, wherein the cleaning chamber comprises} the one or more passive valves; and wherein the configuration of the one or more passive valves is dependent on print _{head orientation. 18. The print head assembly of any one of claims 8 to 17, wherein the print head} comprises a drain port arrangement, comprising: a plurality of drain ports configured to drain cleaning fluid from the enclosed cleaning chamber; and a member rotatable with respect to the drain ports; wherein a subset of the plurality of drain ports are blockable by rotation of the member. 69719087-1

_{19. The print head assembly of any one of claims 8 to 18, wherein the enclosed} cleaning chamber comprises one or more corners, and wherein the enclosed cleaning chamber further comprises a plurality of drain ports, at least one drain port being disposed at each corner of the enclosed cleaning chamber. _{20. The print head assembly of claims 8 to 19, wherein the print head comprises a} first port, exposed at the end face, and the cleaning cap comprises a second port, wherein the first port and second port are aligned, defining a fluid conduit. _{21. A continuous inkjet printer comprising:} a print head assembly according to any of claims 8 to 20; and an ink system for storing ink and supplying ink to the print head. _{22. A continuous inkjet printer according to claim 21, wherein the continuous inkjet printer comprises a mount configured to support the print head assembly in a plurality of orientations, wherein the print head assembly is moveable between: a printing configuration, wherein the print head assembly is supported in a first} orientation; and a _{cleaning configuration, wherein the print head is supported in a second} orientation. _{23. A method for cleaning a print head of a continuous inkjet printer, wherein the} method comprises: coupling a cleaning cap to the print head, defining an enclosed cleaning chamber within the print head; f_{lushing the enclosed cleaning chamber of the print head with cleaning fluid; and} decoupling the cleaning cap and print head. _{24. The method of claim 23, wherein the print head comprises one or more drain ports disposed in the enclosed cleaning chamber, and the method further comprises orienting the print head for printing, such that the one or more drain ports are located} proximate pooling regions of the enclosed cleaning chamber. 69719087-1

_{25. The method of claim 23 or 24, wherein the method further comprises moving the print head between: a printing configuration, wherein the print head is supported in a first orientation;} and a _{cleaning configuration, wherein the print head is supported in a second} orientation; wherein, in the cleaning configuration the enclosed cleaning chamber of the print _{head is flushed with cleaning fluid. 26. A sealing mechanism for sealing a print head of a continuous inkjet printer,} comprising: a casing defining an ink aperture; a moveable body, held moveably captive in the casing; and an exposed engagement feature, coupled to the moveable body; wherein the moveable body is moveable by the exposed engagement feature between: a first configuration, wherein an ink path is defined through the ink aperture; and a second configuration, wherein the moveable body closes the ink aperture. _{27. A washing station for a print head of a continuous inkjet printer, wherein the} washing station comprises: a hose, having a first end and a second end; a cleaning cap, for engagement with the print head, in fluid communication with the first end of the hose; a pump in fluid communication with the second end of the hose; and a cleaning fluid source in fluid communication with the pump. _{28. The washing station of claim 27, wherein the pump is a manual pump. 29. The washing station of claim 27 or 28, wherein the washing station further comprises an inspection section for visual inspection of cleaning fluid. 30. A continuous inkjet printer system, comprising} a washing station, according to any of claims 27 to 29; and a print head; 69719087-1 _{wherein the cleaning cap of the washing station is engaged with the print head. 31. A method for cleaning a print head of a continuous inkjet printer, wherein the} method comprises: e_{ngaging a cleaning cap of a washing station according to any of claims 27 to 29} with the print head; pumping cleaning fluid from the cleaning fluid source into the print head; draining the cleaning fluid from the print head; and disengaging the cleaning cap and print head. 69719087-1