Technical field

The present invention relates to a printhead for a continuous inkjet printer, to a continuous inkjet printer comprising the printhead, and to a method of cleaning the printhead.

Background

In ink jet 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: drop on demand where ink droplets for printing are generated as and when required; and continuous ink jet printing in which droplets are continuously produced and only selected ones are directed towards the substrate, the others being recirculated to an ink supply.

Continuous ink jet printers supply pressurised ink to a printhead drop generator where a continuous stream of ink emanating from a nozzle is broken up into individual regular drops by, for example, an oscillating piezoelectric element. The drops 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. Each charged drop is deflected by the field by an amount that is dependent on its charge magnitude before impinging on the substrate whereas the uncharged drops proceed without deflection and are collected at a gutter from where they are recirculated to the ink supply for reuse. The charged drops bypass the gutter and hit the substrate at a position determined by the charge on the drop and the position of the substrate relative to the printhead. Typically the substrate is moved relative to the printhead in one direction and the drops 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 printhead between drops arriving means that a line of drops would otherwise not quite extend perpendicularly to the direction of movement of the substrate). The various components of the printhead are typically contained within a cover tube or printhead casing.

In continuous ink jet printing a character is printed from a matrix comprising a regular array of potential drop positions. Each matrix comprises a plurality of columns (strokes), each being defined by a line comprising a plurality of potential drop positions (e.g. seven) determined by the charge applied to the drops. Thus each usable drop is charged according to its intended position in the stroke. If a particular drop is not to be used then the drop 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 printhead by an ink supply 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 system includes a main pump that draws the ink from a reservoir or tank via a filter and delivers it under pressure to the printhead. 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 printhead. The unused ink drops 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 as a result 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 so as 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 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. This solvent may also be used for flushing components of the printhead, such as the nozzle and the gutter, in a cleaning cycle.

Cleaning of the printhead is required since there are various sources of contamination during the printing process; during operation of continuous ink jet printheads, the printhead components are known to become lightly coated with ink and other foreign bodies. The principle causes of the coating are a brief transient spray created as the jet is started and stopped, the continuous albeit very light coating caused by charged microsatellites that are formed during the jet breakoff and charging process, and some splash back from the substrate. According to the ink type and application, the customer is required to clean the printhead on a frequent basis ranging from daily to monthly intervals. Some current cleaning processes typically involve stopping the inkjet, removing the printhead from the printing location, removing the cover tube from the printhead, placing the printhead in a waste collection vessel, and spraying or pouring solvent onto the contaminated areas of the printhead to clean those areas. This cleaning process tends to be messy for the customer, requires specialist equipment (for example, gloves and glasses etc.), takes a lot of time, requires large quantities of solvent much of which may go to waste, and if the cleaning process is not performed properly (for example, not performed thoroughly enough and/or on the required time basis) this may lead to printer unreliability.

Some alternative cleaning processes have been implemented in an attempt to overcome one or more of the above mentioned problems.

One such alternative cleaning process involves operating the printhead gutter on a motorised lead screw. The printhead gutter can therefore be driven towards to nozzle to form a seal with the nozzle for cleaning. However, this only facilitates the cleaning of a single component, the gutter, but not the cleaning of other components of the printhead that may also be contaminated with ink. In addition, the parts and mechanisms facilitating this movement may also cause an increase in printhead size, which would be undesirable.

Another such alternative cleaning process involves incorporating an additional, designated solvent spray into the printhead that is arranged to spray solvent onto an external face of the nozzle to clean it. However, this again only facilitates the cleaning of a single component, the external face of the nozzle, but not the cleaning of other components of the printhead that may also be contaminated with ink. In addition, it may be costly to implement such a spray adding to manufacturing costs, and the process may still be messy for the customer and require significant amounts of solvent.

It would therefore be desirable to provide an improved cleaning process for the printhead. It would be desirable to provide a printhead that overcomes one or more of the above problems. It would be desirable to provide a printhead that is configured to perform an improved printhead cleaning process. It would be desirable to provide a printhead that at least partially, or fully, automates the printhead cleaning process. It would be desirable to provide a printhead having a cleaning process that reduces the amount of solvent required and/or allows for ease of re-use of any solvent used.

Summary According to a first aspect of the present invention, there is provided a printhead for a continuous inkjet printer, comprising: an ink gun comprising a nozzle for ejecting an inkjet; at least one electrode for steering the inkjet for printing; a gutter having an ink receiving orifice for receiving parts of the ink jet which are not used for printing; and a housing having a first printing configuration in which parts of the ink jet are permitted to leave the printhead for printing, and a second cleaning configuration in which the housing at least partially encloses a cleaning volume comprising at least a part of the at least one electrode and the ink receiving orifice.

During printing, deposits of ink can form on various components of the printhead, such as, for example, on at least parts of the at least one electrode and on an external surface of the gutter which surrounds the ink receiving orifice. By providing the printhead with a housing that can be switched between a first printing configuration permitting printing, and a second cleaning configuration allowing for various components of the printhead to be cleaned, the cleaning process can be simplified. In particular, by providing the housing with a second cleaning configuration in which it at least partially encloses a cleaning volume and various components, it is possible to insert or inject solvent into this cleaning volume to wash away such deposits of ink from the various components, thereby preventing these deposits from interfering with printing operation. Moreover, having the housing at least partially enclose the cleaning volume in this way means that the housing effectively defines the size of the cleaning volume, and therefore the quantity of solvent being used for cleaning can be more easily controlled. In particular, the housing may hold solvent within the cleaning volume against the various components for cleaning, in which case a set amount of the solvent can be inserted into the cleaning volume for contacting and cleaning the various components, rather than for example spraying solvent onto the various components which is otherwise then lost for cleaning. In addition, providing the cleaning volume with a smaller size may mean that less solvent needs to be inserted into the cleaning volume to contact the various components for cleaning. As such, less solvent may be required to clean the printhead components effectively. For example, a cleaning process of this type may use around 2-5 ml of solvent to effectively clean the components within the cleaning volume, whereas a manual cleaning operation performed using a wash bottle may, for example, use around 35 ml of solvent. Further still, having the cleaning volume comprise the ink receiving orifice means that solvent used for cleaning may be reclaimed by the gutter, which may reduce the amount of solvent wasted during cleaning.

The ink gun may be for forming an ink jet in a printing mode and for forming a solvent jet in a cleaning mode. The ink gun may be configured to generate ink drops from the inkjet, and the at least one electrode may be for steering those ink drops. The at least one electrode may be for trapping electric charges on ink drops of the ink jet and for creating an electrostatic field for deflecting ink drops carrying trapped electric charges. The at least one electrode may comprise an arrangement of electrodes. The at least one electrode may comprise a charge electrode for trapping electric charges on ink drops of the ink jet, and first and second deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges. The ink receiving orifice may be for receiving ink drops which are not used for printing. The parts of the ink jet may be selected ink drops. The cleaning volume may be configured to hold solvent or another cleaning fluid within it for cleaning.

When the housing is in the second cleaning configuration, the housing may enclose the cleaning volume comprising the nozzle, the at least one electrode and the ink receiving orifice.

This may be further beneficial since the cleaning volume may comprise all of the components of the printhead that may require cleaning, in particular all of the printhead components directly in the inkjet path.

The cleaning volume may comprise only the nozzle, the at least one electrode and the ink receiving orifice, but no other major components of the printhead. This may prevent other components that do not need to be cleaned, from being exposed to solvent within the cleaning volume.

At least partially encloses may mean that the housing is open to one or more sides. The housing may be open above a top of the ink gun, the at least one electrode and the gutter.

In the second cleaning configuration, the housing may fully enclose and/or encapsulate the cleaning volume. Fully enclose may mean that the housing is not intentionally open to one or more sides. Fully enclose may mean that an enclosed fluid path is defined between the nozzle and the ink receiving orifice.

Where the housing at least partially encloses, or encloses, or fully encloses, the cleaning volume, the housing may still have an imperfect seal, for example, such that the housing is not watertight, for example such that it may still be possible for some solvent to escape, or to leak out, from within the cleaning volume. An imperfect seal may be present where any flat surfaces only gently abut for example and/or where no gasket is provided between surfaces.

Where the housing at least partially encloses, or encloses, or fully encloses, the cleaning volume, the housing may provide a seal between the cleaning volume and outside of the housing. For example, the housing may be watertight to prevent leaking of solvent from out of the housing. Any one or more surfaces of the housing may comprise a gasket, for example an elastomeric portion, and/or a Teflon blade to achieve this sealing. Any other suitable means of providing a seal may be used.

In the second cleaning configuration, the housing may prevent the ink jet from leaving the housing and so from leaving the printhead for printing.

In the first printing configuration, the housing may define an open region which permits parts of the inkjet to leave the printhead for printing.

During printing, the undeflected and deflected ink drops may define an ink drop plane, and the open region may overlap or cooperate with the ink drop plane.

In the second cleaning configuration, the housing may close the open region.

The open region may comprise an aperture defined by the housing. This may provide a simple way of permitting the inkjet to leave the print head for printing.

In the second cleaning configuration, the housing may close the open region and/or the aperture.

During printing, the undeflected and deflected ink drops may define an ink drop plane, and the aperture may overlap or cooperate with the ink drop plane. The aperture may be a slot. The aperture may be approximately 8mm wide, parallel to the ink drop plane, and/or approximately 2mm high, perpendicular to the ink drop plane. The aperture may be approximately 6-10mm wide, parallel to the ink drop plane, and/or approximately 1-3mm high, perpendicular to the ink drop plane. The open region may be larger than this.

The housing may comprise one or more wall portions around the relevant components to define the cleaning volume. The one or more wall portions may be fixed in place relative to the relevant components. The one or more wall portions may cooperate with a substrate on which the relevant components are connected or mounted to define the cleaning volume there between. A spacing between the one or more wall portions may define the open region. The one or more wall portions may comprise the aperture.

The housing may comprise a moveable cover for cooperating with at least a part of the open region which permits parts of the ink jet to leave the printhead for printing to seal the at least a part of the open region, and when the housing is in the first printing configuration the cover may be withdrawn from the at least a part of the open region, and when the housing is in the second cleaning configuration the cover may cooperate with the at least a part of the open region.

The housing may comprise a moveable cover for cooperating with the aperture to close the aperture, and when the housing is in the first printing configuration the cover may be withdrawn from the aperture, and when the housing is in the second cleaning configuration the cover may cooperate with the aperture.

When the cover is withdrawn from the aperture, the aperture is exposed, and the ink drops for printing can leave the printhead through the aperture. When the cover cooperates with the aperture, the aperture is closed and the housing is effectively complete to at least partially enclose the cleaning volume that can then hold solvent for cleaning; in this second cleaning configuration, the housing does not intentionally provide any aperture through which the ink drops for printing can escape from the housing.

This arrangement may allow for a simple, in particular simple to manufacture, yet effective and reliable, way of providing the first printing configuration and the second cleaning configuration.

The one or more wall portions may comprise a wall portion adjacent the nozzle for cooperating with the nozzle, and/or a wall portion adjacent the ink receiving orifice for cooperating with the ink receiving orifice.

The one or more wall portions may comprise the moveable cover. The moveable cover may be provided on the wall portion adjacent the ink receiving orifice. The moveable cover may be slideable on the one or more wall portions between the first printing configuration and the second cleaning configuration. This may be space saving.

Movement of the cover may be provided by any suitable mechanism. The printhead may comprise one or more actuators for moving the moveable housing portion. The movement may be provided by an electromechanical actuator, or any other mechanical actuator or motor. The movement may be provided by a pneumatic or hydraulic actuator. The movement may be provided by a combination of different actuators.

The housing may be moveable between the first printing configuration and the second cleaning configuration. The housing may comprise a first housing portion having at least one first sealing surface, and a second housing portion having at least one second sealing surface for cooperating with the at least one first sealing surface to at least partially enclose the cleaning volume. The at least one of the first housing portion and the second housing portion may be moveable between the first printing configuration and the second cleaning configuration such that when the housing is in the first printing configuration the at least one first sealing surface and the at least one second sealing surface are separated to permit parts of the ink jet to leave the printhead for printing, and when the housing is in the second cleaning configuration the at least one first sealing surface cooperates with the at least one second sealing surface.

When the first and second sealing surfaces are separated, they will allow ink drops to leave through the space between them for printing. In addition, when the first and second sealing surfaces cooperate, the space is closed, and the housing is effectively complete to at least partially enclose the cleaning volume that can then hold solvent for cleaning; in this second cleaning configuration, the first and second sealing surfaces do not intentionally provide any space through which the ink drops for printing can escape from the housing.

This may provide a more space saving arrangement for the housing. In addition, this arrangement may avoid the need for providing a movement mechanism downstream of the gutter, which may therefore preserve throw distance i.e. the distance between the end of the printhead where ink drops leave for printing and the substrate on which the drops are printed. Moreover, having the sealing surfaces separated in the first printing configuration may provide an open structure that may aid in the drying of the various components after cleaning.

The at least one electrode may comprise a charge electrode for trapping electric charges on ink drops of the ink jet, and first and second deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges. During printing, the deflected ink drops may define an ink drop plane. The at least one first sealing surface may cooperate with, or mate with, the at least one second sealing surface in at least a direction that is parallel to the ink drop plane and is substantially perpendicular to the ink drop axis.

When the housing is in the first printing configuration, the first housing portion and the second housing portion may be separated. When the housing is in the first printing configuration, the first housing portion and the second housing portion may be separated to define the open region to permit parts of the ink jet to leave the printhead for printing. Separated may mean spaced apart from one another in at least the ink drop plane. They may be spaced apart to define the open region. Spaced apart may mean that any part of the first housing portion does not contact any part of the second housing portion.

When the housing is in the first printing configuration, the at least one first sealing surface and the at least one second sealing surface may be separated to define the open region to permit parts of the ink jet to leave the printhead for printing. Separated may mean spaced apart from one another. They may be spaced apart to define the open region. Spaced apart may mean that any part of the first housing portion does not contact any part of the second housing portion.

When the housing is in the first printing configuration, the at least one first sealing surface and the at least one second sealing surface may be separated to define an open region that permit parts of the inkjet to leave the printhead for printing, and when the housing is in the second cleaning configuration the at least one first sealing surface may cooperate with the at least one second sealing surface to close or seal the open region. The movement may be provided by any suitable mechanism. The printhead may comprise one or more actuators for moving the moveable housing portion. The movement may be provided by an electromechanical actuator, or any other mechanical actuator or motor. The movement may be provided by a pneumatic or hydraulic actuator. The movement may be provided by a combination of different actuators.

The moveable housing portion may be slideable along a printhead substrate between the first printing configuration and the second cleaning configuration. Having the moveable housing portion be slideable may be more simple to manufacture and/or to operate.

At least a part of each of the nozzle, the at least one electrode and the ink receiving orifice may be mounted on this printhead substrate.

The housing may be fixable in the first printing configuration and the second cleaning configuration. The housing may be fixable in only the first printing configuration and the second cleaning configuration or the housing may be fixable in the first printing configuration, in the second cleaning configuration in any position between the first printing configuration and the second cleaning configuration. Any suitable fixing means may be used.

The printhead may define a printhead plane. The printhead plane may comprise a substrate on which one or more of the ink gun, at least one electrode and the gutter are mounted or detachably connected. The moveable housing portion may be configured to move in the printhead plane towards and away from the other housing portion, between the first printing configuration and the second cleaning configuration. This movement may be between approximately 3-4 mm, perhaps up to 5 mm.

The moveable housing portion may additionally or alternatively be configured to move in a direction that is substantially perpendicular to the printhead plane towards and away from the other housing portion, between the first printing configuration and the second cleaning configuration. This movement may be between approximately 2-4 mm.

The at least one electrode may comprise a charge electrode for trapping electric charges on ink drops of the ink jet, and may comprise first and second deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges. The moveable housing portion may comprise one of the first and second deflection electrodes.

This may provide for a particularly advantageous arrangement. Having the moveable housing portion comprise one of the deflection electrodes means that the deflection electrodes can be moved closer together for cleaning, and that the cleaning volume can be made smaller for cleaning. Therefore, less solvent may be required for cleaning. This arrangement may also avoid the need for providing a movement mechanism downstream of the gutter, which may therefore preserve throw distance i.e. the distance between the end of the printhead where ink drops leave for printing and the substrate.

Moving from the first printing configuration to the second cleaning configuration may move the first and second deflection electrodes closer together.

The other housing portion may comprise the other one of the first and second deflection electrodes.

The first deflection electrode may be held at ground potential and the second deflection electrode may be configured to have a voltage applied to it. The moveable housing portion may comprise the second deflection electrode.

This may allow for the ink receiving orifice to be placed adjacent a fixed deflection electrode held at ground potential so that undeflected ink drops (as opposed to deflected ink drops) enter the gutter. Alternatively, the moveable housing portion may comprise the first deflection electrode. The printhead may comprise a substrate, or deck, on which at least a part of the relevant components are connected or mounted. The substrate may define a printhead plane. The first and second deflection electrodes may be arranged perpendicular to the substrate, and deflection of the ink droplets may be parallel to the substrate and perpendicular to the deflection electrodes. Alternatively, the first and second deflection electrodes may be parallel to the substrate and deflection of the ink droplets may be perpendicular to the substrate and perpendicular to the deflection electrodes.

The other housing portion may comprise the first deflection electrode.

The deflection electrodes may be mounted on the housing portions to face one another.

The at least one electrode may comprise a charge electrode for trapping electric charges on ink drops of the ink jet, and first and second deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges. The undeflected ink drops may define an ink drop axis, and during printing, the deflected ink drops may define an ink drop plane. The moveable housing portion may be configured to move in a direction that is in the ink drop plane and is substantially perpendicular to the ink drop axis.

It may be more simple, and therefore cheaper, to implement movement in only one direction. In addition, movement in this direction may involve moving the first and second deflection electrodes closer together for cleaning and/or may reduce the size of the cleaning volume so that less solvent may be required for cleaning.

This movement may be particularly suited to the arrangement in which the first and second deflection electrodes are perpendicular to the substrate, and deflection of the ink droplets is parallel to the substrate, since movement in this direction may involve movement along the substrate which may be easier, and therefore less costly, to implement.

The printhead may define a printhead axis, and during printing, the deflected ink drops may define an ink drop plane. The moveable housing portion may be configured to move in a direction that is substantially perpendicular to the ink drop plane and to the printhead axis.

The at least one electrode may comprise a charge electrode for trapping electric charges on ink drops of the ink jet, and first and second deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges. The undeflected ink drops may define an ink drop axis, and during printing, the deflected ink drops may define an ink drop plane. The moveable housing portion may be configured to move in a direction that is substantially perpendicular to the ink drop plane and to the ink drop axis. This may be a particularly advantageous arrangement. Firstly, it may be more simple, and therefore cheaper, to provide movement in only one direction. In addition, as mentioned above, the ink drop aperture or slot required to permit ink drops to leave the printhead for printing, needs to be longer in the ink drop plane to allow for deflection of the ink drops (typically around 8mm). By way of contrast, perpendicular to the ink drop plane, the aperture only needs to be long enough to allow for a single ink drop to pass through it (typically around 2mm). Therefore, by providing movement in this direction, only a relatively small movement is required to be able to open a larger printing gap or aperture. A small movement may be easier and/or more cost effective to implement.

This movement may be particularly suited to the arrangement in which the first and second deflection electrodes are parallel to the substrate and deflection of the ink droplets is perpendicular to the substrate, since movement in this direction may involve movement along the substrate which may be easier, and therefore less costly, to implement.

Moreover, this arrangement, with movement in a direction that is substantially perpendicular to the ink drop plane and to the ink drop axis, may be further advantageous. A consideration of any configuration of deflection electrodes in a printing configuration is that the electric field strength remains constant at, for example, approximately 2kV/mm (voltage divided by distance). The voltage applied may typically be approximately 8kV. Where the moveable housing portion is not configured to move in a direction that is substantially perpendicular to the ink drop plane and to the ink drop axis, the deflection electrodes may need to be spaced further apart for printing. This is because the movement may need to be greater than the span of the ink drops in the ink drop plane from the least deflected position to the most deflected position to permit the ink drops to leave the printhead for printing (e.g. to allow the created open region or aperture to emit the drops). This span may for example be approximately 8mm, and therefore the motion may need to be, for example, approximately 10mm. In this case, if the minimum clearance between the deflection electrodes in the second cleaning configuration is, for example, approximately 1mm, then in the extended first printing configuration, the deflection electrode separation would be approximately 11mm. Therefore, to attain a field strength of approximately 2kV/mm, a voltage of approximately 22kV would need to be applied, which is considerably higher than the 8kV normally used. It may be beneficial to be able to use the lower field strength and/or to apply a lower voltage.

The at least one electrode may comprise a charge electrode for trapping electric charges on ink drops of the ink jet, and first and second deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges. The undeflected ink drops may define an ink drop axis, and during printing, the deflected ink drops may define an ink drop plane. The moveable housing portion may be configured to move in two directions, in a first direction that is in the ink drop plane and is substantially perpendicular to the ink drop axis, and in a second direction that is substantially perpendicular to the ink drop plane and to the ink drop axis.

This may be a particularly advantageous arrangement. Providing movement in the first direction may allow the first and second deflection electrodes to be moved closer together for cleaning, which may reduce the size of the cleaning volume so that less solvent may be required for cleaning. Additionally providing movement in the second direction may mean that only a relatively small movement is required to be able to open a larger printing gap or aperture, which may be beneficial for using the lower field strength and/or to apply a lower voltage, as is explained above.

The moveable housing portion may be configured to move in the first and second directions separately e.g. in only one of these directions at a time. The moveable housing portion may be configured to move in a plane defined by the first and second directions.

The first deflection electrode may be held at ground potential and the second deflection electrode may be configured to have a voltage applied to it. The first deflection electrode may be substantially straight. The first deflection electrode may be substantially parallel to the ink drop axis. The second deflection electrode may be substantially curved, at least in part. The second deflection electrode may comprise a first region, perhaps at an upstream end, that is aligned or substantially parallel with the ink drop axis, and the second deflection electrode may comprise a second region, perhaps at a downstream end, that is angled from the ink drop axis, perhaps angled away from the first deflection electrode.

The first housing portion may have a first inside surface arranged to cooperate with the cleaning volume, and the first inside surface may be recessed from the first sealing surface. The second housing portion may have a second inside surface arranged to cooperate with the cleaning volume, and the second inside surface may be recessed from the second sealing surface. In the second cleaning configuration, the first and second sealing surfaces may cooperate and the first and second inside surfaces may be separated to define the cleaning volume between them and the first and second sealing surfaces. The first housing portion may have a first inside surface arranged to cooperate with the cleaning region, and the first inside surface may be recessed from the first sealing surface. The second housing portion may have a second inside surface arranged to cooperate with the cleaning volume. This second inside surface may be an extension of the second sealing surface. This second inside surface may not be recessed from the second sealing surface. In the second cleaning configuration, the first and second sealing surfaces may cooperate and the first and second inside surfaces may be separated to define the cleaning volume between them and the first and second sealing surfaces.

The second housing portion may have a second inside surface arranged to cooperate with the cleaning volume, and the second inside surface may be recessed from the second sealing surface. The first housing portion may have a first inside surface arranged to cooperate with the cleaning volume. This first inside surface may be an extension of the first sealing surface. This first inside surface may not be recessed from the first sealing surface. In the second cleaning configuration, the first and second sealing surfaces may cooperate and the first and second inside surfaces may be separated to define the cleaning volume between them and the first and second sealing surfaces. The first and second housing portions may have their deflection electrodes integrally formed. The deflection electrodes may have respective surfaces that cooperate with the respective inside surfaces of the deflection electrodes.

The first and second housing portions may be positioned on the printhead substrate. The moveable housing portion may be provided on a part of the substrate that is operable to lift and lower the moveable housing portion.

The printhead may define one or more orifices arranged to cooperate with the cleaning volume when the housing is in the second cleaning configuration for receiving solvent from the cleaning volume. Providing the printhead with one or more orifices in this way may allow the printhead to be cleaned in a different and/or various orientations, and/or it may allow for more solvent or other cleaning fluid to be reclaimed for re-use.

The printhead may define one or more fluid inlets arranged to cooperate with the cleaning volume when the housing is in the second cleaning configuration for injecting or inserting or ejecting solvent or another cleaning fluid into the cleaning volume. This may provide an alternative or additional source for providing cleaning fluid to the cleaning volume.

The ink receiving orifice may be substantially aligned with the nozzle. The printhead may comprise a cover tube or printhead casing for enclosing the ink gun, the at least one electrode and the gutter. The cover tube or printhead casing may comprise an aperture for cooperating with the open region or aperture of the housing.

The ink gun and/or nozzle may be configured to eject solvent into the cleaning volume when the housing is in the second cleaning configuration. By ejecting solvent from the ink gun or nozzle, rather than by performing a manual wash process, it is possible simplify the cleaning process, and to minimise solvent usage (e.g. by ensuring the solvent is accurately directed at the areas of interest).

According to a second aspect of the present invention, there is provided a continuous inkjet printer, comprising: an ink supply system operable to supply ink to a print head; and a printhead operable to receive ink from the ink supply system for printing, the printhead comprising: an ink gun comprising a nozzle for ejecting an inkjet; at least one electrode for steering the inkjet for printing; a gutter having an ink receiving orifice for receiving parts of the ink jet which are not used for printing; and a housing having a first printing configuration in which parts of the inkjet are permitted to leave the printhead for printing, and a second cleaning configuration in which the housing at least partially encloses a cleaning volume comprising at least a part of the at least one electrode and the ink receiving orifice.

The ink supply system may comprise an ink cartridge and a solvent cartridge, and the ink supply system may be operable to supply solvent based ink to the printhead in a printing mode and to supply solvent to the printhead in a cleaning mode.

The ink supply system may comprise an additional cleaning fluid cartridge, and the ink supply system may be operable to supply the cleaning fluid to the printhead, in particular to the cleaning volume, in a cleaning mode.

According to a third aspect of the present invention, there is provided a method of cleaning a printhead for a continuous inkjet printer, the continuous inkjet printer, comprising: an ink supply system operable to supply ink to a print head; and a printhead operable to receive ink from the ink supply system for printing, the printhead comprising: an ink gun comprising a nozzle for ejecting an inkjet; at least one electrode for steering the inkjet for printing; a gutter having an ink receiving orifice for receiving parts of the ink jet which are not used for printing; and a housing having a first printing configuration in which parts of the inkjet are permitted to leave the printhead for printing, and a second cleaning configuration in which the housing at least partially encloses a cleaning volume comprising at least a part of the at least one electrode and the ink receiving orifice; and the method comprising: changing the configuration of the housing from the first printing configuration to the second cleaning configuration; ejecting a cleaning fluid into the cleaning volume; and removing the cleaning fluid from the cleaning volume.

The cleaning fluid may be, or may comprise, solvent. Ejecting a cleaning fluid into the cleaning volume may comprise ejecting a solvent jet though the nozzle and into the cleaning volume.

The cleaning fluid may be ejected into the cleaning volume through a fluid inlet that is arranged to cooperate with the cleaning volume when the housing is in the second cleaning configuration.

The cleaning fluid may be removed through the ink receiving orifice or another drain hole where present. This may be returned to the ink supply system.

Between ejecting the cleaning fluid and removing the cleaning fluid, the method may further comprise, waiting a predetermined time period with the cleaning fluid in the cleaning volume.

The method may further comprise, after removing the cleaning fluid from the cleaning volume, generating an airflow in the cleaning volume for drying. The airflow may be generated with the housing in the first printing configuration or with the housing in the second cleaning configuration. The airflow may be generated in the printhead. The method may further comprise: before ejecting a cleaning fluid into the cleaning volume: removing the printhead from a printing position; and positioning the printhead in a cleaning position in which the printhead is housed in a cleaning vessel; and after removing the cleaning fluid from the cleaning volume: returning the printhead to the printing position.

The printing position may be on the production line.

Positioning the printhead in a cleaning position may comprise supporting the printhead in a substantially vertical orientation in the cleaning vessel such that the ink gun is positioned above the ink receiving orifice. This may be beneficial for allowing the cleaning fluid or solvent to be drained through the ink receiving orifice. The printhead may be positioned in other orientations. The printhead may be oriented substantially horizontally or at a desired angle between the vertical and horizontal. The angle may be selected to aid in the cleaning of a particular printhead component and/or to improve draining of the cleaning fluid or solvent, through the ink receiving orifice or one of the one or more orifices for receiving cleaning fluid or solvent from the cleaning volume where present.

The method may further comprise: before ejecting a cleaning fluid into the cleaning volume: taking the continuous inkjet printer out of a printing mode in which the continuous inkjet printer is configured to supply ink to the ink gun of the printhead; and placing the continuous inkjet printer in a cleaning mode in which the continuous inkjet printer is configured to supply cleaning fluid to the cleaning volume.

Placing the continuous inkjet printer in a cleaning mode may further comprise: the continuous inkjet printer being configured to wait a predetermined time period once a predetermined amount of cleaning fluid has been ejected towards the cleaning volume; and applying a negative pressure to a drain hole of the continuous inkjet printer cooperating with the cleaning volume when the housing is in the second cleaning configuration to draw the cleaning fluid back into the continuous inkjet printer.

The method may further comprise: before ejecting a solvent jet through the nozzle: taking the continuous inkjet printer out of a printing mode in which the continuous inkjet printer is configured to supply ink to the ink gun of the printhead; and placing the continuous inkjet printer in a cleaning mode in which the continuous inkjet printer is configured to supply solvent to the print head for ejecting a solvent jet through the nozzle towards the cleaning volume.

Placing the continuous inkjet printer in a cleaning mode may further comprise: the continuous inkjet printer being configured to wait a predetermined time period once a predetermined amount of solvent has been ejected through the nozzle towards the cleaning volume; and applying a negative pressure to the gutter to draw solvent back into the continuous inkjet printer through the ink receiving orifice.

According to a fourth aspect of the present invention, there is provided a computer readable medium for a continuous inkjet printer, the continuous inkjet printer comprising an ink supply system operable to supply ink to a print head, a printhead operable to receive ink from the ink supply system for printing, and a controller for reading the computer readable medium and controlling operation of the continuous inkjet printer; the printhead comprising: an ink gun comprising a nozzle for ejecting an inkjet; at least one electrode for steering the inkjet for printing; a gutter having an ink receiving orifice for receiving parts of the ink jet which are not used for printing; and a housing having a first printing configuration in which parts of the inkjet are permitted to leave the printhead for printing, and a second cleaning configuration in which the housing at least partially encloses a cleaning volume comprising at least a part of the at least one electrode and the ink receiving orifice; and the computer readable medium is encoded with instructions that, when executed by the controller, cause the continuous inkjet printer to: eject a cleaning fluid into the cleaning volume when the housing is in second cleaning configuration; and remove the cleaning fluid from the cleaning volume.

It will be appreciated that any feature(s) described herein in relation to one aspect, embodiment, example or otherwise, may be combined with any other feature(s) described herein in relation to any other aspect, embodiment, example or otherwise, as appropriate and applicable. Brief description of the drawings

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labelled in every drawing. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic illustration of a continuous inkjet printer in accordance with an embodiment of the present invention;

Figure 2 shows a perspective view of a continuous inkjet printer in accordance with an embodiment of the present invention;

Figure 3 shows a perspective view of a cross section of part of a printhead;

Figure 4 shows a schematic illustration of various components of a printhead, indicating an ink drop plane;

Figure 5 shows the perspective view of figure 3, in this figure the printhead having a housing in accordance with an embodiment of the present invention;

Figures 6a, b show schematic illustrations of a part cross section of a printhead having a housing in accordance with an embodiment of the present invention, figure 6a showing the housing in a first printing configuration and figure 6b showing the housing in a second cleaning configuration;

Figures 7a, b1, b2, c show schematic illustrations of a part cross section of a printhead having a housing in accordance with an embodiment of the present invention, figure 7a showing an exploded view of the housing, figure 7b1, b2 showing the housing in two different printing configurations, and figure 7c showing the housing in a cleaning configuration; and

Figure 8 shows a flowchart illustrating a method of cleaning a printhead in accordance with an embodiment of the present invention.

Detailed description

Aspects and embodiments disclosed herein are not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Aspects and embodiments disclosed herein are capable of being practiced or of being carried out in various ways.

Figure 1 schematically illustrates an inkjet printer 1. Inkjet printer 1 comprises an ink supply system 2, a print head 3 and typically a controller 4. The ink supply system 2 may typically comprise an ink storage system 5 and a service module 6. In Figure 1, fluid flow through the inkjet printer 1 is illustrated schematically by solid arrows and control signals are illustrated schematically by dashed arrows.

The service module 6 typically comprises two cartridge connections for engagement with a fluid cartridge. In particular, the service module 6 may comprise an ink cartridge connection 7 for engagement with an ink cartridge 8 and a solvent cartridge connection 9 for engagement with a solvent cartridge 10. The service module 6 further comprises a printer connection 11 for releasable engagement with an inkjet printer.

The printer connection 11 typically comprises a plurality of fluid ports, each fluid port arranged to connect to a fluid pathway within the inkjet printer 1 to allow fluid to flow between the service module 6 and other parts of the inkjet printer 1, such as the ink storage system 5 and the print head 3. The printer connection 11 further comprises an electrical connector arranged to engage with a corresponding connector on the inkjet printer 1.

Each of the ink and solvent cartridge connections 7, 9 typically comprises a fluid connector for engaging an outlet of respective ink and solvent cartridges 8, 10 so as to allow fluid to flow from the cartridges 8, 10 into the service module 6.

From the service module 6, ink and solvent can flow to the ink storage system 5 via the printer connection 11. In operation, ink from the ink cartridge 8 and solvent from the solvent cartridge 10 can be mixed within the ink storage system 5 so as to generate printing ink of a desired viscosity which 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 storage system 5. When unused ink is returned to the ink storage system 5 from the print head 3, solvent saturated air may be drawn in with ink from a gutter of the print head 3.

The ink jet printer 1 is typically controlled by controller 4. Controller 4 receives signals from various sensors within the inkjet printer 1 and is operable to 10 provide appropriate control signals to the ink supply system 2 and the print head 3 to control the flow of ink and solvent through the inkjet printer 1. The controller 4 may be any suitable device known in the art, and typically includes at least a processor and memory.

The ink cartridge 8 may be provided with an electronic data storage device 12 storing data relating to contained ink (e.g. type and quantity of ink), the solvent cartridge 10 may be provided with an electronic data storage device 13 storing data relating to contained solvent (e.g. type and quantity of solvent), and the service module 6 may comprise an electronic data storage device 14 for storing identification data (e.g. an identification code, a serial number, a manufacture date, an expiration date etc.). The controller 4 may be arranged to communicate with the electronic data storage devices 12, 13 via the service module 6.

In operation, ink is delivered under pressure from ink supply system 2 to print head 3 and recycled back via flexible tubes which are bundled together with other fluid tubes and electrical wires (not shown) into an umbilical cable 1000 (shown in figure 2). The ink supply system 2 is typically located in a cabinet and the print head 3 is disposed 5 outside of the cabinet, connected to the cabinet via the umbilical cable 1000. Figure 2 shows the printhead 3 connected to a printer main body 1002 via the umbilical cable 1000. The printer main body 1002 may comprise the ink supply system 2 and optionally the controller 4, and the printer main body 1002 may have a display 1004 and/or keypad 1006 for use by an operator.

As has already been mentioned, during printing, the printhead 3 components become lightly coated with ink and other foreign bodies. The printhead 3 therefore requires cleaning, which may take place, at least in some situations, in a wash station 15, which will be further discussed below. It will be appreciated that the wash station 15 is an optional feature. An exemplary wash station 15 is shown in figure 2. The wash station 15 comprises a printhead support region 15a and a solvent receptacle 15b. The solvent receptacle 15b may, for example, comprise a bottle attached (e.g. removably) to the bottom of the printhead support region 15a and configured to catch any solvent dripping or flowing from the printhead during the cleaning operation. The printhead support region 15a comprises a support which can support the printhead in an orientation suitable for cleaning. Such wash stations are routinely provided for prior art printers, and may provide a cleaning window 15c through which solvent can be sprayed by a wash bottle to clean the components of the print head 3 which are exposed through the window 15. It will be appreciated that the print head 3, when in use, is typically encased within the printhead cover or casing. However, the printhead cover is typically removed for cleaning purposes.

Turning to the configuration of the printhead 3 as shown in figure 3, the print head 3 has a printhead substrate or deck 17, an ink droplet generator or ink gun 19 having a fluid outlet 20, a charge electrode assembly 21 (or a charge electrode), a high voltage deflection plate or electrode 23A, a zero or negative volt deflection plate or electrode 23B, and a gutter tube 25 having an inlet or ink receiving orifice 27 defining a gutter entrance. Movement from the ink droplet generator 19 to the gutter tube 25 is referred to as moving downstream. Whilst in the embodiment shown in figure 3 the deflection electrodes 23A, 23B are perpendicular to the deck 17 and deflection of the ink droplets is parallel to the deck 17, embodiments are of course possible with the deflection electrodes 23A, 23B and ink droplet deflection in other orientations. For example, the deflection electrodes 23A, 23B may be parallel to the deck 17 and deflection of the ink droplets may be perpendicular to the deck 17, as is shown in figure 4. A cover tube or printhead casing (exemplified in figure 2) typically surrounds the printhead components to protect all of the components from external elements.

Referring to figure 4, in operation, the ink droplet generator 19 generates ink droplets and emits each droplet 24 such that each droplet begins traveling along an undeflected droplet flight path 24a. Each droplet passes through the charge electrode assembly 21 where each droplet may receive a charge. The charge is associated with an amount of deflection the droplet is to undergo as the droplet continues past the deflection electrodes 23A, 23B. If the droplet receives no charge or negligible charge the droplet will continue along its original, undeflected droplet flight path 24a, to enter the inlet 27, and eventually return to an ink well (not shown). This undeflected flight path 24a defines an ink drop axis.

If the droplet receives a charge, the droplet will be deflected to a deflected droplet flight path. A voltage of around 2000 volts may be applied between the first and second deflection electrodes in order to cause the droplets to deflect. The deflected droplet flight path may be any flight path within a range of flight paths bounded by a least deflected droplet flight path 24b and a most deflected droplet flight path 24c, which can be seen for example in figure 4. These deflected flight paths correspond to a minimum and maximum height of a print that results from the ink droplets subsequently landing on a substrate 26. All other (intended) flight paths for printed droplets will be between the least deflected droplet flight path 24b and the most deflected droplet flight path 24c. These intended flight paths therefore define an ink drop plane 29. This ink drop plane can be seen in figure 4, in which the ink drop plane is defined in the plane of the page.

During operation an ink droplet may not travel along its flight path as intended, and/or ink mist may be formed, and the ink mist and/or droplet may deposit on an interior surface of the print head 3. For example, over time, the interior surfaces of the charge electrode assembly 21 and deflection electrodes 23A, 23B may become covered in ink, as well as an external rim of the gutter inlet 27. Repeated deposits may grow over time to form an accumulation of ink 30. A location particularly prone to the accumulation of ink 30 is the external rim of the gutter inlet 27 as is exemplified in figure 4.

Although not described or shown, the printhead 3 may comprise one or more sensors for use in ensuring accurate steering of the inkjet beam and/or in detecting the presence of any ink build-up on one or more of the printhead components.

Turning to figure 5, a printhead 3 is shown which has been modified to improve the printhead cleaning process. The printhead 3 is shown with a housing 31 according to an embodiment of the invention. The housing 31 has a first printing configuration in which parts of the ink jet are permitted to leave the printhead 3 for printing, and a second cleaning configuration in which the housing 31 encloses a cleaning volume containing various components of the printhead 3.

The housing 31 may be substantially fixed in place relative to various printhead components. The housing 31 may comprise one or more walls 32 mounted or detachably connected to the deck 17. It may be the one or more walls 32 that are substantially fixed in place relative to the printhead components. The one or more walls 32 may enclose the relevant components of the printhead 3 between them and the deck 17. For example, as shown in figure 5, the one or more walls 32 may cooperate with the deck 17 to enclose the fluid outlet 20 of the ink droplet generator 19, the charge electrode assembly 21, the deflection electrodes 23A, 23B and the gutter inlet 27 within the housing, to define an enclosed fluid path between the outlet 20 and gutter inlet 27. In this way, the gutter inlet 27 can be used to drain solvent from within the cleaning volume to reclaim and reuse the solvent. The wall 32a or part of the wall positioned downstream of the deflection electrodes 23A, 23B, and perhaps the gutter inlet 27, may have an aperture 33 defined therein that cooperates with at least the ink drop plane 29 to permit ink drops to leave the printhead 3 for printing. The aperture may be approximately 8mm wide, parallel to the ink drop plane 29, and approximately 2mm high, perpendicular to the ink drop plane 29. The cover tube or printhead casing (not shown) also has an aperture that cooperates with this aperture 33 to permit ink drops to leave the printhead 3.

The wall 32a may have an associated moveable cover 35 that is moveable between a first position whereby the cover 35 is withdrawn from the aperture 33 to expose the aperture 33 (corresponding to the first printing configuration of the housing 31), and a second position whereby the cover 35 cooperates with the aperture 33 to close the aperture 33 (corresponding to the second cleaning configuration of the housing 31). In this case, when the moveable cover 35 is in the second position, the housing encloses a cleaning volume between the deck 17 and the one or more walls 32. This facilitates easy cleaning of the printhead 3. Solvent can be ejected through the fluid outlet 20 of the ink droplet generator 19 and into the cleaning volume for the cleaning volume to hold or retain the solvent within the housing, for example to bathe the various printhead components. This solvent can be obtained from the solvent cartridge 10 of the ink supply system 2. The solvent used for cleaning can also be reclaimed by the gutter inlet 27 to be returned to the ink supply system 2 for reuse.

Of course, if the cover 35 was in the first position, solvent could just leave through the aperture 33 to other parts of the printhead and/or out of the printhead cover tube or printhead casing to the surroundings. Any suitable mechanism may be used to provide the moveable cover, which may be moveably mounted on the wall 32a, or on any number of the one or more walls 32, or on the deck 17.

The printhead 3, the housing 31 or the deck 17 may define one or more orifices (not shown) arranged to cooperate with the cleaning volume when the housing 31 is in the second cleaning configuration such that the one or more orifices can receive solvent from the cleaning volume. This may allow the printhead 3 to be cleaned in a different orientation and/or may speed up draining of the solvent once the printhead components have been cleaned. The one or more orifices may be fluidly connected to the ink supply system 2 in a similar way to the gutter 25 so that the solvent can be reclaimed for re-use. The or any drained solvent may alternatively be directed to a waste solvent store or bottle, rather than being for re-use.

Although not shown in the figures, the printhead or housing may comprise one or more fluid inlets or orifices arranged to cooperate with the cleaning volume when the housing is in the second cleaning configuration, such that a cleaning fluid or solvent can be inserted into the cleaning volume through the fluid inlet or orifice for cleaning.

The housing 31 may enclose the printhead components with an imperfect seal. An imperfect seal may mean that an element of sealing is provided by the housing, but that some weeping of solvent from within the housing to the deck 17 and/or other components of the printhead outside of the housing 31 can be tolerated. The one or more walls 32 may be integrally formed, and/or they may cooperate with the deck 17 with an imperfect seal. The one or more walls 32 may cooperate with each other with an imperfect seal. The moveable cover 35 and the aperture 33 may cooperate with each other with an imperfect seal. In other embodiments, the housing 31 may enclose the printhead components with a perfect seal, or watertight seal. This may allow solvent to be inserted into the cleaning volume under a higher pressure. Even a perfect seal may be overcome at high pressure. The one or more walls 32 may be integrally formed, and/or they may cooperate with the deck 17 whereby one of the cooperating surfaces comprises a gasket for preventing solvent from leaking out of the cleaning volume. The one or more walls 32 may cooperate with each other with a perfect seal.

The housing 31 may alternatively be arranged to enclose fewer and/or different printhead components. The housing 31 may be arranged such that the one or more walls 32 and the deck 17 enclose the gutter inlet 27 and a part of the deflection electrodes 23A, 23B. This would therefore allow for at least the gutter inlet 27 and the relevant part of the deflection electrodes 23A, 23B to be cleaned when solvent is inserted into the cleaning volume, and the gutter inlet 27 could still reclaim the solvent for reuse. Such an arrangement may be provided by, for instance, having the housing 31 open at the upstream end of the deflection electrodes 23A, 23B, i.e. the end nearest the ink droplet generator 19, or by providing an aperture in this end for receiving ink from the ink droplet generator 19.

The housing 31 may be arranged such that the one or more walls 32 and the deck 17 enclose the gutter inlet 27 and the deflection electrodes 23A, 23B. The housing 31 may be arranged such that the one or more walls 32 and the deck 17 enclose the gutter inlet 27, the deflection electrodes 23A, 23B and the charge electrode assembly 21.

In some embodiments, the housing 31 may be open to a top side of the housing, the top being the uppermost portion of the housing 31 relative to the deck 17, to form a sort of bath for the printhead components. In this case, cleaning of the printhead 3 may be improved, and leaking of the solvent may be avoided, where the printhead is kept in a substantially horizontal orientation or at an incline whereby the solvent cannot leak out over the open top side of the housing 31. The housing 31 could be tilted during cleaning to aid in the cleaning.

Turning to figures 6a-b and 7a-c, a printhead 3 is shown which has been modified to improve the printhead cleaning process. The printhead 3 is shown with a housing 31 according to an embodiment of the invention. The housing 31 has a first printing configuration, shown in figures 6a, 7b1 and 7b2, in which parts of the inkjet are permitted to leave the printhead 3 for printing, and a second cleaning configuration shown in figures 6b and 7c, in which the housing 31 encloses a cleaning volume containing various components of the printhead 3. The housing 31 or part of the housing 31 may be moveable relative to the various printhead components.

The housing 31 may comprise a first housing portion 37 having one or more first sealing surfaces 39 and a second housing portion 41 having one or more second sealing surfaces 43 for cooperating with the one or more first sealing surfaces 39 to at least partially enclose a cleaning volume. One or both of the first housing portion 37 and the second housing portion 41 may be moveable between a first position and a second position. In this first position, the first housing portion 37 and the second housing portion 41 may be separated such that the one or more first sealing surfaces 39 are separated from the one or more second sealing surfaces 43 to define an open region between them through which parts of the inkjet can leave the printhead 3 for printing (corresponding to the first printing configuration of the housing 31). In this second position, the first housing portion 37 and the second housing portion 41 may be positioned closer together such that the one or more first sealing surfaces 39 cooperate with the one or more second sealing surfaces 43 to enclose the cleaning volume between them (corresponding to the second cleaning configuration of the housing 31). The first and second sealing surfaces 39, 43 may have cooperating shapes so that they mate in at least a direction that is parallel to the ink drop plane and is substantially perpendicular to the ink drop axis.

In embodiments, the first housing portion 37 may comprise the zero volt deflection electrode 23B and may be stationary, and the second housing portion 41 may comprise the high voltage electrode and may be the moveable housing portion. The deflection electrodes 23B, 23A may be integrally formed with the first and second housing portions 37, 41 respectively. The first and second housing portions 37, 41 may also surround the fluid outlet 20 of the ink droplet generator 19, the charge electrode assembly 21, and the gutter inlet 27. Therefore, the first and second housing portions 37, 41 surround the fluid outlet 20 of the ink droplet generator 19, the charge electrode assembly 21, the deflection electrodes 23A, 23B and the gutter inlet 27 such that when the first and second housing portions 37, 41 come together and cooperate, as will be further explained below, these printhead components are enclosed between the first and second housing portions 37, 41.

In figures 6a-b and 7a-c, only parts of the printhead components are illustrated for improved clarity. In figures 6a-b, the ink drop axis A is illustrated, between the fluid outlet 20 of the ink droplet generator 19 and the gutter entrance 27, but is omitted from figures 7a-c for improved clarity. The charge electrode assembly 21 is omitted in figures 6a-b and 7a-c for improved clarity, but would be in its normal position, between the fluid outlet 20 and the deflection electrodes 23A, 23B, aligned with the ink drop axis A. In addition, only an external face of each of the deflection electrodes 23A, 23B are illustrated for improved clarity.

Turning more specifically to figures 6a, b, the first housing portion 37 may comprise one or more first walls 45 mounted to the deck 17. The one or more first walls 45 may alternatively be movably connected to the deck 17. The one or more first walls 45 may comprise a first inside wall 47 that is arranged to cooperate with the cleaning volume and is recessed from the one or more first sealing surfaces 39. As shown in the figures, the first inside wall 47 may be on the side of the first housing portion 37 closest to the second housing portion 41 and/or may face the second housing portion 41. At least parts of the one or more first sealing surfaces 39 may also face the second housing portion 41. A face of a deflection electrode, for example the zero volt deflection electrode 23B, can be seen on the first inside wall 47. The first deflection electrode may be substantially straight to substantially align with the ink drop axis A as shown. This is beneficial for allowing the gutter entrance 27 to be placed adjacent the zero volt deflection electrode 23B to receive substantially undeflected ink drops as indicated.

The second housing portion 41 may comprise one or more second walls 49 movably connected to the deck 17. Whilst not shown, any suitable mechanism for providing this movement, such as a mechanical, electromechanical, pneumatic or hydraulic actuator, may be used. The one or more second walls 49 may alternatively be mounted to the deck 17. The one or more second walls 49 may comprise a second inside wall 51 that is arranged to cooperate with the cleaning volume and may be recessed from the one or more second sealing surfaces 43. It may alternatively be that only one of the first inside wall 47 or the second inside wall 51 may be recessed from their respective sealing surface. As shown in figures 6a, b the second inside wall 51 may be on the side of the second housing portion 41 closest to the first housing portion 37 and/or may face the first housing portion 37. At least parts of the one or more second sealing surfaces 43 also face the first housing portion 37 and the first inside wall 47. A face of a deflection electrode, for example the high volt deflection electrode 23A, is shown on the second inside wall 51. The second deflection electrode may be substantially angled at least in part relative to the ink drop axis A. This angle-ing of the high volt deflection electrode 23A is beneficial for reducing the voltages required to generate an electrostatic field between the deflection electrodes 23A, 23B. Alternatively, the second deflection electrode may be substantially straight to substantially align with the ink drop axis.

Referring to figure 6a, when the first and second housing portions 37, 41 are in this first position, the first and second housing portions 37, 41 are horizontally spaced apart, and an open region 44 is defined between the one or more first sealing surfaces 39, the first inside wall 47, the one or more second sealing surfaces 43 and the second inside wall 51 in this first position. This opening 44 at least cooperates with the ink drop axis A and ink drop plane 29 such that ink drops are permitted to leave the printhead 3 through the open region 44 for printing.

Referring to figure 6b showing the first and second housing portions 37, 41 in this second position, to reach this second position, the second housing portion 41 has moved towards the first housing portion 37 such that the one or more first sealing surfaces 39 have cooperated with the one or more second sealing surfaces 43. In particular, in this embodiment, the second housing portion 41 has moved in a direction that is in the ink drop plane 29 and is substantially perpendicular to the ink drop axis A. With the deflection electrodes 23A, 23B oriented as shown in figures 6a, b, this effectively means that the second housing portion 41 has moved substantially horizontally along the deck 17. The second housing portion 41 may have slid along the deck 17 into this second position, which may be a more simple movement mechanism to implement. In this second position, the opening 44 is substantially closed so that ink drops are not permitted to leave the printhead, with the cleaning volume being defined between the one or more first sealing surfaces 39, the first inside wall 47, the one or more second sealing surfaces 43 and the second inside wall 51. Given that when the first and second housing portions 37, 41 are in the first position the fluid outlet 20 of the ink droplet generator 19, the charge electrode assembly 21, the deflection electrodes 23A, 23B and the gutter inlet 27 are positioned between the first and second housing portions 37, 41, when the first and second housing portions 37, 41 come together to enclose the cleaning volume between them, the cleaning volume comprises the fluid outlet 20, the charge electrode assembly 21, the gutter inlet 27, and the deflection electrodes 23A, 23B.

Turning to the embodiments shown in figures 7a, 7b1, 7b2 and 7c, figure 7a shows an exploded view of the housing 31, figures 7b1 and 7b2 show the housing 31 in two different first printing configurations, and figure 7c shows the housing 31 in the second cleaning configuration. Whilst not clearly shown in the figures, the first and second housing portions 37, 41 may extend further upstream than the deflection electrodes 23A, 23B for enclosing the other relevant printhead components.

Starting with figure 7b1, when the housing is in the first printing configuration, the first and second housing portions 37, 41 may be positioned at different heights relative to the deck 17. The first and second housing portions 37, 41 may be staggered in a direction that is substantially perpendicular to the ink drop plane and to the ink drop axis. In the particular embodiment shown, one housing portion may be positioned on the deck and the other at a raised position relative to the deck. Alternatively, one housing portion may be positioned slightly below the deck and the other housing portion may be positioned slightly above the deck. In the embodiment shown in figure 7b1, at least parts of the first and second sealing surfaces 39, 43 may already cooperate in this position.

However, as shown, the deflection electrodes 23A, 23B are aligned in a direction that is substantially perpendicular to the ink drop plane and to the ink drop axis for ease of creating the electrostatic field for deflecting the ink drops. In the orientation shown in the figure, they are vertically aligned for ease of creating the electrostatic field for deflecting the ink drops.

The first and second housing portions 37, 41 have first and second end faces 53, 55 respectively, connected to at least a part of the first and second sealing surfaces 39, 43 respectively. The first and second end faces 53, 55 are at a downstream end of the first and second housing portions 37, 41. The first and second end faces 53, 55 have cooperating shapes. The first and second end faces 53, 55 may define additional sealing faces 53a, 55b, connecting with the first and second sealing faces 39, 43 respectively, for cooperating to seal the open region or aperture downstream of the deflection electrodes 23A, 23B. The ends may interlock.

In the embodiment shown in figure 7b1, when the housing is in the first printing configuration, the first and second housing portions 37, 41 are separated such that the first and second sealing surfaces 39, 43, and the first and second end faces 53, 55, define an aperture 33 overlapping with the ink drop plane 29. Therefore, ink drops for printing are permitted to leave the printhead through the aperture 33.

To move into the second cleaning configuration, the moveable housing portion moves in a direction that is substantially perpendicular to the ink drop plane and to the ink drop axis, towards the other housing portion, to close the aperture 33, and to thereby enclose the cleaning volume between the first and second housing portions 37, 41 in the second cleaning configuration. In the orientation shown in the figure, this is the vertical direction. Ink drops therefore cannot leave the printhead for printing in the second cleaning configuration. Given that when the first and second housing portions 37, 41 are in the first position the fluid outlet 20 of the ink droplet generator 19, the charge electrode assembly 21, the deflection electrodes 23A, 23B and the gutter inlet 27 are positioned between the first and second housing portions 37, 41, when the first and second housing portions 37, 41 come together to enclose the cleaning volume between them, the cleaning volume comprises the fluid outlet 20, the charge electrode assembly 21, the gutter inlet 27, and the deflection electrodes 23A, 23B.

Providing the movement in a direction that is substantially perpendicular to the ink drop plane and to the ink drop axis, for instance as illustrated in this embodiment, may be beneficial since only a small movement may be required to close/open the aperture 33.

Turning to figure 7b2, when the housing is in the first printing position, the first and second housing portions 37, 41, may be staggered in a first direction that is in the ink drop plane and is substantially perpendicular to the ink drop axis, and in a second direction that is substantially perpendicular to the ink drop plane and to the ink drop axis. In the orientation shown, the first and second housing portions 37, 41 may be positioned at different vertical heights in the embodiment of figure 7b1 , but the first and second housing portions 37, 41 may additionally be horizontally spaced apart, similar to as in the embodiment shown in figure 6a. However, as shown, the deflection electrodes 23A, 23B are aligned in at least the second direction for ease of creating the electrostatic field for deflecting the ink drops. In the orientation shown in the figure, the deflection electrodes 23A, 23B are vertically aligned and their ends are aligned, for ease of creating the electrostatic field for deflecting the ink drops.

The first and second housing portions 37, 41 have first and second end faces 53, 55 respectively, connected to at least a part of the first and second sealing surfaces 39, 43 respectively. The first and second end faces 53, 55 are at a downstream end of the first and second housing portions 37, 41. The first and second sealing faces 53, 55 have cooperating shapes. The first and second end faces 53, 55 may define additional sealing faces 53a, 55b, connecting with the first and second sealing faces 39, 43 respectively, for cooperating to seal the open region or aperture downstream of the deflection electrodes 23A, 23B. The ends may interlock.

In the embodiment shown in figure 7b2, when the housing 31 is in the first printing configuration, the first and second housing portions 37, 41 are separated such that the first and second sealing surfaces 39, 43, and the first and second sealing faces 53, 55, define an open region 44 comprising an aperture 33 overlapping with the ink drop plane 29. Therefore, ink drops for printing are permitted to leave the printhead through the aperture 33.

To move into the second cleaning configuration, the moveable housing portion moves in the first direction and the second direction towards the other housing portion close the open region 44 and aperture 33. In the orientation shown, the moveable housing portion moves vertically and horizontally, perhaps diagonally through a vertical and horizontal axis relative to the deck 17, towards the other housing portion to close the aperture 33 and open region 44, and to thereby enclose the cleaning volume between the first and second housing portions 37, 41 in the second cleaning configuration. Ink drops cannot therefore leave the printhead for printing in the second cleaning configuration. Given that when the first and second housing portions 37, 41 are in the first position the fluid outlet 20 of the ink droplet generator 19, the charge electrode assembly 21, the deflection electrodes 23A, 23B and the gutter inlet 27 are positioned between the first and second housing portions 37, 41, when the first and second housing portions 37, 41 come together to enclose the cleaning volume between them, the cleaning volume comprises the fluid outlet 20, the charge electrode assembly 21, the gutter inlet 27, and the deflection electrodes 23A, 23B.

Providing the movement in both the first and second directions may be beneficial since the deflection electrodes 23A, 23B can be arranged closer together for cleaning, and only a small movement may be required to close/open the open region 44 and aperture 33.

The variations described above relating to the possibility of providing one or more orifices for draining solvent from the cleaning volume, providing one or more fluid inlets for providing solvent to the cleaning volume, varying the strength of the seal between different parts of the housing 31 and/or the deck 17, and varying the printhead components which the cleaning volume comprises all apply equally to these embodiments.

For printing, the printhead housing 31 just needs to be in the first printing configuration. The method of continuous inkjet printing has already been described above.

For cleaning, the printhead housing needs to be reconfigured into the second cleaning configuration as has been described for the various embodiments. However, as will be appreciated, regardless of exactly how the printhead housing achieves its second cleaning configuration, and so regardless of exactly how the cleaning volume is created, the following steps can then be taken to clean the printhead components that the cleaning volume comprises. An exemplary method is shown in figure 8.

Solvent or another cleaning fluid is inserted or injected into the cleaning volume, perhaps through the outlet 20 of the ink droplet generator 19. The solvent is typically inserted at low pressure which allows the seals to be imperfect as described above. Where the seals are tighter or perfect, the solvent can be inserted into the cleaning volume under higher pressure.

The solvent may then be left in the cleaning volume to soak or immerse the printhead components within the cleaning volume, and so to wash away deposits of ink that may have accumulated on these components. For example, a predetermined immersion time may be allowed to elapse whilst the solvent is in the cleaning volume. The immersion time may depend on the ink type and solvent type used.

The solvent may then be drained out of the cleaning volume through the gutter inlet 27 and/or through the one or more additional orifices where present. These may fluidly connect with the ink supply system 2 so that the solvent can be reclaimed for re use. The or any drained solvent may alternatively be directed to a waste solvent store or bottle, rather than being for re-use.

Once the solvent has been drained from the cleaning volume, the printhead may be purged with air to dry the printhead components. Alternatively, before purging with air, the process of ejecting solvent into the cleaning volume, waiting a predetermined immersion time and draining the solvent from the cleaning volume may be repeated. Whether the process is repeated may depend on the ink type and/or circumstances of the clean (for example, a poor shutdown or a long interval between cleans).

The printhead can then be re-configured into its first printing configuration to resume printing.

It will, of course, be appreciated that the process described above may be performed at any convenient interval, or on the basis of any suitable determination that cleaning should be performed. Moreover, while it is described that the process immediately follows, and is followed by, printing operations, in some circumstances, it may be desirable for the cleaning operation to be performed in isolation, or at start-up (i.e. after a period of idle) or at shutdown (i.e. before a period of idle).

The continuous inket printer 1 and printhead 3 may be configured to carry out the cleaning method described. For example, the user may place the printer 1 into a cleaning mode from a printing mode. In doing so, the controller 4 may be configured to control the printhead housing 31 to move it from the first printing configuration to the second cleaning configuration. The controller 4 may be physically connected to the printer 1 or it may be remote from the printer 1. The printer 1 may then be configured to carry out all of the method steps described herein to clean the printhead components. Where the solvent is inserted at a low enough pressure and/or where the relevant seals are strong enough, this may be carried out with the printhead still on the production line. This would be highly beneficial. Alternatively, the printhead can be first moved to a wash station 15 as described so that any leaking of solving from out of the housing can be captured by the wash station 15. The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.