GB2600406A

GB2600406A - Electrode

Info

Publication number: GB2600406A
Application number: GB2016971.0A
Authority: GB
Inventors: Jeffrey Stamp Michael; Smith Robert
Original assignee: Videojet Technologies Inc
Current assignee: Videojet Technologies Inc
Priority date: 2020-10-26
Filing date: 2020-10-26
Publication date: 2022-05-04
Also published as: GB202016971D0

Abstract

A deflection electrode 100 for a printhead for a continuous inkjet printer creates an electrostatic field for deflecting ink drops carrying trapped electric charges for printing. The deflection electrode defines an electrode axis A between its first end 104 and its second end 106 opposite the first end, and a first electrode surface (108, Fig.5) extending in a direction that is parallel to the electrode axis. The deflection electrode comprises an aperture 102 at its first end in at least the first electrode surface, the aperture extending along the first electrode surface in a direction that is parallel to at least a part of the electrode axis. At least two opposed collecting surfaces (112A, 112B, Fig.6) are defined by the aperture, the at least two collecting surfaces extending along a length of the deflection electrode. The collecting surfaces collect small undesirable ink particles called microsatellites that are generated as ink in ejected.

Description

Electrode

Technical field

The present invention relates to a deflection electrode for a printhead for a continuous inkjet printer, and to a method of manufacturing the deflection electrode. The present invention also relates to the printhead and the continuous inkjet printer.

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, the pair comprising a high voltage (or extra high tension (EHT)) plate and a zero or negative voltage plate (the 'ground' plate). 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.

Different inks having different chemical compositions are required for different printing applications, for example to ensure the ink has the required properties for adhering to the desired substrate material. Generally, the adhesion is dictated by the polymer(s) or binder(s) contained within the ink.

During printing, some inks, particularly those with polymers with higher molecular weight, generate what are referred to as 'microsatellites' within the printhead. These microsatellites are very small undesirable ink particles. They form as the continuous stream of ink, or jet, emanating from the nozzle is broken up. These microsatellites have a very low, typically negligible, mass. For example, the microsatellites are typically of the order of approximately 1% of the size of the generated ink droplets, sometimes smaller.

As for the ink drops, the microsatellites may acquire charge from the charge electrode. The microsatellites attract to one of the high voltage plate or the zero or negative voltage plate depending on the charge they acquire (i.e. positive or negative charge) from the charge electrode. In the case where the charge electrode is configured to provide the ink drops with a negative charge, and therefore negatively charged microsatellites form, these microsatellites attract to the high voltage plate and leave a deposit, the deposits forming a line along a surface of the deflection plate due to their different inertia and charges. For the lower mass microsatellites, they tend to attract to the first part of the high voltage plate they come across as they move downstream (i.e. the most upstream point, or point on the high voltage plate closest to the drop generator) and leave a deposit. Over time, these deposits accumulate to form a protrusion or column (sometimes referred to as a 'ligament' or 'stalagmite') that forms towards the ground plate. The protrusion can adversely affect the deflection and path of the ink droplets, which is of course undesirable. In many cases, the field strength may increase locally around the protrusion, over time, breaking down the air and causing the high voltage plate to track to ground and then trip. As such, the printer stops printing causing downtime, which is very undesirable. In addition, given that the protrusion is thin and fragile, it may be destroyed resulting in a pitted surface, which may require the high voltage plate to be replaced. This may cause further printer downtime and may be costly for a user.

Some attempts have been made to try to address this microsatellite problem. For example, some printers or printheads have been provided with one or more additional components that may act as microsatellite catchers. However, these additional components generally require their own complex electronics meaning that their provision adds expense and complexity, and in some cases these additional components can be space consuming, where it is desirable to keep the printheads small.

It would be desirable to provide an electrode for a print head, or a print head, that is able to handle the microsatellites in a more effective manner. It would be desirable to provide an electrode for a print head, or a print head, that alleviates or overcomes one or more of the above mentioned problems.

Summary

According to a first aspect of the present invention, there is provided a deflection electrode for a printhead for a continuous inkjet printer, the deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing, wherein the deflection electrode defines an electrode axis between its first end and its second end opposite the first end, and a first electrode surface extending in a direction that is parallel to the electrode axis, and wherein the deflection electrode comprises: an aperture at its first end in at least the first electrode surface, the aperture extending along the first electrode surface in a direction that is parallel to at least a part of the electrode axis; and at least two opposed collecting surfaces defined by the aperture, the at least two collecting surfaces extending along a length of the deflection electrode.

As explained above, currently, during printing, microsatellites may form in a printhead and if so, depending on the charge acquired, tend to attract to and deposit on one of the deflection electrodes. As explained above, where the microsatellites acquire a negative charge, they generally attract to the high voltage electrode and at its most upstream end in the printhead and/or on the surface of the high voltage electrode facing the ink drops. The deposits generally form in a line along this surface in a plane defined by the deflected ink drops (the ink drop plane), the line due to the microsatellites' different inertia and charges. Over time, these deposits form a protrusion that extends towards the second deflection electrode. The protrusion tends to overlap with the ink drop plane. This can adversely affect the ink drop deflection and path of the ink drops. As the protrusion grows, it can eventually cause a local increase in field strength, air break down and resulting trip of the high voltage deflection electrode. This results in printer downtime and can be costly and time-consuming for the user.

The present deflection electrode for a printhead is configured to handle the microsatellites in a more effective manner, and in particular by providing the present deflection electrode with a modified shape. The aperture and at least two collecting surfaces effectively act as a microsatellite catcher, delaying and potentially preventing the microsatellite deposits from building up on the deflection electrode to a level at which some of the described problems may occur.

In particular, the deflection electrode can be arranged in the printhead so that at least a part of its electrode axis is aligned with an ink drop axis that is defined by the path of the undeflected ink drops during printing. In addition, its first end can be positioned upstream of its second end, and the electrode surface can be arranged to face the ink drops and the corresponding second deflection electrode.

The deflection electrode can be further arranged so that its aperture overlaps with an ink drop plane defined by the plane of the deflected ink drops during printing.

Arranging the aperture in this way removes what would have been the 'nearest' landing points for many of the microsatellites, and at least a part of the deflection electrode where the above mentioned line of deposits may form. Since the 'nearest' landing point tends to lie in the ink drop plane as mentioned above, inhibiting the build up of microsatellite deposits in this plane may delay, or prevent, the protrusions from building up to a problematic level.

Whilst it may be thought that having an aperture in a deflection electrode, in particular in a high voltage electrode, for a printhead may adversely affect the electrostatic field strength and therefore field experienced by the ink drops, somewhat surprisingly, it has been found that such an aperture can be configured to have a minimal effect on the field strength experienced by the ink drops during printing, and more importantly on the force experienced by the ink drops during printing. Having the aperture define two opposed collecting surfaces in the deflection electrode may help ensure that the ink drops are not diverted away from their intended trajectory when the deflection electrode is in place in a printhead during printing. In particular, the surfaces can be arranged to maintain balance in the electrostatic field in the deflection plane of the ink drops to help ensure that the force experienced by the ink drops is balanced so that they follow their intended trajectory.

In addition, having the aperture define the at least two opposing collecting surfaces in the deflection electrode may help delay or prevent the microsatellite deposits from building to a problematic level. Firstly, the collecting surfaces can be arranged to avoid the ink drop plane to prevent deposits from building up in this plane. Secondly, the two opposing collecting surfaces may provide at least two alternative landing points for any given microsatellite. In particular, the provision of two alternative landing points for any given microsatellite means that the microsatellites spread more, for example across two surfaces rather than one, delaying the build up of any microsatellite deposits. In this way, the microsatellite deposits tend to collect in a position that is not between the high voltage electrode and the ground or negative electrode, and so in a position that does not reduce, or adversely affect, the separation between the deflection electrodes and therefore intended path of the ink drops.

This deflection electrode therefore enables printers to print for longer, giving better uptime. In addition, the present deflection electrode provides a low cost solution to the microsatellite problem, involving only a modified shape of an existing component of the printhead, the deflection electrode, and without requiring the provision of, for example, any additional components and/or any additional complicated and/or expensive electronics.

The deflection electrode may be for creating an electrostatic field between it and a second deflection electrode for deflecting ink drops carrying trapped electric charges for printing. The first electrode surface may be for facing the second deflection electrode when in use in a printhead. The first electrode surface may be for facing the ink drops during printing.

During printing, the undeflected ink drops may define an ink drop axis. When the deflection electrode is in place in the printhead, at least a part of the electrode axis may be parallel to the ink drop axis. When the deflection electrode is in place in the printhead, the electrode axis at and/or towards the first end of the deflection electrode may be parallel to the ink drop axis.

The electrode axis may extend through the centre of the deflection electrode. The electrode axis may follow the shape of the deflection electrode from its first end to its second end. The electrode axis may not be straight. The electrode axis may bend at a certain point along the electrode axis. The electrode axis may define a first portion towards the first end of the deflection electrode that extends in a first direction, and a second portion towards the second end of the deflection electrode that extends in a second direction that is angled relative to the first direction. When the deflection electrode is in place in the printhead, the first portion may be parallel to the ink drop axis. When the deflection electrode is in place in the printhead, the second portion may be angled relative to the ink drop axis. The second portion may be angled away from the ink drop axis towards its second end.

Alternatively, the electrode axis may be straight.

During printing, the ink drops may move in a downstream direction through the printhead towards a substrate for printing. \Mien the deflection electrode is in place in a printhead, its first end may be the end that is arranged most upstream. When the deflection electrode is in place in a printhead, its second end may be the end that is arranged most downstream.

During printing, the undeflected ink drops may define an ink drop axis. When the deflection electrode is in place in a printhead, the aperture may extend along the first electrode surface in a direction that is parallel to the ink drop axis. The aperture may extend through the deflection electrode parallel to at least a part of the electrode axis The at least two collecting surfaces may be planar.

The at least two collecting surfaces may be configured to apply an equal but oppositely directed force to an ink drop travelling in the ink drop plane. The at least two collecting surfaces may be configured such that the resultant force experienced by an ink drop is in the ink drop plane.

The at least two collecting surfaces may be symmetrical about an axis of the aperture. The axis of the aperture may pass through the centre of the aperture and may lie parallel to the at least a part of the electrode axis and/or may extend along a length of the deflection electrode.

The at least two collecting surfaces may extend in a direction that is parallel to at least a part of the electrode axis. The at least two collecting surfaces may face one another. The at least two collecting surfaces may taper or curve towards each other or away from one another along a length of the deflection electrode. The length of the electrode may or may not be its longest side. The length of the electrode may be defined between the first end and the second end. The length of the electrode may be defined by the electrode axis, between the first end and the second end.

During printing, the undeflected ink drops may define an ink drop axis, and a deflection plane may be defined that comprises both of the ink drop axis and the electrode axis. Each of the collecting surfaces may be arranged to form an acute angle with the deflection plane. Each of the collecting surfaces may lie parallel to the deflection plane. The at least two collecting surfaces may be symmetrical about the deflection plane. Each of the collecting surfaces may lie substantially perpendicular to the first electrode surface.

During printing, the deflected ink drops may define an ink drop plane. The deflection plane may correspond with the ink drop plane. When the deflection electrode is in place in a printhead, each of the collecting surfaces may be arranged to form an acute angle with the ink drop plane. Each of the collecting surfaces may lie parallel to the ink drop plane. The at least two collecting surfaces may be symmetrical about the ink drop plane.

The aperture may define an opening in the first end of the deflection electrode.

When the deflection electrode is in place in a printhead, this may remove the nearest landing point for the lowest mass microsatellites.

The deflection electrode may be open at its first end. The aperture may take the form of a slot extending from the first end of the deflection electrode. The aperture may be defined in the first end surface. The first end surface may be the surface of the deflection electrode that is positioned most upstream when in place in a printhead.

The deflection electrode may be closed at its first end.

The undeflected ink drops may define an ink drop axis, and a deflection plane may be defined that comprises both of the ink drop axis and the electrode axis, and the aperture may be defined in the deflection electrode to overlap with the deflection plane.

During printing, the deflected ink drops may define an ink drop plane. When the deflection electrode is in place in a printhead, the deflection plane may be in the ink drop plane. The deflection plane may correspond with the ink drop plane. When the deflection electrode is in place in a printhead, the aperture may be defined in the deflection electrode to overlap with the ink drop plane.

Having the aperture defined in this plane may mean that for any given microsatellite, the nearest landing point on the deflection electrode is not in this plane. This may prevent the build up of microsatellites in this plane, which may delay or prevent the deposits from building to a level where they may adversely affect the deflection and path of the ink drops.

The aperture may be symmetrical about the deflection plane.

Having the aperture arranged to be symmetrical about the deflection plane, and therefore potentially the ink drop plane, may help ensure that for any given microsatellite, there are two 'nearest landing points'. This may cause the microsatellites to spread out more evenly, attracting more evenly to each of the two collecting surfaces. This may help further delay the build up of microsatellite deposits on the deflection electrode, and so may further delay or prevent the deposits from reaching a problematic level.

During printing, the deflected ink drops may define an ink drop plane. When the deflection electrode is in place in a printhead, the deflection plane may correspond with the ink drop plane. When the deflection electrode is in place in a printhead, the aperture may be symmetrical about the ink drop plane. This may help ensure that the direction in which the ink drops are forced to travel by the generated electrostatic field is unchanged i.e. the ink drops still follow their intended trajectory.

The collecting surfaces may extend in a direction that is parallel to the deflection plane. The collecting surfaces may be equally spaced above and below the deflection plane. The collecting surfaces may define respective planes that are parallel to the deflection plane and/or the ink drop plane.

When the deflection electrode is in place in a printhead, the collecting surfaces may extend in a direction that is parallel to the ink drop plane. The collecting surfaces may be equally spaced above and below the ink drop plane.

The collecting surfaces may be angled relative to the first electrode surface. The collecting surfaces may be angled relative to the deflection plane. When the deflection electrode is in place in a printhead, the collecting surfaces may form an angle with the ink drop plane.

The deflection electrode may comprise a second electrode surface that is opposite the first electrode surface, and the aperture may be open to the first electrode surface and to the second electrode surface at its first end.

The deflection electrode may comprise a second electrode surface that is opposite the first electrode surface, and the aperture may be open to the first electrode surface and to the second electrode surface.

Having the aperture extend all of the way through the deflection electrode in this direction, may further ensure that the microsatellites deposit on the deflection electrode away from, or outside of, the ink drop plane. This may further delay or prevent the deposits from reaching a problematic level.

The aperture may form a through hole in the deflection plane. The aperture may form a through hole in the ink drop plane. The aperture may overlap with, and/or extend through, the electrode axis.

The first electrode surface may be substantially perpendicular to the deflection plane The first electrode surface may be substantially perpendicular to the ink drop plane The aperture may extend from the first end, along a length of the deflection electrode, along only a part of the distance defined by the electrode axis, and the collecting surfaces may extend along a length of the deflection electrode by the same distance.

This distance may be a good compromise. In particular, the distance may provide a sufficient amount of surface to capture the vast majority of, or all of, the microsatellites that may form, without the distance being too great such that, for instance, the deflection electrode becomes more difficult or complicated to mount within the printhead and/or the intended primary function of the deflection electrode is compromised i.e. to deflect ink drops.

The aperture may extend from the first end, parallel to at least a part of the electrode axis, along only a part of the distance defined by the electrode axis, and the collecting surfaces may also extend parallel to the at least a part of the electrode axis by the same distance.

The distance may be approximately 1-5mm.The distance may be in the region of approximately 1-5mm.

It has been found that this may be a particularly effective length for the aperture and collecting surfaces, to provide a sufficient amount of surface to capture the majority of, or all of, the microsatellites that may form, without the distance being too great such that, for instance, the deflection electrode becomes more difficult or complicated to mount within the printhead.

The distance may be smaller than 1mm or larger than 5mm.

The aperture may extend from the first end of the deflection electrode to over half way between the first end and the second end of the deflection electrode. The aperture may extend from the first end, parallel to at least a part of the electrode axis, along over half of the entire distance defined by the electrode axis, and wherein the collecting surfaces also extend parallel to the at least a part of the electrode axis by the same distance. The aperture may extend to over half way along the full length of the electrode axis. The aperture may extend to over half way along the full length of the deflection electrode.

Having the aperture extend along most of the length of the deflection electrode, or along the majority of the length of the electrode axis, may further ensure that all of the microsatellites are captured.

The deflection electrode may be closed at its second end.

The aperture may extend from the first end, along a length of the deflection electrode defined by the electrode axis, and the collecting surfaces may extend along a length of the deflection electrode by the same distance.

The aperture may extend from the first end, along a length of the deflection electrode defined by the electrode axis, to the second end, and the collecting surfaces may extend along a length of the deflection electrode by the same distance, such that the deflection electrode defines two deflection electrode elements on opposite sides of the aperture.

Having the aperture extend along the full length of the deflection electrode may further ensure that all of the microsatellites are captured by the aperture and collecting surfaces.

The opposite sides of the aperture may be above and below, respectively, the deflection plane and/or the ink drop plane.

The aperture may extend from the first end, along the electrode axis, to the second end.

The deflection electrode may comprise two deflection electrode elements separated by the aperture. The aperture may extend from the first end of the deflection electrode to the second end of the deflection electrode to define the deflection electrode elements. Each one of the two deflection electrode elements may define one of the at least two opposed collecting surfaces. Each one of the two deflection electrode elements may be above and below, respectively, the deflection plane and/or the ink drop plane. The aperture may extend from the first end, parallel to at least a part of the electrode axis, along the entire distance defined by the electrode axis, and the collecting surfaces may also extend parallel to the at least a part of the electrode axis by the same distance.

The aperture may extend along the full length of the electrode axis. The aperture may extend along the full length of the deflection electrode The deflection electrode may be a high voltage electrode for receiving a voltage. The deflection electrode may be configured to receive a voltage. The voltage may be in the region of approximately 2-10 kV. The voltage may be lower than 2 kV and/or higher than 10 kV. The second deflection electrode may be for holding at ground potential and/or for receiving a negative voltage. Alternatively, the deflection electrode may be for holding at ground potential and/or for receiving a negative voltage and/or the second deflection electrode may be a high voltage electrode for receiving a voltage.

The deflection electrode may be forked its first end. The forks may be separated by the aperture.

The deflection electrode may comprise a mounting structure, the mounting structure being separated from the aperture and/or the collecting surfaces.

According to a second aspect of the present invention, there is provided a printhead for a continuous inkjet printer, comprising: a deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing; wherein the deflection electrode defines an electrode axis between its first end and its second end opposite the first end, and a first electrode surface extending in a direction that is parallel to the electrode axis, and wherein the deflection electrode comprises: an aperture at its first end in at least the first electrode surface, the aperture extending along the first electrode surface in a direction that is parallel to at least a part of the electrode axis; and at least two opposed collecting surfaces defined by the aperture, the at least two collecting surfaces extending along a length of the deflection electrode.

During printing, the ink drops may move in a downstream direction towards a substrate for printing, and the first end of the deflection electrode may be the most upstream end of the deflection electrode.

During printing, the undeflected ink drops may define an ink drop axis, and at least a part of the first electrode surface at the first end may extend in a direction that is parallel to the ink drop axis.

During printing, the undeflected ink drops may define an ink drop axis, and the aperture may extend along at least a part of the first electrode surface in a direction that is parallel to the ink drop axis.

The at least two opposed collecting surfaces may extend in a direction that is parallel to the ink drop axis.

The second end of the deflection electrode may be the most downstream end of the deflection electrode.

The printhead may further comprise any one or more of: an ink gun comprising a nozzle for ejecting an ink jet; a charge electrode for trapping electric charges on ink drops of an ink jet; a second deflection electrode for forming a pair of deflection electrodes with the deflection electrode, the pair of deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing; and a gutter having an ink receiving orifice for receiving parts of the ink jet which are not used for printing.

The deflection electrode may comprise any one or more features described above in relation to the first aspect of the present invention.

There may be provided a printhead for a continuous inkjet printer, comprising the deflection electrode in accordance with the first aspect of the present invention.

According to a third 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, wherein the printhead comprises: a deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing; wherein the deflection electrode defines an electrode axis between its first end and its second end opposite the first end, and a first electrode surface extending in a direction that is parallel to the electrode axis, and wherein the deflection electrode comprises: an aperture at its first end in at least the first electrode surface, the aperture extending along the first electrode surface in a direction that is parallel to at least a part of the electrode axis; and at least two opposed collecting surfaces defined by the aperture, the at least two collecting surfaces extending along a length of the deflection electrode.

The deflection electrode may comprise any one or more features described above in relation to the first aspect of the present invention and/or the printhead may comprise any one or more features described above in relation to the second aspect of the present invention.

There may be provided a continuous inkjet printer printhead for 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, the printhead in accordance with the second aspect of the present invention.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a deflection electrode for a printhead for a continuous inkjet printer, the deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing, the method comprising: providing a body of conducting material with an aperture at its first end and at least two opposing collecting surfaces defined by the aperture; wherein the body defines an axis between its first end and its second end opposite the first end, and a first surface extending in a direction that is parallel to the axis, and wherein the aperture extends along the first surface in a direction that is parallel to at least a part of the axis, and the at least two collecting surfaces extend along a length of the body.

The method may involve any steps that enable the body to have any one or more features described above according to the first aspect of the present invention.

According to a fifth aspect of the present invention, there is provided a computer program comprising computer executable instructions that, when executed by a processor, cause the processor to control an additive manufacturing apparatus to manufacture the deflection electrode of the first aspect of the present invention. According to a sixth aspect of the present invention, there is provided a method of manufacturing a deflection electrode via additive manufacturing, the method comprising: obtaining an electronic file representing a geometry of a product wherein the product is a deflection electrode according to the first aspect of the present invention; and controlling an additive manufacturing apparatus to manufacture, over one or more additive manufacturing steps, the product according to the geometry specified in the electronic file.

Feature(s) of one aspect or embodiment or example as described and/or shown herein may be provided in conjunction with any other aspects or embodiments or example, or features thereof, as described and/or shown herein, 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 a schematic illustration of a part of a printhead including a prior art deflection electrode indicating a build up of microsatellite deposits; Figure 6 shows a schematic illustration a part of a deflection electrode for a printhead in accordance with an embodiment of the present invention; Figure 7 shows a perspective view of a cross section of part of a printhead as shown in figure 3 having a deflection electrode in accordance with an embodiment of the present invention; Figure 8 shows a perspective view of a cross section of part of a printhead as shown in figure 3 having a deflection electrode in accordance with an embodiment of the present invention; Figure 9 shows a schematic illustration of a part of a printhead including a deflection electrode in accordance with an embodiment of the present invention indicating a build up of microsatellite deposits.

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 Sand 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 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.

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 surface of the deck 17 and deflection of the ink droplets is parallel to the surface of 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 lie parallel to the surface of the deck 17 and deflection of the ink droplets may be perpendicular to the surface of 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 -for example, the high voltage electrode 23A may be held at 2000 volts and the other deflection electrode 23B may be held at ground potential. 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 is illustrated 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 29 is defined in the plane of the page.

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.

Generally, the electrodes 23A, 23B are fixed in place in the printhead 3 by respective mounting plates (although not shown) that at least connect the respective electrode 23A, 23B to the deck 17, or another part of the printhead. Generally, the electrodes 23A, 23B are elongate, and when in place in the printhead 3, have first ends that are generally aligned along the printhead in the upstream/downstream direction closest to the charge electrode 21, and second ends that are also generally aligned along the printhead in the upstream/downstream direction closest to the gutter 25.

In the following description, whilst the deflection electrode according to various embodiments of the present invention is described generally in relation to a high voltage electrode (for a printhead in which the ink drops and therefore microsatellites acquire a negative charge from the charge electrode), it will be appreciated that the following description may also apply equally where the deflection electrode is a ground, zero voltage or negative voltage deflection electrode (for a printhead in which the ink drops and therefore microsatellites acquire a positive charge from the charge electrode).

Focusing on the high voltage electrode 23A, although the following may also be true of the other electrode 233, the high voltage electrode 23A is elongate, and has a first end 104 and a second end 106. When in place in the printhead, the first end 104 generally lies closest to the charge electrode 21, more upstream, and the second end 106 generally lies closest to the gutter 25, more downstream. The length of the high voltage electrode 23A is generally measured from the first end 104, from a first end surface 104A, to the second end 106, to a second end surface 106A, along an electrode axis, or axis, A of the high voltage electrode. In particular, the axis A may be defined through the centre of the high voltage electrode 23A along its length from the first end 104 to the second end 106. The length may not be the longest side of the high voltage electrode 23A.

The high voltage electrode 23A may be substantially straight. In particular, the axis A of the high voltage electrode 23A may be substantially straight, for example as is illustrated in figure 4. In this case, when in place in the printhead 3, the axis A of the high voltage electrode 23A may be angled relative to the ink drop axis 24A, as is also shown in figure 4. In particular, it may be angled away from the ink drop axis 24A and away from the other electrode 23B in the downstream direction to allow for deflection of the ink drops. Alternatively, when in place in the printhead 3, the axis A of the high voltage electrode 23A may be substantially parallel to the ink drop axis 24A along its entire length (although not shown).

Alternatively, the high voltage electrode 23A may be bent. In particular, the axis A of the high voltage electrode 23A may bend at a certain point P, for example at a certain point along the length of the high voltage electrode 23A, for example as is illustrated in figure 3. In this case, when in place in the printhead 3, a first part or portion A1 of the axis A of the high voltage electrode that is nearest the charge electrode 21 may be substantially parallel to the ink drop axis 24A, and a second part or portion Az of the axis of the high voltage electrode that is nearest to the gutter 25 may be angled relative to the ink drop axis 24A. The first portion Ai of the axis A and the second portion A2 of the axis A may join at the bend, for example at the point P, the first portion Ai being more upstream and the second portion A2 being more downstream. In particular, a second part of the high voltage electrode 23A defining the second portion Az of the axis A, may be angled away from the ink drop axis 24A and the other electrode 23B in the downstream direction to allow for deflection of the ink drops whilst keeping the electrodes 23A, 233 generally closer together along their lengths.

In addition, considering the perpendicular orientation of the deflection electrodes 23A, 233 as shown in figure 3, when in place in the printhead 3, the height H of the high voltage electrode 23A is generally in the direction perpendicular to the surface of the deck 17, and perpendicular to the ink drop plane 29. The width W of the high voltage electrode is generally in the direction that is in the ink drop plane 29, but is perpendicular to the ink drop axis 24A. The length L of the high voltage electrode 23A is generally defined by the axis, A. As is illustrated in figure 3, the axis A or length L of the high voltage electrode 23A is generally its longest side and the width W is generally its shortest side.

As has already been mentioned, during printing, some inks generate what are referred to as microsatellites' within the printhead. These microsatellites are very small undesirable ink particles that form as the continuous stream of ink, or jet, emanating from the nozzle or fluid outlet 20 is broken up into drops. By virtue of the imprecise nature in which these microsatellites form, their size varies. However, they have a very low, typically negligible, mass.

As for the ink drops, the microsatellites may acquire charge from the charge electrode 21, for instance a negative charge. In this case, the microsatellites generally attract to the parts or points of the high voltage electrode 23A that are in the ink drop plane 29 and are nearest the charge electrode 21 and leave a deposit. For the lowest mass microsatellites, they attract to the end of the high voltage electrode that is nearest the charge electrode 21. As can be seen in figure 5, these deposits build up over time, and due to their different inertia and charges, the deposits form in a line 107 along the surface 108 of the deflection plate 23A facing the ink drop axis 24A and other electrode 233. With reference to figure 4 for example, for the lower mass microsatellites, they attract to the first part 30 of the high voltage electrode 23A they come across after receiving charge (i.e. the most upstream point, or point on the high voltage electrode closest to the charge electrode 21 and drop generator 19) and leave a deposit. Over time, these deposits accumulate to form a protrusion or column 110 (sometimes referred to as a 'ligament' or 'stalagmite') that forms or extends towards the ground plate 23B, as is illustrated in figure 5.

The protrusion 109 can adversely affect the deflection and path of the ink droplets, which is of course undesirable. In addition, eventually, the field strength may increase locally around the protrusion 110 to a point at which the air breaks down, causing the high voltage plate 23A to track to ground and then trip. This of course causes printer downtime, which is highly undesirable.

Therefore, in accordance with embodiments of the present invention, a deflection electrode 100 has been provided for a printhead 3 that is configured to handle the microsatellites in a more effective manner, and in particular by providing the present deflection electrode 100 with a modified shape. As will become further apparent from the following description, the deflection electrode 100 has been provided with an aperture 102 and at least two opposing collecting surfaces 112A, 1123 which effectively act as a microsatellite catcher, delaying and potentially preventing the microsatellite deposits from building up on the deflection electrode to a level at which some of the described problems may occur.

In particular, referring to figures 6 to 9, in accordance with embodiments of the present invention, there is provided a deflection electrode, in particular a high voltage electrode, or plate, 100 that is part of a pair of deflection electrodes 100, 23B for creating an electrostatic field for deflecting ink drops in a printhead 3. A part of such a high voltage electrode 100 is shown, for example, in isolation in figure 6. The high voltage electrode is largely the same as, and largely operates in the same way as, the high voltage electrode 23A previously described, except that its shape has been modified to include an aperture 102 or slot as described herein and below, which defines at least two opposed collecting surfaces 112A, 112B.

As previously described, the high voltage electrode 100 defines an electrode axis A between its first end 104 and its second end 106 opposite the first end 104. The electrode axis A passes through the centre of the electrode 100. When the high voltage electrode 100 is in place in a printhead 3, the first end 104 is positioned most upstream nearest the charge electrode 21 and the second end 106 is positioned most downstream nearest the gutter 25. As is referred to above, the high voltage electrode 100 defines a first electrode surface 108 extending between the first end 104 and the second end 106 in a direction that is parallel to the electrode axis A. When the high voltage electrode 100 is in place in a printhead 3, the first electrode surface 108 is the surface that faces the ink drops and the other electrode 23B. The high voltage electrode 100 also defines a second electrode surface 110 opposite the first electrode surface 108, and extending between the first end 104 and the second end 106. In the embodiments shown, this second surface 110 extends in a direction that is parallel to the electrode axis A. When the high voltage electrode 100 is in place in a printhead 3, the second electrode surface 110 is the surface that faces away from the ink drops and other electrode 23B. Typically, the second surface 110 may be any suitable shape to aid in mounting the high voltage electrode 100 in the printhead 3.

The aperture 102 is defined in the high voltage electrode 100 at its first end 104. In the embodiments shown, the aperture 102 is defined in the first end surface 104A and is open to the first end 104. This may ensure that the aperture 102 can be arranged to overlap with what would have been the 'nearest' landing point for the lowest mass microsatellites. In the embodiments shown, the aperture 102 also forms a through hole between the first surface 108 and the second surface 110. The aperture 102 extends from the first end 104 of the high voltage electrode 100 along the first surface 108 and the second surface 110 and through the body of the electrode defined therebetween.

The aperture 102 extends along the axis A of the high voltage electrode 100 and therefore along its length L, towards the second end 106. In the embodiments shown, the aperture 102 extends along and/or in line with the axis A, or to at least a first portion Ai of the axis A. In other embodiments, the aperture 102 may extend parallel to the axis A, or to at least a first portion Ai of the axis A, but may be off axis A. As shown in figures 7 to 9, when the high voltage electrode 100 is in place in a printhead 3, the high voltage electrode 100 can be arranged such that at least the first portion Al of the axis A is parallel to the ink drop axis 24A. In addition, the high voltage electrode 100 can be arranged such that the aperture 102 lies within the ink drop plane 29. Arranging the high voltage electrode 100 and aperture 102 in this way removes what would have been the 'nearest' landing points for many of the microsatellites, and removes at least a portion of the high voltage electrode 100 where the above mentioned line of microsatellite deposits may form.

The aperture 102 defines at least two opposed collecting surfaces 112A, 1123 in the high voltage electrode 100 extending along a length of the high voltage electrode 100. Having the surfaces 112A, 112B opposed may allow them to apply equal and oppositely directed forces to the ink drops. In this way, when the deflection electrodes 100, 23B are in place in a printhead 3, the at least two collecting surfaces 112A, 1123 are configured to apply an equal but oppositely directed force to an ink drop travelling in the ink drop plane. This ensures that the ink drops follow their intended trajectory.

Each of the collecting surfaces 112A, 112B are arranged to form an acute angle with the deflection plane, which is a plane defined by the ink drop axis 24A and the electrode axis A. As such, when the high voltage electrode 100 is in place in a printhead 3, the collecting surfaces 112A, 1128 are arranged to form an acute angle with the ink drop plane 29. This allows for a more even spread of the microsatellite deposits along the surfaces.

In the embodiments shown, the opposed collecting surfaces 112A, 112B are substantially planar and extend substantially parallel to the axis A and deflection plane. The opposed surfaces 112A, 112B therefore substantially face one another. When the high voltage electrode 100 is in place in a printhead 3, the aperture 102 can be arranged to overlap with the ink drop plane 29 and therefore the opposed collecting surfaces 112A, 112B can be arranged to avoid the ink drop plane 29. In particular, in the orientations shown for example in figures 7 to 9, the opposed collecting surfaces 112A, 112B are arranged to lie substantially parallel to, but above and below the ink drop plane 29 respectively. In this way, the microsatellites are forced to attract to and deposit on the opposed collecting surfaces 112A, 1128 as they leave the charge electrode 21, but these surfaces 112A, 112B are now arranged outside of the ink drop plane 29, and so are arranged in planes where this build up is less problematic. In addition, the provision of the two opposed surfaces 112A, 112B, as opposed to just one, means that there are now two surfaces over which the microsatellites can spread. This delays the build up of the microsatellite deposits, and delays the deposits building to a level at which problems may occur. These build ups are shown on the two opposed surfaces 112A, 112B in figure 9 for example.

When the high voltage electrode 100 is in place in a printhead 3, the aperture 102 is arranged to be symmetrical about the ink drop plane 29, and such that the collecting surfaces 112A, 112B are symmetrical about the ink drop plane 29. This may ensure that balance is maintained in the electrostatic field in the ink drop plane, ensuring that the force experienced by the ink drops is balanced so that they follow their intended trajectory. In addition, having this symmetrical arrangement may help ensure that for any given microsatellite, there are now two 'nearest' landing points, one on each of the two collecting surfaces 112A, 112B, which causes the microsatellites to generally spread out more evenly, attracting more evenly to each of the two collecting surfaces 112A, 112B. This may further delay the build up of deposits.

As shown in figures 6 to 9, the provision of the aperture 102 may result in the high voltage electrode 100 being forked at its first end 104, with two prongs or forks 114A, 114B, defined on either side of the aperture 102.

The aperture 102 may typically extend along the axis A, or length L, of the high voltage electrode 100 by a distance of between approximately 1mm and 5mm. For example, a depth D of the aperture, perhaps from the first end 104 of the high voltage electrode 100, may be between approximately 1mm and 5mm. The aperture 102 may extend along a shorter distance, or may have a smaller depth D, as for example is highlighted in figure 7, when compared to figure 8 which shows an aperture 102 having a extending along a greater distance, or having a greater depth D. A greater depth may provide a greater surface area over which the various size of microsatellites can spread, which can be beneficial as described below, however, too great a depth may make it more difficult or complex to mount the high voltage electrode 100 in the printhead 3. In addition, the aperture 102 may be narrower about the deflection plane or ink drop plane 29 as shown in figure 8, or wider about the deflection plane or ink drop plane 29 as shown in figure 7.

In the embodiments shown, a cross section of the aperture 102 (for example, when viewed from the perspective of the other deflection electrode 23B) is substantially U-shaped, although it is of course possible that the cross section has other shapes, for example it may be substantially V-shaped.

As mentioned above, the aperture 102 is defined in the high voltage electrode 100 so that when the high voltage electrode 100 is in place in the printhead 3, the aperture 102 overlaps with the ink drop plane 29. This may generally mean that the aperture 102 is defined in the high voltage electrode 100 to overlap with half of the height H of the high voltage electrode 100 and/or the axis A, as in the embodiments shown. However, the aperture 102 could alternatively be defined in the high voltage electrode 100 so that it lies either above or below the axis A. The exact location of the aperture 102 in the high voltage electrode 100 will depend upon where the ink drop plane 29 lies, and so will depend upon the precise arrangement of the deflection electrodes 100, 233 in the printhead 3, relative to the charge electrode 21, the fluid outlet 20, the gutter 25 etc. In some embodiments, although not shown, the aperture 102 may be arranged towards the first end 104 of the high voltage electrode 100, but the high voltage electrode may be closed at its first end 104. For example, the aperture 102 may not be defined in the first end surface 104A. This may mean that the very lowest mass satellites are not captured by the aperture 102 and collecting surfaces 112A, 112B but may still mean that the majority of the microsatellites are captured by the aperture 102 and collecting surfaces 112A, 112B.

In some embodiments, although not shown, the aperture 102 may not form a through hole in a direction that is in, and/or parallel to, the ink drop plane 29. For example, the aperture 102 may only be open to the first electrode surface 108, but may be closed to the second electrode surface 110. As such, the aperture 102 may instead be a blind hole that is arranged to be open to the first electrode surface 108. In this case, depending on the particular shape and dimensions of the blind hole, the microsatellites may still attract to the two opposed collecting surfaces 112A, 1123, as well as in some instances to a base of the blind hole, where the base would be the surface of the blind hole substantially facing the other electrode 23B when the deflection electrodes 100, 233 are in place in a printhead 3. Such an arrangement still allows for a greater spread of the microsatellite deposits, and the increased distance between the other electrode 233 and the blind hole base, rather than the first electrode surface 108, may further delay the build up from reaching a potentially problematic level.

In the embodiments shown, the aperture 102 extends only along a part of the length of the high voltage electrode 100, or along only a part of the axis A. However, in other embodiments, not shown, the aperture 102 can extend to over half way along the length of the high voltage electrode 100 or axis A. In some embodiments, although not shown, the aperture 102 may extend from the first end 104 to the second end 106, for example from the first end surface 104A to the second end surface 106A. This may ensure that all of the microsatellites are captured by the aperture 102 and/or collecting surfaces 112A, 112B. In this case, the high voltage electrode 100 may comprise two deflection electrode elements separated by the aperture 102, and so one of the deflection electrode elements may define one collecting surface and the other deflection electrode element may define the other, opposed collecting surface.

A deflection plane may be defined that comprises both of the ink drop axis 24A and the electrode axis A. In the embodiments shown, the collecting surfaces 112A, 112B are substantially planar. In addition, the collecting surfaces 112A, 112B lie substantially parallel to the deflection plane and/or to the ink drop plane 29. In alternative embodiments, the collecting surfaces 112A, 112B may be angled relative to the deflection plane and/or the ink drop plane 29. The collecting surfaces 112A, 112B may form respective angles relative to the deflection plane and/or the ink drop plane 29. The respective angles may be opposite and equal to provide balance to the electrostatic field generated. For example, the collecting surfaces 112A, 112B may taper inwards, for example towards the deflection plane or ink drop plane 29, from the first end 104 towards the second end 106, or the collecting surfaces 112A, 112B may taper outwards from the first end to the second end 106. Alternatively, the collecting surfaces may alternate between tapering inwards and outwards between the first end 104 and the second end 106.

In the embodiments shown, the collecting surfaces 112A, 112B lie substantially perpendicular to the first and second surfaces 108, 110. However, in alternative embodiments, the collecting surfaces 112A, 112B may be angled relative to the first and/or second surfaces 108, 110. The first and second surfaces 108, 110 may or may not be substantially parallel to one another.

In the embodiments shown, the collecting surfaces 112A, 112B and other surfaces defined by the aperture 102 are generally substantially planar. These surfaces may in some instances join through a curved region 116 as shown for example in figure 6, or there may be a more defined joint 118 as shown for example in figure 9.

In some embodiments, the collecting surfaces 112A, 112B may be substantially curved. The collecting surfaces 112A, 1128 may have the same radius or radii of curvature such that they provide the ink drops with an equal and opposite deflection force from above and below the ink drop plane 29. For example, the collecting surfaces 112A, 112B may be farthest apart at the first end 104 and/or at the most upstream end of the aperture 102, and/or may be closest together at the most downstream end of the aperture 102, curving gradually therebetween. The collecting surfaces 112A, 112B could instead be farthest apart at any other point. For example, following the contours of the collecting surfaces 112A, 112B as they extend downstream, they could curve apart and then back towards each other at the most downstream end of the aperture 102. Any other suitable arrangement is envisaged.

Where the aperture 102 is a blind hole open to the first electrode surface 108 rather than a through hole between the first and second electrode surfaces 108, 110 as discussed above, the base of the blind hole may be substantially curved. As mentioned above, the base may be the face of the blind hole that substantially faces the corresponding deflection electrode 23B and therefore the ink drops when in place in the printhead 3. The base may be curved such that its radius of curvature is symmetrical about the ink drop plane 29. This may provide the ink drops with an equal and opposite deflection force from above and below the ink drop plane 29 to ensure that the electrostatic field generated still causes the ink drops to follow their intended trajectory. Alternatively, the base may be substantially planar and may be substantially parallel to the first electrode surface 108.

The high voltage electrode 100 may define a central plane that contains the axis A, and also lies parallel to the ink drop plane 29 when the high voltage electrode 100 is in place in a printhead 3. In the embodiments shown, the aperture 102 lies in and is symmetrical about this central plane. However, in some embodiments, the aperture 102 may not lie within the central plane and/or may not be symmetrical about the central plane. When in place in a printhead 3, the high voltage electrode 100 and aperture 102 can still be arranged to overlap with the ink drop plane 29, and so that the aperture 102 is symmetrical about the ink drop plane 29, even if the aperture 102 extends above and below the central plane by different amounts, or is only defined in the electrode 100 to be either above or below the central plane.

The high voltage electrode 100 can be manufactured using any suitable manufacturing process. For example, the high voltage electrode 100 may be formed via casting, machining, molding and/or any other suitable manufacturing process. In some embodiments, the high voltage electrode 100 may be formed using an additive manufacturing process, as is discussed in more detail below.

Manufacturing the high voltage electrode 100 may comprise providing a body of conducting material with an aperture 102 at its first end 104 and providing the body with at least two opposed collecting surfaces 112A, 112B defined by the aperture. The aperture 102 and/or the collecting surfaces 112A, 112B may be formed in one or more molding and/or shaping steps. The method involves forming the aperture 102 so that it overlaps with the deflection plane and/or the ink drop plane 29. The method may include forming the aperture 102 so that it is centred on and/or is symmetric about the deflection plane, and/or the ink drop plane 29. The method may also include forming the at least two opposed collecting surfaces 112A, 112B so that they are symmetric about the about the deflection plane, and/or the ink drop plane 29. The method may include any step that involves providing the body with any feature described above in relation to the high voltage electrode 100.

A related method includes arranging the high voltage electrode 100 within a printhead 3. This may include arranging the high voltage electrode 100 so that its first end 104 is the most upstream, for example closest to the charge electrode 21, and its second end is the most downstream, for example closest to the gutter 25. This method may further include arranging the high voltage electrode 100 so that its first electrode surface 108 faces the other deflection electrode 23B. This method may further include arranging the high voltage electrode 100 so that its aperture 102 is arranged to overlap with and be symmetrical about the ink drop plane 29, and so that its at least two opposed collecting surfaces 112A, 112B are also symmetric about the ink drop plane 29. Examples and embodiments according to the disclosure may be formed using an additive manufacturing process. The deflection electrode described herein may be formed using additive manufacturing processes. In addition, any other part of the printhead or continuous inkjet printer described herein may be formed using additive manufacturing processes.

A common example of additive manufacturing is 3D printing; however, other methods of additive manufacturing are available. Rapid prototyping or rapid manufacturing are also terms which may be used to describe additive manufacturing processes.

As used herein, "additive manufacturing" refers generally to manufacturing processes wherein successive layers of material(s) are provided on each other to "buildup" layer-by-layer or "additively fabricate", a three-dimensional component. This is compared to some subtractive manufacturing methods (such as milling or drilling), wherein material is successively removed to fabricate the part. The successive layers generally fuse together to form a monolithic component which may have a variety of integral sub-components. In particular, the manufacturing process may allow an example of the disclosure to be integrally formed and include a variety of features not possible when using prior manufacturing methods.

Additive manufacturing methods described herein enable manufacture to any suitable size and shape with various features which may not have been possible using prior manufacturing methods. Additive manufacturing can create complex geometries without the use of any sort of tools, molds or fixtures, and with little or no waste material. Instead of machining components from solid billets of plastic or metal, much of which is cut away and discarded, the only material used in additive manufacturing is what is required to shape the part.

Suitable additive manufacturing techniques in accordance with the present disclosure may include, for example, Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjets and laserjets, Sterolithography (SLA), Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), Electron Beam Additive Manufacturing (EBAM), Laser Net Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), Digital Light Processing (DLP), Continuous Digital Light Processing (CDLP), Direct Selective Laser Melting (DSLM), Selective Laser Melting (SLM), Direct Metal Laser Melting (DMLM), Direct Metal Laser Sintering (DMLS), Material Jetting (MJ), NanoParticle Jetting (NPJ), Drop On Demand (DOD), Binder Jetting (BJ), Multi Jet Fusion (MJF), Laminated Object Manufacturing (LOM) and other known processes. The additive manufacturing processes described herein may be used for forming the deflection electrode, and/or any other components of the printhead and/or continuous inkjet printer using any suitable material(s). For example, the additive manufacturing processes described herein may be used for forming the deflection electrode using any suitable conductive material(s). For example, for forming the deflection electrode, the material may be metal, or a conductive composite, ceramic, polymer, resin, or any other suitable conductive material that may be in solid, liquid, powder, sheet material, wire, or any other suitable form or combinations thereof. The additively manufactured component may be formed in part, in whole, or in some combination of materials including but not limited to pure metals, copper, copper alloys, zinc, zinc alloys, nickel, titanium, titanium alloys, magnesium, magnesium alloys, aluminum, aluminum alloys, iron, iron alloys and steel. For example, for forming other parts of the printhead and/or continuous inkjet printer, the material may comprise any of the above, and/or may further include, for example any suitable plastic or polymer. These materials are examples of materials suitable for use in additive manufacturing processes, some or all of which may be suitable for the fabrication of examples described herein.

As noted above, the additive manufacturing process disclosed herein allows a single component to be formed from multiple materials. Thus, the examples described herein may be formed from any suitable mixtures of the above materials and/or any other materials described herein. For example, a component may include multiple layers, segments, or parts that are formed using different materials, processes, and/or on different additive manufacturing machines. In this manner, components may be constructed which have different materials and material properties for meeting the demands of any particular application. In addition, although the components described herein are constructed entirely by additive manufacturing processes, it should be appreciated that in alternate embodiments, all or a portion of these components may be formed via casting, machining, and/or any other suitable manufacturing process. Indeed, any suitable combination of materials and manufacturing methods may be used to form the various components and the deflection electrode described herein.

Additive manufacturing processes typically fabricate components based on three-dimensional (3D) information, for example a three-dimensional computer model (or design file), of the component. Accordingly, examples described herein not only include products or components as described herein, but also methods of manufacturing such products or components via additive manufacturing and computer software, firmware or hardware for controlling the manufacture of such products via additive manufacturing. The structure of one or more parts of the product may be represented digitally in the form of a design file. A design file, or computer aided design (CAD) file, is a configuration file that encodes one or more of the surface or volumetric configuration of the shape of the product. That is, a design file represents the geometrical arrangement or shape of the product.

Design files can take any now known or later developed file format. For example, design files may be in the Stereolithography or "Standard Tessellation Language" (.stl) format which was created for stereolithography CAD programs of 3D Systems, or the Additive Manufacturing File (.amf) format, which is an American Society of Mechanical Engineers (ASME) standard that is an extensible markup-language (XML) based format designed to allow any CAD software to describe the shape and composition of any three-dimensional object to be fabricated on any additive manufacturing printer. Further examples of design file formats include AutoCAD (.dwg) files, Blender (.blend) files, Parasolid (.x_t) files, 3D Manufacturing Format (.3m0 files, Autodesk (3ds) files, Collada (.dae) files and Wavefront (.obj) files, although many other file formats exist.

Design files can be produced using modelling (e.g. CAD modelling) software and/or through scanning the surface of a product to measure the surface configuration of the product.

Once obtained, a design file may be converted into a set of computer executable instructions that, once executed by a processer, cause the processor to control an additive manufacturing apparatus to produce a product according to the geometrical arrangement specified in the design file. The conversion may convert the design file into slices or layers that are to be formed sequentially by the additive manufacturing apparatus. The instructions (otherwise known as geometric code or "G-code") may be calibrated to the specific additive manufacturing apparatus and may specify the precise location and amount of material that is to be formed at each stage in the manufacturing process. As discussed above, the formation may be through deposition, through sintering, or through any other form of additive manufacturing method.

The code or instructions may be translated between different formats, converted into a set of data signals and transmitted, received as a set of data signals and converted to code, stored, etc., as necessary. The instructions may be an input to the additive manufacturing system and may come from a part designer, an intellectual property (IP) provider, a design company, the operator or owner of the additive manufacturing system, or from other sources. An additive manufacturing system may execute the instructions to fabricate the product using any of the technologies or methods disclosed herein. Design files or computer executable instructions may be stored in a (transitory or non-transitory) computer readable storage medium (e.g., memory, storage system, etc.) storing code, or computer readable instructions, representative of the product to be produced. As noted, the code or computer readable instructions defining the product that can be used to physically generate the object, upon execution of the code or instructions by an additive manufacturing system. For example, the instructions may include a precisely defined 3D model of the product and can be generated from any of a large variety of well-known computer aided design (CAD) software systems such as AutoCADO, TurboCADO, DesignCAD 3D Max, etc. Alternatively, a model or prototype of the component may be scanned to determine the three-dimensional information of the component.

Accordingly, by controlling an additive manufacturing apparatus according to the computer executable instructions, the additive manufacturing apparatus can be instructed to print out one or more parts of the product. These can be printed either in assembled or unassembled form. For instance, different sections of the product may be printed separately (as a kit of unassembled parts) and then subsequently assembled. Alternatively, the different parts may be printed in assembled form.

In light of the above, embodiments include methods of manufacture via additive manufacturing. This includes the steps of obtaining a design file representing the product and instructing an additive manufacturing apparatus to manufacture the product in assembled or unassembled form according to the design file. The additive manufacturing apparatus may include a processor that is configured to automatically convert the design file into computer executable instructions for controlling the manufacture of the product. In these embodiments, the design file itself can automatically cause the production of the product once input into the additive manufacturing device. Accordingly, in this embodiment, the design file itself may be considered computer executable instructions that cause the additive manufacturing apparatus to manufacture the product. Alternatively, the design file may be converted into instructions by an external computing system, with the resulting computer executable instructions being provided to the additive manufacturing device.

Given the above, the design and manufacture of implementations of the subject matter and the operations described in this specification can be realized using digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. For instance, hardware may include processors, microprocessors, electronic circuitry, electronic components, integrated circuits, etc. Implementations of the subject matter described in this specification can be realized using one or more computer programs, i.e., one or more modules of computer program instructions, encoded on computer storage medium for execution by, or to control the operation of, data processing apparatus. Alternatively or in addition, the program instructions can be encoded on an artificially generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. A computer storage medium can be, or be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

Although additive manufacturing technology is described herein as enabling fabrication of complex objects by building objects point-by-point, layer-by-layer, typically in a vertical direction, other methods of fabrication are possible and within the scope of the present subject matter. For example, although the discussion herein refers to the addition of material to form successive layers, one skilled in the art will appreciate that the methods and structures disclosed herein may be practiced with any additive manufacturing technique or other manufacturing technology.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

33 Claims 1. A deflection electrode for a printhead for a continuous inkjet printer, the deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing, wherein the deflection electrode defines an electrode axis between its first end and its second end opposite the first end, and a first electrode surface extending in a direction that is parallel to the electrode axis, and wherein the deflection electrode comprises: an aperture at its first end in at least the first electrode surface, the aperture extending along the first electrode surface in a direction that is parallel to at least a part of the electrode axis; and at least two opposed collecting surfaces defined by the aperture, the at least two collecting surfaces extending along a length of the deflection electrode. 15 2. The deflection electrode as claimed in claim 1, wherein the aperture defines an opening in the first end of the deflection electrode.3. The deflection electrode as claimed in claim 1 or 2, wherein the undeflected ink drops define an ink drop axis, and a deflection plane is defined that comprises both of the ink drop axis and the electrode axis, and wherein the aperture is defined in the deflection electrode to overlap with the deflection plane.4. The deflection electrode as claimed in claim 3, wherein the aperture is symmetrical about the deflection plane.5. The deflection electrode as claimed in claim 3 or 4, wherein the collecting surfaces extend in a direction that is parallel to the deflection plane.6. The deflection electrode as claimed in any preceding claim, wherein the deflection electrode comprises a second electrode surface that is opposite the first electrode surface, and wherein the aperture is open to the first electrode surface and the second electrode surface.7. The deflection electrode as claimed in any preceding claim, wherein the aperture extends from the first end, along a length of the deflection electrode, along only a part of the distance defined by the electrode axis, and wherein the collecting surfaces extend along a length of the deflection electrode by the same distance.8. The deflection electrode as claimed in claim 7, wherein the distance is approximately 1-5mm.9. The deflection electrode as claimed in claim 6, wherein the aperture extends from the first end, along a length of the deflection electrode defined by the electrode axis, to the second end, and wherein the collecting surfaces extend along a length of the deflection electrode by the same distance, such that the deflection electrode defines two deflection electrode elements on opposite sides of the aperture.10. A printhead for a continuous inkjet printer, comprising: a deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing; wherein the deflection electrode defines an electrode axis between its first end and its second end opposite the first end, and a first electrode surface extending in a direction that is parallel to the electrode axis, and wherein the deflection electrode comprises: an aperture at its first end in at least the first electrode surface, the aperture extending along the first electrode surface in a direction that is parallel to at least a part of the electrode axis; and at least two opposed collecting surfaces defined by the aperture, the at least two collecting surfaces extending along a length of the deflection electrode.11. The printhead as claimed in claim 10, wherein, during printing, the ink drops move in a downstream direction towards a substrate for printing, and wherein the first end of the deflection electrode is the most upstream end of the deflection electrode.12. The printhead as claimed in claim 10 or 11, wherein, during printing, the undeflected ink drops define an ink drop axis, and wherein at least a part of the first electrode surface at the first end extends in a direction that is parallel to the ink drop axis.13. The printhead as claimed in any of claims 10 to 12, wherein, during printing, the undeflected ink drops define an ink drop axis, and wherein the aperture extends along at least a part of the first electrode surface in a direction that is parallel to the ink drop axis.14. The printhead as claimed in any of claims 11 to 13, wherein the printhead further comprises any one or more of: an ink gun comprising a nozzle for ejecting an ink jet; a charge electrode for trapping electric charges on ink drops of an ink jet; a second deflection electrode for forming a pair of deflection electrodes with the deflection electrode, the pair of deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing; and a gutter having an ink receiving orifice for receiving parts of the ink jet which are not used for printing.15. A continuous inkjet printer, comprising: an ink supply system operable to supply ink to a printhead; and a printhead operable to receive ink from the ink supply system for printing, wherein the printhead comprises: a deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing; wherein the deflection electrode defines an electrode axis between its first end and its second end opposite the first end, and a first electrode surface extending in a direction that is parallel to the electrode axis, and wherein the deflection electrode comprises: an aperture at its first end in at least the first electrode surface, the aperture extending along the first electrode surface in a direction that is parallel to at least a part of the electrode axis; and at least two opposed collecting surfaces defined by the aperture, the at least two collecting surfaces extending along a length of the deflection electrode.16. The continuous inkjet printer of claim 15, wherein, during printing, the ink drops move in a downstream direction towards a substrate for printing, and wherein the first end of the deflection electrode is the most upstream end of the deflection electrode.17. The continuous inkjet printer of claim 15 or 16, wherein, during printing, the undeflected ink drops define an ink drop axis, and wherein at least a part of the first electrode surface at the first end extends in a direction that is parallel to the ink drop axis.18. The continuous inkjet printer of any of claims 15 to 17, wherein, during printing, the undeflected ink drops define an ink drop axis, and wherein the aperture extends along at least a part of the first electrode surface in a direction that is parallel to the ink drop axis.19. The continuous inkjet printer of any of claims 15 to 18, wherein the printhead further comprises any one or more of: an ink gun comprising a nozzle for ejecting an ink jet; a charge electrode for trapping electric charges on ink drops of an ink jet; a second deflection electrode for forming a pair of deflection electrodes with the deflection electrode, the pair of deflection electrodes for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing; and a gutter having an ink receiving orifice for receiving parts of the ink jet which are not used for printing.20. A method of manufacturing a deflection electrode for a printhead for a continuous inkjet printer, the deflection electrode for creating an electrostatic field for deflecting ink drops carrying trapped electric charges for printing, the method comprising: providing a body of conducting material with an aperture at its first end and at least two opposing collecting surfaces defined by the aperture; wherein the body defines an axis between its first end and its second end opposite the first end, and a first surface extending in a direction that is parallel to the axis, and wherein the aperture extends along the first surface in a direction that is parallel to at least a part of the axis, and the at least two collecting surfaces extend along a length of the body.21. A computer program comprising computer executable instructions that, when executed by a processor, cause the processor to control an additive manufacturing apparatus to manufacture the deflection electrode of any of claims 1 to 9.22. A method of manufacturing a deflection electrode via additive manufacturing, the method comprising: obtaining an electronic file representing a geometry of a product wherein the product is a deflection electrode according to any of claims 1 to 9; and controlling an additive manufacturing apparatus to manufacture, over one or more additive manufacturing steps, the product according to the geometry specified in the electronic file.