WO2000068016A1

WO2000068016A1 - Cleaning and maintenance of an ink jet printhead

Info

Publication number: WO2000068016A1
Application number: PCT/GB2000/001737
Authority: WO
Inventors: Jindrich Vosahlo; Richard William Eve
Original assignee: Cambridge Consultants Limited
Priority date: 1999-05-05
Filing date: 2000-05-05
Publication date: 2000-11-16
Also published as: GB0102489D0; GB2354485B; GB9910314D0; GB2354485A

Abstract

A method of cleaning an ink jet printhead (1) having a nozzle plate comprises the steps of emitting ink (2) from the nozzles onto the nozzle plate and wiping the ink from the nozzle plate. By emitting ink onto the nozzle plate before wiping the risk of scratching the nozzle plate can be reduced. The emitting of the ink can also effect priming of the nozzles. In preferred embodiments, the nozzle plate is wiped using an absorbent substrate (3) which can help to remove any dirt and residue.

Description

CLEANING AND MAINTENANCE OF AN INK JET PRINTHEAD

The present invention relates to the cleaning and maintenance of printheads. Preferred embodiments of the invention relate to an automatic cleaning method for a drop on demand ink jet printhead.

A known technique for cleaning drop on demand ink jet printheads is to wipe the face of the nozzle plate with a soft blade to remove debris and excess ink. This can easily scratch the nozzle face as debris is pushed across it. Any damage to the exit area of a nozzle causes errors in the jet angle or may cause build up of a pool of ink preventing droplet ejection. This wiping technique does not re-prime nozzles that have become de-primed.

Hewlett-Packard and Epson desktop printers use such soft wiper blades in automatic printhead cleaning systems.

Another known technique for cleaning drop on demand ink jet printheads is to wipe and/or blot the nozzle plate manually with an absorbent material. This can scratch the nozzle plate if the nozzle plate is dry, and successful cleaning depends on the skill of the operator. Such absorbent wipes are used manually for cleaning the printheads of Trident printers.

An object of the present invention is to provide a method of cleaning an ink jet printhead which does not suffer from one or more of the disadvantages of prior art methods.

It is a further object of preferred embodiments the present invention to provide an automatic method of cleaning an ink jet printhead which removes dirt and residue from the printhead upon cleaning.

According to the invention there is provided a method of cleaning an ink jet printhead having a nozzle plate through which the nozzles exit the printhead, the method comprising the steps of: a) emitting ink from the nozzles onto the nozzle plate; and b) wiping the ink from the nozzle plate.

By emitting ink onto the nozzle plate before the wiping step, the nozzle plate is wetted before cleaning, thus reducing the risk of scratches and damage to the nozzles and/or nozzle plate. Furthermore, the emission of ink from the nozzles acts to re- prime any de-prime nozzles.

Preferably the emitting step and the wiping step are carried out in the predetermined timed sequence. Thus the wiping step can be carried out before the emitted ink dries, and preferably the cleaning method is automated.

In a preferred embodiment of the invention, the step of emitting ink from the nozzles comprises temporarily increasing the pressure of the ink from its normal operating pressure. Preferably the wiping step is carried out once the pressure of the ink has returned to its normal operating pressure. As the ink returns to its normal pressure, some of the ink emitted onto the nozzle plate will normally be drawn back into the nozzles, thus less ink will be wiped from the nozzle plate, reducing wastage of ink.

Preferably the wiping step is substantially simultaneous with the returning of the pressure of the ink to its normal operating pressure. This improves the efficiency of the cleaning and reduces the risk that the ink on the nozzle plate starts to dry before the wiping step is carried out.

Where the printhead includes a row of nozzles, the wiping may be effected in a direction substantially parallel to the row of nozzles, or maybe in another direction, for example substantially perpendicular to the row of nozzles.

Preferably an absorbent substrate is used to wipe the ink from the nozzle plate. The use of an absorbent substrate improves the cleaning of the inks from the nozzle plate as well as encouraging drawing debris from the nozzles by capillary action.

Preferably the absorbent substrate comprises a strip of absorbent material, the method including the step of advancing the strip after the wiping step to provide fresh absorbent substrate for the next wiping step. Thus a clean region of absorbent substrate can be used, either every wiping step or after several wiping steps.

In a preferred embodiment, the absorbent substrate is stored on a storage reel, and the method includes a step of advancing the reel after the wiping. The advancing of the absorbent substrate may occur after every wiping step, or periodically after several wiping steps.

After use, the absorbent substrate may be disposed of or, preferably it is cleaned for reuse. Preferably, after the wiping step, a partial vacuum is applied to the absorbent substrate to clean the substrate. Preferably, the method includes a step of reusing the cleaned substrate.

A further aspect of the invention provides a method of cleaning the nozzles of a printhead, the method comprising the steps of: a) wetting the nozzles of the printhead; and b) wiping the wetted region of the printhead.

Thus the invention is not restricted for use where the printhead includes a nozzle plate but may be used for cleaning other types of nozzle arrangements. Furthermore, the wetting of the nozzles might be carried out using a material other than the ink in the printhead. For example, a liquid material may be sprayed onto the nozzle before the wiping step.

In a preferred embodiment, the present invention provides an automatic cleaning and maintenance method for cleaning and maintaining an ink jet printhead comprising the following steps:

- an ink pressure application step consisting of applying pressure to the ink to cause ink to flow through a set of printhead nozzles and onto a face of a nozzle plate through which the printhead nozzles exit the printhead;

an ink pressure restoration step consisting of restoring the pressure of the ink to its normal operating pressure in order to allow excess ink to be drawn back in to the printhead; and

an absorbent material application step consisting of applying an absorbent material to the ink on the nozzle plate in order to draw out fresh ink and remove dirt and residues from the printhead nozzles;

wherein the ink pressure restoration step and the absorbent material application step are synchronised so as to occur in a predetermined timed sequence.

Examples described below aim to overcome the problems of prior art cleaning methods mentioned above by synchronising an ink pressure purge with the application of an absorbent material. The ink pressure purge ensures the surface of the nozzle plate is wet, reducing the risk of damage to the nozzle plate face. The absorbent material draws ink out of the nozzles by capillary action thus removing dirt and residue.

A further advantage of examples of the system is that most waste ink is retained by the absorbent material, which can easily be disposed of.

The invention also provides an apparatus for cleaning an ink jet printhead by a method as described above.

According to the invention, there is also provided apparatus for cleaning an ink jet printhead having a nozzle plate through which the nozzles exit, the apparatus comprising: a) means for emitting ink from the nozzles onto the nozzle plate; and b) a wiper arranged for wiping the nozzle plate.

Preferably the means for emitting ink includes means for temporarily increasing the pressure of the ink from its normal operating pressure.

Preferably the wiper includes an absorbent substrate. The apparatus may further comprise a reel for the wiper, the reel being adapted to advance the wiper to provide fresh absorbent substrate.

Preferably the apparatus further includes means for applying a partial vacuum to the absorbent substrate to clean the substrate.

According to the invention there is also provided apparatus for cleaning an ink jet printhead, the apparatus comprising: an ink chamber for supplying ink to the printhead at an operating pressure; an absorbent material mounted for wiping residue from the printhead; a control device programmed to control the relative movement of the printhead and absorbent material; and wherein the control device is programmed to apply pressure to the ink chamber to temporarily supply ink to the printhead at a pressure above the operating pressure.

Preferably the control device is programmed to carry out the application of pressure of the ink and the relative movement of the printhead and the absorbent material in a predetermined timed sequence. The control device may comprise a suitably programmed processor.

The invention also provides a printer including apparatus as described above and a printer adapted to carry out a method described above.

The invention also provides a computer program and a computer program product for carrying out any of the methods described herein, and a computer readable medium having stored thereon a program for carrying out any of the methods described herein.

The invention also provides a method substantially as described herein with reference to the accompanying drawings, and apparatus substantially as described herein with reference to and as illustrated in the accompanying drawings.

Apparatus features may be applied to the method features and vice versa. Features of one aspect of the invention may be applied to features of another aspect of the invention. Further aspects, advantages and objectives of the invention will become apparent from a consideration of the drawings and the ensuing description.

Embodiments of the invention will now be described by way of example, having reference to the drawings, of which:

Figure 1 : Schematic side view and end view of a printhead before a cleaning operation;

Figure 2: Schematic side view and end view of a printhead during an ink pressure purge;

Figure 3 : Schematic side view and end view of a printhead after an ink pressure purge;

Figure 4: Schematic side view and end view of a printhead during a wipe with an absorbent material;

Figure 5: Schematic side view and end view of a printhead after a cleaning operation.

The example described below aims to remove ink residue and dirt from the nozzle face and re -prime any de-primed channels, leaving the ink meniscus in good condition for printing. Pressure is applied to an ink chamber for a short period so that ink flows from the nozzles to wet the face of a nozzle plate, this also re-primes some of the de-primed nozzles. When the pressure is returned to the normal operating value, excess ink flows back into the nozzles, leaving some ink on the nozzle plate face. An absorbent material is then put in contact with the nozzle plate face, and wiped along or across to remove the ink, dirt and residue leaving the nozzle plate face clean. The absorbent material also draws fresh ink through the nozzles by capillary action ('wicking'), so that the nozzles are left with fresh ink, and a well-formed meniscus. This re -primes any remaining deprimed nozzles. The sequence is fully automated and hence repeatable. Figures 1 to 5 show the sequence of the cleaning/maintenance operation. Figure 1 shows two orthogonal views of a printhead (1) before a cleaning operation starts. Figure 2 shows the printhead (1) during an ink pressure purge, where ink has flowed from the nozzles over the nozzle face to form a bead (2). An absorbent material (3) is shown below the nozzle plate. Figure 3 shows the printhead after the pressure purge, where the excess bead (2) has been sucked back into the nozzles, and the absorbent material (3) starts to move towards the nozzle plate face. Figure 4 shows the absorbent material (3) half way through a wiping operation, the bead (2) has been removed from the left side. Figure 5 shows the printhead at the end of the operation, the bead has been removed and the absorbent material has started to move away from the nozzle plate face.

The operation has been described for the case where the printhead is stationary and the absorbent material moves. The same operation can be carried out by moving the printhead only, or both printhead and absorbent material, it is the relative movement between the two that is significant.

The operation has been described for the case where the absorbent material is wiped along the line of the nozzles. The operation can also be performed with the absorbent material being wiped across the line of the nozzles.

The absorbent material (3) may comprise a pad of absorbent material. The pad may be held on a formation which may be stationary (in which case the wiping is effected by movement of the printhead), or may be movable. In the example described above, and shown in the figures, the absorbent material (3) is movable both towards and away from the printhead (1) as well as along the face of the nozzle plate. It will be seen that, where a single pad is used for the wiping, the pad will become dirty with use as ink and debris is transferred from the printhead (1) to the absorbent material (3). In one option, the absorbent material (3) is periodically replaced. In another example, the absorbent material comprises a strip of material which is arranged on a reel, the reel being advanced periodically to reveal fresh absorbent material. The reel may be advanced with every cleaning operation or after several cleaning operations. The reel arrangement maybe a reel to reel arrangement.

The absorbent material may be disposed of once it has been used, or it can be cleaned and reused. For example, a partial vacuum may be used to remove the ink and debris from the used absorbent material, but other methods could be used, for example washing with solvents.

The timing of the emission of the ink onto the nozzle plate and the movement of the absorbent material are all carried out by a suitably programmed control device. This control device also controls the advancement of the reel of absorbent material, where used.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Claims

Claims:

1. A method of cleaning an ink jet printhead having a nozzle plate through which the nozzles exit the printhead, the method comprising the steps of:

a) emitting ink from the nozzles onto the nozzle plate; and b) wiping the ink from the nozzle plate.

2. A method according to claim 1 wherein the emitting step and the wiping step are carried out in a predetermined timed sequence.

3. A method according to claim 1 or claim 2, wherein the cleaning method is automated.

4. A method according to any one of the preceding claims wherein the step of emitting ink from the nozzles comprises temporarily increasing the pressure of the ink from its normal operating pressure.

5. A method according to claim 4 wherein the wiping step is carried out once the pressure of the ink has returned to its normal operating pressure.

6. A method according to claim 4 or claim 5 wherein the wiping step is substantially simultaneous with the returning of the pressure of the ink to its normal operating pressure.

7. A method according to any one of the preceding claims wherein the printhead includes a row of nozzles and the wiping is effected in a direction substantially parallel to the row of nozzles.

8. A method according to any one of the preceding claims wherein an absorbent substrate is used to wipe the ink from the nozzle plate.

9. A method according to claim 8, wherein the absorbent substrate comprises a strip of absorbent material, the method including the step of advancing the strip after the wiping step to provide fresh absorbent substrate for the next wiping step.

10. A method according to claim 8 or claim 9, wherein the absorbent substrate is stored on a storage reel, and the method includes the step of advancing the reel after the wiping step.

11. A method according to any one of claims 8 to 10, wherein after the wiping step, a partial vacuum is applied to the absorbent substrate to clean the substrate.

12. A method according to claim 11 including the step of reusing the cleaned substrate.

13. A method of cleaning the nozzles of a printhead, the method comprising the steps of: a) wetting the nozzles of the printhead; and b) wiping the wetted region of the printhead.

14. An automatic cleaning and maintenance method for cleaning and maintaining an ink jet printhead comprising the following steps:

an ink pressure application step consisting of applying pressure to the ink to cause ink to flow through a set of printhead nozzles and onto a face of a nozzle plate through which the printhead nozzles exit the printhead;

15. An automatic cleaning and maintenance method according to claim 14 in which the absorbent material is stored on a storage reel and the storage reel is advanced automatically for each cleaning operation to provide fresh absorbent material.

16. An automatic cleaning and maintenance method according to any of the preceding claims in which the absorbent material is wiped substantially parallel to the line of the printhead nozzles.

17. An automatic cleaning and maintenance method according to either of claims 14 or 15 in which the absorbent material is wiped substantially perpendicularly to the line of the printhead nozzles.

18. An automatic cleaning and maintenance method according to any of claims

14 to 17, wherein the ink pressure restoration step and the absorbent material application step are synchronised so as to be substantially simultaneous.

19. An automatic cleaning and maintenance method according to any of claims 14 to 18 in which after use, the absorbent material is cleaned by applying a partial vacuum.

20. An automatic cleaning and maintenance method according to claim 19 in which, after cleaning of the absorbent material, the absorbent material is reused.

21. Apparatus for cleaning an ink jet printhead by a method according to any one of claims 1 to 20.

22. Apparatus for cleaning an ink jet printhead having a nozzle plate through which the nozzles exit, the apparatus comprising:

a) means for emitting ink from the nozzles onto the nozzle plate; and b) a wiper arranged for wiping the nozzle plate.

23. Apparatus according to claim 21 or claim 22, wherein the means for emitting ink includes means for temporarily increasing the pressure of the ink from its normal operating pressure.

24. Apparatus according to any one of claims 21 to 23, wherein the wiper includes an absorbent substrate.

25. Apparatus according to claim 24, further comprising a reel for the wiper, the reel being adapted to advance the wiper to provide fresh absorbent substrate.

26. Apparatus according to claim 24 or claim 25, including means for applying a partial vacuum to the absorbent substrate to clean the substrate.

27. Apparatus for cleaning an ink jet printhead, the apparatus comprising:

an ink chamber for supplying ink to the printhead at an operating pressure; an absorbent material mounted for wiping residue from the printhead; a control device programmed to control the relative movement of the printhead and absorbent material;

and wherein the control device is programmed to apply pressure to the ink chamber to temporarily supply ink to the printhead at a pressure above the operating pressure.

28. Apparatus according to claim 27, wherein the control device is programmed to carry out the application of pressure of the ink and the relative movement of the printhead and the absorbent material in a predetermined timed sequence.

29. A printer including apparams according to any one of claims 21 to 28.

30. A printer adapted to carry out a method according to any one of claims 1 to 20.