WO2000068017A1

WO2000068017A1 - Pressure regulation system for ink jet printer

Info

Publication number: WO2000068017A1
Application number: PCT/GB2000/001717
Authority: WO
Inventors: Richard William Eve; William James Scott; Ben Arlett
Original assignee: Cambridge Consultants Limited
Priority date: 1999-05-05
Filing date: 2000-05-05
Publication date: 2000-11-16
Also published as: GB9910312D0

Abstract

A pressure regulation system for an ink jet printer comprises an ink pressure sensing means (2) for sensing the pressure of ink at or close to a plurality of nozzles on a printhead (4) of the ink jet printer and producing electrical signal representative of the sensed pressure. The system further comprises an electromechanical ink supply regulating means (5) for regulating the flow of ink, control logic for controlling the electromechanical ink supply regulating means (5) based on the electrical signal from the ink pressure sensing means (2), and ink transfer means (3) for transferring ink from an exit of the electromechanical ink supply regulating means (5) to the plurality of nozzles. At least part of the ink transfer means (3) is such that the volume of that part varies with the pressure of its contents.

Description

PRESSURE REGULATION SYSTEM FOR INK JET PRINTER

The present invention relates to a regulation system for an ink jet printer. Examples of the present invention relate to an ink pressure regulator for regulating the pressure of ink supplied to an ink jet printhead. Preferred embodiments of the invention relate to a sealed ink pressure regulator for use with a drop on demand ink jet printer using a bulk ink supply.

One known technique for regulating the pressure of ink fed to an ink jet printhead is to control the pressure in an ink reservoir which is placed close to or integrated into the printhead. However, this technique is unsuitable for applications with high ink usage and/or long autonomy requirements, where the ink reservoir needs to be large and it is impractical to mount the reservoir in close proximity to a printhead.

For systems which use ink reservoirs which are mounted remotely from the printheads they supply, a known technique for regulating the pressure of ink fed to the printhead is to regulate the ink pressure remotely from the printhead (for example at the reservoir) and connect the pressure regulator to the printhead via a long ink tube. This technique has the disadvantage of there being pressure fluctuations at the printhead due to flow-dependent hydraulic losses in the long ink tube, movement of the long ink tube or from air within the tube. Such fluctuations impair printhead performance.

Prior art pressure regulators generally use either the height of ink to control pressure (level control) or a spring, or capillary action. Examples of level control pressure regulators include Trident International's printing systems for industrial coding applications and Hewlett-Packard's off-axis 'flaccid bag' (see EP-A-0 903 238). An example of a mechanical pressure regulator using a spring mechanism is shown in US 5,844,577. An example of a pressure regulator using capillary action is shown in US 5,745, 138.

Whilst it would be desirable to have a pressure regulator close to or at the printhead, when using a remote ink reservoir, prior art pressure regulators are generally not such that they could be simply mounted at or near the printhead. This is particularly the case when the pressure of the ink needs to be regulated to be negative at the printhead.

Another problem with prior art ink pressure regulators is that, order to regulate the pressure of the ink with respect to, for instance, atmospheric pressure, prior art pressure regulators often require the ink to be in contact with the surrounding atmosphere at some point. This has several drawbacks. Air dissolves into the ink producing bubbles inside the printhead where the ink may be heated. Volatile components of the ink are lost to the air, so that ink constitution is altered. The ink must be formulated so that it is not degraded by contact with air - an unwanted restriction in formulating an effective ink jet ink.

It is an object of embodiments of the present invention to provide a pressure regulation system for an ink jet printer which allows the pressure of the ink to be regulated at or near to the printhead whilst using a remote reservoir.

It is a further object of embodiments of the invention to provide a pressure regulation system for an ink jet printer which may be simply configured such that air is substantially prevented from entering the ink supply system.

According to the invention there is provided an ink supply regulation system for an ink jet printer comprising: an ink chamber for supplying ink to a printhead; an ink supply device for supplying ink to the ink chamber; and means for activating the ink supply device in dependence on the pressure in the chamber.

The chamber may comprise a part of the ink tubing from the ink source to the printhead or, for example, may comprise a separate chamber, connected to the ink supply and the printhead by ink tubing.

By controlling the ink supply device on the basis of the pressure in the ink chamber, close regulation of the pressure of the ink can be obtained. Preferably, the system further includes a pressure sensor for determining the pressure in the chamber.

Preferably the ink chamber comprises compliant material. By providing a compliant chamber, the rapid change of pressure in the ink chamber can be reduced and the required frequency with which the ink supply device is activated can also be reduced.

The volume of the ink chamber is preferably variable and the system further includes means for determining the volume of the chamber. This volume determining means may be provided by the pressure sensor, the pressure in the chamber being derivable from the determination of the volume of the chamber.

Thus the invention further provides an ink supply regulation system for an ink jet printer comprising: an ink chamber for supplying ink to a printhead, the volume of the ink chamber being variable; an ink supply device for supplying ink to the ink chamber; and means for activating the ink supply device in dependence on the volume of the ink chamber.

Preferably the system further includes the sensor for determining the volume of the chamber.

Preferably the ink chamber has at least one movable wall and the system includes a position sensor for determining the position of the wall. The position sensor may be provided by the pressure sensor and the sensor can be used to determine the pressure in the ink chamber. The movable wall of the chamber may comprise flexible material, and may provide the compliance of the chamber.

Also according to the invention there is provided an ink supply regulation system for an ink jet printer comprising: an ink chamber for supplying ink to a printhead; an ink supply device for supplying ink to the ink chamber; and a control device programmed to activate the ink supply device in dependence on at least one of the pressure in the chamber, the volume in the chamber and the position of a part of the chamber.

Preferably the ink supply device comprises an electromechanical device, preferably a solenoid operated valve.

Preferably the ink chamber is adapted to substantially isolate ink in the chamber from the environment. The environment may comprise the atmosphere external to the ink carrying system or other gasses or materials. By isolating the ink in the ink chamber, the risk of air dissolving into the ink or of volatile components from the ink being lost can be reduced.

This feature is of particular importance and is provided independently. The invention also provides an ink supply regulation system for an ink jet printer comprising: an ink chamber for supplying ink to a printhead; and an ink supply device for supplying ink to the ink chamber, wherein the ink chamber is adapted to substantially isolate ink in the chamber from the environment.

Preferably the system is adapted to substantially isolate ink in the system between the ink supply device and the printhead from the environment. In preferred embodiment, all of the ink in the system to the nozzles will be isolated from the environment.

Preferably the ink chamber is adapted to be arranged immediately adjacent the printhead, and preferably immediately adjacent the nozzles of the printhead. Thus close control of the pressure of ink in the printhead can be achieved.

A preferred embodiment of the present invention provides a pressure regulation system for an ink jet printer comprising an ink pressure sensing means for sensing the pressure of ink at or close to a plurality of nozzles on a printhead of the ink jet printer and producing an electrical signal representative of the sensed pressure, an electromechanical ink supply regulating means for regulating the flow of ink, control logic for controlling the electromechanical ink supply regulating means based on the electrical signal from the ink pressure sensing means, an ink transfer means for transferring ink from an exit of the electromechanical ink supply regulating means to the plurality of nozzles, wherein at least part of the ink transfer means is such that the volume of that part varies with the pressure of its contents.

Since the control is electronic rather than mechanical, it is easy to vary the supply pressure in response to printing conditions or for maintenance purposes.

Embodiments of the present invention allow pressure regulation very close to the printhead with a small fluid volume, this is particularly useful for systems where the printheads move, but is also useful for fixed printhead systems.

In a preferred embodiment, the ink transfer means is substantially sealed to the environment apart from at least one entrance orifice at the electromechanical ink supply regulating means and at least one exit orifice at or close to the plurality of nozzles.

Avoiding contact with air means the ink can be supplied degassed (partially or fully), so that air bubbles are unlikely to form in the ink passageways, and if there are any air bubbles they will be absorbed by the ink.

The invention also provides an ink jet printer comprising an ink supply regulation system as described above, a pressure regulation system as described above or a printhead as described above.

Preferably the printer further comprises an ink reservoir for supplying ink to the ink supply device.

Also provided by the invention is a method of controlling an ink supply system in an ink jet printer comprising an ink chamber for supplying ink to a printhead and an ink supply device for supplying ink to the ink chamber, the method including the steps of: determining the pressure of ink in the ink chamber; and activating the ink supply device in dependence on the pressure in the ink chamber. The invention further provides a control device for controlling ink supply in an ink jet printer comprising an ink chamber for supplying ink to a printhead, an ink supply device for supplying ink to the ink chamber and a sensor for monitoring the ink chamber and emitting a signal indicative of at least one of the pressure, the volume and the position of the ink chamber, the control device being programmed to receive the signal from the sensor and emit a signal to the ink supply device in dependence on the signal received from the sensor.

The invention also provides a computer program and 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 to 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, which, by way of example, describe an embodiment of the present invention in which the ink transfer means is realised as a compliant chamber and a solenoid-driven on-off valve is used as the electromechanical ink supply regulating means.

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

Figure 1 : Schematic diagram of an embodiment of the invention.

Figure 1 shows an example of the invention. A pressure sensor (2) senses the pressure of ink held in a compliant chamber (3). A solenoid-driven ink supply valve (5) controls the supply of ink from a supply reservoir (6) to the compliant chamber (3) and ultimately to an ink jet printhead (4) which is connected to the compliant chamber. A control system (1) controls the ink supply valve (5) based on electrical signals received from the pressure sensor (2).

The control system (1) uses the pressure sensor (2) in the 25 compliant chamber (3) to detect ink pressure being supplied to the printhead (4) . If the pressure is below a threshold value, the control system (1) opens the ink supply valve (5) to allow ink to flow from the supply reservoir (6) to the compliant chamber (3). As the ink flows in, the pressure in the compliant chamber rises, the control system (1) turns off the supply valve (5) when the pressure reaches a threshold value (or after a fixed amount of time). Compliance is provided in the system to prevent both the pressure rise within the compliant chamber (3) when the ink supply valve (5) is opened and the pressure drop in the compliant chamber (3) when printing occurs from being too rapid. The stiffness of the compliant chamber is chosen based on the response time of the control system, supply valve and pressure sensor, and also on the required frequency with which the valve is to be turned on and off (cycling frequency) — an overly stiff compliant chamber results in the supply valve cycling frequency being high and reduces the valve's lifetime.

The compliance of the compliant chamber may consist of using a thin diaphragm as a part of an otherwise rigid chamber wall. This compliance may also be built into the printhead design.

The printhead can be flushed through with ink for maintenance by opening the supply valve for a relatively long period of time, allowing the pressure to build up above its normal control value.

In order to cause the ink to flow through the supply valve to the printhead, the supply reservoir (6) may be pressurised. Alternatively, since some printheads act as pumps and so can "suck" in the ink, the supply reservoir may be at ambient (or even negative) pressure. Other means of causing the ink to flow are also known to the person skilled in the art. An electromechanical pump can be used in conjunction with a non-return valve as an alternative to the solenoid-driven ink supply valve.

One embodiment for the pressure sensor is to use a position sensor to sense the position of a flexible membrane which forms part of the compliant chamber. The pressure relates to position via the compliance of the chamber. Other known pressure sensors may also be 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. An ink supply regulation system for an ink jet printer comprising: an ink chamber for supplying ink to a printhead; an ink supply device for supplying ink to the ink chamber; and means for activating the ink supply device in dependence on the pressure in the chamber.

2. An ink supply regulation system according to claim 1 further including a pressure sensor for determining the pressure in the chamber.

3. An ink supply regulation system according to claim 1 or claim 2, wherein the ink chamber comprises compliant material.

4. An ink supply regulation system according to any one of claims 1 to 3, wherein the volume of the ink chamber is variable and the system further includes means for determining the volume of the chamber.

5. An ink supply regulation system for an ink jet printer comprising: an ink chamber for supplying ink to a printhead, the volume of the ink chamber being variable; an ink supply device for supplying ink to the ink chamber; and means for activating the ink supply device in dependence on the volume of the ink chamber.

6. An ink supply regulation system according to claim 4 or claim 5, further including a sensor for determining the volume of the chamber.

7. An ink supply regulation system according to any one of claims 1 to 6, wherein the ink chamber has at least one movable wall and the system includes a position sensor for determining the position of the wall.

8. An ink supply regulation system for an ink jet printer comprising: an ink chamber for supplying ink to a printhead; an ink supply device for supplying ink to the ink chamber; and a control device programmed to activate the ink supply device in dependence on at least one of the pressure in the chamber, the volume in the chamber and the position of a part of the chamber.

9. An ink supply regulation system according to any one of claims 1 to 8, wherein the ink supply device comprises an electromechanical device.

10. An ink supply regulation system according to claim 9, wherein the ink supply device comprises a solenoid operated valve.

11. An ink supply regulation system according to any one of claims 1 to 10, wherein the ink chamber is adapted to substantially isolate ink in the chamber from the environment.

12. An ink supply regulation system for an ink jet printer comprising; an ink chamber for supplying ink to a printhead; and an ink supply device for supplying ink to the ink chamber, wherein the ink chamber is adapted to substantially isolate ink in the chamber from the environment.

13. An ink supply regulation system according to claim 11 or claim 12, wherein the system is adapted to substantially isolate ink in the system between the ink supply device and the printhead from the environment.

14. An ink supply regulation system according to any one of claims 1 to 13, wherein the ink chamber is adapted to be arranged immediately adjacent the printhead.

15. A pressure regulation system for an ink jet printer comprising an ink pressure sensing means for sensing the pressure of ink at or close to a plurality of nozzles on a printhead of the ink jet printer and producing an electrical signal representative of the sensed pressure, an electromechanical ink supply regulating means for regulating the flow of ink, control logic for controlling the electromechanical ink supply regulating means based on the electrical signal from the ink pressure sensing means, an ink transfer means for transferring ink from an exit of the electromechanical ink supply regulating means to the plurality of nozzles, wherein at least part of the ink transfer means is such that the volume of that part varies with the pressure of its contents.

16. A pressure regulation system according to claim 15 in which the ink transfer means is substantially sealed to the environment apart from at least one entrance orifice at the electromechanical ink supply regulating means and at least one exit orifice at or close to the plurality of nozzles.

17. A pressure regulation system according to claim 15 or claim 16 in which the ink transfer means consists of a substantially inflexible chamber with at least one flexible wall.

18. A pressure regulation system according to any one of claims 15 to 17 in which electromechanical ink supply regulating means is a solenoid operated valve.

19. A pressure regulation system according to any one of claims 15 to 18 in which the pressure sensing means comprises a position sensing means which senses the position of a part of the ink transfer means.

20. A pressure regulation system according to claim 19, in dependence on claim 17, in which the position sensing means senses the position of the at least one flexible wall.

21. An ink jet printhead which comprises a pressure regulation system according to any of the preceding claims.

22. An ink jet printer comprising an ink supply regulation system according to any one of claims 1 to 14, a pressure regulation system according to any one of claims 15 to 20 or a printhead according to claim 21.

23. A printer according to claim 22, further comprising an ink reservoir for supplying ink to the ink supply device.

24. A method of controlling an ink supply system in an ink jet printer comprising an ink chamber for supplying ink to a printhead and an ink supply device for supplying ink to the ink chamber, the method including the steps of: determining the pressure of ink in the ink chamber; and activating the ink supply device in dependence on the pressure in the ink chamber.

25. A control device for controlling ink supply in an ink jet printer comprising an ink chamber for supplying ink to a printhead, an ink supply device for supplying ink to the ink chamber and a sensor for monitoring the ink chamber and emitting a signal indicative of at least one of the pressure, the volume and the position of the ink chamber, the control device being programmed to receive the signal from the sensor and emit a signal to the ink supply device in dependence on the signal received from the sensor.