Obtaining high frequency performance by controlling chamber pressure

• US 20040100528A1
• Filed: 11/25/2002
• Published: 05/27/2004
• Est. Priority Date: 11/25/2002
• Status: Active Grant

• Current Assignee: Hitachi Printing Solutions America, Inc.
• Original Assignee: Hitachi Printing Solutions America, Inc.
• Inventors: Willus, Charles A., Howkins, Stuart D.
• Granted Patent: US 6,932,458 B2
• Time in Patent Office: Days
• US Class Current: 347/54
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B41J 2/14201 Structure of print heads with piezoelectric elements
• CPC Class Codes: B41J 2/17556 Means for regulating the pressure in the cartridge
• CPC Class Codes: B41J 2002/14419 Manifold

Abstract

A method and apparatus to prevent ink starvation includes keeping ink in a primary common reservoir at a high pressure. The ink is transferred from the primary common reservoir to a local reservoir when a pressure drop across a restrictor decreases pressure in the local reservoir. The pressure drop across a restrictor results from a higher ink flow rate due to rapid firing of the transducer.

Claims

1. An ink-jet print head, comprising:

a local reservoir to receive ink from a primary common reservoir, wherein the primary common reservoir keeps the ink at a high hydrostatic pressure;

an ink jet chamber to contain the ink, said ink jet chamber including an ink droplet ejection orifice;

an ejection device to eject the ink through the ink droplet ejection orifice; and

a restrictor passage to transmit the ink from the local reservoir to the ink jet chamber.

2. The ink jet print head of claim 1, further including a pressure sensor located in the ink jet chamber to measure pressure within the ink jet chamber and to transmit a signal.

3. The ink jet print head of claim 2, further including a controller to receive the signal from the pressure sensor and to transmit a valve signal.

4. The ink jet print head of claim 3, further including a valve to increase hydrostatic pressure in the local reservoir, wherein the valve receives the valve signal from the controller and the valve opens during rapid firing of the ejection device.

5. The ink jet print head of claim 4, further including a bleed valve coupled to the controller to dissipate pressure from the ink jet chamber, wherein the bleed valve receives the valve signal from the controller and the bleed valve opens when the pressure in the ink jet chamber is too high.

6. The ink jet print head of claim 5, wherein excess pressure dissipated by the bleed valve is transferred to the primary common reservoir.

7. The ink jet print head of claim 5, wherein the valve and the bleed valve are located in one physical valve device.

8. The ink jet print head of claim 1, wherein the primary common reservoir is kept at the high hydrostatic pressure by applying air above the ink by a pressure applying device.

9. The ink jet print head of claim 1, further including a pressure sensor to measure pressure in the local reservoir and a transducer firing rate determiner to identify a firing rate of the transducer, wherein the pressure sensor outputs a signal and the transducer firing determiner outputs a rate signal.

10. The ink jet print head of claim 9, further including a controller to receive the signal from the pressure sensor and the rate signal from the transducer firing rate determiner, to compute the pressure in the ink jet chamber, and to output a valve signal to a valve to open if the pressure is low in the ink jet chamber.

11. The ink jet print head of claim 9, further including a controller to receive the signal from the pressure sensor and the rate signal from the transducer firing rate determiner, to compute the pressure in the ink jet chamber, and to output a valve signal to a bleed valve to open if the pressure is high in the ink jet chamber.

12. The ink jet print head of claim 1, further including:

a pressure sensor in the ink jet chamber to measure pressure in the ink jet chamber and transmit a signal,

a controller to receive the signal and to transmit a displacement signal, and

a displacement device to receive the displacement signal and to displace the local reservoir in or out via a diaphragm to increase or reduce pressure in the local reservoir.

13. The ink jet print head of claim 12, where the displacement device is one of a piezo-electric operated pump, a piezo-electric bender, and a bubble chamber.

14. The ink jet print head of claim 1, further including:

a pressure sensor in the local reservoir to measure pressure in the local reservoir and to transmit a signal;

a transducer firing rate determiner to identify a rate at which the transducer is firing and to transmit a rate signal;

a controller to receive the signal from the pressure sensor and the rate signal from the transducer firing rate determiner, and to transmit a displacement signal; and

a displacement device to receive the displacement signal and to displace the local reservoir in or out, via a diaphragm, to increase or reduce the pressure in the local reservoir.

15. A method to prevent ink starvation in an ink jet print head, comprising:

keeping ink in a primary common reservoir at a high pressure; and

transferring the ink from the primary common reservoir to a local reservoir when a pressure drop across a restrictor decreases pressure in the local reservoir.

16. The method of claim 15, wherein the transferring ink from the primary common reservoir includes opening a valve between the primary common reservoir and the local reservoir.

17. The method of claim 16, further including transferring ink from the local reservoir through the restrictor to an ink jet chamber to prevent starvation.

18. The method of claim 17, wherein the opening of the valve is based on a pressure reading from a pressure sensor.

19. The method of claim 18, further including dissipating pressure in the ink jet chamber by opening a bleed valve.

20. The method of claim 19, wherein dissipating pressure in the ink jet chamber is based on a pressure reading from a pressure sensor.

21. The method of claim 15, wherein transferring ink from the primary common reservoir includes opening a check valve between the primary common reservoir and the local reservoir.

22. The method of claim 21, further including transferring ink from the local reservoir through the restrictor to an ink jet chamber.

23. The method of claim 22, wherein the pressure of the ink being transferred from the local reservoir through the restrictor to the ink jet channel is increased or decreased due to a displacement device displacing in or out of the local reservoir.

24. The method of claim 23, wherein the displacement in or out of the local reservoir is determined by a pressure sensor located within the ink jet chamber.

25. A ink jet printing apparatus, comprising:

a paper feed device to feed paper within the ink jet printing apparatus; and

an ink jet print head, including

a local reservoir to receive ink from a primary common reservoir, wherein the primary common reservoir keeps the ink at a high hydrostatic pressure;

an ink jet chamber to contain the ink, said ink jet chamber including an ink droplet ejection orifice;

an ejection device to eject the ink through the ink droplet ejection orifice and onto the paper; and

a restrictor passage to transmit the ink from the local reservoir to the ink jet chamber.

26. The ink jet printing apparatus of claim 25, further including a pressure sensor to measure pressure within the ink jet chamber and to transmit a signal.

27. The ink jet print head of claim 26, further including a controller to receive the signal from the pressure sensor and to transmit a valve signal.

28. An ink jet print head, comprising:

an ink jet chamber to contain ink, the ink jet chamber including an ink droplet ejection orifice;

a restrictor to transfer the ink from a primary reservoir to the ink jet chamber;

a transducer to eject the ink located in the ink jet chamber through the ink droplet ejection orifice; and

a micro-pump to draw more of the ink from the primary reservoir into the ink jet chamber.

29. The ink jet print head of claim 28, wherein the micro-pump includes a micro-pump transducer to vibrate the diaphragm across the restrictor to draw more ink from the primary reservoir into the ink jet chamber.

30. The ink jet print head of claim 29, wherein the micro-pump is one of several types of acoustic pump, the acoustic pump including a piezo-electric transducer or any other suitable transducer.

31. The ink jet print head of claim 28, further including a micro-pump driving device to transmit a signal to the micro-pump to activate the micro-pump.

32. The ink jet print head of claim 31, wherein the micro-pump driving device is a resistor-capacitor circuit.

33. The ink jet print head of claim 32, wherein the micro-pump driving device is a digital circuit.

34. A method to prevent ink starvation in an ink jet print head, comprising:

keeping ink in a primary reservoir; and

transferring the ink from the primary reservoir through a restrictor to an ink jet chamber by a micro-pump, including a micro-pump transducer, vibrating a diaphragm over the restrictor.

35. The method of claim 34, further including driving the micro-pump based on a firing rate of a transducer with a micro-pump driving device.

36. The method of claim 35, wherein the micro-pump is continuously activated and a magnitude of a micro-pump pumping action is varied depending on the firing rate of the transducer.

37. An ink jet printing apparatus, comprising:

a paper feed device to feed paper within the ink jet printing apparatus; and

an ink jet print head, including

an ink jet chamber to contain ink, said ink jet chamber including an ink droplet ejection orifice,

a primary restrictor to transfer the ink from a primary reservoir to the ink jet chamber,

a transducer to eject the ink located in the ink jet chamber through the ink droplet ejection orifice, and

a micro-pump, including a micro-pump transducer, to vibrate a diaphragm across the restrictor to draw more of the ink from the primary reservoir into the ink jet chamber.

38. The ink jet printing apparatus of claim 37, further including a micro-pump driving device to transmit a signal to the micro-pump to activate the micro-pump.

39. An ink-jet print head, comprising:

an ink jet chamber to contain ink, said ink jet chamber including an ink droplet ejection orifice;

a secondary common reservoir having a low compliance to contain the ink at a slightly higher pressure than pressure of the ink in the ink jet chamber when jetting is taking place;

a primary restrictor to transfer the ink between a primary common reservoir and the ink jet chamber; and

a secondary restrictor to transfer ink from the secondary common reservoir to the ink jet chamber, wherein the secondary restrictor has a low resistance and a high inertance.

40. The ink jet print head of claim 39, wherein the secondary restrictor is of a circular cross-sectional shape.

41. The ink jet print head of claim 39, further including a regulated pressure supply to hold constant the pressure of the secondary common reservoir to keep the compliance of the secondary common reservoir to enable the secondary common reservoir to respond to slow variations in the pressure in the ink jet chamber due to rapid firing of a transducer.

42. The ink jet print head of claim 39, wherein the secondary common reservoir is small in size.

43. The ink jet print head of claim 39, wherein walls of the secondary common reservoir are rigid.

44. The ink jet print head of claim 39, wherein a connection between the secondary common reservoir and the regulated pressure supply is a high inertance path.

45. A method to prevent ink starvation, comprising:

storing ink in a primary common reservoir and a secondary common reservoir;

transferring the ink from a secondary common reservoir through a secondary restrictor to an ink jet chamber, wherein the secondary restrictor is low in resistance and high in inertance.

46. The method of claim 45, further including maintaining a higher ink pressure in the secondary common reservoir as compared to a primary ink pressure in the primary common reservoir.

47. The method of claim 46, wherein a regulated pressure supply maintains the higher ink pressure in the secondary common reservoir.

48. An ink jet printing apparatus, comprising:

a paper feed device to feed paper within the ink jet printing apparatus; and

an ink jet print head, including

an ink jet chamber to contain ink, said ink jet chamber including an ink droplet ejection orifice, wherein a transducer ejects ink droplets out of the ink droplet ejection orifice and onto the paper within the ink jet printing apparatus,

a secondary common reservoir having a low compliance to contain the ink at a slightly higher pressure than pressure of the ink in the ink jet chamber when jetting is taking place,

a primary restrictor to transfer ink between a primary common reservoir and the ink jet chamber, and

a secondary restrictor to transfer ink from the secondary common reservoir to the ink jet chamber, wherein the secondary restrictor has a low resistance and a high inertance.

49. The ink jet printing apparatus of claim 48, further including a regulated pressure supply connected by a high inertance path to the secondary common reservoir to enable the secondary common reservoir to respond to slow variations in pressure in the ink jet chamber due to rapid firing of the transducer and not to respond to fast variations in pressure, the fast variations in pressure utilized to eject the ink droplets.

50. The ink jet printing apparatus of claim 48, wherein the secondary restrictor is of a circular cross-sectional shape.