Ink pressure regulator using air bubbles drawn into headspace

1. An ink pressure regulator for regulating a hydrostatic pressure of ink supplied to an inkjet printhead, said regulator comprising:

an ink chamber having an ink outlet for fluid communication with the printhead via an ink line;

an air inlet open to atmosphere;

a bubble outlet positioned in a headspace of the ink chamber at all operative ink levels, said bubble outlet being positioned for bubbling air bubbles directly into said headspace at all operative ink levels, each air bubble comprising an air cavity trapped inside a film of ink;

a capillary channel in fluid communication with ink contained in the ink chamber, said capillary channel supplying ink from the chamber to the bubble outlet by capillary action; and

an air channel connecting the air inlet and the bubble outlet,

wherein said bubble outlet is dimensioned to control a Laplace pressure of air bubbles drawn into said chamber as result of supplying ink to the printhead, thereby regulating a hydrostatic pressure of the ink.

2. The pressure regulator of claim 1 , wherein said ink chamber is an ink reservoir for a printer.

3. The pressure regulator of claim 1 , wherein said ink chamber has an ink inlet port for fluid communication with an ink reservoir.

4. The pressure regulator of claim 1 , wherein said bubble outlet has a critical dimension controlling the Laplace pressure of the air bubbles exiting the bubble outlet.

5. The pressure regulator of claim 1 , wherein said bubble outlet is configured as a circular opening, such that a radius of said circular opening controls the Laplace pressure of the air bubbles.

6. The pressure regulator of claim 1 , wherein said bubble outlet is configured as a slot having a length dimension and a width dimension, such that said width dimension controls the Laplace pressure of the air bubbles.

7. The pressure regulator of claim 6 , wherein a width of said slot is less than 200 microns.

8. The pressure regulator of claim 1 , further comprising a bubble vent adjacent said bubble outlet, said bubble vent opening into said headspace.

9. The pressure regulator of claim 8 , wherein said bubble outlet and said bubble vent cooperate such that each air bubble breaks through a meniscus of ink pinned across said bubble outlet and vents into said chamber via said bubble vent.

10. The pressure regulator of claim 8 , wherein one wall of said chamber comprises an air intake plate, said plate comprising the air inlet, the air channel, the bubble outlet and the bubble vent.

11. The pressure regulator of claim 10 , wherein said plate comprises a plurality of laminated layers, said layers cooperating to define the air inlet, the air channel, the bubble outlet and the bubble vent.

12. The pressure regulator of claim 11 , wherein said plate comprises:

a first layer having an air inlet opening defined therethrough and an elongate recess defined in a first face thereof, said recess extending longitudinally from a proximal end at said air inlet aperture to a distal end; and

a second layer laminated to said first face, said second layer having a capillary inlet opening and a bubble vent opening defined therethrough,

wherein said capillary inlet opening is positioned towards said distal end of said recess and said bubble vent opening is positioned towards said proximal end of said recess.

13. The pressure regulator of claim 12 , wherein a depth of said recess at said proximal end defines a critical dimension of said bubble outlet, said critical dimension controlling a Laplace pressure of air bubbles exiting said bubble outlet.

14. The pressure regulator of claim 12 , wherein said recess is dimensioned to provide sufficient capillary pressure to raise a column of ink from said distal end to said proximal end.

15. The pressure regulator of claim 12 , wherein said bubble vent opening is dimensioned to pin a meniscus of ink across the opening by surface tension.

16. The pressure regulator of claim 15 , wherein said bubble vent opening is adjacent said bubble outlet.