Ink pressure regulator with regulator channel fluidically isolated from ink reservoir

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;

a regulator channel having a first end communicating with the air inlet and a second end defining a bubble outlet, said bubble outlet being positioned for bubbling air bubbles into a headspace of the chamber at all operative ink levels; and

a wetting system for maintaining at least some liquid in said regulator channel at all operative ink levels, thereby ensuring that air entering the headspace first passes through said liquid;

wherein said regulator channel is dimensioned to control a Laplace pressure of air bubbles drawn from said bubble outlet as result of supplying ink to the printhead, thereby regulating a hydrostatic pressure of the ink; and

wherein said wetting system is fluidically isolated from a reservoir of ink in said ink chamber.

2. The pressure regulator of claim 1 , wherein said wetting system comprises a wetting chamber in fluid communication with said regulator channel.

3. The pressure regulator of claim 2 , wherein said wetting system comprises a first wetting chamber connected to said first end and a second wetting chamber connected to said second end.

4. The pressure regulator of claim 3 , wherein each wetting chamber is configured such that, in use, a volume of liquid is retained therein by surface tension.

5. The pressure regulator of claim 4 , wherein each wetting chamber is configured such that liquid is pinned into edge regions thereof.

6. The pressure regulator of claim 5 , wherein an edge region of each wetting chamber is connected to said regulator channel.

7. The pressure regulator of claim 5 , wherein an annulus of liquid is retained in said edge regions.

8. The pressure regulator of claim 5 , wherein each wetting chamber is generally chamfered such that said edge regions comprise at least two chamber walls meeting at an acute angle.

9. The pressure regulator of claim 3 , wherein said first wetting chamber is open to atmosphere via said air inlet.

10. The pressure regulator of claim 3 , wherein said second wetting chamber has a vent opening into said headspace.

11. The pressure regulator of claim 3 , wherein said wetting chambers and said regulator channel together retain a substantially constant volume of liquid.

12. The pressure regulator of claim 11 , wherein said liquid is transferable between said wetting chambers via said regulator channel.

13. The pressure regulator of claim 12 , wherein, during idle periods, a positively pressurized headspace forces liquid to transfer from said second wetting chamber to said first wetting chamber.

14. The pressure regulator of claim 13 , wherein positively pressurized air in said headspace escapes via said air inlet, having first passed through said liquid.

15. The pressure regulator of claim 1 , wherein said liquid is ink.

16. The pressure regulator of claim 1 , wherein a depth of said regulator channel is less than 200 microns.

17. The pressure regulator of claim 1 , wherein said pressure regulator defines an ink cartridge for an inkjet printer.