Ink supply system with float valve chamber

1. An ink supply system for supplying ink to an inkjet printhead at a predetermined hydrostatic pressure, said ink supply system comprising:

a pressure-regulating chamber having an inlet port and an outlet port, said outlet port being connected to an ink inlet of said printhead, said chamber containing a float valve configured for maintaining a predetermined level of ink in said chamber, said level of ink being below said printhead and controlling said hydrostatic pressure; and

an ink reservoir connected to said inlet port, said ink reservoir being positioned above said predetermined level of ink,

wherein said float valve comprises:

an arm pivotally mounted about a pivot;

a float mounted at one end of said arm; and

a valve head extending from said arm,

wherein said valve head is positioned for sealing engagement with a valve seat at said inlet port.

2. The ink supply system of claim 1 , wherein said hydrostatic pressure, relative to atmospheric pressure, is defined as ρgh, wherein ρ is the density of ink, g is acceleration due to gravity and h is the height of the predetermined level of ink relative to the printhead.

3. The ink supply system of claim 1 , further comprising a printhead priming system.

4. The ink supply system of claim 3 comprising:

an air pump communicating with a headspace above said ink in said chamber; and

a valve positioned between said ink reservoir and said inlet port, wherein, in a priming configuration, said valve is configured to be shut and said pump is configured to positively pressurize said headspace thereby forcing ink from said chamber into an ink inlet of said printhead.

5. The ink supply system of claim 4 , wherein a sensor is positioned for sensing ink in a downstream ink line connected to an ink outlet of said printhead, said sensor cooperating with said pump such that said pump is shut off when said sensor senses any ink.

6. The ink supply system of claim 5 , further comprising means for controlling an amount of ink flowing from said downstream ink line back into said pressure-regulating chamber.

7. The ink supply system of claim 6 , wherein said means is selected from the group comprising:

an electronically-controlled valve;

a check-valve; and

a loop section passing below said predetermined level of ink in said chamber.

8. The ink supply system of claim 5 , wherein said sensor is an optical sensor.

9. The ink supply system of claim 5 , further comprising means for minimizing phantom sensing of ink caused by ink bubbles in said downstream ink line.

10. The ink supply system of claim 9 comprising a bubble-bursting box, said box comprising:

at least one bubble-bursting chamber having a respective chamber inlet; and

an air outlet.

11. The ink supply system of claim 10 , wherein said air outlet is open to atmosphere or said air outlet communicates with a pump inlet of said air pump.

12. The ink supply system of claim 10 , wherein said at least one bubble-bursting chamber is dimensioned to promote expansion and bursting of ink bubbles entering said chamber via said chamber inlet.

13. The ink supply system of claim 12 , wherein said bubble-bursting box comprises a plurality of bubble-bursting chambers, each chamber corresponding to a respective ink channel of said ink supply system.

14. The ink supply system of claim 10 , wherein said bubble-bursting box comprises an air chamber in fluid communication with said at least one bubble-bursting chamber via an air channel defined in a roof of said box, said air outlet being defined in said air chamber.

15. The ink supply system of claim 14 , wherein said air channel is a hydrophobic serpentine channel comprising at least one ink-trapping stomach, said air channel minimizing transfer of ink to said air chamber when said box is tipped.

16. The ink supply system of claim 4 , wherein said pump is a reversible pump.

17. The ink supply system of claim 16 , wherein, in a de-priming configuration, said pump is reversed and ink is pulled from said printhead towards said pressure-regulating chamber.