Pressure-regulating chamber for gravity control of hydrostatic ink pressure and recycling ink supply system

1. A pressure-regulating chamber for maintaining ink contained therein at a predetermined first level relative to a printhead, said chamber comprising:

an inlet port for connection to an ink reservoir via an ink supply line;

an outlet port for connection to an ink inlet of the printhead via an upstream ink line;

a return port for connection to an ink outlet of the printhead via a downstream ink line;

a snorkel extending from said return port and terminating at a snorkel outlet positioned above said first level of ink;

an air vent open to atmosphere, said air vent communicating with a headspace above said ink; and

a float valve for maintaining said predetermined first level of ink by controlling a flow of ink into said inlet port.

2. The pressure-regulating chamber of claim 1 , wherein said float valve comprises:

an arm pivotally mounted about a pivot;

a float mounted at one end of said arm; and

a valve stem attached to said arm, said valve stem having a valve head for closure of a valve seat,

wherein said valve seat is positioned at the inlet port of said pressure-regulating chamber.

3. The pressure-regulating chamber of claim 2 , wherein said valve head comprises an umbrella cap for closure of the valve seat.

4. The pressure-regulating chamber of claim 3 , wherein an outer surface of a base of said chamber comprises said valve seat.

5. The pressure-regulating chamber of claim 3 , wherein said float valve is configured such that downward movement of said valve stem unseats said umbrella cap from said valve seat.

6. The pressure-regulating chamber of claim 5 , wherein a positive ink pressure at said inlet port urges said umbrella cap against said valve seat.

7. The pressure-regulating chamber of claim 6 , wherein the positive ink pressure is provided by an ink reservoir positioned above said chamber and in fluid communication with said inlet port.

8. The pressure-regulating chamber of claim 2 , wherein said valve stem is positioned between said pivot and said float.

9. The pressure-regulating chamber of claim 1 , wherein said inlet port and said outlet port are positioned towards a base of said chamber.

10. The pressure-regulating chamber of claim 1 , wherein said return port is positioned at a base of said chamber.

11. The pressure-regulating chamber of claim 1 , wherein said air vent comprises an air-permeable membrane, which is impervious to ink.

12. The pressure-regulating chamber of claim 1 comprising a roof cavity, and wherein said snorkel has a snorkel outlet positioned in said roof cavity.

13. The pressure-regulating chamber of claim 1 , wherein said return port comprises an inline ink filter.