Print material feed system

1. An inkjet printing device, comprising:

a print assembly; and

a print material feed system coupled to the print assembly, the print material feed system comprising:

a first circulation circuit and a second circulation circuit, the first circulation circuit fluidly coupled between the second circulation circuit and the print assembly, the first circulation circuit comprising a supply reservoir, a drain reservoir, and a negative pressure gas flow unit coupled to the supply reservoir and the drain reservoir to control pressure in the supply reservoir and the drain reservoir, and further comprising a third circulation circuit fluidly coupled to the second circulation circuit and comprising a mixing element.

2. The device of claim 1 , wherein the second circulation circuit comprises a gas extractor.

3. The device of claim 2 , wherein the gas extractor comprises a jacketed porous tube.

4. The device of claim 2 , wherein the supply reservoir and the drain reservoir are configured to maintain a higher pressure in the supply reservoir than in the drain reservoir.

5. The device of claim 4 , further comprising a third circulation circuit fluidly coupled to the second circulation circuit and comprising a mixing element.

6. The device of claim 5 , wherein the mixing element is a stirred vessel.

7. A print material feed system, comprising:

a first circulation circuit comprising:

a print material supply reservoir;

a print material drain reservoir;

a negative pressure gas flow unit coupled to the print material supply reservoir and to the print material drain reservoir;

at least one printhead;

a print material supply line fluidly coupled from the print material supply reservoir to the at least one printhead;

a print material return line fluidly coupled from the at least one printhead to the print material drain reservoir; and

a second circulation circuit comprising:

a circulation supply line coupled to the print material supply reservoir;

a circulation return line coupled to the print material drain reservoir; and

a pump that takes suction from the circulation return line and discharges to the circulation supply line.

8. The print material feed system of claim 7 , wherein the second circulation circuit further comprises a gas extractor coupled into the circulation supply line.

9. The print material feed system of claim 8 , further comprising a bypass line connecting the supply reservoir and the drain reservoir.

10. The print material feed system of claim 9 , further comprising a level sensor coupled to each of the print material supply reservoir and the print material drain reservoir, a bypass valve in the bypass line, and a controller operatively coupled to the level sensors and configured to adjust a pressure difference between the print material supply reservoir and the print material drain reservoir a level detected by the print material drain reservoir level sensor.

11. The print material feed system of claim 10 , further comprising a supply fill control valve in the circulation supply line, wherein the controller is operatively coupled to the supply fill control valve and further configured to adjust a flow a print material in the circulation supply line based on a level detected by the print material supply reservoir level.

12. The print material feed system of claim 10 , wherein the controller is operatively coupled to the negative pressure gas flow unit and is further configured to maintain a higher pressure in the print material supply reservoir than in the print material drain reservoir.

13. The print material feed system of claim 12 , further comprising a circulation return control valve in the circulation return line, wherein the controller is operatively coupled to the circulation return control valve and configured to control the circulation return control valve to set a fluid circulation rate in the second circulation circuit.

14. The print material feed system of claim 13 , wherein the second circulation circuit further comprises a gas extractor and a circulation bypass line from the circulation supply line to the circulation return line.

15. The print material feed system of claim 14 , wherein the second circulation circuit further comprises a print material source vessel fluidly coupled to the circulation supply line.

16. An inkjet printing device having a print material feed system, comprising:

a print assembly;

a bulk circulation circuit;

a middle circulation circuit; and

a local circulation circuit, wherein

the bulk circulation circuit is configured to draw print material from a supply vessel into a mixing vessel and to flow print material around the bulk circulation circuit continuously,

the middle circulation circuit is configured to draw print material from the bulk circulation circuit, to return print material to the bulk circulation circuit, and to flow print material around the middle circulation circuit, and

the local circulation circuit is configured to draw print material from and to return print material to the middle circulation circuit, and to supply print material to the print assembly.

17. The inkjet printing device of claim 16 , further comprising a pressure control system to circulate print material through the local circulation circuit, and a circulation pump in each of the bulk circulation circuit and the middle circulation circuit.

18. The inkjet printing device of claim 17 , wherein the local circulation circuit comprises a supply reservoir, a drain reservoir, a negative pressure gas flow unit coupled to the supply reservoir and the drain reservoir, and a bypass line connecting the supply reservoir to the drain reservoir, wherein the pressure control system is configured to maintain a higher pressure in the supply reservoir than in the drain reservoir.

19. The inkjet printing device of claim 16 , wherein the local circulation circuit comprises a supply reservoir, a drain reservoir, a negative pressure gas flow unit coupled to the supply reservoir and the drain reservoir, and a controller configured to control the negative pressure gas flow unit to maintain a higher pressure at an outlet of the supply reservoir than at an inlet of the drain reservoir.