Printhead assembly comprising ink reservoir containing cleaning liquid

1. A printhead assembly comprising:

(a) an inkjet printhead;

(b) a plurality of ink reservoirs in fluid communication with nozzles in said printhead, wherein at least one of said ink reservoirs contains a cleaning liquid for cleaning an ink ejection face of said printhead;

(c) a pressure device for positively pressurizing said ink reservoir containing said cleaning liquid;

(d) a cleaning fluid conduit providing fluid communication between said ink reservoir containing said cleaning liquid and said printhead; and

(e) a valve in said cleaning liquid conduit for controlling a supply of cleaning liquid to said printhead;

(f) a pressure sensor for measuring a pressure in said ink reservoir containing said cleaning liquid or said cleaning liquid conduit; and

(g) a controller in communication with said pressure sensor, said pressure device and said valve,

wherein said controller is configured to coordinate a printhead purging/cleaning operation, said controller being configured to:

(i) close said valve;

(ii) pressurize said ink reservoir containing said cleaning liquid using said pressure device;

(iii) monitor a pressure in said ink reservoir containing said cleaning liquid or said cleaning liquid conduit using said pressure sensor; and

(iv) open said valve for a predetermined period when a predetermined pressure has been reached, thereby flooding an ink ejection face of said printhead with cleaning liquid.

2. The printhead assembly of claim 1 , wherein said cleaning liquid is water, a dyeless ink base, an aqueous surfactant solution or an aqueous glycol solution.

3. The printhead assembly of claim 1 , wherein said valve is a solenoid valve.

4. The ink supply system of claim 1 , wherein each ink reservoir comprises a pressure-biasing means for biasing a pressure in said reservoir towards a negative pressure.

5. The ink supply system of claim 1 , wherein each ink reservoir comprises an ink bag.