Printhead assembly with ink pump and shut off valve
A printhead assembly for engagement with an ink supply ( 112 ), a printhead integrated circuit (IC) ( 74 ) in fluid communication with the ink supply via an upstream ink line ( 67 ), the printhead IC ( 74 ), a waste ink outlet in fluid communication with the printhead IC ( 74 ) via a downstream ink line ( 106 ), an upstream shut off valve ( 138 ) in the upstream ink line ( 67 ), and, a downstream pump mechanism ( 114 ) in the downstream ink line. With a valve upstream of the printhead and a pump downstream of the printhead, the user has active control of the ink flow upstream, downstream or in the printhead IC. In the event that problems such as ink flooding, color mixing or printhead depriming occur, the user can follow simple troubleshooting protocols to rectify the situation.
1 . A printhead assembly for installation in an inkjet printer, the printhead assembly comprising:
a printhead integrated circuit (IC) having an array of nozzles each with respective actuators for ejecting drops of ink onto print media;
an upstream ink line in fluid communication with the printhead IC, the upstream ink line being configured for releasable engagement with an ink supply;
a downstream ink line in fluid communication with the printhead IC;
a waste ink outlet in fluid communication with the printhead IC via the downstream ink line;
an upstream shut off valve in the upstream ink line; and,
a downstream pump mechanism in the downstream ink line.
2 . A printhead assembly according to claim 1 wherein the pump mechanism is reversible for pumping ink toward the waste ink outlet or toward the printhead IC.
3 . A printhead assembly according to claim 2 wherein the pump mechanism is a peristaltic pump.
4 . A printhead assembly according to claim 1 wherein the ink supply is an ink cartridge and the upstream ink line is configured for releasable sealed fluid engagement with an outlet on the ink cartridge.
5 . A printhead assembly according to claim 1 wherein the shut off valve is biased shut and returns to its shut position when the printhead assembly is installed in the printer and the printer is powered down.
6 . A printhead assembly according to claim 5 wherein the shut off valve displaces ink when moving to its shut position such that when the shut off valves opens, a finite volume of ink is drawn away from the ink cartridge to drop the hydrostatic pressure at the outlet of the ink cartridge.
7 . A printhead assembly according to claim 1 further comprising a capper that is movable between an unsealed position spaced from the nozzles of the printhead IC and a sealed position creating an air tight seal over the nozzles.
8 . A printhead assembly according to claim 7 wherein the array of nozzles is formed in a nozzle plate and the capper is configured to remove ink and particulates deposited on the nozzle plate.
9 . A printhead assembly according to claim 1 further comprising a sensor downstream of the printhead IC for sensing the presence or absence of ink.
10 . A printhead assembly according to claim 9 wherein the sensor is upstream of the peristaltic pump.
11 . A printhead assembly according to claim 3 further comprising a plurality of the ink tanks for separate ink colors, and a plurality of upstream ink lines and downstream ink lines for each colour respectively, wherein the peristaltic pump is a multi-channel peristaltic pump that can pump each ink color simultaneously.
12 . A printhead assembly according to claim 10 further comprising a controller operatively linked to the sensor and the peristaltic pump such that the controller operates the pump in response to output from the sensor.
13 . A printhead assembly according to claim 1 wherein during use, the waste ink outlet is at a less elevated position than the printhead IC.