Printhead assembly with shut off valve for isolating the printhead

Abstract

A printhead assembly with a printhead integrated circuit (IC) and a shut off (138) valve that has a valve body (200) defining an ink inlet (202) for connection to an ink supply, an ink outlet (67) connected to the printhead IC. A moveable valve member (212) is biased into sealing engagement with the valve seat (216) to provide a fluid seal between the ink inlet and the ink outlet. An actuator (204) for unsealing the valve member from the valve seat upon energizing and re-sealing the valve member to the valve seat when de-energized. The valve protects the ink in the ink supply from contaminants that can migrate up the ink line during shut down periods. The valve member is constantly biased to a closed position and so seals the ink supply from the printhead IC as a default condition even in the event of a power failure. The bias is strong enough to provide the fluid seal so that the seal is not compromised when the pressure difference between the inlet and the outlet is small.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

FIG. 1 shows a top perspective view of a prior art printhead assembly;

FIG. 2 shows an exploded view of the printhead assembly shown in FIG. 1;

FIG. 3 shows an inverted exploded view of the printhead assembly shown in FIG. 1;

FIG. 4 shows a cross-sectional end view of the printhead assembly of FIG. 1;

FIG. 5 shows a magnified partial perspective view of the drop triangle end of a printhead integrated circuit module as shown in FIGS. 2 to 4;

FIG. 6 shows a magnified perspective view of the join between two printhead integrated circuit modules shown in FIGS. 2 to 5;

FIG. 7 shows an underside view of the printhead integrated circuit shown in FIG. 5;

FIG. 8 shows a transparent top view of a printhead assembly of FIG. 15 showing in particular, the ink conduits for supplying ink to the printhead integrated circuits;

FIG. 9 is a partial enlargement of FIG. 8;

FIG. 10 is an enlarged view of gas bubbles in the conduits of the LCP moulding;

FIG. 11 is a sketch of the artifacts that can result from bubble contamination of the ink lines;

FIG. 12A is a sketch of the LCP moulding and the printhead IC in a fluidic system of the prior art;

FIG. 12B is a sketch showing the ink line bifurcations in the prior art fluidic system;

FIG. 13A is a sketch of the LCP moulding and the printhead IC in a fluidic system of the present invention;

FIG. 13B is a sketch showing the ink line bifurcations in the fluidic system of the present invention;

FIG. 14 is a schematic cross section of the LCP moulding and the printhead IC in a fluidic system of the present invention;

FIGS. 15A to 15C show the LCP conduit profiling for passive bubble control;

FIGS. 16 to 21 show the various unit operations that are possible with the active control provided by the present invention;

FIG. 22 shows a single pump/four valve implementation of the fluidic system;

FIG. 23 shows a single pump/two valve implementation of the fluidic system;

FIG. 24 is a sketch of another single pump fluidic system;

FIGS. 25A and 25B schematically show the fluidic system FIG. 24 and the initial priming of the printhead IC;

FIGS. 26A to 26E schematically show the operational stages of the fluidic system FIG. 24 moving from standby to print ready mode;

FIGS. 27A and 27B schematically show the fluidic system FIG. 24 moving to a long term power down mode/move printer mode;

FIGS. 28A and 28C schematically show the fluidic system FIG. 24 recovering from long term power down/deprime/gross color mixing;

FIG. 29 is a perspective view of a shut off valve; and,

FIG. 30 is a partial section view of the shut off valve.

Claims

1. A printhead assembly for an inkjet printer, the printhead assembly comprising: a printhead integrated circuit (IC) with an array of nozzles for ejecting ink onto print media; and,a shut off valve having: a valve body defining an ink inlet for connection to an ink supply, an ink outlet connected to the printhead IC, and a valve seat;a valve member biased into sealing engagement with the valve seat to provide a fluid seal between the ink inlet and the ink outlet; and,an actuator for unsealing the valve member from the valve seat upon energizing and re-sealing the valve member to the valve seat when de-energized.

2. A printhead assembly according to claim 1 wherein the valve member has a diaphragm, and the ink outlet and the ink inlet are both in fluid communication with one side of the diaphragm, such that unsealing the valve member draws the diaphragm away from the valve seat to lower the fluid pressure in the ink inlet and the ink outlet.

3. A printhead assembly according to claim 2 wherein the diaphragm is under residual tension when biasing the valve member into sealing engagement with the valve seat.

4. A printhead assembly according to claim 2 wherein the actuator works against the bias of the diaphragm to unseal the valve member from the valve seat.

5. A printhead assembly according to claim 1 wherein the actuator has a solenoid.

6. A printhead assembly according to claim 1 wherein the actuator has a shape memory alloy.

7. A printhead assembly according to claim 6 wherein the shape memory alloy comprises a Nitinol™ wire.

8. A printhead assembly according to claim 2 wherein the diaphragm is polyurethane.

9. A printhead assembly according to claim 2 wherein the actuator draws the diaphragm away from the valve seat more quickly than the diaphragm reseals the valve member to the valve seat.

10. A printhead assembly according to claim 2 wherein the valve seat has a frusto-conical surface for sealing against a complementary surface extending from one side of the diaphragm.