Ink jet nozzle having an actuator mechanism with a movable member controlled by two actuators

1. A nozzle arrangement comprising

a wafer substrate;

a drive circuitry layer that is positioned on the wafer substrate, the wafer substrate and the drive circuitry layer defining an ink inlet channel;

nozzle chamber walls and a roof positioned on the substrate and defining a nozzle chamber into which the ink inlet channel opens;

a shutter member that is movable reciprocally along a path of travel between an open position in which the nozzle chamber is in fluid communication with the ink inlet channel and, a closed position in which the shutter member closes the ink inlet channel; and

at least two actuators that are connected to the shutter member to act on the shutter member, the actuators being configured so that the shutter member is under the influence of at least one of the actuators at substantially all points along the path of travel.

2. A nozzle arrangement as claimed in claim 1 , which includes a pair of operatively opposed actuators.

3. A nozzle arrangement as claimed in claim 1 , which is the product of an integrated circuit fabrication technique.

4. A nozzle arrangement as claimed in claim 3 , in which the actuators are mounted on the substrate at respective ends of the path of travel so that the shutter member is mounted between the actuators.

5. A nozzle arrangement as claimed in claim 4 , in which each actuator is a thermal actuator which comprises an actuator arm and a heating element positioned in the arm, the arm having a coefficient of thermal expansion which is such that, on heating by the heating element, the arm experiences differential thermal expansion to displace the shutter member.

6. A nozzle arrangement as claimed in claim 5 , in which each arm has an elongate structure with end portions fixed to the substrate and an intermediate portion free to move with respect to the substrate, so that, upon said differential thermal expansion of the arm the intermediate portion bends and subsequently displaces the shutter member.

7. A nozzle arrangement as claimed in claim 5 wherein the actuators are substantially identical to each other so that said bending is substantially identical in each actuator.

8. A nozzle arrangement as claimed in claim 5 wherein the actuators have a suitable Young's modulus to ensure that the actuators return to their respective pre-bent conditions upon cooling.

9. A nozzle arrangement as claimed in claim 4 , wherein the actuators are configured to act substantially synchronously on the shutter member.

10. A nozzle arrangement as claimed in claim 1 wherein the wafer substrate is substantially planar and the path of travel is substantially parallel to the substrate.

11. An ink jet printhead, that comprises

a wafer substrate;

a drive circuitry layer positioned on the wafer substrate, the drive circuitry layer and the wafer substrate defining a plurality of ink inlet channels; and

a plurality of nozzle arrangements that is arranged on the substrate, each nozzle arrangement comprising

nozzle chamber walls and a roof that define a nozzle chamber in fluid communication with a respective ink inlet channel and an ink ejection port in fluid communication with the nozzle chamber; and

a shutter member that is movable reciprocally along a path of travel between an open position in which the nozzle chamber is in fluid communication with the respective ink inlet channel and a closed position in which the shutter member closes the ink inlet channel; and

at least two actuators that are connected to the shutter member to act on the shutter member, the actuators being configured so that the shutter member is under the influence of at least one of the actuators at substantially all points along the path of travel.