Inkjet nozzle device with cantilevered actuating arm

1. A nozzle device for an inkjet printer, the nozzle device comprising:

a support structure defining an ink inlet chamber connected to a source of ink;

a nozzle chamber structure defining a nozzle chamber for receiving ink from the ink inlet chamber and a nozzle opening through which ink in the nozzle chamber can be ejected; and

an elongate actuating arm cantilevered relative to the support structure and terminating in a movable free end within the nozzle chamber, the actuating arm comprising an active portion connected electrically to a current source and which heats and expands upon activation of the current source, the actuating arm further comprising a passive portion which is electrically isolated from the current source and is mechanically coupled to the active portion via at least one separating element so that differential expansion between the active and passive portions can cause the actuating arm to bend and the free end of the actuating arm to move within the nozzle chamber to eject ink therein through the nozzle opening.

2. A nozzle device as claimed in claim 1 , further comprising a movement sensor which can facilitate determination of the degree or rate of pivotal movement of the actuating arm.

3. A nozzle device as claimed in claim 2 , wherein the movement sensor comprises a movable contact element extending from the active portion, and a fixed contact element which extends from the support structure in a position so that the movable contact element can contact the fixed contact element upon activation of the current source.

4. A nozzle device as claimed in claim 3 , wherein the active portion is substantially U-shaped and the movable contact element is located proximal to the centre of the active portion.

5. A nozzle device as claimed in claim 4 , wherein the free ends of the active portion define a pair of enlarged contacts.

6. A nozzle device as claimed in claim 1 , wherein the nozzle chamber structure comprises:

a static portion extending from the support structure and which defines the nozzle opening; and

a movable wall portion mounted to the cantilevered actuating arm between its fixed and free ends.

7. A nozzle device as claimed in claim 6 , further comprising a static formation extending from the support structure toward the actuating arm at a location proximal to the movable wall portion, the static formation impeding the escape of ink from within the nozzle chamber during actuation of the actuating arm whereby an ink meniscus is formed between the static formation and the actuating arm.

8. A nozzle device as claimed in claim 7 , wherein the static formation defines a bent free end which bends away from the nozzle chamber.

9. A nozzle device as claimed in claim 8 , wherein the support structure defines a well located in alignment with the bent free end so that any escaped ink from the nozzle chamber can collect in the well.

10. A nozzle device as claimed in claim 1 , wherein the free end of the actuating arm comprises a paddle which spans the nozzle chamber.