Inkjet nozzle device with static and movable nozzle portions

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;

an elongate actuating arm cantilevered relative to the support structure; and

a nozzle chamber structure defining a nozzle chamber for receiving ink from the ink inlet chamber, the nozzle chamber structure comprising a static portion extending from the support structure and defining a nozzle opening through which ink in the nozzle chamber is ejected, the nozzle chamber structure further comprising a movable wall portion mounted to the actuating arm between its ends so that the cantilevered actuating arm terminates in a free end within the nozzle chamber so that, upon actuation of the actuating arm, the free end of the actuating arm moves within the nozzle chamber and ejects ink therein through the nozzle opening wherein

the actuating arm comprises:

an active portion connected electrically to a current source, and which heats and expands upon activation of the current source, and

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, upon activation of the current source, differential expansion of the active and passive portions causes the actuating arm to bend.

2. A nozzle device as claimed in claim 1 , 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 with an ink meniscus formed between the static formation and the actuating arm.

3. A nozzle device as claimed in claim 2 , wherein the static formation defines a free end which is directed away from the nozzle chamber.

4. A nozzle device as claimed in claim 3 , wherein the support structure defines a well located in alignment with said free end so that any ink leakage from the nozzle chamber can collect in the well.

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

6. 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.

7. A nozzle device as claimed in claim 6 , 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.

8. A nozzle device as claimed in claim 7 , wherein the active portion is substantially U-shaped and the movable contact element is located proximal to the centre of the active portion.

9. A nozzle device as claimed in claim 8 , wherein free ends of the active portion define a pair of enlarged contacts.