Inkjet nozzle assembly with thermal bend actuator defining part of nozzle chamber roof

1. An inkjet nozzle assembly comprising:

a nozzle chamber comprising a floor and a roof, said roof having a nozzle opening defined therein, said roof having a moving portion moveable towards the floor; and

a thermal bend actuator for ejecting ink through the nozzle opening, said actuator comprising:

an active beam for connection to drive circuitry; and

a passive beam mechanically cooperating with the active beam, such that when a current is passed through the active beam, the active beam expands relative to the passive beam resulting in bending of the actuator,

wherein the actuator defines at least part of the moving portion of the roof, and wherein the active beam defines an upper layer of the moving portion relative to the passive beam, and the passive beam defines a lower layer of the moving portion relative to the floor.

2. The inkjet nozzle assembly of claim 1 , wherein the passive beam is coplanar with a stationary portion of the roof.

3. The inkjet nozzle assembly of claim 1 , wherein the nozzle opening is defined in the moving portion, such that the nozzle opening is moveable relative to the floor portion.

4. The inkjet nozzle assembly of claim 1 , wherein the nozzle opening is defined in a stationary portion of the roof and the actuator is moveable relative to the nozzle opening.

5. The inkjet nozzle assembly of claim 1 , wherein the active beam is defined by a bent or tortuous beam element, said beam element having a plurality of contiguous beam members.

6. The inkjet nozzle assembly of claim 5 , wherein the plurality of contiguous beam members comprises a plurality of longer beam members extending along a longitudinal axis of the active beam, and at least one shorter beam member extending across a transverse axis of the active beam and interconnecting longer beam members.

7. The inkjet nozzle assembly of claim 1 , wherein said passive beam is a bilayered passive beam.

8. The inkjet nozzle assembly of claim 7 , wherein said bilayered passive beam comprises a layer of insulating material in contact with said active beam.

9. The inkjet nozzle assembly of claim 1 , wherein the active beam is fused to the passive beam by a deposition process.

10. The inkjet nozzle assembly of claim 1 , wherein the active beam is comprised of a material selected from the group consisting of: titanium nitride, titanium aluminium nitride and an aluminium alloy.

11. The inkjet nozzle assembly of claim 1 , wherein the active beam is comprised of an aluminium alloy.

12. The inkjet nozzle assembly of claim 11 , wherein said aluminium alloy comprises aluminium and at least one other metal having a Young's modulus of more than 100 GPa.

13. The inkjet nozzle assembly of claim 12 , wherein said at least one metal is selected from the group consisting of: vanadium, manganese, chromium, cobalt and nickel.

14. The inkjet nozzle assembly of claim 13 , wherein said alloy comprises aluminum and vanadium.

15. The inkjet nozzle assembly of claim 14 , wherein said alloy comprises at least 80% aluminium.

16. The inkjet nozzle assembly of claim 1 , wherein said passive beam is comprised of silicon dioxide.