Nozzle arrangement with a pivotal wall coupled to a thermal expansion actuator

1. A nozzle arrangement for an inkjet printhead, the nozzle arrangement comprising:

a substrate assembly defining an ink inlet channel;

a nozzle chamber structure defining a nozzle chamber in fluid communication with the ink inlet channel, the nozzle chamber structure comprising a roof defining an ink ejection port in fluid communication with the nozzle chamber;

a pivotal wall which is pivotally mounted with respect to the nozzle chamber structure;

a paddle fast with the wall in a cantilever manner and extending into the nozzle chamber;

an anchor extending from the substrate assembly at a location external the nozzle chamber; and

a thermal expansion actuator forming a bridge between the anchor and the pivotal wall which, upon actuation, expands to pivot the wall so that the paddle ejects ink in the nozzle chamber out through the ink ejection port.

2. A nozzle arrangement as claimed in claim 1 , wherein the nozzle chamber structure has a plurality of planar walls so that the nozzle chamber is of box-like shape.

3. A nozzle arrangement as claimed in claim 1 , wherein said ink inlet channel is aligned with said ink ejection port.

4. A nozzle arrangement as claimed in claim 1 , wherein the thermal expansion actuator is of a conductive material and is shaped to define part of a heating circuit.

5. A nozzle arrangement as claimed in claim 1 , wherein the thermal expansion actuator has a pair of arms that are interconnected by a bridge portion.

6. A nozzle arrangement as claimed in claim 1 , wherein the paddle defines a plurality of reinforcing ribs to strengthen the paddle.

7. A nozzle arrangement as claimed in claim 1 , wherein the pivotal wall terminates in a sealing member configured to accommodate pivotal movement of the wall whilst impeding ink leakage from the nozzle chamber.