Method of detecting a blockage within an inkjet nozzle

1. A method of detecting a blockage within an inkjet nozzle, said inkjet nozzle comprising:

an ink chamber;

an opening defined in a roof of said ink chamber;

an actuating arm movable between a rest position and an operating position, said movement causing ejection of an ink droplet through said opening; and

a movement sensor associated with the actuating arm, said movement sensor being activated by movement of the actuating arm to a predetermined position beyond said operating position,

the method comprising the steps of:

(a) passing at least one blockage-detecting current pulse having a predetermined duration t p through the actuating arm;

(b) detecting for movement of the actuating arm to said predetermined position; and

(c) comparing the detected movement with the movement in an unblocked condition, wherein movement of the actuating arm in a blocked condition is less than movement of the actuating arm in an unblocked condition.

2. The method of claim 1 , further comprising the step of:

(d) if a blockage is detected, remedying the blockage by passing at least one further current pulse through the actuating arm at an energy level greater than that of said blockage-detecting current pulse.

3. The method as claimed in claim 1 wherein the movement sensor comprises a moving contact element formed integrally with the actuating arm, a fixed contact element formed integrally with a support structure and electric circuit elements formed within the support structure.

4. The method as claimed in claim 1 wherein a series of current pulses of successively increasing duration tp are induced to pass through the actuating arm over a time period t and detection is made for movement of the actuating arm to said predetermined position within a predetermined time window t w where t>t w >t p .

5. The method of claim 1 , wherein said inkjet nozzle is one of a plurality of nozzles on an inkjet printhead.