Patent ID: 8491531

Claim:
An injector for use with a drug cartridge ( 10 ) comprising: a plunger ( 17 ) for movement in a direction for acting, in use, to expel a dose or part thereof from the cartridge; a power source ( 23 a ) for acting on the plunger to move it in the direction; an escapement ( 21 ) for acting on the plunger to hold it, and release it against the action of the power source ( 23 a ) to control the movement of the plunger in the direction; and a piezoelectric actuator ( 27 ) for moving the escapement between ‘release’ and ‘hold’ positions; wherein the piezoelectric actuator ( 27 ) is in the form of a sheet or beam and bends in response to applied voltage, and further comprises a mechanical amplifier ( 28 ) interconnecting the actuator and the escapement.