Patent ID: 8272285

Claim:
An actuator comprising an actuator shaft mounted for rotation by a drive shaft, a releasable lock operable to restrict axial movement of the actuator shaft relative to the drive shaft, the lock comprising a plurality of radially moveable tines, moveable between a locked position in which they secure the drive shaft and the actuator shaft to one another and an unlocked position in which the lock automatically releases in the event that a predetermined load is applied to the actuator, and an output member co-operating with the actuator shaft such that rotation of the actuator shaft drives the output member for translating movement relative to the actuator shaft, wherein the drive shaft is mounted for rotation and restricted axial movement within a housing, a spring biasing arrangement biasing the drive shaft towards a predetermined axial position, the tines co-operating with a stop to prevent radial movement of the tines to the unlocked position when the drive shaft occupies the predetermined axial position, axial movement of the drive shaft in unison with the actuator shaft through a limited distance in response to the predetermined load beyond a release position causing axial movement of the tines relative to the stop to a position in which the tines no longer co-operate with the stop and permitting radial movement of the tines to release the lock and thereby enable axial movement of the actuator shaft relative to the drive shaft.