A clutch mechanism 20 is provided for a motor 10. The motor has a shaft 12,
a worm 14 associated with the shaft, a gear 16 engaged by the worm, and a
friction surface 27. The clutch mechanism 20 includes a pressure plate 22
mounted for movement with respect to the shaft toward and away from the
friction surface 27. A spring 26 is constructed and arranged to bias the
pressure plate towards the friction surface. A stop 30 is constructed and
arranged to limit movement of the pressure plate in a direction away from
the friction surface. Whereby, under a back drive condition of the motor
when the motor is not energized and the gear is moved by an externally
applied torque causing an axial force to be exerted on the worm inducing
an axial and an angular movement to the shaft, the pressure plate is
constructed and arranged to move towards and engage the friction surface
thereby impeding rotation of the shaft.
