Bi-directional friction clutch assembly for electric motors to prevent backdrive

A clutch assembly for a motor having an armature shaft and a worm shaft having a worm constructed and arranged to engage a gear, the clutch assembly comprising:

• a clutch housing including a race surface,
• a cam coupled to the worm shaft,
• means for pressing, associated with the cam,
• a clutch plate, and
• a clutch coupler associated with the clutch plate, the cam, and the means for pressing, the coupler being coupled to the armature shaft for rotation therewith, such that rotation of the coupler rotates the clutch plate, the cam and means for pressing, and thus the worm shaft,
• whereby during a back drive condition of the motor, when torque is transmitted to the worm shaft and thus to the cam, the cam is constructed and arranged to cause the means for pressing to contact and exert pressure on the race surface thereby preventing rotation of the worm shaft,
• wherein the coupler includes a pair of engagement members disposed in spaced relation with the cam there-between, each engagement member having a pair of side surfaces and a pair of top surfaces, with the top surfaces meeting to define an apex.

A method of controlling back drive in a motor, the motor including an armature shaft and a worm shaft having a worm constructed and arranged to engage a gear, the method including:

• ensuring that a clutch assembly has a clutch housing including a race surface;
• a cam coupled to the worm shaft;
• follower structure associated with the cam;
• a clutch plate;
• and a clutch coupler associated with the clutch plate, the cam, and the follower structure, wherein the coupler is coupled to the armature shaft for rotation therewith, such that rotation of the coupler rotates the clutch plate, the cam and follower structure, and thus the worm shaft, and wherein the coupler includes a pair of engagement members disposed in spaced relation with the cam there-between, each engagement member having a pair of side surfaces and a pair of top surfaces, with the top surfaces meeting to define an apex, and
• ensuring that 1) during a back drive condition of the motor, when the worm shaft is a driving element and when torque is transmitted to the worm shaft and thus to the cam, the cam causes the follower structure to contact and exert pressure on the race surface thereby preventing rotation of the worm shaft, and 2) during a normal operating condition of the motor, when the armature shaft is a driving element, the follower structure does not contact the race surface, thereby permitting the worm shaft to rotate freely.