Torque limiting clutch for electric screwdriver - has capstan type drive through helical coil spring with drum rigidly attached to shaft

摘要

The torque limiting clutch for a hand held electric screw-driver has a drum (1) rigidly mounted on a shaft. The drum fits inside a helical coil spring (2) which grips a second drum (3) when the first drum (1) is rotated. The free end of the spring (2) is retained in a slot in the housing (4) which is driven by the driving ring (5). The driving ring is clamped between the drum and the driving disc (7) by a compression spring. When the required maximum torque is reached the driving balls slip out of their recesses and force the driving disc away from the drum and releasing driving ring (5). The end of the spring (2) is no longer held and so no rotation is transmitted to the drum.