Abstract: A permanent magnet activated wrap spring clutch (10). A coil spring (32) surrounds an input hub (14) and an output hub (22) and is selectively engaged to wrap down upon the hubs for the transmittal of torque. In an unpowered, engaged condition of the clutch, a permanent magnet (40) attracts a control collar (38) attached to the spring into frictional engagement with a rotating input element (20). Rotation of the control collar causes the spring to wrap down from its somewhat oversized diameter at rest to grip the hubs. In a powered, disengaged condition of the clutch, an energized coil (44) causes the magnetic field of the permanent magnet to move away from the control collar, thereby removing the frictional engagement and allowing the spring to unwrap. The clutch provides torque transmittal without electrical power and ensures complete disengagement regardless of a low momentum or high drag on the output.

Abstract: A permanent magnet activated wrap spring clutch (10). A coil spring (32) surrounds an input hub (14) and an output hub (22) and is selectively engaged to wrap down upon the hubs for the transmittal of torque. In an unpowered, engaged condition of the clutch, a permanent magnet (40) attracts a control collar (38) attached to the spring into frictional engagement with a rotating input element (20). Rotation of the control collar causes the spring to wrap down from its somewhat oversized diameter at rest to grip the hubs. In a powered, disengaged condition of the clutch, an energized coil (44) causes the magnetic field of the permanent magnet to move away from the control collar, thereby removing the frictional engagement and allowing the spring to unwrap. The clutch provides torque transmittal without electrical power and ensures complete disengagement regardless of a low momentum or high drag on the output.