The present invention is directed to a mechanical clutch which limits transmission of torque to a desired, predetermined maximum torque from a first clutch plate to a second clutch plate. More specifically, the mechanical clutch includes at least one stepper member, preferably three or more evenly spaced stepper members, which transmit the torque from a first clutch plate to a second clutch plate providing a desired maximum torque is not exceeded. However, if the desired maximum torque is exceeded, the stepper member will rotate and move between the clutch plates so that the torque to the second clutch plate does not exceed the desired maximum torque. The desired maximum torque is set by the axial force compressing the stepper member between the clutch plates and when the applied torque to the first clutch plate exceeds the desired torque, the stepper member will rotate between the clutch plates rather than transmit that torque to the second clutch plate.
A magnetic coupling device has an electroconductive rotor presenting a band of electroconductive material and has a magnet rotor with permanent magnets which are slide-mounted to move radially outward responsive to centrifugal force in opposition to a spring bias. When the magnet rotor is stationary the magnets are radially inward of the orbit of the electroconductive band, and when the magnets have moved outwardly when the magnet rotor is rotating, the magnets are spaced by an air gap from the electroconductive band so that eddy currents are induced in the band resulting in coupling of the rotors. The electroconductive rotor preferably has two such bands positioned on opposite sides of the magnet rotor. The rotors may have sheaves mounted thereon.
