Abstract: A method of forming slots in the metal coupling disc (e.g., the armature or rotor) of an electomagnetic coupling such as a clutch or brake. The method is carried out by effecting relative movement between the coupling disc and a laser beam to cause the beam to melt portions of the disc and thereby form slots through the disc. The laser beam is defocused relative to the disc in order to enable a relatively low powered laser beam to form relatively wide slots in the disc. A pressurized jet of gas is directed against the disc immediately adjacent the beam and acts to blast metal from the slots and assist in the formation of wide slots.

Abstract: An apparatus and method is provided for energizing a multiple-turn winding of an electromagnetic coupling having an armature and a rotor separated by an air gap; in response to the closure of the air gap, the energization of the winding is reduced so as to reduce the torque coupling between the armature and rotor. By reducing the initial torque coupling between the armature and rotor the frictional vibrations of the coupling--which occur during engagement of the armature and rotor and which generate audible noise--are reduced and the coupling engages more smoothly and quietly. Preferably, the energization of the winding is reduced in response to the increased magnetic inductance of the winding resulting from the closure of the air gap between the armature and rotor. Also, the torque coupling between the armature and rotor is preferably minimized in response to the increased magnetic inductance so as to provide 100% slippage upon initial contact of the rotor with the armature.