Patent ID: 7467701

Claim:
An electromagnetic clutch comprising: an armature plate rotatably connected to a shaft, the armature plate being movable axially with respect to the shaft; a pulley, the pulley being rotatable relative to the shaft; a plurality of electromagnetic coils housed within a coil housing being stationary relative to the pulley such that when at least one of the electromagnetic coils is energized a magnetic field will draw the armature plate into contact with the pulley such that the pulley and the shaft are rotatably connected to one another via friction between the armature plate and the pulley; the plurality of magnetic coils being axially aligned with one another at a common radial position and being energized independently of the other coils such that the magnetic coils can be energized individually or in any combination to provide a magnetic field of varying strength without employing a voltage varying device that varies voltage while voltage is being applied.