Armature assembly for an electromagnetic clutch

Claim 1

An armature assembly for an electromagnetic coupling, said assembly comprising a forwardly disposed mounting plate and a rearwardly disposed armature, means connecting said armature and said plate for rotation in unison while permitting said armature to move toward and away from said plate, a hole extending axially through said plate, the periphery of said hole being defined by a first set of circumferentially spaced teeth and by a first set of circumferentially spaced valleys which alternate with the teeth, a shaft having a hub formed on one end portion thereof, said hub having a second set of circumferentially spaced teeth and having a second set of circumferentially spaced valleys which alternate with the second teeth, said hub being telescoped into said hole with the teeth of each set being disposed within and spaced from the valleys of the other set, at least the teeth of one set and the valleys of the other set being flared outwardly in the forward direction, an annulus of elastomeric material disposed within said hole between said hub and the periphery of the hole and having alternating teeth and valleys interfitting with the teeth and valleys on the hub and in said hole, the cross section of said annulus being sized so that the annulus is pre-compressed between the hub and the hole at all points around the periphery of the annulus by forcing the hub inwardly, and means forcing and holding said hub inwardly to pre-compress said annulus and hold the entire annulus in a state of residual compressive stress when torque is applied and transmitted through the annulus between the mounting plate and the armature.