Electromagnetic friction clutch with overload release

Abstract

An electromagnetically operated friction clutch is disclosed of the type including an axially movable armature member which is drawn into frictional driving engagement with a friction surface on an inner body to establish drive through the clutch, in which a torque overload deenergization of the electromagnetic coil is provided. The clutch is provided with a torque boosting arrangement in which the drive from the axially movable armature is transmitted through a series of balls disposed in corresponding pockets formed in a radial face of the armature and an opposing radial face of a clutch element drivingly connected to one of the primary clutch members. The action of the balls in the pockets creates a torque boosting effect increasing the engagement pressure exerted on the frictional engagement surfaces. The torque overload release arrangement includes mounting of the clutch element axially and rotationally so as to be restrained by means of a spring element. The axial movement of the clutch element against the spring bias in response to the transmission of a particular level of torque is employed to sense a torque overload condition, and by positioning a microswitch activated by a predetermined extent of axial movement of the clutch element, the electromagnetic coil is deenergized at a predetermined torque level. The clutch may be reenergized at high speed by a manual switch reenergizing the coil relay which draws the friction surfaces into engagement.