Torque-limiting devices

Claim 1

A torque-limiting device comprising a rotatable drive input member in the form of a hollow sleeve of substantially uniform inner diameter from end to end having means for connecting it to a driving shaft, an output member mounted by bearing means upon and coaxially with said sleeve, a third member coaxially mounted on said sleeve by means that constrains said third and input members to rotate together but provides for axial sliding of said third member along said sleeve, a cage disposed between adjacent axially facing surfaces of said third and output members for retaining a plurality of circumferentially spaced balls, said surfaces being formed with recesses wherein said balls are engageable, resilient means in the form of a coil spring surrounding said sleeve and disposed between said sleeve and said third member for biasing said third member toward said output member whereby to maintain said balls engaged in said recesses during torque transmission through the device, means providing a thrust bearing axially between said output member and said sleeve, said balls being adapted to move out of said recesses to become disposed between non-recessed areas of said surfaces to displace said third member against the force of said spring when the transmitted torque exceeds a predetermined value, and means for holding said third member in displaced position comprising radially open recess means on said sleeve and radially spring biased detent means on said third member for entering said recess means upon predetermined displacement of said third member away from said output member.