Amplifying clutch with radially contractible shoe

Claim 1

A clutch comprising rotatably mounted input and output members, said input member having a hub and having a flange projecting radially from said hub, a rotatably mounted first shoe supported to move axially relative to said input and output members and to turn angularly through a limited distance relative to said output member, coacting friction surfaces on said flange and said first shoe, said friction surfaces engaging one another and causing said first shoe to turn with said input member and through said limited distance relative to said output member when said first shoe is moved axially toward the flange of said input member, said friction surfaces effectively releasing one another and enabling said input member to turn relative to said first shoe when said first shoe is moved axially away from the flange of said input member, and selectively operable means for causing said first shoe to move axially toward and away from the flange of said input member, said clutch being characterized by a second shoe comprising a series of segments spaced angularly around the hub of said input member, a series of angularly spaced lugs rigid with said output member and located between said segments, said lugs circumferentially engaging said segments to couple said segments for rotation with said output member and also supporting said segments to slide radially toward and away from the hub of said input member, said segments radially and frictionally gripping the hub of said input member and turning with said input member when said segments are moved radially toward said hub, said segments effectively releasing said hub and enabling said input member to turn relative to said segments when said segments are moved radially away from said hub, and a helical spring telescoped over said segments and having ends connected to said first shoe and to said output member, said spring wrapping down on said segments and causing said segments to radially and frictionally grip the hub of said input member in response to said first shoe turning through said limited distance, said segments being free of radial frictional engagement with said output member at all times so that the only transmission of torque between said segments and said output member is effected by virtue of the circumferential engagement of said segments with said lugs.