Eccentric pivot arm tensioner

Abstract

An eccentric pivot arm tensioner capable of automatic belt tensioning and substantially simultaneous operating range indexing during installation. The tensioner comprises a stop plate and cooperating lock plate. The tensioner comprises a pivot arm having a pivot arm member that cooperatively engages a base plate member. In a first, or transit mode, the pivot arm member temporarily engages the base plate member to put a torsion spring and thereby the pivot arm in a preloaded condition. The lock plate is engaged with the stop plate. As a mounting fastener is engaged into a mounting surface the pivot arm member is automatically disengaged from the base plate member by an axial movement of the pivot arm, thereby allowing the pivot arm to rotate and thereby impart a torsion spring force to a belt, i.e., tensioning the belt in an operating position. During the initial movement the lock plate remains engaged with the stop plate thereby causing the lock plate to rotate with the pivot arm, which automatically and properly indexes the pivot arm movement travel stop members with respect to the lock plate, thereby automatically setting a working range. As the fastener is then fully torqued down, the lock plate is fully disengaged from the pivot arm and yet fixed in position to allow full operation of the pivot arm in the operating range.