US Patent 7651113 Compact fifth wheel locking mechanism

In a fifth wheel hitch, a locking mechanism for retaining a trailer kingpin within a fifth wheel slot. The locking mechanism includes a jaw assembly comprised of a cam arm pivotally attached at one end to the underside of the hitch plate, a bumper arm pivotally attached by one of its ends to the cam arm, a sliding jaw with a recess for receiving the kingpin shank, and a secondary lock member, pivotally attached at a point intermediate its two ends to the rear portion of the cam arm. The locking mechanism also includes a main spring to pull the free end of the cam arm toward a closed position. A release rod is coupled at one end to secondary lock member at an attachment point that is disposed away from the lock member's axis.