Abstract: An accessory apparatus for uncoupling a king pin of a trailer from a locking device on a fifth wheel. The accessory apparatus includes a power device such as a pneumatic cylinder suspended from the bottom surface of the fifth wheel plate to form a fifth wheel assembly. A cam is mounted on the end of the power device's actuating member. The cam and actuating member are symmetric. A coil spring is held within the power device's housing, and is also symmetric with the longitudinal axes of the cam and actuating member. No external guides or springs are needed. The power device may be energized from a remote location to propel the cam to contact and propel a follower on an operating rod to unlock the fifth wheel jaw to release the king pin.