Abstract: A manually actuable release arm of a fifth wheel coupling is engagable with a plate in a first position wherein the locking member is retracted to allow release (or entry) of a king pin and in a second position wherein the member is projected to hold a locking jaw in its king pin locking position. This may be accomplished by respective engagement of detents in the release arm with the edge of an aperture in the plate flange. To assist release of the king pin, a piston of a fluid actuable piston and cylinder arrangement (38, 39) is connected to the release arm and can be operated to move the release arm against the bias of spring to its first (release) position. In this respect, a plunger on the release arm may be used to actuate a switch which operates the piston.

Abstract: A vehicle coupling device is disclosed that includes a coupling plate provided with a slot for reception of a waisted portion of a king-pin of a trailer, a pivotally mounted coupler jaw for holding the king-pin in the slot and a locking bar for locking the coupler jaw in its closed position. The coupler jaw includes a sensor arm extending in a different (lower) plane to a hook. The arm, in use, is contacted by a lower flange of a correctly aligned king-pin, and causes the jaw to pivot so that the hook engages the waist of the king-pin. By this dual alignment of hook and arm, there is achieved a failsafe means of preventing a king-pin, which enters the slot at the wrong height, from causing actuation of the jaw and the lock bar.