Anti-jackknife device for tractor-trailer combination

Abstract

The anti-jackknife device is installable on a tractor-trailer combination in which the tractor and trailer are detachably connected by a fifth wheel assemblage without any modification in the fifth wheel assemblage. The device includes a stop lug mounted on the underside of the trailer in fixed lateral and endwise position relative thereto, but for movement upwardly and downwardly into and out of engagement, respectively, with a limit stop mounted in fixed position on the tractor. When the lug and stop are interengaged, they permit free relative rotation of the tractor and trailer about the turning axis of the fifth wheel within certain limits extending a few degrees in each direction beyond a median position wherein the tractor and trailer are aligned for straight line travel. The lug and limit stop are spaced a material distance from the fifth wheel and from the turning axis so that the fifth wheel structure, its mounting, and the frame of the tractor are relieved from resisting severe turning moments tending to rotate the tractor and trailer beyond the turning limits imposed by the lug and limit stop and, instead, are subjected to shearing stresses directed generally laterally of the turning axis. The stop lug may be movable downwardly and upwardly by reversible fluid pressure operated motors to which the fluid pressure is supplied from the tractor. The supply is controlled remotely from the cab of the tractor so that the lug and stop can be moved to inoperative position when necessary for effecting sharp turns and for maneuvering in spaces of close clearance.