Patent ID: 7703790

Claim:
An anti-jackknifing system comprising: a tractor; a trailer; a fifth wheel coupler that connects the tractor to the trailer to form a tractor-trailer combination, the fifth wheel coupler including a downwardly extending kingpin mounted to the trailer and a fifth wheel plate mounted to the tractor, the fifth wheel plate rotatably receiving and affixing the kingpin to allow the trailer to rotate horizontally about the kingpin; one or more race plates affixed to the underside of the trailer the race plates each comprising a partially circular slot positioned concentrically to the kingpin; one or more pins mounted to the tractor and positioned to extend into and retract out from the partially circular slot in a corresponding one of the one or more race plates, rotation of the tractor relative to the trailer being restricted when the one or more pins are extended into their corresponding one or more race plate slots; one or more pneumatic or hydraulic pressure vessels that cause extension of the one or more pins into the one or more race slots when a pressure in the one or more pressure vessels is increased and retraction of the one or more pins out from out from the one or more race plate slots when the pressure in the one or more pressure vessels is decreased; a speed sensor that senses a current speed of the tractor-trailer combination; and a controller that receives speed data produced by the speed sensor, the controller providing a signal to the one or more pressure vessels that causes the pressure in the one or more pressure vessels to increase and thereby cause extension of the one or more pins into the one or more race slots when the speed data indicate that the current speed has exceeded a first threshold speed for a first predetermined period of time, the controller causing the pressure in the pressure vessel to decrease when the speed data indicate that the current speed has failed to exceed a second threshold speed for a second predetermined period of time, the second threshold speed being lower than the first threshold speed.