Abstract: In an anti-jackknifing apparatus for a semitrailer rig, upon coupling of a semitrailer to a tractor by insertion of a king pin and a wedge on the trailer into a fifth wheel of the tractor, a pin connected to the wedge traverses a guideway to execute therealong a movement limited and attenuated by double-action hydraulic cylinders connected to hydraulic valve group in turn electrically tied to a control unit. At the guideway, limit switches are provided for setting for each direction of angular motion a predetermined maximum jackknifing angle dependent on vehicle construction. The attenuation of rotary movement between the tractor and the semitrailer is implemented by throttle valves as a function of vehicle speed as measured by a speedometer and as a function of brake pressure as measured by two pressure switches.

Abstract: The invention relates to an apparatus for preventing jackknifing and for improving the lateral travelling stability under critical road and travelling conditions, in connection with semitrailers, articulated buses or vehicles with a towed vehicle part, which comprises a supporting device interconnecting the two vehicle parts pivotably coupled together by means of a pivot joint and a flow limiting device, which prevents an oversteering and uncontrolled swinging of the rear vehicle part of an articulated vehicle comprising two vehicle parts interconnected by a pivot joint, in order to increase the security against jackknifing and the lateral travelling stability of such vehicles.