Load sensing proportioning valve for brake system

In combination with the hydraulic brake system of a vehicle having a master cylinder operatively associated with a brake pedal for supplying pressurized hydraulic fluid to rear wheel brakes through independent pressure lines, means regulating braking pressure supplied to the rear wheel brakes of the vehicle proportional to the weight supported by the rear wheels to reduce or eliminate premature rear wheel locking when applying the brakes on a lightly loaded vehicle and to maintain adequate breaking force for the same vehicle heavily loaded, said means comprising a pair of load sensing devices with a load sensing device interposed between the rear suspension system for each rear wheel and each side of the vehicle frame, each load sensing device providing a supply of incompressible fluid at a pressure proportional to the weight supported by the load sensing device, a load proportioning valve in each independent pressure line between the master cylinder and each rear wheel brake, each proportioning valve including an actuating means, means communicating the supply of pressurized incompressible fluid provided by the load sensing device at one side of the frame to the actuating means included in the proportioning valve in the pressure line to the rear wheel brake at the same side of the frame, said actuating means being responsive to incompressible fluid pressure for regulating the movement of each proportioning valve to independently vary the braking pressure supplied to the respective rear wheel brakes, thereby independently varying the braking torque exerted on each of the rear wheels in response to variation in load on each of the rear wheels.