CONTROLLER FOR HYDRAULIC BRAKE SYSTEM

An arrangement for controlling the supply of pressurized hydraulic fluid from a master cylinder and from a pressure source into hydraulic circuits leading to wheel brake actuating cylinders includes a valve device including a control piston acted upon by a spring-loaded auxiliary piston in one direction and by the pressure in a return conduit in the opposite direction. Upon brake pedal depression, hydraulic fluid pressure from the pressure source acts on the auxiliary piston in opposition to the spring force so that the auxiliary piston ceases to act on the control piston. Then, as hydraulic fluid is discharged from the brake actuating cylinders during antiskid control action, pressure builds up in the return conduit and propagates to the control piston to move the same into its open position in which it admits pressurized fluid from the pressure source to check valves which are acted upon in opposition to their opening by the tandem master cylinder pressures. Hence, any fluid discharged during the antiskid control operation is replenished through the check valves from the pressure source, rather than from the master cylinder.