Dual system hydraulic braking apparatus for vehicle

Claim 1

In a dual hydraulic braking system for use in a vehicle: a pair of braking systems; a pair of hydraulic accumulators, one for each system; a hydraulic pump for supplying hydraulic fluid to said systems; and valve means comprising: a valve body having a cylinder bore; means for closing the opposite ends of said bore; a piston slideably mounted in said bore and cooperating with said bore to define a pair of chambers, each chamber being located between a closed end of the bore and an adjacent end of said piston; means for biasing said piston to a central position in said bore; a pair of first passages, each first passage communicating between said hydraulic pump and one of said chambers; a pair of check valves disposed in said valve body, each check valve being located in one of said first passages to prevent hydraulic fluid flow from a chamber to said hydraulic pump; a pair of second passages, each second passage communicating between one of said chambers and one of said hydraulic accumulators; a pair of third passages including a port located in the means for closing an end of said cylinder bore, each said port being surrounded by a valve seat, each third passage communicating between one of said chambers and one of said braking systems; and means on the opposite ends of said piston to close the third passage adjacent an end of said piston to prevent fluid flow therethrough when said piston is moved in either direction from its central position, each of said accumulators being connected to one of said third passages downstream of said valve seats through a respective transverse passage formed integrally in said valve body, and the means on a respective end of said piston engaging one of said valve seats to effect closure of a third passage.