Hydraulic control valve assemblies for vehicle anti-skid braking systems

Claim 1

An hydraulic control valve assembly for a vehicle anti-skid braking system, comprising a housing having a first inlet port for connection to power steering pump, a first outlet port for connection to power steering means and communicating with the first inlet port, a second inlet port for connection to brake pressure generating means, a second outlet port for connection to at least one brake for a wheel, and a bore, a modulator piston working in said bore in said housing for modulating the supply of hydraulic fluid from said second inlet port to said second outlet port, said modulator piston being movable between a first inoperative position in which substantially unrestricted communication between said second inlet port and said second outlet port is permitted and a second operative position in which at least communication between said second inlet port and said second outlet port is cut-off, resilient means normally urging said modulator piston into said first position, and anti-skid valve means operative in response to a skid control signal to subject said piston to a net hydraulic pressure in a direction opposite to said resilient means and of a mangitude sufficient to urge said modulator piston into the said operative position against the force of said resilient means when the deceleration of the braked wheel exceeds a predetermined value, wherein said housing is provided with a third additional outlet port for direct communication to a reservoir for fluid and said anti-skid valve means normally places opposite faces of said modulator piston in communication with said third outlet port, said anti-skid valve means being operative in response to said skid control signal to isolate said opposite faces of the modulator piston from each other and subsequently place the one face opposite to said resilient means in communication with said first inlet port whereby said modulator piston is moved into the said operative position.