Master cylinder assemblies for vehicle hydraulic braking systems

Claim 1

In an anti-skid braking system for a vehicle comprising brakes on wheels of the vehicle, a source of booster fluid under pressure, a first reservoir for fluid for said source, a master cylinder assembly responsive to said source of booster fluid to apply said brakes, and skid sensing means for providing a signal when at least one of said wheels skids during application of said brake on that wheel, said master cylinder assembly comprising a housing, a booster valve assembly for controlling flow of fluid from said source to a booster chamber in said housing, at least two master cylinder pistons working in separate first bores in said housing to generate hydraulic fluid pressure in pressure spaces for connection to said wheel brakes and defined in said bores ahead of said pistons, normally open valves controlling communication between said pressure spaces and at least one second reservoir, said valves being closed when said master cylinder pistons are advanced in said bores, modulator pistons corresponding in number to said master cylinder pistons working in separate second bores in said housing, means for applying from each modulator piston an operating force to the one master cylinder piston with which it corresponds to advance the said one master cylinder piston in said first bore, valve housings corresponding in number to said master cylinder pistons and each having ports connected respectively to said booster chamber, said modulator piston and the reservoir for said source of fluid pressure, a solenoid operated valve in each of said housings normally occupying a first position connecting the booster chamber port and modulator port while disconnecting the latter and said reservoir port but being movable to a second position disconnecting said booster chamber port and said modulator port while connecting the latter and said reservoir port, and means for actuating said solenoid operated valve to move it from its first normal position to its second position to reduce the force on said modulating piston by relieving the pressure fluid acting thereon to the reservoir for said source of fluid pressure in response to a signal from said skid sensing means when a wheel on which the brake is being applied through said modulator piston skids.