Anti-lock brake system for vehicle

Claim 1

In an anti-lock system for a vehicle having a first valve arranged in a brake fluid pressure transmission line from a master cylinder to each brake device to operate under an anti-lock control signal, a second valve arranged to open for reducing the brake fluid pressure, a pressure fluid return device arranged to bring the brake pressure fluid into an accumulator for returning the pressure fluid to the upstream side of said first valve and a gate valve arranged in between said first valve and said master cylinder, an improvement characterized in that: said gate valve (2) is provided with an axial extending balance piston (12) which is arranged to receive at one end in the axial direction thereof said pressure fluid brought into said accumulator (8) and to receive said pressure fluid of said brake device (W/C) at the other end; said gate valve including a shut-off valve device (13, 14) arranged at an axially intermediate portion of said balance piston between the ends thereof to close a passage between said master cylinder (M/C) and said first valve (3) according to the movement of said balance piston, the balance piston including therein a one-way valve communicating with the other end thereof which permits the flow of the pressure oil from the brake device to the master cylinder but blocks the flow of the pressure oil from the master cylinder to the brake device.