Patent ID: 7794025

Claim:
A braking system including a brake actuator which is moveable by pressurised hydraulic fluid fed to the actuator along a transmission line, in a first direction, to move a brake applying member to apply a braking force to a member to be braked, a master valve including an operating piston which upon operation of a brake operating member, moves in an operating cylinder, to direct the hydraulic fluid under pressure to the transmission line to apply the brake, the system further including a charging valve, the charging valve being operable when activated, to deliver a predetermined volume of pressurised hydraulic fluid to an inlet of the master valve, and hence to the transmission line, so as to move the brake applying member in the first direction towards the member to be braked to reduce the clearance between them, and the operating piston, when the charging valve is deactivated, being moveable in the operating cylinder to allow hydraulic fluid to pass from the transmission line thus to permit the brake actuator to move in a second direction opposite to the first direction to increase the running clearance between the brake applying member and the member to be braked and which includes a source of pressurised hydraulic fluid, the charging valve when activated, permitting the pressurised hydraulic fluid from the source to move a charging piston from an initial position in a charging cylinder, to displace hydraulic fluid which is directed to the master valve, and when deactivated, the charging valve connecting the charging cylinder to a low pressure area to permit the charging piston to return to the initial position.