| 摘要 |
A braking system 20 including a brake actuator 32 which is moveable by pressurised hydraulic fluid in a first direction A, against a restoring force, to move a brake applying member 27 to apply a braking force to a member 26 to be braked, a master valve 22, including a piston assembly 40 which upon operation of a brake operating member 18, directs the hydraulic fluid under pressure to the brake actuator 32 to apply the brake, the system 20 further including a source of pressurised hydraulic fluid 71, 75, and a charging valve 70 which is operable in first and second states, the piston assembly 40 of the master valve including a pair of coupled pistons 41, 44, and a chamber 55 between the pair of pistons 41, 44, the charging valve 70 when operated in a first state communicating the source of pressurised hydraulic fluid 71, 75 to the chamber 55 between the pair of pistons 41, 44 of the master valve 22, the coupling of the pistons 41, 44 permitting the pistons 41, 44 of the pair to move apart in response, up to a maximum distance thereby to direct up to a predetermined volume of hydraulic fluid to the brake actuator 32, to move the brake applying member 27 in the first direction A towards the member to be braked 26 to reduce a running clearance between them, and the charging valve 70 when operated in the second state, communicating the chamber 55 to a lower pressure area 63 to allow the pair of pistons 41, 44 to be moved towards one another, and thus to permit the brake actuator 32 to move in a second direction opposite to the first direction A to increase the running clearance between the brake applying member 27 and the member 26 to be braked. <IMAGE>
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