Piston cylinder air brake for railway vehicle - has compressed air driven parking brake piston and spring-mounted secondary piston with common piston rod(BR 21.7.81)

摘要

The brake-actuating mechanism is used on railway vehicles, combining the functions of service and parking brakes. The service brake uses compressed air to drive a piston (1) and displace threaded rod (2). The parking brake uses springs (5) to drive a second piston (3) once retentive air pressure (F1) has abated. The two pistons (1, 3) drive the same rod (2), with the latter piston (3) being sited so that it prevents air leakage between cylinders (C1, C2). The piston forces may be transferred to the rod threaded by stop bearing (12) mounted on a screw (11), with a spring (10) effecting piston (1) recoil (F4). Manual disarming of the piston (3) may be effected by using a finger ring (9) to withdraw a pawl (7), thus permitting rotation of a ratchet wheel (8) to which the screw is keyed.