PARK BRAKE FOR A DISC BRAKE SYSTEM AND DISC BRAKE SYSTEM INCORPORATING SAME

摘要

A park brake (14) is incorporated into a housing (10) of a disc brake system (12). The housing (10) is in the form of an annular ring having a plurality of cavities (16) for housing service brake pistons which act on brake pads (18) to selectively force the brake pads (18) onto a brake disc to produce a surface brake effect. The park brake (14) includes an actuator (23) supported by the housing (10) which is switchable between an applied state where it forces the brake pad (18) into contact with the brake disc of the system (10) independent of the action of the service brake pistons to produce a park brake effect, and a released state where the actuator (23) allows the brake pad (18) to become disengaged from the brake disc. The actuator (23) includes a hydraulically operated park brake piston (27) having a rod (24) extending therefrom. The rod (24) is slidably retained within a hole (26) formed in the housing (10) and is arranged to abut or otherwise apply force to the brake pad (18). When fluid pressure is applied to the pad brake piston (27) it retracts the rod (27) into the housing (10) releasing the park brake (14). In the absences of the application of fluid pressure, a spring (34) of the actuator (23) operates to switch the actuator (23) to an applied state where the rod (24) pushes on the pad (18) forcing it into contact with the brake disc thereby providing the park brake effect.