| 摘要 |
A fluid pressure operated disc brake having one brake disc affixed to the housing of a brake cylinder unit and the other disc affixed to a service brake piston of the brake cylinder unit, which further includes an auxiliary brake piston between the service brake piston and cylinder head, thereby forming on opposite sides thereof a service brake actuating chamber and an auxiliary brake actuating chamber to which fluid pressure may be admitted via separate service and parking brake valve devices. A filling piece disposed between the brake cylinder housing and auxiliary piston is operatively connected with an actuating cylinder to which the parking brake valve also supplies auxiliary brake pressure to operate the filling piece following an auxiliary brake application, thereby mechanically locking-up the brake discs in the brake application condition to provide a parking brake. In the several embodiments of the invention, the filling piece takes the form of a ring member having an inclined surface that interacts with an inclined surface of the auxiliary piston upon actuation of the ring member, a cam acting against the auxiliary piston, and a ball or roller acting between inclined facing surfaces of the brake cylinder housing and auxiliary piston. Means associated with the filling piece and/or actuating cylinder permit unlimited adjustment of the filling piece in a direction to lock-up the brake discs in brake application position, but only allow limited retraction of the filling piece adjustment when releasing the parking brake to maintain a predetermined brake piston clearance irrespective of brake shoe wear. |
