GB1162191A - Improvements in and relating to Vehicle Braking Mechanisms - Google Patents

Abstract

1,162,191. Locking fluid-pressure operated brakes. AUTOMOTIVE PRODUCTS CO. Ltd. 15 Feb., 1968 [20 Dec., 1966], No. 57011/66. Headings F2E and F2F. In a locking means for holding in the applied position, for parking purposes, a power-applied brake on a vehicle, an abutment pin 18 is carried by a brake-applying push rod 13 moved longitudinally by an air-operated actuator 14 and stop means in the form of a pair of cams 25, pivoted at 24 about an axis normal to the axis of movement of the push rod 13, is provided such that the abutment pin 18 co-operates with the cams to hold the brakes in the applied position. Fig. 1 shows the mechanism in the " brakes off " position in which the push rod 13 is at the limit of its travel in a rightward direction and the abutment pin 18 is engaged by steps 26 on the cams 25. When the brakes are applied by operating a control valve (not shown) to energize the actuator 14 the abutment pin 18 moves with the push rod 13 to the left until it is clear of the steps 26 to bring the cam edges 27 into position behind the abutment pin to prevent the latter from returning (as shown in Fig. 2). The control valve can then be moved to a position in which the actuator 14 is deenergized leaving the brakes applied. To release the brake, the control valve is first moved to a position in which the actuator is again energized to release the load on the cams and fluid pressure is applied simultaneously to a fluid pressure cylinder 32 mounted on a housing 15 so that a piston 33 is moved downwardly against the action of a spring 34 and move the cams 25 to the position shown in Fig. 1 so that the push rod returns to its inoperative position. The control valve is then returned to its initial position thus releasing pressure from the cylinder 32 and leaving the cams 25 free to rotate to their operative position when the brake is again applied. The release of the locking means, instead of being effected by fluid pressure, can be effected by mechanical or electrical means which may be controlled so as to work in association with the control valve controlling the supply of air to the actuator 14. The cams 25 are pivotally mounted on a carrier member 19 which is itself pivotally mounted at 21, about an axis parallel to the cam axis 24, on a fixed structure formed by a pair of parallel plate members 17 lying one on each side of the push rod 13 and rigidly mounted in the housing 15. The carrier member is held resiliently against a pair of coaxial stop pins 22 mounted one on each plate member 17 to prevent the movement of the carrier member about its pivot in one direction and the positions of the abutment and the pivot axes of the cams and carrier member are such that thrust applied to the cams by the abutment pin 18 when the brakes are applied acts on a line passing a short distance to one side of the pivot axis of the carrier member 19 and tends to urge the carrier member against the stop pins 22.