GB1228765A - - Google Patents

Abstract

1,228,765. Lock actuators for brakes. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. 10 July, 1968 [14 July, 1967], No. 32532/67. Headings F2E and F2F. A lock actuator includes a pressure-responsive member, a first member movable on operation of the pressure-responsive member to a "brakeapplied" position, a plurality of wedging elements wedgeable between the first member and a second member in the brake-applied position to lock the first member against movement to a "brake release" position, and means to displace the second member relative to the first member to release the wedging elements to unlock the first member. The first member may be a brake-operating member. As shown in Fig. 2b, a brake-operating rod 7 is moved to the right by either a "service" diaphragm or an "emergency-parking" diaphragm (not shown) for brake application. For service operation, a further fluid pressure is applied to the left of a piston 13, whereby rollers 14 are forced, against the pressure of a spring 15, away from wedging (locking) contact between a surface 17 of an annulus 18 and the brake-operating rod 7. For emergency-parking operation, fluid pressure is relieved to the left of piston 13. In this situation, rightward movement of rod 7 for brake application is permitted, but leftward movement is prevented by the wedging action of the rollers. Before the brakes can be released, the further fluid pressure must be re-applied to piston 13. Mechanical unlocking.-Means are provided for unlocking the mechanism mechanically in the event of failure of the further fluid pressure. The annulus 18 is prevented from rotating relative to the fixed parts of the mechanism by a pin 39, but may be moved axially. A rotatable ring 20 surrounding annulus 18 has a three-start screw thread 37, Fig. 2a, engaging a thread formed on the outer periphery 38 of annulus 18. Normally, ring 20 and annulus 18 are aligned as shown in Fig. 2b. For unlocking, ring 20 is rotated by rotating a bolt 32 having a worm and wheel connection 31, 30, with ring 20, whereby annulus 18 is moved to the left, Fig. 2b, releasing rollers 14 from wedging engagement. In Fig. 3, instead of rollers a multi-split collet 58 is urged leftwards into wedging engagement by a spring 15, the surface 17 this time being provided on a rotatable core 59. Collet 58 has a piston portion 60 co-operating with a chamber 62 supplied with fluid from port 12 via conduit 11. Core 59 has a multistart thread 66 which engages an associated thread on fixed housing 1, the housing having a slot 64 through which access may be gained to a series of holes 65 in core 59. Fluid pressure unlocking is effected by supply of fluid pressure to chamber 62. Mechanical unlocking.-A tommy-bar or the like is inserted through slot 64 into one of holes 65 and core 59 is rotated manually. Core 59 is thereby moved to the left, while leftward movement of collet 58 is limited by engagement of stop portion 41 with an adjacent part of the housing.