GB1354108A - Brake supervisory arrangements - Google Patents

Abstract

1354108 Brake abnormal conditions; indicating BENDIX WESTINGHOUSE Ltd 23 Sept 1971 [1 Oct 1970] 46704/70 Heading F2E Abnormal movement of a brake part, e.g. due to wear or deformation of another part, or abnormal wear of, e.g. a lining or pad of a drum or disc brake serves to vary the pressure in a volume of fluid, and apparatus responsive to such pressure variation indicates it, and thus indicates the abnormal movement or wear giving rise to it. As shown in Fig. 1, an internal shoe drum brake 20 is operated through linkage 12 by an actuator 10 including a diaphragm (not shown) bearing on a follower 11. When the normal limit of travel of the follower is exceeded as a result of wear of the rigging 12 or of the brake lining 22, the follower operates a valve 13 which vents a conduit 14 fed by an auxiliary supply of compressed air at 16, 17, 15. Such venting is made evident by the rise of an indicator located in the top of a device 15, described in more detail below. On release of the brake, pressure conditions in conduit 14 are restored and the indicator is found to be capable of being reset. Alternatively or additionally, conduit 14 may communicate at 19 with a blind hole 23 in brake lining 22, so that on predetermined wear of the lining, the hole is exposed to atmosphere, thereby venting conduit 14. In this case, conditions in conduit 14 cannot be restored on brake release, so the indicator remains up and cannot be reset. A manually-operable valve 18 is provided to test the working of the apparatus. Fig. 3 shows the device 15. Compressed air is supplied at 45 and leaks through a restricted conduit 43 in a piston 42 to an exhaust port 44 connected to conduit 14 (normally closed). Pressures above and below the piston become equalized, and the piston, together with its rod 46 and an indicator member 47 resting on it, sinks. When conduit 14 is vented, restricted conduit 43 is insufficient to maintain the pressures equalized, so the assembly 42, 46, 47 is raised. In the circumstance where this assembly remains raised, a resilient seating 51 serves to cut off conduit 43 (and hence conduit 14) to prevent continued loss of fluid. The indication may be enhanced by making surface 50 of member 47 opaque and the underside transparent, so that in the raised position of member 47, light from a bulb 48 in circuit with the brake stop light passes upwards through it. Alternatively the member 47 may be fluorescent. Re-setting of member 47 may be effected by a return spring instead of manually. The device 15 may be replaced by a low pressure switch operating an indicator lamp. A permanent time record may be associated with the indicator.