GB1267518A - Improvements in or relating to devices for indicating the operating condition of brakes - Google Patents

Abstract

1,267,518. Indicating brake wear. SELF ENERGISING DISC BRAKES Ltd. 4 Nov., 1969 [6 Nov., 1968], No. 52665/68. Heading F2E. A device for indicating the operating condition of a vehicle brake; said device including, or consisting of, a first indicator electrically connectible to a first switching element, a second indicator electrically connectible to a second switching element, the first and second switching elements each being settable into a first state where electrical conduction therethrough is prevented or a second state where electrical conduction therethrough is permitted, each element being normally in its first state, and means for supplying electrical power only when the vehicle brake is operated, said means being connectible to the indicators and associated switching elements so as to be capable of energizing either of said indicators whenever its associated switching element is in its second state; wherein the first switching element is disposed in co-operable relationship with the brake so that it is set to its second state when brake adjustment is required and the second switching element is disposed in co-operable relationship with the brake so that it is set to its second state when excessive brake wear has occurred. In the example shown in Fig. 1, indicators 21-24, which may be lamps, movable arms carrying flags or devices giving an audible or both audible and visual signals, are mounted on a panel disposed in the driving cab of a vehicle, one terminal of each lamp being connected to the stop light S of a trailer and the other terminal of each lamp being connected to two-state switching elements 29-31 of the make-andbreak type and operatively associated with the brakes of the trailer. When the brake pedal is depressed an indication of the state of the brakes of the trailer is given. The circuit may have incorporated therein means for testing the indicators. In Fig. 3, the switching element comprises a stem 40 of electrically conductive material disposed in a brake shoe 42, the head of the stem being coated with a film 46 of insulating material; when the lining 44 and consequently the film have worn away the stem 40 is brought into contact with the brake drum to energize the associated lamp. In modifications, switching contacts are mounted on an axle housing and a cam-shaft, the latter being pivoted to apply the brakes associated with the axle and the contacts engaging when pivotal movement of the cam-shaft is large enough to indicate excessive brake wear, (b) the push rod of a pneumatic diaphragm for applying the brakes carries a contact which is engageable with a contact on an axle housing, and (c) a limit or micro-switch is mounted within a pneumatic diaphragm housing.