Brake lining wear indicator giving early and final warning - uses inverted U=shaped piece with electric connections to each side to signal contact with brake drum and when U=section piece wears through

摘要

The indicator has a sensor placed in a hole perpendicular to the friction surface of the brake shoe or pad at a height marginally above the minimum allowable lining thickness. Two stages of warning are provided: the first where the sensor comes into contact with the brake drum or disc, and the second where the sensor itself has worn down by a preset amount. Beneath a protective plastic cover, an inverted 'U' shaped metal element is connected to flexible braid electric cables at either end of the 'U'. The cables are carried away through an insulated support which is set in the hole in the friction material. A transistor circuit detects the contact of the 'U' shaped piece with the brake drum and gives a visual signal. Further wear on the 'U' piece leads to its breaking and opening the electric circuit between the two cables. This condition is detected by the same transistor circuit and another warning signal given.