Proportional brake lining wear sensor

Claim 1

In a brake: a member to be braked connected to an electrical ground; a friction member having a lining for engagement with said member to be braked and a support carrying said lining; probe means carried by said friction member and including an electrically conductive material having a relatively high resistivity carried in said lining and extending therethrough continuously from the edge of the lining engaging the member to be braked toward said support, the transverse cross-sectional area of said resistance material intermediate the edges of said lining being non-uniform, and a conductor carried by said support and electrically connected to said conductive material, said conductive material defining a circuit path between said conductor and the member to be braked, whereby the resistance of the circuit path between said terminal and the member to be braked during engagement of said lining with the latter will decrease as said material is worn away as the lining wears, said conductor projecting into said electrically conductive material so that the end of the conductor will engage said member to be braked when said lining is worn a predetermined amount, the transverse cross-sectional area of the resistance material tapering from a maximum cross-sectional area at the edge of the lining adapted to engage the member to be braked to a minimum cross-sectional area at the end of said conductor; a warning device; and circuit means for applying a voltage across said probe when the lining is engaged with the member to be braked and actuating said warning device when the voltage drop across said probe drops below a predetermined level.