Automatic slack adjusters for vehicle brake linkages

Claim 1

An automatic slack adjuster for a vehicle brake applying linkage of the type comprising a shaft mounted for rotation about its longitudinal axis for applying or releasing the brake, and a housing which constitutes a lever in the linkage and is mounted for rocking movement about said axis of said shaft and with respect to a relatively stationary part, wherein said adjuster comprises a worm wheel mounted on and secured against rotation relative to said shaft, a worm mounted in said housing and meshing with said worm wheel to transmit angular movement of said lever to said shaft, and automatic worm driving means for rotating said worm with respect to said housing to compensate for slack in said linkage in response to relative movement between said lever and said relatively stationary part, said automatic worm driving means incorporating a connection having a degree of lost-motion equivalent to a desired braking clearance, said connection including a clutch of the multi-plate type comprising a plurality of primary clutch plates coupled to said worm a plurality of secondary clutch plates interposed alternately between said primary clutch plates and resilient means for urging said second clutch plates normally into driving engagement with said first clutch plates, and a linearly slidable pawl acting between said second clutch plates and said stationary part to effect rotation of said secondary clutch plates after relative movement between said lever and said stationary part has exceeded a value equivalent to said degree of lost-motion, each secondary plate being provided with a tooth, and said pawl being provided with a notch in which all said teeth are received, said notch being of greater length than the circumferential length of said tooth to define said lost-motion.