AUTOMATIC ADJUSTER FOR A VEHICLE BRAKE AOTUATOR

摘要

An automatic adjuster for a vehicle brake actuator has a non-rotatable brake shoe-engaging tappet, an adjuster member having a threaded shank threadedly engaged with a nut, the adjuster member co-acting with the tappet so that said rotation of the adjuster member causes axial movement of the tappet. The adjuster member is drivingly coupled by a coupling member to a shaft having an external reversible thread and a spring acting between the tappet and shaft urges the tappet against the shoe. A clutch ring has an internal reversible thread whereby it engages the corresponding thread on the shaft and is resiliently urged towards a fixed clutch face. The clutch ring controls rotation of the adjuster member during brake actuation and release to adjust the retracted position of the tappet to compensate for wear of the brake shoe. The force provided by the spring is relieved upon brake actuation, during which adjustment occurs, so that torque applied through the clutch ring is reduced with a consequent reduction in wear of the ring.