A BRAKE ACTUATOR HAVING AN AUTOMATIC BRAKE ADJUSTER

1,253,489. Brake slack adjuster. GOODYEAR TIRE & RUBBER CO. 23 June, 1970, No. 30438/70. Heading F2E. A brake actuator comprises a cylinder 2 having a piston 10 slidable therein, the piston being formed with a threaded portion 15 for co-operation with a resilient thread engaging means 23. Means 38 are provided for preventing relative rotation of the piston 10 and the thread-engaging means 23 the arrangement being such that the piston and thread-engaging means move together for a predetermined distance on actuation of the brake and thereafter, due to the resilience of the means 23, the piston moves relatively to the means 23. In the construction shown the piston and the adjustment mechanism 11 are spring-biased towards their rest positions. The assembly is retained in the cylinder by a sleeve 5 and a heat insulator 16 is screwed to the outer end of the piston 10. The piston may be made of a heat-insulating material and in this case and when a soft metal, e.g. aluminium, is used a metallic threaded insert is provided to form the threaded portion of the piston (Fig. 6, not shown). The assembly may also be retained in the cylinder by a lock ring engaging a groove adjacent the inner end of the cylinder (Fig. 5 not shown).