Actuator mechanisms for vehicle brakes

An actuator mechanism for a vehicle brake, comprising an axially rotatable actuator shaft and an actuator member which, in use, can be moved to actuate a brake, the actuator shaft and actuator member being interconnected by an assembly which comprises a first fast thread and a second fast thread, said first thread having a greater pitch angle than said second thread and having an operative connection with said actuator member to, in use, move the actuator member to take up any slack until friction surfaces of a brake interengage, said second thread having an operative connection with said actuator member to, in use, subsequently move the actuator member to apply the brake, a spring being coiled around the actuator shaft, one end of the spring being keyed to the shaft and the other end of the spring abutting a projection from an annular member, the annular member being mounted coaxially with the actuator shaft, a toothed disc mounted coaxially and non-rotatably on said actuator shaft being connected by a pin abutment to the annular member, the outer periphery of said annular member engaging with a fixed outer annular member by said first fast thread.