Hydraulic disc brake actuator

An improved brake actuator comprising:

• a fluid pressure motor having a reciprocating piston member for effecting brake applications;
• spring motor means normally restrained by said fluid pressure motor for urging said piston to effect said applications in response to a reduction in pressure in said fluid pressure motor;
• threaded means for threadably engaging said piston member along its axis of reciprocation, said threaded means establishing a frictional resistance with said piston means and including means for selectively, manually rotating said threaded means in a first direction to retract said piston member and compress said spring motor means following brake application by said spring motor or in a second direction to extend said piston member under the action of said spring motor means to effect a brake application without repressurization of said fluid pressure motor;
• and
• resilient torque means engaging said threaded means and being wound during rotation in said first direction to produce a torque initially insufficient to overcome said frictional resistance when said pressure released motor is depressurized but adequate for automatically rotating said threaded means in said second direction when said pressure released motor has been pressurized to compress said spring motor means and to reduce the frictional force between said piston and said threaded means sufficiently to thereby allow said threaded means to rotate under the influence of said resilient means.