Device for discontinuing and automatically restoring the operational function of a spring brake actuator

Claim 1

Means for selectively releasing and thereafter automatically restoring braking in a spring brake actuator comprising in combination, a piston, a threaded push rod movable by the piston to operate the brakes, a spring for moving the piston in a direction applying the brakes, brake release means conveying a force to the piston to move it against the force of said spring to release the brakes, and a conveying mechanism coupled between the piston and push rod for moving said push rod with movement of said piston in a brake applying direction including a selectively operable release mechanism for disconnecting said push rod from said piston and automatically reconnecting it upon said brake release means conveying a force to said piston thereby overcoming the force of said spring, said release mechanism comprising, a nut in non-self-locking engagement on threads on said push rod transmitting braking force from said piston to said rod and rotatable only when the release mechanism disconnects said push rod from said piston, a clutch normally holding said nut rotationally immovable, said clutch comprising one clutch surface on said nut and a rotationally immovable sleeve member disengaged from said piston presenting a mating clutch surface, means moving said sleeve member to disengage said clutch thereby permitting the push rod to move independently of said piston while said nut rotates thereon, and return means permitting said nut to rotate when brakes are applied to reposition said push rod.