Abstract: A brake actuator device having a pneumatic service brake piston and a spring parking or emergency brake piston operation of either one of which effects displacement of a brake actuator rod which includes a screw-threaded spindle that operates in a non-rotatable nut member in order to adjust the length of the actuator rod. The nut member is provided with an external projection to which the vehicle brakes are mounted. A cogwheel is rotatably fixed to the actuator rod and is normally locked against rotation by a locking pin that engages the cogwheel teeth. The actuator rod is formed in two portions that are connected together through a clutch arrangement, the actuator rod portion having the threaded spindle being free to rotate during brake release to increase the actuator rod length and thereby take up the brake slack.

Abstract: A vehicle brake unit having a fluid pressure operated piston arranged perpendicular to a brake push rod on which is provided a pair of diagonally opposed roller members. An actuator member is connected to the piston and is interposed between the piston and push rod to translate the force of the piston to the push rod. A thrust surface having a cam profile is engageable with the roller members of the push rod, while a reaction surface is engageable with the brake unit housing. The actuator reaction surface is convex and the complementary thrust surface of the housing is concave, thereby providing a pivot point about which the actuator is angularly rotated when the piston is operated to establish a brake stroke of the brake push rod.