Long stroke spring brake actuator

Abstract

A long-stroke fail-safe spring brake assembly for heavy duty vehicles comprises aligned first and second cups secured adjacent one another to form a housing for a compressed power spring which biases a spring piston, a hollow tubular push rod having one end open and sealingly secured, preferably by press fitting, to the spring piston and the other end closed and extending sealingly through the second cup for reciprocal control of a brake actuator by the power spring, an annular-shaped flexible diaphragm having an outer periphery radially-sealingly secured adjacent between the cups and an inner periphery sealingly secured adjacent the outer periphery of the spring piston, the intermediate portion of the diaphragm being disposed radially-outwardly of the spring piston. The spring piston is disposed to compress the compressed spring still further toward the first cup under the influence of a compressed fluid medium, the push rod, and the spring piston being sealingly secured to each other. The hollow interior of the push rod houses an elongated caging member having a distal portion confined therein which prevents separation of the compressed spring from the first cup in the event the latter is separated from the second cup. The push rod reciprocates sealingly through the second cup by a centerseal bearing comprising opposed interlocked plastic components sealed to each other by fused contact.