US Patent 7150344 Actuator and slack adjuster

A fluid operated brake actuator is provided composed of a common housing, a shaft rotatable within the housing, the shaft being rotatable to engage and disengage a brake, a vane connected to the shaft, the vane being responsive to fluid pressure to rotate the shaft, a torsion power spring for producing torque to bias the shaft in a first rotational direction; and an inlet port through the housing, the inlet port for introducing fluid pressure into the housing in order to exert a force on the vane in order to rotate the shaft against the bias of the spring.