Patent ID: 7121191

Claim:
An air-operated brake actuator for applying parking brakes of a vehicle, comprising: a sealed housing including a first end wall, a second end wall opposing the first end wall, and a peripheral side wall extending between the first and second end walls, the first end wall, the second end wall and the peripheral side walls together defining an interior cavity therein; a diaphragm spanning the interior cavity, and dividing the interior cavity into a spring chamber located between the diaphragm and the first end wall, and a pressure chamber located between the diaphragm and the second end wall, the diaphragm being in a first position when the pressure chamber is pressurized with fluid and in a second position when the pressure chamber is exhausted; a spring disposed in the spring chamber and biasing the diaphragm toward the second position; a hollow actuator rod having one end coupled to a central opening of the diaphragm and another end extending through the second end wall, wherein when the diaphragm is in the second position the hollow actuator rod is positioned to apply the parking brake and when the diaphragm is in the first position the hollow actuator rod is positioned to release the parking brake; and a control valve positioned within the hollow actuator rod, the control valve including a valve body with an opening formed therein for allowing fluid communication between the spring chamber and a side of the second end wall opposite the pressure chamber through the hollow actuator rod, the control valve including a membrane formed of an elastic material and having a breathing hole formed therethrough, the membrane positioned within the opening of the valve body and configured to seal the opening except the breathing hole when the membrane is subject to a fluid pressure below a threshold level.