Sealed brake actuator

An air-operated diaphragm brake actuator for applying the parking brakes of a vehicle, of the type comprising:

• a sealed housing comprising a first end wall, a peripheral side wall extending away from the first end wall to define a first interior cavity, and a second end wall, opposing the first end wall and closing the first interior cavity;
• a diaphragm having a central opening, 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 pressure chamber being adapted for connection to a source of pressurized fluid where the diaphragm is in a first position when the pressure chamber is exhausted and a second position when the pressure chamber is pressurized;
• a spring disposed in the spring chamber and biasing the diaphragm in a direction toward the second end wall away from the first position where the spring is compressed, toward the second position where the spring is less compressed;
• a hollow actuator rod having one end coupled to the diaphragm at the central opening and another end extending through the second end wall to establish fluid communication between the spring chamber and a side of the second end wall opposite the pressure chamber, 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 one-way valve positioned within the hollow actuator rod to permit the exhausting of fluid from the spring chamber through the hollow actuator rod and prevent the introduction of fluid through the hollow actuator rod and into the spring chamber, the one-way valve including a body having a through opening and positioned within the hollow actuator rod to block fluid flow through the hollow actuator rod except through the through opening, and a poppet mounted within the through opening and moveable between a sealing position where the poppet seals the through opening to prevent the flow of fluid through the body, and an open position where the poppet unseals the through opening to permit the flow of fluid through the body;
• whereby when the pressurized fluid is introduced into the pressure amber, the diaphragm moves from the second position to the first position to reduce the volume of the spring chamber and, as the resulting fluid pressure increase in the spring chamber exceeds a predetermined value, the one-way valve opens to permit the pressurized fluid to pass from the spring chamber and through the hollow actuator rod thereby relieving pressure in the spring chamber.