Patent ID: 8136893

Claim:
A control valve for use in a pneumatic system, comprising: a valve body, wherein the valve body further comprises: at least one supply port for communicating with a source of system operating air pressure; at least one delivery port for communicating with a spring brake; at least one exhaust port for communicating with atmosphere; at least one pilot air inlet for communicating with a source of control air pressure; a pilot air outlet; and an internal cavity comprising top, middle, and bottom chambers, wherein the top chamber is in communication with a first pilot air inlet and the pilot air outlet; the middle chamber is in communication with the at least one supply port; and the bottom chamber is in communication with the at least one delivery port, the at least one exhaust port, and a second pilot air inlet; and a first piston disposed within the top chamber and having a bore passing lengthwise therethrough; a first biasing member disposed within the top and middle chambers and defining an annular orifice therewith, wherein a second piston is in selective engagement with the first piston; a valve member connected to the bottom portion of the second piston; a third piston disposed within the bottom chamber beneath the valve member; and wherein a first positive control air pressure signal applied to the first pilot air inlet moves the valve member to a first position; wherein a second positive control air pressure signal applied to the first pilot air inlet moves the valve member to a second position; and wherein a second biasing member moves the valve member to the second position when the system operating air pressure received by the at least one supply port is below a predetermined pressure.