US Patent 7568502 Coupling for a hydraulic or pneumatic assembly

A coupling (110) comprising a pair of female couplers (116) each independently movable within a respective housing bore (114) among an operating position, a release position, and a coupling position. When a female coupler (116) is moved to the coupling position, a stop member (136) moves the plunger of a pressure relief valve (124) to an open position to allow fluid to be released from the female coupler (116) prior to coupling a male coupler thereto. A cam member (126), which is used to move the respective female coupler (116) from the operating position to the release position, can move away from the plunger when the female coupler (116) is in the coupling position as the pressure relief valve (124) is held open by the stop member (136).