Metering valve

摘要

A metering valve includes a valve body with an inlet passage and an outlet passage defined therein, and a movable stem member disposed between the inlet passage and outlet passage. An inner sleeve member is configured within the valve body and has an inner diameter surface at least partially defining a pressure chamber within a fluid-tight meter chamber, the stem member being movable through the chamber. A piston assembly is disposed within the pressure chamber and is configured with the stem member to move therewith. The piston assembly is movable to an open mode upon actuation of the stem member and automatically moves from the open mode to the closed mode upon release of the stem member. The piston assembly includes a sealing device which engages with the inner sleeve member inner diameter surface during movement of the piston assembly to the closed mode. A metering passage is defined through the stem member between a location above the sealing device to a location below the sealing device such that the rate of return of the piston assembly from the open mode to the close mode is dependent upon the size of the metering passage. At least one additional vent passage is defined from a location above the sealing device to a location below the sealing device in the closed mode. The vent passage includes at least one hole defined above the sealing device completely through the inner sleeve member, and at least a second hole defined below the sealing device completely through the inner sleeve member. The vent passage is only established upon the sealing device passing across the second hole in its movement from the open mode to the close mode.