Metering valve

Abstract

A valve body includes a chamber for the flow of fluid between an inlet and an outlet thereto. The chamber includes an upper portion with an opening therethrough and a lower portion including a valve seat between the inlet and outlet. A bonnet is positioned in the chamber upper portion and is connected to the valve body and extends upwardly therefrom. The bonnet includes a passageway, and a stem is positioned in the passageway for longitudinal movement into and out of sealing engagement with the valve seat. An actuator is rotatably positioned in the bonnet passageway above the stem. A micrometer operating handle is nonrotatably connected to the upper end portion of the actuator to facilitate fine adjustment of the stem position to provide incremental adjustments in the flow rate of fluid between the inlet and outlet. The stem upper end is spaced from the actuator lower end in the bonnet passageway, and a coupling assembly rigidly connects the actuator to the stem for conversion of longitudinal rotational movement of the actuator to nonrotational longitudinal movement of the stem. The coupling assembly includes a housing into which both the actuator and stem extend. The housing is retained on the end of the actuator, and a pin connects the housing to the stem. A bushing is positioned between the adjacent ends of the actuator and stem where one surface of the bushing abuts the actuator and an opposite surface abuts the stem. The stem is sealed in a bellows which exerts an upward compressive force upon the stem to maintain the actuator and stem in contact with the bushing so that, as the actuator rotates, the stem moves longitudinally relative to the valve seat.