| 摘要 |
A valve includes a hollow body having both a valve seat, and a threaded portion having helical right-handed threads. A stem disposed within the body has a threaded portion at one end, with left-hand threads. The stem is moved within the body by turning a cap assembly which has both a left-hand threaded portion engaging the threaded portion of the stem, and a right-hand threaded portion engaging the threads on the valve body. Large stem displacements per turn are realized.
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