| 摘要 |
There is disclosed a valve having a valving element longitudinally reciprocable within a bore in the body of the valve between alternate positions for controlling the flow of a first fluid between lateral ports connecting with the bore. A piston connected to one end of the valving element is urged in a direction to move the valving element to one position by a force due to the pressure of a second fluid acting over the piston, and a stem on the other end extends through the valve body to provide an externally accessible part which may be manipulated to shift the valving element between its alternate positions. Means are provided for holding the valving element in its one position, automatically in response to manipulation of the stem to shift it into that position and irrespective of the pressure of the second fluid acting over the piston.
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