| 摘要 |
PURPOSE:To make a back seal for a fluid inside a housing with certainty at a limit position of a stem, by installing a back seal valve slidably in the stem making a valve body reciprocating inside the housing, while energizing this back seal valve at an interval between the said valve and the valve body. CONSTITUTION:A stem 17 makes a valve body 16 reciprocate inside a housing 11 and opens or closes a fluid passage of the housing 11. In this case, a first annular valve seat 20 is installed in a bottom part of a bonnet 13 of the housing 11 where the stem 17 pierces through, surrounding the stem 17. On the other hand, a back seal valve 21 provided with a second annular valve seat 21 stickable to the said annular valve seat 20 at a seal point diameter D1 is slidably fitted in the stem 17 via an O-ring 23. And, a compression spring 26 is installed interposingly between both valves 22 and 16 so as to have a proper interval between a lower end face of the said valve 22 and an upper edge fece of the valve body 16, energizing the said valve 22. With this constitution, a fluid inside the housing is surely back-sealed at a limit position of the stem 17. |
