| 摘要 |
PROBLEM TO BE SOLVED: To smoothly operate a cylindrical plug without giving a flaw to various members of the cylindrical plug or the like, by providing a scraping part of adhering matter in an internal peripheral edge part in a side of a direction retracting the cylindrical plug of an annular valve seat. SOLUTION: An annular valve seat 4 is formed in a cylindrical shape, an upper part of its internal/external peripheral surface is formed with a step difference, a groove 4a is formed along an internal peripheral circle on an upper side end face, relating to this groove, a slope is formed so as to increase a height toward an internal peripheral side in a hill part in the internal peripheral side, and this acute angular internal peripheral edge part is made to serve as a scraping part 4b of a scale. Scale 9 adhering to an external peripheral surface of a cylindrical plug 5 is scraped off by the scraping part 4b when the cylindrical plug 5 is moved to a lower side, to be dropped down onto an end face of the annular valve seat 4. The scale 9 adhering to a lower part in the external peripheral surface of the cylindrical plug 5 is scraped off by the scraping part 4b when the cylindrical plug 5 is moved to an upper side, to flow out with a liquid. In this way, a valve can be stably opened/closed without giving a flaw to the annular valve seat 4, guide member, cylindrical plug 5, etc., by the scale 9.
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