| 摘要 |
PROBLEM TO BE SOLVED: To provide a vent valve capable of easily regulating a fresh air introduction amount so that a sufficient negative pressure eliminating effect can be provided according to the structure and use environment of drain pipe. SOLUTION: This vent valve 1 is so formed that one or a plurality of generally cylindrical vent valve bodies 2 having vent holes 22 passed through in the inner and outer directions and valve elements 23 capable of opening/closing the inner ends of the vent holes 22 are stackingly installed at the end part of a vent pipe P, and an upper cover 3 is installed on the upper end part of the uppermost vent valve body 2. COPYRIGHT: (C)2004,JPO&NCIPI
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