| 摘要 |
PROBLEM TO BE SOLVED: To provide a backflow prevention device capable surely performing a backflow prevention function by surely performing a drainage function and an air suction function through a drainage port. SOLUTION: The bottom wall 921 of a diagram plate 92 is overlapped on the upper side of a valve 913 of a diagram 91. A peripheral wall 922 is formed integrally with an annular reinforcement rib 925 and radial reinforcement ribs 926, 926... on the upper surface of the circumferential wall 922 around the bottom wall 921 to increase the bending rigidity of the diagram plate. Even if a valve body 9 is pressed against a valve seat 76, the diagram plate 92 keeps the flat state of the valve 913, thus limiting a bite amount of the valve seat 76 to the valve 913 to a constant amount. COPYRIGHT: (C)2009,JPO&INPIT
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