PROBLEM TO BE SOLVED: To provide a swing check valve for checking a backflow by quickly closing a valve element 8 when stopping operation, by holding the valve element 8 in large opening in operation of an aeration blower.;SOLUTION: A cylinder device 21 is attached to an outer wall of a valve casing 7, and a valve rod 9 for rockably supporting the valve element 8 and a piston 23 of the cylinder device 21 are connected by a connecting mechanism, and opening-closing operation of the valve element 8 and reciprocating motion of the piston 23 are interlocked. A cylinder chamber 24 for expanding the volume by the movement of the piston 23 interlocking with opening operation of the valve element 8 is communicated with the upstream side of the valve element 8 by a communicating flow passage 25, and a three-way ball valve 26 is interposed in this communicating flow passage 25. An operation member 35 operating so as to overturn to the downstream side at a preset flow rate or more and rise at the preset flow rate or less, is arranged on the downstream side of the valve element 8 in the valve casing 7. The three-way ball valve 26 communicates the communicating flow passage 25 with a cylinder chamber 24 by overturning to the downstream side of a flapper 36 of the operation member 35, and the three-way ball valve 26 communicates the communicating flow passage 25 with the atmosphere by rising of the flapper 36.;COPYRIGHT: (C)2011,JPO&INPIT
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