| 摘要 |
PROBLEM TO BE SOLVED: To provide a flap valve normally opened with a small quantity of flow, rapidly closed when the water level on the drain place side rises, and capable of holding a float weight in a stable attitude. SOLUTION: A link mechanism 31 for connecting the float weight 21 to a rocking arm 19 of a flap valve element 16 is provided with a first link 34 with one end rotatably fitted to the rocking arm 19 so to be rotatable around the axis of a horizontal support shaft 33; a second link 36 with one end rotatably fitted to the other end of the first link 34 so as to be rotatable around the axis of a horizontal support shaft 35 and with the other end rotatably fitted to the float weight 21 so as to be rotatable around the axis of a horizontal support shaft 37; a first stopper 38 for locking the first link 34 to the rocking arm 19 in the rotating direction of opening the flap valve element 16; and a second stopper 39 for locking the first link 34 and the second link 36 at a specified angle.
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