| 摘要 |
PROBLEM TO BE SOLVED: To provide a duckbill valve in use for a flow path, capable of reliably maintaining the state of closing the mating faces of lip portions in the flow of fluid in the opposite direction, surely preventing the flow of the fluid, and accurately generating air sounds when using gas as fluid in the flow path to flow in a closing system in the forward direction and an abnormal atmospheric opening condition appears at the base end of the flow path. SOLUTION: The duckbill valve 7 comprises the pair of lip portions 2 each having a base end and a front end and tapered off from the base end to the front end for allowing a forward flow from the base end to the front end and preventing the opposite flow from the front end to the base end, and mating faces 3 formed on the lip portions 2. At the base end thereof, an annular portion is provided which has the maximum diameter perpendicular to the mating face 3 and the minimum diameter parallel thereto. COPYRIGHT: (C)2007,JPO&INPIT
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