| 摘要 |
PROBLEM TO BE SOLVED: To provide a ball check valve capable of reducing a size, increasing strength, providing interchangeability with conventional products, and increasing a practical valve by adding a primary air bleeding function to the check valve without increasing a size, and to provide a lifting device applicable to conventional manholes. SOLUTION: In this check valve, a seat part is provided on the inflow side of a body having an inlet and an outlet to retreat a ball valve element seated on the seat part to an retreat passage in the body through a guide part. Ribs provided parallel with a vertical cross section connecting the centerline of the retreat passage and the centerline of the flow passage are formed on the outer peripheral surface of the body positioned on the inside of a flange, and projected parts are formed integrally with each other on the inside of the flange in a direction vertical to the vertical cross section. Inside and outside opening parts formed in the projected parts are allowed to communicate with each other through a communication passage.
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