| 摘要 |
PROBLEM TO BE SOLVED: To provide a back flow check valve for sewer pipe in order to protect a building or structure from back flow of rain water although a heavy storm though water stop panels for guarding around a building or structure have been already developed. SOLUTION: Back flow from a sewer main during heavy storm must be prevented by automatically closing or opening at the terminal manhole. During back flow, a terminal manhole is first filled up with back flow water. A buoy is raised by its buoyancy; a wire and a sheave are connected to the buoy and other end of wire is connected to a spherical plug, and the pipe is plugged by utilizing the hydraulic pressure. When the back flow water runs off, the buoy is lowered and the plug is raised up.
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