| 摘要 |
PURPOSE:To assure operation of a valve by using buoyancy imparted to a piston in a cylinder having one end put in water to detect change of the water level under the water surface. CONSTITUTION:There is attached to a top board of a water tank a piston including a body having a predetermined length such that the piston is put completely under the water surface at a certain depth of water in the water tank. A push rod and a conventional float portion of a valve are movably attached. When the piston is at the lowermost position, the valve is open, and as the water level rises, buoyancy applied to the piston grows. When it pushes up the push rod and reaches to the uppermost water level, the valve is closed. Therefore, even when the water surface is frozen, the operation of the valve can be assured until icing advances down to the piston under the water surface.
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