| 摘要 |
PROBLEM TO BE SOLVED: To provide a pressure relief valve to perform regulation of a pressure by a slight force without being limited by a strong force spring for setting a pressure and perform accurate fine control. SOLUTION: A valve element 3 provided with a seat 30 formed of an elastic material is arranged on the under surface side of a vertically operating diaphragm 2 by sensing a pressure in a secondary chamber (w) on the upper surface side of a valve casing 1, and the valve element is depressed downward through the force of a spring 50 for setting a pressure. A vertical cylindrical part 12 communicated with a drain pipe 11 through a communication port 12a is arranged in a valve casing situated below the valve element, an inner cylindrical valve seat metal fitting 4 is vertically slidable fitted in a watertight state in the cylindrical part. A valve seat 40 is formed in an annular shape at the upper edge of the valve seat metal fitting 4 and a relief port (b) is formed at the inside thereof. Energization to the rising side is effected through the force of a weak spring located between the bottom wall of the cylindrical part and the support metal fitting 42 of the valve metal fitting, and a regulation bar 6 to regulate the end of rising operation of the valve seat metal fitting is vertically regulatably assembled.
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