| 摘要 |
PURPOSE:To prevent previous leakage without the necessity of any additional drive source, by coupling a variable section in a snap mechanism and a displacing section in a pressure displacement converting device to a displacement transmission mechanism. CONSTITUTION:A pressure displacement converting device 41 depresses a movable section in a snap mechanism 21 through a displacement transmission mechanism 61 when the valve inlet port side pressure is lower than a set blow-off pressure. As a result the force of a snap spring 31 acts upon the movable section which therefore depresses a valve rod 7. The valve inlet port side pressure increases approaching the set blow-off pressure, the force depressing the valve rod is decreased. When the valve inlet port pressure increases further, the snap mechanism is reversed. As a result, the balance of thrust forces acting upon a valve element 5 by the valve inlet port side pressure and a valve spring 13 is instantly lost so that the safety valve blows off.
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