| 摘要 |
A combined pressure relief and pressure indicating mechanism includes a diaphragm closing a vent in a housing. The diaphragm is punctured if an excessive overpressure occurs in the housing to relieve same. A movable indicator is held from moving by the diaphragm as long as the housing pressure exceeds a minimum value. If the housing pressure falls below this value the indicator moves, its movement giving a visual indication of an underpressure.
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