| 摘要 |
A valve assembly especially for a breathing apparatus comprises a housing 14, an inlet for admitting gas into the housing from a source of gas at a superatmospheric pressure, a movable valve member 21 which is capable of closing the gas inlet and which, in operation, is acted upon, at least when ist is closed or nearly closed, by a force resulting from the pressure difference between the higher pressure gas upstream of the inlet and the lower pressure gas in the housing 14, the effect of which force is to tend to move the valve member 21 to open the gas inlet, and means 16 responsive to the difference between the pressure in the housing 14 and the ambient pressure, the pressure-responsive means 16 being so connected to the valve member 21 that, if the pressure in the housing 14 exceeds the ambient pressure, at least by a certain amount, the pressure.responsive means 16 exerts a force on the valve member 21 which tends to cause the valve member to move to close the inlet. |
