| 摘要 |
A powered respirator is provided with a device (10) sensitive to the pressure within the respirator in the region of the user's face and adapted to sound a warning in the event that the sensed pressure goes below a selected threshold value. The device includes a flexible diaphragm (13) exposed on its opposite sides to the sensed and atmospheric pressures respectively, and an infra red emitter (21) and receiver (22) arranged so that the level of energy received by the receiver from the emitter depends upon the flexural position of the diaphragm (13). In different embodiments the diaphragm (13) may be arranged to reflect the radiation from the emitter (21) onto the receiver (22) or not, or to interrupt a beam of radiation from the emitter (21) to the receiver (22) or not, depending on the pressure differential across it. In either case, when a sufficient energy level is detected at the receiver (22), indicating a pressure level below the selected threshold, power is switched to a sounder (26) to warn the user of the low pressure condition.
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