| 摘要 |
PCT No. PCT/AU95/00468 Sec. 371 Date Apr. 22, 1997 Sec. 102(e) Date Apr. 22, 1997 PCT Filed Aug. 1, 1995 PCT Pub. No. WO96/04043 PCT Pub. Date Feb. 15, 1996A forced air breathing apparatus which includes a face piece (20a) for covering at least the nose or mouth of a wearer, a pump unit (10) arranged to supply air to a space within the face piece (20a), a filter (13) to filter air entering the face piece (20a) and valve means to control the flow of air from the pump unit (20) to the face piece (20a) during inhalation and from the face piece (20a) during exhalation. The pump unit (20) includes a fan (12) driven by an electric motor (11). The valve means includes an air inlet valve (19) and an air outlet valve (22), the air outlet valve (22) being maintained in a closed position during inhalation through the air inlet valve (19) by air pressure from the pump unit (20) and being opened by exhaled air. The exhaled air also acts to close the air inlet valve (19) and prevents the entry of exhaled air to the pump unit (20). The fan (12) is a centrifugal fan driven at a substantially constant speed. A valve (14) is provided on the air inlet side of the pump unit (10) and is arranged to close when a defined air pressure is present within the pump unit (10) downstream of the fan (12).
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