| 摘要 |
<p>A mask (10) for breathing apparatus, provided with one-way air inlet (12) and one-way air outlet valves (14) of variable elasticity, in which said outlet or expiration valve (14) has an opening pressure selected between a first and a second predetermined values by means of a prearrangement control member (24). The expiration valve (14) comprises an airtight diaphragm (16) elastically pushed to close an expiration passageway (13) by means of two springs (19, 25) in series with each other, the former (19) having an elastic coefficient greater than the latter (25); the control member (24) is movable between a position of non-interference and a position of interference with the elastic movement of the second spring (25) under the action of a pressure acting on the diaphragm (16). <IMAGE></p> |
