| 摘要 |
Protective repiratory masks with excess pressure make sure that an excess pressure is maintained during both the inhalation and exhalation, whereby a penetration into the mask of the ambient atmosphere is prevented. A lung demand valve or control for the mask is divided by a control diaphragm into a respiratory chamber, and an outer chamber. The respiratory chamber communicates with, and follows the pressure in, the interior of the mask; to admit breathing gas, the respiratory chamber is connectable to the source through an inlet valve which is controlled by the control diaphragm through a lever and a rod. The outer chamber accommodates a locking mechanism which is manually actuable through a slide and by which the control diaphragm may be held in a pressure-relieved locked position in which also the inlet valve is closed. During periods where the mask is not in use, unnecessary supply of respiratory gas is interrupted. As soon as the mask is put on, the control diaphragm is released from its locked position by the started respiration alone, without any other manipulation on the part of the user, thus making possible a normal lung demand respiration with maintained excess pressure in the interior of the mask.
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