| 摘要 |
The device comprises an expandable chamber (13) having an outlet (23) for connection to a facepiece, for example a face mask (26) and an inlet (12) connected to pump means (2, 3, 4, 5) for drawing ambient air into the device through a filter (8) and pumping it into the chamber. In use the wearer of the face mask draws air from the chamber and that air is replenished by operation of the pump means. …<??>Means (19) are provided for sensing the degree of expansion of the expandable chamber and are coupled with means (22) for varying the power supplied to the pump means so that the pump means supplies only sufficient filtered air to maintain the chamber inflated. A bias is provided on the chamber advantageously coupled with the sensing means for maintaining a positive pressure in the chamber. …<??>The device allows close control of the amount of air passing through the respirator so as to substantially reduce the amount of air which is filtered but unbreathed to extend the life of the filter means. |
