| 摘要 |
The present invention relates to an improved air-purifying device for respirators of the positive pressure type. The device comprises an expandable chamber having an outlet for connection to a facepiece, for example, a face mask, and an inlet connected to a pump for drawing ambient air into the device through a filter 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. Apparatus is provided for sensing the degree of expansion of the expandable chamber and is coupled with a device for varying the power supplied to the pump 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 apparatus for maintaining a positive pressure in the chamber. An air-purifying 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. |
