| 摘要 |
1,107,726. Centrifugal fans etc.; silencing gaseous flow. SOUND ATTENUATORS Ltd. July 7, 1965 [July 7, 1964], No.27898/64. Headings F1B and F1C. The casing 2 of a centrifugal fan is lined with a slab 10 of air-permeable sound-absorbent material such as expanded polyurethane (which may be of laminated construction), expanded polystyrene or bonded mineral fibres affording the volute surface 9. The material absorbs noise generated within the fan and also attenuates noise which might otherwise be transmitted through the fan from, e. g., the exterior of a building in the case of a fan built into a wall-mounted ventilator drawing fresh air into a room from outside the building. The fan impeller 7 surrounds the electric driving motor which is resiliently mounted on the back plate 1 of the casing. A filter 11 may be mounted in front of the inlet 3. Air-impermeable baffles extending from the surface 9 to the wall of the casing 2 may be provided to divide the slab 10 into a number of chambers of different shape and size and having different frequency bands of maximum sound attenuation. Two impellers may be mounted in a common casing having a common outlet and a separate inlet for each impeller. |
