| 摘要 |
PURPOSE:To reduce the noise by providing apertures in the guide wall of the tongue part of the volute casing which guides the air flow delivered from an impeller to an air discharged opening, and forming a hermetic space part which communicates with only the apertures on the outside of the volute casing. CONSTITUTION:A dust collecting filter 14 is disposed on the suction side of the inner part of a main body 11 and the impeller 16 driven by an electromotor 15 is provided in the rear of the dust collecting filter 14. The air flow delivered from the impeller 16 is guided to an air discharge opening 13 by the volute casing 17. At least one aperture 20 is provided in the guide wall 19 of the tongue part 18 of the volute casing 17, and the hermetic space part 21 communicating with only the aperture 20 is formed on the outside of the volute casing 17. Namely, the aperture 20 and the space part 21 constitute a resonance box. By utilizing this phenomenon, the noise due to the collision against the tongue part by the air flow of uneven denseness delivered from the impeller, is reduced. |
