| 摘要 |
PURPOSE:To make it possible to improve noise absorption effect, reduce the noise, and change the flow passage with ease by providing a space and a shutter which are extended from a ventilation fan mounting section by a specified dimension inside a casing. CONSTITUTION:An indoor air is sucked up from a ventilation duct 23 by way of a space 15 and discharged outdoors by way of the ventilation duct 23 as indicated in the arrow by driving a blower of a ventilation fan main body 16. During this operation, an acoustic material 22 mounted in the space 15 absorbs the noise generated by the blower 21. In the case when a ventilation air capacity is small and the ventilation is not sufficient, the acoustic material 22 in the space 15 is replaced and another ventilation fan main body 16 formed in a similar way to the ventilation fan main body 16 is mounted instead by way of an opening 13, the ventilation air capacity is increased and sufficient ventilation is carried out. When it is necessary to prevent the inflow of an open air indoors under the installation state, the acoustic material 22 in the space 15 is replaced so as to mount a frame member 24 and a shutter 25 instead, which is rotatively supported with this frame member and opens and closes an air duct by wind pressure by way of the opening. |
