To make a device into quiet sound by expanding the former half specified range of the length of a channel more than scroll exit area of channel cross section from a scroll exit to a discharge port of a supply air system discharge channel and making the remaining range of the latter half of the channel into the channel in which area is reduced.
An intake discharge noise reduction channel 5 is constituted of side wall P 30 and side wall Q 31 from a scroll exit 8 constituted of each sound absorbing material to an intake discharge port 6, a partition wall to be a bulkhead with a channel around an exhaust motor and space surrounded by the lower surface of an upper cover 20. The side wall P 30 is formed into a shape which linearly connects a point of the scroll exit 8 and a supply air discharge port 6, and the side wall Q 31 describes a curved line from the starting point of the side wall Q and is connected with the supply air exit 6. In channel cross section, the part up to the location of 45 to 75% of the former half of the channel is determined for a cross section expanding part, a smooth expanding is performed up to 150 to 200% of exit area of a nose 9, the range of 55 to 25% of the latter half of the length of the channel is made a cross section reducing part leading to the supply air discharge port 6 and cross section is smoothly changed. Thus, flow velocity is lowered and an effective noise reduction is made possible.
YAMAZAKI SUSUMU
TAKATSU YASUSHI
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