| 摘要 |
A ring-like rib 19 is erected on an inner circumferential edge of an insertion hole 11, which is opened in the scroll casing 1 so that the fan f is inserted therethrough, while a side wall 18 facing the ring-like rib 19 is provided in the bracket 15 blocking the insertion hole 11. A helical groove portion 20 and a protruding portion 21 are formed in one of an outer surface of the side wall 18 and an inner surface of the ring-like rib 19 and in the other thereof, respectively. The bracket 15 is caught in the scroll casing 1 by turning the bracket 15 in a direction opposite to a direction of rotation of said fan f. Further, during the engagement therebetween, a cooling duct 4 is formed.
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