| 摘要 |
PURPOSE:To sharply reduces the amount of noise generated by a ventilating fan, by a method wherein an annular projection is formed on the outer periphery of the edge on the suction side of a cylindrical frame having an axial vane. CONSTITUTION:A cylinder part 14, the front end of which is formed in the shape of a bell-mouth and which forms the fan casing of an axial vane 24, is formed to a cylindrical frame 6, made of synthetic resin, of a ventilating fan, and an annular projection 23 is formed on the front edge part of the cylinder part 14 integrally with a cylindrical frame 15 by using synthetic resin. When an axial vane 24 is rotated, the projection 23 resists air being about to come in from a peripheral direction, most of indoor air is sucked, as shown by an arrow mark A, from a position in front of the axial vane 24, and there is little air coming in from a peripheral direction. This constitution sharply reduces noise level.
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