PURPOSE: To preventing the generation of noise without reducing blowing efficiency, to stabilize the operation of ventilating fans by placing a shutter component plate so that the inclined face thereof may form a non-orthogonal angle with blowing direction and so that such a force works as to assist the opening of shutter.
CONSTITUTION: When a blowing means 1 is driven, a shutter component plate 6 is turned on a fulcrum 7 by the air current generated thereby 7 until contacting with a stopper 9. The air current from said blowing means 1, contacts with the inclined 10 formed so that the upper surface of the end portion on which said blowing means 1 is located is more distant than said fulcrum 7 of said shutter component plate 6. Consequently, such a force works as to press against said stopper 9 said end portion on which said blowing means 1 is located works rather on said shutter component plate 6 than on said fulcrum 7 so that the operation of a ventilating fan is stabilized to reduce noise. The reduction blowing efficiency can be prevented since said inclined 10 is not orthogonal with blowing direction.
ASANO SEIJIROU
KOBAYASHI KAZUO
ASABUKI HIROSHI
