IMPELLER OF FAN

摘要

The impeller includes at least one impeller section comprising a pair of circular plates which confront each other so as to be spaced at a predetermined interval. A number of blades are mounted, at opposite ends on the plates along circumferences of the plates so as to extend between the plates such that the blades are circumferentially spaced at random pitch angles without periodicity. Since the blades are arranged at non-uniform pitch angles, the interference noises are produced at non-uniform pitches by the respective blades. Their frequencies thus vary according the non-uniform pitch angles.