Patent ID: 8221069

Claim:
A multi-blade fan comprising: a spirally-shaped casing including a bellmouth-shaped inlet and an outlet at one side; an electric motor disposed inside the casing; a main plate provided perpendicular to a rotation axis of the electric motor and having a ventilation hole; first blades disposed at a side of the inlet of the main plate; and second blades disposed at an opposite side of the inlet of the main plate; wherein a diameter of the main plate is smaller than an outer diameter of the first blades and an outer diameter of the second blades and the diameter of the main plate is larger than an inner diameter of the first blades and an inner diameter of the second blades, and an outlet angle of at least one of the first blades is changed sequentially in an axis direction such that the outlet angle of the one of the first blades at an inlet side of the one of the first blades is smaller than an outlet angle of the second blades and the outlet angle of the one of the first blades at a main plate side of the one of the first blades is larger than the outlet angle of the second blades.