Patent ID: 7736129

Claim:
A centrifugal fan mounted on a rotating shaft of a rotating machine for introducing cooling air to said rotating machine, said centrifugal fan comprising: a hub mounted about said rotating shaft; a main plate formed in a ring shape and disposed concentrically at said hub; a side plate in a ring shape having an outer circumference smaller than an inner circumference of said main plate and formed integrally with said hub so that said side plate is disposed with an interval to said main plate in an axial direction of said rotating shaft; and a plurality of flat impeller blades implanted on said hub, and disposed along the axial direction of said rotating shaft, and regularly spaced in a radial direction so as to connect said main plate to said hub to form a space between said main plate, said side plate and said hub, some of said impeller blades reaching an outermost circumference portion in said radial direction, while others of the impeller blades reaching only a middle portion in said radial direction, said main plate and said side plate being formed so that said main plate and said side plate avoid overlapping with each other when seen from the axial direction of the rotating shaft, and the others of said impeller blades being gouged at portions outward in the radial direction and forming spaces on both sides of the some impeller blades.