US Patent 7244099 Multi-vane centrifugal fan

A multi-vane centrifugal fan has a fan housing and an impeller. The impeller includes a plurality of vanes arranged with a prescribed spacing in the circumferential direction and fixed to a hub rotatably driven around a shaft core. The impeller further includes an annular member for reinforcement that is provided on a side of the vanes opposite the hub. The fan housing has a bell mouth with a recessed part that is provided around a circumference of an air suction port of the fan housing. The recessed part has air suction port side end parts positioned on the side of the vanes opposite the hub and rotatably inserted in the recessed part without having a shroud.