Patent ID: 7745967

Claim:
A cooling fan comprising: a fan housing having a central tube extending upwardly therefrom; a bearing received in the central tube, and defining a bearing hole therein; a stator mounted around the central tube; a rotor comprising a hub, a plurality of blades extending outwardly from the hub, and a shaft extending downwardly from the hub into the bearing hole of the bearing; and a cover mounted around the shaft and arranged on the bearing to seal a top end of the bearing, the cover being made of powders by sintering; wherein a shaft seat is formed at a center of the hub for receiving a top end of the shaft therein, the shaft seat having an annular protrusion extending downwardly from an outer periphery thereof, the cover comprising an outer ring, an inner ring and a flange interconnecting the inner and outer rings, a canal being defined between the inner and outer rings over the flange, the protrusion of the shaft seat extending into the canal of the cover, and a curved interspace being defined between the cover and the shaft seat; and wherein an annular groove is defined in an outer circumferential surface of the shaft near the top end configured for preventing lubricant oil from continuously creeping up along the shaft during operation of the cooling fan, and the inner ring of the cover abuts the outer circumferential surface of the shaft at a position above the annular groove.