Patent ID: 7922465

Claim:
A cooling fan comprising: a fan housing having a central tube extending upwardly therefrom; a bearing received in the central tube, the bearing being made of iron-copper alloy susceptible to a magnetic force; a stator mounted around the central tube; a rotor having a shaft extending into the bearing, a hub and a shaft seat extending downwardly from a center of the hub, the shaft seat comprising an inner ring receiving a top end of the shaft and an outer ring being arranged around the inner ring with an annular groove defined therebetween, a bottom end of the outer ring being lower than a bottom end of the inner ring, a concave recess being thus defined in the outer ring of the shaft seat around the shaft; and a magnetic ring being received in the concave recess of the shaft seat and being fixedly connected to the bottom end of the inner ring of the shaft seat and mounted around the top end of the shaft to rotate with the rotor during operation of the cooling fan, a bottom side of the magnetic ring being approximately at the same level as the bottom end of the outer ring of the shaft seat, the magnetic ring being made of hard magnetic material and exerting a magnetic attraction on the bearing, whereby the rotor is pulled downwardly by a magnetic attraction of the bearing on the magnetic ring.