US Patent 7745967 Cooling fan

A cooling fan includes a fan housing (10) having a central tube (102) extending upwardly therefrom, a bearing (40) received in the central tube, a stator (20) mounted around the central tube, a rotor (30), and a cover (50). The bearing defines a bearing hole (47) therein. The rotor includes a hub (32), a plurality of blades (34) extending outwardly from the hub, and a shaft (36) extending downwardly from the hub into the bearing hole of the bearing. The cover is mounted around the shaft and arranged on the bearing to seal a top end of the bearing. The cover is made of powders by sintering and thus has a plurality of pores to generate capillary force to absorb lubricant oil leaking out of the bearing.