Patent ID: 7037089

Claim:
A cooling fan having dual blade sets, comprising a shell ( 10 ), a stator assembly ( 20 ) mounted in the shell ( 10 ) and an impeller ( 30 ), wherein the impeller ( 30 ) has a rotatable hub ( 31 ) having a bottom surface and an outer surface, a rotor ( 33 ) with a spindle ( 32 ) mounted at the bottom surface of the rotatable hub ( 31 ), a plurality of mini blades ( 36 ) formed on the bottom surface of the rotatable hub ( 31 ), a plurality of guide blades ( 34 ) formed on the outer surface of the rotatable hub ( 31 ) and a plurality of holes ( 35 ) defined through the bottom surface of the rotatable hub ( 31 ), wherein each hole ( 35 ) is adjacent to a respective one of the mini blades ( 36 ); the stator assembly ( 20 ) is mounted in the shell ( 10 ) by using bolts ( 23 ), wherein an insulation sheet ( 15 ) separates the stator ( 20 ) and the shell ( 10 ); and the shell ( 10 ) defines a housing ( 11 ) with a bottom plate ( 12 ) to receive the stator assembly and the impeller ( 30 ), wherein a bearing ( 14 ) surrounded by a sleeve ( 13 ) extends from the bottom plate ( 12 ), such that the insulation sheet ( 15 ) and stator assembly ( 20 ) are to be aligned with the bearing ( 14 ) at the center; when the stator assembly ( 20 ) is mounted over base plate ( 12 ), the rotor ( 33 ) is coupled with the stator ( 20 ), and the spindle ( 32 ) extending from the rotatable hub ( 31 ) is inserted through the bearing ( 14 ), wherein as the impeller ( 30 ) rotates, the guide blades ( 34 ) create an air flow to cool down a host machine, and the mini blades ( 36 ) drive out hot air within the housing ( 11 ) between the impeller ( 30 ) and the shell ( 10 ) and through the holes ( 35 ).