Patent ID: 8241011
Filing Date: 2012-08-14
Classification: F04D

Abstract:
1. A fan comprising: a main impeller; a main motor comprising a main rotor and configured for driving the main impeller to rotate along a first circular direction; a secondary impeller; and a secondary motor comprising a secondary rotor and configured for driving the secondary impeller to rotate along a reverse direction of the first circular direction; wherein the power of the main motor is greater than the power of the secondary motor, and the main rotor is rotationally connected to the secondary rotor; wherein the main rotor is tube shaped and defines a plurality of threaded holes therethrough around the main rotor, the secondary rotor is cylindrical and defines a groove around the secondary rotor, the secondary rotor rotationally inserting the main rotor so that the threaded holes are aligned with the groove, the fan further comprising a plurality of screws screwing through the threaded holes respectively and slidably received in the groove.