US Patent 7766627 Motor device for a fan

A fan motor device includes a fan base, an impeller set and a motor set. The fan base extends a central barrel with ball bearings fitting with the barrel. The impeller set further includes an impeller, a shaft, a spring, a motor case and a magnet. The motor set further includes an insulation frame, a silicone sheet set, a coil and a circuit board. The barrel has an annular deep groove between the inner circumferential side and the outer circumferential side thereof for a stop ring being attached to an inner wall surface of the groove to reinforce the outer circumferential side so as to prevent the barrel from bending deformation and the motor set from displacing eccentrically or loosening off.