Patent ID: 7737583

Claim:
A rotor assembly comprising: an inner rotor and an outer rotor for rotating in a magnetic field of a motor, said inner rotor comprising a main inner rotor cavity, and a plurality of first holes being formed between said inner rotor and said outer rotor; two side boards, each side board having a main side board body; a main side board cavity, and being perforated by a plurality of second holes; two damping elements, each damping element comprising a main damping element cavity; a plurality of rubber sleeves, each rubber sleeve having a rubber sleeve lip; and a plurality of third holes; an axle; and a plurality of positioning pins; wherein said axle extends through said main inner rotor cavity, two said main side board cavities, and two said main damping element cavities; said main side board body extends over said main damping element cavity and partially over said main rotor cavity; said plurality of said rubber sleeves is disposed respectively in said plurality of said first holes; said rubber sleeve lip forms a buffer between said inner rotor/outer rotor and said side board; said plurality of said positioning pins traverses said first holes, said second holes, and said third holes, respectively; said damping element, said side boards, and said positioning pins are made of vibration-damping material, said inner rotor and said outer rotor are firmly sandwiched between two said side boards and two said damping elements, and the rotor assembly is layered from one end to another as follows: side board, damping element, inner rotor/outer rotor, damping element, side board.