Patent ID: 7230357

Claim:
An electric motor ( 20 ) comprising: a stator assembly ( 70 , 80 , 90 ) and an external rotor assembly ( 22 , 24 , 28 , 52 , 60 ) adapted to be rapidly mated together; said external rotor assembly including a rotor cup ( 24 ) coupled to a central shaft ( 28 ) having a proximal end ( 26 ) adjacent said rotor cup ( 24 ) and a distal end ( 34 ) provided with an enlargement ( 32 ); said stator assembly ( 90 ) including a bearing support tube ( 70 ) formed with an opening ( 78 ), facing said rotor cup, for receiving said central shaft ( 28 ) of said rotor assembly; a plurality of bearings ( 52 , 60 ) which are mounted on said shaft for insertion into the bearing support tube ( 70 ), radial outer surfaces ( 54 , 62 ) of said bearings being guided in an inner opening ( 78 , 80 ) of the bearing support tube ( 70 ), said bearings serving to support said shaft ( 28 ), and of which a proximal bearing ( 52 ) is arranged closer to the rotor cup ( 24 ) than a distal bearing ( 60 ), the shaft ( 28 ) being axially displaceable with respect to the bearings ( 52 , 60 ); a retaining member ( 50 ), arranged between the rotor cup ( 24 ) and the proximal bearing ( 52 ), said retaining member serving to immobilize at least the proximal bearing ( 52 ) in its position in the bearing support tube ( 70 ) after assembly; a spring member ( 48 ), effective between the proximal bearing ( 52 ) and the rotor cup ( 24 ), that pushes the rotor cup ( 24 ) away from the proximal bearing ( 52 ) in order to push the enlargement ( 32 ) provided on the shaft ( 28 ) in the direction of the distal end of the distal bearing ( 60 ); and a spacer ( 58 ) axially displaceably arranged in the bearing support tube ( 70 ) and defining a predetermined distance between the proximal bearing ( 52 ) and the distal bearing ( 60 ).