EXTERNAL ROTOR CUP WITH ANNULAR FLANGE EXTENDING THEREFROM

An electric motor includes a rotor cup housing having an annular flange extending circumferentially from a sidewall. The motor further includes a stator including a stator core having a winding thereon and a rotor positioned at least partially around the stator. A rotor shaft is positioned at least partially within the stator.

DETAILED DESCRIPTION FIG. 1 is a perspective view of a known rotor cup 10 including a closed end 12 , an open end 14 , and a sidewall 16 extending between open end 14 and closed end 12 . Open end 14 is defined by a lower edge 18 of sidewall 16 and includes a substantially uniform circumferential thickness 20 . FIG. 2 is a perspective view of a rotor cup 22 including an annular flange 24 . In one embodiment, flange 24 is unitary with rotor cup 22 . Rotor cup 22 further includes a circumferential sidewall 26 having a first diameter 28 , a top surface 30 , and an open bottom 32 . Sidewall 26 has a height 34 measured between top surface 30 and a top edge 36 of annular flange 24 . Annular flange 24 is fabricated from the same material as rotor cup 22 . In one embodiment, annular flange 24 is fabricated from stamped steel. Annular flange 24 is substantially circular in shape and has an inside diameter 28 and an outside diameter 40 . Inside diameter 38 is smaller than outside diameter 40 . Annular flange 24 has a height 42 measured between a bottom edge 44 and top edge 36 . In addition, annular flange 24 is outwardly flared from sidewall 26 by an angle &phgr; measured between sidewall 26 and bottom edge 44 . Angle &phgr; permits annular flange 24 to have an outwardly flared curved edge 46 which allows rotor cup 22 to lay flat on a surface (not shown in FIG. 2 ). Annular flange 24 increases rotor cup 22 stiffness. In addition, because curved edge 46 is outwardly flared by an angle &phgr;, edge 46 provides additional surface area and strength to support rotor cup 22 . FIG. 3 is a perspective view of an inside-out motor 50 including flanged rotor cup 22 shown in FIG. 2 . Rotor cup 22 includes annular flange 24 and top surface 30 . Sidewall 26 extends to top surface 30 so that a top edge 52 is rounded. Inside-out motor 50 further includes a rotor shaft 54 , a rotor 56 , a stator (not shown), and a frame 58 . Rotor shaft 54 is mounted on frame 58 which is attached to the stator such that rotor 56 rotates freely relative to the stator without contacting the stator. In one embodiment, rotor cup 22 is balanced to rotate without vibration. Annular flange 24 permits weights to be attached to flange 24 to achieve a desired level of rotor balance. In another embodiment, material is machined away from flange 24 to achieve a desired level of rotor balance. FIG. 4 is a side view of inside-out motor 50 shown in FIG. 3 positioned to be attached to a load 60 . In one embodiment, load 60 is a fan. Inside-out motor annular flange 24 rests on a surface 62 of a tooling apparatus 64 while supporting rotor cup 22 . Load 60 is pressed onto rotor cup 22 in a vertical direction 66 . Annular flange 24 provides a smooth surface when load 60 is pressed onto rotor cup 22 . Annular flange 24 has an increased surface area because of outwardly flared edge 37 (shown in FIG. 2 ). FIG. 5 is a perspective view of rotor cup 22 including annular flange 24 positioned to receive a magnet 68 . Annular flange 24 is configured in a lead-in position to receive circumferential magnet 68 . Annular flange 24 is outwardly flared by an angle &phgr; and is tapered which assists to guide magnet 68 into rotor cup 22 . While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.