CO N UT OF S OUTE SUPPORT WITH COJI NETE ALI N EABLE FOR AN ELECTRIC MOTOR
BACKGROUND OF THE INVENTION This invention relates generally to electric motors and, more particularly, to a shield support assembly for an electric motor. The commonly known electric motors include a motor housing, a stator, and a rotor assembly. The rotor assembly includes a rotor core and a rotor shaft extending through the core. The housing includes a helmet and two shield supports and houses at least a portion of the rotor assembly. The electric motors also include at least one bearing to receive the rotor shaft. Commonly, the bearings are coupled to the shield supports with springs, brackets or other assemblies. The shield supports are attached to ends of the housing shell. For optimum motor operation, the bearings need to align with the rotor axis, ie, the center of the bearing housing opening needs to align with the center line of the rotor shaft. Each part of the bearing and shield support assembly is manufactured to a tolerance, and the tolerance of the assembly is the sum of the tolerances of the parts. The mounting configurations of the known shield support and cartridge bearing produce additive tolerances. The additive tolerances of the parts of the assembly can cause misaligned bearings and associated engine and wear problems. Therefore, it would be desirable to provide a shield should and shield assembly that would not produce additive tolerances, thus producing lower tolerances in the final engine assembly. It would also be desirable to provide a bearing and shield support assembly having a reduced number of parts and providing accurate support of the bearing element and allowing alignment of the limited bearing. BRIEF DESCRIPTION OF THE INVENTION In an exemplary embodiment, a shield support assembly for an electric motor includes a metal shield support, a bearing assembly, and a central injection molded metal housing that couples the bearing assembly to the metal shield support. The bearing assembly is dimensioned to receive a central axis of the electric motor and includes a cylindrical housing having an external surface. The central housing includes a plurality of projections extending from the inner surface of a cylindrical wall. The projections are positioned around the circumference of the inner surface of the central housing to engage an outer surface of the bearing housing. The projections are alternated around the circumference of the central housing so that each projection contacts the outer surface of the bearing housing on an opposite side of a circumferential center line of the bearing housing rather than an immediately adjacent projection. The shield support assembly is manufactured by placing the metal shield support in a mold / workpiece holder. The bearing assembly is also placed in the mold / workpiece holder so that a center line of the opening of the bearing assembly is aligned with a center line of the central opening of the shield support. Then, the central housing is formed around the bearing assembly by the known process of injection molding. The molten metal is injected into the mold so that the metal forms an injection molded metal housing which contacts the metal shield support and the bearing assembly for coupling the bearing assembly to the metal shield support. The shield support assembly described above includes a reduced number of parts compared to known bearing and shield support assemblies. As the shield support assembly uses a mold / workpiece holder to align the metal shield support and the bearing assembly during the injection molding of the central housing, there are no additive tolerances. The tolerances of the bearing assembly and the shield support are absorbed by the central molded metal housing by injection. The shield support assembly also provides precise support of the bearing assembly and allows limited bearing alignment. BRIEF DESCRIPTION OF THE DIAMETERS Figure 1 is a side sectional view of an electric motor including a shield support assembly in accordance with one embodiment of the present invention; Figure 2 is a sectional side view with separate parts of a shield support assembly shown in Figure 1; and Figure 3 is a sectional view through line AA of the shield support shown in Figure 2. DETAILED DESCRIPTION OF THE INVENTION Figure 1 is a sectional side view of an electric motor assembly 10 in accordance with one embodiment of the present invention. The motor assembly 10 includes a cylindrical motor housing 12, a first shield support assembly 14 coupled to a housing 12 at a first end 16, and a second shield support assembly 18 coupled to the housing 12 at a second end 20. The motor assembly 10 includes a stator 22 and a rotor assembly 24. The rotor assembly 24 includes a rotor core 26 and a rotor shaft 28 that extends through the rotor core 26. The rotor assembly 24 it also includes a plurality of fan blades 30 coupled to the rotor core 26 to cool the windings of the stator 22. The rotor shaft 28 is rotatably supported by the bearing assemblies 32 and 34. The stator 22 includes operating windings ( not shown) and start windings (not shown). The starting windings, in combination with the operating windings, are used to initiate the rotation of the rotor core 26 and the rotor shaft 28. Once the rotor shaft 28 has achieved sufficient rpm to achieve a normal operating speed , the starting winding will "cut" the motor circuit so that the starting winding does not adversely affect the operation of the motor. A centrifugal switch mechanism 36 is used to cut a start winding (not shown) when the rotor shaft 28 reaches a previously set rotating speed. The centrifugal switch mechanism includes a base collar 38 positioned on the axis of the rotor 28 adjacent to! bearing assembly 34. Particularly, a pulse rotor 40 is positioned adjacent to the bearing assembly 34, and a spacer 42 is positioned between the pulse rotor 40 and the base collar 38. A retaining ring 44 is placed on the shaft of the rotor 28 adjacent to the base collar 38. The retaining ring 44 is fixed on the rotor shaft 28 and keeps the base collar 38 in contact with the spacer 42, which in turn remains in contact with the pulse rotor 40 which in turn, it remains in contact with the bearing assembly 34. The centrifugal switch mechanism 36 also includes a thrust collar 46 configured to slide axially in the base collar 38. The thrust collar 46 engages with the arm of the switch 48. As the rotor shaft 28 rotates, the thrust collar 46 moves axially along the base collar 38 towards a flange 48 of the base collar 38 positioned adjacent the retainer ring 44. The movement The thrust collar 46 causes the switch arm 48 to move to the off position to sever the starter winding (not shown). Referring also to Figures 2 and 3, the first shield support assembly 14 includes a metal shield support 50, bearing assembly 32, and an injection molded metal central housing 52 which engages the bearing assembly 32 as shown in FIG. metal shield support 50. The bearing assembly 32 includes a central opening 33 sized to receive the central shaft 28 of the engine 10 and includes a cylindrical housing 54 having an external surface 56. The central housing 52 includes a cylindrical wall 58 which it has an inner surface 60 and an outer surface 62, and a plurality of projections 64 that extend from the internal surface 60 of the cylindrical wall 58. The projections 64 are positioned around the circumference of the inner surface 60 of the central housing 52 for coupling the outer surface 56 of the bearing housing 54. The projections 64 are alternated around the circumference of the center housing l so that each projection 64 makes contact with the outer surface of the bearing housing 54 on an opposite side of a circumferential center line of the bearing housing 66 rather than an immediately adjacent projection 64. Each projection 64 contacts the bearing housing 54 of the centerline 66 to a rim of the bearing housing 54. In one embodiment, the central housing includes six projections 64 with the first three projections 64 positioned on one side of the center line 66, and the second three projections 64 positioned on an opposite side of the center line 66. The metal shield support 50 includes a flange 68 defining a central opening 70. The central opening 70 is dimensioned so that the central housing 52 can extend through the central opening 70. The flange 68 is coupled to the central housing 52. The first shield support assembly 14 also includes an anti-rotating vessel 72. The anti-rotational key 72 is dimensioned to fit in an anti-rotating keyhole 74 formed in the central housing 52 and the bearing housing 54. The bearing housing 54 includes a first portion of anti-rotating keyhole 76, and the central housing 52 includes a second anti-rotating keyhole portion 78. The first and second anti-rotational keyhole portions. 76 and 78 are configured to be aligned to form the anti-rotating keyhole 74. The anti-rotation key 72 prevents the bearing assembly 32 from rotating in the central housing 52. Also, the first shield support assembly 14 includes a plate terminal 80 which is coupled to central housing 52 for closing a first end 82 of central housing 52. Terminal plate 80 includes an aperture sized to allow rotor shaft 28 to extend through terminal plate 80. A washer 86 is coupled to a second end 88 of the central housing 52 for closing the second end 88. An opening 90 in the washer 86 is dimensioned to allow the rotor shaft 28 to extend through the second end 86 of the center housing 52. To maintain the rotor shaft 28 in the proper position, a pulse rotor 92 is positioned adjacent the bearing assembly 32 and a spacer 94 is positioned adjacent to the impeller rotor. or 92. A retaining ring 96 is positioned on the rotor shaft 28 adjacent to the separator 94. The retaining ring 96 is fixed on the rotor shaft 28 and keeps the separator 94 in contact with the pulse rotor 92 that at its it is maintained in contact with the bearing assembly 32. The second shield support assembly 18 is similar to the first shield support 14, except that the second shield support assembly 18 includes a terminal plate 98 that does not include an opening. The second shield support assembly 18 includes a metal shield support 100, bearing assembly 34, and a central injection molded metal housing 102 which couples the bearing assembly 34 to the metal shield support 100. The assembly of bearing 34 is sized to receive the central shaft 28 of the engine 10 and includes a cylindrical housing 104 having an external surface 106. The central housing 102 includes a cylindrical wall 108 having an inner surface 1 10 and an outer surface 1 12, and a plurality of projections 1 14 extending from the inner surface 1 10 of the cylindrical wall 1 18. The projections 1 14 are positioned around the circumference of the internal surface 1 10 of the central housing 102 for coupling the external surface 106 of the bearing housing 104. The metal shield support 100 includes a flange 1 16 defining a central opening 1 18. The central opening 1 18 is dimensioned from so that the central housing 102 can extend through the central opening 1 18. The flange 1 16 is coupled to the central housing 102. The second shield support assembly 18 also includes an anti-rotation key 120. The anti-rotation key Rotary 120 is dimensioned to fit in an anti-rotating keyhole 122 formed in central housing 102 and bearing housing 104. Bearing housing 104 includes a first anti-rotating keyhole portion 124, and central housing 102 includes a second anti-rotating keyhole portion 126. The first and second anti-rotating keyhole portions 124 and 126 are configured to be aligned so as to form anti-rotating keyhole 122. The first shield support assembly 14 is manufactured by placing the metal shield holder 50 in a mold / workpiece holder (not shown). The bearing assembly 32 is also placed in the mold / workpiece holder (not shown) so that the center line of the opening of the bearing assembly 33 is aligned with the center line of the central opening 70 of the shield support 50. Then, the central housing 52 is formed around the bearing assembly 32 by the known process of injection molding. The molten metal is injected into the mold so that the metal forms an injection molded metal housing 52 which contacts the metal shield support 50 and the bearing assembly 32 for coupling the bearing assembly 32 to the shield support of metal 50. Particularly, the flange of the metal shield support 68 is encased in the wall 58 of the central housing 52. The plurality of projections 64 extending from the internal surface 60 of the central housing 52 make contact with the external surface 56 of the bearing housing 54. The bearing housing 54 is then separated from the projections 64 of the central housing. The bearing housing 54 is held in place by the projections of the central housing 64, but is allowed to rotate in the central housing 52. By separating the bearing assembly 32 from the central housing 52, the bearing assembly 32 has a limited range of movement between the projections of the central housing 64 which allows a limited bearing alignment when the shield support assembly 14 is installed in the motor 10. Commonly, the bearing housing 54 is separated from the central housing 52 by raising the temperature of the assembly 2. The anti-rotation key 72 is installed in the shield support assembly 14 by rotating the bearing housing 54 to align the first keyhole portion 76 located in the bearing housing 54 with the second keyhole portion 78 located in the bearing housing. the central housing 52 for forming the anti-rotating keyhole 74. The second shield support assembly 18 is manufactured in an identical way. The shield support assembly 14 described above includes a reduced number of parts than the known bearing and shield support assemblies. Since the shield support assembly 14 uses a mold / workpiece holder to align the metal shield support 50 and the bearing assembly 32 during injection molding of the center housing 52, there are no additive tolerances. The tolerances of the bearing assembly 32 and the metal shield support 50 are absorbed by the injection molded metal center housing 52. The shield support assembly 14 also provides precise bearing bearing assembly 32 support and allows limited bearing alignment . Although the invention has been described and illustrated in terms of several 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. For example, shell bearing constructions have been described, however, ball bearing assemblies can also be used in the practice of this invention, specifically, the inner ball bearing shell is inserted into the mold and the central housing is molded by metal by injection around the ball bearing liner as mentioned above. This metal injection molding construction eliminates the need to mold a separate outer metal coating around the inner ball bearing shell and then machine the outer housing to obtain concentricity and size.