Abstract:
A bearing seat includes a cylindrical scat defining a cylindrical pocket for at least partially containing a bearing. The cylindrical seat includes a cylindrical first wall and an end wall extending from the cylindrical first wall. The cylindrical first wall has an inner face and the end wall includes an integral shim extending outwardly therefrom. The integral shim is configured to contact a side of an outer race of a bearing such that the side of the outer race of the bearing seats firmly against the integral shim.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to bearings and more particularly to cylindrical bearing pockets. 
     Cylindrical bearings typically require proper diametrical clearance between the outer race of the bearing and the cylindrical bearing pocket in which the bearing rests. To ensure proper pre-loading of the bearing, the clearance must be large enough to allow the bearing to slide axially in the bearing pocket. However, the clearance between the outer race of the bearing and the bearing pocket must also be small enough to restrict side to side movement and rotation of the bearing, which may cause unwanted noise or premature failure of the bearing due to “pound-out.” 
     Cylindrical bearing pockets are typically stamped from thin sheets of steel into a stamped steel “cap and can” construction. The stamped steel “cap and can” construction is capable of maintaining the proper cylindrical shape throughout most of the bearing pocket. However, the diameter at the bottom of the pocket is often too small thereby inhibiting axial motion of the bearing within the bearing pocket. Because the bearing cannot seat firmly against the bottom of the pocket, the bearing may become pinched and thus may not slide freely within the pocket. Therefore, some bearing pockets are enlarged with a secondary finishing process, such as machining. Machining, however, adds additional cost to the manufacture of the bearing pocket and may also raise quality issues. Roller-burnishing processes have also been used to enlarge the diameter at the bottom of the bearing pocket but are disadvantageous because other areas of the bearing pocket will also be enlarged, possibly becoming oversized. In addition, roller burnishing adds considerable cost to the manufacture of the bearing pocket. Separate spacers or shims have also been employed to address the clearance between the bearing pocket and the outer race of the bearing. Including extra spacers or shims is problematic because of the increased number of parts, manufacturing complexity and cost. Further, extra spacers or shims increase the possibility of improper assembly. For example, the spacer or shim may not be included in the bearing pocket assembly. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a bearing seat is provided that comprises a cylindrical seat defining a cylindrical pocket for at least partially containing a bearing. The cylindrical seat includes a cylindrical first wall and an end wall extending from the cylindrical first wall. The cylindrical first wall has an inner face and the end wall includes an integral shim extending outwardly therefrom. The integral shim is configured to contact a side of an outer race of a bearing such that the side of the outer race of the bearing seats firmly against the integral shim. 
     In another aspect, a cap and bearing assembly is provided which comprises a bearing that includes an outer race. The outer race includes a side. The assembly further comprises a cap that includes a cylindrical seat that defines a cylindrical pocket for at least partially containing a bearing. The cylindrical seat includes a cylindrical first wall and an end wall that extends from the cylindrical first wall. The cylindrical first wall includes an inner face and the end wall includes an integral shim that extends outwardly from the end wall. The integral shim is configured to contact the side of the outer race of the bearing such that the side of the outer race of the bearing seats firmly against the integral shim. 
     In yet another aspect, a method is provided for locating a bearing within a cylindrical seat. The bearing includes an outer race having a side and the cylindrical seat includes a cylindrical first wall and an end wall. The method comprises providing an integral shim that extends outwardly from the end wall of the cylindrical seat, and disposing the bearing within the cylindrical seat such that the side of the outer race of the bearing seats firmly against the integral shim. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-section of a conventional cap and bearing assembly. 
     FIG. 2 is a cross-section of one embodiment of the cap and bearing assembly of the present invention. 
     FIG. 3 is a flow chart illustrating the steps for locating a bearing within a cylindrical seat. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and in particular to FIG. 1, a known cap and bearing assembly  10  comprises a cap, or endshield,  12  for an electric motor (not shown). Cap  12  includes a cylindrical bearing seat  14  that defines a cylindrical bearing pocket  16 , which contains a ball bearing  18 . Bearing seat  14  includes a cylindrical first wall  20  having a central axis  22  extending through the length thereof, a first end  24 , a second end  26  and an inner face  28 . Bearing  18  rests within cylindrical bearing pocket  16  and includes an inner race  30  and an outer race  32 . Inner face  28  defines the inner diameter of first wall  20  and an outer face  34  of outer race  32  defines the outer diameter of bearing  18 . Outer race  32  includes a first side  36  and a second side  38 . The intersections of outer face  34  with first side  36  and second side  38  are rounded  40  due to manufacturing procedures. Bearing seat  14  further includes a second wall, or end wall,  42  extending from first end  24  of first wall  20 . End wall  42  faces generally perpendicular to central axis  22  and the intersection of end wall  42  with first wall  20  includes a fillet  44  due to manufacturing procedures. In one embodiment, fillet  44  has a maximum radius of 0.03 inches. End wall  42  includes an annular opening  46  concentric with central axis  22 . 
     FIG. 2 illustrates one embodiment of a cap and bearing assembly  60  comprising a cap  62  for an electric motor (not shown). Cap  62  includes a cylindrical bearing seat  64  that defines a cylindrical bearing pocket  66 , which contains a ball bearing  68 . In an alternative embodiment, bearing  68  may be a roller bearing or other type of bearing. Bearing seat  64  includes a cylindrical first wall  70  having a central axis  72  extending through the length thereof, a first end  74 , a second end  76  and an inner face  78 . Bearing  68  rests within cylindrical bearing pocket  66  and includes an inner race  80  and an outer race  82 . Inner face  78  defines the inner diameter of first wall  70  and an outer face  84  of outer race  82  defines the outer diameter of bearing  68 . Outer race  82  includes outer face  84 , an inner face  85 , a first side  86 , and a second side  88 . In one embodiment, shown in FIG. 2, the intersections of outer face  84  with first side  86  and second side  88  are rounded  90  due to manufacturing procedures. In one embodiment, round  90  has a corner radius of 0.079/0.024 inches. 
     Bearing seat  64  further includes a second wall, or end wall,  92  extending from first end  74  of first wall  70 . End wall  92  faces generally perpendicular to central axis  72  and the intersection of end wall  92  with first wall  70  includes a fillet  94 . In one embodiment, fillet  94  has a radius that is less than one-half of a thickness between inner face  85  and outer face  84  of outer race  82 . End wall  92  includes an integral shim  96 , described in further detail below, that extends outwardly from end wall  92  toward bearing  68  and second end  76  of first wall  70 . End wall  92  further includes a circular opening  98  concentric with central axis  72  for accommodating a rotor shaft (not shown) of an electric motor. 
     The clearance between bearing  68  and first wall  70  must be sufficiently large to allow bearing  68  to slide within bearing seat  64  and bearing pocket  66  along central axis  72 , thus allowing proper pre-loading of bearing  68 . However, the clearance between bearing  68  and first wall  70  must also be sufficiently small to prevent bearing  68  from rotating within bearing seat  64  and to prevent bearing  68  from wobbling within bearing seat  64  perpendicularly to central axis  72 . Eliminating rotation and wobbling of bearing  68  significantly reduces bearing noise and premature failure of bearing  68  due to “pound out.” In one embodiment, the outer diameter of bearing  68  is slightly smaller than the inner diameter of first wall  70  such that there is a clearance of 0.0011 inches between inner face  78  of first wall  70  and outer face  84  of outer race  82 . In another embodiment, the clearance between inner face  78  and outer face  84  is between 0.0011 inches and 0.0020 inches. Alternatively, it will be understood that the clearance between inner face  78  and outer face  84  may be any distance that allows bearing  68  to slide within bearing seat  64  and bearing pocket  66  along central axis  72 , and prevents bearing  68  from unwanted rotation and wobble. 
     In one embodiment, bearing seat  64 , including integral shim  96 , is an integral piece that is stamped out of steel. Alternatively, it will be understood that in other embodiments bearing seat  64  may be stamped from other suitable metals. For example, in one embodiment, bearing seat  64  is stamped from aluminum. 
     Referring now to FIGS. 1 and 2, the stamping process is capable of forming cylindrical first walls  20 ,  70  into the shape and diameter that provides the proper clearance, discussed above, between outer faces  34 ,  84  and cylindrical first walls  20 ,  70  respectively. However, the stamping process cannot produce the shape and diameter that provides the proper clearance at the intersection of cylindrical first walls  20 ,  70  and end walls  42 ,  92 , respectively. Rather, the stamping process produces fillets  44 ,  94 . Referring now to FIG. 1, fillet  44  reduces the diameter of first end  24  of cylindrical first wall  20  thereby inhibiting axial motion of bearing  18  along central axis  22 . Further, because the diameter of fillet  44  is greater than the diameter of round  40 , when bearing  18  is pre-loaded such that first side  36  of outer race  32  contacts fillet  44 , bearing  18  may become pinched within cylindrical first wall  20 . Thus, the central axis (not shown) of bearing  18  will no longer be concentrically aligned with central axis  22 . Pinching of bearing  18  restricts bearing  18  from sliding freely within bearing seat  14  and bearing pocket  16  along central axis  22 . In addition, pinching of bearing  18  may inhibit proper rotation of inner race  30  of bearing  18  thereby causing operational failure of bearing  18 . 
     Referring now to FIG. 2, integral shim  96  spaces bearing  68  away from end wall  92 , and thus fillet  94 , and provides a uniform seating surface  100  for first side  86  of outer race  82  to contact. Integral shim  96  includes seating surface  100  and a first side  102 , and is separated from cylindrical first wall  70  by a trough  104 . Trough  104  is defined by first side  100  of integral shim  96 , an end portion  106  of inner face  78  of first wall  70 , and a bottom  108  that is a portion of end wall  92 . Integral shim  96  spaces bearing  68  away from bottom  108  at a distance such that outer race  82  does not contact fillet  94 . Therefore, the proper clearance between outer face  84  of outer race  82  and inner face  78  of first wall  70  is maintained throughout the axial length of bearing  68 . In one embodiment, shown in FIG. 2, seating surface  100  of integral shim  96  is spaced 0.040 inches from bottom  108  of trough  104 , and thus integral shim  96  spaces first side  86  of outer race  82  0.040 inches from bottom  108 . Alternatively, seating surface  100  of integral shim  96  may be spaced from bottom  108  at a distance other than 0.040 inches. It will be understood that the distance that seating surface  100  of integral shim  96  is spaced from bottom  108 , and thus the distance that integral shim  96  spaces first side  86  from bottom  108 , will depend on the application and capability of the manufacturing process forming bearing seat  64 . In one embodiment, integral shim  96  is annularly, or ring, shaped and is concentric with first wall  70 . Alternatively, in another embodiment, integral shim  96  is annularly shaped and is not concentric with first wall  70 . Furthermore, it will be understood by one skilled in the art that integral shim  96  may be any shape that provides a uniform surface, such as seating surface  100 , for first side  86  of outer race  82  to contact and spaces bearing  68  away from bottom  108  at a distance such that outer race  82  does not contact fillet  94 . For example, in one embodiment, integral shim  96  comprises a plurality of extensions that extend outwardly from bottom  108  toward second end  76  of first wall  70 . 
     By maintaining the proper clearance between outer face  84  of outer race  82  and inner face  78  of first wall  70 , and by providing a secure surface  100  for first side  86  of outer race  82  to firmly seat against, the present invention prevents wobble, rotation and pinching of bearing  68 . The present invention thus eliminates unwanted noise and premature failure due to “pound out” thereby greatly improving the quality of cap and bearing assembly  60 . Also, because shim  96  is an integral part of bearing seat  64 , no additional parts are required thus reducing the cost of bearing seat  64  and cap and bearing assembly  60 . Integral shim  96  further reduces the cost of bearing seat  64  and cap and bearing assembly  60  by eliminating the need for subjective and time-consuming inspection of the intersection of first wall  70  and end wall  92 . 
     FIG. 3 is a flowchart  200  illustrating a method  202  for locating bearing  68  (shown in FIG. 2) within bearing seat  64  (shown in FIG. 2) and bearing pocket  66  (shown in FIG.  2 ). The method includes providing  204  an integral shim  96  (shown in FIG. 2) that extends outwardly from end wall  92  (shown in FIG.  2 ), and disposing  206  bearing  68  within bearing seat  64  and bearing pocket  66  such that first side  86  (shown in FIG. 2) of outer race  82  (shown in FIG. 2) seats firmly against integral shim  96 . The clearance between first side  86  of outer race  82  and cylindrical first wall  70  of bearing seat  64  is checked  208  to ensure that outer race  82  of bearing  68  cannot rotate and/or wobble within cylindrical bearing seat  64  when bearing  68  is pre-loaded. Clearance check  206  also ensures that bearing  68  can slide within cylindrical bearing seat  64  along central axis  72  before bearing  68  is pre-loaded, such that bearing  68  will not become pinched when bearing  68  is pre-loaded. 
     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.