Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is related to, and claims priority from, U.S. Provisional Patent Application Ser. No. 61/152,829 filed on Feb. 16, 2009, and which is herein incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present disclosure is related generally to small angular contact ball bearings, and in particular, to a small angular contact ball bearing for use in an application having only a limited axial space for a ball retainer. 
         [0004]    Within an angular contact ball bearing assembly, a traditional angular contact ball bearing (ACBB) retainer, such as shown in  FIG. 1 , is an annular structure which protrudes past both sides of, or completely surrounds, the ball elements which are disposed within openings about the circumference of the structure. An alternative configuration, known as a crown retainer, is shown in  FIGS. 2 and 3 , and protrudes past only one side of each ball elements which are contained within the open-sided pockets, but because the crown retainer must snap-fit over each ball element, it permits a larger axial movement in one direction than the other. Both traditional angular contact ball bearing (ACBB) retainers and crown-type retainers require a minimum amount of axial distance to operate correctly. For some bearing applications, this required minimum axial distance may be greater than the available axial distance inside the bearing, particularly when considering requirements of closures, clearances, room for lubricant, etc. In some cases, a wider bearing can be used in the final application. In other cases, a narrower bearing must be used. When a narrower bearing is required, with the traditional type ACBB retainers and crown-type retainers, sometimes there is insufficient room for all the desired components. 
         [0005]    Some angular contact ball bearing applications require a lower mass retainer, for either retainer dynamic issues, or to help reduce the overall mass of the bearing assembly. A traditional ACBB retainer has more mass than a crown-type retainer, since a traditional crown-type retainer typically is designed for a deep groove ball bearing, and has fewer balls than an angular contact ball bearing. Fewer balls in a ball bearing means the bearing typically has a reduced load capability. 
         [0006]    Traditional crown-type retainers are either of the “ball piloting” design or the “ring piloting” design. With the “ball piloting” design, the crown retainer is less tolerant of misalignment and very high speeds, and the piloting dimensions can reduce the introduction of lubricant to the ball/retainer interface. In contrast, with the “ring piloting” design, the crown-type retainer is more tolerant of higher speeds and misalignment, but the design has more ball pocket clearance, and the axial movement of the retainer caused by the loose pocket clearances required may result in problems. 
         [0007]    Some larger angular contact ball bearings require one or two axial end closures to help to keep contaminants out of the bearing, and/or to keep particles generated by the bearing inside the bearing. For very small angular contact ball bearings such as those used in medical and dental devices, the inclusion of a second closure can be beneficial to bearing life, however, due to width requirements of the final bearing, traditional angular contact ball bearing retainers cannot be fitted into the available space envelope. While traditional angular contact retainers can be manufactured with one regular width rail and one very narrow rail to fit into smaller space envelopes, due to the extremely small size of some medical bearings, a traditional angular contact retainer with one regular width rail and one very narrow rail is not practical to manufacture. Furthermore, the narrow rail can cause manufacturing problems that make the design impractical and can be a source of later retainer fractures or failures. 
         [0008]    Accordingly, it would be advantageous to provide a ball bearing retainer which is suitable for use in angular contact ball bearings, such as those used in medical and dental devices, and which has high tolerances to correctly limit movement during bearing operation, a reduced axial width for use in those bearings that require space within which to fit one or more closures (typically a shield or seal), and which can be used in those bearings that require a retainer with reduced mass. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Briefly stated, the present disclosure provides an angular contact ball bearing retainer with reduced axial width and a “crown” shape. However, in contrast to standard “crown” type snap-in retainers, the present invention retainer does not provide a snap fit about the ball elements. Rather, the retainer of the present invention is installed onto the inner or outer ring along with the balls, and then the other ring is assembled, typically using thermal heating and/or cooling of the bearing rings. The lack of snap fitment on the retainer limits axial movement or clearance of the retainer, so as to correctly limit its movement during bearing operation. The present invention crown style retainer further has a reduced axial width for use in bearings requiring more room to fit one or more axial closures (typically a shield or seal), and may be used in those bearings that require a retainer with reduced mass. 
         [0010]    The foregoing features, and advantages set forth in the present disclosure as well as presently preferred embodiments will become more apparent from the reading of the following description in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0011]    In the accompanying drawings which form part of the specification: 
           [0012]      FIG. 1  is a perspective view of a prior art angular contact ball bearing retainer; 
           [0013]      FIG. 2  is a perspective view of a prior art stamped metal crown ball bearing retainer; 
           [0014]      FIG. 3  is a perspective view of a prior art machined or molded “snap-in” style of crown ball bearing retainer; 
           [0015]      FIG. 4  is a sectional view of a crown-type ball bearing retainer of the present disclosure; 
           [0016]      FIG. 5  is a top plan view of a section of the crown-type ball bearing retainer of  FIG. 4 ; 
           [0017]      FIG. 6  is a sectional view of a bearing assembly incorporating the crown-type bal bearing retainer of  FIG. 4 ; and 
           [0018]      FIGS. 7A-7C  illustrate a limited range of movement for ball elements secured within the bearing retainer of the present disclosure. 
           [0019]      FIGS. 8A-8T  illustrates exemplary retainer cross sections for the crown type ball bearing retainer of  FIG. 4 . 
       
    
    
       [0020]    Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts set forth in the present disclosure and are not to scale. 
         [0021]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. 
       DETAILED DESCRIPTION 
       [0022]    The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the present disclosure, and describes several embodiments, adaptations, variations, alternatives, and uses of the present disclosure, including what is presently believed to be the best mode of carrying out the present disclosure. 
         [0023]    Turning to the Figures, and to  FIGS. 4-6  in particular, an improved angular contact ball bearing retainer  100  of the present disclosure is shown to be different than both the traditional angular contact ball bearing (ACBB) retainers and the traditional stamped, machined, or molded crown-type and snap-in retainers. The preferred embodiment of the present disclosure is a cylindrical retainer body  102 , with cylindrical ball pockets  104  arrayed around the circumference of the retainer body  102  as shown in  FIG. 5 . The axis X of each cylindrical ball pocket  104  intersects an axial centerline of the retainer body. As best seen in  FIG. 4 , the sidewall  106  of each ball pocket  104  is open on one axial end of the retainer, defining a slot  108 . Remaining portions of the retainer body  102  disposed between each slot  108  define a set of prongs  105 , similar to a “crown” configuration. Axially opposite from the slots  108 , the structure of the retainer body  102  defines a single continuous side rail  110 . Those of ordinary skill in the art will recognize that while the retainer body  102  is shown to have a cylindrical configuration with a rectangular cross-section, as best seen in  FIG. 8A , the cross-sectional configuration, including the orientation of the cylindrical ball pockets  104 , may be varied to accommodate the particular bearing assembly  10  into which the retainer  100  is to be utilized, as is shown by the exemplary cross-sectional configurations of  FIGS. 8B-8T . 
         [0024]    Preferably, the retainer  100  is machined from metallic or polymer stock, but those of ordinary skill will recognize that the retainer may be manufactured from a molded polymer or metallic material. The retainer  100  is manufactured with precision manufacturing practices, including broken/blended/deburred surface intersections to promote correct piloting of the retainer  100  on the bearing inner and outer rings ( 10 A,  10 B) and balls  12 . In basic appearance, the retainer  100  of the present disclosure appears similar to a traditional crown retainer, but it is different in a number of ways, as shown below. 
         [0025]    First, the retainer  100  of the present disclosure is a non-snap design, i.e., the retainer  100  cannot be assembled into a ball bearing  10  after the inner ring  10 A, outer ring  10 B, and ball elements  12  are assembled and correctly spaced. Rather, the retainer  100  is installed onto the inner ring  10 A or outer ring  10 B along with the balls  12 , prior to the assembly of the remaining ring ( 10 B or  10 A), which is typically done using thermal heating and/or cooling of the bearing rings ( 10 A,  10 B). The bearing assembly ( 10 ) may then be provided with optional closures ( 14 ) at one or both axial ends. 
         [0026]    Second, the retainer  100  of the present disclosure is preferably configured to have a smaller range of axial movement than a traditional crown-type snap-in retainer, because the retainer  100  can envelope more of the circumference of each ball element  12 , as best seen in  FIGS. 7A-7C . A traditional crown-type snap-in retainer must have a relatively large slot width, so that the prongs of the retainer can elastically deform enough to slip past the larger ball diameters during assembly and then return to their original design shape for use, to retain the retainer inside the bearing. Large axial movement requires more room inside the bearing  10 , which reduces available room for additional closures or a volume of lubricant. While some traditional crown-type snap-in retainers have very low axial movement due to very flexible prongs and very small ball pocket clearance, they also tend to be “ball piloting” designs, which are less favorable for high speed and/or high misalignment operation. 
         [0027]    The improved retainer  100  of the present disclosure is axially and radially narrower, creating more room inside the bearing  10  for closures or lubricant. 
         [0028]    The improved retainer  100  of the present disclosure is lighter than a traditional ACBB retainer, and so contributes less mass to the total mass of the bearing  10 . 
         [0029]    The improved retainer  100  of the present disclosure has increased compliance, because of the presence of the slots  108  axially opposite from the single side rail  110 , which alters the retainer dynamics, affecting correct bearing operation and/or noise generation of the bearing assembly  10 . 
         [0030]    The improved retainer  100  of the present disclosure is more open on one axial side due to the presence of the slots  108  (i.e., the ball elements  12  are more exposed), so the introduction of lubricant to the balls elements  12  during a lubrication process is easier. 
         [0031]    The cylindrical sidewalls  106  of the ball pockets  104  in the retainer  100  allow the retainer  100  to be piloted primarily on the lands of one of the bearing rings ( 10 A or  10 B), and secondarily on the ball component  12 , so that the retainer  100  is suitable for high speed bearing operation with minimum friction and wear. Because the ball elements  12  are not retained in the retainer  100  when the retainer is not installed in a bearing, the ball pocket  104  and ring land clearances can be optimized for high speed or alternately for lower speed operation. 
         [0032]    The improved retainer  100  of the present disclosure, although it is of the “crown type”, can be manufactured with a greater number of ball pockets  104  than a traditional snap-in style retainer of the same diameter, because the retainer  100  is assembled into an angular contact ball bearing  10  using typical angular contact ball bearing assembly methods, and without the need to permit resilient flexing or movement required by a traditional snap-in crown-type retainer to fit over the ball elements  12 . The improved retainer  100  can be manufactured with the same number of ball pockets  104  as a traditional angular contact ball bearing (ACBB) retainer. 
         [0033]    As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Technology Category: 2