Abstract:
A compliant bearing sleeve resides between a bearing and a bearing seat, thus opening tolerance requirements, and providing thermal and mechanical insulation of the bearing from the bearing seat. The bearing sleeve comprises alternating outside and inside ribs residing on a sleeve body. In a relaxed state (i.e., not inserted into a motor) the sleeve body is cylindrical. When the bearing sleeve is inserted into the motor, the ribs cause the sleeve body to deform to allow the sleeve to fit between the bearing seat and the bearing. The bearing sleeve preferably includes an axial bearing stop to retain the bearing, and is preferably made of a high temperature material.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a sleeve for supporting a bearing and in particular to a sleeve providing thermal and mechanical insulation, and opening tolerance requirements, for a bearing.  
         [0002]     Electric motors generally include bearings to allow low friction rotation of a motor armature. In high performance motors, ball, needle, or roller bearings are often used to minimize rotating friction. The fits between the bearing and the motor case or endbell often have very close tolerances. In the instance of a motor with an anodized endbell, the close tolerances are complicated by effects of anodizing. The variation in tolerances after anodizing often reduce production yield.  
         [0003]     U.S. Pat. No. 6,749,342 for “Bearing System, Especially for Yarn Feed Device,” describes a squeeze element 36 residing between an outer bearing race and a bearing seat  21 . In a preferred embodiment, the squeeze element  36  is a smooth cylinder and the bearing seat  21  includes inward facing the ribs  26  which cause the squeeze element  36  to deform (see  FIGS. 3-5 ). In another embodiment, the squeeze element comprises a body  36   a  and squeeze regions  36   b  spaced angularly apart at equal intervals along the body  36   a  (see  FIGS. 6 and 7  of the &#39;342 patent). The squeeze element is described as being made from a polymer, but no further details are provided. Unfortunately, the squeeze regions  36   b  are likely to be scraped, and thus damaged, when the squeeze element in inserted into an endbell. Further, the squeeze element is open at both ends, requiring the bearing to seat axially against the endbell, thus allowing the transfer of both heat and vibrations directly from the endbell to the bearing.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     The present invention addresses the above and other needs by providing a compliant bearing sleeve which resides between a bearing and a bearing seat, thus opening tolerance requirements, and providing thermal and mechanical insulation of the bearing from the bearing seat. The bearing sleeve comprises alternating outside and inside ribs residing on a sleeve body. In a relaxed state (i.e., not inserted into a motor) the sleeve body is cylindrical. When the bearing sleeve is inserted into the motor, the ribs cause the sleeve body to deform to allow the sleeve to fit between the bearing seat and the bearing. The bearing sleeve preferably includes an axial bearing stop to retain the bearing and is preferably made of a material resistance to high temperature.  
         [0005]     In accordance with one aspect of the invention, there is provided an electric motor having an armature with an armature shaft, a case enclosing the armature, an endbell at an open end of the case, a bearing seat in the endbell, a bearing between the endbell and the armature shaft, and a bearing sleeve between the bearing and the bearing seat. The bearing sleeve comprises a deformable cylindrical sleeve body having an outside surface and an inside surface, outside ribs angularly spaced apart on the outside surface, and inside ribs angularly spaced apart on the inside surface and in angular gaps between the outside ribs. The sleeve body is deformed when in an assembled motor by the inward biasing of the outside ribs by the bearing seat and the outward biasing of the inside ribs by the bearing, and a resistance to deformation of the sleeve body providing a firm fit for the bearing into the bearing seat. The bearing sleeve preferably is made from a polymer resistance to high temperature, and preferably includes an axial bearing stop to prevent direct axial contact of the bearing with the bearing seat. The number of insides ribs is preferably equal to the number of outside ribs.  
         [0006]     In accordance with another aspect of the invention, there is provided a bearing sleeve comprising a deformable cylindrical sleeve body having an outside surface and an inside surface, outside ribs angularly spaced apart on the outside surface, and inside ribs angularly spaced apart on the inside surface and angularly spaced between the outside ribs. The sleeve body is deformed when residing between a bearing and a bearing seat by the inward biasing of the outside ribs by the bearing seat and the outward biasing of the inside ribs by the bearing, a resistance to deformation of the sleeve body providing a firm fit for the bearing into the bearing seat. The bearing sleeve may support bearings in a variety of applications including electric motors, axles, transmissions, and any application including bearings. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0007]     The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:  
         [0008]      FIG. 1  is an exploded view of an electric motor including a bearing sleeve according to the present invention.  
         [0009]      FIG. 2  is a detailed perspective view of the bearing sleeve.  
         [0010]      FIG. 3  is a side view of the bearing sleeve.  
         [0011]      FIG. 4A  is a cross-sectional view of the bearing sleeve taken along line  4 A- 4 A of  FIG. 3 .  
         [0012]      FIG. 4B  is a cross-sectional view of the bearing sleeve taken along line  4 B- 4 B of  FIG. 3 .  
         [0013]      FIG. 4C  is a cross-sectional view of the bearing sleeve taken along line  4 C- 4 C of  FIG. 3 .  
         [0014]      FIG. 5  depicts the deformation of a sleeve body of the bearing sleeve when the bearing sleeve resides between a bearing and a bearing seat. 
     
    
       [0015]     Corresponding reference characters indicate corresponding components throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.  
         [0017]     An exploded view of an electric motor  10  including a bearing sleeve  12  according to the present invention is shown in  FIG. 1 . The motor  10  further includes an armature  14  having an armature shaft  14   a . The armature shaft  14   a  is supported in an endbell  18  by an endbell bearing  16 , and in a motor case  22  by a case bearing  20 . Brushes  24  reside in the endbell  14 , and endbell screws  26  attach the endbell  18  to the case  22 . The bearing sleeve  12  is retained in a bearing seat  16   a  in the endbell  18  by a clip  13 . Although the invention is shown in a brush type motor, the present invention applies equally to a brushless motor, and a brushless motor including a bearing sleeve as described herein is intended to come within the scope of the present invention.  
         [0018]     A detailed perspective view of the bearing sleeve  12  is shown in  FIG. 2 . The bearing sleeve  12  includes an outside surface  12   a  and an inside surface  12   b . Angularly spaced apart axially running outside ribs  28  reside on the outside surface  12   a , and angularly spaced apart axially running inside ribs  30  reside on the inside surface  12   b . The bearing sleeve  12  interior defines a bearing sleeve cavity  12   c  wherein the bearing  16  resides in an assembled motor  10 .  
         [0019]     The outside ribs  28  preferably are uniformly angularly spaced apart, and preferably run substantially the length (see  FIG. 4B ) of the bearing sleeve  12 . While the outside ribs  28  do not necessarily run the entire length of the bearing sleeve  12 , they preferably run a sufficient length to prevent the bearing sleeve  12  from wobbling in the bearing seat  16   a . The inside ribs  30  preferably are uniformly angularly spaces apart, and preferably run substantially the length (see  FIG. 4B ) of the bearing sleeve cavity  12   c . While the inside ribs  28  do not necessarily run the entire length of the bearing sleeve cavity  12   c , the inside ribs  28  preferably run a sufficient length to prevent the bearing  16  from wobbling in the bearing sleeve cavity  12   c . The inside ribs  30  are preferably angularly spaced approximately half way between pairs of the outside ribs  28 , and the number of inside ribs  30  is preferably equal to the number of outside ribs  28 .  
         [0020]     A side view of the bearing sleeve  12  is shown in  FIG. 3  and a cross-sectional view of the bearing sleeve  12  taken along line  4 A- 4 A of  FIG. 3  is shown in  FIG. 4A . The bearing sleeve  12  has a sleeve length L S  and a sleeve diameter D S . The length L S  is preferably approximately 0.172 inches and the diameter D S  is preferably approximately 0.423 inches not including the outside ribs  28 , and is approximately 0.438 inches including the outside ribs  28 . The outside ribs  28  are substantially semi circular in shape with a radius of preferably approximately 0.0075 inches.  
         [0021]     The sleeve cavity  12   c  cavity length L C  and a cavity diameter D C . The cavity length L C  is preferably approximately 0.155 inches and the cavity diameter D C  is preferably approximately 0.389 inches not including the inside ribs  30 , and the diameter including the inside ribs  30  is approximately 0.374 inches. The inside ribs  30  are substantially semi circular in shape with a radius of preferably approximately 0.0075 inches. The sleeve body  34  is preferably approximately 0.034 inches thick. The inside diameter D ST  of the stop  32  is preferably approximately 0.225 inches. The dimensions of the bearing sleeve  12  are for a particular bearing and endbell. The stop  32  preferably extends inwardly to an inner bearing race, and preferably substantially covers the exposed portion of the bearing only leaving the inner bearing race exposed, but preferably does touch the inner bearing race. In low RPM applications the stop may contact the inner bearing race to provide free seal.  
         [0022]     The bearing sleeve  12  dimensions may vary for different bearings, endbells, and fit requirements, and any bearing sleeve having spaced apart exterior ribs, and spaced apart interior ribs residing angularly offset from the exterior ribs, is intended to come within the scope of the present invention.  
         [0023]     A cross-sectional view of the bearing sleeve taken along line  4 B- 4 B of  FIG. 3  is shown in  FIG. 4B , and cross-sectional view of the bearing sleeve  12  taken along line  4 C- 4 C of  FIG. 3  is shown in  FIG. 4C . The inside ribs  28  are seen to be angularly spaced between the outside ribs  28 . The bearing stop  32  partially encloses one end of the bearing sleeve  12 . The outside ribs  28  preferably comprise 29 outside ribs and the inside ribs  30  preferably comprise 29 inside ribs. The numbers of outside ribs  28  is preferably the same as the number of inside ribs  30 , with the inside ribs  30  residing centered between each adjacent pair of outside ribs.  
         [0024]     The deformation of the sleeve body  34  of the bearing sleeve  12 , when the bearing sleeve  12  resides between the bearing  16  and the bearing seat  16   a  of an assembled motor  12  is shown in  FIG. 5 . The outside ribs  28  are biased inwardly along arrows  38  by the bearing seat  16   a  and the inside ribs  30  are biased outwardly along arrows  36  by the bearing  16 . As a result of the biasing, the sleeve body  34  is deformed. The resistance of the sleeve body  34  to the deforming provides a firm fit of the sleeve  12  into the bearing seat  16   a , and of the bearing  16  into the sleeve cavity  12   c.    
         [0025]     The firmness of the fit between the bearing, the bearing sleeve, and the bearing seat is limited to prevent crush of an outer race of the bearing. Such fit may be controlled, for example, by the thickness of the sleeve body  34 , and/or the number of outer ribs  28  and/or the inner ribs  30 . For example, the number of inner ribs  30  may be one half the number of outer ribs  28 , wherein the inner ribs  30  may be spaced between alternate pairs of outer ribs  28 . The resistance to crush of the outer bearing race is generally provided as part of the bearing specification. A particular bearing sleeve design may be analyzed using one of the commonly available structural analysis programs such as Cosmos® advanced professional non-linear structural analysis tools from Structural Research &amp; Analysis Corporation in Santa Monica, Calif. working with SolidWorks® software from SolidWorks Corporation in Concord Mass. The bearing sleeve may thus be designed to provide a sufficiently firm fit to hold the bearing without exceeding crush tolerance of the bearing. The design may further be evaluated over a range of bearing seat inside diameters to ensure that manufacturing tolerances for the bearing seat are acceptable.  
         [0026]     The bearing sleeve  12  is preferably made from a high temperature polymer, and more preferably from a glass fiber reinforced lubed nylon, and most preferably from Zytel®  7 0G33 available from E. I. duPont de Nemours &amp; Co. Wilmington, Del., or any material with similar mechanical properties. The ribs  28  and/or  30  may be square, oval, and may be segmented or continuous as depicted herein.  
         [0027]     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.