Patent Publication Number: US-2012045157-A1

Title: End cap for a bearing assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 12/062,841, filed Apr. 4, 2008 and which claims the benefit of U.S. provisional application No. 60/921,949 filed Apr. 4, 2007, both of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention is generally directed to an end cap with a retaining portion for a bearing and is more specifically directed to a light weight end cap having a retaining portion capable of removably securing the end cap to a bearing assembly and resisting inadvertent removal from the bearing. 
     BACKGROUND OF THE INVENTION 
     Many types of bearings can be used to support radial, thrust, or combination radial and thrust loads. Such bearings include ball, roller, plain, journal and tapered roller types. To reduce friction, a lubricant such as a grease or oil can be introduced into the bearing. 
     Bearing performance can degrade, or severe and even catastrophic damage can occur, if insufficient lubricant is provided to the bearing. Where a bearing contains rolling elements, rotation of these rolling elements can act to pump lubricant out of the bearing. In addition, bearing performance can be detrimentally affected as a result of contamination of the lubricant and/or the introduction of foreign matter into the bearing. Seals have been used to help retain the lubricant within the bearing and to minimize contamination and foreign matter from entering therein. Such seals are typically made from a resiliently compliant material such as rubber, synthetic rubber or a composition thereof, such as Viton®. 
     A fitting, such as a grease fitting, can be positioned accordingly to provide a location for the introduction of the lubricant into the bearing. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, an end cap for a bearing includes a first body section which is substantially symmetric about a central axis of the end cap. The end cap has a first seating surface defining an opening extending through the first body section coaxially with the central axis. The end cap also includes a second body section extending away from the first seating surface and terminating at a second seating surface. The opening is operable to receive a portion of an inner member of the bearing. The first seating surface is operable to engage a portion of the inner member. The second seating surface is operable to slidingly engage a portion of an outer ring which is disposed around a portion of the inner member. 
     The end cap can be made from a resilient plastic, a resilient metal or a resilient composite material. 
     According to another aspect of the present invention, a bearing includes an outer ring having a substantially cylindrical internal bearing surface and an inner member having a substantially cylindrical external bearing surface. A portion of the inner member is coaxially disposed within the outer ring. The external bearing surface and the internal bearing surface cooperate to define an annular cavity therebetween. A plurality of rolling elements is disposed within the annular cavity. The rolling elements are in rolling engagement with the external bearing surface and the internal bearing surface. The inner member defines a recess for engaging a portion of an end cap, as described further below. 
     In addition, the bearing includes an end cap defined by a first body section which is substantially symmetric about a central axis of the end cap. The first body section also has a first seating surface which defines an opening extending through the first body section coaxially with the central axis. The end cap also defines a second body section extending away from the first seating surface and terminating at a second seating surface. A portion of the inner member is positioned in the opening with the first seating surface being seated in the recess of the inner member. The second seating surface engages a portion of the outer ring. The end cap extends between the inner member and the outer ring. 
     In one embodiment, the recess of the inner member defines a circumferential groove in which the first seating surface is disposed. The groove can be located on a portion of the inner member positioned outside of the outer ring. 
     In another embodiment, the outer ring defines a recess in which the second seating surface is sealingly engaged. 
     In addition, the first seating surface and the second seating surface can be substantially perpendicular to one another. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional side view of a shaft and bearing assembly including an end cap in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross sectional view of the end cap and a cut away portion of the shaft of the assembly of  FIG. 1 , wherein the end cap is inserted into the shaft. 
         FIG. 3  is an end view of the end cap of  FIG. 2 . 
         FIG. 4  is a cross sectional view similar to  FIG. 2 , but with end cap only partially inserted into the shaft, so that the detent member is in a compressed state. 
         FIG. 4A  is a detail view of a part of  FIG. 2 . 
         FIG. 5  is a cross sectional view of the end cap with a shank having a through-bore, inserted into a shaft. 
         FIG. 6  is a cross sectional view of an end cap including a castellated shank having a through-bore. 
         FIG. 7  is an end view of the end cap of  FIG. 6 . 
         FIG. 8  is a cross sectional view of the end cap including a castellated shank having a through-bore and outwardly projecting protrusions extending therefrom. 
         FIG. 9  is a partial cross sectional view of an end cap installed on a bearing assembly in accordance with another embodiment of the invention. 
         FIG. 10  is a cross sectional view of the end cap of  FIG. 9 . 
         FIG. 11  is a bottom view of the end cap of  FIG. 10 . 
         FIG. 12  is a detail view of a portion of  FIG. 9 . 
         FIG. 13  is a detail view of the seating portion in the outer ring shown in  FIG. 9 . 
         FIG. 13A  is a partial cross sectional view of an end cap installed on a bearing assembly in accordance with another embodiment of the invention. 
         FIG. 14  is a cross sectional view of an end cap including a castellated retaining portion according to another embodiment of the invention. 
         FIG. 15  is a bottom view of the end cap of  FIG. 14 . 
         FIG. 16A  is a schematic cross-sectional view of a shaft and bearing assembly with an end cap according to yet another embodiment of this invention. 
         FIG. 16B  is a detail view of a portion of  FIG. 16A . 
         FIG. 17  is a schematic cross-sectional view of a shaft and bearing assembly with an end cap according to yet another embodiment of this invention 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , a shaft and bearing assembly generally designated by the reference numeral  10  has an end cap  12  mounted thereon. The shaft and bearing assembly  10 , may be a cam follower or a yoke roller or the like. The shaft and bearing assembly  10  is composed of a substantially cylindrical shaft  30  and a bearing  72  mounted thereon. The bearing  72  includes an outer ring  16  and an inner bearing, for example, an inner ring  14 . A plurality of rolling elements  28  is positioned between the outer ring  16  and the inner ring  14 . The inner ring  14  has a substantially cylindrical external bearing surface  18  including at least one outwardly projecting shoulder  24 . The inner ring  14  includes a substantially cylindrical inner wall  19  defining a bore which extends through the inner ring. The outer ring  16  of the bearing  72  has a substantially cylindrical internal bearing surface  20  including at least one inwardly projecting shoulder  26 . The inner ring  14  is coaxially disposed within the outer ring  16 . The inner ring  14  and the outer ring  16  cooperate to define an annular cavity  22  therebetween. A plurality of rolling elements  28 , which may be needles, balls, rollers, or the like, are disposed in the annular cavity  22 . The rolling elements  28  are in rolling engagement with the external bearing surface  18  and the internal bearing surface  20  so that the inner ring  14  and the outer ring  16  are rotatable relative to each other about their common axis A. The plurality of rolling elements  28  are positioned between the outwardly projecting shoulders  24  and the inwardly projecting shoulders  26 . The bearing  72  also includes two seals  32  disposed between the external bearing surface  18  and the internal bearing surface  20  for retaining a lubricant within the annular cavity  22 . One of the seals  32  is positioned at an outboard end  36  of the bearing  72  and another one of the seals  32  is positioned at an in-board end  44  of bearing. While two seals  32  have been shown and described, the present invention is not limited in this regard as less than or more than two seals can be employed without departing from the broader aspects of the present invention. 
     The portion of the shaft  30  disposed in the bore of the inner ring  14  is substantially cylindrical. The inner ring  14  may be pressed, shrunk, or otherwise secured onto the shaft  30 . The inner ring  14  and the portion of the shaft  30  therein cooperate to form an inner bearing structure of the shaft and bearing assembly  10 . 
     The shaft  30  has a bore  52  that is formed, cut or otherwise disposed in a distal end  39  of the shaft. The bore  52  has a first portion  53  that is adjacent to the distal end  39  of the shaft  30  and that has a diameter d 1 . A second portion  55  of the bore  52  is adjacent to the terminal end  56  of the bore and has a diameter d 2 . The diameter d 2  is larger than d 1 , such that a shoulder  54  is defined in the bore  52  between the first portion  53  and the second portion  55 , as seen in  FIG. 4 . 
     Referring to  FIGS. 1-4 , the end cap  12  has a body portion  40  that has an outer engagement portion and a central engagement portion. The outer engagement portion engages the outer ring of the bearing  72 , and the central engagement portion engages the shaft  30  or inner ring  14 . The engagement may be mutual surface contact that may inhibit the passage of particles, liquid and vapors therethrough (“sealing engagement”), or the engagement may be a mechanical coupling sufficient to retain the end cap  12  on the bearing  72  or on the shaft  30 . Sealing engagement may include sliding contact between the mutually engaging structures. In the end cap  12 , the central engagement portion includes a substantially cylindrical shank  46  projecting outwardly from the body portion. The shank  46  has a first end  43  which defines a circumferential seating groove  59  for receiving a resilient split ring  51  having a gap  57  ( FIG. 3 ) defined thereby. 
     The split ring  51  is configured to have, in a relaxed state, an outside diameter that exceeds the diameter d 1  in the bore  52  and an inside diameter that does not exceed the diameter of the shank  46  (so that even in the relaxed state, the split ring  51  remains seated in the seating groove  59 ). In addition, the split ring  51  and the seating groove  59  are configured so that the split ring can be compressed to conform to a diameter dl. When the shank  46  is inserted into the shaft  30 , the inner wall  63  of the first portion  53  of the bore  52  applies a force F (indicated in  FIG. 4 ) on the split ring  51  that causes the split ring to compress, thus allowing the split ring  51  to advance through the first section  53  to the second section  55 . In the second section  55 , the split ring  51  expands and inhibits the withdrawal of the shank  46  from the bore  52  by bearing against the shoulder  54 . Thus, the split ring  51  and the second section  55  and the shoulder  54  function as a seat on the shaft for engaging the split ring  51  and together cooperate to for a detent mechanism. In this way, the shank  46  mechanically couples the end cap  12  to the shaft  30  without the need for supplemental mounting means such as screws, bolts, adhesive, etc. 
     Preferably, the shank  46  releasably engages the seating portion so that the end cap  12  can be removed from the shaft and bearing assembly  10  and may then be replaced, e.g., to temporarily expose the end of the shaft  30  and the outboard end  36  of the bearing  72  for inspection, maintenance or any other purpose. For example, the split ring  51  contacts the shoulder  54  at a point near its circumferential perimeter, i.e., at a radial distance Dc from the axis A to a point on the split ring beyond the greatest diameter DR of the split ring measured parallel to the axis A, as seen in  FIG. 4A . An adequate withdrawal force can then cause the split ring  51  to again compress and allow the shank  46  to be withdrawn from the shaft  30 , thus allowing the end cap to be removed from the shaft and bearing assembly  10 . Alternatively, or in addition to contacting the split spring  51  as just described, the shoulder  54  may be slanted so that the shoulder acts as the surface of a cam that compresses the split spring as the end cap  12  is withdrawn from the bore  52 . 
     The body portion  40  of the end cap  12  has a disc-like configuration which extends from the central engaging portion (i.e., from the shank  46 ) radially outward, across the annular cavity to an outer engagement portion  42  disposed thereon which sealingly engages the mating surface  34  of the outer ring  16 . Thus, the end cap  12  provides a barrier to the introduction of contamination and foreign matter into the annular cavity  22 . 
     Although the detent mechanism is shown as a split ring  51  fitted into a seating groove  59 , the present invention is not limited in this regard, as other suitable detent mechanisms can be used to mechanically couple the end cap  12  to the shaft and bearing assembly  10 , including but not limited to ball and spring mechanisms, protrusions or resilient fingers projecting outwardly from the outer surface  50 , or a combination thereof. Furthermore, the seat on the shaft and bearing assembly  10  that engages the detent member may be a detent-receiving groove of any form suitable to the detent member. Moreover, although a detent mechanism is shown and described, the present invention is not limited in this regard, as it will be apparent to one of ordinary skill in the art that the engagement portion on the end cap  12  that mechanically couples the end cap to the shaft and bearing assembly  10  may comprise a seating portion for a detent on the shaft and bearing assembly. 
     While the shank  46  has been described above as being substantially cylindrical, the present invention is not limited in this regard as the shank can be of any suitable cross-sectional shape including but not limited to hexagonal, square and star-shaped cross sections. The end cap  12  can be manufactured from a resilient plastic material such as polyurethane and the split ring  51  can be manufactured from spring steel, however, the invention is not limited in this regard as other materials may be used for the end cap  12 , including but not limited to metals, composite materials and combinations thereof, and/or other materials may be used for the split spring  51  or other detents, including but not limited to other metals, composite materials and combinations thereof. 
     While the bearing  72  is shown with two sets of rolling elements  28  separated by a shoulder  24  that projects from the inner ring  14 , this is not a limitation on the invention, and various other configurations of bearings, rolling elements, etc. are known in the art and, in view of the disclosure herein, all such bearings and shaft and bearing assemblies can employ an end cap as described herein. 
     The end cap  112  shown in  FIG. 5  is similar in configuration to the end cap  12  shown in  FIGS. 1-4 , and the foregoing description of end cap  12  will apply to end cap  112  correspondingly, with the following differences. The end cap  112  has a hollow shank  146  which defines a passage  147  that extends from the first end  43  of the shank to the second end  48  and through the body portion  40 . The shank  146  sealingly engages the inner wall  63 . The passage  147  allows the escape of air from the bore  52  to avoid compressing air therein while the end cap  112  is mounted on the shaft and bearing assembly  10 . 
     The end cap  212  shown in  FIGS. 6 and 7  is similar in configuration to the end cap  112  shown in  FIG. 5 , and the foregoing description of end cap  112  will apply to end cap  212  correspondingly, with the following differences. The end cap  212  includes a shank  246  which is a substantially hollow cylindrical shell open on opposing ends and defining a passage  247  extending therethrough. The shank  246  includes a castellated portion defined by a plurality of slits  258  formed at the first end  243  and terminating between the first end and the second end  248 . The slits  258  define a plurality of shank segments  288 . The slits  258  allow the shank segments  288  to flex when sliding the shank  246  into the shaft  30  to engage the seating portion in the shaft. 
     The end cap  312  shown in  FIG. 8  is similar in configuration to the end cap  212  shown in  FIGS. 6 and 7 , the foregoing description of end cap  12  will apply to end cap  312  correspondingly, with the following differences. The end cap  312  includes a shank  346  which is a substantially hollow cylindrical shell open on opposing ends and defining the passage  347  extending therethrough. The shank  346  further includes a castellated portion defined by a plurality of slits  358  formed in the first end  343  and defining a plurality of flexible shank segments  388 . There is no split ring or seating groove to correspond to split ring  251  and seating groove  259 , but the shank  346  includes detent members having protrusions  360  projecting outwardly from the shank segments  388 , at the first end  343  of the shank. The protrusions  360  can engage the seating portion of the shaft and bearing assembly  10  in a manner similar to that described above for the split ring  51  of end cap  12 . 
     The shaft and bearing assembly  410  shown in  FIGS. 9-13  are similar in configuration to the shaft and bearing assembly  10  shown in  FIGS. 1-4 , the foregoing description of the shaft and bearing assembly  10  will apply to the shaft and bearing assembly  410  correspondingly, with the following differences. The outer ring  416  of the bearing assembly  410  defines a detent-receiving groove  462  disposed on an end  436  of the outer ring, to provide a seating portion. The detent-receiving groove  462  is disposed on an end surface  434  on an end  436  of the outer ring  416  which is substantially perpendicular to the axis A. 
     The detent-receiving groove  462  is formed, cut or otherwise disposed in the end  436  and defines a shoulder  464 . The shoulder  464  is defined by a transition between a first section  466  of the detent-receiving groove  462  having an inside diameter d 3  and a second section  468  of the detent-receiving groove  462  having an increased diameter d 4  adjacent the terminal end  470  of the bore, wherein d 4  is greater than d 3 . 
     The inner ring  414  extends axially towards the end of the shaft  430  than does the outer ring  416 , so that part of the substantially cylindrical external bearing surface  418  extends beyond the annular cavity  422 . 
     The end cap  412  on the shaft and bearing assembly  410  has a body portion  440  but no shaft portion. The end cap  412  is manufactured from a resilient plastic material such as polyurethane. The body portion  440  has an annular configuration having an inner portion  413   a  which provides the central engagement portion of the end cap  412 . The annular inner portion  413   a  mechanically engages a groove (unnumbered) on the inner ring  414 , the groove providing a seat for retaining the end cap  412  on the shaft and bearing assembly  410 . 
     The end cap  412  includes a lip  415  ( FIG. 10 ) to provide a retaining portion projecting from the body portion  440 . The lip  415  is a resilient cylindrical shell disposed about a periphery of the body portion  440 . The lip  415  includes a protrusion  417  to provide a detent member for sealingly and releasably securing the end cap  412  to a seating portion the bearing assembly  410 . 
     Referring to  FIGS. 12 and 13 , when the lip  415  is inserted into the detent-receiving groove  462  within the first section  466 , a radially and inwardly directed reaction force applied by the detent-receiving groove  462  onto the protrusion  417  causes the lip  415  to deform and allows the lip  415  to travel into the bore. When the protrusion  417  moves into the second section  468 , the protrusion  417  relaxes and abuts the shoulder  464  thus inhibiting removal of the lip  415  from the detent-receiving groove  462 . 
     The shaft  430  includes flow paths  480  and a port  482  for conveying a lubricant to the annular cavity  422  via an inner ring flow path aperture  480   a.  In operation, the lubricant can by supplied to the bearing assembly  410  without removing the end cap  412 . 
     While the end cap  412  is shown engaging inner ring  414 , the present invention is not limited in this regard as an inside circumferential surface may alternatively engage a portion of a shaft in the bearing. For example, in the shaft and bearing assembly  410 ′ shown in  FIG. 13A , which has generally the same configuration as the shaft and bearing assembly  410  shown in  FIG. 9 , the inner ring  414 ′ does not extend as far in the axial direction along the shaft  430  as the inner ring  414  of  FIG. 9 , and so the cylindrical mating portion  430   a  on the shaft is exposed. The end cap  412 ′ has a larger body portion  440 ′ than the body portion  440  of the end cap  412 , and the larger body portion  440 ′ reaches over the inner ring  414 ′ from the outer ring  416  to engage the mating portion  430   a.    
     The end cap  512  shown in  FIGS. 14 and 15  is similar in configuration to the end cap  412  shown in  FIGS. 9-12 , and the foregoing description of end cap  412  will apply to end cap  512  correspondingly, with the following differences. The lip  515  has a castellated configuration defined by a plurality of axially extending slits  558  formed, cut or otherwise disposed in the cylindrical shell and defining a plurality of segments  588  ( FIG. 15 ). The slits  558  extend between the first end  543  and the second end  548  and allow the segments  588  to flex when sliding the lip  515  into the seating portion. The end cap  512  can be used on a shaft and bearing assembly in the same manner as end cap  414 , e.g., in one embodiment the inside circumferential surface  513  may sealingly engage an inner ring  414  or a shaft  430 . 
     In another embodiment, the inner bearing structure is integral with the shaft, as seen in the shaft and bearing assembly  610  of  FIG. 16 . Accordingly, the outer ring  616  is coaxially disposed about the end of the shaft  630  to define an annular cavity  622  between the outer ring and a cylindrical stepped end portion  630   a  of the shaft. The cylindrical stepped end portion  630   a  of the shaft provides a substantially cylindrical external bearing surface  618 , and the rolling elements  628  are disposed in the annular cavity in rolling contact with the outer ring  616  and the shaft  630 . An end cap  612  is mounted on the shaft and bearing assembly  610 . The end cap  612  has a body portion  640  that includes a shank  646  extending therefrom for insertion into a bore  652  in the end of the shaft  630 . The bore  652  may have a hexagonal configuration. The shank  646  has a bore therethrough and has, at the insertion end, a castellated configuration provided by slits  658  that divide the shaft into flexible segments  688 . The shank  646  includes barbs  651  on the flexible segments  688 , and the bore  652  in the shaft  630  includes an internal rib or undercut  654  in the bore  652 . As seen in  FIG. 16B , each barb  651  has an outward-facing wedge surface  651   a  and a stop shoulder  651   b.  The barb  651  is configured so that as the end cap  612  is inserted into the bore  652 , the wedge surface  651   a  engages the rib  654  and, as the shank  646  advances in the bore, the barb causes the segment on which it is disposed to flex inward. Then, once the shoulder  651   b  passes the rib  654 , the segment flexes outward and the shoulder  651   b  engages the rib  654  to inhibit removal of the end cap  612  from the shaft  630 . In this way, the shoulder  654  provides a seat for receiving the barb  651 , whereby to retain the end cap  612  on the shaft and bearing assembly  610 . The body portion  640  of the end cap  612  is configured so that when the barb  651  engages the rib  654 , the body portion extends across the annular cavity  622  to where an annular sealing surface  642  on the body portion engages an annular recessed mating surface  634  on the outer ring  616 . 
     As illustrated in  FIG. 17 , the shaft and bearing assembly  710  includes an outer ring  716  having a substantially cylindrical internal bearing surface  720 . A shaft  730  is coaxially disposed within the outer ring  716 . The shaft  730  defines a stepped portion  730   a  which provides a substantially cylindrical external bearing surface  718 . An annular cavity  722  is defined between the internal bearing surface  720  and the external bearing surface  718 . A plurality of rolling elements  728  are disposed in the annular cavity  722 . The rolling elements  728  rolling engage the internal bearing surface  720  and the external bearing surface  718 . 
     A recessed mating surface  734 , for example, a groove, is formed into a transverse end, for example an end face, of the outer ring  716  for receiving a portion of an end cap  710 , as described below. An end portion  793  of the shaft  730  extends out of the outer ring  716 . A portion of the shaft  730  adjacent to the end  793  defines an external surface  794 . Another recessed mating surface  747 , for example, a groove, is formed into the external surface  794  of the shaft  730 . 
     The shaft and bearing assembly  710  also includes an end cap  712  which is removably disposed thereon. The end cap  712  defines a first body portion  740  that has a central opening  741  defined by a generally annular first seating surface  745  that is seated in the recessed mating surface  747  in the shaft  730 . The end cap  712  includes a second body portion  739  which extends away from the first seating surface  745  and terminates at a substantially circular second seating surface  742 . The second seating surface  742  sealingly and slidingly engages the recessed mating surface  734  on the end of the outer ring  716 . The end cap  712  is illustrated having a bend  790  which defines the junction of the first body portion  740  and the second body portion  739 . The bend  790  is configured to position the first seating surface  745  and the second seating surface  742  substantially perpendicular to one another. 
     While the central opening  741  is shown and described as being defined by a generally annular first seating surface  745 , the present invention is not limited in this regard, as other shapes and configurations may be employed including but not limited to rectangular and hexagonal shapes. Although the second seating surface  742  is shown and described as being substantially circular, the present invention is not limited in this regard as other shapes and configurations may be employed including but not limited to hexagonal and elliptical shapes. 
     The end cap  712  can be manufactured from a resilient plastic material such as polyurethane, however, the invention is not limited in this regard as other materials may be used, including but not limited to metals, composite materials and combinations thereof. 
     The opening  741  is operable to receive an end of the shaft  730 . In addition, during installation, the end cap  712  is elastically deformed by expanding the opening  741  onto the shaft  730 . When the end cap  712  is installed on the shaft  730  with the second seating surface  745  removably secured and seated in the groove  747 , the end cap returns to an un-deformed state. 
     Although the present invention has been disclosed and described with reference to certain embodiments thereof, it should be noted that other variations and modifications may be made, and it is intended that the following claims cover the variations and modifications within the true spirit of the invention.