Patent Publication Number: US-2007116394-A1

Title: Slewing ring having improved inner race construction

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority of U.S. Provisional Patent Application Ser. No. 60/738,959 filed Nov. 22, 2005, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to ring bearings and specifically relates to a slewing ring with enhanced dimensional stability.  
     BACKGROUND OF THE INVENTION  
      Bearings are widely used to minimize friction between rotatably coupled components that exhibit movement relative to one another. Components used in the fields of medicine, automotive manufacturing, power generation, and the like, can require two components to rotate relative to one another and maintain tight tolerances with respect to their location about a axis. A slewing ring affords for one component to rotate about a axis relative to a second component. However, some applications expose the components and the slewing ring to shearing or off-axis loading which can subsequently cause excess movement in undesirable off-axis directions and/or increase the friction between said components. Therefore, it is desirable to improve the performance of slewing rings, particularly when said rings are under high stress or loading conditions. The stewing ring of the present invention affords for enhanced dimensional stability of the ring and components attached thereto. These and other advantages of the invention will be apparent from the drawings and discussion presented herein.  
     SUMMARY OF THE INVENTION  
      A slewing ring affording enhanced dimensional stability is provided. The ring includes an annular outer race and an annular inner race rotatably coupled to the outer race. The outer race and the inner race are arranged concentrically about an axis. At least one ball bearing is located between the outer race and the inner race. In addition, the inner race includes an annular upper member and an annular lower member. The upper member of the inner race has a retaining segment that extends coaxially with the axis. The lower member of the inner race has a U-shaped recess that is adapted to accept the retaining segment. The retaining segment in combination with the U-shaped recess affords for a slewing ring with increased capability to handle applied shearing or off-axis loading, and thereby provides enhanced dimensional stability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates a top view of an inventive slewing ring;  
       FIG. 2  illustrates a first cross-sectional side view of the inventive slewing ring;  
       FIG. 3  illustrates a second cross-sectional side view of the inventive slewing ring; and  
       FIG. 4  illustrates a third cross-sectional side view of the inventive slewing ring.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIG. 1 , a top view of a ring bearing  10 , also known as a slewing ring by those skilled in the art, is shown. The slewing ring  10  has an annular inner race  12  and an annular outer race  14 . The inner  12  and outer  14  races are arranged concentrically about an axis  5 . Preferably the axis  5  is fixed, but this is not required for the present invention to be operative. The inner  12  and outer  14  races are rotatably coupled to each other for relative rotation about the axis  5 . The inner race  12  can have a plurality of apertures or bores  16  allowing attachment of the inner race  12  to a first component (not shown) and the outer race  14  can have a plurality of apertures or bores  18  allowing attachment of the outer race  14  to a second component (not shown). By this arrangement, the ring  10  rotatably couples a first component to a second component and affords relative rotation between said components about a common axis.  
      Turning to  FIGS. 2-4 , various cross-sectional side views of the slewing ring  10  are shown, revealing the present invention in more detail. The outer race  14  has a generally rectangular cross section defined by opposite inner  20  and outer  22  walls which extend in an axial direction, and opposite top  24  and bottom  26  ends which extend in a radial direction.  
      The inner wall  20  is defined by first  28 , second  30  and third  32  surfaces, and a step  34 . The third surface  32  is disposed adjacent the bottom end  26  of the cross section. The third surface  32  has a diameter that is smaller than the first  28  and second  30  surfaces wherein said diameter is measured from the axis  5 . In the alternative, the third surface  32  has a diameter that is larger than the first  28  and second  30  surfaces. The first surface  28  is disposed adjacent the top end  24 . The first  28  and second  30  surfaces have generally the same diameter. In the alternative, the first  28  and second  30  surfaces do not have the same diameter.  
      The step  34  is positioned between the first  28  and second  30  surfaces and protrudes radially inwardly towards axis  5  relative to said surfaces  28  and  30 . The step  34  has a diameter that is smaller than that of the third  32  surface, or in the alternative step  34  has a diameter that is large than that of the third surface  32 .  
      Radii  40  are defined between the step  34  and the first  28  and second  30  surfaces, and thereby afford a first bearing ring seat surface  29  having the radius  40  and a second bearing ring seat surface  31  having the radius  40 .  
      The inner race  12  has annular upper  42  and lower  44  members. The upper member  42  is fixedly secured to the lower member  44  using any attachment means known to those skilled in the art, illustratively including a plurality of bolts, rods or pins (not shown) with corresponding apertures. In one embodiment bolts extend through corresponding bores  45  and  57  formed in the upper  42  and lower  44  members, respectively, as shown in  FIG. 4 .  
      Although not required for the present invention to be operative, one embodiment includes the upper member  42  of the lower race  12  with a generally rectangular cross section, the length of which is arranged orthogonally with respect to the length of the outer race  14 . The upper member  42  has opposite upper  46  and lower  48  walls, and opposite inner  50  and outer  52  ends. The outer end  52  has a diameter that is larger than the diameter of the outer wall  22  of the inner race  12 .  
      The plurality of apertures or bores  16  of the inner race  12  can be formed in the upper member  42  and arranged along a region defined between the outer end  52  of the upper member  42  and the outer wall  22  of the outer race  14 . Bolts, pins or rods can be placed at least partially within the bores  16  in order to afford attachment of a component to the upper member  42 .  
      A flange  60  extends in an axial direction from the lower wall  48  of the upper member  42 , as shown in  FIG. 2 . The flange  60  includes a middle surface  62  that is parallel and spaced apart from the lower wall  48 . In the alternative, the middle surface  62  is not parallel to the lower wall  48 .  
      A first  64  and second  66  retaining segments extend coaxially, with respect to the axis  5 , from the middle surface  62 . The first  64  and second  66  retaining segments are generally parallel with each other, such that a generally U-shaped upper pocket  65  is formed therebetween, as shown in  FIGS. 2 and 3 . For the purposes of the present invention, the term generally parallel is defined as two lines or surfaces being parallel to each other or deviate from being parallel to each other not more than  15  degrees. The first retaining segment  64  can be longer than the second retaining segment  66  and has an inside surface  68  with at least part of said surface  68  including helical threads extending radially inwardly.  
      The distal end of the second retaining segment  66  has an angled surface  70  facing radially inwardly toward the first retaining segment  64  at a 45 degree, or otherwise acute, angle with respect to the middle surface  62  of the flange  60 . The second retaining segment  66  has an outside surface  65  opposite and generally parallel to the inside surface  68  of the first retaining segment  64 . The outside surface  65  has a smaller diameter than that of the first surface  28  of the outer race  14  and is adjacent thereto.  
      The lower member  44  of the inner race  12  can optionally have a generally L-shaped cross-section. The lower member  44  includes an outside surface  72  having helical threads for threadingly engaging the threads on the inside surface  68  of the upper member  42 . A step  74  extends radially outwardly relative to the outside surface  72  of the lower member  44 . The step  74  is positioned below the outside surface  72  of the lower member  44 .  
      A third retaining segment  76  extends axially from the step  74  and toward the flange  60  of the upper member  42 . The distal end of the third retaining segment  76  has an angled surface  82  spaced apart and opposing the radial surface  70  of the second retaining segment  66 . The third retaining segment  76  is generally parallel to and spaced outwardly relative to the outside surface  72  of the lower member  44 .  
      The third retaining segment  76  and the outside surface  72  define a U-shaped recess  80  therebetween, said recess  80  adapted to accept the first retaining segment  64  of the upper member  42 , as shown in  FIG. 2 . The U-shaped recess has a first side parallel to the outside surface  72  and a second side spaced apart and oppositely disposed from the first side. Adjoining the first side and the second side of the recess  80  is a bottom surface. The first retaining segment  64  likewise has a first side, said first side parallel to the inside surface  68 , and a second side spaced apart and oppositely disposed from the first side. Adjoining the first side and the second side of the first retaining segment  64  is a bottom surface. The inventive slewing ring  10  affords for the first retaining segment  64  of the upper member  42  to extend into the U-shaped recess  80  defined between the third retaining segment  76  and the outside surface  72  of the lower member  44 . The acceptance of the first retaining segment  64  into the recess  80  enhances the dimensional stability of the inner race  12  and reduces the effects of shearing or off-axis loading on the slewing ring  10  and any components attached thereto.  
      Preferably the depth of the U-shaped recess  80  and the portion of the third retaining segment  76  accepted therein is between 0.05 and 35% of the overall axial height of the inner race  12 . More preferably the depth of the recess  80  is between 1 and 25% of the overall axial height of the inner race  12 , and even more preferably is between 1 and 15%. Even yet more preferably, the depth of the U-shaped recess is between 2 and 10% of the overall axial height of the inner race  12 .  
      The step  74  of the lower member  44  includes an angled surface  86  opposite the angled surface  82  on the third retaining segment  76 . The angled surface  86  is oriented at a 45 degree, or otherwise acute, angle relative to the axis  5  of the ring bearing  10 .  
      A leg  90  extends radially outward relative to, and is positioned below, the step  74 . A fourth retaining segment  92  extends axially from the leg  90  in a direction towards the flange  60 . The distal end of the fourth retaining segment  92  has an angled surface  94  spaced apart and generally parallel with the angled surface  86  of the step  74 . The fourth retaining segment  92  is generally parallel to and spaced apart from the step  74  and defines a lower pocket  95  therebetween. The lower pocket  95  is generally symmetrically opposite to the upper pocket  65  of the upper member  42 .  
      The upper pocket  65  and lower pocket  95  each include a corner  67  and  97 , respectively, as shown in  FIG. 3 . Adjacent to and in contact with corners  67  and  97 , corner inserts  69  and  99  can be included. Corner inserts  69  and  99  each have a radius  40  which faces, but is oppositely disposed from, the radius  40  between the step  34  and the first  28  and second  30  surfaces of outer race  14 . The radii  40  of corner inserts  69  and  99  afford a third bearing ring seat surface  61  and a fourth bearing ring seat surface  91 , respectively.  
      A first bearing ring  101  and a second bearing ring  102 , each having a radius  40 , are seated on opposite sides of the step  34  of the outer race  14 . A third bearing ring  103  and a fourth bearing ring  104 , also having a radius  40 , are seated adjacent to corners  67  and  97 . Specifically, the rings  101 ,  102 ,  103  and  104  are seated against first seat surface  29 , second seat surface  31 , third seat surface  61  and fourth seat surface  91 , respectively.  
      Each of the rings  101  through  104  include bearing surfaces  105 , said surfaces  105  being arcuate and having the same curvature as a ball bearing to be placed in contact therewith. In the alternative, the bearing surfaces  105  are non-acruate surfaces adapted to accept a bearing that is located adjacent to and in contact therewith. In the present embodiment, spaces are defined between the bearing surfaces  105  of rings  101  and  103 , and the bearing surfaces  105  of rings  102  and  104 , said spaces affording support for a plurality of bearings  110  located therebetween. For the purposes of the present invention, the term bearing, when used as a noun, is defined as an element that rolls between two races of a slewing ring, for example a ball.  
      The bearings  110  roll adjacent to and in between the bearing surface  105  of rings  101  and  103 , and the bearing surfaces  105  of rings  102  and  104 , and reduce friction between components rotating about the axis  5  and coupled to the slewing ring  10 . For illustrative purposes only, the bearings  110  shown in the figures are in the form of ball bearings, however any type of bearing can be used in the present invention including roller bearings, needle roller bearings, tapered roller bearings and spherical roller bearings. For the purposes of the present invention, ball bearings are bearings in the form of spheres, roller bearings are bearings in the form of cylinders with a slightly greater length than diameter, needle roller bearings are bearings in the form of long and thin cylinders, tapered roller bearings are bearings in the form conical rollers, and spherical roller bearings are bearings in the form of rollers that are thicker in the middle and thinner at the ends.  
      The inner race  12  and the outer race  14  can each include additional apertures, bores and/or pins, as illustratively shown by the positioning pin  6  in  FIG. 2  and the lifting bore  17  in  FIG. 4 . The positioning pin  6  affords assistance in the positioning and subsequent attachment of the slewing ring  10  to a component, and the lifting bore  17  can aid in the lifting, movement and positioning of the ring  10 . In addition, the slewing ring  10  of the present invention can optionally include a lubricant fitting  77  for introducing grease or similar lubricants between the inner  12  and outer  14  races, as shown in  FIG. 3 .  
      The invention has been described in an illustrative manner. It is, therefore, to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Thus, within the scope of the appended claims, the invention may be practiced other than as specifically described.