Abstract:
A method of manufacturing a bearing assembly includes the steps of providing first ( 38 ) and second ( 42 ) cage frames, each including a plurality of holes ( 46 ) spaced along a circumference of the respective first and second cage frames ( 38, 42 ), positioning a plurality of rollers ( 22 ) between the first and second cage frames ( 38, 42 ), each of the rollers ( 22 ) including a bore ( 26 ) coaxial with a rotational axis ( 30 ) of the respective rollers ( 22 ), aligning the bore ( 26 ) of a first of the plurality of rollers ( 22 ) with a first hole ( 46 ) in each of the respective first and second cage frames ( 38, 42 ), then sliding a threaded end ( 54 ) of a pin ( 50 ) through the first hole ( 46 ) in the first cage frame ( 38 ) and the first roller ( 22 ) a sufficient distance to engage the second cage frame ( 42 ). The method further includes rotating the pin ( 50 ) to form a screw thread in the first hole ( 46 ) of the second cage frame ( 42 ) with the threaded end ( 54 ) of the pin ( 50 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to co-pending U.S. Provisional Patent Application No. 61/669,811 filed on Jul. 10, 2012, the entire content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to bearing assemblies, and more particularly to pin-type roller bearings. 
       BACKGROUND OF THE INVENTION 
       [0003]      FIG. 1  illustrates a typical pin-type roller bearing assembly including an outer ring, an inner ring, and rollers arranged and positioned between the outer ring and the inner ring. A cage assembly maintains separation of the rollers and interconnects the rollers for uniform rotation with respect to the outer and inner rings. The cage assembly includes spaced cage frames between which the rollers are positioned, and pins having sufficient lengths to extend through holes in the respective cage frames and the rollers. Each pin has a threaded end that is received within a corresponding pre-threaded hole in one of the cage frames. Competing tolerances exist between the minimum torque value to which the threaded end of each pin should be tightened to the pre-threaded hole, and the protruded distance of the threaded end of each pin through the particular cage frame having the pre-threaded holes. Additionally, pre-threading numerous holes in one of the cage frames is a time-consuming and costly manufacturing step, requiring consumable tooling and specialized tolerance gages. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides, in one aspect, a method of manufacturing a bearing assembly. The method includes providing first and second cage frames, each including a plurality of holes spaced along a circumference of the respective first and second cage frames. The method also includes positioning a plurality of rollers between the first and second cage frames, each of the rollers including a bore coaxial with a rotational axis of the respective rollers. The method further includes aligning the bore of a first of the plurality of rollers with a first hole in each of the respective first and second cage frames, then sliding a threaded end of a pin through the first hole in the first cage frame and the first roller a sufficient distance to engage the second cage frame. The pin includes a head opposite the threaded end. The method further includes rotating the pin to form a screw thread in the first hole of the second cage frame with the threaded end of the pin. 
         [0005]    Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is perspective view of a typical pin-type roller bearing. 
           [0007]      FIG. 2  is a partial cross-sectional view of a bearing assembly in accordance with an embodiment of the invention. 
           [0008]      FIG. 3  is a side view of a pin of the bearing assembly of  FIG. 2 . 
           [0009]      FIG. 4  is an end view of the pin of  FIG. 3 . 
       
    
    
       [0010]    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 following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
       DETAILED DESCRIPTION 
       [0011]      FIG. 2  illustrates a portion of a bearing assembly  10  according to an embodiment of the invention. The bearing assembly  10  includes spaced, coaxial rings  14   a ,  14   b  having respective raceways  18   a ,  18   b  and a plurality of rollers  22  positioned between the raceways  18   a, b . In the illustrated construction of the bearing assembly  10 , the rollers  22  are oriented such that each roller  22  has a first end  22   a  relatively farther from a central axis  24  of the bearing assembly  10  in a radial direction and a second end  22   b  relatively nearer to the central axis  24  in the radial direction. The rollers  22  are configured as tapered cylinders and are inclined with respect to the central axis  24  to allow the bearing assembly  10  to carry both a radial load and an axial (i.e., thrust) load. Alternatively, the rollers  22  may be configured in any of a number of different shapes, thereby imparting different configurations to the bearing assembly  10 . Each of the plurality of rollers  22  includes a bore  26  coaxial with a rotational axis  30  of the respective rollers  22 . 
         [0012]    With continued reference to  FIG. 2 , the bearing assembly  10  further includes a cage assembly  34  including a first cage frame  38  and a second cage frame  42 . In the illustrated construction of the bearing assembly  10 , the second cage frame  42  is diametrically larger than the first cage frame  38 . Alternatively, the cage frames  38 ,  42  may be the same size, or the first cage frame  38  may be larger than the second cage frame  42  depending upon the particular configuration and/or application of the bearing assembly  10 . Each cage frame  38 ,  42  includes a plurality of holes  46  spaced equally from each other and arranged in a circular array on the respective cage frame  38 ,  42 . The number of holes  46  in each of the cage frames  38 ,  42  is equal to the number of rollers  22  included in the bearing assembly  10 . The cage assembly  34  further includes a plurality of pins  50  for coupling the rollers  22  to the first and second cage frames  38 ,  42 . Each pin  50  has a threaded end  54  with a tapered shape and a head  58  opposite the threaded end (best illustrated in  FIGS. 3 and 4 ). In other embodiments, the threaded end  54  can have a straight (i.e., not tapered) shape, or any other shape as may be desired. The threaded end  54  is hardened by quenching and tempering, precipitation hardening, carburizing, or another suitable method so that it has a hardness higher than that of the second cage frame  42 . The head  58  includes a torque receiving portion  62  (e.g., a protrusion or slot) that is shaped to receive a torque input from a wrench, machine, or other source. 
         [0013]    In at least the second cage frame  42 , the holes  46  are first drilled to a diameter smaller than the diameter of the pins  50 , and then reamed to a shape that generally matches the shape of the threaded ends  54  of the pins  50 . In the illustrated embodiment, the holes  46  in the second cage frame  42  are reamed to a tapered shape that generally matches the tapered shape of the threaded ends  54  of the pins  50 . The holes  46  in the first cage frame  38 , however, are drilled to a slightly larger diameter to provide a snug, sliding fit with the pins  50 . Each of the pins  50  is inserted through one of the holes  46  in the first cage frame  38  and extends through the bore  26  in a corresponding one of the rollers  22 . The threaded end  54  of each pin  50  is received in a corresponding one of the holes  46  in the second cage frame  42 . As is described in more detail below, the threaded end  54  of the pin  50  shapes or otherwise forms threads in the hole  46  as it is displaced into the hole  46 . All of the rollers  22  are secured to the cage assembly  34  in this manner. 
         [0014]      FIG. 2  illustrates the bearing assembly  10  post-assembly. A method of manufacturing the bearing assembly  10  in accordance with the invention is described below. 
         [0015]    First, the ring  14   b  is provided on a horizontal support surface with the raceway  18   b  facing upwardly. The cage frames  38 ,  42  are then provided, each including a circular array of unthreaded holes  46 . Further, the rollers  22  are positioned on the raceway  18   b  individually or as a group using a jig, and the first cage frame  38  is lowered onto the rollers  22  such that the first cage frame  38  is supported directly by the respective ends  22   b  of the rollers  22 . The second cage frame  42  is then brought into contact with the respective ends  22   a  of the rollers  22 , with the bores  26  of the respective rollers  22  being aligned coaxially with the unthreaded holes  46  in the respective cage frames  38 ,  42 . 
         [0016]    Next, the pins  50  are individually inserted through the holes  46  in the first cage frame  38  and the bores  26  in the respective rollers  22  until the threaded ends  54  of the respective pins  50  engage the corresponding unthreaded holes  46  in the second cage frame  42 . Torque is applied to the torque receiving portion  62  of the pin head  58  by a wrench, machine, or other suitable source of torque in conjunction with a force along the axis  30 . The torque applied to the head  58  causes the hardened, threaded end  54  of the pin  50  to shape or otherwise form threads into the initially unthreaded hole  46  of the second cage frame  42 , thereby engaging the threaded end  54  of the pin  50  with the second cage frame  42 . In the illustrated embodiment, the threaded end  54  of the pin  50  cold-forms threads in the hole  46  of the second cage frame  42  by displacing material within the hole  46  without cutting or creating chips. In other embodiments, the threaded end  54  may cut threads in the hole  46  of the second cage frame  42 . The pin  50  is threaded into the second cage frame  42  until a distal surface  66  of the threaded end  54  is at least flush with a peripheral surface  70  of the second cage frame  42 . This process is repeated for each of the plurality of pins  50  and rollers  22  until all of the rollers  22  are secured to the cage assembly  34 . Lastly, the ring  14   a  may be positioned on the plurality of rollers  22 . 
         [0017]    In a typical pin-type roller bearing assembly as shown in  FIG. 1 , competing tolerances exist between the minimum torque value to which the threaded end of each pin should be tightened to the pre-threaded hole, and the protruded distance of the threaded end of each pin through the particular cage frame having the pre-threaded bores. For example, when assembling the typical pin-type roller bearing assembly of  FIG. 1 , it is possible that one of the specifications (e.g., the minimum torque specification) may not be achievable without conflicting with another of the specifications (e.g., the protruded distance of the pin tip). In the method according to the invention, the process of cutting or otherwise forming threads into the initially unthreaded holes  46  of the second cage frame  42  with the hardened, threaded ends  54  of the pins  50  requires that an increased amount of torque be applied to the head  58  compared to the conventional method using pre-threaded bores in one of the cage frames. The increased amount of torque sufficiently exceeds the minimum torque value to which the threaded end  54  of the pin  50  should be tightened to the hole  46  of the second cage frame  42  under current specifications using the conventional assembly method described in the Background section of the specification. Accordingly, the pin  50  can be tightened until the distal surface  66  of the threaded end  54  is at least flush with the peripheral surface  70  of the second cage frame  42  without competing or otherwise conflicting with the minimum torque value tolerance otherwise necessitated by the conventional assembly method. The pin  50  may alternatively be tightened until the distal surface  66  of the threaded end  54  protrudes a predetermined distance from the peripheral surface  70  of the second cage frame  42 . In some embodiments, the pin  50  may be tightened until the distal surface  66  of the threaded end  54  protrudes less than or equal to about 0.031 inches from the peripheral surface  70  of the second cage frame  42 . 
         [0018]    In some embodiments, the head  58  of each pin  50  may be fixed to the first cage frame  38  after the threaded end  54  is fully engaged (i.e., threaded) with the second cage frame  42 . This prevents the threaded ends  54  of the pins  50  from backing out of the second cage frame  42  as a result of vibration or other in-service conditions. Each of the respective heads  58  may be fixed to the first cage frame  38  by welding, brazing, or any other suitable process. In other embodiments, the heads  58  of at least two adjacent pins  50  may be interconnected with a clip or a like fixture (not shown), such that the adjacent pins  50  cannot rotate during operation, but may still be removable while servicing the bearing assembly  10  to facilitate inspection of the rollers  22 . In yet other embodiments, such clips may be omitted, leaving the heads  58  of at least two adjacent pins  50  exposed to facilitate removal of the pins  50  and inspection of the rollers  22  and races  18   a  or  18   b . In such an embodiment, the torque specification required to shape or otherwise form the threads in the holes  46  of the second cage frame  42  is sufficiently high to effectively prevent vibration or other in-service conditions from causing the pins  50  to back-out of the holes  46  in the second cage frame  42 . 
         [0019]    Various features of the invention are set forth in the following claims.