Patent Publication Number: US-11396909-B2

Title: Expandable stacked thrust bearing assembly

Description:
TECHNICAL FIELD 
     The disclosure pertains to the field of roller bearings. More particularly, the disclosure pertains to the field of dual row, unitized axial roller bearings. 
     BACKGROUND 
     Rotational bearings are used to separate parts that have relative rotation. Roller bearings utilize a set of rollers in predominantly rolling contact with hardened races. The bearing permits transmission of large forces between components with relative rotation. In an axial bearing, the force is parallel to the axis of rotation. Due to the rolling contact, resistance to relative rotation is minimal. For axial roller bearings, the races are commonly formed in washers which are considered part of the bearing assembly. Each washer contacts one of the components, either a housing or a shaft, and does not rotate with respect to that component. Many bearing assemblies utilize a cage to circumferentially position the rollers with respect to one another. 
     Some bearing assemblies rely on mating parts, such as the housings or shafts being separated, to retain the components of the bearing with respect to one another. Such bearing assemblies may require an assembly fixture to keep the bearing assembly together prior to and during installation. If the parts separate during operation, there is a risk of parts of the bearing assembly from falling out of position. A unitized bearing assembly, on the other hand, is designed to stay together when not installed without reliance on assembly fixtures or special handling. In operation, a unitized bearing does not depend on surrounding parts to retain its components. 
     SUMMARY 
     An axial bearing includes a compressible ring, first and second inner washers, first and second outer washers, and first and second rows of rollers. The first and second inner washers are on opposite axial sides of the compressible ring. The first row of rollers axially separates the first inner washer from the first outer washer. Similarly, the second row of rollers axially separates the second inner washer from the second outer washer. The first outer washer is retained to the compressible ring. The compressible ring may be, for example, a rubber washer. Alternatively, the compressible ring may be a spring such as a garter spring. First and second cages may be configured to circumferentially position rollers of the first and second rows of rollers, respectively. A retaining element may be configured to retain the first cage and the second cage with the first outer washer retained by the first cage and the compressible ring retained between the first and second inner washers. The second outer washer may be retained by the second cage. The compressible ring may include an axial extension configured to retain the first inner washer. The first inner washer may include a first cylindrical extension configured to retain the first cage. The first outer washer may be retained to the first cage. The second inner washer may include a second cylindrical extension configured to retain the second cage. The second outer washer may be retained to the second cage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cut-away pictorial view of a fully unitized double row axial bearing with shafts separated. 
         FIG. 2  is a cross-section of the bearing of  FIG. 1  with the shafts compressed against one another. 
         FIG. 3  is a cut-away pictorial view of a variant of the bearing of  FIG. 1 . 
         FIG. 4  is a cut-away pictorial view of a partially unitized double row axial bearing with shafts separated. 
         FIG. 5  is a cross-section of the bearing of  FIG. 4  with the shafts compressed against one another. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It should be appreciated that like drawing numbers appearing in different drawing views identify identical, or functionally similar, structural elements. Also, it is to be understood that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     The terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the following example methods, devices, and materials are now described. 
       FIGS. 1 and 2  show a first embodiment of a stacked thrust bearing arrangement  10  designed to transmit axial loads between two shafts  12  and  14  while permitting relative rotation between the shafts and also permitting some degree of relative axial movement between the shafts. In some applications, one of the two shafts may be a stationary housing as opposed to a rotatable shaft. In  FIG. 1 , shaft  12  is shown axially displaced. In  FIG. 2 , shaft  12  is shown in contact with the bearing assembly  10 . The bearing assembly  10  includes a first outer washer  16  that directly contacts shaft  12  and a second outer washer  18  that directly contacts shaft  14 . A compressible ring  20  is positioned axially between the first washer  16  and the second washer  18 . Two inner washers,  22  and  24  are on opposite axial sides of the compressible ring  20 . In the embodiment of  FIGS. 1 and 2 , compressible ring  20  is a rubber washer  26 . The compressible ring is free to rotate at a speed that is not constrained by the rotational speed of either shaft  12  or  14 . A first set of rollers  28  axially separates the first outer washer  16  from the first inner washer  22 . Specifically, the rollers  28  are in predominantly rolling contact with washers  16  and  22  to permit relative rotation with minimal resistance. Similarly, a second set of rollers  30  axially separates the second outer washer  18  from the second inner washer  24 . A first cage  32  positions the rollers  28  circumferentially with respect to each other. Cage  32  rotates at a speed between the speed of washer  16  and the speed of compressible ring  20 . Similarly, a second cage  34  positions the rollers  30  circumferentially with respect to each other. 
     The bearing assembly of  FIGS. 1 and 2  is a unitized bearing assembly. Retaining element  36  has lips  38  which extend radially far enough to prevent cages  32  and  34  from coming off axially without substantial force. The parts are flexible enough that the cages and the compressible ring can be pushed on from at least one side during assembly of the bearing assembly. First and second washers include a cylindrical portion  40  that positions the washer radially with respect to shaft  12  or  14 . The inner side of the cylindrical portion  40  is bent over at  42  to retain the washer with respect to the cage. Since the washers are retained with respect to the cages and the cages and compressible ring are retained with respect to the retaining element  36 , the bearing assembly can be treated as a single unit during assembly of the overall product. 
     In operation, shafts  12  and  14  can rotate with respect to one another with minimal drag. Compressive axial forces are transmitted from one shaft, through one of the washers and one of the rows of rollers to the compressible ring  20 . From the compressible ring, the axial load is transferred through the other set of rollers and the other washer to the other shaft. The load will tend to compressible ring  20 . If shafts  12  and  14  briefly move away from one another during operation, the bearing assembly  10  will stay together as a unit. When the shafts come back together, the compressibility of ring  20  ensures that the axial forces due to impact loading are not excessive. 
       FIG. 3  illustrates a second stacked thrust bearing arrangement  10 ′. Parts which are the same as the bearing arrangement of  FIGS. 1 and 2  are labeled with the same reference number. In the embodiment of  FIG. 3 , compressible ring  20 ′ takes the form of a garter spring  50 . Alternatively, garter spring  50  could be replaced with a wave spring or other type of compression spring. Operation of the embodiment of  FIG. 3  is the same as the embodiment of  FIGS. 1 and 2 . 
       FIGS. 4 and 5  show a third embodiment of a stacked thrust bearing arrangement  10 ″. In  FIG. 4 , shaft  12  is shown axially displaced. In  FIG. 5 , shaft  12  is shown in contact with the bearing assembly  10 ″. Parts which are the same as the bearing arrangements of  FIGS. 1 through 3  are labeled with the same reference number. Inner washer  22 ′ includes a cylindrical extension  60  with a lip  62  which extends radially far enough to prevent cage  32  from coming off axially without substantial force. The parts are flexible enough that the cages and the compressible ring can be pushed on from at least one side during assembly of the bearing assembly. Compressible ring  20 ″ includes a first axial extension  64  which radially aligns inner washer  22 ′ with the compressible ring but does not retain it axially. Inner washer  24 ′ includes a cylindrical extension  66  with a lip  68  which extends radially far enough to prevent cage  34  from coming off axially without substantial force. Compressible ring  20 ″ includes a second axial extension  70  which radially aligns and retains inner washer  24 ′. 
     When shafts  12  and  14  are pressed together, the embodiment of  FIGS. 4 and 5  operates the same way as the embodiment of  FIGS. 1 and 2 . If shafts  12  and  14  briefly move away from one another during operation, as shown in  FIG. 4 , some portions of bearing assembly  10 ″ stay with shaft  12  and the remainder stays with shaft  14 . Specifically, outer washer  16 , inner washer  22 ′, cage  32 , and rollers  28  stay with shaft  12 . When the shafts come back together, first axial extension  64  ensures radially alignment. The compressibility of ring  20 ″ ensures that the axial forces due to impact loading are not excessive. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the disclosure that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.