Abstract:
A bearing assembly including an inner ring, an outer ring, a ball bearing assembly, a needle bearing assembly, and seals. The inner ring defines a ball raceway and a needle bearing raceway. The outer ring defines a ball raceway and a needle bearing raceway. A plurality of circumferentially arranged balls are received by said inner and outer ring ball raceways and a plurality of circumferentially arranged needle rollers are received by said inner and outer needle bearing raceways. The seals seal each end of the assembly.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/505,148 filed on Sep. 23, 2003. 
    
    
     BACKGROUND 
     The present invention relates to a bearing assembly for use with a shaft or spindle, for example, in a commercial lawnmower spindle assembly or a like device. More particularly, the present invention relates to a unitized bearing assembly. 
     Many shaft applications require a bearing assembly that provides both axial thrust and radial load bearing. Some applications have addressed such by providing two spaced apart rows of bearing elements, with at least one of the bearing elements being balls that are received in a groove in the shaft to provide axial support for the shaft. The second row of bearing elements has been provided as a separate unit that is assembled about the shaft and thereafter the two bearing assemblies unitized. 
     SUMMARY 
     The present invention provides a bearing assembly including at least one inner ring defining a ball raceway and a needle bearing raceway. An outer ring having first and second ends with a ball raceway and a needle bearing raceway defined therebetween is positioned about the inner ring. A plurality of circumferentially arranged balls are received by said inner and outer ring ball raceways and a plurality of circumferentially arranged needle rollers are received by said inner and outer needle bearing raceways. A seal is positioned in and retained by each end of the outer ring. Each seal includes a seal lip engaging the at least one inner ring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view, in cross section, of a bearing assembly that is a first embodiment of the present invention positioned about an illustrative shaft. 
         FIG. 2  is an exploded isometric view of the bearing assembly of  FIG. 1 . 
         FIG. 3  is a side elevation view, in cross section, of a bearing assembly that is a second embodiment of the present invention. 
         FIG. 4  is an exploded isometric view of the bearing assembly of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Certain terminology, for example, “top”, “bottom”, “right”, “left”, “front”, “frontward”, “forward”, “back”, “rear” and “rearward”, is used in the following description for relative descriptive clarity only and is not intended to be limiting. 
     Referring to  FIGS. 1 and 2 , a bearing assembly  20  that is a first embodiment of the present invention will be described. The bearing assembly  20  is shown positioned about an illustrative shaft  10 . The shaft  10  is shown with a first portion  12  of a given diameter and a reduced diameter portion  14  with a shoulder  16  defined therebetween. A bushing  18  is positioned between the shoulder  16  and the bearing assembly  20 . Other shaft configurations and mounting arrangements may also be utilized. 
     The bearing assembly  20  generally comprises an outer ring  22 ; a ball bearing assembly  30 ; a needle bearing assembly  40 ; and a pair of end seals  50  and  60 . The outer ring  22  is defined by a tube that may be manufactured from various materials including metals and polymers. The outer ring  22  is configured for attachment or other engagement with a housing, for example, a lawn mower housing. The outer ring  22  is shown as having a cylindrical configuration, but may have other external configurations to facilitate such engagement. The inside surface of the outer ring  22  has a circumferential groove  35  to define an outer bearing surface for the ball bearing assembly  30 . The inside surface of the outer ring  22  also has a cylindrical surface  45  to define an outer bearing surface for the needle bearing assembly  40 . 
     The ball bearing assembly  30  includes an inner ring  32  and a plurality of balls  34 . In the preferred embodiment, the balls  34  are retained in a cage  36  or the like. The inner ring  32  has an external circumferential groove  33  to defined an inner bearing surface for the balls  34 . Referring to  FIG. 1 , the inner ring  32  is positioned within the outer ring  22  with the grooves  33  and  35  aligned and the balls  34  positioned therebetween. The balls  34  so positioned provide radial support and axial support between the inner ring  32  and the outer ring  22 . The inner ring  32  is preferably interference fit about the shaft  10  such that axial support is provided between the outer ring  22  and the shaft  10 . While an interference fit is preferred, the inner ring  32  may otherwise be interconnected with the shaft  10 . 
     The needle bearing assembly  40  includes an inner ring  42  and a plurality of needle rollers  44 . In the preferred embodiment, the needle rollers  44  are retained in a cage  46  or the like. The needle rollers  44  are positioned about the inner ring  42  and the assembly is positioned within the outer ring  22 , aligned with the cylindrical surface  45 . In the present embodiment, a pair of snap rings  47 ,  49  are received in grooves  24 ,  26  on the internal surface of the outer ring  22  to limit axial movement of the needle bearing assembly  40 . The inner ring  42  has a cylindrical inner surface that is interference fit about the shaft  10 . Again, while an interference fit is preferred, the inner ring  42  may otherwise be interconnected with the shaft  10 . The needle bearing assembly  40  provides radial support for the shaft  10 . The needle rollers  44  and the outer and inner rings  22 ,  42  are sized and manufactured from a desired material to meet the intended load requirement. In the lawn mower application, the components are generally manufactured to endure and dissipate impact loading, for example, when the mower blade hits a rock or the like. 
     To prevent ingress of unwanted contaminants, a seal  50 ,  60  is provide at each end of the bearing assembly  20 . The seal  50  adjacent the ball bearing assembly  30  is shown having a spring type retainer  52  biased against the outer ring  22  and a polymer seal member  54  engaging the ball bearing inner ring  32 . The seal  60  adjacent the needle bearing assembly  40  includes an outer cup  62  interference fit within the outer ring  22 . A polymer seal member  64  extends from the cup  62  and engages the needle bearing inner ring  42 . A support ring  66  or the like may be provided about the seal member  64  to increase the sealing force between the seal member  64  and the needle bearing inner ring  42 . Other seal configurations may also be utilized. 
     As can be seen in  FIG. 1 , the ball bearing assembly  30 , the needle bearing assembly and the seals  50 ,  60  are all retained in the outer ring  22  independent of the shaft  10 . The bearing assembly  20  can be easily assembled into a pre-assembled component independent of the shaft  10 . The shaft  10  does not require any special machining, hardening or other treatment. Instead, the shaft  10  can simply be positioned in to the bearing assembly  20 . Such allows for easy assembly of the bearing assembly  20  and allows for easier field maintenance if required. 
       FIGS. 3 and 4  show a bearing assembly  120  that is a second embodiment of the present invention. The bearing assembly  120  is similar to the first embodiment and includes an outer ring  122 , a ball bearing assembly  130 , a needle bearing assembly  140  and a pair of seals  60 . The inside surface of the outer ring  122  again has a circumferential groove  135  to define an outer bearing surface for the ball bearing assembly  130 . The inside surface of the outer ring  122  also has a cylindrical surface  145  to define an outer bearing surface for the needle bearing assembly  140 . A pair of shoulders  124  and  126  are provided about the cylindrical surface  145  to define axial stops for the needle bearing assembly  140 , thereby eliminating the snap rings of the previous embodiment. Also in distinction from the previous embodiment, the inner bearing surfaces are defined by a single inner ring  150  having a cylindrical bearing surface  152  providing a bearing surface for the needles  144  and a circumferential groove  133  providing an inner bearing surface for the balls  134 . Receipt of the balls  134  in the opposed grooves  133  and  135  and of the needles  144  between the shoulders  124  and  126  unitizes the assembled bearing assembly  120 . Again, seal members  60  or the like may be provided at each end to seal the bearing assembly  120 .