Abstract:
A bearing assembly is disclosed including an inner race and an outer race that is radially spaced from the inner race for receiving roller elements therebetween. A collar is adjacent to and fixed relative to the inner race. A sealing member is fixed relative to the outer race. The sealing member slidably and sealingly engages the collar axially and radially to maintain a seal between the sealing member and the collar during a misalignment of the inner race relative to the outer race and a predetermined degree of misalignment of the inner race relative to the outer race.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Not applicable. 
     STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a bearing assembly. In particular, this invention is directed at a seal structure in a bearing assembly which minimizes the internal contamination of the bearing assembly. 
     Conventionally, bearings include an inner race and a separate outer race which is movable relative to the inner race. To provide fluid rotation of the inner and outer races relative to one another, most bearings aim to smooth and/or minimize the frictional resistance between the components of the bearing. Often, this is achieved by selecting the bearing surfaces of the races and any intermediate bearing elements to have desirable tribological features (i.e., to have low coefficients of friction). In some cases, lubrication may also be provided between the bearing components. 
     However, when the space between the bearing surfaces becomes contaminated by debris or the like, the operation of the bearing degrades. After a sufficient amount of contamination, the bearing must then either be replaced or subjected to maintenance to clear the contamination. Both replacement and maintenance are costly and require downtime. 
     Complex bearings are particularly susceptible to contamination from the external environment. For example, in certain applications, a bearing may need to be operable in an misaligned condition in order to accommodate the connected surrounding structure. When conventional bearing structures are moved to operate in a misaligned condition, gaps may temporarily form between the bearing components due to uneven seals or the like, exposing the internal cavity of the bearing. 
     Hence, a need exists for bearing assembly that can operate in a misaligned condition while minimizing exposure of the internal cavity to contaminants. 
     SUMMARY OF THE INVENTION 
     This disclosure provides a bearing assembly with a sliding seal that permits the operation of the bearing assembly in a misaligned condition without compromising the quality of the seal. The sliding seal is formed between a specially shaped collar and a sealing member which radially and axially engages the collar. During operation of the bearing assembly, at least up to a predetermined degree of misalignment, the sealing member maintains a seal with the collar to prevent the ingress of debris and other contaminants that may adversely impact the performance of the bearing assembly. 
     A bearing assembly includes an inner race and an outer race. The outer race is radially spaced from the inner race for receiving roller elements therebetween. The bearing assembly further includes a collar adjacent the inner race which is fixed relative to the inner race. A sealing member is fixed relative to the outer race. The sealing member slidably and sealingly engages the collar axially and radially to maintain a seal between the sealing member and the collar during alignment of the inner race relative to the outer race and a predetermined degree of misalignment of the inner race relative to the outer race. 
     By shaping the collar appropriately, a seal is maintained during operation of the bearing assembly though a range of alignment positions. Further, as the sealing member contacts the collar with both an axial and a radial force consistently over the length of the seal, when the races are moved relative to one another, the movement of the components forming the seal are less likely to allow for the entrance of contaminants into the inner cavity. 
     These and still other advantages of the invention will be apparent from the detailed description and drawings. What follows is merely a description of a preferred embodiment of the present invention. To assess the full scope of the invention the claims should be looked to as this preferred embodiment is not intended to be the only embodiment within the scope of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a bearing assembly; 
         FIG. 2  is a cross-sectional perspective view of the bearing assembly of  FIG. 1 ; 
         FIG. 3  is a cross-sectional side view of the bearing assembly in an aligned position; and 
         FIG. 4  is a cross-sectional side view of the bearing assembly in a misaligned position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to  FIGS. 1 and 2 , a bearing assembly  10  is shown. The bearing assembly  10  is a roller bearing which may be suitable for use in any of a number of applications including, for example, in a flight control actuator of an aircraft. 
     The bearing assembly  10  includes an inner race  12 , an outer race  14 , and a plurality of roller elements  16  positioned between the inner race  12  and the outer race  14  in a double row annular configuration. The roller elements  16  are generally hourglass-shaped and each have a concave contact surface  18 . This concave bearing surfaces  18  of the roller elements  16  engage both a convex bearing surface  20  on the inner race  12  that faces generally radially outward and further engages one of a pair of convex bearing surfaces  22  on the outer race  14  that face generally radially inward. The roller elements  16  are angularly inclined with respect to the central axis of the bearing assembly  10  such that the centrally-located ends of the roller elements  16  are a greater radial distance from the central axis of the bearing assembly  10  than the lateral ends of the roller elements  16 . 
     As will be described in further detail below, the concavity of these bearing surfaces allow the bearing assembly  10  to operate in a misaligned position in which the central axis of the outer race  14  deviates from the central axis of the inner race  12 . According to the disclosed structure, when the central axis of the outer race  14  tilts relative to the central axis of the inner race  12 , the roller elements  16  tilt with the outer race  14  as the pair of convex bearing surfaces  22  in the outer race  14  are sized to roughly match the width of the roller elements  16 , albeit with some room for play. 
     It will be appreciated that there may be other bearing structures that allow the misaligned operation of the bearing assembly  10 . For this reason, the disclosed embodiment is intended to be illustrative, but not limiting. 
     In the form shown, the bearing assembly  10  has a double row annular configuration of roller elements  16  (i.e., there are two rings of roller elements  16  between the inner race  12  and the outer race  14 ). It is contemplated, however, that other configurations may be employed as well. For example, the bearing assembly may be of a single row annular configuration (i.e., there is only a single row of roller elements  16  between the inner race  12  and the outer race  14 ). Moreover, spacers or the like may be used to position the rolling elements  16  or rows of rolling elements  16  relative to one another. 
     A set of collars  24  are positioned adjacent the inner race  12  at the axial ends of the inner race  12 . As best seen in  FIG. 2 , both the inner race  12  and the set of collars  24  are supported by a central shaft  25  that is tubular in shape. 
     Each of the collars  24  has a stop surface  26  which faces radially outward and axially inward. This stop surface  26  extends radially past the convex bearing surface  20  at the lateral ends of the inner race  12 . 
     The stop surfaces  26  on the collars  24  ultimately prevent the central axis of the outer race  14  from exceeding a predetermined angle of misalignment with the central axis of the inner race  12 . As noted above, the roller elements  16  travel side-to-side with the outer race  14 , as the outer race  14  is tilted relative to the inner race  12 . At least for the disclosed rolling element  16  configuration, this stop surface  26  prevents the lateral ends of the roller elements  16  from moving past the stop surface  26  of the collars  24  as the outer race  14  skews relative to the inner race  12 . In one form, the geometric placement of the collars  24  relative to the inner race  12  and the roller elements  16  allows a maximum predetermined degree of misalignment between the central axis of the outer race  14  and the central axis of the inner race  12  to be 10 degrees. 
     Each of the collars  24  also have a sealing surface  28  which is an axially and radially outward facing surface. In the form shown, the sealing surfaces  28  are frusto-spherical in shape. However, as will be described below with reference to the functionality of the sealing surfaces  28 , the sealing surfaces  28  may be differently shaped and still achieve the desired function. 
     A pair of sealing members  30  are affixed to the outer race  14  and extend in a generally radial direction toward the collars  24 . More specifically, a radially outward peripheral edge  32  of each of the sealing members  30  is affixed one of the axial ends of the outer race  14  such that the sealing members  30  moves with the outer race  14 . In some forms, shields (not explicitly shown in  FIGS. 1 and 2 ) may be attached to the axial ends of the outer race  14  and the sealing members  30  may be affixed to the shields. 
     Radially inward peripheral edges  34  of the sealing members  30  each contact one of the sealing surfaces  28  of one of the collars  24  to form a sliding seal. The sealing members  30  are spatially arranged and sufficiently elastically deformable such that the radially inward peripheral edge  34  of the sealing member  30  applies a force that is radially and axially inward on the collar  24  to form a seal between each of the sealing members  30  and a corresponding collar  24 . 
     Now with additional reference to  FIGS. 3 and 4 , an aligned position ( FIG. 3 ) and a misaligned position ( FIG. 4 ) are illustrated. One difference between the depiction of the bearing assembly in  FIGS. 3 and 4  and the depiction of the bearing assembly in  FIGS. 1 and 2  is that the shields  36  and the sealing members  30  are explicitly identified as separate items. It will be appreciated that, at least in some forms, the seals and shields may be bonded together before being installed in the bearing. In one possible way of making the bearing assembly  10 , the sealing members  30  are orbital formed into shield  36 . 
     Notably,  FIG. 4  illustrates the operation of the bearing at a 5 degree angle of misalignment. The outer lateral end of one of the roller elements  16  contacts the stop surface  26  of the collar  24  preventing further axial misalignment. Even at this level of misalignment (for the particular geometry shown), the quality of the seal formed between the sealing members  30  and the collar  24  is the same as in the aligned position shown in  FIG. 3 , given the spherical shape of the sealing surface  28  in the collar  24 . 
     If the outer race  14  tilts relative to the inner race  12  to a misaligned position, then the seals formed between the sealing members  30  and the collars  24  shift to accommodate this new operational position. The quality of the seals are maintained as, as the seal location shifts, the points of contact forming the seal are substantially circular (defined by the radially inward peripheral edge  34 ) traveling over a spherical surface (defined by the sealing surface  28  of the collar  24 ). Thus, at least within a predetermined range of motion, no gaps are formed along the seal during misalignment of the inner race  12  and outer race  14  and no new stresses are introduced. Notably, if stresses were differentially created over the seal, then it is possible that when the bearing is in use, the sealing members would be subject to cyclic stress which might fatigue the sealing members and compromise the quality of the seal. 
     Although ideal geometric conditions may be preferable to ensure the quality of the seal, the components may deviate from the ideal geometry without necessarily compromising the quality of the seal. For example, ideally the convex bearing surface  20  on the inner race  12  as well as the sealing surfaces  28  of the collar  24  would be frusto-spherical and have center points  38  which are substantially identical. However, as the sealing members  30  may be elastically deformable and the range of misalignment over which a suitable seal may be maintained is relatively narrow, some deviation from the ideal geometry may not significantly impact the quality of the seal. 
     The inner race  12 , the outer race  14 , the collars  24 , and the sealing members  30  (and, in some cases, the shield) define the inner cavity of the bearing assembly  10 . This inner cavity may receive additional lubrication, if desired, depending on the tribological qualities of the bearing surfaces. According to some constructions, one or more of the bearing surfaces could be composed of self-lubricating material. 
     In any event, by forming slidable seals between the sealing surfaces  28  of the collars  24  and the radially inward peripheral edges  34  of the sealing members  30 , the entrance of contamination or debris from the outside environment into the inner cavity is minimized. By reducing the rate at which contamination enters the inner cavity, the operational life of the bearing assembly  10  is lengthened. This equates to a significant cost savings as, when a bearing assembly  10  remains operable for a longer time, the overall device in which the bearing assembly  10  is a part does not need to be taken out of service to either replace the bearing assembly  10  or to service the bearing assembly  10 . 
     Thus, a bearing assembly is disclosed in which the bearing assembly maintains a sliding seal between a sealing surface of a collar and sealing member. This bearing assembly provides a seal regardless of whether the bearing assembly is operating in an aligned state or in a misaligned state. By maintaining the seal in the misaligned state, the inner cavity of the bearing assembly is less likely to be contaminated by debris or the like which adversely impacts the performance of the bearing assembly compared to other bearing assemblies. 
     Further, to the extent that the sealing surface of the collar is shaped to match the rotational path of the radially inward peripheral edge of the sealing member, when the sealing member applies a force in forming the seal, the force of the seal is relatively consistent over the angular range of operation thereby preventing the ingress of fluid or particulate contaminants. 
     Although a particular configuration for a bearing assembly  10  is depicted in  FIGS. 1 through 4 , variations may be made. For example, instead of employing roller elements  16  having concave bearing surfaces  18  to allow the bearing assembly  10  to operate in a misaligned state, other types of roller elements may be used. Additionally, certain structural elements may be combined with one another and still achieve the same described functionality. For example, the inner race  12  and the collars  24  may be integrally formed with one another. Moreover, certain structural elements may be relocated without deviating from the spirit of the invention. For example, instead of locating the stop surface  26  on the axially inside edge of the collar  24 , a stop surface may be formed centrally as a ridge on the inner race  12  such that the centrally-located ends of the roller elements  16  would contact the ridge if the outer race  14  is tilted a sufficient distance with respect to the inner race  12 . 
     It should be appreciated that various other modifications and variations to the preferred embodiments can be made within the spirit and scope of the invention. Therefore, the invention should not be limited to the described embodiments. To ascertain the full scope of the invention, the following claims should be referenced.