Abstract:
A spherical bearing including a generally annular first portion having at least a partial substantially spherical outer surface and a generally annular second portion having at least a partial substantially concave surface, the outer surface at least partially engaging the concave surface, at least one of the outer surface and the concave surface having a plurality of frayed polytetraflouroethylene fibers exposed therefrom.

Description:
This application claims the benefit of provisional application No. 60/361,578, filed Mar. 4, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a spherical bearing, and, more particularly, to a composite spherical bearing. 
   2. Description of the Related Art 
   Spherical and semi-spherical bearings are known. A typical spherical bearing may include an inner partially spherical bearing with a surface that interacts with a substantially spherical concave outer retaining portion. The retaining portion may be connected to a linkage or similar mechanical device. A shaft is often attached to the inner spherical portion or is integral with the inner spherical portion such as a tie rod end on a vehicle. 
   Spherical bearings have spherical contact surfaces which allow the inner ring to rotate freely with multiple degrees of freedom while positioned within the bearing outer retaining portion. The multiple degrees of freedom allows a spherical bearing the ability to self-align such that it automatically adjusts to any misalignment, which may occur due to application requirements, machining tolerances, welding distortions or mounting deformations due to static and dynamic forces. Machining and distortion misalignment difficulties normally generate considerable end loading and cause the early failure of conventional cylindrical sleeve bearings. Spherical bearings are devised for the purpose of accommodating application, manufacturing and distortion misalignment for which sleeve bearings are not capable or are inadequate. 
   What is needed in the art is a spherical bearing, which provides for an easy and reliable manufacture of the bearing parts in a time efficient manner, and which doesn&#39;t require an addition of a lubrication film. 
   SUMMARY OF THE INVENTION 
   The present invention provides a spherical bearing which is self lubricating and has a surface with a self healing characteristic. 
   The invention comprises, in one form thereof, a spherical bearing including a generally annular first portion having at least a partial substantially spherical outer surface and a generally annular second portion having at least a partial substantially concave surface, the outer surface at least partially engaging the concave surface, at least one of the outer surface and the concave surface having a plurality of frayed polytetraflouroethylene fibers exposed therefrom. 
   An advantage of the present invention is that the elastic nature of the retaining surface allows the spherical bearing portion to be snapped into place. 
   Another advantage is that at least one of the surfaces of the bearing interface is self lubricating. 
   Yet another advantage is that the bearing surface has a self-healing characteristic. 
   A further advantage of the present invention is that the lubricating film if removed replenishes itself from the surrounding material. 
   A still further advantage is that the present invention provides a dampening characteristic to shock or impact loads due to the elastic characteristics of the composite structure. 
   Another still further advantage is that the present invention is several times more elastic under radial load than metallic bearings, thereby providing a cushioning feature under shock load conditions. 
   And, yet another advantage is that the present invention provides a bearing that is reduced in weight as compared to a metallic bearing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of a spherical bearing assembly illustrating an embodiment of the present invention; 
       FIG. 2  is a cross-sectional view of an inner portion of the spherical bearing of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view of an intermediate portion of the spherical bearing of  FIG. 1 ; 
       FIG. 4  is a cross-sectional view of the outer portion of the spherical bearing of  FIG. 1 ; 
       FIG. 5  is a cross-sectional view along section line  5 — 5  of the assembled spherical bearing of  FIG. 1 ; and 
       FIG. 6  illustrates a bearing surface with frayed polytetraflouroethylene fibers exposed therefrom, the bearing surface included in the spherical bearing assembly of FIG.  1 . 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings, and more particularly to  FIGS. 1-5 , there is shown a spherical bearing assembly  10  which generally includes a first bearing portion  12 , a second bearing portion  14  and a third bearing portion  16 . 
   First bearing portion  12 , also known as spherical portion  12 , includes a substantially convex spherical outer surface  18 , a substantially cylindrical inner surface  20 , a first shoulder  22  and a second shoulder  24 . Spherical outer surface  18  is shaped to interface with intermediate portion  14 . Outer surface  18  may be finished to a relatively smooth surface finish. Cylindrical inner surface  20  is sized to accommodate a shaft or fastening device to connect spherical portion  12  to another movable object (not shown). Alternatively, cylindrical inner surface  20  may be replaced with an integral protruding part to which a linking item may be connected (not shown). Shoulders  22  and  24  are provided to allow a fastening device to be secured thereagainst. 
   Second portion  14 , also known as intermediate portion  14 , includes concave inner surface  26 , a first inner shoulder  28 , a second inner shoulder  30 , a first outer shoulder  32 , a second outer shoulder  34  and an outer locking surface  36 . Concave inner surface  26  is generally shaped to accommodate convex spherical outer surface  18  of spherical portion  12 . Concave inner surface  26  may have a diameter which is either the substantially the same as or in slight variance with the spherical diameter of outer surface  18 . Inner shoulders  28  and  30  are sized to allow spherical outer surface  18  of spherical portion  12  to be pressed against either inner shoulder  28  or  30 . The flexible nature of intermediate portion  14  allows spherical portion  12  to be inserted into intermediate portion  14  by the expansion of inner shoulder diameter  28  or  30 . Alternatively, if spherical portion  12  is made of a deformable resilient material, then both intermediate portion  14  and spherical portion  12  may flex in a co-acting manner, thereby allowing spherical portion  12  to be inserted into intermediate portion  14 . Outer shoulders  32  and  34  along with outer locking surface  36  are sized and shaped to accommodate locking features of outer portion  16 . Alternatively, intermediate portion  14  may have differing external features, which allow the direct connection of intermediate portion  14  to a mounting object (not shown). Such an arrangement allows portion  14  and spherical portion  12  to be the entire spherical bearing without the need for outer portion  16 . In addition, intermediate portion  14  may have a split S that extends from one side to the other, thereby allowing intermediate portion  14  to expand around spherical portion  12 . 
   Third bearing portion  16 , otherwise known as outer portion  16 , includes inner locking surface  38 , a first locking protrusion  40 , a second locking protrusion  42 , a first insertion aid  44 , a second insertion aid  46 , a first angled surface  48 , a second angled surface  50  and an interface surface  52 . The resilient nature of intermediate portion  14  allows a slight deformation thereof upon insertion into outer portion  16 . Inner locking surface  38  interacts with outer locking surface  36  as intermediate portion  14  is pressed into outer portion  16 . Locking protrusions  40  and  42  serve to prevent lateral movement of intermediate portion  14  once it is inserted into outer portion  16 . Insertion aids  44  and  46  are angled surfaces that allow the directing of and compression of outer locking surface  36  as it is inserted into outer portion  16 . Angled surfaces  48  and  50  are shaped to retain intermediate portion  14  within outer portion  16 . Inner locking surface  38  may be sized to accommodate the outer diameter of outer locking surface  36  or may be sized to have a slight interference fit to prevent the rotation of intermediate portion  14  within outer portion  16 . Interface surface  52  has been shown as generally cylindrical in nature. However, interface surface  52  may have tabs, mounting protrusions or other integral features to allow the connection of outer portion  16  to other mechanical devices. 
   The assembly of spherical bearing assembly  10  is accomplished by inserting spherical portion  12  into intermediate portion  14  then inserting the resulting subassembly into outer portion  16 . The assembly process may require a press operation in order to take advantage of the resiliency of spherical portion  12 , intermediate portion  14  and outer portion  16 . Once assembled, spherical portion  12  may rotate in direction D as shown in  FIG. 5  to accommodate misalignment between an object connected to interface surface  52  and a shaft or connecting device going through cylindrical inner surface  20 . Spherical portion  12  may also rotate in direction E about axis A as shown in FIG.  1 . Alternatively, an initial application of a film of PTFE powder, such as Whitcon TL-171, onto spherical portion  12  and/or intermediate portion  14  before assembly will assist in reducing friction, particularly during an initial break-in period. 
   Now, additionally referring to  FIG. 6 , spherical portion  12 , intermediate portion  14  and/or outer portion  16  are made of a composite material that may include polytetraflouroethylene (PTFE) fibers, polyester and glass fibers. Whereas the needed resiliency of spherical portion  12 , intermediate portion  14  and outer portion  16  may differ, the composition of each are varied to meet the intended use. In use the PTFE and polyester migrate under pressure to concave inner surface  26  and/or convex spherical outer surface  18  thereby forming a self-lubricating film between the co-engaged surfaces. Spherical outer surface  18  and/or concave inner surface  26  have ends of fibers protruding from the composite material, which are frayed. The machining of convex spherical outer surface  18  and/or concave inner surface  26  tends to fibrillate the ends of the PTFE fibers leaving them frayed, which is instrumental in the formation of the self-lubricating film to the extent observed. Alternatively, spherical portion  12  and/or outer portion  16  may be made of metal such as 4140 steel instead of composite materials. 
   Spherical portion  12  may be formed primarily of fiberglass which has a substantial hardness. Spherical portion  12  made of glass fibers has a hardness of approximately Rockwell 48C and the surface finish may range from 60 Ra to 100 Ra. The fiberglass is contained in an epoxy matrix and it is the combination of materials and surface finish that provides a superior surface, as compared to metallic spheres, for accepting a lubricant film formed of materials from intermediate portion  14 . Intermediate portion  14  includes approximately 10% PTFE fiber, 12% polyester fiber and 60% fiberglass filament wound at an angle to the rotation angle. The angle, for example, may be, but not limited to, ±45° to thereby enhance shear and overall strength properties. These materials are encapsulated in an epoxy matrix. 
   Frayed PTFE fibers have the ability to deposit a lubricating film on the interface between spherical outer surface  18  and concave inner surface  26 . In addition, there is a self-healing characteristic in this arrangement in that the lubricant film on the surface has the ability to reform, if the prior film is wiped, worn or abraded off of a surface. It is the combination of composite materials that advantageously aids in the ability to transfer a lubricant film to the surfaces of spherical outer surface  18  and concave inner surface  26 . This ability to transfer a lubricant film to a steel or chromed spherical surface, of bearings currently available, has not been observed and these surfaces likewise do not indicate signs of healing when lubricating films from those surfaces are removed. 
     FIG. 6  illustrates a magnified cross-sectional view of a finished surface  54  of spherical outer surface  18  and/or concave inner surface  26  with PTFE fibers  56  protruding therethrough. The ends of PTFE fibers  56  are frayed at  58  due to the orientation of the PTFE fibers and the machining of surface  54 . 
   Alternatively, spherical portion  12  and/or intermediate portion  14  may be of layered construction with the advantageous self-lubricating properties primarily located on spherical outer surface  18  and/or concave inner surface  26 . Further, spherical portion  12  and/or intermediate portion  14  may be of a gradient construct. The gradient construction being such that the composite part may have a non-uniform composition with the advantageous self-lubricating properties primarily concentrated on spherical outer surface  18  and/or concave inner surface  26 . 
   The present invention advantageously, is completely non-metallic, having high strength and is self-lubricating. Also, the present invention provides a dampening characteristic to shock or impact loads due to the elastic characteristics of the composite structure. Tests have shown that the bearing of the present invention is approximately 15 times more elastic under radial load than metallic bearings, thereby providing a cushioning feature under shock load conditions. Further, the elastic properties of the spherical bearing provide acoustical dampening, thereby reducing the transmission of acoustical energy to devices connected thereto. 
   A key issue with the load capacity of bearings is not how much load a bearing will carry, but how well it performs under load. While a steel spherical bearing can carry a tremendous load, the friction of a steel spherical bearing is considerably higher than the spherical bearing of the present invention particularly if the lubricating film is wiped off during use. 
   While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.