Abstract:
A seal component ( 100, 200 ) having a triple-lip configuration for sealing against a moving surface, such as the inner ring race surface ( 12, 12 ′) of a spherical plain bearing ( 14, 14 ′). The triple-lip configuration incorporates a pair of outward inclined seal lips ( 102, 202, 104, 204 ) for providing protection from external contaminates, and a third inwardly inclined seal lip ( 106, 206 ) which is orientated to provide lubricant or grease retention within the sealed bearing ( 14, 14 ′). The size and configuration of the third seal lip ( 106, 206 ) is selected to minimize surface friction and to avoid seal lip inversion during oscillatory motion of the bearing components during use. A retention surface ( 110   a,    210 ) is disposed to abut against the outer ring race surface ( 10   b,    10   b ) to resist roll-out displacement of the seal component ( 100, 200 ) during use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is related to, and claims priority from, U.S. Provisional Patent Application Ser. No. 61/056,574 filed on May 28, 2008, and which is herein incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention is related generally to bearing seals, and in particular, to a triple-lip seal for use with a spherical bearing assembly such as a sealed spherical plain bearing. 
         [0004]    Sealed spherical plain bearings are predominantly used in construction and mining applications, and have dimensions which are standardized by ISO 12240 and ABMA 22.2 to facilitate mechanical design, support manufacturing efficiency, and promote interchangeability between manufacturers. The spatial constraints of maintaining standardized envelope dimensions, combined with seal installation, often require a reduction in the area available for bearing contact surfaces. The most common damage mode observed in or on these bearing contact surfaces in construction and mining environments is abrasive and adhesive wear at the race contact surfaces. Existing commercially available seals for sealed spherical plain bearings incorporate both single and double lip seals, such as shown in  FIGS. 1 and 2 , with the seal lips oriented outward along the surface of the bearing inner ring race to prevent contamination ingress. Conventional seals may include configurations having an internal stiffening ring or member within an annular seal body. 
         [0005]    In addition to harsh environmental conditions, sealed spherical plain bearing assemblies must withstand application loading and machine/vehicle positioning which can cause significant housing deflections. These deflections are transmitted to the outer ring of the bearing and often compromise the retention features of the seals. Traditional seals, such as shown in  FIGS. 1  and  2 , are commonly retained with an interference fit between the seal OD and the outer ring seal groove. A radial interference between seal OD and seal groove diameter is used in some designs while others use an axial interference between the seal width and outer ring seal groove (see  FIG. 1 ). Adhesives and/or plastic deformation of the seal groove material (otherwise known as staking) against the seal&#39;s outer diameter have also been utilized for seal retention. Due to deflections of the housing, and consequent outer ring deflections, combined with the moment loads generated by the seal drag during bearing oscillations, contamination ingress and loss of seal retention is not uncommon. 
         [0006]    The seal shown in  FIGS. 1 and 2  is comprised of three surfaces which make point contact with the inner ring or inner race surface. Because of the point contact of the seal with the inner race, the deflection of the seal, resulting from movement of the outer race relative to the inner race, could result in a discontinuity in seal contact, thereby allowing contaminants into the bearing assembly or allowing lubricant to escape the bearing assembly. 
         [0007]    Accordingly, it would be advantageous to provide a spherical plain bearing assembly with a seal component which is capable of maintaining an adequate seal between the inner and outer ring race surfaces during outer ring deflections and bearing oscillations, and which provides improved sealing functionality together with lubricant retention. It would be further advantageous to provide such a seal component without compromising bearing load capacity or altering standardized dimensions. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    Briefly stated, the present disclosure provides a seal component carried by an outer ring race and having a triple-lip configuration for sealing against a moving surface, such as the inner ring race surface of a spherical plain bearing. The triple-lip configuration of the seal component incorporates a pair of outward inclined seal lips for providing protection from external contaminates, and a third inwardly inclined seal lip which is orientated to provide lubricant or grease retention within the sealed bearing. The size and configuration of the third seal lip is selected to minimize surface friction and to avoid seal lip inversion during oscillatory motion of the bearing components during use. 
         [0009]    In accordance with one aspect, the seal component is further provided with an outwardly projecting flange shoulder configured to abut the surfaces of the outer ring and prevent “roll-out” of the seal from a retention groove within the outer ring in response to inner ring rotational movement. 
         [0010]    In another aspect, the inboard side of the seal has a diameter sized to facilitate centering of the seal in the outer ring during installation. The outboard face of the seal was designed with a planar surface to facilitate uniform installation of the seal into the bearing. 
         [0011]    The foregoing features, and advantages set forth in the present disclosure as well as presently preferred embodiments will become more apparent from the reading of the following description in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    In the accompanying drawings which form part of the specification: 
           [0013]      FIG. 1  is a sectional view of a prior art double-lip seal positioned in a bearing assembly; 
           [0014]      FIG. 2  is an enlarged sectional view of the prior art double-lip seal of  FIG. 1 ; 
           [0015]      FIG. 3  is a sectional view of a triple-lip seal of the present disclosure, incorporating a retaining flange; 
           [0016]      FIG. 4  is a sectional view of the triple-lip seal of  FIG. 3  positioned in a bearing assembly; 
           [0017]      FIG. 5  is a sectional view of an alternative embodiment of the triple lip seal, incorporating a retaining flange; and 
           [0018]      FIG. 6  is a sectional view of the triple-lip seal of  FIG. 5  positioned in a bearing assembly. 
       
    
    
       [0019]    Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts set forth in the present disclosure and are not to scale. 
         [0020]    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 drawings. 
       DETAILED DESCRIPTION 
       [0021]    The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the present disclosure, and describes several embodiments, adaptations, variations, alternatives, and uses of the present disclosure, including what is presently believed to be the best mode of carrying out the present disclosure. 
         [0022]    Turning to the figures, and to  FIGS. 3 and 4  in particular, a seal component  100  of the present disclosure is shown for application between the outer race  10  and an inner race  12  of a bearing assembly  14 , such as a spherical plain bearing. Generally, the seal component  100  of the present disclosure is formed from a homogenous resilient material, and includes two outboard resilient seal lips  102  and  104  that provide protection from contamination. A third (inboard) resilient seal lip  106  is oriented to maximize grease retention within the internal spaces of the bearing assembly  14 . The third seal lip  106  minimizes adhesive wear, decreases re-lubrication intervals, and results in an extended bearing service life. In view of the resiliency of the seal lips  102 ,  104  and  106 , movement of the outer race and inner race relative to each other will not result in deflection of the seal that would cause the seal lips to break engagement with the bearing inner race  12 . 
         [0023]    The seal component  100  is comprised of an annular seal body  108 , which may be composed of any suitable material, such as a thermoplastic, selected for use in the application environment. For example, the material can be a thermoplastic elastomer (TPE) such as sold by Ticona under the name RiteFlex® or by DuPont under the name Hytrel®. The annular seal body  108  has a projection or an outer diameter  108   0D  which is configured for retention in a corresponding seal retention groove  16  in the surface of the outer ring  10 , as seen in  FIG. 4 . Retention of the seal component  100  within the seal retention groove  16  may be by an interference fit alone, and/or may optionally include the use of suitable adhesives. Preferably, the material of the seal component body  108  elastically deforms during installation, and complies with surface variations in the rings. 
         [0024]    To prevent the ingress of contaminates from the outboard (external) environment into the sealed inboard (internal) environment of the bearing assembly  14 , the first and second seal lips  102 ,  104  of the seal body  108  project generally outwardly from the seal body  108 , and are configured to resiliently engage the surface of the inner ring race  12 . Each of the first and second seal lips  102 ,  104  has a cross-sectional length which exceeds the associated cross-sectional width, to define an elongated extension from the annular seal body  108 . The material stiffness, lubricity characteristics, and contact angle of the first and second outboard seal lips  102 ,  104  result in an interference fit that will not invert while the surface of the inner ring  12  displaces during the application. However, as noted above, the resiliency of the seal lips  102 ,  104  will maintain the seal lips in sealing contact with the inner race  12  as the seal lips wear or due to movement of the inner and outer races relative to each other. The first and second outboard seal lips  102 ,  104  are further configured with curved tips  102   a,    104   a  which minimize seal drag while maximizing the contact surface are in engagement with the surface of the inner ring race  12 . 
         [0025]    To facilitate the retention of lubricants, such as grease, within the sealed bearing assembly  14 , the third lip  106  of the seal component seal body projects inward from the seal body  108  and is configured to resiliently engage the surface of the inner ring race  12 . The third seal lip  106  has a cross-sectional length which is dimensioned to obtain suitable stiffness characteristics to prevent inversion of the third seal lip  106  upon installation of the seal component  100 , and while in use. As with the first and second seal lips  102 ,  104 , the cross-sectional length to width ratio of the inboard (third) seal lip  106  and the mechanical properties of the seal body  108  material create the rigidity needed to prevent the third seal lip  106  from inverting during oscillatory motion of the inner and outer bearing components. However, as noted above, the resiliency of the seal lip  106  will maintain the seal lip in sealing contact with the inner race  12  as the seal lip wears or due to movement of the inner and outer races relative to each other. Additionally, the installed bore dimension and contact angle of the inboard (third) seal lip  106  provides an interference fit at the interface between the tip  106   a  of the third seal lip and the inner ring race  12  spherical outer diameter to minimize lubricant or grease purge from within the sealed bearing assembly  14 . 
         [0026]    A retention (or anti-rotation) flange  110  extends outwardly from the seal body  108  to inhibit rotation of the seal body  108  during movement between the inner race  12  and outer race  10  of the bearing assembly  14 . The seal body  108  may be provided with the retention flange  110 , as seen in  FIGS. 3 and 4 . The retention flange  110  is disposed to extend outward from the seal body  108  and includes an upper surface  110   a  which abuts against an inner surface  10   b  of the outer race  10 . Preferably, the retention flange  110  has a generally rectangular cross-section, and is orientated at an acute angle α 1  of less than 90° relative to the seal body  108 , and at a second acute angle α 2  between 45° and 80° relative to the first seal lip  102 . The retention flange  110  is configured to dynamically react to clockwise moment forces (with respect to the Figures) generated by a seal drag friction force on the seal lips  102  and  104  due counter-clockwise movement (with respect to the Figures) of the inner race  12 , to resist oscillation, and to thereby preventing a “roll-out” of the seal body  100  from the outer ring seal retention groove  16 . 
         [0027]    Turning to  FIGS. 5 and 6 , an alternative embodiment  200  of the seal is shown. The seal  200  is generally similar to the seal  100 , and includes a seal body  208 , a projection  209  which is received in a retention groove  16 ′ of the bearing outer race  10 ′. Three resilient seal lips  202 ,  204  and  206  extend from the seal body  208  to resiliently engage, and seal against, the bearing inner race surface  14 ′. The seal lips  202  and  204  extend generally radially, whereas the inner lip  206  extends generally axially. The seal lips  202 ,  204  and  206  all have a length such that the lips will be deflected upon assembly of the seal  200  into the bearing  14 ′. In  FIG. 6 , the seal lips  202 ,  204  and  206  are drawn as extending into the bearing inner race surface  12 ′. As can be appreciated, the seal lips will not penetrate the inner race surface  12 ′. Rather,  FIG. 6  demonstrates the extent of the interference between the seal lips and the inner race surface  12 ′ and the extent to which the seal lips will be deflected upon assembly of the seal  200  into the bearing  14 ′. As with the seal lips  102 ,  104  and  106  of the seal  100 , the seal lips  202 ,  204  and  206  of the seal  200  has a length-to-width ratio which will give the material from which the seal is made sufficient stiffness such that the lip will not invert during use. Yet the resiliency of the seal lips will maintain seal contact with the inner race  12  as the inner and outer race move relative to each other or due to wear. Hence, the interference or deflection of the middle seal lip  204  is less than the in the interference or deflection of the inner and outer seal lips  206  and  202 , respectively. 
         [0028]    A seal&#39;s performance can be compromised if it is excessively distorted at installation. To reduce the amount of distortion of the seal during installation, the seal  200  includes an outboard diameter  210  and an inboard diameter  211  on opposite sides of the projection  209 . As seen, the diameter of the inboard surface  211  is slightly less than the diameter of the outboard surface  210 . By way of example, the difference in diameter can be as little as 0.010″-0.012″ (˜0.25 mm-˜0.30 mm). As shown schematically in  FIG. 6 , the outboard diameter  210  forms an interference fit with the outboard surface  10   b ′ of the bearing outer ring or bearing outer race  10 ′. The seal inboard surface  211 , on the other hand, forms a clearance fit with the inboard surface  10   c ′ of the bearing outer race  14 ′. The inboard surface  211  aligns the seal  200  concentrically to the outer race or outer ring bore. This alignment feature minimizes distortion of the seal  200  when the seal OD to seal groove interference fit occurs. The seal surface  210  will also function as a retention member to prevent “roll-out” of the seal, as described above with the retention flange  110  of the seal  100 . 
         [0029]    Finally, the outboard seal face  212  is designed as a planar surface. At seal installation, the assembly of  FIG. 6  is rotated 90° such that the seal face  212  is horizontal. The seal installation force is uniformly distributed over that surface, minimizing seal distortion during installation. 
         [0030]    Preferably, the standardized envelope dimensions of the bearing assemblies  14  are not affected by the seal component  100 ,  200  of the present disclosure, so there is no decrease in the existing static or dynamic load ratings for standardized bearing assemblies  14 . As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.