Abstract:
A seal is for a rolling bearing including inner and outer rings relatively rotatable about an axis. The seal includes a generally annular body having a radial portion with inner and outer ends. A static sealing portion at least partially surrounds one of the inner and outer ends of the body radial portion and is configured to form a static seal with a proximal one of the bearing inner and outer rings. A dynamic sealing rim extends generally axially from the other one of the inner and outer ends of the body radial portion, the rim being configured to form a dynamic seal with the other one of the bearing inner and outer rings and being spaced radially from the other one of the inner and outer rings so as to define an annular space for receiving a lubricant.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to French patent application no. 0958721, filed on Dec. 7, 2009, which is incorporated fully herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to the field of seals and in particular the seals used in rolling bearings. 
         [0003]    In a typical rolling bearing, one or more seals are usually provided to retain the lubricant, such as grease, inside the bearing and prevent the penetration of contaminating elements. Usually, the seals are fixed to one of the rings of the bearing and interact directly or indirectly with the other ring to provide the seal. 
         [0004]    The seals may comprise a thin annular body mounted by crimping in a groove arranged on one of the rings of the bearing. However, during the crimping operation, there is a risk of deforming or off-centering the body, which can reduce the radial clearance provided between the body and the other ring. The rolling bearing can therefore have, in the mounted state, a friction torque higher than that initially intended. 
         [0005]    To remedy this drawback, French Patent 1 581 126 recommends covering with deformable material the edge of the body being mounted in the groove of the associated ring in order to make it easier to insert and position the body. In addition, this makes it possible to perfect the seal in this zone. 
         [0006]    In this document, the opposite edge of the body can come to face the other ring so as to form a seal by means of a narrow passageway, or be covered also with deformable material and rub against the said ring. 
         [0007]    In the first case, the seal obtained can be found to be insufficient in certain operating conditions. In contrast, the second solution is particularly effective with respect to the seal but is likely to consume a relatively high quantity of energy. Moreover, the friction between the deformable material and the associated ring generates heat and can cause a rise in temperature that can be harmful for the rolling bearing, in particular at high speed and/or under high loads. Moreover, the crimping operation also has the risk of deforming the ring of the bearing onto which the body is crimped. Merely a few microns of deformation cause an unacceptable increase in the internal clearance of the bearing and therefore in its level of vibration. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the present invention is therefore to remedy these drawbacks. 
         [0009]    More particularly, the object of the present invention is to provide a seal capable of ensuring an effective seal while limiting the energy dissipations as much as possible. 
         [0010]    A further object of the present invention is to provide a seal that is particularly easy to manufacture and install. 
         [0011]    A final object of the present invention is to provide a seal suitable for a rolling bearing. 
         [0012]    The present invention relates to a seal designed to be mounted between two elements that can rotate relative to one another about an axis, notably rings of a rolling bearing. The seal comprises an annular body and sealing portions respectively capable of performing a dynamic seal with one of the elements and a static seal with the other element. The static sealing portion includes a sealing portion surrounding at least partly a first end of a radial portion of the annular body. The annular body includes a rim extending from a second end of the radial portion radially opposite to the first end and forming the dynamic sealing portion. The rim is situated axially protruding relative to the radial portion of the annular body and is capable of delimiting with the associated element an annular space that can be filled with lubricant. 
         [0013]    “Static seal” means in this instance the seal produced between two parts without relative movement and “dynamic seal” means a seal between two parts having a relative movement. In one embodiment, the axial dimension of the rim is between 2 and 10 mm. 
         [0000]    The rim can extend axially or obliquely. It can also have a sinuous or flat shape. The rim can extend on the side of the space to be protected, i.e. on the side of the rolling elements when it is mounted between the rings of a rolling bearing. Alternatively, the rim can extend on the side opposite to the space to be protected. 
         [0014]    In one embodiment, the annular body includes an axial portion axially extending the first end of the radial portion of the said body. The axial portion is advantageously embedded within the sealing portion. The sealing portion can entirely cover a transverse surface of the radial portion of the body. The annular body may be formed of a metallic material or a synthetic material. 
         [0015]    The invention also relates to a rolling bearing comprising two rings that can rotate relative to one another about an axis, rolling elements placed between the rings, and at least one seal as defined above and fixed to one of the rings. 
         [0016]    The radial distance separating the rim and the associated ring facing it is between 0.05 and 1 mm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention will be better understood on studying the detailed description of embodiments taken as non-limiting examples and illustrated by the appended drawings in which: 
           [0018]      FIG. 1  is a half-view in axial section of a rolling bearing according to a first embodiment of the invention; 
           [0019]      FIG. 2  is a detail view of  FIG. 1 , and 
           [0020]      FIGS. 3-6  are detail views of rolling bearings according to second, third, fourth and fifth embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    In  FIG. 1 , a rolling bearing  10 , with an axis  12 , comprises an outer ring  14 , an inner ring  16 , a plurality of rolling elements  18 , in this instance made in the form of balls, and a cage  20  for maintaining the even circumferential spacing of the rolling elements. 
         [0022]    On each of the opposite sides of the rolling bearing  10 , an annular seal  22 ,  24  is provided to close the radial space to be protected that exists between the rings  14 ,  16 . The seals  22 ,  24  are identical to one another and symmetrical relative to a radial mid-plane of the rolling bearing  10  passing through the centre of the rolling elements  18 . 
         [0023]    The outer ring  14  comprises an axial outer surface  14   a , a stepped bore  14   b , two opposite radial transverse surfaces  14   c  and  14   d , and a raceway  14   e  with a deep channel formed substantially in the middle of the bore  14   b  and having in cross section a concave inner profile suitable for the rolling elements  18 , the said raceway being directed radially inwards. The outer ring  14  also comprises two annular grooves  26 ,  28  formed radially towards the outside from the bore  14   b , respectively in the vicinity of the transverse surfaces  14   c  and  14   d . The grooves  26 ,  28  are symmetrical relative to the mid-plane of the bearing passing through the centre of the rolling elements  18 . 
         [0024]    Similarly, the inner ring  16  comprises a bore  16   a , an axial outer surface  16   b , two opposite radial transverse surfaces  16   c  and  16   d  and a raceway  16   e  with a deep channel formed substantially in the middle of the outer surface  16   b  and having in cross section a concave inner profile suitable for the rolling elements  18 , the said raceway being directed radially outwards. The transverse surface  14   c ,  14   d  is respectively situated in a radial plane containing the transverse surface  16   c ,  16   d.    
         [0025]    The outer ring  14  and the inner ring  16  are preferably substantially solid or of “one-piece” construction; in other words, each ring  14 ,  16  is preferably formed by machining a tube, bar or forged and/or rolled blanks. 
         [0026]    As illustrated more visibly in  FIG. 2 , the seal  22  comprises an insert or generally annular body  30 , preferably in the form of a rigid annular disc onto which a flexible sealing portion  32  is overmoulded or vulcanized. 
         [0027]    The sealing portion  32  can, for example, be made of nitrile rubber or with another elastomer. It forms an outer peripheral sealing portion performing a static seal with the outer ring  14 . The sealing portion  32  is inserted by force into the groove  26  of the outer ring  14  in order to fix the seal  22  to the said ring. At the groove  26 , the sealing portion  32  matches the said groove in shape in order to form a means for fixing the seal  22  to the outer ring  14 . The sealing portion  32  radially and axially surrounds the outer periphery of the body  30  so that only the sealing portion  32  is in contact with the outer ring  14 . This promotes a good positional hold of the seal  22  inside the groove  26  by force-mounting and by friction. 
         [0028]    The seal annular body  30  is advantageously made of metal, for example of steel by stamping and folding a metal sheet blank. It can also be made of stainless steel or of aluminum, or else of a synthetic material such as a polyamide. The body  30  is made in a single piece. It comprises an annular radial portion  34  which is extended, at a large-diameter outer end, axially towards the inside of the bearing by an annular outer axial portion  36 . The small-diameter opposite inner end of the radial portion  34  is extended axially towards the inside by an axial portion or annular inner rim  38  having an axial dimension substantially equal to that of the axial portion  36 . The outer axial portion  36  radially surrounds the inner axial rim  38 . 
         [0029]    The outer axial portion  36  of the body is axially and radially surrounded by the sealing portion  32 . In other words, the axial portion  36  is entirely embedded into the latter. The sealing portion  32  also partly covers the large-diameter end of the outer transverse radial surface  30   a  of the radial portion  34  of the body which is oriented axially towards the outside of the rolling bearing  10 . The radial surface  30   a  is axially set back towards the inside of the bearing relative to the radial surfaces  14   c ,  16   c  of the outer ring  14  and inner ring  16 . 
         [0030]    The inner rim  38  of the annular body  30  extends generally axially towards the inside in the direction of the rolling elements  18  from the small-diameter end of the radial portion  34 , forming an annular narrow passageway or space  40  with the outer surface  16   b  of the inner ring  16 . The radial distance separating the outer surface  16   b  of the bore from the rim  38  can for example be between 0.05 and 1 mm. Preferably, the radial distance is approximately 0.2 mm. 
         [0031]    The rim  38  forms an inner peripheral sealing portion radially opposite to the sealing portion  32  and performing a dynamic seal with the inner ring  16 . The rim  38  is delimited axially by a transverse inner radial surface  38   a  which is in this instance offset axially towards the radial portion  34  relative to the portion of the sealing portion  32  axially pressing into the groove  26  of the outer ring  14 . 
         [0032]    The rim  38  that protrudes axially inwards relative to the radial portion  34  of the body makes it possible to increase the axial dimension of the portion of the body  30  facing the outer surface  16   b  of the inner ring  16  and forming the space  40 . As an indication, the axial distance separating the outer radial surface  30   a  of the radial portion  34  and the inner radial surface  38   a  of the rim can for example be between 2 and 10 mm. 
         [0033]    By increasing the axial dimension of the portion or zone of the body  30  that radially faces the outer surface  16   b  of the inner ring  16 , a space  40  is obtained extending axially over a sufficient length to simultaneously be filled with lubricant, such as grease, and allow the retention of this sealed wad of lubricant in operation in order to limit the intrusion of contaminating agents into the rolling bearing  10 . Specifically, with a body not having the rim  38  protruding relative to the radial portion  34 , the lubricant that is present between the free end of the radial portion of the body and the outer surface of the inner ring tends to escape to the outside of the bearing. 
         [0034]    In operation, the rim  38  may also make it possible to obtain a recirculation of the lubricant that is present in the rolling bearing  10  by a centrifugal effect. The rim  38  promotes the recirculation of the lubricant that is present in the bearing towards the outer periphery of the body  30  and towards the outer ring  14  when the said ring is rotating. 
         [0035]    Moreover, with seals  22 ,  24  that are each provided with an annular body  30  including an outer axial portion extending inwards, the axial distance separating the radial portions of the bodies is increased, which makes it possible to increase the space available inside the bearing for, for example, the mounting of the cage  20  and the quantity of lubricant that can be provided between these bodies. 
         [0036]    In the variant embodiment illustrated in  FIG. 3 , in which the identical elements bear the same reference numbers, the annular body  30  of the seal  22  comprises an oblique portion  42  or rim extending the small-diameter end of the radial portion  34 . The oblique portion  42  extends axially towards the inside of the bearing in the direction of the rolling elements and radially towards the outer surface  16   b  of the inner ring  16 . The oblique portion  42  protruding axially inwards relative to the radial portion  34  forms with the said outer surface  16   b  a narrow space  44  that can be filled with lubricant. The axial dimension of the space  44  formed between the inner edge of the body and the inner ring is in this instance slightly greater than that of the embodiment described above. The orientation of the oblique portion  42  promotes the recirculation of the lubricant inside the rolling bearing by centrifugal effect when the outer ring  14  is rotating. 
         [0037]    Alternatively, as illustrated in the embodiment of  FIG. 4  in which the identical elements bear the same reference numbers, the small-diameter end of the radial portion  34  of the body  30  can be extended by an oblique portion  46  or rim extending radially outwards and protruding axially inwards relative to the radial portion  34 . In a manner similar to the embodiment described above, this portion delimits with the outer surface  16   b  of the inner ring  16  a narrow passageway  48  extending axially. 
         [0038]    In another variant embodiment illustrated in  FIG. 5  in which the identical elements bear the same reference numbers, it is possible to provide, as a replacement of the axial portion  38  of the first embodiment, a rim  50  extending substantially axially inwards and having a sinuous shape delimiting with the outer surface  16   b  of the inner ring  16  a sinuous space  52  extending axially. 
         [0039]    The embodiment illustrated in  FIG. 6  differs from the first embodiment only in that the sealing portion  32  entirely covers the outer radial surface  30   a  of the radial portion  34  of the body and axially and radially surrounds the inner axial portion  38  so that the said portion is entirely shrouded. This arrangement of the sealing portion  32 , notably on the radial surface  30   a , makes it possible to protect the body from external chemical attacks, such as corrosion, to which the rolling bearing is subjected. Naturally, such a sealing portion could also be provided in the second, third and fourth embodiments described. 
         [0040]    In the embodiments illustrated, the rim of the body forming a portion that protrudes axially relative to the radial portion  34  of the said body extends on the inside of the rolling bearing  10 , i.e. axially on the side of the rolling elements  18 . Alternatively, it could be possible to provide these rims so as to protrude relative to the radial portion  34  towards the outside of the rolling bearing. However, the embodiments illustrated allow a recirculation of the lubricant inside the rolling bearing  10  when the outer ring  14  is rotating. The rolling bearings described can be used with one of the rings rotating while the other is fixed or also rotating. 
         [0041]    In the embodiments described, the bodies of the seals of the rolling bearing  10  each comprise static and dynamic sealing portions formed respectively on the outer and inner peripheral edges of the said bodies. Alternatively, it could also be possible to provide the static and dynamic sealing portions respectively on the inner and outer peripheral edges of the bodies. 
         [0042]    The rolling bearings described above are provided with seals comprising annular bodies each having an outer axial portion extending inwards so as to increase the axial distance separating the radial portions of the bodies. It is however possible, without departing from the context of the present invention, to provide seals without such outer axial portions. 
         [0043]    In the exemplary embodiments described, the seals are used in rolling bearings. However, it is also possible to use such seals in other applications by mounting them between two elements that can rotate relative to one another.