Abstract:
The bearing seal assembly ( 50 ) includes a metal shield ( 70 ) and a resilient multi-lip sealing gasket ( 60 ) secured to the metal shield. The metal shield is supported in use by an outer ring ( 20 ) of a rolling contact bearing and includes a diagonally extending central portion ( 72 ). The sealing gasket ( 60 ) provides a number of contacting lips ( 62 - 64 ) facing an inner ring of the rolling contact bearing. A first, main contacting lip ( 66 ) exerts a first radial load on the inner ring. A second contacting lip ( 62 ) extends from the first lip ( 66 ) and exerts a second radial load on the inner ring lower than the first radial load. A third contacting lip ( 64 ) is on the opposite side of the second lip ( 62 ) with respect to the first lip ( 66 ) and exerts a third radial load on the inner ring lower than the first radial load but greater than the second radial load.

Description:
CROSS-REFERENCE 
     This application is the US national stage of International Application No. PCT/EP2009/056293 filed on May 25, 2009. 
     TECHNICAL FIELD 
     The present invention relates to a bearing seal assembly, particularly for use in agricultural applications. More particularly, the present invention relates to a bearing seal assembly suitable to be assembled with bearing units which enable moderate errors of alignment to be compensated for. 
     RELATED ART 
     U.S. Pat. No. 7,258,491 discloses a bearing seal assembly for harsh environmental conditions such as agricultural tillage applications, having a multi-lip seal and an associated lip seal to provide a primary and a secondary sealing barrier respectively. The primary sealing barrier is supported by the outer ring and includes: 
     a sheet metal shroud extending between an inner circumference of the outer ring and an outer circumference of the inner ring and having a diagonally extending central portion; and 
     a multi-lip seal which is supported by the inwardly directed face of the diagonally extending portion of the metal shroud. 
     The secondary sealing barrier is supported by the inner ring and includes: 
     a slinger which is connected to the inner ring for rotation with the inner ring outwardly adjacent the seal shroud; and 
     a lip seal located between the seal shroud and the slinger. 
     The slinger abuts a stepped portion of the inner ring, and the shroud includes an end portion projecting closely adjacent the stepped portion to provide a tortuous path between the slinger and the multi-lip seal. 
     The bearing seal assembly which is disclosed in the above identified document suffers from the following drawbacks:
     1) the multi-lip seal which is defined by three squat and tough lips is sensitive to the eccentricity causing high friction against the inner rotating ring and this high friction causes early wear of the lips and involves a considerable waste of energy;   2) whenever the shroud comes out of alignment, the three squat and tough lips will not provide the same sealing action;   3) despite the two sealing barriers, the whole sealing action does not perform properly as the slinger and shroud could change their positions due to the possible misalignments of their supports.   

     SUMMARY 
     It is a general object of the present invention to provide a bearing seal assembly, particularly for use in agricultural applications, capable of overcoming one or more of the above prior art drawbacks. Particularly, it is a significant object of the invention to enhance the seal&#39;s effectiveness without increasing friction for any kind of bearing arrangements requiring a high degree of reliability, even under extremely contaminated conditions and further with some misalignment between the bearing rings. 
     These and other objects are achieved by a bearing seal assembly as defined in appended claim  1 . Advantageous embodiments of the invention are defined in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the present invention may be well understood, there will now be described a preferred embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG. 1  illustrates, in an axial cross sectional view, a preferred embodiment of a bearing seal assembly, particularly for use in agricultural applications, according to the present invention, and 
         FIG. 2  is an enlarged view of the bearing seal assembly  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , numeral  50  designates, as a whole, a bearing seal assembly which is suitable for being installed on either side of a bearing unit  10 . The bearing unit  10  is adapted for receiving a shaft (not shown) for rotation about an axis x, and includes an outer ring  20 , an inner ring  30  axially extended on both sides, and a single row of balls  40 . The outer ring  20  has two inner circumferential grooves  22  adjacent to both sides of the balls  40  and an outermost convex spherical surface  21  which accommodates moderate misalignment but without permitting axial displacement. Each circumferential groove  22  is laterally bounded towards the balls  40  by a respective annular surface  24  which is perpendicular to the axis x and is arranged axially inwardly with respect to a relevant outwardly facing wall  23  of the outer ring  30 . 
     The inner ring  30  is rotatable with respect to the outer ring  20 . Inner ring  30  provides an outer cylindrical surface  32  faced toward the outer ring  20  and an inner cylindrical cavity  31  in which the shaft is to be secured for rotation about the axis x. 
     The bearing seal assemblies  50  are fitted at the axially outer ends of the outer ring  20 , thereby sealingly bridging the annular space between the inner ring  30  and outer ring  20 , in order to prevent contaminants from entering the bearing unit  10  while keeping the lubricating grease within it. 
     As better shown in  FIG. 2 , each assembly  50  includes an annular sheet metal stiffening insert  70  and a multi-lip resilient annular gasket  60  of elastomeric or rubber-like material (preferably made from acrylonitrile-butadiene rubber) which is coupled by vulcanization with the insert  70 . The insert  70  comprises: 
     an outer edge  71  which is suitable for being crimped into the relevant groove  22  to anchor the assembly  50  in its working position, 
     a disc annular portion  73  which extends radially inwardly from the edge  71  and is perpendicular to the axis x in order to abut the relevant annular surface  24 , and 
     an axially angled or conical portion  75  which is linked to the disc annular portion  73  by the edge  71 . 
     The insert  70  further comprises another axially angled or conical portion  72  which is parallel to the portion  75  and linked to the disc annular portion  73  at the radially inner circumference of the disc-annular portion  73 ). 
     The metal insert  70  serves also as a barrier against solid contaminants and since the outer edge  71  is crimped into the relevant groove  22 , such a plastic deformation provides a steady mounting of the assembly  50  onto the bearing unit  10 . Furthermore, due to the fact that the outer edge  71  is plastically deformed and the disc annular portion  73  abuts against the relevant surface  24 , these two portions define a rigid support for the angled portion  72  which in turn defines an elastic support for the gasket  60  so as to allow the gasket  60  to be always kept in contact with the surface  32 , as better explained herein after. 
     In the preferred embodiment of the invention the multi-lip sealing gasket  60  is vulcanized to the insert  70  and comprises: 
     a main body  69  which is in direct contact with the angled portion  72  and 
     five lips  61 - 65  which extend generally radially inwardly from the main body  69 . Of these five lips, the lips  61  and  65  are non-contacting lips as they are radially spaced apart from the surface  32  and are located at the opposite axial ends of the main body  69  so as to protect and axially contain the lips  62 - 64  between them. The lips  62 - 64  are intermediate contacting lips and are arranged to slide against the outer cylindrical surface  32  (shown in phantom in  FIG. 2 ) of the inner ring. It should be noted that in the appended drawings the resilient sealing gasket  60  is depicted in its non-deformed condition. 
     The non contacting lip  61  is an axially outermost lip and defines a labyrinth seal to prevent inwardly acting coarse contaminants from damaging the inner lips  62 - 64 . The lip  61  is a conical lip axially delimited by two conical, axially outwardly and radially inwardly tapering surfaces  61   s . The lip  61  is also provided with a free end  61   e  which terminates closely adjacent the surface  32  without contacting it. 
     The non-contacting lip  65  is the axially innermost lip and projects closely adjacent the surface  32  and acts as a grease retainer for keeping, although only partially, the lubricating grease within the bearing unit  10 . The lip  65  defines another labyrinth seal and it is inwardly axially delimited by a conical tapering surface  65   s  which is joined to an axially recessed, radial flat surface  69   s  of the main body  69  in order to facilitate the recirculation of the grease within the bearing unit  10 . 
     The lip  64  is adjacent to the lip  65  and shares with the lip  65  a common root portion  68  originating for the main body  69 . The lip  64  is shaped as a conical wall. It is longer and more flexible than lip  65 , and extends substantially parallel to the lip  61  from the root portion  68  and in an axially opposite direction with respect to the lip  65 . The lip  64  defines with the lip  65  an intermediate annular cave  64   s  which is able to receive some lubricating grease which may leak from the lip  65 . 
     The lip  63 , which extends substantially parallel and adjacent to the lip  64 , is shaped as a conical wall and has a thickness which is almost twice that of the lip  64 . The lip  63  is provided with a root portion  67  located approximately in the middle of the main body  69  and originates from an axially inner position with respect to the root portion  68 . Opposite to the root portion  67 , the lip  63  is provided with a sturdy contacting lip  66  with a tip about 90 degrees wide and which defines with the lip  63  and the lip  64  a further cave  63   s . The diameter at the bottom of cave  63   s  is greater than the bottom diameter of cave  64   s . The cave  63   s  extends into the main body  69  so as to partially split the two root portions  68  and  67 . Besides being pre-greased with specific lubricating grease, the cave  63   s  is also able to receive some of the lubricating grease which may leak passing over lip  64 . This will help to further reduce the wear of the lip  66 . 
     The lip  62  is the only contacting lip which does not originates for the main body  69  as it originates directly from the lip  63  and it is provided with a root portion  62   r  extending from the lip  63  nearby the lip  66 . Also lip  62  is shaped as a conical wall, but it is the longest and most flexible among the lips above mentioned. 
     The lip  66 , the lip  62  and the main body  69  define a further cave  66   s  which is outwardly radially delimited by a bottom cylindrical surface  62   s  whose diameter is greater than the diameter at the bottom of cave  63   s.    
     Due to the above construction and arrangement, the lip  63  acts as the main sealing lip and is able to exert the greatest value of radial pressure against the surface  32 , whereas the second lip  64  is able to exert a medium value of radial pressure and lower than that of the value of the radial pressure of lip  63 . Finally, the lip  62  will be able to exert a lower radial pressure as compared to the other two contacting lips  64  and  63 , and is able to act as an anti-dust lip to protect the main lip  63 . 
     Whilst it is not desired to be bound to any specific theory in this connection, tests carried out by the Applicant show that, as a result of the above arrangement, the lip  63  acts as a pivot or fulcrum when some misalignment takes place between the shaft and the stationary parts of the bearing. As a result, the contact radial pressure exerted by the lip  62  will increase, whereas the radial pressure of the lip  64  will decrease or vice versa, depending on the direction of the relative inclination between the inner and outer bearing rings. However, in the worst misalignment conditions, at least one of the lips  62 ,  64 , on opposite sides of the lip  66 , will remain in sliding contact with the inner ring  30  together with the main lip  66 , but without increasing the overall pressure, owing to their thin, elongate and flexible construction. Therefore, the sealing assembly  50  assures that at least two sliding lips are permanently in sliding contact with the inner ring, like a dual barrier stopping contaminants from entering the bearing. 
     Finally, in order to increase the overall sealing performances of the above described assembly  50 , the sealing gasket  60  further comprises a static seal  160  in form of a layer which is made of the same material of the main body  69  and which covers almost completely the side of the annular portion  73  which abuts the surface  24 . 
     While a specific embodiment of the invention has been disclosed, it is to be understood that such disclosure has been merely for the purpose of illustration and that the invention is not to be limited in any manner thereby. Various modifications will be apparent to those skilled in the art in view of the foregoing example. The scope of the invention is to be limited only by the appended claims.