Patent Publication Number: US-7900933-B2

Title: Bearing seal with flexible lip

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The application is a continuation of U.S. patent application Ser. No. 11/151,021 filed Jun. 13, 2005, which claims priority to U.S. Provisional Application 60/600,871, filed Aug. 12, 2004. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to flexible seals for bearing applications, and is concerned in particular with a flexible lip seal of the type employed in rolling mill oil film bearings. 
     2. Description of the Prior Art 
     One example of a prior art seal design is disclosed in U.S. Pat. No. 2,868,574, wherein a seal is surrounded by a stationary circular seal end plate having a radially inwardly extending rigid flange separating oppositely arranged shoulders. The flexible seal has radially outwardly extending flexible flanges which are in sliding contact with inclined surfaces on the shoulders of the seal end plate. The flange/shoulder surface interface on the inboard side serves to retain bearing lubricant in the bearing, and the flange/shoulder surface interface on the outboard side serves to exclude contaminants such as cooling water, mill scale, etc. from penetrating into the bearing. 
     This design exhibits problems such as leakage of the bearing lubricant, contaminant entering the bearing chamber and excessive wear of the seal components. These problems are due in large part to the seal flanges which are thick and heavy throughout their length. Therefore, the flanges are not as flexible as they should be and have a tendency to become distorted and fail to provide an effective seal. 
     In the seal design disclosed in U.S. Pat. No. 4,165,881, these problem were addressed by providing the seal flanges with peripheral relatively thin flexible lips. This design resulted in improved sealing performance, but leakage problems persisted when the seal was not properly aligned with respect to the seal end plate. 
     A need has continued to exist, therefore, for a seal that can operate effectively under all operating conditions, including those in which the seals are improperly aligned with respect to the seal end plates. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an improved seal has a circular seal body with a central axis and at least one radially outwardly extending flange joined by a hinge to an angularly extending sealing lip. The hinge has a reduced thickness as compared to the thicknesses of the flange and lip. The lip has converging sides leading to an enlarged rim, and the rim has angled peripheral faces that converge to an outer edge. 
     In its operating environment, the seal is mounted on the tapered section of a roll neck, with the outer edge of the sealing lip in sliding contact with an adjacent shoulder of a seal end plate. Flexure of the sealing lip at the hinge serves in concert with the increased mass and stiffness of the enlarged rim and the angular relationship of the peripheral faces to maintain line contact between the outer edge of the sealing lip and the shoulder of the seal end plate. 
     These and other features and advantages of the present invention will now be described in further detail with reference to the accompanying drawings, wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view taken through the seal assembly of a rolling mill oil film bearing, and showing a flexible neck seal in accordance with the present invention; 
         FIG. 2  is an enlarged cross-sectional view of the inboard flange on the neck seal depicted in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, and with initial reference to  FIG. 1 , there is shown at  2  a roll having an end face  4  and a roll neck with a tapered intermediate section  6  leading to a more gradually tapered end section  8 . A sleeve  10  is mounted on the tapered end section  8  and is fixed relative to the roll neck by conventional means (not shown) for rotation therewith. The sleeve  10  has an outer bearing surface  12  which is journalled for rotation within an interior bearing surface  14  of a fixed bushing  16  which is carried in a roll chock  18 . 
     The sleeve  10  rotates with the roll while the roll chock  18  and the fixed bushing  16  are stationary. Oil in flooding quantity is fed continuously between the bearing surfaces  12  and  14 . A circular extension  20  of the roll chock provides at its bottom portion a sump  22  in which the oil emerging from the bearing is continuously collected. The oil is drawn away from the sump to be recycled back to the bearing surfaces. 
     Where the roll  2  is operating under “wet” conditions, coolant fluid is constantly flooding over the roll  2  and down over the end face  4 . In spite of the centrifugal forces which tend to throw the coolant off of the roll, some of the coolant tends to work its way along the roll neck in the direction of the bearing. The objective of the seal assembly generally indicated at  26  and the flexible neck seal  28  which forms a part of the bearing assembly, is to prevent any of the coolant fluid from reaching and contaminating the bearing oil and, vice versa, preventing loss of oil from the bearing. 
     The flexible neck seal  28  includes a flexible circular seal body  30  having inner surfaces  32   a ,  32   b  adapted to be mounted in sealing engagement on the tapered section  6  of the roll neck. The neck seal  28  is molded of a suitable resilient rubber-like material. Optionally, the seal body  30  is internally reinforced by an embedded combination of a coiled spring  34  and a steel cable  36 . 
     The seal body  30  has an exterior cylindrical surface  38  parallel to its central axis “A”. Inboard and outboard circular flexible flanges  40 ,  42  extend radially from the seal body  30  at opposite ends of surface  38 . 
     The outboard flange  42  is provided with a conventional flexible lip  44  joined to the flange by a hinge  46  of reduced thickness. Referring additionally to  FIG. 2 , the inboard flange  40  also has a lip  48  joined to it by a hinge  50  of reduced thickness. 
     In accordance with the present invention, lip  48  has converging first and second sides  48   a ,  48   b  leading to an enlarged rim  52 . The rim  52  has first and second peripheral faces  54   a ,  54   b  that converge to an outer edge  56 . When the seal is in a relaxed unstressed state (not confined or otherwise distorted), the outer edge  56  is contained in a reference plane “P” parallel to the central axis “A”. 
     When the seal is in its operating environment as depicted in  FIG. 1 , both lips  44  and  48  are in respective sliding contact with adjacent shoulders  58  of a seal end plate  60 . The conventional lip  44  is only relatively lightly loaded against its respective shoulder  58 , and the resulting area contact at the lip/shoulder interface is not conducive to maintaining a hydrodynamic condition. Seal misalignment further exacerbates this condition, causing accelerated wear and leakage. 
     In contrast, the outer edge  56  of lip  48  is in line contact with its respective shoulder  58 . As the neck seal rotates with the roll neck, the extra mass of the enlarged rim  52  serves to centrifugally urge the outer edge  56  into sealing contact with the surrounding shoulder surface. The angled relationship of the peripheral faces  54   a ,  54   b  coupled with the increased stiffness of the enlarged rim  52  ensures hydrodynamic action on both sides of the outer edge  56  as the lip  48  flexes about the hinge  50  to compensate for seal misalignment. 
     In order to further enhance the aforesaid advantages, and as can best be seen in  FIG. 2 , the first and second sides  48   a ,  48   b  are arranged to define an included angle {acute over (α)} 1  of between about 4° to 10°, with the preferred angle being about 7°. 
     In the relaxed unstressed state, the first side  48   a  of the lip is arranged at an angle of {acute over (α)} 2  with respect to reference plane P of between about 46° to 54°, with an angle of about 50° being optimal. The second side  48   b  is arranged at an angle {acute over (α)} 3  with respect to the reference plane P of between about 39° to 47°, with an angle of 43° being optimal. The included angle {acute over (α)} 4  defined by peripheral faces  54   a ,  54   b  is preferably between about 90° to 106°, with 98° being optimal. 
     Advantageously, the first side  48   a  and the first peripheral face  54   a  define an included angle {acute over (α)} 5  of between about 66.5° to 77.5°, with 72° being optimal. The second side  48   b  and the second peripheral face  54   b  define an included angle {acute over (α)} 6  of between about 157.5° to 168.5°, with 163° being optimal. 
     The first side  48   a  is advantageously provided with a protuberance  62  spaced inwardly from the juncture of the first side  48   a  with the first peripheral face  54   a . Protuberance  62  is preferably formed as a semi-circular rib. 
     The aforesaid angular relationships contribute to enhanced sealing performance of the hinged lip  48  as incorporated in a range of seal sizes. Line contact of the outer edge  56  with an adjacent fixed surface is maintained regardless of the degree of seal misalignment, thus optimizing retention of lubricant and exclusion of contaminants. 
     Although not shown, it will be understood that instead of being provided with a conventional lip  44 , the outboard flange could also be provided with a lip  48  in accordance with the present invention.