Abstract:
A seal system for use in high speed, high pressure applications including a rigid retainer and a resilient body covering the retainer having pressure balancing control. Reduced clearance of the metal case retainer prevents seal extrusion.

Description:
CONTINUATION DATA  
       [0001]    This application claims the benefit under Title 35, United States Code §119(e) of any U.S. application No. 60/306,113 filed on Jul. 17, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates generally to radial lip seals, and more particularly, to radial lip seals which can accommodate shaft deflection in an environment in which the shaft rotates at high speed, and under high torque conditions and in which the fluid being sealed attains high pressures.  
           [0004]    2. Description of the Related Art  
           [0005]    Lip seals are usually molded of a resilient elastomeric or polymeric material. They are secured in fluid tight relation to a housing and surround a rotating shaft which extends through an aperture in the housing wall. The sealing lip is in sealing relationship to the shaft to contain the fluid in the housing.  
           [0006]    Lip seal&#39;s components or elements include a rigid case or retainer to add rigidity and to unitize the seal assembly. The case also aids in the installation, withdrawal and retention of the seal relative to the housing. The resilient body includes a secondary seal to seal against the housing and one or more resilient sealing lips which are maintained in sealing contact with the shaft.  
           [0007]    Lip seals experience a wide variety of uses in which operating temperature and pressure conditions, expected shaft speeds, and the make-up of the medium to be contained dictate the requirements of a particular construction. Typically, however, the rigid component or retainer is formed of hard plastic, such as phenolic, steel or stainless steel and the resilient lips are defined by elastomeric or polymeric members such as molded rubber, polytetrafluoroethylene or other known materials. The resilient element may be molded as a single body or may comprise a plurality of separate elements connected together in fluid tight relation.  
           [0008]    The nature of lip seal applications expose the seal to conditions of significant shaft movement relative to the surrounding housing. Shaft deflection relative to either the housing or the bore results in a wobble of the shaft during rotation of the shaft, also referred to as shaft run-out. A significant degree of shaft run-out often challenges the effectiveness of the lip seal.  
           [0009]    Specific applications for lip seals may include automotive, appliance and industrial applications. Certain applications subject lip seals to extreme service conditions such as in air conditioning compressors, where the shaft is typically driven by a belt and pulley through an electric clutch, and in oil pumps which generally pressurize oil to high pressures, to thereby permit effective circulation of the oil through the engine and oil filter. Compressor and oil pump design typically results in shaft wobble, bending distortion and misalignment of the shaft axis relative to the housing aperture. Ideally, the lip seal assembly takes into account the established tolerances of the devices in which the lip seal is used in order to minimize the associated manufacturing costs.  
           [0010]    Efforts to provide a lip seal to accommodate shaft run-out or misalignment include use of extended conical shapes, multiple lips and other variations and alterations of the resilient element. An effective arrangement is disclosed in U.S. Pat. No. 5,503,408, issued Apr. 2, 1996, and commonly assigned with this invention to John Crane Inc., Morton Grove, Ill. The seal disclosed and claimed in U.S. Pat. No. 5,503,408 embodies multiple resilient lips which provide for an auxiliary or alignment lip interposed between the shaft and the sealing lip for centering the lip seal. Under conditions of misalignment, the auxiliary lip contacts the underside of the primary sealing lip and causes a displacement of that lip in the direction of displacement of the shaft relative to the center of its associated housing bore. Displacement of the auxiliary lip causes the primary sealing lip to “follow” the shaft and, thereby, maintain the integrity of its sealing relation to the shaft. The lip seal described in U.S. Pat. No. 5,503,408 is used in relatively low pressure type applications. U.S. Pat. No. 5,975,538 uses an inner support member to accomplish enhanced sealing.  
           [0011]    In the event that the fluid being sealed attains high pressures, the lip seal becomes subject to deformation from axially directed pressure forces, resulting from the high pressures acting on the radial area of the lip seal, which press the radial sealing lip against the bearing. At high pressures, the radial seal lip is further subject to folding over at the shaft, thereby resulting in a loss of sealing capacity.  
           [0012]    To some extent, bearing members which are utilized in the efforts and examples described above maintain seal lip centering and also contain the seal lip in the desired orientation and position between the bearing and the high pressure fluid being sealed. However, bearings, by the nature of their construction and function, extend from the seal lip and provide rigid axial support to the retainer member relative to the shaft. In most instances, the outer diameter of the bearing is flush against the inner diameter of the rigid retainer member, so that any shaft deflection causes the bearing to impart that deflection to the retainer, thereby maintaining a predetermined relative orientation between the lip seal and the rotating shaft. Dampening action of a resilient mounting between the bearing and the retainer member absorbs the majority of the deflection. However, even in the resilient mounting example, the abutment of the bearing member with the resilient retainer subjects the bearing to continual repeated stress, which over extended periods of time can cause the deterioration and destruction of the bearing.  
           [0013]    The present invention addresses the needs of the seals in some applications to accommodate a greater amount of pressure and inflexibility which results from the increased pressure sealed fluid environments. The ability of the improved lip seal according to the present invention to accommodate great pressures also allows for the elimination of expensive case pressure drain systems that are required in some high pressure applications.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention is directed to a unitary lip seal assembly which includes a rigid retainer and a resilient member secured thereto with at least one generally radially directed lip for sealing engagement with an associated shaft. The retainer member defines a radial support surface for maintaining the radial sealing lip intermediate the radial support surface and the high pressure medium being sealed. The retainer member is shaped and dimensioned and has an inner diameter adapted to maintain a predetermined spatial separation between the retainer member inner diameter portion and the shaft extending portion of the support member irrespective of the operational conditions, such as amount of shaft deflection, or of the pressure of the medium being sealed.  
           [0015]    The rigid metal container case has a sharp corner at the inside diameter facing the open end and resilient member. This sharp corner prevents the lip of the resilient member from wedging between the case and the shaft and then extruding.  
           [0016]    The rigid container further is not totally encased by the resilient member. Therefore, the back surface of the rigid retainer is in direct thermal contact with the housing or end plate. This increases thermal conductivity between a seal and the housing and allows for dissipation of heat that builds up within the seal system.  
           [0017]    Another portion of the invention is that the geometry of the seal lip at the flex and head area is pressure balanced. This pressure balancing is a combination of particular angles and surface areas and allows the pressure to exert force vectors that offset some of the force that can lift the lip from the rotating shaft. A combination of particular geometrical shapes permits the creation of a new class of vector forces upon the seal lip area. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    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:  
         [0019]    [0019]FIG. 1 is a sectional view of an installed seal assembly according to the present invention;  
         [0020]    [0020]FIG. 2 is a front view, showing the seal assembly of the present invention uninstalled in a housing;  
         [0021]    [0021]FIG. 3 is a sectional side view of the seal assembly shown in FIG. 2, the cross-section taken approximately along the line  3 - 3 ;  
         [0022]    [0022]FIG. 4 is an enlarged section of FIG. 3 about line  4 ; and  
         [0023]    [0023]FIG. 5 is an enlarged sectional view of FIG. 4. 
     
    
       [0024]    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  
       [0025]    Referring to FIGS. 1 through 3, a lip seal assembly, generally designated  10 , is illustrative of the principles of the present invention. Lip seal assembly  10  comprises several components, and is shown in FIG. 1. The seal assembly illustrated in FIG. 1 is rendered in an assembled and installed condition. FIG. 1 illustrates lip seal assembly  10  installed in a hydraulic application, such as a motor or oil pump, and disposed about a shaft  12  which extends through an aperture in the pump housing  14 . The invention is particularly well suited for high speed high pressure hydraulic applications.  
         [0026]    The aperture is defined by a cylindrical wall  16  which surrounds shaft  12  in spaced relation. Pump housing  14  is shown in partial section in FIG. 2, with shaft  12  extending through the aperture. Lip seal assembly  10  seals the aperture to minimize leakage from the pump housing even when the oil is under great pressure which are generated by the rotor (not shown) which is attached to shaft  12 . It is understood by those having skill in the art that all of the seal members shown in FIG. 1 are annular members which are disposed concentrically with shaft  12 . The elements are shown in the drawing figures in partial cross-sectional views for convenience. That is, those portions of lip seal assembly  10  and housing  14  which extend therebelow are not shown. These elements would be essentially identical to the portions above the centerline, and the convention is to illustrate only one-half of the members to allow illustration in greater detail.  
         [0027]    Housing  14  defines internal chamber  18  which surrounds shaft  12  and is filled with a lubricant, such as oil. When the shaft is rotating together with the attached rotor (not shown), pressure is generated within chamber  18 . Oil pump components, such as the rotor (not shown), are disposed inboard of housing  14  and operate to generate pressure of the oil which is then pumped through the lubrication system of the hydraulic system or other application requiring a hydraulic pump or motor for low speed, high pressure applications.  
         [0028]    Lip seal assembly  10  is annularly disposed axially outboard of housing  14  and adjacent aperture cylindrical wall surface  16 . Lip seal assembly  10  maintains a seal at the aperture and produces a sealing relation between the surface of shaft  12  and radial surface  15  of housing  14 . Seal assembly  10  separates chamber  18  from the environment which is external to housing  14 .  
         [0029]    Lip seal assembly  10  is retained in place by a conventional end plate assembly as known in the art. The end plate assembly comprises generally an annular end plate  20  which is removable.  
         [0030]    The details of lip seal assembly  10 , in an installed condition, are illustrated in FIG. 1. Lip seal assembly  10  includes an annular resilient seal body  30  bonded to a rigid retainer  32 . Resilient seal body  30  may be formed from an elastomeric material, such as hard rubber, and rigid retainer  32  may be formed from a metallic material, e.g. steel.  
         [0031]    Rigid retainer  32  is an annular, ring-like structure which includes an axially extending collar  34  at the outer diameter, a shortened radially extending flange  36  at the inner diameter to flange  36 . A curved connecting portion  38  extends radially inwardly from collar  34  and connects collar  34  to flange  36 . In cross-section, rigid retainer  32  appears in the shape of an “L”, or as a widened “V” as is shown in FIGS. 1, 4 and  5 .  
         [0032]    Resilient seal body  30  is an integral elastomeric or polymeric element, as shown, and is formed by a molding or injection process. Typically, the forming of resilient seal body  30  and its bonding to rigid retainer  32  occur simultaneously during the molding process. Resilient seal body  30  includes an annular ring portion  42  which is bonded to the outer diameter surface of the annular, axially extending collar  34 . Ring portion  42  includes a circumferential extension section  44  which is formed at a corner of resilient seal body  30  on an outer surface thereof and may be flared at each end to provide a better interference fit in the installed condition.  
         [0033]    Installation of the seal as illustrated in FIG. 1 causes extension section  44  to sealingly engage the annular cylindrical wall  23  of housing  14 . In order to ensure a fluid tight seal between the outer diameter wall of resilient seal body  30  and the inner diameter of annular cylindrical wall  23 , the outer diameter of extension section  44  is formed to be slightly larger than the inner diameter of annular cylindrical wall  23 . A limited amount of compression of extension section  44  and of ring portion  42  occurs upon installation, which aids in creating a fluid tight seal.  
         [0034]    Referring again to FIG. 1, a shallow layer of the elastomeric material which defines a central covering portion  48  extending radially inwardly from ring portion  42  and is disposed on the inner curved section of connecting portion  38 . Preferably, central covering portion  48  is molded onto connecting portion  38  so that the elastomeric material encloses and isolates rigid retainer  32  from the process fluid contained under pressure within internal chamber  18 . This aids in avoiding corrosion of rigid retainer  32 . The opposite side (outside) is in thermal connection with annular end plate  20  and preferably housing  14 .  
         [0035]    Extending radially inwardly from the central covering portion  48  is a sealing lip  50 . Sealing lip  50  is integral with the central covering portion  48  and is molded onto the short radially extending flange  36  of rigid retainer  32 . Sealing lip  50  comprises a main body and a contacting point  52  for sealing contact with the surface of shaft  12 . In the uninstalled condition, sealing lip  50  extends at an angle in a radially inward direction relative to the center line CL and axially away from the body of the seal assembly  10  toward the direction where the pressurized hydraulic fluid would be disposed as shown in FIG. 4, preferably 55°±10°.  
         [0036]    Extending axially and radially from resilient seal body  30  is a projection portion  60  which extends axially of the end of collar  34  of rigid retainer  32  for a predetermined distance. Projection portion  60  acts to maintain the desired axial spacing of lip seal assembly  10  in relation to a radially extending wall  27  and radial surface  15  of annular end plate  20  and housing  14 , respectively. Projection portion  60  may include a chamfer  62 , as shown, to permit easier installation of lip seal assembly  10  within annular end plate  20 .  
         [0037]    Resilient seal body  30  is disposed between annular end plate  20 , annular cylindrical wall  23 , and radial surface  15  defining the space accepting lip seal assembly  10 . The outer diameter of ring portion  42  seals against annular cylindrical wall  23  and sealing lip  50  seals against shaft  12 . The spacing S between flange  36  and shaft  12  is critical for rigid retainer  32  to act as a single and sole backup ring for lip seal assembly  10 . Flange  36  has a height of d as shown in FIG. 1. The spacing S from shaft  12  must be within 0.0 to 10% of the length of d for most effective operation. An non-chamfered corner is also of assistance in preventing extrusion. Four to eight thousandths of an inch is preferred for space S.  
         [0038]    Resilient seal body  30  is molded onto and bonded to rigid retainer  32 . Resilient seal body  30  and rigid retainer  32  together define a radially fixed mounting for sealing lip  50  which is able to angularly shift its position to accommodate shaft deflection while at all times maintaining a seal against the surface of shaft  12 . In the installed position of seal assembly  10  (FIGS. 2 and 3), contacting point  52 , which extends circumferentially around the shaft  12 , contacts the surface of shaft  12 . Similarly, extension section  44  of ring portion  42  contacts annular cylindrical wall  23  and possibly radial surface  15  of housing  14  to provide a fluid tight seal against housing  14 .  
         [0039]    An annular undercut or recess  54  is formed in the resilient seal body  30  which permits controlled flexing or bending of sealing lip  50  as the shaft runout causes radial movement or shaft deflection upon rotation. Walls  56 ,  58  forming the undercut are positioned, dimensioned and oriented to cause sealing lip  50  to pivot about an annular circumference which is approximately disposed about flange  36 .  
         [0040]    As indicated in FIG. 5, particularly surfaces indicated as  1 ,  2 , and  3  create the vector forces as indicated in FIG. 1, shown with arrows X, Y, Z. During operation, pressure on the surfaces create the vector forces X which push the sealing lip  50  down to shaft  12 . Such vector forces also push the seal to the right in FIG. 1. Pressure forces Y created during operation push the seal down to shaft  12  and further push sealing lip  50  to the left, as shown in FIG. 1. Vector forces Z created during seal operation push the seal up from shaft  12  and towards the left of the seal in FIG. 1. The creation of particular surfaces along with the orientation of the angle A of approximately 90°±20° creates the new novel X vector forces as shown in FIG. 1.  
         [0041]    An angle A of 90°±10° is preferred. Angle B has a preferred angle of approximately 120°±10°. The shape of rigid retainer  32  and its disposition fairly close to shaft  12  provides a rigid base, so that sealing lip  50  will provide an effective seal without failure for long periods of time.  
         [0042]    Other modifications may become apparent to a person of ordinary skill in the art upon achieving an understanding of the inventive concept described herein. Accordingly, this invention is not limited by the illustrated embodiments shown and described herein, but is limited only by the following claims.  
         [0043]    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.