Abstract:
The present invention discloses a method of sealing dynamic shaft applications. The method comprises providing a dynamic shaft assembly containing a bore for receiving a seal, providing a unitized seal, and placing the unitized seal on the shaft, thus sealing the assembly so that lubricants may not escape, and foreign material may not enter. The unitized seal can provide permanently lubricated sealed bearings in severe service conditions such as rollers and idlers of track-driven vehicles and agricultural equipment.

Description:
RELATED APPLICATIONS  
       [0001]    This Application is a Continuation-in-Part of Co-pending U.S. patent application Ser. No. 08/937,427, filed Sep. 25, 1997. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present disclosure is related to the field of seals for sealing dynamic shafts, generally, and methods of using the same. The methods and apparatus are particularly related to the field of unitary combination lip and sleeve seals. More specifically, this is a method for using an improved seal adapted for use in severe duty applications including construction equipment, agricultural machinery, track driven vehicles, and other applications where oil or grease must be held in contact with dynamic shaft assemblies. This seal and other seals of this type must also operate as excluder seals to keep lubricated surfaces free from corrosives, acids, other chemicals, dirt, mud, dust, abrasives, water and other contaminants. Even more particularly, this seal incorporates design features that enhance performance (compared to usual original equipment seals) when installed on shafts that have been slightly damaged by normal wear. Most specifically, this seal can be used as a roller or idler seal for track driven vehicles.  
         BACKGROUND  
         [0003]    The method of using the present seal structure yields a very important benefit that has eluded other persons skilled in the art. It can be retrofitted to existing, worn machinery to enhance the protection of costly lubricated machine components. This seal can replace existing seals, and the performance of this seal exceeds that of all other standard-sized, commercially available, conventional, lip and sleeve type seals. The only commercially available type of seal with performance comparable to this embodiment is the dual cone face seal. It is known by those in the art that dual cone face seals have disadvantages that significantly restrict their use. The seal disclosed here overcomes the two major inherent disadvantages of dual cone face seals—overall width and high cost.  
           [0004]    Conventional unitized lip and sleeve seals are much thinner than dual cone face seals. Since this seal can be installed as a direct replacement for ordinary seals, it can be specified and used without making any modifications to the design of an existing machine. The shaft, the bore, and the housing in which the seal operates are identical whether the present seal or conventional seals are used. Wherever dual cone face seals are desired, the machine must have been originally designed specifically for their use. They cannot fit all of the machine locations because of design constraints.  
           [0005]    However, the availability of a seal having the superior performance characteristics of an embodiment according to the present disclosure in a package the size of ordinary seals gives additional freedom to designers of heavy machinery and severe duty assemblies. Many new design possibilities are made available by this seal because of the unitized style of the seal and the small width requirements as compared to dual cone face seals.  
           [0006]    The selling price a seal according to the present disclosure is substantially less than the selling price of dual cone face seals. A preferred embodiment of the present disclosure is expected to be two to three times the cost of a conventional seal. In some applications, such as crawler vehicles, which currently use dual cone face seals, a single machine will typically require 40 to 60 roller seals, each of which is subjected to extremes of heat, cold, moisture, dust, abrasives, acids and alkalis. Replacing the 40 to 60 dual cone face seals with seals according to the present disclosure will result in substantial savings without deviating from quality.  
           [0007]    An important benefit of the method of using the seal disclosed is that it can create permanently lubricated shaft and bearing assemblies that can withstand severe use. The method of using this seal may enable equipment manufacturers to improve the performance of their machinery by reducing maintenance requirements. It is believed that existing vehicles and other machines can be retrofitted advantageously by replacing the original re-greasable seals with this new permanently lubricated seal. The lifetime of the new seal can last substantially longer than current lip seals. It is to be understood, however, that the present seal can be used to seal in either oil or grease and to substantially exclude all environmental contaminants that do not attack the materials from which the seal is manufactured.  
           [0008]    It is an object of the invention to accomplish the foregoing and to teach the structure and method of using a retrofittable severe duty seal for a shaft.  
           [0009]    It is a further object of this disclosure to show a method useful for sealing bearings in shaft-mounted dynamic rollers used in track-driven vehicles.  
           [0010]    Another object is to provide a method that may be useful in any application where a shaft and shaft bearing or bushing surfaces may be exposed to mud, dust, abrasives, cement, submersion, abrasive liquids or other substances that could damage relative dynamic mechanical components.  
           [0011]    Another object hereof is to disclose a method of using a seal that lasts longer than previously known low cost seals adapted for severe duty applications.  
           [0012]    Another object of the present disclosure is to make essentially all of the important benefits of a dual cone face seal available at a much lower cost.  
           [0013]    Yet another object hereof is to make essentially all of the important benefits of a dual cone face seal available in a physically smaller assembly.  
           [0014]    It is an object to make essentially all of the important benefits of a dual cone face seal available in an assembly having the same physical dimensions as a conventional single lip or double lip seal.  
           [0015]    Another object hereof is to provide a method for sealing a shaft and bearing assembly using a seal as an excluder seal, as a grease seal, as an oil seal, and as a seal for other liquids at low and moderate pressures.  
           [0016]    Another object of this disclosure is to provide a method for using a seal having a shaft-contacting sleeve that enables the seal to be installed on and to operate reliably with shafts having imperfections such as those ordinarily caused by wear and use.  
           [0017]    Another specific object is to provide a method of sealing a shaft and bearing assembly, using an unitary seal structure that both improves reliability, and makes seal installation easier compared to installation of seals that are composed of two or more separable parts.  
           [0018]    A further object is to provide a method of using a seal with sealing elements that includes: a main sealing lip with a garter spring that biases the main sealing lip against the outside of the sleeve, at least one dust lip that contacts the sleeve, at least one dust lip that contacts the inner surface of the housing, at least one face dust lip that contacts the inner surface of the faceplate, and an elastomeric, shaft-contacting faceplate ring.  
           [0019]    These and further objects of the apparatus taught in accordance with this specification, the claims, and the appended drawing figures are set forth below.  
         SUMMARY  
         [0020]    The present disclosure shows a method using a retrofittable, radial lip seal for sealing a paired shaft and bore assembly rotatable with respect to one another, the seal having a sleeve that may be disposed coaxially on the shaft. The sleeve has an inner end (oil or grease side) that would normally be in contact with the grease, oil, or other fluid to be contained within a housing, an outer end (dirt side) opposite, a bore that has an elastomeric coating, and a sleeve flange extending radially outward from the outer end of the sleeve and generally perpendicular to the sleeve axis. The sleeve flange is terminated with an outer edge. One or more circular elastomeric faceplate-contacting lips extend coaxially opposite the oil side from the sleeve flange outer face.  
           [0021]    A circular elastomeric perimeter lip extends radially and outwardly from the outer edge of the sleeve flange to contact a generally cylindrical hollow seal case adapted for fitting into a bore, such as a bore that is formed through a roller end plate, the wall of a housing, or other securement.  
           [0022]    The case is formed from a generally cylindrical case body having an outside surface, or outside diameter, that may be disposed within a bore and in contact with the wall of the bore. An elastomeric coating may be affixed to the outside of the case body. By coating the outside of the metal case body with an elastomeric coating or layer, it is possible for the seal to securely fit a bore that has become slightly damaged through use.  
           [0023]    The inner surface of the case is smoothly finished in the region close to the outer end to properly adapt it for maintaining continuous operating contact with the perimeter lip of the sleeve flange. The case has an inner, fluid-contacting, end opposite the outer end; the inner end is sometimes referred to as the “oil side.” A case skirt extends radially outward from, and generally perpendicular to, the outside end of the case. Although it is believed preferable to form the case skirt from the case body, it may be possible to form the case skirt by attaching a separate piece Various processes such as drawing, coining, or forging may be employed to make the case body and the case skirt as a unit from a single piece of cylindrical tubular material. An equivalent case body and case skirt assembly may also be formed by joining separate component parts.  
           [0024]    A case inner flange is located between the outer end and the fluid end of the case. The case inner flange extends radially inwardly from, and generally perpendicular to, the longitudinal axis of the inside of the case. It is believed preferable to draw the case inner flange from the material of the case body. When formed in that manner, the material of the case body is doubled back on itself to yield two thicknesses of the case material for the distance between the case inner end and the case inner flange. The case reinforcement provided by the double layer of metal allows the use of a slightly thinner material to form the case body than would be necessary if the case material was a single thickness. Other methods of construction may be adopted, however, without departing from the scope of the invention disclosed. For example, a case inner flange could be formed from a cup-shaped blank that is inserted into the case body and secured in place.  
           [0025]    At least one sleeve-contacting, elastomeric, sealing lip extends from the case inner flange to operatively contact the outer surface of the sleeve at a region near the inner end of the sleeve. The main sealing lip may be fitted with a garter spring to enable the assembly to operate at higher pressures. Testing has confirmed that the seal disclosed herein can operate reliably at a pressure of one atmosphere (15 p.s.i.) with shaft speeds of 1500 feet per minute.  
           [0026]    The maximum pressure at which this seal, like seals in general, can reliably operate decreases with increasing shaft speed. Testing may show that operation is satisfactory at pressures of approximately 100 p.s.i. or that slight changes could allow the seal to operate in the range of 100 p.s.i. However, testing at higher pressures and rotational velocities had not been concluded before preparation of the present disclosure.  
           [0027]    The main sealing lip and garter spring portion extends inwardly, toward the inner end of the sleeve, coaxially with the sleeve. At least one, and preferably two dust lips are positioned to extend inwardly from the case into coaxial contact with the sleeve outer surface. One of the inwardly oriented dust lips, the mid-sleeve dust lip, may be disposed generally between the case inner flange aperture and the sleeve outer surface. The second sleeve contacting dust lip, the forward sleeve dust lip, is disposed generally midway between the sleeve flange and the case inner flange. A third dust lip, the case flange dust lip, extends forwardly from the front surface of the case inner flange. The three dust lips and the main sealing lip are molded at high temperatures in one piece using a single mold operation and bonded to the insert with suitable bonding agents.  
           [0028]    A resilient layer may cover the outside of the case to improve sealing in conditions where soft, damaged, or other less than optimal bore conditions exist that would impair reliable sealing with a steel outer case surface. It is possible to cover the oil side insert and form the primary seal element similarly. In applications that might expose the sealed materials to corrosion, it is preferred to cover with resilient rubberized material all of the portions of the seal case that are likely to contact the corrosive agents.  
           [0029]    The case elastomeric coating is formed with a chamfer to minimize the likelihood that the seal will be damaged during installation. One or more optional radial case relief channels may be formed in the case elastomeric coating. A relief channel may reduce relieves the tendency of the elastomeric coating to form a bulge that could cause the seal to become unseated and move axially after installation. It is also possible to provide radial ribs on the outer surface of the case elastomeric coating for the purpose of providing desired installation properties.  
           [0030]    The seal is made into a unitary structure by inserting the sleeve inner end through the case inner flange so that the sleeve flange is inside the case near the case skirt. All of the voids between the lips, and the voids between the lips and the case, must be packed with grease before final assembly of the seal. The faceplate is then attached to the case skirt thereby retaining the sleeve within the case portion. It has been found that a high quality water-resistant grease is needed. One satisfactory grease is made by Esso Corporation and sold under the trade name “BEACON 325” although other products may serve quite satisfactorily. The faceplate is attached to the case skirt and disposed in contact with the face lips that extend axially from the face of the sleeve flange and packed with grease. Although it is believed preferable to attach the faceplate to the case by crimping the peripheral edge of the faceplate around the outer edge of the case skirt, the faceplate may also be attached to the skirt by brazing, welding, adhesive bonding, or by any other of the usual means of connecting such items. It is desired that the junction between the case skirt and the faceplate be impervious to external contaminants and internal lubricants at the temperatures, pressures, and other conditions in which the seal is operated.  
           [0031]    A generally planar circular faceplate has an inside surface, an outside surface, and a central aperture slightly larger than the inside diameter of the sleeve. The plane of the inner faceplate surface is disposed generally parallel to the case skirt and the face of the sleeve flange. An elastomeric portion, or faceplate wiper ring, can be attached to the faceplate at the central aperture so that the faceplate wiper ring extends between the faceplate and the shaft. The faceplate wiper ring has an internal diameter that allows it to contact the shaft and thereby exclude contaminants from the remainder of the seal and the sealed components.  
           [0032]    The sleeve bore is preferably coated with an elastomeric, or rubberized, coating to make it possible to obtain adequate sealing performance when the shaft condition is substandard due to wear, eccentricity, or other causes. A sleeve radial channel may be formed generally midway between the sleeve inner end and the sleeve outer end. The channel relieves shear tension that may develop during installation. The result is that it is easier to install the sleeve and the potential for damage to the sleeve during installation is reduced.  
           [0033]    Chamfers are provided at both the inner end and at the outer end of the sleeve bore to reduce the potential for damage to the seal, the shaft, or the housing during installation. In addition, the inner end of the case outer surface is chamfered to make insertion of the sleeve through the housing easier and less likely to damage the dust lips or other components.  
           [0034]    The flange peripheral lip and face lips may be formed in the same molding operation that is used to mold the sleeve bore elastomeric coating. The face lips may be designed with shapes similar to those of the peripheral lip and the three dust lips. However, an alternative design for the face lips is disclosed herein. The undercut face lips are adapted to provide superior performance in severe duty operating conditions. The advantage accrues because the undercut lip inside surface responds with increasing pressure in response to contact with materials that would penetrate the seal. The other lips contact the mating seal surface at distinctly different approach angles and with quite different elastomer shapes and configurations.  
           [0035]    An alternative form of the embodiment replacing the main sealing lip is favored for some very dirty applications, such as in agricultural machinery, or in applications where the width of the seal is severely limited due to the assembly configuration. One example in which the alternative embodiment of the seal can be used is in cultivator hub wheels. This type of equipment does not typically have much room for a seal around the bearing, and contains only grease in the assembly. In the alternative embodiment, the main sealing lip and the garter spring are replaced by at least one radial wiper, or excluder lip. In addition, the two sleeve contacting dust lips may also be eliminated in this alternative embodiment. The flat lip design may be less susceptible to catastrophic damage by the infiltration of small amounts of foreign materials than are the usual main seal lip and garter spring sets. It is also possible to produce the design with more lips; for example, a triple or quadruple lip design may be desired in some applications. Eliminating the garter spring and main sealing lip portions allows the seal to have a width of 5 mm inside the bore. This seal replaces typical triple lip seals commonly used in such applications, wherein the sealed portion must constantly be filled with grease to force out the grease, because it has either leaked out, or contains foreign material (e.g., dirt, dust, etc.), because those seals do not effectively keep the materials out. In contrast, the seal of the alternative embodiment does not have to be regreased, and is virtually maintenance free, because it effectively excludes foreign material from entering the sealed area, and does not allow the grease to leak out of the sealed area.  
           [0036]    It is preferred to have the inner side of the faceplate smoothly finished to reduce wear on the face lips of the seal. Likewise, the outer surface of the sleeve, the sleeve flange inner face, and the perimeter lip-contacting medial insert inside cylindrical surface may be finished to a condition of low surface roughness to reduce the amount of wear to which the various elastomeric excluder and seal lips are subjected. For this reason, it is generally preferred to make the sleeve, case, and faceplate of metal such as stainless steel, carbon steel, or similar materials. It is to be understood, however, that the sleeve, case, and faceplate may be made from other metals and also from non-metallic materials.  
           [0037]    In seals of this nature, the seals are normally described by reference to the cross-sectional configuration. The seal of the present embodiment may readily be manufactured in sizes between 0.5 inches and 26 inches with other sizes available on request. By way of example only and without any limitation on the configuration of embodiments of this disclosure, a representative seal may have an inside (shaft) diameter of 3⅛″, an outside (bore) diameter of 4⅛″, with an overall width of about 1″. The various dimensions do not scale proportionately. For example, the same type of seal may be manufactured for a 6¼″ shaft diameter but still have an overall width of 1″ and be designed to fit into a 7¾″ bore. Seals adapted to various purposes may vary in width from less than ⅛″ to over 1″ but generally have a width between ¼″ and ¾″.  
           [0038]    It is to be understood, as well, that many different formulations of the elastomeric, or rubberized, elements may function satisfactorily. Viton®, nitrile, carboxylated nitrile, polyacrylate, ACM, fluroelastomers, and silicone compounds are known to provide useful operational characteristics when adapted for incorporation within the seal presently disclosed. Other materials may also be incorporated to confer chemical resistance, extreme temperature resistance, expanded operating pressure range, wear resistance, or other desired properties to the final seal assembly. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0039]    [0039]FIG. 1 shows a cross-sectional profile of a retrofittable severe duty seal for a shaft according to the present disclosure.  
         [0040]    [0040]FIG. 2 shows a cross-sectional profile of an alternative embodiment of the retrofittable severe duty seal for a shaft of FIG. 1 having an alternative configuration for the main sealing lip.  
         [0041]    [0041]FIG. 3 shows an alternative configuration of the seal of FIG. 1 that has an alternative shape for the face lips.  
         [0042]    [0042]FIG. 4 shows a representative assembly of a type that is adapted for receiving the retrofittable seal of FIG. 1 
     
    
     DETAILED DESCRIPTION  
       [0043]    Referring now to the various figures of the accompanying drawing, FIG. 1 depicts a cross-sectional profile of an embodiment of the retrofittable severe duty seal  20  fitted onto a shaft  21 . A cylindrical sleeve  22  component is disposed coaxially over, and in contact with, the shaft  21  so that when installation is complete, the sleeve  22  is affixed to the shaft  21 . The sleeve inner end  24  extends into the sealed region, normally a housing or containment for oil or grease used to lubricate gears, bearings, or other moving parts.  
         [0044]    To simplify nomenclature in this specification, the side or end or surface of a component that is oriented toward the lubricants, lubricated components, or other media from which it is desired to exclude dust, water, mud, and other environmental contaminants may be referred to using the terms “inner,” “inward,” “inside,” and similar terms. The words “outer,” “outward,” “outside” and similar terms may be used to refer to a side, end, or surface of a component that is oriented away from the sealed region, toward the exterior of a housing, or toward the unsealed overall environment into which a shaft extends.  
         [0045]    Between the sleeve inner end  24  and the sleeve outer end  26 , the sleeve bore  28  may optionally be coated with an elastomeric coating  30 . The optional sleeve bore elastomeric coating  30  is desirable because it may prevent leakage from between the seal  20  and the shaft  21  even when the shaft is worn, damaged, or otherwise imperfect.  
         [0046]    The sleeve flange  32  extends radially outwardly from the sleeve outer end  26  and has a sleeve flange outer edge  34  at its outer periphery. At least one, and preferably two, face lips  36  extend coaxially outwardly from the sleeve flange  32  outer face  38  and a perimeter lip  40  extends radially outwardly from the sleeve flange outer edge  34 . The sleeve bore elastomeric coating  30 , the face lips  36 , and the perimeter lip  40  may be integrally formed and bonded to the sleeve  22  in a single injection molding operation.  
         [0047]    A seal case  50  is disposed coaxially outside the sleeve  22 . The seal case  50  has a generally cylindrical case body  52  designed so that the case outside surface  54  can fit into and seal against a bore in a housing or flange through which the shaft  21  to be sealed extends. It is preferred to enclose the case outside surface  54  with an optional case elastomeric coating  56 . The seal  20  is less likely to leak when installed in a damaged bore if the optional case elastomeric coating  56  is provided. The case body  52  has a case inner surface  58  that may be smoothly finished in the region near the case outer end  60  if the perimeter lip  40  will contact it.  
         [0048]    The case inner end  62  is axially opposite the case outer end  60  and the case skirt  64  that extends radially outwardly from the case outer end  60 .  
         [0049]    A case inner flange  66  extends radially inwardly from the case body  52  toward the sleeve  22  The case inner flange  66  has a circular central aperture through which the shaft  21  and sleeve  22  fit. When the case inner flange  66  is drawn or otherwise made from the case body  52  it is possible to simultaneously form a case reinforcement  68  with a double layer of the material from which the case body  52  is made.  
         [0050]    The main sealing lip  70  attaches to the case inner flange  66  and extends both axially inwardly and radially inward from the case inner flange  66 . The main sealing lip  70  contacts the sleeve outer surface  72  to form the primary sealing element by which the contents of the sealed volume are prevented from transferring to the outside of the assembly. The main sealing lip  70  is optionally biased against the sleeve outer surface  72  by a garter spring  74 . The sleeve outer surface  72  may be polished or otherwise finished to reduce wear of the main sealing lip  70 .  
         [0051]    Additional sealing elements are situated axially outwardly from the main sealing lip  70 . These additional dust lips may extend between the case body  52 , particularly the case inner flange  66 , and the sleeve outer surface  72 .  
         [0052]    A mid-sleeve dust lip  75  may be located generally between the case inner flange  66  and the sleeve outer surface  72 . A forward sleeve dust lip  76  may be disposed against the sleeve outer surface  72  at a location close to the sleeve flange  32 . A case flange dust lip  77  may extend from the case inner flange  66  to contact the sleeve flange  32 . The case elastomeric coating  56 , the main sealing lip  70 , the mid-sleeve dust lip  75 , the forward sleeve dust lip  76  and the case flange dust lip  77  may be integrally formed and bonded to the case body  52  and case inner flange  66  in a single injection molding operation.  
         [0053]    On the inner end of the case body  52 , the case elastomeric coating  56  is finished with a case elastomeric coating chamfer  78  to make it easier to install the seal  20  without distortion or damage. A case outside diameter relief channel  79  is formed in the case elastomeric coating  56 . The optional relief channel  79  relieves axial shear stresses from the case elastomeric coating  56  that may be induced by the process of installing the seal  20  into a bore.  
         [0054]    Three main sub-assemblies, the sleeve  22 , the case  50 , and the faceplate  81  are interconnected to form a complete seal  20 . These three sub-assemblies are normally made primarily of steel or other metal that is shaped, worked, and polished using conventional metalworking techniques and commercially available equipment. It may be advantageous to smooth the metal surfaces that are contacted by the various elastomeric components to obtain a metal finish having low surface roughness. Carefully shaped and molded elastomeric compounds are bonded to the metal components in the configurations shown in the accompanying drawing. It is possible to form the elastomeric components and attach them to the metal structures in a variety of ways; however, injection molding is believed preferable for these purposes.  
         [0055]    Final assembly of the seal  20  is performed by carrying out four additional steps. First, water-resistant grease  80 , such as Esso Beacon 325™ is packed to fill all of the voids between the lips and between the case inner flange  66  and the case skirt  64 . Second, the sleeve  22  is inserted into the seal case  50  so that the sleeve flange dust lip  77  contacts the sleeve flange  32  and the perimeter lip  40  contacts the perimeter lip-contacting case inner surface  58 . Third, grease  80  is packed into the interstices between the individual face lips  36  and also between the perimeter lip  40  and the outermost of the face lips  36 . Fourth, the faceplate  81  is affixed to the case skirt  64  by crimping or other means to complete the assembly and unitizing process.  
         [0056]    After the faceplate  81  is attached to the case skirt  64 , the faceplate inner side  82  contacts the face lips 36  and the sleeve flange inner face  84  is brought into contact with the case flange dust lip  77 .  
         [0057]    An optional elastomeric faceplate wiper ring  86  can be bonded to a central aperture in the faceplate  81  coaxial with, and through which, the shaft  21  extends. The periphery of the faceplate  81  may be finished with a peripheral faceplate crimp edge  88  for crimping over the case skirt  64  when the faceplate  81  is attached by crimping.  
         [0058]    A sleeve radial channel  90  is preferably formed within the sleeve bore elastomeric coating  30  to relieve shear as the seal  20  is fitted to a shaft. The sleeve  22  is finished with a sleeve outer end chamfer  92  and a sleeve inner end chamfer  94  to reduce the potential for tearing of the sleeve bore elastomeric coating  30  and for distortion of the sleeve  22  during installation of the seal  20 . Likewise, the seal case  50  may be fitted with a case inner end chamfer  96  to reduce damage to the case elastomeric coating  56  when the case is fitted with elastomeric coating and to prevent case distortion in embodiments without case elastomeric coating  56 .  
         [0059]    It is believed preferable for the face lips  36  to be sharply angled radially inwardly with an acute point at the innermost portion of each of the face lips  36 . In order to form a lip having such a shape, it may be necessary to include a face lip undercut angle  98  that is less than 90 degrees to obtain the desired performance characteristics. The face lips  36  may be formed having a generally triangular cross-section.  
         [0060]    [0060]FIG. 2 shows an embodiment wherein the single main sealing lip  70  and garter spring  74  shown in FIG. 1 are replaced with a triple lip main seal  100 . It may be desirable to also eliminate the mid-sleeve dust lip  75  and the forward sleeve dust lip  76  from embodiments having the main sealing lip  70  replaced by the triple lip main seal  100 . This embodiment is especially useful for situations in which the space allowed for a seal in the assembly is less than approximately ¼″, and where the lubricant contained in the sealed area is grease, such as in cultivator hub wheels.  
         [0061]    [0061]FIG. 3 shows an alternative embodiment of the seal  20  wherein the spacing relationship between the dust lips  75   76   77  is modified slightly from the relationship depicted in FIG. 1.  
         [0062]    [0062]FIG. 4 shows a representative application in which the seal  20  may be installed, specifically, a worm gear drive assembly  101 . The seal  20  is fitted into the bore of a housing  102  to seal a bearing  104  from outside contaminants and to prevent lubricants from leaking out of the housing  102  around the output shaft  106  of the worm gear drive assembly  101 .  
       Industrial Applicability  
       [0063]    From the foregoing, it may be readily understood by those skilled in the art that the embodiments disclosed are applicable to industry and mechanical power transmission generally, and to machinery and vehicles that are operated in severe environments, particularly. Incorporation of the prevent embodiment into new and existing equipment is expected to substantially reduce the maintenance requirements of many types of construction and agricultural equipment.  
         [0064]    To use the seals as described, a dynamic shaft assembly is provided, wherein a housing containing the assembly has a bore through which the assembly extends. A seal  20  as described above is coaxially fitted onto the shaft, and is designed so that the case body  52  can fit into and seal against the bore, thus sealing the bearing, and preventing lubricants from escaping the assembly, and foreign materials from entering.  
         [0065]    Changes and modifications in the specifically described embodiments can be carried out without departing from the scope of the invention which is intended to be limited only by the scope of the appended claims.  
         [0066]    With regard to means for fastening, mounting, attaching or connecting the components of the present invention to form the seal as a whole, unless specifically described otherwise, such means are intended to encompass conventional fasteners such as nut and bolt-type connectors, threaded connectors, snap members, clamps and the like, rivets, toggles, pins and the like. Components may also be connected by welding, friction fitting or deformation, if appropriate. Electrical connections, if any, for use in or during the process, may be made using appropriate electrical components and connection methods, including conventional components and connectors. Suitable computers, microprocessors and the like may be used in the method. Unless specifically otherwise disclosed or taught, materials for making components of the present invention are selected from appropriate materials such as metal, metallic alloys, fibers, plastics and the like, and appropriate manufacturing or production methods including casting, extruding, molding and machining may be used.  
         [0067]    Any references to front and back, right and left, top and bottom and upper and lower are intended for convenience of description, not to limit the present invention or its components to any one positional or spacial orientation.