Patent Abstract:
A dynamic shaft seal assembly has inner and outer cases that are clamped together to secure a seal element therebetween for dynamic sealing about a rotatable shaft. The inner case is formed with integral pull tabs that are engageable by a seal removal tool to facilitate the removal of the seal assembly from a bore in which the seal assembly is installed.

Full Description:
This application claims the benefit of U.S. Provisional Application No. 60/676,496, filed Apr. 29, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates generally to shaft seals, and more particularly to those having features that enable the seal to be removed from a bore after installation. 
     2. Related Art 
     Automotive air conditioning compressor seals that require removal for service rely on three know methods for providing a surface that can be engaged by a tool so that the seal can be removed once it is installed in a bore. One approach is to provide a recessed step in the outer casing of the seal. Such a recessed step is difficult to manufacture consistently and the removal tool must be capable of exerting sufficient inward radial force in order to grip the recessed step with sufficient strength to enable the seal to be pulled from the bore. Another approach is to add a separate pull ring component to the seal assembly. An example of this type is shown in U.S. Pat. No. 4,623,153. This involves stamping the separate ring piece with slots and tabs and then clamping this piece between the inner and outer seal cases. This approach adds cost and complexity to the manufacture of seals. The third known approach utilizes the end flange of the outer case that is curled over the end of the inner case to secure the cases together and to clamp the seal element between the cases. The curled end flange is extended beyond the inner case to present a tool-engaging edge. However, the curl over is often thinner than the rest of the outer casing and is prone to tearing out under the extraction force of the tool or doesn&#39;t have sufficient length to allow easy removal. 
     SUMMARY OF THE INVENTION 
     A dynamic seal assembly constructed according to a presently preferred embodiment of the invention includes inner and outer annular cases between which a seal element is clamped. The inner seal element is formed with integral pull tabs for engagement by a seal removal tool. According to particular preferred feature, the pull tabs project from an inner mouth of the inner case. 
     The invention also provides a method of removing a dynamic shaft seal assembly from a bore comprising the steps of engaging pull tabs formed as one piece with an inner case of the seal assembly with a seal removal tool from an air side of the seal assembly; and applying an axial pulling force on the pull tabs to withdraw the seal assembly. 
     The invention has the advantage of providing a simple, low cost, robust solution to the removal of shaft seal assemblies. Incorporating the pull tabs into the inner casing minimizes parts and overcomes the shortcomings of the prior known solutions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein: 
         FIG. 1  is a cross-sectional view of an embodiment of a shaft seal assembly shown installed in a bore; 
         FIG. 2  is an end view of the inner casing of the seal of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken generally along lines  3 - 3  of  FIG. 2 ; 
         FIG. 4  is perspective view of a shaft removal tool that can be used in connection with the seal assembly of  FIGS. 1-3 ; and 
         FIG. 5  is a perspective view of an inner casing according to an alternative embodiment; and 
         FIG. 6  is a view like  FIG. 1 , but incorporating the inner casing of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     A dynamic shaft seal assembly constructed according to an embodiment of the invention is shown generally at  10  in  FIG. 1  and includes an outer annular rigid support housing or metal case  12  having bonded thereto an elastomeric seal body  14 , an inner annular rigid support housing or metal case  16 , and a dynamic seal element  18  clamped between the inner and outer cases. As shown in  FIG. 1 , the case  16  is nested in the case  12 . The seal assembly  10  is installable in a bore  20  of housing  22  to dynamically seal a rotatable shaft  24  extending through the bore  20 . The seal assembly  10  has an air side  26  and an oil side  28  in relation to its orientation when installed in the bore  20 . The seal assembly  10  operates to contain lubricant within the housing on the oil side  28  of the seal assembly  10  and to exclude contaminants from entering the housing  22  from the air side  26  of the seal assembly  10 . 
     The outer case  12  includes an axially extending cylindrical mounting portion  30 . An annular flange portion  32  projects radially inwardly from the mounting portion  30  at the oil side  28  of the seal assembly. The flange portion  32  has an axially inwardly facing surface  34  and an axially outwardly facing surface  36 . The seal body  14  is molded about the flange portion  32  and extends over the opposite surfaces  34 ,  36  as well as extending onto the outer surface of the mounting portion  30  to provide a fluid tight seal between the outer case  12  and the wall of the bore  20 . The seal body  14  includes an annular seal lip  38  extending radially inwardly from the flange portion  32  for encircling and sealingly engaging the shaft  24  in operation. 
     The inner case  16  has a generally L-shaped cross section and includes an axially extending outer leg or cylindrical portion  40  located radially inwardly of the mounting portion  30  of the outer case  12 . An annular inner leg or flange portion  42  extends radially inwardly of the cylindrical portion  40  adjacent the annular flange portion  32  of the outer case  12 . The flange portion  42  has an inwardly facing clamping surface  44  that is spaced axially from the face  34  of the outer case  12 . A radially outer end of the seal element  18  extends between the clamping surface  44  and the seal body material  14  molded to the surface  34  of the outer case  12 . An axially outer end  46  of the outer case  12  is forceably curled over an axially outer end  48  of the inner case  16  and operates to urge the outer and inner cases  12 , 16  axially toward one another thus generating a compressive load on the seal element  18  to thereby securely clamp the seal element  18  between the flange portions  32 ,  42  of the outer and inner cases  12 ,  16  and to keep the cases  12 , 16  from separating axially from one another or unlocking. 
     The seal element  18  is preferably fabricated of PTFE material and is in the preferred form of a disc-like wafer that is clamped at its outer diameter and extends radially inwardly to define a lay-down sealing collar or lip  50  the lays down against and encircles the shaft  24 . The seal assembly up to this point is of conventional construction and the invention contemplates within its scope variations on the general seal design having inner and outer cases without departing from the intended scope. 
     Referring now additionally to  FIGS. 2 and 3 , it will be seen that the inner case  16  has at least one and may have a plurality of pull tabs  52  formed of one piece with the inner case  16  of the same material. The pull tabs  52  may be in opposing relationship to one another if there are two such tabs  52  as illustrated. The inner case  16 , as well as the pull tab features  52 , is preferably formed as a stamping from steel material. The inner boundary of the flange portion  42  defines a mouth edge  54 . The pull tabs  52  preferably extend from the mouth edge  54  both radially inwardly and axially outwardly at an acute angle of about 30 degrees. The pull tabs  52  define lobes or ears that are spaced circumferentially from one another. The regions between the pull tabs  52  defines radially enlarged openings or recesses  56 . Those skilled in the art will appreciate that the same or equivalent structure of the tabs and recesses can be derived by calling the inner edge of the pull tab regions the mouth edge and cutting away material to form the recesses, and that either way one ends up with a plurality of tabs and intervening spaces. 
     It will be seen from  FIG. 1  that the pull tabs  52  extend axially away from the seal element  18  such that a backside of the pull tabs  52  are spaced from the seal element  18  and define inner pull surfaces  58 . The pull tabs  52  are exposed to and accessible from the air side  26  of the seal assembly  10  when the assembly  10  is installed in the bore  20 . The space between the seal element  18  and the pull surfaces  58  is unoccupied; thus a removing tool can be moved into the space. 
       FIG. 4  illustrates a seal removal tool  60  that can be employed in conjunction with the integrated pull tabs  52  to remove the seal assembly  10  from the bore  20 . The tool  60  has a cylindrical body  62  formed at its leading end with a plurality of radially outwardly projecting ears  64 . The cylindrical body  62  is sized to be extendible through the opening in the inner case defined by the inner margin of the pull tabs  52 . The ears  64  are of a size and shape to be insertable through the recesses or openings  56  between the pull tabs. Once the ears are extended through the recesses  56 , the tool  60  is turned (e.g., 90 degrees) to position the ears in the open space behind the pull tabs  52 . A pulling force can then be applied to the tool  60  to urge the ears  64  against the inner pull surfaces  58  of the pull tabs  52  to draw the inner case  16  and thus the seal assembly  10  axially out of the bore  20 . The combined views reveal that when the pulling force is applied to the tabs  52  the force will be transmitted through the inner case  16  to the outer case  12 ; specifically, through the cylindrical portion  40  abutting the outer end  46 . This cooperative action results in the entire assembly  10  will be removed by the application of the pulling force on the tabs  52 . Also, the application of the pulling force will be concurrently directed to both cases  12 ,  16  and will thus not affect the compressive load acting on the sealing element  18 . 
       FIGS. 5 and 6  illustrate an alternative embodiment where an inner case  16 ′ is shown having the same general L-shaped configuration, including cylindrical portion  40 ′ and flange portion  42 ′ with clamping surface  44 ′ as that of the first embodiment, and with primed numbers being used to represent like or similar features as those of the first embodiment of the inner case  16 . The inner case  16 ′ also includes a plurality of pull tabs  52 ′ extending from the mouth edge  54 ′. However, in this second embodiment, the pull tabs  52 ′ are stepped such that the inner pull surface  58 ′ is generally parallel to the clamping surface  44 ′, or perpendicular to the surface of the shaft or the cylindrical portion  40  of the inner case or generally perpendicular to a longitudinal axis A of the inner case  16 ′. This stepped configuration includes an offset shoulder region  59  formed as one piece with the inner case  16 ′ and serving as a transition between the pull tabs  52 ′ and the flange portion  42 ′. The stepped clamping surface  44 ′ enables full, flush contact with the ears  64  of the removal tool  60 . This enhances the contact surface area and may increase the load capacity of the pull tabs  52 ′ and minimize any bending or pull out of the tool  60  past the tabs  52 ′. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Technology Classification (CPC): 5