Patent Publication Number: US-2002004975-A1

Title: Seal cover for shaft assembly

Description:
BACKGROUND OF THE INVENTION  
       [0001] Shaft assemblies such as motors and speed reducers generally include a housing in which a shaft is rotatably disposed. Motors generally include means for rotationally driving the shaft, which extends out of the housing through a bore. Speed reducers generally include a driven input shaft that rotationally drives one or more output shafts through gearing that controls the rotational speed of the output shaft(s). The input and output shafts extend into and out of the housing through respective bores. Shaft assemblies such as motors and speed reducers sometimes have a double output shaft.  
       [0002] Such assemblies often include a lip seal at the housing bore that extends between the housing and the shaft. The lip seal typically includes a rigid outer portion secured within the bore by an interference fit between the seal&#39;s outer circumferential surface and the bore&#39;s inner circumference. An elastomeric portion extends inward from the rigid outer portion to engage the shaft. This elastomeric lip bends axially inward toward the shaft assembly&#39;s interior, thus preventing the escape of lubricant from the interior area while providing an effective seal that prevents entrance of exterior contaminants into the interior area.  
       SUMMARY OF THE INVENTION  
       [0003] The present invention recognizes and addresses disadvantages of prior art construction and methods.  
       [0004] Accordingly, it is an object of the present invention to provide a tool for driving an annular seal into a cavity defined by a shaft assembly housing that surrounds a rotatable shaft.  
       [0005] It is a further object of the present invention to provide a seal cover for a shaft rotatably disposed in a cavity defined by a housing surrounding the shaft.  
       [0006] One or more of these objects are achieved by a tool for driving an annular seal into a cavity defined by a shaft assembly housing that surrounds a rotatable shaft. The tool includes an elongated body having an interior cavity that opens at a first end of the body for receiving the shaft. The body defines an annular surface at the first end to abut the seal. The annular surface has an inner diameter greater than an outer diameter of the shaft and an outer diameter forming a removable frictional seal with an inner diameter of the interior cavity.  
       [0007] In another embodiment, a seal cover for a shaft that is rotatably disposed in a cavity defined by a housing surrounding the shaft includes an elongated body having an enclosed, generally cup-shaped, interior cavity that opens at an end of the body for receiving the shaft. The body defines an annular outer surface at the end to abut the housing. 
     
    
    
     [0008] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which:  
     [0010]FIG. 1 is an exploded perspective view of preferred embodiments of a shaft assembly for use with a tool or cover according to the present invention;  
     [0011]FIG. 2 is a partial cross-sectional view of a shaft assembly for use with a tool or cover according to a preferred embodiment of the present invention;  
     [0012]FIG. 3 is a partial cross-sectional view of the shaft assembly as in FIG. 2;  
     [0013]FIG. 4 is a partial cross-sectional view of the shaft assembly as in FIG. 2;  
     [0014]FIG. 5 is an exploded view of a shaft assembly for use with a tool or cover according to a preferred embodiment of the present invention;  
     [0015]FIG. 6 is a partial cross-sectional view of the shaft assembly as in FIG. 5;  
     [0016]FIG. 7 is a partial cross-sectional view of the shaft assembly as in FIG. 5;  
     [0017]FIG. 8 is a partial cross-sectional view of a shaft assembly for use with a tool or cover according to a preferred embodiment of the present invention;  
     [0018]FIG. 9 is a partial exploded view of a shaft assembly for use with a tool or cover according to a preferred embodiment of the present invention;  
     [0019]FIG. 10 is a partial perspective view of the shaft assembly as in FIG. 9;  
     [0020]FIG. 11 is a partial cross-sectional view of the shaft assembly as in FIG. 9;  
     [0021]FIG. 12 is a perspective view of a shaft assembly according to a preferred embodiment of the invention; and  
     [0022]FIG. 13 is a partial cross-sectional view of the shaft assembly as in FIG. 12.  
    
    
     [0023] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.  
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     [0024] Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.  
     [0025] Referring to FIG. 1, a speed reducer  10  includes a housing  12  and an output shaft  14  extending through a bore  16  in the housing. The output shaft is driven by an input shaft surrounded by a bell portion  17  of housing  12 . Although speed reducers are shown in the illustrated embodiments herein, it should be understood that this is for exemplary purposes only and that any suitable shaft assembly may be employed within the present invention.  
     [0026] An annular seal  18  extends between shaft  14  and the inner circumference of bore  16 . Referring also to FIG. 2, the lip seal construction of seal  18  should be well understood by those skilled in this art. Seal  18  includes a rigid outer portion  20  secured to the inner circumference of bore  16  by an interference fit and an elastomeric portion  22  extending from rigid portion  20  to shaft  14 . Rigid portion  20  may be formed from any suitable material, for example steel or hard polymer materials. Elastomeric portion  22  may be formed from any suitable elastomer material. Elastomeric portion  22  deflects axially inward, with respect to shaft  14 , toward an interior area  24  of speed reducer  10  as portion  22  extends from rigid portion  20  to engage shaft  14 . Thus, seal  18  is able to retain lubricant in area  24  while effectively preventing entrance of external contaminants.  
     [0027] Referring to FIGS. 1 and 3, an auxiliary seal comprised of a second annular seal member  26  and a third annular seal member  28  is placed over shaft  14 . A hollow tool  30  as described below is then placed over shaft  14  and hammered axially inward, as indicated by arrow  32 , to drive the second and third members into position as shown in FIG. 4. This drives seal  18  axially inward within bore  16  from its position shown in FIG. 2 to its position shown in FIG. 4.  
     [0028] An inner circumferential surface  36  of second member  26  establishes an interference fit with shaft  14 , and second member  26  therefore rotates with the shaft. An outer circumferential surface  38 , however, sufficiently clears an inner circumferential  40  of third member  28  to allow relative rotation between the second and third members. An outer circumferential surface  42  of third member  28  forms an interference fit with the internal circumference of bore  16 . An annular lip portion  44  of third member  28  abuts a radially extending edge  46  of bore  16 .  
     [0029] Accordingly, referring specifically to FIG. 4, third member  28  and annular seal  18  are rotationally fixed to housing  12 , while second member  26  is rotationally fixed to shaft  14 . Third member  28  includes a first annular portion  48  extending between housing  12  and second member  26  and a second annular portion  50  extending from the housing to the shaft, thereby forming a groove that receives second member  26 . Thus, the interfaces between second annular portion  50  and shaft  14 , between third member  28  and second member  26 , and between second member  26  and seal  18  form a labyrinth between the exterior area and the point at which elastomeric portion  22  engages the shaft. The labyrinth protects the flexible lip portion of seal  18  from dust and other debris and from direct contact with pressurized water used to clean the speed reducer.  
     [0030] Referring again to FIG. 1, third member  28  in a second embodiment includes a radially extending flange  52  so that the third member may be secured to housing  12  by bolts  54  that extend through holes  56  and threadedly engage tapped holes (not shown) in housing  12 . In this embodiment, therefore, outer circumferential surface  42  of first annular portion  48  need not form an interference fit with the inner circumference of bore  16 .  
     [0031] In a preferred embodiment, second member  26  and third member  28  are formed by a hard plastic material such as DELRIN.  
     [0032] It should be understood that the seal assembly formed by seal  18  and the auxiliary seal may be constructed in any suitable manner and that the embodiments illustrated in the Figures are provided for exemplary purpose only. Thus, for example, an elastomeric inner portion of seal  18 , when present, need not deflect axially inward. Further, while in each three-part seal assembly shown herein, the first and third annular members are rotationally fixed to the housing, and the second member is rotationally fixed to the shaft, it should be understood that these arrangements may be reversed.  
     [0033] Referring to FIGS. 1 and 2, annular seal  18  initially surrounds rotatable shaft  14  at the edge of bore  16 . Referring also to FIGS. 3 and 4, second member  26  and third member  28  are then placed over rotatable shaft  14  and seated against annular seal  18 . Tool  30  is placed over the shaft so that the shaft is received by an interior cavity  106  and so that an annular surface  100  defined at the tool&#39;s open end  102  abuts third member  28 . Upon applying axial force  32  to tool  30 , for example by hammer blows, annular surface  100  impacts third member  28 , thereby pushing second member  26  and third member  28  to their positions as shown in FIG. 4.  
     [0034] In another embodiment of the invention as illustrated in FIGS. 12 and 13, a tool  31  is used with a speed reducer having a double extended shaft to cover a shaft  14  not in use and the outlet of bore  16 . As discussed above regarding tool  30 , tool  31  may be used to drive seal  18  back into the bore, as shown in FIG. 13, when the seal is initially disposed at the bore&#39;s edge. The frusto-conically shaped tool  31  defines an interior diameter  104  larger than diameter  108  of shaft  14  so that the shaft turns freely within cavity  106 . Outer diameter  110  of end  102  measures slightly greater than the inner diameter of bore  16  so that the tool is held in place against housing  112  through a removable frictional seal between the inner circumferential surface of bore  16  and the outer circumferential surface of tool  31 . Thus, the tool may both receive the shaft and be contained by the bore.  
     [0035] The removable frictional seal seal holds the tool in place despite the effects of gravity and normal vibrations but may be loosened to remove the tool without damage thereto by applying a force  114  generally perpendicular to the axial direction of the rotatable shaft  14 . The tool&#39;s frusto-conical shape facilitates rotation of end  102  within bore  16  upon application of force  114  so that the upper edge of end  102  is released from the bore.  
     [0036] In one preferred embodiment, tool  31  is constructed from a suitable polymer such as DELRIN or polypropylene. It should be appreciated, however, that the tool&#39;s configuration, including the shapes of its exterior surface and its interior cavity, may vary. Additionally, the tool may be used to drive or cover seals of various configurations. Thus, it should be understood that the embodiment illustrated in FIGS. 12 and 13 is provided for exemplary purposes only.  
     [0037] In certain embodiments, a lip seal such as shown in FIGS.  2 - 4  is fixed to the housing bore and extends radially inward to engage the shaft. A second annular member is rotationally fixed to the shaft axially outward of the elastomeric portion and extends radially outward from the shaft to cover the elastomeric portion. That is, in comparison to the embodiment shown in FIG. 4, third member  28  is omitted, and second member  26  may be extended radially outward.  
     [0038] In another preferred embodiment of the present invention shown in FIG. 5, a speed reducer  10  includes a shaft  14  extending from a bore  16  of housing  12 . As the present invention may be installed as a retrofit, an originally installed seal  18   a  is removed as indicated by arrow  58  and is replaced by a seal assembly comprising a first seal member  18   b , a second seal member  26  and a third seal member  28 . Referring also to FIGS. 6 and 7, lip seal  18   b  and second member  26  are placed on shaft  14  and tapped into position by a first tool  30   a  as indicated by arrow  60 .  
     [0039] Lip seal  18   b  includes a rigid outer portion  20  and an elastomeric inner portion  22  that deflects axially inward as it extends from the rigid outer portion to engage the shaft. Lubricant may be maintained in an interior area  24  defined axially inward of seal  18   b.    
     [0040] Second member  26  includes a first annular portion  66  extending between housing  12  and outer portion  20  of lip seal  18   b . Annular portion  66  defines an outer circumferential surface  68  received by bore  16  in an interference fit to rotationally fix second member  26  to the housing. The outer portion of the lip seal is, in turn, received by annular portion  66  in an interference fit. Thus, the lip seal may be pressed into annular portion  66  prior to mounting onto shaft  14  so that the lip seal and second member may be installed together. A second annular portion  70  of second member  26  defines a first inner circumferential surface  72  and a second inner circumferential surface  74  axially and radially outward of surface  72 .  
     [0041] Tool  30   a  has a body  124  with a first end  101  in which is formed an interior cavity  106 . An approximately centered protrusion or central stem portion  62  extends axially from end  101 . Central stem portion diameter  122  is smaller than hollow rotatable shaft interior diameter  120  so that stem portion  62  may be slidably received by hollow rotatable shaft  14 . Once the stem portion is inserted into the shaft so that a cup-shaped outer portion  67  abuts second member  26 , as shown in phantom in FIG. 6, hammer blows received at end  101  push lip seal  18   b  and second member  26  into position about shaft  14 .  
     [0042] Cup-shaped outer portion  67  defines cavity  106 , which in turn defines an interior cavity diameter  104  that is greater than hollow rotating shaft exterior diameter  108 . Thus, if necessary, hollow shaft  14  may extend into interior cavity  106 . Cup-shaped portion  67  mates with flange  126  on second member  26  so that flange  126  is not deformed as second member  26  is pushed into position around shaft  14 .  
     [0043] In the particular speed reducer  10  shown in FIGS. 5 and 7, a machine shaft (not shown) is inserted into the bore of shaft  14  and is secured by set screws  76 . If third annular member  28  were to be placed on shaft  14  at the same time as seal  18   b  and second member  26 , it would cover the set screws and prevent their tightening onto the machine shaft. Accordingly, following the placement of seal  18   b  and second member  26  on shaft  14 , third member  28  is placed over the machine shaft, which is then inserted into the bore of shaft  14  and secured to shaft  14  by the set screws. An operator may then slide third member  28  up to second member  26  and drive it into position by a tool  30   b . Tool  30   b  includes a cut out portion  78  (FIG. 5) to receive the machine shaft and/or shaft  14  so that the tool may be placed against third member  28  as indicated by arrow  80 .  
     [0044] Third member  28  rotates with shaft  14 , while second member  26  and lip seal  18   b  are fixed to the housing. Third member  28  defines an inner circumference  81  that forms an interference fit with shaft  14  as member  28  is tapped onto the shaft by hammer blows to tool  30   b . It also includes a first annular portion  82  defining an outer circumferential surface  84  and a second annular portion  86  defining an outer circumferential surface  88 . Referring also to FIG. 8, as shown at the right hand side of gear reducer  10 , first annular portion  82  is received within inner circumferential surface  72  of second member  26 , and second annular portion  86  is received within surface  74 . Thus, the second and third members form interengaging grooves, and a labyrinth is formed between second member  26  and third member  28  and between third member  28  and seal  18   b  from the exterior to the point at which seal  18   b  engages shaft  14 .  
     [0045] Referring specifically to FIGS. 5 and 8, speed reducer  10  includes a central shaft  14  extending entirely though housing  12  so that the reducer may be positioned at a desired axial point on a machine shaft. That is, the speed reducer may be slidably moved on the machine shaft to properly position the speed reducer with respect to an input drive shaft (not shown). If, however, the machine shaft does not extend entirely through shaft  14 , an end cap  90  may be used to cover bore  16  and the open end of shaft  14 . Cap  90  has a cup-shaped body defining an annular flange portion  92  extending about an open end of the body and surrounding a central portion  94 . Flange  92  includes an inwardly curving edge that is received within a gap defined between housing  12  and an annular lip  96  of annular portion  86  of second member  26 .  
     [0046] Thus, cap  90  is axially fixed to the housing through the engagement of opposing lips formed by the cap and the seal assembly. The opposing lips on the cap and seal need not be continuous. For example, the cap lip may comprise fingers received in spaced apart recesses in the housing or seal. The cap is preferably made from a flexible polymer material so that it may be removed.  
     [0047] As shown at the left hand side of FIG. 8, the third annular member  28  is not installed since the machine shaft is not attached at this end. Thus, cap  90  protects annular lip portion  22 . Of course, provided there is no interfering machine shaft, cap  90  may be used to cover bore  16  even where third member  28  is present, as indicated in phantom at the right hand side of FIG. 8.  
     [0048] Referring now to FIGS. 9, 10 and  11 , a speed reducer  10  includes an output shaft  14  disposed in a housing  12 . Depending on the reducer&#39;s design, one or two ends may be connected to a machine shaft. Speed reducers, such as illustrated in these and other figures herein, should be well understood in this art and are therefore not discussed in detail. It should be understood, however, that any suitable means for attaching the machine shaft to the output shaft may be used. In the example shown in FIGS.  9 - 11 , the interior bore of shaft  14  is tapered, with the diameter expanding outward towards the shaft&#39;s end. An attachment collar  98  includes a central section  103  received in the shaft bore and having an outer circumferential surface  105  defining a taper that corresponds to the shaft taper. Collar  98  defines a radial cut  109  so that compression of the collar reduces the diameter of the collar&#39;s central bore  111 . Thus, when the center portion of collar  98  is pushed axially into the shaft bore, the diameter of bore  111  is reduced as the outer tapered surface  105  of collar  98  slides down against the inner tapered surface of shaft  14 , thus securing a machine shaft (not shown) to shaft  14 . Collar  98  is rotationally fixed to shaft  14  by friction or other means.  
     [0049] Collar  98  includes an annular flange  107  having holes through which three bolts  113  extend. Bolts  113  threadedly engage holes in a ring  115  axially retained on shaft  14  by a clip  117 . As bolts  113  are tightened into ring  115 , collar  98  is pulled axially inward into shaft  14 , thus tightening the collar onto the machine shaft.  
     [0050] An annular seal  119 , for example made of an elastomeric material, is rotationally fixed to housing  12  in bore  16  and retains lubricant within interior area  24  of gear reducer  10 . To provide auxiliary protection, an annular ring  121  is received about ring  115  and flange  107 . Ring  121  is attached to housing  12  by screws  123  received in threaded holes  125  tapped into housing  12 . Ring  121  may be made, for example, from a metal or a hard polymer material such as DELRIN. Although ring  121  is attached to the housing block axially and radially outward of bore  16 , it may also be considered an extension of the bore from the block so that flange  107  and ring  115  form annular members creating a labyrinth between the exterior area and seal  119 .  
     [0051] While one or more preferred embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. For example, the present invention may be embodied in a variety of shaft assemblies in which a rotatable shaft is disposed in a housing and within a bore in the housing extending between the exterior area and an interior area. Thus, the present invention is not limited to motors and speed reducers, and the embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. Thus, it should be understood by those of ordinary skill in this art that the present invention is not limited to these embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the literal or equivalent scope of the appended claims.