Abstract:
An arrangement and method for removing a shaft from a gearbox housing without having to totally disassemble the housing. The gear box has an aperture in the housing. The aperture is used to gain access to the retaining ring that locks the shaft within the housing. Once the retaining ring is removed, the shaft may then slide out of the housing. A plug member is used to cover the aperture when it is not necessary to remove the shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/544,648, filed Feb. 13, 2004. 

   FIELD OF THE INVENTION 
   The present invention relates to a gearbox arrangement for removing a shaft from a housing without having to disassemble the entire housing. 
   BACKGROUND OF THE INVENTION 
   There are two output shaft arrangements that are generally used in transfer case arrangements. They are one-piece and two-piece output shafts. Each have their own distinct advantages and disadvantages. The one-piece output shaft provides good radial runout performance and is economical to manufacture. However, the seal that extends between the shaft and the transfer case housing can only be serviced after the output shaft is completely disassembled from the transfer case. The second type of output shaft arrangement is the two-piece shaft. This type of arrangement allows for external seal servicing, but has poor radial runout performance and is more costly than a one-piece shaft. Thus it is more desirable to use a one-piece shaft because it is more cost efficient and it provides better run out performance. However external seal servicing is a significant drawback that will often limit how often one-piece shafts are used in transfer case applications. Therefore, it is an object of the present invention to provide gearbox arrangements that permit a one-piece shaft to be easily removed from a housing for seal service. Thus, significantly shortening the time consuming process of disassembling the output shaft form the transfer case in order to service the seal. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a gearbox arrangement having a serviceable seal. The gearbox arrangement has a housing with a shaft having a first end in the housing and a second end positioned outside of the housing. Inside of the housing there is a sprocket that is splined to the shaft. At the point where the shaft leaves the housing there is a seal that prevents exposure of the inside of the housing to the external environment. At times it is necessary for the seal to be serviced. In order for this to take place it will be necessary to remove the shaft from the housing. The present invention is directed to various gearbox arrangements for releasing the shaft from the housing without disassembling the entire housing. The invention includes a means for uncoupling the shaft from the gearbox to allow the shaft to slide axially outside of the housing. In particular, there are two means for doing this which include the compressible retaining ring arrangement and the plug and aperture arrangement. The two gearbox arrangements described herein are the compressible retaining ring gearbox arrangement and the plug and aperture gearbox arrangement. Both gearbox arrangements ease the burden of removing the shaft from the housing by eliminating the arduous task of disassembling the entire housing. 
   With respect to the compressible retaining ring arrangement, a portion of the shaft located inside the housing has a groove circumscribing the shaft. Inside of the groove a compressible retaining ring is placed that holds the shaft in place to prevent a shaft from sliding axially outside of the housing. To remove the shaft from the housing, a sufficient amount of axial force is applied to the shaft in order to compress the compressible retaining ring. A second groove inside of the sprocket has a ramped or tapered surface that aids in the compression of the retaining ring by allowing the retaining ring to slide along the ramped surface. Once the retaining ring compresses the shaft can slide axially out of the housing. 
   A second plug and aperture arrangement incorporates an aperture formed through the wall of the housing that is adjacent to the end of the shaft that terminates inside of the housing. Located near the end of the shaft inside of the housing is a retaining ring that prevents the shaft from sliding axially out of the housing. The retaining ring can be removed via the aperture, thus allowing the shaft to be removed from the housing. A removable plug member is configured to seal off the aperture. 
   Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a cross-sectional plan view of a gearbox housing having an output shaft inserted using the compressible retaining ring embodiment of the invention; 
       FIG. 2  depicts the same view as  FIG. 1 , wherein the output shaft is shown outside of the housing prior to installation; 
       FIG. 3  shows the same view as  FIGS. 1 and 2  showing the output shaft partially inserted inside of the gearbox housing at an intermediate stage of the installation; 
       FIG. 4  shows a cross-sectional plan view of a gearbox housing having an aperture formed in the wall of the gearbox housing to allow access to disengage the output shaft; and 
       FIG. 5  is an exploded cross-sectional plan view of the embodiment shown in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     FIG. 1  depicts a cross-sectional view of the compressible retaining ring embodiment of the invention incorporated in a gearbox  10 . The gearbox arrangement  10  has a housing  12  that contains a sprocket  14  having splines  16  that are connected with splines on a shaft  18 . The embodiments of the invention shown in  FIG. 1  depict the gearbox arrangement  10  as a transfer case having a shaft  18  that is a one-piece front output shaft of a transfer case. However, it is also possible for the shaft  18  to be an input shaft, an axle or a transmission output shaft depending on where the invention is being incorporated. The housing  12  can be a transfer case housing or any other portion of the vehicle drive train that incorporates the use of seals that close off the housing  12  to the outside environment. For example, the housing  12  could also be a differential or transmission housing. 
   The shaft  18  has a first end  20  that terminates inside of the housing  12 . The portion of the shaft  18  located inside of the housing  12  is suspended by ball bearings  26  that allow the shaft  18  to rotate about its radial axis. A second end  22  is located outside of the housing, forming what is referred to as the flanged section of the shaft  18 . The second end of the shaft  22  interfaces with a shaft coupling (constant velocity joint, universal joint, etc.). 
   A retaining ring  28  is disposed around the radial surface of the shaft  18  that is located inside of the housing  12 . The retaining ring  28  is arranged inside of a first groove  30  that is located on the radial surface of the shaft  18 . The retaining ring  28  serves the purpose of holding a portion of the shaft  18  within the housing  12 . In particular, the retaining ring  28  is located on the region of the shaft  18  that is aligned with the splines  16  of the sprocket  14 . As shown in further detail on  FIG. 2 , the retaining ring  28  will align with a second groove  32  that extends perpendicular across the spline  16  of the sprocket  14  and is parallel to the first groove  30 . 
     FIG. 2  shows the shaft  18  located outside of the housing  12 , while  FIG. 3  shows the shaft  18  inside the housing during installation. During installation of the shaft  18 , force is applied along the longitudinal axis of the shaft  18  in order to slide a portion of the shaft  18  into the housing  12 . During insertion of the shaft  18 , the retaining ring  28  will compress into the first groove  30  until the first end of the shaft  20  is inserted to the correct depth. The shaft  18  has been inserted into the correct depth when the retaining ring  28  is aligned with the second groove  32 , thus allowing the retaining ring  28  to expand into the second groove  32 . At this point, the shaft  18  will be locked into place within the housing  12 . 
   The seal  34  is configured to circumscribe the shaft  18 . During installation, the shaft  18  will be inserted through a seal  34  and garter spring  36  arrangement. The seal  34  functions to close off the housing  12  from the outside environment in order to prevent fluid within the housing  12  from leaking out, as well as to protect the inside of the housing  12  from the outside environment. During the lifetime of the vehicle it can be necessary to replace the seal  34  when it becomes cracked or deteriorates. In order to service the seal  34  it is often necessary to remove the shaft  18  from the housing  12 . In most vehicle applications the gearbox  10  will contain lubricating fluids such as oil. Thus it is desirable for the method of carrying out the invention to include the step of draining lubricating fluids from the housing  12  in a conventional manner. The next step entails applying a sufficient amount of force along the longitudinal axis of the shaft  18  in a direction that moves the first end of the shaft  20  outside of the housing  12 . The second groove  32  on the sprocket  14  has a ramped edge  38  that helps slide the retaining ring  28  out of the second groove  32  and compress the retaining ring  28  into the first groove  30 . Once the retaining ring is compressed  28  the shaft  18  can then be removed by simply pulling the shaft  18  out of the housing  12 . The amount of force required to remove the shaft  18  for seal  34  servicing is significantly greater than the forces encountered by the shaft during normal operation of the gearbox arrangement  10 . The seal  34  can then be serviced. The shaft  18  can then be reinstalled following the same steps that were described for the installation of the shaft  18 . 
   When the shaft  18  is removed from the housing  12  the sprocket  14  is prevented from moving axially with the shaft  18  during removal by the roller bearing  26 . When the shaft  18  is removed the sprocket  14  will rest against an annular shoulder  37  formed by the housing  12  in order to prevent the sprocket  14  from moving laterally. This ensures that when the shaft  18  is reinserted into the housing  12  the sprocket  14  will not be misaligned. 
   A second embodiment of the invention can be seen in  FIGS. 4 and 5 . This particular embodiment is directed to a gearbox arrangement  10  having a housing  102 . The housing  102  in this particular embodiment can be a transfer case housing or any other configuration on a vehicle that must be sealed from the outside environment. For example, the housing  102  could also be a transmission housing or front or rear differential. A shaft  104  has first end of the shaft  106  that terminates inside of the housing  102 . A second end  108  of the shaft  104  terminates outside of the housing  102  and forms a flanged section of the shaft  104 . The second end  108  of the shaft  104  interfaces with a shaft coupling (constant velocity joint, universal joint, etc.). In the present invention the shaft  104  is a one-piece front output shaft of a transfer case. However, the shaft  104  can consist of more than one piece. Additionally, the shaft  104  can also be a different kind of shaft such as a rear output shaft, an input shaft, an axle or a transmission output shaft depending on the particular gearbox arrangement  10 . In order to permit the shaft  104  to rotate freely within the housing  102 , the portion of the shaft  104  located inside of the housing  102  is suspended by ball bearings  105  that allow the shaft  104  to rotate about its radial axis. 
   Adjacent the first end  106  of the shaft  104  is a retaining ring  112  which is connected to the shaft  104  at a groove  114  on the shaft  104 . The retaining ring  112  functions to hold a portion of the shaft  104  within the housing  102  during vehicle operations by preventing the shaft  104  from sliding axially out of the housing  102 . Inside of the housing  102 , a sprocket  116  has splines  118  that interact with splines radially disposed about a portion of the shaft  104 . The housing  102  also has a seal  120  and garter spring  122  that functions to seal the housing  102  from the outside environment. The seal  120  circumscribes a portion of the shaft  104  where the shaft  104  extends outside of the housing  102 . 
   In order to remove the shaft  104  from the housing  102  in the event that the seal  120  needs to be serviced, the housing  102  has an aperture  124  located near the first end  106  of the shaft  104  and the retaining ring  112 . The aperture  124  can be used to drain lubricating fluids such as oil from the housing  102 . It is also possible to remove the lubricating fluids by other conventional methods known to those having ordinary skill in the art. The aperture  124  also functions to provide access for removal of the retaining ring  112  from the groove  114  on the shaft  104 . Once the retaining ring  112  has been removed, the shaft  104  can slide along its longitudinal axis out of the housing by pulling the shaft in a direction toward the second end  108 . A plug member  126  is disposed within the aperture in order to seal the housing  102  when it is not necessary to remove the shaft  104 . The plug  126  functions to contain fluids within the housing  102  while at the same time preventing contaminants from the outside environment from entering through the aperture  124 . When the shaft  104  is inserted into the housing  102  the retaining ring  112  can be placed in the groove  114  through the aperture  124 . Once the shaft  104  has been secured, the aperture  124  can be covered using the plug  126 . The plug  126  can also be press fit to the housing, or it can be attached with fasteners or adhesives.  FIGS. 4-5  depict a threaded plug  126  that is configured to be threaded onto threads on the sides of the aperture  124 . However, it is possible for any suitable plug configuration to be used that will seal the aperture  124  so it will not leak or allow contaminants into the housing  102 . 
   When the shaft  104  is removed from the housing  102  the sprocket  116  is prevented from moving axially with the shaft  114  during removed by the roller bearings  105 . When the shaft  104  is removed the sprocket  116  will rest against an annular shoulder  107  formed by the housing  102  in order to prevent the sprocket  116  from moving laterally. This ensures that when the shaft  104  is reinserted into the housing  102  the sprocket  116  will not be misaligned. 
   The compressible retaining ring arrangement and the plug and aperture arrangement both describe a means for uncoupling the shaft from the gearbox arrangement to allow the shaft to slide axially outside of the housing of the gearbox arrangement. 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the scope of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.