Abstract:
A specialized tool for replacing brake camshaft bushings in suspension chassis is disclosed. The tool is modular in construction and comprises a universal handle, a detent limiting depth of tool insertion into a chassis bore, a push ring for engaging an end of the camshaft bushing, and a bushing carrier respectively connected in sequence by a threaded fastener extending through axially aligned through-holes in the bushing carrier, push ring, and detent for mating with a tapped hole in the handle. A plurality of interchangeable push rings of different sizes and a plurality of interchangeable bushing carriers of different sizes enable the tool to accommodate camshaft bushings of different sizes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to specialized tools for performing vehicle maintenance, and more particularly to an improved modular tool for replacing a brake camshaft bushing seated within a bore in a suspension chassis of a truck or other vehicle. 
     2. Description of the Related Art 
     Attention is directed initially to FIG. 1 for an explanation of the relevant prior art. Heretofore, the task of inserting a camshaft bushing  6  housed within a bore  4  in a suspension chassis  2  has commonly been performed using a tool  10 . Tool  10  is formed from a solid length of round steel bar stock and includes a handle portion  12 , a proximal end  14 , and a radial step  16  for transition to a radially reduced portion  18 . The diameter of radially reduced portion  18  is sized for axially slidable fit within camshaft bushing  6 , while the diameter of handle portion  12  is undersized relative to the diameter of chassis bore  4 . In a typical replacement procedure according to the prior art, a mechanic pries the existing grease seals  8 A,  8 B out of chassis bore  4  using a screwdriver or similar tool, inserts reduced portion  18  of tool  10  into camshaft bushing  6  until an end of the camshaft bushing is engaged by radial step  16 , and then drives the tool  10  by striking proximal end  14  with a hammer to push camshaft bushing  6  out the opposite end of the chassis bore. It is also possible for the mechanic to push the backside grease seal  8 B out along with camshaft bushing  6  using tool  10 . Insertion of a new camshaft bushing  6  into chassis bore  4  is performed by sliding the camshaft bushing onto radially reduced portion  18  of tool  10 , driving tool  10  with camshaft bushing  6  axially into the bore by striking proximal end  14  with a hammer until the camshaft bushing is at a suitable depth allowing space in the bore for greases seals  8 A,  8 B, and then hammering the grease seals in place in the bore. 
     Certain drawbacks of this prior art methodology can be attributed to tool  10 . First, it is necessary for a service station to absorb the expense of owning six or more tools  10  of different sizes to accommodate the common camshaft bushing sizes known in the industry. Second, tool  10  does not limit or control the depth to which camshaft bushing  6  is inserted into the bore, leaving this to the skill of the mechanic. Third, tool  10  does not install grease seals  8 A,  8 B, and the mechanic must perform the additional operation of hammering the grease seals into the bore. This operation can prove frustrating and imprecise, since the greases seals tend to flip or rotate back and forth in the bore with each off-center hammer blow. Fourth, the design of tool  10  is inherently massive since handle portion  12  is radially larger than reduced portion  18 , thereby offering significant resistance to the transfer of driving force from a hammer to the camshaft bushing  6 . Fifth, the unitary construction of tool  10  necessitates replacement of the entire tool even if only a portion of the tool is damaged. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide an improved tool for replacing a brake camshaft bushing in a suspension chassis that is capable of performing both removal and installation functions with respect to the camshaft bushing and associated grease seals. 
     It is another object of the present invention to provide an improved tool for replacing brake camshaft bushings of different sizes, thereby eliminating the need to purchase a set of differently sized tools. 
     It is another object of the present invention to provide an improved tool for replacing brake camshaft bushings that is less massive than tools of the prior art for better transfer of driving forces. 
     It is another object of the present invention to provide an improved tool for replacing brake camshaft bushings that includes removable parts that are less expensive to replace than an entire tool of the prior art in cases of wear or damage. 
     It is a further object of the present invention to provide an improved tool for replacing brake camshaft bushings that is modular in design for realizing the objects stated above. 
     In view of these and other objects, a modular tool formed in accordance with a preferred embodiment of the present invention includes a handle, a detent, a push ring, and a bushing carrier respectively connected in sequence by a threaded fastener extending through axially aligned through-holes in the bushing carrier, push ring, and detent for mating with a tapped hole in the handle. The detent is preferably a washer that is oversized relative to the chassis bore to limit insertion of the tool. The push ring is preferably a smaller washer having an outside diameter that allows the push ring to engage an annular end of the camshaft bushing without extending beyond the outside diameter of the camshaft bushing. The bushing carrier is a cylindrical component sized for slidably receiving the camshaft bushing thereon. Accordingly, a plurality of push rings and bushing carriers of different sizes can be provided along with the handle and the detent to accommodate different standard bushing sizes. 
     The tool is configured without the detent for driving an existing camshaft bushing and grease seals out of the chassis bore by striking an end of the handle with a hammer. The tool is configured with the detent for installing a new camshaft bushing and grease seals mounted on the bushing carrier, whereby the push ring sets the camshaft bushing and a distal grease seal at a proper depth in the bore and the detent applies evenly distributed pressure to a proximal grease seal to be flush with an end of the bore when the handle is struck with a hammer. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the preferred embodiments taken with the accompanying drawing figures, in which: 
     FIG. 1 is a perspective view showing a prior art tool for replacing a camshaft bushing and the environment in which the prior art tool is used; 
     FIG. 2 is an exploded side view of a tool formed in accordance with a preferred embodiment of the present invention for replacing a camshaft bushing; 
     FIG. 3A is a perspective view of the tool shown in FIG. 2 configured for removing an existing camshaft bushing and grease seals from within a chassis bore; 
     FIG. 3B is a perspective view similar to that of FIG. 3A, however also showing the camshaft bushing and grease seals; 
     FIG. 4A is a perspective view of the tool shown in FIG. 2 configured for installing a new camshaft bushing and grease seals within a chassis bore; and 
     FIG. 4B is a perspective view similar to that of FIG. 4A, however also showing the camshaft bushing and grease seals. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Attention is now directed to FIGS. 2 and 3 of the drawings, wherein a tool formed in accordance with a preferred embodiment of the present invention is shown and designated generally by the reference numeral  20 . Tool  20  comprises a handle  30 , a detent  40  located at a distal end  31  of the handle, a push ring  50  adjacent detent  40 , and a cylindrical bushing carrier  60  adjacent push ring  50 . 
     As can be seen in the exploded view of FIG. 2, tool  20  is preferably modular in construction, such that handle  30 , detent  40 , push ring  50 , and bushing carrier  60  are separable constituent parts of tool  20 . More specifically, handle  30  is provided with an axially extending tapped hole  32  opening through distal end  31 , and the remaining parts—namely detent  40 , push ring  50 , and bushing carrier  60 —include respective axial through-holes  42 ,  52 , and  62  through which a socket head cap screw  70  or other suitable fastener extends to mate with tapped hole  32 , thereby removably connecting constituent parts  40 ,  50  and  60  to handle  30 . While this completely modular construction is preferred for reasons given below, it is understood that tool  20  can be made as a unitary construction, for example by turning the outer diameter of a cylindrical length of stock material on a lathe to form handle  30 , detent  40 , push ring  50 , and bushing carrier  60 . Alternatively, varying degrees of modularity are possible. As a first example, tool  20  could be made such that only bushing carrier  60  is removably connected to handle  30 , while detent  40  and push ring  50  are permanently connected or integrally formed with handle  30 . As a second example, tool  20  could be made such that both bushing carrier  60  and push ring  50  are removably connected to handle  30 , while detent  40  is permanently connected or integrally formed with handle  30 . However, it is noted that if detent  40  is permanently fixed to handle  30 , the usefulness of tool  20  is limited to insertion of a new camshaft bushing and grease seals and does not include the capability of removing an existing camshaft bushing and grease seals from within chassis bore  4 . 
     Each of the constituent parts of tool  20  will now be described in detail, beginning with handle  30 . Handle  30  preferably comprises a cylindrical metal bar having a chamfered proximal end  33  opposite distal end  31 . The length and diameter of handle  30  are sized for gripping by a user, and an outer surface portion  34  of the handle is preferably knurled to reduce slippage. In a currently favored design, handle  30  is 5.5″ in length and 1.25″ in diameter. As mentioned, handle  30  includes tapped hole  32  that extends along a central axis of the handle, beginning at distal end  31  and continuing to a depth suitable for tight connection of constituent parts  40 ,  50 , and  60  by fastener  70 . In the currently preferred design, tapped hole  32  is a ½-13 threaded hole that reaches a depth of 1.25″ from distal end  31 . 
     Detent  40  of the preferred embodiment is in the form of a round washer having central through-hole  42 . Detent  40  functions to limit the depth of insertion of tool  20  within chassis bore  4  and to force an adjacent grease seal into the bore, and thus it is of critical importance that the outside diameter of detent  40  be oversized relative to the inner diameter of the chassis bore. Since chassis bores typically range from 1.4375″ to 2.0″ inches in diameter, a preferred outside diameter for detent  40  is 2.125″ inches. The inside diameter of detent  40  corresponding to through-hole  42  is 0.5″ to match the diameter of tapped hole  32 . A suitable axial length (thickness) of detent  40  is 0.375″. 
     Push ring  50  is also in the form of a round washer, and includes central through-hole  52 . As will be explained further below, push ring functions to push an existing camshaft bushing and grease seals from within chassis bore  4  and push a new camshaft bushing and second grease seal into the chassis bore. Therefore, the outside diameter Y of push ring  50  should be no greater than the diameter of the chassis bore and outside diameter of the camshaft bushing, and preferably just slightly less than the bore diameter to allow some clearance for insertion. However, the outside diameter of the push ring must be greater than the inside diameter of the camshaft bushing so that it can push the camshaft bushing in end-to-end abutment. Best performance in pushing is achieved where the push ring outside diameter Y is nominally equal to the outside diameter of the bushing being pushed. With these criteria, it is possible to have a plurality of push rings  50  having different outside diameters Y suitable for typical camshaft bushings and bore diameters. The table below provides outside diameter specifications of push rings matched for use with six common sizes of camshaft bushings used in trucks, trailers, and tractors: 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 PUSH RING OD 
               
               
                   
                 BUSHING SIZE 
                 “Y” 
               
               
                   
                   
               
             
             
               
                   
                 1.25″ ID, 1.625″ OD 
                 1.625″ 
               
               
                   
                 1.25″ ID, 1.875″ OD 
                 1.875″ 
               
               
                   
                 1.50″ ID, 1.625″ OD 
                 1.625″ 
               
               
                   
                 1.50″ ID, 1.6875″ OD 
                 1.625″ 
               
               
                   
                 1.50″ ID, 1.875″ OD 
                 1.875″ 
               
               
                   
                 1.625″ ID, 2.00″ OD 
                 2.00″  
               
               
                   
                   
               
             
          
         
       
     
     Consequently, a set of three push rings having respective outside diameters Y of 1.625″, 1.875″, and 2.00″ is preferably provided for improving the versatility of tool  20 . Similar to detent  40 , the inside diameter of push ring  50  defined by through-hole  52  is 0.5″ to match the diameter of tapped hole  32 . The axial length (thickness) of push ring  50  controls the depth of insertion of camshaft bushing  6  into bore  4 , and is preferably 0.270″. 
     The last part connected to handle  30  is bushing carrier  60 , which is in the form of a cylinder having an outside diameter X that corresponds to an inside diameter of an associated camshaft bushing for slidably receiving the bushing thereon. Accordingly, several bushing carriers each having a different X dimension can be provided for selective incorporation as part of tool  20  depending upon the inside diameter of the particular camshaft bushing to be installed or replaced. Accordingly, with reference to the table presented above, a set of three bushing carriers having respective outside diameters X of 1.25″, 1.50″, and 1.625″ is preferably supplied for versatility of tool  20 . The other dimensions of bushing carrier  60 , namely the length and inner dimensions of through-hole  62 , can be held constant. In particular, a suitable length for bushing carrier  60  is 2.50″, which is sufficient to extend beyond the longest camshaft bushings in common use. Through-hole  62  is preferably a stepped hole for permitting access to the head of fastener  70 . In the preferred embodiment shown in FIG. 2, the diameter of through-hole  62  matches the diameter of tapped hole near proximal end  61  of bushing carrier  60  positioned adjacent push ring  50 . The inside diameter of through hole  62  increases at a radial step  65  to a preferred diameter of 1.00″, which provides a clamping surface for the head of fastener  70  and can be the same regardless of the outside diameter X of the bushing carrier. The axial position of step  65  is chosen close to proximal end  61 , for example 0.5″ therefrom, to avoid use of an unnecessarily long fastener. 
     The parts  30 ,  40 ,  50 , and  60  described above are preferably formed of 4140 alloy steel heated treated to 38-40 Rockwell C hardness for tool durability, although other materials and or treatments can be used without straying from the present invention. 
     Handle  30  and bushing carrier  60  are typically machined from round bar stock, detent  40  and push ring  50  can be machined or purchased as “off the shelf” items, and fastener  70  is an off the shelf item, preferably a ½-13 by 1.5″ long socket head cap screw. 
     The manner of assembling and using tool  20  will now be described. Tool  20  is first assembled without detent  40  for use in removing an existing camshaft bushing and grease seals. The first step in such assembly is to choose a suitably sized push ring  50  and a suitably sized bushing carrier  60  depending upon the dimensions of the camshaft bushing involved in accordance with the criteria discussed above. The next step is to arrange handle  30 , push ring  50 , and bushing carrier  60  in sequence and coaxially align the through-holes  52 , and  62  with tapped hole  32  in handle  30 . Finally, fastener  70  is inserted successively within through-holes  62  and  52 , and then tightened in threaded mating with tapped hole  32  to form the tool as shown in FIG.  3 A. 
     Tool  20 , as assembled according to FIG. 3A, is used to remove an existing camshaft bushing  6  and grease seals  8 A,  8 B from within chassis bore  4  in the following manner. The user holds handle  30 , aligns bushing carrier  60  coaxially with the camshaft bushing and grease seals, and drives the tool  20  by striking a hammer upon proximal end  33  of handle  30 . This serves to mount the camshaft bushing  6  and grease seals  8 A,  8 B on bushing carrier  60 , as shown in FIG.  3 B and push these parts out an opposite end of bore  4 . Since detent  40  was omitted from tool  20  during assembly, insertion of tool  20  within bore  4  is not limited and the tool is sized to drive out the camshaft bushing and grease seals from the bore. 
     Tool  20  can also be assembled to perform installation of a new camshaft bushing and grease seals within an empty chassis bore. Assembly is essentially the same as described above in connection with FIG. 3A, except that detent  40  is positioned between handle  30  and push ring  50 . Accordingly, tool  20  appears as shown in FIG.  4 A. 
     Tool  20 , assembled as shown in FIG. 4A, is used to install a camshaft bushing  6  and grease seals  8 A,  8 B within chassis bore  4  in the following manner. The user successively slides first grease seal  8 A, new camshaft bushing  6 , and second grease seal  8 B onto bushing carrier  60  such that first grease seal  8 A is in abutment with detent  40  and camshaft bushing  6  is in abutment with push ring  50 . The user holds handle  30 , aligns bushing carrier  60  coaxially with chassis bore  4 , and drives the tool  20  by striking a hammer upon proximal end  33  of handle  30  until detent  40  engages the chassis casting to prevent further insertion. Detent  40  not only prevents further assertion of tool  20  within the bore, but also applies even pressure about the entire circumference of grease seal  8 A. Push ring  50  forces camshaft bushing  6  and grease seal  8 B to a predetermined depth dictated by the thickness push ring  50 . Consequently, grease seals  8 A,  8 B and camshaft  10  bushing  6  are evenly seated within the chassis bore. The user then pulls tool  20  out, leaving the camshaft bushing and grease seals in place within chassis bore  4 . 
     Several advantages of the present invention over the prior art are readily apparent. The insertion operation is faster and more precise because the grease seals do not have to be separately hammered into place. The modular design of the preferred embodiment allows a common handle  30 , which is the heaviest part of tool  20 , to be used for variety of differently sized camshaft bushings. Thus, the requirement of six separate tools of different sizes is overcome by the modular design, and replacement parts can be obtained in case of damage or defect rather than replacing the entire tool. Because handle  30  does not include a radial step serving as a push ring as in the prior art, handle  30  can be reduced in diameter relative to the prior art construction to decrease the overall mass of tool  20  and improve transfer of drive force to the grease seals and camshaft bushing.