Patent Publication Number: US-6711791-B2

Title: Slide hammer tool and method of removing a keeper ring

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 09/356,559 filed Jan. 7, 1999, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to earth trenching equipment, and more particularly to apparatus for removing and installing trencher teeth. 
     2. Description of the Prior Art 
     Machines that cut trenches in the earth are subjected to severe operating conditions. That is especially true for the trencher teeth, which are carried in an endless track of chain links. 
     The trencher teeth are generally cylindrical in shape, having a head and a shank. The teeth are retained in respective collars in the chain links. The track is powered by the machine to move the teeth heads into direct sliding contact with soil, rocks, and water. That action imparts shock loads and abrasion to the teeth. For proper operation, it is important that the teeth rotate about their longitudinal axes as they are powered through the earth. 
     To increase the service lives of the teeth, their heads are usually hardened. In addition, it is well known to make the head working tips from a carbide material. Nevertheless, the teeth wear relatively rapidly, especially when used in rocky conditions. For economical operation of the trencher equipment, it is vital that a worn tooth be quickly replaced with a new tooth. 
     Prior trencher teeth were retained in the chain link collars by a band of thin resilient metal that fit loosely within a groove in the tooth shank. The band was cut through longitudinally, and the ends were spaced apart a short distance. Consequently, the band could collapse and expand radially. A number of small rounded bumps protruded from the band outer surface circumferentially around the band. The bumps of the uncollapsed band defined a circle having a diameter slightly larger than the diameter of the tooth shank. The prior trencher teeth were assembled to the chain link collars by inserting a tooth shank end into a close fitting hole in the collar until the band bumps contacted the collar. Then the tooth head was struck with a hammer or similar tool. The resulting impact on the tooth and the band bumps caused the band to radially collapse such that the bumps slid into the collar hole. The tooth was pushed into the collar until the band became aligned with a circumferential groove in the collar hole. At that point, the band resiliently returned to its original configuration, such that the bumps entered the collar groove. At that point, the tooth was firmly retained in the collar. 
     The prior tooth, band, and collar design was not entirely satisfactory. During operation, soil and small stones tended to become embedded in the tooth shank groove and in the collar groove. Consequently, the tooth seized in the collar and wore much faster than was tolerable. 
     A further disadvantage of the prior tooth design was that a worn tooth was difficult to remove. The design of the trenching machine chain links was such that the tooth could not be driven out from the shank end. The only way to remove the tooth was by using a forked puller tool. The fork was placed in a circumferential groove in the tooth head. A hard blow on the tool was required. That was because the pulling force had to be enough to collapse the band bumps from the collar groove. The tooth removal process was laborious and undesirably time consuming. 
     In an attempt to solve the problems associated with the band-type trencher teeth, a modified tooth with a longer shank was developed. The shank was long enough to extend completely through and emerge from the collar on the opposite side as the tooth head. A groove near the shank free end was exposed outside the collar. A heavy open keeper ring in the shank groove cooperated with the head to retain the tooth in the collar. 
     The new tooth design was an improvement. As one advantage, the tooth had a lesser tendency to seize in the collar. 
     However, installation and removal of the teeth remained difficult. The teeth shanks easily slid into the collar holes to expose the shank grooves, but the heavy and relatively rigid keeper rings were difficult to seat into and remove from the shank grooves. To seat a keeper ring, a mechanic was required to hold the keeper ring against the groove with one hand, usually using a pliers. He then struck the ring a hard blow, using a hammer, with his other hand. Ideally, the keeper ring would then instantaneously expand radially and slide fully into the groove. However, any misalignment of the keeper ring adjacent the tooth or inaccuracy of the hammer blow resulted in a failure to seat the keeper ring. In addition, the design of the trencher machine and track provided only limited space for the mechanic&#39;s hands to hold the keeper ring and to swing the hammer. 
     It was even more difficult to remove the keeper ring from a worn tooth. The only practical way to remove the keeper ring was by manually prying its two ends apart with a pair of screwdrivers or the like. The mechanic was required to manipulate the screwdrivers together as levers acting against the keeper ring open ends. The screwdrivers had to simultaneously spread the keeper ring and apart and pry the keeper ring out of the shank groove. That process, performed in a limited space, was frustrating and time consuming. It was not unusual for a person to waste 15 minutes manually prying off the keeper ring from a single tooth. 
     Thus, a need exists for improvements in the way teeth are installed into and removed from trenching machines. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a slide hammer tool is provided that greatly eases the task of seating an open keeper ring onto and removing it from a cylinder. This is accomplished by apparatus that includes a heavy hammer handle that slides along a rod having opposite ends configured to conform to the shape of radial end surfaces of the keeper ring. 
     There are first and second stops near the respective ends of the rod that limit the travel of the hammer along the rod. The rod first end has two flat surfaces that are immoveable relative to each other and that lie in respective planes that converge toward a longitudinal centerline. There is a generally U-shaped cutout in the converging surfaces that is symmetrical about the longitudinal centerline. The cutout includes an arcuate surface that preferably is continuous and uninterrupted. The radius of the cutout arcuate surface is slightly larger than the radius of the cylinder. If desired, the cutout and the converging surfaces can be formed in a separate piece that is rigidly held to the first end of the rod. 
     The second end of the rod is configured with a concave surface having the same diameter as the keeper ring outer diameter. The depth of the concave surface is slightly less than the radial thickness of the keeper ring. 
     To remove a keeper ring from a cylinder using the slide hammer tool of the invention, the tool first end is used. The rod converging surfaces are placed in abutting contact against corresponding radial end surfaces of the keeper ring. The hammer is slid rapidly against the tool first stop. The impact on the first stop is transmitted to the two keeper ring radial end surfaces simultaneously. The tool converging surfaces act as a rigid wedge to expand the keeper ring end surfaces. The impact is sufficient to push the keeper ring off the cylinder. 
     To use the slide hammer tool to seat a keeper ring on a cylinder, the open end of the keeper ring is placed against the cylinder. The concave surface of the tool second end is placed in abutting contact against the keeper ring outer diameter opposite the keeper ring open end. The hammer is slid rapidly along the rod to strike the second stop. The impact of the hammer on the second stop is transmitted to the keeper ring, forcing its end surfaces to expand and slide over the cylinder and then immediately close. The keeper ring is then seated on the cylinder. 
     The method and apparatus of the invention, using rod ends that conform to the shape of a keeper ring, thus greatly simplifies the task of seating the keeper ring onto and removing it from a cylinder. The keeper ring is under spatial control at all times during the seating and removing processes, even though it is subjected to high impacts from the hammer. 
     Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of typical chain links of a trenching machine that include teeth that are installed and removed using the present invention. 
     FIG. 2 is a cross-sectional view through a collar of a chain link and through a tooth in the collar. 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG.  2 . 
     FIG. 4 is a front view of the present invention. 
     FIG. 4A is an enlarged view taken along line A—A of FIG.  5 . 
     FIG. 5 is a top view of FIG.  4 . 
     FIG. 6 is a partial view showing the present invention in use to remove a tooth from a chain link collar. 
     FIG. 7 is a view generally similar to FIG. 6, but showing the keeper ring removed from the tooth by using the present invention. 
     FIG. 8 is a view showing the present invention in use to install a tooth in a chain link collar. 
     FIG. 9 is a partial view of a modified embodiment of the invention. 
     FIG. 10 is an end view of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto. 
     FIG. 1 illustrates a few chain links  1  of an endless track of chain links of a typical trenching machine. As illustrated, each chain link  1  has two collars  19 , and each collar removeably retains a tooth  3 . The design, construction, and use of the trenching machine, chain links  1 , and teeth  3  may be entirely conventional, and those components form no part of the present invention. Nevertheless, an understanding of the chain links and the teeth is necessary for an understanding of the invention. 
     Also looking at FIGS. 2 and 3, each tooth  3  is generally cylindrical in shape, having a longitudinal axis  5 . One end of the tooth has a carbide tip  7 . The carbide tip  7  is brazed or otherwise permanently joined to a head  9  of the tooth. There is a frusto-conical surface  11  between the head  9  and a shank  13 . A groove  15  is in the shank  13  near the tooth second end  17 . 
     Each chain link collar  19  has a first inner diameter  21  that is slightly larger than the diameter of the tooth head  9 . The collar also has a second inner diameter  23  that is slightly larger than the diameter of the tooth shank  13 . A frusto-conical surface  25  connects the collar inner diameters  21  and  23 . When the tooth frusto-conical surface  11  is against the collar frusto-conical surface  25 , the tooth groove  15  and the tooth second end  17  extend past the collar back end  27 . 
     To retain the tooth  3  in the collar  19 , a heavy C-shaped keeper ring  29  is employed. The keeper ring  29  has an inner diameter  31  that is normally slightly larger than the diameter of the groove  15 , and an outer diameter  33  that is larger than the diameter of the collar inner diameter  23 . The particular keeper ring shown has an opening defined by two radial end surfaces  35 . The end surfaces  35  subtend an angle of approximately 90 degrees. 
     In operation, the chain links  1  are driven as an endless track into the earth. The teeth tips  7  and heads  9  contact and cut the soil and rocks to dig a trench in the earth. The clearances between the teeth  3  and the associated collars  19  enable the teeth to rotate about their longitudinal axes  5 . That action prolongs tooth life. Eventually, however, the teeth tips  7  and heads  9  wear out, and the teeth must be replaced. 
     In accordance with the present invention, and looking at FIGS. 4,  4 A, and  5 , a slide hammer tool  37  greatly facilitates the removal of worn teeth  3  from and the installation of new teeth into the chain links  1 . The slide hammer tool  37  is constructed with a long steel rod  39  having a longitudinal axis  40 , a first end  41 , and a second end  43 . There is a first stop  45  proximate the rod first end  41  and a second stop  47  proximate the rod second end  43 . The stops  45  and  47  are secured rigidly to the rod  39  by pins  49  or other fasteners. 
     A hammer  51  is slidable on the rod  39  in the directions of arrows  53  and  55 . In the preferred embodiment, the hammer  51  has a cylindrical middle section  50  and large flanges  52  on both ends of the middle section. The travel of the hammer is limited by the stops  45  and  47 . 
     In the illustrated construction, the rod first end  41  has a slot  59 . One end of a steel wedge  61  is rigidly held in the slot  59  by one or more pins  63 . The wedge  61  and slot  59  may have respective widths that are slightly less than the width of the tooth groove  15  (FIG.  2 ). The second end of the wedge defines a pair of surfaces  65  that are immoveable relative to each other and that converge toward the rod longitudinal axis  40 . The converging surfaces  65  are at an included angle that is the compliment of the angle subtended by the keeper ring end surfaces  35  (FIG.  3 ). 
     There is a cutout  67  in the converging surfaces  65 . The cutout  67  is preferably symmetrical about the rod longitudinal axis  40 . The cutout  67  has opposed straight sides  69  that connect the converging surfaces with an arcuate surface  71 . Preferably, the straight sides  69  are parallel. The radius of the arcuate surface  71  is preferably slightly larger than the radius of the groove  15  of the tooth  3  (FIG.  2 ). However, if desired, the radius of the arcuate surface  71  may be made slightly larger than the radius of the tooth shank  13 . According to one aspect of the invention, the arcuate surface is continuous and uninterrupted. The center  73  of the cutout arcuate surface  71  is set back a distance X from a line through the intersections  75  of the cutout sides  69  with the converging surfaces  65 . The surfaces  65  are hardened. 
     There is a concave surface in the rod second end  43  in the particular construction shown, the concave surface is in the form of an arcuate groove  78 . The width of the arcuate groove  78  is slightly larger than the width of the keeper ring  29 , and the depth of the groove is slightly less than the radial thickness of the keeper ring. The groove has a bottom surface  80  with a radius that is the same as the radius of the keeper ring outer diameter  33  (FIG.  2 ). A pair of parallel surfaces  82  intersect the groove bottom surface  80  and the second end  43 . The rod second end is hardened and also magnetized. The rod  39  may be formed with opposed flats  57  adjacent the second end. The distance T between the flats  57  is larger than the width of the groove  78 . 
     To use the slide hammer tool  37  to remove a worn tooth  3  from a chain link  1 , a person places the converging surfaces  65  of the wedge  61  into abutting contact with the end surfaces  35  of the keeper ring  29 . See FIG.  6 . At the same time, the wedge cutout  67  passes a short distance over the tooth groove  15 . See FIG.  6 . The person grasps the middle section  50  of the hammer  51 . He slides the hammer rapidly in the direction  53  until the hammer strikes the stop  45 . The impact of the hammer on the stop  45  is transmitted through the rod  39  and converging surfaces  65  simultaneously to the keeper ring surfaces  35 . The tooth groove  15  acts as a reaction member on the junctions  77  between the keeper ring inner diameter  31  and the end surfaces  35 . The impact force of the immoveable converging surfaces  65  on the keeper ring surfaces  35  cooperates with the reaction force of the tooth groove on the keeper ring junctions  77  to expand the keeper ring junctions apart. The expansion of the keeper ring is sufficient to slide the junctions  77  over the groove diameter and push the keeper ring off the tooth in the direction  53 . See FIG.  7 . The wedge arcuate surface  71  contacts the tooth groove to limit any overtravel of the slide hammer tool in the direction  53  due to the impact of the hammer on the stop  45  after the keeper ring has been pushed off the tooth groove. The keeper ring removal process takes only a few seconds time. The large flanges  52  on the hammer protect the person&#39;s fingers during the removal process. In addition, the slide hammer tool occupies a minimum amount of space, so it is easily used adjacent the chain links  1  of a trenching machine. 
     After the keeper ring  29  is of f the worn tooth  3 , the tooth is pulled from the chain link collar  19 . A new tooth is inserted into the collar. The junctions  77  of the keeper ring are placed against the tooth groove  15 , FIG.  8 . The concave surface  78  of the tool second end is pressed in abutting contact against the keeper ring outer diameter  33 . The person slides the hammer  51  rapidly in the direction  55  against the stop  47 . The impact of the hammer on the stop  47  is transmitted through the rod bottom surface  80  to the keeper ring. The tooth groove acts as a reaction member against the keeper ring junctions. The impact force on the keeper ring outer diameter cooperates with the reaction force of the tooth groove to cause the keeper ring junctions  77  to expand an amount sufficient for the keeper ring to slide over the tooth groove. Then the keeper ring immediately collapses to its original shape, and it is seated on the tooth, FIGS. 2 and 3. 
     FIGS. 9 and 10 show a modified first end  79  of the rod  39 ′. The first end  79  is formed with an enlarged cylindrical portion  81  that is integral with the rod  39 ′. As shown, flats  83  are on the cylindrical portion  81 . There are converging surfaces  65 ′ that are immoveable to each other, a cutout  67 ′ with opposed sides  69 ′, and an arcuate surface  71 ′ in the cylindrical portion  81  between the flats  83 . The geometries and dimensions of the converging surfaces  65 ′, cutout  67 ′, sides  69 ′, and arcuate surface  71 ′ are the same as for the corresponding components of the wedge  61  described previously in connection with FIGS. 4 and 5. Similarly, the operation and functions of the modified embodiment of FIGS. 9 and 10 are identical to those of the wedge  61 . 
     In summary, the results and advantages of earth trenching machines can now be more fully realized. The slide hammer tool  37  provides both rapid and safe removal of worn teeth  3  as well as equal ease in installing new teeth. This desirable result comes from using the combined functions of the hammer  51  and the stops  45  and  47 . When a worn tooth is to be removed, the converging surfaces  65  are placed against the keeper ring end surfaces  35 . The impact of the hammer on the stop  45  causes the wedge to expand the keeper ring  29  and push it off the tooth groove  15 . Installing a new tooth requires merely that the rod end  43  be abutted against the keeper ring outer diameter  33 . The impact of the hammer on the stop  47  causes the keeper ring to become seated in the tooth groove. 
     It will also be appreciated that in addition to the superior performance of the slide hammer tool, its construction is such as to be of modest cost in relation to the benefits it provides. In fact, the tool pays for itself very quickly by greatly reducing the time required to replace the trencher teeth compared with using prior tools and methods. Moreover, the rugged and simple design of the tool assures that it will give a long service life with minimal maintenance. 
     Thus, it is apparent that there has been provided, in accordance with the invention, a slide hammer tool that fully satisfies the aims and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.