Patent Publication Number: US-2007107274-A1

Title: Ground engaging tool retention system

Description:
TECHNICAL FIELD  
      The field of this invention is ground engaging tools, and more specifically systems for retaining ground engaging tools on buckets, blades, and other work tools.  
     BACKGROUND  
      Many construction and mining machines, such as excavators, wheel loaders, hydraulic mining shovels, and draglines employ buckets to dig material out of the earth. The abrasion and impacts experienced during digging subject the buckets to extreme wear. In addition to buckets, other construction and mining machines, such as bulldozers, motor graders, and scrapers, employ blades or other types of earth-working tools to move soil and rock. Like buckets, these blades and other types of earth-working tools also experience extreme wear through abrasion and other mechanisms.  
      Buckets, blades, and other earth-working tools can be protected against this wear by including ground engaging tools (GET). GET is typically fashioned as teeth, edge protectors, sidebar protectors, wear plates, etc. which are attached to the bucket or blade in the area where the most damaging abrasion and impacts occur. The GET includes sacrificial wear material that will gradually wear away as it scrapes against the soil and rocks. For example, the cutting edge of a bucket can be protected with edge protectors, one type of GET, that wrap around and protect the edge.  
      The GET can be removed when it has been worn and replaced at a reasonable cost with new GET to continue to protect the bucket, blade, or other earth-working tool. Large buckets for draglines and hydraulic shovels can cost a considerable amount, so protecting them against wear is important. It is more economical to wear out and replace the GET than to wear out and replace an entire bucket.  
      Besides protection against wear, another purpose of GET may be to provide more effective digging. A tooth mounted on the edge of a bucket, for example, may allow the bucket to penetrate into the soil or rock and dig more effectively with less effort. A tip mounted on the wheel of a trash compactor machine will grind and compress garbage so it occupies less space in a landfill.  
      Owners and operators of these construction and mining machines, and the technicians who maintain and repair them, expect that the GET will remain attached to the machine during use, but that it will also be easily and quickly removable when it is worn and needs replacement. A retention system performs the job of reliably holding the GET on the machine during use, then permitting easy and quick detachment during service.  
      Many retention systems have been proposed and used for removably attaching GET to buckets, blades, and other earth-working tools. One common type of retention system produced by several manufacturers includes a shear pin which holds the GET onto an adapter or base. One example of this type of shear pin system is shown in U.S. Pat. No. 5,009,017 issued Apr. 23, 1991.  
      Problems can exist with these known systems. For example, installing the shear pin may require a hammer to drive the pin into the bore formed in the GET and the adapter. On large GET systems, the hammer required to drive in the pin may likewise be very large, and swinging such a large hammer in difficult field conditions can be objectionable to the technician. Sometimes the spacing of teeth on the edge of a bucket does not provide a comfortable amount of space between the teeth to swing the hammer and drive the shear pins.  
      As an example of another problem or shortcoming with these known retention systems, the shear pin may “walk” out of the bore and unintentionally release the GET from the adapter. The retention system must be very secure and not permit the GET to fall off of the bucket, blade or other earth-working tool, even when the GET is worn extensively. If the GET falls off, it could be fed into a crusher or other processing machine and cause damage. Missing GET can result in extensive wear and damage of the bucket, blade, or other earth-working tool if the missing GET is not immediately detected and replaced. Other problems may also occur if the GET unintentionally falls off the bucket. The known retention systems have not always held the GET to the bucket or other work tool with adequate reliability.  
      In general, the proposed and known retention systems leave room for improvement. This invention provides several improvements.  
     SUMMARY OF THE INVENTION  
      According to one embodiment of the invention, a retainer assembly may include a pin elongated in the direction of a longitudinal axis, the pin being generally cylindrical in shape with an outer, cylindrical surface, a first axial end, and a second axial end opposite the first axial end, the first axial end having a threaded bore formed therein, and the second axial end having means for connecting to a tool to apply torque to the pin. The retainer assembly may also include a generally annular-shaped washer having a central bore, an axial first end, and an axial second end opposite the axial first end, a bolt having a threaded shank and a head, and the head having means for connecting to a tool to apply torque to the bolt. The diameter of the washer may be greater that the diameter of the cylindrical surface of the pin and the diameter of the head of the bolt. The threaded shank of the bolt may pass through the central bore of the washer, and thread into the threaded bore of the pin.  
      According to another embodiment of the invention, a method of attaching a ground engaging tool to a work machine, the adapter being attached to a work machine, the method may comprise positioning a washer in a pocket formed on one of the tip or the adapter, sliding the tip over a portion of the adapter in a sliding direction so that the washer is trapped and not removable from between the tip and the adapter in the pocket, sliding the tip further in the sliding direction over the portion of the adapter until a first bore formed in the tip aligns with a second bore formed in the adapter, inserting a pin into the first and second bore such that the pin prevents the tip from being slid in a direction opposite the sliding direction off of the adapter, and attaching a bolt with a shank to the pin, the shank passing through a central bore in the washer, and the shank being threaded and engaging a threaded bore in the pin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an isometric view of a retainer assembly.  
       FIG. 2  is an isometric exploded view of the retainer assembly of  FIG. 1 .  
       FIG. 3  is a side plan view of the retainer assembly of  FIG. 1 .  
       FIG. 4  is a front view of the retainer assembly of  FIG. 1 .  
       FIG. 5  is a back view of the retainer assembly of  FIG. 1 .  
       FIG. 6  is a sectional view of the retainer assembly of  FIG. 1  being installed with a GET tip and adapter system.  
       FIG. 7  shows the retainer assembly and tip and adapter system of  FIG. 6  in a fully installed state, the retainer assembly acting to retain the tip on the adapter.  
       FIG. 8  shows an alternate embodiment of a retainer assembly installed on a GET tip and adapter system. 
    
    
     DETAILED DESCRIPTION  
      A principal exemplary embodiment which illustrates the principles of the invention will be described below. The exemplary embodiment is shown in  FIGS. 1-7 . By showing a single principal embodiment, however, it is not intended that the scope of patent protection be limited to this embodiment only. Those of skill in the art will be able to adapt the inventive principles taught herein to construct other embodiments of an inventive retainer system, and it is intended that these other embodiments also be included in the scope of patent protection, as defined by the appended claims.  
      With reference first to  FIGS. 1 and 2 , the exemplary retainer assembly  10  includes three components: a pin  20 , a washer  30 , and a mechanical fastener such as bolt  40 .  FIG. 1  illustrates the pin  20 , washer  30 , and bolt  40  in an assembled state, while  FIG. 2  illustrates them in an exploded view.  
      The pin  20  is elongated in a longitudinal direction running from a first end  21  to a second end  22 . The pin may be generally cylindrical in shape with an outer, cylindrical surface  23 , with the first end  21  and opposite second end  22  forming the opposite, axial ends of the cylinder. The first end  21  may include a threaded bore  24 . A chamfer  26  can be provided between the threaded bore  24  and the first end  21 . The second end  22  may include a socket  25  for allowing a tool to rotate the pin  20  (see  FIG. 5  for the socket  25  which will be further described below).  
      Washer  30  is generally annular in shape, with a central bore  31 , an axial first end  32  and an axial second end  33  opposite the first end. Central bore  31  may include a tapered portion  34  where the inside diameter of the bore increases along the axis thereof approaching the second end  33 . The radial exterior surface  37  of washer  30  may also include rounds or chamfers  35  and  36  between the radial exterior surface  37  and the first and second ends  32  and  33  (see  FIG. 3 ).  
      Bolt  40  includes a shank  41  which is threaded to match threaded bore  24  of pin  20 . A head  42  attaches to the shank  41 . Head  42  may include a socket  43  for receiving a driving tool, such as an impact wrench or torque wrench. The underside of the head  42  may include a tapered portion  44  (see  FIG. 6 ) extending between the head  42  and the shank  41 , whose taper angle generally corresponds to the taper angle of tapered portion  34 .  
      When the retainer assembly  10  is assembled, the shank  41  of bolt  40  passes through the central bore  31  of washer  30 . The shank  41  further threads into the threaded bore  24  of pin  20 . Tapered portions  34  and  44 , if included, will abut one another, and first end  32  of washer  30  will abut first end  21  of pin  20 . As the torque on bolt  40  relative to pin  20  is increased, the tapered portions  34  and  44  will direct the compressive stress between bolt  40  and pin  20  into hoop stress in the washer  30 . The resulting strain will help lock together the three components, the bolt  40 , washer  30 , and pin  20 , so that vibrations will not cause them to unintentionally disengage.  
       FIG. 3  shows the assembled retainer assembly  10  in a side view.  FIGS. 4 and 5  illustrate front and back views of the assembled retainer assembly  10 . In  FIGS. 4 and 5 , the sockets  43  and  24  are visible. These sockets may take any desirable form to match a tool to be used in the assembly process. One way to torque the retainer assembly  10  together would be to use a socket wrench in socket  24  to provide back torque to the pin  20 , while using an impact wrench in socket  43  to apply torque to the bolt  40  relative to the pin  20 . However, other arrangements are possible and can be adopted depending upon the type of tool that is desired for the assembly. For example, protrusions may be provided instead of sockets so that an open-end or closed-end wrench may apply torque to the pin  20  and bolt  40 . Also, the pin  20  may be shaped such that it will not turn when assembled inside of a GET adapter, obviating the need for the back torque applied to socket  24 .  
       FIG. 6  illustrates the retainer assembly  10  with an adapter  50  and a replaceable wear tip  60  (shown only partially). GET systems with an adapter or base attached to the machine (such as to the bucket or blade) and a replaceable wear member, such as tip  60 , attached to the adapter are well known to those of skill in this art. The exemplary adapter  50  and tip  60  are representative of the many different structures which the retainer assembly  10  could hold together. For example, tip  60  could be a tip on a compactor wheel with adapter  50  welded to the circumferential surface of the wheel. Or, tip  60  could be an edge protector for a bucket, with adapter  50  attached to the bucket edge, or adapter  50  representing the bucket edge itself. Or, as illustrated, tip  60  may be a replaceable ground engaging tooth and the adapter  50  may be mounted to a bucket.  
      Adapter  50  includes a nose portion  51  which fits into a pocket  61  formed in the tip  60 . The tip  60  slides onto the nose portion  51  of the adapter  50  in a sliding direction indicated by the arrow in  FIG. 6 . The nose portion  51  and pocket  61  are typically shaped so that they fit closely together, with little or no appreciable movement possible between the adapter  50  and the tip  60  when they are assembled.  
      In  FIG. 6 , the washer  30  has been placed in a pocket  52  formed in the adapter  50 . Alternatively, a pocket for the washer  30  may be formed in the tip  60 . The pocket  52  is formed on the adapter  50  at the opening of a through bore  53 . In the illustrated example, the pocket  52  is a counterbore with a diameter larger than the diameter of the bore  53 .  
      The washer  30  remains in pocket  52  while the tip  60  slides onto the nose portion  51 . When the tip  60  is slid to a certain extent onto the nose portion  51 , the tip traps the washer  30  in the pocket  52  so that it is between the tip and the adapter  50  and cannot be removed.  
      When the tip  60  slides further onto the nose portion  51  so that it fits snugly into the pocket  61 , a bore  62  formed on the tip will align with the bore  53  on the adapter  50 . This is illustrated in  FIG. 7 . At this point, the washer  30  continues to be trapped in the pocket  52 . The washer  30  cannot pass through bores  53  or  62  because the diameter of the washer is greater than their diameters.  
      The pin  20  may then be inserted in one side of the aligned bores  53  and  62  until its first end  21  abuts the first end  32  of washer  30 . The bolt  40  may also be inserted in the opposite end of aligned bores  53  and  62 . The shank  41  passes through the central bore  31  of washer  30 , and engages the threaded bore  24  of pin  20 . Tapered portion  44  and chamfer  26  can help align the bolt  40  with the central bore  31  and the threaded bore  24 . The pin  20  and the bolt  40  are torqued relative to one another until tapered portion  44  contacts tapered portion  34  of washer  30 . Further torquing will lock the pin  20 , washer  30 , and bolt  40  together so that they will not release unless an opposite releasing torque is applied. In  FIG. 7  it can be seen that the tapered portion  44  and the tapered portion  34  may be positioned and sized so that when the bolt  40  is assembled with the washer  30  in the central bore  31 , the head  40  does not protrude axially any further than second end  33 .  
      Once the pin  20 , washer  30 , and bolt  40  are attached, the retainer assembly  10  cannot be removed from the adapter  50  or tip  60  because the diameter of the exterior radial surface  37  of washer  30  is too great to pass through bores  53  or  62 . However, the diameter of the cylindrical surface  23  and the diameter of the head  42  of bolt  40  may each be less than, the diameter of bore  52  and/or the diameter of bore  63  so that the pin  20  and bolt  40  can pass through these bores. By implication, the diameter of exterior radial surface  37  is greater than the diameter of head  42  and cylindrical surface  23 .  
      Also, the pin  20  is positioned both in bore  62  of tip  60  and bore  53  of adapter  50 . Pin  20  acts as a shear pin to block tip  60  from being removed from adapter  50 .  
       FIG. 8  illustrates an alternate embodiment of retainer assembly  10 . In  FIG. 8 , the washer  30  and bolt  40  have been combined into a single part, end cap  70 . In likewise fashion, end cap  70  is trapped in pocket  52  and includes a shank  41  which threads into the threaded bore  24  of pin  20  during installation.  
      The pin  20 , washer  30 , and bolt  40  may each be made from steel for strength and durability, and optionally from stainless steel so that they will not deteriorate in the damp and difficult conditions they will experience in the field.  
     INDUSTRIAL APPLICABILITY  
      The retainer assembly  10  disclosed above may be used in industry to retain a ground engaging tool onto a work machine. The assembly  10  provides certain advantages over prior art systems. For one, a hammer is not necessary to install the system  10 . Some prior art systems required the technician to swing a large hammer in order to drive a shear pin between the tip and adapter. The system  10  can be applied more conveniently, but still only requires simple hand tools. The torque between the bolt  40  and pin  20  creates a tight, reliable attachment that will not unintentionally release due to vibrations or other loads. And finally, the pin  20  is strong and can reliably retain the tip or other GET onto the adapter or other part of the machine without breaking.