Abstract:
A tooth and adaptor assembly for a dipper bucket includes an adaptor having a rear portion for attaching to the dipper bucket, a tooth capable of releasable attachment to the adaptor and a retainer pin for securing the tooth to the adaptor. The adaptor further includes a tapering intermediate portion that narrows to a rectangular front portion. The adaptor further includes a planar surface on a portion of its intermediate portion and a cavity on the planar surface for receiving the retainer pin. The tooth has a tip at its front end for digging and a socket at its rear end configured to receive the front and intermediate portions of the adaptor. A small opening on the rear end of the tooth aligns with the cavity when the tooth is seated on the adaptor. The retainer pin is urged outward of the cavity by a biasing element to engage the small opening on the tooth so as to secure the tooth to the adaptor.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to excavating equipment, more particularly, to bucket tooth and adaptor assemblies for use on dipper buckets. 
         [0003]    2. Description of the Related Art 
         [0004]    Excavation in construction and mining applications is carried out more efficiently when ground-engaging penetration attachments, such as tooth and adaptor assemblies, are securely mounted on the leading digging edge of the excavation dipper bucket and/or excavation equipment. Usually, adaptors are rigidly attached to the bucket by either welding or some form of mechanical fastener. 
         [0005]    A chisel-like tooth of the assembly reduces the initial contact mass of the bucket edge moving into the material being excavated by focussing the accumulated digging forces at the leading edges of the tooth, thereby maximizing the penetration efficiency of the excavating equipment. The loosened material can then be freely loaded into the excavation bucket or simply diverted around the assembly when materials are only being broken up. Abrasive grinding, multidirectional stresses and shock loading at exceedingly high levels can continuously and abruptly breach the integrity of the tooth and adaptor assembly during any given excavation application. 
         [0006]    Canadian Patent 1,243,059 and U.S. Pat. No. 4,481,728 are exemplary of the first generation elliptical tooth and adaptor system. This system demonstrated the use of a three-piece system in mining applications. This system enabled the user to replace the primary consumable tooth separate from the fixed carrier adaptor. Any number of consumable teeth could then be readily fitted to the adaptor and replaced as each became worn out. Although this tooth and adaptor system is functional, it requires certain installation and removal techniques that are not desirable for use in the field. Some of this assembly&#39;s limitations include the use of an oversized locking pin that incorporates compressive elastomeric material vulcanized between two rigid members of the locking pin. 
         [0007]    Excessive force has to be applied by a sledgehammer to sufficiently compress the pin to permit full insertion into a smaller hole that receives the lock pin. Installation and removal of the locking pin is also time consuming and physically difficult, particularly if the head of the pin became flattened (mushroom shaped) from repeated hammer blows. This arduous practice of changing out worn teeth and installing new teeth has eventually become a safety concern. This original design is no longer acceptable to maintenance workers in certain mining applications. In addition, several other features of this design eventually became a concern. 
         [0008]    Another problem with this type of tooth and adaptor system is the physical properties of the vulcanized elastomeric material used in a lock pin to maintain the tooth fully on the adaptor. Deterioration of the elastomeric material is a common occurrence thereby making the locking pin non reusable. In addition, the structural design of this tooth and adaptor system restricted the possibility of establishing a locking system that would better preserve this important component. 
         [0009]    The extreme flowing pressures (several tons) of excavated materials beneath the shovel bucket tend to force this type of locking pin upward and out of the locked position. Occasionally, these pins are actually forced out completely and allow the tooth to fall off. 
         [0010]    Other limitations of this tooth and adaptor system include its design of an aligning common-through hole located centrally in both mated structural members when the tooth was fully fitted to the adaptor to accept the locking pin. The loss of structural mass in the tooth sidewalls weakened the tooth and, occasionally, will break when subjected to severe digging applications. 
         [0011]    Other systems include large gaps on the assembled tooth and adaptor, and within and around the lock pinholes. This leaves the mating fit surfaces of the assembly, the lock pin bearing support surfaces and its related structural members vulnerable to the extreme flowing pressures (several tons) of excavated materials that are readily forced into these gaps. The abrasive qualities of the ore, combined with any movement between the assembled components during the excavation process, create an aggressive grinding effect that can deteriorate these important dimensional load-bearing surfaces. 
         [0012]    The resulting wear can contribute to a “loose fit” condition affecting all three assembled components. This condition is especially true when certain “self-lubricated” and highly abrasive ores such as tar sand are being excavated. These ores have the inherent ability to quickly enter all gaps and internal aspects of the mated assembly. In addition, the elastomeric material incorporated in the retainer pin is exposed to the chemical effects of the ore (i.e., tar sand) and this contributes to the premature breakdown of this material diminishing its ability to lock the tooth to the adaptor. If the retainer lock pin does become loose and falls out, the tooth and adaptor can uncouple, leaving the less wear-resistant adaptor male mating nose exposed to harsh wear from the continuing excavation process. 
         [0013]    It is, therefore, desirable to provide a tooth and adaptor assembly for a dipper bucket that overcomes the limitations of the conventional equipment described above. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    According to the preferred embodiment of this invention, a tooth and adaptor assembly for a dipper bucket includes an adaptor having a front portion, an intermediate portion and a rear portion. The rear portion is adapted for attaching to a conventional dipper bucket. The intermediate portion extends between the front and rear portions and has a substantially circular base adjacent to the rear portion. The intermediate portion tapers or narrows in cross-section from its base to the front portion. According to one arrangement, the intermediate portion has an elliptical cross-section and the front portion has a substantially flat front end. According to another arrangement, a portion of the exterior surface of the intermediate portion is substantially planar thereby making the intermediate portion approximately D-shaped in cross section. A cavity is disposed on the planar surface, this cavity being transverse to a longitudinal axis passing through the intermediate portion. The cavity can be circular, rectangular or square in cross-section. 
         [0015]    The preferred assembly also includes a tooth having a front tip portion adapted for excavating and a rear portion extending from the front end. The rear portion of the tooth includes a socket configured to accommodate the front and intermediate portions of the adaptor in a coupled position. Specifically, the socket has an opening adapted to mate with the base of the intermediate portion and a bottom with a flat surface to mate with the front portion of the adaptor. The socket has an interior wall surface that is initially cylindrical at the entrance and then tapers to the bottom, the interior wall surface having a portion that is planar such that it mates with the planar portion of the exterior surface of the intermediate portion of the adaptor. 
         [0016]    The rear portion of the tooth also has a smaller opening, which secures a retainer pin. The aperture is in alignment with the adaptor passageway when the tooth is fully seated on the adaptor. In the preferred embodiment, the aperture extends through the tooth thereby providing communication from the outer tooth surface to the passageway. The retainer pin is disposed in the adaptor passageway to extend toward and engage the aperture in the tooth thereby securing the tooth on the adaptor. The retainer pin can be extracted from the smaller opening in the tooth by external means. 
         [0017]    In an alternative embodiment, the assembly utilizes a compressible retainer pin to engage and disengage the tooth from the adaptor. There is no bottom through-hole in the bottom of the tooth to “drift” the retainer pin out in order to disassemble the tooth from the adaptor. This prevents the entry of highly pressurized compaction forces from beneath that can force the typical base exposed retainer pin upward and out of their latched position. 
         [0018]    In yet another embodiment, the assembly includes a tooth, an adaptor, a retainer pin and a biasing element. The tooth and adaptor are configured such that the mated surfaces of the assembled components minimize debris from entering the interstitial space between the tooth and the adaptor when they are in a coupled and latched position. Preferably, the retainer pin is a solid pin, tapered at one end, having a square cross-section with rounded corners. The biasing element can consist of an elastomeric plug and/or a spring element that maintains outward pressure on the retainer pin to promote locking engagement within the small hole of the tooth. A ramp disposed in the socket between the mouth of the socket and the small hole of the tooth compresses the biasing element of the retainer pin as the tooth is seated onto the adaptor. As the small hole of the tooth begins to align with the adaptor cavity, the retainer pin passes over the crest of the ramp and is urged forward by the biasing element to engage the small hole thereby securing the tooth on the adaptor. 
         [0019]    According to another arrangement, the adaptor front portion has a rectangular front end and enlarges in cross-section towards the substantially circular base of the intermediate portion. The intermediate portion incorporates a ¾ round cylindrical shank having a flat side surface containing a cavity formed thereon. The front and intermediate portions are adapted to conform to an interior configuration of the tooth socket so as to prevent the tooth from rotating on the adaptor in the coupled position. These additional mated-load bearing surfaces help to keep the tooth stable on the adaptor while a maintenance worker is changing out the tooth. One or more stabilizing lugs protrude outward from the adaptor thrust bearing surface that mate with positioning slot(s) positioned on the thrust bearing surface of the tooth. 
         [0020]    The complementary shapes of the front and intermediate portions of the adaptor and the tooth socket more effectively distribute the shock and bearing loads throughout the assembly. The front and intermediate portions form multi-directional load-bearing surfaces so as to reduce the possibility of tooth and/or adaptor nose breakage. 
         [0021]    The retainer pin can be easily manipulated externally with a simple tool, such as a drift punch, entered into the small hole of the tooth to permit installation and removal of the tooth. The configuration of the retainer pin prevents chemically active ore from entering the adaptor cavity and having an adverse effect on an elastomeric biasing element. Accordingly, the elastomeric material and/or spring mechanism and retainer pin can be used over the course of several tooth change outs, if necessary. 
         [0022]    According to one aspect of the invention, an adaptor for releasably attaching a bucket tooth to an excavation tool includes a rear portion adapted for attaching to an excavation tool; a front portion adapted for a sliding fit with a corresponding socket disposed on a bucket tooth; an intermediate portion comprising an exterior surface and a base adjacent to the rear portion, the intermediate portion narrowing in cross-sectional area from the base to front portion; a substantially planar surface disposed on a portion of the exterior surface; and a passageway extending from the planar surface at least partially into the adaptor, the passageway being adapted to receive a retainer pin for releasably attaching the bucket tooth to the adaptor. 
         [0023]    According to another aspect of the invention, a bucket tooth for releasably attaching an adaptor to an excavation tool includes a longitudinal body that has a front tip portion adapted for excavating disposed on one end and a rear portion disposed on an opposing end; a socket disposed on the rear portion, the socket having a mouth, a side wall and an interior mating surface adapted for a sliding fit onto an exterior surface of an adaptor; a substantially planar surface disposed on a portion of the interior mating surface; an aperture disposed on the planar surface, the aperture being adapted to substantially align with a passageway disposed on the adaptor; and a catch disposed on the planar surface between the mouth and the aperture, the catch being adapted to secure a retainer pin disposed in the passageway to the aperture, the retainer pin including a biasing element adapted to urge the retainer pin to engage the aperture when the tooth is substantially seated on the adaptor thereby preventing the tooth from being removed from the adaptor. 
         [0024]    According to yet another aspect of the invention, a retainer pin is adapted for releasably attaching a bucket tooth to an adaptor, the tooth including a socket having an interior surface and adapted for sliding fit on to the adaptor, a longitudinal body having first and second ends, the body being adapted to be inserted into a passageway disposed on an adaptor; a biasing element disposed on the first end; and the second end adapted to seat in an aperture disposed on a socket interior surface of a bucket tooth when the retainer pin is inserted first end first into the passageway of the adaptor thereby retaining the tooth on the adaptor once the tooth is substantially seated on the adaptor. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0025]      FIG. 1  is a perspective view depicting a tooth uncoupled from an adaptor that is mounted to a dipper bucket. 
           [0026]      FIG. 2  is a perspective view depicting a tooth being seated on an adaptor. 
           [0027]      FIG. 3  is a side elevational view depicting the tooth and adaptor assembly of  FIG. 1  with the tooth seated on the adaptor. 
           [0028]      FIG. 4  is a top plan view depicting the tooth and adaptor assembly of  FIG. 1  with the tooth seated on the adaptor. 
           [0029]      FIG. 5  is a side elevational view depicting the tooth and adaptor assembly of  FIG. 1  with the tooth uncoupled from the adaptor. 
           [0030]      FIG. 6  is a top plan view depicting the tooth and adaptor assembly of  FIG. 1  with the tooth uncoupled from the adaptor. 
           [0031]      FIG. 7  is a left side elevational cross-section view depicting a tooth of  FIG. 4  as shown along section lines VII-VII. 
           [0032]      FIG. 7A  is a left side elevational cross-section view depicting the tooth of  FIG. 7  with a slot for a stabilizing lug. 
           [0033]      FIG. 8  is a right side elevational cross-section view depicting the tooth of  FIG. 4  shown along section lines VIII-VIII. 
           [0034]      FIG. 9  is a top plan cross-sectional view depicting the tooth of  FIG. 3  as shown along section lines IX-IX. 
           [0035]      FIG. 10  is a left side elevational view depicting the adaptor of  FIG. 1 . 
           [0036]      FIG. 10A  is a left side elevation view depicting the adaptor of  FIG. 10  with a stabilizing lug. 
           [0037]      FIG. 11  is a top plan view depicting the adaptor of  FIG. 1 . 
           [0038]      FIG. 11A  is a top plan view depicting the adaptor of  FIG. 11  with a stabilizing lug. 
           [0039]      FIG. 12  is a side elevational view depicting a retainer pin for use with the tooth and adaptor assembly of  FIG. 1 . 
           [0040]      FIG. 13  is a top cross sectional plan view depicting the tooth and adaptor assembly of  FIG. 3  as shown along section lines XIII-XIII. 
           [0041]      FIG. 13A  is a top cross sectional plan view displaying an alternate embodiment of the retainer pin. 
           [0042]      FIG. 14  is an end elevational cross-section view depicting the tooth and adaptor assembly of  FIG. 4  as shown along section lines XIV-XIV. 
           [0043]      FIG. 15  is a perspective view depicting a backhoe with a dipper bucket. 
           [0044]      FIG. 16  is an elevational side view depicting an excavator with a dipper bucket. 
           [0045]      FIG. 17  is an elevational side view depicting a front-end loader with a mining bucket. 
           [0046]      FIG. 18  is a perspective view depicting a bucket-wheel trencher excavator with a plurality of toothed buckets. 
           [0047]      FIG. 19  is a perspective view depicting a trencher with a chain equipped with a plurality of tooth and adaptor assemblies. 
           [0048]      FIG. 20  is an elevational side view depicting a cutting head for a dredging excavator. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    Referring to  FIGS. 1 and 2 , a representative embodiment of the present invention is shown. The tooth/adaptor assembly  10  broadly consists of excavation tooth  12 , adaptor  14 , retainer pin  16 , and biasing element  17 . Adaptor  14  comprises elongated U-shaped member  15  that attaches to dipper bucket  18  on bucket lip  19  as well known to those skilled in the art. Tooth  12  is seated onto adaptor  14  and secured by retainer pin  16  that is forced outwardly from the adaptor cavity  20  by the biasing element  17  to fit snugly into aperture  21  on tooth  12 . Tooth  12  is designed to bear the brunt of the wearing forces caused by excavating and will wear out over time. As tooth  12  wears out to the point that it is no longer serviceable, tooth  12  can be removed from adaptor  14  by inserting a tool, such as a drift punch or similarly shaped device, into aperture  21  to engage pin  16  and compress biasing element  17 . This causes pin  16  to disengage from aperture  21  on tooth  12  thereby allowing tooth  12  to be removed from adaptor  14 . 
         [0050]    Referring to  FIGS. 3 and 4 , side and top views of assembly  10  is shown with tooth  12  fully seated on adaptor  14 . Tooth  12  has a pointed tip  22  designed for excavating. As more clearly shown in  FIG. 13 , tooth  12  is secured to adaptor  14  with retainer pin  16  seated in cavity and engaging aperture  21 . Referring to  FIGS. 5 and 6 , side and top views of assembly  10  is shown with tooth  12  uncoupled from adaptor  14 . Adaptor  14  comprises base portion  23  that is generally circular in cross-section, intermediate elliptical tapered cone portion  24  and front block portion  35 . 
         [0051]    One side of the base  23  and intermediate portions  23  and  24  have a flat surface  25  that gives the base portion  23  and intermediate portion  24  a generally D-shaped or ¾ round cross-section. The flat surface  25  has a planar axis that can be positioned substantially vertical on adaptor  14 , although other configurations can be used. Retainer pin cavity  20  on flat surface  25  can be transverse to longitudinal axis  11  of assembly  10 . To couple tooth  12  and adaptor  14  together, tooth  12  comprises socket  26  that receives front, intermediate and base portions  35 ,  24  and  23  of adaptor  14 . When tooth  12  is seated on adaptor  14 , thrust bearing surface  27  of tooth  12  contacts thrust bearing surface  31  of adaptor  14 . Load forces passing from adaptor  14  to tooth  12  and from tooth  12  back to adaptor  14  are transmitted via these uniform mated fit surfaces. 
         [0052]    Moreover, when tooth  12  is seated on adaptor  14 , aperture  21  aligns with cavity  20  to provide a substantially continuous passageway  28  for receiving retainer pin  16 . Front portion  35  is a key adapted to prevent tooth  12  from rotating on adaptor  14  when fully seated on adaptor  14 . In the embodiment described herein, front portion  35  has a rectangular cross-section. The cross-section of front portion  35  can be of any suitable cross-sectional shape that will prevent tooth  12  from rotating on adaptor  14  when fully seated on adaptor  14 . Examples of suitable polygon shapes for front portion  35  include triangle, square, rhombus, trapezoid, pentagon, hexagon, heptagon and octagon. Front portion  35  can also be elliptical in cross-section in addition to any other curved cross-section that will prevent tooth  12  from rotating on adaptor  14 . 
         [0053]    In  FIGS. 7 and 8 , side cross-sectional views of tooth  12  are shown.  FIG. 9  illustrates a top plan cross-sectional view of tooth  12 . Tooth  12  is intersected by a socket-opening  26  that has a substantially circular interior load bearing surface  29  to match base  23  of adaptor  14 . Relief cavity  33  is a relief groove that separates load surface  29  from elliptical cone surface  30 . Relief cavity  33  is relatively circular in shape and offers additional relief clearance for adaptor transition zone edges  32  on tooth  12  when tooth  12  is fully seated on adaptor  14 . 
         [0054]    Sidewalls  34   a  to  34   d  and primary thrust bearing surface  39  of key-way  52  provide an opening to receive front block  35  of adaptor  14  in a sliding fit. In one embodiment, front block  35  of adaptor  14  and key-way  52  are rectangular in cross section. The cross-section of key-way  52  can be of any suitable cross-sectional shape that will prevent tooth  12  from rotating on adaptor  14  when fully seated on adaptor  14 . Examples of suitable polygon shapes for key-way  52  include triangle, square, rhombus, trapezoid, pentagon, hexagon, heptagon and octagon. Key-way  52  can also be elliptical in cross-section in addition to any other curved cross-section that will prevent tooth  12  from rotating on adaptor  14  so long as key-way  52  and front portion  35  are complementary in shape and fit. 
         [0055]    Cone surface  30  and circular base  29  further comprises flat surface  38  that give this intermediate portion of socket  26  a generally D-shaped or ¾ round cross-section. Ramp  60  leads from thrust bearing surface  27  in socket  26  towards ramp crest  62  that is adjacent to aperture  21 . In one embodiment, aperture  21  is tapered, or frusto-conical, in shape and configuration. 
         [0056]    Referring to  FIGS. 10 and 11 , side and top views of adaptor  14  are shown, respectively. Adaptor  14  comprises of adaptor base  23 , which is generally circular, elliptical body  24  and front block  35 . Front block  35  is, preferably, rectangular and comprises of sidewalls  36   a  to  36   d  and primary thrust surface  37 . Elliptical body  24  tapers from transition  32  to front block  35 . Flat surface  25  is disposed on elliptical body  24  and adaptor base  23 . Retainer pin cavity  20  is disposed on flat surface  25  and is generally transverse to the horizontal axis of adaptor  14 . Retainer pin cavity  20  aligns with aperture  21  of tooth  12  when tooth  12  is fully seated onto adaptor  14 . Front block  35  is adapted for a sliding fit with the bottom of tooth socket  26  which is defined by sidewalls  36   a  to  36   d  and thrust bearing surface  37 . In one embodiment, adaptor front block  35  can have a generally rectangular cross section, with flat front mating surface  37  having a width that is greater than its height, that is, top and bottom mating surfaces  36   a  and  36   c  are wider than flat side mating surfaces  36   b  and  36   d.    
         [0057]    Referring to  FIGS. 7A ,  10 A and  11 A, another embodiment of tooth  12  and adaptor  14  are shown. As illustrated in  FIGS. 10A and 11A , adaptor  14  further comprises at least one stabilizing lug  66  extending away from base portion  23  and bearing thrust surface  31 . In this embodiment, stabilizing lug  66  fits into positioning slot  67  located on tooth  12 , as shown in  FIG. 7A , to further stabilize tooth  12  when tooth  12  is substantially seated on adaptor  14 . 
         [0058]    A side view of retainer pin  16  is shown in  FIG. 12 . Retainer pin  16  comprises main body  40 , O-ring groove  41 , tapered tip  42  and biasing element  17 . Referring to  FIGS. 13 and 13A , pin tip  42  is tapered in one embodiment to ensure firm engagement into aperture  21  to prevent debris from entering cavity  20 . This uniform metal-to-metal surface contact is maintained by the outward compression, as described below, that encloses passageway  28  and the interior of assembly  10 . Positioned firstly within the adaptor retainer pin hole  20  is biasing element  17  which urges the retainer pin  16  outward to insert retainer pin tip  42  into aperture  21 , thereby securing the tooth  12  firmly on the adaptor  14 . In one embodiment, biasing element  17  can be made of corrosion resistant spring material. 
         [0059]    In  FIG. 13 , front cross-sectional views of assembly  10  are shown with spring mechanism  17  and retainer pin  16  housed in the adaptor retainer pin cavity  20 . The coupling of tooth  12  onto adaptor  14  forces tapered tip  42  of retainer pin  16  to travel up ramp  60  thereby compressing biasing element  17 . As tapered tip  42  passes over ramp crest  62 , biasing element  17  urges tapered tip  42  into aperture  21  when tooth  12  is fully coupled to adaptor  14 . 
         [0060]    In another embodiment, biasing element can be a resilient elastomeric plug made of rubber, polyurethane or any other suitable elastomer material as known to those skilled in the art that can provide the force required to urge retainer pin  16  toward and engage aperture  21  on tooth  12  when tooth  12  is seated on adaptor  14 . In another embodiment, as shown in  FIG. 13A , biasing element  17  can be a pair of magnets  48  and  50  placed in cavity  20  such that magnets  48  and  50  repel one another. In this manner, the magnetic force that causes magnets  48  and  50  to repel one another urges retainer pin  16  toward aperture  21  and engage it thereby retaining tooth  12  on adaptor  14 . To retract retainer pin  16  from aperture  21 , a simple tool is inserted into aperture  21  and inward force is applied to move retainer pin  16  back onto biasing element  17  thereby disengaging retainer pin  16  from aperture  21  so that tooth  12  can be removed from adaptor  14 . Retainer pin  16  is of a rigid construction and may be manufactured from steel or alloys having suitable strength, wear and corrosion resistant properties. 
         [0061]    Referring to  FIG. 14 , a cross-sectional rear view of tooth  12  seated on adaptor  14  is shown. Flat surface  38  of tooth  12  aligns and mates with flat surface  25  of adaptor  14 . Cavity  20  aligns with aperture  21  to form passageway  28 . Adaptor  14  is sized to provide a close fit with socket  26  of tooth  12 . With tooth  12  and adaptor  14  configured in this manner, tooth  12  is prevented from rotating on adaptor  14 . 
         [0062]    The embodiments shown herein are related to tooth and adaptor assemblies for use with dipper buckets. However, it should be obvious to those skilled in the art that the tooth and adaptor assemblies described herein can be used on a variety of heavy equipment and excavating tools. As an example, tooth and adaptor assemblies can be used on backhoes  70  ( FIG. 15 ) and excavators  72  ( FIG. 16 ) in addition to mining shovel buckets or front-end loader buckets  74  ( FIG. 17 ). 
         [0063]    Other types of excavating tools include bucket wheel and chain trenchers. Bucket wheel trenchers are large diameter wheels having a plurality of buckets spaced about the circumference of the wheel. Each bucket, in turn, has a number of teeth and adaptor assembles. Bucket wheels are typically used in open-pit mining operations and to excavate pipeline trenches. An example of such a bucket wheel  76  is shown in  FIG. 18 . Chain trenchers are a different type of excavating tool as they comprise an endless chain having a plurality of tooth and adaptor assemblies attached around the chain not unlike a chainsaw. Trenchers are used to cut trenches in the ground. An example of such a trencher  78  is shown in  FIG. 19 . Yet another example of excavating tools that use tooth and adaptor assemblies are cutterheads as used on dredging equipment. These cutterheads are rotary cutting devices and have the teeth and adaptor assemblies disposed about the semispherical surface of the cutterhead such that they are pointed in the direction of cutterhead rotation. An example of a cutterhead  80  is shown in  FIG. 20 . 
         [0064]    Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.