Patent Publication Number: US-9428886-B2

Title: Implement tooth assembly with tip and adapter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 13/644,518, filed Oct. 4, 2012, and entitled “IMPLEMENT TOOTH ASSEMBLY WITH TIP AND ADAPTER,” which is based upon and claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/545,107 to Renski et al. filed on Oct. 7, 2011, the disclosures of both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to earth working machines with ground engaging implements and, in particular, to tooth assemblies with replaceable tip and adapter systems attached to the leading or base edges of such ground engaging implements. 
     BACKGROUND 
     Earth moving machines known in the art are used for digging into the earth or rock and moving loosened work material from one place to another at a worksite. These machines and equipment typically include a body portion housing the engine and having rear wheels, tracks or similar components driven by the engine, and an elevated cab for the operator. The machines and equipment further include articulating mechanical arms or other types of linkages, such as Z-bar linkages, for manipulating one or more implements of the machine. The linkages are capable of raising and lowering the implements and rotating the implements to engage the ground or other work material in a desired manner. In the earth moving applications, the implements of the machines or other equipment are buckets provided with a beveled lip or blade on a base edge for moving or excavating dirt or other types of work material. 
     To facilitate the earth moving process, and to prolong the useful life of the implement, a plurality of tooth assemblies are spaced along the base edge of the implement and attached to the surface of the implement. The tooth assemblies project forward from the base edge as a first point of contact and penetration with work material, and to reduce the amount of wear of the base edge. With this arrangement, the tooth assemblies are subjected to the wear and breakage caused by repetitive engagement with the work material. Eventually, the tooth assemblies must be replaced, but the implement remains usable through multiple cycles of replacement tooth assemblies. Depending on the variety of uses and work material for the equipment, it may also be desirable to change the type or shape of the tooth assemblies to most effectively utilize the implement. 
     In many implementations, installation and replacement of the tooth assemblies may be facilitated by providing the tooth assemblies as a two-part system. The system may include an adapter that is attached to the base edge of the implement, a ground-engaging tip configured to be attached to the adapter, and a retention mechanism securing the tip to the adapter during use. The adapter may be welded, bolted or otherwise secured to the base edge, and then the tip may be attached to the adapter and held in place by the retention mechanism. The tip endures the majority of the impact and abrasion caused by engagement with the work material, and wears down more quickly and breaks more frequently than the adapter. Consequently, multiple tips may be attached to the adapter, worn down, and replaced before the adapter itself must be replaced. Eventually, the adapter may wear down and require replacement before the base edge of the implement wears out. 
     One example of a digging tooth assembly is illustrated and described in U.S. Pat. No. 4,949,481 to Fellner. The digging tooth for a bucket has a concave top surface and a convex bottom surface which intersect forming a forward cutting edge. Sidewalls connect the two surfaces and are concave having a moldboard shape. The rear portion of the tooth is provided with a mounting assembly for mounting the digging tooth to a bucket. The bottom surface continuously diverges from the forward cutting edge to the rear portion; whereas the top surface first converges then diverges from the forward cutting edge to the rear portion. The rear portion includes a shank receiving cavity with top and bottom walls that converge as the cavity extends forwardly within the tooth to give the cavity a triangular or wedge shape when viewed in profile. 
     An example of a loader bucket tooth is provided in U.S. Pat. No. 5,018,283 to Fellner. The digging tooth for a loader bucket includes a top surface having a concave configuration and a bottom surface having a flat forward portion and a convex rear portion. The flat forward portion and the top surface intersect to form a forward cutting edge. Sidewalls connect the two surfaces and are concave having a plowshare shape. The rear portion of the tooth is provided with a mounting assembly for mounting it to a bucket. The bottom surface continuously converges from the forward cutting edge to the rear portion; whereas the top surface first converges then diverges from the forward cutting edge to the rear portion. The rear portion includes a shank receiving cavity with bottom wall extending inwardly, and a top wall having a first portion extending approximately parallel to the bottom wall and a second portion angled toward the bottom wall and extending to a rounded front portion. 
     U.S. Pat. No. 2,982,035 to Stephenson provides an example of an excavator tooth having an adapter that attaches to the leading edge of a dipper body, and a tip that attaches to the adapter. The tip includes an upper surface and a lower surface that converge into a relatively sharp point, with the tip having a horizontal plane of symmetry. Upper and lower surfaces of the adapter have recessed central surfaces, with the upper central surface having a forward surface that diverges upwardly from the plane of symmetry and rounds into a forward surface of the adapter. The interior of the tip has corresponding planar surfaces that are received by the central surfaces of the adapter, and include forward surfaces diverging from the plane of symmetry as they approach a forward surface, with one of the forward surfaces of the tip abutting the forward surface of the adapter when the parts are appropriately assembled. 
     The implements as discussed may be used in a variety of applications having differing operating conditions. In loader applications, buckets installed on the front of wheel or track loaders have the bottom surfaces and base edges scrape along the ground and dig into the earth or pile of work material as the loader machine is driven forward. The forces on the tooth assembly as the bucket enters the pile push the tip into engagement with the corresponding adapter. The bucket is then raised and racked with the load of work material, and the loader moves and dumps the work material in another location. As the bucket is raised through the work material, force is exerted downwardly on the tooth assembly. With the combination of scraping and engagement with the work material, and in other types of bottom-wearing applications in which the bottom surface typically wears more quickly due to more frequent engagement with the work material, the wear material of the tip wears away from the front of the tip and from the bottom surface of the tip and adapter. The loss of wear material at the front of the tip converts the initially pointed front end of the tip into a rounded, blunt surface, similar to changing the hand from having extended fingers to having a closed fist. The worn down shape is less efficient at digging through the work material as the loader moves forward, though the tip may still have sufficient wear material to be used on the implement for a time before replacement. 
     In excavator applications and other types of top-wearing applications where the top surface typically wears more quickly due to more frequent engagement with the work material, the buckets engage and pass through the ground or work material at different angles than in bottom-wearing applications such as loader applications described above, and therefore cause wear material of the tooth assemblies to wear away in a different manner. An excavator device, such as a backhoe, initially engages the work material with the base edge and tooth assemblies oriented close to perpendicular with respect to the surface of the work material and generally enter the work material in a downward motion. After the initial penetration into the work material, the mechanical arm further breaks up the work material and collects a load of work material in the bucket by drawing the bucket back toward the excavator machine and rotating the bucket inwardly to scoop the work material into the bucket. The complex motion of the bucket causes wear at the tip of the tooth assembly during the downward penetration motion when the forces act to push the tip into engagement with the adapter. After the initial penetration, the bucket is drawn toward the machine and rotated to further in a scooping motion to break up the work material and begin to load the implement. During this motion, the forces initially act in a direction that is initially mostly normal to the top surface of the tooth assembly, and the work material passes over and around the top of the tooth causing wear on the top surface of the tooth. As the implement rotates further and is drawn through the work material, the forces and work material again act on the tip of the tooth to cause wear at the tip. As with the loader tooth assemblies, the excavator tooth assemblies wear down to less efficient shapes after repeated forays into the work material, but may still retain sufficient wear material for continued use without replacement. In view of this, a need exists for improved tooth assembly designs for loader and excavator implements that distribute the wear material such that the tips dig into the work material more efficiently as wear material wears away from and reshapes the tips until the tips ultimately must be replaced. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect of the present disclosure, the invention is directed to a ground engaging tip of a tooth assembly for a base edge of a ground engaging implement, wherein the tooth assembly includes an adapter configured for attachment to a base edge of the ground engaging implement and having a forwardly extending adapter nose. The ground engaging tip may include a rear edge, a top outer surface, a bottom outer surface, wherein the top outer surface and the bottom outer surface extend forward from the rear edge and converge at a front edge, oppositely disposed lateral outer surfaces extending upwardly from the bottom outer surface to the top outer surface, and an inner surface extending inwardly into the ground engaging tip from the rear edge and defining a nose cavity within the ground engaging tip having a complementary shape to the adapter nose of the adapter for receiving the adapter nose therein. The inner surface may include a bottom inner surface extending inwardly from the rear edge and oriented approximately perpendicular to the rear edge of the ground engaging tip, a front inner surface, a top inner surface having a first support portion proximate the front inner surface, a second support portion proximate the rear edge of the ground engaging tip, and an intermediate portion extending between the first support portion and the second support portion, where a distance between the first support portion and the bottom inner surface is less than a distance between the second support portion and the bottom inner surface, oppositely disposed side inner surfaces extending upwardly from the bottom inner surface to the top inner surface 
     In another aspect of the present disclosure, the invention is directed to an adapter of a tooth assembly for a base edge of a ground engaging implement. The adapter may include a rearwardly extending top strap, a rearwardly extending bottom strap having a top surface, wherein the top strap and the bottom strap define a gap there between for receiving the base edge of the ground engaging implement, and a forward extending adapter nose. The nose may include a bottom surface extending forward relative to the top strap and the bottom strap, a front surface, a top surface having a first support surface proximate the front surface, a second support surface proximate the top strap and the bottom strap, and an intermediate surface extending between the first support surface and the second support surface, where a distance between the first support surface and the bottom surface is less than a distance between the second support surface and the bottom surface, and oppositely disposed side surfaces extending upwardly from the bottom surface to the top surface. 
     Additional aspects of the invention are defined by the claims of this patent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a loader bucket having tooth assemblies in accordance with the present disclosure attached at a base edge thereof; 
         FIG. 2  is an isometric view of an excavator bucket having tooth assemblies in accordance with the present disclosure attached at a base edge thereof; 
         FIG. 3  is an isometric view of a tooth assembly in accordance with the present disclosure; 
         FIG. 4  is a side view of the tooth assembly of  FIG. 3 ; 
         FIG. 5  is an isometric view of an adapter of the tooth assembly of  FIG. 3 ; 
         FIG. 6  is a side view of the adapter of  FIG. 5  attached to a base edge of an implement; 
         FIG. 7  is a top view of the adapter of  FIG. 5 ; 
         FIG. 8  is a bottom view of the adapter of  FIG. 5 ; 
         FIG. 9  is a cross-sectional view of the adapter of  FIG. 5  taken through line  9 - 9  of  FIG. 7 ; 
         FIG. 10  is an isometric view of a tip of the tooth assembly of  FIG. 3 ; 
         FIG. 11  is a side view of the tip of  FIG. 10 ; 
         FIG. 12  is a top view of the tip of  FIG. 10 ; 
         FIG. 13  is a bottom view of the tip of  FIG. 10 ; 
         FIG. 14  is a front view of the tip of  FIG. 10 ; 
         FIG. 15  is a cross-sectional view of the tip of  FIG. 10  taken through line  15 - 15  of  FIG. 12 ; 
         FIG. 16  is a cross-sectional view of the tip of  FIG. 10  taken through line  16 - 16  of  FIG. 14 ; 
         FIG. 17  is a rear view of the tip of  FIG. 10 ; 
         FIG. 18  is an isometric view of an alternative embodiment of a tip for a tooth assembly in accordance with the present disclosure; 
         FIG. 19  is a top view of the tip of  FIG. 18 ; 
         FIG. 20  is a front view of the tip of  FIG. 18 ; 
         FIG. 21  is a side view of the tip of  FIG. 18 ; 
         FIG. 22  is a cross-sectional view of the tip of  FIG. 18  taken through line  22 - 22  of  FIG. 19 ; 
         FIG. 23  is an isometric view of an alternative embodiment of an adapter for an tooth assembly in accordance with the present disclosure; 
         FIG. 24  is a side view of the adapter of  FIG. 23 ; 
         FIG. 25  is a cross-sectional view of the adapter of  FIG. 23  taken through line  25 - 25  of  FIG. 24 ; 
         FIG. 26  is an isometric view of an alternative embodiment of a tip for a tooth assembly in accordance with the present disclosure; 
         FIG. 27  is a side view of the tip of  FIG. 26 ; 
         FIG. 28  is a front view of the tip of  FIG. 26 ; 
         FIG. 29  is a top view of the tip of  FIG. 26 ; 
         FIG. 30  is a cross-sectional view of the tip of  FIG. 26  taken through line  30 - 30  of  FIG. 29 ; 
         FIG. 31  is an isometric view of a further alternative embodiment of a tip for a tooth assembly in accordance with the present disclosure; 
         FIG. 32  is a side view of the tip of  FIG. 31 ; 
         FIG. 33  is a front view of the tip of  FIG. 31 ; 
         FIG. 34  is a front view of the tip of  FIG. 31  with the front edge partially elevated to show the bottom outer surface; 
         FIG. 35  is a rear view of the tip of  FIG. 31 ; 
         FIG. 36  is a cross-sectional view of the tip of  FIG. 31  taken through line  36 - 36  of  FIG. 35 ; 
         FIG. 37  is an isometric view of an additional alternative of a tip for a tooth assembly in accordance with the present disclosure; 
         FIG. 38  is a top view of the tip of  FIG. 37 ; 
         FIG. 39  is a front view of the tip of  FIG. 37 ; 
         FIG. 40  is a side view of the tip of  FIG. 37 ; 
         FIG. 41  is a cross-sectional view of the tip of  FIG. 37  taken through line  41 - 41  of  FIG. 39 ; 
         FIG. 42  is an isometric view of a top-wearing application tooth in accordance with the present disclosure; 
         FIG. 43  is a front view of the tooth of  FIG. 42 ; 
         FIG. 44  is a side view of the tooth of  FIG. 42 ; 
         FIG. 45  is a top view of the tooth of  FIG. 42 ; 
         FIG. 46  is an isometric view of a bottom-wearing application tooth in accordance with the present disclosure; 
         FIG. 47  is a front view of the tooth of  FIG. 46 ; 
         FIG. 48  is a side view of the tooth of  FIG. 46 ; and 
         FIG. 49  is a top view of the tooth of  FIG. 46 ; 
         FIG. 50  is a cross-sectional view of the tooth assembly of  FIG. 3  taken through line  50 - 50  with the tip as shown in  FIG. 16  installed on the adapter of  FIG. 6 ; 
         FIG. 51  is the cross-sectional view of the tooth assembly of  FIG. 50  with the tip moved forward due to tolerances within a retention mechanism; 
         FIGS. 52A, 52B, 52C, 52D, 52E, and 52F  are schematic illustrations of the sequence of orientations of the tooth assembly of  FIG. 3  when an excavator implement gathers a load of work material; 
         FIG. 53  is the cross-sectional view of the tooth assembly of  FIG. 50  with the section lines removed and showing a force applied to the tooth assembly when the excavator implement is in the orientation of  FIG. 52A ; 
         FIG. 54  is the cross-sectional view of the tooth assembly of  FIG. 53  showing a force applied to the tooth assembly when the excavator implement is in the orientation of  FIG. 52C ; 
         FIG. 55  is an enlarged view of the tooth assembly of  FIG. 54  illustrating forces acting on the nose of the adapter and the nose cavity surfaces of the tip; 
         FIG. 56  is the cross-sectional view of the tooth assembly of  FIG. 53  showing a force applied to the tooth assembly when the excavator implement is in the orientation of  FIG. 52E ; 
         FIG. 57  is a top view of an alternative embodiment of a tooth assembly in accordance with the present disclosure; 
         FIG. 58  is a front view of the tooth assembly of  FIG. 57 ; 
         FIG. 59  is the cross-sectional view of the tooth assembly formed by the adapter of  FIG. 23  and the tip of  FIG. 26  and showing a force applied to the tooth assembly when a loader implement digs into a pile of work material; 
         FIG. 60  is the cross-sectional view of the tooth assembly of  FIG. 59  with the tooth assembly and loader implement directed partially upward and showing forces applied to the tooth assembly when the loader implement is raised up through the pile of work material; 
         FIG. 61  is an enlarged view of the tooth assembly of  FIG. 60  illustrating forces acting on the nose of the adapter and the nose cavity surfaces of the tip; 
         FIG. 62  is a side view of the tooth assembly of  FIG. 3 ; 
         FIG. 63  is a cross-sectional view of the tooth assembly of  FIG. 62  taken through line  63 - 63 ; 
         FIG. 64  is a cross-sectional view of the tooth assembly of  FIG. 62  taken through line  64 - 64 ; 
         FIG. 65  is a cross-sectional view of the tooth assembly of  FIG. 62  taken through line  65 - 65 ; 
         FIG. 66  is a cross-sectional view of the tooth assembly of  FIG. 62  taken through line  66 - 66 ; 
         FIG. 67  is a cross-sectional view of the tooth assembly of  FIG. 62  taken through line  67 - 67 ; 
         FIG. 68  is a cross-sectional view of the tooth assembly of  FIG. 62  taken through line  68 - 68   
         FIG. 69  is a side view of the tooth assembly formed by the adapter of  FIG. 23  and the tip of  FIG. 26 ; 
         FIG. 70  is a cross-sectional view of the tooth assembly of  FIG. 69  taken through line  70 - 70 ; 
         FIG. 71  is a cross-sectional view of the tooth assembly of  FIG. 69  taken through line  71 - 71 ; 
         FIG. 72  is a cross-sectional view of the tooth assembly of  FIG. 69  taken through line  72 - 72 ; 
         FIG. 73  is a cross-sectional view of the tooth assembly of  FIG. 69  taken through line  73 - 73 ; 
         FIG. 74  is a cross-sectional view of the tooth assembly of  FIG. 69  taken through line  74 - 74 ; and 
         FIG. 75  is a cross-sectional view of the tooth assembly of  FIG. 69  taken through line  75 - 75 . 
     
    
    
     DETAILED DESCRIPTION 
     Although the following text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims. The detailed description is to be construed as exemplary only and does not describe every possible embodiment of the invention. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention. 
     It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘ —————— ’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. §112, sixth paragraph. 
     Referring now to  FIG. 1 , there is shown an implement for a bottom-wearing application, such as a loader machine, in the form of a loader bucket assembly  1  that incorporates the features of the present disclosure. The loader bucket assembly  1  includes a bucket  2  which is partially shown in  FIG. 1 . The bucket  2  is used on the loader machine to excavate material in a known manner. The bucket assembly  10  may include a pair of oppositely-disposed support arms  3  on which corresponding corner guards  4  may be mounted. The bucket assembly  1  may further included a number of edge protector assemblies  5  interposed between tooth assemblies  1  in accordance with the present disclosure, with the edge protector assemblies  5  and the tooth assemblies being secured along a base edge  18  of the bucket  2 .  FIG. 2  illustrates an implement for a top-wearing application, such as an excavator, in the form of an excavator bucket assembly  6 . The excavator bucket assembly  6  includes a bucket  7  having corner guards  4  connected on either side, and a plurality of tooth assemblies  10  attached across the base edge  18  of the bucket  7 . Various embodiments of tooth assemblies are described herein that may be implemented in bottom-wearing and top-wearing applications. Even where a particular tooth assembly or component embodiment may be described with respect to a particular bottom-wearing or top-wearing application, those skilled in the art will understand that the tooth assemblies are not limited to a particular type of application and may be interchangeable between implements of various applications, and such interchangeability is contemplated by the inventors for tooth assemblies in accordance with the present disclosure. 
       FIGS. 3 and 4  illustrate an embodiment of a tooth assembly  10  in accordance with the present disclosure that may be useful with earth moving implements, and have particular use in top-wearing applications. The tooth assembly  10  may be used on multiple types of ground engaging implements having base edges  18 . The tooth assembly  10  includes an adapter  12  configured for attachment to a base edge  18  of an implement  1 ,  6  ( FIGS. 1 and 2 , respectively), and a tip  14  configured for attachment to the adapter  12 . The tooth assembly  10  further includes a retention mechanism (not shown) securing the tip  14  to the adapter  12 . The retention mechanisms may utilize aspects of the adapter  12  and tip  14 , such as retention apertures  16  through the sides of the tip  14 , but those skilled in the art will understand that many alternative retention mechanisms may be implemented in the tooth assemblies  10  according to the present disclosure, and the tooth assemblies  10  are not limited to any particular retention mechanism(s). As shown in  FIG. 4 , once attached to the adapter  12 , the tip  14  may extended outwardly from a base edge  18  of the implement  1 ,  6  for initial engagement with work material (not shown). 
     Adapter for Top-Wearing Applications ( FIGS. 5-9 ) 
     An embodiment of the adapter  12  is shown in greater detail in  FIGS. 5-9 . Referring to  FIG. 5 , the adapter  12  may include a rear portion  19  having a top strap  20  and a bottom strap  22 , an intermediate portion  24 , and a nose  26  disposed at the front or forward position of the adapter  12  as indicated by the brackets. The top strap  20  and the bottom strap  22  may define a gap  28  there between as shown in  FIG. 6  for receiving the base edge  18  of the implement  1 ,  6 . The top strap  20  may have a bottom surface  30  that may face and be disposed proximate to a top surface  32  of the base edge  18 , and the bottom strap  22  may have a top surface  34  that may face and engage a bottom surface  36  of the base edge  18 . 
     The adapter  12  may be secured in place on the base edge  18  of the implement  1 ,  6  by attaching the top strap  20  and the bottom strap  22  to the base edge  18  using any connection method or mechanism known to those skilled in the art. In one embodiment, the straps  20 ,  22  and the base edge  18  may have corresponding apertures (not shown) through which fasteners (not shown) such as bolts or rivets may be inserted to hold the adapter  12  in place. Alternatively, the top and bottom straps  20 ,  22  may be welded to the corresponding top and bottom surfaces  32 ,  36  of the base edge  18  so that the adapter  12  and the base edge  18  do not move relative to each other during use. To reduce the impact of the top and bottom surface welds on the strength of the metal of the base edge  18 , the straps  20 ,  22  may be configured with different shapes so as to minimize the overlap of the welds formed on the top surface  32  and bottom surface  36  of the base edge  18 . As seen in  FIGS. 7 and 8 , an outer edge  38  of the top strap  20  may have a different shape than an outer edge  40  of the bottom strap  22  so that the top strap  20  may generally be shorter and wider than the bottom strap  22 . In addition to the strength maintenance benefits, the additional length of the bottom strap  22  may also provide additional wear material at the bottom surface  36  of the base edge  18  of the implement  1 ,  6 . Additionally, the top strap  20  may be thicker than the bottom strap  22  to provide more wear material on the top of the adapter  12  where a greater amount of abrasion may occur in top-wearing applications. 
     Those skilled in the art will understand that other connection configurations for the adapter  12  may be provided as alternatives to the top and bottom straps  20 ,  22  illustrated and described above. For example, the rear portion of the adapter  12  may be provided with a single top strap  20  and no bottom strap  22 , with the top strap  20  being attached to the top surface  32  of the base edge  18 . Conversely, a single bottom strap  22  and no top strap  20  may be provided, with the bottom strap  22  being attached to the bottom surface  36  of the base edge  18 . As a further alternative, a single center strap may be provided on the rear portion of the adapter  12 , with the center strap being inserted into a gap in the base edge  18  of the implement  1 ,  6 . Further alternative adapter attachment configurations will be apparent to those skilled in the art, and are contemplated by the inventor as having use in tooth assemblies in accordance with the present disclosure. 
     Returning to  FIG. 5 , the intermediate portion  24  of the adapter  12  provides a transition between the straps  20 ,  22  and the nose  26  extending outwardly from the front end of the adapter  12 . The nose  26  is configured to be received by a corresponding nose cavity  120  ( FIG. 16 ) of the tip  14  as will be described more fully below. As shown in  FIGS. 5 and 6 , the nose  26  may have a bottom surface  42 , a top surface  44 , opposing side surfaces  46 ,  48 , and a front surface  50 . The bottom surface  42  may be generally planar and inclined upwardly relative to the top surface  34  of the bottom strap  22  and, correspondingly, the bottom surface  36  of the base edge  18 . An angle of incline δ of the bottom surface  42  may be approximately 5° with respect to a substantially longitudinal axis “A” defined by a major base edge-engaging surface of one of the straps  20 ,  22  of the adapter  12 , such as the top surface  34  of the bottom strap  22 , as shown. Depending on the implementation, the angle δ of the bottom surface  42  may be increased by an additional 1°-3° to facilitate the removal of the adapter  12  from a mold or die in which the adapter  12  is fabricated, and the mating of the nose  26  within the nose cavity  120  ( FIG. 16 ) of the tip  14 . 
     The top surface  44  of the nose  26  may be configured to support the tip  14  during use of the implement  1 ,  6 , and to facilitate retention of the tip  14  on the nose  26  when bearing the load of the work material. The top surface  44  may include a first support surface  52  disposed proximate the front surface  50 , an intermediate sloped surface  54  extending rearwardly from the first support surface  52  toward the intermediate portion  24 , and the second support surface  56  located between the intermediate surface  54  and the intersection with the intermediate portion  24  of the adapter  12 . Each of the surfaces  52 ,  54 ,  56  may have a generally planar configuration, but may be oriented at angles with respect to each other. In the illustrated embodiment, the first support surface  52  may be approximately parallel to the bottom surface  42 , and may have a draft angle with respect to the bottom surface  42  to facilitate removal from a mold or die. The second support surface  56  may also be oriented approximately parallel to the bottom surface  42  and the first support surface  52 . Further, relative to the longitudinal axis “A”, the second support surface  56  may be disposed at a higher elevation on the adapter  12  than the first support surface  52 . The intermediate surface  54  extends between a rear edge  52   a  of the first support surface  52  and a forward edge  56   a  of the second support surface  56 , with the distance between the intermediate surface  54  and the bottom surface  42  increasing as the intermediate surface  54  approaches the second support surface  56 . In one embodiment, the intermediate surface  54  may be oriented at an angle α of approximately 30° with respect to the bottom surface  42  of the nose  26 , the first support surface  52 , and the second support surface  56 . The slope of the intermediate surface  54  facilitates insertion of the nose  26  into the nose cavity  120  ( FIG. 16 ) of the tip  14 , while the breadth of the intermediate surface  54  limits the twisting of the tip  14  once the tip  14  is installed on the nose  26 . The first and second support surfaces  52 ,  56  also assist in maintaining the orientation of the tip  14  on the adapter  12  as will be discussed more fully below. 
     The side surfaces  46 ,  48  of the nose  26  may be generally planar and extend upwardly between the bottom surface  42  and the top surface  44 . A pair of projections  58 , one on each of the side surfaces  46 ,  48  (only one shown in  FIG. 6 ), are substantially coaxially oriented along an axis “B”. The axis “B” is approximately perpendicular to the longitudinal axis “A”. The projections  58  function as part of a retention mechanism (not shown) for holding the tip  14  on the nose  26 . The projections  58  may be positioned to align with the corresponding apertures  16  ( FIG. 3 ) of the tip  14 . The side surfaces  46 ,  48  may be approximately parallel or angled inwardly at a longitudinal taper angle “LTA” of approximately 3° with respect to the axis “A” (shown in  FIG. 7  with respect to a line parallel to the axis “A” for clarity) as they extend forward from the intermediate portion  24  toward the front surface  50  the nose  26 , such that the nose  26  is tapered as shown in  FIGS. 7 and 8 . As best seen in the cross-sectional view of  FIG. 9 , the side surfaces  46 ,  48  may be angled so that the distance between the side surfaces  46 ,  48  decreases substantially symmetrically at vertical taper angles “VTA” of approximately 6° with respect to parallel vertical lines “VL” oriented perpendicular to the axes “A” and “B” as the side surfaces  46 ,  48  extend downwardly from the top surface  44  toward the bottom surface  42 . Configured in this way, and as shown in cross-section in  FIG. 9 , the nose  26  may have a substantially keystone-shaped contour  62  defined by the bottom surface  42 , top surface  44  and side surfaces  44 ,  46  wherein the nose  26  has a greater amount of material proximate the top surface  44  than proximate the bottom surface  42 . This contour  62  may be complementary to contours  93 ,  131  ( FIG. 17 ) of the tip  14  which may provide additional wear material at the top of the tooth assembly  10  where a greater amount of abrasion occurs in top-wearing applications, and may reduce drag as the tip  14  is pulled through the work material as discussed further below. 
     The front surface  50  of the nose  26  may be planar as shown in  FIG. 6 , or may include a degree of curvature. As shown in the illustrated embodiment, the front surface  50  may be generally planar, and may be angled away from the intermediate portion  24  as it extends upwardly from the bottom surface  42 . In one embodiment, the front surface  50  may extend forward at an angle γ of approximately 15° with respect to a line  50   a  perpendicular to the bottom surface  42 . With the front surface  50  angled as shown, a reference line  60  extending inwardly approximately perpendicular to the front surface  50  and substantially bisecting the projections  58  would create angles β 1 , β 2 , each measuring approximately 15° between the bottom surface  42  and the reference line  60 , and also between the intermediate surface  54  of the top surface  44  and the reference line  60 . The reference line  60  may also approximately pass through a point of intersection  60   a  of lines  60   b ,  60   c  that are extensions of the bottom surface  42  and intermediate surface  54 , respectively. Using the bottom surface  42  as a base reference, the reference line  60  is oriented at angle β 1  with respect to the bottom surface  42  and bisects the projections  58 , the intermediate surface  54  is oriented at angle β 2  with respect to the reference line  60 , and the front surface  50  is approximately perpendicular to the reference line  60 . In alternate embodiments, the angle β 1  may be approximately 16° to provide approximately 1° of draft angle to facilitate removal from a mold or die during fabrication. Similarly, the angle α may be approximately 29° to provide approximately 1° of draft angle. 
     General Duty Tip for Top-Wearing Applications ( FIGS. 10-17 ) 
     The tip  14  of the tooth assembly  10  is shown in greater detail in  FIGS. 10-17 . Referring to  FIGS. 10 and 11 , the tip  14  may be generally wedge-shaped, and may include a rear edge  70  having a top outer surface  72  extending forward from a top edge  70   a  of the rear edge  70 , and a bottom outer surface  74  extending forward from a bottom edge  70   b  of the rear edge  70 . The top outer surface  72  may be angled downwardly, and the bottom outer surface  74  may extend generally perpendicular to the rear edge  70  such that the top outer surface  72  and the bottom outer surface  74  converge at a front edge  76  at the front of the tip  14 . The top outer surface  72  may present a generally planar surface of the tip  14 , but may have distinct portions that may be slightly angled with respect to each other. Consequently, the top outer surface  72  may include a rear portion  78  extending from the rear edge  70  to a first top transition area  80  at a first downward angle “FDA” of approximately 29° with respect to a line perpendicular to a plane “P” defined by the rear edge  70 , a front portion  82  extending forward from the transition area  80  at a second downward angle “SDA” of approximately 25° with respect to a line perpendicular to the plane “P,”, and a tip portion  84  extending from a second tip transition area  82   a  between the front portion  82  and the tip portion  84  at a third downward angle “TDA” of approximately 27° relative to a line perpendicular to the plane “P”. The generally planar configuration of the top outer surface  72  may allow work material to slide up the top outer surface  72  and toward the base edge  18  of the implement  1 ,  6  when the front edge  76  digs into a pile of work material with less resistance to the forward motion of the implement  1 ,  6  than may be provided if the tooth assembly had a top outer surface with a greater amount of curvature or with one or more recesses redirecting the flow of the work material. 
     The bottom outer surface  74  may also be generally planar but with an intermediate orientation change at a bottom transition area  80   a  on the bottom outer surface  74 . Consequently, a rear portion  86  of the bottom outer surface  74  may extend from the rear edge  70  in approximately perpendicular relation to the plane “P” defined by the rear edge  70  toward the transition area  80   a  until the bottom outer surface  74  transitions to a downward angle at a lower front portion  88 . The front portion  88  may be oriented at an angle θ of approximately 3°-5° with respect to the rear portion  86 , depending on the sizing of the tooth assembly  10 , and may extend to the front edge  76  at an elevation below the rear portion  86  by a distance d 1 . By lowering the front portion  88  of the bottom outer surface  74 , some of the flow and drag relief benefits discussed below that are provided by the substantially keystone-shaped contour of the tip  14  may be realized when the base edge  18  of the implement  1 ,  6  moves the front edge  76  forward through the work material. 
     The tip  14  also includes lateral outer surfaces  90 ,  92  extending between the top outer surface  72  and the bottom outer surface  74  on either side of the tip  14 . Each of the lateral outer surfaces  90 ,  92  may have a corresponding one of the retention apertures  16  extending therethrough in a location between the rear portions  78 ,  86 . As best seen in the bottom view of  FIG. 13  the front view of  FIG. 14 , and the cross-sectional view of  FIG. 15 , the lateral outer surfaces  90 ,  92  may be angled so that the distance between the lateral outer surfaces  90 ,  92  decreases as the lateral outer surfaces  90 ,  92  extend downwardly from the top outer surface  72  toward the bottom outer surface  74 . Configured in this way, the tip  14  may have a substantially keystone-shaped contour  93  in substantial correspondence to the substantially keystone-shaped contour  62  described above for the nose  26 . 
     The tip  14  is provided with a greater amount of wear material proximate the top outer surface  72  where a greater amount of abrasion may occur, and a lesser amount of wear material proximate the bottom outer surface  74  where less abrasion may occur in top-wearing applications. In this configuration, the amount of wear material, and correspondingly the weight and cost of the tip  14 , may be reduced or at least be more efficiently distributed, without reducing the useful life of the tooth assembly  10 . The tapering of the lateral outer surfaces  90 ,  92  from top to bottom to produce the substantially keystone-shaped contour  93  of the tip  14  may reduce the amount of drag experienced by the tip  14  as it is pulled through the work material. As the top outer surface  74  is pulled through the work material, the work material flows over the top outer surface  74  outwardly and around the tip  14  as indicated by the arrows “FL” in  FIG. 15 , with less engagement of the lateral outer surfaces  90 ,  92  than if the lateral outer surfaces  90 ,  92  were parallel and maintained a constant width as they extend downwardly from the top outer surface  74 . 
       FIGS. 12-15  further illustrate that the tip  14  may be configured to taper as the lateral outer surfaces  90 ,  92  extend from the rear edge  70  toward the front edge  76 , with the lateral outer surfaces having an intermediate change in the taper of the lateral outer surfaces  90 ,  92 . The lateral outer surfaces  90 ,  92  may have rear portions  94 ,  96  extending forward from the rear edge  70  toward the front edge  76  and oriented such that the distance between the rear portions  94 ,  96  decreases as the rear portions  94 ,  96  approach a side transition area  97  with a side taper angle “STA” of approximately 3° with respect to a line perpendicular to the plane “P”. It should be noted that the side taper angle “STA” is approximately equal to the longitudinal taper angle “LTA” of the nose  26  of the adapter  12 . Beyond the transition area  80 , the lateral outer surfaces  90 ,  92  transition to front portions  98 ,  100  that that may be approximately parallel or converge at a shallower angle relative to a major longitudinal axis “D” defined by the tip  14  as the front portions  98 ,  100  progress forward to the front edge  76 . The reduction in the tapering of the front portions  98 ,  100  of the lateral outer surfaces  90 ,  92  behind the front edge  76  may preserve wear material proximate the front edge  76  the front of the tip  14  where the amount of abrasion experienced by the tip  14  is greater than at the area proximate the rear edge  70  of the tip  14 . 
     As shown in  FIG. 13 , the front portion  88  of the bottom outer surface  74  may include a relief  102 . The relief  102  may extend upwardly from the bottom outer surface  74  into the body of the tip  14  to define a pocket “P” in the tip  14 . The cross-sectional view of  FIG. 16  illustrates the geometric configuration of one embodiment of the relief  102 . The relief  102  may include an upward curved portion  104  extending upwardly into the body of the tip  14  proximate the front edge  76 . Looking at the relief  102  as it extends from proximate the front edge  76  toward the rear edge  70 , as the curved portion  104  of the relief  102  extends upwardly, the relief  102  transitions into a tapered portion  106 . The tapered portion  106  may extend downward as it extends rearward toward the rear edge  70 , and ultimately terminate at the transition area  80  and the rear portion  86  of the bottom outer surface  74 . The illustrated configuration of the relief  102  reduces the weight of the tip  14 , reduces resistance of the movement of the tip  14  through the work material, and provides a self-sharpening feature to the tip  14  as will be described more fully below. However, alternative configurations for the relief  102  that would provide benefits to the tip  14  will be apparent to those skilled in the art and are contemplated by the inventors as being within the scope of tooth assemblies  10  that are in accordance with the present disclosure. 
     The tip  14  may be configured to be received onto the nose  26  of the adapter  12 . In the rear view of the tip  14  in  FIG. 17 , a nose cavity  120  may be defined within the tip  14 . The nose cavity  120  may have a complementary configuration relative to the nose  26  of the adapter  12 , and may include a bottom inner surface  122 , a top inner surface  124 , a pair of opposing side inner surfaces  126 ,  128 , and a front inner surface  130 . As seen from behind, the nose cavity  120  may have a substantially keystone-shaped contour  131  in a manner complementary to the contour  93  of the exterior of the tip  14  and the contour  62  of the nose  26  of the adapter  12 . The distances between the top outer surface  72  and top inner surface  124 , and between the bottom outer surface  74  and bottom inner surface  122 , may be constant in the lateral direction across the tip  14 . The side inner surfaces  126 ,  128  may be angled inwardly so that the distance between the side inner surfaces  126 ,  128  decreases as the side inner surfaces  126 ,  128  extend downwardly from the top inner surface  124  toward the bottom inner surface  122 . Oriented in this way, the side inner surfaces  126 ,  128  mirror the lateral outer surfaces  90 ,  92  and a constant thickness is maintained between the side inner surfaces  126 ,  128  of the nose cavity  120  and the lateral outer surfaces  90 ,  92 , respectively, on the exterior of the tip  14 .  FIG. 17  further illustrates that the nose cavity  120  may include recesses  140  in the side inner surfaces  126 ,  128  that may be configured to receive the projections  58  of the nose  26  of the adapter  12  when the nose  26  is inserted into nose cavity  120 . Once received, the retention mechanism (not shown) of the tooth assembly  10  may engage the projections  58  to secure the tip  14  on the adapter  12 . 
     The cross-sectional view of  FIG. 16  illustrates the correspondence between the nose cavity  120  of the tip  14  and the nose  26  of the adapter  12  as shown in  FIG. 6 . The bottom inner surface  122  may be generally planar and approximately perpendicular to the rear edge  70 . The bottom inner surface  122  may also be generally parallel to the rear portion  86  of the bottom outer surface  74 . If the bottom surface  42  of the adapter  12  has an upward draft angle, the bottom inner surface  122  of the tip  14  may have a corresponding upward slope to match the draft angle. 
     The top inner surface  124  may be shaped to mate with the top surface  44  of the nose  26 , and may include a first support portion  132 , a sloped intermediate portion  134 , and a second support portion  136 . The first and second support portions  132 ,  136  may be generally planar and approximately parallel to the bottom inner surface  122 , but may have a slight downward slope corresponding to the orientation that may be provided in the first and second support surfaces  52 ,  56  of the top surface  44  of the nose  26  to facilitate removal from a mold or die. The intermediate portion  134  of the top inner surface  124  may extend between a rear edge  132   a  of the first support portion  132  and a forward edge  136   a  of the second support portion  136 , with the distance between the intermediate portion  134  and the bottom inner surface  122  increasing in a similar manner as between the intermediate surface  54  and the bottom surface  42  of the nose  26  of the adapter  12 . Consistent with the relationship between the bottom surface  42  and intermediate surface  54  of the nose  26  of the adapter  12 , the intermediate portion  134  of the nose cavity  120  of the tip  12  may be oriented at an angle α of approximately 30° with respect to the bottom inner surface  122  and the first and second support portions  132 ,  136 . 
     The front inner surface  130  of the nose cavity  120  has a shape corresponding to the front surface  50  of the nose  26 , and may be planar as shown or have the necessary shape to be complementary to the shape of the front surface  50 . As shown in  FIG. 16 , the front inner surface  130  may be angled toward the front edge  76  at an angle γ of approximately 15° with respect to a line  130   a  perpendicular to the bottom inner surface  122 . A reference line  138  may extend inwardly substantially perpendicular to the front inner surface  130  and substantially bisect the retention aperture  16 . To match the shape of the nose  26 , the reference line  138  may be oriented at an angle β 1  of approximately 15° with respect to the bottom inner surface  122  of the nose cavity  120 , and at an angle β 2  of approximately 15° with respect to the intermediate portion  134  of the top inner surface  124 . The shapes of the nose  26  and nose cavity  120  are exemplary of one embodiment of the tooth assembly  10  in accordance with the present disclosure. Those skilled in the art will understand that variations in the relative angles and distances between the various surfaces of the nose  26  and nose cavity  120  may be varied from the illustrated embodiment while still producing a nose and nose cavity having complementary shapes, and such variations are contemplated by the inventors as having use in tooth assemblies  10  in accordance with the present disclosure. 
     Penetration Tip for Top-Wearing Applications ( FIGS. 18-22 ) 
     Where the tooth assemblies  10  are being used in rocky environments where a greater ability to penetrate the work material may be required, it may facilitate excavation by providing a tip having a sharper penetration end for breaking up the work material. Referring to  FIGS. 18-22 , a penetration tip  150  is illustrated wherein surfaces and other elements of the tip  150  that are similar or correspond to elements of the tip  14  are identified by the same reference numerals, and may include a rear edge  70 , a top outer surface  72  and a bottom outer surface  74 , with the top outer surface  72  and bottom outer surface  74  extending forward from the rear edge  70  and converging to a front edge  76 . Lateral outer surfaces  90 ,  92  may include retention apertures  16  as described above. The top outer surface  74  may have a rear portion  78  and a front portion  82 , and the bottom outer surface  76  having a rear portion  86  and a front portion  88 . As with the tip  14 , the rear portion  86  of the bottom outer surface  74  may be approximately perpendicular to the rear edge  70  and approximately parallel to the bottom inner surface  122  of the nose cavity  120  ( FIGS. 21 and 22 ). The front portion  88  may be oriented at angle θ in the range of 8°-10°, and may be approximately 9°, with respect to the rear portion  86 , depending on the sizing of the tooth assembly  10 , and may extend to the front edge  76  at an elevation below the rear portion  86  by a distance d 2 . The sizing of the tip assembly  10  may also determine whether the tip outer surface  72  includes a hook  152  extending therefrom that may be used to lift and position the tip  150  during installation. 
     The rear portions  78 ,  86  may extend forward from the rear edge  70  with the rear portions  94 ,  96  of the lateral outer surfaces  90 ,  92  being tapered and converging as the lateral outer surfaces  90 ,  92  extend from the rear edge  70  at the side taper angle “STA” of approximately 3°. As the rear portions  78 ,  86  approach the front edge  76 , the top and bottom outer surfaces  72 ,  74  may transition into the front portions  82 ,  88 . The lateral outer surfaces  90 ,  92  may transition into the front portions  98 ,  100  that may initially be approximately parallel and then further transition as the front portions  98 ,  100  approach the front edge  76  to having a greater taper at a penetration taper angle “PTA” of approximately 20° with respect to a line perpendicular to the plane “P” to converge at a greater rate than the convergence within the rear portions  94 ,  96 . Consequently, the front edge  76  may be narrower in relation to the general width of the penetration tip  150  as best seen in  FIG. 19  than in the embodiment of the tip  14  as shown in  FIG. 12 . The narrow front edge  76  of the tip  150  may provide a smaller surface area for engaging the rocky work material, but increase the force per unit of contact area applied to the rocky work material by the series of tooth assemblies  10  attached at the base edge  18  of the implement  1 ,  6  to break up the rocky work material. 
     In addition to narrowing the width of the front edge  76  of the tip  150 , the ability of the tip  150  to penetrate rocky work material as wear material wears away from the tip  150  over time may be further enhanced by reducing the overall vertical thickness of the tip  150 . In the illustrated embodiment, reliefs  154 ,  156  may be provided on either side of the front portion  82  of the top outer surface  72 , and reliefs  158 ,  160  may be provided on either side of the front portion  88  of the bottom outer surface  74 . The reliefs  154 ,  156 ,  158 ,  160  may extend rearwardly from the front edge  76  and tip portion  84 . As wear material wears away from the front  76  of the tip  150  toward the rear edge  70  of the tip  14  over time, a thickness T of the remaining work material-engaging surface of the tip  150  may initially increase as the material of the tip portion  84  wears away. When the wear material wears away and the work material-engaging surface reaches the reliefs  154 , the thickness T may remain relatively constant with the exception of the areas of the front portions  82 ,  88  between the reliefs  154 ,  156 ,  158 ,  160  where the thickness will gradually increase as the wear material continues to wear away in the direction of the rear portions  78 ,  86 . 
     Adapter for Bottom-Wearing Applications ( FIGS. 23-25 ) 
     As mentioned above, bottom-wearing applications may involve differing operating conditions than top-wearing applications and, consequently, may present differing design requirements for the adapters and tips of tooth assemblies that may result in more efficient digging and loading of the work material. For example, it may be desirable to align bottom surfaces of bottom-wearing tips parallel to the ground and parallel to the bottom surface of the implement  1  to facilitate moving along the ground to collect work material, whereas it may be desirable for top-wearing tips as described above to more closely extend the shape of the implement  6  to facilitate scooping work material into the bucket  7  of the implement  6 . The differing design requirements may lead to differences in the designs of both the adapters and the tips of the tooth assemblies. 
       FIGS. 23-25  illustrate an embodiment of an adapter  170  of tooth assembly  10  in accordance with the present disclosure that may have particular use on an implement  1  for a bottom-wearing application as well as other types of ground engaging implements  1 ,  6  having base edges  18 . The surfaces and other elements of the adapter  170  that are similar or correspond to elements of the adapter  12  as described above are identified by the same reference numerals. Referring to  FIGS. 23 and 25 , the adapter  170  may include a top strap  20 , a bottom strap  22 , an intermediate portion  24 , and a nose  26 , with the top strap  20  and the bottom strap  22  defining a gap  28  therebetween for receiving the base edge  18  of the implement  1 ,  6 . The top strap  20  may have a bottom surface  30  that may face and be disposed proximate to a top surface  32  of the base edge  18 , and the bottom strap  22  may have a top surface  34  that may face and engage a bottom surface  36  of the base edge  18 . Depending on the size of the application and, correspondingly, the tooth assembly  10 , the adapter  170  may include a hook  172  extending upwardly from the top strap  20  for attachment of a lifting device (not shown) that may be used to lift and position the adapter  170  on the base edge  18  during installation. The adapter  12  as described above may similarly be provided with hook  172  if necessary in larger applications. 
     The straps  20 ,  22  of the adapter  170  may be configured similar to the adapter  12  with different shapes so as to minimize the overlap of the welds formed on the top surface  32  and bottom surface  36  of the base edge  18 . In bottom-wearing applications, though, it may be desirable to make the top strap  20  longer than the bottom strap  22 , and to make the bottom strap  22  thicker than the top strap  20  to provide additional wear material on the bottom of the adapter  170  where additional abrasion may occur as the adapter scrapes along the ground in bottom-wearing applications. 
     The nose  26  may also have the same general configuration as the nose  26  of the adapter  12  and be configured to be received by corresponding nose cavities  120  of tips that will be described more fully below. The nose  26  may have a bottom surface  42 , a top surface  44 , opposing side surfaces  46 ,  48 , and a front surface  50 , with the top surface  44  having first and second support surfaces  52 ,  56  and intermediate surface  54  extending therebetween. The side surfaces  46 ,  48  of the nose  26  may be generally planar and extend vertically between the bottom surface  42  and the top surface  44  as best seen in  FIG. 25 , and may be approximately parallel or angled inwardly as they extend from the intermediate portion  24  so that the nose  26  is tapered from rear to front. The side surfaces  46 ,  48  may be angled so that the distance between the side surfaces  46 ,  48  decreases as the side surfaces  46 ,  48  extend downwardly from the top surface  44  toward the bottom surface  42  due to the vertical taper angle “VTA” to define a substantially keystone-shaped contour  174  similar to those described above. The substantially keystone-shaped contour  174  of the adapter  170  may be complementary to the contours of the tips described below. 
     Relative to the nose  26  of the adapter  12  for top-wearing applications, the nose  26  of the adapter  170  may be oriented downwardly with respect to the straps  20 ,  22  to make the angle δ (top-wearing version shown in  FIG. 4 ) approximately 0°. At this orientation, the bottom surface  42  may be generally planar and approximately parallel to the top surface  34  of the bottom strap  22  and, correspondingly, the bottom surface  36  of the implement  1 ,  6 . Further, relative to the substantially longitudinal axis “A,” the bottom surface  42  may be disposed lower on the adapter  12  than the top surface  34  of the bottom strap  22 . The remaining relative positioning of the surfaces of the adapter  12  may be maintained. Consequently, using the bottom surface  42  as a base reference, the reference line  60  is oriented at angle β 1  with respect to the bottom surface  42  and bisects the projections  58 , the intermediate surface is oriented at angle β 2  with respect to the reference line  60 , and the front surface  50  is approximately perpendicular to the reference line  60 . The angles β 1 , β 2  may each be approximately 15°, the intermediate surface  54  may be oriented at an angle α of approximately 30° with respect to the bottom surface  42  of the nose  26 , the top surface  34  of the bottom strap  22 , and the first and second support surfaces  52 ,  56 , and the front surface  50  may extend forward at an angle γ of approximately 15° with respect to a line  50   a  perpendicular to the bottom surface  42  or top surface  34  of the bottom strap  22 . The orientation of the nose  26  of the adapter  12  with respect to the straps  20 ,  22  coupled with the configurations of the tips described below may align the bottom outer surfaces of the tips approximately parallel to the bottom of the implement  1 ,  6  and the ground in order to enable the overall bottom of the tooth assembly  10  to slide along the surface of the ground and into the work material to load the implement  1 ,  6 . 
     General Duty Tip for Bottom-Wearing Applications ( FIGS. 26-30 ) 
     In addition to the adapter  170 , tips of the tooth assembly  10  may be configured for improved performance in bottom-wearing applications. One example of a general duty tip  180  for use with the adapter  170  is shown in greater detail in  FIGS. 26-30  where similar surfaces and components as previously discussed with respect to tip  14  are identified by the same reference numerals. Referring to  FIGS. 26 and 27 , the tip  180  may be generally wedge-shaped with top and bottom outer surfaces  72 ,  74  extending forward from a top and bottom edges  70   a ,  70   b , respectively, of the rear edge  70  and converging at front edge  76 . The top outer surface  72  may be angled downwardly similar to the tip  14 , and the rear portion  78  may have a first downward angle “FDA” of approximately 29°, the front portion  82  may have a second downward angle “SDA” of approximately 25°, and the tip portion  84  may have a third downward angle “TDA” of approximately 27°. The generally planar configuration of the top outer surface  72  may allow the work material to slide up the top outer surface  72  and into the bucket (not shown) of the machine (not shown) when the front edge  76  digs into a pile of work material. As best seen in  FIG. 28 , the lateral outer surfaces  90 ,  92  may be angled so that the distance between the lateral outer surfaces  90 ,  92  decreases as the lateral outer surfaces  90 ,  92  extend downwardly from the top outer surface  72  toward the bottom outer surface  74  at vertical taper angles “VTA” of approximately 3° to define a substantially keystone-shaped contour  188  complimentary to the contour  174  described above for the nose  26  of the adapter  170   
     The bottom outer surface  74  may also be generally planar but with an intermediate elevation change at transition area  80   a . The rear portion  86  of the bottom outer surface  74  may extend forward approximately perpendicular to the rear edge  70  to the transition area  80  where the bottom outer surface  74  transitions to lower front portion  88 . Front portion  88  may also be oriented approximately perpendicular to the rear edge  70 , and may extend to the front edge  76  at an elevation below the rear portion  86  by a distance d 3 . When the tooth assembly  10  of an implement  1 ,  6  digs into the work material, a majority of the abrasion between the tip  180  and the work material occurs at the front edge  76 , tip portion  84  of the top outer surface, and the front portion  88  of the bottom outer surface  74  of the tip  14 . By lowering the front portion  88  of the bottom outer surface  74 , additional wear material is provided at the high abrasion area to extend the useful life of the tooth assembly  10 . 
     The top outer surface  72  of the tip  180  may include a relief  182  extending across the front portion  82  and adjacent parts of the rear portion  78  and tip portion  84 . As seen in  FIGS. 28-30 , the relief  182  may extend downwardly from the top outer surface  72  into the body of the tip  180  to define a pocket in the tip  180 . The cross-sectional view of  FIG. 30  illustrates the geometric configuration of one embodiment of the relief  182 . The relief  182  may include a downward curved portion  184  extending downwardly into the body of the tip  180  proximate the tip portion  84  and the front edge  76 . As the curved portion  184  extends downwardly, the relief  182  may turn rearward toward the rear edge  70  and transition into a rearward tapered portion  186 . The tapered portion  186  may extend upward as it extends rearward toward the rear edge  70 , and ultimately intersect with the transition area  80  and the rear portion  78  of the top outer surface  72 . The illustrated configuration of the relief  182  reduces the weight of the tip  180 , reduces resistance of the movement of the tip  180  through the work material, and provides a self-sharpening feature to the tip  180  as will be described more fully below. However, alternative configurations for the relief  182  providing benefits to the tip  180  will be apparent to those skilled in the art and are contemplated by the inventors as having use in tooth assemblies  10  in accordance with the present disclosure. 
     The tip  180  may be configured to be received onto the nose  26  of the adapter  170  by providing the nose cavity  120  with a complementary configuration relative to the nose  26  of the adapter  170  similar to the nose cavity  120  of the tip  14 , including a keystone-shaped contour that is complementary to the contour of the exterior of the adapter  170 . The cross-sectional view of  FIG. 30  illustrates the correspondence between the nose cavity  120  of the tip  180  and the nose  26  of the adapter  170 . The bottom inner surface  122  may be generally planar and approximately perpendicular to the rear edge  70 , and may also be generally parallel to the rear portion  86  and front portion  88  of the bottom outer surface  74  to orient the bottom outer surface  74  approximately parallel to the base edge  18  of the implement  1 ,  6  when the tip  180  is assembled on the adapter  170 . In other respects, the top inner surface  124 , side inner surfaces  126 ,  128  and front inner surface  130  may have complementary shapes to the corresponding surfaces of the nose  26  so that the surfaces face and engage when the tip  180  is assembled on the adapter  170 . 
     Abrasion Tip for Bottom-Wearing Applications ( FIGS. 31-36 ) 
     Depending on the particular earth moving environment in which the tooth assemblies  10  are being used, the tip  180  of the tooth assembly  10  as illustrated and described above with respect to  FIGS. 26-30  may be modified as necessary. For example, where the machine may be operating on work materials that are highly abrasive and may wear down tips at a much greater rate, it may be desirable to provide more wear material at the front and on the bottom of the tip.  FIGS. 31-36  illustrate one embodiment of a tip  190  having use in loading abrasive work materials. The tip  190  may have the same general wedge-shaped configuration as discussed above for the tip  180  with the top and bottom outer surfaces  72 ,  74  extending forward from the rear edge  70  and converging to the front edge  76  as shown in  FIGS. 31 and 32 . To reduce weight in lower wear areas and to provide a measure of self-sharpening performance, the front portion  82  of the tip outer surface  72  may be provided with reliefs  192 ,  194  on either side ( FIGS. 33 and 34 ). The reliefs  192 ,  194  may extend rearwardly proximate the tip portion  84 . As wear material wears away from the front of the tip  190  over time, the height of the material-engaging surface of the tip  150  proximate the outer edges of the front portion  82  of the top outer surface  72  may remain relatively constant. To further reduce the weight of the tip  190 , a further relief  196  may be provided in the bottom outer surface  74 . The relief  196  may extend upwardly into the body of the tip  190 , and may be disposed further rearward than the top reliefs  192 ,  194  so as not to remove too much wear material from the high abrasion areas at the proximate the front edge  76 . 
     To compensate for the greater abrasion experienced by the tip  190 , the bottom outer surface  74  may be widened to provide additional wear material. As best seen in  FIGS. 33 and 35 , the upper portion of the tip  190  has a similar keystone-shaped contour as the tips discussed above that is complimentary to the contour of the adapter nose  26 . Proximate the intersection of the lateral outer surfaces  90 ,  92  with the bottom outer surface  74 , side flanges  198 ,  200  extend laterally from the lateral outer surfaces  90 ,  92 , respectively, to widen the bottom outer surface  74 . The side flanges  198 ,  200  may extend the entire length of the tip  190  from the rear edge  70  to the front edge  76 . Top flange surfaces  202 ,  204  may extend forward approximately perpendicular to the rear edge  70  of the tip  190 , and the bottom outer surface  74  is also a bottom flange surface, and may be angled downwardly relative to the top flange surfaces  202 ,  204  at the angle θ in the range of 1°-3°, and may be approximately 2°. More specifically, the angle θ is between the bottom outer surface  74  and a line approximately perpendicular to the rear edge  70  and approximately parallel to the top flange surfaces  202 ,  204  as shown in  FIGS. 32 and 35 . With this configuration, the distance between the bottom outer surface  74  and the top flange surfaces  202 ,  204  may increase as the side flanges  198 ,  200  extend forward from the rear edge  70  toward the front edge  76  until the top flange surfaces  202 ,  204  intersect the tip portion  84  of the top outer surface  72 , which in turn is converging with the bottom outer surface  74  toward the front edge  76 . With this arrangement, the side flanges  198 ,  200  provide additional wear material at the front and bottom of the tip  190  where maximum abrasion may occur. With further reference to  FIG. 36 , the nose cavity  120  as illustrated is similar in configuration to the nose cavities  120  as described above and complimentary to the nose  26  of the adapter  170 , with the bottom inner surface  122  being approximately perpendicular to the rear edge  70 . 
     Penetration Tip for Bottom-Wearing Applications ( FIGS. 37-41 ) 
     Where the tooth assemblies  10  are being used in rocky environments where a greater ability to penetrate the work material may be required, it may be required to provide the tip having a sharper penetration end for breaking up the work material. Referring to  FIGS. 37-41 , a penetration tip  210  is illustrated with the top outer surface  72  and bottom outer surface  74  extending forward from the rear edge  70  and converging to the front edge  76 . The top outer surface  72  may include reliefs  212 ,  214  on either side of the front portion  82  similar to the reliefs  192 ,  194  described above. The rear portion  78  of the top outer surface  72  may extend forward from the rear edge  70  with the lateral outer surfaces  90 ,  92  being approximately parallel or slightly tapered at a side taper angle “STA” of approximately 3° to match the taper of the nose  26  of the adapter  170  and converging as the lateral outer surfaces  90 ,  92  extend from the rear edge  70 . As the rear portion  78  approaches the front edge  76 , the top outer surface  72  may transition into the front portion  82 . The lateral outer surfaces  90 ,  92  having a greater taper such that the lateral outer surfaces  90 ,  92  may transition into the front portions  98 ,  100  that may initially be approximately parallel of have an intermediate taper angle “ITA” of approximately 0.8° and then further transition as the front portions  98 ,  100  approach the front edge  76  to have a greater taper at a penetration taper angle “PTA” of approximately 10° with respect to a line perpendicular to the plane “P” to converge at a greater rate than the convergence within the rear portion  78 . Consequently, the front edge  76  may be narrower in relation to the general width of the penetration tip  210  than in the other embodiments of the tip  180 ,  190 . The narrow front edge  76  may provide a smaller surface area for engaging the rocky work material, but increase the force per unit of contact area applied to the rocky work material by the series of tooth assemblies  10  attached at the base edge  18  of the implement  1 ,  6  to break up the rocky work material. 
     While wear material may be removed from the penetration tip  210  by narrowing the front edge  76 , additional wear material still may be provided to the bottom outer surface  74  by angling the bottom outer surface  74  downwardly as it extends from the rear edge  70  as shown in  FIGS. 40 and 41 . The nose cavity  120  has the configuration described above with the bottom inner surface  122  extending approximately perpendicular to the rear edge  70  of the tip  210 . The bottom outer surface  74  may be angled downwardly relative to a line approximately parallel to the bottom inner surface  122  and approximately perpendicular to the rear edge  70  at angle θ that is in the range of 6°-8°, and may be approximately 7°. 
     Unitary Tooth for Top-Wearing Applications ( FIGS. 42-45 ) 
     The tooth assemblies discussed above are each comprised of an adapter and a tip attached thereto. In some applications, it may be desirable to attach a unitary component to the implement  1 ,  6  to, for example, eliminate the risk of failure of the retention mechanism attaching a tip to an adapter nose. To accommodate such implementations, the various combinations of adapters and tips set forth above may be configured as unitary components providing operational benefits described herein. As an example,  FIGS. 42-45  illustrate an integrally formed unitary general duty tooth  270  for top-wearing applications having characteristics of the adapter  12  and the tip  14 . The tooth  270  may include rear top and bottom straps  272 ,  274 , respectively, and a front tip portion  276  connected by an intermediate portion  278 . The tip portion  276  may include a top outer surface  280  and a bottom outer surface  282  extending forward from the intermediate portion  278  and converging at a front edge  284 . The top and bottom outer surfaces  280 ,  282  may have generally the same geometries as the top and bottom outer surfaces  72 ,  74 , respectively, of the tip  14 , and the bottom outer surface  282  may include a relief (not shown). The tip portion  276  may further include oppositely disposed lateral outer surfaces  286 ,  288  extending between the top outer surface  280  and the bottom outer surface  282 . 
     As best seen in  FIG. 43 , the lateral outer surfaces  286 ,  288  may be angled so that the distance between the lateral outer surfaces  286 ,  288  increases as the lateral outer surfaces  286 ,  288  extend vertically from the bottom outer surface  282  toward the top outer surface  280 . Configured in this way, the tip portion  276  may have a similar keystone-shaped contour as the tip  14  to provide a greater amount of wear material proximate the top surface  280  than proximate the bottom surface  282  where a greater amount of abrasion and wear occur in top-wearing applications. Due to the geometric similarities, the tip portion  276  may have wear material wear away over time in a similar manner as the tip  14  as illustrated in  FIGS. 63-70  and described in the accompanying text. 
     In order for the tooth  270  to be replaceable, the tooth  270  may be bolted or similarly demountably fastened to the base edge  18  of the implement  1 ,  6  instead of being welded to the surface. The straps  272 ,  274  may be configured for such attachment to the base edge  18  by providing apertures  290 ,  292  through the straps  272 ,  274 , respectively, as seen in  FIGS. 42, 44 and 45 . During assembly, the apertures  290 ,  292  may be aligned with corresponding apertures of the base edge  18 , and appropriate connection hardware may be inserted to retain the tooth  270  on the base edge  18  of the implement  1 ,  6 . After the tip portion  276  wears down to the point of requiring replacement, the connection hardware may be disconnected and the remains of the tooth  270  may be removed and replaced by a new tooth  270 . 
     Unitary Tooth for Bottom-Wearing Applications ( FIGS. 46-49 ) 
     It may also be desirable in bottom-wearing implementations, such as loader buckets, to attach a unitary component to the base edge  18  of the implement  1 ,  6 .  FIGS. 46-49  illustrate an integrally formed unitary general duty tooth  300  for bottom-wearing applications having characteristics of the adapter  170  and general duty tip  180 . The tooth  300  may include rear top and bottom straps  302 ,  304 , respectively, and a front tip portion  306  connected by an intermediate portion  308 . The tip portion  306  may include a top outer surface  310  and a bottom outer surface  312  extending forward from the intermediate portion  308  and converging at a front edge  314 . The top and bottom outer surfaces  310 ,  312  may have generally the same geometries as the top and bottom outer surfaces  72 ,  74 , respectively, of the tip  180 , and the top outer surface  312  may include a relief  316 . The tip portion  306  may further include oppositely disposed lateral outer surfaces  318 ,  320  extending between the top outer surface  310  and the bottom outer surface  312 . As best seen in  FIG. 47 , the lateral outer surfaces  318 ,  320  may be angled so that the distance between the lateral outer surfaces  318 ,  320  increases as the lateral outer surfaces  318 ,  320  extend vertically from the bottom outer surface  312  toward the top outer surface  310 . Due to the geometric similarities, the tip portion  306  may have wear material wear away over time in a similar manner as the tip  180  as illustrated in  FIGS. 70-75  and described in the accompanying text. 
     In order for the tooth  300  to be replaceable, the tooth  300  may be bolted or similarly demountably fastened to the base edge  18  of the implement  1 ,  6  instead of being welded to the surface. The straps  302 ,  304  may be configured for such attachment to the base edge  18  by providing apertures  322 ,  324  through the straps  302 ,  304 , respectively, as seen in  FIGS. 46, 48 and 49 . During assembly, the apertures  322 ,  324  may be aligned with corresponding apertures of the base edge  18 , and appropriate connection hardware may be inserted to retain the tooth  300  on the base edge  18  of the implement  1 ,  6 . After the tip portion  306  wears down to the point of requiring replacement, the connection hardware may be disconnected and the remains of the tooth  300  may be removed and replaced by a new tooth  300 . 
     INDUSTRIAL APPLICABILITY 
     Tooth assemblies  10  in accordance with the present disclosure incorporate features that may extend the useful life of the tooth assemblies  10  and improve the efficiency of the tooth assemblies  10  in penetrating into the work material. As discussed above, the substantially keystone-shaped contour  93  of the tip  14 , for example, places a greater amount of wear material towards the top of the tip  14  where a greater amount of abrasion occurs in top-wearing applications. At the same time, wear material is removed from the lower portion of the tip  14  where less abrasion occurs, thereby reducing the weight and the cost of the tip  14 , though in some implementations the top strap  20  may need to be thicker than dictated by abrasion to provide sufficient strength and help prevent breakage due to the loading forces. In bottom-wearing applications, the tips  180 ,  190 ,  210  may be provided with additional wear material proximate the bottom of the tips  180 ,  190 ,  210  where a greater amount of wear occurs as the tips  180 ,  190 ,  210  scrape along the ground. 
     The design of the tooth assemblies  10  in accordance with the present disclosure may also reduce the stresses applied to the projections  58  and the retention mechanism connecting the tips  14 ,  150 ,  180 ,  190 ,  210  to the adapters  12 ,  170 . Using the adapter  12  and tip  14  for illustration in  FIGS. 51 and 52 , based on the machining tolerances required in the retention apertures  16 , the projections  58  and the corresponding components of a retention mechanism (not shown), the tip  14  may experience movement relative to the adapter  12 , and in particular to the nose  26 , during use of the machine. The relative movement may cause shear stresses in the components of the retention mechanism as the adapter  12  and tip  14  move in opposite directions. In prior tooth assemblies where a nose of an adapter may have a triangular shape in cross-section, or may have a more rounded shape than the substantially keystone-shaped contour  62  of the nose  26 , facing surfaces of the nose of the adapter and the nose cavity of the tip may separate and allow the tip to rotate about a longitudinal axis of the tooth assembly relative to the adapter. The twisting of the tip may cause additional shear stresses on the components of the retention mechanism. 
     In contrast, in the tooth assemblies  10  in accordance with the present disclosure, the support surfaces  52 ,  56  of the adapter nose  26  may be engaged by the corresponding support portions  132 ,  136  that define the nose cavity  120 . As shown in the cross-sectional view of  FIG. 50 , when the tip  14  is installed on the adapter nose  26  and disposed at a maximum engagement position, the planar surfaces of the nose  26  are engaged by the corresponding planar portions of the surfaces that define the nose cavity  120  of the tip  14 . Consequently, the bottom surface  42  of the adapter  12  may face and engage the bottom inner surface  122  of the tip  14 , the support surfaces  52 ,  54 ,  56  of the top surface  44  of the adapter  12  may face and engage the corresponding portions  132 ,  134 ,  136  of the top inner surface  124  of the tip  14  and the front surface  50  of the adapter  12  may face and engage the front inner surface  130  of the tip  14 . Though not shown, the side surfaces  46 ,  48  of the nose  26  of the adapter  12  may face and engage the side inner surfaces  126 ,  128 , respectively, of the nose cavity  120  of the tip  14 . With the surfaces engaging, the tip  14  may remain relatively stationary with respect to the nose  26  of the adapter  12 . 
     Due to the tolerances within the retention mechanism, the tip  14  may be able to slide forward on the nose  26  of the adapter  12  is illustrated in  FIG. 51 . As the tip  14  slides forward, some of the facing surfaces of the nose  26  of the adapter  12  and the nose cavity  120  of the tip  14  may separate and disengage. For example, the intermediate portion  134  of the top inner surface  124  of the tip  14  may disengage from the intermediate surface  54  of the nose  26  of the adapter  12 , and the front inner surface  130  of the tip  14  may disengage from the front surface  50  of the adapter  12 . Because the distance between the side surfaces  46 ,  48  of the nose  26  of the adapter  12  may narrow as the nose  26  extends outward from the intermediate portion  24  of the adapter  12  as shown in  FIGS. 7 and 8 , the side inner surfaces  126 ,  128  of the tip  14  may separate from the side surfaces  46 ,  48 , respectively. Despite the separation of some surfaces, engagement between the nose  26  of the adapter  12  and nose cavity  120  of the tip  14  may be maintained over the range of movement of the tip  14  caused by the tolerances within the retention mechanism. As discussed previously, the bottom surface  42  and support surfaces  52 ,  56  of the nose  26  of the adapter  12 , and the bottom inner surface  122  and support portions  132 ,  136  of the top inner surface  124  of the tip  14 , may be generally parallel. Consequently, the tip  14  may have a direction of motion substantially parallel to, for example, the bottom surface  42  of the nose  26  of the adapter  12 , with the bottom surface  42  maintaining contact with the bottom inner surface  122  of the nose cavity  120  of the tip  14 , and the support portions  132 ,  136  of the top inner surface  124  of the tip  14  maintaining contact with the support surfaces  52 ,  56  of the adapter  12 , respectively. With the planar surfaces remaining in contact, the tip  14  may be constrained from substantial rotation relative to the nose  26  that may otherwise cause additional shear stresses on the retention mechanism components. Even where draft angles may be provided in the bottom surface  42 , the bottom inner surface  122 , the support surfaces  52 ,  56  and the support portions  132 ,  136 , and a slight separation may occur between the facing surfaces, the rotation of the tip  14  may be limited to an amount less than that at which shear stresses may be applied to the components of the retention mechanism. By reducing the shear stresses applied to the retention mechanism, it is anticipated that the rate of failure of the retention mechanisms, and correspondingly the instances of the breaking off of the tips  14  prior to the end of their useful lives, may be reduced. 
     The configuration of the tooth assemblies  10  according to the present disclosure may also facilitate a reduction in the shear stresses on the retention mechanisms when forces are applied that may otherwise tend to cause the tips  14 ,  150 ,  180 ,  190 ,  210 ,  220  ( FIGS. 57 and 58 ) to slide off the nose s 26  of the adapters  12 ,  170 . Because adapter noses known in the art typically have a generally triangular configuration and taper laterally as the noses extend forward away from the straps, forces applied during use may generally influence the tips to slide off the front of the adapter noses. Such movement is resisted by the retention mechanism, thereby causing shear stresses. The noses  26  of the adapters  12 ,  170  in accordance with the present disclosure may at least in part counterbalance to forces tending to cause the tips  14 ,  150 ,  180 ,  190 ,  210 ,  220  to slide off the adapter noses  26 . 
       FIGS. 52A, 52B, 52C, 52D, 52E, and 52F  illustrate the orientations of the tooth assembly  10  formed by the adapter  12  and the tip  14  as the implement of a top-wearing application, such as the excavator bucket assembly  6 , digs into the work material and scoops out a load. The adapter  12  and tip  14  are used for illustration in  FIGS. 52-56 , but those skilled in the art will understand that the various combinations of the adapters  12 ,  170  and the tips  14 ,  150 ,  180 ,  190 ,  210 ,  220  would interact in a similar manner as described hereinafter. The front edge  76  of the tooth assembly  10  initially penetrates the work material downwardly with an orientation slightly past vertical as shown in  FIG. 52A . After the initial penetration, the implement  6  and tooth assemblies  10  may be rotated rearward and drawn toward the earth moving machine by the boom of the machine, thereby rotating through the orientations shown in  FIGS. 52B, 52C, and 52D . During this movement through the work material, the top outer surfaces  72  of the tips  14  form the primary engagement surface with the work material, and the tips  14  may encounter the greatest forces as they break through the work material. The tips  14  also experience the greatest abrasion on the top outer surfaces  72 . The substantially keystone-shaped contour  93  of the tips  14  provides additional wear material at the top outer surfaces  72  to prolong the useful life of the tips  14 . The substantially keystone-shaped contour  93  also facilitates the movement of the tips  14  through the work material, as the work material will flow around the edges of the top outer surfaces  72  with less engagement of the tapering lateral outer surfaces  90 ,  92 . 
     The implement  6  eventually rotates the tooth assembly  10  to the horizontal orientation shown in  FIG. 52E . At this point, the implement  6  is drawn further rearward toward the machine, with the front edge  76  leading the tooth assembly  10  through the work material. Finally, after further rotation of the implement  6  to the position shown in  FIG. 52F , the tooth assembly  10  may be oriented upwardly, and the implement  6  may be lifted out of the work material with the excavated load. 
       FIG. 53  illustrates the tooth assembly  10  with the generally vertical orientation of  FIG. 52A  that may occur when the implement  6  is being driven downward into a pile or surface of work material in the direction indicated by arrow “M”. The work material may resist penetration of the tooth assembly  10 , resulting in the application of a vertical force F V  against the front edge  76 . The force F V  may push the tip  14  toward the adapter  12  and into tighter engagement with the nose  26  of the adapter  12  without increasing the shear stresses on the retention mechanism. 
     In  FIG. 54 , the tooth assembly  10  is illustrated in the position of  FIG. 52C  wherein the implement  6  may be partially racked upwardly as the machine draws the implement  6  rearward and upward to further break and gather a load of work material as indicated by the arrow “M”. As the implement  6  is drawn through the work material, a force F may be applied to the top outer surface  72  of the tip  14 . The force F may be a resultant force acting on the front portion  82  and/or the tip portion  84  of the tip  14  that may be a combination of the weight of the work material and resistance of the work material from being dislodged. The force F may be transmitted through the tip  14  to the adapter nose  26  and the top inner surface  124  of the nose cavity  120  of the tip  14  for support, and thereby yielding a first resultant force F R1  on the front support surface  52  of the adapter  12 . Because the line of action of the vertical force F V  is located proximate the front edge  76 , the vertical force F V  tends to rotate the tip  14  in a counterclockwise direction as shown about the nose  26  of the adapter  12 , with the first support surface  52  of the adapter  12  acting as the fulcrum of the rotation. The moment created by the vertical force F V  causes a second resultant force F R2  acting on the bottom surface  42  of the adapter  12  proximate the intermediate portion  24  of the adapter  12 . 
     In previously known tip assemblies having continuously sloping top surfaces of the noses, the first resultant force F R1  would tend to cause the tip to slide off the front of the nose, and thereby cause additional strain on the retention mechanism. In contrast, the orientation of the front support surface  52  of the adapter  12  with respect to the intermediate surface  54  of the adapter  12  causes the tip  14  to slide into engagement with the nose  26 .  FIG. 55  illustrates an enlarged portion of the adapter nose  26  and the tip  14 , and shows the resultant forces tending to cause movement of the tip  14  relative to the adapter nose  26 . The first resultant force F R1  acting on the front support surface  52  of the adapter  12  and first support portion  132  of the tip  14  has a first normal component F N  acting perpendicular to the front support surface  52 , and a second component F P  acting parallel to the front support surface  52  and the first support portion  132 . Due to the orientation of the front support surface  52  of the adapter  12  and first support portion  132  of the tip  14  relative to the intermediate surface  54  of the adapter  12  and intermediate portion  134  of the tip  14 , the parallel component F P  or the first resultant force F R1  tends to cause the tip  14  to slide rearward and into engagement with the nose  26  of the adapter  12 . The parallel component F P  tending to slide the tip  14  onto the nose  26  reduces the shear stresses applied on the components of the retention mechanism and correspondingly reduces the incidence of failure of the retention mechanism. 
       FIG. 56  illustrates the tooth assembly  10  in the generally horizontal orientation shown in the  FIG. 52E  as may occur when the implement  6  is being drawn rearward toward the machine in the generally horizontal direction of arrow “M”. The work material may resist the movement of the tooth assembly  10 , resulting in the application of a horizontal force F H  against the front edge  76 . Similar to the vertical force F V  in  FIG. 53 , the horizontal force F H  may push the tip  14  toward the adapter  12  and into tighter engagement with the nose  26  without increasing the shear stresses on the retention mechanism. 
     As discussed above, the substantially keystone-shaped contour  93  of the tip  14  may provide soil flow with reduced drag when the tip  14  moves through the work material with the top outer surface  72  leading as in  FIGS. 52B, 52C, and 52D . However, this benefit of the substantially keystone-shaped contour  93  may be minimal when the tooth assembly  10  of  FIG. 3  is oriented as in  FIGS. 52A, 52E, and 52F  and moving though the work material with the front edge  76  leading.  FIGS. 57 and 58  illustrate an alternative embodiment of a tip  220  configured to reduce drag from soil flow as the front edge  76  leads the tip  220  through the work material. In this embodiment, similar elements are indicated by the same reference numerals as used it the discussion of the tip  14 . The tip  220  may be longitudinally configured with a substantially hourglass-shaped contour. The rear portions  94 ,  96  of the lateral outer surfaces  90 ,  92  may taper inwardly as they extend forward from the rear edge  70  such that the distance between the rear portions  94 ,  96  decreases as the rear portions  94 ,  96  approach the side transition area  97 . Beyond the transition area  97 , the front portions  98 ,  100  may diverge as the front portions  98 ,  100  progress forward to a maximum width proximate the front edge  76 . The tapering of the front portions  98 ,  100  of the lateral outer surfaces  90 ,  92  behind the front edge  76  may reduce the amount of drag experienced by the tip  220  as it passes through the work material. As the front edge  76  digs into the work material, the work material on the sides flows outwardly and around the tip  220  as indicated by the arrows “FL” in  FIG. 57 , with less engagement of the lateral outer surfaces  90 ,  92  than if the front portions  98 ,  100  were parallel and maintained a constant width as the front portions  98 ,  100  extend toward the rear edge  70  from the front edge  76 . 
     The discussion of  FIGS. 52-56  above set forth the performance of the components of the tooth assemblies  10  in accordance with the present disclosure during the range of motion of an implement  6  in a top-wearing application. The adapter nose  26  in accordance with the present disclosure may similarly counterbalance forces tending to cause the tips  14 ,  150 ,  180 ,  190 ,  210 ,  220  to slide off the adapter noses  26  of the adapters  12 ,  170  in bottom-wearing applications, such as during the loading sequence shown in  FIGS. 59-61 .  FIG. 59  illustrates the tooth assembly  10  formed by the adapter  170  and tip  180  with a generally horizontal orientation as may occur when the machine is being driven forward into a pile of work material as indicated by arrow “M”. The work material may resist penetration of the tooth assembly  10  into the pile, resulting in the application of a horizontal force F H  against the front edge  76 . The force F H  may push the tip  14  toward the adapter  12  and into tighter engagement with the nose  26  without increasing the shear stresses on the retention mechanism. 
     In  FIG. 60 , the tooth assembly  10  is illustrated in a position wherein the implement  1  may be partially racked upwardly as the machine begins to lift a load of work material out of the pile in the direction indicated by arrow “M”. As the implement  1  is lifted out of the work material, a vertical force F V  may be applied to the top outer surface  72  of the tip  180 . The vertical force F V  may be a resultant force acting on the front portion  82  and/or tip portion  84  that may be a combination of the weight of the work material and resistance of the work material from being dislodged from the pile. The vertical force F V  may be transmitted through the tip  180  to the adapter nose  26  for support, and thereby yielding a first resultant force F R1  on the front support surface  52  of the adapter nose  26 . Because the line of action of the vertical force F V  is located proximate the front edge  76 , the vertical force F V  tends to rotate the tip  180  in a counterclockwise direction as shown about the nose  26  of the adapter  170 , with the first support surface  52  of the nose  26  acting as the fulcrum of the rotation. The moment created by the vertical force F V  causes a second resultant force F R2  acting on the bottom surface  42  proximate the intermediate portion  24  of the adapter  170 . In previously known tip assemblies having continuously sloping top surfaces of the noses, the first resultant force F R1  would tend to cause the tip to slide off the front of the nose, and thereby cause additional strain on the retention mechanism. 
     In contrast, the orientation of the front support surface  52  with respect to the intermediate surface  54  causes the tip  180  to slide into engagement with the nose  26 .  FIG. 61  illustrates an enlarged portion of the nose  26  of the adapter  170  and the tip  180 , and shows the resultant forces tending to cause movement of the tip  180  relative to the nose  26 . The first resultant force F R1  acting on the front support surface  52  of the adapter  170  and the first support portion  132  of the tip  180  has a first normal component F N  acting perpendicular to the front support surface  52 , and a second component F P  acting parallel to the front support surface  52  and first support portion  132 . Due to the orientation of the front support surface  52  and first support portion  132  relative to the intermediate surface  54  of the adapter  170  and the intermediate portion  134  of the tip  180 , the parallel component F P  of the first resultant force F R1  tends to cause the tip  180  to slide rearward and into engagement with the nose  26  of the adapter  170 . The parallel component F P  tending to slide the tip  180  onto the nose  26  reduces the shear stresses applied on the components of the retention mechanism, and correspondingly reduces the incidence of failure of the retention mechanism. 
     In addition to the retention benefits of the configuration of the noses  26  of the adapters  12 ,  170  and the nose cavities  120  of the tips  14 ,  150 ,  180 ,  190 ,  210 ,  220  as discussed above, the tooth assemblies  10  may provide benefits in during use in top-wearing and bottom-wearing applications. The geometric configurations of the tips  14 ,  150 ,  190  of the tooth assemblies  10  in accordance with the present disclosure may provide improved efficiency in penetrating work material in top-wearing applications over the useful life of the tips  14 ,  150 ,  190  as compared to tips previously known in the art. As wear material is worn away from the front of the tips  14 ,  150 ,  180 ,  190 ,  210 , the reliefs  102 ,  158 ,  160 ,  196  may provide self-sharpening features to the tips  14 ,  150 ,  190  providing improved penetration where previously known tips may become blunted and shaped more like a fist than a cutting tool. Using the tip  14  as an example for purposes of illustrating the self-sharpening feature, the front view of the tip  14  in  FIG. 14  shows the front edge  76  forming a leading cutting surface that initially enters the work material.  FIG. 62  is a reproduction of  FIG. 4  showing the tooth assembly  10  formed by the adapter  12  and tip  14 , and the cross-sectional views shown in  FIGS. 63-68  illustrate changes in the geometry of the cutting surface as wear material wears away from the front of the tip  14 .  FIG. 63  shows a cross-sectional view of the tooth assembly  10  of  FIG. 62  with the section taken between the front edge  76  and the relief  102 . After abrasion wears away the tip  14  to this point, a cutting surface  330  of the tip  14  now presents a cross-sectional area engaging the work material that is less sharp than the front edge  76  as the machine digs the implement  1  into the work material. It will be apparent to those skilled in the art that abrasion from engagement with the work material may cause the outer edges of the cutting surface  330  to become rounded, and for the portions  78 ,  82 ,  84  of the top outer surface  72  to wear away as indicated by the cross-hatched area  330   a  and thereby reduce the thickness of the cutting surface  330 . 
     The wear material of the tip  14  continues to wear away rearwardly toward the relief  102 .  FIG. 64  illustrates a cross-section of the tooth assembly  10  at a position where the front of the tip  14  may have worn away into the portion of the tip  14  providing the relief  102  to form a cutting surface  332 . At this point, the tip  14  may have worn through the curved portion  104  of the relief  102  so that the cutting surface  332  includes an intermediate area of reduced thickness. The area of reduced thickness may cause the cutting surface  332  to have a slight inverted U-shape. The wear material removed from the cutting surface  332  by the relief  102  reduces the cross-sectional area of the leading cutting surface  332  of the tip  14  to “sharpen” the tip  14 , and correspondingly reduces the resistance experienced as the tips  14  of the implement  1  enter the work material. Wear material continues to wear away from portions  78 ,  82 ,  84  as indicated at cross-hatched area  332   a  to further reduce the thickness of the tip  14 . At the same time, wear material wears away from the front portions  98 ,  100  of the lateral outer surfaces  90 ,  92 , respectively, to reduce the width at the front of the tip  14 . The tapered portion  106  of the relief  102  allows the work material to flow through the relief surface  102  with less resistance than if the rear portions of the relief  102  were flat or rounded and facing more directly toward the work material. The tapering of the tapered portion  106  reduces forces acting normal to the surface that may resist the flow of the work material and the penetration of the tip  14  into the work material. 
       FIGS. 75 and 76  illustrate further iterations of cutting surfaces  334 ,  336 , respectively, as wear material continues to wear away from the front end of the tip  14  and from the portions  78 ,  82  of the top outer surface  72 , and the front portions  98 ,  100  of the lateral outer surfaces  90 ,  92 , as denoted by the cross-hatched areas  334   a ,  336   a . Due to the shape of the relief  102 , the portions of the cutting surfaces  334 ,  336  carved out by the relief  102  may initially increase as the leading edge of the tip  14  progresses rearwardly to the cutting surface  334 , and eventually decrease as wear continues to progress to the cutting surface  336 . Eventually, wear material wears away from the front of the tip  14  toward the rearward limits of the relief  102 . 
     As shown in  FIG. 67 , a cutting surface  338  closely approximates the cross-sectional area of the tip  14  near the rearward end of the relief  102 , thereby creating a relatively large surface area for attempted penetration of the work material. The large surface area may be partially reduced by wear indicated by the cross-hatched area  338   a . The tip  14  begins to function less efficiently at cutting into the work material as the tip  14  nears the end of its useful life. Wearing away of the tip  14  toward the end of the relief  102  may provide a visual indication for replacement of the tip  14 . Continued use of the tip  14  causes further erosion of the wear material at the front of the tip  14 , and may ultimately lead to a breach of the nose cavity  120  at a cutting surface  340  as shown in  FIG. 68 . Wear progressing inwardly from the outer surfaces  72 ,  74 ,  90 ,  92  as indicated by the cross-hatched area  340   a  may eventually cause further breaches of the nose cavity  120  with continued use of the tooth assembly  10 . At this point, the nose  26  of the adapter  12  may be exposed to the work material, and may begin to wear away, possibly to the point where the adapter  12  must also be removed from the base edge  18  of the implement  1  and replaced. 
     The geometric configurations of the tips  150 ,  180 ,  190 ,  210  may also provide improved efficiency in penetrating work material over the useful life of the tips  150 ,  180 ,  190 ,  210 . The reliefs  154 ,  156 ,  182 ,  192 ,  194 ,  212 ,  214  on the top outer surfaces  72  may provide a self-sharpening features to the tips  150 ,  180 ,  190 ,  210  providing improved penetration as wear material is worn away from the front of the tip. As an example,  FIG. 69  illustrates the tooth assembly  10  that may be formed by the adapter  170  and the general duty tip  180 , and the cross-sectional views shown in  FIGS. 70-75  illustrate changes in the geometry of the cutting surface as wear material wears away from the front of the tip  180 .  FIG. 71  shows a cross-sectional view of the tooth assembly  10  of  FIG. 69  with the section taken between the front edge  76  and the relief  182 . After abrasion wears away the tip  180  to this point, a cutting surface  350  of the tip  180  now presents a cross-sectional area engaging the work material as the machine drives forward that is less sharp than the front edge  76 . It will be apparent to those skilled in the art that abrasion from engagement with the work material may cause the outer edges of the cutting surface  350  to become rounded, and for the front portion  88  of the bottom outer surface  74  to wear away as indicated by the cross-hatched area  350   a  and thereby reduce the thickness of the cutting surface  350 . 
     The wear material of the tip  180  continues to wear away rearwardly toward the relief  182 .  FIG. 71  illustrates a cross-section of the tooth assembly  10  at a position where the front of the tip  180  may have worn away into the portion of the tip  180  providing the relief  182  to form a cutting surface  352 . At this point, the tip  180  may have worn through the curved portion  184  of the relief  182  such that the cutting surface  352  includes an intermediate area of reduced thickness. The area of reduced thickness may cause the cutting surface  352  to have slight U-shape. The wear material removed from the cutting surface  352  by the relief  182  reduces the cross-sectional area of the leading cutting surface  352  of the tip  180  to “sharpen” the tip  180 , and correspondingly reduces the resistance experienced as the tips  180  of the implement  1  enter the work material. Wear material continues to wear away from the front portion  88  of the bottom outer surface  76  to reduce the thickness of the cutting surface  352 , and wear material wears away from the front portions  98 ,  100  of the lateral outer surfaces  90 ,  92 , respectively, to reduce the width at the front of the tip  180 , as indicated at cross-hatched area  352   a . The tapered portion  186  of the relief  182  allows the work material to flow through the relief  182  with less resistance than if the rear portions of the relief  182  were flat or rounded and facing more directly toward the work material. The tapering of the tapered portion  186  reduces forces acting normal to the surfaces that may resist the flow of the work material and the penetration of the tip  180  into the work material. 
       FIGS. 72 and 73  illustrate further iterations of cutting surfaces  354 ,  356 , respectively, as wear material continues to wear away from the front edge  76  of the tip  180  and from the front portion  88  of the bottom outer surface  74  of the tip  180  and the front portions  98 ,  100  of the lateral outer surfaces  90 ,  92  of the tip  180 , as denoted by the cross-hatched areas  354   a ,  356   a . Due to the shape of the relief  182 , the portions of the cutting surfaces  354 ,  356  carved out by the relief  182  may initially increase as the leading edge of the tip  180  progresses rearwardly to the cutting surface  354 , and eventually decrease as wear continues to progress to the cutting surface  356 . Eventually, wear material wears away to the rearward limits of the relief  182 . 
     As shown in  FIG. 7 , a cutting surface  358  closely approximates the cross-sectional area of the tip  180  behind the relief  182 , thereby creating a relatively large surface area for attempted penetration of the work material. The large surface area may be partially reduced by wear indicated by the cross-hatched area  358   a . The tips  180  begin to function less efficiently at cutting into the work material as the tips  180  near the end of their useful life. Wearing away of the tips  180  beyond the relief  182  may provide a visual indication for replacement of the tips  180 . Continued use of the tips  180  causes further erosion of the wear material at the front of the tips  180 , and may ultimately lead to a breach of the nose cavity  120  at a cutting surface  360  as shown in  FIG. 75 . Wear progressing inwardly from the outer surfaces  72 ,  74 ,  90 ,  92  as indicated by the cross-hatched area  360   a  may eventually cause further breaches of the nose cavity  120  with continued use of the tooth assembly  10 . At this point, the nose  26  of the adapter  170  may be exposed to the work material, and may begin to wear away, possibly to the point where the adapter  170  must also be removed from the base edge  18  of the implement  1  and replaced. 
     While the preceding text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment of the invention since describing every possible embodiment would be impractical, not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention.