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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
       [0001]    This invention relates to loading buckets. In particular, this invention relates to teeth used on loading buckets and means for retaining the teeth on the bucket. 
       BACKGROUND OF THE INVENTION 
       [0002]    A loading bucket for heavy machinery typically includes a number of teeth on the ground-engaging surface of the bucket. 
         [0003]    As shown in the prior art images of  FIGS. 1 and 2 , a bucket tooth  12  is installed on a shank  10  in a mating relationship so that the stresses on the tooth are conveyed over relatively large and angled contact surfaces  14  to the shank. A lock pin  16  extends through both the shank  10  and the tooth  12  to ensure that the tooth remains on the shank during use. 
         [0004]    Referring to  FIGS. 2 and 4 , an aperture  18  extends through the sides of the tooth  12  and through the shank  10  to receive the pin  16 . The outer edges of one side of the aperture are formed with a seat  20  to accommodate a locking ring  22 . Referring to  FIG. 5 , the prior art pin  16  includes a larger diameter portion  17  and a reduced diameter portion  19  that is sized to receive ring  22 . Locking ring  22  seats in the reduced diameter portion  19  of the pin  16  in the assembled configuration. Locking ring  22  serves to hold the pin  16  in the aperture  18  when the tooth  12  is installed over the shank  10 . As seen in  FIG. 3 , ring  22  includes a cut  23  with a corresponding gap  25  to allow the ring  22  to be more easily deformed when being fitted over the regular diameter portion of the pin  16  until it reaches the reduced diameter portion  19 . A ring sleeve  24  may be used to cover the ring  22 , as shown in  FIGS. 3 and 4 . Note that  FIG. 4  does not show the pin  16  or the shank  10 . 
         [0005]    The assembly of the tooth to the shank involves first inserting the locking ring  22 , usually along with ring sleeve  24  into the seat  20  of the shank  10 . The tooth  12  is then installed over the shank  10 . Locking pin  16  is then inserted into the aperture  18  and the pin is hammered into place through the ring  22  which deforms radially outward around larger diameter portion  17  of the pin. The pin  16  is pushed through until the ring  22  seats in the reduced diameter portion  19  of the pin to result in the assembly shown in  FIG. 2 . 
         [0006]    According to the prior art, the locking pin  16  and the ring  22  are typically made of similar materials. As a result, rust tends to set in causing adhesion of the ring to the pin. When it is necessary to change the tooth on a bucket, a hammer must be used to disengage the ring and the pin. In many cases, the difficulty of disengaging it can result in injuries to the operator. 
         [0007]    It is therefore an object of this invention to provide a tooth retaining means that is more easily and reliably removed than the aforementioned prior art systems. 
         [0008]    This and other objects of the invention will be better understood by reference to the detailed description of the preferred embodiment which follows. Note that not all of the objects are necessarily met by all embodiments of the invention described below or by the invention defined by each of the claims. 
       SUMMARY OF THE INVENTION 
       [0009]    According to the invention, the ring is made of a dissimilar material to the locking pin. The ring is provided with a cam surface that mates with a corresponding cam portion of a ring seat that is provided on the sides of the shank. The cam surface and cam portion of the seat cooperate to prevent the ring from turning in the seat in the event that the pin is rotated. 
         [0010]    The pin is provided with a shoulder to abut against one side of the locking ring when the pin is inserted into the apertures of the shank and tooth, thereby preventing the pin from proceeding further through the apertures. 
         [0011]    A locking lobe is provided on the pin and a correspondingly sized axial slot is provided on the inside surface of the ring to allow the pin and its lobe to slide through a portion of the ring when the pin is being inserted into the shank and tooth. The ring is further provided with an inner diameter channel that is closed at each end by shoulders adjacent the slot. 
         [0012]    The pin is inserted through the ring by aligning the lobe with the slot and inserting the pin until the lobe is aligned with the channel between the shoulders. The pin is then rotated within the ring. The cam portion of the seat holds the ring against rotation, allowing the rotation of the pin to force the locking lobe over one of the shoulders and into the channel. The channel walls prevent the pin from being withdrawn from the ring longitudinally. The pin is thereby effectively held in the assembly by the ring that is retained in the ring seat within the tooth and shank assembly. 
         [0013]    In order to disassemble the assembly, the pin is rotated, for example by means of a hex wrench or other corresponding tool, to force the locking lobe back over one of the channel shoulders into position in the ring socket, from where the pin can be withdrawn axially from the ring and from the apertures in the shank and the tooth. 
         [0014]    In one aspect the invention is therefore a bucket tooth assembly. The assembly comprises a shank having an aperture extending therethrough. The aperture has an enlarged portion forming a ring seat at one end. The ring seat is partly circular and further has a cam portion. A tooth is adapted to fit over the shank and has aligned apertures in opposed walls of the tooth. A ring is seatable in the ring seat and has a cam portion corresponding to the cam portion of the ring seat. The ring also has an inner wall defining a recess. The is a locking pin for extending through the shank aperture and through at least one of the opposed apertures of the tooth. The locking pin has a protrusion adapted to be retained in the recess of the ring when the pin is disposed in the apertures. 
         [0015]    In another aspect, the recess is a channel formed along the inner wall of the ring but extending less than 360 degrees along the inner wall. 
         [0016]    In another aspect, the ring further comprises an axially oriented slot whose dimensions accommodate the protrusion on the pin. 
         [0017]    In yet another aspect, the slot extends to a portion of the inner wall to which the channel does not extend. 
         [0018]    In a sub-assembly aspect of the invention, the invention is a sub-assembly for a bucket tooth assembly. The sub-assembly comprises a shank for receiving a bucket tooth, a ring seat in the shank and a ring shaped and sized to seat in the ring seat, the shapes of the ring seat and of the ring preventing rotation of the ring when it is seated in the ring seat and a locking pin having an element that is selectively securable in a portion of the ring to prevent axial withdrawal of the pin from the ring. 
         [0019]    In another aspect, the portion of the ring of the sub-assembly comprises a cavity. In a further aspect, the cavity comprises a channel along a portion of an inner wall of the ring and the element of the locking pin comprises a protrusion on a surface of the pin. 
         [0020]    In a different aspect, the invention is a ring for use in a bucket tooth and shank assembly. The ring has a generally circular shape with a portion that engages a surrounding surface so as to prevent rotation against the surface. The ring also has a cavity for receiving and preventing a portion of a locking pin from sliding axially out of engagement with the ring. 
         [0021]    In another aspect of the ring of the invention, the portion of the ring is eccentric. In a further aspect, the cavity is a channel along a portion of an inner wall of the ring. 
         [0022]    In a different aspect, the invention is a shank for a bucket tooth and shank assembly. The shank has an aperture extending through the shank. The aperture has an enlarged portion forming a ring seat at one end that is generally circular with an eccentric portion. 
         [0023]    In yet a different aspect, the invention is a pin for use in a bucket tooth and shank assembly wherein the pin is generally cylindrical and has a frusto-spherical lobe on the surface thereof. 
         [0024]    In a method aspect, the invention comprises a method for assembling a tooth to a bucket shank. A ring is placed in ring seat on a bucket shank, the ring and ring seat being respectively shaped to prevent rotation of the ring in the ring seat. A bucket tooth is installed over the shank. A generally cylindrical locking pin having a protrusion on the surface thereof is inserted into apertures in the tooth and the shank such that the protrusion engages and is retained by the ring against axial withdrawal of the pin from engagement with said ring. 
         [0025]    In a more detailed method aspect, the ring includes an axially extending slot of a size to accommodate movement of the protrusion along the slot, and a channel on an inner wall of the ring for retaining the protrusion against axial displacement. The step of inserting the pin involves sliding the pin such that the protrusion moves axially along and within the slot, then rotating the pin so as to cause the protrusion to be located within the channel. 
         [0026]    The foregoing was intended as a summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiments. Moreover, this summary should be read as though the claims were incorporated herein for completeness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The invention will be described by reference to the detailed description of the preferred embodiment and to the drawings thereof in which: 
           [0028]      FIG. 1  is a longitudinal side view of a replaceable bucket tooth installed on a shank according to the prior art. 
           [0029]      FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 . 
           [0030]      FIG. 3  is a perspective exploded view of the ring and sleeve according to the prior art; 
           [0031]      FIG. 4  is a cross-sectional view of the shank showing the aperture, the ring seat and the ring and sleeve according to the prior art; 
           [0032]      FIG. 5  is a side elevation of the pin according to the prior art; 
           [0033]      FIG. 6  is a longitudinal cross-section of the pin according to the preferred embodiment. 
           [0034]      FIG. 7  is an end view of the pin according to the preferred embodiment; 
           [0035]      FIG. 8  is an isometric view of the ring according to the preferred embodiment of the present invention; 
           [0036]      FIG. 9  is plan view of the ring according to the preferred embodiment of the present invention; 
           [0037]      FIG. 10  is sectional view taken along lines  10 - 10  of  FIG. 9 ; 
           [0038]      FIG. 11  is a sectional view taken along lines  11 - 11  of  FIG. 9 ; 
           [0039]      FIG. 12  is a sectional view taken along lines  12 - 12  of  FIG. 9 ; 
           [0040]      FIGS. 13 and 14  are isometric views of a ring sectioned along lines  12 - 12  of  FIG. 9 ; 
           [0041]      FIG. 15  is a radial sectional view of the ring of  FIG. 9 ; 
           [0042]      FIG. 16  is a side view of the shank showing the ring seat and pin aperture; 
           [0043]      FIG. 17  is a longitudinal section view of the shank; 
           [0044]      FIG. 18  is a cross sectional view of the shank, ring and pin; 
           [0045]      FIG. 19  is a longitudinal side elevation of the shank, pin and ring; 
           [0046]      FIG. 20  is a perspective view of the tooth; and, 
           [0047]      FIG. 21  is a longitudinal side elevation of the assembled shank, pin, ring and tooth. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0048]      FIGS. 16 ,  17  and  18  show a shank  50  according to the preferred embodiment of the invention. As best seen in the sectional views of  FIGS. 17 and 18 , the shank  50  includes an aperture  52  extending laterally through the shank for receiving a pin  58  through the aperture. One side of shank  50  further comprises a ring seat  54  for receiving a ring as will be described below. Ring seat  54  is preferably generally circular but including an eccentric cam portion  56 , as is best appreciated by reference to  FIG. 16 . 
         [0049]      FIGS. 6 and 7  show the pin  58  according to the preferred embodiment. Pin  58  may be of steel. Pin  58  includes a shoulder  60  between a larger diameter portion  62  and a smaller diameter portion  64 . A locking lobe  66  is provided on the surface of the smaller diameter portion  64  of the pin  58 . As will be described below, lobe  66  is sized to be accommodated and seated in a channel formed along the inner wall of the ring. In the preferred embodiment, the lobe is a frusto-spherical protrusion on the surface of pin  58 . 
         [0050]    The end  68  of the pin  58  may be formed with a hexagonal head  70  to assist in rotating pin  58  when it is being installed or removed from the tooth-shank assembly using a hexagonal wrench or other tool. 
         [0051]    A ring  72  is shown in  FIGS. 8 to 15 . Ring  72  should be of a material that is dissimilar to the material forming the pin  58 . In the preferred embodiment, the ring  72  is made of urethane. 
         [0052]    Ring  72  is generally circular but its outer perimeter is provided with an eccentric cam surface  74  corresponding in dimensions to the cam portion  56  of the ring seat  54 . As a result, when the ring  72  is seated in the ring seat  54 , the corresponding cam portions  56  and  74  cooperate to prevent rotation of the ring  72  within the ring seat  54 . 
         [0053]    The inner wall  76  of the ring  72  is circular save for an axially oriented slot  78  dimensioned to correspond to the dimensions of the locking lobe  66  and to accommodate the locking lobe  66  in the slot  78  and to allow movement of the lobe  66  along the slot  78  as the pin  58  is being inserted through the center of the ring  72 . 
         [0054]    The inner wall  76  of the ring includes a recess forming a channel  80  along a portion of the inner wall  76 . The channel  80  does not however extend 360 degrees around the entire length of the inner wall  76 . Instead, it is bounded by shoulders  82  that terminate the channel short of the slot  78 , as best appreciated by reference to  FIG. 14 . As in the prior art, a ring sleeve may also be provided between the ring  72  and the seat  54  but the ring sleeve is not shown in the drawings of the preferred embodiment. 
         [0055]    The slot  78  enables the lobe  66  of the pin  58  not to impede the insertion of the pin  58  through the central aperture of the ring  72  provided the pin is arranged so that the lobe  66  is aligned with the slot  78 . Once the lobe  66  has been inserted along the slot  78 , rotation of the pin  58  forces the lobe  66  to ride over the shoulders  82  to rest within the channel  80 . When positioned within the channel  80 , the channel prevents the lobe portion of the pin from sliding axially out of engagement with the ring. 
         [0056]    Referring to  FIG. 20 , the tooth  86  is shaped to fit and be installed over the shank  50 . Tooth  86  includes aligned apertures  88 ,  90  in the opposed side walls  92 ,  94  of the tooth to align with the aperture  52  in the shank. 
         [0057]    In order to assemble the unit, the ring  72  (and the sleeve  84  if used) is first seated in the ring seat  54  of the shank  50 . The tooth  86  is then installed over the shank  50 . The smaller diameter end  68  of the pin  58  is inserted through at least aperture  88  of the tooth  86  and through aperture  52  of the shank from the end that is opposite the ring seat  54 . Unless the lobe  66  of the pin  58  happens to be perfectly lined up to enter slot  78  of the ring, the lobe will engage a side of the ring. The user then rotates the pin until the lobe finds and slides along the slot  78 . If a sleeve  84  is being used, the shoulder  60  of the pin  62  will then abut the sleeve  84  at  96  to assist in indicating that the pin is inserted to the intended depth for the lobe to be aligned with the channel of the ring. 
         [0058]    At this point, the lobe  66  is positioned between the shoulders  82  of the channel  80  of the inner wall  76  of the ring  72 . A hex wrench is then used to rotate the pin  58  to urge the lobe  66  over the shoulders  82  and into the channel  80 . The pin  58  is thus retained in engagement with the ring  72  by means of the lobe  66  being captive within the channel  80 . The pin  58  may still rotate relatively freely within the channel until the lobe  66  reaches one of the channel terminating shoulders  82 . 
         [0059]    The assembly may be dismantled by again using a hex wrench to rotate the pin  58 . As the lobe  66  reaches one of the channel terminating shoulders  82 , the pin  58  is forcibly urged into further rotation to cause the lobe  66  to ride across the shoulder  82  and into the slot  78 . The ring  72  is otherwise restrained from rotation during rotation of the pin  58  by the seating of the ring&#39;s cam surface  74  into the cam portion  56  of the ring seat  54 . 
         [0060]    The assembly may therefore be both assembled and disassembled with relative ease. The fact that the pin is made of a different material than the ring, and the fact that the pin can rotate within the ring&#39;s channel each contribute to minimizing seizing up of the assembly and enhancing the ease of disassembly. 
         [0061]    It will be appreciated that prior art tooth designs can be suitable for use with the system of the invention. A prior art tooth design may be assembled about a sub-assembly according to the invention comprising a shank with a ring seat as described above, a ring with a recess as described above and a pin with a protrusion as described above. 
         [0062]    In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Summary:
A system to attaching a tooth to a bucket shank comprises a ring seat in the shank having a cam. A locking ring having a corresponding cam is seated in the seat and has an interior channel bounded by shoulders. A locking pin of a dissimilar material to the ring includes a lobe sized to correspond to the channel. Once inserted through apertures in the tooth and the shank, the pin may be rotated to force the lobe over the shoulders and to be housed in the channel to securely hold the pin in place.