A coupling for connecting ground engaging tools to a lip of an excavator bucket or similar is disclosed. The coupling uses an eccentric rotating lock, whereby rotation of the lock alters the distance between bearing surfaces and thus allows tightening of the lock.

FIELD OF THE INVENTION 
       [0001]    The present invention relates to the connection of wearing elements to machinery. It is particularly directed to the connection of ground engaging tools such as teeth to excavator buckets, but may have wider application. 
       BACKGROUND TO THE INVENTION 
       [0002]    Buckets of excavating equipment are subject to significant abrasive wear during use. For this reason, replaceable ground engaging tools (GET) are located about the buckets in the areas most susceptible to wear. A number of different GET are used, including heel shrouds, lip shrouds, adaptors, wear plates and, importantly, teeth. 
         [0003]    The connection of teeth to adaptors has presented a consistent challenge, and there are many different systems currently available which seek to perform this task in an efficient manner. Many of the systems use a locking pin, which passes through a bore of the adaptor. Such an arrangement has an inherent problem in that the provision of a bore weakens the adaptor, as well as encouraging stress concentrations within the adaptor. In addition, locking pins have a tendency to bend in use, and removal of a bent locking pin may be difficult. 
         [0004]    Other systems use a latching system. These are problematic in that there is usually no ability to adjust or tighten the connection, hence the teeth are liable to become loose. 
         [0005]    The present invention seeks to provide an arrangement for connection of wearing elements, particularly teeth, which addresses some of these problems. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one aspect of the present invention there is provided a coupling for connecting a wear member to a base, the base including a first bearing surface, the wear member including a second bearing surface; the coupling including a rotatable lock having a first face arranged to bear against the first bearing surface and a second face arranged to bear against the second bearing surface, the relative positions of the first and second face varying around a central axis of the lock, such that in use rotation of the lock alters the distance between the first and second bearing surfaces. 
         [0007]    It is preferred that the first face and the second face of the rotatable lock are both arcuate and have respective radii of curvature, with the radius of curvature of at least one of the first or second face varying around the lock central axis. In a preferred embodiment of the invention, the second face of the rotatable lock has a constant radius of curvature; that is, is part-cylindrical; whereas the first face has a varying radius of curvature; that is, is shaped like a spiral. 
         [0008]    The wear member may be arranged to align about the base along a longitudinal axis. The central axis of the lock may be perpendicular to this longitudinal axis, but it is preferred that that the central axis of the lock be oriented at about 10° to 20° relative to the perpendicular. 
         [0009]    The first face and second face of the rotatable lock may be located on a single bearing member. It is preferred that the bearing member includes a body portion, which is cylindrical, and has an outer surface forming the second face of the rotatable lock. It is also preferred that the bearing member has an engaging portion protruding from one side of the body portion, the engaging portion having an outer surface, at least a part of which forms the first face of the rotatable lock. 
         [0010]    The engaging portion may be formed from an introductory portion, which may include a substantially straight outer edge, joined to a spiralling portion. The engaging portion may be generally annular, with an outside wall and an inside wall. In this arrangement the outside wall of the spiralling portion forms the first face of the rotatable lock. 
         [0011]    The height of the engaging portion relative to the body portion may vary around the annulus. It is preferred that the height of the spiralling portion be a minimum at one end of the introductory portion, and at a maximum at a location on the spiralling portion which is located on a line which is perpendicular to the introductory portion and which passes through the central axis of the lock. 
         [0012]    The bearing member may be coupled to an operable member. In a preferred embodiment, the operable member includes a keyed projection which engages with a keyed recess in the bearing member. 
         [0013]    It is preferred that the rotatable lock is retained within the wear member. The wear member may have an internal cavity, with an aperture passing through a side wall of the wear member into the cavity, and the lock being receivable within the cavity. It is preferred that the cavity includes an inner region in which the bearing member can be received, the inner region including the second bearing face, and an outer region in which the operable member can be received. In a preferred embodiment of the invention, the inner and outer regions are separated by a toothed ring, arranged to engage with a toothed ring located about the rotatable lock. At least one of the toothed rings is resilient, such that engagement of the respective teeth will maintain the lock in a desired angular position, but whereby the application of an angular force to the operable member will cause deformation of the resilient toothed ring to allow rotation of the lock. 
         [0014]    In a preferred embodiment of the invention, the operable member includes a tool-receiving recess in which is located a plug formed at least partially of resilient material. The arrangement is such that insertion of a tool within the tool-receiving recess causes compression of the plug, and removal of the tool allows return of the plug to its uncompressed state. 
         [0015]    The base may include a side wall having a recess, the recess having an arcuate wall which forms the first bearing surface. It is preferred that the recess be generally tapered towards the arcuate wall. The recess may include a boss spaced from the arcuate wall, the boss being arranged to engage with the inside wall of the engaging portion of the bearing member in some angular positions, to promote disengagement of the wear member from the base during removal. 
         [0016]    The wear member may be an excavator tooth, and the base may be an adaptor. In this embodiment, it is preferred that the adaptor includes a nose having a top and a bottom, each of the top and the bottom including two substantially flat bearing surfaces separated by concave joining surfaces. 
         [0017]    The excavator tooth has a cavity substantially complementary in shape to the adaptor nose, having substantially flat bearing surfaces separated by convex joining surfaces. The convex joining surfaces of the tooth have curvature slightly less than the concave joining surfaces of the adaptor nose. 
         [0018]    In accordance with a second aspect of the present invention there is provided a coupling for connecting a wear member to a base, the base including a first bearing surface, the wear member including a second bearing surface; the coupling including a rotatable lock having a first face arranged to bear against the first bearing surface and a second face arranged to bear against the second bearing surface, the lock having a central axis about which it can be rotated, the first and second face being both axially and circumferentially spaced relative to central axis of the lock, such that in use the lock can be rotated between a position in which the first and second face bear against the first bearing surface and second bearing surface respectively, and a position in which the first face does not bear against the first bearing surface or the second face does not bear against the second bearing surface. This allows for selective engagement and disengagement of the lock by virtue of turning. Although in a preferred embodiment the present invention allows for tightening of the lock, it will be appreciated that in its simplest form the invention may simply act as a latch to engage the coupling. 
         [0019]    In accordance with a third aspect of the present invention there is provided a coupling for connecting a wear member to a base, the coupling including a lock having at least two positions: a locked position whereby the wear member is restrained from moving relative to the base and an unlocked position in which the wear member is able to move relative to the base in an unrestrained manner, and wherein moving the lock from the locked position to the unlocked position urges the wear member away from the base. 
         [0020]    It is preferred that the lock be rotatable, and that the two positions correspond to two angularly spaced positions of the lock, and that rotation of the lock from the locked position to the unlocked position causes movement of the wear member relative to the base. The movement of the wear member is preferably translational, and may be radial relative to the lock rotation. 
         [0021]    In a fourth aspect of the invention the lock of the third aspect functions simply as a release mechanism for the wear member, rather than as a lock. In accordance with this fourth aspect of the invention there is provided a release mechanism for a wear member mounted onto a base, the release mechanism having at least two positions: a first position in which the wear member is able to be coupled to the base, and a second position in which the release mechanism urges the wear member away from the base. 
         [0022]    It is preferred that the release mechanism be rotatable, and that the two positions correspond to two angularly spaced positions of the release mechanism, and that rotation of the release mechanism from the first position to the second position causes movement of the wear member relative to the base. The movement of the wear member is preferably translational, and may be radial relative to the release mechanism rotation. 
         [0023]    In accordance with a fifth aspect of the present invention there is provided a lock for coupling a wear member to a base, the lock including a hollow for engagement with a tool, wherein a plug is contained within the hollow, the plug being resiliently compressible such that a tool can engage with the hollow by compressing the plug. When the tool is removed, the plug can return to its original configuration. In this way, the ingress of dust and particulate matter into the hollow is substantially impeded. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    It will be convenient to further describe the invention with reference to preferred embodiments of the coupling mechanism of the present invention. Other embodiments are possible, and consequently the particularity of the following discussion is not to be understood as superseding the generality of the preceding description of the invention. In the drawings: 
           [0025]      FIG. 1  is a perspective of an adaptor and tooth having a coupling in accordance with the present invention, shown prior to coupling; 
           [0026]      FIG. 2  is a perspective of the adaptor and tooth of  FIG. 1  shown coupled; 
           [0027]      FIG. 3  is a front perspective of a nose of the adaptor of  FIG. 1 , showing a first side; 
           [0028]      FIG. 4  is a rear perspective of the adaptor nose of  FIG. 3 , showing a second side; 
           [0029]      FIG. 5  is an external view of a lock-receiving aperture in the tooth of  FIG. 1 , shown prior to receiving a toothed ring; 
           [0030]      FIG. 6  is an internal view of the lock-receiving aperture of  FIG. 5 ; 
           [0031]      FIG. 7  is an external view of the lock-receiving aperture of  FIG. 5 , shown with the toothed ring inserted; 
           [0032]      FIG. 8  is an internal view of the lock-receiving aperture of  FIG. 7 ; 
           [0033]      FIG. 9(   a ) is a side view of the lock-receiving aperture of  FIG. 5 ; 
           [0034]      FIG. 9(   b ) is a cross section through line P-P marked on  FIG. 9   a;    
           [0035]      FIG. 10  is an exploded view of a lock from the coupling of  FIG. 1 , viewed from the outside; 
           [0036]      FIG. 11  is an exploded view of the lock of  FIG. 10 , viewed from the inside; 
           [0037]      FIG. 12  is a set of side and plan views of a bearing member within the lock of  FIG. 10 ; 
           [0038]      FIG. 13  is a set of side and plan views of an operable member within the lock of  FIG. 10 ; 
           [0039]      FIG. 14(   a ) is a side view of the bearing member of  FIG. 12 ; 
           [0040]      FIG. 14(   b ) is a cross section through line D-D marked on  FIG. 14(   a ); 
           [0041]      FIG. 14(   c ) is a cross section through line E-E marked on  FIG. 14(   a ); 
           [0042]      FIG. 14(   d ) is a cross section through line F-F marked on  FIG. 14(   a ); 
           [0043]      FIG. 14(   e ) is a cross section through line G-G marked on  FIG. 14(   a ); 
           [0044]      FIG. 14(   f ) is a cross section through line H-H marked on  FIG. 14(   a ); 
           [0045]      FIG. 14(   g ) is a cross section through line I-I marked on  FIG. 14(   a ); 
           [0046]      FIG. 14(   h ) is a cross section through line J-J marked on  FIG. 14(   a ); 
           [0047]      FIG. 15(   a ) is a rear view of the tooth of  FIG. 1 , shown receiving the lock of  FIG. 10 ; 
           [0048]      FIG. 15(   b ) is a rear view of the tooth of  FIG. 15   a , shown with the lock in place; 
           [0049]      FIG. 16  is a side view of the adaptor and tooth of  FIG. 1  during coupling; 
           [0050]      FIG. 17  is a cross section through line A-A marked on  FIG. 16 ; 
           [0051]      FIG. 18  is a cross section through line O-O marked on  FIG. 17 ; 
           [0052]      FIG. 19  is an enlargement of a portion of  FIG. 17  showing the lock of  FIG. 10 ; 
           [0053]      FIG. 20  is a side view of the adaptor and tooth of  FIG. 1  following coupling; 
           [0054]      FIG. 21  is a cross section through line C-C marked on  FIG. 20 ; 
           [0055]      FIG. 22  is a cross section through line K-K marked on  FIG. 21 ; 
           [0056]      FIG. 23  is an enlargement of a portion of  FIG. 21  showing the lock of  FIG. 10 ; 
           [0057]      FIG. 24  is a perspective of a driving tool being used to operate the coupling of  FIG. 1 ; 
           [0058]      FIG. 24(   a ) is an exploded view of a portion of the lock of  FIG. 10 ; 
           [0059]      FIGS. 25(   a ) to  25 ( c ) are sequential cross sections of the driving tool of  FIG. 24  in use; 
           [0060]      FIG. 26  is a plan view of the adaptor and tooth of  FIG. 1 ; 
           [0061]      FIG. 27  is a cross section through line Q-Q marked on  FIG. 26 ; 
           [0062]      FIG. 28  is a plan view of the adaptor and tooth of  FIG. 1 ; 
           [0063]      FIG. 29  is a cross section through line Z-Z marked on  FIG. 28 ; 
           [0064]      FIG. 30  is a plan view of the adaptor and tooth of  FIG. 1 ; 
           [0065]      FIG. 31  is a cross section through line R-R marked on  FIG. 30 ; 
           [0066]      FIG. 32  is a cross section through line W-W marked on  FIG. 31 ; 
           [0067]      FIG. 33  is a cross section through line X-X marked on  FIG. 31 ; 
           [0068]      FIG. 34  is a perspective of the nose of the adaptor of  FIG. 1 , showing some of the bearing areas of the nose; 
           [0069]      FIG. 35  is a perspective of a bucket lip and lip shroud having a coupling in accordance with the present invention, shown prior to coupling; 
           [0070]      FIG. 36  is a perspective of the bucket lip and lip shroud of  FIG. 35  shown coupled; 
           [0071]      FIG. 37  is a rear perspective of the lip shroud of  FIG. 35 ; 
           [0072]      FIG. 38  is a rear perspective of the lip shroud of  FIG. 35  shown with an exploded view of a lock from within the coupling of  FIG. 35 ; 
           [0073]      FIG. 39  is a cross section of the bucket lip and shroud of  FIG. 35  during coupling; and 
           [0074]      FIG. 40  is a cross section of the bucket lip and shroud of  FIG. 35  shown coupled. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0075]    Referring to the Figures,  FIG. 1  shows a portion of a lip  10  of an excavator bucket, onto which is located an adaptor  20 . A tooth  70  is shown ready for attachment to the adaptor  20 . 
         [0076]    The adaptor  20  has a body part  21 ; a nose  22  extending forwardly of the body part  21  onto which the tooth  70  can be located, and two legs  24  extending rearwardly of the body part  21  about the lip  10 . 
         [0077]    The nose  22  can be more clearly seen in  FIGS. 3 and 4 . It has a front wall  26 , a top  28 , a first side wall  30 , a bottom  32 , and a second side wall  34 . The top  28  and the bottom  32  each extend from the body part  21  to the front wall  26 . The top  28  and the bottom  32  are not parallel, but are generally angled towards each other such that the nose  22  reduces in height towards the front wall  26 , with the front wall  26  being about half the height of the body part  21 . 
         [0078]    The first and second side walls  30 ,  34 , each extend from the body portion  21  to the front wall  26 . The first and second side walls  30 ,  34  are each stepped in from the body portion  21 , but thereafter are generally parallel towards the front wall  26 . The top  28 , bottom  32  and front wall  26  are thus all generally rectangular, whereas the first and second side walls  30 ,  34  are generally trapezoid. 
         [0079]    The precise shapes of these surfaces will be discussed further below. 
         [0080]    The first side wall  30  and the second side wall  34  each include a recess  40 . The recess  40  has a rear edge  42 , which is generally parallel to the rearmost part of the respective side wall  30 ,  34 , and an arcuate front edge  44 , which extends from either end of the rear edge  42  towards the front wall  26 . 
         [0081]    The recess  40  is generally tapered, such that it increases in depth towards the front wall  26 . The recess  40  has a base  46 , which is part frusto-conical in shape, the cone axis being nearly perpendicular to the side wall  30 ,  34  and being located towards the rear edge  42 , and the cone angle being extremely shallow. In the embodiment shown, the cone axis is actually about 11° away from the perpendicular, with an outer end of the axis closer to the front wall  26  than an inner end. The base  46  is thus slightly convex. The rear of the base  46 , which is the rear edge  42 , is substantially level with the side wall  30 ,  34 . The front of the base  46 , which is located beneath the centre of the front edge  44 , is inwardly spaced from the side wall  30 ,  34 . An arcuate recess wall  48  extends between the front edge  44  and the base  46 . The recess wall  48  is oriented at about 75° to the side wall  30 ,  34 . The height of the recess wall  48  thus tapers from zero at its outer edges, at the ends of the rear edge  42 , to a maximum height at the centre of the front edge  44 . 
         [0082]    Each side wall  30 ,  34  also includes a locating boss  50 . The boss  50  is located within the recess  40 , and has an outer face  52 . The outer face  52  is generally rectangular with parallel upper and lower edges  54  extending from the rear edge  42  of the recess  40  towards the front wall  26 . The outer face  52  is slightly convex, with the upper and lower edges  54  being parallel to a central axis of the adaptor nose  22  and being level with the rear edge  42 , and a centre line of the outer face  52  protruding slightly higher. 
         [0083]    The outer face  52  has a front edge  55 . The corners between the front edge  55  and the upper and lower edges  54  are radiussed, with a radius of curvature about one-third of the length of the front edge  55 . The boss  50  has a side wall  56  which is generally perpendicular to the outer face  52 , and extends between the outer face  52  and the recess base  46 . The side wall  56  consists of two flat triangular portions beneath the upper and lower edges  54 , a rectangular front portion  58 , and two part-conical joining portions. The front portion  58  is spaced from a front-most part of the recess wall  48 . 
         [0084]    The tooth  70  has an internal cavity  72  which is generally complementary in shape to the nose  22  of the adaptor  20 . The tooth  70  has a first side wall  74  which locates over the first side wall  30  of the nose  22 . 
         [0085]    A lock-receiving aperture  76  extends through the first side wall  74  between an outside surface of the tooth  70  and the internal cavity  72 . The aperture  76  is generally circular, and arranged to align with the recess  40  when the tooth  70  is located about the adaptor  20 . The lock-receiving aperture  76  is shown in detail in  FIGS. 5 to 9 . 
         [0086]    The aperture  76  is not perpendicular to the first side wall  74 , but is in fact oriented at an angle of about 10° to 15° toward the rear of the cavity  72 . This can be most clearly seen in  FIG. 9 . 
         [0087]    The lock-receiving aperture  76  has three parts: a tooth recess  78  extending into the first side wall  74  from the internal cavity  72 ; a lock-locating recess  80  extending into the first side wall  74  from the outside surface of the tooth  70 ; and a ring-receiving portion  82  located between the tooth recess  78  and the lock-locating recess  80 . The tooth recess  78  and the lock-locating recess  80  are both circular, being coaxial and of similar diameter. The ring-receiving portion  82  is substantially circular, and is of smaller diameter than the tooth recess  78  and lock-locating recess  80 . The aperture  76  therefore has a stepped configuration. 
         [0088]    The ring-receiving portion  82  has a number of keyed apertures around its periphery, in order to securely receive a toothed ring  84  within. The toothed ring  84 , which may be made of aluminium or a hard plastic, has a generally circular internal surface formed by a plurality of retaining teeth  86 . The toothed ring  84  has outer keyed projections sized and shaped to be press fitted into the ring receiving portion  82  of the aperture  76 . When the toothed ring  84  is thus fitted within the aperture  76 , as shown in  FIG. 7 , the teeth  86  define the separation between the tooth recess  78  and the lock-locating recess  80 . 
         [0089]    The tooth  70  is coupled to the nose  22  of the adaptor  20  by means of a lock  100 . The lock  100  can be seen in  FIGS. 10 and 11 . 
         [0090]    The lock  100  includes a bearing member  102 , a toothed engaging ring  104 , and an operable member  106 . The lock  100  also includes a screw  108  and a plug  110 . 
         [0091]    The bearing member  102 , which is shown in  FIG. 12 , has a generally cylindrical body portion  112  sized to locate within the tooth recess  78  of the tooth  70 . The body portion  112  has a first side  114  oriented, in use, towards the outside of the tooth  70 ; and a second side  116  oriented, in use, towards the cavity  72 . 
         [0092]    The first side  114  includes a centrally positioned, keyed recess  118  extending into the body portion  112 . 
         [0093]    An engaging portion  120  is located on the second side  116 , extending outwardly from the body portion  112 . 
         [0094]    The engaging portion  120  has a generally annular outer face  122 , which is angled relative to the sides  114 ,  116  of the body portion  112 . The engaging portion  120  thus has an outside wall  124  and an inside wall  125  which extend at an angle of about 75° to 80° from the second side  116  of the body portion  112 , the outside wall  124  and inside wall  125  both extending between the second side  116  of the body portion  112  and the outer face  122 . The height of the outside wall  124  and inside wall  125  vary circumferentially about the outer face  122 . 
         [0095]    Although the outer face  122  has been described as generally annular, the annulus is not circular. It includes an introductory portion  126 , the introductory portion having an outer edge (that is, part of the outside wall  124 ) including both a part-cylindrical portion, having a radius close to the radius of the body portion  112  and a substantially straight portion. The outer face  122  also includes a spiralling portion  127  which gradually increases in radius through about 300°, from a minimum radius where it joins the substantially straight edge portion of the introductory portion  126 , to a maximum radius where it joins the part-cylindrical portion of the introductory portion  126 . The height of the outside wall  124  and the inside wall  125  are at a minimum at the part-cylindrical portion of the introductory portion. The height of the outside wall gradually increases along the introductory portion  126  and then the spiralling portion  127 , reaching a maximum height at a location about 215° around the annulus from the minimum height portion. The height then decreases through the remaining 135° of the spiralling portion  127 . This can be seen through consideration of the sequential cross sections of  FIG. 14 . 
         [0096]    It will also be observed that the outside wall  124  and inside wall  125  are not the same height, with the outside wall  124  being higher than the inside wall around the spiralling portion  127  and the inside wall being higher than the outside wall along the introductory portion  126 . 
         [0097]    A screw receiving aperture  128  passes centrally through the body portion  112 , inside the annulus of the engaging portion  120 . The screw receiving aperture  128  is countersunk on the second side  116  of the body portion  112 , again inside the annulus of the engaging portion  120 . 
         [0098]    The toothed engaging ring  104  has engaging teeth  130  arranged about its outside, sized to engage with the retaining teeth  86  of the toothed ring  84 . The toothed engaging ring  104  is formed from a resilient material such as rubber. 
         [0099]    The toothed engaging ring  104  has a keyed central aperture  132  which corresponds with the keyed recess of the bearing member  102 . 
         [0100]    The operable member  106 , best seen in  FIG. 13 , has a generally cylindrical body portion  134  sized to locate within the lock-locating recess  80  of the tooth  70 . The body portion  134  has a first side  136  oriented, in use, towards the outside of the tooth  70 ; and a second side  138  oriented, in use, towards the cavity  72 . 
         [0101]    The first side  136  includes a centrally positioned, square-sided hollow or recess  140  extending into the body portion  134 . 
         [0102]    A keyed projection  142  is located on the second side  138 , extending outwardly from the body portion  134 . The keyed projection  142  is sized and shaped to engage with both the central aperture  132  of the engaging ring  104  and the keyed recess  118  of the bearing member  102 . The keyed projection  142  includes a centrally located screw receiving aperture  144 . 
         [0103]    The plug  110  is square sided, and arranged to be located within the square-sided recess  140 . The plug  110  is formed of a resilient material fixed to a rigid base plate. The base plate includes an internally threaded screw engaging aperture  145 . 
         [0104]    The arrangement is such that the engaging ring  104  and the bearing member  102  can be fitted in turn on the keyed projection  142  of the operable member  106 , and these three elements of the lock  100  can be held together by the screw  108  passing through respective receiving apertures  128 ,  144  and being screwed into screw engaging aperture  145 . It will be appreciated that the keyed arrangement prevents relative rotation, and the screw  108  clamps the components together to prevent relative axial movement. It is also noted that the engaging ring  104 , being rubber, may be vulcanised to the operable member  106 . 
         [0105]    The lock  100  can be fitted into the tooth  70  as shown in  FIGS. 15(   a ) and  15 ( b ), with the bearing member  102  inserted from the cavity  72  and the operable member  106  inserted from outside the tooth  70 . 
         [0106]    Operation of the lock  100  in coupling the tooth  70  to the adaptor nose  22  will now be described. 
         [0107]    To prepare the coupling for use, the lock  100  is rotated within the tooth aperture  76  to a position whereby the introductory portion  126  of the engaging portion  120  is oriented towards the front of the tooth  70 . This means that the outer face  122  of the engaging portion  120  is generally parallel to the inside of the tooth side wall  74 , as the maximum height region of the engaging portion  120  is located within the portion of the tooth recess  78  which extends furthest inward from the inside wall. 
         [0108]    The tooth  70  can now be slid over the adaptor nose  22 , to the position shown in  FIGS. 16 to 19 . In this position the highest part of the outer face  122  of the engaging portion  120  locates adjacent a rear part of the outer face  52  of the boss  50  of the adaptor nose  22 . A portion of the inside wall  125  of the engaging portion  120  adjacent to the introductory portion  126  abuts and bears against the front portion  58  of the side wall  56  of the boss  50 . 
         [0109]    Clockwise rotation of the lock  100  causes movement of the engaging portion  120  relative to the adaptor recess  40 . Due to the increasing radius of the spiralling portion  127 , as the lock  100  is rotated the inside wall  125  of the engaging portion  120  ceases to bear against the boss  50 , but the outside wall  124  of the engaging portion  120  bears against the recess wall  48 . The higher part of the engaging portion  120  moves into the recess  40 , thus increasing the contact bearing area between the outside wall  124  and the recess wall  48 . 
         [0110]    Rotation of the lock  100  through 180° is shown in  FIGS. 20 to 23 . In this position the lock  100  firmly holds the tooth  70  relative to the adaptor  20 . In particular, the outside wall  124  of the engaging portion  120  is a first face of the lock  100 , bearing against a first bearing surface  150  being the recess wall  48  of the adaptor  20 ; and the outer periphery of the body portion  112  of the bearing member  102  is a second face of the lock  100 , bearing against a second bearing surface  152  being the tooth recess  78  of the tooth  70 . 
         [0111]    It will be appreciated that the arrangement is such that the lock tightens against both first and second bearing surfaces  150 ,  152  without necessarily requiring 180° rotation. 
         [0112]    When removal of the lock  100  is required, the lock  100  can be rotated in the opposite direction. When the inside wall  125  comes into contact with the boss  50 , further rotation acts to push the tooth  70  away from the body part  21  of the adaptor  20 , allowing for easy removal of the tooth  70 . This may be viewed as movement of the lock  100  between a locked position, in which the lock bears against both first and second bearing surfaces  150 ,  152 ; and an unlocked position in which the inside wall  125  bears against the front portion  58  of the boss  50 , thus urging the tooth  70  away from the adaptor  20 . It will be appreciated that the tooth  70  is urged away in a radial direction from the lock  100 , and that its movement is therefore translational. 
         [0113]    In this way the lock  100  functions as a release mechanism for the tooth  70 , moving between a first position (the locked position) in which the tooth  70  can be coupled to the adaptor  20  and a second position (the unlocked position) in which the tooth  70  is urged away from the adaptor  20 . 
         [0114]    The lock  100  is maintained in a desired angular position by engagement between the retaining teeth  86  of the toothed ring  84  and the engaging teeth  130  of the engaging ring  104 . When rotation of the lock  100  is required, this may be effected using a square-ended driver  160  as shown in  FIGS. 24 and 25 . 
         [0115]    The plug  110  is resilient, with an outer cover  111 . Insertion of the square-ended driver  160  into the square-sided recess  140  causes compression of the plug  110 , within the square-sided recess  140 . When the driver  160  is removed, the plug  110  expands to again fill the recess  140 . This sequence can be seen in  FIGS. 25(   a ) to  25 ( c ). 
         [0116]    In addition to the lock  100 , coupling of the tooth  70  to the adaptor  20  is assisted by the complementary shape of the adaptor nose  22  and the tooth cavity  72 . 
         [0117]    The top  28  and bottom  32  of the nose  22  each have a contoured surface, and include a first bearing surface  170  and second bearing surface  172 , which are substantially flat, and are separated by concave joining surfaces  174 . The first and second bearing surfaces  170 ,  172  are each narrower than the width of the nose  22 , with the first bearing surface  170  being located within an apparent scooped portion  176  of the top  28  and bottom  32  near the front wall  26 . 
         [0118]    The tooth cavity  72  is largely complementary in shape to the adaptor nose  22 , with convex surfaces having curvature slightly less than the concave joining surfaces  174 . This ensures small clearances around the curved surfaces, and full contact along the flat bearing surfaces  170 ,  172 . 
         [0119]    The bearing connection between the adaptor  20  and the tooth  70  is in a centre portion of the adaptor nose  22 . This can be seen in a comparison between a cross section taken through the centre, as in  FIG. 27 , and a cross section taken towards the side, as in  FIG. 29 . 
         [0120]    Although the coupling has been described as between a tooth and adaptor, it will be appreciated that other GET couplings can be locked together in a similar fashion.  FIGS. 35 to 40  show a lip shroud  180  being connected to a bucket lip  10 , onto which has been mounted a lock coupling  182  similar to the first side wall  30  of the adaptor nose  22 . A lock  100  identical to that described in relation to the tooth  70  can be used to couple the lip shroud  180  to the lock coupling  182  in an analogous manner. 
         [0121]    Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.