Abstract:
A fastener for fastening at least two work pieces together comprises a body and a pin. The body has a head, a shaft extending from the head and an open hollow core extending into the shaft. The shaft has a retaining means spaced from the head to accommodate the work pieces. The retaining mechanism has a contracted configuration where it is sized to pass through holes in the work pieces and an expanded configuration where it is expanded in size or spacing such that the shaft is unable to be removed from the holes in the work pieces. The retaining mechanism defines a constriction in the core at which the core has a first width when the retaining mechanism is in its contracted configuration. The pin is locatable in the core. The pin has a least a first portion with an external width greater than the first width of the core. The pin is movable within the core and is arranged to cause the retaining mechanism to change to the expanded configuration as the first portion of the pin moves into contact with the constriction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119 to PCT/AU2006/000522, filed Apr. 18, 2006, which claims priority to AU 2005901861 and AU 2006900759, which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a fastener for fastening two or more work pieces together. 
     BACKGROUND OF THE INVENTION 
     Plates of hardened material, such as steel and steel alloys, are often used to minimise the effect of wear on structural elements of a piece of equipment. Often, these hardened plates are called wear plates because the material of the plate is selected for its resistance to wear. Examples of equipment which use wear plates includes hoppers, bins and chutes used in rock handling equipment and in an ore processing plant. This sort of equipment can be exposed to wear in the form of sliding and/or gouging abrasion. The wear plates act as a sacrificial element so that the plates are worn rather than the structural element of the equipment. The plates can be readily exchanged once worn, thus extending the life of the working equipment. 
     Typically, the wear plates are fastened to the structural elements using threaded fasteners. However, where access is limited such threaded fasteners can be difficult to use. There is a need for a non threaded fastener which can fasten two work pieces together, such as a wear plate to a structural element. It is noted that the fastener of the present invention has broader application than fastening a wear plate to a support structure. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided a fastener for fastening at least two work pieces together, each work piece having a hole therein, the fastener comprising:
         a body having a head, a shaft extending from the head and an open hollow core extending into the shaft, wherein the shaft has a retaining means spaced from the head to accommodate the work pieces, wherein the retaining means has a contracted configuration where it is sized to pass through the holes in the work pieces and an expanded configuration where it is expanded in size or spacing such that the shaft is unable to be removed from the holes in the work pieces, wherein the retaining means defines a constriction in the core at which the core has a first width when the retaining means is in its contracted configuration; and   a pin locatable in the core, the pin having a least a first portion with an external width greater than the first width of the core, wherein the pin is movable within the core and is arranged to cause the retaining means to change to the expanded configuration as the first portion of the pin moves into contact with the constriction;   whereby, in use, the body is inserted through the holes in the work pieces such that the shaft extends through the hole in at least a second of the work pieces and then pin is subsequently driven through the core such that the first portion of the pin contacts the constriction in the core thereby causing the retaining means to expand to retain the work pieces together between the head and the expanded retaining means.       

     According to a second aspect of the present invention there is provided a fastener for fastening at least two work pieces together, each work piece having a hole therein, the fastener comprising:
         a body having a head, a shaft extending from the head and an open hollow core extending into the shaft, wherein the shaft has an expandable means spaced from the head to accommodate the work pieces, wherein the expandable means defines a constriction in the core at which the core has a first width when the expandable means is not expanded; and   a pin locatable in the core, the pin having a least a first portion with an external width greater than the first width of the core, wherein the pin is movable within the core and is arranged to expand the expandable means as the first portion of the pin moves into contact with the constriction;   whereby, in use, the body is inserted through the holes in the work pieces such that the shaft extends through the hole in at least a second of the work pieces and then pin is subsequently driven through the core such that the first portion of the pin contacts the constriction in the core thereby causing the expandable means to expand so that the shaft is unable to be removed from the holes in the work pieces thereby fixing the work pieces together between the head and the expanded expandable means.       

     Typically, the expanding action of the retaining/expandable means works against the second work piece to apply a force to draw the head toward the second work piece. The head applies a force to a first of the work pieces which resists the applied force, creating a clamping force between the head and the retaining/expandable means that clamps the two work pieces together. 
     In one embodiment the retaining means/expandable means works directly against the second work piece. In another embodiment the retaining means/expandable means works directly against the second work piece through an intermediate element. 
     Preferably, the pin is removable from the core. Even more preferably, the pin can be removed in the same direction as it is inserted. 
     Preferably, the retaining/expandable means is retractable to a state substantially the same as before it was expanded when the pin is removed from the core. 
     Typically the first width is smaller than a second width of an adjacent non-expandable portion of the core. Typically the external width of the pin is substantially the same as the second width of the core. 
     Preferably, the core extends through the length of the body. 
     In one embodiment, the retaining/expandable means comprises one or more balls each positioned within a tunnel extending radially from the core such that, in use, the pin forces the balls radially outward through the respective tunnels. Thus, the pin forces the balls to at least indirectly bear against a portion of the second work piece. In a preferred form of this embodiment the one or more balls project inwardly into the core to form the constriction. 
     In one embodiment the constriction is in the form of one or more balls which project inwardly into the core. 
     Preferably, the pin has a conical portion which, in use, aids the expansion of the retaining/expandable means by acting in a wedge-like manner when a larger part of the conical portion contacts the constriction in the core. 
     Preferably, the retaining/expandable means may further comprise an annular sleeve disposed about the shaft to retain the balls within the tunnels. Thus the sleeve is an intermediate element between the balls and the second work piece. 
     In one embodiment the annular sleeve is made of a ductile material such that the annular sleeve is deformed as the balls are forced out of the respective tunnels. Preferably, the sleeve is resilient. 
     In another embodiment the annular sleeve has a core there through with a middle portion being sized to accept the balls when they are forced radially by action of the pin, and the core on either side of the middle portion is sized to retain the expanded balls in the middle portion. Preferably the sleeve has a largest outer diameter larger than the diameter of the hole through the second work piece. 
     Preferably the sleeve has a smallest outer diameter smaller than the diameter of the hole through the second work pieces so that the portion having the smallest outer diameter sits at least partly within the hole of the second work piece. 
     In an alternative embodiment, the retaining/expandable means comprises a narrow portion of the core in which the cross section of the core narrows to define the constriction. The narrow portion is arranged such that the cross section of the core narrows toward the end of the shaft remote from the head. Thus, the wall thickness of the shaft about the narrow portion increases as the cross section narrows. 
     Thus, as the pin is inserted into the core and the first portion of the pin contacts the narrow portion is expanded. Typically the expansion of the narrow portion works against the second work piece to apply a force to draw the head toward the second work piece. Preferably the narrow portion is divided into a plurality of expanding fingers which move radially as the pin is driven into the constriction. 
     The pin may further comprise an annular recess in which a spring clip is provided, the body being arranged to allow the spring clip to pass through the core in one direction. In its relaxed state the spring clip has an outer dimension larger than of the pin. The spring clip is compressible such that the outer dimension can be reduced to be the same as that of the pin. Thus, the spring clip can be compressed as it passes through the constriction of the core. 
     In one embodiment the head is integrally formed on the shaft. In another embodiment the head is threadingly engaged with the shaft such that the location of the head on the shaft is adjustable. This is advantageous when the spacing between the head and the retaining/expanded means needs to be adjusted to provide snug contact and a desired clamping force between the head and the retaining/expandable means. 
     Preferably, the head has a frusto-conical portion. More preferably, the frusto-conical portion has a half opening angle in the range of 5° to 50°. Even more preferably, the frusto-conical portion has a half opening angle of 15°. 
     Preferably, the smallest outer diameter of the head is larger than the outer diameter of the shaft adjacent the head. Thus, there is a step between the head and the shaft. 
     In another embodiment the head is of a regular cylindrical shape having a diameter larger than the diameter of the shaft adjacent the head. 
     Preferably, the hole in the first work piece has a shape that complements the shape of the head such that the head can be received within the hole in the first work piece. 
     In one embodiment, the head is hardened to at least a Brinnell Hardeners of 350 BH. 
     In another embodiment the pin is removable from the shaft. Upon removal of the pin the retaining/expandable means is able to contract thereby allowing the shaft to be removed from the holes of the work pieces to remove the fastener. 
     According to a third aspect of the present invention, there is provided a method for fastening at least two work pieces together, each work piece having a hole therein, the method comprising the steps of:
         providing a fastener having a body having a head, a shaft extending from the head and an open hollow core extending into the shaft, wherein the shaft has an expandable means spaced from the head to accommodate the work pieces, wherein the expandable means defines a constriction in the core at which the core has a first width when the expandable means is not expanded, and a pin locatable in the core, the pin having at least a first portion with an exterior width greater than the first width of the core, wherein the pin is movable within the core and is arranged to expand the expandable means when the first portion of the pin moves into contact with the core constriction;   aligning the work pieces such that the holes overlap;   inserting the body through the holes such that at least the shaft has passed through the holes of all the work pieces; and   driving the pin through the core such that the first portion of the pin contacts the constriction in the core thereby causing the expandable means to expand so that the shaft is unable to be removed from the holes in the work pieces thereby fixing the work pieces together between the head and the expanded expandable means.       

     Preferably, expanding the expandable means involves, at least in part, radial expansion of the expandable means. 
     Preferably, the pin has a conical portion such that, when driving the pin through the core, the conical portion contacts the constriction in the core which facilitates the radial movement of the expandable means. 
     According to a fourth aspect of the present invention there is provided a fastener for fastening at least two work pieces together, each work piece having a hole therein, the fastener comprising:
         a body having a frustoconical wear resistant head and a shaft extending from the head, the shaft having an expandable means spaced from the head to accommodate the work pieces;   wherein the smallest outer diameter of the head is larger than the outer diameter of the shaft adjacent the head;   whereby, in use, the body is inserted through the holes in the work pieces such that the shaft extends through the hole in at least a second of the work pieces and then the expandable means is expanded so that the shaft is unable to be removed from the holes in the work pieces thereby fixing the work pieces together between the head and the expanded expandable means.       

     According to a fifth aspect of the present invention there is provided a fastener for fastening at least two work pieces together, each work piece having a hole therein, the fastener comprising:
         a body having a frusto-conical hardened head and a shaft extending from the head, the shaft having an expandable means spaced from the head to accommodate the work pieces;   wherein the smallest outer diameter of the head is larger than the outer diameter of the shaft adjacent the head;   whereby, in use, the body is inserted through the holes in the work pieces such that the shaft extends through the hole in at least a second of the work pieces and then the expandable means is expanded so that the shaft is unable to be removed from the holes in the work piece thereby fixing the work pieces together between the head and the expanded expandable means.       

     According to a sixth aspect of the present invention there is provided a fastener for fastening at least two work pieces together, each work piece having a hole therein, the fastener comprising:
         a body having a head, a shaft extending from the head and an open hollow core extending into the shaft, wherein the shaft has an expandable and contractible means spaced from the head to accommodate the work pieces; and   a pin locatable in the core, wherein the pin is movable within the core and is arranged to expand the expandable and contractible means as the pin moves into the core;   wherein the expandable and contractible means contracts when the pin is removed from the core;   whereby, in use, the body is inserted through the holes in the work pieces such that the shaft extends through the hole in at least a second of the work pieces and then pin is subsequently inserted into the core such that the first portion of the pin contacts the constriction in the core thereby causing the expandable and contractible means to expand so that the shaft is unable to be removed from the holes in the work pieces thereby fixing the work pieces together between the head and the expanded expandable and contractible means, and when the pin is removed from the core the expandable and contractible means is caused to contract thereby enabling the shaft to be removed from the holes in the work pieces to release the fastener.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be more easily understood, embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1 : is an cross sectional side elevation view of a fastener according to a first embodiment of the present invention in a first configuration; 
         FIG. 2 : is a cross section view of the fastener of  FIG. 1 , as viewed along the line II-II; 
         FIG. 3 : is a cross sectional side elevation view of the fastener of  FIG. 1  in a second configuration; 
         FIG. 4 : is a cross sectional side elevation view of the fastener of  FIG. 1  in a third configuration; 
         FIG. 5 : is a cross sectional side elevation view of the fastener of  FIG. 1  in a fourth configuration; 
         FIG. 6 : is an cross sectional side elevation view of a fastener according to a second embodiment of the present invention in a first configuration; 
         FIG. 7 : is a cross sectional side elevation view of the fastener of  FIG. 6  in a second configuration; 
         FIG. 8 : is a schematic cross sectional side elevation view of a fastener according to a third embodiment of the present invention in a first configuration; 
         FIG. 9 : is a schematic cross sectional side elevation view of the fastener of  FIG. 8  in a second configuration; 
         FIG. 10 : is a schematic cross sectional side elevation view of a fastener according to a fourth embodiment of the present invention in a first configuration; 
         FIG. 11 : is a schematic cross sectional side elevation view of the fastener of  FIG. 10  in a second configuration; 
         FIG. 12 : is a schematic exploded cross sectional side elevation of the fastener of  FIG. 10  showing individual elements of the fastener; 
         FIG. 13 : is a schematic cross sectional side elevation view of a fastener according to a fifth embodiment of the present invention in a first configuration; 
         FIG. 14 : is a schematic cross sectional side elevation view of the fastener of  FIG. 13  in a second configuration; 
         FIG. 15 : is a schematic cross sectional side elevation view of the fastener in the configuration shown in  FIG. 14  having been subject to wear; 
         FIG. 16 : is a schematic cross sectional side elevation view of the fastener shown in  FIG. 15  in a third configuration; and 
         FIG. 17 : is a schematic cross sectional side elevation view of the fastener of  FIG. 15  in a fourth configuration. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 to 5  show an elongate fastener  10  according to a first embodiment of the present invention. The fastener  10  comprises a body  12  and a pin  14 . The body  12  has a head  16  from which a shaft  18  extends. The body  12  has an opening  20  in the head  16  and an opening  22  in the end of the shaft  18 , such that the openings  20 ,  22  are provided on opposing surfaces of the body  12 . A hollow core  24  defines an axial throughway between the openings  20 ,  22 . The wall surface  25  of the core  24  is of a constant cross section along its length. 
     In this embodiment, the head  16  is frusto-conical in shape. The diameter of the shaft  18  is smaller than the smallest external diameter of the head  16 . 
     The shaft  18  has three tunnels  26  which extend radially from the core  24 . Each tunnel  26  is provided with a ball  28 . The tunnels  26  are dimensioned such that each ball  28  can pass through the respective tunnel  26 . A retaining sleeve  30  is provided which surrounds a portion of the shaft  18  such that the openings  33  of the tunnels  26  in the circumferential wall of the shaft  18  are covered. The retaining sleeve  30  is made of a ductile material (such as mild steel, aluminum, rubber or plastic) so that it is deformable. An adhesive product, such as Silastic®, is used to adhere the retaining sleeve  30  to the shaft  18 . 
     The pin  14  has a generally conical first portion  32 , which is tapered to form a small rounded end  34 . A second portion  36 , contiguous with the first portion, of the pin member  14  has a constant cross section such that the shape and size of the second portion  36  complements that of the core  24 . The pin  14  terminates with a head  40 . 
       FIG. 1  shows the fastener  10  employed to fasten two work pieces, such as wear plate  54  and backing plate  56 , together. The body  12  of the fastener  10  is first inserted into concentric holes  50 ,  52  in the wear plate  54  and the backing plate  56 , respectively. The head  16  is profiled such that it complements the shape of the hole  50  in the wear plate  54 . The surface  38  adjacent the opening  20  is approximately flush with the wearing surface  60  of the wear plate  54 . 
     The pin  14  is inserted into the core  24  such that the conical end  34  is adjacent the balls  28 , as shown in  FIG. 1 . The pin  14  is then driven into the core  24 , for example by hammering the head  40 . Initially, the balls  28  are positioned such that each ball  28  is partly in the core, as shown in  FIG. 2 , thereby constricting the width of the throughway of the core at that position. Due to the tapered shape of the first portion  32 , the balls  28  are each pushed by the pin  14  through their respective tunnels  26 . As the balls  28  move outwards, the retaining sleeve  30  is expanded at least in the regions in contact with the balls  28 . The pin  14  is driven into the core  24  until the head  40  of the pin  14  is approximately flush with the wearing surface  38  of the head  16 , as shown in  FIG. 3 . 
     By forcing the balls  28  radially outward through the tunnels  26 , force is applied by the retaining sleeve  30  against the rear surface  58  of the backing plate  56 . This force creates a wedging action, which draws the head  16  against the hole  50  in the wear plate  54 . Accordingly, a compressive force is generated that fastens the wear plate  54  and backing plate  56  together. 
     Clearly, the position and direction of the tunnels  26  relative to the position of rear surface  58  will have an influence on the level of the compressive force generated. Ideally, the fastener  10 , and thus the position of the tunnels  26  along the length of the shaft  18 , will be selected according to the thickness of the backing plate  56 . It will be appreciated that one or more washers may be provided about the shaft  18  and abutting the backing plate  56  in situations where the thickness of the backing plate  56  is less than is required to generate a compressive force. 
     In use, the head  16  and the wear plate  54  are both exposed to abrasion by material such as ore. Accordingly, both the head  16  and wear plate  54  will wear. Ultimately, the fastener  10  and the wear plate  54  need to be replaced. 
     To release the fastener  10 , the pin  14  is first extracted from the core  24 , as shown in  FIG. 4 . The pin  14  can be extracted by driving the pin  14  out of the core  24  from the head  16 , such that it exits the opening  22  in the shaft  18 . The balls  28  are then released so that they can move into the core  24 . As shown in  FIG. 5 , the retaining sleeve  30  can be removed from the shaft  18  and the body  12  withdrawn from the holes  50 ,  52 . 
     The fastener  10  can be applied to, and removed from, the work pieces  54 ,  56  from the side of the wear surface  60  only. In other words, access to the rear side of the backing plate  56  is not required. This can be advantageous where access to the rear side of the backing plate  56  is inhibited or impossible. 
     The frusto-conical shape of the head  16  in this embodiment has a half opening angle of approximately 15°. However, the frusto-conical shape may have a half opening angle in the range of 5° to 50°. The hole  50  in the wear plate  54  is of complementary shape to the head  16 , such that the head  16  can be received within the hole  50 , as shown in the figures. 
     Where the fastener  10  is to be used in fastening a wear plate  54  to a backing plate  56 , the head  16  of the fastener is hardened to approximately the same hardness as the wear plate  54  a Brinnell Hardness. In practice, the head  16  would be hardened to at least about a Brinnell Hardness of 350 BH. 
       FIGS. 6 and 7  depict a fastener  110  according to a second embodiment of the present invention. The fastener  110  comprises a body  112  and a pin  114 . The body  112  has a head  116  from which a shaft  118  extends. The body  112  has an opening  120  in the head  116  and an opening  122  in the end of the shaft  118 , such that the openings  120 ,  122  are provided on opposing surfaces of the body  112 . A hollow core  124  defines an axial throughway between the openings  120 ,  122 . 
     The shaft  118  comprises two sections. The first section  142  has a constant wall thickness. In the first section  142 , the core  124  also has a constant cross section. The second section  144  has a varied wall thickness. The wall thickness in the second section is generally increased when compared with that in the first section  142 . In the second section  144 , the core  124  reduces in cross section toward the opening  122  thereby creating a constriction in the core  124 . The first section  142  is between, and contiguous with, the head  116  and the second section  144 . 
     In this embodiment, the head  116  is frusto-conical in shape. The diameter of the shaft  118  is smaller than the smallest external diameter of the head  116 . 
     The pin  114  comprises a generally conical first portion  132 , which is tapered to form a small rounded end  134 , and a second portion  136 , which has a constant cross section. The shape and size of the second portion  136  complements that of the core  124  in the first section  142 . The pin member  114  terminates with a head  140 . 
     An annular recess  130  is provided along the length of the pin  114  within the second portion  136 . Alternatively, the annular recess  130  can be provided at the interface between the first and second portions  132 ,  136 . A spring clip  128  is received within the annular recess  130 . The spring clip  128 , in its relaxed state, has an outer diameter larger than the diameter of the pin member  114  in the second portion  136 . However, the spring clip  128  is radially compressible such that the outer diameter can be reduced to be approximately that of the second portion  136 . 
     As shown in  FIG. 6 , the narrow end  134  of the pin member  114  is to be inserted through the opening  120  into the core  124 . The opening  120  has a bevelled edge such that the spring clip  128  is radially compressed as the pin member  114  is inserted into the core  124 . 
       FIG. 6  shows the fastener  110  employed to fasten two work pieces, such as wear plate  154  and backing plate  156 , together. The body  112  of the fastener  110  is first inserted into concentric holes  150 ,  152  in the wear plate  154  and the backing plate  156 , respectively. The head  116  is profiled such that it complements the shape of the hole  150  in the wear plate  154 . The surface  138  adjacent the opening  120  is approximately flush with the wearing surface  160  of the wear plate  154 . 
     The pin  114  is inserted into the core  124  such that the pointed end  134  is within the second section  144 , as shown in  FIG. 5 . The pin  114  is then driven into the core  124 , for example by hammering the head  140 . Due to the tapered shape of the first portion  132 , the shaft  118  in the second section  144  is expanded as the pin  114  is driven into the core  124 . 
     Once the spring clip  128  passes through the opening  122 , the spring clip  128  will no longer be in contact with the shaft  118  and will revert to its relaxed state. In this position, the spring clip  128  is unable move into the core  124 . 
     By expanding the second section  144  of the shaft  118 , force is applied by the shaft  118  against the rear surface  158  of the backing plate  156 . This force creates a wedging action, which draws the head  116  against the hole  150  in the wear plate  154 . Accordingly, a compressive force is generated that fastens the wear plate  154  and backing plate  156  together. 
     Clearly, the location of the interface between the first and second sections  142 ,  144  relative to the backing plate  156 , and the wall thickness of the second section  144  will influence the level of the compressive force generated. Ideally, the fastener  110  will be selected according to the thickness of the backing plate  156 . It will be appreciated that one or more washers may be positioned about the shaft  118  and abutting the backing plate  156  in situations where the thickness of the backing plate  156  is less than is required to generate a compressive force. 
     A number of slits (not shown) may be provided to facilitate the expansion of the narrowing portion  126  during application to a work piece. The slits are aligned with the elongate axis of the shaft  118 . 
     To remove the fastener  110 , the pin  114  is extracted from the core  124 . The pin  114  can be extracted by driving the pin  114  out of the core  124  from the head  116 , such that it exits the opening  122  in the shaft  118 . An extraction device (such as a hydraulic pin hammer) can be used to drive the pin  114  from the core  124  prior to withdrawing the body  112 . Subsequently, the body  112  can be removed from the holes  150 ,  152 . Alternatively, the exposed part of the shaft  118 , including the pin  114 , can be cut leaving a remaining part of the fastener  110 , which can readily be removed from the work piece. 
       FIGS. 8 and 9  show an elongated fastener  200  according to a third embodiment of the present invention. This embodiment is similar to the first embodiment with the main differences being in the number of tunnels and balls and the retaining sleeve as described below. The fastener  200  comprises a body  212  and a pin  214 . The body  212  has a head  216  from which extends a shaft  218 . A hollow core  224  extends from an opening in the head  216  at one end of the body  212  to an opening in the shaft  218  at the other end of the body  212 . In this embodiment the shaft has two tunnels  226 , which extend radially from the core  224  in opposite directions. Each tunnel  226  is provided with a ball  228 . The tunnels  226  have dimensions such that each ball  228  can pass through the respective tunnel  226 . 
     A retaining sleeve  230  is also provided. The retaining sleeve  230  has a through hole  260  extending axially through the sleeve  230 . Through hole  260  has a radially extending channel  262  within a retaining portion  264  of the sleeve  230 , which is coaxially aligned with the tunnels  226 . The channel  262  is dimensioned to receive the respective balls  228  into either end of the channel  226  as the pin  214  is driven into the body  212  and as shown in  FIG. 9 . The through hole  260  is sized to receive the shaft  218 . 
     An end portion  268  of the sleeve  230  is smaller in size than the retaining portion  264 . The retaining portion  262  is sized to be larger than the size of the hole  252  through the second work piece. The size of the end portion  268  is approximately the same size as the size of the hole  262  so that it can fit within the hole  252 . 
     The manner of use of this embodiment is similar to the previous embodiment. The fastener  200  is inserted through aligned holes  250  and  252  in the work pieces  254  and  256  so that the head  216  is substantially located within the hole  250 . The end portion  268  of the sleeve  260  fits within the hole  252 . Surface  266  of the retaining portion  264  abuts surface  258  of the second work piece  256 . The shaft  218  passes through the through hole  260  such that an end portion projects past the retaining portion  264  as shown in  FIG. 9 . The pin  214  is then driven into the body  214  which in turn forces the balls  228  to expand radially thereby partly leaving the tunnels  226  and partly entering the channel  262 . The positioning of the balls (as shown in  FIG. 9 ) thus provides a mechanical bar to the sleeve  230  from being removed from the hole  252  and also provides a bar to the body  212  also from being removed from the hole  250  thereby fixing the two work pieces together. As in the previous embodiment, due to the tapered shape of the channel  262  and the shape of the balls, a wedging action may additionally draw the head  216  against the hole  250  and likewise the surface  266  will be drawn hard up against the surface  258  of the second work piece, thereby providing a compressive force between the work pieces, thus clamping the work pieces together. 
       FIGS. 10-12  show a fourth embodiment of the present invention. This embodiment is similar to the previous third embodiment, with the main differences relating to the head. In this embodiment it can be seen that head  316  is provided with an internal thread  392  and shaft  318  is provided with an external thread  390  thus the head  316  threadingly engages the shaft  318 . This arrangement allows for adjustment and the relative positioning of the head  316  in relation to the shaft  318 . Adjustment in this way is useful so that upon driving the pin into the body  312  the desired amount of clamping force is provided. If the head  316  is wound too far onto the shaft  318 , too much clamping force may be provided or the balls  328  may be incorrectly positioned within the sleeve  330 . If the head  316  is not wound enough onto the shaft, insufficient or no clamping force may be provided. Where no clamping force is provided, the head  316  may not properly nest within the hole  250 . This will allow axial movement of the fastener  310  relative to the work pieces  354  and  356  which may allow movement of the work pieces relative to one another. However they will still be loosely fixed together. In this embodiment the sleeve  330  is shown welded by weld spots  370  to the second work piece  356 . Additionally in this embodiment a sealant such as a corrosion resistant silicone product  372  may be provided within the core  224  and tunnels  326 . The sealant  372  will keep the balls  328  in place prior to use of the fastener. The sealant will be ejected from the opening  374  when the pin  314  is driven into the body  312  as shown in  FIG. 11 . 
     Referring to  FIGS. 13 to 17 , a fifth embodiment of the present invention is shown. This embodiment is similar to the first embodiment of  FIGS. 1 to 5  with the main difference being the shape of the head. This fastener  400  includes a body  412  and a pin  414 . The body  412  has a head  416  and a shaft  418  extending from the head  416 . A hollow core  424  extends through the body  412 . Radially extending tunnels  426  receive balls  428  and allow the balls  428  to expand radially when pin  414  is driven into the core  424 . Sealing compound  472  prevents corrosion and holds the balls  428  in place. Surrounding the shaft  418  is a cylindrical sleeve  430  similar to the sleeve  30  of the first embodiment. The head  416  is a regular cylindrically shaped annulus of larger diameter than the diameter of the shaft  418 . In use the fastener  400  is inserted through a hole  450  in the first work piece  454  such that head  416  is sized to be approximately the diameter of the hole  450 . The first work piece  454  has a second through hole  451  of narrower diameter than the hole  450  thereby providing a shoulder  455  on which the under side  415  of the head  416  abuts. The diameter of the head  416  is larger than the diameter of the hole  451 . The diameter of the hole  451  is approximately the same diameter as the diameter of hole  452  through the second work piece  456 . The diameter of the shaft  418  and the diameter of the sleeve  430  are less than the holes  451  and  452  so that the shaft  418  and sleeve  430  can pass there through as shown in  FIG. 14 . 
     In this embodiment the fastener  400  is adapted to accept a plug  490  on top of the head  416  to fill the remainder of a hole  450  so that the upper surface of the plug  490  is substantially level with the rest of the upper surface of the first work piece  454 . An example of the first work piece in this situation is a wear plate formed of rubber material. This type of wear plate is used where resilience of a wear plate is more important than hardness of the wear plate so that material impacting on the wall of the wear plate tends to bounce off. 
     Where the fastener  400  such as that shown in  FIG. 15  is to be replaced, where, for example, the wear plate  454 ′ has worn to a replacement level (and possibly the head  416 ′ of the fastener as well), the pin  414  is driven through the core  424  so that it is removed. The balls  428  can then travel through the tunnels  426  and re-enter the core  424 . This is assisted if the sleeve  430  is resilient. Once the balls have re-entered the core  424  as shown in  FIG. 17 , the body  412  can then be removed. Additionally, the sleeve  430  can be removed. The work pieces are then unfastened so that for example the first work piece  454 ′ can be replaced. 
     It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the scope of the invention. For example, the head may be a conical frustum of elliptic or pyramid in shape. In a further alternative form, the head may be prismatic body, such as a cylinder. The hole in the first work piece (the wear plate  54  in  FIGS. 1 to 5 ) would need to be provided with a shoulder against which the head  16  can abut in use. 
     Throughout this specification, except where the context requires otherwise due to express language or necessary implication, the words “comprise” or variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.