Patent Abstract:
An anchor ( 910 ) for mounting to a hollow wall (W) made of friable material comprises a proximal flanged end ( 918 ) adapted to be engaged by a rotatable tool (B) to rotate the anchor ( 910 ) about a longitudinal axis (A) thereof and to cause is to gradually engage the wall (W). The anchor ( 910 ) also includes a distal end ( 912 ) adapted to cut through the wall (W) as the anchor ( 910 ) is rotated, and a shank ( 920 ) extending between the proximal and distal ends ( 918, 912 ). The shank ( 920 ) includes at least one expandable leg ( 924 ) that is in a collapsed position thereof when the anchor ( 910 ) is rotated to mount it to the wall (W) and that is located distally beyond a non visible surface of the wall (W) once the anchor ( 910 ) has been mounted to the wall and is in a first position thereof. The wall anchor ( 910 ) includes an outer thread ( 922 ) that securely engages the wall (W). A threaded fastener (B), e.g. a screw, is adapted to be introduced in the anchor ( 910 ) and to threadably engage the same distally of the leg ( 924 ) such that sufficient rotation of the threaded fastener (B) retracts the distal end ( 912 ) towards the proximal end ( 918 ) thereby causing the leg ( 924 ) to displace to a laterally expanded position thereof and to engage the non visible surface of the wall (W).

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a National Entry Application of PCT Application Ser. No. PCT/CA2003/002041, filed on Dec. 11, 2003, which itself claims priority on Canadian Application Ser. No. 2,414,436, filed on Dec. 11, 2002 and on U.S. Application Ser. No. 60/435,369, filed on Dec. 23, 2002. All documents above are herein incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to wall anchors and, more particularly, to self-drilling anchors for use typically in hollow walls made of friable materials, e.g. plasterboard, gypsum, etc. 
   2. Description of the Prior Art 
   The Ernst et al, Gianuzzi and McSherry U.S. Pat. Nos. 4,601,625, 5,234,299 and 5,529,449, respectively, each disclose an anchor which is turned in a wall made of friable material and is retained in the wall by virtue of the friable material being compressed between the root and deep thread spiraled along the cylindrical body of the anchor and between the proximal end of the thread and flanged end of the anchor which becomes embedded in the front surface of the wall. A work piece is then fastened to the wall by a screw fastener that is screwed into the visible open end of the anchor and holds the workpiece between the flanged end of the anchor and the head of the screw fastener. 
   Toggle bolts are also known, such as in U.S. Pat. No. 6,435,789 issued on Aug. 20, 2002 to Gaudron. Generally a self-drilling toggle anchor includes a drilling member and a toggle member. The drilling member is adapted to drill through the wall hole with the toggle member in its retracted position, i.e. extending axially along the drilling member, whereby the whole anchor is inserted longitudinally in the wall with the toggle member being located completely behind the wall. The toggle member defines a threaded opening that extends transversally therethrough and that has, in the retracted position of the toggle member, its axis perpendicular to the drilling member and to the longitudinal orientation of the whole anchor when it drilled into the wall. In a second step, a screw is rotatably inserted in the anchor and, at one point, a tip of the screw engages the toggle member and causes it to pivot an extended position thereof, wherein the toggle member extends at right angles to the drilling member and to the general orientation of the anchor. The screw then engages the threaded opening of the toggle member. Once the head of the screw abuts the front of the wall or the head of the anchor, it cannot displace longitudinally, such that further rotation of the screw draws the toggle member translationally towards the head of the screw and thus towards the rear face of the wall until is abuts firmly the same, whereby the anchor is fixed to the wall. Alternatively, the drilling tip can be provided on the toggle member, and in such cases the above drilling member remains similar in that it fixedly depends from the anchor head but it does not perform the drilling action. Such designs are somewhat costly, as the anchor requires two distinct components (e.g. the above drilling and toggle members) that also must be assembled together. 
   SUMMARY OF THE INVENTION 
   It is therefore an aim of the present invention to provide an improved anchor adapted to be securely mounted to a hollow wall such that an item can be attached thereto, e.g. via an elongated fastener engaged in the anchor. 
   Therefore, in accordance with the present invention, there is provided an anchor for mounting to a hollow wall, comprising a proximal end adapted to be engaged by a rotatable tool to rotate said anchor about a longitudinal axis thereof and to cause it to gradually engage a wall, a distal end adapted to cut through the wall as said anchor is rotated, and a shank between said proximal and distal ends, said shank including at least one expandable leg, said expandable leg being in a collapsed position thereof when said anchor is rotated to mount it to the wall and being located distally past a rear surface of the wall once said anchor is mounted to the wall, said anchor including outer threads, said anchor being adapted to receive therein a threaded fastener and to threadably engage the same distally of said leg such that sufficient rotation of the threaded fastener retracts said distal end towards said proximal end thereby causing said leg to displace to a laterally expanded position thereof. 
   Also in accordance with the present invention, there is provided an anchor assembly for mounting to a hollow wall, comprising a threaded fastener and an anchor; said anchor including a proximal end adapted to be engaged by a rotatable tool to rotate said anchor about a longitudinal axis thereof and to cause it to gradually engage a wall, a distal end adapted to cut through the wall as said anchor is rotated, and a shank between said proximal and distal ends, said shank including at least one expandable leg, said expandable leg being in a collapsed position thereof when said anchor is rotated to mount it to the wall and being located distally past a rear surface of the wall once said anchor is mounted to the wall, said anchor including outer threads, said anchor being adapted to receive therein said threaded fastener and to threadably engage the same distally of said leg such that sufficient rotation of said threaded fastener retracts said distal end towards said proximal end thereby causing said leg to displace to a laterally expanded position thereof. 
   Further in accordance with the present invention, there is provided an anchor for mounting to a hollow wall, comprising a proximal end adapted to be engaged by a rotatable tool to rotate said anchor about a longitudinal axis thereof and to cause it to gradually engage a wall, a distal end and a shank between said proximal and distal ends, said shank including at least one expandable means, said expandable means being in a collapsed position thereof when said anchor is rotated to mount it to the wall, said anchor including outer threads, said anchor being adapted to receive therein a threaded fastener and to threadably engage the same distally of said expandable means such that sufficient rotation of the threaded fastener retracts said distal end towards said proximal end thereby causing said expandable means to displace to a laterally expanded position thereof behind the wall. 
   Still further in accordance with the present invention, there is provided a method for mounting an anchor to a hollow wall, comprising the steps of:
         a) providing a hollow anchor including outer threads and having a proximal end, a distal end and a shank between said proximal and distal ends;   b) installing said anchor in a wall; and   c) rotatably driving a threaded fastener in said anchor such that said threaded fastener engages distal end and causes, once said fastener cannot further advance translationally in said anchor, said distal end to retract towards said proximal end thereby deforming said shank such that said shank laterally expands behind the wall.       

   Still further in accordance with the present invention, there is provided a method for forming inner threads in a hollow anchor adapted for a hollow wall, comprising the steps of:
         a) providing a core pin having outside threads thereon;   b) molding an anchor in a mold with said core pin therein such that said core pin is at least partly surrounded by plastic; and   c) translationally removing said core pin, without substantially rotating it, from the molded anchor without stripping the female threads formed by said core pin in said anchor.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which: 
       FIG. 1  is a schematic side view, partly in cross section, showing a first wall anchor in accordance with the present invention, engaged into a wall and in a collapsed position thereof; 
       FIG. 1   a  is an end view of the wall anchor of  FIG. 1 ; 
       FIGS. 1   b  and  1   c  are end views of variants of the wall anchor of  FIGS. 1 and 1   a;    
       FIG. 2  is a schematic side view, partly in cross section, that is similar to  FIG. 1 , but shows the wall anchor of  FIG. 1  in an expanded position thereof; 
       FIG. 2   a  is an end view of the wall anchor of  FIG. 2 ; 
       FIGS. 2   b  and  2   c  show the variants of  FIGS. 1   b  and  1   c  in the second position of the wall anchor; 
       FIG. 3  is a schematic side view, partly in cross section, of a second wall anchor in accordance with the present invention, which is similar to  FIG. 1  and which is shown in a collapsed position thereof; 
       FIGS. 3   a  to  3   c  are similar to  FIGS. 1   a  to  1   c , but pertain to the wall anchor of  FIG. 3 ; 
       FIGS. 4 and 4   a  to  4   c  are similar to  FIGS. 2 and 2   a  to  2   c , but pertain to the second wall anchor of  FIG. 3  that is shown in an expanded position thereof; 
       FIG. 5  is a schematic side view, partly in cross section, of a third wall anchor in accordance with the present invention, shown in a collapsed position thereof; 
       FIG. 5   a  is an end view of the wall anchor of  FIG. 5 ; 
       FIG. 6  is a schematic side view, partly in cross section, of the wall anchor of  FIG. 5 , but showing the wall anchor in an expanded position thereof; 
       FIG. 6   a  is an end view of the wall anchor of  FIG. 6 ; 
       FIGS. 7 and 7   a  to  7   c  are similar to  FIGS. 1 and 1   a  to  1   c , but show a fourth wall anchor in accordance with the present invention and in a collapsed position thereof, with  FIG. 7  being a cross-sectional view; 
       FIGS. 8 and 8   a  to  8   c  are similar to  FIGS. 2 and 2   a  to  2   c , but pertain to the wall anchor of  FIG. 7  that is shown in an expanded position thereof, with  FIG. 7  being a cross-sectional view; 
       FIGS. 9 and 9   a  to  9   c  are similar to  FIGS. 1 and 1   a  and  1   c , but show a fifth wall anchor in accordance with the present invention and in a collapsed position thereof; 
       FIGS. 10 and 10   a  to  10   c  are similar to  FIGS. 2 and 2   a  to  2   c , but pertain to the wall anchor of  FIG. 9  that is shown in an expanded position thereof; 
       FIG. 11  is a schematic side view, partly in cross section, of a sixth wall anchor in accordance with the present invention, shown in a collapsed position thereof; 
       FIG. 12  is a view similar to  FIG. 11 , but shows the sixth wall anchor in an expanded position thereof; 
       FIG. 13  is a side view, partly in cross section, that is similar to  FIG. 1 , but shows a seventh wall anchor in accordance with the present invention and in a collapsed position thereof; 
       FIG. 14  is a side view, partly in cross section, of the wall anchor of  FIG. 13 , but in an expanded position thereof; 
       FIG. 15  is a side view, partly in cross section, of an eighth wall anchor in accordance with the present invention, shown in a collapsed position thereof; 
       FIG. 16  is a side view, partly in cross section, of the wall anchor of  FIG. 15 , but shown in an expanded position thereof; 
       FIG. 17  is a side view of an anchor section of the wall anchor of  FIG. 15 ; 
       FIG. 18  is a side view of a locking member of the wall anchor of  FIG. 15 ; 
       FIG. 19  is a schematic side view of a ninth wall anchor in accordance with the present invention, also shown being a molding pin used in the manufacture of the ninth anchor; 
       FIG. 20  is an end view of the wall anchor of  FIG. 19 ; 
       FIG. 21  is a cross-sectional view of the wall anchor of  FIG. 19 ; 
       FIG. 22  is a side view of a tenth wall anchor, similar to that of  FIG. 3 , and also in accordance with the present invention; 
       FIG. 23  is an end view of the tenth anchor of  FIG. 22 ; 
       FIGS. 24 ,  25  and  26  are cross-sectional views taken respectively along lines  24 - 24 ,  25 - 25  and  26 - 26  of  FIG. 22 ; 
       FIGS. 27   a  to  27   d  are successive partly cross-sectional side views showing the installation of the tenth anchor of  FIG. 23  into a wall; 
       FIGS. 28 and 29  are respectively a side view and a longitudinal cross-sectional view of the tenth anchor of  FIG. 23  provided with a core pin therein that is used during the molding thereof; 
       FIGS. 30 and 31  are respectively a side view and a partly cross-sectional view of part of the core pin. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In accordance with the present invention,  FIG. 1  illustrates a wall anchor  10  in its first, i.e. insertion, position, with  FIG. 1  showing the wall anchor  10  fully inserted through a wall W and with a screw S engaged in the wall anchor  10  and holding an item I against the wall W. In  FIG. 2 , the wall anchor  10  is shown in a second, i.e. expanded, position thereof wherein the wall anchor  10  is further secured to the wall W, as explained in details hereinafter. The wall anchors described herein are generally all made of plastics material, e.g. nylon. 
   The wall anchor  10  is hollow, for receiving the screw S therein, and comprises a pointed distal tip  12  provided with a partial thread  14  therearound and defining an opening  16 . Proximally, the wall anchor  10  includes a head  18  and, between the head  18  and the distal tip  12 , the wall anchor  10  comprises a shank  20 . The proximal portion of the shank  20  includes a thread  22  and, between the threads  14  and  22 , the shank  20  includes a system of expandable legs  24 . In the embodiment shown in  FIGS. 1 and 2 , the shank  20  includes four such legs  24  which, in the collapsed position of  FIG. 1 , are linked together by frangible films  26 , although such films can be absent, in which case the legs  24  extend along side each other but are not connected together. 
   The head  18  can be engaged by a torque driven rotational tool, such as a screwdriver, manual or powered. For instance, the head  18  can define a cruciform recess (see reference  819  in  FIGS. 20 and 919  in  FIG. 23 ) for receiving a Phillips-type screwdriver bit. This allows the wall anchor  10  to be rotatably driven, as a screw, through the wall W, with the distal tip  12  assisting in penetrating the wall  10  and with the threads  14  and  22  consecutively engaging the friable material of the wall W and, in fact, tapping the same such that the wall anchor  10  is secured to the wall by way of the threads  22 . The opening  16  assists in evacuating the friable material that has been removed from the wall W by the wall anchor  10 . Once the wall anchor  10  is in its position shown in  FIG. 1  with respect to the wall W, the screw S, with or without the item I located between the head of the screw S and the front or visible surface of the wall W, is rotatably engaged into the wall anchor  10  until it assumes its position shown in  FIG. 1 . 
   Once the head of the screw S cannot further axially translationally advance (in  FIG. 1  because of its abutment with the item I, or alternatively because it has engaged the head  18 , or even the visible surface of the wall W), further rotation of the screw S causes the distal tip  12  of the wall anchor  10  to be pulled towards the wall W in view of the threaded engagement between the screw S and the wall anchor  10 , typically at section  28  thereof that has been tapped by the screw S (although female threads may alternatively have been formed by molding within the section  28 ). The gradual retraction of the distal tip  12  towards the head  18  causes the legs  24  to outwardly expand and, initially, any frangible film  26  between adjacent legs  24  is ruptured. 
   Each leg  24  has a shorter proximal portion  30  and a longer distal portion  32  that connect at pivot  33 . The expansion of the legs  24  is interrupted by the proximal leg portions  30  abutting the rear or non-visible surface of the wall W, as seen in  FIG. 2 , in which position the proximal and distal leg portions  30  and  32  form with the screw S a substantially right angled triangle. 
   Additionally, the shank  20 , for instance inwardly of (i.e. within) the legs  24 , may include a stopper which, for example, extends around the screw S and which extends rearwardly from a proximal end of the distal tip  12  (examples of stoppers are shown at  234  and  334  of the further embodiments of  FIGS. 5 and 6  and  FIGS. 7 and 8 , respectively). Such a stopper does not extend the full length of the legs  24  when they are in their collapsed position of  FIG. 1 , such that a proximal end of the stopper engages, in  FIG. 2 , the non-visible surface of the wall W inwardly of the proximal leg portions  30  of the legs  24  and/or the inner ends of the proximal leg portions  30 , thereby significantly impeding further retraction of the distal tip  12  towards the wall W. Even though the proximal leg portions  30 , when they engage the non-visible surface of the wall W, offer resistance to such a further retraction of the distal tip  12 , over-rotation of the screw S could cause the proximal leg portions  30  to dig into the wall W. With the stopper, which is of a length which substantially correspond to the third side of the right angled triangle that has the proximal and distal leg portions  30  and  32  as its two other sides, it is ensured that the end position of the wall anchor  10  will be that illustrated in  FIG. 2 . In other words, the proximal leg portions  30  and/or the stopper will substantially prevent the screw S from being over-rotated. 
     FIGS. 1   b ,  2   b ,  1   c  and  2   c  show alternate shanks which, instead of having four legs  24  as in  FIGS. 1 and 2 , have five and three such legs, respectively. Other numbers of legs can also be contemplated. 
     FIGS. 3 and 4  illustrate a second wall anchor  110 , also in accordance with the present invention, which is similar to the first wall anchor  10 , except that a shank  120  of the wall anchor  110  includes a thread  121  therearound that is substantially continuous with the threads  114  and  122 . Also, in the wall anchor  110 , the proximal and distal leg portions  130  and  132  of the legs  124  thereof are of a same length such that they assume the general flattened end position shown in  FIG. 4 , with the threads  121  of the proximal leg portion  130  engaging the non-visible surface of the wall W. In  FIGS. 3 and 4 , the screw S that is illustrated has a larger pitch wood-type thread that makes the installation of the screw S (including the expansion of the wall anchor  110 ) faster, i.e. with less rotations being required from the screw S. As for the first wall anchor  10 , the second wall anchor  110  includes a distal tip  112 , an opening  116 , a head  118  and a tapped section  128 , and can also include frangible films  126 , such as frangible films  26  of the first wall anchor  10 . 
     FIGS. 3   b ,  4   b ,  3   c  and  4   c  show variations of the wall anchor  110 , i.e. with five and three legs instead of the four legs  124  shown in  FIGS. 3 and 4 . 
   As a variant to the second wall anchor  110  (and possibly also to other wall anchors, e.g. to the first wall anchor  10 ), the section  128  of the shank  120  can include a metal insert provided with inner threads (i.e. it does not need to be tapped by the screw S) and mounted, for instance molded, into the plastic shank  120  of the wall anchor  110 , the inner threads of such a metal insert (which acts as a nut) being typically adapted to receive a machine screw. 
     FIGS. 5 and 6  illustrate a third wall anchor  210 , which is somewhat similar to the first wall anchor  10 , except that it includes only two, diametrically opposed, legs  224 . A pair of stoppers  234  are part of the shank  220  and extend between the legs  24  and rearwardly from a proximal end of the distal tip  212 . The proximal ends of the stoppers  234  are adapted to limit the retraction of the distal tip  212  towards the head  218  such that the wall anchor  210  assumes, in its final position, the general configuration shown in  FIG. 6 . 
   The wall anchor  210  further includes a distal thread  214 , a distal opening  216 , a proximal thread  222 , a tapped section  228  and proximal and distal leg portions  230  and  232 . 
     FIGS. 7 and 8  illustrate a fourth wall anchor  310  in which a stopper  334  takes the form of a cylinder that extends rearwardly from the distal tip  312  and within the legs  324 . The stopper  334  can take the form, as illustrated, of a rearward extension of the tapped section  328  such that it is also tapped by the screw S. The number of legs  324  in the shank  320  can vary, as seen for instance in  FIGS. 7   a  and  8   a ,  7   b  and  8   b , and  7   c  and  8   c  where four, five and three legs are illustrated, respectively. 
   The fourth wall anchor  310  also includes a distal thread  314 , a distal opening  316 , a proximal head  318 , a proximal thread  322  and proximal and distal leg portions  330  and  332 . Frangible sections can also be provided between adjacent legs  324 , as in the first wall anchor  10  of  FIGS. 1 and 2 . 
     FIGS. 9 and 10  illustrate a fifth wall anchor  410  also in accordance with the present invention, which is similar to the first wall anchor  10  of  FIGS. 1 and 2 , but which shows a variant distal tip  412  that is based on the distal section of the self-drilling anchor of aforementioned U.S. Pat. No. 5,234,299. The distal tip  412  of the wall anchor  410  could also take the shape of the blade of the self-drilling threaded insert of aforementioned U.S. Pat. No. 4,601,625. In fact, these Variant distal tips as well as others can be contemplated for the various wall anchors disclosed herein. 
   With the illustrated distal tip  412 , the wall anchor  410  is initially punched through the wall W before being rotated such that the proximal threads  422  thereof engage the wall W. The wall anchor  410  also includes a head  418 , a shank  420 , legs  424 , frangible films  426 , a tapped section  428  and proximal and distal leg portions  430  and  432 . 
     FIGS. 9   a  and  10   a  show the shank  420  having four legs  424  as in  FIGS. 9 and 10 , whereas  FIGS. 9   b ,  10   b ,  9   c  and  10   c  show alternate leg configurations consisting of five and three legs  424 . 
   In  FIGS. 11 and 12 , a sixth wall anchor  510  is shown, wherein a shank  520  includes side-by-side legs  524  which are slightly angled with respect to a longitudinal axis of the wall anchor  510  and in a direction that is opposite the torque exerted when the wall anchor  510  is rotatably inserted in the wall W in order to provide added rigidity to the shank  520  during the rotary installation of the wall anchor  510 . The legs  524  are detachably connected together by way of frangible portions  526  which, as in previous embodiments, provide additional rigidity to the shank when compared to legs that are not initially connected together. The shank  520 , as the shank  120  of  FIGS. 3 and 4 , includes a thread  521  that provides with the proximal thread  522  and the distal thread  514  a substantially continuous thread. Once expanded, as seen in  FIG. 12 , the wall anchor  510  defines a bundle that is in abutment with the non-visible surface of the wall W, this bundle being formed by the deformed legs  524 . 
   The sixth wall anchor  510  also includes a distal tip  512 , a distal opening  516 , a proximal head  518  and a tapped section  528 . 
     FIGS. 13 and 14  show a seventh wall anchor  610  in accordance with the present invention, which is similar to the first wall anchor  10 , except that two of its legs  624  expand inwardly, such legs being designated by reference numerals  634  in  FIGS. 13 and 14 . These inwardly deflecting legs  634  act as a stopper to resist further retraction of the distal tip  612  towards the wall W once the wall anchor  610  has generally assumed its second position shown in  FIG. 14 . 
   The wall anchor  610  also includes a distal thread  614 , a distal opening  616 , a head  618 , a shank  620 , a proximal thread  622 , frangible films  626 , a tapped section  628  and proximal and distal leg portions  630  and  632 . 
     FIGS. 15 and 16  show an eighth wall anchor  710  in accordance with the present invention that consists of two separate components and, more particularly, of a threaded anchor section  711  (shown in isolation in  FIG. 17 ) and an expandable locking member  724  (shown in isolation in  FIG. 18 ). The anchor section  711  includes a distal tip  712 , a distal thread  714 , a distal opening  716 , a proximal head  718 , a shank  720 , and a proximal thread  722 . 
   The locking member  724  is initially collapsed, as seen in  FIG. 15 , being partly received in longitudinal grooves defined on diametrically opposed sides of the shank  720 . The locking member  724  defines a pair of notches  726  that are adapted to engage a proximal end of the shank  720 , when the locking member  724  is collapsed, wherein tips  728  defined by the notches  726  are held inwardly of the shank  720 . The locking member  724  also includes a distal cylindrical member  730  that can be tapped by the screw S. 
   Once the screw S has been sufficiently inserted in the anchor section  711 , it contacts the locking member  724  and displaces it axially away from the head  718  thereby disengaging the tips  728  of the locking member  724  from the shank  720  of the anchor section  711 . As the locking member  724  is spring loaded, its release from the shank  720  causes it to automatically deploy to its position shown in  FIG. 18 . The cylindrical member  730  of the locking member  724  is then tapped by the screw S and with subsequent rotation of the screw S, the locking member  724  is retracted towards the wall W until it assumes the position shown in  FIG. 16 . In fact, the locking member  724  basically acts as a toggle that is displaced between a collapsed idle insertion position ( FIG. 15 ) and a wall engaging expanded position ( FIG. 16 ). 
   The locking member  724  is inserted by the manufacturer of the wall anchor  710  through the central bore of the anchor section  711 , from the head  718  towards the distal tip  712 , that is until the collapsed locking member  724  extends partly in the longitudinal grooves of the shank  720  while the tips  728  of the locking member  724  are prevented from expanding by the proximal end of the shank  722 . Again, once the screw S has been sufficiently inserted, it axially moves the locking member  724  along the bore of the anchor section  711  until the tips  728  are disengaged from the shank  720  and are spring biased exteriorly through the longitudinal grooves of the shank  720 . 
     FIGS. 19 and 20  illustrate a ninth wall anchor  810  in accordance with the present invention, which is characterized by having inside threads  828  defined in the distal end of the shank  820  and, interruptingly, in the open distal end  812 . The threads  828  defined in the shank  820  are continuous, but the inside threads  828  defined in the distal tip  812  are interrupted by the distal opening  816 . The inside threads  828  of the wall anchor  810  are obviously adapted to be engaged by the outside threads of the screw S (not illustrated). This configuration provides more threads in the wall anchor  810  that can be engaged by the threads of the screw S thereby providing more strength at the level of the engagement of the screw S with the wall anchor  810 , which thus prevents stripping of the threads  828  of wall anchor  810  when the screw S is further rotated in order to retract the distal tip  812  rearwardly towards the wall for expanding the legs  824  provided on the shank  820 . 
   A pin P is located in the anchor  810  and is used during the molding process to define the female inside threads  128 . The structure of this pin P and how it is used will be described in details hereinafter. 
   The wall anchor  810  also includes a distal thread  814 , a proximal head  818 , a proximal thread  822 , and a thread  821  around the legs  824  so as to provide, with the threads  814  and  822 , a continuous outside male thread (although interrupted at the distal opening  816 ). A tube  834  is provided in the shank  820  of the wall anchor  810  to provide more rigidity when the wall anchor  810  is installed in the wall. 
     FIGS. 22 to 26  show a tenth wall anchor  910  in accordance with the present invention, which is similar to that of  FIG. 3  although the wall anchor  910  includes an inner thread  928  (as in  FIG. 19 ) located interruptingly inside the distal tip  912  and un-interrruptingly within a cylindrical section  936  that extends axially between a distal end of the shank  920  and a proximal end of the distal tip  912 . This inner thread  928  is adapted to be engaged by the thread of the screw S upon rotation thereof, and once the screw S is prevented from further advancing into the anchor  910  (e.g. because it has abutted item I or the head  918  of the anchor  910 ), further rotation of the screw S causes the distal tip  912  to be axially and translationally drawn towards the head  918  thereby causing the deformation (i.e. outward expansion) of the legs  924  onto the hidden face of the wall W. A longitudinal axis of the anchor  910  is denoted by “A”, and such an axis characterizes each of the anchors described herein. 
   The provision of female threads  128  both in the cylindrical section  936  and in the distal tip  912  increases the overall female thread length that can be engaged by the threads of the screw S thereby providing more strength at the level of the engagement of the screw S with the wall anchor  910 , which thus prevents stripping of the threads  928  of wall anchor  910  when the screw S is further rotated in order to retract the distal tip  912  rearwardly towards the wall for expanding the legs  924  provided on the shank  920 . 
     FIGS. 27   a  to  27   d  illustrate the installation sequence of the present anchors and will now be described with reference to the tenth wall anchor  910 . As seen in  FIG. 27   a , the wall anchor  910  is positioned with its distal tip  12  against the visible side of the wall W, and it is rotatably engaged therein using an appropriate torque-inducing tool, such as a screwdriver, having a bit formed to fit in the recess defined in the head  918  of the anchor  910 . Here, a Phillips-type screwdriver bit B is used to fit into the cruciform recess  919 . The anchor  910  is rotated until its head  918  abuts the visible side of the wall W, as seen in  FIG. 27   b . The screw S is then rotatably engaged in the wall anchor  910  using the screwdriver bit B and the screw translationally advance into the wall W until it reaches its position shown in  FIG. 3 , whereat it is prevented from further advancing by the item I firmly abutting the wall W. As explained above and as seen in  FIG. 27   c , subsequent further rotation of the screw S causes, in view of the male threads of the screw S being engaged with the female threads  928  of the anchor  910 , the distal tip  912  to be axially and translationally drawn towards the head  918 , thereby causing the deformation (i.e. outward expansion) of the legs  924  onto the hidden face of the wall W and firmly securing the anchor  910  to the wall W. As seen in  FIG. 27   d , such a deformation results in some of the threads  921 , provided around the arms  924 , engaging (e.g. piercing into) the hidden face of the wall W. 
     FIGS. 28 and 29  illustrate the tenth anchor  912  of  FIG. 22  with a core pin P therein that is used during the molding thereof to form the through passage extending axially through the anchor  910 , including the inner threads  928  thereof. More particularly, the core pin P includes a main pin section  1000  (also shown in isolation in  FIGS. 30 and 31 ) that has a first portion  1002  adapted to form the inside of the head  918 , of the expandable legs  924  and of the part of the shank  920  that extends between the head  918  and the expandable legs  924 , and a second portion  1004  adapted to form the female threads  128  of the cylindrical section  936 . The core pin P also includes a secondary pin section  1006  that is adapted to form the threads  928  located in the distal tip  912  of the anchor  910 . A distal end  1008  of the second portion  1004  of the main pin section  1000  is shaped so as to mate with a proximal end  1010  of the secondary pin section  1006 , and this ensures the alignment of the main pin section  1000  and the secondary pin section  1006 , and thus a female thread  128  that is substantially uninterrupted at a junction of where it was formed by the main pin section  1000  and where it was formed by the secondary pin section  1006 , and that has a constant pitch. 
   The mold also includes two outer mold sections that will provide the shape to the outside of the anchor  910 , and once the plastic has been injected in the mold, the main pin section  1000  is pulled out axially and translationally from the mold, while the secondary pin section  1006  is removed laterally from the distal end  912 , i.e. through the opening  916  thereof. It is noted that the main pin section  1000  is pulled out from the mold during a specified period after the injection process, such that the main pin section  1000  does not strip the female threads  128  that is has molded, these female threads completely solidifying after the main pin section  1000  has been so removed. In the prior techniques, the pin would be rotatably removed from the molded anchor, which is much more time consuming than the present translational withdrawal thereof.

Technology Classification (CPC): 5