WO2009127865A1

WO2009127865A1 - Fixing

Info

Publication number: WO2009127865A1
Application number: PCT/GB2009/050365
Authority: WO
Inventors: Philip Russell
Original assignee: Philip Russell
Priority date: 2008-04-15
Filing date: 2009-04-14
Publication date: 2009-10-22
Also published as: GB0806827D0; GB0808977D0

Abstract

A fixing (10) for holding a fastener (40) in a hole is disclosed. The fixing comprises an elongate (12) body defining a longitudinal axis of the fixing, the body (12) being arranged to receive a fastener (40) that can be turned with respect to the longitudinal axis within the body. The body comprises an anchor formation (14) adapted to restrain a first part of the body against angular movement within the hole in use, a coupling (16) cooperabie with the fastener (40) to transmit torque from the fastener (40) to a second part of the body in use, and a twist formation (10) between the anchor formation (14) and the coupling (16). The twist formation (18) is arranged to expand transversely with respect to the longitudinal axis by virtue of untwisting deformation in response to the application of torque from the fastener (40) via the coupling in use.

Description

FIXING

Field of the invention

This invention relates to a device for holding a fastener in a hole, in particular, but not exclusively, the invention relates to a fixing or anchor for securing a fastener in a hole in a wall, ceiling, floor or other structure.

During construction, fitting out, decoration, maintenance, repair and improvement of buildings, a commonplace task is to fix fasteners in a wail so that the fastener is held securely to or in the wail.

For example, in the home, fasteners such as screws and boits are used for securing furniture, shelves, electrical fittings, decorative fittings and so on to the walls. Other fasteners, such as eyelets and hooks, may be also used, for example to provide storage. During construction of buildings, fasteners are used to fix timber frames to masonry walls, to attach hinges to door frames, and in many other situations.

In each of these cases, one or more fasteners bear the weight of a component attached to the wail and associated ioads resulting from use of the component. The fastener must transfer the load to the wali to support the component. If the fastener is not securely anchored in the wall against the forces it experiences, then the component may become loose or even fall away from the wall. This is dearly undesirable. A loose component may be unsightly or unusable as a result, and significant damage and injury can result when a component falls from the wall,

in timber structures, fasteners can be secured relatively easily using threaded screws. Typically, a pilot hole is driiled and a tapered wood screw is driven into the hole. The threads of such screws cut into the timber to form grooves which anchor the threads, and hence the screw, in the structure. Furthermore, the tapered shape of the screw causes compression of the wood around the screw as it is driven further into the structure. The screw therefore experiences a compressive force from the surrounding wood, which grips the screw.

The fixing of fasteners in walls made of plasterboard, masonry and similar substrates is not so straightforward, particularly when the material is soft (such as plasterboard) or brittle (such as concrete). Unlike timber, such materials cannot withstand large shear forces. Instead, they tend to break up or crumble under the shear forces that would arise if a tapered screw were to be driven into the materia!.

One approach that can be taken for fixing in relatively soft materials such as plasterboard is to use screw anchors which are, in essence, large-diameter tapered screws having particularly deep and sharp threads. These anchors are arranged to spread the load over a greater area of the wall. However, over-tightening or over-loading of the anchors often results in crumbling of the plasterboard so that the anchors become loose.

To avoid this problem, it is common to use a fixing such as a wall plug, anchor or dowel mounted in a hole in the wall. The role of the fixing is to provide a structure which is capable of receiving a screw or bolt, but which applies substantially only radial compressive forces to the wall, via the interior of the hole.

One of the simplest fixings is a wooden or plastic dowel, with or without a central bore. A hole is drilled in the wall, and the dowel is pushed into the hole. The size of the hole is such that the dowel is a snug fit in the hole. In other words, the dowel deforms under radial compression to fit the hole. Similarly, the wall around the hole may deform slightly under radial compression. A screw can then be screwed into the dowel. The dowel, particularly if made from a plastics material, may expand laterally when the screw is driven into the dowel, causing further compression of the wail and the dowel and thus increasing the gripping force on the dowel.

One disadvantage of such fixings is that the hole must be carefully sized to accommodate the dowel. If the hole is too large, the dowel will be loose in the hole. If the hole is too small, the dowel may not fit and the wall may be damaged if the dowel is forcibly inserted. This problem is exacerbated by the difficulty of making holes of a specific size in materials such as plasterboard and concrete.

A host of more complex expandable fixings also exist, which are designed to have greater tolerance with respect to the size of the hole. In some cases, these fixings are adapted to accommodate a screw which, when driven into the fixing, causes a lateral or radial expansion of the fixing with respect to a longitudinal axis. The expansion may, for example, be caused by the deployment of wings that extend outwards when a screw is inserted. Typicaily, ridges, ribs and similar features are provided on the fixing to help the fixing to grip the interior of the hole, and to prevent rotation of the fixing in the hole

In other cases, fixings are designed so that the fastener engages with a dista! end of the fixing. In use of the fixing, the fixing is inserted distally into the hole, and the fastener is turned to cause the distal end of the fixing to move towards the proximal end. In other words, the fixing shortens along its length, parallel to the axis of the hole in the wall. Shortening of the fixing in this way causes parts of the fixing to move outwards to push against the interior of the ho!e.

For example, in one such fixing, the distal end comprises a threaded nut to cooperate with a bolt. The nut is held to a face plate at the proximal end of the fixing by an arrangement of metal arms disposed around a body of the fixing The arms are formed in a shallow V shape, with the point of the V facing outwards. In use, the body of the fixing is inserted, nut first, into a hole in a wall. The face plate lies against the surface of the wall, around the hole, and is provided with barbs which bite in to the wall to prevent rotation of the face plate, and hence the fixing. As the bolt is turned in a tightening motion, the nut moves distally along the bolt to shorten the fixing. The arms accommodate the shortening movement by bending into a steeper V shape. In this way, the points of the V-shaped arms move outwards towards, and then press against, the interior of the hole to anchor the fixing in the hole.

In some cases, the wall comprises a gap or cavity behind a facing. For example, an internal dividing wall may comprise two plasterboard facings separated by a cavity in which a timber frame is arranged.

Fixings designed for use in such cases typically have laterally-expanding portions arranged to expand within the cavity to press against the back surface of the plasterboard In such cases, the plasterboard is held in compression through its thickness, and the load on the fastener is spread across a larger area than would otherwise be the case

For example, spring toggles have two or more foldable spring-loaded arms mounted on a bolt The arms are folded against the bolt to allow the bolt to be inserted into a hole in the plasterboard. Once they have passed fully through the hole, the arms spring open in the cavity The arms then act against the back face of the plasterboard so that the bolt can be tightened against the wall. Other arrangements use gravity or lateral expansion to achieve a similar result. However, these fixings rely on there being a cavity of sufficient depth behind the plasterboard to accommodate the extra length of the fixing which is required to reach through the hole. Large cavities are, however, not always present: for example, frame members or plaster dabs may lie behind a hole. Often, the only way to determine whether such a cavity is present is to drill a hole through the plasterboard.

Some fixings are adapted to expand laterally against both the interior of the hole and within a cavity behind the plasterboard. The portion of the fixing which expands in the cavity acts against the back of the plasterboard to anchor the fixing, and the portion that expands within the ho!e provides additional anchoring and prevents the fixing from rotating.

While the fixings described above can be adequate when used in appropriate circumstances, it is often difficult to choose the correct fixing for a given application, especially when the nature of the wail is not fully known. It would also be more convenient and cost-effective for a user to buy one type of fixing that can be used for different applications such as masonry and plasterboard. Thus it would be desirable to provide a fixing which is usable in a wide range of substrates and in many applications. Furthermore, many existing fixings are relatively difficult to use, particularly for inexperienced users, with the result that the fastener is not as secure as it otherwise would be. It would therefore also be desirable to provide a fixing which is easier to use than the fixings of the prior art, without compromising the quality of the fixing.

it is against this background that the present invention has been devised.

Summary of the invention

In accordance with a first aspect of the present invention, there is provided a fixing for holding a fastener in a hole. The fixing comprises an elongate body defining a longitudinal axis of the fixing, and the body is arranged to receive a fastener that can be turned with respect to the longitudinal axis within the body. The body comprises an anchor formation adapted to restrain a first part of the body against angular movement within the hole in use, a coupling cooperabSe with the fastener to transmit torque from the fastener to a second part of the body in use, and a twist formation between the anchor formation and the coupling. The twist formation is arranged to expand transversely with respect to the longitudinal axis by virtue of untwisting deformation in response to the application of torque from the fastener via the coupling in use.

The untwisting deformation of the twist formation is advantageous because it allows the fixing to expand in a manner that conforms readily to the available space within and, in some circumstances, behind the hoie, hence improving the grip of the fixing within substrates such as plasterboard and masonry.

Preferably, the coupling can be turned with respect to the anchor formation to cause untwisting deformation of the twist formation.

The anchor formation is suitably toward a proximal end of the body, and the coupling is suitably toward a distal end of the body.

The anchor formation may comprise one or more grip formations, which may comprise one or more barbs arranged to pierce a surface adjacent to the hoie in use. Alternatively or in addition, the grip formation may comprise one or more fins arranged to engage with the periphery of the hole in use, and/or one or more flared regions to wedge the first part of the body in the hole in use. If fiared regions are provided, they may comprise a plurality of ribs that taper distally.

The anchor formation may comprise a plate having a central opening for the fastener, in which case the plate may comprise a distal face having a peripheral chamfer. The peripheral chamfer can help the plate to bed into a surface adjacent to the hole, so that the fixing lies flush with the surface.

Conveniently, the plate may comprise one or more barbs extending longitudinally from the plate, the barbs being arranged to pierce a surface adjacent to the hole, in use, as described above. The barbs may be bent from the remainder of the plate into a iongitudinally-extending orientation during manufacture of the fixing.

The twist formation preferably comprises one or more elements defined by gaps extending helically around the body. The elements may, for example, be bands defined by slits in the body. Alternatively, the gaps may be wide with respect to the slits. The elements lie at an angle with respect to the longitudinal axis of the fixing. The angle can be chosen to ensure that the fixing performs optimally in a given application, taking into account the materia! of the fixing, the dimensions of the fixing, and the substrate or range of substrates in which the fixing is to be installed. It will be appreciated that the angle at which the elements lie with respect to the longitudinal axis cannot be at or very close to 0°, since there would be no useful untwisting deformation of the twist formation if that angle is too small. Similarly, the angle must be somewhat less than 90°, since elements lying only at 90° to the longitudinal axis would not form a twist formation.

Preferably, the elements lie at an angle of between about 15° and about 60° with respect to the longitudinal axis. More preferably, the elements iie at an angle of between about 30° and about 60° with respect to the longitudinal axis. Still more preferably, the elements lie at an angle of between about 30° and about 45° with respect to the longitudinal axis. In one currently preferred example, the elements lie at an angle of about 45° with respect to the longitudinal axis whereas, in another currently preferred example, the elements lie at an angle of about 30° with respect to the longitudinal axis.

The elements may be provided with teeth for engagement with the interior of the hole in use, and the teeth may be arranged in helical formation. Advantageously, the teeth are offset from the angle of the elements. The angle of the teeth to a plane orthogonal to the longitudinal axis may be approximately half of the angle of the elements to that plane. The teeth may for example be disposed at an angle of between 60° and 90° with respect to the longitudinal axis. In one currently preferred embodiment, the teeth are disposed an angle of about 67.5° with respect to the longitudinal axis, in another currently preferred embodiment, the teeth are disposed at an angle of 90° with respect to the longitudinal axis.

In one embodiment, at least one of the teeth is disposed at a first angle with respect to the longitudinal axis, and at least another one of the teeth is disposed at a second angle with respect to the longitudinal axis. Advantageously, the angle between the teeth and the longitudinal axis of the fixing decreases moving distally along the fixing.

The teeth may be associated with apertures in the elements. For example, the teeth may be part-spherical, and the associated apertures may be part-circular. The relative deformability of the elements is influenced by the presence of and the dimensions of such apertures so, advantageously, a plurality of teeth is provided on each element, and the size of the apertures associated with the teeth varies along each element. The size of the apertures may, for example, increase moving towards the longitudinal centre of the twist formation.

The relative deformabiiity of each element may vary along the element. In a preferred embodiment, the deformabiiity of each element increases moving towards the longitudinal centre of the twist formation. The relative deformabiiity of the element may be influenced by apertures or by other regions of weakness, or even by stiffening features.

in a particularly advantageous embodiment of the invention, the twist formation is arranged also to expand transversely by virtue of shortening of the fixing along the longitudinal axis.

The coupling may be movable along the longitudinal axis towards the anchor formation to shorten the fixing, in which case the coupling may be cooperable with the fastener to convert turning movement of the fastener to axial movement of the coupling in use. The coupling may have internal threads to mate with a threaded region of the fastener to cause axial movement of the coupling upon turning of the fastener in use.

Preferably, the coupling is arranged to transmit torque from the fastener to the body upon initial turning of the fastener in use, and to convert turning movement of the fastener to axia! movement of the coupling upon further turning of the fastener. In this way, installation of the fixing to hold a fastener in a hole comprises a two-stage process, wherein the twist formation initially undergoes untwisting deformation to engage the interior of the hole, and then undergoes axial shortening to tighten against the interior of the hole. In plasterboard applications, axial shortening also expands the fixing in a cavity behind the plasterboard panel.

The fixing may comprise engagement means for engaging the coupling with the fastener to transmit torque from the fastener to the body in use. The engagement means may be further arranged to disengage to allow the coupling to cooperate with the fastener to convert turning movement of the fastener to axial movement of the coupling in use. To achieve this, the engagement means may, for example, break off or away from the body or the fastener to disengage the fastener and the coupling in use. The engagement means may comprise at least one lug arranged to engage an engagement region of the fastener in use, in which case one or more lugs may extend radially inwards from a peripheral region of the coupling In one example, at least two lugs are spaced around the longitudinal axis One or more lug may be bent into a radially-extending orientation during manufacture of the fixing

Where one or more !ugs are provided, at least a part of the or each !ug is arranged to break away from the body in response to the application of a breaking torque to the fastener in use For example, one or more lugs may comprise a fracture zone arranged to cause fracture of the lug in response to the application of the breaking torque The fracture zone may comprise a scored, perforated, notched or relatively thin region of the lug, or any combination of these or other features that weaken the !ug in a particular location

In one embodiment, the lugs comprise cutting means for cutting into a substrate in use of the fixing The cutting means may, for example, comprise cutting edges of the lugs The cutting edges may be inclined to form a pointed distal end region of the fixing in this way, a hole for the fixing can be created in a substrate by pressing the distal end of the fixing against the substrate and rotating the fixing

As an alternative to lugs, the engagement means may comprise a plate having an aperture for receiving a self-tapping threaded region of the fastener This allows a conventional self-tapping fastener to be used with the fixing The plate may be bent into a radially-extending orientation during manufacture of the fixing, for example if the plate and the twist formation are initially made by forming a blank from a sheet material

The engagement means may comprise a threaded region for receiving a threaded region of the fastener, and one or more stop members to limit turning of the fastener with respect to the coupling in use In this case, breakable attachment means for attaching one or more stop members to the fixing may be provided The attachment means may, for example, comprise an adhesive

The stop member may comprise a plate that closes a distal end of the fixing, or a film arranged to be ruptured by the fastener in use to disengage the engagement means In another embodiment of the invention, the coupling comprises a lock nut, and the stop member comprises a locking element of the iock nut. The lock nut may be a conventional lock nut, such as a nylon insert lock nut, which can be attached to the fixing. Accordingly, the invention also extends to a twist formation for a fixing in which the coupling comprises a lock nut, wherein the twist formation comprises support means for holding the iock nut, The support means may comprise support lugs arranged to embrace the lock nut.

Embodiments of the fixing can be used with conventional fasteners such as bolts. Other embodiments require specialiy-adapted fasteners. Accordingly, in a second aspect the present invention extends to a fastener for use with the fixing described above, and comprising a turnable shaft having a threaded region and an engagement region for cooperation with the coupling.

The engagement region may, for example, comprise a slotted end of the fastener or a plate-like end of the fastener. In the latter case, the plate-iike end may be flat or twisted. When the plate-like end is twisted, axial movement of the fastener can give rise to untwisting deformation of the fastener. The engagement region may instead comprise one or more helical splines on an end region of the fastener.

The invention further extends to a combination of a fixing according to the first aspect of the invention, and a fastener according to the second aspect of the invention, and such a combination wherein the fastener is received within the fixing.

According to a third aspect of the invention, a method for holding a fastener in a hole is provided. The method comprises inserting a fixing in the hole, anchoring a first part of the fixing with respect to the hole, applying a torque to a fastener received within the fixing, and transmitting that torque to a second part of the fixing to cause untwisting deformation of the fixing that expands the fixing laterally against the interior of the hole.

The method may further comprise pushing the fixing into the hole to anchor the first part of the fixing with respect to the hole. For example, the method may comprise pushing a grip formation of the fastener into the periphery of the hole, pushing a grip formation of the fastener into a surface adjacent to the hole, wedging the first part of the fixing in the hole, or any combination of these or other actions. Preferably, the method further comprises turning the fastener to cause further lateral expansion of the fixing by shortening of the fixing along the longitudinal axis.

One expression of the method comprises engaging the fastener with engagement means which transmit torque from the fastener to the second part of the fixing, optionally by turning the fastener in engagement with the engagement means to cause untwisting deformation of the fixing.

Preferably, the method also comprises disengaging the fastener from the engagement means, for example by turning the fastener to disengage the fastener from the engagement means. The method may, for example, comprise breaking, bending or rupturing the engagement means to disengage the fastener.

A particularly preferred expression of the method comprises turning the fastener to cause further lateral expansion of the fixing by shortening of the fixing with respect to the longitudinal axis after disengaging the fastener, in this case, the method preferably comprises turning the fastener to effect an automatic transition between the regimes of untwisting deformation and axial shortening.

The method may comprise inserting the fixing into the hole so that a distal end of the fixing passes into or through a gap behind the hole, in which case the lateral expansion or further lateral expansion of the fixing causes a part of the fixing to expand behind the hole.

In a fourth aspect, a method of manufacturing a fixing according to the first aspect of the invention is provided. The method comprises forming the twist formation of the fixing by rolling a blank into a cylindrical formation. Such a method provides a cost-effective and straightforward way of manufacturing the fixing.

The method may further comprise forming the blank from a sheet material, for example by cutting, stamping, pressing, milling and/or punching the blank from the sheet material before rolling. Optionally, the method comprises deforming the blank to form teeth on the elements of the twist formation before roiling.

Furthermore, the method may comprise attaching an anchor formation to the cylindrical formation. Similarly, the method may further comprise attaching a coupling to the cylindrical formation Alternatively, the coupling may be formed by bending one or more parts of the cylindrical formation into a radially-extending orientation

it will be appreciated that the present invention is not limited to holding fasteners in walls, but would be equally useful to hold fasteners in other structures such as ceilings or floors Similarly, the present invention is suitable for use in a wide range of substrates, including plasterboard, masonry, piaster, brick, concrete, breeze blocks, stone and so on

Brief description of the drawings

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which like reference numerals are used for like features, and in which

Figure 1 is a perspective view of a fixing according to a first embodiment of the present invention,

Figure 2 is a perspective view of a fastener for use with the fixing of Figure 1 ,

Figure 3 is a schematic part-sectional view of the fixing of Figure 1 being used to hold the fastener of Figure 2 in a hole,

Figure 4 is a schematic end view, from the distal end, of the fixing of Figure 1 being used to hold the fastener of Figure 2 in a hole,

Figure 5 is a perspective view, from the distal end, of a fixing according to a second embodiment of the present invention,

Figure 6 is a perspective view of a fastener for use with the fixing of Figure 5,

Figure 7 is a side view of a fixing according to a third embodiment of the present invention,

Figure 8 is a perspective view, from the distal end, of the fixing of Figure 7, Figure 9 is a distal end view of the fixing of Figure 7;

Figure 10 is a perspective view, from the proximal end, of a fixing according to a fourth embodiment of the invention;

Figure 1 1 is a second perspective view, from the distal end, of the fixing of Figure 10;

Figure 12 is a proximal end view of the fixing of Figure 10;

Figure 13 is a distal end view of the fixing of Figure 10, with lugs at the distal end of the fixing being bent radially inwardly;

Figure 14 is a perspective view, from the distal end, of a fixing according to a fifth embodiment of the invention;

Figure 15 is an exploded perspective view of a fixing according to a sixth embodiment of the invention; and

Figure 16 is a perspective view, from the proximal end, of part of the fixing of Figure 15.

Detailed description of embodiments of the invention

Referring to Figure 1 , in a first embodiment of the present invention, there is provided a fixing 10 comprising an elongate body 12 that defines a longitudinal axis of the fixing 10. The body 12 comprises an anchor formation 14, located at a proximal end of the fixing 10, and a coupling 16 located at a distal end of the fixing 10. As will be described in more detail below, the dista! end of the fixing 10 is inserted into a hole In a wall, ceiϋng, floor or similar surface in use of the fixing 10.

Between the anchor formation 14 and the coupling 16, part of the body 12 is shaped into a twist formation 18. In this example, the body 12 is generally cylindrical, and the twist formation 18 is formed from a number of elements or bands 20 which extend helically around the body 12 of the fixing 10. in other words, a number of helical slits 22 extend around the body 12 to define and separate the helical bands 20. The bands 20 lie at an angle of about 45° with respect to the longitudinal axis of the fixing 10. The bands 20 are provided with ridges or teeth 24 on their outermost surfaces. The teeth 24 comprise elongate raised members arranged in a helical formation around the body 12. The pitch of the helix defined by the teeth 24 is half that of the pitch of the heϋx defined by the bands 20 and slits 22, so that the teeth 24 form an angle of about 22.5° with respect to the slits 22 and an angle of about 67.5° with respect to the longitudinal axis.

The anchor formation 14 comprises an annular plate 26 affixed to the proximal end of the body 12. A central opening in the plate 26 (not shown in Figure 1 ) allows a fastener to be inserted into the fixing 10 when the fixing is in use, so that the fastener is received within the hollow body 12 of the fixing 10.

The anchor formation 14 is also provided with fins 28 (only one of which is shown in Figure 1 ) which extend a short way along the body 12 and which are attached to the distal face of the plate 26. An outer edge of each fin 28 is curved to define an arc that extends from the plate 26 to the body 12. The fins 28 extend a short way along the body 12.

The coupling 16 comprises a cylindrical disc or end plate 30 having a central opening 32. The opening 32 is internally threaded to mate, in use, with external threads provided on the shaft of the fastener. Two lugs 34 extend radially inwards from the periphery of the opening 32 in the end plate 34. As will be described in more detail below, the lugs 34 form sacrificial engagement means for engaging the coupling 16 with the fastener to transmit a torque applied to the fastener to the body 12 in use. The lugs 34 are arranged to break away from the fixing 10 when the torque that acts on the lugs 34 reaches a predetermined value or breaking torque.

Figure 2 shows a fastener 40 adapted for use with the fixing 10 of Figure 1. The fastener comprises a bolt 40 having a domed head 42, a shaft 44, and an engagement region 46, As is conventional, the head 42 is slotted to receive a screwdriver, and the shaft 44 is threaded.

The engagement region 46 comprises an unthreaded, flat, plate-like formation 48 at the end of the bolt 40 opposed to the head 42. The plate-like formation 48 extends diametrically across the bolt 40, and has a width slightly less than the diameter of the bolt 40. The plate-like formation 48 extends a short distance beyond the end of the shaft 44 of the bolt 40.

The process of using the fixing to hold a fastener in a ho!e wil! now be described with reference to Figure 3 which shows the fixing 10 of Figure 1 in use to hold the fastener 40 of Figure 2 in a hoie in a wal! 50, and Figure 4 which shows some of the stages shown in Figure 3, viewed from the inside of the wall 50 so that the distal end of the fixing 10 can be seen.

In this example, the fixing 10 is used in a wall 50 comprising a plasterboard face 52 over a blockwork backing 54, as shown in Figure 3(a). As is conventional, a gap or cavity 56 separates the plasterboard 52 from the blockwork 54. For ciarity, the blockwork backing 54 is not shown in Figures 3(b) to 3(e).

First, a hole 58 is drilled in the plasterboard 52 as shown in Figure 3(a). The hole 58 is of a diameter suitable to accommodate the body 12 of the fixing 10 with a small clearance between the interior surface 60 of the hoie 58 and the fixing 10.

As shown in Figure 3(b), the fixing 10 is inserted into the hoie 58 so that the plate 26 of the anchor formation 14 lies against the plasterboard 52. The fixing 10 is pushed into the hole 58 so that the fins 28 dig in to the plasterboard 52 around the periphery of the hole 58 to stop the fixing 10 rotating in the hole 58.

It is to be noted that, since the body 12 of the fixing 10 is of cylindrical form, it is not necessary to squeeze or otherwise compress the fixing 10 so that it fits into the hole 58. Also, the operation of the fins 28 is unencumbered by insertion of the body 12 into the hoie 58, allowing the fixing 10 to be easily and positively located in the correct position.

Figure 4(a) shows the distal end of the fixing 10 deployed within the hoie 58. The coupling 16, with its end plate 30, opening 32 and iugs 34, can be seen in Figure 4(a).

The bolt 40 is then inserted into the fixing 10. As shown in Figures 3{c) and 4(b), the p!ate-like formation 48 at the end of the bolt 40 is narrow enough to fit through the opening 32 in the coupling 16. The plate-like formation 48 is long enough so that, at this stage, the threads of the bolt shaft 44 do not engage with the interna! threads of the opening 32 of the coupling 16. A torque is then applied to the bolt 40, so that the bolt 40 turns clockwise with respect to the longitudinal axis within the body 12. The plate-like formation 48 engages the lugs 34 of the coupling 16 so that the lugs 34, and hence the coupling 16, turn relative to the anchor formation 14 of the fixing 10.

The twist formation 18 is therefore subjected to a torque as the coupling 16 turns. Because the sense of the helix formed by the bands 20 of the twist formation 18 is opposite to the sense of the screw threads on the shaft 44 of the bolt 40, the twist formation 18 undergoes an untwisting deformation, in other words, the bands 20 unwind as the coupiing 16 turns.

As shown in Figures 3{d) and 4(c), the twist formation 18 expands transversely with respect to the longitudinal axis of the fixing 10 as the untwisting deformation proceeds The bands 20 therefore move outwards to press against the wall 60 of the hole 58 in the plasterboard 52 This helps to anchor the fixing 10 in the hole 58 against increasing torque acting through the bolt 40.

The teeth (24 in Figure 1, not shown in Figures 3 or 4) bite into the internal wall 60 of the hole 58 as the bands 20 move outwards, which also helps to anchor the fixing 10 in the hole 58. Because the teeth 24 are oriented at an angle to the bands 20, the teeth 24 tend to pull the bands 20 further into the hole 58 as the bands 20 turn and move outwards, it will be appreciated that the extent to which the bands 20 turn during the untwisting deformation varies along the length of the fixing 10. the bands 20 closest to the coupling 16 turn to a greater extent than the bands 20 closest to the anchor formation 14

Another consequence of the untwisting deformation is that the fixing 10 undergoes an axial extension as the bands 20 untwist. As a result, the fixing 10 extends further into or beyond the hole 58

As the bolt 40 is turned further, the untwisting deformation and consequent lateral expansion of the fixing 10 continues Eventually, the lateral expansion of the fixing 10 becomes restrained by the hole 58 and the torque applied to the lugs 34 increases The application of the torque causes the lugs 34 to experience shear forces The lugs 34 are designed so that, when the applied torque exceeds the breaking torque, the shear forces cause the lugs 34 to break away from the coupling 16

When the lugs 34 have broken away, the plate-like formation 48 is no longer engaged with the coupling 16 Because deformation of the bands 20 is predominantly plastic, the coupling 16 is not substantially displaced from its position when the lugs 34 break away and the bands 20 remain pressed against the interior surface 60 of the hole 58 to anchor the fixing 10 in the hole 58

In this position, the threaded shaft 44 of the bolt 40 mates with the threaded opening 32 in the coupling 16 Further turning of the bolt 40 then causes relative movement of the coupling 16 and the bolt 40 along the longitudinal axis

Initially, the relative axial movement causes the bolt 40 to move towards the surface of the plasterboard 52 Eventually, when the bolt head 42 contacts the fixing 10 or a workpiece (not shown) through which the bolt 40 extends, the bolt 40 cannot move further in an axial direction with respect to the plasterboard 52 As shown in Figures 3(e) and 4(d), the relative axial movement the causes the coupling 16 to move axially along the bolt 40 towards the anchor formation 14 This causes further radial expansion of the twist formation 18, so that the bands 20 bite further into the inside surface 60 of the hole 58 in the plasterboard 52 in this way, the fixing 10 becomes firmly anchored in the hole 58, and the fastener 40 is retained within the fixing 10 by engagement with the threaded opening 32 of the coupling 16

The fixing 10 is therefore designed to operate in a two-stage manner during installation in the first stage, the coupling 16 turns in engagement with the fastener 40 to cause the twist formation 18 to undergo lateral expansion by virtue of an untwisting deformation In the second stage, the coupling 16 does not turn, but moves axiaily along the fastener 40 to shorten the fixing 10 to cause further lateral expansion of the twist formation 18

During the first stage, the action of the moving bands 20 and the teeth 24 anchor the fixing 10 to a sufficient degree to hold the fixing 10 in the hole Furthermore, the helical formation of the bands 20 means that the parts of the bands 20 which press against and bite into the interior 60 of the hole 58 are uniformly distributed around the circumference of the fixing 10, and therefore cause the fixing 10 to become centred with respect to the hole 58. Furthermore, again by virtue of the heiical formation of the bands 20, the fixing 10 expands in a manner that conforms readily to the shape of the hole 58.

The first stage takes place requires only a small turning movement of the fastener 40. As a result, the fixing 10 is held within the hole 58, albeit with less than the eventual degree of security, quickly and easily. Aside from the benefit of securing the fixing 10 early in the installation procedure to ease the rest of the installation process, the rapid nature of the first stage gives the user of the fixing 10 confidence that installation of the fixing 10 is proceeding successfully.

At the beginning of the second stage, the bands 20 are already pressed against and have bitten into the interior surface 60 of the hole 58. This substantially prevents any further turning movement of the bands 20 with respect to the hole 58. In the second stage, therefore, the fixing 10 becomes more firmly anchored in the hole 58 and bites into the plasterboard 52 without causing damage that could result if the bands 20 were able to turn.

Both stages are driven by turning motion of the fastener 40 so that no user intervention is required to make the transition from the first stage to the second stage. The user need simply turn the fastener 40 in a conventional manner to anchor the fixing 10 in the hole 58 and to anchor the fastener 40 in the fixing 10.

Although most of the deformation of the bands 20 is plastic and hence irreversible, an elastic deformation also takes place that acts on the coupling 16 to push the coupling 16 away from the anchor formation 14. Consequently, when the fastener 40 and the coupiing 16 are in threaded engagement and the fastener 40 is pulled away from the installed fixing 10, the fastener 40 tends to be pulled back into the fixing 10. in this way, the fixing 10 applies an additional elastic holding force or puil to the fastener 10.

After installation of the fixing 10, the fastener 40 can be removed from the fixing 10 by unscrewing the fastener 40, preferably keeping any axial force on the fastener 40 to a minimum while unscrewing. The coupling 16 remains approximately in its final position when the fastener 40 has been removed, so that the fastener 40 can be re-inserted into the fixing 10 and re-tightened. In a variant of the first embodiment, the fixing 10 shown in Figure 1 can also be used with an alternative fastener (not shown) having an engagement region comprising a twisted plate formation instead of the flat plate formation of the fastener of Figure 2 When this alternative fastener is inserted into the fixing 10, the twisted plate formation engages with the lugs 34 On pushing the fastener into the fixing 10, without applying a turning movement to the fastener, the helically-twisted arrangement of the plate formation causes a torque to be applied to the coupling 16, via the lugs 34, which causes an initial untwisting deformation of the bands 20 similar to that shown in Figure 3(d)

Installation of the fixing then proceeds as described above with reference to Figures 3 and 4, wherein turning of the fastener eventually causes the lugs 34 to break so that the threaded shaft of the fastener mates with the threaded opening 32 in the coupling 16

In this variant, the initial stage of anchoring the fixing 10 in the hole can be at least partially achieved simply by pushing the fastener axialiy into the fixing !t will be appreciated that a similar result could be achieved by providing helical slots in an end region of the fastener, arranged such that the lugs engage in the slots

In another variant (not shown) of the first embodiment of the invention, the coupling is provided with slots in place of the lugs The slots of the coupling are configured to accept helical splines, which are attached to or formed in the outside surface of the end region of a complementary threaded fastener In use, the fastener is inserted into the fixing so that the spimes engage with the slots of the coupling On pushing the fastener into the fixing, without turning, the helical arrangement of the splines causes a torque to be applied to the coupling of the fixing, which causes the initial untwisting deformation of the bands of the fixing In this case, turning of the fastener eventually causes the splines to break away from the fastener, so that the threaded shaft of the fastener mates with the threaded opening in the coupling

Figure 5 shows a fixing 1 10 according to a second embodiment of the invention during an intermediate stage of manufacture of the fixing 1 10, and Figure 6 shows a fastener 140 for use with the fixing 1 10 of Figure 5 The fixing 1 10 of the second embodiment is similar to the fixing of the first embodiment, and so only the differences with respect to the first embodiment will now be described In this case, the engagement means of the coupling 116 comprises two lugs 134 that, as shown in Figure 5, extend longitudinally with respect to the fixing 1 10 during an intermediate stage of its manufacture. At a later stage of manufacture (not shown), the lugs 134 are bent into a radially-extending orientation to lie diametrically across the coupling 116. The direction of bending of the lugs 134 is shown by the arrows labelled 'A' in Figure 5.

The coupling 116 comprises recesses 162 to accommodate the lugs 134, so that the lugs 134 lie flat across the coupling 1 16 when in the radially-extending orientation. When bent into position, therefore, the lugs 134 form a bar-like cross member across the distal end of the coupling 116.

The fastener 140 shown in Figure 6 comprises a bolt having a head 42, a threaded shaft 44, and an engagement region 146 opposed to the head 42. The engagement region 146 comprises an unthreaded cylindrical element 164 having a smaller diameter than the shaft 44. A slot 166 is provided across the end of the cylindricai element 164.

In use, the slot 166 in the engagement region 146 of the fastener 140 engages the lugs 134. As in the first embodiment of the invention, the lugs 134 are arranged to break away from the fixing 1 10 when the torque applied to the lugs 134 exceeds a breaking torque. In this way, the fixing 1 10 of the second embodiment operates in the same way as the fixing of the first embodiment of the invention.

Figures 7, 8 and 9 show a fixing 170 according to a third embodiment of the invention, which differs from the first and second embodiments of the invention in the arrangement of the teeth provided on the outermost surface of the bands, and in the arrangement of the coupling. Otherwise, the features of the third embodiment are similar to those of the first and second embodiments described above: like reference numerals are therefore used for like parts.

As shown most clearly in Figure 7, the bands 20 of the twist formation 18 are provided with teeth 24 as in the first embodiment of the invention. In this third embodiment, however, the orientation of the teeth 24 with respect to the longitudinal axis of the fixing 170 varies along the length of the fixing. A first group of teeth (one of which is indicated at 24a in Figure 7) closest to the coupling 116 are oriented at an angle of about 67.5° with respect to the longitudinal axis of the fixing 170, while a second group of teeth (one of which is indicated at 24c) closest to the anchor formation 14 are oriented at an angle of 90° to the longitudinal axis A third group of teeth (one of which is indicated at 24b) lie mid-way between the first and second groups of teeth 24a, 24c and are oriented at an angle of approximately 79° to the longitudinal axis

Thus, the angle between the teeth 24 and the longitudinal axis of the fixing 170 decreases moving distaily along the fixing 170 This variation in angle is to take account of how the fixing 170 deforms in use Specifically, the relatively distal teeth 24a are on bands 20 that will tend to deform more in use than the bands 20 carrying the relatively proximal teeth 24c That deformation will tend to increase the angle between the teeth 24 and the longitudinal axts of the fixing 170 It is advantageous if, after deformation and when engaging with the inside of a hole, the teeth 24 are close to 90° to the longitudinal axis of the fixing 170 This is because the teeth will then cut most effectively into the inner surface of the hole in a circumferential direction without grinding a groove having a longitudinal component So, the relatively distal teeth 24a start from an angle sufficiently ϊess than 90° to allow for the expected deformation of the fixing 170 in use

Moreover, in this case the engagement means of the coupling 171 comprises two lugs 172 which, as shown most clearly in Figures 8 and 9, extend diametrically across the opening 32 in the end plate 30 The lugs 172 do not meet one another, but instead define a gap or channel between the lugs 172 Each lug 172 is attached to the end piate 30 near its outermost edge by way of a relatively thin connecting member 174 serving as a fracture zone whereby the lugs 172 will detach during use in a similar manner to that described above

The fastener 140 shown in Figure 6 is suitable for use with a fixing 170 according to the third embodiment of the invention As in the second embodiment of the invention, in use, the slot 166 in the engagement region 146 of the fastener 140 engages the lugs 176 so that torque applied to the fastener 140 causes the fixing 170 to rotate

In this embodiment, a hole need not be drilled in the substrate before insertion of the fixing Instead, the lugs 172 are shaped to provide a self-drilling action when the distal end of the fixing 170 is pressed against a plasterboard or similar substrate and the fixing 170 is rotated by turning the fastener 140 with a screwdriver or the like To this end, the thickness of each lug 172 increases longitudinally moving from the outermost edge of a lug 172 towards its innermost edge. In this way, the lugs 172 taper distally. The lugs 172 are therefore shaped to define, in combination, a pointed dista! end of the fixing 170.

Furthermore, each lug 172 is shaped to form a cutting edge 176 along its distal edge. In other words, the distal end face of each lug is inclined with respect to the end plate 30, so that a relatively sharp long edge of the lug 172 is presented at the distal end of the fixing 170. As shown most cleariy in Figure 9, the cutting edge 176 of each lug 172 lies on the opposite edge to the cutting edge 176 of the other lug 172. In this way, the cutting edges 176 of both lugs 172 act upon the substrate as the fixing is rotated in use.

In use_> the dista! end of the fixing can be pressed against the substrate, so that the pointed distal end of the fixing 170 bites into the surface of the substrate. Then, torque is applied to the fastener 140 to rotate the fixing 170 by virtue of engagement between the slot 166 of the fastener 140 with the lugs 172 of the fixing 170. As the fixing rotates, the cutting edges 176 of the lugs 172 carve out or drill material of the substrate, so that a hole is formed in the substrate as the fixing is rotated. In this embodiment, therefore, the fixing 170 advantageously provides a self-drilling action as the fixing is driven into the substrate. Debris from the drilling action can, for example, pass through the opening 32 in the end plate 30, via the channel between the lugs 176, through the fixing 170, and then out of the fixing 170 through its proximal end. It will be noted in this respect that when the slot 166 of the fastener 140 is engaged with the lugs 172 of the fixing 170, the unthreaded portion 164 of the fastener 140 lies within the threaded opening 32 of the end-plate 30 while leaving a clearance through which debris from the drilling action can pass. Debris can also be expelled laterally or distally when the fixing 170 extends through a panel-like substrate such as plasterboard.

As in the first and second embodiments, the lugs 176 are arranged to break away from the fixing 170 when the torque applied to the lugs 176 exceeds a breaking torque. This occurs after the hole has been formed by the self-drilling action of the fixing and the fixing is located in the hole by untwisting deformation. Breakage occurs by failure of the connection members 174. After the initial insertion of the fixing 170 into the substrate, therefore, the fixing 170 of the third embodiment thereafter operates in the same way as the fixings 10, 1 10 of the first and second embodiment of the invention. It is conceivable that the fixing 170 of the third embodiment of the invention couid be used in a substrate with a pre-dril!ed hole, in which case the fixing 170 would operate in entirely the same way as the fixings of the first and second embodiment of the invention. It is also possible to use the fixing 170 of the third embodiment with a pilot hole that is narrower than the fixing 170 in its initial, non-deformed state.

Preferably, the fixing 170, including the end plate 30, lugs 172 and connecting members 174, is formed as a unitary component, although it will be appreciated that a multi- component arrangement could be used if necessary for ease of manufacture.

A fourth embodiment of the invention is shown during an intermediate stage of manufacture in Figures 10 to 12, and in a later stage of manufacture in Figure 13. The fourth embodiment comprises a fixing 210 that is similar to the fixing of the first to third embodiments, and on!y the differences will be described.

The anchor portion 214 of the fixing 210 comprises a plate 226 formed from a sheet material and having a central opening 227. The plate 226 has a peripheral chamfer 250 around its distal face. In use of the fixing 210, the chamfer 250 helps the plate 226 to bed into a substrate (not shown in Figures 10 to 13), so that the plate 226 and hence the fixing 210 can lie substantially flush with the external surface of the substrate.

The anchor portion 214 further comprises barbs 228, which have the same function as the fins 28 of the first to third embodiments of the invention. However, in this fourth embodiment of the invention, the barbs 228 comprise portions of the sheet materia! of the plate 226 which are bent into a longitudinal orientation during manufacture of the fixing 210.

The anchor portion 214 of this embodiment can be manufactured by cutting or stamping from a sheet material a circular disc having a central opening 227. The chamfer 250 is then formed around the periphery of the disc. Alternatively, the anchor portion 214 may be formed from a chamfered disc-shaped washer. Each barb 228 is formed by slitting or cutting the disc part-way along a chord of the disc which lies close to, but which does not intersect, the central opening 227. A cut edge 229 is thereby created which extends inwardly from the periphery of the disc. The portion of the disc that lies adjacent to the cut edge 229 is then bent so that it lies perpendicular to the plane of the disc, so as to form the barb 228. In this embodiment, the cut edge 229 extends more than half-way across the chord of the disc, so that the bent barb 228 lies in a radially-extending piane with respect to the central opening 227 of the disc as shown most dearly in Figures 12 and 13. However, should shorter or longer barbs 228 be required, the cut edge 229 could be respectively shortened or extended further along the chord, as appropriate. Furthermore, although two barbs 228 are illustrated, fewer or more barbs could be provided.

It will be appreciated that these manufacturing operations could be combined into a single manufacturing step, or split into multiple manufacturing steps. In either case, the completed anchor portion 214 is attached to the body 212 of the fixing 210 by welding or another appropriate method.

As can be seen most cleariy in Figure 1 1 , an outer edge of each of the barbs 228 made in this way forms an arc that extends from the plate 226 to the body 212 of the fixing.

Although in this example the barbs 228 do not meet the body 212 - as can be seen in

Figure 13 - in other examples the barbs 228 may touch the body 212 along their inside edges. Because the chamfer 250 extends along the outer edge of each barb 228, the barbs 228 are advantageously shaped so as to pierce the substrate when the fixing 210 is pushed into a hole, in use.

The body 212 of the fixing 210 of the fourth embodiment of the invention differs from the body of the previous embodiments in that, in the fourth embodiment, the bands 220 lie at an angle of about 30° with respect to the longitudinal axis of the fixing 210. Furthermore, the teeth 224 on the bands 220 of the fourth embodiment of the invention lie approximateiy perpendicuiar to the longitudinal axis of the fixing 210.

Furthermore, in this embodiment, the teeth 224 are formed by stamping or pressing the material of the bands 220 outwardly, so that each tooth 224 comprises a generally part- spherical protrusion which overlays a corresponding part-circular aperture 225 in the band 220.

Preferably, the body 212 is formed by cutting or stamping apertures or slits in an initially flat sheet of material to define the bands 220 therebetween, then rolling the sheet into the cylindrical form of the body 212. Thus, in this case, the teeth 224 can conveniently be formed by stamping the teeth 224 into the flat sheet before rolling. Preferably, the sheet is cut to size, the slits defining the bands 220 are formed, and the teeth 224 are stamped into the sheet in a single pressing or stamping operation

The apertures 225 associated with the teeth 224 influence the deformation behaviour of the bands 220 It will be appreciated that forming an aperture 225 in a band 220 creates a region of the band 220 that is substantially easier to deform than the rest of the band

220 A larger aperture 225 gives rise to a region of the band 220 that is more readily deformable than a region of the band 220 associated with a smaller aperture 225 Thus the size of the apertures 225 associated with the teeth 224 can be tailored to control the deformation behaviour of the bands 220

As shown most clearly in Figure 10, in the fixing 210 of the fourth embodiment of the invention the teeth 224a closest to the centre of the body 212, and hence the corresponding apertures 225, are larger than the teeth 224b and the corresponding apertures 225 closest to the ends of the body 212 Thus, in the centre of the body 212, the bands 220 are more readily deformable than at the ends of the body 212

The coupling 216 of the fixing 210 is similar to the coupling 1 16 of the third embodiment of the invention As in the third embodiment, the coupling 216 comprises a pair of diametrically opposite lugs 234 which extend longitudinally with respect to the fixing 210 during an intermediate stage of its manufacture, as shown in Figure 1 1 At a later stage of manufacture, shown in Figure 13, the lugs 234 are bent into a radially-extending orientation to lie diametrically across the coupling 234 The arrows labelled 'A' in Figure 1 1 show the direction of bending of the lugs 234

Since, in this fourth embodiment of the invention, no recesses are provided in the coupling 216 to accommodate the lugs 234, the lugs 234 can be formed during the sheet pressing or stamping operation during manufacturing of the body, as described above In the finished product, the folded lugs 234 protrude beyond the distai end of the body 212

In a fifth embodiment of the invention, shown during an intermediate stage of manufacture in Figure 14, a fixing 310 is provided which differs from the fixing of the fourth embodiment only in the configuration of the coupling 316 at the distal end of the fixing, and only these differences will be described Like reference numerals are used in Figure 14 where the features of the fifth embodiment of the invention correspond to those of the fourth embodiment of the invention The coupling 316 comprises an annular coupling plate 320 having a central aperture 322. In the intermediate stage of manufacture shown in Figure 14, the coupling plate 320 lies in a plane that projects longitudinally from one side of the distal end of the body 312, In a later stage of manufacture (not shown), the coupling plate 320 is bent through approximately 90° at a hinge region 324 so that the coupling plate 320 partially closes the distal end of the body 312. The arrow labelled 'A' in Figure 14 shows the direction of bending of the coupling plate 320.

To aid alignment of the coupling plate 320 with the end of the body 312, a slot 326 is provided in the coupling plate 320 diametrically opposite the hinge region 324. When the coupling plate 320 is bent over, the slot 326 engages with a longitudinally-extending tab 328 which projects from the end of the body 312.

After the coupling piate 320 has been folded into position over the end of the body 312, it is fixed into place, for example by welding the coupling plate 320 to the tab 328 or to the end of the body 312.

Unlike in the previously-described embodiments of the invention, in this fifth embodiment, the coupling 316 does not initially include a threaded region. Instead, the periphery of the central aperture 322 is unthreaded so that the fixing 310 can be used with a fastener having a self-tapping screw thread (not shown).

As is known in the art, such self-tapping fasteners include an externally-threaded, tapered end region that is adapted to cut an internal thread into a bore or aperture, and an externally-threaded cylindrical shaft that mates with the internal thread cut by the tapered end region.

The central aperture 322 of the coupling 316 has a slightly smaller diameter than the body region of the fastener, so that, when the fastener is inserted into the fixing 310, the tapered end region of the fastener locates in the aperture 322, but the cylindrical shaft of the fastener cannot pass through the aperture 322.

When a torque is applied to the fastener, the threads of the tapered end region of the fastener dig or bite in to the periphery of the aperture 322, thereby causing the fastener to engage with the coupling 316. initially, the coupling 316 turns with the fastener, so that the twist formation of the fixing 310 undergoes an untwisting deformation, in the same way as described above with reference to the first embodiment of the invention

Once the lateral expansion of the fixing 310 becomes restrained by the hoie in which it is deployed, the torque applied to the coupling plate 320 increases Eventually, the fastener begins to turn with respect to the coupling 316, and the self-tapping action of the fastener causes a thread to be tapped into the coupling plate 320 at the periphery of the aperture 322

Once a thread has been formed, the coupiing 316 no longer turns with the fastener Instead, the threaded shaft of the fastener mates with the now threaded aperture 322 in the coupling plate 320 As in previous embodiments of the invention, further turning of the fastener causes relative movement of the coupiing 316 and the fastener along the longitudinal axis, resulting in further radial expansion of the bands 220 to secure the fixing 310 in the substrate

Thus, in the fifth embodiment of the invention, the tapping of screw threads in the coupling plate 320 causes the coupling 316 to disengage the fastener to ailow the coupling 316 to cooperate with the fastener to convert turning movement of the fastener to axia! movement of the coupling 316

As in the fourth embodiment of the invention, the anchor portion 214 and the body 312 of the fixing 310 of the fifth embodiment can optionally be manufactured from a sheet material in particular, the coupiing plate 320 can be formed during pressing or stamping the body 312 from the sheet material After rolling of the sheet into a cylinder to form the body 312, the coupling plate 320 projects longitudinally from one ssde of the distal end of the body 312, as shown in Figure 14 The coupling plate 320 can then be bent over at the hinge portion 324 and attached to the tab 328 as previously described

A fixing according to a sixth embodiment of the invention is shown in Figures 15 and 16 Figure 15 is an exploded view of the fixing 410, showing three components of the fixing, namely the anchor portion 214, the body 412 and the coupling 416, separated along the longitudinal axis of the fixing 410 Since the anchor portion 214, body 412 and coupling 416 are manufactured separately and then joined together, Figure 15 could also be considered to show the fixing 410 in an intermediate stage of manufacture The anchor portion 214 of this sixth embodiment is the same as in the fourth and fifth embodiments of the invention described above. Figure 15 shows the anchor portion 214 after the barbs 228 have been bent to lie perpendicular to the piane of the plate 226, and before the anchor portion 214 is attached to the body 412 by welding or another suitable attachment method.

The coupling 416 comprises a conventional lock nut 45O₁ such as a nylon insert lock nut. As is known in the art, the lock nut 450 comprises an internally-threaded region and, at the distal end of the nut in Figure 15, a collar insert (not shown) of nylon or a similar material.

In this sixth embodiment, the body 412 of the fixing 410 is similar to the bodies of the fixings of the fourth and fifth embodiments of the invention. As in those previously- described embodiments, the body 412 can be manufactured by punching, pressing, cutting or stamping a suitable blank from a sheet material, including apertures to define the bands 220, and cuts and indentations to form the teeth 224. The blank is then rolled into a cylindrical shape to form the body 412, which is shown in more detail in Figure 16.

As can be seen in Figure 16, the body 412 includes two break lines 440 where two opposing ends of the blank face one another when the blank has been rolled into the cylindrical form of the body 412. The break lines 440 extend from the proximal and distai ends of the body 412 to a helicai slit 422 between two of the bands 220. The two opposing ends of the blank thus form the opposing edges of the helical slit 422. In the example shown in Figure 16, the opposing ends of the blank are not joined at the break lines 440. However, it will be appreciated that the opposing ends of the blank could be welded or otherwise joined across the break lines 440.

The body 412 also includes two diametrically-opposed support lugs 452 which extend longitudinally from the distal end of the body 412. During assembly of the fixing 410, the lock nut 450 is inserted between the support lugs 452 and pushed into position abutting the distal end of the body 412. The support iugs 452 conveniently embrace the lock nut 450 across opposed flats of the lock nut 450, with the internal face of each support lug 452 bearing against the respective flat. The lock nut 450 is held in place by welding or another suitable method. Conveniently, the lock nut 450 and the anchor portion 214 can be attached to the body 412 in a smgle welding process. First, the lock nut 450 and the anchor portion 214 are held in position against the body 412 by a suitable assembly tool (not shown). Then, the lock nut 450 and the anchor portion 214 are flash-welded to the body 412 by passing an electric current through the components.

The fixing 410 is used with a fastener (not shown) having a conventional threaded bolt shaft. The collar insert of the lock nut 450 has a diameter that is smaller than the major diameter of the threads of the bolt shaft The collar insert is elastically deformable to accommodate the bolt shaft, conforming to its thread. However, once the lock nut 450 is engaged with the bolt shaft, the collar insert squeezes on the bolt shaft to impede the turning motion of the bolt shaft relative to the lock nut 450. Additionally, the elasticity of the collar insert tends to push the threads of the bolt shaft against the internal threads of the lock nut 450, creating a high-friction coupling between the respective threads

As a consequence, the lock nut 450 becomes locked on the bolt shaft, and the bolt shaft can only be turned with respect to the lock nut 450 once a sufficient torque is applied to the bolt shaft to overcome the frictional forces The collar insert thereby functions as a stop member that stops relative axial movement of the bolt shaft with respect to the lock nut 450 unless a sufficiently high torque is applied.

In use, the end of the bolt shaft initially easily screws in to the internally-threaded region of the lock nut 450. Then, when the end of the bolt shaft meets the collar insert of the lock nut 450, the lock nut 450 locks onto the bolt shaft as described above. Thus, in this condition, the lock nut 450, and hence the distal end of the body 412, turn with the fastener to effect the untwisting deformation of the bands 220.

Once the bands 220 have become restrained by the hole in which the fixing 410 is deployed, the torque applied to the lock nut 450 by the bolt shaft increases. Eventually, the torque becomes sufficient to overcome the locking action of the lock nut 450, and the bolt shaft is able to turn with respect to the lock nut 450 In this condition, the lock nut 450, and hence the coupling 416, moves axially with respect to the anchor formation 214, resulting in further lateral expansion of the fixing as in the previously-described embodiments of the invention Because the fixing 410 of the sixth embodiment of the invention employs a conventional lock nut 450 for the coupling 416, the manufacturing cost and complexity of this fixing 410 is minimised.

A variant of the sixth embodiment of the invention (not shown) differs from the sixth embodiment in that, in place of a lock nut, the coupling of the fixing comprises a body having a threaded opening, and a stop member. The body couSd, for example, be a conventionai nut. The stop member comprises a disc that is adhesively attached to the coupling to close the distal end of the fixing.

The coupling is arranged to receive a conventional bolt. In use, the bolt is screwed into the coupling until the end of the boit reaches the disc. The disc prevents further relative turning movement of the coupling and the bolt. Instead, the coupling begins to turn in conjunction with the bolt, to effect untwisting deformation of the twist formation as described above.

The force acting on the disc by virtue of the bolt increases as the untwisting deformation proceeds and the bands press against the interior of the hole. Eventually, when a predetermined force is reached, the adhesion of the adhesive is overcome and the disc breaks away from the fixing. This allows the bolt once again to turn with respect to the coupling, and transverse expansion can occur by axial shortening of the fixing as in the previously-described embodiments of the invention.

In a further variant of the sixth embodiment, the coupling comprises a body having a threaded opening and a stop member in the form of one or more lugs similar to the Sugs of the first and second embodiments. As for the disc described above, the lugs prevent the bolt from turning relative to the coupling in the first stage of operation, and then break away from the body to allow the coupling to move axially along the bolt in the second stage of operation.

In yet another variant, the stop member is a metal or plastics film that extends across the threaded opening of the body of the coupling to close the distal end of the fixing. In this case, the bolt abuts the film to prevent the relative movement of the bolt and the coupling in the first stage of operation, and is ruptured by the bolt when a pre-determined force is reached to allow the bolt to pass through the film in the second stage of operation. In this case, the bolt may comprise a pointed end that serves to puncture the film when the predetermined force is reached.

In each embodiment of the Invention described above, the body is made from a relatively soft, deformable metal, which is ductile and malleable so as to resist fracture during the substantia! plastic deformation that occurs during installation of the fixing. Suitable metals include steel, copper, zinc, tin and aluminium.

It will be appreciated that other materials with relatively Sow yield strengths, such as a plastics material, could also be used. Suitable plastics materials include nylons (polyamides) and polypropylene.

Several manufacturing processes are suitable to manufacture fixings according to the invention. As already described, some embodiments of the invention can be manufactured by pressing, stamping, embossing and/or cutting a sheet material to form blanks for one or more components of the fixing, and then shaping the blank to form the component by rolling and/or folding the blank.

Other suitable manufacturing methods include casting, injection moulding, machining, milling, sintering and so on. As will be understood by those skilled in the art, the choice of manufacturing method depends upon the material chosen, the size of the fixing to be produced, the costs involved and so on.

When the invention is embodied in a plastics material, injection moulding is particularly suitable for manufacturing the fixings. In this case, a thin film of plastics, known as flash, may wholly or partially occlude the siits or gaps between the bands of the fixing.

Normally, flash would be removed during manufacture of the fixing. However, to reduce manufacturing costs, the flash could be left in place. The presence of a small amount of flash does not affect the operation of the fixing, since any flash that bridges the slits or gaps between two adjacent bands readily tears upon untwisting deformation of the fixing in use.

Similarly, flash may also arise where an injection moulding or casting process is used to manufacture a fixing from a metal. Again, any metal flash between the bands is torn when the untwisting deformation occurs. After tearing the plastics or metal flash during use of the fixing, remnants of flash may remain on the edges of the bands. This remaining flash typically forms a sharp edge along the edges of the bands, which can help the bands to dig or bite in to the wali of the hoie in the substrate during installation of the fixing.

When the manufacturing process of the fixing does not give rise to flash, the bands may be intentionally provided with sharp edges to help the bands to dig or bite in to the wail of the hole. For example, the bands may be formed with chamfered edges, or the edges of the bands may be sharpened in a suitable machining process. It is also conceivable that the bands could include serrated or toothed edge regions to provide the same advantage.

Part or all of the coupling may be made from a different material, such as mild stee! or brass, which has a higher yield strength than the body to prevent deformation of the screw threads in use of the fixing. In such cases, for example in the sixth embodiment of the invention, the coupling may be formed as a nut or similar component which is attached to the body by welding, brazing or the like, or by connection elements such as lugs or ridges formed by or attached to the body. Similarly, part or all of the anchor formation may be made from a different material to the body.

When the engagement means comprises lugs or similar elements, the lugs may be arranged to disengage the fastener by breaking away from the body as described above. In such cases, the lugs may remain partially attached to the fixing, or may fall away entirely. Alternatively, the lugs maybe arranged to bend when the torque acting on them exceeds the breaking torque.

The lugs may be deliberately weakened so that fracture or bending of a lug occurs at a particular location, for example close to where the lug meets the body of the fixing. Such weakening may be achieved by providing scored, perforated or thinned regions of the lug. These weakening features can also be designed to ensure that the lug breaks or bends when the appropriate torque is applied.

The lugs or similar elements, such as splines, may be provided instead on the fastener, in such a case, the lugs or similar elements preferably break away from the fastener to disengage the fastener from the coupling, leaving the fastener free to turn with respect to the coupling. The fixing may include guides to ensure that the fastener remains generally aligned with the longitudinal axis of the fixing in use, particularly during the first stages of instaliation. For example, the centra! opening in the annular plate of the anchor formation may be of only slightly larger diameter than the shaft of the fastener that enters the fixing. Guide means may also be provided in the form of longitudinaϋy-extending ribs arranged around the interior of the body.

The present invention is suitable for use in blind holes (i.e. holes which extend into, but not through, a substrate), as well as in through-holes that extend fully through a substrate as shown in Figure 3.

In Figure 3, the fixing does not extend significantly into the cavity behind the plasterboard, and therefore the example shown in Figure 3 would apply equally to a blind hole in masonry, for example. However, if the fixing extends into a cavity behind a substrate and a portion of the twist formation extends beyond the hole, that portion of the twist formation can expand transversely within the cavity so as to act on the back face of the substrate around the hole.

A single universal fixing can therefore be used for both solid and cavity wall applications. Optionally, however, a cavity wall fixing may be provided which is arranged to expand substantially oniy within the cavity, for example by providing a plain tubular body section, of similar length to the thickness of the intended substrate, between the twist formation and the anchor formation.

Similarly, the fixing may bridge a cavity between two substrates, in this case, the fixing extends through a through-hole in a first substrate, and into a blind hole in the second substrate. In this case, a portion of the twist formation may expand transversely within the cavity to press against the back face of the first substrate around the through-hole. Furthermore, the portion of the expanded twist formation may also press against the face of the second substrate.

The design of the fixing can be adapted for optimal performance in a particular application. For example, the number of bands and the angle that the bands form with the longitudinal axis of the fixing can be adjusted to determine the amount of deformation that the fixing undergoes in operation, and in particular the amount of outward radial pressure that the twist formation applies to the interior of the hole. For example, the fixing of Figure 1 has four bands, arranged at an angle of approximately 45° with respect to the longitudinal axis of the fixing. The fixing of Figure 10 likewise has four bands, but arranged at an angle of approximately 30° with respect to the longitudinal axis of the fixing. Thus, for a given thickness and width of the bands and dimensions of the fixings, the fixing of Figure 10 would undergo an untwisting deformation which is smaller in radial extent but which applies a higher outward gripping force than the untwisting deformation of the fixing of Figure 1. Further variations are shown in Figure 5, wherein the fixing comprises only two, relatively wide bands, and in Figure 7 wherein the fixing comprises five bands. It will be appreciated that any reasonable number of bands from two upwards could be provided.

It is conceivable that the twist formation could comprise a plurality of relatively thin wires in place of the bands. In this case, the fixing could be manufactured by joining pre- shaped wires to an anchor formation and a coupling. Alternatively, straight wires could be joined to the anchor formation and the coupling, and then an appropriate twisting deformation could be applied to the fixing to form the wires into the twist formation.

The shape of the bands may differ from the examples shown in the accompanying drawings. For example, the angle that a band forms with respect to the longitudinal axis of the fixing may vary along the band. In some cases, no teeth are provided on the bands. However, if desired, apertures in the bands such as those shown in Figures 10, 11 , 15 and 16, or other regions of weakness, can still be provided to influence the deformation behaviour of the bands. Furthermore, in cases where teeth are provided, deformation-influencing apertures or similar features that are not associated with the teeth can be provided in the bands in addition to or instead of apertures associated with the teeth. Other deformation-influencing features, such as slits, cut-outs, thinned regions, stiffening ribs and so on could be provided in or on the bands in addition to or instead of apertures.

The diameter of the fixing, and hence the diameter of the twist formation, can also be varied. A larger diameter fixing will typically be required when the fixing must support a heavy load, whereas a smaller diameter fixing will be suitable for lighter loads. For example, the fixing of the sixth embodiment of the invention, shown in Figures 15 and 16, could be arranged to accommodate an M3 lock nut for light-duty applications, an M5 lock nut for medium-duty applications, or an M8 lock nut for heavy-duty applications. The length of the twist formation can also be chosen for a particular application. Furthermore, two or more twist formations could be provided along the length of the body of the fixing, neighbouring twist formations being connected to one another by a short tube section which transmits torque from one twist formation to the next.

Although the embodiments described above refer to the use of a bolt, it will be appreciated that many types of fastener could be used or adapted for use with the fixing of the present invention. For example, the fastener could be a hook, eye, stud, or other fixing. The fastener could be formed integrally with another component to be affixed to the wall. In some cases, it is advantageous to provide fixings with pre-inserted fasteners, so that the fastener and the fixing are inserted into the hole together. In other cases, the fasteners and the fixings are provided separately.

Claims

1. A fixing for holding a fastener in a hole, the fixing comprising:

an elongate body defining a longitudinal axis of the fixing, the body being arranged to receive a fastener that can be turned with respect to the longitudinal axis within the body, wherein the body comprises

an anchor formation adapted to restrain a first part of the body against angular movement within the hole in use;

a coupling cooperable with the fastener to transmit torque from the fastener to a second part of the body in use; and

a twist formation between the anchor formation and the coupling;

the twist formation being arranged to expand transversely with respect to the longitudinal axis by virtue of untwisting deformation in response to the application of torque from the fastener via the coupling in use.

2. The fixing of Claim 1 , wherein the coupling can be turned with respect to the anchor formation to cause untwisting deformation of the twist formation.

3. The fixing of Claim 1 or Claim 2, wherein the anchor formation is toward a proximal end of the body.

4. The fixing of any preceding claim, wherein the coupling is toward a distal end of the body.

5. The fixing of any preceding claim, wherein the anchor formation comprises one or more grip formations.

6. The fixing of Claim 5, wherein a grip formation comprises one or more barbs arranged to pierce a surface adjacent to the hole in use.

7. The fixing of Claim 5 or Claim 6, wherein a grip formation comprises one or more fins arranged to engage with the periphery of the hole in use.

8. The fixing of any of Claims 5 to 7, wherein a grip formation comprises one or more flared regions to wedge the first part of the body in the hole in use.

9. The fixing of Claim 8, wherein the flared regions comprise a plurality of ribs which taper distally.

10. The fixing of any preceding claim, wherein the anchor formation comprises a plate having a central opening for the fastener.

1 1. The fixing of Claim 10, wherein the plate comprises a distai face having a peripheral chamfer.

12. The fixing of Claim 10 or Claim 1 1 , wherein the plate comprises one or more barbs extending longitudinally from the plate, the barbs being arranged to pierce a surface adjacent to the hole, in use.

13. The fixing of Claim 12, wherein the barbs are bent from the remainder of the plate into a longitudinaliy-extending orientation during manufacture of the fixing.

14. The fixing of any preceding claim, wherein the twist formation comprises one or more elements defined by gaps extending helically around the body.

15. The fixing of Claim 14, wherein the elements are bands defined by slits in the body.

16. The fixing of Claim 14 or Claim 15, wherein the elements lie at an angle of between 15° and 60° with respect to the longitudinal axis.

17. The fixing of Claim 16, wherein the elements lie at an angle of about 45° with respect to the longitudinal axis.

18. The fixing of Claim 16, wherein the elements lie at an angle of about 30° with respect to the longitudinal axis.

19. The fixing of any of Claims 14 to 18, wherein the elements are provided with teeth for engagement with the interior of the hole in use.

20. The fixing of Claim 19, wherein the teeth are arranged in heϋcal formation.

21. The fixing of Claim 19 or Claim 20, wherein the teeth are disposed at an angle of between 60° and 90° with respect to the longitudinai axis.

22. The fixing of Claim 21 , wherein the teeth are disposed at an angle of 90° with respect to the longitudinal axis

23. The fixing of Claim 21 , wherein at least one of the teeth is disposed at an angle of about 67.5° with respect to the longitudinal axis.

24. The fixing of any of Claims 19 to 23, wherein at least one of the teeth is disposed at a first angle with respect to the longitudinai axis, and at least another one of the teeth is disposed at a second angle with respect to the longitudinal axis.

25. The fixing of Claim 24, wherein the angle between the teeth and the longitudinal axis of the fixing decreases moving distally along the fixing.

26. The fixing of any of Claims 19 to 25, wherein the teeth are associated with apertures in the elements.

27. The fixing of Claim 26, wherein the teeth are part-sphericai, and the associated apertures are part-circular.

28. The fixing of Claim 26 or Claim 27, wherein a plurality of teeth is provided on each element, and the size of the apertures associated with the teeth varies along each element.

29. The fixing of any of Claims 26 to 28, wherein the size of the apertures increases moving towards the longitudinal centre of the twist formation.

30. The fixing of any preceding claim, wherein the relative deformability of each element varies along the element.

31 . The fixing of Ciaim 30, wherein the deformability of each element increases moving towards the longitudinal centre of the twist formation.

32. The fixing of any preceding claim, wherein the twist formation is arranged also to expand transversely by virtue of shortening of the fixing along the longitudinal axis.

33. The fixing of Claim 32, wherein the coupling is movable along the longitudinal axis towards the anchor formation to shorten the fixing.

34. The fixing of Claim 33, wherein the coupling is cooperable with the fastener to convert turning movement of the fastener to axial movement of the coupling in use.

35. The fixing of Claim 34, wherein the coupling has internal threads to mate with a threaded region of the fastener to cause axial movement of the coupling upon turning of the fastener in use.

36. The fixing of Claim 34 or Claim 35, wherein the coupling is arranged to transmit torque from the fastener to the body upon initial turning of the fastener in use, and to convert turning movement of the fastener to axial movement of the coupling upon further turning of the fastener.

37. The fixing of any preceding claim, and comprising engagement means for engaging the coupling with the fastener to transmit torque from the fastener to the body in use.

38. The fixing of Claim 37, wherein the engagement means is further arranged to disengage to allow the coupling to cooperate with the fastener to convert turning movement of the fastener to axial movement of the coupling in use.

39. The fixing of Claim 38, wherein the engagement means breaks off or away from the body or the fastener to disengage the fastener and the coupling in use.

40. The fixing of Claim 39, wherein the engagement means comprises at least one lug arranged to engage an engagement region of the fastener in use.

41. The fixing of Claim 40, wherein one or more lugs extend radially inwards from a peripheral region of the coupling.

42. The fixing of Claim 41 , comprising at ieast two lugs spaced around the longitudinal axis.

43. The fixing of any of Claims 40 to 42, wherein one or more lug is bent into a radially-extending orientation during manufacture of the fixing.

44. The fixing of any of Claims 40 to 43, wherein at least a part of the or each lug is arranged to break away from the body in response to the application of a breaking torque to the fastener in use.

45. The fixing of Claim 44, wherein one or more lugs comprise a fracture zone arranged to cause fracture of the lug in response to the application of the breaking torque.

46. The fixing of Claim 45, wherein the fracture zone comprises a scored region of the lug.

47. The fixing of Claim 45 or Claim 46, wherein the fracture zone comprises a perforated region of the lug.

48. The fixing of any of Claims 45 to 47, wherein the fracture zone comprises a relatively thin region of the lug.

49. The fixing of any of Claims 45 to 48, wherein the fracture zone comprises a notched region of the lug.

50. The fixing of any of Claims 40 to 49, wherein the lugs comprise cutting means for cutting into a substrate in use of the fixing.

51 The fixing of Claim 50, wherein the cutting means comprises cutting edges of the lugs

52 The fixing of Claim 51 , wherein the cutting edges are inclined to form a pointed distal end region of the fixing

53 The fixing of Claim 37 or Claim 38, wherein the engagement means comprises a plate having an aperture for receiving a self-tapping threaded region of the fastener

54 The fixing of Claim 53, wherein the plate is bent into a radially-extending orientation during manufacture of the fixing

55 The fixing of any of Claims 37 to 39, wherein the engagement means comprises a threaded region for receiving a threaded region of the fastener, and one or more stop members to limit turning of the fastener with respect to the coupling in use

56 The fixing of Claim 55 when dependent on Claim 39, comprising breakable attachment means for attaching one or more stop members to the fixing

57 The fixing of Claim 56, wherein the attachment means comprises an adhesive

58 The fixing of any of Claims 55 to 57, wherein the stop member comprises a plate that closes a distal end of the fixing

59 The fixing of Claim 58, wherein the stop member is a film arranged to be ruptured by the fastener in use to disengage the engagement means

60 The fixing of Claim 55 when dependent on Claim 37 or Claim 38, wherein the coupling comprises a lock nut, and the stop member comprises a locking element of the lock nut

61 A twist formation for a fixing according to Claim 60, comprising support means for holding the lock nut

62 The twist formation of Claim 62, wherein the support means comprises support lugs arranged to embrace the lock nut

63 A fastener for use with the fixing of any of Claims 34 to 59, comprising a turnable shaft having a threaded region and an engagement region for cooperation with the coupling.

64 The fastener of Claim 63, wherein the engagement region comprises a slotted end of the fastener

65. The fastener of Claim 63, wherein the engagement region comprises a plate-like end of the fastener

66 The fastener of Claim 65, wherein the plate-like end of the fastener is flat

67 The fastener of Claim 65, wherein the piate-like end of the fastener is twisted

68 The fastener of Claim 63, wherein the engagement region comprises one or more helical splines on an end region of the fastener

69 In combination, a fixing according to any of Claims 34 to 59, and a fastener according to any of Claims 63 to 68

70 The combination of Claim 69, wherein the fastener is received within the fixing

71 A method for holding a fastener in a hole, comprising

inserting a fixing in the hoie,

anchoring a first part of the fixing with respect to the hole,

applying a torque to a fastener received within the fixing, and

transmitting that torque to a second part of the fixing to cause untwisting deformation of the fixing that expands the fixing laterally against the interior of the hole

72. The method of Claim 71 , comprising pushing the fixing into the hole to anchor the first part of the fixing with respect to the hole.

73. The method of Claim 72, comprising pushing a grip formation of the fastener into the periphery of the hole.

74. The method of Claim 72 or Claim 73, comprising pushing a grip formation of the fastener into a surface adjacent to the hole.

75. The method of any of Claims 72 to 74, comprising wedging the first part of the fixing in the hole.

76. The method of any of Claims 71 to 75, comprising turning the fastener to cause further lateral expansion of the fixing by shortening of the fixing along the longitudinal axis.

77. The method of any of Claims 71 to 76, comprising engaging the fastener with engagement means which transmit torque from the fastener to the second part of the fixing.

78. The method of Claim 77, comprising turning the fastener in engagement with the engagement means to cause untwisting deformation of the fixing.

79. The method of Claim 77 or Claim 78, further comprising disengaging the fastener from the engagement means.

80. The method of Claim 79, comprising turning the fastener to disengage the fastener from the engagement means.

81. The method of Claim 79 or Claim 80, comprising breaking the engagement means to disengage the fastener.

82. The method of any of Claims 79 to 81 , comprising bending the engagement means to disengage the fastener. 83 The method of Claim 82, comprising rupturing the engagement means to disengage the fastener

84 The method of any of Claims 79 to 83, comprising turning the fastener to cause further lateral expansion of the fixing by shortening of the fixing with respect to the longitudinal axis after dtsengagtng the fastener

85 The method of any of Claims 71 to 84, comprising inserting the fixing into the hole so that a distal end of the fixing passes into or through a gap behind the hole

86 The method of Ciaim 85, wherein the lateral expansion or further latera! expansion of the fixing causes a part of the fixing to expand behind the hole

87 A method of manufacturing a fixing according to any of Claims 1 to 60, the method comprising forming the twist formation of the fixing by rolhng a blank into a cylindrical formation

88 The method of Claim 87, further comprising forming the blank from a sheet material

89 The method of Claim 88, comprising cutting, stamping, pressing, milling and/or punching the blank from the sheet material before rolling

90 The method of any of Claims 87 to 89, comprising deforming the blank to form teeth on the elements of the twist formation before rolling

91 The method of any of Claims 87 to 90, further comprising attaching an anchor formation and a coupling to the cylindrical formation

92 The method of any of Claims 87 to 90, further comprising forming the coupling by bending one or more parts of the cylindrical formation into a radially-extending orientation