Traditionally the most common type of railway sleepers (called ties in some places) are made from timber. Although in recent years concrete and steel sleepers have penetrated the market heavily, particularly in specialized applications, such as in heavy haul railways tunnels and bridges, timber sleepers are still very cost effective.

In Australia at least, timber sleepers are exclusively hardwood. The rails are generally held to the sleepers by use of a sleeper plate (or tie plate) between the rail and the sleeper and steel spikes are driven through holes in the tie plate into the sleeper until the head of the spike bears against the foot of the rail. Sometimes screws are used instead of spikes.

A major disadvantage of timber sleepers is that after some time and use of the track the spikes become loose in their holes and are incapable of asserting sufficient downward force on the rail. Additional holes may be provided in tie plates so that in such circumstances a spike may be driven into a fresh position. However eventually all available positions may be used and the fastening still becomes loose. Such sleepers are commonly referred to as having been spike killed.

There have been many proposals for fastenings that can be used in such situations in order to gain a few more years use out of a sleeper after it has been spike killed. Such proposals include the screwing of a sleeve into the hole and then screwing the rail and tie plate to the sleeve, but this requires the difficult task of raising the rail off the sleeper in order to insert the sleeve. This must be done because the sleeve has a larger diameter than the overlying hole in the tie plate. Another proposal which does not

require lifting of the rail, use the casting or moulding of a solid plug of material in the hole and inserting a screw into the plug, but this has the problem that such plugs often pull out easily.

A variety of expanding plug type fasteners which engage the internal wall of a hole are well known. These usually take the form of a cylindrical plug of plastics material having a central hole and surrounding axial slits. The plug is placed to neatly fit into a predrilled hole and a screw is screwed into the central hole which expands the plug to tightly compress it between the screw and hole. The compressive stresses created maintain friction between the plug and the wall of the hole. But the plastic relaxes over time and the compressive stresses reduce, so reducing the friction between the plug and the hole. Therefore in use of such fastening systems, the plug often slips because of insufficient friction between it and the hole. Also the screw thread can easily tear out of the plug due to low strength plug materials.

A variety of expanding shell type fasteners that engage the internal wall of a hole are well known. These are of heavier duty than the expanding plastic plug type fasteners and are most commonly used in masonry applications. These operate usually by expanding a sheet metal shell of a fastener assembly outwardly from the central bolt or screw. The expansion is facilitated usually by the screw drawing a tapered nut into the shell. Other systems using split nuts and other devices are also in use. With all of these the effectiveness of the fastening is again dependent on the friction between the fastener and the wall of the hole into which it is fastened.

All of the expanding plug and expanding shell type fastener systems work on the basis of a cylindrical hole which is only slightly larger than the diameter of the fastener. Typically the fastener can workably expand by about only 10% of its diameter, although in some cases the expansion may be up to 20%. Effective performance of such fasteners is therefore relatively sensitive to the diameter of the hole. Another problem is that any significant tapering of the hole, with it becoming wider towards the mouth, would mean that any slight movement of the fastener would result in it quickly loosening.

In a railway track environment there are two major problems to be overcome by a fastener intended to be used in spike holes. The first is that the size of the hole in the timber is at least substantially the same as the hole in the tie plate. In practice, the hole in the timber is in fact usually larger than the hole in the tie plate due to degradation of the timber. Thus, unless you have the ability to enlarge the hole in the tie plate, either by drilling out the hole or replacing the tie plate with another having a larger hole, you are restricted to use of a replacement fastener no larger than the original fastener diameter. A fastener or sleeve having a larger diarneter cannot be screwed or hammered into the hole in the timber if it cannot be fed through the hole in the tie plate.

The second major problem is that if spikes have loosened in a timber sleeper, the hole remaining when the spike is removed commonly has walls with weakened wood due to rot or other damage. Dirt and other extraneous material is also often present in the hole. Thus expanding fasteners which operate by pressing out against the walls of the hole do not work well, due to the spongy or otherwise degraded wood and any foreign materials, and particularly given the maximum size limitation imposed by the hole size in the tie plate.

A new type of expanding fastener has now been developed to address the above problems. It provides a repair system for holding railway rails to sleepers which solidly engages with the timber by penetrating into the timber to provide a positive mechanical interlock rather than frictionally engaging with the walls, with consequent improved performance in pull out strength and lifespan. It also provides a fastener which, because of its large degree of expansion, may be inserted through an unmodified tie plate but still expand out sufficiently to solidly engage with the surrounding timber. Expansions of up to 90% in diameter have been demonstrated with this concept.

Accordingly, in one aspect the invention provides a method of attaching a threaded fastener assembly to a substrate comprising: (i) inserting a first portion of the assembly into a hole in the substrate, said first portion comprising a stacked array of generally planar blade members, (ii) engaging a thread on a shank portion of the assembly with said first portion and rotating the shank portion about its longitudinal axis to drive the shank portion into said first portion, and (iii) engaging the thread with the blade members to force each blade member to move outwardly from the axis of the shank to penetrate the substrate surrounding the hole while remaining engaged with said thread on the shank.

In another aspect the invention provides a fastener assembly for engaging with a hole in a substrate said fastener assembly comprising a shank portion and a cartridge portion, the shank portion having a longitudinal axis and a helical thread thereon, the cartridge portion having a plurality of generally planar blade portions stacked around said axis and aligned perpendicular to said axis such that a hole is provided through the stack of blade portions at the axis, such that when the shank portion is screwed into the hole in the cartridge the thread engages with each blade portion to drive it outwards from the axis.

In a further aspect the invention provides a cartridge or package of blade portions aligned around an axis for use as described above.

Use of the invention is not limited to the above described railway purposes. It provides the opportunity for a premium performance fastener with an excellent degree of retention in all timber fastening applications, especially where access into the timber is limited and/or the timber is of poor strength such as with some chipboard or particleboard products. In addition, the invention is not limited even to use in timber however; it is also applicable to a wide range of plaster, plastic and mortar substrate materials.

Examples of the invention will now be described with reference to the attached drawings where: Figure 1 is a general view of a fastener assembly according to a first embodiment of the invention; Figure 2 is a detailed view of one component of a fastener assembly according to a second embodiment of the invention which is very similar to the embodiment shown in Figure 1; Figure 3 is a view of a component of a fastener according to a third embodiment of the invention, the component being similar to that shown in Figure 2; Figure 4 is a cross section view along B-B shown in Figure 3; Figure 5 is a view of some parts of the fastener assembly according to the second embodiment of the invention, shown during installation; Figure 6 is a view of parts of the fastener assembly in Figure 5 shown a little later in the installation procedure; Figure 7 is a view of part of the fastener assembly in Figure 6 shown later in the installation procedure than in Figure 6; Figure 8 a diagrammatic axial view illustrating the motion of components of the third embodiment during an installation; Figure 9 is a partial cross section through the screw shown in Figure 5; Figure 10 is a general view of a fastener assembly according to a fourth embodiment of the invention; Figure 11 is a detail view of one component of the assembly shown in Figure 10; Figure 12 is an isometric view of one component of a fastener assembly according to a fifth embodiment of the invention; Figures 13 and 14 show the interaction in use between two components, similar to that shown in Figure 12, which form part of a fastener assembly according to a sixth embodiment of the invention; Figures 15 and 16 show further details of the spatial relationships of the arrangements shown in Figures 13 and 14 respectively when seen in the direction indicated by arrow A;

Figure 17 is a view of a wire frame retention means which may be used in conjunction with the fastener assemblies of the invention; Figure 18 is a view showing the relationship in use between the frame in Figure 17 ° and other components of the invention.

Referring to Figure 1, the fastener assembly comprises a screw portion 4 and a cartridge portion 20. The screw 4 has a shank 6 with an unthreaded portion 10 near the head 5 of the screw, a helical thread 8 on the remaining cylindrical portion of the shank 6 and a thread 15 along the tapered tip 14. Towards the head 5 of the screw is a wide shoulder 12 which, in Figure 1 is obscuring the head of the screw which is formed with a 6-lobed or fluted drivehead. The shoulder 12 has a sloped face 13 on its shank-facing side and this is angled to, in use, smoothly bear down onto the tapered foot of a railway rail. The longitudinal axis 17 of the screw passes through the centre of the drivehead and the tapered tip 14.

The cartridge portion 20 of the fastener assembly comprises seventy-two blades 22 stacked in face to face contact in a repeating sequence of 4 orientations 90° apart around the longitudinal axis 24 of the cartridge. The stacking of the blades 22 is such that each is rotationally offset by 90° about the axis 24 in the direction of a right-hand helix. Running up the longitudinal axial centre of the cartridge 20 is a bore 26 formed by the alignment of cutaways in the blades 22. Each blade 22 has two sharp blade edges 28 and 30 and a scalloped support edge 32. The function of these edges is explained later in this specification.

Figure 2 shows a detailed view of a blade of a slightly different configuration to that shown in Figure 1 but which performs essentially the same function. The blade 38 has a single sharp edge 40 and scalloped support edge 42. The support edge 42 has a central arc 44 and two outer arcs 45.

Referring to Figures 3 and 4, the alternative blade 48 shown therein has the same shaped scalloped support edge 52 as blades 22 and 38, having a central arc 54 and two outer arcs 55. However its blade edge 50 is different to that of the blades 22 and 38

shown in Figures 1 and 2 respectively. A central straight portion 59 of sharp edge 50 is flanked at each end by a scalloped portion 58 of the sharp edge.

The relative motion of components during installation of the fastener of the invention will now be described with reference to Figures 5 to 8. Figures 59 6 and 7 utilise blade components 62 of the same shape as blade 38 shown in Figure 2. Although Figure 8 differs in that it utilises blade components the same shape as blade 48 shown in Figure 3, the principles of engagement and motion remain the same.

In Figure 5 the screw 4 is shown having just engaged with the first blade 62 as the tip 14 of the screw is screwed into the bore of the cartridge of blades. At this stage the axis 24 of the cartridge and the axis 17 of the screw are aligned. Also at this stage the centre of the central arc 44 on the support edge 42 is fully engaged with the thread 15 on the tip of the screw. The blade 62 is prevented from rotating by means described later in this specification.

As the screw 4 is rotated relative to the blade 62, the blade is forced outwards from axis 24 as the diameter of the portion of the tip it is engaged with increases. After three further turns of the screw, the position in Figure 6 is reached whereby the screw has advanced into the stack of blades, so that relatively the blade 62 has now advanced up the tapered tip of the screw causing its blade edge to be pushed radially outwards into the timber surrounding the hole. To enable the relative relationships in Figure 6 to be more clearly illustrated, only half of the blades engaged with the screw have been shown in the drawing.

In Figure 7 a cartridge of forty-eight blades 38 has been fully engaged with the screw 4. The screw has been screwed into the cartridge until all of the blades have reached the thread 8 on the cylindrical section of the shank and the blades are thus at their maximum radial extension. At this stage the outer arcs 45 are fully engaged with the troughs in the thread 8.

Four ranks or rows 91 to 94 of blades extend outwardly from the thread 8, each rank extending outwardly at right angles to its neighbouring rank. So, for example, rank 92 is oriented outwardly from the axis 17 at right angles to ranks 91 and 93 and directly opposite to rank 94. Each rank has twelve blades 38 aligned face to face and spaced from each other. That spacing allows wood fibres to be pressed in between the blades so providing a strong keying action into the wall of the hole in the wood.

In practice any suitable number of blades may be selected for a cartridge, depending on the strength of the fastening required. Of course a corresponding length of the screw should be selected accordingly. Also, alternative alignments of ranks of blades may be selected so, for example, three ranks of blades could be created, each aligned at 120° to the other two.

The installation torque may be reduced by making the taper on the screw tip sharper.

In relation to Figure 8, the dashed circle 70 indicates the minimum diameter hole into which the cartridge may be inserted. The circle 70 also corresponds to the diameter of the shank 6 of the screw to be inserted into the cartridge. It can be seen that the legs 80 of the blade each extend out to touch the circle 70 at two points, and the scalloped sharp edge 50 touches the circle at four points. Before engagement with the screw, the central arcs 54 on all of the blades line up to form a bore down the centre of the cartridge. This bore is sufficiently large in diameter to receive the point of the tip 14 of the screw so that the blades can be engaged by the thread 15 on the tapered portion of the screw.

Blades shown in Figure 8 in positions 72,73 and 74 illustrate stages in the travel of a blade radially outwards. Positions 74,75,76 and 77 are all at the maximum outward distance. The legs 80 of the blades at these most outwardly positions are seen to have their outer arcs inwardly of the circle 70 because they are bearing on the bottom of the threads 8 formed into the shank of the bolt. The peaks of the threads 8 are shown by the dashed circle 70.

With reference to Figures 3 and 4, the following dimensions are for a blade 48 sized to suit a screw having a shank diameter of l9mm, a thread depth of 1.5mm on its cylindrical shank, and a thread pitch of 2.4mm. length (dimension a): 16. Omm width (dimension b): 18. Omm thickness (dimension c) 1.2mm radius of central arc 54 : 3. Omm radius of outer arcs 55: 8. Omm radius of scallops 58: 4.0mm diameter of hole 57: 3.0mm relief angle (dimension A) 28° angle of edge (dimension 300 The holes 57 in the blades line up to form four rows or alignments in the assembled cartridge before use. Those alignments of holes are conveniently used to ensure correct positioning of the blades. This may be conveniently achieved by threading a frangible component down each row of holes. The frangible component may conveniently be copper wire which is easily tied at each end of the cartridge, or a brittle plastics material which may be formed as a four-pronged former onto which the blades are loaded. In any case, any locating means threaded through the holes 57 should be selected so they are easily cut or broken by movement of the blades in order to not unduly restrict the blades'outwards movement and penetration into the timber.

Referring to Figure 2, the support edge 42 of blade 38 has a central arc 44 and two outer arcs 45. These meet at apices 46. Central arc 44 is curved at its centre but has a generally straight portion 49 near each apex 46. These generally straight portions diverge at a relief angle 0 of 28° to enable the blades to be pressed radially outwards more efficiently from the screw as the tapered tip penetrates into the cartridge. Outer arcs 45 are of uniform curvature and dimensioned to suit the valley of the thread on the cylindrical portion of the screw. The gap between the outer arcs 45 on each blade also allows the support edge 42 to straddle a thread ridge when in use in an engaged fastener.

The different shaped sharp edges on the various embodiments of blade represent some of the possibilities which can be optimised for use in different substrates to which the fastener is being fastened. The gently curving sharp edge 40 in Figure 2 would have particular use in soft timbers such as pine and low-strength chipboard, whereas the scalloped blade edge 50 in Figure 3 could be more appropriate with harder timbers.

The scallop 29 between sharp edges 28 and 30 in Figure 1 produces four channels down the outside of the cartridge which may be used for alignment of the blades in a frame in much the same way as was described above in relation to the frame threaded through the holes 57.

As shown in Figure 9, the threadform 8 on the cylindrical portion of the screw is significantly different to the threadform 15 on the tapered tip of the screw. On the cylindrical portion the thread has an approximately square threadform. It is a close approximation to an Acme thread which is a thread which is almost but not quite square in form. The top 96 and bottom 97 of the threadform are flat but the walls 98 are slightly sloped. The effect of this near square profile is such that when the legs of the blade engage the thread, there is maximum interlocking between thread and blades, so the legs are less likely to be pulled out of the thread, and this minimises the possibility for angular misalignment. Compared to rounder and sharper alternatives, this threadform gives greater support to the blades to help prevent them moving away from their alignment when an axial load is placed on the screw.

On the tapered tip 14, the thread 15 has a pointed profile similar to the triangular shape of a standard metric bolt thread. This is because on the tip of the screw the thread has a different function as it is required to correctly engage or"pick up"the blades separately and work them outwardly in a radial direction into the timber. If a square-type thread was used on the tip there would be a greater possibility of having the outside of the thread pick up a blade, so causing it to misengage. At the tapered tip there is not as strong an interlocking between the blade and the thread, but that is not the prime requirement at that point. The thread there must separate the blades and carefully urge them outwardly in a radial direction. During this process each blade is

moved up along the tapered tip 14 of the screw and some downwardly axial pressure on the screw is required to hold the blades in position. Each of the blades are supported by their neighbouring blades above and below and this maintains their orientation.

It is not unusual to have some axial component to the displacement of the blades at the top and bottom of the cartridge, but it has been found that this does not lead to a significant degradation in the performance of the joint. It will be appreciated that the larger the number of blades, the greater the length of thread engaged with them and the greater the pull-out load of the fastener from the timber.

In the above described embodiments the blades are set at 90° to each other and there is thus a four-way symmetry in the motion of the blades. The blades are displaced outwards in four ranks. However this could be made a three-way symmetry (set at 120° to each), a two-way symmetry (180°) or with a random angular alignment.

Symmetrical patterns using three to six blades are preferred and four-way symmetry is the most preferred.

Referring now to Figure 10, the fastener assembly of this fourth embodiment is essentially the same as that described above except that the screw is fed into the stack of blades by way of a bobbin component 102 which is placed between the stack of blades and the screw 4. The bobbin 102 is provided to users as part of a cartridge 98 which comprises a stack 100 of blades and the bobbin 102 packaged axially in line ready for use. The packaging is formed so that there is little movement in the cartridge 98 between the bobbin 102 and the stack 100 of blades.

The bobbin 102 is shown in more detail in Figure 11. It is formed from plastics material and has the shape of a hollow, truncated cone 103 with a thin, readily frangible wall 104, and four hollow side posts 106 which provide strengthening. The cone 103 is open at both its ends 107 and 108. The interior of the cone 103 has the same angle as that of the screw tip 14 and is a neat fit thereupon.

The bobbin's function is to provide a guiding socket by which an engaging screw tip is led to the small central hole at the entrance to the stack of blades and also cause the screw to adopt an alignment which is coaxial with the bore in the cartridge. The ends 107 of the four posts 106 form a flat surface that the blades can bear against at the smaller end of the cone and thus maintain proper alignment.

The interior of the bobbin 102 is preferably not threaded. When the screw is pressed into the cone 103 and first turned, the sharp thread 15 on the screw bites into the conical surface and draws the screw harder into the cone. This causes the bobbin to split along the four lines of weakness in the cone surface between each of the four posts 106.

For supply to a user, the bobbin 102 may be held in place against the blades by means of frangible plastic rods or wire as an extension of the technique as described above for holding the stack of blades together. Each post 106 on the bobbin may have a longitudinal bore to carry a wire or the like for retaining the bobbin and blades.

However preferably the blade elements, with or without a bobbin, are held in place relative to each other by means of surrounding them with a thin layer of plastics material, such as a thin hot-shrink plastic tubular envelope.

More preferably the blade elements, with or without a bobbin, are held in place relative to each other by applying a layer of adhesive to the outer surface of the cartridge. The use of such an adhesive has been found to be superior to the use of separate frames described above in relation to the blades in Figures 1 and 3.

Preferably the adhesive is a hot melt adhesive. In this case, as the screw is rotated and work is performed on the blades to drive them out into the timber, sufficient heat may be generated by friction to melt the adhesive. After all the blades have moved outwards and further rotation of the screw is stopped, the adhesive cools and solidifies, bonding the blades into position and providing a secondary means for holding the fastener assembly in place. It is anticipated that this feature will be

particularly advantageous in applications where high-cycle low-amplitude loads are applied to the fastener.

In addition to bonding the blades to the screw shank, the hot melt adhesive used in the cartridge can provide another significant function upon melting and solidifying during the assembly process. The adhesive may provide a waterproof seal to the centre portion of the hole, stopping the ingress of water to the top and/or bottom hole openings.

Most rail sleepers being installed in Australia at the present time are drilled right through their thickness, thus allowing water ingress from underneath as well as rain coming in from the top. Water is the major cause of corrosion and rot which limit the life of fastenings, so such a way of reducing water penetration is greatly beneficial. In order to further improve this benefit, in addition to the thin layer of hot melt adhesive applied over the outside of the cartridge, an additional amount (about 1 gram) may be applied at the top and bottom of the cartridge to help plug the hole.

The adhesive is applied preferably to only the outside of the cartridge. In this way, when it resets it assists bonding between the blades and the timber rather than between the blades and the screw. It has been found from experiments that hot melt glue in the bore of a cartridge can substantially degrade its installation procedure apparently due to an adverse effect from lowering the friction between the screw and blades, which leads to the blades slipping from their engagement with the root of the thread.

As noted above, the embodiment of the invention described with reference to Figures 3 and 4 has blades of 1.2 mm thick, while the pitch of the thread on the screw is 2.4 mm. It will be appreciated that if every blade was to immediately engage with a valley in the thread 15, then the cartridge would expand in length considerably at that point. In practice it does not appear to happen in that way. It may be that initially, every second blade"engages"with the thread valley and it is these blades which the screw uses to draw itself further into the cartridge. The remaining blades bear

initially on the thread ridge and are supported by the"engaged"blades to each side as all the blades are pressed radially outwards into the timber as the screw feeds further into the cartridge. Eventually the length of thread valley available to adjacent blades is sufficient for all the legs 80 to engage a thread valley and be fully supported Careful examination of experimental fastenings has shown that the legs 80 of a blade often lock into the thread in an orientation so that a ridge of the thread passes between the two legs. Often the leg of one blade engages a valley between the legs of another blade. Such interlocking assists in strengthening the structure of the configuration of expanded blades.

When the blades expand out into the timber, the forces acting upon them come from many sources. First there is the radially driving force from the screw as its diameter (as seen by each blade) increases. Also there is a force component from the walls of the thread valley being engaged and which tends to tilt the blade relative to the screw axis by an angle equal to the helix angle of the thread. Counteracting that is the force component exerted from the blades on each side of the blade under consideration and this tends to maintain alignment of the blade at right angles to the thread axis. In practice it is found that a slight tilting of the blades occurs, but not to the extent of the helix angle, and accommodation is made by the legs of the blades twisting slightly as they bend around the legs of adjacent blades to locate in available spaces in the thread valley.

An alternative and significantly different blade configuration is shown in Figures 12 to 16. This involves pairs of blades with curled arms so that each blade in the pair interlinks with the other. An individual blade 110 is shown in Figure 12. It has a curved sharp edge 112, two parallel side edges 113 and a pair of curled arms 114.

Like the blades described with references to other embodiments, the blade 110 has a support edge 118 comprising a central arc 115 with two outer arcs 116. This support edge 118 operates in the same manner as equivalent support edges 42 and 52 in earlier described embodiments.

The blades 110 are adapted to work in pairs. Figure 13 shows two blades 119 interengaged by their curled arms 114. These blades are very similar to blade 110 in Figure 12, the difference being that the support edges 132 and 133 are formed as a single arc rather than the multiple arcs of blade 110. In Figure 13 the pair of blades 130 and 131 is placed face to face, being reversed and inverted relative to each other and the sharp edge 112 and following body of each blade is slid within the curled arms 114 of the mating blade 131 and 130 respectively. Pairs of blades so coupled are then stacked to form a cartridge with each pair interengaged in the manner shown in Figure 13. The axial view in Figure 15 shows the bore 117 in the cartridge just large enough to engage the tip 14 of a screw. The tip is indicated by the broken line 14 and the threaded shank of the screw in indicated by the broken line 8.

The blades 130 and 131 are driven in opposite directions by the screw penetrating between them until the faces 135 make contact and further enlargement of the bore is prevented. This position is shown in Figures 14 and 16. At this stage the diameter of the bore 117 is between the outside and root diameters of the thread on the shank of the screw, so each one of the pair of blades 130 and 131 prevents the other from escaping from engagement with the thread.

The main advantage of the interlocked-pair embodiments described with reference to Figures 12 to 16 is that the blades are more strongly linked to the shank of the screw.

These embodiments therefore have an advantage where the substrate is very strong such as with masonry or concrete. However a significant limitation is that the expansion ratio (ie. expanded diameter divided by initial diameter) is lower than possible with other embodiments. A further limitation is that the interlocked-pair is restricted to use in only 2,4 or 6 blade symmetrical arrangements.

With respect to Figures 17 and 18, a wire basket 120 is shown which may be dropped into a hole which has no bottom such as a rail spike hole which has rotted through the bottom of its sleeper. The wire basket 120 has four upwardly extending legs 124 which are bent at right angles to form the bottom 126 of the basket. The legs 124 hook outwardly at their tops 125 (mostly obscured in Figures 17 and 18) to rest upon

a washer 122 which acts to prevent the basket from falling fully into the hole in the sleeper. The washer 122 may be attached, by welding for example, to one or more of the hooked tops 125, or it may be slidable along the length of the basket 120, or even removed if required provided the basket 120 could be satisfactorily supported by the hooks 125 engaging the upper surface of the tie plate or sleeper as appropriate.

A tab 137 extends downwardly from the underside of the washer 122. The tab is formed from bending at a right angle portion of the metal displaced during formation of the square hole 123 in the washer. The length of the tab 137, in the axial direction of the screw, is substantially the same as the height of the edge of a rail foot. Thus, when the basket 120 is placed down a hole at the edge of a rail foot, with the washer resting on the rail foot, the bottom edge 138 of the tab 137 can rest on the rail tie to prevent the basket from tipping.

When the basket 120 is in place, a cartridge 20 of blades is then pushed into and held within the basket 120 and the screw 4 is screwed into the cartridge. The upward support provided by the wire frame bottom 126 of the basket 120 provides the necessary support to the cartridge 20 and permits the screw to fully engage and drive the blades outwardly between the wires into the wood. A bobbin 102 may be incorporated into the cartridge as described with reference to Figures 10 and 11. The basket, cartridge and bobbin may be provided as a single package ready to immediately drop into the hole and insert a screw. The lengths of the basket 120, cartridge 20 and screw 4 are chosen such that the blades 22 are pressed into the wall of the hole deep within that hole.

The basket 120 is sized and positioned relative to the cartridge 20 so that the sharp edges of the blades 22 pass between the legs 24 as the array of blades is expanded when the screw is engaged.

The embodiments of the invention described above have a far greater expansion in diameter for in-hole fasteners than has hitherto been available from the prior art. The cartridge can be inserted through a hole which is the same diameter as the bolt and the

cartridge can then be activated to a diameter of about twice its original diameter and in a configuration which penetrates into the timber structure and is thus not reliant upon frictional engagement. The invention may be used in holes with a substantial clearance between the cartridge and the hole walls, and can be used in square holes without concern about relaxation of a plastic plug material into the corners of the hole. The depth of penetration of the blades into the timber substrate material means that dirt, rot or other damaged substrate in the hole is not significantly detrimental providing sound timber is present within reach behind it. The problem that friction- held fastenings have with tapered holes does not arise with the present invention and it reliably gives a high hold-down force.

It is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention. For example while the screw described in the preferred embodiments has a 6-lobed or fluted drivehead, any desired head configuration, such as a plain hexagonal head or hex-socket head for example may be utilised. Also, while the screw described in the preferred embodiments has a tapered wide shoulder 12 in order for it to mate with the inclined top face of a rail foot, the shoulder may be shaped to suit whatever purpose is desired.

Also, a loose washer could be used instead of the integrally formed shoulder on the screw.

The blades in the cartridge are described as being aligned in a right-hand helix. It may be thought intuitively that a right-hand helical alignment is required if the screw has a right-hand thread. But a left-hand helical blade alignment may also be used with a right-hand threaded screw and, depending on the hole diameter, screw pitch and blade thickness, this may be a preferred configuration. The blade thickness is preferably about half the thread pitch.

A finer pitch on the screw means that the blades penetrate outwards less with each rotation of the screw. The additional leverage thus accorded the installer means the torque required for installation is lower. However the finer the pitch, the thinner the

blade must be, and the greater the risk of blade buckling. For soft substrates a slender blade is acceptable. Blades 0.5mm thick are suitable for use in softwoods. But harder substrates require a thicker blade. Blades may be hardened to cope with harder substrates and tighter holes.

Finally, throughout this specification, unless the context requires otherwise, the word "comprise", and variations such as"comprises"and"comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.