The invention relates to a wall tie for a cavity wall, and particularly although not exclusively to a remedial wall tie for insertion in such cavity walls after they are constructed.

Wall ties are used for holding together inner and outer leaves forming a cavity wall. Cavity walls may for example comprise inner and outer leaves of masonry or timber inner leaves with masonry outer leaves.

Wall ties are usually incorporated in cavity walls when they are constructed but may also be inserted in previously constructed cavity walls. Such remedial wall ties may be necessary to replace existing wall ties which have failed, or because no wall ties or insufficient numbers of wall ties were used when the wall was constructed.

Many forms of remedial wall tie are known in the prior art. They are often constructed of ridged central rods, bars or hollow tubes which may be resin grouted or driven into position, or may incorporate expanding mechanical sleeves at each end.

Different construction materials expand and contract to different extents and at different rates as they heat up and cool down and as a result of water penetration. It is common for the two leaves in twin leaf walling to be constructed from different materials, for example inner leaves are often constructed from concrete blocks whilst outer leaves may be made from brick. In such situations there may be considerable differential expansion between the two leaves. All the above referred to types of remedial wall tie constructed from a central ridged bar, rod or tube, suffer from the disadvantage that they do not readily accommodate differential movement in twin leaf wallings.

When the two leaves of a cavity wall move, and the wall ties do not flex to allow for the movement, then the leaves tend to become damaged. This may occur as a results of the wall ties moving in their fixing holes, gradually enlarging those holes, and thus working loose such that they no longer act to tie

the leaves together. Alternatively, if the wall ties are more firmly fixed in their fixing holes, the leaves themselves may crack.

Other forms of prior art wall tie, both remedial and suitable for installation in walls during construction, tend to bend when the leaves of a cavity wall undergo differential expansion. However, having bent as necessary to accommodate the movement of the leaves they do not return to their original form when the leaves move back. Once bends are present in such wall ties their effectiveness is reduced and may tend to hold the leaves of the wall closer together, with a narrower cavity, than intended, or alternatively they pull out of their fixings.

Further, in countries where earthquakes are prevalent, disadvantages are encountered in using conventional wall ties.

It is an object of the present invention to provide a wall tie which reduces some at least of the aforementioned problems.

According to a first aspect of the invention there is provided a wall tie comprising an elongate flexible shank and anchorage means to anchor the tie within respective holes in two substantially parallel walls, wherein the shank comprises multi-strand metal rope.

By the term "multi-strand" as used herein we mean more than one strand, but preferably a sufficient number to provide the shank with some stiffness. The number selected will depend upon the required performance, and may be greater than six e.g. having one central core strand and five planetary strands wound around the core strand.

Wall ties according to the invention provide the advantage that they are significantly more flexible than prior art remedial wall ties whilst being of relatively simple construction. The anchorage means may be of any appropriate form and may comprise the ends of the shank itself.

The shank of wall ties according to the invention may comprise a single piece of multi-strand metal rope. Alternatively, the shank may comprise two pieces of multi-strand metal rope and a coupler.

One or both anchorage means may comprise means for tensioning the shank. Such an embodiment provides the advantage that tension of the wall tie, and thus its flexibility and resilience, may be selected as appropriate for its particular location in use.

Preferably the strands of the shank are of spring steel, but other materials may be utilised, e.g. preferably wall ties according to the invention also comprise a means to promote dripping of liquid from the wall tie in use, thus preventing free passage of water along the wall tie from one leaf to the other.

According to a second aspect of the invention there is provided a method of tying together two leaves of a cavity wall including incorporating into the wall a wall tie having a shank comprising multi-stranded metal rope.

Embodiments of wall ties according to the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates a wall tie according to the present invention when in use;

Figure 2 illustrates an alternative form of shank for inclusion in a wall tie according to the present invention;

Figures 3 - 8 illustrate alternative forms of anchorage means;

Figures 9 and 10 illustrate couplers by means of which anchorage means may be attached to the shank; and

Figure 11 illustrates a wall tie according to the invention in an alternative manner of use.

A wall tie 10, particularly suitable for use as a remedial wall tie, comprises a shank 11 with towards each end a resin stop ring 12, and at one end a dual function resin applicator and centralising attachment 13 having two or more blade formations 13a. Positioned in the central region of the shank 11 is

The wall tie 10 is inserted into an existing cavity wall as follows. A hole 20 is drilled through an outer leaf 22 and an aligned hole 24 is drilled

through part of the depth of the inner leaf 26. The hole 24 is filled with resin 28 and the wall tie 10 is then inserted through the hole 20 until the leading end, bearing the dual function attachment 13, is inserted into the hole 24 in the inner leaf 26. During insertion the wall tie 10 is rotated such that the blade formations 13a _. scrape the surface of the hole 24, mixing any loose dust into the resin 28 and ensuring good adhesion of the resin 28 to the surface of the hole 24. The hole 20 is filled with resin 28 and the resin stop rings 12 are located at the entrances to the holes 20, 24.

The wall tie 10 provides the advantage that it is sufficiently flexible to accommodate differential expansion and contraction between the inner and outer leaves 22, 26 of the wall and sufficiently resilient to subsequently return to its original shape. This prevents structural damage to the leaves 22, 26 and the wall tie 10.

Preferably the shank 11 is constructed from compacted multi-stranded steel rope, such as "Dyform" (Registered Trade Mark). This is made up of a number of steel wires spun into a strand which is then subjected to a diameter reduction through a compacting process. This process is achieved by means of drawing the stand through a series of dies resulting in a greater cross-sectional steel area for a given diameter of strand when compared to the conventional product. The metallic cross-sectional area of the wire remain almost unaltered whereas their shape (profile) changes.

Alternatively it may be constructed from any other multi-stranded metal rope having appropriate properties, such as non-compacted multi-stranded steel rope. Typically, the rope will have a diameter in the range 4 to 7mm and will be of 1 x 19 (9/9/l)(i.e. one central core with 18 further strands in two planetary layers) or 1 x 7 (6/l)(i.e. one central core with 6 further strands in one planetary layer) construction. The diameter and construction of the rope is selected as appropriate for the use of the wall tie.

Referring now to Figure 2, an alternative form of shank 11 comprises two pieces of multi-stranded metal rope 11a, lib. having attached at their inner

ends threaded portions 30. A coupler 32 is of a generally tubular construction and internally threaded to accommodate the threaded portions 30 of shank pieces 11a, lib. The coupler 32 also comprises a drip ring 14.

Remedial wall ties according to the invention may be fixed in the leaves of the wall by any appropriate means several of which are illustrated in Figures 3 to 8.

Figure 3 illustrates an anchorage means for mechanically fixing ties to the leaves. The anchorage means comprises a sleeve component 40 having a sleeve tube with an external engineering thread 42 and a stop ring 44. In use, the sleeved component 40 is generally located within a female component having an appropriate internal thread which is fixed into a respective hole in a leaf. Alternatively the sleeved component 40 may be grouted into a hole or may be screwed into a wooden inner leaf, if a pilot hole is drilled first.

Figure 4 illustrates an anchorage means in the form of an end sleeve 50 of an irregular shape, incorporating a stop ring 52, for resin bonding in the inner leaf.

Figure 5 illustrates an anchorage means in the form of a wood-type screw end 60. This variation of anchorage means is suitable for installation where the inner leaf of the wall is constructed in timber framing. In general in such circumstances the external leaf of the wall will be formed of masonry.

Figure 6 shows an alternative form of anchorage means 62 suitable for use in resin fixing. The anchorage means 62 comprises a hollow tube 64 formed with keyways 66, and a resin stop 68. The shank 11 may be fixed into the anchorage means 62 by resin or by swaging of the tube 64.

Figure 7 illustrates a form of anchorage means for tensioning the multi-stranded metal rope shank 11. The component 70 comprises a central screw 72 for attachment to the shank 11. The component 80 further comprises a spring 74, retaining washers 76, 78, a conventional expanding anchor 80, and a conical screw wedge 82. The component 70 is used in the through hole 20 in the outer

leaf 22 in order that the wall tie 10 may be tensioned by means of screwing the wedge 82 into the expanding anchor 80.

Figure 8 illustrates a wall tie 90 comprising a shank 11 and drip ring 14. It further comprises anchorage means 91 and 92. Anchorage means 91 is constructed for use on the leading end of the wall tie for insertion in the hole 24 in the inner leaf 26. It comprises a sleeved component 93, a conical wedge 94 and a threaded component 95. The anchorage means 92 is constructed for use on the other end of the wall tie 10 in the through hole 20 in the outer leaf 22. It comprises a sleeved component 96 identical to the sleeved component 93, a conical 97 wedge, a nut 98 and a threaded portion 99 having at its end a key formation 100.

The wall tie 90 is inserted as follows. After drilling of the holes 20, 24 the wall tie is inserted until the leading end anchorage means 91 is located in the hole 24 in the inner leaf 26 and the anchorage component 92 is in the hole 20 in the outer leaf 22. A tool (not shown) is then located on the key formation 100 and rotated, to rotate the threaded portion 99 shank 11 and threaded portion 95. This action pulls the conical wedge 94 into the sleeve component 93, opening the sleeve component and forcing it against the sides of the hole 24. When the anchorage means 91 has been tightened as described the key is removed from the key formation. The nut 98 is then screwed inwards to force the conical wedge 97 into the sleeve component 96. This results in the sleeve component 96 being opened and forced against the edges of the hole 20. The two anchorage means, 91, 92 are actuated to achieve the desired tension in the shank 11.

The ability to tension the shank 11, and thus to select the flexibility and resilience of the shank 11, enables the properties of the wall tie to be selected for its particular location in use.

Figure 9 shows a coupler 110 incorporating an internal screw thread 112 and a plain bore 114. Optional anchorage components of any appropriate form may then be attached to the coupler 110 by means of the screw thread 112, or by means of press fixing to engage in the plain bore 114.

Figure 10 illustrates an alternative form of coupler 115, which comprises a tube of hexagonal external cross-section and circular internal cross- section. One end of a piece of wire rope is inserted into one end of the coupler 115 and one end of a threaded portion is inserted into the other end of coupler 115, the coupler 115 is then swaged to retain the wire rope and threaded portion within the coupler. The coupler 115 provides the advantage that it is of simpler construction and therefore cheaper than the coupler 110.

Wall ties 10 according to the invention may comprise the same form of anchorage means at both ends, or different forms at the two ends, as appropriate. For example, the leading edge of the wall tie 10 may be fixed into hole 24 in the inner leaf 26 by means of a resin grouted anchorage means, e.g. sleeve 50, while the other end may be fixed in hole 20 in the outer leaf 22 by means of tensioning anchorage means, e.g. component 80.

A number of different anchorage means are described above, however, there are many other forms which may be incorporated in wall ties according to the present invention. In particular the anchorage means may comprise the end of the shank 11.

Figure 11 illustrates another embodiment of a wall tie according to the invention, in an alternative manner of use in which the wall tie is not perpendicular to the leaves of the wall. This manner of use is appropriate in certain construction techniques.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.