GB2359109A

GB2359109A - Wall tie

Info

Publication number: GB2359109A
Application number: GB0002885A
Authority: GB
Inventors: Paul Ernest Kemp
Original assignee: CHESHUNT ENGINEERING Ltd
Current assignee: CHESHUNT ENGINEERING Ltd
Priority date: 2000-02-09
Filing date: 2000-02-09
Publication date: 2001-08-15
Also published as: GB0002885D0

Abstract

The wall tie 1, particularly for use in remedial work, comprises an elongate strip that has at least one cutting surface 2,3 substantially perpendicular to the longitudinal axis of the tie such that during installation in a bore 10 which has a diameter 11 smaller than the maximum outside diameter of the tie the cutting edge removes material from the periphery of the bore so as to define a helical channel within which the strip is retained. The tie is preferably formed from a helically wound flat strip of material that has a constant cross-section, e.g. a square cross-section. The tie is preferably formed from stainless steel, of which at least the leading edges are coated with a corrosion resistant material, and is provided with two, three or four cutting surfaces which are sharpened.

Description

2359109 TIE DESCRIEPTION This invention relates to a tie and more

specifically to a method of inserting a tie which affords, for example, a so-tied wall greater stability than that provided by the conventional methods of insertion.

Wall ties are used, for example, to secure inner and outer leaves of io cavity walls to one another, or indeed for attaching timber and other materials together. In certain circumstances, one may require, for example, timber to be secured to masonry or blockwork or indeed blockwork to blockwork and all such connexions may be facilitated by ties. Conventionally, once installed, they retain, for example, the leaves of a wall relative to each other, helping the leaves to overcome the many forces which act upon them. Ties may be elongate helical structures formed from twisting a flat strip of material. They are often formed from austenitic stainless steel Type 304, although for particularly corrosive or aggressive conditions Type 316 may be utilised.

To insert a conventional tie, a hole is pre-drilled in the inner leaf and a wall tie, which terminates in a point, is driven into the so-called pilot hole. The pilot hole has a smaller diameter than the outside diameter or other maximum transverse dimension of the tie, such that the transverse periphery of the tie, adjacent its longitudinal edges, has to be driven through and, consequently, is retained in, the inner leaf. The tie is of sufficient length that it bridges the cavity and extends so that it can be embedded in the mortar of the outer leaf of the wall as the wall is being constructed. The ties are inserted at regular intervals, to ensure that the outer and inner leaves are securely connected to one another.

It is often necessary to install remedial ties due to corrosion of the originally installed ties. Damage to ties can lead to cracking of the mortar and, in some cases, failure of the wall in which the ties are inserted. To install remedial ties the originals are removed by drilling the mortar and pulling out the ties. The hole, which is left in the wall, is then cleaned, which may necessitate ffirther drilling and the dust and other extraneous matter removed. The hole is then repaired using a suitable filler and the tie is driven into the substrate. Once installed to the correct depth, resin is injected into the hole of the outer leaf to bond the tie therein. The outer leaf is then re-pointed to finish 10 the repair.

Such methods have been used with wall materials as diverse as concrete block, poured concrete, brick work, block masonry and hardwood studs.

Is However, it has been found that conventional pointed wall ties suffer from an important defect. Becausethe tie is finished in a point, the part of the point adjacent the longitudinal edges, which is to say the portion of the point which is actually in contact with the masonry, is not effective in cutting a full thread into the substrate. This means that either upon insertion the leading edges can destroy some of the masonry into which the tie is being inserted due to inter alia unwanted expansive forces, or that it can lead to inaccurate insertion of the tie. The point of the tie is usually formed as a wedge-shape which, as the tie is driven into the substrate, causes the material that has been, or is being, removed to compact about the point. This material compaction, and the action of driving the tie into the substrate, may cause mechanical damage to parts of the substrate which otherwise would not have been damaged thereby, for example, widening the pilot hole and reducing the pullstrength of the tie.

Furthermore, when fitting remedial ties the point can "catch" and often this leads to the longitudinal axis of the tie not being parallel with the desired insertion axis. Such non-alignment can lead to other stresses and strains being placed on the tie. Defective installation of a wall tie reduces the pull strength thereof, which is to say the force required to pull the tie from the material in which it is inserted.

Accordingly, it is an object of the current invention to provide a tie and method of inserting a tie to obviate or at least substantially reduce the above- io identified problems.

According to a first aspect of the invention there is provided a tie comprising an elongate strip provided with at least one cutting surface substantially perpendicular to the longitudinal axis of the tie wherein during installation in a bore whose diameter is less than the outside diameter or other maximum transverse width of the strip, the at least one cutting surface removes material from the periphery of the bore and in so-doing defines a helical channel in which a longitudinal edge of the strip is retained.

A second aspect of the invention provides a method of installing a tie comprising driving a tie through a bore in a substrate, wherein the tie has at least one cutting surface substantially perpendicular to its longitudinal axis and the bore has a diameter which is less than the transverse width of the wall tie.

Preferably, the tie is a helix formed from a helically wound flat strip of material, which may be any suitable material, for example, stainless steel.

Alternatively, the tie may be formed from an elongate element of constant cross-section, such as a bar of square section, which is helically wound.

The tie may be provided with two, three or four cutting surfaces, at least a part of the leading edge of which may be sharpened.

The method may further comprise percussively driving the tie into the 5 bore such that it is inserted to the required mandatory depth, At least a portion of the tie may be coated to improve the corrosion resistance thereof The coating may be applied to at least the leading edges and may further be applied to the body of the tie.

In this specification the terms tie and wall tie are intended to relate to a tie which can be inserted into a substrate such as timber, concrete, blockwork and other forms of masonry, to provide a connection between two materials of the same or different composition. For example, to tie the leaves of a cavity 15 wall together or to attach timber to masonry.

In order that the two aspects of the invention may be more fully understood, it will now be described by way of example and with reference to the accompanying drawings in which..

Figure 1 shows a plan view of a tie; Figure 2a shows an isometric view of the tie of Figure 1 being inserted; Figure 2b shows a plan view of the tie of Figure 1 partially inserted; and Figure 3 shows the tie installed in a cavity wall.

Referring firstly to Figure 1 and Figure 2a, there is shown a tie generally indicated at 1, comprising a regular helical structure of constant pitch. The tie 1 is further provided with cutting surfaces 20, 30, the leading edges 2, 3 of which are perpendicular to the longitudinal axis Y of the tie 1.

Figures 2a and 2b show the tie 1 presented to a pre-drilled pilot hole 10 provided in a substrate such as a wall. The hole 10 has a diameter 11 less than the major transverse width X of the tie 1. As can be seen, the leading edges 2, 3 are on opposed faces of the tie 1.

To install a tie 1 in a wall, a bore 10 is pre-drilled in the inner and outer wall leaves and the wall tie 1 presented to it. A cylindrical sleeve (not shown) may be placed over the wall tie to abut the outer wall leaf, to ensure that the tie 1 is only inserted to the correct depth. The end of the wall tie 1 is then driven into the wall leaves to the correct depth as determined by the sleeve by means of an electric drill which is provided with an adapter to enable the drill to be connected to the wall tie 1. The action of the drill causes the tie 1 to rotate as it is driven into the wall leaf and the leading edges 2, 3 of the cutting surfaces 20, 30 are driven through the wall leaf material.

The cutting edges 20, 30 of the wall tiel each define a helical channel which winds its way around the pilot hole 10. Once inserted to the correct depth, the tie 1 is ffictionally held within the bore 10.

Figure 3 shows an alternate method of installing a wall tie 1. The tie 1 is secured within a cavity wall comprising an inner leaf 101, a cavity 102 and an outer leaf 103. The tie 1 is secured in the inner leaf 101 according to the above-exemp 1 i fled method and may be retained within the outer leaf 103 by mortar 104 placed between two vertically adjacent courses of bricks. A tie 1 is installed every six courses of bricks to ensure the stability of the wall.

In both cases, the cutting surfaces, which are perpendicular to the axis of insertion, ensure that the tie 1 is driven into the bore in alignment therewith, and that the axis of insertion does not stray from the longitudinal axis of the bore 10.

The wall tie 1 may be helically formed with a 'Y' or '+' shaped crosssection, providing three or four cutting surfaces respectively. Other crosssections may be used which provide the tie with a plurality of cutting surfaces. Alternatively, the tie may comprise an elongate bar of square cross-section which is helically wound and which would provide four cutting surfaces, one at each of the apices of the face presented to the substrate during installation.

The leading and the trailing edges may be sharpened to facilitate the installation of the wall tie and at least the leading edges may be coated to improve the corrosion resistance of the tie. Furthermore, the or each leading edge may have a profile which is toothed, or of other form, to further facilitate installation of the tie 1, and the cutting surfaces may be a few degrees greater or less than perpendicular to suit the substrate material.

It has been found that the pull-out strength of the tie 1 is greater than that of a conventional pointed tie when installed to an equivalent depth in an identical material.

Claims

1. A tie comprising an elongate strip provided with at least one cutting surface substantially perpendicular to the longitudinal axis of the tie, wherein, during installation in a bore whose diameter is less than the outside diameter or other maximum transverse width of the strip, the at least one cutting surface removes material from the periphery of the bore and in so- doing defines a helical channel in which a longitudinal edge of the strip is retained.

io Z. A tie according to claim 1 in the form of a helix formed from a helically wound flat strip of material.

3. A tie according to claim 1 formed from an elongate element of constant cross-section which is helically wound.

4. A tie according to claim 3, wherein the elongate element is a bar of square section.

5. A tie according to any preceding claim made of stainless steel.

6. A tie according to any preceding claim provided with two, three or four cutting surfaces.

7. A tie according to claim 6, wherein at least a part of the leading edge 25 of the two, three or four cutting surfaces is sharpened.

8. A tie according to any preceding claim, wherein at least a portion of the tie is coated, to improve the corrosion resistance thereof.

9. A tie according to claim 8, wherein the coating is applied to at least the leading edge(s).

10. A tie according to claim 9, wherein the coating is further applied to the body of the tie.

11. A tie substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of installing a tie comprising driving a tie through a bore in a substrate, wherein the tie has at least one cutting surface substantially perpendicular to its longitudinal axis and the bore has a diameter which is less than the transverse width of the tie.

13. A method according to claim 12, wherein the tie is a helix formed from a helically wound flat strip of material.

14.. A method according to claim 12, wherein the tie is formed from an elongate element of constant cross-section which is helically wound.

15. A method according to claim 14, wherein the elongate element is a bar 20 of square section.

16. A method according to any of claims 12 to 15, wherein the tie is made of stainless steel.

17. A method according to any of claims 12 to 16, wherein the tie is provided with two, three or four cutting edges.

18. A method according to claim 17, wherein at least a part of the leading edge of the two, three or four cutting surfaces is sharpened.

1 19. A method according to any of claims 12 to 18, wherein at least a portion of the tie is coated, to improve the corrosion resistance thereof 20. A method according to claim 19, wherein the coating is applied to at least the leading edge(s) of the tie.

21. A method according to claim 20, wherein the coating is further applied to the body of the tie.

21 A method according to any of claims 12 to 21 further including percussively driving the tie into the bore, such that it is inserted to the required mandatory depth.

23. A method of installing a tie substantially as hereinbefore described.