GB2213173A

GB2213173A - Wire cavity wall tie

Info

Publication number: GB2213173A
Application number: GB8828321A
Authority: GB
Inventors: Colin Jackson; N E Smith
Original assignee: PIT PARTS Ltd
Current assignee: PIT PARTS Ltd
Priority date: 1987-12-03
Filing date: 1988-12-05
Publication date: 1989-08-09
Anticipated expiration: 2008-12-05
Also published as: GB2213173B; GB8828321D0

Abstract

A cavity wall tie 100 is formed from a single length of wire to have a shank 16 and two heads 14. Each head is U-shaped to provide two lengths 18, 20 lying perpendicular to the shank 16, thereby improving keying to the mortor of the cavity skins 30. <IMAGE>

Description

Tie The present invention relates to ties, in particular to cavity wall ties for use in constructing cavity walls in which both skins of the wall are formed by multiple courses of building units such as bricks or blocks held together by mortar.

Cavity wall ties are used to tie together the two skins, of the cavity wall by extending across the cavity and keying to the mortar of each skin. Various designs of tie have been proposed. A first type uses steel wire bent to for two heads of generally triangular form.

Another proposal is to stamp out teeth from a length of metal strip, the teeth keying to the mortar while an unstamped intermediate length of the strip extends across the cavity. Finally, a moulded plastics tie has been proposed. It is difficult to select a plastics material which can provide both adequate keying and sufficient tie strength without the thickness of the tie exceeding the maximum permissible for use in standard brickwork.

The present invention seeks to provide a cavity wall tie which is relatively simple to make and use and which provides adequate performance.

The invention provides a cavity wall tie formed from a length of wire and comprising two heads which are located, in use, between courses of building units in respective skins of a cavity wall, and a shank which connects the heads and which, in use, spans the cavity, each head comprising a first portion, the first portions of each head extending substantially parallel to each other and, in use, substantially parallel to the plane of the wall, and each head further comprising an intermediate portion which extends between the corresponding first portion and the shank and which is directed substantially parallel to the first portion at at least one point along its length.

Preferably the intermediate portion of each head comprises a second portion which extends substantially parallel to the first portions.

The first portion and the intermediate portion of each head may form a hook having parallel sides formed by the first portion and the second portion and connected by a connecting web. Each hook may be generally U-shaped. The second portion of each head may be different in length to the first portion. The first portion of each head may be longer than the second portion.

Preferably at each end of the shank, a first curved portion connects the shank to the second curved portion, and the other end of the second portion is connected by a second curved portion to the said first portion. Preferably the first portion extends back past the line of the shank, whereby keying is provided to both sides of the shank.

Preferably the first portions is perpendicular to the shank.

Preferably the tie lies substantially wholly within a single plane. The shank is preferably deformed part way along its length to form a dripping centre.

The tie may terminate at each end in a loop of material.

In another aspect, the invention provides a method of building a cavity wall having two skins formed by multiple courses of building units, in which a cavity wall tie according to the first aspect of the invention is incorporated in the wall by embedding the two head portions wholly within respective skins of the wall, whereby the first portion and the intermediate portion of each head provide keying with the corresponding skin, and the shank extends extends across the cavity.

The invention further provides a cavity wall comprising two skins formed by multiple courses of building units, and further comprising at least one wall tie according to the first aspect of the invention, the head portions of the tie being embedded wholly within respective skins of the wall, whereby the first portion and the intermediate portion of each head provide keying with the corresponding skin, and the shank extends across the cavity.

One embodiment of a cavity wall tie according to the invention and its manner of use will now be described in more detail, by way of example only, and with reference to the accompanying drawings in which : Fig. 1 is a plan view of a cavity wall tie according to the invention; Fig. 2 is an elevation of part of the tie shown in Fig. 1; and Fig. 3 is a plan view of a modified version of the wall tie of Fig. 1.

The tie 10 shown in the drawings comprises a length 12 of steel wire. This is bent to provide two heads 14 which are located, in use, between the courses of building units, such as bricks, in respective skins of a cavity wall, and a shank 16 which connects the heads 14 and which, in use, spans the cavity. Each head 14 comprises a first portion, 20 of wire which are parallel and, in use, are parallel to the plane of the wall. Each head further comprises an intermediate portion, 18, 22, 24 which extend between the corresponding first portion 20 and the shank 16. The intermediate portion is directed at 18 substantially parallel to the first portion 20.

The tie is formed in a simple bending operation from steel wire which may for instance be stainless steel wire of a 4 mm maximum diameter, or galvanised steel wire of 4.5 mm maximum diameter and having a galvanised layer of 940 g/m . Other diameters and materials could be used. The whole length of the wire forming the tie lies in a single plane except as will be described below.

Each head 14 is generally U-shaped. The first portions 18, 20 and a length 18 of the intermediate portion form the sides of the 'U' . The sides are parallel, and perpendicular to the shank 16. One end of the second portion 18 is connected to an end of the shank 16 by a short curved portion 22 of wire. The curvature at this point is preferably as great as possible without seriously weakening the wire by excessive bending. The second end of the second portion 18 is connected to the first portion 20 by a curved web portion 24 whose dimensions are chosen to space the portions 18, 20 as desired. The first portion 20 extends away from the web 24 back to and past the line 26 of the shank 16. This ensures, that in use, keying is provided to both sides of the line 26.

Two dripping centres 28 are provided part way along the shank 16 by deforming it slightly out of the plane of the rest of the tie, to form V-shaped projections. These encourage moisture on the tie to collect and drip off into the cavity, to reduce the risk of corrosion of the tie 10.

When the tie is installed, each head 14 is embedded in mortar of a brickwork or blockwork skin of the cavity wall, with the shank 16 extending across the cavity, generally perpendicular to the skins. In this arrangement, the first and second portions 18, 20 lie in the mortar parallel to the plane of the skins, to provide keying. Skins are indicated schematically in Fig. 1 by broken lines 30.

After installation, forces applied to the heads 14 will be applied by the shank 16 in a direction generally perpendicular to the portions 18, 20, so that effective keying is provided. Keying is mainly provided by the portion 20, in view of its greater length, but the provision of two keying portions is expected to ensure satisfactory performance even if one or other portion 18, 20 is not functioning fully, for instance because of defective mortar.

It is believed that the tie described above can be formed in a simple, single pressing operation, although a second operation may be needed to form the dripping centres.

Fig. 3 shows a variation of the embodiment of Figs. 1 and 2. In this variation, the free ends of the portions 20 are turned back to form a small loop at each end of the tie. These are provided for various reasons.

Firstly, they enhance the safety of the tie during use, because sharp wire ends are no longer present. Such ends could present dangers during handling of the tie, or if ties are initially incorporated into one skin of a wall and remain projecting out and uncovered until the second skin has been erected. The free ends of the tie for incorporation into the second skin could be dangerous to workmen.

The loops at each end of the ties also provide a convenient point for collecting ties into bundles by passing a wire or string through one loop on each tie.

The loops could also be used during manufacture for holding the ties or for transporting the ties by sliding them along a wire which passes through one loop, or two wires which pass through respective loops.

Variations and modifications to the ties described above can be made without departing from the spirit and scope of the present invention. Other materials could be used and could be formed into other shapes. The shapes of the heads described above could be modified by increasing or reducing the length of the portion 18, even by reducing it to the extent that the web portion 24 merges with the curved portion 22, and the portion 18 is reduced to a single point at which the wire is directed parallel to the portion 20.

The term wire is used throughout this document because it is expected that the tie will be manufactured from a metallic wire. However, it is to be understood that other materials which can form a filament of sufficiently high strength and sufficiently small diameter are also envisaged as falling within the scope of the present invention, and the term "wire" should be construed accordingly.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A cavity wall tie formed from a length of wire and comprising two heads which are located, in use, between courses of building units in respective skins of a cavity wall, and the shank which connects the heads and which, in use, spans the cavity, each head comprising a first portion, the first portions of each head extending substantially parallel to each other and, in use, substantially parallel to the plane of the wall, and each head further comprising an intermediate portion which extends between the corresponding first portion and the shank and which is directed substantially parallel to the first portion at at least one point along its length.

2. A tie according to claim 1, wherein the intermediate portion of each head comprises a second portion which extends substantially parallel to the first portions.

3. A tie according to claim 2, wherein the first portion and the intermediate portion of each head form a hook having parallel sides formed by the first portion and the second portion and connected by a connecting web.

4. A tie according to claim 3, wherein each hook is generally U-shaped.

5. A tie according to claim 2, 3 or 4, wherein the second portion of each head is different in length to the corresponding first portion.

6. A tie according to claim 5, wherein the first portion of each head is longer than the second portion.

7. A tie according to any of claims 2 to 6, wherein the first portion of each head is spaced further from the shank than the second portion.

8. A tie according to any of claims 2 to 7, wherein, at each end of the shank, a first curved portion connects the- shank to the second portion, and wherein the other end of the second portion is connected by a second curved portion to the said first portion.

9. A tie according to claim 8, wherein the first portion extends back past the line of the shank, whereby keying is provided to both sides of the shank.

10. A tie according to any preceding claim, wherein the first portion is perpendicular to the shank.

11. A tie according to any preceding claim, wherein the tie lies substantially wholly within a single plane.

12. A tie according to any preceding claim, wherein the shank is deformed part way along its length to form a dripping centre.

13. A tie according to any preceding claim, wherein the tie terrninates at each end in a loop of material.

14. A tie substantially as described above, with reference to the accompanying drawings.

15. A method of building a cavity wall having two skins formed by multiple courses of building units, in which a cavity wall tie according to any preceding claim is incorporated in the wall by embedding the two head portions wholly within respective skins of the wall, whereby the first portion and the intermediate portion of each head provide keying with the corresponding skin, and he shank extends across the the cavity.

16. A cavity wall comprising two skins formed by multiple courses of building units, and further comprising at least one wall tie according to any of claims 1 to 14, the head portions of the tie being embedded wholly within respective skins of the wall, whereby the first portion and the intermediate portion of each head provide keying with the corresponding skin, and the shank extends across the cavity.

17. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.