GB2367324A

GB2367324A - Anchor; wall tie

Info

Publication number: GB2367324A
Application number: GB0023680A
Authority: GB
Inventors: Gerald Ford
Original assignee: PERMAGARD PRODUCTS Ltd
Current assignee: PERMAGARD PRODUCTS Ltd
Priority date: 2000-09-27
Filing date: 2000-09-27
Publication date: 2002-04-03
Also published as: GB0023680D0

Abstract

An anchor includes an element 14 slit along substantially its entire length and compressible between conical elements 4 and 9 so as to expand into a bore. A remedial wall tie comprises two anchors 30 and 32, the latter having rotation inhibiting means such as deformed thread, so that application of torque to nut 12 rotates shaft 2 to first expand sleeve 14' in a first leaf of a wall: when sleeve 14' is firmly gripped the rotation inhibiting means can be overcome by further torque to expand sleeve 14 in the other leaf.

Description

FIXING AND WALL TIE INCLUDING SUCH A FIXING The present invention relates to a fixing for a securing an item to a wall or other suitable solid substrate, and also to a wall tie utilising such a fixing.

Buildings having a cavity wall construction have wall ties which extend between an outer wall of bricks or breeze-blocks and a similarly constructed inner wall. The wall ties hold the walls to one another and provide strength to the structure of the building. Many buildings have wall ties formed of galvanised iron or mild steel. It has been found that these ties can corrode. During the corrosion process, rust is formed which occupies a greater volume than the original wall tie. This exerts pressure on the surrounding bricks which can cause the wall to become cracked or displaced. Furthermore, the corrosion of the wall tie reduces its physical strength and has resulted in wall ties failing completely. This reduces the strength of the building and has, in extreme cases, resulted in the collapse of an outer wall of a building when subjected to a wind loading.

There is a growing need to perform in situ replacement of failed wall ties. The position of wall ties may be identified using a metal detector or by careful visual inspection of the wall. An inspection hole may be drilled near the wall tie and an endoscope inserted in order to examine the wall tie. Alternatively, bricks may be removed adjacent the wall tie in order to perform an inspection. The removal of bricks also enables the failed wall tie to be removed and replaced, although this process is necessarily labour intensive and hence expensive. It can also be damaging to the cosmetic appearance of the wall.

A known replacement wall tie comprises a bar having its ends bent in a serpentine manner.

The end of the tie is inserted into a channel which has been drilled in the wall and filled with resin. The resin is allowed to cure in order to engage the wall tie with the wall. Such a wall tie can be formed by simply bending a stainless steel rod and hence it is mechanically simple and inexpensive to make. However, the slowly meandering surface of the tie does not realise the full potential of the bond to the bricks. Furthermore, the insertion of such ties can be a relatively slow process because of the need to allow the resin sufficient time to cure before a load can be applied to it.

GB2335457 discloses a wall tie having elastomeric fixing elements engaged between respective shoulders and rotatable nuts. Movement of the nuts towards one another causes the elastomeric element to expand radially. However the resiliently deformable nature of the elastomeric element limits the load which can be applied to the wall tie as the

6 5 elastomeric element has the potential to"tear". Other known wall ties comprise metallic anchor elements in which a plurality of tines are (and remain in use) attached to a ring. This configuration may be provided by forming slots at opposing ends of a cylindrical anchor element. Only the ends of the anchor expand radially outwardly. The central portion of the anchor remains at a constant diameter, and thereby does not participate in the anchoring process.

According to a first aspect of the present invention, there is provided an anchor comprising an anchor element supported on a rigid member and first and second relatively movable elements which can move to compress the anchor element therebetween, the anchor element having a slot along all or most of its length and the relatively movable elements and the anchor element having co-operating camming surfaces such that movement of the relatively movable elements into engagement with the anchor element causes the anchor element to expand along its length.

It is thus possible, by provision of the slot, to enable the anchor element to expand along the entirety of its length as the relatively movable elements progressively extend into the interior of the anchor element. This increases the area of contact between the anchor element and the wall.

Advantageously the slot extends all along the length of the anchor element. This enables the entirety of the anchor element to expand. However, metal may bridge the slot, either by being formed across the slot after the slot has been made, or by cutting a slot, or co-operating slots, that do not extend fully along the anchor. The basic operation of the anchor need not change provided that the bridge fails during the anchoring process, thereby allowing the anchor element to expand along the entirety of its length. Preferably the anchor element is made of metal, such as brass or steel. This ensures that the anchor element has high strength. Advantageously the surface of the anchor element may be ridged or corrugated in order to further increase its anchoring properties.

Alternatively hard, high tensile polymer materials such as nylon or reinforced resins may be used to form the anchor elements.

Preferably the rigid member is a bar carrying a helical thread in an end portion thereof.

Preferably the first relatively movable element forms an abutment. The abutment is advantageously fixed with respect to the rigid member. In use, the abutment may be formed by a nut which is locked to the helical thread, optionally by a further lock nut, or which is wound to the region where the helical thread terminates thereby preventing further motion of the first relatively movable element.

Preferably the first and second relatively movable elements have a tapered profile. The profile may, for example, be conical as this provides a uniform expansion force around the entirety of the anchor element, causes the anchor element to centre on the rigid member and is also an economic shape to produce.

- Preferably the second relatively movable element is movable along the rigid member.

Thus, in use, the second relatively movable element may be in threaded engagement with the rigid element and may be wound along the thread in order to compress the anchor element between the first and second relatively movable elements. Thus, the second relatively movable element can be regarded as an anchor control element.

Preferably the anchor element comprises at least one further slot which extends along a significant portion of the anchor element but not along the entirety thereof. The provision of one or more additional slots effectively subdivides the anchor element into segments, each segment being free to move outwardly from the axis of the rigid element in order to be wedged between the first and second relatively movable elements and the wall or other substrate into which the anchor is fixed. In a preferred embodiment of the present invention, there is provided an anchor comprising a rigid element, a first anchor element, a first anchor control element, and a first abutment, wherein the first anchor element is provided intermediate the first anchor control element and the first abutment and said first anchor element, first anchor control element and first abutment are carried on the rigid element, the anchor element and the abutment are arranged such that relative motion of the abutment into the first anchor element causes the anchor element to expand outwardly, the anchor element and the first anchor control element are arranged such that relative motion of the first anchor control element into the first anchor element causes the anchor element to expand outwardly, and the anchor element has a slit extending along its length such that expansion of the anchor element occurs along substantially the entirety of the length of the anchor element.

According to a second aspect of the present invention, there is provided a wall tie including an anchor element according to the first aspect of the present invention.

Advantageously the wall tie has anchor elements according to the first aspect of the invention provided at opposing ends thereof.

Preferably, a first one of the anchor elements has wall engaging means provided on the second relatively movable element (or anchor control element) such that this element is held against rotation when in place in a wall. Thus the first anchor element may be inserted into a wall and caused to tighten and engage with the wall by virtue of turning the rigid element, thereby causing translation of the anchor control element along a threaded portion of the rigid element towards the abutment so as to compress the anchor element therebetween. The second anchor may have a second anchor control element which translates along a respective threaded portion of the rigid element in order to control operation of the second anchor.

The second anchor control element or the associated threaded portion may have rotation inhibiting means formed thereon in order that relative rotation between the second anchor control element and the rigid element is selectively inhibited. Thus, if a drive tool is applied to the second anchor element, once the second anchor element engages with the rotation inhibiting means the rotation of the second anchor element is transferred to the rigid element, and hence to the first anchor thereby operating the first anchor to engage with the wall. Once the first anchor has engaged with the wall, the back torque resulting therefrom causes the second anchor control element to overcome the rotation inhibiting means and then to translate towards the abutment of the second anchor thereby causing the second anchor to engage with the wall.

The present invention will further be described, by way of example, with reference to the accompanying drawings in which: Figure 1 schematically illustrates an anchor constituting an embodiment of the present invention; Figure 2 illustrates a wall tie utilising the anchor shown in Figure 1 ; Figure 3 schematically illustrates a deformed thread in order to form rotation inhibiting means; Figure 4 schematically illustrates a lock nut having an omitted portion of thread in order to form rotation inhibiting means; and Figures 5a and 5b schematically illustrate alternative constructions of the anchor element.

The anchor shown in Figure 1 comprises a cylindrical bar 2 which carries a fixed element 4 thereon. The fixed element 4 may be formed by a nut secured to the bar by welding, or forced into engagement with a non-threaded section of the bar. The element 4 carries a conical portion 6, wherein the radius decreases with decreasing distance towards an end portion 8 of the bar 2. An anchor control element 9 is also provided on the bar and comprises a conical element 10 co-operating with a nut 12. The conical element 10 is orientated such that its radius decreases with increasing distance from the end 8.

Interposed between the fixed element 4 and the anchor control element 9 is an anchor element 14. The anchor element comprises a hollow cylindrical tube having a slot 16 (as shown in Figure 2) extending along the entirety of its length. The anchor element 14 is typically made of brass or mild steel as these materials do not rust but also exhibit high strength. The slot need not be continuous. More specifically a bridge of material can extend from one side of the slot to the other. This does not effect the working of the anchor provided that the bridge fails during operation of the anchor so as to allow the entirety of the anchor to expand.

In use, the anchor element is inserted to a suitably sized hole drilled in a substrate, such as a wall, and the nut 12 is rotated with respect to the rigid element 8 in order to cause the nut 12 to translate along a threaded portion 18 of the bar 2. This causes the conical element 12 to move towards the fixed abutment 4 thereby engaging the anchor element 14 therebetween. Further movement of the elements towards each other causes the anchor element to start to splay open thereby forcing its outer surface 20 into frictional engagement with the substrate surrounding it. The outer surface 20 is advantageously profiled, for example in an undulating or ridged manner in order to enhance its gripping capabilities.

The element 14 may have further slots formed therein, extending from one end thereof towards the other, but not actually reaching the other end, so as to effectively divide the element 14 into a plurality of segments. These segments remaining interconnected, at least whilst the anchor element is unused. The act of the operating the anchor element by moving the anchor control element 9 towards the fixed abutment 4 may then cause the anchor element 14 to fracture into its plurality of segments. However, each of these is then wedged between the substrate and the conical surfaces 6 and 10.

Figure 2 illustrates a wall tie constituting an embodiment of the present invention. First and second anchors 30 and 32, respectively, are provided at opposing ends of the bar 2. A drip ring 33 is provided on the bar 2 to stop moisture flowing along the bar. The anchors are of similar construction and hence like parts are referred to by like reference numerals with the parts of the first anchor being denoted by an apostrophe next to their reference numeral. The anchor control element 9'of the first anchor 30 is modified so as to have at least one projection 34 extending thereon which serves to engage with the substrate surrounding the element 9'in order to hold it against rotational with respect to the substrate. In use a passage is drilled through the inner and outer leaves of a wall and the wall tie is inserted through the passage. The passage is selected so as to have a diameter only slightly greater than that of the outside diameter of the anchor elements. The projection 34 is arranged such that it is a tight sliding fit within the passage. Once the wall tie has been inserted sufficiently to move the anchors into their respective positions, the rod 2 is rotated in the sense required to cause the anchor control element 9'to translate along the threaded portion towards the fixed element 4'. This causes the conical surfaces of the abutment and the anchor control element to come into abutment with the material of the anchor element 14'and thereby urge the anchor element to expand radially outwards. In order to cause this rotation, a part of the thread of the threaded portion 18 of the second anchor 32 or of the thread within the nut 12 may be omitted or damaged in order to provide rotation inhibiting means. Thus, if a tool is engaged with the nut 12 rotation of the nut will be transferred to the shaft 2 by the rotation inhibiting means thereby causing relative rotation between the shaft and the first anchor control element 9'. Once the first anchor 30 has engaged with the wall, the back torque that this creates becomes sufficient to overcome the rotation inhibiting means thereby allowing the nut 12 to cut a new thread and then translate along the threaded portion 18 thereby causing the second anchor 14 to expand in order to engage the wall.

Figure 3 schematically illustrates one way in which the rotation inhibiting means may be formed. As shown, the threaded portion 18 may be modified to include a sub-portion 36 where the thread is deformed. This distortion may be formed by exerting a compressive force on the thread, for example by clamping. Alternatively, as shown in Figure 4, an internal thread 38 within the nut 12 may not extend along the entirety of the nut. The chain line 40 represents the axis of rotation of the nut 12. In each case, the further application of rotational force of the nut enables the distortion or omitted thread to be overcome such that the nut can then continue to translate along the bar 2.

Figures 5a and 5b show modifications in which the slot 16 is interrupted by a bridge 50 towards a central region of the slot or a bridge 52 towards the end of the slot 16. It is thus possible to provide an effective yet inexpensive anchor, and a wall tie including the same.

Claims

Claims 1. An anchor comprising an anchor element supported on a rigid member, and first and second relatively movable elements which can move to compress the anchor element therebetween, the anchor element having a slot along all or most of its length and the relatively movable elements and the anchor element having co-operating camming surfaces such that movement of the relatively movable elements into engagement with the anchor element causes the anchor element to expand along its length.
2. An anchor as claimed in claim 1, wherein the first relatively movable element is a fixed abutment carried on the rigid member.
3. An anchor as claimed in claim 1 or 2 wherein the abutment has a tapered profile, with a thinner end of the taper facing towards the anchor element.
4. An anchor as claimed in any one of the preceding claims in which the second relatively movable element is movable with respect to the rigid member in order to compress the anchor element between the first and second relatively movable elements.
5. An anchor as claimed in claim 4, wherein the second relatively movable element is carried on and in screw threaded engagement with the rigid member.
6. An anchor as claimed in any one of the preceding claims, further comprising a further slot in the anchor element, said further slot extending from one end of the anchor element towards, but terminating before reaching an opposing end of the anchor element.
7. A wall tie including one or two anchors as claimed in any one of the preceding claims.
8. A wall tie as claimed in claim 7, wherein there are two anchors, a first anchor for fixing to a first leaf of a wall and second anchor for fixing to a second leaf of a wall, wherein both anchors engage a wall by virtue of an anchor element being operated by the relative motion of associated first and second relatively movable elements, and wherein the second relatively movable element of the second anchor or the rigid member has a rotation inhibiting means such that upon application to a torque to the second relatively movable element it transmits torque to the rigid member to cause rotation thereof, thereby causing the first anchor to expand to grip the first leaf, said act of fixing serving to resist rotation of the rigid member, thereby resulting in the second relatively movable element overcoming the rotation inhibiting means and moving towards the first relatively movable element thereby causing the second anchor to engage the second leaf of the wall.
9. A wall tie as claimed in claim 8, in which the rotation inhibiting means is a modified or omitted thread between the second relatively movable member and the rigid member.
10. An anchor as claimed in any one of claims 1 to 6, in which the anchor element is of unitary construction.