GB2095305A

GB2095305A - Wall-tie

Info

Publication number: GB2095305A
Application number: GB8206578A
Authority: GB
Original assignee: Expanded Metal Co Ltd
Current assignee: Expanded Metal Co Ltd
Priority date: 1981-03-19
Filing date: 1982-03-05
Publication date: 1982-09-29
Also published as: GB2095305B

Abstract

This is a strip of metal 1 which, at each of 2 positions spaced from each end of the strip, has been slit and expanded to provide a pair of strands, 2, 2 and 2', 2', each pair forming a closed loop, and each pair of strands being connected at one end to a central portion 3 of strip 1. The central portion 3 of strip 1 has a drip-forming depression 5. The wall-tie is formed by slitting a strip of metal (1) at each end to form the strands (2, 2') and subsequently spreading each pair of strands apart. Apparatus for this purpose is disclosed. <IMAGE>

Description

SPECIFICATION Wall-tie Wall-ties are commonly used by the construction industry to supply rigidity to a pair of adjacent leaves of a cavity wall. The wall-tie extends between the two leaves, in each of which it is partly embedded.

The important characteristics which a wall-tie should possess are firstly that it is strong enough to provide sufficient rigidity to the leaves while also keying well into each leaf; secondly that the width of the tie should be minimized to avoid the possibility of buildup of debris on the upper surface of the tie; and thirdly the tie should prevent the transmission of moisture between the two walls.

A major drawback of previous known ties is that they are expensive to produce, particularly in the case of galvanised ties.

In accordance with one aspect of the present invention, a wall-tie comprises a strip of metal which at positions spaced from each end of the strip, has been slit and expanded to provide a pair of strands, each pair of strands being connected at one end to a central portion of the strip and being connected together at a position spaced from the one end to form a closed loop, the central portion of the strip being provided with a drip forming formation.

If each pair of strands is embedded in a respective leaf then a good key is provided while the unslit connecting portion which extends between the leaves is narrow so that very little debris can build up on the wall-tie.

In accordance with a second aspect of the present invention, a wall tie comprises a strip of metal which, at positions spaced from each end of the strip, has been slit and expanded to provide a pair of strands, each pair of strands being connected at one end to a central portion of the strip, the central portion being twisted transversely to the plane of each pair of strands and being provided with a drip forming formation.

With this wall-tie only a very narrow surface is provided so that very little debris can build up.

These wall-ties are very economical since the weight of metal used is small. This is particularly convenient when a relatively expensive metal such as stainless steel is used.

The drip forming formation may be provided by a depression in the central portion of the wall-tie, and the depression may extend transversely to the plane of each pair of strands.

It might be possible to obtain our wall-ties by suitably cutting a sheet of expanded metal but this is not ideal since firstly a compiex arrangement of knives would be required, secondly there would be wastage of metal, and thirdly the strength of the metal forming the tie would be weakened.

We have therefore developed a new method of manufacturing a wall-tie which, in accordance with the present invention, comprises cutting a strip of metal from a length of metal; and slitting the metal strip at positions spaced from each end of the strip to provide a pair of strands.

With this method each wall-tie is manufactured separateiy thus avoiding wastage of metal and enabling simple forming apparatus to be used. The order of carrying out the cutting and slitting steps is a matter of choice but most conveniently the slitting step is carried out before the cutting step.

The slit strip of metal may be formed using a reciprocating knife metal expanding machine provided with a knife specially adapted for the purpose. Although each pair of strands may be spread apart sufficiently during the slitting step, it is particularly convenient if the method further comprises positioning the slit strip of metal at a spreading station; and spreading apart each pair of metal strands. This enables each pair of strands to be spread widely apart so that the wall-tie keys well into each leaf. The slit strips may be manually or automatically positioned at the spreading station.

Preferably, the portion of the metal strip between each pair of strands is twisted transversely to the plane of each pair of strands and a drip forming formation may be formed in that portion of the metal strip. Where the strands are spread apart at a spreading station, it is particularly convenient if the metal strands are spread apart substantially simultaneously with the formation of the drip forming formation since this enables the rapid manufacture of a large number of wall-ties.

In one example where the spreading step is carried out subsequently to the slitting step, a plurality of support members are caused to move along a closed path from a feed station at which slit strips of metal are guided to respective support members, via the spreading station, to a removal station where each strip of metal is removed from its support member.

In accordance with a further aspect of the present invention, apparatus for manufacturing a wall-tie comprises a plurality of support members connected together to move along a closed path; a feed station at which strips of metal each of which, at positions spaced from each end of the strip, has been slit to provide a pair of strands, are fed to a respective support member; a spreading station comprising a pair of spreader members arranged to force apart the pairs of strands; and a removal station at which the strips of metal are removed from their respective support members.

Thus, by coordinating movement of the support members and spreader members, wallties can be manufactured at a relatively rapid rate.

Preferably, a depressing member is positioned between the two spreader members for the formation of a drip forming formation in the portion of each metal strip between the respective pairs of metal strands. Thus, each walltie is produced from a slit strip of metal by a single movement of the spreader members/depression member tool.

An example of a wall-tie, and an apparatus for manufacturing the wall-tie, in accordance with the present invention are illustrated in the accompanying diagrammatic drawings, in which: Figure 1 is a perspective view of the wall tie; Figure 2 illustrates the wall tie in position between two leaves of a cavity wall; Figure 3 illustrates the formation of a slit strip of metal on a reciprocating knife expanding metal machine; Figures 4 to 6 are views taken on the line A-A in Figure 3 with the knife tray and lower knife omitted for clarity, showing the variation in position of the upper knife in the machine shown in Figure 3; and Figure 7 illustrates apparatus for spreading apart each pair of strands of the strip formed by the apparatus of Figure 3.

The wall-tie shown in Figures 1 and 2 comprises a strip of metal 1 (stainless steel, mild steel or the like) which has been split along its length at each end to form two pairs of strands 2, 2'. Each pair of strands 2, 2' is integrally connecfed at one end to a central portion 3 of the strip 1. They are also integrally connected together at their other ends 4, 4' so that each pair of strands forms a closed, substantially square loop. A depression 5 is formed in the central portion 3. Typically, the width of the metal strand is about 5 mm so that the central portion 3 has a cross-section of about 5 mmx2 mm and a length of about 6 cm. Each strand 2, 2' has a thickness substantially half the width of the original strip, that is about 2.5 mm so that its cross sectional dimensions are 2.5 mm x 2 mm.The largest distance between each pair of strands 2, 2' is substantially 5.5 cm while the overall length of the wall-tie is about 18cm.

In use, the wall-tie is positioned between two leaves 6 of a cavity wall, as shown in Figure 2.

Each pair of strands 2, 2' is received by a respective one of the leaves 6 to which it is cemented or otherwise fixed in a conventional manner while the depression 5 is positioned between the two leaves 6. The depression 5 acts as a drip forming formation to prevent the passage of moisture from one leaf 6 to the other.

The depth of the depression 5 is relatively small so that the strength of the wall-tie is not significantly reduced after the depression has been formed. Each pair of strands 2, 2' provides a good key into the respective leaves 6, so providing a strong connection between the leaves.

A method of manufacturing the wall-tie shown in Figure 1 is illustrated in Figure 3 to 7. The method is in two stages, the first stage being carried out on a reciprocating knife expanding metal machine shown diagrammatically in Figure 3. A strip of material 7 is fed towards a pair of cooperating knives by means of feed rolls 8.

Alternatively, a gripper feed could be used. The cooperating knives comprise a fixed lower knife 9 and novel, upper, reciprocating knife 10 mounted to a conventional knife tray 1 The strip of metal is fed by the feed rolls 8 until it engages the knives 9, 10. A trimming cut is then made to the front edge of the strip 7 and then with the knife 10 in the position shown in Figure 4 the strip 1 is fed to the left, as seen in Figure 3, by an amount equal to a strand width. The knife 10 is then moved downwardly to cause two knife edges 12 on the knife 10 to slit the strip 7 at two spaced positions. Simultaneously, the knife 10 stretches each strand 2, 2' formed by its slitting action to form respective gaps 13, 13'.The size of the gaps 13, 1 3' is dependent upon the profile of the knife 10 and the depth of penetration, that is the amount by which the knife 10 overlaps the lower knife 9.

The upper knife 10 then returns to the top of its stroke and moves transversly to this upward movement, to the right in Figure 3, by an amount equal to half the pitch of the profile of the knife 10. At the same time, the strip 7 is fed towards the knives 9, 10, by an amount equal to a strand width.

The upper knife 10 then descends towards the strip 7 so that its central knife edge 12 slits the strip 7 to produce the central portion 3 of the tie (Figure 5). The knife 10 then returns again to the top of its stroke and moves in a transverse direction opposite to the previous transverse movement (to the left as shown in Figure 6) by an about equal to half the pitch of the profile of the knife. The strip 7 is not fed further forward at this stage so that when the knife 10 descends the two knife edges 12 are in line with the cut made on the original downward stroke. On this downward stroke, however, the knife 10 continues downwardly until the partially formed wall-tie is cut completely from the strip 7.

The knife 10 then returns upwardly and the entire procedure isthen repeated to produce further slit strips.

The partially formed wall-tie is then transferred either manually or automatically to a feed station 14 of an expanding machine 1 5 shown in Figure 7. The machine 1 5 comprises a plurality of support or forming blocks 16 mounted on a conveyor 1 7 entrained around two idlers 18. Each forming block 17 is arranged to move beneath a spreading tool 19 mounted on a "C" frame press (not shown). The spreading tool 19 comprises two punches 20 (one of which may be seen in Figure 7) and a depressing member 21 positioned between the punches 20.

When a partially formed wall tie 3 is brought beneath the spreading tool 19 on a forming block 16, the conveyor 1 7 is stopped, the tool 1 9 is then moved downwardly to cause each punch 20 to enter into a respective gap 13, 13' of the walltie 3 to spread the gap to the required amount while the depressing tool 21 engages the central portion 3 of the wall-tie to form the drip forming formation 5. The upper surface of the forming block 16 is contoured to enable each punch 20 to pass through the respective gaps 13, 13' and to allow the central portion of the tie to be depressed.

Movement of the conveyor 17 is caused by a conventional compressed air piston/cylinder arrangement 22. To move the upper part of the conveyor 1 7 to the left, as seen in Figure 7, compressed air is fed to the cylinder 22 by means not shown to cause a piston rod 23 to move to the left, abutment between a nose 24 mounted on the piston rod 23 and a forming block 1 6 causing the conveyor to move. The piston rod 23 is then retracted by supplying compressed air to another part of the cylinder 22 by means not shown, the nose 24 being moved to avoid contact with the next succeeding forming block 16, in a conventional manner.

The motion of the conveyor 1 7 and the spreading tool 1 9 can be synchronized so that while the spreading tool 1 9 moves upwardly, the conveyor 1 7 is urged to bring the next wall-tie to the spreading station, downward movement of the tool 1 9 occurring while the piston rod 23 is retracted.

After the strands 2' 2' have been spread by the tool 19, the forming block 16 moves towards a removal station 25 adjacent the left hand idler 1 8 wherein the wall-tie either falls or is stripped from the forming block 1 6.

The finished wall-tie on leaving the conveyor 17 can fall into a suitable carton or sack ready for despatch.

Claims

1. A wall tie comprising a strip of metal which, at positions spaced from each end of the strip, has been slit and expanded to provide a pair of strands, each pair of strands being connected at one end to a central portion of the strip and being connected together at positions spaced from the one end to form a closed loop, the central portion of the strip being provided with a drip forming formation.

2. A wall tie comprising a strip of metal which, at positions spaced from each end of the strip, has been slit and expanded to provide a pair of strands, each pair of strands being connected at one end to a central portion of the strip, the central portion being twisted transversely to the plane of each pair of strands and being provided with a drip forming formation.

3. A wall tie according to claim 2, wherein the loop formed by each pair of strands forms substantially a square.

4. A wall tie according to any of the preceding claims, wherein the drip form formation is provided by a depression in the central portion of the wall tie.

5. A wall tie according to claim 4, when dependent upon claim 2, wherein the depression extends transversely to the plane of each pair of strands.

6. A wall tie according to claim 1 or claim 2, substantially as described with reference to the accompanying drawings.

7. A method of manufacturing a wall tie, the method comprising cutting a strip of metal from a length of metal; and slitting the metal strip at positions spaced from each end of the strip to provide a pair of strands.

8. A method according to claim 7, further comprising positioning the slit strip metal at a spreading station; and spreading apart each pair of metal strands.

9. A method according to claim 7 or claim 8, wherein each pair of strands is connected together at a position spaced from a central portion of the metal strip to form a closed loop.

10. A method according to any of claims 7 to 9, wherein the portion of the metal strip between each pair of strands is twisted transversely to the plane of each pair of strands.

11. A method according to any of claims 7 to 10, further comprising the step of forming a drip forming formation in the portion of the metal strip between each pair of metal strands.

12. A method according to claim 11, when dependent upon claim 8, wherein the metal strands are spread apart substantially simultaneously with the formation of the drip forming formation.

13. A method according to at least claim 8, wherein a plurality of support members are caused to move along a closed path from a feed station at which slit strips of metal are guided to respective support members, via the spreading station, to a removal station where each strip of metal is removed from its support member.

14. A method according to claim 7, substantially as described with reference to the accompanying drawings.

1 5. Apparatus for manufacturing a wall tie according to any of claims 1 to 6, the apparatus comprising a plurality of support members connected together to move along a closed path, a feed station at which strips of metal, each of which, at positions spaced from each end of the strip, has been slit to provide a pair of strands, are fed to a respective support member; a spreading station comprising a pair of spreader members arranged to force apart the pairs of strands, and a removal station at which the strips of metal are removed from their respective support members.

1 6. Apparatus according to claim 15, further comprising a depressing member positioned between the two spreader members for the formation of a drip forming formation in the portion of each metal strip between the respective pairs of metal strands.

17. Apparatus according to claim 15, substantially as described with reference to the accompanying drawings.