GB2116599A

GB2116599A - Plaster lath bead

Info

Publication number: GB2116599A
Application number: GB8306579A
Authority: GB
Inventors: Frank Barnett
Original assignee: Expanded Metal Co Ltd
Current assignee: Expanded Metal Co Ltd
Priority date: 1982-03-11
Filing date: 1983-03-10
Publication date: 1983-09-28
Also published as: GB2116599B; GB8306579D0

Abstract

The bead, which can be bent to meet a curved corner such as might be found in an arch, is formed from a strip of parallel strand expanded metal mesh. A central row 3 of parallel strands 5 is bent to form a nib 10 between side flanges 11, 12, so as to enable the nib to be bent along its length to meet the curved corner. <IMAGE>

Description

SPECIFICATION Plaster lath bead The present invention relates primarily to plaster laths formed from expanded metal mesh, and more particularly to plaster lath beads which can be used at an external corner formed at the junction of two surfaces to be plastered or rendered, the expanded metal mesh providing a key for the plaster against the surface.

Conventionally, a plaster lath bead has a pair of elongate angled flanges of expanded metal mesh connected integrally by a central elongate nib portion which provides a guide for the plasterer's trowel and forms a neat and smooth straight edge at the corner of the plastered surface.

Whilst such plaster lath beads are used extensively in the building industry, a problem arises from the fact that the central or nib part of the bead is solid, being formed from unexpanded material having no apertures and the bead is therefore difficult to bend into a smoothly curved form such as might be required around an arch.

To overcome this problem and in accordance with the present invention a plaster lath bead having a pair of side flanges and a central nib portion integrally formed therewith, is formed from parallel strand expanded metal mesh, the nib portion extending along a row of parallel strands substantially perpendicular to the strands so that the strands in that row form the curved envelope of the nib.

Parallel strand expanded metal mesh is a form of expanded metal where the apertures, instead of being diamond shaped or substantially hexagonal, are elongate slits, the strands on either longitudinal side of the slits being parallel to one another and pairs of short angled strands of lesser width than the parallel strands closing the ends of the slots.

By forming the nib along a row of the parallel strands the nib itself is able to flex in a plane intersecting the angle between the flanges so that the bead can be curved to provide a smoothly curved guide-line or corner where required.

Preferably, the bead comprises a strip of expanded metal mesh having, across its width, three rows of parallel strands, the strands extending perpendicular to the longitudinal direction of the strip, and the central row being bent into substantially a U-shape to form the nib.

The bead can then be curved along its length to the desired shape, the outer ends of the slits between the parallel strands in the outer rows possibly diverging slightiy as the bending is carried out to ease the bending process.

It is an advantage if the parallel strand expanded metal mesh is flattened before or during bending. Normally, the parallel strands of the mesh are twisted as a result of the expanding process out of the general plane of the sheet material from which the mesh is formed and this provides a measure of resistance against bending.

Flattening the strands before or during bending provides a smoother edge to the bead.

Whilst it is intended that the plaster lath bead according to the invention may be an independent bead for conventional plaster work it is also envisaged that such a bead may be incorporated in an arch former of expanded metal mesh type, the arch former comprising a first planar wall of expanded metal mesh and, substantially perpendicular to it a curved arch-forming wall.

Pairs of such arch formers can be used to form arches in square openings, with a bead being provided at the corner between the arch-forming wall and the planar wall. A bead according to the present invention can be used, the flange on one side of the bead being connected to the edge of the planar wall by, for example, spot welding, and the other flange being connected or formed integrally with the curved-arch-forming wall. Thus it will be appreciated that the bead-forming member in such an arch former may have flanges of unequal width, the larger of the flanges actually forming the arch-forming wall.

The invention includes a method of manufacturing a bead according to the invention, the method comprising flattening at least one row of parallel strands in a strip of parallel strand expanded metal mesh, and thereafter of simultaneously bending that row to form a nib, the portions of the mesh on either side of the nib being angled to one another to form flanges, whereby the nib can be curved to a desired shape in use. Preferably, the strands in one row on either side of the nib are flattened prior to the formation of the nib.

The cross-section of the nib is generally U-shaped, but may be flattened itself if the depth of the nib is to be increased.

An example of a plaster lath bead is shown in the accompanying drawings in which: Figure 1 is a plan view of an expanded metal strip prior to bending; Figure 2 is a front view of the bead after the strip of material has been shaped; Figure 2A is a cross-section on Figure 2; and, Figure 3 shows the bead after it has been curved along its length.

A strip of parallel strand expanded metal mesh 1 comprises three rows 2, 3 and 4 of the parallel strands 5 extending along the length of the strip. It can be seen that the parallel strands 5 are connected at their ends by short angled strands 6 so that elongate slits 7 are formed between each pair of adjacent parallel strands. At the edges of the strip 1 part strands 8 with open slits 9 between them complete the edge of the strip.

The strip shown in Figure 1 has been flattened, that is to say the strands 5 which are normally angled out of the general plane of the strip have been rolled or otherwise flattened after initial forming or during the initial forming process.

Figures 2 and 2A show the bead after it has been bent along its length, by a conventional bending process to form a nib 10 and a pair of side flanges 11 and 12. It will be appreciated that the nib comprises the parallel strands 5 of the row 3 after bending into a general U-shape and that the flanges comprise the remainder of the strip of parallel strand expanded metal mesh.

The bead shown in Figure 2 can be bent as required to meet a given curved line or to form a required curve as shown in Figure 3. Figure 3 shows the bead after curving, the parallel strands 5 of the nib 10 being distorted towards one another to close the slots between them at the apex of the nib.

To the side flanges 12 a sheet of conventional or parallel strand expanded metal mesh 13 can be spot-welded if required, and likewise a sheet (not shown) can be spot welded to the flange 11 thereby to form part of an arch-former of the general type described in British patent specification 2,015,633 A.

It will be appreciated that the bead constructed in accordance with the present invention can be used on its own, for example, when it is required to plaster around a curved angle such as might be present at an arch in a wall, or may (as described above) form part of a prefabricated arch-former for subsequent plastering-up.

Conventional bending techniques can be used to form the straight bead from the initial blank of expanded metal mesh and the bead itself can be bent by hand to meet any required curved shape.

As has been specifically mentioned above, the attachment of other expanded metal to the side flanges would normally be achieved by spotwelding. However, there may be occasions when it is required to form the curved bead to a nonstandard shape for attaching to the edge of a sheet of expanded metal and in this case if the operation is carried out on site it may be inconvenient to spot-weld. To overcome this problem a number of the part strands 8 at the edges of the bead can be bent out of the plane of the respective side flange, located through an aperture in the sheet of expanded metal to be attached to the bead and then bent over one or more of the strands in that sheet. This technique is particularly useful for forming non-standard arch formers where sheet expanded metal to form the faces of the arch can be cut to any desired shape and the bead itself attached thereafter.

Claims

1. A plaster lath bead having a pair of side flanges and a central nib portion integrally formed therewith, the bead being formed from parallel strand expanded metal mesh, the nib portion extending along a row of parallel strands substantially perpendicular to the strands so that the strands in that row form a curved envelope of the nib.

2. A bead according to claim 1 comprising a strip of expanded metal mesh having three rows of parallel strands, the strands extending perpendicular to the longitudinal direction of the strip and the central row being curved into a substantially U-shape to form the nib.

3. A plaster lath bead substantially as described with reference to the accompanying drawings.

4. A method of manufacturing a bead according to claim 1, the method comprising flattening at least one row of parallel strands in a strip of parallel strand expanded metal mesh, and thereafter or simultaneously bending that row to form a nib, the portions of the niesh or either side of the nib being angled to one another to form flanges, whereby the nib can be curved to a desired shape in use.

5. A method according to claim 4, wherein the strands of expanded metal mesh in one row on either side of the nib are flattened prior to the formation of the rib.

6. A method of manufacturing a plaster lath bead, substantially as described with reference to the accompanying drawings.

7. An arch former comprising a first planar wall of expanded metal mesh and, substantially perpendicular to it, a curved arch forming wall, the planar wall and the arch forming wall being connected to respective side flanges of a bead according to any of claims 1 to 3.

8. An arch former according to claim 7, wherein the planar and arch forming wall of expanded metal mesh are spot-welded to the bead.

9. An arch former according to claim 7, wherein at least one of the planar and arch forming walls of expanded metal mesh are attached to the bead by edge strands of the bead bent out of the plane of the respective flange, inserted through apertures in the expanded metal mesh wall and bent over the strands in the wall to positively locate the bead in position on the wall.

10. An arch former substantially as described with reference to Figure 3 of the accompanying drawings.

11. An arch former comprising a first planar wall of expanded metal mesh, attached at a curved edge to a flange of a bead according to any of claims 1 to 3, the other flange on the bead forming a curved arch-forming wall.