GB2226581A - Lintel - Google Patents

Abstract

A lintel comprises two similar but oppositely facing metal elements 12, 13 of lazy Z section secured in position with their webs 12a, 13a parallel and the lower flanges 12c, 13c extending away from each other. The elements may be secured together by welding the upper flanges 12b, 13b and/or filling the space between them by a resin, e.g. polyisocyanarate foam 14. The outer surfaces may be protected from corrosion by an outer skin 15 of a synthetic resin denser than the infill 14. A wide variety of shapes of upper flanges 12b, 13b is disclosed. Strengthening ribs and corrugation for keying to plaster are described. <IMAGE>

Description

STRUCTURAL BEAM This invention relates to structural beams, the kind usually referred to as lintels, for spanning openings, for example window or door openings in building cavity walls, in order to support the courses of bricks, blocks, or other constructional materials in both the inner and outer leaves of the wall above the opening.

In the past lintels have been manufactured as pre-cast concrete beams, rolled steel joists, and more recently lintels have been fabricated from mild steel sheet. The present invention is concerned with the latter type of lintel, and it is an object of the present invention to provide such a lintel in a simple and convenient form.

In accordance with the present invention there is provided a lintel comprising first and second, elongate, sheet metal elements, each element having a generally planar web portion and integral therewith first and second generally planar flange portions, said first flange portion of each element lying perpendicular to the respective web portion and said first and second flange portions of each element extending respectively in opposite direction from respective opposite longitudinal edges of the respective web portion, said first and second elements being positioned with their web portions parallel and spaced by a predetermined distance with said first flange portions extending in directions away from one another, said first and second elements being secured in position relative to one another.

Conveniently the first and second elements are secured in position relative to one another by welding together of said first flange portions.

Preferably the first and second elements are secured together by a rigid, foamed, synthetic resin material infill in the void defined between the web portions of the two elements, said infill being bonded to the first and second elements.

Conveniently the first flanges are welded together to locate the first and second elements in a predetermined relative positions prior to introducing the synthetic resin material infill.

Preferably said infill is moulded onto said elements.

Desirably the exposed surfaces of the first and second elements are coated with a skin of synthetic resin material.

Desirably said skin is formed from the same synthetic resin material as the infill, but of greater density.

One example of the invention is illustrated in the accompanying drawings wherein, Figure 1 is a diagrammatic cross-sectional view of a lintel, Figure 2 is a perspective view of part of the lintel of Figure 1.

Figures 3a to 3i illustrate diagrammatically alternative lintel constructional elements, Figures 4a to 4i show alternative lintels embodying Z-shaped elements, and, Figure 5 is a view similar to Figure 1 of an alternative configuration.

Referring first to Figures 1 and 2 of the drawings, the lintel includes first and second sheet metal elements 12, 13 each of which is elongate and generally Z-shaped in transverse cross section.

Conveniently both elements 12, 13 are formed from respective elongate strips of thin mild steel sheet by a cold roll forming technique. However, it should be recognised that the elements can, if desired, be formed from other metals, and by other technqiues such as press brake forming.

Each of the elements 12, 13 is formed by bending an elongate strip of mild steel sheet parallel to its length so as to define a planar web portion (indicated in Figure 1 by the suffix a) having integral therewith first and second planar flange portions (indicated in Figure 1 by the suffix b and c respectively). The first and second flange portions of each element lie in parallel planes perpendicular to the plane of the respective web portion and extend outwardly from respective opposite longitudinal edges of the web portion in opposite directions respectively.

In order to construct the lintel the two elements 12, 13 are positioned with their web portions 12a, 13a parallel, but spaced apart by a predetermined distance, and their first flange portions extending towards one another with the flange portion 12b overlying the flange portion 13b. In this position the flange portions 12c and 13c extend outwardly in opposite directions. In a preferred embodiment the spacing between the flanges 12b and 12c is so chosen in relation to the spacing between the flanges 13b and 13c that when the flanges 12b and 13b are in facial contact then the flanges 12c and 13c are co-planar.

In its simplest form the lintel consists of only the two elements 12, 13 secured together by lightly tack welding the flange portion 12b to the flange portion 13b. It will be recognised that a range of lintel thicknesses can be produced using one size of element 12 and one size of element 13, simply by varying the amount by which the flange portions 12b, 13b overlap. Moreover, when the lintel is in use the flange portion 12c will carry the weight of the upper courses of the inner leaf of a cavity wall while the flange portion 13c will carry the weight of the upper courses of the outer leaf of the cavity wall. It may be that the load to be carried by the flange portion 13c will be greater than that to be carried by the flange portion 12c and in such circumstances the element 13 could be formed from a thicker gauge of sheet material than the element 12 and/or from different material.Moreover, the construction of the lintel from two separately formed Z-shaped elements facilitates the production of a lintel having a greater depth to thickness ratio than would be possible in a lintel of unitary construction. The production of cold roll forming machinery, and tools therefor, to produce the lintel in one piece from sheet steel, and having an equivalent large depth to thickness ratio, would be prohibitively expensive.

It will be understood that when the lintel is in place in the wall of the building the interconnection of the flange portions 12, 13b is of little or no significance provided that the two elements are each, individually, strong enough to accept the loads to be imposed upon them. However, even in such a lintel the flange portions 12b, 13b would be welded to one another sufficiently strongly to faciliate handling of the lintel as a unit during building of the wall utilizing the lintel.

If desired the void defined between the web portions 12a, 13a could be packed with a thermally insulating material, for example mineral wool or a preformed block or blocks of foamed synthetic resin material. Moreover, the flanges 12b, 13b could be spaced apart by thermal insulation material, the flange portions being interconnected at spaced points by welding, or by connecting devices such as self-tapping screws. Such an arrangement would provide a "thermal break" between the elements 12 and 13.

In a preferred example of the lintel the elements 12, 13 are secured in position relative to one another by an infill of thermally insulating material.

In the production of such a lintel elements 12 and 13 appropriate to the intended application of the lintel are placed in a mould or a jig which locates the two elements in the desired relative positions preferably with the overlapping flange portions 12, 13b slightly spaced apart. A synthetic resin material, in liquid form, is then introduced into the void defined between the web portions 12a, 13a and is caused, or permitted, to foam so filling the void and flowing into the space between the flange portions 12b, 13b. The synthetic resin material is then allowed, or caused, to cure or set thus defining a rigid, foamed, synthetic resin material infill bonded to the mutually presented surfaces of the web portions 12a and 13a and also to the flange portions 12b and 13b. The bonding of the synthetic resin infill to the elements 12, 13 provides a structrual interconnection between the elements.

Thus the lintel is capable of being handled as a unit.

Polyisocyanurate foams are currently considered to be the preferred infill material although it is possible that other foamed or foamable synthetic resin materials will prove suitable.

It will be recognised that since the infill (indicated in Figure 1 at 14) is rigid and is bonded over a large surface area to both of the elements 12 and 13, then in addition to securing the elements 12 and 13 together the infill material 14 provides structural strength. It follows that for a given load bearing capacity thinner gauge material can be used for the elements 12, 13 since a proportion of the bearing capability of the lintel is derived from the rigid, thermally insulating, infill 14. The spacing of the flange portions 12b, 13b is not essential, but it is desirable since it provides the above mentioned "thermal break" between the elements 12, 13.

It will be recognised that it is not essential to tack weld or otherwise interconnect the flange portions 12b, 13b since in the finished lintel the elements 12, 13 are secured in position relative to one another by the infill material. However, it may be convenient to tack weld or otherwise secure the flange portion 12b to the flange portion 13b to facilitate handling of the elements 12, 13 when introducing them into the mould or jig.

There are a number of ways in which the exterior surfaces of the elements 12, 13 may be protected against corrosion. For example, the surfaces of the elements 12, 13 may be galvanised prior to introduction of the infill 14, or the exposed surfaces after introduction of the infill may be coated with an appropriate corrosion resistant paint. However, it is preferred to provide the exterior of the lintel with a skin of synthetic resin material which bonds to the outer surfaces of the elements 12, 13 and also to the exposed end surface of the infill 14. A convenient coating material is the same polyisocyanurate foam which is used for the infill 14, but since the flange portions 12c, 13c are to be directly load bearing it is desirable that the polyisocyanurate foam skin has a greater density than the infill 14 so as to be resistant to crushing in use.It is probable that the skin (shown at 15 in the drawings) will not be applied during the same operation in which the infill 14 is introduced into the void between the elements 12, 13, and will probably be applied subsequently in a spraying operation. However, if the chosen infill material has a "self-skinning" capability then it may be possible to mould the skin 15 around the elements 12, 13 at the same time that material is introduced in the void to constitute the infill 14.

It will be recognised that the end of the lintel seen in Figure 2 is a cut end since normally the elements 12, 13 would not be visible. The skin 15 is sufficiently rough in texture on the lower face of the flange portions 12, 13e to provide a key for plaster or other finishing materials.

The production of the elements 12, 13 by roll forming permits the incorporation of ribs in the web portions and/or the flange portion if desired. Such ribs could be incorporated to enhance the rigidity of the lintel, and additionally would provide a mechanical keying action between the rigid infill 14 and the elements 12, 13.

If desired the free edge of the flange portion 13c which will be at the outermost edge of the outer leaf of the wall in use, may be turned downwardly to faciliate shedding of rain in use.

Figures 3a to 3i illustrate diagrammatically alternative shapes for the element 13 and it will be recognised that similar variants of the elements 12 are also possible. It is not essential that a given element 13 from the range illustrated is associated with the equivalent element 12 and lintels can be produced using a wide range of alternative element shapes preferably with the bonded, moulded in situ infill and skin 15 described above.

Figures 4a to 4e illustrate variants of Figures 1 and 2 all using the basic Z-shaped elements 12 and 13 again preferably with the bonded, moulded in situ infill 14 and skin 15. The lintels of Figures 4h and 4i are similar to those of Figures 4f and 4g except in that the uppermost flanges of the elements are inclined rather than parellel in relation to the lowermost flanges of the elements. Moreover, in Figures 4g and 4i the upturned portion of the top flange of one of the elements is extended, and the extended portion is bent obliquely to form a stiffening formation, and also to assist in deflection of moisture within the wall cavity in use towards the outer leaf of the wall. The strength of such lintel constructions permits the use of relatively thin metal in the formation of the elements 12, 13, for example mild steel sheet of the order of 1.6 mm thickness may be used in some applications.

Figure 5 is a view similar to Figure 1 illustrating a different configuration of elements 12, 13. The webs 12a, 13a are formed with respective longitudinal ribs 17 to enhance their strength and if desired the ribs 16 could be incorporated. The flange 12c is longitudinally corrugated both to increase its rigidity (resistance to transvere bending) and to provide an irregular surface to act as a plaster key in use. The lower surface of the infill 14 is ridged also to provide a plaster or mortar key.

Claims (8)

CLAIMS:

1 A lintel comprising first and second, elongate, sheet metal elements, each element having a generally planar web portion and integral therewith first and second generally planar flange portions, said first flange portion of each element lying perpendicular to the respective web portion and said first and second flange portions of each element extending respectively in opposite direction from respective opposite longitudinal edges of the respective web portion, said first and second elements being positioned with their web portions parallel and spaced by a predetermined distance with said first flange portions extending in directions away from one another, said first and second elements being secured in position relative to one another.

2 A lintel as claimed in Claim 1 wherein the first and second elements are secured in position relative to one another by welding together of said first flange portions.

3 A lintel as claimed in Claim 1 wherein the first and second elements are secured together by a rigid, foamed, synthetic resin material infill in the void defined between the web portions of the two elements, said infill being bonded to the first and second elements.

4 A lintel as claimed in Claim 3 wherein the first flanges are welded together to locate the first and second elements in a predetermined relative positions prior to introducing the synthetic resin material infill.

5 A lintel as claimed in Claim 3 or Claim 4 wherein said infill is moulded onto said elements.

6 A lintel as claimed in any one of Claims 1 to 5 wherein exposed surfaces of the first and second elements are coated with a skin of synthetic resin material.

7 A lintel as claimed in Claim 6 wherein said skin is formed from the same synthetic resin material as the infill, but of greater density.

8 A lintel substantially as hereinbefore described with reference to any one of the accompanying drawings.