GB2217360A

GB2217360A - Lintels with plaster keys

Info

Publication number: GB2217360A
Application number: GB8908472A
Authority: GB
Inventors: John Plunkett Coyle; Seamus Mcaleer; Eamonn Laverty
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-04-20
Filing date: 1989-04-14
Publication date: 1989-10-25
Anticipated expiration: 2009-04-14
Also published as: GB8809324D0; GB8908472D0; GB2217360B

Abstract

In a channel section lintel comprising an inverted channel portion 10 and first and second laterally extending leaves 12, 14 a plaster key 24 is retained in position by having a portion 26 bent so as to extend into the interior of the channel portion 10 and embedded in a filling of foamed plastic material 22, preferably polyurethane, timber blocks are embedded in the plastic filling, and the plaster key affixed thereto. The density of the foamed filling may be controlled to enhance the structural properties of the lintel, as well as providing thermal insulation. <IMAGE>

Description

"IMPROVEMENTS IN OR RELATING TO LINTELS" The present invention relates to lintels for use in bridging openings such as doors or windows in cavity walls and is particularly, but not exclusively, concerned with pressed-metal, channel-section lintels having a foamed plastic filling.

Sheet metal lintels require a "plaster key" of expanded metal mesh or similar to be affixed to any surfaces to which plaster or the like is to be applied in order to ensure proper adhesion of the plaster. A typical channel section lintel comprises an inverted channel portion having first and second substantially horizontal leaves extending outwardly from the free edges of the channel, and a plaster key affixed to the underside of at least one of said leaves. The plaster key can be fixed to the leaf by a number of means such as spot welding, stapling to a timber spacing member wedged into the channel (as disclosed in UK Patent No 1566160) or by having a free edge thereof inserted into a slot formed in the underside of a cast plastics spacer member located in the channel (as disclosed in UK Published Patent Application No 2110262A).

All of these methods require the plaster key to be applied and fixed in an extra process step bnce the lintels is substantially complete, and/or require the use of specifically shaped and dimensioned components, thus adding to the expense of the finished article.

It is an object of the present invention to obviate or mitigate these disadvantages of existing lintels.

Accordingly, the present invention provides a lintel comprising a central, inverted channel portion having first and second laterally extending leaves projecting outwardly therefrom and having a plaster key located adjacent the underside of at least one of said leaves, said channel portion being at least partially filled with foamed plastic material, and wherein c said plaster key is secured to the lintel by means of at least one member embedded in and retained by said foamed plastic material.

In a preferred embodiment, said member comprises a portion of said plaster key shaped so as to extend into the interior of said channel portion.

Alternatively, said at least one member may comprise a plurality of timber blocks located at intervals along the open end of said channel portion, said plaster key being secured to said blocks.

The foamed plastic material may be of sufficient density to resist inward deformation of the side walls of said channel portion, and may also be a thermally insulating material.

It is particularly preferred that the foamed plastic material is a polyurethane foam.

According to a second aspect of the invention, a method of forming a foamed plastics filling in, and attaching a plaster key to a channel section lintel having a central, inverted channel portion and first and second laterally extending leaves, comprises the steps of inverting the lintel, locating at least one member to which a plaster key is or may be attached in the opening of said channel portion, and introducing a foaming plastics material into said channel portion such that it expands to surround said at least one member.

In a preferred embodiment, said member comprises a portion of said plaster key, and the plaster key is located on the lintel with said portion thereof extending into the interior of said channel portion prior to the introduction of said foaming plastic material.

Alternatively, said at least one member comprises a plurality of timber blocks located at intervals along the length of said channel portion, and wherein the plaster key is affixed to said blocks once said foaming plastic material has set.

Preferably, the expansion of said foaming plastic material is controlled such that the density of the foamed plastic material is sufficient to resist inward deformation of the side walls of said channel portion.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is an end view of a lintel embodying the invention; and Fig. 2 is an end view of an alternative lintel construction embodying the invention.

Referring now to Fig. 1 of the drawings, a lintel, formed from a single sheet of material, such as galvanized steel, comprises, in cross-section, an outer horizontal portion or leaf 12, a substantially parallel and co-planar inner horizontal portion or leaf 14, and a central channel portion 10 comprising outer and inner upwardly extending portions 16 and 18 connected to the innermost edges of the outer and inner horizontal portions 12 and 14 respectively, and an intermediate portion 20 interconnecting the upper edges of the upwardly extending portions 16 and 18.The outer upwardly extending portion 16 is of lesser height than the inner portion 18 so that the intermediate portion 20 is inclined upwardly from left to right in the drawings whereby an obtuse angle A is formed between the outer upwardly extending portion 16 and the intermediate portion 20 and an acute angle B between the inner upwardly extending portion 18 and the intermediate portion 20.

Furthermore, whilst the inner upwardly extending portion 18 is substantially vertical with respect to the inner horizontal portion 14, the outer upwardly extending portion 16 is disposed at an angle C, greater than 900, with respect to the outer horizontal portion 12 such that it is also inclined slightly towards the right in the drawings.

This sectional configuration ensures that when the lintel is in situ between the outer and inner skins of a cav L wall (not shown) the inner portion 18 of the channel 10 is flush with the inner skin of the wall whilst the surfaces of portions 16 and 20 slope downwardly toward the outer skin. Thus, any moisture deposited on the lintel, by condensation or otherwise, is directed toward the outer skin.

The channel portion 10 of the lintel is filled with a foamed plastic material 22 (preferably polyurethane foam), which adheres to the inner surfaces of portions 16, 18 and 20, and a plaster key 24, in the form of a sheet of expanded metal mesh or the like, is located on the underside of the inner leaf 14. The plaster key 24 is retained in position by having its inner edge 26 bent upwardly, so as to project into the interior of the channel portion 10, and embedded in the foamed plastic 22. The opposite edge 28 of the plaster key 24 is formed in a Ushape and engages the free edge 30 of the inner leaf 14 for additional security. The edge 28 may be a planar metallic strip formed integrally with the mesh of the plaster key 24, as shown, or the outer edge of the mesh may simply be folded around the free edge 30 of the leaf 14.

The foamed plastic filling is formed and the plaster key 24 secured by inverting the lintel, locating the plaster key 24 on the leaf 14 and introducing the foaming plastics material into the channel 10 in liquid form such that it subsequently expands to fill the channel 10 and surround the edge 26 of the plaster key 24. Simple mechanical means are required to close off the ends of the lintel and to restrain the upward expansion of the foam 22, and to retain the plaster key 24 in position so that it is not displaced by the expanding foam. The expansion of the foam may be controlled such that the filling is of sufficient density to assist in resisting inward deformation of the open end of the channel 10 in response to a vertical load applied to the leaves 12 and 14.The tensile strength and adhesion of the foam to the lintel will also assist in resisting outward deformation, and the mechanical properties of the foam may thus enhance the structural strength of the lintel. These aspects may be the primary consideration in the formation of the foam filling, with its thermally insulating properties being a secondary benefit.

The edge 26 of the plaster key 24 may project upwardly into the channel 10 at any point across its width and may extend vertically, as illustrated, or at an angle.

Plaster keys may be applied to either or both of the leaves 12 and 14 and the portion thereof embedded in the foam 22 may be a folded edge, as in this example, or a fold formed at an intermediate point in the plaster key. More than one foldXbent portion could be provided, possibly projecting into the channel 10 at differing angles.

The foamed plastic insulating filling is thus formed and the plaster key 24 secured in a single process step, thereby simplifying manufacture and reducing production costs. Polyurethane foam is particularly preferred since it is tenacious to metal surfaces prior to polymerization (or cross-linking), even when the surfaces are wet.

Fig. 2 of the drawings shows an alternative embodiment of the invention, wherein like parts are given the same reference numerals as in Fig. 1.

In the embodiment of Fig. 2 the bent portion 26 of the plaster key 24 is omitted, and the key 24 is attached, by means of staples or the like (not shown), to timber blocks 32 which are located at intervals along the open end of the channel 10. The blocks 32 are retained in position by the foamed plastic filling, and need not be wedged in any way into the channel 10.

The foamed plastic filling is formed, in this case, by inverting the lintel as before, placing the timber blocks 32 in the mouth of the channel 10 (where they are retained in position, temporarily, by virtue of the slightly convergent walls 16 and 18 of the channel 10), and introducing the foaming plastics material. Again, the expansion of the foam must be controlled (eg by means of a weighted lid applied to the up-turned base of the lintel), to prevent displacement of the blocks 32. Once the foam has set, the plaster key 24 may be applied to the lintel and stapled to the blocks 32.

The first embodiment of Fig. 1 is preferred, since it is simpler in practice, however the embodiment of Fig. 2 also offers advantages over prior art lintels since the design and manufacture of the basic lintel section does not need to take account of any deformation caused by the introduction and wedging of the timber blocks.

Claims

1. A lintel comprising a central, inverted channel portion having first and second laterally extending leaves projecting outwardly therefrom and having a plaster key located adjacent the underside of at least one of said leaves, said channel portion being at least partially filled with foamed plastic material, and wherein said plaster key is secured to the lintel by means of at least one member embedded in, and retained in position by said foamed plastic material.

2. A lintel as claimed in claim 1 wherein said member comprises a portion of said plaster key shaped so as to extend into the interior of said channel portion.

3. A lintel as claimed in claim 1 wherein said at least one member comprises a plurality of timber blocks located at intervals along the open end of said channel portion, said plaster key being secured to said blocks.

4. A lintel as claimed in any of claims 1 to 3, wherein an outer edge of the plaster key, remote from said channel portion, is shaped so as to engage the outer edge of the leaf adjacent to which it is located.

5. A lintel as claimed in any preceding claim, wherein said foamed plastic material is of sufficient density to resist inward deformation of the side walls of said channel portion.

6. A lintel as claimed in any preceding claim wherein said foamed plastic material is a thermally insulating material.

7. A lintel as claimed in any preceding claim, wherein said foamed material is a ployurethane foam.

8. A method of forming a foamed plastic filling in and attaching a plaster key to a channel section lintel having a central, inverted channel portion and first and second laterally extending leaves, comprising the steps of inverting the lintel, locating at least one member to which a plaster key is or may be attached in the opening of said channel portion, and introducing foaming plastic material into said channel portion such that it expands to surround said at least one member.

9. A method as claimed in c-laim 8, wherein said member comprises a portion of said plaster key, and wherein the plaster key is located on the lintel with said portion thereof extending into the interior of said channel portion prior to the introduction of said foaming plastic material.

10. A method as claimed in claim 8, wherein said at least one member comprises a plurality of timber blocks located at intervals along the length of said channel portion, and wherein the plaster key is affixed to said blocks once said foaming plastic material has set.

11. A method as claimed in any of claims 8 to 10, wherein the expansion of said foaming plastic material is controlled such that the density of the foamed plastic material is sufficient to resist inward deformation of the side walls of said channel portion.