WO1992011422A1

WO1992011422A1 - Lintel

Info

Publication number: WO1992011422A1
Application number: PCT/GB1991/002230
Authority: WO
Inventors: William Lowes; Anthony John Pensom
Original assignee: Birtley Building Products Limited
Priority date: 1990-12-20
Filing date: 1991-12-16
Publication date: 1992-07-09
Also published as: GB9312664D0; GB2271367B; GB9027744D0; GB2271367A; ZA914069B

Abstract

A lintel of a 'top hat' type made from a single metal member having an outer flange (11), an upright outer face elements (16), a steeply upwardly inclined cavity element (18), an upright inner face element (17), and an inner flange (13), the lintel having a foam (20) such as a self-skinning polyurethane foam formed within its interior. The foam (20) is contiguous with the flanges (11 and 13) at the downwardly facing opening of the space (19) so as to form a key for direct application of mortar or plaster in use. Keying formations may be moulded onto the foam or its skin may be scored or cut off to reveal open cell structure and assist keying.

Description

LINTEL

This invention relates to a lintel.

For efficiency in bricklaying, it is desirable for a lintel for use in cavity walls to be capable of use without interrupting the coursing of masonry in the inner or outer leaf. Lintels of the so-called "top hat" type are therefore used, consisting of a first, outer flange adapted to support the outer leaf masonry, a second, inner flange adapted to support the inner leaf masonry, and a cavity-bridging web portion projecting upwardly between the first and second flanges.

However, conventional "top hat" lintels have certain disadvantages, including the need to use a damp-resisting membrane or dpc, which is laid separately over the lintel, to shed water in the cavity towards the outer leaf. The dpc also protects the lintel from the effects of mortar build-up in the construction of masonry courses above the lintel. It would be desirable to be able to avoid using a separate dpc but this has hitherto not been possible while meeting the requirements of building regulations

There is a trend towards the use of cavity wall insulation as standards of building improve. The problem of cold-bridging can then occur due to conduction through the lintel so it has been proposed to use insulation within the lintel web in an attempt to reduce this bridging.

It is an object of the present invention to provide a new or improved lintel of the "top hat" type and a method of making such a lintel, with a view to overcoming or reducing these disadvantages.

From a first aspect, the invention υrovides a lintel comprising a first, outer flange, adapted to support an outer leaf of masonry; a second, inner flange adapted to support an inner leaf of masonry; and a cavity-bridging member defining a downwardly open space within the cavity-bridging member, said space being at least substantially filled with a foamed synthetic plastics insulation material foamed in situ, said foam being contiguous with the first and second flanges at the downwardly facing opening of said space to form a key for the application of mortar or plaster.

The cavity-bridging member may comprise an upright outer face element, and upright inner face element, and a steeply upwardly-inclined cavity element integrally connected between the outer and inner face elements.

The foam may comprise a polyurethane foam. Where the foam is a self-skinning polyurethane foam, the surface may be cut off at said opening to reveal open cell structure of the foam. Alternatively, the foam may be scored to reveal open cell structure. As a still further alternative, or in addition, the foam may be formed with mechanical keying formations.

The foam may be protected before use by a coating of a water resistant or damp-proofing material such as a paint or tape.

The lintel may include one or more spacers extending across the space within the lintel. It may also or alternatively include a pair of end closure plates disposed wholly within said downwardly open space.

Viewed from a further aspect, the invention provides a method of making a lintel of the "top hat" type, the method comprising the steps of constructing a metal lintel body having a first, outer flange, adapted to support an outer leaf of masonry, a second, inner flange adapted to support an inner leaf of masonry and generally aligned with said first flange, and a cavity-bridging member defining a downwardly open space within the cavity-bridging member; and forming in situ in said space a foamed synthetic plastics insulation material foamed so as at least substantially to fill said space, said foam being contiguous with the first and second flanges at the downwardly facing opening of said space to form a key for the application of mortar or plaster.

The cavity-bridging member may have an upright outer face element, an upright inner face element and a steeply upwardly- inclined cavity element integrally connected between the outer and inner face elements.

The foam may comprise a polyurethane foam and may be formed in situ by curing a mixture of an isocyanate and a polyol.

The curing may take place at a temperature of between 25 and 45 degrees Celsius and preferably at 35 degrees Celsius.

The lintel body may be hot-dip galvanised before the formation of the foam, and may be partly cooled towards ambient temperature to achieve the optimum curing temperature before foam formation.

A closer plate may be positioned over the inverted lintel body to cover the foam during formation and may be provided with mechanical key-defining formations whereby the foam, when it expands during curing, takes on the form of the closer plate.

The closer plate may be treated with a release agent such as a wax or grease before foam formation.

Where the foam is a self-skinning polyurethane foam, the method may include the further step of cutting off the surface skin at said opening to reveal open cell structure of the foam. Alternatively, it may include the step of scoring the foam to reveal open cell structure. A lintel embodying the invention, and a method of manufacture will now be described in more detail by way of example only with reference to the accompanying drawings in which:-

FIGURE 1 is a sectional view of a lintel in use in a cavity wall.

Referring to the drawing, a lintel generally indicated at 10 comprises a first, outer flange 11, adapted to support an outer leaf 12 of masonry; a second, inner flange 13 adapted to support an inner leaf 14 of masonry and generally aligned with the first flange 11 and a cavity-bridging member generally indicated at 15 having an upright outer face element 16, an upright inner face element 17, and a steeply upwardly- inclined cavity element 18, integrally connected between the outer and inner face elements 16 and 17, so as to define a downwardly open space 19 within the cavity-bridging member 15. This space 19 is at least substantially filled with a foamed synthetic plastics insulation material 20 foamed in situ, the foam being contiguous with the first and second flanges 11 and 13 at the downwardly facing opening of the space 19 to form a key for the application of mortar or plaster.

The lintel body is made of sheet steel in generally known manner and is hot dip galvanised for corrosion protection. The lintel body is shaped so as to require no separate dpc. The steeply inclined portion bridging the cavity has a depth of more than 100 mm and an angle of inclination of typically 25 degrees or less for 50mm cavity wall^'s, and 25 to 40 degrees for wider cavities of 70mm or 100mm. Thus, any moisture in the cavity is diverted outwardly towards the outer leaf and can be shed from a drip formation on the outer edge of the first flange 11. Mortar falling within the cavity from upper levels cannot build up sufficiently to fill the space on the outer side of the cavity bridging member of the lintel and cause inward water penetration. It will be seen that the lintel insulation greatly resists heat transfer through the body of the lintel and leaves only the relatively long conduction path through the metal itself, except in small localised regions where the front and back of the lintel are attached by spacers (not shown) for rigidity. The cavity can be insulated in any desired manner, either by the use of foam formed in situ, by slab insulation or by granular insulation fed into the cavity. It is possible to insulate the entire cavity space right up to the lintel.

The foam has been found to provide an excellent plaster key. The surface reveals the open cell structure to which the plaster is keyed. For a self-skinning polyurethane foam, it may be necessary to score or scrape the foam surface 21, for example with a trowel when applying the plaster, or the surface layer can be trimmed off in manufacture. Alternatively the surface may be cut off as a manuf cturing operation. It may then be protected by means of a water- resistant layer of paint or tape for example, to avoid water penetration on site, before the lintel is put in place.

The foam is formed by mixing a polyol and an isocyanate and introducing the mixture into the inverted lintel body. Where the lintel body has been hot dip galvanised, the metal can be partially cooled towards ambient temperature to the region of 25 to 45 degrees Celsius, and preferably to 35 degrees Celsius, at which temperature rapid and complete curing takes place, resulting in excellent adhesion to the metal body. The quantity of foam can be calculated to fill, or substantially fill the space within the lintel, possibly with some slight overflow, to be removed after curing to provide an open cell structure at the surface as described.

The foaming process may be carried out automatically on a production line in which close control of temperature is achieved using heating and cooling zones to ensure optimum foam formation. The foam formation may be contained within the lintel body firstly by a pair of end plates (not shown) , which are localised within the space 19 and prevent foam from being lost at the ends of the lintel. The end plates also perform a strengthening function, resisting crushing and/or buckling of the lintel.

Foam formation may also be contained by a closer plate, which can have mechanical keying formations on its surface, to be impressed in the eventual surface of the foam plaster key. The closer plate may also serve to control the density of the foam. A release composition such as a wax or grease is used on the closer plate to enable it to be removed after curing of the foam.

The closer plate can be extended over the underside of the inner flange 13 to form a foam skin on this flange to act as a plaster key. This obviates the need to provide a metal lathing or punched metal key, reducing both metal requirement and weight. This skin will also provide a very effective barrier against potential cold bridging by maintaining a thermal break between the lintel and the fabric of the wall and/or plaster.

Claims

1. A lintel (10) comprising a first, outer flange (11) adapted to support an outer leaf (12) of masonry; a second, inner flange (13) adapted to support an inner leaf (14) of masonry; and a cavity-bridging member defining a downwardly open space within the cavity-bridging member (15) , characterised in that said space (19) is at least substantially filled with a foamed synthetic plastics insulation material (20) foamed in situ, said foam (20) being contiguous with the first and second flanges (11,13) at the downwardly facing opening of said space to form a key for the application of mortar or plaster.

2. A lintel according to claim 1 f rther characterised in that the cavity-bridging member (15) comprises an upright outer face element (16), an upright inner face element (17) and a steeply upwardly-inclined cavity element (18) integrally connected between the outer and inner face elements.

3. A lintel according to Claim 1 or Claim 2 f rther characterised in that the foam (20) comprises polyurethane foam.

4. A lintel according to Claim 3 further characterised in that said polyurethane foam (20) is of a self-skinning type.

5. A lintel according to Claim 4 further characterised in that the surface (21) of the self-skinning polyurethane foam (20) is cut off at said opening to reveal open cell structure of the foam.

6. A lintel according to Claim 4 further characterised in that the surface (21) of said self-skinning polyurethane foam is scored at said opening to reveal open cell structure.

7. A lintel according to any preceding Claim further characterised in that the foam (20) is provided with mechanical keying formations at said downwardly facing opening.

8. A lintel according to any preceding Claim and further characterised in that it includes one or more spacers extending across the space within the lintel (10).

9. A lintel according to any preceding Claim further characterised in that a pair of end closure plates are provided disposed wholly within said downwardly open space at end portions of said lintel (10).

10. A lintel according to any preceding Claim and further characterised by having removable protection means comprising a coating of water resistant or damp proofing material such as a paint or tape.

11. A method of making a lintel of the "top hat" type, the method comprising steps of constructing a metal lintel body having a first, outer flange (11) , adapted to support an outer leaf (12) of masonry, a second, inner flange (13) adapted to support an inner leaf (14) of masonry and generally aligned with said first flange (11), and a cavity-bridging member (15) defining a downwardly open space (19) within the cavity- bridging member (15) ; characterised in that it includes the step of foaming in situ in said space (19) a foamed synthetic plastics insulation material (20) foamed so as at least substantially to fill said space (19), said foam (20) being contiguous with the first and second flanges (11,13) at the downwardly facing opening of said space (19) to form a key for the application of mortar or plaster.

12. A method according to Claim 11 further characterised in that the cavity-bridging member (15) has an upright outer face element (16), an upright inner face element (17) and a steeply upwardly-inclined cavity element (18) integrally connected between the outer and inner face elements.

13. A method according to Claim 11 or Claim 12 further characterised in that the foam (20) comprises a polyurethane foam.

14. A method according to Claim 13 further characterised in that said polyurethane foam (20) is formed in situ by curing a mixture of an isocyanate and a polyol.

15. A method according to Claim 14 further characterised in that said curing takes place at a temperature of between 25 and 45 degrees Celsius.

16. A method according to Claim 15 further characterised in that said curing takes place at 35 degrees Celsius.

17. A method according to any one of Claims 11 to 16 further characterised in that the lintel body is hot-dip galvanised before the formation of the foam.

18. A method according to Claim 17 further characterised in that the lintel body is partly cooled towards ambient temperature to achieve an optimum curing temperature before foam formation.

19. A method according to any one of Claims 11 to 18 further characterised in that a closer plate is positioned over the inverted lintel body to cover the foam during formation.

20. A method according to Claim 19 further characterised in that the cover plate is provided with mechanical key-defining formations whereby the foam, when it expands during curing, takes on the form of the closer plate.

21. A method according to Claim 19 or Claim 20 further characterised in that the closer plate is treated with a release agent such as a wax or grease before foam formation.

22. A method according to any one of Claims 13 to 21 further characterised in that the polyurethane foam is a self-skinning polyurethane foam and the method includes the further step of cutting off the surface skin (21) at said opening to reveal open cell structure of the foam.

23. A method according to any one of Claims 13 to 21 further characterised in that said polyurethane foam is a self- skinning polyurethane foam and the method includes the further step of scoring the foam at said opening to reveal open cell structure.