GB2037857A - Lintels - Google Patents

Abstract

A steel lintel for a cavity wall has a box section and a flange (49) extending along it. The flange (49) projects at an angle from the front wall (48) of the box section and includes a first portion (50) which extends forwardly and downwardly with respect to the front wall (48) and a second portion (51) which lies in substantially the same plane as a base wall (44) of the box section. At least the second portion (51) of the flange is provided by a single layer of sheet steel. The flange can be integral with a portion of the box section or it can include a longitudinal tab portion welded to the front wall of the box section. The whole or a part of the flange can be made of sheet steel which differs from that used for a whole or a part of the box section. The optimum gauge of sheet steel can thus be selected for any part of the lintel. <IMAGE>

Description

SPECIFICATION Lintels The present invention relates to lintels for use in the building industry.

To support a wall or other building structure above an opening such as a window or door space a lintel of greater length than the width of the door or window is used as a bridge to span the space. Traditionally a baulk of timber was used to serve this purpose and in the course of time a solid block of concrete replaced the use of a timber beam. In the construction of a cavity wall having an outer skin and an inner skin it is known to combine a concrete lintel with a steel lintel, the concrete lintel spanning the opening at a position corresponding to the inner skin of the wall and supporting the steel lintel which extends forwardly to support the outer skin of the wall.It is also known to use a two-part steel lintel in which a part supporting the outer skin is supported by and welded to another part which is usually channel shaped and which is adapted to span the inner skin of the wall such that the channel can be filled in with brick or other block work to form a solid lintel to support the inner skin or other construction built above it. A more recent development has been to replace the channel shaped part by a hollow box section so that no filling in is required and the lintel can be easier to fit and lighter to handle. Various shapes of such box-type lintels are known from for example U.K. Patent Specifications 1 298 798, 1488121,1488 122 and 1 503491.

An advantage common to all the steel lintels mentioned is that the part supporting the outer skin can be in the form of a flange which in use lies in a horizontal plane and can be hidden in the first course of mortar laid above it as the start of the outer skin of the wall. The sometimes unsightly appearance in a finished building of a concrete lintel laid flush with the outer surface of the outer skin, but of a colour and texture different from the building material used for the outer skin, is thus avoided. The use of a steel lintel can thus permit the building material to start immediately above the opening in order to give the wall a uniform appearance.

A design of a steel lintel must be considered with regard to the load which it is to carry which is determined both by the width of the opening which it is to span and the building structure completed above it. Both the gauge of sheet metal comprising the lintel and the particular shape from which it is made can affect its strength.

It is an object of the present invention to provide an improved lintel having a box section. It is a further object of the present invention to provide a lintel having a box section at a reduced cost.

According to the present invention there is provided a steel lintel suitable for use in a cavity wall the lintel having a box section and a flange extending longitudinally therealong wherein the box section is adapted to support an inner skin and has a top wall, a base wall substantially parallel to the top wall, a rear wall and a front wall and the flange projects at an angle from the front wall of the box section and includes a first portion which extends forwardly and downwardly with respect to the front wall and a second portion which lies in substantially the same plane as the base wall of the box section, the second portion providing a surface adapted to support an outer skin and being provided by a single layer of sheet steel.

Preferably the first portion of the flange is adjacent the box section and the second portion of the flange is adjacent the first portion. The layer of steel providing a part or a whole of the flange may have a gauge different to that employed for forming a part or a whole of the box section.

A lintel embodying the present invention can thus, in some instances, advantageously be made from a number of lengths of sheet steel bent and welded together in which the different lengths are of a different gauge. Different parts of the lintel are required to carry different loads. By selecting the optimum gauge of steel for each particular part according to the weight which it has to bear a minimum amount of steel can be used and hence the cost of the material comprising the lintel can be reduced to a minimum. For example, the box section can be made of sheet steel of one gauge and the whole of the flange from sheet steel of another gauge.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, wherein: Fig. 1 shows in end view a first embodiment in situ; Fig. 2 is an end view of a lintel in situ which is similar to that illustrated in Fig. 1, but has a box section of a different construction; Fig. 3 illustrates in situ a second embodiment in end view; Fig. 4 shows an end view of a third embodiment in situ and; Fig. 5 illustrated in situ a modification of the embodiment of Fig. 4.

Referring firstly to Fig. 1, a box section 1 of a lintel 2 which is shown in situ in a cavity wall 60 having an outer skin 61 and an inner skin 62 comprises: a channel section 3 which provides a top wall 4, a front wall 5, and a base wall 6; and a rear section 7 which provides a rear wall and longitudinally extending tab portions 8 which are welded to the channel section 3 at 9. A flange 10 extends longitudinally of the box section 3 and comprises a single layer of sheet metal bent along its length at three places. The flange 10 thus has four longitudinally extending portions: a tab portion 11 welded to the front wall 5 of the box section 1, a downwardly and forwardly projecting portion 12, a horizontal portion 13 disposed in the same plane as the base wall 6 and a lip portion 14.

To make the lintel, pieces of sheet steel of the appropriate gauge and size are selected for each part and bent longitudinally to the required shape.

Oblique angle a at which the sloping portion 12 extends away from a vertical portion of the front wall 5 extending above the flange can be chosen having regard to a width of the horizontal portion 13 and the load which it will have to bear and is, as in the present example, suitably 135 . To assemble the various pieces of the lintel the flange 10 is first positioned against the front wall 5 of the channel section 3 and then the longitudinal tab portion 11 is welded thereto.

Secondly the rear portion 7 is positioned within the channel section 3 and welded thereto to complete the box lintel.

In use a lintel is selected of greater length than the width of the opening to be spanned. The overlap required at each end of the opening must be sufficent to ailow the lintel to be firmiy lodged in place. The amount of overlap depends on the length of the lintel but can suitably be of the order of 1 50 mm. at each end. In spanning the opening the lintel is positioned so that the box section 1 rests on parts of an inner skin of the cavity wall adjacent the opening and the flange 10 must be such that the portion 12 lies within the cavity so that the portion 13 can extend forwardly to lie at each end on parts of an outer skin adjacent the opening and for the rest of its length in a position to support the outer skin 61 to be built above the opening.The combined width of the horizontal portion 13 and the lip portion 14 of the flange 10 is preferably such that in the finished building the flange does not project beyond an outer surface of the wall. Portion 13 can thus be embedded in a course of mortar (not shown in Fig. 1) laid above the lintel and be hidden from sight. According to conventional practice drainage holes can be provided in this layer of mortar above the flange to permit moisture in the cavity wall which has run down the sloping portion 12 to escape through the holes and over the lip portion 14.

The size of the lintel and the gauge of sheet steel from which it is made are chosen according to the span which it has to bridge and the load which it has to bear. As an example a window 1050 mm. wide in the ground floor of a twostorey house could on average be called upon to support a maximum load of 2 tons. Conveniently the gauge of steel from which the flange is made is greater than that of the steel providing the box section so that a sufficiently strong cantilever is provided for the outer skin by a single layer of steel. For the example given above sheet steel of 2.5 mm thickness can suitably be used for the flange 10 and 2 mm. thick sheet steel for the box section 1.

The height of the lintel can be chosen to correspond to, for example, two or three units of building blocks and their associated layers of mortar so that the continued building of both the inner and outer skins is not disjointed at the ends of the lintel. The span of the flange portion 12, and hence its height of attachment to the front wall 3 assuming the angle of a is 135 , is to some extent determined by the cavity of the wall.

It cannot be more than the width of the cavity, but it may be less if either or both the horizontal portion 13 and part of the front of the box section 1 lies within the cavity.

Conveniently, as is well known, keying elements 18, such as expanded metal mesh, can be placed along faces of the lintel to which plaster is to be applied to provide a broken surface on which to key the plaster.

The lintel shown in Fig. 2 is a variation of that illustrated in Fig. 1. The only difference resides in the construction of the box section 1. Instead of a channel section 3 and a rear portion 7 two Lsection parts 1 5 and 1 6 are fitted together and welded at 1 7. Preferably the flange 10 is secured to the front wall 5 before the box is assembled for ease of welding of these two parts. The reference numerals included in Fig. 2 are the same as those used in Fig. 1 where they represent like parts. The same considerations of manufacture and use apply to the lintel of Fig. 2 as those described for the lintel of Fig. 1.

Referring now to Fig. 3 a fivesided box section 20 is made up of two parts: a channel section 21 and a rear section 22, the channel section 21 providing a base wall 23, a sloping portion 24, a front wall 25 and a top wall 26 parallel to the base wall 23. A flange 27 extends longitudinally of the box section 20 and comprises, as in the embodiment illustrated in Fig. 1, a single layer of sheet metal bent along its length at three places to provide a tab portion 28, a downwardly and forwardly projecting portion 29, a horizontal portion 30 and a lip portion 31. The tab portion 28 is welded to the front wall 25 of the box section 20 at such a height and the portion 29 chosen to project at such an angle that the horizontal portion 30 lies in substantially the same plane as the base wall 23 and provides a surface for supporting the outer skin 61.The rear section 22 is welded to the channel section 21 at tab portion 32, 33 preferably after the flange has been joined to the channel section so that welding of the tab portion 28 can be carried out before the box is completed. As above keying elements 34 can be provided.

The same considerations of manufacture and use with regard to the present lintel apply as for those mentioned for the lintel of Fig. 1. As can be seen from Fig. 3 however the box section 20 is wider than box section 1 and in use extends into the cavity of the cavity wall 60.

Referring now to Fig. 4 a five-sided box section 40 is provided by three members 41, 42 and 43.

Member 42 is of the same shape as section 22 in Fig. 3 and provides a rear wall for the box section 40 and backwardly extending tab portions for welding member 42 to members 41 and 43 respectively. Member 43 provides a horizontal base wall 44, a sloping portion 45 and a tab portion 46 for welding to member 41. Member 41 provides horizontal top wall 47 parallel to the base wall 44, a vertically extending front wall 48 and an integral flange 49. As in the embodiments illustrated in Figs.1,2 and 3 respectively the present flange has a portion 50 projecting downwardly and forwardly from the front wall 48, a horizontal portion 51 in substantially the same plane as the base wall 44 and a downwardly turned lip portion 52.As in the embodiment illustrated in Fig. 3, the present lintel thus includes an inverted "V" shaped longitudinal groove in its underside, the groove being formed between a lower surface of the portion 50 of the flange and the portion 45 of the box section lying between the base wall 44 and the junction of the flange with the box section. As above, keying elements 53 are provided.

The width of box section 40 is such that in use as shown in Fig. 4, and as with the lintel illustrated in Fig. 3, it extends about half way across the cavity of the cavity wall 60. In both Figs. 3 and 4 it can be seen that both sloping portions 29, 24 and 50, 45 of each lintel respectively lie within the cavity and have no brick or other block work forming either the inner skin 62 or the outer skin 61 placed vertically above them.

A modification of Fig. 4 is illustrated in Fig. 5 in which sloping portion 45 is omitted as member 43 is formed as a right-angled section to provide a rectangular box section 40. The box section of Fig. 5 is of narrower width than that of Fig. 4 and only extends a short way into the cavity. As a consequence sloping portion 50 of the flange 49 which is integral with the front wall 41 of the box section is of a greater length than its counterpart in Fig. 4 in order to span the cavity.

The same criteria of width of opening which the lintel has to span and the load which it has to carry as discussed above must be taken into account in the design of the lintel of Fig. 4 or Fig.

5. One particular use of these lintels having integral top and front walls and flange is found in spanning openings of widths greater than about 4200 mm. In such cases the load borne by the lintel, especially that borne by the flange portion, is distributed along its length to such an extent that member 41 can be made of sheet steel of a gauge less than that required for members 43 and 42. As an example, to span an opening of 4200 mm. in the ground floor of a two-storey house a steel lintel can be expected to bear a load of the order of 3 tons and sheet steel of a thickness 3 mm. can be used for the member 41, and of 4 mm. for members 42 and 43.

Each of the box lintels described above can be designed to match an individual requirement.

Alternatively, or as well as, for each embodiment of lintel a range of lintels can be manufactured and stocked varying in, for example, length, height, overall width, steel gauge of flange portion, etc., in order to supply a builder's requirements in constructing a building with standard sized windows and doorways and a recognised cavity width.

Each of the lintels described herein is preferably protected from corrosion and hence potential failure in its capacity to carry the load for which it has been designed. To give the lintel a life of about 60 years, a length of time comparable with the expected life of the building in which it is to be used, the complete lintel after having been assembled from its respective parts by bending and welding can be hot dipped galvanised to provide a covering of zinc inside and out to the requirements of British Standard Specification 729. The use of pre-galvanised sheet metal in manufacturing the lintel is not recommended. At each bend imparted to the lintel in its manufacture the layer of zinc, both on the inside and the outside of the bends, can become cracked and will provide no protection from rusting to the lintel in use.In addition the layer of zinc will be damaged at the weld points and will not necessarily repair itself.

The present invention can thus provide a steel lintel whose design can either be manufactured to a particular customer's requirements or be mass produced in standardised sizes using in either case an optimum amount of steel to reduce the cost of the finished product. The embodiments illustrated in the accompanying drawings and described herein exemplify the versatility in design which can be incorporated in the present lintels. For example, the embodiments illustrated in Figs. 1 and 2 respectively show that the strength of the flange due to the gauge of the steel from which it is made can be chosen independently from the construction of the box section. All known prior art box lintels have been restricted in design to a box section of sheet steel of a certain gauge from which a double layer of sheet steel has to be arranged to project in order to form a flange of sufficient strength to support, for example, the continued building of the outer skin of a cavity wall.

Claims (12)

Claims

1. A steel lintel suitable for use in a cavity wall the lintel having a box section and a flange extending longitudinally therealong wherein the box section is adapted to support an inner skin and has a top wall, a base wall substantially parallel to the top wall, a rear wall and a front wall and the flange projects at an angle from the front wall of the box section and includes a first portion which extends forwardly and downwardly with respect to the front wall and a second portion which lies in substantially the same plane as the base wall of the box section, the second portion providing a surface adapted to support an outer skin and being provided by a single layer of sheet steel.

2. A lintel according to claim 1 wherein the first portion of the flan6b' is adjacent the box section.

3. A lintel according to claim 2 wherein the second portion of the flange is adjacent and integral with the first portion.

4. A lintel according to any one of claims 1 to 3, wherein at least the second and the first portions of the flange are provided by a single layer of sheet steel.

5. A lintel according to any one of claims 1 to 4, wherein the layer of steel providing a part or a whole of the flange has a gauge different to that employed for forming a part or a whole of the box section.

6. A lintel according to any one of the preceding claims wherein the front wall of the box section includes a vertical portion extending above the flange, the first portion of which makes an angle of 1 35C therewith.

7. A lintel according to any one of the preceding claims including an inverted "V" shaped longitudinal groove in its underside, the groove being formed between a lower surface of the first portion of the flange and a portion of the box section lying between the base wall of the box section and the junction of the flange with the box section.

8. A lintel according to any one of the preceding claims wherein a longitudinal tab portion of the flange is welded to the front wall of the box section.

9. A lintel according to any one of claims 1 to 7 wherein the flange is integral with a longitudinal portion of the front wall of the box section.

10. A lintel according to claim 9 wherein the said portion of the front wall is integral with the top wall of the box section.

11. A lintel according to any one of the preceding claims wherein the lintel once formed is hot dipped galvanised.

12. A steel box lintel substantially as herein described with reference to any one of Figs. 1 to 5 of the accompanying drawings.