GB2079812A - Lintel - Google Patents

Abstract

A lintel is made up of a pair of elongate L or lazy Z cross-section rolled or pressed sheet metal members, (11, 12) secured by fasteners such as nails or screws (21, 22) to opposed sides of an incompressible spacer block (19). Where the sheet metal members of of lazy Z cross- section, their top flanges (13, 14) overlap and are secured to the block (19). The block may be recessed at the foot (27) of the lintel to receive a head of a window frame. The spacer block may be continuous or made up in a number of pieces which may be separated. Different widths of lintel may be obtained by using different spacer blocks (see dashed line 12 a). <IMAGE>

Description

SPECIFICATION Lintel This invention relates to lintels for buildings, which are intended to bridge a gap in a wall and support masonry above the gap, and such floor and roof loads as are imposed directly or indirectly on the lintel.

Commonly used lintels are usually either of reinforced concrete or are prefabricated boxsection structures of galvanised steel sheet.

The former have the disadvantages of being very heavy to handle on site and being prone to accidental damage if dropped. The latter, being fabricated by welding, may not be satisfactorily protected against long term corrosion because of the difficulty of maintaining the galvanic coating at the welds.

It has also been proposed to form a nonwelded galvanised metal lintel in the form of a "top hat" section. Such lintels are generally regarded as unsatisfactory except for bridging relatively short gaps and carrying relatively light loads. This is the case because the neutral axis of the section used for the determination of strength characteristics is too close to the lower flanges, leading to low strength to weight ratio. Also where both the lower flanges of the top hat section are loaded, there is a tendency for the mouth of the top hat section to close and the flanges to sag. It is also difficult to form a section of sufficient depth and of sufficiently thick gauge metal to support the loading likely over a long gap.

It is an object of the present invention to provide a new or improved lintel overcoming or reducing these disadvantages.

According to the invention there is provided a lintel comprising a pair of sheet metal members each having, in use, a generally vertical web and a generally horizontal flange extending from, or from near, the foot of the web, the lintel further comprising a substantially incompressible spacer block having a cross-section which is bounded by a rectangle (as herein defined), the webs of the sheet metal members being secured to opposed faces of the spacer block by fasteners with the flanges extending away from each other.

The flanges may be generally co-planar.

The spacer block may be arranged so as not to project, in use, below the flanges.

The spacer block may be off-set upwardly from the flanges so that a recess is provided between the feet of the webs.

The spacer block may extend throughout the length of the lintel. Alternatively, a plurality of spacer blocks may be provided along the length of lintel. The spacer blocks may be spaced apart.

The or each spacer block may be made of wood.

The fasteners securing the sheet metal members to the spacer blocks may comprise nails. Alternatively, the fasteners may comprise screws.

Each sheet metal member may comprise a further flange extending from, or from near, the upper edge of the web in a direction generally parallel to and away from said flange so that each sheet metal member is of lazy Z cross-section, the further flanges of the respective sheet metal members being at least partly overlapped substantially against the spacer block to which they are secured by fasteners.

The further flange of each sheet metal member may be provided with a plurality of fastener receiving openings disposed in a row along the length thereof.

Two or more such rows may be provided, spaced apart across the width of the further flange so that the amount of overlap between the further flanges can be selected.

At least some of the nails can be formed integrally with the sheet metal members.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings in which: Figure 1 shows a transverse section through a lintel embodying the invention with an alternative width lintel and an alternative height lintel shown in dotted and chain dotted outline respectively.

Figure 2 is a similar view of a modified lintel.

As shown in Fig. 1, a lintel 10 of generally top hat cross-section is formed from a pair of substantially similar metal sections 11 and 1 2. Each section is of a "lazy Z" cross-section with an upper horizontal flange 1 3 or 14 and a lower horizontal flange 1 5 or 1 6 directed oppositely from the upper flange 1 3 or 14.

The upper and lower horizontal flange of each section, for example the flanges 1 3 and 15, are generally parallel to each other and extend on opposite sides of a vertical web 1 7 which is generally at right angles to the horizontal flanges. A corresponding vertical web 1 8 is provided on the other section.

The top hat section lintel shown is formed by securing the sections 11 and 1 2 rigidly by means of fasteners to a substantially incompressible spacer block 1 9 of generally rectangular cross-section. It is acceptable for the spacer block to be hollow or of for example channel cross-section provided that its crosssection is bounded by a rectangle and provided that the block has, at least at some positions along the length of the lintel, a pair of opposed faces to which generally vertical webs of the sheet metal members can be secured. A suitable material for the spacer block is wood which may be impregnated with a suitable chemical to prolong its life.

Alternatively, some forms of plastics material or other materials may be found suitable. The main requirements are that the block should be substantially incompressible, reasonably light in weight and not prone to rapid deterioration in use.

It will be seen that the spacer block extends upwardly to the top of the top hat section where is it secured to the upper horizontal flanges 1 3 and 1 4 which are overlapped fully in the drawing. Fasteners such as nails or screws 20 are driven through the upper horizontal flanges into the block 1 9. Similarly, fasteners 21, 22 are driven into the spacer block 1 9 through the vertical webs 1 7 and 18. It will be appreciated that securing is carried out at suitable intervals along the length of the lintel so as to ensure a rigid structure.

If the sections 11 and 1 2 are formed by pressing, it may be possible to press integral nail formations from the material of the sections. These can be used to secure the vertical webs in place. Fastener holes may then be provided in the horizontal flanges to assist in securing them to the spacer block.

In dotted outline, the drawing shows an alternative position of the section 1 2 which is indicated at 1 2a. It will be seen that the upper flange 14 of the section 1 2 is provided with two sets of fastener receiving openings 23 and the upper flange 1 3 of the section 11 is similarly provided with two sets of fastener receiving openings 24.

In order to construct a lintel for use in a wider cavity than that shown in full lines in the Figure, the sections 11 and 1 2 can be secured allowing for less overlap at the top with a wider spacer block provided between them so that the position 1 2a is adopted by the section 1 2. The duplication of fastener receiving openings 23 and 24 enables the same section to be used for two alternative widths of lintel.

However, if desired, sections allowing for a full width overlap of the upper horizontal flanges 1 3 and 14 could be manufactured and used with the wider spacer block to accommodate a cavity of for example 75 millimetres as against the more conventional 59 millimetre cavity.

In chain dotted lines, the positions of alternative upper horizontal flanges 1 3a and 1 4a are shown. The shallower cross-section lintel is constructed on the same principle as that shown in full lines but of course modified metal sections are required.

It is envisaged that the lintel shown is particularly suitable for manufacture in relatively thick gauge metal by cold rolling, as distinct from pressing. It has proved difficult in the past to make a top hat lintel of a sufficiently deep section to enable it to be used over any but the smallest openings and under light loads. Using the details of construction described above, relatively deep lintels can be made by roll forming the sections and overlapping the upper horizontal flanges.

Masonry can then be built up to the lower horizontal flanges 1 5 and 1 6 as required. One or both of these flanges can be provided with a drip lip 26 to drain moisture from the external masonry.

In use, when the masonry has been built up on the flanges 1 5 and 16, these have a natural tendency to sag downwardly at the outer edges, tending to compress the mouth 27 of the top hat lintel.This tendency is resisted by the spacer block 1 9 which rigidifies the structure. Provided that adequate fastenings are made along the length of the lintel, substantial loads can be carried. In use, masonry is built up against both vertical webs 17 and 18, constraining the fasteners 21, 22 from being pulled out of the spacer block.

Additionally, the securing through the upper horizontal flanges 1 3 and 14 assists in holding the structure together.

Referring to Fig. 2 of the drawings, there is shown a second embodiment of lintel somewhat similar to that shown in Fig. 1, and reference numerals of Fig. 2 are the same as those of corresponding parts on Fig. 1.

However, the sheet metal members forming the lintel are in this case no longer of lazy Z cross-section but are of angle section, comprising a vertical web 17, 1 8 and a single horizontal flange 1 5 or 1 6 extending from the foot of the web. It will be appreciated that the upper and lower horizontal flanges in either embodiment need not extend from precisely the top or bottom of the web but could be offset slightly for manufacturing or other reasons.

Since the loading of the lintel tends to compress the mouth 27, and since the vertical webs 1 7 and 1 8 are constrained by the bounding cavity, it has been found unnecessary in some instances to provide the overlapping upper horizontal flanges, shown in Fig.

1. It will be appreciated that the lintel is normally used with a damp proof membrane (not shown) when used in an external wall and this protects the head of the timber spacer blocks from water penetration. Additionally, the treatment of the block has been referred to.

Since the front and back sheet metal members are not in contact with each other, they may be made of different materials. For example the front may be of stainless steel to withstand the more corrosive environment at the outer side of the cavity, while the back member may be of galvanised mild steel.

It will be seen that the spacer block 1 9 does not extend fully into the mouth of the lintel 27 since a gap is advantageously left to accommodate the head of a window or door frame for example. However, the timber spacer block can be used to assist in securing on fittings such as curtain fittings when the lintel is in use.

Particularly where the horizontal flanges 1 3 and 14 are fully overlapped, the bearing strength of the lintel is improved compared with that of a one-piece top hat lintel, even if it could be constructed to the same depth.

It is possible to vary the lintel shown by, for example, using a heavier gauge of metal for one of the sections 11 or 1 2 if the lintel is to be assymetrically loaded.

Where used in external walls, the lintel will normally require a separate damp proof membrane. It will, however, be appreciated that the metal of the lintel can be galvanised and there are not welds to interrupt the galvanic coating so it is likely that the corrosion problem will be minimised.

Where timer is used for the spacer block, it reduces the overall thermal conductivity of the lintel and hence the lintel is less likely to form a cold bridge than, for example, is the case with a conventional box-section metal lintel.

Although the spacer block is preferably provided in one piece, it will be appreciated that it is not placed under any substantial tension in the direction of the axis of the lintel and therefore it could be provided in the form of a plurality of spacer blocks. These could even be spaced apart along the length of the lintel provided that they afforded adequate volume for the metal sections to be secured to. On this basis, the spacer blocks could be made from timber off-cuts or scrap of suitable crosssection, preferably treated with a suitable chemical to reduce the risk of decay occurring.

If desired, a suitable form a plaster key can be secured to one or both of the lower horizontal flanges.

The terms "upper" and "lower" and similar expression are used in this Specification and the appended claims to describe the positions of the various parts in normal use of the lintel. Expressions such as "vertical" and "horizontal" are not to be taken as strictly limitative, as will be appreciated by those skilled in the art.

In fact, it may be desirable to put a distinct slope on the forward face at least of the lintel, particularly in the version shown in Fig. 2, to provide damp-resistance, where the width of the cavity permits.

Claims (16)

1. A lintel comprising a pair of sheet metal members each having, in use, a generally vertical web and a generally horizontal flange extending from, or from near, the foot of the web, the lintel further comprising a substantially incompressible spacer block having a cross-section which is bounded by a rectangle (as herein defined), the webs of the sheet metal members being secured to opposed faces of the spacer block by fasteners with the flanges extending away from each other.

2. A lintel according to Claim 1 wherein the flanges are generally co-planar.

3. A lintel according to Claim 1 or Claim 2 wherein the spacer block does not project, in use, below the flanges.

4. A lintel according to Claim 3 wherein the spacer block is off-set upwardly from the flanges so that a recess is provided between the feet of the webs.

5. A lintel according to any preceding claim wherein the spacer block extends throughout the length of the lintel.

6. A lintel according to any one of Claims 1 to 4 wherein a plurality of spacer blocks are provided along the length of the lintel.

7. A lintel according to Claim 6 wherein the spacer blocks are spaced apart.

8. A lintel according to any preceding claim wherein the or each spacer block is of wood.

9. A lintel according to any preceding claim wherein each sheet metal member comprises a further flange extending from, or from near, the upper edge of the web in a direction generally parallel to and away from said flange so that each sheet metal member is of lazy Z cross-section, the further flanges of the respective sheet metal members being at least partly overlapped substantially against the spacer block to which they are secured by fasteners.

10. A lintel according to any preceding claim wherein the fasteners securing the sheet metal members to the spacer blocks comprise nails.

11. A lintel according to Claim 10 wherein at least some of the nails are formed integrally with the sheet metal members.

12. A lintel according to any one of Claims 1 to 9 wherein the fasteners securing the sheet metal members to the spacer block comprise screws.

1 3. A lintel according to Claim 9 wherein the further flange of each sheet metal member is provided with a plurality of fastener receiving openings disposed in a row along the length thereof.

14. A lintel according to Claim 1 3 wherein two or more such rows are provided, spaced apart across the width of the further flange so that the amount of overlap between the further flanges can be selected.

1 5. A lintel substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawings.

16. A lintel substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawing.

1 7. Any novel feature or features taken singly or in combination as set out in the foregoing description.