GB2025503A

GB2025503A - Thermally-insulated structural members

Info

Publication number: GB2025503A
Application number: GB7915166A
Authority: GB
Original assignee: Granges Aluminium AB
Current assignee: Granges Aluminium AB
Priority date: 1978-05-02
Filing date: 1979-05-01
Publication date: 1980-01-23
Also published as: FI64833C; FI791368A; DE2917551A1; FI64833B; GB2025503B; DK151719C; NO791433L; SE7805028L; DK179779A; NO150449C; NO150449B; SE426333B; DK151719B

Abstract

An elongate thermally insulated structural member for use in buildings, especially intended for use as rafters and studs in roof and wall structures, comprises an elongate core e.g. 10 of heat insulating material and at least two covering sheets, e.g., 11, 12 disposed to cover at least a portion of two opposing surfaces of the core. The covering shots are retained on the core by means extending between the covering sheets. The retaining means consist preferably of straps 13 or wire loops tightened externally around the member, but may comprise one or more sheets of plastics material, e.g. The core may comprise mineral wool or rigid foamed plastics, and a central stiffening web (18), Fig. 2 (not shown), or a pair of edge stiffening webs (23), Fig. 3 (not shown) may extend between the covering sheets, which are preferably metal. The edge stiffening members, which box in the core, may be of wood-based material. <IMAGE>

Description

SPECIFICATION Improvements in or relating a structural member The present invention relates to a structural member and more particularly to an elongate structural member for use in the construction of buildings, especially industrial buildings, dwellings and similar buildings. Members in accordance with the invention especially intended for use as rafters, and as studs in roof and wall structures which comprise an inner lining and an external cladding and at least one intermediate layer of heat insulating material, although members in accordance with the invention can also be used when making door frames, window frames etc.

It is known, when providing a roof on a building, for example, to provide a ceiling and a roof covering kept apart by means of rafters of wood or metal. Such roof structures often tend to be heavy, however, and furthermore the presence of rafters made from metal or even wood gives rise to thermal bridges extending between the roof covering and the ceiling, resulting in poor heat insulation, even if insulation mats have been placed in the spaces between the rafters. It is also known, e.g. from Swedish Patent Specification No.

210 266, to use beams or elongate structural members having a core of heat insulating material (e.g. glass fibre insulation wool) and elongate reinforcing lining profiles on two opposing sides of the core, in order to prevent the occurrence of such thermal bridges. These lining profiles are bonded to the heat insulating core by means of a resin binder. As a result, the manufacture of the structural member is comparatively complicated, since the application of the binder, and the joining of the core with the elongate lining profiles, as well as curing the the joint between the core and the lining profiles, requires several separate working operations. Furthermore, the strength of the joints, and consequently the bearing capacity of the beam or structural member will be dependant on the ambient temperature, which is a substantial disadvantage, at least in some cases.

According to this invention there is provided an elongate structural member, comprising an elongate core having at least two opposing surfaces and made from a material with good thermal insulating properties, at least two sheets disposed to cover at least part of said opposing two surfaces of the core, and a retaining means with low thermal conduction capacity extending substantially perpendicular to the longitudinal direction of the core between said sheets at parts spaced along said core to retain the sheets on the core.

Since a member in accordance with the invention comprises a core of heat insulating material, which is preferably hard mineral wool, thermal bridges are avoided and a light structure is obtained, and since the member is provided with two opposing cover sheets retained on the core by fastening means with low thermal conduction capacity, sufficient strength is obtained for the member without any significant thermal bridges being formed, and the member will also be cheap to manufacture.

In order that the invention may be more readily understood and so that further features thereof may be appreciated the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view of part of a first embodiment of an elongate structural member in accordance with the invention; Figure 2 is a perspective view of part of a second embodiment of the invention; Figure 3 is a perspective view of part of a third embodiment of the invention and Figure 4 is a plan view of a fourth embodiment of the invention.

The elongate structure member illustrated by way of example in Fig. 1 is primarily intended for use as a spacer member, stud or rafter in building structures. The member comprises an elongate core 10 of heat-insulating material, suitably hard mineral wool, said core having a rectangular cross section. The core is provided with two metal covering or cladding sheets 11, 1 2 disposed on two opposing sides of the core so that they cover these opposing sides. The direction of the fibres in the mineral wool is substantially perpendicular to the major surface of the sheets 11, 1 2. The sheets are retained on the core by means of a plurality of spaced metal straps 13, each running in a closed loop around the outside of the member.The ends of each strap are joined by means of a sleeve 1 4 of metal sheet, which is nipped over the strap ends. The straps are pretensioned before the sleeve joining the strap ends is clamped tight, so that the straps effectively press the opposing sheets towards each other and against the core.

In the embodiment illustrated in Fig. 1, the covering sheets 11, 1 2 are provided with upstanding edge flanges 1 a, 11 band 1 2a, 1 2b so as to have a substantially channel or U-shaped cross section with two parallel edge flanges. These flanges are arranged to straddle the core 10 and engage the side surfaces of the core so that the sheets cannot be displaced in the transverse direction of the elongate structural member when subjected to a load. The outer faces of the covering sheets are also provided with depressions 1 5 so that corresponding projections are formed on the surfaces of the sheets facing towards the core.

These projections are pressed into the core and serve also to reduce the risk of the sheets being displaced in relation to the core, when the member is loaded.

A second embodiment of the invention which can be considered to be a modification of the embodiment in Fig. 1, is illustrated in Fig. 2. This elongate structural member is intended for use as a load-bearing member and is therefore provided with a supporting wall or web 1 8 extending between cladding sheets 1 6, 1 7. This web is intended to be disposed in a vertical plane when the member is in use in a building.The bending of the structural member when loaded is substantially reduced by the presence of this supporting web 1 8. The web 1 8 extends longitudinally from one end of the member to the other and is inserted between a pair of parallel flanges 19, 20 on the inner face of sheet 16 and a similar pair of flanges 21, 22 on the inner face of sheet 1 7. These pairs of flanges extend between the ends of the member with a spacing between the flanges such that the supporting web 18 is retained between them.

Due to the presence of the web 1 8 the core 10 of heat-insulating material is divided into two parts 1 Oa, 1 Ob arranged on either side of the supporting web, which is disposed in the central plane of the member.

The elongate structural member illustated in Fig. 3 can also be considered to be a modification of the member shown in Fig. 1. In this embodiment, the central web in Fig. 2 is replaced by two supporting walls 23, 24, one on either side of the core 1 0. The member illustrated in Fig. 3 can thus be used to advantage as a load-bearing beam, since its deflection when loaded will be comparatively small. In the embodiment illustrated in Fig. 3, the supporting walls 23, 24 consist of two boards placed adjacent or against the side surfaces of the core and with their edges extending between the edge flanges 25a, 25b, and 26a, 26bofthe covering sheets 25, 26 and the core 1 0. The boards will thus be retained against the core by the edge flanges of the sheets.The boards suitably consist of a wood-based material, and are preferably laminated boards, e.g. plywood although the boards could be of chipboard or even planks of wood. Punched in the flanges at the edges of the cladding sheets are tags or tabs 27 which project into the boards and hold the same against movement relative to the sheets.

In a modification of the embodiment shown in Fig. 3 a web corresponding to the web 1 8 of Fig. 2 may be provided in addition to the walls 23, 24.

Fig. 4 illustrates, in a side view, a particularly preferable configuration of the ends of an elongate structural member made in accordance with the invention, e.g. a member as shown in Fig. 1. In this embodiment, the end edges 11c, 11 dank 12c, 12dof the covering sheets 11, 1 2 are axially spaced relative to the end surfaces lOc, 1 O d of the core 10 in that the sheets have substantially the same length as the core but are displaced longitudinally relative thereto, so that the core projects beyond the end edges of the sheets at one end of the member, whereas at the other end of the member the sheets project beyond the end of the core.The advantages gained by this construction reside in the fact that the elongate structural members can be joined together in a simple way by inserting the end of the member with the projecting core in the opposite end of an adjacent member, thus facilitating splicing several members together.

The embodiment shown in Figs. 2 and 3 can, of course, be modified in a corresponding way.

A preferred member in accordance with the invention as described above is relatively light and is very easy and cheap to manufacture, since the different parts thereof can be put together in a simple work operation. The member illustrated in Fig. 1 is, for example, manufactured by providing a prefabricated core of heat insulating material with prefabricated covering sheets on two opposing sides, subsequent to which straps are positioned round the member and drawn taut by means of a suitable, conventional tightening device, the strap ends being attached to each other by means of a special clamping sleeve which is placed over the strap ends and clamped or compressed, whereby the sheets are retained against the core. The strapping bands used as retaining means are mutually spaced and a suitable number of such straps are provided, so that the necessary retaining forces are obtained.The members illustrated in Figs. 2 and 3 are manufactured in a corresponding way, the supporting central flange and the supporting side walls, respectively being positioned on one covering sheet on which the core is placed before the other covering sheet is placed on the core. In the embodiment illustrated in Fig. 4, the covering sheets only need to be displaced axially relative to the core whilst the member is being assembled.

Although only three embodiments of the elongate structural member in accordance with the invention have been described above, it is to be understood that many other embodiments of the member are possible within the scope of the invention. Wire can be used instead of straps or bands to surround the member. The strapping band or wire does not need to be of metal. What is important, however is that if strapping or wire of a material with good heat conductivity is used, these retaining means shall have a small cross-sectional area, so that they have only a small capacity for conducting heat and thus do not form any significant thermal bridges. If a strapping band or wire of a material with poor heat conductivity is used, it is not so important for the cross-sectional area to be small.The retaining means need to consist of loops placed round the member but even straps or wire-like means fastened to the cladding or covering sheets, e.g. by riveting or welding, can be used, if the strap or wire ends can be tensioned and attached to each other so that they form retaining means extending between the covering sheets. In this case the retaining means do not need to be arranged opposite each other but can be arranged in a zig-zag configuration along the length of the member, so that the retaining means on one side of the member are located between the retaining means on the other side of the member. It is not necessary for the retaining means to correct the sheets at the side edges of the member, since they can be passed through the core between the sheets, e.g. along a longitudinal central plane through the core.It is, of course, important that the retaining means can be given sufficient tension positively to retain the sheets to the core.

The retaining means can also consist of plastics material strip or tape, for example, which either runs round the whole member or is glued or otherwise adhered to the covering or cladding sheets. Other conceivable types of retaining means might comprise a plurality of axially extending sleeves made from a plastics material and placed one after the other along the member, or a single elongate sleeve extending at least over the greater part of the length of the member. In the latter case, the elongate sleeve can be regarded as a plurality of retaining means placed after each other and mutually cohesive, and in any event parts of the sleeve are located at points spaced along the core.The covering or cladding sheets can furthermore be manufactured from a material other than metal, e.g. plastics material or wood based material such as plywood or chipboard, and be provided where appropriate, with projections in many different forms. It is not necessary to provide the covering or cladding sheets with flanges at their edges, but flat covering or cladding sheets can be used. If the sheets are provided with edge flanges, the supporting side walls, if provided, do not necessarily need to be fitted inside these edges, even if this is usually most suitable. The covering or cladding sheets can also be arranged solely in the regions of the retaining means, the cladding sheets thus only covering a part of the core.

The covering or cladding sheets can be provided with outwardly projecting handles, ears or flanges for facilitating the erection of the member in a building structure. As heat insulating material, other light insulating material with the necessary mechanical strength can be used, e.g. rigid foamed plastics material.

Claims

1. An elongate structural member, comprising an elongate core having at least two opposing surfaces and made from a material with good thermal insulating properties, at least two sheets disposed to cover at least part of said two opposing surfaces of the core, and a retaining means with low thermal conduction capacity extending substantially perpendicular to the longitudinal direction of the core between said sheets at parts spaced along said core to retain the sheets on the core.

2. A member as claimed in claim 1, wherein said retaining means comprises means located on two opposed sides of said elongate core.

3. A member as claimed in claim 1 or 2, wherein said retaining means comprises a plurality of bands, straps or wires.

4. A member as claimed in claim 3, wherein said retaining means consist of a plurality of band or wire loops tightened externally around the member.

5. A member as claimed in claim 1 or 2, wherein said retaining means consist of one or more axially extending sleeves of plastics externally enclosing the member.

6. A member as claimed in any one of claims 1 to 5, wherein at least one of said sheets has a U-shaped cross section comprising a substantially flat part and upstanding flanges at two opposed side edges of said flat part, the said flanges straddling said core.

7. A member as claimed in any one of the claims 1 to 6, having a core with a rectangular cross section, wherein the two surfaces of said core which are perpendicular to said two opposing surfaces are at least partially covered by support walls providing the member an increased rigidity against bending.

8. A member as claimed in claim 7 as dependant upon claim 6 wherein said support walls extend inside of the flanges of said Ushaped sheets.

9. A member as claimed in claim 8, wherein the flanges of the sheets are each provided with one or more projections directed inwards and gripping into the support walls.

10. A member as claimed in claim 6 or any claim dependant thereof, wherein the core comprises two parallel elements of thermal insulating material, and a support web is disposed between said two elements and extends all the way between said two sheets.

11. A member as claimed in any one of the claims 1 to 10, wherein the axial ends of said sheets are axially spaced from the axial ends of the core in such a way that at one end of the web the sheets are projecting axially beyond the core whereas at the other end of the member the core is projecting axially beyond the sheets.

1 2. A member as claimed in any one of the claims 1 to 11, wherein the sheets are provided with projections on the surfaces of the sheets facing the core, said projections being pressed into said core and preventing a mutual displacement of the sheets relative to the core.

1 3. A member as claimed in any one of the claims 1 to 12, wherein said thermal insulating material consists of mineral wool and the fiber direction of the mineral wool is substantially perpendicular to said sheets.

14. A structural member substantially as herein described with reference to and as shown in Fig. 1 of the accompanying drawings.

1 5. A structural member substantially as herein described with reference to and as shown in Fig. 2 of the accompanying drawings.

1 6. A structural member substantially as herein described with reference to and as shown in Fig. 3 of the accompanying drawings.

1 7. A structural member substantially as herein described with reference to and as shown in Fig. 1 or Fig. 2 or Fig. 3 as modified by Fig. 4 of the accompanying drawings.

18. Any novel feature or novel combination of features disclosed herein.