GB2259723A - Thermally insulated structural member - Google Patents

Abstract

A thermally insulated structural member comprises an elongate core 12 of a heat insulating material held between two elongate sheet members 14, 16 formed at least partially as channel sections. The two sheet members are provided with outwardly extending flanges 18, 20 and 22, 24 respectively which are connected together by fixing means 26, 28 arranged on each side of the core 12. As the fixing means 26, 28 e.g. screws or bolts have a relatively small cross-section the effect of thermal conduction therealong is reduced. <IMAGE>

Description

THERMALLY INSULATED STRUCTURAL MEMBER This invention relates to a thermally insulated structural member for use in leisure, commercial or domestic buildings especially intended for use as rafters, studs and intermediate purlins in roof and for wall structures.

When providing a roof or wall on such buildings it is known to provide roof floor or wall structures, the inner and outer elements of which must be kept apart buy means of, for example, wooden rafters or metal rails. The disadvantage of providing such intermediate members is that it will increase the weight of the overall structure and the presence of rafters or intermediate purl ins of metal or wood can give rise to a thermal bridge extending between the inner and outer elements thus allowing energy e.g. heat, to be dissipated by conduction.

Swedish Patent No. 210266 describes the use of beams or elongate structural members having a core of a heat insulating material for example a glass fibre insulating wool. The core is provided with elongated reinforcing lining profiles on two opposing sides in order to prevent occurance of a thermal bridge between the two profiles. The lining profiles are bonded to the core by means of a resin binder.

Such a construction is complicated to manufacture since the application of the binder, the joining of the core with the elongate line profiles and the curing of the joint between the core and the lining profiles requires several separate working operations. Additionally, the strength of the joints and the bearing capacity of the structural member will be dependent on the hunidity and ambient temperature and can vary according to difference therein.

British Patent No. 2025503 provides a thermally insulated structural member with at least a portion of the opposing surfaces of the core covered between elongate cover sheets of metal. These cover sheets are joined together with straps or bands arranged around the construction to prevent the occurance of thermal bridges. The strength of such members is dependent on the strength of the straps or bands and their own joints and they require reinforcement to prevent relative movements of the top and bottom channels when the member is loaded in the axial plane. Furthermore the strength of the member as a whole can be inadvertently reduced during construction due to penetration of the strap by fasteners actually intended to secure outer weather sheets or inner linings to the member.

It is an object of the invention therefore to provide a thermally insulated structural member for use in the construction of industrial or leisure buildings, dwellings or similar structures which is simple to construct and minimise the provision of a thermal bridge between respective inner and outer linings.

With this object in view the present invention provides an elongate structural member comprising an elongate core of a thermally insulating material providing at least two opposing surfaces, at least two sheet members disposed to cover at least part of the said two opposing surfaces of the core and each sheet member being formed substantially as channel sections so as to at least partly cover the elongate core's sides, the structural member being further provided with elongate fixing means adapted for attachment to mutually opposed channel sides such that the two sheet members are rigidly connected thereby.

Advantageously each sheet member is provided with two laterally extending flanges arranged so as to oppose each other on opposite sides of the core and the elongate fixing means are attached to mutually opposed flanges.

Preferably the fixing means is provided by a plurality of low thermal conduction capacity screws, plates or pillars which are arranged to extend substantially perpendicular to the longitudinal direction of the core.

In a preferred embodiment of the invention the core has a rectangular cross section such that two surfaces of the core are perpendicular to the said opposing surfaces and these perpendicular surfaces are at least partially covered by the two sheet members so as to provide the member with an increased rigidity and resistance to bending.

The thermally insulating material may consist of a very high density mineral wool with the fibres laid in a unidirectional manner so as to increase the structural properties of the core of the member against compression by the two sheet members.

In an alternative embodiment the two opposing sheet members or channel section are kept apart under compression loads by tubular members formed of, for example, plastics or epoxy resin, the members being adapted to retain screws inserted therein and the opposed end faces of the members bearing against the flanges of the two opposed sheet members.

The invention will be described further by way of example with reference to the accompanying drawing in which: Fig. 1. is a perspective end view of a first embodiment of the invention; and Fig. 2. is a perspective end view of a second embodiment of the invention.

In Fig. 1. an elongate structural member is referred to generally by the reference numeral 10 and is intended primarily for use as a spacer member, stud or rafter in a building structure. The member 10 comprises ati elongate core 12 of a heat insulating material for example a suitably hard mineral wool, plastic or a rigid foam. In a preferred embodiment the core 12 has a rectangular cross section providing four substantially planar surfaces.

The member 10 also includes two elongate sheet members 14, 16 having a substantially U-shaped cross section and formed of a rigid material for example a metal' so as to provide the elongate member with a rigid structure. The two sheet members 14, 16 are each provided with two outwardly extending flanges 18, 20 and 22, 24 respectively. These flanges are shown to extend from the lower edges of the Ushaped members 14 although in practice the flanges may extend from any point on the upstanding walls of the U-shape.

The two sheet members 14, 16 are arranged such that the rectangular cross section core 12 is partially enclosed in each U section. The sheet members 14, 16 thus provide rigid bracing for the relatively flexible elongate core 12. The pairs of flanges 18, 20 and 22, 24 of each sheet member 14, 16 are thus disposed generally parallel to each other and extending laterally with respect to the longitudinal direction of the elongate core 12.

In order to secure the two sheet members 14, 16 together and provide the necessary rigidity to the overall structural member 10 opposed flanges 18, 22 and 20, 24 are secured by way of a plurality of elongate fixing means 26, 28 for example relatively slender screws or threaded posts. These posts 26, 28 are arranged at, for example, regular intervals along the respective member 10 such that the rigidity of the member is relatively evenly arranged. The elongate screws 26, 28 may be located through pre-drilled holes in the flanges 18, 20, 22, 24 or the holes could be drilled as required. Where the holes are pre-drilled an elongate bolt may be secured by a nut bearing on the opposed flange.

In order that the formation of a thermal bridge between the two opposed metal sheet members is avoided the screws or posts have a relatively small cross sectional area such that they have a low heat conductance. Additionally the structural integrity of the member will not be compromised by the requirement for additional screws fasteners rivets or welding etc required to connect the outer structure and internal linings to the member when it is used as a spacer or rafter in a commercial or domestic building.

The screws 26, 28 may be provided with external coatings of a tubular material such as plastic or epoxy resin having a low thermal conductivity in order to provide greater carrying capacity between the opposed flanges.

It will be understood that this embodiment of the invention provides an elongate structural member having good thermal insulating properties and which is easily attached both to internal and external members whilst maintaining good thermally insulating properties and without the formation of a thermal bridge to compromise any thermal insulation.

In Fig. 2. a second embodiment is referred to generally by the reference numeral 30 and comprises two elongate Ushaped sheet members 32, 34 enclosing a core 12 formed substantially as in Fig. 1. of a heat insulating material.

In this embodiment the members 32, 34 are connected by a plurality of elongate fixing means in the form of stainless steel straps 36. These straps are linear in configuration and are bolted directly to the upper and lower elongate members 32, 34. The bolts 38 are preferably arranged so as to space the straps 36 away from the members 32, 34 so as to minimise heat conductions therethrough. Alternatively, a heat insulating washer could be used.

In some twin skin roof constructions thermal moments caused by expansion and/or construction of the external sheet can cause excessive 'noise'. The stiffness of known purl ins will resist the rolling moment leading to 'slotting' i.e. wear of the screw holes, of the external sheet. The proposed purl in construction preferably includes a thread free zone at the top of the screw permitting the external sheet secured to the member to freely expand and contract.

The invention is not confined to the foregoing details and variations may be made thereto within the scope of the invention.

Claims (7)

1. A thermally insulated structural member comprising an elongate core of a thermally insulating material providing at least two opposing surfaces, at least two sheet members disposed to cover at least part of the said two opposing surfaces of the core and each being formed substantially as channel sections so as to a least partly cover the elongate core's sides, the member being further provided with elongate fixing means adapted for attachment to mutually opposed channel sides such that the two sheet members are substantially rigidly connected thereby.

2. A member as claimed in Claim 1 in which each sheet member is provided with two laterally extending flanges arranged so as to oppose each other on opposite sides of the core and the elongate fixing means are attached to mutually opposed flanges.

3. A member as claimed in Claim 2 wherein the fixing means is provided by a plurality of low thermal conduction capacity screws arranged to extend substantially perpendicular to the longitudinal direction of the core.

4. A member as claimed in Claim 1 in which the fixing means is a plurality of fixing members arranged on each side of the core with the fixing members free ends each being attached to the mutually opposed channel sides.

5. A member as claimed in any preceding claim wherein the core has a rectangular cross section such that two surfaces of the core are perpendicular to the said opposing surfaces, which perpendicular surfaces are at least partially covered by the two sheet members.

6. A member as claimed in Claim 2 or Claim 3 wherein the opposed flanges are connected by tubular members placed therebetween, which members are adapted to retain screws inserted therein through the flanges and having opposed end faces which bear against the opposed flanges.

7. A thermally insulated structural member substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

7. A member as claimed in Claim 6 wherein the members are formed of a plastics material.

8. A thermally insulated structural member substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Amendments to the clans have been filed as follows 1. A thermally insulated structural member comprising an elongate core of a thermally insulating material providing at least two opposing surfaces, at least two channel members disposed to cover at least part of the said two opposing surfaces of the core and each channel member having flanges extending laterally from channel sides thereof such that the flanges are mutually opposed on opposite sides of the core, the member being further provided with elongate fixing means adapted for attachment to mutually opposed flanges such that the two channel members are substantially rigidly connected thereby.

2. A member as claimed in Claim 1 wherein the fixing means comprise a plurality of fixing members arranged on each side of the core, each fixing member being attached by its free ends to the mutually opposed channel sides.

3. A member as claimed in Claim 2 wherein the fixing means are provided by a plurality of low thermal conduction capacity screws arranged to extend substantially perpendicular to the longitudinal direction of the core 4. A member as claimed in any preceding claim wherein the core has a rectangular cross section such that two surfaces of the core are perpendicular to the said opposing surfaces, which perpendicular surfaces are at least partially covered by the two sheet members.

5. A member as claimed in Claim 1 wherein the opposed flanges are connected by tubular members placed therebetween, which members are adapted to retain screws inserted therein through the flanges and having opposed end faces which bear against the opposed flanges.

6. A member as claimed in Claim 5 wherein the members are formed of a plastics material.