GB2371076A

GB2371076A - Insulated frame members

Info

Publication number: GB2371076A
Application number: GB0200901A
Authority: GB
Inventors: Brian Paul Booth
Original assignee: Sapa Building Systems Ltd
Current assignee: Hydro Building Systems UK Ltd
Priority date: 2001-01-16
Filing date: 2002-01-16
Publication date: 2002-07-17
Anticipated expiration: 2022-01-16
Also published as: GB0200901D0; GB2371076B; WO2002057582A1; GB0101105D0

Abstract

A glazing frame member has inner and outer aluminium alloy sections 6, 22, connected by a pair of thermally insulating webs 8, 10 each formed with a matrix of hollow chambers 12. The chambers 12 may be of hexagonal cross section and may be tessellated such that the chamber walls are all of uniform thickness. The outwardly facing surface of each web may have a thin outer skin forming the wall of an array of truncated chambers 15 and the inwardly facing surface of each web may have opposing fins 16.

Description

Insulating Frame Members

This invention relates to insulating frame members and more particularly to thermally broken frame members for glazing applications such as windows, doors, conservatories and other structures.

For certain applications, glazing frames fabricated from extruded aluminium alloy glazing bars remain the preferred choice, having superior strength, stability, durability and other advantages compared with frames of pvcU plastics material.

A recognised disadvantage of window frames or door frames fabricated from aluminium bars is that, in the event of low external temperatures occurring, the good thermal conductivity of aluminium may result in the cooling of the interior-facing surfaces of the frame resulting in heat loss and also condensation, if the interior atmosphere is sufficiently warm and humid.

Many proposals have been made to mitigate this problem by introducing so called'thermally broken'designs in which the inner and outer sections of an extruded frame member

(which may be referred to herein as a'profile') are inter-connected by means of a rigid member of heat insulating material which substantially reduces heat conductivity between the inner and outer sections of the profile.

It is an object of this invention to provide a thermally broken glazing frame or the like having improved thermal insulation for use in the construction of a glazed window, door or other article, of improved U value.

This invention consists in a frame member having an inner profile section and an outer profile section of thermally conducting material interconnected by an elongate web of thermally insulating material characterised in that the web is formed with a plurality of longitudinally extending thin walled chambers such that the web, in cross section, is formed by a matrix of rows and columns of the cross sections of the said chambers.

Preferably, the chambers have cross section of polygon form of and, more preferably, the cross sectional form is such that the form of matrix consists in a tessellated array in which the chamber walls are all of uniform thickness. An array of chambers each having the same hexagonal cross sectional form is particularly advantageous and provides a'honeycomb'matrix. Other single forms that tessellate exactly are equilateral triangles and rectangles although arrays of mixed forms will also tessellate exactly.

The web may have a thin outer skin, which forms the wall of a truncated array of chambers along the boundary of the web.

Except for conduction through any such thin outer skin, the lengths of the various conduction paths through the chamber walls between the inner and outer edges of the web will generally be greater, and potentially substantially greater, than the width of a corresponding

solid web. Together with the relative thinness of the chamber walls the thermal conductivity of the web in accordance with this invention will result in substantially lower heat loss by conduction compared with the case a conventional web.

The chamber wall thickness should be a rather small fraction of the depth of the web, between the inner and outer ends thereof, and preferably be about 1%-5% of the overall web depth.

Preferably, the frame member has a pair of spaced apart webs of the kind described. Advantageously, the interior facing surfaces of such first and second spaced apart webs are each provided with a plurality of opposed fins, which reduced heat transfer by convection and radiation between the inner and outer frame members.

In order that the invention may be more clearly understood one embodiment will now be described with reference to the accompanying drawing which illustrates a cross section of a window frame member which is part of a

standard 1200mm x 1200mm window assembly not shown, incorporating a 24mm sealed double glazing unit.

Referring to the drawing, the window frame member shown generally as 2 has an inner aluminium alloy profile 4 and an outer aluminium alloy profile 6 which are connected together a pair of extruded spaced apart polyamide web members 8,10. Each web, which is 36 mm deep between the inner and outer edges, is formed with a plurality of longitudinally extending thin walled chambers 12 of hexagonal cross sectional form. Each web, in cross section, is formed by a matrix of rows and

columns of the hexagonal cross sectional forms of the chambers. The illustrated array is tessellated, that is each hexagonal form is disposed as an element of a mosaic with uniform wall thickness (of 0.6 mm in the case illustrated) between each chamber.

Each web has a thin (0.6mm) outer skin 14 which forms the outer wall of an array of truncated chambers 15 of semi hexagon formed along the outer surface. The opposed inner surface is formed with a plurality of pair of inwardly directed fins 16 which reduce heat transfer within the cavity formed between the webs 8,10 by radiation and convection between the inner and outer elements 4,6.

The window assembly is completed in a standard way: the sealed unit 18 is retained in the glazing rebate 20 formed by rebate profile 22 an associated gasket 24 and the external glazing bead 26 which retains gasket 28 in contact with the outer marginal edge of sealed unit 18.

Conduction between the normally warmer interior section 4 towards the normally cooler exterior section 6 occurs through the walls of the hexagonal chambers 12 and 15.

Not only is the conduction path length through the chamber walls greater than the 36mm depth of the web but the relative wall thinness also contributes substantially to a reduction in conductivity compared with a conventional web.

Overall, calculations have shown that the 1200mm x 1200mm window assembly incorporating a 24 mm sealed double glazing unit in an aluminium alloy frame provided with thermally insulating webs as described with reference to the accompanying drawing benefits from a 5% reduction in heat loss (an increase of 5% in U value) under industrystandard test conditions, (CEN) compared with an otherwise identical window assembly provided with a standard solid polyamide insulator of the same 36mm depth.

Claims

1. A frame member having alloy inner and outer sections interconnected by a web of thermally insulating material characterised in that the web is formed with a plurality of thin walled hollow chambers such that the web, in cross section, is formed by a matrix of rows and columns of the said chambers.

2. A frame member as claimed in Claim 1 in which the chambers of the web have cross section of polygon form.

3. A frame member as claimed in Claim 2 in which the matrix is in the form of a tessellated array in which the chamber walls are all of uniform thickness.

4. A frame member as claimed in Claim 3 in which the chambers each have the same hexagonal cross sectional form so as to provide provides a honeycomb matrix.

5. A frame member as claimed in any preceding Claim in which the web has a thin outer skin, which forms the wall of a truncated array of chambers along the boundary of the web.

6. A frame member as claimed in any preceding claim in which the chamber wall thickness is a small fraction of the depth of the web, between the inner and outer ends thereof.

7. A frame member as claimed in Claim 6 in which the thickness of the chamber wall is between a 1% and 5% of the overall web depth.

8. A frame member as claimed in any preceding Claim having a pair of spaced apart webs.

9. A frame member as claimed in Claim 8 in which the interior facing surfaces of such first and second spaced apart webs are each provided with a plurality of opposed fins, to reduced heat transfer between the inner and outer frame members.

10. A frame member as claimed in any preceding Claim in whch a web is formed as an extrusion of polyamide.