GB2123468A - Method of making a thermally broken frame and frame made thereby - Google Patents

Abstract

A heat conductive frame has inner and outer wall portions 2, 6 which are thermally isolated by a longitudinal slot 22, sealed by an impervious thin and flexible polymeric tape 26 bonded to projections 16, and into which a thermally insulating member 28 is then cast. <IMAGE>

Description

SPECIFICATION Method of making a thermally broken frame and frame made thereby This invention relates to a method making thermally broken frame, particularly door or window frame, members of extruded aluminium and to frames made thereby.

Various proposals have been put forward for producing a thermal break between the inner and outer sides of a heat conductive frame member.

Hollow frame members are commonly formed as an integral extrusion in which the inner and outer sides are connected by spaced heat conducting transverse webs. In order to prevent heat loss between the inner and outer sides of a hollow extruded frame, a method has been proposed, in UK Patent Application 2060750, of manufacturing a thermally insulating sash bar comprising the steps of providing a hollow sash bar with spaced apart transverse webs, each of which is formed with a longitudinal channel; introducing a thermally insulating synthetic resin and curing the same in one of the channels; forming a longitudinal gap in and along each of the channels; covering the gap in the unfilled channel with a thermally insulating strip; and introducing more resin into the second channel, to provide a sash bar, the inner and outer sides of which are connected by means of two thermally insulating members.

An important disadvantage of this method is that some liquid resin mixture seeps around and under the strip of thermally insulating material, empoyed to cover the gap in the unfilled channel, which resin sets in the central cavity of the frame between the transverse webs. This set material obstructs the use of forming tools, intended to be used in the central cavity of the frame, and causes fabrication difficulties when components such as locks are fitted. Leakage also results in a loss of valuable resin material and may reduce the mechanical strength of the cast insulating member.

The inherent incapacity of the known cover strip to provide a good seal is made worse by the fact that the strip is normally unreeled from a coil, which causes some curvature along the length of the strip.

It will be appreciated that one thermal break, i.e. one of the longitudinal gaps, may be formed during the extrusion of a hollow frame member, so that only one gap may need to be formed by a subsequent cutting operation.

This invention consists in a method of producing a thermally broken elongate frame member comprising: providing a frame member having thermally conductive inner and outer wall portions, means defining a channel in an integral web connecting the inner and outer wall portions, forming a longitudinally extending slot in the channel to provide a thermal break in the integral web between the inner and outer wall portions, covering the slot with a thermally insulating strip member, casting a thermally insulating member in situ in the channel characterised in that the thermally insulating strip member is a thin and flexible impervious tape member which is bonded to the channel so as to seal the slot.

It will be understood that the term "thermally insulating strip" means a strip of negligible heat conducting capacity, due to its materials of manufacture, cross sectional area, or both.

Preferably the tape is self-adhesive.

The main advantage of the invention is that the slot in the channel is effectively sealed along its entire length and prevents the leakage of liquid resin into the central cavity of the frame.

The tape may be applied to the interior of the channel by means of a pressing tool adapted to conform therewith.

The interior surface of each channel may be formed with longitudinally extending projections such as tongues, barbs, ribs or interlocking formations adapted to interengage with the insulating synthetic resin cast therein. Where such projections are provided along a marginal region adjacent to a longitudinal edge of the slot, the polymeric tape is pressed into conformity therewith by means of a tool of complimentary shape.

It will be appreciated that the tape material and the adhesive employed are chosen to maintain a seal, without collapse or substantial deformation, during the subsequent operation of pouring in the reaction mixture or substance constituting the fluid synthetic resin, and during any chemical reaction, with possible increase in temperature, until the mixture or substance has substantially solidified.

Where the synthetic resin is formed in situ by the exothermic chemical reaction of two or more substances, the softening point of the material of the tape should be over 1 000C. One suitable material is polypropylene.

The elongate opening defining the mouth of a channel may be narrower than the width of the tape mamber provided to cover the slot formed along the base of the channel. Accordingly the tape member is advantageously resiliently deformable so as to flex about its longitudinal axis as it is pressed through a relatively narrow mouth of a channel and after which the original form of the strip is elastically restored.

The tape member may be automatically dispensed from a reel of tape under tension in which case the tensile strength and elongation of the tape under the applied tension should be such that fracture or excessive stretching of the tape member is avoided.

A non-limiting embodiment of the invention will be described with reference to the accompanying drawings in which Figure 1 is a cross sectional elevation of an unbroken, hollow extruded aluminium frame; Figures 2 and 3 are enlarged fragmentary views of the channel portions of the frame shown in Figure 1 provided with a thermal break in accordance with the method of this invention.

Referring to the drawings, Figure 1 shows an extruded aluminium frame having inner/outer portions 2,4 interconnected by spaced transverse webs 6, 8 each of which is formed with a longitudinal channel 10, 12 respectively, having internal projections in the form of ribs 14, 16 18 as shown.

In order to produce a thermally broken frame i.e. one in which the outer portions 2,4 are thermally isolated from each other, a fluid synthetic resin is cast in situ in channel 12 to provide a thermally insulating member 20, interengaged with ribs 18, as shown in Figure 3.

The base of each channel 10, 12 is now formed with longitudinal slots 22 and 24 respectively, by milling, sawing or other conventional operation to remove the metal entirely, providing a thermal break between the outer portions 2, 4 of the frame.

A self adhesive resilient polypropylene tape 26 (the properties of which are shown in Table 1 below) is dispensed from a reel, not shown, and pressed through the relatively narrow mouth of channel 10 defined by the opposed ribs 14. The tape 26, which is about the same width as the internal width of channel 10, resiliently flexes as it passes through the mouth of channel 10 after which the original shape of the strip is elastically restored. The tape 26 is then pressed, by means of a pressing tool, not shown, into conformity with the base of channel 10 sealing slot 22 along its entire length and covering the ribs 16 provided adjacent to the longitudinal side edges of the slot 22.

TABLE 1 Characteristics of self adhesive sealing tape Material Polypropylene Adhesion 900 9/25 mm width Tensile Strength 50 Kg/25 mm width Thickness 0.1 mm Elongation 30% Softening Point Greater than 1000C.

As will be seen from Figure 2, tape 26 is sufficiently thin anf flexible to conform to the mutually outwardly facing surfaces of the ribs 16.

A fluid synthetic resin is now cast in situ in channel 10, the base of which is covered, and sealed by the tape 26. The ribs 14 and 16 cooperate with the cast-in-situ insulating member 28, and ribs 18 co-operate with the insulating member 20 to retain the outer portions 2,4 of the frame against expansive and compressive forces.

Claims (8)

1. A method of producing a thermally broken elongate frame member comprising: providing a frame member having thermally conductive inner and outer wall portions, means defining a channel in an integral web connecting the inner and outer wall portions, forming a longitudinally extending slot in the channel to provide a thermal break in the integral web between the inner and out wall portions, covering the slot with thermally insulating strip member, casting a thermally insulating member in situ in the channel characterised in that the thermally insulating strip member is a thin and flexible impervious tape member which is bonded to the channel so as to seal the slot.

2. A method according to Claim 1 in which the tape member is pressed into conformity with longitudinally extending projections formed adjacent to the opposed longitudinal side edges of the slot.

3. A method according to Claim 1 or 2 in which the tape member is pressed into conformity with the surface of the channel by means of a pressing tool adapted to conform to the profile of the channel.

4. A method as claimed in Claim 1,2 or 3 in which the tape member is resiliently flexible about its longitudinal axis.

5. A method according to any preceding claim in which the insulating member is formed in situ by an exothermic chemical reaction, and the material of the tape has a softening temperature above about 1000C.

6. A thermally broken frame member comprising conductive outer wall portions formed with inwardly directed members defining a channel wall portion having a longitudinally extending slot, the slot being covered by an insulating strip member, the channel containing a cast-in-situ insulating member, characterised in that the insulating strip member is a thin and flexible impervious tape bonded to the wall portion of the channel so as to seal the slot.

7. A method of forming a thermally-broken frame member substantially as described with reference to the accompanying drawings.

8. A thermally broken frame member substantially as described with reference to the accompanying drawings.