GB1581881A

GB1581881A - Method of forming a compound section structural element

Info

Publication number: GB1581881A
Application number: GB8920/77A
Authority: GB
Original assignee: Anglian Windows Ltd
Current assignee: Anglian Windows Ltd
Priority date: 1978-03-03
Filing date: 1978-03-03
Publication date: 1980-12-31

Description

(54) METHOD OF FORMING A COMPOUND SECTION STRUCTURAL ELEMENT (71) We, ANGLIAN WINDOWS LIMITED, a British Company of 114 Oak Street, Norwich, Norfolk NR3 3BP, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method which it is to be performed, to be particularly described in and by the following statement: This invention relates to constructional means for the formation of a compound section structural element in which two elongate outer portions are interconnected throughout their length by a body of heat insulating material and to an improved method of constructing a compound section structural element.

Constructional means such as this are described in British Patent Specification No.

1347275 and as described therein are suitable for the manufacture of frame members of the kind in which elongate outer portions, for example, made of a light metal such as aluminium, are interconnected by means of a body of heat insulating material for fabricating frames for windows, doors and facade sections in which it is important to prevent or impede the heat flow resulting from differential temperatures from one face of the frame to the other.

It is known from the aforementioned British Patent Specification No. 1347275 to provide constructional means for the formation of a compound section structural element in which two elongate outer portions are interconnected throughout their length by a body of heat insulating material, in which the constructional means comprises the two elongate outer portions together with two detachable panels for holding the two outer portions in fixed spaced relation so as to form a hollow cavity within the constructional means for casting the body of heat insulating material, the two panels being integrally connected to the two outer portions and formed with external weakening notches at junctions between the panels and the outer portions for removal of the panels from the outer portions, after casting the body of heat insulating material, without cutting.

The aforementioned Patent Specification also describes the method of forming a compound structural element using the said constructional means which involves the steps of casting the body of heat insulating material in the hollow cavity of the constructional means and subsequently removing the detachable panels without cutting, for example, by tear ing or the invention described It Is clalmeu that the invention described and claimed in British Patent Specification 1347275 affords the advantage that, the resistance of the compound section structural element to deformation and the required stability of the element are not reduced by the foaming pressure of the nascent insulator and the panels interconnecting the outer portions may be removed without having to carry out any cutting operation. In this way the body of heat insulating material is thus not exposed to any danger of being damaged upon removal of the panels.

This last feature is of importance since much of the strength of the cast body of certain foamed or expanded synthetic resin materials lies in the surface of the cast body which on setting forms a hard rigid skin around the relatively soft porous core. If the surface skin is damaged for example by a cutting blade used to remove the detachable panels, the strength of the compound section structural element is considerably reduced and in addition water vapour can enter the soft porous interior of the cast body which will result in breakdown of the body within a relatively short period of time both from a structural and thermally insulating standpoint.

What is perhaps more important is that Applicants have found nevertheless that it is often impossible to remove the detachable panels without disturbing and breaking up the surface skin of the cast body of foamed or expanded synthetic resin material unless particular procedures are followed.

It is therefore an object of the present invention to provide an improved method of making a compound section structural element in which two elongate outer portions are interconnected throughout their length by a body of heat insulating material.

It is another object of the present invention to provide an improved compound section for use as a window or door frame.

According to one aspect of the present invention a method of forming a compound structural element from a constructional means comprising two elongate outer portions and two detachable Panels holding the two outer portions in fixed spaced relation so as to form a hollow cavity within the constructional means comprises covering the internal surfaces of at least the detachable panels with a liquid film and casting a body of heat insulating material within the cavity, the liquid film serving to prevent the surface of the body of heat insulating material from sticking to at least the internal surfaces of the removable panels, and removing the panels from the outer portions after casting the body of heat insulating material so as to leave a compound section structural element in which the two elongate outer elements are interconnected throughout their length by the cast body of heat insulating material.

The invention allows the detachable panels to be removed from the constructional means without damage to the surface of the cast body of heat insulating material.

Where the whole of the interior of the cavity is coated, the film of liquid will also prevent the body of heat insulating material from sticking to the two elongate outer portions of the constructional means and preferably therefore each of the said elongate outer portions includes integral inwardly directed projections which become embedded in the body of heat insulating material as the latter sets during the casting process so as to prevent the withdrawal of the cast body of heat insulating material from the elongate outer portions other than perhaps by relative sliding of the cast body of heat insulating material and elongate outer portions along the length direction of the latter. Alternatively or in addition the internal cross section of each elongate outer portion is at least in part trapezoidal so that the body of heat insulating material which is cast therein is wedgeshaped and is thereby prevented from being pulled out of the elongate outer portion other than by relative sliding in the length direction of the elongate outer portion.

Where the constructional means is formed from extruded aluminium section, the invention is most simply put into practice by protecting the interior surface of the cavity within the constructional means during the anodising process to which the aluminium section is invariably subjected. The protection is most simply afforded by inserting bungs into the two ends of the said cavity before the section is dipped into the various surface treatment baths. t is found that sufficient die lubricant from the extruder remains on the surface of the interior of the cavity to constitute the desired liquid film so as to prevent a body of heat insulating material subsequently cast within the cavity from sticking to the inside surfaces of the cavity so as to facilitate removal of the detachable panels in accordance with the invention.

Alternatively, the complete aluminium section may be subjected to its normal surface treatments including anodising treatment, after which a suitable liquid is sprayed or poured into the cavity so as to form a thin liquid film on the entire interior surface of the cavity after which the body of heat insulating material can be cast in the cavity.

The properties of the liquid which is sprayed or poured into the cavity must be such that the liquid wets the interior surface of the cavity and does not react with the material forming the cavity nor with the heat insulating material either before or after the latter has set and which remains stable or at least inert at the temperatures and pressures associated with the casting process. A suitable liquid comprises a die lubricant as conventionally employed in aluminium extrusion processes.

In accordance with a preferred method the die lubricant which remains on the interior surface of the cavity after extrusion is retained thereon by inserting bungs into the ends of the aluminium section, each of the bungs itself having a small diameter passage which is closed by means of a separate bung whilst the aluminium section is subjected to surface treatment and anodising but which can be removed to allow a foaming plastics material to be injected into the interior of the cavity to completely fill the same upon setting to thereby form the body of heat insulating material therewithin, the two first mentioned bungs being removed after the body of heat insulating material has been so cast.

In the preferred method the bungs and separate bungs are preferably formed from Polyethylene.

Preferably, the liquid film is only provided on the inside surfaces of the detachable panels of the said constructional means so as not to impair the key between the two elongate outer portions of the constructional means and the body of heat insulating material.

Where the constructional means is formed from extruded aluminium section, this alternative method is most simply put into effect by subjecting the complete aluminium section (both inside and outside of the cavity) to the conventional surface treatment steps and anodising steps so that both the inside and outside surfaces of the cavity are cleaned and anodised after which the liquid film is applied to only the inside surfaces of the two detachable panels of the constructional means by causing a liquid transfer means to traverse the interior of the cavity from one end of the aluminium section to the other so as to deposit liquid on the inside surface of the cavity but only in the region of the inside surfaces of the said detachable panels.

Liquid transfer means for effecting this method conveniently comprises a reservoir of liquid adapted to fit within the cross section of the cavity, guide means for locating the said reservoir in sliding relation within the cavity thereby to allow the said reservoir to be pushed from one end of the cavity to the other, the reservoir maintaining its relative position within the cavity during the entire traverse of the cavity and further comprising means for transferring liquid from the reservoir to the inside surfaces of the detachable panels which extend from one end of the constructional means to the other and form part of the wall of the cavity.

The means for conveying liquid from the reservoir to the inside surfaces of the detachable panels may for example comprise rotatable members such as wheels or rollers which are maintained in engagement with the inside surface of each of the detachable panels for example by spring means or gravity and are located within the reservoir so that rotation of the members causes the surface thereof to pick up liquid which is then transferred to the said interior surface of a detachable panel as the member rotates with the linear progression of the reservoir through the constructional means.

According to a preferred feature of the present invention in a constructional means from which a compound section structural element is formed by the method of the invention in which two elongate outer portions are interconnected throughout their length by a body of heat insulating material, which constructional means comprises two elongate outer portions and two detachable panels for holding the two outer portions in fixed spaced relation so as to form a hollow cavity within the constructional means for casting a body of heat insulating material, the two panels being integrally connected to the two outer portions, internal weakening notches are formed at the junctions between the detachable panels and the outer portions of the panels to facilitate the removal of the detachable panels from the outer portions after casting the body of heat insulating material, and also to define the surfaces within the cavity to which a liquid film must be applied.

Conveniently the internal notches constitute linear guides for guiding a liquid transfer device for coating the internal surfaces with liquid, which extend from one end of the cavity to the other.

The material which is cast in the cavity is preferably a synthetic resin material which foams or expands to fill the cavity.

A compound section constructed in accordance with the invention can be used to form a frame for a window or a door wherein the one elongate outer portion comprises the external surface of the frame and the other elongate outer portion comprises the inner face of the frame and the body of heat insulating material reduces the transfer of heat from the inside face of the frame to the outside face of the frame when a temperature differential exists thereacross.

According to a further preferred feature of the invention, each detachable panel includes an elongate enlargement of the thickness thereof immediately adjoining the notches so as to reduce the risk of the tearing lines departing from those defined by the notches.

Preferably each elongate increase in thickness of the detachable panel comprises an internally projecting elongate protrusion along each of the detachable panels, but it is to be understood that the preferred feature of the invention is not limited solely to internally directed protrusions but includes an enlargement of the thickness of the panel in both an internal and external direction so as to form a ridge on both the inside and outside surfaces of each detachable panel along the two opposite parallel edges thereof.

It will be seen that by providing at least an internally directed elongate protrusion along each of the edges of the detachable panel, so an elongate furrow or indentation will be formed in the surface of the cast member which are revealed when the panel is removed immediately adjacent each of the torn edges. This facilitates the removal of burrs and sharp edges from the torn edges on opposite sides of the gap after a detachable panel has been removed since it allows a rotating tool or planing device operation at an angle (of for example 45 ) to remove the right- angled corner of the material forming the edge (which may or may not be jagged or torn badly) with the lower corner of the tool contained within the elongate indentation or furrow, with little or no risk of the tool touching the surface of the cast body.

The provision of the regions of increased thickness along the two parallel edges of each tearaway strip or detachable panel thus provide a dual function: (a) they resist non-parallel tearing of the strip and (b) they form elongate indentations in the surface of the cast body at a convenient position in the surface thereof so as to accommodate the edge of a finishing tool applied to remove burrs and sharp corners from the exposed torn edges on opposite sides of the gap left when the panel or strip is removed.

One material for casting in the section comprises a rigid Polyurethane integral skin foam material such as Baydur 60 as manufactured and sold by the Bayer Company.

Another material for casting in the section comprises a casting synthetic resin plastics material such as a two-part chemically unfilled high strength Polyurethane resin.

Where the first mentioned material is employed the method additionally includes the step of heating the compound structural element uniformly along its length, typically to 400C.

The invention will now be described by way of example with reference to the accompanying drawing.

Fig. 1 is a cross section through a constructional means employed in a method based on the invention, Fig. 2 is a cross section through a portion of the wall of the constructional means of Fig. 1 when the interior thereof is completely filled with a heat insulating material.

Fig. 3 is a similar cross section with the detachable panel removed so as to leave the compound structural element in which the two metal sections are joined by the body of heat insulating material, and Fig. 4 is a similar view to that of Fig. 3 and illustrates how a finishing tool can be applied to remove burrs and sharp edges from the exposed torn edges on opposite sides of each gap in the compound structural element.

In Fig. 1 there is shown in cross section the cavity formed in an extruded aluminium section generally designated 10 two walls of which include detachable panels 12 and 14.

With the panels detached, the two metal sections left are joined by a body of heat insulating plastics material which is cast into the cavity 16 during the process of manufacture of the compound structural element from the extruded aluminium section (elsewhere referred to as a constructional means).

Each detachable panel is defined by a pair of parallel internally formed notches 18 and 20 on the one hand and 22 and 24 on the other hand. The depth of the notches is such as to leave a very thin bridge which can be broken by a tearing action. The strip can thus be removed by rolling the torn-off strip back on itself in much the same way as a domestic can-opener will roll back a detachable panel or lid of a hermetically sealed can.

In order to reduce the risk of the tearing line departing from the two parallel lines formed by the vertices of the two parallel grooves 18 and 20 on the one hand and 22 and 24 on the other hand, the two parallel edges of the detachable strip are reinforced by internally directed elongate protrusions or ridges 26 and 28 on the one hand and 30 and 32 on the other hand.

Referring now to Fig. 2, this shows part of the wall section in the immediate vicinity of one of the tear-off strips 12 and shows to an enlarged scale the internal notches 18 and 20 and the edge.enlargements 26 and 28. The interior of the cavity 16 is shown as being filled with a synthetic resin plastics material generally designated 34 having a high resistance to the transfer of heat.

One material which may be used is a twopart chemically unfilled high strength Polyurethane casting resin, as manufactured by Berger Chemicals Limited of Portland Road, Newcastle-upon-Tyne and sold under the trade name PR459.

An alternative material which may be used is a rigid Polyurethane integral skin foam material such as produced by the Bayer Company of West Germany under the trade name Baydur 60. In this case the cavity must be uniformly warmed to 40"C before the material is added.

Referring now to Fig. 3, the compound structural element is formed by removing the detachable panel 12 (and likewise the detachable panel 14) by a tearing action along the two imaginary lines at the vertices of the internally formed grooves 18, 20, etc.

The gap left when a panel 12 is removed is shown in Fig. 3, as are the elongate indentations 36 and 38 left in the surface of the heat insulating material 34 in the immediate vicinity of each of the torn edges 40 and 42.

As shown in Fig. 4, burrs and sharp protrusions from the exposed torn edges 40 and 42 can be removed using a finishing tool which may include a rotating wheel or may simply be in the form of a file with the working surface of the tool or file set at an angle of for example 45" as is shown in the drawing. The tool can be used without any special precautions to prevent the tool edge from touching the surface of the heat insulating material since the indentation 36 or 38 will allow the lower edge of the tool when viewed in cross section to occupy the place which would otherwise have been occupied by the heat insulating material if the indentation was not provided, and in this way the exposed edges left when the panel 12 is removed can be de-burred and rendered aesthetically pleasing and safer than would otherwise be the case.

It has been found to be an advantage to use a casting synthetic resin plastics material as opposed to a foaming material since by using a casting material a better guarantee that the cavity has been completely filled is obtained which is not the case when reliance for complete filling is placed on the expansion factor of a foaming material.

In accordance with the invention a film of a suitable liquid such as an aluminium extrusion die lubricant is left on, or applied to the internal surfaces of at least the tear-off strips 12, 14 before the plastics insulating material is cast in the cavity 16. This is found to prevent the strips 12, 14 from sticking to the plastics material. The film may be left by blocking up the ends of the cavity 16 before the extrusion is subjected to the usual clearing and plating baths. Alternatively a reservoir of the liquid (not shown) having one or more rollers, may be pushed through the extrusion from one end to the other after the extrusion has been cleaned and plated or anodised, so as to deposit on the internal surfaces of the tear-off strips a suitable liquid before the plastics insulating material is injected into the cavity and cast therein.

The method and constructional elements described herein are also described in our copending Patent Application No. 9487/78 (Serial No. 1581882) divided herefrom.

WHAT WE CLAIM IS: 1. A method of forming a compound structural element from a constructional means comprising two elongate outer portions and two detachable panels holding the two outer portions in fixed spaced relation so as to form a hollow cavity within the constructional means comprising the steps of: - covering the internal surfaces of at least the detachable panels with a liquid film, - casting a body of heat insulating material within the cavity, the liquid film serving to prevent the surface of the body of heat insulating material from sticking to at least the internal surfaces of the removable panels, and - removing the panels from the outer portions after casting the body of heat insulating material so as to leave a compound section structural element in which the two elongate outer elements are interconnected throughout their length by the cast body of heat insulating material.

2. A method as claimed in claim 1 in which each of the said elongate outer portions includes integral inwardly directed projections which become embedded in the body of heat insulating material as the latter sets during the casting process so as to re- vent the withdrawal of the cast body of heat insulating material from the elongate outer portions other than by relative sliding between the cast body of heat insulating material and elongate outer portions in a direction parallel to the length direction of the latter.

3. A method as claimed in claim 1 or 2 in which the internal cross section of each elongate outer portion is at least in part trapezoidal so that the body of heat insulating material which is cast therein is wedge-shaped and is thereby prevented from being pulled out of the elongate outer portion other than by relative sliding parallel to the length direction of the elongate outer portion.

4. A method as claimed in any of the claims 1 to 3 in which the constructional means is an aluminium extrusion of box section which is extruded through a die using a lubricating liquid which forms a film over the surface of the aluminium and the method includes the step of blocking-off the interior of the extruded box section whilst the latter is subjected to de-greasing and anodising treatment.

5. A method as claimed in claim 4 in which the interior of the box-section is blocked off by bungs.

6. A method as claimed in claim 5 in which each of the bungs has a small diameter passage therethrough which is normally closed by means of a subsidiary bung, and the method further comprises the steps of removing the subsidiary bungs, injecting a foaming plastics material into the interior of the cavity to completely fill the same and upon setting to form the body of heat insulating material therewithin, and removing the first mentioned bungs after the body of heat insulating material has been so cast.

7. A method as claimed in claim 6 in which the bungs and subsidiary bungs are formed from Polyethylene.

8. A method as claimed in any of claims 1 to 3 in which the constructional means is an aluminium extrusion of box section which after extrusion is subjected to its normal surface treatments including anodising treatment, after which a liquid is sprayed or poured into the cavity so as to form a thin liquid film on the interior surface of the cavity whereafter the body of heat insulating material is cast in the cavity.

9. A method as claimed in any of claims 1 to 3 in which the constructional means is extruded aluminium section, having a box cross section and the method comprises the steps of subjecting the extrusion both inside and outside the box section to the conventional surface treatment and anodising steps so that both the inside and outside surfaces of the cavity are cleaned and anodised and thereafter causing a liquid transfer means to traverse the interior of the box-section cavity from one end to the other so as to deposit a liquid on the inside surface of the cavity on the inside surfaces of the said detachable panels.

10. A method as claimed in claim 9 in which the liquid transfer means comprises a reservoir of liquid adapted to fit within the box section of the cavity, guide means for locating the said reservoir in sliding relation within the cavity thereby to allow the said reservoir to be pushed from one end of the cavity to the other, the reservoir maintaining its relative position within the cavity during the entire traverse of the cavity and further

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. In accordance with the invention a film of a suitable liquid such as an aluminium extrusion die lubricant is left on, or applied to the internal surfaces of at least the tear-off strips 12, 14 before the plastics insulating material is cast in the cavity 16. This is found to prevent the strips 12, 14 from sticking to the plastics material. The film may be left by blocking up the ends of the cavity 16 before the extrusion is subjected to the usual clearing and plating baths. Alternatively a reservoir of the liquid (not shown) having one or more rollers, may be pushed through the extrusion from one end to the other after the extrusion has been cleaned and plated or anodised, so as to deposit on the internal surfaces of the tear-off strips a suitable liquid before the plastics insulating material is injected into the cavity and cast therein. The method and constructional elements described herein are also described in our copending Patent Application No. 9487/78 (Serial No. 1581882) divided herefrom. WHAT WE CLAIM IS:

1. A method of forming a compound structural element from a constructional means comprising two elongate outer portions and two detachable panels holding the two outer portions in fixed spaced relation so as to form a hollow cavity within the constructional means comprising the steps of: - covering the internal surfaces of at least the detachable panels with a liquid film, - casting a body of heat insulating material within the cavity, the liquid film serving to prevent the surface of the body of heat insulating material from sticking to at least the internal surfaces of the removable panels, and - removing the panels from the outer portions after casting the body of heat insulating material so as to leave a compound section structural element in which the two elongate outer elements are interconnected throughout their length by the cast body of heat insulating material.

comprising means for transferring liquid from the reservoir to the inside surfaces of the detachable panels which extend from one end of the extrusion to the other.

11. A method as claimed in claim 10 in which the means for conveying liquid from the reservoir to the inside surfaces of the detachable panels comprises one or more rotatable members such as wheele or rollers which are maintained in engagement with the inside surface of each of the detachable panels for example by spring means or gravity and are located within the reservoir so that rotation of the members causes the surface thereof to pick up liquid which is then transferred to the said interior surfaces of detachable panels as the members rotate as the reservoir progresses through the extrusion.

12. A method as claimed in any of the preceding claims which further comprises the step of forming internal weakening notches at the junctions between the detachable panels and the outer portions of the panels to facilitate the removal of the detachable panels from the outer portions after casting the body of heat insulating material, and also to define the surfaces within the cavity to which a liquid film must be applied.

13. A method as claimed in claim 12 in 'which the internal notches constitute linear guides for guiding a liquid transfer device for casting the internal surfaces with liquid, which extend from one end of the cavity to the other.

14. A method as claimed in any of the preceding claims in which the material which is cast in the cavity is a synthetic resin material which foams or expands so as to fill the cavity.

15. A method as claimed in claim 12 or 13 or 14 in which each detachable panel includes elongate enlargements of the thickness thereof immediately adjoining the notches so as to reduce the risk of the tearing lines departing from those defined by the notches.

16. A method as claimed in claim 15 in which each elongate increase in thickness of the detachable panel comprises an internally projecting elongate protrusion along each of the edges of the detachable panel.

17. A method as claimed in claim 16 in which the internally directed elongate protrusions along each of the edges of the detachable panel form two parallel elongate furrows or indentations in the surface of the cast member which are revealed when the panel is removed immediately adjacent each of the torn edges.

18. A method as claimed in claim 17 which further comprises the step of removing burrs and sharp edges from the torn edge on opposite sides of the gap after the detachable panel has been removed using a rotating tool or planing device operating at an angle so as to remove the right-angled torn corner of the material forming the edge with the lower corner of the tool contained within the elongate indentation or furrow, with little or no risk of the tool touching the surface of the cast body.

19. A method as claimed in anyofclaims 1 to 18 in which the material which is cast in the cavity is a rigid Polyurethane integral skin foam material.

20. A method as claimed in claim 19 which includes the additional step of heating the compound structural element uniformly along its length to 400C.

21. A method as claimed in claim 1 in which the material cast in the cavity is a casting synthetic resin plastics material such as a two-part chemically unfilled high strength Polyurethane resin.

22. A compound section constructed in accordance with the method as claimed in any one of the preceding claims when forming a frame for a window or a door wherein the one elongate outer portion comprises the external surface of the frame and the other elongate outer portion comprises the inner face of the frame and the body of heat insulating material reduces the transfer of heat from the inside face of the frame to the outside face of the frame when a temperature differential exists thereacross.

23. A method of forming a compound structural element from a constructional means as herein described with reference to and as illustrated in the accompanying drawings.