GB2427428A - Composite door - Google Patents

Abstract

A composite door 10 has a sub-frame 12 manufactured from lengths of extruded aluminium and side panels 14 mounted to either side of the frame to form the face details of the door. The door comprises means 48 (58, Figure 9) for reducing the thermal conductivity across the extruded aluminium components of the sub-frame from one side of sub-frame to the other. The components of the sub-frame may be hollow and the means for reducing the thermal conductivity across the components may include filling them with a material 48 having a lower thermal conductivity than aluminium. The material 48 may be expanded polyurethane foam. In addition or as an alternative, the sub-frame components may include regions (58, Figure 9) of a material having a lower thermal conductivity than aluminium which act as a thermal break.

Description

DOOR The present invention relates to a door and in particular to a composite door. Known composite doors consist of a sub-frame clad in two side panels, often referred to as skins, which form the face details of the door. The usually rectangular sub-frame can be constructed from a variety of materials, including timber and laminated veneer lumbers (LVL), the outer surface of which may be capped. It is also known to manufacture the sub-frame from solid or hollow plastics extrusions and from aluminium extrusions. Doors constructed with a timber sub-frame are particularly susceptible to bow and twist and moisture ingress can cause swelling of the door leaf. LVL doors are more resilient to bow and twist but are still vulnerable to swelling and distortion caused by moisture ingress. Doors having a sub-frame constructed from plastics extrusions require additional reinforcement to provide the necessary rigidity and thermal stability. A door having an extruded aluminium sub-frame offers the necessary rigidity and thermal stability without the need for additional reinforcing, and is totally resistant to distortion caused by moisture ingress. However, the use of extruded aluminium components within doors has not found acceptance because of the difficulties in achieving good thermal insulation performance. There is a need, therefore, to provide a composite door construction which overcomes, or at least mitigates, the problems of the known prior art doors. In accordance with the invention, there is provided a door having a subframe manufactured from lengths of extruded aluminium and side panels mounted to either side of the frame to form the face details of the door, in which the door comprises means for reducing the thermal conductivity across the extruded aluminium components of the sub-frame from one side of subframe to the other. The extruded aluminium components may be hollow and the means for resisting the transfer of heat may include filling the hollow extruded components with a material having a low thermal conductivity compared with aluminium. Preferably the hollow components are filled with an expanded foam material such as polyurethane. Preferably the expanded foam material is injected into the door to fill the hollow components and a central space between the sub-frame and the outer skins. The components of the sub-frame may be provided with air bleed holes so that the expanded foam material can be injected to fill the central space and the hollow components. The air bleed holes may be off-set.In one embodiment, a least some of the extruded aluminium components of the sub-frame have an inner wall facing the central cavity and an outer wall opposite the inner wall, air bleed holes being provided in both the inner and outer walls, the air bleed holes through the inner wall being offset from the air bleed holes in the outer wall. As an alternative to filling the hollow components with a material of low thermal conductivity, or in addition thereto, the means for resisting the transfer of heat may comprise incorporating a thermal break in the extruded aluminium components of the sub-frame. The thermal break may be in the form of a region or regions of material having a relatively low thermal conductivity compared with aluminium. The sub-frame components having a thermal break may be manufactured using a co-extrusion process. The outer edges of some or all of the sub-frame components may be adapted to receive lippings or edge caps that define the edge details. The lippings or edge caps may be manufactured as extrusions of aluminium or plastics. Several embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a door in accordance with the present invention, with part of a skin of the door cut-away to show the internal details; Figure 2 is a partial view in an enlarged scale of the cut-away portion of the of the door of Figure 1; Figure 3 is a cross-sectional view through a sub-frame for use in a door in accordance with the invention; Figure 4 is an exploded view of the components of the sub-frame of Figure 3; Figure 5, is a cross sectional view through a corner insert forming part of the sub-frame of Figure 3; Figure 6 is a cross-sectional view through an extruded aluminium component forming part of the sub-frame of Figure 3 taken on line A-A;Figure 7 is a cross-sectional view taken through a lipping or edge cap for mounting to an edge of the sub-frame of Figure 3; Figure 8 is a view similar to that of Figure 7 but showing an alternative lipping or edge cap; and Figure 9 is a view similar to that of Figure 6 but showing an alternative form of extruded aluminium component incorporating a thermal break. A composite door 10 in accordance with the invention comprises a subframe 12 and two skins or side panels 14 (only one of which is shown), one skin attached to either side of the frame to provide the face details of the door. The skins 14 can be manufactured from any suitable material and may be moulded GRP or a formed plastics sheet. The skins 14 can be provided with different finishes/details to provide doors having different appearances. Glazing panels may also be incorporated if required in a manner known in the art. The sub-frame 12 is shown in more detail in Figures 3 to 8 and comprises a number, four in this case, of elongate, hollow aluminium extrusions 16, 18, 20, 22 that together define a generally rectangular frame. The ends of the elongate extrusions are mitred and are held together at the corners of the frame by four right angled inserts 24 that engage within the hollow cavities 26 of adjacent pairs of extrusions. The inserts 24 are also manufactured as aluminium extrusions but could be made from extruded plastics instead. In the present embodiment, the inserts are firmly fixed within their respective elongate extrusions by cleating. To this end, each insert has two indentations 28, 30 adjacent the outermost corner into which material of a respective elongate extrusion may be pressed. To construct the sub-frame 14, the elongate extrusions 16, 18, 20, 22 are cut to length and the ends mitred. The elongate extrusions are then assembled into a frame using the corner inserts 24 and are cleated to the inserts. This provides a rigid frame that is dimensionally accurate and stable and which can be handled without any further processing. It will be appreciated that other methods of connecting the elongate aluminium extrusions to form a frame could be used. For example, the ends of the extrusions 16, 18, 20, 22 could be connected together by welding, bonding or using any suitable mechanical fastener, either with or without the use of corner inserts 24 and using any suitable type of joint, such as a mitre or a butt joint as appropriate. Once the sub-frame has been completed, the skins 14 are mounted to the side faces 32 of the frame. Preferably the skins 14 are bonded to the frame using an adhesive, but any suitable means of mounting the skins can be used. The side faces 32 of the elongate extrusions may be serrated or provided with some other suitable surface finish to provide an improved adhesive bond. Any suitable adhesive may be used as will be known in the art. In the present embodiment, the outer edges of the elongate extrusions 16, 18, 20, 22 are provided with formations adapted to receive lippings or end caps 34 that define the edge detail of the door. As shown in Figure 6, these formations include a pair of flanges 36 that project outwardly on either side of the extrusions. In the present embodiment, the flanges 36 comprise an extension of the side faces 32 of the extrusions. At the ends of each flange 36 is an inwardly directed lip 38. Figures 7 and 8 illustrate two types of lipping 34A, 34B that might be employed. Figure 7 shows standard edge cap 34A whilst Figure 8 shows a so called "Euro" edge cap 34B. The lippings 34 are formed as powder coated aluminium extrusions but could also be made from extruded plastics or any other suitable material. Projecting from the inner face 40 of the lippings 34A, 34B are two flanges 42 that are positioned so as to be a snug or interference fit between the flanges 36 on the outer edge of a corresponding one of the elongate extrusions 16, 18, 20, 22 of the sub-frame. A recess 44 is formed at the inner end of each the flanges 42 into which the lip 38 on the end of a respective one of the flanges 36 is received. The arrangement is such that the lippings 34A, 34B can be clipped firmly into place on the elongate extrusions. Two support members 46 project outwardly from the outer face of the elongate extrusions 16, 18, 20, 22 and are arranged to contact the inner surface of the lippings 34 to provide additional support. As can be seen from Figure 2, the skins 14 are sized so as to cover the elongate extrusions forming the frame 12 right up to the ends of the outwardly projecting flanges 36. The lippings 34 are sufficiently wide that the cover the edges of the skins 14 to provide a neat finish. The shape of the lippings 34 can be adapted to meet any particular requirements. On the edge of the door 10 having a lock, the lipping 34 may incorporate the lock whilst on the hinge side; the lipping 34 may incorporate hinge recesses. The use of separate side caps or lippings 34 means that the same extrusion can be used on all sides of the sub-frame, helping to reduce manufacturing costs. Furthermore, it will be possible to replace the lippings 34 in case of damage during use or fitting. However, it will be appreciated that the elongate extrusions 16, 18, 20, 22 could be produced without the need to fit separate lippings. In order to ensure the door 10 provides adequate thermal insulation, the inner core is filled with polyurethane foam 48 or other suitable insulating material. In accordance with the invention, the foam 48 is arranged to fill not only the central cavity 50 between the sub-frame components 16, 18, 20, 22 but also fills the hollow cavities 26 of the components themselves. This is preferably achieved by injecting the foam into the central cavity 50 and allowing the foam to enter the elongate extrusions 16, 18, 20, 22 and the corner inserts 24 through air bleed holes 52, 54. As can be seen best in Figures 2 and 4, air bleed holes 52 are provided in both the inner and outer walls of the elongate extrusions and this enables the air to bleed to atmosphere from the central cavity as the foam is injected. As the central cavity fills, the foam will also pass through the bleed holes 52 in the inner walls of the elongate extrusions to fill the extrusions (as indicted by the arrows 52A in Figure 4), as the air in the extrusions is forced out through the air bleed holes 52 in the outer walls (as indicated by the arrows 52B in Figure 4). Preferably, the air bleed holes 52 in the inner wall of each extrusion are offset from those in the outer wall. It should be noted that whilst air bleed holes 52 are shown only in the left hand side elongate member 22 in Figure 4, similar air bleed holes will be provided in all the elongate members. The amount of foam to be injected is calculated to minimise the over flow excess. By offsetting the air bleed holes 52, and injecting the correct amount of foam, it is possible to promote the flow of the expanding foam into the cavity of the elongate extrusions, throughout their entire lengths, without excess overflow out of the door construction, where it becomes difficult to remove. Alternatively, the central cavity 50 can be filled using a block of thermally insulating material inserted before the second skin 14 is applied so that expanding foam is injected into the sub-frame components only. In a further alternative arrangement, the components of the sub-frame can be prefilled with an insulating material before being assembled. By filling the cavities in the hollow extruded components 16, 18, 20, 22, 24 of the sub-frame with a thermally insulating material, the thermal insulation performance of the door 10 can be improved to meet required standards. Figure 9 illustrates an alternative form of elongate aluminium extrusion 56 that incorporates a thermal break 58. In this arrangement, a region of material 58 having a lower thermal conductivity than aluminium is co-extruded to provide a thermal resistance in the thermal path from one side of the extrusion to the other. The thermal break 58 preferable comprises plastics or like material. This arrangement by be used as an alternative to or in addition to filling the internal cavities of the sub-frame components with an insulating material. For the avoidance of doubt, it should be understood that references to aluminium and extruded aluminium include aluminium alloys and extruded aluminium alloys. Whereas the invention has been described in relation to what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed arrangements but rather is intended to cover various modifications and equivalent constructions included within the spirit and scope of the invention.

Claims (15)

1. A door having a sub-frame manufactured from lengths of extruded aluminium and side panels mounted to either side of the frame to form the face details of the door, in which the door comprises means for reducing the thermal conductivity across the extruded aluminium components of the sub-frame from one side of sub-frame to the other.

2. A door as claimed in claim 1, in which the extruded aluminium components of the sub-frame are hollow and are filled with a material having a lower thermal conductivity than aluminium.

3. A door as claimed in claim 2, in which the material is expanded foam.

4. A door as claimed in claim 2 or claim 3, in which the material is polyurethane.

5. A door as claimed in any one of claims 2 to 4, in which the material is injected into the door to fill the hollow components.

6. A door as claimed in claim 5, in which the foam is injected into the door to also fill a central cavity between the sub-frame components.

7. A door as claimed in claim 5 or claim 6, in which the components of the sub-frame are provided with air bleed holes.

8. A door as claimed in claim 7, in which at least some of the bleed holes are off-set.

9. A door as claimed in claim 7, in which at least some of the extruded aluminium components of the sub-frame have an inner wall facing the central cavity and an outer wall opposite the inner wall, in which air bleed holes are provided in both the inner and outer walls, the air bleed holes through the inner wall being offset from the air bleed holes in the outer wall.

10. A door as claimed in any previous claim, in which a thermal break is incorporated into the extruded aluminium components of the sub-frame to reduce thermal conductivity from one side sub-frame to the other.

11. A door as claimed in claim 10, in which thermal break comprises a region or regions of a material having a lower thermal conductivity than aluminium.

12. A door as claimed in claim 10 or claim 11, in which the sub-frame components are manufactured using a co-extrusion process.

13. A door as claimed in any previous claim, in which outer edges of some or all of the sub-frame components are adapted to receive lippings or edge caps that define the edge details of the door.

14. A door as claimed in claim 13, in which the lippings or edge caps are manufactured as extrusions of aluminium or plastics.

15. A door substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.