GB2169943A - Residential door leaf - Google Patents

Abstract

A door leaf comprises glassfibre reinforced resin shell(s) 11, encasing an expanded foamed plastics core 12 and joined thereto by a composition 13 comprising a mixture of polyester resin and glass microspheres. A layer 14 of the composition joins the two halves of the leaf together. <IMAGE>

Description

SPECIFICATION Residential door leaf Field of the Invention The invention relates to residential doors and specifically to door leaves which instead of being formed traditionally as a combination of woods are formed from glassfibre reinforced plastics (GRP) resins encasing a core.

Review of Art known to the Applicant It has been proposed to construct residential door leaves by laying up a GRP shell and foaming a plastics core into one of the shell halves before laying up the other shell half on top of it. This theoretically results in a door which is light in weight and can have a self-coloured smooth surface finish. It is found in practice however that the door can easily distort during or immediately after manufacture due to the fact that the two shells are not cured simultaneously.

Attempts have been made to overcome this drawback by manufacturing the two shell halves and joining them to one another around a preformed rigid sheet core in such a way that they cure substantially simultaneously. The resulting door leaf however can still be relatively prone to damage and it is especially difficult to produce satisfactorily a GRP-based door leaf which incorporates reduced-thickness panel sections and which is strong enough to resist everyday use.

The invention seeks to utilise the availability of modern materials and methods to produce a GRPbased door leaf into which considerable variations of thickness by way of recessed panelling can be incorporated whilst still possessing the necessary strength to withstand normal impact in use.

Summary of the Invention The invention is based on the use of glass microspheres, which are known in themselves and which comprise hollow spheres of a complex inorganic silicate in glassy form varying typically in size from 10 to 250 micron. One commercially available form of glass microspheres is sold under the trade mark ARMOSPHERES in the United Kingdom by Armoform Marketing Limited, of Beverley (North Yorkshire) and Dewsbury (West Yorkshire) and is described generally under the heading "Composites News" at page 7 of the magazine "Composites" March 1971 Issue.

According to the broadest aspect of the invention, a residential door leaf comprises a glassfibre reinforced resin shell encasing an expanded foamed plastics core and with the shell being joined to the core by a composition comprising a mixture of polyester resin and glass microspheres.

Preferably the same mixture comprises polyester resin and glass microspheres mixed in a ratio within the range 1:1 and 1:2 parts by volume.

Preferably also the glass microspheres have a specific gravity of approximately 0.6, a bulk density of approximately 0.25 grammes per cubic centimeter and are sized within the range 10 to 250 micron.

Advantageously the glassfibre reinforced resin shell is at least twice, preferably approximately three times, the thickness of the mixture of polyester resin and glass microspheres. It has been found that if the shell is less than approximately twice the thickness of the mixture, then the door leaf is unacceptably weak.

Where the door leaf incorporates reducedthickness panels, a further layer of polyester resin mixed with glass microspheres may advantageously run through thre core; and such further layer is preferably approximately twice the thickness of the composite layer of resin and microspheres which bonds the GRP shell to the core.

In any door leaf embodying the invention, the foamed core is preferably formed from initially rigid preformed expanded polyurthane foam.

Brief Description of the Drawings The accompanying drawings show embodiments of the invention. They are only examples of forms which the invention might take within its broadest aspect, but they are currently the best way known to the applicant of putting the invention into practice.

In these drawings: Figure 1 shows in cross section one residential door leaf embodying the invention, sectioned across its width; Figure 2, drawn to an enlarged scale, shows in cross section the left or right side, and top, region of the door leaf of Figure 1; Figure 3 shows the same door leaf in vertical section; Figure 4 shows the sectioned bottom region of a door leaf modified to incorporate a weatherbar; Figure 5 shows the glass-surrounding region of yet another door leaf embodying the invention, in cross section; and Figure 6 shows diagrammatically the way a door leaf embodying the invention might be fitted into a metal sub-frame which is itself then fitted within the confines of an existing wooden door frame with door-stop section removed.

Description of the Preferred Embodiments In Figures 1,2,3 and 4, the door leaf comprises a glassfibre reinforced resin shell 11 encasing an expanded polyurethane foam core 12 and with the shell being joined to the core by a layer 13 comprising a mixture of a polyester resin and glass microspheres. The microspheres are sold under the trade mark ARMOSPHERES and are marked in the United Kingdom byArmoform Marketing Limited.

Each door leaf shown in Figures 1 to 4 is panelled, the panels are of reduced thickness when compared with the overal thickness of the door leaf, and the decorative relieved mouldings which bound the panels are reduced again in thickness. A further layer 14 of resin and microspheres runs through the core 12 in the panel, and completely fills the space between the opposite halves of the shell 11 in the very thinnest panel edge regions where there is no foamed core 12 and no layer 13 of resin and microsperes. The layer 14, in the regions where it extends through the panels and is sandwiched between core layers 12, is approximately twice the thickness of the layer 13 and that layer 13 is, throughout the door leaf, approximately one third of the thickness of the shell 11.

The door leaves illustrated are produced in a range of glazed or unglazed designs, and two sizes i.e. 6'6" x 2'9" and 6'6" x 2'6". The mould of the front half of the door shell incorporates all four door leaf edges and a release flange. It also includes an integral letterbox sleeve. The mould of the back half of the door shell is the face only, with an inverted release flange. The length and width of the back mould are each 12 mm less than the corresponding dimensions of the front mould, enabling the two halves to be bonded together as illustrated in Figures 2 and 4.

Each half of the door shell is moulded at the same time. Release agent is applied to the moulds. Sheet wax is cut to size of hinge leaf and door lock plate and stuck to required edges of the front mould.

These sheets form recesses in the door at predetermined positionsforthe required door fittings to finish flush. Metal or plastics formers, secured with screws, could be used instead.

Gel coat is applied to the moulds (two coats) to a thickness of 0.020 inches. 30z laminate is applied to the gel coat (i.e. 307. per square foot or chopped strand mat) impregnated with polyester resin. The laminate on back mould is green trimmed to its edges.

Wood is set on the weatherbar 16 on the door leaf on a bed of resin and armosphere paste filler flush with the laminate. This filler is a stiff paste filler.

Expanded polyurethane foam sheet of a density 51b per cubic foot is precut to thicknesses of 33 mm and 6 mm. The 6 mm foam is bonded to the recessed panels on back and front moulds. The 33 mm foam is bonded to areas of full depth on the front mould only. A mixture of one part resin to two parts armospheres by volume is used to bond the foam to the laminate. It is brushed on to the laminate at a thickness of 1 mm and then the foam is pressed into position. Suction holds the foam firmly and evenly in place until its is set.

a" X aS wood strip 15 is set into the foam using the same mix. So too are wooden blocks set into position for sercuring hinges, door lock and letterbox.

The back of the door is bonded in whilst still attached to the mould. This is to ensure that the back is set in level and even. Again a mixture of one part resin and two part armospheres is used, brushing 1 mm thickness on top of 33 mm foam. A stiff paste is applied to 6 mm foam and to edges of patterns in blobs, allowing it to spread when compressed by the back of the door. The back is lowered into position, and pressed firmly until resin and armosphere mix oozes out all round. The weight of the mould holds the back in place until set.

A minimum of 24 hours must elapse before removing the door shell from the mould to enable a full cure to take place. The back mould is removed, and then the door is removed from the front mould.

The door is then trimmed, using a router and appropriate bit. A slot for a water drip is cut in the underside of the weatherbar. On glazed doors (Figure 5) only the front lip is trimmed to a uniform depth of 10 mm from front face. A resin and armosphere stiff filler paste is pressed into the cavity and screeded level to form a rebate for the glass. A bead 18 of silicone adhesivelsealant is applied to rebate and double glazes sealed unit is pressed into place. A glazing wedge 19 is inserted into a precut slot to retain the glass 21.

The trimmed edge around perimeter of the door is covered by a two part plastics strip 22, 23. Part 22 is screwed into position. Part 23 is a snap-in cover. All the door furniture is fixed to the door.

The door is now hung in an especially designed aluminium sub-frame. Wooden door frames are built to standard sizes but vary from one manufacturer to another by up to a3" on any one dimension (height or width). When the door and sub-frame is fitted to an existing wood door frame 24 a gap is left between the sub-frame 25 and existing frame on the sides and top, which is hidden on the outside by the flange of the sub-frame. The gap on the inside is hidden by either (a) silicone bead, (b) a wood quandrant pinned to existing wood frame or (c) a flat plastics strip stuck to sub-frame with silicone sealant adhesive as illustrated at 26.

The door leaves illustrated are strong, light in weight, and readily produced. The method of fixing them via a sub-frame to an existing wooden frame gives a neat and easily achieved installation.

The latterbox sleeve could be incorporated into the back half, rather than the front half, of the door shell mould.

The "stiff" paste filler regions comprise a mixture of from 4 to 6 parts microspheres to 1 part resin.

This mixture has a trowelling consistency.

The foam core may, as stated, be approximately 3 to 5 Ib per cubic foot in density but it could be very much more dense; for example a high security door leaf might incorporate a foam core of approximately 20 Ib per cubic foot density.

The term "door leaf" is intended to include a panel, suitable for incorporating into a peripheral framework which is then hung inside a door uprights and connecting lintel to form a residential door.

Claims (9)

1. A panel, in particular a residential door leaf, comprising a glassfibre reinforced resin shell encasing an expanded foamed plastics core and with the shell being joined to the core by a composition comprising a mixture of polyester resin and glass microspheres.

2. The invention of Claim 1 and in which the said mixture comprises polyester resin and glass microspheres mixed in a ratio within the range 1;1 and 1:2 parts by volume.

3. The invention of Claim 1 or Claim 2 and in which the glass microspheres have a specific gravity of approximately 0.6 and a bulk density of approximately 0.25 grammes per cubic centrimetre and are sized within the range 10 to 250 micron.

4. The invention of any one of the preceding claims and in which the glassfibre reinforced resin shell is at least twice, preferably approximately three times, the thickness of the mixture of polyester resin and glass microspheres.

5. A panel, in particulasr a door leaf, in accordance with any of the preceding claims and incorporating reduced-thickness areas of panel, and in which a further layer of polyester resin mixed with glass microspheres runs through the core, the said further layer being approximately twice the thickness of the composite layer of resin and microspheres which bonds the shell to the core.

6. The invention in accordance with any one of the preceding claims and in which the foamed core is formed from initially rigid preformed expanded polyurethane foam.

7. A residential door leaf substantially as described herein with reference to and as illustrated in Figures 1 to 3 of the accompanying drawings.

8. A door leaf according to CLaim 7 when modifed substantially as described herein with reference to and as illustrated in Figure 4 of the accompanying drawings.

9. A method of making a panel, in particular a residential door leaf, carried out substantially as described herein with reference to Figures 1 to 3 of the accor lpanying drawings.