PREFABRICATED WINDOW SILL

Abstract

A prefabricated window sill (10) suitable for external use comprises a closed cast outer shell (12) having at least an upper surface (16), a lower surface (18), a front surface (20), a rear surface (22) and first and second end surfaces (24, 26). The shell is made from a composite of a plastic polyester resin mixed with either crushed marble or crushed glass, with a catalyst which causes the resin to set; the shell being filled with an expanded plastics foam.

Claims

1-16. (canceled)

17. A prefabricated window sill suitable for external use comprising a closed cast outer shell having at least an upper surface, a lower surface, a front surface, a rear surface and first and second end surfaces, the shell being made from a composite of a plastic polyester resin mixed with either crushed marble or crushed glass, and a catalyst, causing the resin to set; the shell being filled with an expanded plastics foam.

18. A prefabricated window sill as claimed in claim 17, in which the resin is an isophthalic neopentyl glycol unsaturated polyester resin.

19. A prefabricated window sill as claimed in claim 17, in which the catalyst is a methyl ethyl ketone peroxide.

20. A prefabricated window sill as claimed in claim 17 in which the outer shell is between 1 millimetre and 20 millimetres in thickness.

21. A prefabricated window sill as claimed in claim 17, in which the outer shell is substantially 12 millimetres in thickness.

22. A prefabricated window sill as claimed in claim 17, in which the outer shell is substantially 6 millimetres in thickness.

23. A prefabricated window sill as claimed in claim 17, in which at least one aperture provided in the shell for injecting the expanded plastics foam.

24. A prefabricated window sill as claimed in claim 23, in which two apertures are provided in the sill for injecting the expanded plastics foam.

25. A prefabricated window sill as claimed in claim 24, in which the apertures are provided through the upper surface of the sill.

26. A prefabricated window sill as claimed in claim 17, in which the expanded plastics foam is polyurethane.

27. A prefabricated window sill as claimed in claim 26, in which the polyurethane is composed of a liquid polyisocyanate and a polyol which is mixed in a nozzle on injection.

28. A prefabricated window sill as claimed in claim 17, in which reinforcing is disposed inside the shell.

29. A prefabricated window sill as claimed in claim 28, in which the reinforcing is of steel or carbon fibre.

30. A prefabricated window sill as claimed in claim 28, in which an elongate recess is provided along the lower surface of the shell for serving as a drip bead.

31. A prefabricated window sill as claimed in claim 30, in which a portion of the upper surface is sloped downwardly towards one side thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings, in which:

[0028] FIG. 1 shows a perspective view of a first embodiment of a prefabricated window sill;

[0029] FIG. 1A shows a cross-section through the sill of FIG. 1;

[0030] FIG. 2 shows a perspective view of an alternative embodiment of a prefabricated window sill; and

[0031] FIG. 2A shows a cross-section through the sill of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0032] Referring firstly to FIGS. 1 and 1A, a first embodiment of a prefabricated window sill is indicated generally at 10. The sill 10 has a closed cast outer shell 12 and an expanded foam inner 14. In the embodiment shown, the sill 10 is a stooled sill, which is a well-known design shape of sill. The outer shell 12 has an upper surface 16, a lower surface 18, a front surface 20, a rear surface 22 and first and second end surfaces 24, 26. A front area of the upper surface 16 is effectively cut away and slopes downwardly to allow water to run off in conventional manner. Non-sloping areas of the upper surface 16, i.e. substantially parallel with the lower surface 18, are provided at each end of the sill. These areas are preferably rectangular and can be built off, being capable of bearing significant load. A longitudinally extending groove or recess 28 is provided in the upper surface 16 of the sill to provide a key for mortar. Additionally, a second longitudinally extending groove or recess 29 is provided on the lower surface 18 of the shell 12, providing a drip bead. Grooves of this nature are conventional in the field.

[0033] The outer shell 12 is made from polyester resin in a silicone mould. The mould itself is made from liquid silicone with silicone thickener in a catalysed process. Glass fibre and burlap is used to strengthen the mould as the layers of silicone are laid down, which add both elasticity and strength. The layers of silicone are brushed on evenly by hand and allowed to dry between coats.

[0034] The outer shell 12 is cast as a closed casting in a rotational casting machine. Resin, preferably a polyester resin and more preferably an isophthalic neopentyl glycol unsaturated polyester resin, sold under the trade name CRYSTIC 935PAHR is mixed with a catalyst of methyl ethyl ketone peroxide, and a quantity of crushed marble or glass. The crushed marble or glass may take the consistency of a powder. The resin of the outer shell 12 is allowed to cure, initially at room temperature for around 24 hours, and is then heated to 60 degrees Celsius for around four hours. The heating accelerates the curing process, which at 15 degrees Celsius would take twenty-eight days for an equivalent cure hardness. On removal from the silicone mould, the outer shell 12 has the appearance of a solid casting, but in fact is hollow.

[0035] Alternatively, a composite plastics resin, or more preferably a mixture of at least one orthophthalic unsaturated polyester resin, is used instead of the polyester resin described above. The curing and post-curing processes may differ somewhat from the above temperatures and timescales, depending on the resin used. The catalyst may be another ketone peroxide, or another class of catalyst, where the catalyst used initiates a radical chain reaction (to induce resin setting) and releases a by-product which readily evaporates or dissipates (e.g. acetone, butanone, ether). This allows the resin to dry without retaining solvents which could damage or dissolve other sill components.

[0036] The ideal wall thickness of the outer shell 12 has been found to be around 6 mm. However, wall thicknesses between 1 mm and 20 mm are contemplated for different applications and subject to controlled testing. A thicker outer shell of 12 mm thickness is also a suitable compromise for increased sill strength at the expense of increased sill weight, relative to a shell of 6 mm thickness.

[0037] Two small holes (not shown) are provided in the top of the outer shell 12, towards respective ends, on the upper surface 16 towards the rear surface 22. The expanded foam insulation 14 is injected through these holes simultaneously to fill the outer shell 12. The expanded plastics foam is expanded polyurethane and is composed of a liquid polyisocyanate and a polyol which is mixed in the injection nozzle(s) on injection. It falls within the class of substances, generally known as a Bio Foams. Advantageously, the expanded polyurethane does not incorporate VOCs (volatile organic compounds), CFCs (chlorofluorocarbons), HFCs (hydrofluorocarbons) or urea.

[0038] The density of the foam can be controlled to produce a required insulation value, as required. The foam has an r-value of 0.025. If the density of the foam is increased, the strength of the window sill in both compression and bending can be improved. The foam has no food value for rodents or insects and is self-bonding. It is also envisaged that expanded plastics foam of the type commercially known as Icynene is suitable in the same way as expanded polyurethane. A key factor in the choice of the resin and foam is that they must not react together and degenerate in any way. For example, the resin must not break down bonds in the foam causing it to effectively dissolve.

[0039] Referring now to FIGS. 2 and 2A, the window sill may also be provided as a standard non-stooled sill, indicated generally at 30. It will be appreciated that in view of the manufacturing process of the window sill, decorative features can be added as desired, as long as they can be moulded effectively. The shell can be moulded around reinforcing material, which may be steel, carbon fibre or engineered plastics, and the foam then injected around the reinforcing. High density polyurethane foam can also be reinforced with strands of fibreglass to make structurally reinforced foam.

[0040] It will be appreciated that the window sills described are extremely strong, light to handle, do not have sharp edges, can withstand all weather conditions, have the appearance of stone and, most importantly, can be used with or without external insulation systems to meet required insulation standards. By the use of plastics, cold bridges are entirely avoided. Temperatures inside the structure are therefore less dependent on exterior conditions, remaining warmer in winter and cooler in summer than they might otherwise be, potentially contributing to a reduction of heating costs.

[0041] The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.