GB2295184A - Transparent glazing frame - Google Patents

Abstract

Framing members for the construction of windows (or glass screens internal to a building or as part of the external envelope) are made of a light transmitting material, for example clear PVCu plastics, which thereby allows for the construction of areas of glazing without opaque or solid components thus providing optimum transparency or light transmission. Fig 4 illustrates an extruded clear glazing frame in which glass sheets 5 are secured by beads 9 and bedded in clear plastics adhesive strips 10. The frame can be stiffened by a rib 11 or by a separate clip-on stiffening rib (13, Fig 5) or by a glass fin (15, Fig 6) bedded in clear adhesive and attached by plastic pegs. <IMAGE>

Description

TRANSPARENT GLAZING FRAME This invention is a treatment of components that comprise systems for the structural support and framing of areas of glazing. It is intended for use in building construction.

Contemporary building design often places a premium on the provision of maximum daylight to the interior of buildings. In much "commercial" building design in particular, large areas of continuous glazing are increasingly proposed and constructed to provide daylight to 'atrium', circulation and working areas as daylight is considered more energy efficient and more healthy than the artificial alternative.

To achieve large areas of continuous glazing the use of 'frameless' glazing systems is becoming increasingly popular. Typically such systems use steel structural webs to support and to stiffen the areas of glass. Large planes of glass can now be fabricated as 'curtains' made up of multiple individual glass panels, of handleable size, all fixed into suspended steel lattices.

All systems for large areas of glazing have to overcome two conflicting technical demands: first the onerous structural design that is required to hold the glass in place and secondly, the objective of achieving maximum transparency over the glass plane as a whole.

The use of solid materials, usually metal and occassionally timber, for the supporting structures means that these structural elements themselves will always obscure part of the transmitted light.

Where large areas of glass are often used in 'commercial' and public buildings, 'domestic' design (housing) still follows traditional lines in most commonly providing smaller areas of glass, with each individual pane supported in a substantial frame, which is itself built into the solid fabric of the building. Where timber has traditionally been used for this purpose in domestic construction, an equally common option today is the use of aluminium, plastics and occassionally steel.

This invention is concerned with plastics framing techniques. Whilst other alternative compounds are used, the predominant plastics framing material is unplasticized Polyvinyl Chloride (PVCu).

Despite its durability and insulating qualities PVCu window frames are nonetheless still felt to be unpopular because of their aesthetic shortcomings eg. the artificiality of colouring and the large size of components reducing the areas of glass relative to the area of frame for any given structural opening size, compared to the timber or metal alternatives.The development of PVCu window frames has concentrated on the reduction of component sizes. Most contemporary systems utilise steel bars or rods embedded into the plastics frame to give increased rigidity and so enable the reduction in girth of the glazing member.

The development of plastics glazing sheet materials has, by contrast, concentrated on providing good glass substitutes.

Polycarbonate is the most common sheet glass substitute, offering good transparency, and resilience to impact though disavantaged by a tendency to discolour or cloud with prolonged external exposure.

Polycarbonate as used in glazing sheets is a completely different material to PVCu as used in frames. PVCu is, however, just as capable of being manufactured in a transparent form.

Furthermore, in terms of durability and maintenance of transparency in external conditions, it outperforms polycarbonate in most situations.

This invention is concerned with the application of methods of production of plastics glazing sheet to the manufacture of plastics glazing framing. The invention will make it possible to erect large areas of continuous glazing without any visually opaque elements.

According to the present invention there is provided a system of framing for the erection of large areas (eg 20m x 20m) of continuous glazing, where the light transmitting screen material is of glass or of plastics as in conventional use, and where the screen material is fixed onto or within a frame which is fabricated itself from light transmitting plastics material, for example, transparent PVCu.

It will be appreciated that when plastics are used in a conventional opaque form for window framing, the size or bulk of the framing members (relative to the size of the alternative metal or timber framing members) is considered aesthetically disadvantageous.

However, when the members are themselves transparent, as defined by this specification, the increased size of the frame member would increase its transparency. Hence a noted shortcoming of plastics (eg. PVCu) frames is turned to an advantage, because where the geometry of the extruded plastic member itself can be comprised of larger widths of material, so the distortion of light passing through the transparent member is reduced.

It will be seen that in a transparent form and where applied to the erection of large areas of continuous glazing, a frame work of PVCu can be made up of wide or deep extruded planes, so the structural performance of the plastic can be exploited, and the need for metal reinforcing of the frame, (as commonly used embedded in conventional opaque PVCu window frames as a means of reducing the bulk of the framing members), avoided, and that both the increase in size of the members and the lack of metal reinforcing both contribute to the optimising of the degree of transparency of the frame.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which FIG 1 shows a cross section through a conventional opaque PVCu extruded glazing frame FIG 2 shows an equivalent conventional extruded steel frame FIG 3 shows a conventional system of supporting frameless' continuous glass panels.

FIG 4 shows a possible embodiment of the invention in the form of a cross section through a transparent plastics glazing frame.

FIG 5 shows a second embodiment of the invention where the frame is comprised of two principle components, rather than a single extrusion.

FIG 6 shows a version of the frame system shown in Fig 5 which is stiffened with glass fins.

Referring the FIG 1, the frame comprises an extruded body (1), densely structured with stiffening beads and webs (2) and further stiffened with an embedded steel rod (3). The intention of the design is to achieve optimum stiffness with the smallest possible overall dimension. It can also be seen that the frame has a recess (4) provided for the installation of the glass sheet (5) and sealant strip (6).

Referring to FIG 2 it can be seen that an equivalent steel frame is more simple. There are no internal stiffening mouldings because the inherent strength of the material makes it sufficient in this form to support the glass satisfactorily as a simple hollow tube.

Hence it will be seen by comparison of FIG 1 with FIG 2 that there is no practical reason that the plastics frame cannot be fabricated as a much more simple extrusion without internal beads or other reinforcing, provided it would be acceptable to increase the size of the plastics member until it offers a similar rigidity to the steel alternative.

Such a plastics frame may be several times larger than the steel alternative.

FIG 3 shows a typical system of supporting 'frameless' continuous glass planes.

Individual glass panels are drilled and fitted with bolts (7) that are then fixed to the suspended steel lattice (8). It will be obvious from this that, although the plane of glass is not interrupted by framing members, the complexity of the steel supporting lattice is such that it forms a considerable obstruction to the overall transparency of the glass wall.

FIG 4 shows an extruded clear plastics glazing frame for supporting large areas of continuous glass. Applying the principles of the frames shown in FIG 1 and FIG 2, the frame is large and of a simple extruded cross section.Glass sheets (5) are secured by clip on beads (9) and bedded in flexible clear plastics adhesive strips (10) Light will, therefore, pass through the frame with relatively little distortion. The largest dimension is in the depth of the member where optimum resistance to movement caused, for example, by wind loading is provided(11).

This is in a plane perpendicular to the plane of the glass wall.

Such a frame may comprise vertical members only. There is no limit other than practicality of transportation and handling, to the lengths of extrusions that may be manufactured. If horizontal members are not used the PVCu framing effectively performs as a secondary structural column with the glass affixed, transferring the weight of the glass and framing to the primary structure of the building.

Given that glazing frameworks often carry a range of structural loadings (a 'curtain wall' system for example carries a greater load in its structure near the top because of the weight of the area of glass hanging below), and for economy of manufacture, it may be practicable to produce a system of transparent glazing members that comprises seperate components for gripping the edges of the glass sheet and for performing the structural stiffening role. A combined system of this sort is shown in FIG 5. The glass-gripping component (12) is shown 'clipped' onto a stiffening rib (13), both elements being of extruded transparent plastics. The depth of the rib member will be varied according to the span or load (14).

Just as 'glass fins', fixed by bolting onto frameless glazing systems, vertically and perpendicular to the glass screen at the junctions of adjacent glass panels, are commonly used together with steelwork to stiffen the glass plane, so the transparent plastics 'glass gripping' section may also provide for the fixing of glass fins. Such a combination is shown in FIG 6. This is similar to the two-piece plastics frame suggested in FIG 5, but uses glass rather than plastics for the principle structural component, the fin' (15) .The glass fin is bedded into a cushion of clear plastics adhesive (16) and bolted with clear plastics pegs (17). The objective of optimum transparency is not compromised.

Further, this invention can be developed into systems that still incorporate opaque elements for example, steel lattice work or bolts or other fixings if such alternatives are more acceptable for aesthetic functional or economic reasons to specific purchasers.

The full application of transparent plastics as glazing structural framing would, however, use a rigid clear plastic section for retaining and restraining the transparent screen panels whilst junctions of horizontal, vertical and any diagonal bracing members would be made by adhesive bonding, clear plastics pegs or bolts or shims, and weather sealed with clear plastics sealant strips or mastic.

Similarly, various common techniques of fixing the frame onto the surrounding superstructure may be employed, metalwork being the obvious device. As these edge fixtures are not relevant to the transparency of the overall frame they are not relevant to the scope of the invention.

Claims (1)

1. A system of framing for areas of glazing, intended for use in building construction, in which the framing members are themselves made of light transmitting material such as transparent PVCu plastics.

   A system of light transmitting framing for areas of glazing, as descibed in Claim 1, in which the members comprise a series of transparent components allowing for a range of structural performance and methods of application of glass to the frame.