According to the present invention there is provided a panel assembly comprising a plurality of elongate support members defining at least one substantially rectangular opening and a substantially rectangular panel secured along at least one edge to a respective edge of the opening by at least one retaining member which is snap-fitted to the respective support member.

In one embodiment of the invention the adjacent edges of a pair of panels overlap opposite longitudinal edges of an elongate support member and are there held in place by an elongate retaining member which overlaps such edges on the opposite side thereof to the support member, the retaining member being snap-fitted to the support member through a gap between the adjacent edges of the panels so that the retaining member exerts pressure on the edges of the panels.

In another embodiment of the invention the panel is mounted by its edges in a substantially rectangular frame, and wherein a plurality of retaining members secure the edges of the frame to the respective support members such that the edges of the panel are secured indirectly to the support members via the frame.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a perspective cutaway view of part of a double glazed curtain wall embodying the present invention; Fig. 2 is a cross-sectional view showing the retaining member of Fig. 1 at an initial stage of being snap- fitted to the mullion; Fig. 3 is a cross-sectional view showing the retaining member of Fig. 1 after it has been snap-fitted to the mullion; Fig. 4 is a cross-sectional view showing the retaining member at an initial stage of being snap-fitted to the mullion in a second embodiment of the invention; Fig. 5 is a cross-sectional view showing the retaining member of Fig. 4 after it has been snap-fitted to the mullion; Fig. 6 is a cross-sectional view through the retaining member and mullion in a third embodiment of the invention; Figs. 7A and 7B show a modification of the third embodiment; and Fig. 8 is a cross-sectional view of a fourth embodiment of the invention

In the various embodiments the same reference numerals have been used for the same or equivalent components.

Referring to Figs. 1 to 3, a curtain wall comprises a rectangular grid of elongate support members, i. e. vertical mullions 10 and horizontal transoms 12, defining a plurality of rectangular openings 14 (in Fig.

1 only the intersection of one mullion with one transom is shown). Each rectangular opening 14 is occupied by a respective rectangular double glazed sealed unit 16 which is secured along its edges to the respective edges of the aperture 14, i. e. to the support members 10 and 12 surrounding and defining the opening, in the following manner (the following description will describe the fixing of the opposite vertical edges of the units 16 to the mullions 10, but essentially the same arrangement applies to the fixing of the upper and lower horizontal edges of the units 16 to the transoms 12).

The adjacent vertical edges 18 of each pair of adjacent units 16 overlap the opposite longitudinal edges 20 of a mullion 10, and are there held in place by an elongate retaining member 22 which overlaps the edges 18 on the opposite side thereof to the mullion 10 and which is fixed to the mullion 10 through a gap 24 between the adjacent edges 18 of the units 16 so as to exert pressure on the edges 18 of the units. To avoid damage to the units 16 the retaining member 22 does not directly bear against the edges 18 of the unit 16, nor does the latter directly bear against the edges 20 of the mullion 10. Rather, the pressure is transmitted via pairs of gaskets 26 and 28 carried by the retaining member 22 and mullion 10 respectively. The method of

fixing the retaining member 22 to the mullion 10 uses a snap-fitting, as will now be described.

The mullion 10 has a pair of longitudinally extending jaws 30 opening towards the retaining member 22, and the retaining member has a longitudinally extending tongue 32 for insertion between the jaws. The tongue 32 has in cross-section an enlarged arrow-shaped head 34 and each jaw 30 has, on its internal surface adjacent its free end, a respective wedge 36 pointing in the opposite direction to the arrow-shaped head 34. To fix the retaining member 22 to the mullion 10, the head 34 is inserted between the jaws 30 and the retaining member 22 pushed towards the mullion 10. This initially causes the head 34 to resiliently force the jaws 30 apart, Fig.

2, to allow the head 34 to pass between the wedges 36.

However, upon further insertion the head 34 clears the wedges 36 so that the jaws 30 can close, by relaxation of the resilient deformation, such that the wedges 36 snap-engage behind the head 34 and lock the retaining member 22 to the mullion 10, Fig. 3.

It will be noted that the retaining member 22 is fixed to the mullion 10, as described above, before the gaskets 26 are fitted to the retaining member. This provides for easier assembly. The gaskets 26 are so- called wedge gaskets which are pushed into place from the side of the retaining member 22 afterwards.

If desired, the retaining member 22 can additionally be fixed by a series of auxiliary screws 38 which penetrate the jaws 30 at intervals along the length of the mullion 10. Finally, a cover 40 is snapped into place on the retaining member 22.

In a second embodiment of the invention, Figs. 4 and 5, the tongue 32 on the retaining member 22 is replaced by a further pair of jaws 42 each having, on its external surface adjacent its free end, a respective wedge 44 pointing in the opposite direction to the internal wedges 36 on the jaws 30. In this case, as the jaws 42 are inserted between the jaws 30, Fig. 5, they are initially resiliently squeezed together by the wedges 36 on the jaws 30 (in this case, the jaws 30 are connected together by a crosstie 46 near to their free ends, making them substantially less resilient than in the first embodiment).

However, upon further insertion the wedges 44 clear the wedges 36 so that the jaws 42 can open, by relaxation of the resilient deformation, such that the wedges 44 snap- engage behind the wedges 36 and lock the retaining member 22 to the mullion 10, Fig. 4.

In a third embodiment of the invention, Fig. 6, the tongue 32 of Fig. 1 is replaced by a channel member 48 which has in cross-section an arrow-shaped head 50 and whose opposite sides 52 are integral with the opposite edges 54 of the retaining member 22. In use the channel member 48 is inserted head first between the jaws 30, and initially the opposite sides 52 of the channel member 48 are resiliently squeezed together by the jaws 30 as the arrow-shaped head 50 passes between the wedges 36.

However, upon further insertion the arrow-shaped head 50 clears the wedges 36 so that the opposite sides 52 of the channel member 48 can open, by relaxation of the

resilient deformation, such that the arrow-shaped head 50 snap-engages behind the wedges 36 and locks the retaining member 22 to the mullion 10.

The advantage of this third embodiment is that the opposite sides 52 of the channel member 48 can be manually compressed together by squeezing the opposite longitudinal edges 54 of the retaining member 22 such that the arrow-shaped head 50 can be disengaged from the wedges 36 and the channel member 48 withdrawn from the jaws 30. This allows the retaining member 22 to be readily removed from the mullion 10 if necessary, for example to replace a broken or defective unit 16.

In a modification of the third embodiment, Fig. 7A, an elongate wedge member 56 is forced into the mouth 58 of the channel member 48 so as to maintain the opposite sides 52 apart and prevent inadvertent removal of the retaining member 22 from the mullion 10, especially before the cover 40 is snapped into place. As shown, the member 56 has rearwardly directed resilient barbs 60 which, when the member 56 is fully engaged in the channel member 48, Fig. 7B, engage behind stepped portions 62 in the interior of the channel member 48 to retain the wedge member 56 in place. If necessary, the wedge member 56 can be prised out of the channel member 48 to allow removal of the retaining member 22. To this end the wedge member 56 is made of a relatively deformable plastics material.

In the foregoing embodiments the various components can be made from extruded aluminium or moulded in plastics material.

In the preceding embodiments the edges of the sealed units 16 are, save for the gaskets 26, secured directly to the supports 10,12. Fig. 8 illustrates a fourth embodiment wherein each unit 16 is mounted in a respective rectangular frame and the edges of the unit are secured indirectly to the support members by securing the edges of the frame to the support members.

Fig. 8 is a vertical cross-section of part of a panel assembly showing a horizontal transom 12 and the adjacent edges of two rectangular double glazed sealed units 16 disposed vertically one above the other and secured to the transom. It will be understood that the transom 12 is one of a plurality of such transoms which, together with a plurality of vertical mullions, form a rectangular grid defining a plurality of rectangular openings 14 as described for Fig. 1. Each rectangular opening 14 is occupied by a respective unit 16 secured by its edges to the respective mullions and transoms in the manner now to be described. Although the following description primarily refers to the edges of the units 16 seen in Fig. 8, i. e. the upper edge of the lower panel 16 and the lower edge of the upper panel 16, essentially the same fixing arrangement is used for all four edges of each unit 16 except that the vertical edges are secured to the relevant mullion 10 rather than the transom 12 shown.

Each unit 16 is mounted by its edges in a respective rectangular frame 70 comprising an inner rectangular subframe 70A and an outer rectangular subframe 70B. It will be understood that the inner and outer subframes 70A, 70B are each made up of four lengths of extruded

metal having the cross-section shown in Fig. 8 which are mitred together at the corners of the frame 70. The subframes 70A, 70B are secured together by a rigid thermally insulating material such as a resin 72 which thermally insulates the inner subframe 70A from the outer subframe 70B. The inner subframe 70A is within the outer subframe 70B and is offset relative to the outer subframe 70B in a direction normal to the units 16 and towards the transoms 12 and mullions 10 (not shown).

Within the frame 70 each unit 16 is mounted in the respective outer subframe 70B and there retained in place by four clips 74 each extending along a respective one of the four edges of the unit 16. Each clip 74 is of generally of L-shaped cross-section and engages the outer subframe 70B in the manner shown and presses on the outer surface of the unit 16 via a gasket 76. This maintains the respective edge of the unit 16 under pressure between the gasket 76 and a further gasket 78 which is carried by the inner subframe 70A and presses on the inner surface of the unit 16. The four clips 74, one along each edge of the frame 70, are, like the subframes, mitred together at the corners of the frame.

L-shaped cleats 80 are inserted into the mitred ends of the clips 74 at each corner of the frame to strengthen the corner against a tendency for the clips to open under strain.

Although each unit 16 is physically located within the outer subframe 70B, substantially its entire weight is actually supported by the inner subframe 70A. To this end, the lower edge of each unit 16 rests upon and is supported by one or more generally L-shaped metal support members 82 which engage in a slot 84 in the

inner subframe 70A and extend outwardly beneath the lower edge of the unit 16, the upper surface of each support member 82 having a plastics pad 86 to avoid direct glass-metal contact.

The panel unit 16 is thus mounted in complete thermal isolation from the outer subframe. The inner subframe, being thermally insulated from the exterior and form the outer subframe, is not subject to the condensation problems normally affecting the interior of a metallic window frame.

It will be understood from the foregoing that each frame 70 with its respective unit 16 mounted therein as described is a self-supporting assembly which can be fitted to a pre-assembled grid of mullions and transoms as now described.

Along each edge of the outer subframe 70B a plurality of retaining members 88 are snap-fitted into a slot 90 which extends along the edge of the outer subframe 70B.

Each retaining member 88 is in the form of a channel member with an arrow-shaped head 50', similar to the arrow-shaped head 50 of the Fig. 6 embodiment, and an extended leg 91 on one side which snap-fits into the slot 90. In order to mount the frame 70 to the grid of mullions and transoms, along each edge of the frame the arrow heads 50'of the retaining members 88 are snap- fitted between the jaws 30 of the respective transom or mullion, and wedge members 56 are inserted to prevent inadvertent removal, as previously described for Figs. 6 and 7. Since each set of jaws 30 has to receive retaining members 88 fitted to the edges of two adjacent outer subframes 70B, the arrow-heads 50'of the

retaining members 88 fitted to these outer subframes are inserted alternately into the jaws along the length thereof. Finally, a resilient web 92 is fitted between each pair of adjacent outer subframes 70B to provide a first line of defence against the weather and to conceal the underlying structure.

An advantage of this fourth embodiment is that an opening window vent can be fitted in place of the outer subframe 70B without detracting from the overall appearance of the assembly. It will be understood that although the snap-fit retaining member used in the fourth embodiment is similar to that shown in Fig. 6 and 7, the retaining member could be similar to that used in either of the first two embodiments.

Various modifications to the above embodiments are possible. For example, the jaws 30 could be on the retaining member 22 and the tongue 32, jaws 42 or channel member 48 could be on the support member 10 or 12. Also, although the embodiments have described the use of the invention in the construction of a multi- light curtain wall, the invention is useful in many other situations where it is desired to assemble a plurality of panels.

The invention is not limited to the embodiment described herein which may be modified or varied without departing from the scope of the invention.