Previously, when windows were constructed from wood, it was common practice to make windows in a so-called Georgian style with an arrangement of smaller panes attached to a matrix of horizontal and vertical bars, thereby forming an overall larger window. Such constructions were originally adopted due to the fact that production of large panes of glass was either impossible or prohibitively expensive. Nowadays, it is easy to produce large panes of glass, and it is more expensive to produce a window with smaller individual panes as this necessitates a more complex construction and is more labour-intensive, especially when a window is double glazed.

However, it is often desirable for aesthetic reasons to simulate the appearance of a Georgian style window, whether it be on a sash, casement or other type.

Previous attempts have been made to simulate a Georgian style on a window made with frame members of modern materials such as aluminium or plastics. To achieve this, separate lengths of glazing bar have been adhered to the surface of a large pane of glass (or double glazing unit) to give the impression that a number of smaller panes make up the window.

Often, these bars are provided on both inner and outer surfaces of the window. The bars are adhered to the glass surface using a variety of different adhesives, but this method suffers from a serious drawback. The adhesives used are all subject to degradation and once the adhesive has degraded beyond a certain critical point it is no longer able to hold the glazing bars securely to the glass. Should the glazing bars fall off, this creates an extremely undesirable visual effect. The problem of adhesive degradation is particularly acute on the external face of a window due to repeated exposure to moisture and the elements, but can also be a problem

on the internal face. The problem of glazing bars falling from the widow is made worse by the fact that the appearance of a complex matrix of glazing bars is actually created by using numerous separate pieces of glazing bar. This means that if the adhesive degradation is bad in one spot, the portion or portions of glazing bar in that area will fall, regardless of the state of the adhesive holding the other pieces. This can lead to a highly undesirable effect.

The present invention stems from the desire to attach glazing bars to windows in a more reliable fashion. Our co-pending international application [filed 16th February 2001 and claiming priority from GB0003813. 3] describes a method of attaching a glazing bar or bars to a window, which glazing bars are much less susceptible to becoming detached from the glass due to degradation of the adhesive. Said method utilises concealed clips to hold the end of the glazing bars.

It has been appreciated that the use of clips as proposed in that application is not always necessary to ensure that a suitably reliable glazing bar matrix is formed. It has been discovered that the use of adhesive to affix the glazing bars to a pane can be sufficient if the glazing bars are connected together into a single unit. Such a unit will remain attached as long as only a couple of good adhesive bonds remain un-degraded. Consequently only complete degradation of all adhesive bonds between glazing bars and pane will cause the any of the glazing bars to fall from their correct position.

Therefore according to the present invention there is provided a method of forming an intersection between two Georgian-effect plastics material glazing bars having the same cross-sectional shape and which reduces in width from the back face of the bar intended to lie on a pane towards the front face of the bar, comprising the steps of: -cutting a first slot transversely across one bar, from the rear face thereof and for a first pre-set depth through the thickness of the bar, the width of the first slot varying so as substantially to correspond to the width of the glazing bar over that first pre-set depth; -cutting a second slot transversely across the other bar, from the front face thereof and for a second pre-set depth through the thickness of the bar

where the sum of the first and second pre-set depths is substantially equal to the thickness of the bars, the width of the second slot varying so as substantially to correspond to the width of the glazing bar over that second pre-set depth; and then -flexing the other bar so as to open the width of the second slot sufficiently to permit the uncut part of the one bar to be entered into the second slot, with the uncut part of the other bar then being located in the first slot ; and -allowing or encouraging the other bar to return to its original state before being flexed.

In most circumstances the method is used to produce an intersection which is substantially rectangular, with the bars at right angles to each other.

However it is possible for the glazing bars to intersect at angles other than 90°, in which case the first and second slots will need to match the projected area of the remaining portion of the opposing bar.

Whilst the production of simple slots as described above will allow the joining of glazing bars, it has also been discovered that the present invention can be significantly improved by increasing the flexibility of the other bar, in the region of the slot therein. Therefore, according to a highly preferred embodiment of the present invention, a notch is formed through the remaining material of the other bar, in the region of the second slot and either essentially simultaneously with or after the cutting thereof.

The provision of a notch offers several major improvements over the basic method as described above. Firstly, glazing bars used in the present invention are usually formed from plastic material such as PVC or PVC-U, as this material is cheap, easy to mould and matches the material used to form window frames. However, whilst such material posses sufficient flexibility to be used in the present invention, it can be susceptible to permanent distortion if flexed (for example, when inserting the uncut part of the one bar into the second slot) so far as to go past the elastic limit of the material. This distortion can leave the rear face of the other bar non-planar, which prevents or inhibits the attachment of the glazing bars to a pane.

Secondly, when the other bar is flexed, stress lines are concentrated around the second slot and cause high stress points. This stress concentration can lead to the formation of cracks in the material of the other bar.

Thirdly, the notch increases the flexibility of the other bar so that it may be flexed further and consequently the second slot may be opened wider. This wider opening permits a relatively wide remaining portion of the one bar to be inserted into a second slot having a much smaller width, before flexing.

Fourthly, the notch allows the second slot to be cut shallower, without adversely affecting the flexibility off the other bar. This permits the relative cutting of the first and second slots to be better tailored to the cross-sectional shape of the glazing bars. Overall the sum of the first and second pre-set depths must remain substantially equal to the thickness of the bars, but the relative depth of each slot can be suited more conveniently to the particular bar.

The notch is formed in the remaining material of the other bar, either from the bottom of the second slot or from the rear face of the other bar.

The notch may be part-circular, triangular or of other cross-sectional shape.

Part circular is preferred as it mitigates the formation of stress points, which as mentioned above promote cracking.

Glazing bars take a variety of shapes, but to ease formation of the slots it is preferred that the cross-sectional shape of each bar defines a land on both sides of the section, part-way between the front and rear faces, and the two slots are cut from the respective face to the land. The cross-section of the bar may be substantially constant from the rear face to the land, and the width of the first slot may therefore be substantially constant.

According to the present invention there is also provided an intersection between two Georgian-effect plastics material glazing bars having the same cross-sectional shape and which reduce in width from the back face of the bar intended to lie on a pane towards the front face of the bar, wherein:

-one bar has a f rst slot extending transversely thereacross from the rear face thereof and fcr a first pre-set depth through the thickness of the bar, the width of the first slot varying so as substantially to correspond to the width of the glazing bar over that first pre-set depth; -the other bar has a second slot transversely across from the front face thereof and for a second pre-set depth through the thickness of the bar, the sum of the first and second pre-set depths being substantially equal to the thickness of the bars, and the width of the second slot varying so as substantially to correspond to the width of the glazing bar over that second pre-set depth; whereby the uncut part of one bar is accommodated in the slot of the other bar and the uncut part of the other bar is accommodated in the slot of the one bar following the flexing of the other bar so as to permit the inter-engagement of the bars to complete the intersection.

For the reasons discussed above it is highly preferred that there is a notch in the remaining material of the other bar, either from the bottom of the second slot or from the rear face of the other bar. The notch may be any suitable shape such as part-circular or triangular in cross-section. Part circular is preferred as it mitigates the formation of stress points, which as mentioned above promote cracking Glazing bars joined by the method of the present invention or incorporating an intersection as described above are intended primarily for attachment to window panes. Therefore it is preferred that the rear surfaces of both bars are provided with adhesive material such as double-sided adhesive tape, which adhesive may be used to stick the glazing bars to the glass.

The cross-section of the glazing bars may be such that lands are formed on one or both sides of the front surface. As mentioned above these can help the formation of the slots by simplifying the cutting pattern required for the bars to neatly inter-engage. In addition the use of lands eases the cutting of the slots, which may often be done by hand.

Frequent, it is desired to have a window with the appearance of a matrix of several glazing bars, dividing a single large pane into several

smaller ones. Using the present invention this can be far better achieved by forming a matrix of intersecting glazing bars all of substantially the same cross- sectional shape, where all intersections between glazing bars are formed as described above. This results in a rigid matrix of glazing bars that can be attached to a pane, parts of which matrix will not individually fall from that pane.

Instead, only a few points of attachment to the pane are needed, such as adhesive tape or clips as mentioned in our co-pending application, referred to above, to prevent any part of the matrix from becoming detached from the pane.

To create an improved simulation of a Georgian-style window, it may be preferred for glazing bars to be fitted to both sides of the pane, or the inner and outer panes in the case of a double-glazed unit, in alignment with each other.

By way of example only certain specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows cross-sections of a glazing bar; Figure 2 shows side and end views of a glazing bar with a second slot cut therein; Figure 3 shows side and end views of a glazing bar with a first slot cut therein; Figure 4 shows a side view of a different embodiment of glazing bar with a second slot cut therein and a notch at the base of the slot ; Figures 5A to 5D is a series of four drawings illustrating steps in the joining of two glazing bars; and Figures 6A to 6D is a series of four drawings illustrating steps in the joining of an embodiment of glazing bars incorporating a notch in the base of the second slot.

Figure 1 shows two different views of the same generally hollow glazing bar for use in a joining method of the present invention. A simple cross-sectional view is shown on the left hand side, and a cross-sectional part perspective view is shown on the right hand side. The glazing bar has a rear face 10, and a profiled front face 12 which includes matching opposite

sides 14 and 16. A lower land 15 and an upper land 17, which are generally parallel to the lower face, are formed on each side 14 and 16 as part of the profiling thereof. The profile shown is of a typical design of Georgian effect glazing bar, but other profiles may also be joined by a method according to the present invention, as long as they are narrower at a plane above the rear face than at the rear face. The glazing bar is usually positioned against a window pane with the rear face 10 disposed thereagainst and held by adhesive material such as double side tape (not shown).

Figure 2 shows a glazing bar 18, corresponding to that of Figure 1, but with a second slot 20 cut into in the front surface 12 thereof, and which forms the"other glazing bar"described above. The bottom or base 21 of the second slot 20 is level with the lower land 15 and the sides of the slot 20 are cut to match the upper profile of the glazing bar. On the right hand side of Figure 2 there is shown a cross-section along line A-A of the other glazing bar 20.

Figure 3 shows a glazing bar 22 again corresponding to that of Figure 1, but with a first slot 24 cut therein. The glazing bar 22 forms the"one glazing bar"as described above and will be described as such. The first slot 24 extends upwards from the rear face 10 to approximately the level of the lower land 15. Again, there is shown on the right hand side of Figure 3 a cross-section along line B-B through the one glazing bar 22.

Figure 4 shows an alternative configuration for the so-called other glazing bar. In this preferred embodiment, a notch 26 is formed in the base 21 of the second slot 20 in the glazing bar 25. This notch 26 increases the flexibility of the glazing bar 25 so that problems such as distortion, cracking and limited slot opening are solved. The notch 26 narrows the remaining material of the glazing bar thereby permitting more flexibility. The notch is concealed by the one glazing bat when connected into the second slot 20, consequently maintaining the correct visual appearance.

Referring to Figures 5A to 5D, there are shown four sequential stages of the process of joining two glazing bars formed with slots as depicted in Figures 2 and 3. To join the one glazing bar 22 and the other glazing bar 18,

the first slot 24 is positioned close to the second slot 20. Then as. shown in Figure 5B the other bar 18 is flexed so that the mouth of the second slot 20 opens wider. Once the mouth of the second slot 20 is opened sufficiently wide, the remaining portion of the one glazing bar 22, in region where the first slot is cut, is inserted into the second slot 20 (Figure 5C). The other glazing bar 18 is then allowed or encouraged, to resume its normal pre- flexed linear state, thereby closing the mouth of the second slot 20 around the one glazing bar 22 (Figure 5D). The one glazing bar 22 is therefore firmly interconnected with the other glazing bar 18 and is held in a fixed spatial arrangement relative thereto.

As mentioned above, it is preferred that a notch 26 is provided in the second slot 20. Figure 6A to 6D show a similar series of drawings to those of Figures 5A to 5D save that a different embodiment of other glazing bar 25 with a notch 26 is used. The one glazing bar 22 is as shown in Figure 3 and the other glazing bar 25 is as shown in Figure 4. The notch allows a greater degree of flexibility in the other glazing bar 25 so that it more easily flexes to open the mouth of the second slot 20. The use of a notch permits a method of joining according to the present invention to be used on a far greater variety of differently-profiled glazing bars. This has helped to remove previous constraints on glazing bar aesthetic design. Once the one glazing bar 22 is held in the slot of the other glazing bar 25, the notch 26 is concealed by the one glazing bar 22.

The slots and notches formed in the glazing bars may be created by any suitable means. Hand cutting of the slots offers greater adaptability but the speed of cutting can be prohibitively slow for large scale operation.

Machine cutting is more accurate and faster.