WO2008138032A1

WO2008138032A1 - Panel and method of forming same

Info

Publication number: WO2008138032A1
Application number: PCT/AU2008/000522
Authority: WO
Inventors: Daniel Gerard Carrick
Original assignee: INSITE MANUFACTURING Pty Ltd
Current assignee: INSITE MANUFACTURING Pty Ltd
Priority date: 2007-05-16
Filing date: 2008-04-11
Publication date: 2008-11-20
Anticipated expiration: 2009-11-16
Also published as: AU2008251003B2; NZ581082A; AU2008251003A1

Abstract

A method of cold forming a length of polycarbonate sheet, including the step of feeding the polycarbonate sheet through a roll forming station. A security panel having opposed side edges bent to extend back over a central portion of the panel between the side edges so as to form retaining rails for retaining the security panel within a channelled frame of a security closure, wherein the opposed side edges are bent by a method of roll forming.

Description

PANEL AND METHOD OF FORMING SAME

Field of the Invention

This invention relates to method of forming a length of polycarbonate sheet, and to a panel for mounting in a channelled frame of a closure.

Background of the Invention

It is known to provide a folding security closure, for example of the kind used to close the entrance to a shop overnight. This kind of security closure may be in the form of an articulated screen formed of a series of hinged panels which can be drawn across the shopfront, or folded at the hinges so as to be stored at one side of the shopfront when not in use.

The panels of existing folding security closures are formed of tempered glass, polycarbonate, solid aluminium, perforated extruded aluminium or perforated steel, and each panel is held within a hinged frame. It is advantageous for the panels to be formed of polycarbonate which is both strong and transparent, enabling potential shoppers to view goods within a shop through the closure. However, where the panels have been formed of polycarbonate in previously proposed closures, they have been formed of flat panels with side edges of the panels being held in channels of the frame. During use, these sheets are sometimes subjected to force, for example when being kicked by vandals, and the applicant has identified the existing polycarbonate sheets do not stand up well to such abuse as they tend to bend under force such that they "pop out" from the frame.

Moreover, where the panels have been formed of aluminium, they have been formed by a process of extrusion which requires a minimum material thickness of approximately 3mm to a panel width of 240mm. The applicant has identified there is wastage of material in such panels. Also, extrusion tolerances are difficult to maintain over long runs, and line bending is very time consuming and the cross-sections achievable are limited. Strip heating is also very time consuming.

Examples of the present invention seek to provide an improved security panel and a method forming same which overcomes or at least alleviates one or more of the above- mentioned disadvantages.

Summary of the Invention

In accordance with one aspect of the present invention, there is provided a method of cold forming a length of polycarbonate sheet, including the step of feeding the polycarbonate sheet through a roll forming station.

Preferably, the method includes the step of feeding the polycarbonate sheet through a plurality of roll forming stations.

More preferably, the method includes the steps of feeding the polycarbonate sheet through a first roll forming station so as to bend side edges of the polycarbonate sheet beyond an elastic limit to a first bending angle; and subsequently feeding the polycarbonate sheet through a second roll forming station so as to further bend the side edges of the polycarbonate sheet beyond an elastic limit to a second bending angle, wherein the second roll forming station is configured to accept the polycarbonate sheet from the first roll forming station after the edges of the sheet have resiliently partially sprung back from the first bending angle.

Even more preferably, the method includes the step of subsequently feeding the polycarbonate sheet through third and subsequent roll forming stations so as to further bend the side edges of the polycarbonate sheet beyond an elastic limit to third and subsequent bending angles, with each of said bending angles being greater than the bending angle of the preceding roll forming station, wherein each of the third and subsequent roll forming stations is configured to accept the polycarbonate sheet from the preceding roll forming station after the edges of the sheet have resiliently partially sprung back from the bending angle of the preceding roll forming station.

Preferably, a final one of the roll forming stations has a bending angle of greater than 90 degrees. More preferably, the final one of the roll forming stations has a bending angle of approximately 180 degrees whereby the side edges of the polycarbonate sheet are bent back over onto the sheet. Other parts of the cross-section, other than or in addition to the side edges, may be bent back over onto the sheet using a similar process.

Preferably, the step of feeding the polycarbonate sheet through the first roll forming station bends opposite side edges of the polycarbonate sheet beyond an elastic limit toward the same side of the sheet.

Preferably, the roll forming stations are arranged inline.

In one preferred example, there is a total of five roll forming stations.

Preferably, the method includes the step of drawing the polycarbonate sheet through the roll forming stations with a rubber surfaced roller of at least one of the roll forming stations. More preferably, the method includes the step of drawing the polycarbonate sheet through the roll forming stations with a rubber surfaced roller of the final roll forming station.

Preferably, at least one of the one or more roll forming stations has rollers which define therebetween a gap smaller than a thickness of the polycarbonate sheet so as to reduce the thickness of the polycarbonate sheet as it is fed through.

In a preferred example, at least one of the one or more roll forming stations has a roller with a step for preventing flow of polycarbonate material beyond the step so as to set a width tolerance of the sheet. Preferably, the method includes the step of feeding the length of polycarbonate sheet from a roll of polycarbonate sheeting.

Preferably, the method further includes the step of cutting the length of polycarbonate sheet into smaller lengths so as to form security panels with bent side edges suitable for engagement within a channelled frame of a security closure for retaining the security panels within the channelled frame.

In accordance with another aspect of the present invention, there is provided a panel having opposed side edges bent to extend back over a central portion of the panel between the side edges so as to form retaining rails for retaining the panel within a channelled frame of a closure, wherein the opposed side edges are bent by a method of roll forming.

Preferably, the panel is a security panel. More preferably, the closure is a security closure. For example, the security closure may be of the kind typically used to close a shopfront.

Preferably, each of the opposed side edges is bent to extend over the same side of the panel.

Preferably, the panel is formed of polycarbonate. In a preferred form of the invention, the panel is formed by a method as described above.

Alternatively, the panel may be formed of other materials such as, for example, aluminium, acrylic or fibreglass. Brief Description of the Drawings

The invention is described, by way of non-limiting example only, with reference to the accompanying drawings in which:

Figure 1 is a cross-sectional view of an edge portion of a polycarbonate security panel in accordance with an example of the invention, shown engaged within a channelled frame of a security closure;

Figure 2 is a cross-sectional view of the polycarbonate security panel of Figure 1, shown with side edges engaged within opposed channels of the frame;

Figure 3 is a perspective view of a section of the polycarbonate security panel of Figures 1 and 2, shown with side edges engaged within opposed channels of the frame;

Figure 4 is a perspective view of the polycarbonate security panel of Figures 1 to 3, shown with side edges engaged within opposed channels of the frame;

Figure 5 is a cross-sectional view of an edge portion of an aluminium security panel in accordance with another example of the present invention, shown engaged within a channel of a frame;

Figure 6 is a cross-sectional view of the aluminium security panel of Figure 5, shown with edges engaged within opposed channels of the frame;

Figure 7 is a perspective view of a section of the aluminium security panel of Figures 5 and 6, shown with edges engaged within opposed channels of the frame;

Figure 8 is a side view of a first roll forming station;

Figure 9 is a side view of a second roll forming station; Figure 10 is a side view of a third roll forming station;

Figure 11 is a side view of a fourth roll forming station;

Figure 12 is a side view of a fifth roll forming station;

Figure 13 is a perspective view of the first to fifth stations shown in an inline configuration for forming a security panel in accordance with the present invention;

Figure 14 is a perspective view of an inline set of roll forming stations;

Figure 15 is a further inline set of roll forming stations for roll forming one side of a sheet;

Figure 16 is a perspective view of a polycarbonate panel, shown with all four edges having been roll formed;

Figure 17 is an end view of the polycarbonate panel shown in Figure 16;

Figure 18 is a detailed view of the corner labelled "M" of the polycarbonate panel shown in Figure 16;

Figures 19a to 19c show a first example of a polycarbonate roofing system having corrugated roofing panels; and

Figures 20a to 20c show a second example of a polycarbonate roofing system having corrugated roofing panels. Detailed Description

With reference to Figures 1 to 4 of the accompanying drawings, there is shown a polycarbonate security panel 10 in accordance with an example of the present invention, having opposed side edges 12 bent to extend back over a central portion 14 of the panel 10 between the side edges 12, so as to form retaining rails 16 for retaining the security panel

10 within a channelled frame 18 of a security closure. The opposed side edges 12 are bent by a method of roll forming such that each of the bent edge portions 20 is at an angle of almost 180 degrees to the original orientation of that portion in the polycarbonate sheet prior to forming.

Advantageously, the bent edge portions 20 form the retaining rails 16 having a thickness greater than that of the panel thickness, and these retaining rails dramatically increase the force required to kick out the security panel 10 from the channelled frame 18, when compared to a typical previously proposed flat polycarbonate panel without upturned edges. This is due to a tip 22 of each of the bent edge portions 20 abutting against lips 24 of the channelled frame 18, in combination with a resistance of the polycarbonate panel 10 from uncurling the bent portion 26. Whereas in previously proposed polycarbonate security panels strength has been attained by increasing the thickness of the panel to resist deformation, the present polycarbonate panel 10 achieves a much higher resistance force through the provision of the bent side edges 12, while saving material due to the lack of reliance on material thickness.

With reference to Figure 2, the opposed side edges 12 are bent in the same direction relative to the central portion 14, which has been found by the applicant to provide increased resistance to force from that direction. Accordingly, it has been identified that, in use, the polycarbonate panel 10 is orientated in a security closure with the opposed side edges 12 facing outwardly, so that the security closure has optimum strength in preventing vandals from breaking inwardly to a shop protected by the security closure. In testing, the applicant has found the polycarbonate security panel made from

1.4mm thick polycarbonate sheeting in accordance with the present invention provides far greater resistance to being kicked from the channelled frame 18 than does a polycarbonate security panel formed of 3mm thick sheeting without bent opposed side edges.

With reference to Figures 3 and 4, it can be seen that the channelled frame 18 is formed of an extrusion having an integral hinge component 28. These hinge components 28 interlock such that a series of adjacent security panels 10 can be coupled together in hinged relationship to form the security closure.

With reference to Figure 5, there is shown a security panel 30 which is similar to the security panel 10 of Figures 1 to 4, except that it is formed of aluminium rather than polycarbonate. The aluminium security panel 30 is also formed by a method of roll forming to have opposed side edges 32 which are bent back over a central portion 34 of the panel 30 in an arcuate configuration. This arcuate configuration, in functional similarity to the bent edge portion 20 of the polycarbonate security panel 10, forms retaining rails 36 on either side of the aluminium security panel 30 (see Figures 6 and 7) for retaining the security panel 30 within the channelled frame 18 of a security closure. The aluminium panel 10 may be perforated, as shown in Figure 7, to allow vision through the panel 30, and to reduce the cost and weight of the panel 30.

Advantageously, in having the opposed side edges 32 bent to the same side of the panel 30 the applicant has found the panel 30 has increased resistance to kicking from the direction opposite to that side of the panel 30. Accordingly, in the case of the aluminium security panel 30, the panel is mounted such that the bent opposed side edges 32 face inwardly toward the shop protected by the security^ closure - in this way, optimum resistance to vandals is achieved. In addition to the force required to remove the panel 30 from the channelled frame 18 being increased by tips 38 of the opposed side edges 32 abutting the lips 24 of the channelled frame 18, the panel 30 also increases the force required for removal by absorbing energy from any kicking or the like by gradual uncurling of the arcuate portions. With reference to Figures 8 to 13, there is shown an apparatus for use in a method of cold forming a length of polycarbonate sheet to form the polycarbonate security panel shown in Figures 1 to 4. Figure 8 shows a first roll forming station 40 through which the polycarbonate sheet is fed. The profile of the polycarbonate sheet prior to being fed through the first station 40 is shown in the inset diagram of Figure 8, and is indicated with the reference numeral 42. As can be seen, the profile of the polycarbonate sheet prior to being passed through the first station is flat. The first station 40 is formed of two rollers 44, 46 which together define a gap 48 into which the polycarbonate is forced when fed through the first station 40, such that - when passing through the station 40 - the edge portions 20 are bent to an angle of 50 degrees, relative to the flat plane of the material prior to forming. The position of the side edges 12 while passing through the first station 40 is represented by reference numeral 50 in the inset of Figure 8. Such bending will extend the polycarbonate material beyond its elastic limit such that plastic deformation is achieved, however the material will relax by virtue of its resilience such that the angle of the side edges after passing through the first station 40 becomes approximately 20 degrees to the flat plane (see reference numeral 52 in the inset of Figure 8).

The gap 48 may be formed so as to be smaller than a thickness of the polycarbonate sheet prior to forming so as to reduce the thickness of the polycarbonate sheet and to achieve "roller forging" of the material, whereby the thickness of the polycarbonate is reduced during the roll forming process. The upper roller 44 is provided with a step 54 for preventing flow of the polycarbonate material beyond the step 54 so as to set a width tolerance of the sheet.

Each of the rollers 44, 46 is provided with a central rubber surface 56 to assist in gripping the polycarbonate sheet, and in drawing of same through the roll forming process.

A second roll forming station 58 is similar to the first roll forming station 40, and like features are indicated with like reference numerals. However, the second roll forming station 58 is configured to accept the polycarbonate sheet from the first roll forming station

40 after the edges 12 of the sheet have resiliently partially sprung back from the first bending angle of 50 degrees to 20 degrees. The rollers 44, 46 of the second roll forming station 58 are formed with a sharper angle than in the first roll forming station 40, such that the side edges of the polycarbonate sheet are again bent beyond an elastic limit to a second bending angle of 80 degrees. After the polycarbonate sheet has passed through the second roll forming station 58, the edges 12 of the sheet resiliently partially spring back to an angle of 50 degrees relative to the flat plane.

As can be seen in Figures 10 and 11 , the structure of the third roll forming station 60 and the fourth roll forming station 62 is somewhat different, in that each of the third and fourth forming stations 60, 62 have a pair of rollers 64, 66 on the left-hand side of the polycarbonate sheet to form the left-hand edge 12 of the sheet, and a mirror image pair of rollers 64, 66 to the right-hand side of the polycarbonate sheet to form the right-hand edge 12 of the sheet. The rollers 64, 66 rotate about axes which are inclined to the horizontal, as opposed to the rollers 44, 46 of the first and second stations 40, 58 which rotate about horizontal axes. The bending angle defined by the profile of the rollers 64, 66 of the third station 60 is 110 degrees, while the bending angle defined by the profile of the rollers 64, 66 of the fourth roll forming station 62 is 140 degrees. The applicant has found that the polycarbonate material resiliently relaxes to an angle of 80 degrees and 1 10 degrees, respectively, after passing through the third roll forming station 60 and the fourth roll forming station 62. Each of the third and fourth roll forming stations 60, 62 also has a step 64 formed in the profile of the upper roller 64 for preventing flow of polycarbonate material beyond the step 54 so as to set a width tolerance of the sheet.

The fifth, and final, roll forming station 68 is shown in Figure 12, and consists of a pair of rollers 70, 72, each of which has a flat cross section. As seen in the inset of Figure

12, the rollers 70, 72 of the fifth roll forming station 68 are configured to accept the polycarbonate sheet from the fourth roll forming station after the edges 12 of the sheet have resiliently partially sprung back to 110 degrees, and to bend the edges 12 to a bending angle of 180 degrees. The edges 12 subsequently resiliently partially spring back to an angle of approximately 165 degrees, which is the angle at which the edges 12 are depicted in Figures 1 to 3. The rollers 70, 72 of the fifth roll forming station 68 are each provided with a rubber surface 56 so as to assist in drawing the polycarbonate sheet through the roll forming stations. The rubber surface 56 provides improved friction and enables the obtaining of more intricately shaped cross-sections than would be achievable using straight line bending.

The five roll forming stations are shown in an inline configuration in Figure 13 in which they are to operate in succession to form the polycarbonate security panel 10 in accordance with the present invention. A cutter (not shown) is used downstream of the fifth roll forming station 62 to cut the polycarbonate sheet into separate security panels.

The polycarbonate material can also be taken from a roll, roll formed, and then put back into a roll into which form it may be delivered to the customer. The customer can then cut the polycarbonate to any length with no cut off waste.

Advantageously, the present invention enables security panels to be manufactured from a roll of polycarbonate material due to the roll forming process being continuous. This process is more efficient than the line bending process previously used in forming polycarbonate sheet which must be performed section-by-section, and which is greatly limited in the cross-sections achievable by way of the inherent limitations of the apparatus. Furthermore, the process is more efficient in time and labour than strip heating, and is able to maintain tolerances more easily than extrusion or heated processes.

With reference to Figure 14, there is shown an inline set of roll forming stations comprising the first five roll forming stations 40, 58, 60, 62 and 68, as shown in Figure 13, with the addition of eight extra finishing rollers 74, such that there are nine flat finishing rollers in total. The presence of these additional flat finishing rollers 74 have been found by the applicant to improve the quality of the roll formed product.

Figure 15 shows a further inline set of roll forming stations for roll forming a polycarbonate sheet one edge at a time in a cantilever style roll forming process. The set of roll forming stations includes five roll forming stations 40a, 58a, 60a, 62a and 68a, each of which is similar to the corresponding one of the roll forming stations 40, 58, 60, 62 and 68 shown in Figure 13, except with only one side of the station being adapted to roll form a polycarbonate sheet. Use of a process utilising the set of roll forming stations shown in Figure 15 would allow forming of a turned edge polycarbonate sheet on any size of sheet, by roll forming the polycarbonate sheet one edge at a time. For example, a polycarbonate panel 76 as shown in Figures 16 to 18 may be formed by using the set of roll forming stations shown in Figure 15. The polycarbonate panel 76 has a folded edge along each of its sides 78, 80, 82, 84 and may be particularly suitable for use in machine guards, bus shelters, and the like. The polycarbonate panel 76 with all four edges bent can be made of any length and width, particularly as all four edges 78, 80, 82 and 84 are supported. Furthermore, forming of all four of the edges in this way may facilitate use of thinner polycarbonate sheeting, as the strength of the panel 76 when fitted within a frame is enhanced by the bent edges which assist in preventing the panel 76 from popping out from the frame.

With reference to Figure 18, corner portions 86 may be removed from the polycarbonate panel 76 to avoid interference between adjacent bent edges of the polycarbonate panel 76, and this may also facilitate fitting of the panel 76 within a frame.

The applicant has also identified that in phone booths, machine guards, security doors, green houses, bus shelters and the like security panels are typically secured to a surrounding frame by either inserting a flat panel into a channel which is not secured as has already been discussed, or by drilling of holes and bolting the polycarbonate panel to the frame, and that this is typically very time consuming and costly. With the cantilever set of roll forming stations shown in Figure 15, the applicant has determined that a polycarbonate panel 76 could be formed according to specific size requirements by simply cutting the panel to the correct length and width, notching out all four corners so that the edges 78, 80, 82 and 84 of the panel 76 may be folded. A channelled aluminium section to suit the polycarbonate panel 76 could be sold alongside the panel 76 to form the frame for housing the panel 76. Such an aluminium section could be bolted to any surface for retaining the polycarbonate panel 76. Figures 19a to 20c show a polycarbonate roofing system incorporating corrugated polycarbonate roofing panels with interlocking edges. More specifically, Figures 19a to 19c show a first example of a polycarbonate roofing system 88 incorporating a plurality of corrugated polycarbonate roofing panels 90, each of the panels 90 having interlocking edges 92. Figure 19b depicts an end view of the roofing panels 90, shown interlocked, and Figure 19c shows a detailed end view of the interlocking edges 92, when interlocked. Each of the interlocking edges 92 includes a first fold 94, in which the panel 90 is folded in a first direction, and a second fold 96, in which the panel 90 is folded again in the same direction closer to the edge of the material. Owing to resilience of the polycarbonate material, the polycarbonate roofing panels 90 may be interlocked by simply sliding one interlocking edge 92 into an opposed interlocking edge 92, during which action outer lips 98 of the two interlocking edges 92 fold inwardly so as to slide one relative to the other until they lock in place as shown in Figures 19b and 19c.

Figures 20a to 20c show a similar polycarbonate roofing system 88a in which the corrugated polycarbonate roofing panels 90a have square corrugations rather than the round corrugations shown in Figures 19a to 19c, however the operation is fundamentally the same. Like features are indicated with like reference numerals, only with a suffix of the letter "a" so as to distinguish over the roofing system 88 shown in Figures 19a to 19c. As can be seen in Figure 19b and Figure 20b, the roofing panels 90, 90a are arranged such that, when interlocked, the corrugations of the roofing systems 88, 88a are maintained with a substantially uniform arrangement.

The applicant has determined that the corrugated polycarbonate roofing panels 90,

90a may be either roll formed or extruded. It is foreseen that the polycarbonate roofing systems 88, 88a may be particularly advantageous when roll formed as the roofing panels 90, 90a would have a high degree of clarity. Furthermore, the panels 90, 90a may be provided with or without interlocking edges 92, 92a on both sides of the panels 90, 90a so that adjacent panels 90, 90a can be interlocked, keeping out water and reducing overlap (and thus cost). The applicant has also identified that present polycarbonate roofing is difficult to keep square with roof supports and facia, due to the fact that a thin sheet of polycarbonate tends to move around on a roof surface thus making it very difficult to align the sheet at one end, screw the sheet in at that end, and then move to the other end without bulging in a middle section of the roofing. The interlocking edges 92, 92a of the corrugated polycarbonate roofing panels 90, 90a shown in Figures 19a to 20c may overcome or at least alleviate these problems by keeping the panels 90, 90a square during installation.

While an example of the present invention has been described above, it should be understood that it has been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by the above described example. In particular, it will be understood by those skilled in the art that the applicability of the method of the present invention is not limited to the forming of a security panel, and that, on the other hand, the security panel of the present invention is not limited to being roll formed of aluminium or polycarbonate (as other materials may also be used). Also, although the present invention has been described with reference to security closures it will be understood by those skilled in the art that the method of the invention may also be applied in relation to roller doors and other applications that would be suited to a panel strength above and beyond that of a flat sheet.

In one alternative example, a polycarbonate panel may be formed having perforations and turned edges. Such a polycarbonate panel may be suitable for use in large shopping centres and airports where it is desirable to allow airflow through the panels.

Although perforated panels have previously been made from steel or aluminium, with the added strength of the turned edge polycarbonate, the applicant has identified that polycarbonate may be used to make perforated security panels, which may provide significant cost advantages. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and

"comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method of cold forming a length of polycarbonate sheet, including the step of: feeding the polycarbonate sheet through a roll forming station.

2. A method of cold forming a length of polycarbonate sheet as claimed in claim 1, including the step of: feeding the polycarbonate sheet through a plurality of roll forming stations.

3. A method of cold forming a length of polycarbonate sheet as claimed in claim 2, including the step of: feeding the polycarbonate sheet through a first roll forming station so as to bend at least one side edge of the polycarbonate sheet beyond an elastic limit to a first bending angle; and subsequently feeding the polycarbonate sheet through a second roll forming station so as to further bend the side edge(s) of the polycarbonate sheet beyond an elastic limit to a second bending angle, wherein the second roll forming station is configured to accept the polycarbonate sheet from the first roll forming station after the edge(s) of the sheet has/have resiliently partially sprung back from the first bending angle.

4. A method of cold forming a length of polycarbonate sheet as claimed in claim 3, including the step of: subsequently feeding the polycarbonate sheet through third and subsequent roll forming stations so as to further bend the side edge(s) of the polycarbonate sheet beyond an elastic limit to third and subsequent bending angles, with each of said bending angles being greater than the bending angle of the preceding roll forming station, wherein each of the third and subsequent roll forming stations is configured to accept the polycarbonate sheet from the preceding roll forming station after the edge(s) of the sheet has/have resiliently partially sprung back from the bending angle of the preceding roll forming station.

5. A method of cold forming a length of polycarbonate sheet as claimed in claim 4, wherein a final one of the roll forming stations has a bending angle of greater than

90 degrees.

6. A method of cold forming a length of polycarbonate sheet as claimed in claim 5, wherein the final one of the roll forming stations has a bending angle of approximately 180 degrees whereby the side edge(s) of the polycarbonate sheet is/are bent back over onto the sheet.

7. A method of cold forming a length of polycarbonate sheet as claimed in claim 6, wherein the plurality of roll forming stations includes at least three finishing roll forming stations, each of the finishing roll forming stations having a bending angle of approximately 180 degrees.

8. A method of cold forming a length of polycarbonate sheet as claimed in any one of claims 2 to 7, wherein the roll forming stations are adapted to roll form one edge of the polycarbonate sheet at a time.

9. A method of cold forming a length of polycarbonate sheet as claimed in any one of claims 3 to 7, wherein the step of feeding the polycarbonate sheet through the first roll forming station bends opposite side edges of the polycarbonate sheet beyond an elastic limit toward the same side of the sheet.

10. A method of cold forming a length of polycarbonate sheet as claimed in any one of claims 3 to 9, wherein the roll forming stations are arranged inline.

11. A method of cold forming a length of polycarbonate sheet as claimed in any one of claims 3 to 10, wherein there is a total of five different geometry roll forming stations.

12. A method of cold forming a length of polycarbonate sheet as claimed in any one of claims 2 to 11, including the step of: drawing the polycarbonate sheet through the roll forming stations with a rubber surfaced roller of at least one of the roll forming stations.

13. A method of cold forming a length of polycarbonate sheet as claimed in claim 12, including the step of: drawing the polycarbonate sheet through the roll forming stations with a rubber surfaced roller of the or each final roll forming station.

14. A method of cold forming a length of polycarbonate sheet, as claimed in any one of claims 1 to 13, wherein at least one of the one or more roll forming stations has rollers which define therebetween a gap smaller than a thickness of the polycarbonate sheet so as to reduce the thickness of the polycarbonate sheet as it is fed through.

15. A method of cold forming a length of polycarbonate sheet, as claimed in any one of claims 1 to 14, wherein at least one of the one or more roll forming stations has a roller with a step for preventing flow of polycarbonate material beyond the step so as to set a width tolerance of the sheet.

16. A method of cold forming a length of polycarbonate sheet, as claimed in any one of claims 1 to 15, further including the step of feeding the length of polycarbonate sheet from a roll of polycarbonate sheeting.

17. A method of cold forming a length of polycarbonate sheet, as claimed in any one of claims 1 to 16, further including the step of cutting the length of polycarbonate sheet into smaller lengths so as to form security panels with bent side edges suitable for engagement within a channelled frame of a security closure for retaining the security panels within the channelled frame.

18. A panel having opposed side edges bent to extend back over a central portion of the panel between the side edges so as to form side retaining rails for retaining the panel within a channelled frame of a closure, wherein the opposed side edges are bent by a method of roll forming.

19. A panel as claimed in claim 18, wherein a surface of the panel is perforated.

20. A panel as claimed in claim 18 or claim 19, wherein the panel is a security panel.

21. A panel as claimed in any one of claims 18 to 20, wherein the closure is a security closure.

22. A panel as claimed in any one of claims 18 to 21, wherein each of the opposed side edges is bent to extend over the same side of the panel.

23. A panel as claimed in any one of claims 18 to 22, wherein opposed end edges of the panel are bent to extend back over the central portion of the panel between the end edges so as to form end retaining rails for retaining the panel within the channelled frame of the closure, wherein the opposed side edges are bent by a method of roll forming.

24. A panel as claimed in claim 23, when dependent on claim 22, wherein each of the opposed end edges is bent to extend over the same side of the panel as the side edges.

25. A panel as claimed in claim 24, wherein the channelled frame is fitted about the panel to form the closure, and the channelled frame is adapted for being bolted to a structure for mounting the closure to the structure.

26. A panel as claimed in any one of claims 18 to 25, wherein the panel is formed of polycarbonate.

27. A panel as claimed in any one of claims 18 to 25, wherein the panel is formed of aluminium.

28. A panel as claimed in claim 26, wherein the panel is formed by a method as claimed in any one of claims 1 to 17.

29. A polycarbonate roof panel including a formed edge, arranged such that like roof panels are able to be coupled together by interlocking the formed edges of the panels, wherein the formed edge is folded inwardly such that when the like panels are brought together the formed edges abut then deflect to allow one formed edge to slide past the other formed edge until the edges are sufficiently clear to return resiliently so as to interlock.

30. A polycarbonate roof panel as claimed in claim 29, formed according a method as claimed in any one of claims 1 to 4.

31. A method of cold forming a length of polycarbonate sheet substantially as hereinbefore described with reference to the accompanying drawings and/or

Examples.

32. A panel substantially as hereinbefore described with reference to the accompanying drawings and/or Examples.