AU2007216940B2 - Roofing and cladding sheet - Google Patents

Abstract

A roofing or cladding sheet with concealed fixing and capillary break seals at the edge overlaps. The sheet is given hook formations at one edge and grip formations at the other edge, which confer an enhanced interlock at overlaps. This allows an additional flange previously used at an edge to be omitted, allowing enhanced width coverage. Edge flanges are given a bend, which stiffens the flanges. The profile allows high tensile, low elongation material to be used. (~LO co C~C'4

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION STANDARD PATENT ROOFING AND CLADDING SHEET The following statement is a full description of this invention including the best method of performing it known to me: FIELD OF THE INVENTION This invention lies in the field of roofing sheets primarily, the sheets can also be used for cladding e.g. vertical and other surfaces, but their properties are 5 especially valuable for roofing. The sheets have concealed fastenings and are not perforated by the fastenings. BACKGROUND 10 The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge. U.K. patent 0120 234 (and a sister U.S. patent 4 610 121) for Roof Cladding 15 disclosed roof sheets of the imperforate kind, held down on roof structure by cleats that do not perforate the sheet and allow harmless longitudinal expansion and contraction (e.g. due to the swing of daytime and night time temperatures), by the sheet sliding on the cleats. This goes a long way in ensuring a leak proof roof, but the patent further described interlock 20 formations at the longitudinal sheet edges that are contiguous when installed, which create two capillary breaks to prevent capillary action from drawing water through the interlocking edges and producing leaks in this way. The sheet interlock formations are also well adapted to facilitate erection. 25 These sheets compete against conventional corrugated sheets (i.e. that are perforated by the roof nails), which tend to give wider coverage, being simpler profiles as they do not have interlocking and capillary break features. There is interest therefore in making an interlocking sheet with capillary break, which has a more competitive coverage factor. 30 The sheet has been manufactured in several common roofing materials like galvanized steel, copper, titanium zinc and other reasonably ductile metals. A ductile elongation of at least 10% has been recommended in building regulations as appropriate for roofing sheets. Driven by cost pressures, the 2 sheet-roofing field has shown a general tendency towards the use of thinner material and a high tensile steel sheet has come into use in other roofing profiles. This is "E" grade ASTM 446 steel, that has a yield strength close to 5 its ultimate tensile strength, thus very low elongation (close to 1%). This lack of ductility of these sheets has resulted in them suffering from premature corrosion due to micro-cracks at bends in the profiles that have been used for them up to now. The rusting can result in huge liability or insurance claims and the disruption of re-roofing. There is therefore interest in making the use 10 of such high tensile material satisfactory. SUMMARY OF INVENTION A roofing panel in accordance with this invention comprises a longitudinally 15 extending sheet material, which has a profile formed in it that extends transversely, which profile includes a central ridge, a first edge ridge and a second edge ridge, which edge ridges extend along opposed elongate edges of the panel, which profile includes valleys between the central ridge and the edge ridges, the central ridge comprising a crest and flanks on either side of 20 the crest, the first edge ridge comprising a flange that has a bend in it that stiffens the flange, a web that is directed from the flange towards the central ridge and a hook that is formed by a downwardly directed re-entrant bend near the sheet edge, wherein the web is inclined from the hook to the flange, the second edge ridge comprising a flange that has a bend in it that stiffens it, 25 an upper web directed away from the central ridge, a grip formed by a downwardly directed re-entrant bend that leads to a lower flange directed towards the central ridge with a catch at the end of the lower flange. The valleys preferably have indentations in them to enhance stiffening of the 30 sheet and resistance to creasing while undergoing roll forming. Features of the invention that are significant for the interlocking function of contiguous sheets in use are the hook on one side edge and the catch on the other side edge. When two or more panels are joined with each other along 3 their longitudinal edges, as in covering a roof with the panels, the hook of each panel engages the catch of an adjacent panel to provide an interlock. This interlock allows the join to be preserved even when pressure is placed on the sheets, which can occur if the spans are rather large and especially with 5 thin high tensile sheets. With these sheets the tensile strength is sufficient, but the deflection is large. Where the pressure is large enough to deflect the sheets downwards in mid-spans, the edges would otherwise tend to separate, causing leaks, which the interlock prevents. 10 This problem is dealt with in the prior art design described in the patents referred to in the background discussion above by including an additional stiffening flange in the edge of the panel, which is omitted in the present invention. Alternatively in the prior art the contiguous sheets are riveted together, which destroys the crucial feature of maintaining imperforate sheets. 15 It is the omission of the additional stiffening flange added to the flange with a bend, in the present invention that allows the greater coverage than the prior art panel described in the patents specified in the background discussion above. 20 The profile allows that bends may be given a radius that is large enough to allow use of low elongation steel, which is not the case with prior art designs such as that referred to in the background discussion above. 25 The bends in the flanks of the ridge and in the flanges at the panel edges increase stiffness of the panel. The catch in the second edge formation may be enhanced by being formed into a further re-entrant bend or a turn-up that is a partial but not a fully formed 30 re-entrant bend. The sheets are held down onto supporting structure by cleats that clasp around the hook and are secured by suitable fastening means to the supporting structure.

4 THE DRAWINGS The invention is more fully described by way of example, with reference to the 5 drawings, in which . Figure 1 is a transverse section of a panel, showing the transverse profile, Figure 1A is a similar section of an edge of the panel showing an alternative 10 formation, Figure 2 a transverse section showing a join between contiguous longitudinally extending edges of two panels, 15 And Figure 3 is a transverse section showing a hold down cleat at a join between contiguous longitudinally extending edges of two panels. 20 THE PREFERRED EMBODIMENTS As shown in figure 1, the roofing panel 1 comprises a transverse profile formed in a longitudinally extending sheet material, the profile includes a central ridge 2 and flanking valleys 3 and 4 between first and second edge 25 formations 5 and 6 that extend along opposed elongate edges 7 and 8 of the panel. The central ridge comprises a crest 9 and flanks 10 and 11 on either side that are bent at the bends 12 and 13 respectively. The first edge formation comprises a flange 14 that is bent at bend 15, a bend 16, a web 39 that is directed towards the central ridge and a hook 17 that is formed by a 30 downwardly directed re-entrant bend near the sheet edge 18. The web 5 between the re-entrant bends 16 and 17 is inclined to the main plane 37 of the sheet at an angle of about 10 degrees, towards the plane 37 from bend 16 towards bend 17.

5 The second edge comprises a flange 19 that is bent at bend 20, a bend 38, a crest 21 directed away from the central ridge, a re-entrant bend 22 and a catch 23 at the edge 24 of the sheet. 5 Figure 1A shows a profile that is the same as that shown in figure 1, except that an enhanced or more pronounced catch 25 is provided, giving a more secure interlock between contiguous panels. The selection of the catch may be made according to a particular installation, where span length, expected loadings, material specification (e.g. thickness and strength) and possibly 10 other factors will influence the selection. The object is to ensure that the interlock is not lost under anticipated conditions, for example, when persons walk on the roof sheeting. The valleys preferably have indentations 26, 27, 28 and 29 in them to 15 enhance stiffening of the sheet and resistance to creasing while undergoing roll forming. Fig. 1 also shows that the sheet is bowed in the transverse direction by a slight angle 42 on either side of the central crest, to ensure that this part of the 20 sheet presses firmly against the supporting structure. Figure 2 shows how contiguous edges of two panels are interlocked. A space 30 between two contact positions 31 and 32 provides a capillary break that prevents capillary action drawing water from above the panels to below the 25 panels at the join. The catch will engage the hook if there arises any force tending to separate the panels and thus provides a positive interlock. This is important at mid-span positions where loading on the panel e.g. due to people walking on the panels at a join or heavy snow or water causes depression of the panels at the contiguous edges. This tends to pull the panel edges apart 30 but the interlock prevents it. Another important feature of the edge formations is that the length 40 of the web is greater than the length of the gap 41 under the crest. This also provides an assurance against the interlocked sheets coming apart.

6 Comparison may be made to an example of Canadian patent 1 123 568 where the contiguous edges are riveted together, to deal with this problem. A different example is shown in US patent 4 266 385 where the same problem is 5 dealt with by doubling up the "limb 40" by "limb 44" and a "locator flange 54". These prevent the pull-apart as can be seen in the view of figure 4 in that patent. Figure 3 shows a cleat 33 that is hooked over the hook at the edge of the 10 panel 34 and is fastened by a nail 35 (for example) to supporting structure (not shown). Cleats are provided usually at purlins or other supports over which the panels span. The contiguous panel 36 is then joined and work proceeds with successive panels to cover a roof area. A feature of the invention is that the cleats can not be disengaged under any normal 15 circumstances and forces far in excess of those that can arise in use would be necessary to pull them out. The reason is that the cleats are clamped between the edge formations of adjacent sheets, which themselves are locked together, as has been described. The arrangement as shown in figure 3 allows flashing. to be engaged with an edge formation of a sheet in a way that 20 also achieves secure interlock with the sheet. The flashing would substitute the sheet 36 shown in figure 3. Radiuses at all bends are kept above a specified minimum according to the material used to ensure a sound roofing and the profile of the invention as 25 shown herein is of such a nature that allows safe radii for the use of very low elongation steels. Merely as an example to give a non-limiting illustration of the improved effective coverage, a 600 mm sheet can be formed into the profile shown, to 30 give an effective coverage width of 440 mm. By comparison a 600 mm sheet formed into the profile described in the prior patents referred to in the background discussion above, would give a 385 mm coverage width. The 55 mm gain is seen to be significant where typically a large number of sheets are joined and a 14 % coverage increase realises a 14% cost advantage. In a 7 fiercely competitive market this can mean an important price differentiation for the panel from its competitors. The coverage gain is achieved by the feature of this invention that there is no doubling up of a limb or locator flange, as is used in the prior patents referred to above, nor is there riveting together of 5 edge formations. Instead, the present invention provides a solution to this problem by the hook and catch formations, obviating the need for the use of additional material at the edge formations and allowing use of this material to give greater coverage from a standard stock roll of sheet. 10 REFERENCE NUMERALS 1 Roofing panel 2 central ridge 3 valley 15 4 valley 5 first edge formation 6 second edge formation 7 panel elongate edge 8 panel elongate edge 20 9 crest 10 flank 11 flank 12 bend 13 bend 25 14 flange 15 bend 16 re-entrant bend 17 hook 18 sheet elongate edge 30 19 flange 20 bend 21 crest 22 re-entrant bend 23 catch 8 24 sheet elongate edge 25 enhanced catch 26 indentation 27 indentation 5 28 indentation 29 indentation 30 capillary break space 31 contact positions 32 contact positions 10 33 cleat 34 panel 35 nail 36 panel 37 main plane of the sheet 15 38 bend at edge formation 39 web 40 length of web 41 length of gap under crest 42 angle that sheet is bowed. 20 Embodiments of the present invention are in some respects an evolution of the type of panel design mentioned in the background discussion above, offering greater effective coverage but retaining the sliding cleat securing, the interlock that has capillary breaks and easy installation advantages. The new 25 panel also can be manufactured successfully from low elongation metal. The term "comprises" and its derivatives and variations including "comprising" is used herein in an inclusive, rather than exhaustive, sense and not to the exclusion of additional integers. 30

Claims (14)

1. A roofing panel which comprises a longitudinally extending sheet material, which has a profile formed in it that extends transversely, which profile includes a central ridge, a first edge ridge and a second edge ridge, which edge ridges extend along opposed elongate edges of the panel, which profile includes valleys between the central ridge and the edge ridges, the central ridge comprising a crest and flanks on either side of the crest, the first edge ridge comprising a flange that has a bend in it that stiffens the flange, a web that is directed from the flange towards the central ridge and a hook that is formed by a downwardly directed re-entrant bend near the sheet edge, wherein the web is inclined from the hook to the flange, the second edge ridge comprising a flange that has a bend in it that stiffens it, an upper web directed away from the central ridge, a grip formed by a downwardly directed re-entrant bend that leads to a lower flange directed towards the central ridge with a catch at the end of the lower flange.

2. A roofing panel as claimed in claims, in which the valleys have indentations in them to enhance stiffening of the sheet and resistance to creasing while undergoing roll forming.

3. A roofing panel as claimed in either one of claims 1 or 2, characterised by the omission of an additional stiffening flange to the flange which has a bend in it.

4. A roofing panel as claimed in any one of claims 1 to 3, in which the bends in the profile are given a radius that is large enough to allow use of low elongation steel. 10

5. A roofing panel as claimed in any one of claims 1 to 4, in which the catch in the second edge ridge is enhanced by being formed into a turn-up that is a partial but not a fully formed re-entrant bend.

6. A roofing panel as claimed in any one of claims 1 to 5, in which the sheets are held down onto supporting structure by cleats that clasp around the hook and are secured by suitable fastening means to the supporting structure.

7. A roofing sheet as claimed in any one of claims 1 to 6, in which the sheet is bowed in the transverse direction by a slight angle on either side of the central crest, the bow being convex downwards.

8. A roofing panel as herein described and as illustrated in figure 1 of the drawings.

9. A roofing panel as herein described and as illustrated in figure 1A of the drawings.

10. A roofing panel as herein described and as illustrated in figure 2 of the drawings.

11. A roof panel and clip combination as herein described and as illustrated in figure 3 of the drawings.

12. A roof made using panels as claimed in any one of claims 1 to 9.

13. A surface of a building clad with roofing panels as claimed in any one of claims 1 to 11.

14. A method of cladding a surface of a building that includes use of roofing panels as claimed in any one of claims 1 to 11.