AU2011372482B2

AU2011372482B2 - Method and apparatus for forming corrugated panels

Info

Publication number: AU2011372482B2
Application number: AU2011372482A
Authority: AU
Inventors: John Alastair Easling; Brian Douglas Watson
Original assignee: Revolution By Dg Pty Ltd
Current assignee: Revolution By Dg Pty Ltd
Priority date: 2011-07-06
Filing date: 2011-12-21
Publication date: 2017-03-02
Anticipated expiration: 2031-12-21
Also published as: WO2013003880A1; NZ620655A; AU2011372482A1

Abstract

A method of forming a corrugated panel from sheet metal, the corrugated panel having a plurality of alternating, concave and convex ribs, the method including the steps of forming an interim profile in the sheet metal, the interim profile including alternating, concave and convex interim ribs, each of the interim ribs having alternating, concave and convex rib segments; and flattening each rib segment of each interim rib so that the interim ribs become smoothly curved to form ribs of the corrugated panel.

Description

PCT/AU2011/001652 WO 2013/003880 - 1 -

METHOD AND APPARATUS FOR FORMING CORRUGATED PANELS

Field of the Invention

The present invention relates to corrugated panels of the type typically used as a building material. Such panels are normally formed from sheets of iron or steel strengthened by being formed into a series of smoothly curved, alternating, concave and convex ribs (presenting a generally sinusoidal profile), often galvanized, powdercoated or anodized for weather resistance and/or appearance.

Background of the Invention

Corrugated panels are building materials that have been used successfully for many years. There have of course been developments to corrugated panels, which have mainly related to the adoption of profiles other than the traditional, generally sinusoidal profile (such as profiles having square, trapezoidal, rectangular or triangular ribs rather than smoothly curved ribs, or complex arrangements of combinations of these other types of profiles). In the normal course, it will also be appreciated that the usual geometric variables of a corrugated panel are also often adjusted, such as the height (or depth) of the ribs, the radius of the rib arcs, the thickness of the sheet metal, the pitch of the ribs (being the crest-to-crest distance of the ribs), and the size of the flat section between alternating ribs.

Additionally, different materials will often have different tensile strengths, which give rise to different difficulties during the manufacture of corrugated panels of this type. In this respect, the manufacture of corrugated panels has typically been by way of cold roll forming where ribs are rolled into a flat sheet of metal in progressive steps, the flat sheet being passed between different stages (or stations) of cooperating rollers that have surfaces configured with a desired profile able to impart a shape to a sheet of material passed therebetween, with PCT/AU2011/001652 WO 2013/003880 -2- intermediate stages providing an intermediate form to the sheet metal, and the last stage finalising the exact form of the desired profile.

The number and type of the intermediate stages, and the configuration of the surface profiles of the rollers for those intermediate stages, will depend upon the thickness and tensile strength of the metal and of course the nature of the final desired profile. Indeed, profiles that are reasonably complex might require intermediate stages to only contact the sheet at some locations across its width, or might require overbending or underbending of certain sections of the profile, in order to eventually result in the desired profile after passing through subsequent stages having rollers of different profiles. Indeed, the setting up of a roll forming machine to produce a desired profile is typically a time consuming process of trial and error where rollers of different profiles are trialled with the desired sheet metal and a variety of rollers with different surface profiles with the aim of producing a roll formed sheet of a certain final profile. A common design difficulty brought about by the tensile strength and thickness of some metals is that a desired bend in a metal may not be achievable due to the phenomenon of “springback”, even when a reasonably significant overbend is allowed for in one of the intermediate passes. As a result, with corrugated panels formed from sheet metal it has thus been virtually impossible to achieve (at an acceptable cost) ribs with a reasonably large radius, particularly with thinner materials and/or materials of higher tensile strength. For example, efforts to use traditional roll forming processes to achieve corrugated panels having a rib radius above about 25mm, and particularly above 40mm to 50mm (or more), particularly with material thicknesses as low as 0.3 to 0.4 mm (or lower), have typically failed to produce an acceptable product at an acceptable price. Of course, material thicknesses at this level are desirable in order to reduce cost, albeit not while sacrificing panel strength, so a reduction in thickness has typically only possible with a material of higher tensile strength, which then tends to exacerbate forming problems such as springback. PCT/AU2011/001652 WO 2013/003880 -3-

This problem is of course accentuated with wider corrugated panels that have a large number of ribs, particularly in relation to the ribs at the edges of the corrugated panels where, irrespective of cost, it has been very difficult to edge a panel with an acceptable profile as it has not been possible to overbend the edge to the required extent to obtain the desired profile after springback.

As a result, there is currently only very little variation in the profiles of commercially available corrugated panels, in terms of rib radius and material thickness, with the vast majority of commercially available corrugated panels having a rib radius at or about 25mm (or less) with material thicknesses at or about 0.4mm (or more).

It is thus an aim of the present invention to provide an improved method of producing a corrugated panel from sheet metal (particularly with thinner materials) such that a corrugated panel having ribs with a reasonably large radius can be formed. Of course, it must be appreciated that the method of the present invention is not limited only to the formation of corrugated panels having ribs with a reasonably large radius, but may be used to also produce corrugated panels of different geometries and certainly maybe be used to form corrugated panels having profiles currently commercially available.

Before turning to a summary of the present invention, it must be appreciated that the above description of the prior art has been provided merely as background to explain the context of the invention. It is not to be taken as an admission that any of the material referred to was published or known, or was a part of the common general knowledge in Australia or elsewhere.

Summary of the Invention

The present invention provides a method of forming a corrugated panel from sheet metal, the corrugated panel having a plurality of alternating, concave and convex ribs, the method including the steps of: PCT/AU2011/001652 WO 2013/003880 -4- • forming an interim profile in the sheet metal, the interim profile including alternating, concave and convex interim ribs, each of the interim ribs having alternating, concave and convex rib segments; and • flattening each rib segment of each interim rib so that the interim ribs become smoothly curved to form ribs of the corrugated panel.

In one form of the present invention, the interim profile is formed, and the rib segments are then flattened, using traditional cold roll forming techniques and rollers whose surface profiles have been adapted to form the required interim and final profiles. However, it will be appreciated that other forming techniques could also be used, such as press forming (press breaking) or roll forming using barrel rollers.

With reference to the formation of an interim profile, it must be appreciated that the interim profile need not actually be brought into existence during the manufacturing process in the form of a sheet where interim ribs (each having rib segments) are present across the full lateral extent of the sheet. This of course is contrary to the profile of the final product, where the smoothly curved, alternating, concave and convex ribs will physically exist in the final product and will indeed extend across the full lateral extent of the corrugated panel.

For example, in roll forming, and as mentioned above, it is likely that the ribs of a corrugated panel (and the interim ribs in the present invention) will be formed in stages along the length of a roll forming machine, with the innermost ribs of a sheet generally formed first. Thus, if one were to stop the roll forming machine at any time, and view a sheet being moved therethrough, ribs will be evident at some locations and not others, and interim ribs (being ribs defined by rib segments of the type mentioned above) will also be evident at some locations and not others.

Thus, the rib segments formed in accordance with the method of the present invention will also be evident in some locations and not others. In the case of the rib segments, that will be because, in some sections, the rib segments will PCT/AU2011/001652 WO 2013/003880 -5- not have been formed and because, in other sections, they will have been formed but already flattened. Indeed, given that the presence of smoothly curved ribs formed by flattened rib segments is advantageous for subsequent stages in the forming method of the present invention, it is envisaged that the flattening of a rib segment will ideally occur soon after a rib segment is formed, such as in the next forming stage.

Additionally, some interim ribs may not yet have rib segments formed across the entire lateral extent thereof (but only partly thereacross). Indeed, some interim ribs may not require rib segments to be formed continuously across the entire lateral extent thereof. Indeed, the innermost ribs of a corrugated panel tend to be easier to form and thus tend to be impacted less by the forming difficulties mentioned above. It is thus possible that these innermost ribs will be formed satisfactorily with fewer rib segments being formed and flattened than might be required for the outermost ribs at the edges of the sheet.

Of course, by the time the corrugated panel is completed and is exiting the roll forming machine, ribs will have been formed across the full extent of the panel, interim ribs having rib segments will have been formed as necessary, and those rib segments will have been flattened in each interim rib where they were formed, in order to form the smoothly curved ribs desired for the corrugated panel. Indeed, the use of the terms “interim profile” and “interim ribs”, and the reference to “each” of the interim ribs “having” rib segments, are to be understood in this context.

It must also be appreciated that the reference above to the corrugated panel having a plurality of smoothly curved, alternating, concave and convex ribs is intended to be a reference to the generally sinusoidal profile that is traditional in corrugated panels. The reference to “smoothly curved” is important and is intended to distinguish from the interim profile where the interim ribs will not be smoothly curved as they will each be defined by the presence of the alternating concave and convex rib segments. In a purely geometrical sense, a smoothly curved rib is thus one which generally comprises only a single arc, being a PCT/AU2011/001652 WO 2013/003880 -6- single arc from which a single radius is able to be determined, not the plurality of arcs as present in the interim ribs (provided by the rib segments) of the invention.

However, it will be recognized by a skilled addressee that while this will be the manufacturing aim, normal manufacturing tolerances generally will not permit the ribs of the final profile to be perfectly geometrically curved. Indeed, it is proposed that an acceptable final profile for a corrugated panel produced by the present invention would be a profile where the rib segments have been flattened to an extent that the smoothly curved ribs do not have rib segments that can be seen by the naked eye when viewed at a distance of from about 2 to about 5 metres.

Alternatively, a more preferred outcome would be for the rib segments to be flattened to an extent that the smoothly curved ribs of the final profile will not have rib segments that can be felt by a person rubbing their finger over the rib, nor seen by that person when standing within touching distance of the corrugated panel.

Before turning to a brief discussion of apparatus suitable for use in the method of the present invention, and noting the comment above that the method of the present invention may be used to form corrugated panels with a variety of geometries and dimensions (including currently known geometries and dimensions), in a preferred form corrugated panels formed in accordance with the method will have a rib radius above about 25mm with sheet metal having a thickness of from about 0.45mm or smaller. In another form, corrugated panels formed in accordance with the method will have a rib radius above about 40mm with sheet metal having a thickness of from about 0.45mm or smaller.

Turning now to a brief discussion of the apparatus, the present invention also provides apparatus for forming a corrugated panel from sheet metal, the corrugated panel having a plurality of alternating, concave and convex ribs, the apparatus including: PCT/AU2011/001652 WO 2013/003880 -7- • a primary forming means configured to form an interim profile in the sheet metal, the interim profile including alternating, concave and convex interim ribs, each of the interim ribs having alternating, concave and convex rib segments, and • a secondary forming means configured to flatten each rib segment of each interim rib so that the interim ribs become smoothly curved to form ribs of the corrugated panel.

In a preferred form, the primary and secondary forming means are roll formers that are a part of a cold roll forming machine. In particular, the rib segments can be formed in the interim profile by use of a roller having a surface that has been adapted to provide the required segments. Ideally, the rib segments are themselves a series of alternating, concave and convex segments that are formed by correspondingly shaped segments on the surface of a roller. In one form, the surface profile of the roller may thus include a series of scalloped grooves extending about the periphery thereof, adjacent grooves being separated by a ridge therebetween, the ridge also extending about the periphery thereof. The pitch, depth and radius (the curvature) of the scalloped grooves may be altered in accordance with the dimensions and profile required for the rib segments. A similarly profiled roller may then be adapted for use in a next stage, but with oppositely configured scalloped grooves and ridges in order to flatten the rib segments in the manner mentioned above to form smoothly curved ribs. Thus, the ridges of such an oppositely configured roller would align with the grooves of the rib segments, and the grooves of such an oppositely configured roller would align with the ridges of the rib segments, as the sheet with the interim profile is passed therethrough.

It will be appreciated that rollers for use in roll forming are generally provided as a set of rollers, with each set comprising a male and a female roller that together form a cooperating roller set. The roll forming process then utilizes a number of adjacent roller sets in stages, there being multiple stages along the PCT/AU2011/001652 WO 2013/003880 -8- length of a roll forming machine, through which the sheet metal is passed for the corrugated panel to be formed. As mentioned above, the sheet metal ordinarily passes though many such stages, having rollers with varying surface profiles, before the final desired profile is formed.

Brief Description of the Drawings

Having briefly described the general concepts involved with the present invention, a preferred embodiment of the invention will now be described. However, it is to be understood that the following description is not to limit the generality of the above description.

In the drawings:

Figure 1 is a cross-section of a corrugated panel (showing the final profile) formed by the method and apparatus of an embodiment of the present invention;

Figure 2a is a cross-section of the interim profile formed during the production of the corrugated panel of Figure 1, showing the interim ribs;

Figure 2b is an exploded view of a portion of the interim profile of Figure 2a, showing the rib segments of an interim rib of the interim profile;

Figure 3 is a cross-section of part of a stage of rollers able to be used to form the corrugated panel of Figure 1, showing a formed metal sheet therewithin;

Figure 4a is a cross-section of a roller set from the stage of rollers of Figure 3, again showing a formed metal sheet therewithin; and

Figure 4b is an exploded cross-section of a portion of the male roller of Figure 4a, showing the scalloped grooves and ridges used to form the rib segments of the interim profile of Figure 2a. PCT/AU2011/001652 WO 2013/003880 -9-

Description of a Preferred Embodiment

Illustrated in Figure 1 is the final profile of a corrugated panel 10 that is generally of the traditional generally sinusoidal profile, the panel 10 having a plurality of alternating, concave ribs 10a and convex ribs 10b across the entire lateral extent thereof. In this illustration, the panel 10 is said to have 6½ “ribs” due to the counting of “ribs” normally regarding a concave/convex rib pair (10a,10b) as a single “rib” for industry purposes, although for the purposes of this patent specification reference is being made to both the concave “ribs” 10a and the convex “ribs” 10b as being ribs that together make up the profile of the corrugated panel. Indeed, it follows that the “pitch” of the panel 10 is the crest-to-crest distance P as shown in Figure 1, and the height of the ribs 10a,10b is the distance H. In this respect, in industry it is common to refer to corrugated panels only in terms of their pitch and material thickness, although reference will also sometimes be made to a rib height.

The ribs 10a, 10b of the panel 10 are shown in Figure 1 as being smoothly curved in that a single radius R is defined by the continuous arc 12a,12b of each rib 10a, 10b, the arc being defined by a radial angle 0. In this respect, it will be noted that when the angle Θ is maximized, there will be no flat portion 14 between the arcs 12a,12b. The arcs 12a,12b can of course be easily illustrated as being perfectly smoothly curved (in a geometric sense), thus having a single radius R across their full length, although in practice these arcs 12a,12b will only be close to “smoothly curved” as will be explained below.

Indeed, in a first preferred form (and to put some of these dimensions in context), the corrugated panel 10 will have an overall width of about 835mm (formed from a metal sheet having an initial width of about 990mm) and a pitch P of about 76mm (or 3 inches), which results in 10½ “ribs” being present as referred to above. In this first preferred form, the height H of the ribs will be about 21 mm, the radius R will be about 21 mm (with a radial angle of about 48°), and the material thickness T and material tensile strength will be about 0.42mm and 550MPa respectively. Variations of the preferred form are also envisaged PCT/AU2011/001652 WO 2013/003880 - 10- with the panel 10 having different metal thicknesses such as 0.35mm, 0.48mm, and 0.60mm, and different metal sheet sizes such as 762mm. In use, the minimum roof pitch for the panel 10 is 3° and, in addition to roofing, the panel 10 can be used for walling and fencing applications.

In a second preferred form, the corrugated panel 10 will have an overall width of about 831mm (again formed from a metal sheet having an initial width of about 990mm) and a pitch P of about 121mm (or 4½ inches), which results in 7 “ribs” being present. In this second preferred form, the height H of the ribs will be about 35mm, the radius R will be about 32mm (with a radial angle of about 47°), and the material thickness T and tensile strength will be about 0.42mm and 550MPa respectively. Again, the panel 10 can have different metal thicknesses such as 0.35mm, 0.48mm, and 0.60mm, and different metal sheet sizes such as 735mm. Furthermore, in use, the minimum roof pitch for the panel 10 is 2° and, in addition to roofing, the panel 10 can be used for walling applications.

In a third preferred form, the corrugated panel 10 will have an overall width of about 800mm (again formed from a metal sheet having an initial width of about 990mm) and a shallower pitch P of about 38.1mm. In this second preferred form, the height H of the ribs will be about 10mm. The panel 10 has a metal thickness of 0.48mm and, in use, can be used for walling, ceiling, verandah and canopy applications.

As can thus be seen, the method of the present invention is able to produce corrugated panels of the dimensions of both of these preferred forms, using relatively thin sheet metal, resulting in significant cost savings per unit area of panel. Also, these corrugated panel profiles have other advantages over existing panels such as having deeper corrugations and being stronger.

Figures 2a and 2b are provided to illustrate one type of interim profile 20 that could be formed in accordance with the method of the present invention. In this respect, the interim profile 20 illustrated in Figure 2a includes interim ribs 20a,20b that each have alternating, concave rib segments 22a and convex rib PCT/AU2011/001652 WO 2013/003880 - 11 - segments 22b, although given the scale of the drawing the rib segments 22a,22b are only barely visible (upon very close inspection by the naked eye) in Figure 2a and indeed are not identified in Figure 2a by reference numerals. Flowever, the rib segments 22a,22b are visible in the exploded view of an interim rib 20b provided in Figure 2b and are illustrated in the form of scalloped grooves (22a) separated by ridges (22b). In this form, the grooves 22a are defined by an arc with a radial angle θι and a radius Ri, whereas the ridges are defined by a smaller arc with a smaller radial angle 02 and a smaller radius R2.

Specifically, and with reference to the utilization of the method to produce corrugated panels 10 of both the first and second preferred forms referred to above, rib segments 22a,22b having grooves 22a of radius Ri of 15.5mm and a radial angle θι of 14° (or a radius Ri of 15.0mm and a radial angle θι of 17°) could be used in conjunction with ridges 22b with a radius R2 of 3.4mm and a radial angle 02 of 23°.

As has been broadly discussed above, in one form of the present invention the interim profile 20 is formed, and the rib segments 22a,22b are then flattened, using traditional cold roll forming techniques and rollers whose surface profiles have been adapted to form the required interim profile 20 and final profile of the panel 10.

With reference to the formation of the interim profile 20, although an interim profile 20 is illustrated in Figures 2a and 2b, it must be appreciated that the interim profile 20 need not actually be brought into existence during the manufacturing process in the form of a sheet where interim ribs 20a,20b, each having a full series of rib segments 22a,22b, are present across the full lateral extent (width) of the sheet. As mentioned above, in roll forming it is likely that the ribs 10a,10b of a corrugated panel 10 (and the interim ribs 20a,20b of the interim profile 20) will be formed in stages along the length of a roll forming machine, with the innermost ribs of a sheet generally being formed first. Thus, if one were to stop the roll forming machine at any time, and view a sheet being moved therethrough, ribs 10a,10b will be evident at some locations and not PCT/AU2011/001652 WO 2013/003880 - 12 - others, and interim ribs 20a,20b (being ribs defined by rib segments 22a,22b) will also be evident at some locations and not others.

Furthermore, the rib segments 22a,22b will also be evident in some locations and not others because, in some sections, the rib segments 22a,22b will not have been formed and because, in other sections, they will have been formed but already flattened. Additionally, some interim ribs 20a,20b may not yet have rib segments 22a,22b formed across the entire width thereof (but only partly thereacross.

In relation to the apparatus aspects of the present invention, and with reference to the drawings of Figures 3, 4a and 4b, the primary and secondary forming means mentioned above are roll formers that are a part of a cold roll forming machine. In this respect, rollers for use in roll forming are generally provided in stages 30, with each stage 30 including the desired number of roller sets 32 (shown as 32a, 32b and 32c in Figure 3), with each set 32 comprising a male roller 34 and a female roller 36 that together form a cooperating roller set (32b). The roll forming process then utilizes a number of adjacent roller sets 32 in stages 30, there being multiple stages 30 along the length of a roll forming machine, through which the sheet metal (identified in Figure 3 by the letter A) is passed for the corrugated panel 10 to be formed. As mentioned above, the sheet metal ordinarily passes though many such stages, having rollers (34,36) with varying surface profiles, before the final desired profile of the panel 10 is formed.

In particular, the rib segments 22a,22b as shown in Figure 2b can be formed in the interim profile 20 by use of a roller 34 having a surface 34a that has been adapted to provide the required segments. As shown in Figure 2b, the rib segments 22a,22b are themselves a series of alternating, concave and convex segments and they are formed in this form by correspondingly shaped segments on the surface of the roller 34. In this form, the profile of the surface 34a of the roller 34 includes a series of scalloped grooves 37 extending about the periphery thereof, with adjacent grooves 37 being separated by ridges 38 PCT/AU2011/001652 WO 2013/003880 - 13- therebetween, the ridges 38 also extending about the periphery thereof. The pitch, depth and radius (the curvature) of the scalloped grooves 37 and of the ridges 38 may be altered in accordance with the dimensions and profile required for the rib segments 22a,22b of the interim profile 20. The female roller 36 is of course similarly profiled.

In this form, a similarly profiled roller set is then adapted for use in a next stage, but with oppositely configured scalloped grooves and ridges in order to flatten the rib segments 22a,22b in the manner mentioned above to form the smoothly curved ribs 10a, 10b of the final profile of the panel 10. Thus, the ridges of such an oppositely configured roller would align with the grooves 22a of the interim ribs 20a,20b, and the grooves of such an oppositely configured roller would align with the ridges 22b of the interim ribs 20a,20b, as the sheet with the interim profile 20 is passed therethrough.

As mentioned above, an acceptable final profile for a corrugated panel 10 produced by the present invention would be a profile where the rib segments 22a,22b have been flattened to an extent that the smoothly curved ribs 10a,10b do not have rib segments that can be seen by the naked eye when viewed at a distance of from about 2 to about 5 metres. Alternatively, a more preferred outcome (which is envisaged to be possible from, for example, the adoption of more accurate roller profiles or a more accurate flattening process) would be for the rib segments 22a,22b to be flattened to an extent that the smoothly curved ribs 10a, 10b of the final profile of the panel 10 will not have rib segments that can be felt by a person rubbing their finger over the ribs 10a, 10b, nor seen by that person when standing within touching distance of the corrugated panel 10.

In conclusion, it must be appreciated that there may be other variations and modifications to the configurations described herein which are also within the scope of the present invention.

Claims

The claims defining the invention are as follows:

1. A method of forming a corrugated panel from sheet metal, the corrugated panel having a plurality of alternating, concave and convex ribs, the method including the steps of: • forming an interim profile in the sheet metal, the interim profile including alternating, concave and convex interim ribs, each of the interim ribs having alternating, concave and convex rib segments; and • flattening each rib segment of each interim rib so that the interim ribs become smoothly curved to form ribs of the corrugated panel.
2. A method according to claim 1, wherein the rib segments are formed across the full extent of the interim rib.
3. A method according to claim 1, wherein the rib segments are formed continuously across the full extent of the interim rib.
4. A method according to any one of claims 1 to 3, wherein all smoothly curved ribs of the corrugated panel are formed by the method.
5. A method according to any one of claims 1 to 4, wherein the forming and flattening steps occur in stages and the flattening of a rib segment occurs in the stage immediately following the stage in which the rib segment is formed.
6. A method according to any one of claims 1 to 5, wherein interim ribs formed towards an edge of the sheet metal have more rib segments than interim ribs formed towards the center of the sheet metal.
7. A method according to any one of claims 1 to 6, wherein the rib segments are flattened to an extent that the smoothly curved ribs do not have rib segments that can be seen by the naked eye when viewed at a distance of from about 2 to about 5 metres.
8. A method according to any one of claims 1 to 6, wherein the rib segments are flattened to an extent that the smoothly curved ribs do not have rib segments that can be felt by a person rubbing their finger over a smoothly curved rib, nor seen by that person when standing within touching distance of the corrugated panel.
9. A method according to any one of claims 1 to 8, wherein the smoothly curved ribs of the corrugated panel have a rib radius above about 25mm and the sheet metal has a thickness of from about 0.45mm or smaller.
10. A method according to any one of claims 1 to 8, wherein the smoothly curved ribs of the corrugated panel have a rib radius above about 40mm and the sheet metal has a thickness of from about 0.45mm or smaller.
11. A method according to any one of claims 1 to 10, wherein the interim profile is formed, and the concave and convex rib segments in the interim ribs are flattened, using cold roll forming techniques and rollers whose surface profiles have been adapted to form the interim and final profiles.
12. Apparatus for forming a corrugated panel from sheet metal, the corrugated panel having a plurality of alternating, concave and convex ribs, the apparatus including: • a primary forming means configured to form an interim profile in the sheet metal, the interim profile including alternating, concave and convex interim ribs, each of the interim ribs having alternating, concave and convex rib segments, and • a secondary forming means configured to flatten each rib segment of each interim rib so that the interim ribs become smoothly curved to form ribs of the corrugated panel.
13. Apparatus according to claim 12, wherein the primary and secondary forming means are roll formers that are a part of a cold roll forming machine.
14. Apparatus according to claim 13, wherein the rib segments are formed in the interim profile by use of a roller having a surface that has been adapted to provide the rib segments.
15. Apparatus according to claim 14, wherein the rib segments are formed by correspondingly shaped segments on the surface of a roller.
16. Apparatus according to claim 15, wherein the surface profile of the roller includes a series of scalloped grooves extending about the periphery thereof, adjacent ones of the grooves being separated by a ridge therebetween, the ridge also extending about the periphery thereof.
17. Apparatus according to claim 16, including a subsequent roller adapted for use in a next stage, the subsequent roller including oppositely configured scalloped grooves and ridges in order to flatten the rib segments to form the smoothly curved ribs of the corrugated panel.