Background Art Roof cladding elements, in the following also called plates and panels, of the present type are described, for instance, in two Danish-language pamphlets"Gi'dit hus en ny profil..."and"Vejledning-projectering og mon- tage"issued by Lindab Profil A/S in 1994, as well as in the German-language pamphlet"Lindab Dachpfannen"issued by Lindab VM GmbH. This roof cladding system is marketed under the trademark LindabTopline@.

Equipment for producing such roof cladding elements of sheet metal is disclosed, for instance, in the appli- cant's pamphlet"Integrated Sheet Metal Technology"which was distributed in the early nineties. In this pamphlet, there is described a roll-forming machine for profiling a sheet metal strip in the longitudinal direction in such way that the strip is given a wave-shaped cross-section.

Then the profiled strip is stepped in the transverse direction for forming tile-like formations similar to traditional roof tiles of clay. The known machine also includes a cutting unit for cutting the plates and panels in desired lengths. At the end of the production line there is a stacking unit for stacking the finished pro- duct. An example of such a product, that is a roof clad- ding panel, is shown in the Danish Utility Model Publica- tion DK-U-96 00008 corresponding to the German Utility Model Publication DE-U-297 00 208.

Traditionally, the roof cladding elements discuss- ed above are delivered in lengths of several metres, so-

called full-length plates which require two people in mounting on the roof. Lately, however, the market has demanded shorter roof cladding elements of this type, so-called panels having a length of about 1-2 m which can be mounted by a single person. Such short roof clad- ding panels are advantageous since they can be stored in standard lengths, can easily be placed on a small trailer for transport and can easily be mounted on the roof by one person.

When mounting these known roof cladding elements (plates and panels), however, specific problems arise due to the overlap between the panels. These problems occur in particular when the roof cladding is built up from several short panels leading to a plurality of four-corner joints on the roof. Since the panels are mounted in an overlapping manner, these four-corner joints include the corner portions of four adjacent panels. Thus, each four-corner joint has four layers of sheet metal leading to a build-up in height throughout the roof cladding, making it difficult to mount the panels in a straight horizontal direction. Of course, the corresponding problem arises in the longitudinal direction of the roof cladding.

Another inconvenience is that the person mounting the roof cladding elements does not know where to put the fastening screws on the elements for attachment to the underlying supporting structure of the roof. The supporting structure is simply hidden by the panels.

Summary of the Invention An object of the present invention is to provide an improved method and an improved apparatus for manufactur- ing roof cladding elements of the present type, by means of which the above-mentioned disadvantages can be reme- died. A particular object of the invention is that the manufacturing allows easy switch from short panels to long plates and also allows various tile formations on the strip.

These and other objects, which will appear from the following description, are achieved by a method having the features defined in appended claim 1, preferred variants thereof being set forth in the subclaims 2-9.

The objects of the invention are also achieved by an apparatus having the features defined in appended claim 10, preferred embodiments thereof being set forth in the subclaims 11-18.

The invention confers several advantages. Owing to the new corner notching technique, two diagonally oppo- site corner portions of each roof cladding element are obliquely cut in a special manner so that the overlap problem in the four-corner joints, in mounting the panels, is remedied. Further, a very effective and flex- ible production of the new roof cladding elements is achieved.

Brief Description of the Drawings The invention will be described more in detail in the following with reference to the accompanying drawings which illustrate non-limiting embodiments and variants of the invention.

Fig. 1 is a side view of a production line for manu- facturing roof cladding elements in accordance with the invention.

Fig. 2 is a partial plan view of the production line showing the manufacture of short panels having two step- like tile formations.

Fig. 3 is a corresponding plan view showing the ma- nufacture of a panel having only one tile formation.

Fig. 4 is a schematic perspective view of a part of the production line.

Fig. 5 shows a detail of a pressing assembly of Fig. 4.

Fig. 6 shows a scrap portion cut away from a metal strip in a cutting assembly of Fig. 4.

Figs 7-11 show schematically stepping and cutting steps of the inventive concept.

Fig. 12 is a plan view of a roof cladding panel pro- duced in accordance with the invention.

Fig. 13 is an end view of the panel.

Fig. 14 is a perspective view of the panel.

Fig. 15 is a perspective view of four panels as in Figs 12-14, portions of the four panels being cut away.

Fig. 16 is a perspective view of three of the four panels in assembling.

Fig. 17 is a perspective of the four panels when assembled.

Description of Preferred Embodiments In Fig. 1, there is shown a production line for the manufacture of rectangular roof cladding elements in ac- cordance with the present invention. A strip 1 of sheet metal is fed from a coil supply 2 to a roll-forming assembly 3, further to a cutting and pressing arrangement 4, and finally to a stacking assembly 5. At the end of the production line, there is a conveyor 6 for transpor- tation of piles of stacked roof cladding elements manu- factured in accordance with the invention.

In the roll-forming assembly 3, the metal strip 1 is profiled in the longitudinal direction such that the strip 1 is given a wave-shaped cross-section (cf.

Fig. 13). In a part of the cutting and pressing ar- rangement 4, the metal strip 1 is formed with trans- verse steps (cf. Figs 12 and 14).

As can be seen in Fig. 2, the cutting and pressing arrangement 4 includes a corner notching assembly 7, a step pressing assembly 8 and a transverse cutting assem- bly 9, said assemblies being further described below. The cutting and pressing arrangement 4 also includes means 10 for forming indentations in the strip 1 as will be de- scribed below as well.

When the strip 1 in a manner known per se has been profiled in the roll-forming assembly 3, it first encoun- ters the corner notching assembly 7 where each longitudi- nal edge portion la, 1b is notched in a particular man-

ner. The notches 11,12 in the strip 1 are shown in Fig. 2. The tools 13,14 of the corner notching assembly 7 which cut the notches 11,12 are schematically shown in Fig. 2. The notches 11,12 constitute two diagonally opposite corner portions of the finished product, that is the roof cladding element 15 in Fig. 2 which in this embodiment is a so-called short-tile panel.

In the embodiment shown, the means 10 for forming indentations 16 in the strip 1 are arranged in connection with the corner notching assembly 7. Preferably, these means 10 comprise projections extending downwardly from the upper members of the corner notching tool.

For explanatory purposes, a dotted transverse line 17 on the strip 1 is shown in Fig. 2 between the corner notching assembly 7 and the step pressing assembly 8. The transversely opposite notches 11,12 are cut on either side of this transverse line 17 so that one corner notch will constitute an upper obliquely cut corner portion 11 of a first panel 15 whereas the other corner notch will constitute a lower obliquely cut corner portion 12 of a second panel 15 following the first panel in the produc- tion direction shown by the arrow A in Fig. 2. The panels 15 are separated, that is cut, along the transverse lines 17.

In Fig. 2, there is also shown a wave-shaped dotted line 18 which together with the transverse straight line 17 define a transverse scrap portion 19 which is shown separately in Fig. 6. Preferably, the obliquely cut cor- ner portions 11,12 are notched partially overlapping the transverse scrap portion 19 to be cut away from the strip 1. Thanks to this overlap, the exact position of the front edge of the panels 15 to be stepped and transverse- ly cut is not crucial in the production.

The arrangement shown in Fig. 3 corresponds to the arrangement of Fig. 2. In Fig. 3, however, the arrange- ment has been adjusted for production of another type of panels 15'having only one long-tile formation. For

accomplishing this alternative production, the corner notching assembly 7 and the transverse cutting assembly 9 have been moved in relation to the step pressing assem- bly 8 which is stationary. By adjustment of the stepwise movement of the strip 1 in the production direction A, the step formations on the strip 1 can easily be varied in accordance with the desired finished panel.

It should be noted that the described production line can also be used for the production of so-called full-length roof cladding plates of several metres. The equipment is easily adapted for the manufacture of diffe- rent roof cladding elements thanks to the movability of the assemblies 7 and 9 as well as a simple variation of the step-wise movement of the strip 1.

Fig. 4 shows the cutting and pressing arrangement 4 in perspective. The profiled strip 1 is fed to the corner notching assembly 7 in which the corner portions 11 and 12 of the panel 15 are notched and the indentations 16 of the same are formed.

The notched strip 1 is fed to the step pressing assembly 8, which includes an upper tool 20 and a lower tool 21 which will be described below. Fig. 5 schemati- cally shows how a wave-shaped step 22 is formed in the assembly 8 by pressing the upper tool 20 against the lower tool 21 in the direction of the arrows B.

The transverse cutting assembly 9 includes an upper tool 23 and a lower tool 24. These tools 23,24 cut and separate the panels 15, and in this cutting operation the transverse scrap portion 19 (see Fig. 6) is cut away and collected under the cutting assembly 9. The leading edge of the scrap portion 19 in view of the production direction A is straight, whereas the tailing edge is wave-shaped. Thus, the finished panel 15 will have one straight transverse edge 17 and one wave-shaped trans- verse edge 18 (see Fig. 12).

The stepping and transverse cutting operations are schematically shown in Figs 7-11. The upper pressing tool

20 consists of two tool members 20a, 20b, and the lower pressing tool 21 also consists of two tool members 21a, 21b. The upper cutting tool 23 is a single member, where- as the lower cutting tool 24 consists of two spaced tool members 24a, 24b.

First, the profiled strip 1 is fed in between the upper pressing tool member 20a, 20b and the lower press- ing tool members 21a, 21b (Fig. 7). Then the strip 1 is clamped between the tool members 20a and 21a and shortly after this clamping (with a delay of a few tenths of a second), the strip 1 is initially stepped by pressing the upper tool member 20b against the lower tool member 21b (Fig. 8). Thus, the tool members 20a, 21a and 20b, 21b, respectively, cooperate in the transverse stepping opera- tion. Preferably, these respective pairs of tool members 20a, 21a and 20b, 21b are arranged close to each other.

In the stepping operation, the strip 1 is stepwise moved in a direction, shown by the arrow C, opposite to the production direction A. This so-called first material flow is indicated by the reference D1 in Fig. 8.

In Fig. 9, it is shown how the strip 1 is trans- versely cut or sheared by moving of the upper cutting tool 23 towards the lower cutting tool members 24a, 24b, thus cutting away the scrap portion 19. The left edge of the upper tool 23 and the left lower tool member 24a cooperate for cutting along a wave-line 18, whereas the right edge of the upper tool 23 and the right lower tool member 24b cooperate for cutting along a straight line 17 (cf. Fig. 2).

Fig. 10 shows how the upper pressing tool member 20b is pressed further down against the lower pressing tool member 21b for pressing to full step height. In doing so, a slight material flow back in the production direction A is obtained leading to a so-called final material flow indicated by D2 in Fig. 10. The stepping and shearing operations are now finished, and the respective tool mem- bers are moved from each other to the positions shown in

Fig. 11. The cut away scrap portion 19 is collected under the cutting tools 23,24a, 24b. The strip 1 is then moved forward stepwise for new stepping and cutting operations.

Preferably, the forming of the transverse steps 22 and the transverse cutting are performed approximately at the same time, or alternatively with a delay of a few tenths of a second (the cutting being the last step).

The finished product, that is an improved roof clad- ding panel 15, is shown in Figs 12-14.

Figs 16-17 show how roof cladding panels 15a, 15b, 15c, 15d manufactured in accordance with the invention are assembled to form a roof cladding. Thanks to the obliquely cut corner portions 11,12, the overlap problem mentioned in the introductory portion of this description is avoided since there will only be two layers of mate- rial in the four-corner joint along the connection where the cut corner portions 11,12 are put together edge-to- edge. This is easily appreciated from Figs 15-17. Prefer- ably, the edges of the cut corner portions 11,12 are at least partially in abutment with each other.

Finally, it should be mentioned that the invention is by no means restricted to the embodiments described, and several modifications are feasible within the general scope of the appended claims. For instance, the specific design of the finished product, such as the tile forma- tions, etc, is not crucial to the invention.