Roofs at present are covered with many different materials, for example tiles and sheets. Tile roofs are attractive, and many private persons want the roofs of their own homes be covered with tiles. Tiles, however, are expensive, and moreover, the art field, i.e., the manufacture of roof tiles, is gradually ceasing to exist due to lack of profitability, factors which will result in a future shortage of roof tiles.
The tin (metal) roofs available prior to applicant's invention consist of flat sheets or of conventionally roll-formed sheets of different appearance, or of trapezoid corrugated sheets, and the like.
The present invention refers to a kind of sheet-tile roof, which means that the roofing consists of sheets, but has the appearance of tiles, and will be referred to hereinafter as tiles. The new sheet-tile roof is manufactured in large units which include a plurality of "tiles", so that several rows of tiles are obtained in both directions, vertically as well as in lateral direction. The large units then can be cut to desired sizes. The individual "tile" in the large unit, besides, can be manufactured in different sizes (modules) according to desire. This new roofing is cheaper to manufacture and cheaper to lay (mount) on the roof than a conventional clay or ceramic tile roof. It has the look, besides, of a usual tile roof and, therefore, the new roofing also is attractive to many people. The new roofing also is attractive compared with conventional roofing of sheet material, because of the appearance of a clay tile roof. The new roofing, besides, has economically advantageous aspects in production, shipping, storage and installation.
My co-pending application Ser. No. 219,831 discloses a roofing, the appearance of which resembles that of a clay tile roofing. The method of manufacturing such roofing which also is described in said patent specification is characterized substantially in that a flat sheet in a first step is preformed by roll-forming, so that the sheet by a first cross forming operation is provided with a contour perpendicularly to its surface extension which in cross-section is a curved, or multi-wave shape, e.g., a sinus-shaped section. In a second step the preformed sheet is provided with stepped jags of a certain step height by some kind of stretch-pressing operation, at which a special pressing tool is used. The basic pressing tool comprises two pairs of tools, which are movable individually relative to each other in a direction perpendicular to the surface extension of the sheet. At the forming of the step-like jag the preformed sheet is held down, retained, by each pair of tools in a clamping condition, i.e., in a blankholding condition, whereafter the tool pairs are moved relative to each other through a distance corresponding to the step height, so that the sheet by the second forming operation perpendicularly to its surface extension and to said first cut is given a step-formed section.
The tools then are separated from each other, and the sheet is advanced through a predetermined distance. Thereafter the next step is formed, and so on.
The result thereof is a sheet having a form corresponding to a portion of a clay tile roof.
The method referred to above, however, involves problems, viz. that the distance between two subsequent jags, i.e. a distance corresponding to the length of a tile, is difficult to control. Furthermore, uncontrolled wrinkling and/or tearing occurring in connection with making the jag is difficult to avoid. These problems emanate from difficulties in controlling and guiding the movements of the sheet relative to the tool surfaces of the tool pairs. This in its turn depends on the clamping force with which the two respective tool pairs are held against the sheet.