The present invention relates to a shingle-pattern roofing sheet manufactured of sheet metal profile by means of bending or press-forming, wherein the strength and ductility properties of the sheet material are utilized in order to achieve an advantageous, durable and attractive shingle-like appearance.

At present a large variety of roof deck materials and elements are used for roofing, for example tile, minerit board, sheet metal etc. Among these roofing materials, tile is becoming obsolete owing _. to high costs and difficulties in the installation work.

Minerit boards have not gained much popularity, partly because they are expensive and their durability is weak, and partly because their raw material contains asbestos.

Sheet metal roofs, are made of smooth sheet metal or corrugated plate; they can be for instance tile imitations made of sheet metal having the form of sine curve and being compressed into form by means of stretching or bending. As a whole, the prior art sheet metal roofing elements include a large variety of different form and structure designs.

The Swedish Patent Publication No. 166 921 introduces corrugated plates comprising several parallel riser members and therebetween, at a lower l evel , other separate members, and the side edges of the riser members are provided with means for coupling the plates together in succession.

The Finnish Patent Publication No. 50 728 introduces a building element for roofing, wherein the elements are provided with means for joining a chosen number of plates

together in a row in succession, in two directions which are vertical to each other. In the direction parallel to the wall or the roof inclination, the building elements of the said invention are step-like, and the means for joining the plates together comprise a tongue and a groove.

The step-like members of the said patent application are formed of assembled portions, the assembling whereof is difficult, complicated and expensive, and requires special equipment for carrying out the assembly work.

The US Patent Publication No. 3 875 715 introduces a prefabricated sheet metal roofing module comprising specially shaped planar steps. At right angles to the steps there are joining compression junctures.

The German Patent Application No. 2 404 515 introduces a roof element characterized by an appearance resembling a flake or a roof tile.

One of the drawbacks of the prior art roofing methods has been the fact that the bending strength of the various roofing materials has been poor. The employed materials are particularly sensitive to the growth of the longitudinal moment, so that for instance the weight of snow has made the element bend. Consequently it has been necessary to space the supporting structures at short intervals on the roof frame. Round forms are also easily damaged during handling, and their installation is cumbersome. It has proved particularly difficult to seal the screw joints of roofing elments with a round-shaped profile.

The object of the present invention is to elminate the drawbacks of the prior art roofing materials. The roofing element according to the present invention is not only

durable and practical but also attractive, because the pattern gives an impression of a shingle roof. The shape of the element allows for press-forming the step-like profile by means of bending, without stretching the material.

The shingle-like roofing element of the invention is developed with the aim to remove the drawbacks existing in the prior art. The invention is characterized by the novel features apparent from the patent claim 1.

The greatest advantage of the present invention is that the longitudinal bending strength of the shingle-like roofing element of the invention is essentially improved as compared to the prior art. By employing the shingle roof of the invenntion, the sheathing can be spaced remarkably wider than berfore. This saves the material expenses and makes both the planning and installation of the roof structure easier.

The advantegous shape of the bending angle of the shingle roof profile also helps at the manufacturing stage of the roofing element, because the shape allows for press-forming the shingle-like step by means of bending, without having to stretch the material in order to create the profile.

In the following the shingle-like roofing element of the invention is explained with reference to the appended drawings, where Figure 1 is a top-side view illustration of the roofing element of the invention, and

Figure 2 is a cross-sectional view of the element of figure 1.

Figure 1 illustrates the shingle roof element seen askant from above. In top-side view, the roof pattern resembles

the surface pattern of a shingle roof, where the shingles 1 are formed of octagonal steps 2 which are bent to opposite directions. The bent sides of the successive steps are made so that the bending directions 3 and 4 of the sides of the steps point to opposite directions, which shape arrangement substantially improves the longitudinal bending strength of the roofing element.

Figure 2 illustrates a cross-sectional view of the shingle element, where the shingle element is shown in longitudinal section along the line A-A of figure 1. The bending angles of the element steps are chosen so that the sides 5 and 6 , bent to opposite directions, are bent without embossing so that it is unnecessary to stretch the material in order to create the profile.

The bending angles are suitably arranged so that every second step has a positeive bending angle ( O ) and the rest have a negative bending andle (-OC). The roofing element is so designed that the shingles are formed for example of larger 7 and smaller 8 rectangles. These rectangles are arranged in adjacent rows 9 so that the adjacent rows are separated from each other by means of inclined trapeziums 10. By varying the lateral angle and the vertical angle of the trapeziums, it is possible to vary the shape of the side profile and the pattern of the roofing element so that the shingle-like appearance can be modified as desired.

The above specification is a description of one preferred embodiment of the invention. Naturally the shingle-pattern roofing element of the invention, manufactured by bending or press-forming, allows for a variety of modifications wihtin the scope of the appended patent claims.