The invention relates to a shaped roof element according to the preamble of claim 1 and particularly to a roof element for a roof covering, the shaped roof element being manufactured of a plate material, the roof element comprising a first and a second side edge, an upper edge and a lower edge, a profile substantially parallel with the side edges and a series of steps comprising two or more steps extending substantially parallel to the upper and the lower edges, the steps being produced so that the lower edge is one of the steps.
Steel sheet roofs are subject to cut edge corrosion, when precut roof elements joined together to overlap at their border areas become wet. Generally the reason for this is that the borders of the roof elements are not coated, whereby moisture is allowed to penetrate between the sheet and the coating and cause detachment of the coating. Water tends to penetrate between the overlapping roof elements due to capillary force, for example, and other properties of the seam areas, which significantly enhances edge corrosion. In the prior art, attempts have been made to prevent edge corrosion by painting or lacquering the edges of roof elements in different ways. Also seams running parallel to the eaves between successive roof elements in the direction of the roof pane have been formed with the view of preventing water from flowing between the roof elements in the seam area. When different roof elements comprising steps parallel to the eaves are used, the seam area is produced to the vertical portion of the roof element steps, where the wet period is significantly shorter than in seam areas parallel to the surface of the roof elements. In the prior art it has been possible to provide these vertical step portions with different drips by bending the edge of the topmost plate at the seam area away from the vertical portion for preventing water from running between the roof elements. An alternative known method is to provide these vertical portions with different round bends, in which the edge of the roof element is bent out of sight underneath the roof element.
A problem with the above prior art arrangements is that different ways of painting and lacquering the edges are not cost-effective from the manufacturing point of view because of the drying time needed for the paints and the lacquers. Moreover, the paints and lacquers may easily crack and become detached during the installation or use of the roof elements. Although in the prior art seams have been made to vertical portions of roof elements arranged stepwise in the direction of the roof pane, these seams, together with drips, if any, associated with them are not capable of solving the problem of cut edge corrosion these seams are subjected to, because despite its shape, the cut edge of the roof element edge parallel to the eaves is subjected to moisture from the environment. In addition, solutions employing different round bends, in which the edge of a roof element is bent underneath the roof element, create a problem of mechanical abrasion when overlapping roof elements move in relation to one another during installation and normal use. The edge or fold bent as a round end underneath the roof element thus rubs against the plate underneath, thereby damaging its surface and exposing the rubbed area to corrosion.
It is therefore an object of the invention to provide a roof element that allows the above problems to be solved. The object of the invention is achieved by a shaped roof element according to the characterizing part of claim 1, the roof element being characterized in that the vertical profile of the step provided at the lower edge substantially corresponds to the profile shape parallel to the side edges of the shaped roof element.
The preferred embodiments of the invention are disclosed in the dependent claims.
The invention is based on preventing corrosion at the cut edge of the shaped roof element by bending the lower edge of the roof element in such a way that it is not exposed to edge corrosion and does not cause problems of abrasion with another similar shaped roof element. The shaped roof element made of plate material, which comprises a first and a second side edge, an upper and a lower edge, and which shaped roof element is stepped by two or more steps substantially parallel to the upper and lower edge, has a step provided at the lower edge thereof in such a way that the lower edge of the shaped roof element forms a portion bent downward from the surface of the shaped roof element. The step is produced to the lower edge of the shaped roof element by bending the edge downward. According to the present invention the lower edge is bent further underneath the shaped roof element to provide the lower edge with round bend extending downward and underneath the upper surface of the shaped roof element. Moreover, the step and/or the round bend at the lower edge are produced in such a way that their shape and profile substantially correspond to the profile aligned with the side edges of the shaped roof element. In other words, the step or round bend provided at the lower edge has a wavelike profile parallel to the side edges, the profile corresponding to a typical wavelike profile of a shaped roof covering.
An advantage of the method and system of the invention is that since the cut edge of the lower edge is bent underneath the roof element, it is not visible and exposed to environmental corrosive conditions. Instead, it is protected underneath the roof element. In addition, this allows the joint and the seam area between successive roof elements in the direction of the roof pane to be implemented to a vertical surface, on which water is allowed to flow away from the seam area. Moreover, the seam will have an excellent outer appearance, because it is not on the surface of the roof element but at the edge and the step, whereby even a roof made of element pieces such as these looks uniform. In addition, a shaped roof element provided with a profile shape parallel to the side edges and with steps transverse in relation to the side edges stiffens the roof element in two directions, whereby it does not bend and move easily under load. Consequently, overlapping shaped roof elements do not move easily with respect to each other and thereby do not cause abrasion either at the seam on the lower edge between these overlapping shaped roof elements. In that case in particular the stiffening caused by the profiling prevents the upper plate from rubbing against the lower plate when the upper plate is subjected to a load. Moreover, the shape of the roof element together with the profile shape of the lower edge and the round bend thereof enable the roof elements to be positioned in connection with their mounting without having to slide the plates against each other, which further reduces abrasion between the plates. In addition, the profile shape of the roof element and the lower edge reduce reciprocal sliding of superimposed overlapping plates caused by thermal expansion.
In the following the invention will be disclosed in greater detail with reference to preferred embodiments and the accompanying drawings, in which
Reference is made to
The upward extending portion 18 of the lower edge 10 is substantially parallel with the downward extending portion 16, the lower edge 10 being thus provided with a U-shaped cross-section that opens upward in the longitudinal direction thereof and underneath the roof element 1. Alternatively, the upward extending portion 18 of the lower edge 10 extends diagonally upward toward the downward extending portion 16 to provide an overbend to the round bend 20. Alternatively, the upward extending portion 18 of the lower edge 10 extends diagonally upward away from the downward extending portion 16. However, because of the joint between two roof elements, it is not advantageous for the upward extending portion 18 to extend away from the downward extending portion 16, because in that case the round bend 20 protrudes away from the step 12 of the lower roof element. The bending radius in the round bend 20 between the downward extending portion 16 and the upward extending portion 18 is 1 to 5 times the thickness of the plate-like material of the roof element 1. Preferably the bending radius is 1 to 2.5 times the thickness of the plate-like material of the roof element 1 and most preferably 1.5 to 2 times the thickness of the plate-like material of the roof element 1. With smaller bending radiuses the coating provided on the roof element 1 becomes easily damaged, which may cause corrosion and other problems. Then again, with greater bending radiuses the thickness of the round bend increases unnecessarily.
Further, the round bend 20 may be filled with a sealant or a filling material, if desired, to prevent the formation of a water pocket. The filling may be carried out using a foamy or solid filling material, for example. Alternatively, or additionally, one or more holes or openings are provided to the bottom of the round bend 20 to remove water from the round bend 20.
The lower edge of the roof element 1 may be cut in such a way that the lower edge is straight, or, that the height and/or length direction of the lower edge presents a waveform, or the like, corresponding to that of the profile of the roof element or the steps 12 of the roof element. It is also possible to cut the upper edge of the roof element straight or into a waveform corresponding to that of the roof element profile or the steps 12. The side edges are preferably straight. In addition, the lower edge 10 may be bent to provide different folds and/or stiffeners (not shown) that enhance the stiffness of the lower edge 10 and the roof element 1. In complex shaped roof coverings the bending of the lower edge 10 may also require lightening cuts (not shown) to the lower edge 10 for producing the round bend of the invention, because the plate-like material is required to both stretch and to compress in areas close to one another.
In addition to the above, according to the invention the upper edge 8 and/or second or both side edges 4, 6 of the shaped roof element 1 are provided with a round bend, the upper edge 8 and/or the second or both side edges 4, 6 being bent underneath the shaped roof element 1. This allows also edge corrosion to be prevented at these other edges. In addition, the steps 12 or the step 14 on the lower edge 10 are provided with one or more location recesses for positioning a fastening screw.
A person skilled in the art will find it apparent that as technology advances the basic idea of the invention may be implemented in various ways. Therefore the invention and its embodiments are not restricted to the examples described above but may vary within the scope of the claims.
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20075777 | Nov 2007 | FI | national |
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PCT/FI2008/050614 | 10/30/2008 | WO | 00 | 6/11/2010 |
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