A range of roof panels are available. One of the problems with conventional roof panels, however, is that they are generally of uniform cross section and provide an outer appearance which is substantially uniform.

There is therefore a need for a new roof panel which will provide non-uniform outer appearance, which can be readily manufactured on a large scale, which is easy to assemble on site with other similar panels, and which provides desired properties in use.

Statements of Invention According to the invention there is provided a roof tile panel comprising an inner backing sheet, an external roof sheet, and a body of insulating foam between the sheets, the external roof sheet having a transversely extending front lip, a transversely extending rear portion and a plurality of transversely extending step sections which are spaced-apart longitudinally between the front lip and the rear portion.

In a preferred embodiment the front lip portion projects forwardly of the backing sheet and the insulating foam material.

Preferably the rear portion is raised with respect to adjacent step section.

In one embodiment the backing sheet and insulating foam terminate substantially in- line with a free edge of the rear portion.

Preferably the external roof sheet extends transversely beyond a side edge of the backing sheet and the insulating foam to define an overlapping portion for overlapping, on assembly, with an opposite side of an adjacent roof tile panel.

In one embodiment an opposite side edge of the roof sheet has a trough portion which is overlapped by the overlapping portion of the roof sheet of an adjacent panel. Preferably the trough portion has a flat portion to receive a fastener system.

In one embodiment there are at least four step sections in the external roof sheet.

The backing sheet is usually substantially flat.

In a preferred embodiment the external roof sheet is profiled to define a number of longitudinally extending peaks and valleys across the width of the external sheet.

In a preferred embodiment the tile profile comprises a plurality of periodic segments extending across the panel, each segment defining a wavelength and having a number of generally tangential arcs. The tangential arcs comprise a first arc leading from a peak to a valley, a second arc defining a valley and a third arc extending from the valley to a peak. In a preferred embodiment a generally non-tangential line extends between the second arc and the third arc.

Brief Description of the Drawings The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawings, in which:- Fig. 1 is a top-side perspective view of a roof tile panel according to the invention; Fig. 2 is a top-side plan view of the tile panel of Fig. 1; Fig. 3 is an under-side plan view of the tile panel of Fig. 1; Fig. 4 is an under-side perspective view of the roof tile panel of Fig. 1; Fig. 5 is a front partially cross sectional view of the roof tile panel of Fig. 1; Fig. 5A is a cross sectional view on an enlarged scale at a side overlap between adjacent panels.

Fig. 6 is a rear partially cross sectional view of the roof tile panel of Fig. 1; Fig. 6A is a cross sectional view of portion of the panel on an enlarged scale.

Fig. 7 is a left side view of the roof tile panel of Fig. 1; Fig. 8 is a right side view of the roof tile panel of Fig. 1; Fig. 9 is a top perspective view of a roof tile panel with three step sections; Fig. 10 is a top perspective view of a roof tile panel with five main step sections;

Fig. 11 is a top perspective view of a roof tile panel with sixteen step sections; Fig. 12 is a top perspective view of a roof tile panel with twenty-seven step sections; Fig. 13 is a top perspective view of a roof tile panel with thirty-eight step sections; and Fig. 14 is a top perspective view of a roof tile panel with forty-nine step sections.

Detailed Description Referring to the drawings there is illustrated a roof tile panel comprising a substantially flat backing sheet 5, a profiled external roof sheet 6, and a body of insulating foam 7 between the sheets 5,6. Both the backing sheet 5 and external sheet 6 are typically of metal, especially steel. The insulating foam 7 is of polyurethane or any similar suitable material to provide desired insulating and structural properties.

The external sheet 6 has a transversely extending front lip 10, a transversely extending rear portion 11 and number of transversely extending step sections 15 which are spaced-apart longitudinally between the front lip 10 and the rear portion 11.

The front lip portion 11 projects forwardly of the backing sheet 5 and the insulating foam 7 for mounting to a support structure. The backing sheet 5 and foam 7 terminate substantially in-line with a free edge of the rear portion. For over lapping adjacent sheets the external roof sheet 6 extends transversely beyond a side edge of the backing sheet and the insulating foam to define an overlapping portion 20 which is overlapped, an assembly, with an opposite side of an adjacent roof tile panel.

The external roof sheet 6 is in this case profiled to define a number of longitudinally extending peaks 30 and valleys 31 across the width of the external sheet. These are interrupted transversely by the step sections 15 to provide a panel with the appearance of comprising a plurality of separate roof tiles. The panels are substantially cheaper, have better insulation properties and are easily assembled on site.

The tile profile comprises a plurality of periodic segments extending across the panel, each segment defining a wavelength and having a number of generally tangential arcs. The tangential arcs comprise a first arc Ri leading from a peak to a valley, a second arc R2 defining a valley and a third arc R3 extending from the valley to a peak. A generally non-tangential line Ll extends between the second arc R2 and the third arc R3. The non-tangential line Ll is blended with small fillet radii. This profile is important in ensuring that pressure generated by foam expansion during manufacture is more evenly distributed.

The side overlap detail with a seal 53 between adjacent panels allows an edge fastener 50 to be concealed in the overlap. This enables the number of visible fasteners 51 to be reduced. The trough at the overlap has a flat zone 52 to accommodate a washer of the preferred diameter of 19mm.

The panels are manufactured by on-line cold rolling a decoiled thin sheet of steel to form a desired profile of external sheet as illustrated. The outer face of the external sheet is lowermost and liquid foam reactants are applied to the inner face of the external sheet. A backing sheet is then led over the external sheet and foam reactants. The panel thus formed is then heated in an oven and the liquid foam reactants expand to form a panel comprising the profiled external sheet, the inner backing sheet and insulating foam between the sheets.

The panels may be manufactured to any desired length, depending on the required span. The external sheet 6 may be profiled to form any desired number of step

sections 15. Usually, for spanning, there will be at least five step sections as illustrated in Fig. 10. Increasing numbers of step sections are formed in the panels illustrated in Figs. 11 through 14. There may be any desired number of such step sections and the distance between adjacent step sections may be of any length required.

Many variations on the invention will be readily apparent and accordingly the invention is not limited to the embodiments hereinbefore described which may be varied in detail.