DESCRIPTION

Field of the invention

The present invention relates to the field of roofing panels, particularly to insulated panels . More particularly, the invention relates to those panels that, for reasons of structural strength and heat insulation, provide for the coupling of a corrugated panel metal sheet and a smooth metal sheet with the interposition of an insulating layer of a foam material.

Background art

Among the technigues known for roof claddings, which are guite widespread, especially in the industrial field, are the so- called corrugated insulated panels, i.e., panels consisting of a set of two metal sheets, typically one corrugated sheet and one flat, which are sandwiched into one layer of insulating material of greater or lesser thickness.

When the corrugated panels are used for covering inclined roofs, the corrugated sheet can be placed either on the outside or on the inside; in the first case, the corrugated contour of the panel forms side-by-side channels, arranged along the slope main axis of the roof, which therefore constitute channels for rainwater to flow and to facilitate water drainage.

In these cases the panels are mounted so as to create a slight overlap between the last crest on the corrugation on one panel and the first crest on the corrugation of the adjacent panel. This method of installation is sufficient to prevent water infiltration. So the sheet is protected simply by passivation or by painting.

In the case of flat roofs, such as those that for various reasons must create a level surface or do not have enough of a grade to create slopes, the corrugation cannot be put on the external side because it would inevitably tend to create barriers to the free evacuation of water. The panels are therefore arranged with the flat sheet facing upwards: in this case it is necessary to provide for some other device to prevent water infiltration between one panel and the other, because it is not possible to configure a flat overlay effective against infiltration.

For this reason, the entire surface of the flat sheet is usually coated with a high strength PVC membrane, forming a layer especially effective for water-tightness. Thanks to the presence of this membrane, once the various panels are combined together in place, the gap between panels can also be sealed by applying a PVC strip that is heat sealed (heat welded) to the contiguous parts of two adjacent panels. This strip applied to the work is also called a bridging strip or "pontage".

Operationally, firstly all the panels are mounted that are reguired to form the cladding of the roof, which can also be very large. At the end of the installation, on the junction lines of the panels, bridging strips are applied at the gaps, usually through hot-welding technigues, sealing the covering completely. This seguence derives from a convenience of installation, but also from an efficiency of eguipment use.

EP1375770 discloses such a panel of the prior art.

This system however suffers from at least two serious drawbacks, one connected to the installation step and the other to the production step.

The first drawback occurs when the covering is very large.

This problem stems from the fact that the installation of the panels can take several hours, if not days, so the joints between panels remain exposed to the environment for some time, awaiting the heat sealing operation with the bridging strips, which is done upon the complete assembly of all the panels. Obviously, then, if the assembly of the panels takes a relatively long time, during this period certain weather events might occur that lead to the deposit of water, or even just moisture, on the surface of the panels, which therefore tends to infiltrate to the bottom layers through the free gaps of the joints between panels.

A second drawback occurs under certain manufacturing conditions, when the flat metal sheet is coupled with the PVC layer immediately after the sheeting or lamination, thus before undergoing a process of bending in a suitable form for the composition of the panel. In particular, before being coupled with the corrugated sheet and the intermediate insulating layer (usually made of mineral wool or polyurethane foam) , the flat metal sheet is subjected to continuous bending to form edges with a C or U shape, which then create profiles for containing the insulating material as well as the finishing edge of the panel. Continuous bending is achieved with special machinery systems having bending rollers, which exert a considerable bending force on the peripheral areas of the sheet, also producing significant localised deformations at the corners of the bends . This bending process can adversely affect the PVC coating.

Other examples of prior art panels are disclosed by WO2005/059265 and EP409513, where the bridging strip is integral with an edge of the insulating membrane. In this case, the bridging strip is in the shape of a flap extending from the panel, which results in a number of problems both in the manufacturing step and in the storage of the panels.

Summary of the invention

The problem at the base of the invention is therefore to propose a new structure of panels coated with PVC and the related installation process, to solve the problems mentioned above, facilitating the work of assembly and ensuring a longer life against the weather elements .

This purpose is achieved through the features mentioned in the independent claims annexed hereto. The subordinate claims describe preferred features of the invention. In particular, according to a first aspect of the invention, it is supplied a composite panel for external cladding, consisting of a pair of opposite sheets sandwiching a layer of insulating material, at least one of the sheets, making up the outer surface of the panel, being substantially flat except in correspondence with the longitudinal sides where bead-like bendings are provided, wherein said substantially flat sheet has an external surface layer/membrane of weldable protective material which extends across the entire surface of the sheet except on two peripheral, opposite longitudinal guard bands in correspondence with the longitudinal sides of said sheet, said bands being continuous.

According to an additional aspect, said outer surface layer/membrane of weldable protective material is applied onto said substantially flat sheet before performing a bending operation for defining said bead-like bendings.

Preferably, said weldable protective material is PVC .

According to another aspect, it is supplied a method for cladding roofs with a plurality of panels as described above, wherein the installation of the cladding occurs in two steps

- a first step, wherein each panel is mounted adjacent to a panel mounted earlier and the joint gap between said two panels is temporarily sealed with the application of an adhesive tape laid on said continuous guard bands,

- a second step wherein, at the end of the mounting of said plurality of panels, weldable bridging strips are heat welded in correspondence of said joint gaps between panels, said strips being wider than the overall width of two adjacent guard bands.

Preferably, the adhesive tape is of the alluminum foil type.

According to a further aspect, it is provided a metal sheet for manufacturing a panel as described above, wherein a surface thereof is provided with an outer surface layer/membrane of weldable protective material which extends across the entire surface of the sheet except on two peripheral, opposite longitudinal guard bands in correspondence with the longitudinal sides of said sheet, said bands being continuous.

Brief description of the drawings

However, additional features and benefits of the invention are becoming more evident from the following detailed description of a preferred embodiment, given purely by way of example and not limited thereto, and illustrated in the enclosed drawings, in which :

Fig. 1 is a perspective view, from the top end, of a panel according to the invention;

Fig. 2 is a sectional view of two panels of the invention coupled and mounted;

Fig. 3 is a interrupted perspective view of a pair of panels according to the invention, in one phase of coupling;

Fig. 4 is a view similar to that in Fig. 3 in a subseguent phase of implementation.

Detailed description of a preferred embodiment

As shown in Fig. 1, an insulated panel 1 consists, in a manner known per se, of a first flat sheet 10 and an opposite sheet 11, preferably with a corrugated shape, between which is sandwiched a layer of insulating material 12, for example, mineral wool or polyurethane foam.

The panel - and conseguently the related sheets 10 and 11 - has two longitudinal sides (right and left in fig. 1) of indefinite length and two end sides (front and back in Fig. 1), determined at the time of the cross cutting of the panel, of a length egual to the width of the laminated sheet. The two longitudinal sides are suitably finished to hold inside the insulating material 12, while the end sides have rough cuts that reveal the insulating material 12.

The sheets are preferably made of a metallic material, such as galvanised steel, and have a variable thickness, typically from 0.6 mm to 1 mm when they are smooth and from 0.4 to 1 mm, pre- painted, when corrugated.

As shown in the figures, the corrugated sheet 11 is clearly shaped using special bending eguipment; but the flat sheet 10 also has longitudinal terminal edges bent in a C or U shape defining finishing longitudinal edges for the containment of the insulating material 12.

The flat sheet, on the outside of the panel, has a surface layer or membrane 10' made of PVC, or another protective and weldable plastic material, having a proper thickness.

According to a first essential feature of the invention, the surface layer 10' of protective material - instead of covering the entire surface of the raw flat sheet, as in the prior art extends only on a portion of the raw flat sheet 10, leaving two uncovered continuous guard bands along the longitudinal periphery 10", adjacent to the two longitudinal edges of the flat sheet 10.

These two peripheral longitudinal guard bands 10" have a width sufficient to leave uncovered and expose strips of the metal sheet even after the bending and shaping of the longitudinal finishing edges. The two peripheral longitudinal bands 10", however, have smaller width than the half-width of a bridging strip which must be applied to the panels in the next phase of mounting the array of panels and sealing them each other.

As clearly visible in fig. 1, the panel according to the invention hence has two longitudinal peripheral bands where the flat sheet remains uncovered and exposed and has no protective PVC membrane/layer 10' .

The partial coating of PVC 10' according to the invention, can be applied at an earlier stage to that of bending the longitudinal edges of the flat sheet 10. In this way, leaving the peripheral longitudinal bands 10" without protective membrane/layer, the bending operation can take place effectively and undisturbed, without causing any harm to the surface of the PVC coating 10' . Therefore a first actual beneficial effect is obtained in relation to the stage of manufacturing the panel.

With the panel of the invention a second and synergistic effect is also obtained. In fact, two peripheral longitudinal bands 10" without protective PVC covering are located adjacent to each other along the seam joint line between two panels, as shown in Fig. 4. In this condition, an adhesive tape can be effectively applied over the seam line . The smooth and rigid nature of the sheet material at the bands 10", without the presence of PVC coating, in fact ensures a stable adhesion for any adhesive commonly used on adhesive tapes; in contrast, the irregular and soft surface of the PVC coating 10' would prevent an effective attachment of an adhesive tape.

With the panel configuration according to the invention, in addition to the manufacturing advantages seen above, it then opens up further synergistic possibilities for working effectively in the implementation phase of the panel array. The ability to make an adhesive tape adhere effectively in the seam area allows the guick and easy creation, without the aid of special eguipment, of a temporary sealing between the panels along the way as they are placed next to each other. By doing so, water infiltration under the panels can be prevented even before completing the assembly and final installation of the welded bridging strips (which create the final seal ) .

The installation method according to the invention therefore foresees two distinct phases, namely, one step of mounting the panels adjacent each other with simultaneous temporary covering of the joint gap with adhesive tape, and a later step of applying and welding the bridging strip of final covering. In the first step, the operator undertakes to place the panels side by side and secure them, one at a time, as usual. The attachment of the two contiguous panels 1 and 2 can be done, in a manner already known per se, by using a retaining plate 3 into which an anchor screw 4 is inserted, that is fixed below the support frame (fig. 3) . Once the two panels are assembled side by side, the operator immediately - that is, before moving on to mounting another panel - makes the provisional covering of the gap between the panels, easily applying adhesive tape across the borders of the two panels involved. For the adhesive tape, a commercial product can be used, for example, aluminum foil tape.

The adhesive tape is able to adhere perfectly on the bare metal surface of the flat sheet panel, establishing a temporary, but very secure, protection suitable for making the reguired seal on the seam between the panels, at least for the whole time intervening until the start of the second step of the installation process, which can take place even after some days.

At the end of the installation and fixing all the panels that comprise the surface to be covered (for example a roof) , the bridging strips 5 (fig. 4), made of a material weldable to the PVC sheet 10', are applied using the usual hot welding technigues. The strips must have a width greater than the sum of the widths of the bare bands 10" so as to be welded to the panel area provided with the PVC layer 10' . The adhesive tape for the temporary sealing can be left in position, not interfering with the process of welding.

This second step which, as mentioned, is the hot application of the bridging strips, can thus be performed upon completion of the installation of all the panels on the roof surface without fear of water or moisture penetrating into the gaps between the panels during the period between one step and the other, for as long as the period of the first step may be.

As understood from the above description, with the coated sheet and panel according to the invention, the purposes set out in the introduction are achieved perfectly. The arrangement originally suggested makes it possible to bend the flat sheet, with no harm to its surface finish. Additionally, this configuration allow to carry on an installation procedure that is more secure and faster, even in the case of large areas to be covered .

It is however understood that the invention does not have be considered as limited to the particular arrangement shown above, which is only an exemplifying embodiment thereof, as several variations are possible, all within the reach of a skilled in the field, without thereby departing from the scope of protection of the same invention, as defined by the attached claims.

In particular, the specific material of the sheet and the coating layer may also be different to what is stated, depending on the specific needs or developments in technology.