Composite roof panels of this type are known and are widely used for pitched roofs.

Flat roofs or those having a small pitch angle of less than about 2° are generally covered by metal sheets extending between and fixed to purlins and/or supports. An insulation material such as sheets of insulating foam are then laid on site on the metal sheets and the insulating material is covered with a weatherproof membrane. Such a system is generally inconvenient because of the difficulties in performing such work on site. Such systems are slow to build. In addition, there is a risk of damage to the membrane by installers. Further, known systems are generally not rigid or stiff and the load bearing capacity is very limited.

This invention is directed to providing an improved flat roof panel and panel assembly which will address at least some of these problems.

Statements of Invention According to the invention there is provided a composite roof panel for a flat or substantially flat roof comprising : a generally flat external sheet; a profiled internal sheet; and

an insulating core between the external sheet and the internal sheet; the panel having a first overlap portion extending along one side and a second overlap portion extending along an opposite side; the internal sheet having an internal sheet first overlap portion on one side and an internal sheet second overlap portion on the opposite side, the first overlap portion of the internal sheet being substantially free of insulating core; the side edge of the insulating core at the first overlap portion having a first inclined wedge face and the side edge of the insulating core at the second overlap portion having a second inclined wedge face which is oppositely directed to the first inclined wedge face at the first overlap portion; the internal sheet overlap portions and the wedge faces of the insulating core of adjacent like panels being interengagable on assembly.

In one embodiment one of the wedge faces of the insulating core extends at an angle of from 70° to 80° and the other of the wedge faces of the insulating core extends at a corresponding angle of from 110° to 100°. Preferably, one of the wedge faces of the insulating core extends at an angle of approximately 75° and the other of the wedge faces of the insulating core extends at a corresponding angle of approximately 105°.

In one embodiment the internal sheet comprises a plurality of generally trapezoidal portions. The generally trapezoidal portions may have stepped side walls.

In one embodiment the internal sheet overlap portions are defined by part trapezoidal portions.

Preferably, the trapezoidal portions have a depth of at least 90mm, most preferably about 110mm.

In one embodiment the external sheet has an external sheet first overlap portion on one side and an external sheet second overlap portion on the opposite side. The external sheet may have an outer male projecting part and an inner recess part on one side, and a corresponding outer recess part and projecting inner male part respectively on the opposite side of the panel.

On assembly, the outermost edges of adjacent panels may be spaced-apart at a joint therebetween to define a gap.

In one embodiment the gap defines a locator for an external reinforcing plate extending between the external sheets of adjacent panels, on assembly.

The invention also provides an insulated panel assembly comprising a plurality of the panels of the invention.

In one embodiment the assembly comprises a reinforcing plate for extending across a joint between adjacent panels.

In a preferred embodiment the reinforcing plate has a locator which may be for engagement in a gap between external sheets of adjacent panels.

Preferably the reinforcing plate has a hole to receive a joint fastener.

The invention also provides a reinforcing plate for an insulated panel assembly as described and illustrated.

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 perspective view of a roof panel according to the invention; Fig. 2 is a cross-sectional view of the panel of Fig. 1; Fig. 3a is a cross sectional view of a portion of two adjacent panels according to the invention separated; Fig. 3b is a cross-sectional view of the panels jointed together; Fig. 3c is a cross-sectional view of adjacent panels with a reinforcing plate in place; Fig. 4 is a cross sectional view of adjacent panels with fixings in place; Fig. 5 is a cross sectional view of an external sheet of the panel; Fig. 6 is a cross sectional view of a joint detail between external sheets of adjacent panels; Fig. 7 is a cross sectional view of an internal sheet of the panel; and Fig. 8 is a view on A-A in Fig. 7.

Detailed Description of the Drawings Referring to the drawings, there is illustrated an insulated panel according to the invention comprising a generally flat external sheet 2, a profiled internal decking sheet 3, and an insulating core 4 between the external sheet 2 and internal sheet 3. The sheets 2 and 3 are typically of steel material and the core 4 is of polyurethane or polyisocyanurate foam material which fills the space between the sheets 2,3. The panel 1 is used for a flat or low pitch (less than 2°) roofing system.

The outer flat steel sheet 2 may have a prebonded weather membrane such as a plastics membrane, for example of polyvinylchloride. In this case the PVC membrane is heat sealed at the panel joint when assembled on site. The outer sheet 2 may have a prebonded bitchumen type membrane to which a further bitchumen type membrane may be applied on site. The outer sheet 2 may also not have a prebonded weather membrane. In this case, a weather membrane such as a PVC membrane may be applied on site.

The external sheet 2 and internal sheet 3 have profiled joint-forming portions for connecting adjacent panels, on assembly as illustrated. In this case the external sheet 2 has an external male projecting part 10 and an internal recess part 11 on one side for engagement, on assembly, with a corresponding external recess part 12 and projecting inner male part 13 respectively on the opposite side of the panel.

At least a portion of the side edges 21,22 of the insulating core 4 between the joint forming portions of the external sheet and the internal lining sheet has an inclined profile and the inclined profiles of the side edges 21,22 of the insulating core 4 form oppositely directed wedge faces. A side edge 22 of the insulating core 4 of one panel 20A is matched with the opposite side edge 21 of an adjacent panel 20B, on assembly.

For optimum performance one wedge face of the insulating core extends at an angle of from 70° to 80°, ideally about 75° and the opposite wedge face extends at a corresponding angle of from 110° to 100°, ideally about 105°.

The internal decking sheet 3 has a plurality of generally trapezoidal portions. For improved performance the side walls of the trapezoidal portions are stepped. The bases of the trapezoidal sections also have transversely extending reinforcing ribs 60.

For optimum performance the depth of the trapezoidal portions is at least 90mm, preferably about 110mm. The thickness of the insulating foam between the portion of the internal sheet between the trapezoidal portions and the external sheet is generally at least 50mm and may be at least 70mm.

The inner sheet 3 comprises a first overlap portion 31 on one side which extends laterally of the external sheet 2 and is free of insulation. The inner sheet 3 also has a second overlap portion 32 on the opposite side of the panel. On assembly, the first overlap portion 31 of the panel receives the second overlap portion 32 of the adjacent panel.

It will be noted that on assembly of adjacent panels a gap 35 is defined between the outermost edges of the external sheet 2. A joint reinforcing plate 40 has a downwardly extending locator defined by a projection 41 which is located in the gap 35 to ensure that the reinforcing plate 40 is accurately positioned relative to the joint.

The plate 40 has two holes 42,43 to receive joint fasteners 44,45. Thus the reinforcing plate 40 ensures that the fasteners 44,45 are correctly located at the joint which is important in ensuring the integrity of the fastened joint, especially in relation to the fastener 44 which may extend through several plys of the joint forming portion of both the external and internal sheets 2,3. The fasteners 44,45 have low profile heads to facilitate application of a weather seal plastics (such as PVC) strip 46 over the fastener plates 40 and the joint.

It will be appreciated that, if desired, one or more factory applied and/or site applied seals may be provided at the joint between adjacent panels. For example, a seal may be located in the gap 35. One or both of the side edges of the insulating core may be covered with an insulating tape.

The invention provides an insulating flat roof panel which facilities a high quality joint between adjacent panels. The joint ensures a high level of insulation and fire performance but also has a high mechanical strength by virtue of the wedge faces of the insulating core at the joint and the overlap. Because of these features the panel may be used in wider spans than has heretofore been possible. The panels are easily handled and can be built up to achieve a 5 to 6 metre double span. The reinforcing plate and associated fasteners also assist in optimising the strength of the assembled panels.

Thus, the invention provides an insulated flat roof panel with highly efficient installation, insulation, fire performance and mechanical performance.

It will be appreciated that the panels may be provided with opposite side edges or two different panels with a similar profile on both side edges may be provided.

The invention is not limited to the embodiments hereinbefore described which may be varied in construction and detail.