The invention relates to a roof panel comprising a frame of at least two longitudinal side beams and an in¬ flexible plate such as a multi-ply board fixed on these longitudinal beams. Such a roof panel is known from the international application WO 85/03540. In this known roof panel the frame is assembled from the longitudinal side beams and crossbeams fixedly welded therebetween at the ends. At its bottom end one of the longitudinal beams comprises an outwardly orien- ted hook-shaped flange in which can be received the bottom part of the longitudinal beam of a roof panel adjoining at that point. The known roof panel is suitable for a very heavy roof loading such as can occur in the Scandinavian countries for example as a result of a heavy snow load. Mutual sealing of the panels at the ends is diffi¬ cult to achieve. Because of the expansion and shrinkage occurring as a result of temperature differences the seams between the panels will develop gaps whereby moist air from the space under the panels can penetrate into the gaps and moisture present can condense therein with all the drawbacks this entails.

The invention now has for its object to further develop a roof panel of this type such that it can be produ¬ ced and fitted simply and therefore for relatively little cost, wherein problems relating to sealing between the panels are to a considerable degree prevented.

According to the invention this is achieved with a roof panel comprising a frame of at least two longitudinal side beams^ an inflexible plate, for example a multi-ply board, fixed shifted in two mutually perpendicular directi¬ ons onto the longitudinal beams, which plate has a length corresponding to the effective length of the beams and a width corresponding to the distance between mutually remote

surfaces of the beams such that the plate forms flanges protruding along two adjoining sides, and a bottom plate fixed at a distance from the top plate close to the undersi¬ de of the longitudinal beams. The mutual joining of the roof panels takes place in a suitable manner using the protruding flanges formed by the inflexible top plate. This enables simple fitting. Because the roof panel is substantially open on at least one end and resilient insulation material is arranged between the top plate and the bottom plate, the insulation material comes to lie against the adjoining roof panel in the assembled state so that an insulated seal is formed in effective manner. Expansion and shrinkage in lengthwise direction does not hereby lead to gaps in which condensation forming can occur. The step from claim 2 is preferably applied. Because the insulating material bulges out it is pressed resiliently during assembly against the adjoining parts of the following roof panel. Any irregularities in the surface of the insula¬ ting material are fully compensated hereby so that a good connection is ensured at all times and the occurrence of gaps is prevented. In preference the step from claim 3 is herein applied.

A further favourable development is characterized in claim 4. Each roof panel is fixed onto a support constructi- on with the mounting support protruding outward on the underside. The following connecting roof panel comes to rest on the edge of an already fitted roof panel via the mounting support protruding on the top side. By directly connecting the protruding legs of the mounting supports, for example with screws, to the beams of the already fitted panel, good force transmission directly to the underlying support con¬ struction is obtained and accurate mutual positioning of the roof panels is moreover obtained in simple manner.

A further preferred embodiment is characterized in claim 5. By making use of per se known C-profiles the assem¬ bly operations on the roof panels are kept to a minimum which is of course favourable for a low cost price.

A further development of this aspect is characteri¬ zed in claim 6. The wider the panels become, one or more central longitudinal beams can be arranged accordingly. Due to the chosen dimensioning the mounting of these central longitudinal beams is very simple.

Good transmission of the forces of the supported end of each roof panel is obtained with the step of claim 7. Because of the transverse angle profile a rigid and robust construction is achieved at the location of the end. In the assembled situation the supported end of the roof panel likewise utilizes the transverse angle profile to transfer forces between the longitudinal beams close to that end since the mounting supports of the supported roof profile are likewise joined to the transverse angle profile. A good connection of the panels at the ends is moreover ensured with the step of claim 8. Because the top plate coincides with the flange of the mounting support profile, protection of the top plate against damage is realized while it is moreover ensured that the top plates come to lie tightly against each other. To minimize the operations relating to further finishing the roof formed by the roof panels the step of claim 6 is preferably applied. The protruding overlap is connected watertight in per se known manner to the top side of the water-impermeable sheet of the adjoining roof panels.

The invention will be further elucidated in the following description of a preferred embodiment.

Fig. 1 shows an assembly of a number of roof panels according to the invention, partially in section, in the assembled state.

Fig. 2 shows a roof panel from fig. 1 in a partially broken away view with separated parts.

Fig. 3 shows a section along line III-III in fig. 1 on a larger scale. The roof 1 shown in fig. 1 comprises a number of roof panels 2 according to the invention fixed onto I-beam supports 3 of a support construction. Each roof panel 2 comprises two longitudinal side beams 4 which are manufactu-

red from cold rolled steel plate in a C-profile and a Z- profile respectively. In the embodiment of the roof panel 2 shown a central longitudinal beam 7 is likewise arranged. Fixed onto the longitudinal beams 4, 7 is an inflexible plate 5 which is preferably a multi-ply board.

The dimensions of the board 5 are equal to the length and width of the rectangles defined by the longitudi¬ nal side beams 4. The board 5 is however fixed slightly shifted in two mutually perpendicular directions onto the longitudinal beams. In the embodiment shown the inflexible board 5 is fitted shifted respectively to bottom right and to top right. The distance over which the inflexible board 5 is shifted lies preferably in the order of magnitude of half the width of the longitudinal beams 4. As shown in the figures, the one longitudinal side beam 4 of a roof panel according to the invention is embo¬ died as a cold rolled C-profile with the open side facing inward. A bottom plate 6, which is a corrugated plate in the embodiment shown, rests on the bottom flange 14 of this C- profile. An angle profile 16 on which the bottom plate 6 rests is arranged on the inside of the opposite Z-shaped longitudinal beam. In each case the C-profile of the mutual- ly adjoining panels rests on the outward protruding flange 17 of the adjacent Z-profile. The bottom plate 6 has no actual supporting function and can be replaced by any other plate as desired. The bottom plate 6 can for example be manufactured of perforated steel plate in order to obtain a certain amount of sound¬ proofing. Resilient insulating material 11 such as for example mineral wool or glass wool is arranged between the top plate 5 and the bottom plate 6. The thickness of the insulating material 11 depends on the desired insulating qualities of the roof panel. The insulation material can fill up the entire space between the top plate 5 and the bottom plate 6. According to the invention at least one end of the roof panel is open. In the embodiment shown in the figures the roof panel is open at one end, that is, the left-hand

end as seen in fig. 1 and 2. The insulating material 11 can hereby lie via the open side against the following roof panel in order to ensure good sealing and thereby prevent forming of condensation. As shown in fig. 3, the roof panel 1 according to the figures is closed off at its other end with an mounting support profile 10. This profile 10 has an L-shape and the upper flange thereof protrudes outward. The end edge of the roof board 5 coincides with the end edge of the upper flange of the profile 10. A moisture-inhibiting layer 20 arranσed under the insulation layer 11 is fixed by means of mastic 21 to the inside of the mounting support profile 10.

A transverse angle profile 9 is arranged along the top on the open end of the roof panel. The layer of moistu- re-inhibiting foil 20 is fixed to the inside of the downward leg of the angle profile 9 by means of a mastic joint 23. Insulation material is arranged along the entire height of the open end of the roof panel _a An extra strip of insulating material 19 is received above the insulation material 11 which only extends over a part of the height of the roof panel. This strip of insulating material 19 is supported on the inside by a support profile 18 arranged between the longitudinal profiles of the roof panel. The support profile 18 is arranged at such a position and the thickness of the extra insulating material 19 is such that in the unmounted situation the insulating material bulges out of the open end of the roof panel. The insulation material 11 also bulges out through the open end. When the roof panels are fitted, the right-hand panel as seen in fig. 3 is first arranged on two supports 3 after which the left-hand panel is laid on the already fitted panel. The protruding upper flange of the mounting support profile 10 therein comes to lie on the upper flange of the already fitted panel. Fixing takes place using for example self-boring and self-tapping screws 24. When the left-hand panel as seen in fig. 3 is positioned the bulging insulating material is pressed to the right so that a very good sealing of the gaps between the adjoining roof panels occurs. Because the moisture-inhibiting foil 20 is

pulled through upwards in the above described manner, this comes to lie against the mounting support profile 10. The moisture-inhibiting foil 20 protects the insulation material 11 and 19 at the open end of the roof panel as long as the panel has not yet been fitted.

As can be seen clearly in the figures, the roof panels are fixed to the supports 3 with the protruding legs of the mounting supports on the underside.

In the embodiment shown a water-impermeable sheet, for example, of PVC material, is arranged on the inflexible top plate 5. As fig. 1 clearly shows, these impermeable sheets have an overlap protruding on two sides. After fit¬ ting of the roof panels the overlapping portions are given a watertight finish, for example by glueing. The roof panel according to the invention can be embodied in relatively great lengths, for example up to 12 metres. Depending on the conditions the dimensioning of the component parts, in particular of the longitudinal beams 4, 7 and the mounting supports 8, are adapted for the anticipa- ted loads.