WO2007104482A1

WO2007104482A1 - Roof panel

Info

Publication number: WO2007104482A1
Application number: PCT/EP2007/002051
Authority: WO
Inventors: Jacques Roblot
Original assignee: Renolit Ondex S.A.S.
Priority date: 2006-03-14
Filing date: 2007-03-09
Publication date: 2007-09-20
Also published as: EP1835087A1

Abstract

Roof panel for light constructions, in particular for a greenhouse roof, comprising at least one plate (1), (V) made of synthetic material inserted over at least a part of its perimeter into a rigid fastening section (2), (3) having a thickness at least three times the thickness of the plate.

Description

Roof panel

The invention relates to a roof panel from synthetic material, more particularly a pane for a greenhouse roof.

Greenhouses are light constructions with transparent walls designed for growing plants. Their transparent walls and, in particular, their roofs make it possible to transmit the light energy necessary for the growth of the plants, to maintain a favourable temperature in the greenhouse and to protect the plants from adverse weather conditions. These roofs are usually initially made of glass or honeycomb polycarbonate panels. Honeycomb polycarbonate panels however have a limited resistance to impacts, mainly to the impacts of hail. When certain cells are damaged the water vapour enters the cells of the panel which causes mosses to appear which reduce the transparency. Glass panels are stronger. However, their great rigidity frequently causes them to break due to the slow but inevitable deformations of greenhouses as they get older. Glass panels are quite costly to replace.

It is a known practice to replace the damaged glass panels with plates from synthetic material, usually made of polyvinyl chloride. These plates are usually corrugated to increase their rigidity and bi-oriented by biaxial drawing to increase their resistance t impacts. However, the rigidity of such plates remains inferior to that of glass plates, which requires, during renovation, the addition of reinforcement bars to the supporting structure of the greenhouse, the synthetic plates being fastened to these bars. The result of this is a complexity of renovation and a loss of transparency of thi walls due to the presence of the bars.

The object of the invention is to provide a panel from synthetic material for roofs of light constructions, in particular for a greenhouse, which is suitable to replace glas plates during renovation of greenhouses in an easy and economic way without losses of transparency of the walls.

Therefore, the invention relates to roof panels for light constructions, in particular to greenhouse roofs, comprising at least one plate made of synthetic material inserted over at least a part of its perimeter into a rigid fastening section having a thickness at least three times the thickness of the plate.

In all of this specification, "roof is the external covering of constructions and comprises both the roof proper and the vertical weatherboarding, gable coverings, etc. In the case of greenhouses, virtually the whole external surface of the greenhouse may consist of panels according to the invention.

The panels according to the invention comprise plates inserted over at least a part of their perimeter into a rigid fastening section. Usually being substantially rectangular, the plates are advantageously inserted into sections on at least two, preferably three, of their sides. More preferably, their whole perimeter is inserted into sections. Since this or these sections have a thickness at least three times, advantageously 4 times, preferably 5 times the thickness of the plate, an increased rigidity of the plate is obtained. The plates are inserted into the section, which therefore has a corresponding channel.

The plates used in the panel according to the invention commonly have a thickness lying between 0.5 and 1.5 mm, preferably lying between 0.6 and 1.1 mm. The fastening section advantageously has a thickness, measured perpendicular to the surface of the plate, lying between 3 and 10 mm, preferably between 4 and 7 mm. The plates, usually rectangular, have a width lying between 40 and 80 cm and a length lying between 1 and 2 m.

The plates according to the invention are thus particularly thin and as a result of very leight weight and at the same time cost effective. This is possible because the plates need not provide the necessary rigidity to be self supporting. A measure for rigidity is the modulus El defined as the NF Standard T:54-406 as product of Young's modulus in flexion (E) and the moment of Inertia (I). Typically, flat polyvinyl chloride sheets with a thickness of 1 mm have an El of 2,7x10^'5 Nm², sheets with a thickness of 4 mm have an El of 1 ,7x10^"3 Nm², flat sheets of polycarbonate with a thickness of 1 mm have an El of 1.9X10^"5 Nm² and glass panels with a thickness of 4mm have an El of 420 Nm². The sections into which the edge or edges of the plates are inserted according to the invention serve to provide the necessary rigidity and other mechanical properties to the panels to resist to climatic stress like wind and snow and assure the stability without any link to other parts of the structure. In this way the panels according to the invention combine the adavantages of the thin plates used so far with additional base contruction with the self supporting performance so far only achieved with much thicker and therefore heavier and more costly panels. It is of course also possible to use the sections with thicker plates to impart exceptional stability where this is desired.

The plates may be made of any synthetic material appropriate for a roof. The material must therefore have good mechanical properties (rigidity and resistance to impacts) and a good resistance to solar radiation, in particular to ultraviolet radiation. It is recommended that the synthetic material is selected from polyvinyl chloride, polycarbonate, polymethyl methacrylate, polyethersulphone. Polyvinyl chloride is preferred.

Plates made of polyvinyl chloride (PVC) are also advantageously bioriented. This expression means plates in which the polymeric molecules are preferably oriented in two mutually perpendicular directions. This biorientation is usually obtained by biaxial drawing of the plate. Biorientation is reputed to increase the resistance to impacts of the polymer. Plates made of bioriented PVC are also advantageously corrugated, which further improves their rigidity in the direction of the corrugations. The corrugations also reduce the dimensional variations of the plates during temperature variations. The corrugations may be rounded or trapezoidal or even rectangular. The amplitude of the corrugations preferably lies between 4 and 30 mm, advantageously between 4 and 8 mm. Plates whose amplitude of corrugation lies between 4 and 6 mm, which corresponds to the most advantageous thickness of the fastening sections, are particularly suitable.

The synthetic plates may be transparent, translucent or even, in exceptional circumstances, opaque for certain uses. It is recommended that they are transparent. In the panels according to the invention, the sections situated at the perimeter of the plates are at least three times thicker than the plates.

The increased thickness of the edges of the panels has several advantages, in addition to improving the rigidity of the panel. Specifically, this increased thickness makes it possible to attach the panel simply to the supporting structure of the construction when the latter has rough surfaces (11) that may come into contact with an inner face (10) of the fastening sections (see fig. 15). This situation is particularly valuable when the supporting structure comprises structural sections (5) having whole faces forming such rough surfaces, because then the two sections (fastening and structural) can come into contact over a greater area which improves the attachment of the panels according to the invention.

For this purpose, in an advantageous embodiment of the panel according to the invention, the fastening sections have an attachment face substantially perpendicular to the surface of the plate allowing them to be attached to a structural section of the roof. "Substantially perpendicular" means an orientation allowing the attachment face to remain attached to the structural section under the action of a force parallel to the surface of the plate, directed towards the centre of the panel. Such a force results, for example, from stress of the plate. An inclination of the attachment face towards the inside of the panels is therefore to be avoided because it would promote sliding under the action of such a force. A slight inclination in the opposite direction would, however, be acceptable or even beneficial in some cases. In the case of greenhouses, such structural sections usually form the glazing bars of the greenhouse. Specifically, the supporting structure of a glass greenhouse comprises on the one hand the posts, trusses and purlins but also a secondary structure fastened to the purlins and comprising the glazing bars, to which the glass panels are fastened. In this embodiment, it is recommended that the fastening sections have an approximately rectangular cross section, so as to reproduce the shape of the edge of the glass plates. This embodiment is particularly advantageous when the structural sections have a groove (9), called a drainage groove, in which the increased thickness of the fastening sections may be housed. The panels according to the invention may also comprise several plates, connected in twos by fastening sections. Consequently, in an advantageous mode of execution, the panel comprises at least two adjacent plates joined by a joining section comprising two channels into which the adjacent plates are inserted.

Furthermore, in another advantageous mode of execution of the panel according to the invention, the latter also comprises a synthetic film covering one of the surfaces of the plate without adhering thereto, so as to be able to arrange a volume of air between the plate and the film. In this mode of execution, the panel somewhat forms a double envelope and provides an additional thermal insulation, thanks to the volume of air arranged between the plate and the film.

The fastening sections into which the plates are inserted may be made of different materials. Rigid synthetic materials (having a modulus of stress greater than 1000 MPa) such as PVC or polypropylene or polycarbonate, or metals such as steel or aluminium are recommended. Aluminium is preferred. The fastening sections may be fixedly attached to the plates by any means such as bonding, welding or mechanical fastenings. When the fastening sections are made of aluminium, a mechanical fastening by crimping is preferred. In this case, the inside of the section that is in contact with the plate is advantageously furnished with gripping teeth as shown in Figure 15 for example. Such teeth slightly deform the plate when the section is crimped, which ensures that the section is fastened. When the fastening sections are made of plastic, they are advantageously bonded to the plates.

The increased thickness of the edges of the panels makes them particularly suitable as roof panels for light constructions, in particular of greenhouses and more particularly still for the renovation of greenhouses having a glass roof. Specifically, the panel has, at its perimeter, thanks to this increased thickness, a thickness close to that of glass plates used in light construction roofs. This generally allows the damaged glass plates to be easily substituted by panels according to the invention, the panel being able to be inserted in the fastening devices provided for the glass plates. Consequently, the invention also relates to a greenhouse roof comprising structural sections and at least one panel according to the invention, fastened to a structural section. The greenhouse roof according to the invention comprises a secondary supporting structure consisting of structural sections. Such structural sections are commonly called "glazing bars". The greenhouse roof according to the invention may have very different structural sections. It is advantageous for the structural sections of the roof to have been designed to accept glass panels, because the panels according to the invention make it possible to replace them easily. The structural sections may be made of wood, plastic or metal. It is recommended that they are made of aluminium. The aluminium structural sections may be extruded or even cast. It is however preferred that they are produced by stamping of aluminium sheets. The panels may be fastened to the sections by any appropriate technique.

However, in a first variant of the roof according to the invention, the panels are mechanically fastened to the structural sections. The mechanical fastening may consist of screws, bolts, rivets, etc.

In a second variant, which is recommended, the structural sections have drainage grooves in which the panel or panels are attached. In this variant, the increased thickness formed by the panel-fastening sections according to the invention is housed in the drainage grooves. When the fastening sections have an attachment face that is substantially perpendicular to the face of the plates, such a variant allows the panels to be simply and effectively attached to the roof structure.

The invention also relates to a roof system for greenhouses comprising a set of synthetic panels according to the invention, at least a portion of the adjacent panels having a portion of their fastening sections in common, the said sections in common having two channels into which the adjacent plates are respectively inserted. In the roof system according to the invention, the plates advantageously have a reduced thickness, preferably less than 0.8 mm. Plate thicknesses lying between 0.4 and 0.7 mm are recommended. The roof system may be completely assembled on site, initially with panels according to the invention, in the vicinity of the greenhouse or even in situ. It may also be partly preassembled, preassemblies of two to ten panels, for example, then being assembled to form a complete roof.

In an advantageous variant of the roof system according to the invention, the fastening sections are furnished with feet (3b, 4b) making it possible to separate the panels from the supporting structure of the construction, while allowing them to be fastened to the latter.

The roof system according to the invention, and in particular the variant in which the sections are furnished with feet, is specially adapted to light constructions with no structural sections. The roof system is then fastened directly to the primary structure (purlins, trusses).

Finally, the invention also relates to a greenhouse renovation method, comprising glass walls, according to which the damaged glass panels are replaced by panels according to the invention. In this method, the greenhouses advantageously have structural sections (glazing bars), preferably furnished with drainage grooves.

The appended figures serve to illustrate the invention. Identical reference numbers are given to the corresponding elements of the various figures.

Figures 1 to 3 illustrate in section a panel edge comprising a plate inserted into a fastening section having a channel.

Figures 4 to 14 illustrate in section a portion of panel comprising two adjacent plates inserted into fastening sections having two channels.

Figures 15a to 15c illustrate the attachment of a panel according to a preferred mode of execution of the invention to a secondary greenhouse structure, consisting of structural sections.

In the panel edge illustrated in Figure 1 , a plate 1 is inserted and crimped into an aluminium section having gripping teeth. Figure 2 illustrates the situation before crimping. In the situation illustrated in Figure 3, the section is made of plastic (PVC) and the plate is bonded in the channel.

Figures 4 to 7, representing various modes of joining adjacent plates by means of fastening sections with two channels, show the situations in which the plates are crimped in aluminium sections (Figures "a") and those in which the plates are bonded in plastic (PVC) sections (Figures "b").

In the corresponding Figures 8 to 11 , the sections are furnished with feet 2b, 3b, making it possible to separate the plates 1 , 1' from the structure 4 of the light construction to which the plates are fastened.

In Figures 12 to 14, the plates 1 , 1", both crimped and bonded, have an additional mechanical fastening: bolts for Figures 12 and 14, rivets for Figures 13.

Figures 15a to 15c represent a preferred mode of execution of the invention, in which a plate (1) is inserted into a fastening section (2) comprising an attachment face (10). The section is placed in the drainage groove (9) of a structural section (5). The groove is furnished with a face forming a rough surface (11) making it possible to attach the face (10) of the fastening section. In the embodiment shown, the section (2) is also fastened by mechanical means (6) (bolt in Figure 15b, rivet in Figure 15c). A seal (7), for example made of mastic, is also shown. A clasp (8) may be provided as a substitute or addition to the mechanical fastening means (6).

Claims

1. Roof panel for light constructions, in particular for a greenhouse roof, comprising at least one plate (1), (V) made of synthetic material inserted over at least a part of its perimeter into a rigid fastening section (2), (3) having a thickness at least three times the thickness of the plate.

2. Roof panel according to claim 1 , in which at least a portion of the fastening sections has an attachment face (10) substantially perpendicular to the surface of the plate allowing them to be attached to a structural section of the roof.

3. Roof panel according to claim 2, in which the attachment face (10) is an inner edge of the fastening sections.

4. Roof panel according to any one of claims 1 - 3, in which the fastening section is made of a metal.

5. Roof panel according to any of claims 1 - 4, in which the plate is fastened to the fastening section by crimping.

6. Roof panel according to any of claims 1 - 5, comprising at least two adjacent plates (1 ), (1¹) joined by a fastening section (2), (3) comprising two channels into which the adjacent plates are inserted.

7. Roof panel according to any of claims 1 - 6, also comprising a synthetic film covering one of the surfaces of the plate without adhering thereto, so as to be able to arrange a volume of air between the plate and the film.

8. Greenhouse roof comprising structural sections (5) and at least one panel according to at least one of claims 1 - 7, fastened to a structural section.

9. Greenhouse roof according to claim 8, in which the panel or panels are mechanically fastened to the structural sections.

10. Greenhouse roof according to claim 8, in which the structural sections (5) have drainage grooves (9) in which the panel or panels are attached.

11. Roof system for greenhouses comprising a set of synthetic panels according to at least one of claims 1 to 7, at least a portion of the adjacent panels having a portion of their fastening sections in common, the said sections in common having two channels into which the adjacent plates (1 ), (1¹) are respectively inserted.

12. Roof system according to claim 11 , in which the sections are furnished with feet (2b), (3b) making it possible to separate the panels from the supporting structure of the greenhouse.

13. Renovation method for greenhouses comprising glass walls, wherein the damaged glass panels are replaced by panels according to one of claims 1 to 7.