Such an elongate retaining element is known from GB-2167101-A, which discloses a retaining element having a head part and a base part connected by a connecting flange. The head part engages with the free end of at least one building sheet, which is at least partially curved over the head part of the retaining element.

This known elongate retaining element is made from a metal, in particular from extruded aluminium alloy.

Another elongate retaining element is known from EP-1236840-A1, which is made from a thermoplastic material and having a metallic reinforcement core that is fully embedded in the thermoplastic material. Such a reinforced retaining element provides a high durability against disengagement of the thermoplastic material from the reinforcement. Furthermore, it avoids thermal-bridges, being conductive heat transport via the retaining element. However, a disadvantage of such reinforced retaining element is that it is difficult to manufacture, and requires multiple processing steps.

An object of the present invention is to provide an elongate retaining element that reduces to occurrence of thermal bridges when used in engagement with building sheets. Another object is to provide an elongate retaining element that is much easier to manufacture than the known reinforced thermoplastic retaining element.

One or both of these objects are achieved by a retaining element wherein the elongate retaining element is made from a plastic material and is provided with means for connecting said plastic elongate retaining element to a support structure via a fastening element passing simultaneously through a part of the head part and the connecting flange into the support structure.

This achieves the effect that an elongate retaining element is obtained that in use does not form a thermal-bridge since there is no direct contact between metal

parts, and thereby avoids all disadvantages associated therewith. The use of a plastic material for the retaining element significantly reduces the friction between the head part and the engageable building sheet enabling the building sheet to slide easily over the head part of the retaining element without generating an unpleasant noise commonly experienced while sliding metallic parts over each other. Furthermore, the elongate retaining element does not have the fully embedded complex shaped metallic reinforcement core and thereby avoids all disadvantages associated therewith including a considerable cost advantage in manufacturing such a retaining element according to this invention. The fastening element acts to a very large extend similar as a reinforcement, but which is inserted firstly on a construction site. Another advantage is that the amount of dead weight in the retaining element is reduced. Yet another advantage is that the retaining element is much easier to install since there is only one fastening element used, and in an embodiment two or more. And in use on a roof or façade structure, the tension forces on a retaining element caused by wind suction will be conducted directly by the fastening element to the support structure underneath the base part of the retaining element. Furthermore, the buckling behaviour of the retaining element is improved because any compressive force will be carried by the stiff fastening element or elements which is optionally supported by the plastic material instead of as known from EP-1236840-A1 only a thin and perforated metal sheet which is much more slender.

In an embodiment the head part is provided with at least one recess to accommodate the head part of the fastening element, and thereby enabling engagement of the head part with a building sheet without the risk that the head part of the fastening element is in direct contact with the head part of the retaining element as to avoid frictional contact or thermal contact.

In an embodiment the head part comprises a reinforcement extending in the direction of elongation of the retaining element and is embedded in the plastic material of the head part. This achieves the effect that any mechanical load is better distributed over the connecting flange of the retaining element, such as to avoid amongst others any stress-corrosion of the plastic material when the fastening element is fastened with a too high force.

In an embodiment at least the connecting flange has a passage allowing the insertion of the fastening element. This allows appropriate guidance of the fastening element passing through the connecting flange into the direction of a support structure. The passage can extend into only a part of the connecting flange.

In an embodiment such a passage has a diameter smaller than the diameter of the fastening element to be inserted. This allows a tight fitting between the retaining element and the fastening element, and in the case where the fastening element is provided in part or in whole with a thread it allows fast and accurate insertion of such a fastening element while obtaining a reliable connection between the retaining element and the fastening element.

In an embodiment such a passage has a diameter slightly larger than the diameter of the fastening element to be inserted. This allows for easy insertion of the fastening element at a construction site and large flexibility during fastening into a support structure.

In an embodiment the fastening is an elongate screw, and which may be provided in part or in whole with a thread.

In an embodiment the elongate retaining element is provide with two or more fastening elements, thereby increasing the load bearing capacity of the retaining element according to the invention.

In an embodiment the plastic material is an injection moulded plastic material.

Herewith an elongate retaining element is provided which is easy and very cost effective to manufacture.

In an embodiment the plastic material is a thermoplastic material such as PVC, PA, PE, PUR, PP, PTFE (polytetrafluoroethylene) or cellulose polymers. In particular advantageous are thermoplastic selected from a polyester, a polyamide, a modified polyester, or a modified polyamide. These thermoplastic materials have one or more of the properties of low friction, high wear resistance, good temperature stability to temperatures up to 100°C, good elastic properties, and high flame resistance.

Furthermore, these thermoplastic materials can be processed via injection moulding techniques. Polyamides ("PA") in general are found to be sufficiently durable, and to have a favourable low coefficient of friction and good flame resistance and are an accepted construction material.

In an embodiment plastic material is a thermosets, such as phenolics, amino- plastics, epoxys, polyurethanes and polyester. These thermosets materials can be processed via injection moulding techniques.

In an embodiment the head part of the elongate retaining element is substantially triangular in cross section, and preferably with rounded vertices, for example as known from UK-2167464-B, and Fig. 3 and Fig. 4 in particular.

Alternatively, the head part of the elongate retaining element has an asymmetrical cross section, for example as known from DE-10144119-A1, and Fig. 2 in particular.

In both embodiments the free-ends of the head part may be rounded-off, for example as known from DE-10144119-A1, and Fig. 1 in particular. Both prior art references UK- 2167464-B and DE-10144119-A1 are incorporated herein by reference.

According to the invention in another aspect, there is provided an assembly of at least one such elongate retaining element and at least one building sheet mounted thereby on a support structure, and whereby the free ends of two adjacent building sheets are flanged one on top of the other along the longitudinal head part of the elongate retaining element.

The invention will now be illustrated by several non-limitative embodiments, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic perspective view of a plastic elongate retaining element according to the invention and which is provided with a fastening element ; Fig. 2 shows a cross-section of a plastic elongate retaining element according to the invention and which is provided with a fastening element ; Fig. 3 shows a side-view of a plastic elongate retaining element according to the invention and which is provided with a fastening element ; Fig. 4 shows a detail of the head section of the plastic elongate retaining element according of Fig. 1; Fig. 5 shows a top-view of the plastic elongate retaining element according to the invention and which is provided with a fastening element and having a substantially rectangular base section.

Fig. 6 shows a top-view of the plastic elongate retaining element according to the invention in the embodiment with a substantially circular base section.

Fig. 1 shows schematically an elongate retaining element consisting of a non- hollow head part 1 of substantially triangular cross-section and which is substantially symmetrical with the central longitudinal axis of the connecting flange, a connecting flange 2, and a base part 3 for mounting on a support structure. The head part can work together with sheet-like building elements, whereby the free ends of two adjacent sheet-like building elements are flanged one on top of the other along the longitudinal head part. The elongate retaining element is provided one each side of the connecting flange with one or more supporting ribs 4 extending between the base part 3 and the connecting flange 2, and preferably two on each side. Herewith, additional mechanical stability is provided, or the transverse stiffness of the retaining element is further improved. The choice of the geometry of said rib or ribs allows for optimisation of the transverse stiffness, which is of particularly importance in designing elongate retaining elements with various restraining distances between the base part and the

head part. The base part 3 is preferably devoid of upstanding flanges near its free ends so as to avoid the formation of drainage channels or the like. The elongate retaining element is provided with one fastening element 5, typically an elongate screw and which is provided in part or in whole with a thread, which passes through the head part 1 and through the connecting flange 2 into a support structure, thereby coupling the retaining element to the support structure. The head part 1 of the elongate retaining element is provided preferably with a recess to accommodate the corresponding head part of the fastening element, the recess preferably arranged substantially perpendicular to the direction of elongation of the retaining element. It will be apparent for the skilled person that in another embodiment the retaining element may be provided with two or more fastening elements at spaced interval for each other, thereby improving the load bearing capacity of the retaining element.

Fig. 2 shows schematically a cross-section of the retaining element as shown in Fig. 1. The elongate retaining element is provided with a fastening element 5, typically an elongate screw, which passes through the head part 1 and through the connecting flange 2 into a support structure (not shown), thereby coupling the retaining element to the support structure. In this schematic figure the thickness of the connecting flange is not appropriate for the diameter of the screw used. In practice the thickness of the connecting flange will typically be in a range of 3 to 15 mm, whereas the diameter of the shaft of the fastening element would be typically in a range of 2 to 10 mm.

Fig. 3 shows schematically a side-view of the retaining element shown in Fig. 1, and clearly showing the recess to accommodate the corresponding head part of the fastening element. The advantages of which has been mentioned above.

Fig. 4 shows a perspective view of a detail of the head part of the retaining element shown in Fig. 1. In this embodiment the head part only is provided with a reinforcement 6 embedded in the head part 1. The reinforcement can be made of a metal, e. g. aluminium alloy, stainless steel or carbon steel, or metal coated carbon steel, for example with a zinc coating. Alternatively the reinforcement can be made of another stiff material, such has another suitable plastic material or a glass-fibre material and materials providing similar stiffness and which do not adversely interact with the plastic material used for the retaining element.

Fig. 5 show a schematic top-view of the retaining element according to the invention and which is provided with a fastening element. The base part 3 of the retaining element has a rectangular shape. Whereas Fig. 6 shows a similar top-view for the embodiment where the base part 3 has a circular shape, and which may have alternative forms such as an elliptical periphery. The skilled person will immediately

recognize that there is a large flexibility possible in the shape of the base part in the retaining element of this invention, for example it can be made to fit with an obstacle such as a pipe or adjusted such that it can be mounted on an uneven surface of a support structure.

Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made without departing from the spirit or scope of the invention as hereon described.