A POST

Abstract: A post (1), which is particularly a hollow, tubular piece, and is intended to be used as a post for traffic lights, streetlights, signs, or similar, and is formed of at least two layers. The post has at least one layer (3) made of fibre-reinforced thermoplastic, and at least one layer (4) of thermoplastic, but which is not, however, a single layer of polyolefin. The post may also include other layers.

Description: A pos t The present invention relates to a post, particularly, but not exclusively, to a post that can be used, for example, in traffic signs, streetlights, traffic lights, and various signposts. Conventional power and telephone posts naturally also form a large group of applications. Posts for the aforementioned purposes are manufactured from many materials. Posts are generally hollow for many reasons, such as saving material. Metal posts are probably the most generally used. Other alternatives are posts manufactured from reinforced or other plastics. Wooden posts are also widely used. In certain situations, the weight of the post is a significant factor. Thus, the weight of metal posts and solid wooden posts is often unnecessarily great for the intended purpose. Attempts have been made to resolve the weight problem by using reinforced plastic, for example. However, such posts have their own specific weaknesses, such as fragmentation in collisions. Another post is known, with an inner layer of fibre-reinforced plastic and an outer of polyolefin. This construction has the drawback that the polyolefin layer is not sufficiently flexible in all situations. In addition, the effect of extreme conditions, in particular the embrittling effect of cold, is a drawback, especially in winter. The present invention is intended to create a post, in which it is possible to avoid some of the drawbacks relating to posts according to the state of the art referred to above, and to achieve a light and durable post for a wide range of applications. The aforementioned and other benefits and advantages of the invention are achieved in the manner referred to in the characterizing sections of the accompanying Claims. In the following, the invention is described in detail with reference to the accompanying diagrammatic drawings, which depict some embodiments of the invention, in which: Figure 1 shows a cross-section of one embodiment of the post according to the invention; Figure 2 shows a longitudinal section of the construction according to Figure 1 ; and Figure 3 shows a partial longitudinal section according to Figure 2 of another embodiment of the invention. Thus, Figure 1 shows, by way of illustration and without considering scale, a cross- section of one post 1 according to the invention. The post is, in particular, hollow and thus incorporates a longitudinal cavity 2. The basic construction of the post is layered, with an inner layer 3 and an outer layer 3 and possibly other layers too. The wall thickness of each layer used can be varied as necessary. According to the invention, the inner layer 3 may be of fibre-reinforced, thermoplastic, to ensure a combination of lightness and strength. The outer layer 4, in turn, may be of an elastomer or synthetic rubber or related copolymers, or of natural rubber, or a mixture of two or more of these. The construction may also include a layer of a polyolefin, such as a polyamide, which will create an extremely tough structure. The intention is to ensure that the outer layer will remain sufficiently flexible and elastic under all conditions, but also to ensure that nevertheless the inner layer or layers remain in place even if they fragment, and thus will not cause a substantial danger to the surroundings, for example, due to flying splinters. Another property of the outer layer is that it must be sufficiently tough to be able to resist, to a certain extent, the breaking of the post. A post that remains intact is safer than a post that breaks completely, some part of which may gain significant penetrating inertia from the effect of a collision and thus cause considerable damage. As stated above, an additional layer of a polyamide, such as nylon, may be used to increase toughness. The elastic properties of the outer layer are also beneficial in that the layer remains intact, thus protecting the underlying structure from, for example, the effect of water. If the surface cracks, water can penetrate to the interior, resulting in structural problems. Because the construction according to the invention can be used to avoid the creation of cracks and holes, the posts will have a very long life under normal conditions. In the same way, substances protecting against ultraviolet light can be added to the outer layers, thus also ensuring that the construction does not become brittle, when used outdoors. Figures 2 and 3 show two longitudinal sections, applying a construction according to the invention. In the embodiment shown in Figure 2, the inner layer is formed by a unified tubular component, but in Figure 3, the construction comprises parts joined together, as disclosed in detail in the following. In both alternatives, the tube or tubes may be of uniform diameter, or may especially taper. The outer layer completely covers and protects the inner layer, as disclosed above. Thus, Figure 3 shows another embodiment, in which the inner tubular component is assembled from two or more separate tubes with different diameters, which fit into each other to create a post construction that narrows in steps. The unified outer layer 4 also covers the shoulder sections thus formed, for example, in the manner shown at the right-hand side of Figure 3, or more probably in the manner shown at the left- hand side of Figure 3, i.e. covering the shoulder section very tightly. It is obvious that, in the figure, the layers are drawn to appear separate from each other only for reasons of clarity, as in reality layers 3 and 4 form a solid totality. It is also obvious that many different thermoplastics can be used to manufacture the innermost layer and that many different kinds of fibre reinforcement can be considered. Glass-fibre is one conventional fibre material, but there are also other very strong fibre materials on the market nowadays, such as Kevlar-fibre and carbon- fibre. In terms of the basic idea of the invention, it is obvious that both the plastic materials and the fibre materials may be selected to suit the intended application. As stated above, the twin-layer construction given as an example is by no means the only possible alternative. For example, if desired, an outer-layer material of the type disclosed above may also be used on the inner surface of the tubular structure of the post. On the other hand, the actual body can be made of several layers of material, which may be of the same or different materials. The layered construction makes it possible to achieve excellent strength properties. If necessary, it is possible to use an adhesive or otherwise glue-like material, which can be especially added between the layers, for example, during the extrusion of the next layer on top of a previous layer. The glue-like material may be as such a plastic- based material. Those versed in the art will know many plastics with adhesive qualities, permitting a suitable choice to be made. The outer surface of each layer can also be manufactured in a way that will improve adhesion, for example, by roughening it or even by using fine crushed material from damaged posts. All in all, a post prefabricated according to the invention will provide a post that is more useful and durable, but nevertheless light, thus gaining significant advantages over the posts presently used. It will also have significant properties improving traffic safety.

Claims: Claims 1. A post (1), which is particularly a hollow, tubular piece and is intended for use as a post for traffic lights, streetlights, signs, or similar, and which is formed of at least two layers, characterized in that it incorporates at least one layer (3) made of fibre- reinforced thermoplastic and at least one layer (4) of thermoplastic, which is not, however, a single layer of polyolefin. 2. A post according to Claim 1 , characterized in that at least one layer (4) is of an elastomer or its copolymer, or of a synthetic rubber or its copolymer, or of natural rubber, or of a combination of two or more of the above. 3. A post according to Claim 1 , characterized in that it also includes a layer of a polyolefin or polyamide, such as nylon. 4. A post according to Claim 1 , characterized in that the layer (4) is situated on top of the layer (3) and is a unified and continuous layer. 5. A post according to Claim 1 , characterized in that the fibre-reinforced layer (3) contains glass-fibre, Kevlar-fibre, carbon-fibre, or similar. 6. A post according to Claim 1 , characterized in that the outer surface of the layer (3) is treated to improve adhesion and that there is an adhesive material, such as a glue-like material, between the layers (3, 4). 7. A post according to Claim 6, characterized in that the glue-like material has a thermoplastic base. 8. A post according to one of the above Claims, characterized in that at least one of the layers (3) of fibre-reinforced thermoplastic is constructed to taper without shoulders.

Inventors: JERNSTROEM ROLF, JERNSTROEM, ROLF
Applicants: JERNSTROEM ROLF, JEROL IND AB, JERNSTROEM, ROLF, JEROL INDUSTRI AB
Application year: 2000
Main classification: E01F9
IPC codes: E01F9, E04H12