Description of the prior art Fence posts of the prior art basically comprise an elongated body to be driven into the ground, herein designated as the post body, and which is generally provided with through apertures or slots for passing wires through. Such a post body may be made of wood, metal, concrete or plastics, the latter being preferable due to its avantages with re- spect with low cost and also by virtue of the simplicity in mounting, greater durability, insula- tion against electric discharges and other advantages. In addition to the post body there are other devices which are necessary for mounting the post, namely the post driver for driving the post into the ground, clamps for securing the wires to said post body, etc.

GB 1402481 shows a hollow plastic post which replaces known wooden, con- crete or steel posts. Also a driving cap is provided, which assists in driving the post body into the ground, preventing it from being damage. Since the post body is hollow, it may be filled with concrete or any other substance in order to give it greater strength. A drawback of this

post is that its body has low tensile strength, if it is not filled with a reinforcing substance.

This filling causes the post to become more resistant, but the act of filling the post with con- crete or another substance is troublesome and time-consuming, which makes labour expen- sive.

US 4070007 discloses an injection-moulded plastic post having high tensile strength and excellent durability. In addition, it also has lugs for securing either ordinary or barbed wires. US 4070007 does not show the way in which the post is driven into the ground, nor the apparats for this purpose. Thus, the post might be driven into the ground and mounted with equipment which might not be appropriate or could damage it or not fix it properly.

FR 2568926 discloses a plastic post which serves for both fencing off fields and supporting vines and other kinds of plants, besides supporting straw coverings for vines and orchards. This known plastic post can be provided with a metallic point to facilitate insertion in the soil.

DE 3316790 discloses a post made of plastic with cross-shaped, star-shaped, triangular or square sections, which is resistant to atmospheric influences, corrosion and UV radiation. In addition, it has a tapered end to penetrate the ground easily. An apparats for driving it is not disclosed.

DE 35017746 refers to a plastic post having a more or less oval or cross-shaped body, which has holes for passing wires through. Due to its large thickness, this post has the drawback of being heavier than other known posts, which entails a greater difficulty in trans- portation and greater costs in manufacturing.

US 3955801 and US 4540160 disclose pre-fabricated fences made of plastic posts provided with slots for receiving one end of plastic rails. US 4702459 discloses a fence assembly including fence posts which are provided with pockets adapted to receive ball shaped sockets dispose at each end of a crossrail in order to allow for incline positioning of such crossrails to satisfy ground contour conditions.

Among the described plastic posts or plastic fence assemblies of the prior art, a common disadvantage relies in that plastic posts have a limited mechanical resistance due to their constant cross section, which is probably due to a preferred manufacturing process by extrusion. Moreover, each post of the prior art is more or less specifically designed for certain purposes, such as to permit construction of wire fences or rail fences, a complete

modular assembly allowing several configurations not being provided. Another aspect which is not mentioned in the above documents relies in that posts which are located at the ends of a fence may act as tensioning posts, that is to say, posts which serve for tensioning the wires, which posts shall be properly anchored by means of a prop. The cited documents do not disclose any specific element for engaging with such a prop.

Summary of the invention The object of the instant invention relies in eliminating the above drawbacks of the known plastic posts and to provide a structural element with enhanced mechanical re- sistance and an assembly which can be used either for wired fences-whether smooth or barbed wires-or for fences of crossrails. Another object of the present invention is to pro- vide a system of structural elements, particularly a plastic post system which is easier to drive into the soil than those of the prior art. A further object of the present invention is to provide a structural element which may be of various shapes, preferably L-shaped, T- shaped and cross-shaped. Still another objective of the invention is to provide a post which can penetrate in hard soils with reduced risk of breaking its the lower end. Another object of the invention is to provide a post head protection cap, which will serve for any post having an "L","T","H"or cross shape section. Another object of the invention is to provide a support for crossrails or boards, so that they can be positioned on any type of ground, irrespective of the slope.

According to the invention a plastic structural element is provided having an elongated body formed by at least two plate portions joined along one edge thereof and forming an angle between them, said element having an upper end and a lower end and being provided with through apertures and slots distributed along the element, said slots extending from one free edge of one of the plate portions, said apertures and slots being adapted for the passage of several parallel extending wires or barbed wires, said lower end of the element being tapered as to facilitate penetration on the soil, whereby transversal re- inforcing crossbars are provided along the element joining said plate portions. Also accord- ing to the instant invention, a structural assembly comprising at least one plastic structural element further inclues a tip provided at said lower end of the structural element and being made of a material which is more resistant than that of the structural element.

The structural element or post of the present invention is easy to handle, by vir- tue of the fact that it is made in a massive way from plastics of high tensile strength, as well

as a complete system for installing it very easily and rapidly. In this way, an excellent tensile strength is achieved, without the need for adding structures or substances inside the post body for this purpose. The present invention also suggests a complete post system which, in addition to having through apertures and slots for passing the wires though, is provided with devices for use in installing crossrails or fencing boards, which are widely used by breeders of horses or other animais. By making the ground-penetrating tip of the post out of metal, its ability to penetrate into the ground is enhanced, in that the post will overcome obstacles en- countered in its way more easily. In order to facilitate the construction of larger structures by assembling several posts, posts in accordance with the present invention may have a re- movable metallic tip for facilitating mounting of the structural element, without the drawback of having exposed pointed ends and also to prevent the post from breaking while it is being driven into the ground. The invention also provides an equipment to be used for driving the post. In addition, a device is provided which allows an ordinary post to become a tensioning post.

Detailed description of preferred embodiments of the invention Some preferred embodiments of the system of structural elements, particularly a fence post, will now be described in further details with reference to the drawings, in which: -figure l a is a front view of a first preferred embodiment of a structural element, particularly an L-shaped post, the metallic tip of which is cast onto the post body; -figure 1 b is a top view of the L-shaped post, where the reinforcing crossbar of the post sides can be seen; -figure 1c is a side view of the L-shaped post, the metallic tip of which is cast onto the post; -figure 2a shows a front view of a second preferred embodiment of the structural element, particularly an T-shaped post with the metallic tip cast onto the post; -figure 2b shows a top view of the T-shaped post, where the reinforcing crossbar joined to the walls of the post can be seen; -figure 2c shows a back view of the T-shaped post with the metallic tip cast onto the post;

-figure 2d shows a side view of the T-shaped post with the metallic tip cast onto the post; -figure 3a shows a front view of the prop-supporting plate for a tensioning post; -figure 3b shows a side view of the prop-supporting plate for a tensioning post -figure 4a shows a front view of a board support; -figure 4b shows a side view of a board support; -figure 5a shows a perspective view of a crossrail or fence board; -figure 5b shows a side view of the board; -figure 6a shows a perspective view of a post head protection cap; -figure 6b shows a cross-section view of the post head protection cap; -figure 6c shows a bottom view of the post head protection cap; -figure 7 shows a perspective view of a post driver; -figure 8 shows, in perspective, a third embodiment of the structural element, in which the post is L-shaped, with a detachable tip and elliptical apertures for passing smooth wires through and coupling to another structural element; -figure 9 is a perspective view showing the removable tapered tip of the L- shaped post; -figure 10 schematically shows the coupling of two L-shaped structural elements when used for the construction of structures; -figure 11 shows a perspective view of a fourth embodiment, where the post is T-shaped and has a detachable tip; and -figure 12 shows a tapered tip removable form the T-shaped post.

As shown in figure l a, the L-shaped post body 1 has plate walls 2 with through apertures 3 for the passage of smooth wires and slots 4 for the passage of barbed wires. At one end of this post a metallic tip is provided so as to facilitate penetration into the ground.

This metallic tip is tapered at a junction 5, so that the metal and the plastic can join to form a single body.

As one can infer from figures 1 a and 1 c, the through apertures 3 and slots 4 for the passage of the respective wires are provided in the two walls 2 of the post, at a distance which does not impair the tensile strength of the post body. This also enables the placing of wires on either or both sides. Besides, one can see that the oblique slots 4, essentially in form of an inverted"Y", for fixing barbed wire is made so as to ensure that the wire remains as secure as possible. Reinforcing crossbars 6 can be seen on figures 1 b and 1 c, which pre- vent easy torsion of the post, thus increasing its rigidity.

A further embodiment of the post is shown in figures 2a to 2d. A T-shaped post 7, which may be used either for fencing off fields with smooth or barbed wire or for placing crossrails to be used in stables or corrals. Similarly to the previous embodiment, wires are passed through apertures 3 and slots 4 provided in the leg portion of the"T" (figure 2d), i. e. on wall 12, while additional rows of through apertures 9 are provided in the upper portion of the"T", i. e. on wall 8, for receiving fixing means (e. g., pins or screws) for fixing a crossrail support 17 (figures 4a, b), as it will be further explained in more details. The T-shaped post is also provided with reinforcing crossbars 11 and with a metallic tip cast onto the post body at the junction 10.

The present invention also suggests a prop-supporting plate 13 (figures 3a and 3b) having through apertures 16 and an integral support element 14 in the form of a nose, which provides a support surface 15. The prop-supporting plate 13 can be fixed by any suit- able fixing means to the apertures of a post, e. g. to apertures 9 of the T-shaped post of fig- ures 2a-2c, whereby the through apertures 16 match the through apertures 3 or 9 of the post body. Plate 13 is to be fixed to the end posts of a fence in order to ensure proper tensioning of the post by anchoring the latter by means of a prop. The prop is fixed to the ground and rests against support surface 15, thus causing the post to resist the traction which is neces- sary from time to time for keeping the wires always stretched.

Figures 4a and 4b show the support 17 for fitting the boards or crossrails 22 (figures 5a and 5b), which are used in connection with T-shaped posts. The crossrails have a hollow section, preferably in the form of a"C". The crossrails 22 are attache to the wall 8 of a post body 7 by fixing the support 17 by screws or pins, which pass through the through apertures 9 and 18 of the post body 7 and support 17, respectively. Each end of a crossrail 22 is then fitted on a respective support 17 by slidingly fitting the hollow crossrail 22 over the

support 17. Because the through aperture 18 of the support 17 is centred and single, the support may rotate, thereby allowing the crossrail to assume incline positions when the posts are placed on an uneven surface. Hence, when adjacent posts are placed in an in- clined terrain, the crossrails will follow this inclination. According to another possible em- bodiment (not illustrated), the support is fixedly secured to a post, e. g. directly into through apertures 3 by means of a screw, and has a rounded surface which allows the crossrail to fit against the support at different angles, thereby providing the same adaptation capability as the illustrated embodiment.

A post head protection cap 26 can be seen in figures 6a-6c. Said cap 26 has a cylindrical shape, and contains a cylindrical lateral wall 28, a massive metallic plate 27 on the top, internal walls 30 spaced apart (29) from the top, whereby the internal walls 30 form a"+"guiding space 31. The protection cap 26 is used for protecting the upper end of a post, when the post is hammered to be driven into the ground, thus avoiding any damage to the post. This protection cap 26 serves to several types of posts, e. g., having"L","T"or"+" cross sections because of its"+"guiding space, which cause the post to be tightly accom- modated therein, thus also preventing the post from bending or warping while it is being driven.

Figure 7 shows a post driver 32, which adjusts adequately onto the protection cap 26. This post driver 32, driven by the handles 34, hit the surface 27 of the protection cap 26 with the end 33, thus driving the post into the ground.

In order to allow several posts 35 to be attache one over the other by comple- mentary fitting of lower and upper ends of adjacent posts, an L-shaped post may be pro- vided with elliptical through apertures 36 (figure 8), while the metallic tip 37 is foreseen as a separate element (figure 9) which can be fitted on the lower end of the lowest post of a row of assemble posts. The elliptic form of the through apertures 36 compensates for the mis- alignment between the apertures of the posts which occurs when one L-shaped post is placed in partial juxtaposition with another, i. e., when the lower end of one post is fitted within the"L"of the upper end of another post. Posts can thus be assemble together (figure 10) by pins, screws or the like. This stackable post can be also used for the construction of structures, and only the lowest post will be provided with a detachable metallic tip 37, which conforms to the profile of the post. The fixation of the metallic tip 37 to the post 35 is also effected by means of a pin, which is pressed into the through aperture 41 of the post 35.

Another embodiment of the structural element, particularly a T-shaped fence post is shown in figure 11. In this embodiment, posts can be fixed one to another by means of screws, by making the flat sides of each post face the flat side of another post and aligning the respective apertures for passing a fixing means, such as a pin. This post can also be provided with a removable tip 39, so that, again, only the lowest post of a row of assemble posts will be provided with a tip.

It should be understood that the structural elements and the system of driving them into the ground described above are only some preferred embodiments of the present invention, the actual scope of which is defined in the claims.