The parts according to the present invention are applicable in the field of telecommunications, where they are used in the construction of antennae support towers with a height up to 50 meters and with variable cross-sections.

Similarly, the parts obtained according to the present invention are applicable, in general, in the electrical power distribution network, in particular in the construction of low, medium and high tension cable support networks and as towers for public lighting.

Without excluding other possible applications within the scope of the invention, other important fields of application of the present invention are public water supply conduits and collectors for waste or domestic waters.

Background of the Invention Presently, in the telecommunication field, antennae support towers are produced in concrete, either reinforced or prestressed concrete, or in steel, in trestlework or tubular shape.

The raw materials used-concrete or steel-lead to very high and penalising costs and consequently the telecommunication operators have tried to overcome this enormous disadvantage.

Besides this inconvenience, the products used and above referred to present other important disadvantages, such as: * Difficult transportation and application-due to the weight of the materials used, mainly where concrete towers are concerned; High maintenance costs-namely in the steel towers; Reduced durability-when subject to aggressive environments, such as maritime areas and/or industrial and urban zones with strong population density; Opacity or non-transparency to the radio frequency waves.

Brief Description of the Invention and of its advantages The present invention has as an object a process of production of hollow tubular parts, with cylindrical, polygonal, truncated cone or other suitable shape by moulding, as well as to said parts.

This process of production by injection moulding allows the execution of parts with thin walls, with reduced thickness from 15 to 40 mm, with a high degree of precision and homogeneity, guarantying its final quality.

Thus, through the present invention, a product economically competitive is obtained, with a much easier transportation and application, due to its lesser weight, high resistance to the aggressive environments and, consequently, with a greater durability and greater transparency to the radio frequency. Benefits concerning expenses with the maintenance which are very much reduced ought to be added as well.

According to the final end or application, the hollow tubular parts thus produced can be used isolated or conjugating several parts by coupling them together. The assembling method of the parts comprises the following operations: Efficient cleaning of the contact surfaces in order to exempt them of waste or dusty matters.

'Uniform app ! ication over said surfaces, of epoxy-type resins, to guarantee a homogeneous gluing Compression of the parts towards the longitudinal axle, with or without using definitive post-tensioning cables in graphitized steel, fibres, or other material.

Brief Description of the Drawings Figure 1 is an upright view of a part (1) according to the present invention.

Figure 2 is a cross-section of part (1) shown in figure 1.

Figure 3 is a perspective sectional view of the wall of part (1) shown in figure 1.

Figure 4 is a longitudinal horizontal cross-section view of the internal mould (2) according to the present invention.

Figure 5 is a longitudinal horizontal cross-section view of the external mould (3) according to the present invention.

Figure 6 is a top elevational view of the mould towards the insertion of the internal mould (2) into the external mould (3) during phase I of moulding of part (1) according to the present invention.

Figure 7 is a longitudinal horizontal cross-section view of the moulding unit (4) at phase I of moulding of part (1) according to the present invention with the hydraulic elements (15) in deactivated state.

Figure 8 is a longitudinal vertical cross-section view of the moulding unit (4) at phase I of moulding of part (1) according to the present invention with the hydraulic elements (15) in deactivated state.

Figure 9 represents the equipment line used in the injection for production of part (1), according to the present invention.

Figure 10 is a top elevational view of the mould towards the removal of the internal mould (2) during phase 11 of de-moulding of part (1), according to the present Invention.

Figure 11 is a longitudinal horizontal cross-section view of the moulding unit (4) at phase 11 of de-moulding of part (1) according to the present invention with the hydraulic elements (15) activated.

Figure 12 is a longitudinal vertical cross-section view of the moulding unit (4) at phase 11 of de-moulding of part (1) according to the present invention with the hydraulic elements (15) activated.

Figure 13 is a longitudinal horizontal cross-section view of the internal mould (2) at phase 11 of de-moulding of part (1) according to the present invention for the removal of the internal mould (2).

Figure 14 represents a main elevational upright view of the tower (14) with the various parts (1) already assembled according to the present invention.

Figure 15 is a vertical cross-section view amplified by line/A from the top of the upper part of the tower (14) represented in Figure 14.

Figure 16 represents a transversal cross-section view amplified by line/A of the top of the upper part of the tower (14) represented in Figure 14.

Figure 17 represents a vertical cross-section amplified by line/B of the tower (14) represented in Figure 14.

Figure 18 represents a transversal cross-section amplified by line/B of the tower (14) represented in Figure 14.

Figure 19 represents a vertical cross-section amplified by line/C of the tower (14) represented in Figure 14.

Figure 20 represents a transversal section amplified by line/C of the tower (14) represented in Figure 14.

Detailed description of the preferred embodiment of the invention The invention will now be described in detail in relation to its preferred embodiment in a non-limitative and exemplificative way, with reference to the accompanying drawings.

The process of production by moulding of the present invention of hollow tubular parts (1), of cylindrical, polygonal, truncated cone or other suitable shape,

of cement paste matrix of'GRC'type containing carbon fibres (6), as represented in figures 1,2 and 3, is characterised by the moulding in tridimensional moulds (figures 4 and 5), metallic or of other material. From figure 3, representing the wall of part (1) in a perspective cross-section, it can be seen a net like structure (5) and carbon fibre cables (6) inside a cement paste matrix.

The moulds for carrying out the process according to the present invention, had been designed comprising two pieces: a movable internal mould (2), as represented in figure 4 and a stanch and detachable external jacket (3), as represented in figure 5, forming both moulds a unit (4), shown for example in figures 11 and 12, constituting a sufficiently rigid assembly to stand the injection pressures of the cement paste matrix.

In a first phase I the moulding by injection is carried out, and in a second phase I I is carried out the de-moulding operation.

In a first step of phase I of moulding, on internal mould (2), a net type structure (5) in stainless steel, glass or in any other suitable material is thereto placed. Over this structure (5) will be laid the carbon fibre cables (6) with a length up to 13 meters, longitudinally placed to the axle of the part (1) in its entire perimeter with suitable distance in between. This set (net-type structure (5) and carbon fibre cables (6)) is positioned in a suitable manner halfway the thickness of the part walls, as can been seen from figure 3, on the surface of the internal mould (2).

As a second step, and as shown in figure 6, the internal mould (2) thus prepared is introduced in the external mould (3) being its positioning thoroughly determined and adjusted (figures 6,7 and 8), in order to allow the subsequent injection operation, the hydraulic elements (15) which are foreseen to remove the internal mould (2) being de-activated.

The strictness of the construction either of the external mould (3) or of the internal (2) one, will allow a thoroughly positioning that it has great importance for the final result of the part.

Finally, there follows the injection of the"GRC"-type cement paste matrix, added with polymers and alkali-resistant glass fibres, of carbon or stainless steel, evenly spread, in the void space between the internal mould (2) and the external mould (3), on the referred net-type structure (5) and carbon fibre cables (6), employing or not combined processes of micro-vibration and centrifugation, said set formed by the net like structure (5), of stainless steel or glass, and by the cables (6) of carbon fibres or other material, with a length up to 13 meters, serving as reinforcement and support armature to said cement paste matrix.

The injection is performed using a device as the one represented in figure 9, comprising a engine (7), a reducing device (8), a shaft (9), a clutch (10), a reservoir (11) for feeding"GRC"to the pump, a spindle (12), an'GRC'injection pipe (13), an (internal (2)/external (3)) moulding unit (4) of the'GRC'like cement paste matrix.

Having in attention the specificity of the productive process, during the injection, the moulds may be placed either in a horizontal or in an incline position, in conformity with the association of the injection methods-so that the required exhaustion of the gas and/or air existing in the walls carried out in a suitable manner so as to guarantee the product quality.

Upon the suitable cure time having elapsed, the operation of de-moulding II will be carried out. As can be seen by Figures 10,11,12 and 13, the de- moulding of the tubular part (1) is easily done. On a first step, the internal mould (3) of mould unit (4) is removed by means of activation the hydraulic elements

(15) (figures 11 and 12)-and followed, in a second step, by the opening of the external mould (3). After this, and as shown in figure 13, the internal mould (2) is remove, thus releasing de finished part (1).

Afterwards, the coupling of parts (1), represented in figure (1), can be done. To obtain a tower (14) as represented in figure 14, the coupling of several parts (1) is carried out, in this case using three parts (1).

For this at first an efficient cleaning of the contact surfaces is carried out in order to exempt them of waste or dusty matters. Then a uniform application over said surfaces, of an epoxy-type resin, to guarantee a homogeneous gluing, as shown figure 17 and 18. Finally, the parts (1) are compressed towards the longitudinal axle, using definitive post-tensioning cables (16), through the interior of the tubular part, as represented in figures 15 and 16 and 19 and 20. After the polymerisation period has elapsed, tower (14) can then be utilise.

Other embodiments of the present invention can be envisaged without leaving the scope and spirit of the present invention as described in the following claims.