The present invention falls within the technology of technical textiles and pretends to develop a fabric with a multi-axial structure as well as the respective mechanical system that may produce the same.

Therefore, it was intended to develop a novel system aiming the production in series of a fabric having a multi-axial flat textile structure, as outlined in Figure 1, mainly intended for technical applications, namely aircraft's fuselage, automobiles, boats, civil construction and the like.

Technical field to which the invention pertains The invention falls within the field of building textile machines, with the intention of supplying the market of technical textiles with a mechanical system capable of performing a mass production of a fabric having a multi-axial structure. Multi-axial fabrics fit into a perspective of the ratio increase between mechanical performance and weight of the material.

Related state of the art and evaluation thereof With this product, resulting from a re-engineering of textile structures, it is intended to be able to interfere in the mechanical properties of the fabric, the designer being allowed some versatility in the manufacture of laminates with controlled anisotropy, thus meeting the Customer's specifications and objects, in accordance with a set of well defined technical parameters.

Technical textiles represent a sector that is strongly developing and which has a market not yet perfectly stabilised. It can be expected that, in a near future, they may advantageously substitute some traditional materials, namely metals in mechanical construction and concrete in civil construction. These products may be used in very different fields as transport industry, civil construction, medicinal applications, protection garments, sports items, military and defence articles, among others.

1) In transports, technical textiles find an application in vehicles of all kinds, from the common automobile or bicycle to space vessels.

They contribute to optimise the fuel efficiency and economy because technical textiles allow for the conjugation of low weight and excellent mechanical properties. We may, thus, find applications for these fabrics in inner linings, security belts, tyres, filters, airbags and insulation, as well as, more and more, structural elements and components subjected to a high mechanical and thermal performance.

2) In civil construction, geotextiles are employed to perform separation, reinforcement, filtering, draining and protection functions. They can be textile materials covered with polymers in several uses as in building covers of large dimensions, namely stadiums, airports or sports pavilions. The great advantage of the use of these fabrics in civil construction lays in its low weight, which allows for an increase of bays between supports, making it easier to build and to repair. Besides, architects are allowed more freedom to design shapes and styles.

3) In articles of medicinal application, textile materials either in fibres, woven or knitted are used in surgical interventions in implants, filters and blood vessels. In the case of implants, the textile structures are identified by its construction, composition, superficial behaviour of the fibres and resistance to decay. Hence, the materials used in implants, besides having to meet requirements of mechanical order, must likewise be biocompatible so that the human body does not reject them.

4) In protective garments they are used to provide a protection against dangerous environments that may cause personal damages. Such a protection may be mechanical, (bullet-or stabbing-proof garments), chemical, electrical, radiological and bacteriologic. The choice of the material to be used depends on the type and the degree of protection intended for. For instance, the garments used by firemen have to provide for thermal and chemical protection.

Thermostable fabrics are chosen therefor, such as aramides or other fibres the finishing of which are flame retarders.

5) In sports articles, the fibres and fabrics of high performance are used, e. g. , in sports garments. In the last few years we have seen the development of garments with characteristics permitting athletes to increase their performance, namely to increase thermal comfort during sports events. In this case multi-layer structures are used, which allow sweat to migrate towards the outside, the inner layer, which is in direct contact with the skin, being kept dry.

There are also composite fabrics, reinforced by textile materials, in countless applications in this field, namely in bicycle frames, tennis rackets, skis, surfboards, etc.

6) Textile materials used in military and defence articles depend on the requirements they are to be subjected to. In protective garments and individual equipment as uniforms, bullet-proof jackets, helmets and the like, fabrics in polyamide and carbon fibres are mostly employed. In materials used in the manufacture of missile and fighting aircrafts are used several layers of aramide fabric.

7) Other uses of technical textiles may be found in several fields as: conveyor belts used in several industries, satellites, crafts, thermal and acoustic insulation, boat sails and fishing nets.

In the market of technical textiles in general and in the field of multi-axial fabrics in particular, there are the materials manufactured by the company Karl Mayer Textilmaschinenfabrik GMBH, called"Multiaxial Fabric Constructions", which result from the stacking of layers of several bi-axial fabrics bound together by a knitted warp. In this kind of fabric, the risk of separation of the several layers that compose the fabric is considerable due to the fact that layers of threads sewn together form its structure.

There are also some patents of mechanical systems proposing the manufacture of this kind of multi-axial fabric, namely: European Patent Application number 0263392 A2, "Tetraxial woven fabrics and tetraxial weaving machine thereof', concerns a machine that manufactures a multi-axial fabric exhibiting an isotropic behaviour which is higher than that of the tri-axial fabric and is composed by weft, warp and diagonal threads.

United States Patent number 5351722,"Tetraxial fabric and weaving machine for its manufacture", refers a mechanism that is capable of producing the multi-axial fabric formed by crossing the weft and warp threads with the diagonal threads which have two directions.

United States Patent number 5375627, "Method and weaving machine for production multi-axial fabric", refers a method for the production of a multi-axial fabric which construction is stable and compact.

Another object of this patent is the invention of the machine capable of manufacturing such a fabric at a low cost.

Summary of the invention The multi-axial fabric is manufactured in a machine whose basic mechanical principles were acquired from a conventional loom to which are added and adapted the new components with the function of introducing and weaving the diagonal threads of the fabric, in the directions of +45° and-45° with the warp and weft threads.

The main advantage the invention wishes to present in relation with the fabric manufactured by Karl Mayer lays in the kind of the resulting structure because, contrary to the Karl Mayer fabric, all the threads are interwoven.

From the comparison with patent EP0263392 A2, it can be concluded that, in the latter, the processing of the diagonal threads may be problematic because a cylinder with a helical groove provides the movement thereof. The diagonal threads pass through such a groove and are carried to the end and, thereafter, are transferred to another cylinder, which is responsible by the reverse movement. In this transfer operation there is a risk of losing control over the diagonal threads.

The mechanism to displace the diagonal threads of US patent 5351722 uses a closed conveyor belt that is duly perforated to allow the threads to be passed there through. Connected with this model there is a drawback during the weaving cycle, caused by the movement of the diagonal threads reversal, which is not instantaneous, running along half of the perimeter of the pulley outside the weaving area.

Brief description of the drawings The following description is based in the attached drawings, which character, nevertheless, should not be considered as limiting but rather as an example. In the drawings: Figure 1 shows a schematic view of the fabric with a multi-axial flat textile structure that is the object of the invention; Figure 2 shows a perspective view of the mechanical system for the production of the fabric that is the object of the invention; Figures 3 to 7 represent views of parts of the mechanical system represented in Figure 2; Figures 8 and 9 represent the several phases of the manufacturing process of the fabric that is the object of the invention.

Description of an embodiment of the invention The mechanical system developed herein is composed by 3 subgroups that control and co-ordinate the movement of 3 sets of threads in the multi-axial fabric, i. e.: warp, weft and diagonal. Figure 2 represents the most significant aspects of this system, outstanding the set responsible for the guidance and movement of the diagonal threads. In order to simplify the representation, neither the weft insertion systems, nor the reed and the feeding systems are fully represented therein.

Warp threads The feeding of the warp threads to the weaving area is made from an organ of conventional warp passing through one or more heddles (11).

Weft threads The insertion of the weft may be performed in two different sheds, one at the front and another at the rear, in relation to the plan of diagonal threads.

The weft insertion device (14) shall have two movements: one, in the loom's transverse direction for the proper introduction of the weft thread along the fabric's width and the other, perpendicular to the former direction, to position the weft insertion system in the active shed.

Diagonal threads Diagonal threads come from bobbins positioned on a stand placed above the weaving area. It has a circular shape and is supported by a central shaft allowing a rotational movement step by step. Each bobbin has a stretching gear to control the tension of the outgoing thread, thus ensuring a better formation of the fabric. The diagonal threads are then passed through a set of thread guides (10) which perform a linear trajectory, in one of the senses of the loom's transversal direction and, thereafter, in the opposite sense. These thread guides (10) are moved by the action of actuators (1) to (8), inside the thread-guide carrier (9).

The thread-guides (10) move step by step, linearly and in two opposite senses up to the end of the thread-guide carrier (9). Having reached the end of the course, they change path and reverse the sense of motion. In such a way a trajectory in a rectangular shaped closed circuit is obtained allowing the lateral and step by step movement of the diagonal threads, in synchron with the remaining movements of the loom, namely the shed opening, the insertion of the weft, the beating of the reed and the rotation of the diagonal threads bobbins stand. At the end, the fabric is pulled by drawing rollers (12), which the movement of is also synchronised with the speed of fabric formation. The thread guide moves inside the chamber formed between the thread-guide carrier (9) and its lid (18) that has an opening (16) through which the diagonal threads pass starting at the feeding area.

As it can be seen, the structure (13) has the function of supporting the thread-guide carrier (9) components, the warp supporting heddle (11), and the drawing rollers (12), in their respective positions during the fabric production.

The weaving cycle Phase 1 (Figure 8. 1) : The formation of the fabric is initiated with the insertion of the weft in the 1st shed formed between the warp threads and the diagonal threads.

Phase 2 (Figure 8. 11) : Immediately after the weft is totally inserted in the shed, the thread guides displacing the diagonal threads move transversally towards the space freed by the thread guide that has changed path; those of the front line to the right and those of the rear line to the left.

Phase 3 (Figure 8. 111) : The next step consists in the formation of the 2nd shed due to the progress of the heddle amongst the diagonal threads, the same appearing between the diagonals and the warp, which allowed the shed to go from a front position to a rear position in relation to the plan formed by the diagonal threads.

Phase 4 (Figure 8. IV) : In the next movement, the end thread guides will move longitudinally towards the free spaces exchanging lines, passing from the front to the rear and vice-versa.

Phase 5 (Figure 9. V) : After this phase is completed, the weft is inserted in this new shed.

Phase 6 (Figure 9. VI) : Immediately afterwards, the heddle goes back to its initial position, the weft thread being caught between the diagonal threads and the warp threads, thereafter providing the insertion and the beating of the reed and starting, thus, the same movement registered in Figure 1. Thereafter, the procedure is cyclically repeated.

Several detail changes in respect of the above mentioned embodiment should be apparent to those skilled in the art. The invention must only be considered as limited by the scope of the claims hereafter.