A process for manufacturing tridimensional structures

Technical Field The technique used in the production of tridimensional structures, like: tensile structures, architectonic roofing of various kinds, or sails for boats, consists in covering the relevant surfaces with partially superimposed panels formed of structured fabric, so as to be able to support the expected working load. These panels, which are called "cloths", are superimposed in such a way that by their ordered and repeated combination the desired tridimensional contour can be obtained. In case the working load is considerable, or in applications concerning sailboats used in competitions, very sophisticated assembling techniques are employed in order to obtain a high efficiency of the tridimensional structure.

Background Art These techniques imply the use, or even the specific realization, of fabric material which is laminated in a unidirectional manner. These fabrics have the capacity to resist to extremely high stresses in a well-defined direction, and they have performances that outstrip other structures with regard to both the resistance to traction and the stability of the desired tridimensional structure. Unfortunately, the techniques used in the manufacturing of individual "cloths" or "monoliths" that form said structures, are extremely sophisticated and require use of advanced data processing systems for their implementation; therefore, in their totality, these techniques are extremely expensive and require very skilled manpower. Another limitation of the presently employed techniques is that some manufacturers are forced to use external films of considerable thickness, because of the processes needed in the manufacturing of these structures. The result is that by these techniques the final tridimensional structure is endowed with a weight and a thickness that exceed the desired ones, thereby rendering the structure suited only for high loads.

Disclosure of Invention The present invention provide a method of manufacture of tridimensional structures which are suited to resist to working loads that may be more or less high, without incurring the expenses and problems typical of presently commercialized unidirectional fabrics, both when these fabrics are specifically manufactured or when they are purchased for the purpose of assembling them like panels.

Brief Description of Drawings Fig. 1 shows the initial plane structure realized on a pavement or planar surface, wherein 1 denotes the threads or bundles of structural threads, 2 is the net used to prevent transversal sliding movements of said threads, and 3 refers to the lines of superposition between individual cloths.

Fig. 2 shows the planar structure which has been cut into horizontal cloths, before the latter are superimposed and joined to give rise to the final, desired tridimensional structure.

Fig. 3 illustrates the final, desired tridimensional structure, according to the manufacturing method of the present invention, wherein the structural threads are arranged on the triangular surface with curvilinear behavior, without carrying out repeated superposition of the threads or thread bundles.

Best Mode of carryng out the invention The method of manufacture of tridimensional structures according to the present invention is based on the simple concept of initially creating a planar structure, like that shown in Fig. 1, which is slightly larger than the desired tridimensional structure. This planar structure will be subsequently horizontally cut into horizontal cloths, as shown in Fig. 2, so as to obtain - according to a technique known to all skilled persons in this field - independent cloths that are partially superimposed according to the depth or maximum camber to be attributed to the final tridimensional structure. Said initial planar structure may be easily decomposed (divided) into a variable number of horizontal cloths, as shown in Fig. 2, by effecting simple horizontal cuts by means of scissors, since it is structurally very thin. The very small thickness of the structure is a consequence of the innovative method of the present invention, given that the initial planar structure is formed by two or more thin, external polymeric films, consisting of (for instance, but not limited to) polyester or polypropylene, or of any other similar polymer with similar thickness, containing between them an interposed supporting net formed of (for instance, but not limited to) polyester, carbon, or araniid fibres, this net allowing the robust threads or bundles of inextensible fiber threads — which are also located inside the structure - , to be firmly anchored to the same structure, thereby preventing undesired lateral sliding movements and displacements. Said threads, or inextensible bundles of threads 1, as shown in Fig. 3, will have a thickness suited for the intended working load and will partially or totally cross the said structure, by taking a curvilinear path with a constant radius of curvature. These curvilinear structural threads will therefore be oriented along the curvilinear lines of feree of the structure itself, and will approximately follow its tridimensional contour. Said threads, or structural thread bundles, will be twisted and subsequently flattened by a simple mechanical squeezing process, onto the initial planar structure, before the assembling of the latter is completed with the application of the upper polymeric layer. Said winding and the subsequent squeezing of the structural threads will be performed in order to allow an easier envelopment of the structural threads by the external polymeric films and in order to insure stability of the tridimensional shape (contour) even without resorting to a pre-tensioning of the threads. Due to the very small overall thickness of the structure according to the invention, this structure can be easily cut horizontally, using simple scissors, as shown in Fig. 2. In order to facilitate said division of the initial planar surface into horizontal cloths, the arrangement of the structural threads avoids repeated and excessive superposition between said threads or bundles of threads at the points of greatest load of the structure, thereby preventing delamination, internal dislocations of the bearing surface, and excessive thickness increase that would noticeably hinder said division of the initial structure into independent cloths. Once the desired division of the initial planar structure into separate cloths has been achieved, the latter are partially superimposed one on the other, and are cold-glued or hot-glued or sewn by the usual methods as shown in Fig. 3, taking account of the fact that, as already known to any skilled person, the depth to be attributed to the final tridimensional structure will depend on the extension and shape of these superposition zones. The cloths themselves will be cut according to this tridimensional parameter and according to the dimensions of the available working table, without resorting to expensive apparatus used for lamination, such as an expensive press or rolls (calender). The final tridimensional structure will consequently have a smaller size than the initial flat surface and will be smaller exactly by an amount corresponding to the extension of the superposition zones that have been obtained, and depending on the depth amount that has been attributed this structure. These amounts of superposition and depth are easily "subtracted" from the initial planar surface and so they can be easily calculated by a technician of average skill, who will therefore obtain a tridimensional surface of the desired size and depth. The object of the present invention is to disclose a new method for manufacturing tridimensional structures endowed with a noticeable shape stability and that are easy and extremely cheap to manufacture compared with the elaborate manufacturing technologies currently in use. This method for the production of tridimensional structures, starting from a plane surface as shown in Fig. I5 will be easy to carry out for a technician of average skill, and will do without any kind of data processing means or any instrument or apparatus apt to pretension (prestress) said structural threads which are arranged between the external polymeric films; moreover it is much more economical than any other already known method. The absence of centers or vertexes of "irradiation" of these structural threads, avoids a concentration of these threads at the points of maximum load, thereby distributing said structural threads, or thread bundles, on a vast area of greater load, preventing at the same time any localized increase in thickness of the structure and the possibility that any stress - not corresponding to the usual lines of force - will either deform or damage the tridimensional structure; the latter will then have a longer life and enjoy a broader application field.