Computerized plant for producing structures made of resin, composites, or the like

Field of the invention The present invention relates to a system for producing structures made of resin, composites, and the like, for example, pipes, bottles or cylinders, and containers for transporting compressed gases and liquids, tanks, helicopter blades, structural parts for use in nautical, avionic, or space applications, electronics, etc., polymerized in real time. State of the prior art

Currently, all the above structures are obtained with different types of machines and plants for producing the desired shape and structure, such as, for example, with filament- winding machines, automatic-tape-placement machines, etc., but all have in common the «curing» technique, i.e., the step of polymerization of the resin matrix that impregnates tapes, and fibres of various types and compositions. Said common technique consists in the use of heat for polymerization of the matrix, said heat being supplied by ovens, or autoclaves, where associated to the heat is, in succession, vacuum for expelling occluded gases during manufacture and pressure for better compacting of the structure. In the case, as in space applications, the cost is not a significantly important variable and the thickness of the structure is considerable, such as for the launching motors for launching rockets such as Atlas, Ariane, Proton, etc., the polymerization is performed with the end structure, using beams of electrons accelerated up to 20-100 MeV inside bunkers made of reinforced concrete of a thickness of various metres, which have a cost that is not sustainable by industry. Sometimes, when the thickness is particularly large even for electrons having the values of energy mentioned above, these electron beams have to be converted into X-rays, which have a higher power of penetration than electrons. As may be readily understood, this method is not suited for the industrial production of the composite structures mentioned above, and for this reason today it is customary to resort to thermal polymerization with all the drawbacks that this involves and that may be readily understood from the extremely low energy efficiency and the long times for polymerizing the entire structure, and in addition, since obviously the heat reaches the external surface, this surface polymerizes (i.e., becomes rigid) before the inside, thus giving rise to significant strains and stresses. Summary of the invention

The purpose of the invention is to provide an efficient solution to the aforesaid problems, and said purpose is achieved thanks to a computerized flexible innovative plant as defined in the ensuing claims. Thanks to the invention, not only are the problems set forth above overcome or eliminated easily, but there is also achieved a significant improvement in the quality of the product, and a substantial reduction in the times and costs, in so far as the product is polymerized step-by-step during the manufacturing process so that, for example, when a cylinder exits from the winder, it is already polymerized and finished. All this is obtained with further advantages, as will be better pointed out and clarified hereinafter, resorting to the computerized flexible plant according to the present invention, characterized in particular by the use of a self- shielded electron gun for generating electrons accelerated at a voltage of between 100 and 300 kV such as to polymerize the resin matrix, which impregnates the fibre or the tape, during manufacture of the product.

Consequently, the structure being produced is polymerized step-by-step during the manufacturing process as may be understood more fully from the ensuing description of the computerized flexible plant as a whole. Brief description of the drawings The invention will now be described in detail with reference to the annexed drawings, which are provided purely by way of non-limiting example and in which:

- Figure 1 is a schematic perspective view of a computerized flexible plant according to the invention; - Figure 2 is a view identical to that of Figure 1, at a reduced scale, highlighted in which is the detail illustrated in Figure 3 and

- Figure 3 is a partial cross-sectional view, at a larger scale, of the detail highlighted in Figure 2.

Detailed description of the invention The figures illustrate the following elements:

1) Filament winding of cylinder tanks for compressed gases, with degrees of freedom and corresponding feed

2) Possible variants of filament winding

3) Cylinder with the minimum number of degrees of freedom necessary to have different layers of fibres in series and in parallel, and corresponding scars (Kevlar)

4) Cylinder on a robot

5) Structure on a portal (Prima Progetti, Comau)

The computerized innovative flexible plant according to the invention, for producing structures made of resin, composites, and the like, envisages the availability of all the degrees of freedom necessary for producing structures from the simplest ones to the most complex ones. The plant is characterized by the insertion in an appropriate position of at least one electron gun of low energy (100-300 keV) capable of obtaining step-by-step polymerization, in real time, of the structure during growth by supply of an appropriate resin or composite, etc., fed by the dispenser for dispensing resin, pre-impregnated fibre, etc., which can be polymerized by e-beams (Figure 1).

The plant may have the configuration of a portal, of a filament-winding machine, of an automatic-tape-placement machine, of a robot, etc., but will in any case be characterized by:

1) the presence of a self-shielded rasterizable electron gun with acceleration voltage comprised between 100 and 300 kV and in any case sufficient for the polymerization of thin layers of resin, composites, and the like;

2) the availability of all those degrees of freedom necessary for producing structures made of resin, composites or the like from the simplest ones to the most complex ones (Figure 2);

3) the use of programmable motors, such as for example, stepper motors or d.c. linear motors and encoders;

4) the possibility of having available a supply of a number of types of resins, fibres of different composition, impregnated either with the same matrix or with a different, but compatible, matrix, as likewise pre-impregnated tapes (Figure 2);

5) being completely computerized.

There is hence obtained the possibility of producing any type of structure, with the fundamental advantage that the structure thus obtained, for example, a tank for compressed gases, is already polymerized at the end of the winding operation, curing of the resin for impregnation of the fibre having already been obtained as a result of the energy transferred by the electron beam.

With the above type of plant there are thus enhanced all the advantages of electron-beam curing as compared to conventional thermal curing, in so far as it is performed during the manufacturing process; namely: a) the curing time using the e-beam technique is faster by one to three orders of magnitude than thermal curing; b) in the case of e-beam curing, no initiators are used in the resins so that the pot life coincides with the shelf life; the dispensers of pre-impregnated fibres do not have any need for frequent recleaning, and moreover the viscosity of the resin can be reduced by heating; c) the production of volatile elements is basically zero in e-beam polymerization so that problems of environmental pollution are eliminated or at least mitigated; d) e-beam polymerization is performed at room temperature and on a step-by- step basis so that there is elimination of the mechanical strains and stresses induced by oven and autoclave treatments, where the heating, which comes necessarily from outside, hardens the external layers of the structure before the more internal ones; e) there do not exist upper limits to the thickness of a product in so far as this is polymerized step-by-step during its growth; f) with this step-by-step polymerization no migrations or splitting of resin and fibres can occur, as, instead, did occur during winding followed by thermal curing; g) step-by-step polymerization also enables development a new software that will maximize the mechanical resistance (e.g., the maximum pressure in the case of a tank for compressed gas) in so far as it is possible to wind the fibre on appropriate lines that will not necessarily be the geodetic lines; h) the flexible plant proposed is also able to program step-by-step the degree of tensioning of the fibre so as to obtain, for example, matrices precompressed along pre-chosen layers of the pressurized casing; i) furthermore, on account of the availability of a number of dispensers for different types of fibre and/or matrix (but in any case ones that can be polymerized with e-beam), the plant makes possible the production in succession or in parallel of layers having characteristics that differ from one another (Figure 3), but are compatible with one another, thus opening the way to a new design method (and software) aimed at obtaining structures that are less expensive and more resistant than the current ones.