LU84215A1 - PROCESS AND DEVICE FOR MANUFACTURING HOLLOW BODIES IN REINFORCED RESIST, ESPECIALLY PROTECTIVE HELMETS - Google Patents

Description

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The present invention relates to a method and a device for producing hollow bodies of reinforced resin, for example helmets and the like.

The imperatives of end use of reinforced resin hollow bodies are well known and, in the particular case of protective helmets, to which the present invention applies in particular but not exclusively, said hollow bodies must have a structure enabling them to resist to shocks, even repeated, and they must also be of light weight.

We tried to meet the above requirements by making hollow bodies in molded resin, reinforced with an appropriate textile reinforcement. However, the structures of the hollow bodies thus obtained have only partially satisfied the desired requirements and have not satisfied other important requirements, in particular as regards their resistance to repeated impacts. In short, the structure of the aforementioned devices must be such that, under the action of repeated impacts, even if they are constantly located in the same zone, the structure can react elastically without producing cracks or flaking which could damage structure and which would ensure that shocks are not reacted in a large area. In the case of helmets, in particular, the formation of fractures and ruptures along the meridian planes of the structure must be avoided, since this can be detrimental to the safety of the user.

The object of the invention is to provide hollow bodies, shaped in particular in the form of headgear and suitable for use as impact resistant protective helmets and in which a suitable textile reinforcement is embedded in the bonding resin so to form an elastic structure whose resistance is as uniform as possible.

The invention also aims to provide a hollow body of the specified type, the internal and external surfaces of which are smooth and can therefore constitute the finished surface which can be easily provided with patterns and marks,) also when the textile reinforcement , or the elements forming 2 thereof, are constituted by threads or fibers, having a certain degree of rigidity and tending to protrude from said surface.

The invention further aims to provide hollow bodies whose external surface requires practically no finishing work and which, in relation to the imperatives of end use, has the desired coloring and / or the desired models in order to satisfy aesthetic imperatives.

The invention also aims to provide hollow resin bodies having discontinuous shapes and parts. cut out and being arranged so that parts of their surfaces make angles of less than 90 ° to a vertical plane.

The method according to the invention, according to which the hollow body is provided with a reinforcement formed by a plurality of layers of woven and / or mesh fabric, incorporated in a bonding resin, is characterized in that the layers of textile reinforcement are applied to one of the two parts of a mold and in that at least part of the peripheral edges of said reinforcement is fixed to said mold, in that a controlled tension is exerted on the textile reinforcement, in that this tension is maintained during the next molding phase, and in particular during the solidification or polymerization of the bonding resin, and in that the hollow body thus formed is removed from the mold, so that the textile reinforcement is incorporated and maintained in the resin in a state of stress.

The woven and / or mesh textile reinforcement according to the present invention consists of several elements, preformed with the profile of caps, at least part of which is obtained by weaving the central zone of the hat in the form of a spiral. As a variant, the elementary caps are obtained from a woven tubular body, one end of which is profiled in a crown, the edges of the crown portions of said crown being joined by sewing, or else, in the case of materials containing thermoplastic wires, by welding, λ while the caps obtained are mutually superimposed,

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* 3 with an angular and successive offset of the junction zones to form a homogeneous layer of practically uniform thickness.

Depending on the end use and the requirements relating to the hollow body, the weaving of the elementary caps can be carried out so as to form zones having different weaving densities and which, during the molding of the body, are subjected to a tension controlled produced by a pressurized fluid.

The application of the controlled tension to the textile reinforcement can be carried out taking into account appropriate criteria such as the physical characteristics of the threads or filaments forming the caps and / or the weaving characteristics of said caps. For example, the tension applied to the textile reinforcement can be determined by taking into consideration, as a limit value, the modulus of elasticity or the tensile strength of the filament or thread used in each case. It is obvious that the tension previously applied to the textile reinforcement must be related to the molding and processing temperatures of the bonding resins used to obtain the hollow body considered.

Also, with regard to the end use of the hollow bodies obtained, the textile reinforcement may be associated with lining layers, placed inside and / or outside the hollow body considered, said layers possibly being formed. by suitable resin films, for example thermoplastic resin films, with a view to incorporating them into the bonding resin, or else by thermosetting resins.

In the latter case, it is possible to easily and quickly produce hollow bodies, in particular helmets, the outer surface of which is smooth and does not in practice require any finishing operation. Furthermore, said coating films can be profiled in advance in the form of external and / or internal caps so as to determine the final surfaces and the desired characteristics of said bodies. Thus, for example, an outer cap formed of a! suitable material, for example a thermoplastic resin, 4 makes it possible to obtain uniform and smooth surfaces and to prevent seals or projections formed by the threads of the textile reinforcement from protruding from the surface of the hollow body. In addition, the covering film or the cap may be provided with models or figures which can be reproduced on the surface of the hollow body, in particular when the bonding resin of the textile reinforcement is transparent, even to a limited degree.

Other advantages and characteristics of the invention will be highlighted, in the following description, given by way of nonlimiting example, with reference to the appended drawings in which: - FIG. 1 is a partial schematic sectional view of the mold for implementing the method according to the present invention; Fig. 2 is a similar section of a variant of the mold; Figs. 3 and 4 show, on an enlarged scale and in a conventional manner, the fragmentary sections of two hollow bodies produced in accordance with the present invention.

The process according to the invention will now be explained with reference to FIGS. 1 and 2 of the attached drawings and the manufacture of a protective helmet.

To make the helmet in question, it is necessary to first prepare the textile reinforcement formed by two or more overlapping woven layers and containing suitable threads of synthetic material (thermoplastic resins) and / or natural materials: vegetable materials ( such as linen, cotton or the like) or mineral (such as asbestos, glass). Advantageously, woven and / or net textiles have been used, prepared at least in part with yarns or filaments of thermoplastic resins, such as vinyl, acrylic / polystyrene resins, polyamides, polyurethane, etc. and, in particular, filaments of aramid resins known under the designation "KEVLAR".

K The textile reinforcement according to the invention is formed by several superimposed layers which may vary

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5 both with regard to the composition of the threads or filaments used and the number of threads in each layer.

In addition, the weaving density can also vary.

Each layer of the textile reinforcement consists of a woven cap 5 which is wound in a spiral to a given diameter, beyond which the weaving continues in a helix, that is to say that the number of stitches for each turn of the cap during formation is kept practically constant. Alternatively, the cap is made from a tubular textile element woven of an appropriate diameter. To obtain elements, of the desired length, one end of each element is sewn in the form of a crown. The lobes or points of each crown are then bent inwards so as to position the crests of the lobes on the axis of the tubular textile element. Lastly, the edges or edges of the lobes are joined together by sewing or, in the case of synthetic threads, also by welding, so as to thus form the caps.

A number of caps thus prepared (in practice, this number can vary from two upwards) are superimposed so as to form a textile reinforcement having the desired characteristics.

When the base of the caps consists of lobes which were welded during the covering phase of the caps 25 D, the meridian joining ribs are angularly offset from one another so that the thickness and the structure of the reinforcement textile thus obtained are homogeneous and practically uniform.

The edges DI of the caps D can be widened so as to ensure their attachment during the following phase of tensioning so that, during this operation, the different textile layers can slide freely one over the other in order to be put in tension.

The woven caps D thus prepared can be subjected, before the molding operation, to a preliminary treatment, for example by being soaked in suitable materials, by being pre-profiled, etc., so as to satisfy the particular requirements imposed on the final product to be produced in each case.

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Again considering Figs. 1 and 2, it can be seen that two embodiments of the mold have been represented with the aid of which the method according to the invention is put into practice in order to manufacture, in the particular case envisaged, a protective helmet, similar to that described in another patent filed by the same inventor.

The mold shown consists of a female matrix A, and a male matrix B, which is provided with a profiled body B1 forming said male matrix, this body is fixed on a supporting plate B2 and it is housed, as this will be specified below, in a profiled cavity Al of the female matrix in order to reproduce, in negative, the shape of the helmet.

The two parts A and B of the mold are fixed to each other, in a known manner, on the fixed and mobile plates 15 of a press so as to cooperate with each other as will be described below.

According to the present invention, the profiled body B1 retains an elastic covering C constituting a profiled bladder which is fixed by a collar C1 in a groove B3 20 formed in the upper part of said profiled body.

There is thus created between said parts a gap C2 which is connected by conduits B4 with a source of fluid under appropriate pressure which has the function of causing the bladder C to expand and deform; preferably, oil or compressed air is introduced in the interval C2 under an appropriate pressure, for example under a pressure of 20 bars.

In Fig. 1, the peripheral edge of the profiled cavity Al of the female matrix A is provided with a shoulder A2, the base of which is inclined and converges downwards. The shoulder-30 is closed by a plate B2 of the male matrix B in order to form a blocking element for the textile reinforcement D, as will be explained below.

Again considering the implementation of the method according to the invention, the set of superimposed caps D 35 forming the textile reinforcement is introduced into the cavity Al of the female matrix A of FIG. 1. In the case shown, the textile reinforcement D is pre-formed between an external cap F and an internal cap G having characteristics suitable for obtaining the expected result and which will be described thereinafter.

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The outer cap F, which is close to or in contact with the wall of the cavity A1, is formed from a suitable material, for example a woven fabric based on cotton or a similar material, in order to form a layer. or an outer coating of suitable consistency to prevent sharp or similar parts of the plastic caps D from protruding from the surface of the helmet after molding. The cap F can advantageously be formed by a layer or film of thermoplastic resin, for example polyethylene, polyvinyl chloride or the like, so that, during the next molding phase, it is incorporated into the bonding resin for to form a smooth and uniform finishing surface having the desired characteristics. In particular, it is possible to manufacture helmets having the desired aesthetic characteristics since the cap F can be colored at will and can also be provided, beforehand, with suitable models, whether the caps are made of textile or thermoplastic materials. In both cases, the cap F 20 is fixed and incorporated into the bonding resin during the molding phase. Similar results are obtained with the internal cap G which is however also provided with a protective element for the elastic bladder C or for other parts of the mold.

25 Again considering FIG. 1, it can be seen that, after the set of superimposed caps D, F, G has been placed in the female matrix A, the enlarged edges DI of the textile caps D are folded outwards and are partially engaged in the shoulder A2 of the female matrix, the depth of which is less than the thickness formed by said edges DI. The outer cap F can be arranged so that its edge F1 is separated from the shoulder A2 of the mold so that, during molding, said cap adheres to the | profiled cavity Al of the mold. A similar result can be obtained using a cap F correctly dimensioned and arranged so as to adhere continuously to the cavity A1, even when the edge of said cap is fixed to the base of the shoulder A2, thus allowing an appropriate tension to always be exerted on the textile reinforcement 40 J during the molding phase.

8 The male element Bl is then introduced into the opening of the textile reinforcement D and into the caps F and G previously housed in the cavity Al; this operation is easily carried out since the elastic bladder C adheres to the profiled surface of said male element. The coupling of the two parts A and B of the mold brings the plate B2 into contact with the edges DI of the caps D, which are consequently applied tightly against the base of the peripheral shoulder.

10 Next, a fluid under pressure is introduced in the interval C2, for example oil at a pressure of 10 to 30 bars, which causes a deformation of the elastic bladder C and which generates a tension in the textile reinforcement. D. This operation is carried out in an appropriate manner and so as to apply a gradual pressure to the different textile layers of the caps D to make them fully match the profile of the walls of the cavity A1. In particular, the value of the pressure exerted in the interval C2 is also determined taking into account the textile structure used, both with regard to the different caps D and the different zones of each of said caps of the textile reinforcement, as shown in FIGS. 3 and 4.

In particular, the value of the pressure, and consequently of the tension, applied to the caps D of the textile reinforcement of the helmet is related to the physical characteristics of the threads forming said textile reinforcement, as well as to the objectives and the imperatives of end use of the hollow bodies obtained in each case. In the particular case of helmets, it is necessary to have a high impact resistance in order to avoid the formation of cracks or else a separation of the layers forming the structure of the helmet.

In general, the tensioning of the textile reinforcement D is carried out so as not to exceed the tensile strength of the wire forming the reinforcement D and, in particular in the case of helmets, one should not exceed the elastic modulus of the thread constituting the textile reinforcement.

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It is evident that, with reference to Figs. 3 and 4, the tension applied to the textile reinforcement D can vary from one zone to another of said reinforcement. In this case, the elastic bladder C is provided with zones of different elasticities, for example of different thicknesses, so as to generate a greater or lesser tension in the zone considered of the textile reinforcement. In cases where the hollow body has projecting or profiled parts, the male matrix D can exploit the characteristics of said other patent of the inventor JtiSme 10 to reproduce the profiles necessary in said body.

After tensioning of the reinforcement D, a suitable resin is introduced into the cavity A1 of the mold via the conduit B4 placed in an appropriate position in the male die B, this resin being for example a thermosetting resin, a epoxy resin or polyester. The bonding resin can be introduced beforehand into the cavity A1 of the mold, after insertion of the cap F in said cavity, in particular when this cap F is formed from a synthetic thermoplastic material, to constitute the external surface of the body. hollow. The bonding resin injected into the cavity Al soaks the textile reinforcement D and, when the assembly is subjected to a pressure by the elastic bladder C, it takes the form of said cavity Al.

When the bonding resin has polymerized and solidified, the pressure is released from the bladder C, the mold is opened and the helmet is removed from the female matrix A; the textile reinforcement D of the helmet is embedded and fixed in the bonding resin and it is maintained in a constant state of tension. The external surface of the hollow body thus obtained is smooth and does not require any finishing in practice, also considering that said surface is colored if necessary, since, as has already been specified, the outer cap F can be colored and / cu provided 1 35 days of models or similar items.

! The hollow body, in particular the helmet, thus obtained | is perfect in all respects because the external surface is free of protrusions or parts with sharp edges, even J when the textile reinforcement D consists of threads or

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filaments with limited flexibility, as in the case of synthetic resins.

It should be noted that the same considerations as those given for the mold of FIG. 1 also apply to the mold of FIG. 2, also with regard to the implementation of the method. In this case, the widened edges DI of the reinforced caps D are engaged in a peripheral groove B3 of the profiled body B1 which also keeps the fixing collar Cl in place. The fixing of the caps D on the male matrix B of the mold facilitates manufacture of the hollow body since the assembly formed by the caps D and FG can be anchored, if necessary, on the said male matrix and since the assembly is always easy to engage in the cavity A.

In consideration of the above, it is confirmed that the objective of the present invention is to obtain hollow bodies resistant to mechanical stresses, in particular impact, so that the walls of said hollow bodies react elastically to said stresses due to the presence of the textile reinforcement, which is in a state of permanent stress.

As regards the tensioning of the textile reinforcement D, this operation can be carried out so as to deform the woven or mesh fabric in a direction essentially parallel to radial or essentially radial planes of the hollow body obtained. The tension can be applied to the layers constituting the textile reinforcement D so that, from the inner layers, the tension varies gradually in the direction of the outer layers, for example by varying the weaving density and / or the characteristics of the yarn forming the various caps of the reinforcement, as well as the dimensions of said caps.

It is obvious that the same criterion can be applied in a case where it is desired to exert an essentially uniform and constant tension in the different layers of the textile reinforcement D.

Of course, the present invention is not limited to the embodiments described above, which can be the subject of numerous variants.

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Claims (11)

1. Method for producing hollow bodies of reinforced resin, in particular protective helmets, said reinforcement consisting of a plurality of woven and / or mesh textile layers which are embedded in a bonding resin, method characterized in that '' the textile reinforcement layers (D) are positioned on one of the two parts of a mold (AB), in that at least part of the peripheral edges (Dl) of said reinforcement are fixed to said mold, in that a controlled tension is applied to said textile reinforcement which is maintained * in the next molding phase, in particular during the polymerization and solidification, and in that the hollow body thus formed is removed from the mold, so that the textile reinforcement of said body is incorporated and retained by the resin in a stressed state. 2. Method according to claim 1, characterized in that a tension which varies from the inner layers towards the outer layers of the textile reinforcement is applied to the layers forming the textile reinforcement (D), and in that said tension is maintained during the molding phase. 3. Method according to claim 1, characterized in that an essentially constant tension is applied to the layers forming the textile reinforcement (D) and that this tension is maintained during molding. 25 4.- Method according to one of claims 1 and 2, charac terized in that it ensures the preforming of the textile reinforcement (D) for example to the profile of a cap, and in that it fixes at least one part of the edges (Dl) of the elementary cap on one of the parts (AB) of the mold, ensuring their maintenance 30 during the tensioning of said reinforcement. 5. Method according to one of claims 1 to 4, characterized in that the controlled tension is applied to the layers of the textile reinforcement (D) using a bladder (C) which is elastically deformable by a fluid under pressure, preferably a liquid. 6. Method according to one of claims 1 to 5, charac- | Terisê in that one applies to the textile reinforcement (D) a jktension lower than the modulus of elasticity of the filament or wire 12 used to produce the textile part of said reinforcement. 7, - Method according to one of claims 1 to 6, characterized in that the textile reinforcement consists of a plurality of caps in woven fabric (D), whose edges (Dl) 5 are, at least in part , widened to form an anchor during the tensioning of the caps. 8, - Method according to one of claims 1 to 7, characterized in that interposed between the textile reinforcement (D) and the mold walls (AB) at least one layer or film (FG)> 10 which forms at minus part of the external and / or internal surface of the hollow body. 9 - A method according to claim 8, characterized in that colors and / or 'patterns which are transferred, during molding, onto the surface of the hollow body are reproduced in advance on the film (F) mold. 10.- Method according to one of claims 8 and 9, characterized in that as the peripheral film (F-G) is used a film of thermoplastic material which is incorporated and fixed in the structure of the hollow body during the molding operation. 11.- Method according to one of claims 1 to 10, charac terized in that used as material for textile reinforcement (D) son or fibers of natural and / or synthetic materials, at least part of which are thermoplastics, to be incorporated into the bonding resin during molding. 12.- Mold for implementing the method according to any one of claims 1 to 11, the female matrix of which reproduces in negative the profile of the hollow body to be obtained, characterized in that it comprises means for fixing at least part of the edges (Dl) of the textile reinforcement (D), while at least part of the walls (C) of the mixed matrix (B) of said mold is formed from an elastically deformable material and creates gaps (C2 ) for a pressurized fluid which breaks through said walls, in order to apply said tension controlled to said textile reinforcement (D). 13. Mold according to claim 12, characterized in that r "“ ~ “" ”“ 13 * a peripheral groove (B3) in which are held the two edges (Bl) of the caps of the textile reinforcement, as well as the edge of a elastically deformable bladder (C) which puts said caps under tension. 14. Mold according to claim 12, characterized in that there is provided a peripheral shoulder (A2) and a corresponding projecting part (B2) which are placed between the edge of the opening of the cavity (Al) of the matrix female (A) and the male matrix plate (B) in order to fix together at least part of the edges (Dl) of the caps (D) of the textile reinforcement, while said male matrix (B) comprises at least one bladder elastic (C) used to place said caps in. voltage. 15.- hollow body of reinforced resin, in particular a protective helmet, manufactured by the method according to any one of claims 1 to 10, characterized in that its reinforcement (D), being in the form of a textile woven or net, is incorporated in a state of stress in the bonding resin for said reinforcement. 16. A hollow body according to claim 15, characterized in that its surface and / or internal, consisting of layers (FG) kept tightly fixed on the structure of said body, is arranged so as to prevent spikes or parts similar formed by the filaments or son of the textile reinforcement protrude from said surfaces. 17. A hollow body according to claim 16, characterized in that its outer surface layer (F) consists of at least one sheet of thermoplastic material which can be incorporated in the bonding resin of said hollow body. 18.- hollow body according to one of claims 16 and 17, characterized in that its external surface (F) is provided with the desired patterns and / or colorings, which are essentially reproduced due to the transparency of the body surface well said. ^ 1