GB2100662A

GB2100662A - Moulding hollow bodies from reinforced resinous materials

Info

Publication number: GB2100662A
Application number: GB08217654A
Authority: GB
Inventors: Pier Luigi Nava
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-06-22
Filing date: 1982-06-18
Publication date: 1983-01-06
Also published as: AU8504282A; BE893604A; FR2507956A1; IT1138798B; DE3222939C2; NL8202501A; ES511535A0; DE3222939A1; NO822066L; BR8203596A; ZA824364B; IL66098A; CH650445A5; DK277482A; JPS6040963B2; PT75090B; SE8203842L; PT75090A; GB2100662B; SE8203842D0

Abstract

A process for producing hollow bodies from resin reinforced with woven and/or net fabrics, consists in securing edges D1 of a plurality of textile layers D to male die part B of a mould A-B which houses an expandable bladder or membrane C. Chamber C2 formed between die part B and membrane C is connectible to a pressurised fluid source so that, after securing the textile caps D to said male die part, and introducing the latter, together with the caps, into female die part A of the mould, pressurised fluid can be introduced into chamber C2, thereby imparting a controlled pressure to said caps. Either before or after the application of pressure resin is introduced into the mould to incorporate the textile reinforcement D under pressure, which is thus maintained in a state of constraint during and after curing. <IMAGE>

Description

SPECIFICATION Improvements in and relating to the production of hollow bodies from reinforced resinous materials This invention cconcerns improvements in and relating to the production of hollow bodies from reinforced resinous materials, for example, helmets and the like. The invention relates to a process, to the mould used therein and to the product resulting therefrom.

The end use requirements of reinforced resin hollow bodies are well known and, in the specific case of protective helmets~ where this invention finds particular, but not exclusive application-such hollow bodies must have a structure capable of withstanding shocks, often repeated, and must also be light in weight.

Attempts have been made to meet the above requirements by providing hollow bodies in moulded resin, reinforced with a suitable textile reinforcement. However, the resultant hollow bodies only partially satisfy the desired requirements and do not fulfil other important requirements, especially with regard to their resistance to repeated shocks.

Briefly, the structure of such bodies must be such that under repeated shocks, even if constantly localized in the same area, it will re-act resiliently without producing cracks or flaking that could damage the structure, thereby ensuring that the shock will be distributed over a wider area. In the case of helmets in particular, the formation of cracks and breaks along the meridian planes of the structure must be avoided as these can prejudice the safety of the user.

This invention proposes to provide hollow bodies, in particular headgear, often used as shock resistant protective helmets, in which a suitable textile reinforcement is embedded in the bonding resin in a manner such as to form a resilient structure, the resistance of which is as uniform as possible.

A further object or the invention is to provide a hollow body of the specified type, the internal and external surfaces of which are smooth and can thus constitute the finished surface which may easily be provided with designs and markings. When the textile reinforcement or elements forming same are of yarn or single thread fibres, they have a certain degree of rigidity, and tend to project from the surface of the reinforcement. The invention seeks to avoid this and provide the smooth finished surface mentioned.

A further object of the invention is to provide hollow bodies, the external surface of which requires practically no finishing work and which, in relation to end use requirements, has the desired colouring and/or designs, to meet aesthetic requirements.

A further object of the invention is to provide hollow bodies in resin having discontinuous shapes and undercuts and being such that parts of their surfaces form angles of less than 90 with respect to a vertical plane.

According to the present invention, a process for producing hollow bodies from reinforced resin, the reinforcement consisting of a plurality of woven and/or net textile layers embedded in a bonding resin, is characterized by positioning the layers of textile reinforcement on one of the two parts of a mould, securing at least a part of peripheral edges of the reinforcement to said one part of the mould, applying a controlled tension to said textile reinforcement and maintaining it in during the subsquent moulding phase including polymerization and solidification of the resin and in removing the hollow body obtained from the mould so that the textile reinforcement of said body is incorporated in and retained by the resin in a state of constraint.

The woven and/or net textile reinforcement according to the invention may consist of a plurality of elements, preformed in the shape of caps, at least part of which is obtained by weaving the central zone of each cap in the form of a spiral. Alternatively, the elementary caps may be obtained from a woven tubular body, one of the ends of which is crown shaped, the edges of the cusps of said crown being joined by sewing or, in the case of materials having thermoplastic yarns, by welding, whilst the caps so obtained are superimposed on each other, angularly shifting successively the joined areas, to form a homogeneous layer of practically uniform thickness.

Depending on the end use and requirements for the hollow body, the weaving of the elementary caps may be effected in such way as to provide areas of different density or weave closeness which, during the moulding of the body, are subjected to a controlled tension produced by a fluid under pressure.

The prior application of the controlled tension to the textile reinforcement can be effected with suitable criteria correlated to the physical characteristics of the threads or yarns forming the caps and/or the weave characteristics of the caps. For example, the tension applied to the textile reinforcement may be referred to and considered as a limiting value, the resilience module or tensile strength of the thread or yarn used in each case. Obviously, the tension previously applied to the textile reinforcement must be correlated to the temperatures of moulding and treatment of the bonding resins used to obtain the hollow body under consideration.

Again with regard to the intended end use of the hollow bodies obtained, the textile reinforcement can be associated with lining layers, internal and/or external of the hollow body, which layers may consist of suitable resin films, for example, thermoplastic resin films, to be incorporated in the bonding resin or by thermo setting resins. In this later case, it is possible to easily and quickly obtain hollow bodies, in particular helmets, the outer surface of which is smooth and requires practically no finishing operation. Moreover, said lining films may be shaped in advance as external and/or internal caps to determine the finished surfaces and the desired characteristics of the bodies.Thus, for example, an external cap of suitable material, for example, thermoplastic, makes it possible to obtain smooth even surfaces and avoids joints or projections being formed by the textile reinforcement threads projecting from the surface of the hollow body. Furthermore, the lining film or cap may be provided with designs or figures which would be reproduced on the surface of the hollow body, especially when the bonding resin of the textile reinforcement is transparent, even to a limited degree.

Also according to the present invention, a mould for use in the process described having a female die part of the two part mould reproducing in intaglio the shape of the hollow body required, is characterised by means for securing at least a part of edges of the textile reinforcement while at least a part of the walls of a male die part of the two-part mould is made of elastically deformable material and provides a chamber for a pressurized fluid which deforms those walls, imparting the controlled tension to the textile reinforcement.

Furthermore, according to the present invention, a hollow body of reinforced resin produced by the aforesaid process and in the abovementioned mould is characterised in that its reinforcement, in the form of a woven textile or net, is incorporated in a state of constraint within the bonding resin.

The invention will now be further explained, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partial schematic cross section of the mould used in the process according to the invention; Figure 2 is a similar cross section of a variant of the mould; and Figures 3 and 4 show to an enlarged scale and in a conventional manner, fragmentary sections of two hollow bodies according to the invention.

The process according to the invention will now be explained with reference to Figs. 1 and 2 of the accompanying drawings, and to the construction of a protective helmet.

To obtain the helmet in question, it is necessary first to prepare the textile reinforcement formed by two or more overlapping woven layers having suitable yarns of synthetic materials (thermoplastic resins) and/or natural materials: vegetable (such as linen, cotton or the like) or mineral (such as asbestos, glass and so on). Advantageously woven and/or net textiles are used, prepared at least in part with threads or filaments of thermoplastic resins, such as vinyl, polystyrene, acrylic, polyamine, polyurethane resins, or the like. Preferably filaments of those aramidic resins known as "KEVLAR" ("RTM") are used.

The textile reinforcement according to the invention is formed by a pluarlity of superimposed layers, which may vary both as to the composition of the threads or filaments used, and as to the number of threads in each layer.

Furthermore, the weave density or closeness may also vary. Each layer of the textile reinforcement consists of a woven cap D which is spirally wound up to a given diameter, beyond which the weave continues helically, that is. the number of stitches for each turn of the cap under formation is kept practically constant. Alternatively, the cap is obtained by starting from a tubular woven textile of suitable diameter. To obtain elements of the desired length, one of the end of the each is sewn in the shape of a crown. The cusps or points of each crown are then ben inwardly so as to position the peaks of the cusps on the axis of the tubular textile. Lastly, the edges or borders of the cusps are joined to each other by stitching. or in the case of synthetic threads, also by welding, to thus form the caps.

A certain number of caps so prepared (in practice the number may vary from two upwards) are superimposed to form a textile reinforcement of the desired characteristics.

When the bottom of the caps consists of cusps welded during the overlapping phase of caps D, the meridian joining ribs are angularly displaced with respect to each other in such a way that the thickness and the structure of the textile reinforcement obtained is homogeneous and practically uniform.

Edges D1 of caps D may be enlarged to ensure their anchorage during the subsequent tensioning so that during this operation the different textile layers may freely slip over one another to become tensioned.

The woven caps D thus prepared, and before the moulding operation, may be sub- jected to preliminary treatment, for example, imbibition with suitable material, preshaping and so on, in order to meet the particular requirements of the finished product resulting in each case.

Again with reference to Figs. 1 and 2 of the drawings, these illustrate two forms of embodiment of the mould by means of which the process according to the invention is carried out which, in the specific case illustrated, provides a protective helmet.

The mould illustrated consists of a female die A and a male die B, the latter being in the form of a profiled body B1 which is secured to a supporting plate B2 and housed as described herein in profiled cavity Al of the female die, which reproduces, in the negative or intaglio, the desired shape of the helmet.

The two die parts A and B of the mould are presented to each other in known manner by the stationary and movable plates of a press which urge them towards each other as hereafter described.

According to the present invention, profiled body B1 retains an elastic lining C constituting a shaped bladder, cushion or membrane held by a collar C1 in a groove B3 provided in the upper part of the profiled body. There is thus obtained between parts B1 and C, a sealed chamber C2 connected by means of conduits B4 to a suitable pressurized fluid source, for dilating and deforming bladder or membrane C. Preferably, the source of fluid pressure is oil or compressed air introduced into chamber C2 at a suitable pressure, for example at 20 atm (1,961,400 Pa).

In Fig. 1, the peripheral edge of profiled cavity Al of female die A is provided with a shoulder A2, the bottom of which is inclined and converges downwardly. The shoulder is closed by plate B2 of male die B to form a blocking member for textile reinforcement caps D, as disclosed hereinafter.

The plurality of superimposed caps D, forming the textile reinforcement, are introduced into profiled cavity Al of female die A (Fig.

1). In the case illustrated, textile reinforcement D is pre-arranged between an external cap F and an internal cap G having characteristics suitable for the purpose to be achieved and which will be disclosed hereafter. External cap F, which is close to or in contact with the wall of profiled cavity Al, is made of suitable material, for example of textile woven with cotton or similar yarn, to form an external layer or coating of suitable consistency to prevent points or the like of caps D of synthetic material projecting from the helmet surface after moulding. Cap F may advantageously consist of a lamina or film of thermoplastic resin, for example, polyethylene, PVC or similar material, so that during the subsequent moulding phase it is incorporated into the bonding resin to form a smooth and well finished outer surface having the desired characteristics.It is possible, in particular, to produce helmets having the desired aesthetical features, since cap F can be coloured, as desired, and have designs applied to it in advance, whether the cap be of textile or of thermoplastic materials. In both cases cap F is secured and incorporated in the bonding resin during the moulding phase. Similar results are achieved with internal cap G which, however, is also provided as a protective element for elastic bladder or membrane C and for other parts of the mould.

Again with reference to Fig. 1 of the drawing, after having placed the set of superimposed caps F, D and G in female die A, the enlarged edges D1 of textile caps D are folded outwardly and are partly housed within shoulder A2 of the female die, the depth of which is less than the thickness formed by those edges D1. External cap F can be shaped and arranged in such a way that its edge F1 is not engaged by shoulder A2 of the mould so that during moulding, it adheres to profiled cavity Al of the mould. A similar result can be obtained by shaping and arranging cap F so that is adheres uniformly and continuously over the surface of profiled cavity Al, even when the edge of the cap is fixed at the base of shoulder A2, thus ensuring that adequate tension is always imparted to textile reinforcements D during the moulding phase.

Male die element B1 is then offered up to the textile reinforcements D and caps F and G, previously housed in profile cavity Al, this operation being readily effected because elastic bladder or membrane C is secured and adheres to the surface of the male die element. Coupling of the two die parts A and B of the mould engages plate B2 with edges D1 of caps D which are thus pressed and gripped between plate B1 and the base of the peripheral shoulder A2.

Subsequently, a presurized fluid is introduced into chamber C2, for example oil at a pressure of between 10 - 30atm (980,700 2,942,100 Pa), which deforms elastic bladder or membrane C and imparts a tensioning force to textile reinforcements D. This operation is performed in a suitable manner and is such as to apply the pressure gradually to the different textile layers of caps D to cause these to conform completely to the shape of the walls of profiled cavity Al. In particular, the amount of pressure in chamber C2 is determined with regard to te textile structure used, both as to the different caps D and to the different zones of each of said caps of textile reinforcement D, as shown in Figs. 3 and 4.

In particular, the amount of pressure, and hence the tensioning force applied to caps D of the textile reinforcement of the helmet, is correlated to the physical characteristics of the threads forming said textile reinforcement and to the purposes and end use requirements of the hollow bodies obtained in each case. In the specific case of helmets, a high resistance to shocks is required to avoid the formation of cracks or delamination of the layers forming the helmet structure.

Generally, the tensioning of texture reinforcement D is performed in such a way as not to exceed the tensile strength of the yarn forming reinforcement D and, in the case of helmets in particular, the resilience module of the yarn of the textile reinforcement must not be exceeded.

Obviously, and with reference to Figs. 3 and 4 of the drawings, the tension applied to textile reinforcement D may vary from zone to zone of said reinforcement D may vary from zone to zone of said reinforcement. In this case, elastic bladder or membrane C is provided with zones of different elasticity, for example of different thickness, to impart thereby a lesser or greater tensioning force to the corresponding zone of said textile reinforcement.

After tensioning reinforcement D, a suitable resin is introduced into cavity Al of the mould through conduit B5 located in a suitable position in male die B, for example a thermosetting bonding resin of epoxy or polyester. The bonding resin can be introduced beforehand into cavity Al of the mould, after having inserted cap F into said cavity, especially when cap F is made of synthetic thermoplastic material, to form the external surface of the hollow body. The bonding resin injected into cavtiy Al enrobes textile reinforcement D and when the assembly is subjected to pressure exerted through the elastic bladder or membrane C, it takes on the form of said cavity Al.

When the bonding resin has polymerized and solidified, the pressure is discharged from chamber C2, the mould is opened and the helmet is removed from female die A; textile reinforcement D of the helmet is embedded and fixed in the bonding resin and is maintained in a constant state of tension. The outer surface of the hollow body thus obtained is smooth and requires practically no finishing. Moreover that surface is self-coloured as required, since, as already stated, external cap F can be coloured and/or provided with designs or the like.

The hollow body, and in particular the helmet, obtained is complete in all respects in that its external surface is free from projections or sharp points, even when the textile forming reinforcement D consists of threads or filaments having a limited flexibility, as in the case of synthetic resins.

Slight variation of the process and mould is shown with reference to Fig. 2. In this case, enlarged edges D1 of reinforcement caps D are housed in peripheral groove B3 of profiled body B1 which also holds securing collar C1.

The securing of caps D to male die B of the mould facilitates production of the hollow body since the assembly formed by caps D and F-G can be anchored, as required, to said male die and the entire assembly is thereafter readily offered up to cavity A.

As described, the present invention provides hollow bodies, resistent to mechanical stresses, in particular shock stresses, in such way that the walls of said bodies resiliently react to said stresses due to the presence of the textile reinforcement, which is in a state of permanent constraint.

With regard to the tensioning of textile reinforcement D, this operation can be performed in a manner such as to deform the woven or net textile in a direction substantially parallel to radial or substantially radial planes of the hollow body obtained. The tensioning can be applied to the layers constituting textile reinforcement D in such way that starting from the internal layers, the tension varies gradually towards the outer layers, for example, by varying the closeness of the weave and/or the type of the yarn forming the different caps of the reinforcement, as well as the dimensions of said caps. It is obvious that the same criterion can be applied in the event it is desired to apply a substantially uniform and constant tension to the different layers of textile reinforcement D. Other variants and modifications may be introduced either in the process according to the invention or in the mould utilized, depending on the end use requirements of the hollow bodies obtained by the process, without departing from the scope of the present invention as defined in the

Claims

appended claims. CLAIMS

1 Aprocess for producing hollow bodies from reinforced resin, in particular protective helmets, the reinforcement consisting of a plurality of woven and/or net textile layers embedded in a bonding resin, characterised by positioning the layers of textile reinforcement (D) on one of the two parts of a mould (A-B). securing at least a part of peripheral edges (D 1 ) of the reinforcement to said one part of the mould, applying a controlled tension to said textile reinforcement and maintaining it in during the subsequent moulding phase including polymerization and solidification of the resin, and in removing the hollow body obtained from the mould so that the textile reinforcement of said body is incorporated in and retained by the resin in a state of constraint.

2. A process as claimed in claim 1, characterised by applying to the layers forming the textile reinforcement (D) a tension which varies from the internal layers towards the external layers thereof and in maintaning such graduated tension during the subsequent moulding phase.

3. A process as claimed in claim 1, characterised by applying to the layers forming the textile reinforcement (D) a substantially constant tension, and in maintaining such uniform tension during the subsequent moulding phase.

4. A process as claimed in claim 1, 2 or 3, characterised by pre-shaping the textile reinforcement (D) in the form of a cap, and fixing at least part of edges (D1) of the elementary cap to one of parts (A-B) of the mould,

5. A process as claimed in any one of claims 1 to 4, characterised by applying the controlled tension to the layers of textile reinforcement (D) by means of a bladder or membrane (C) which is elastically deformable by a pressurised fluid.

6. A process as claimed in any one of claims 1 to 5, characterised by applying to textile reinforcement (D) a tension lower than the resilience module of the thread or yarn of the textile reinforcement.

7. A process as claimed in any one of claim 1 to 6, characterised in that the textile reinforcement consists of a plurality of woven textile caps (D), the edges (D1) of which are, at least in part, enlarged to form an anchorage during tensioning of the caps.

8. A process as claimed in any one of claims 1 to 7, characterised by locating on one or both sides of the textile reinforcement (D) at least one peripheral layer or film (F-G) which forms at least part of the external and/or internal surface of the hollow body.

9. A process as claimed in claim 8, characterised in reproducing in advance on film (F) colours and/or designs which will be embodied, during moulding, in the surface of the moulded hollow body.

10. A process as claimed in either claim 8 or 9, characterised in using as the peripherical layer (F-G) a film of thermoplastic material which is incorported and fixed in the structure of the hollow body during the moulding operation.

11. A process as claimed in any one of claims 1 to 10, characterised by utilizing yarns or fibres of natural and/or synthetic materials at least a part of which are thermoplastic, as the material for textile reinforcement (D) to be incorporated in the bonding resin during moulding.

12. A mould for use in the process as claimed in any one of claims 1 to 11, a female die part of the two-part-mould reproducing in intaglio the shape of the hollow body to be contained, characterised by means for securing at least a part of edges (D1) of the textile reinforcement (D) while at least part a part of the walls (C) of a male die part (B) of the two-part mould is made of elastically deformable material and provides a chamber (C2) for a pressurised fluid which deforms those walls, imparting the controlled tension to the textile reinforcement (D).

13. A mould as claimed in claim 12, characterised in that its male die part (B) has, towards one of its ends, a peripheral groove (B3) in which both edges (D1) of the caps of the textile reinforcement and the edge of an elastically deformable bladder or membrane (C) which tensions the caps are held.

14. A mould as claimed in claim 12, characterised by the provision of a peripheral shoulder (A2) on the female die part (A) and a corresponding projection (B2) on male die part (B) for match-mating between the edge of the aperture (Al) of female die part (A) and the plate of male die part (B) , to hold at least a part of edges (D1) of caps (D) of the textile reinforcement tightly together, while the male die part (B) has at least one elastic bladder or membrane (C) to place the reinforcing layers under tension.

15. A hollow body in reinforced resin produced by the process as claimed in any one of claims 1 to 10, characterized in that its reinforcement (D), in the form of a woven textile or net, is incorporated in a state of constraint within the bonding resin.

16. A hollow body as claimed in claim 15, characterised in that its external and/or internal surface, consisting of layers (F-G) held tightly to the structure of the body, acts to prevent the projection from those surfaces of points or the like formed by the filaments or threads of the textile reinforcement.

17. A hollow body as claimed in claim 16, characterised in that its external surface layer (F) consists of at least one lamina of thermoplastic material which may be incorporated into the bonding resin of the hollow body.

18. A hollow body as claimed in claim 16 or 17, characterised in that external surface layer (F) is provided with the designs and/or colourings, which are substantially reproduced due to the transparency of the surface of the body itself.

19. Processes for producing hollow bodies in reinforced resin substantially as herein described with reference to the accompanying drawings.

20. Moulds for use in the process of any one of claims 1 to 11 and 19 substantially as herein described with reference to and as illustrated in the accompanying drawings.

21. Hollow bodies when produced by the process of any of claims 1 to 11 and 19 or in moulds according to any one of claims 12 to 18 and 20.