WO2009081371A1

WO2009081371A1 - Apparatus for moulding synthetic-fibre articles

Info

Publication number: WO2009081371A1
Application number: PCT/IB2008/055464
Authority: WO
Inventors: Gianluca Cavalieri
Original assignee: Gianluca Cavalieri
Priority date: 2007-12-21
Filing date: 2008-12-19
Publication date: 2009-07-02
Also published as: ITBO20070847A1

Abstract

The apparatus for moulding synthetic fibre articles, obtained from at least one layer of impregnated thermoplastic material, comprise a shell (2, 3) suitable to define a moulding chamber (4) sealed off and connected to suction means to be put in depression during the moulding phese. Inside the moulding chamber (4), a first heating plate (5) and a second heating plate (6) are arranged mutually facing and opposite, between which a forming member (10) of the article to be manufactured is suitable to be pre-set, consisting of a first forming member (11) and of a second forming member (12) opposite, between which the layer of impregnated thermoplastic material (13) is interposed. During the moulding phase, the forming members (11, 12) opposite are suitable to be heated respectively by said heating plates (5, 6) and to be compressed one against the other under the action of the actuators (9).

Description

APPARATUS FOR MOULDING SYNTHETIC-FIBRE ARTICLES

Technical Field

[1] The present invention relates to an apparatus for moulding synthetic-fibre articles, of the type of carbon and similar. Background Art

[2] At present, some apparatuses are known for the moulding of synthetic-fibre articles, in particular carbon fibre, suitable to be used in completely different fields, for instance in the aeronautical, automotive and similar fields, to realize components such as bodywork and similar. The synthetic-fibre compounds have particularly advantageous structural features, since they associate with a relatively low specific weight, resistance features, in particular to traction, comparable, if not superior, to those of many types of steels. The synthetic-fibre articles are generally obtained from materials so-called pre- impregnated, consisting of stringing suitable to give the desired resistance, for instance in carbon or glass, arranged aligned according to the same direction or weaved according to a determined weft, and immersed in a resinous thermoplastic phase, for instance of epoxy resin, suitable to give to the same stringing a stratiform solid shape. One or more layers of pre-impregnated material are cut according to a fixed shape, determined by the flat profile of the piece to obtain or of a part of it, and placed upon a suitable forming mould made of material suitable for moulding. The pre-impregnated material pre-set on the mould is then inserted in a shell of flexible material, commonly said sack, suitable to be hermetically sealed and to be connected to a suction device to realize the vacuum inside it. The sack is placed inside the moulding apparatus, generally consisting of an autoclave suitable to make the pre-impregnated material undergo a thermal cycle, for the forming of the article.

[3] More precisely, the pre-impregnated material undergoes a heating up to a fixed temperature of vitreous transition of the resin forming the compound, and a compression action suitable to determine the adhesion of the material to the mould in order to obtain the desired article. In the known apparatuses this compression derives from the combined action of the compressed air injected inside the autoclave and of the depression exerted by the cited suction device inside the sack. At the end of the operating cycle, the article is extracted from the sack and removed from the forming mould.

[4] A crucial aspect of these apparatuses is the fact that the heating and compression cycle of the material inside the autoclave requires relatively long time and considerable energy consumption.

[5] In particular, the apparatuses of known type require a high thermal energy waste to heat and maintain at desired temperature the material to form. In fact, it has to be pointed out that in these apparatuses the thermoplastic material to be formed is heated by the heating walls of the autoclave, basically through radiation. Therefore, in order for the heating to uniformly take place, also the environment surrounding the sack should result equally heated for the entire duration of the forming cycle. The result is that, for the dimensions that these apparatuses normally have, the amount of thermal energy dispersed inside the autoclave to heat the environment surrounding the material is a considerable share compared with that usefully given to the material to form.

[6] Similarly, these apparatuses require a quantity of compressed air considerably higher compared with that effectively acting upon the surface of thermoplastic material, since the main part of it acts on the inner walls of the autoclave.

[7] It must also be pointed out that the apparatuses of known type often have further limits, since they do not allow, for instance, to obtain the same moulding quality on both sides of the moulded article. In fact, the known apparatuses generally allow to control the finishing state of the only side adhering to the mould, whereas the opposite side facing the sack can result of much lower quality. The finishing state of the side opposite to the mould can be further compromised by the presence of residual air, in case trapped inside the thermoplastic material to form. This can happen if, for instance, the void realized inside the sack is not uniform. The residual air, in consequence of the heating, can expand in bubbles and originate flaws, for instance blowing, which damage the outer surface of the article and weaken its structure.

[8] In relation to this issue, American patent US 5,593,633 illustrates a method and an apparatus to produce synthetic-fibre articles, in which the arrangement of a layer of metal wire above the thermoplastic material to form is provided, in order to promote the uniform realization of the void inside the forming sack.

[9] The moulding methods and apparatuses known at present do not allow, though, to solve in a reliable and effective way the cited problems. Disclosure of Invention Disclosure

[10] The aim of the present invention is to overcome the cited drawbacks by devising an apparatus that allows to optimize the energy consumption and to reduce the time required for the moulding of synthetic-fibre articles.

[11] Within this scope, it is a further aim of the claimed invention to devise an apparatus that allows to operate the moulding of synthetic-fibre articles in an effective and re- peatable way.

[12] Another aim of the claimed invention is to provide an apparatus which allows to effectively control the state of surface finishing of both sides of the manufactured article.

[13] A further aim of the present invention is to provide an apparatus of simple con- structive and functional conception, with reduced dimensions, but also of reliable functioning and versatile use.

[14] The cited aims are reached, according to the claimed invention, by the apparatus for moulding synthetic-fibre articles according to claim 1. Description of Drawings

[15] Description details of the invention will be further evident in the illustrations of preferred embodiments of the apparatus for moulding synthetic-fibre articles according to the invention, illustrated in the guidelines drawings attached, wherein:

[16] Fig. 1 illustrates a sectional front view according to a vertical plane of the apparatus according to the invention;

[17] Fig. 2 illustrates a sectional front view according to a vertical plane of a different embodiment of the claimed invention. Best Mode

[18] With reference to figure 1, the numeral 1 refers to the apparatus for moulding synthetic-fibre articles. The apparatus 1 comprises a shell suitable to shape a sealed-off moulding chamber 4. The shell suitably consists of a support surface 2 suitable to be closed in the upper part by a covering dome 3. The moulding chamber 4 is pre-set for the connection, through suitable suction intakes 7, to air-suction means, per se known and therefore not illustrated for the sake of simplicity.

[19] Inside the moulding chamber 4 a first heating plate 5 and a second heating plate 6 are provided, arranged facing and opposite on parallel planes, basically horizontal, respectively lower and upper. The heating plates 5, 6 are equipped with heating members preferably of the resistance electric type.

[20] The lower heating plate 5 is fixed to the support surface 2. The upper heating plate 6 is supported by a frame 8 mobile according to a vertical direction, orthogonal to the same heating plates 5, 6, upon operation of a suitable actuator 9, for instance a pneumatic cylinder fixed underneath the support surface 2, outside the moulding chamber 4. The mobile frame 8 suitably consists of an upper crossbeam 13 bearing fixed the upper heating plate 6. The upper crossbeam 6 is fastened to vents 14, which cross the support surface 2 by respective holes, through interposition of suitable seal means 15. Underneath the support plane 2, the vents 14 are fastened to a lower crossbeam 16, which is fixed to the stem 19 of the actuator 9.

[21] Between the lower and upper heating plates 5, 6, inside the moulding chamber 4, a forming member 10 of the manufactured article is suitable to be pre-set. The forming member 10 consists of a first forming member 11 and of a second forming member 12 opposite, between which a layer of pre-impregnated thermoplastic material 20 is suitable to be interposed. The first forming member 11 usefully consists of a mould ad- equately shaped to define a first surface of the article to realize and it is arranged, during the moulding phase, in rest on the lower heating plate 5. The second forming member 12 consists, in its turn, of a die counter suitably shaped to define a second surface of the article to realize and it is arranged, during the moulding phase, against the upper heating plate 6. Therefore, during the moulding phase, the mould 11 and the die counter 12 receive heat through conduction respectively from the first heating plate 5 and from the second heating plate 6.

[22] The mould 11 and the die counter 12 contribute to define, in working coupled configuration, a gap between them, suitable to receive the layer of pre-impregnated thermoplastic material 20 and coinciding, in substance, with the shape of the article to obtain. It is clearly possible that the pre-impregnated thermoplastic material 20 to mould consists of more layers, in a per se known way.

[23] Furthermore, the apparatus provides for means of known type to control the temperature of the heating plates 5, 6 during the moulding phase.

[24] The functioning of the apparatus for moulding synthetic-fibre articles is described as follows.

[25] During the set-up phase, on the outside of the apparatus 1, it is provided for arranging the suited layer of pre-impregnated thermoplastic material 20 between the mould 11 and the die counter 12 of the forming member 10. The forming member 10 thus pre-set is then inserted between the heating plates 5, 6, in rest on the lower heating plate 5.

[26] The moulding chamber 4 is then hermetically sealed, so that the suction means can be operated to realize a suited depression inside the same chamber 4. The depression determines the ejection of the air, in case present in the layer of thermoplastic material 20.

[27] Subsequently the operation of the actuator 9 is driven, which operates in traction on the mobile frame 8, causing the compression of the die counter 12 on the mould 11 and therefore the compression of the layer of thermoplastic material 20 housed inside the forming member 10.

[28] In suitable phase relation with this compression action, the heating members are operated, with which the heating plates 5, 6 are equipped. The heat is transmitted through conduction by the heating plates 5, 6 respectively to the mould 11 and to the die counter 12 and from these to the layer of thermoplastic material 20, to realize the thermal cycle of the same layer of thermoplastic material. In particular, the forming member 10 is initially pre-heated at a temperature of, for instance, 8O⁰C with low pressure load.

[29] When the thermoplastic material reaches the pre-set temperature of preheating, for instance the polymerization temperature of the material, the actuator 9 is further activated to increase the compression action upon the material to form, while the temperature is, in its turn, raised to the working value, for instance 125⁰C.

[30] Once the forming cycle is completed, the forming member 10 is extracted from the moulding chamber 4 for the separation of the article thus formed.

[31] The described apparatus reaches therefore the aim to carry out in optimal way the moulding of synthetic-fibre articles, to optimize the energy consumption and to reduce the time required for the moulding. This result is reached, in particular, thanks to the action of the heating plates 5, 6, which produce the direct heating of the forming member 10 and, at the same time, operate the compression of the layer of thermoplastic material 20 to form inside said forming member 10. The thermal energy required is therefore substantially only the amount necessary to heat through heating plates 5, 6 the mould 11 and the die counter 12 of the forming member 10. In particular, such heating basically takes place through conduction, thus allowing to reach the desired threshold temperature on the material in the fastest and most effective way.

[32] Similarly the compression action exerted through the reciprocal approaching motion of the heating plates 5, 6 is transmitted directly to the mould 11 and to the die counter 12 in order to form the layer of thermoplastic material 20 without energy waste.

[33] For the same reasons, the claimed apparatus allows to remarkably reduce the duration of the moulding cycle of the synthetic-fibre articles.

[34] Therefore, the claimed apparatus allows to obtain in a much faster and more economic way any type of article, making, as a consequence, the use of synthetic-fibre composites more advantageous.

[35] A prerogative of the invention consists in the fact that both sides of the article are formed in a precise way and with a high quality of surface finishing. In fact, the adhesion of the layer of thermoplastic material 20, both on the mould 11 and on the die counter 12 determines the finishing of both the above-mentioned sides.

[36] It is necessary to point out that the apparatus allows the realization through moulding of articles also of complex shape, basically presenting two opposite forming sides. In particular, for the sake of simplicity it has been previously described the moulding of an article of simple shape through a mould and a respective die counter, but for the article of complex shape it is possible to provide for the use of a forming member consisting of more pieces.

[37] Finally, it has to be noticed that the apparatus according to the invention has a simple structure, compact and with reduced dimensions. Therefore, this apparatus is suitable to be easily installed in any industrial site.

[38] In fig. 2 a different embodiment of the apparatus is illustrated, in which the second forming member consists of a flexible covering 22, for instance of a material such as silicone, suitable to be overlapped adherent to the layer of thermoplastic material 20 to form. The flexible covering 22 adequately extends beyond the margins of the mould 11, in order to adhere with a peripheral end portion to a base 21 interposed between the lower heating plate 5 and the mould 11. On the base 21 suction holes 23 are made, in the area occupied by the mould 11, and come out into a duct 24 which is connected with the moulding chamber 4, in order to facilitate the outflow of the residual air in case present in the layer of thermoplastic material when the cited suction means are operated.

[39] Fencing means 17 are further provided in the forming area comprised between the heating plates 5, 6, consisting for instance of a tubular member suitable to contain the forming member 10 and the flexible covering 22. The tubular member 17 below shapes an annular seat suitable to house the peripheral portion of the flexible covering 22, in order to hold it during the operating cycle. Furthermore, the tubular member 17 is suitable to be connected through a duct 18 to means for feeding compressed air. In particular, through the duct 18, the controlled inlet of compressed air inside the space bounded by the tubular member 17 is operated, to produce the adhesion of the flexible covering 22 to the layer of thermoplastic material 20 arranged on the mould 11.

[40] In this case, during the set-up phase, the silicone flexible covering 22 is overlapped to the layer of thermoplastic material 20 already pre-set on the mould 11, mounted on the base 21. The mould 11 is placed inside the moulding chamber 4, above the lower heating plate 5, and held by the tubular member 23. On the tubular member 23 the upper heating plate 6 is then clamped, through operation of the actuator 9, in order to close the forming area bounded by the tubular member 23. This allows to operate the supply of compressed air inside the above-mentioned forming area bounded by the tubular member 23, causing the compression of the flexible covering 22 on the mould 11 and, as a consequence, the compression of the layer of thermoplastic material 20 housed between this flexible covering 22 and the mould 11 of the forming member 10.

[41] At the same time, the operation of the cited suction means is controlled, to put the moulding chamber 4 in depression, and the operation of the heating plates 5, 6 to heat the forming area up to the prearranged temperature, according to what already described above.

[42] Therefore, also in this case the apparatus allows to operate the moulding with limited consumption of thermal energy and with reduced operating time compared to the traditional techniques, and also to obtain a suitable surface finishing of both sides of the synthetic-fibre article.

[43] Materials adopted for the actual realisation of the invention, as well as their shapes and sizes, can be various, depending on the requirements.

[44] Where technical features mentioned in any claims are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each member identified by way of example by such reference signs.

Claims

[1] Apparatus for moulding synthetic-fibre articles, obtained from at least one layer of impregnated thermoplastic material, characterized in that it comprises a shell (2, 3) suitable to define a moulding chamber (4) sealed-off and connected to suction means to be put in depression during the moulding phase; heating means (5, 6) arranged inside said moulding chamber (4); a forming member (10) of the article to be manufactured, suitable to be prearranged in contact with said heating means (5, 6), inside said moulding chamber (4), and consisting of at least a first forming member (11) and of at least a second forming member (12) opposite, between which said layer of impregnated thermoplastic material (20) is suitable to be interposed, said forming members (11, 12) opposite being suitable to be heated respectively by said heating means (5, 6) during the moulding phase; means (9) suitable to carry out the compression of said second forming member (12) against said first forming member (11) during the moulding phase; means suitable to control the temperature of said heating means (5, 6) during the moulding phase.

[2] Apparatus according to claim 1, characterized in that said heating means (5, 6) comprise a first heating plate (5) and a second heating plate (6) arranged opposite and mutually facing inside said moulding chamber (4).

[3] Apparatus according to claim 2, characterized in that said first heating plate (5) and second heating plate (6) are arranged opposite and facing on parallel planes, basically horizontal, respectively lower and upper.

[4] Apparatus according to claim 3, characterized in that said lower first heating plate (5) is fixed to support surface (2) and said upper second heating plate (6) is supported by a frame (8) mobile according to a direction orthogonal to the said heating plates (5, 6), upon operation of suitable actuators (9), to operate said compression of said second forming member (12) against said first forming member (11) during the moulding phase.

[5] Apparatus according to claim 2, characterized in that said first forming member

(11) and second forming member (12) comprise at least one mould (11) and a die counter (12) suitably shaped to define a first surface and a second surface of the article to be manufactured, and arranged, during the moulding phase, resting respectively on said first heating plate (5) and said second heating plate (6), in order to receive the heat through conduction.

[6] Apparatus according to claim 3, characterized in that said mould (11) and said die counter (12) contribute to define, in an operational coupled configuration, a gap between them suitable to receive said layer of impregnated thermoplastic material (20) and essentially coinciding with the shape of the article to obtain.

[7] Apparatus according to claim 2, characterized in that said heating plates (5, 6) are internally equipped with heating members of the electric resistance type.

[8] Apparatus according to claim 1, characterized in that said second forming member comprises a flexible covering (22), suitable to be overlapped adherent to said layer of impregnated thermoplastic material (20) to be formed, pre-set on said first forming member (11).

[9] Apparatus according to claim 8, characterized in that it comprises fencing means

(17) of the forming area comprised between said heating means (5, 6), suitable to define a closed compartment containing said first forming member (11) and said flexible covering (22), said compartment being connected to a duct (18) for the controlled inlet of compressed air suitable to produce the adhesion of said flexible covering (22) to said layer of impregnated thermoplastic material (20) during the moulding phase.

[10] Apparatus according to claim 8, characterized in that said flexible covering (22) is realized of a material of the silicone type.

[11] Apparatus according to claim 8, characterized in that said first forming member

(11) is arranged on a base (21) having suction holes (23), which are connected to said moulding chamber (4), in order to facilitate the outflow of the residual air in case present in said layer of thermoplastic material (20) when said suction means are activated.

[12] Apparatus according to claim 1, characterized in that means suitable to control the temperature of said heating means (5, 6) during the moulding phase are provided to operate a preheating of said forming member (10) at a first temperature with low pressure load and a subsequent heating at a second working temperature, higher than said first preheating temperature, with simultaneous increase of the pressure load, at the moment in which said thermoplastic material reaches said pre-heating temperature.