FR2649916A1 - Universal mould with adaptable moulding surfaces for moulding plastic, ceramic or other materials - Google Patents

Abstract

The object of the invention is to provide a mould, consisting of at least two mould parts 1, 1', the moulding surfaces 7, 7' of which may be formed and adapted to a desired form by virtue of a model (template) in a simple manner and may be modifiable as desired according to another model. According to a preferred embodiment, to this end, the mould in accordance with the invention consists of two half-moulds 1, 1', each half-mould including a moulding element A, A' which can be deformed by depression (reduced pressure), the moulding surface of this element 7, 7' taking the form of the moulding impression by envelopment (encasement) of a model positioned between the two assembled half-moulds 1, 1' from an inactive position represented in Figure 1. This mould permits the moulding of liquid materials in the cold or hot state up to a temperature of between approximately 250 DEG C and 300 DEG C.

Description

 The invention relates to a universal mold with adaptable molding surfaces allowing the molding of plastics, ceramics or other materials, according to different shapes and dimensions.

 The molding techniques are various today, for example molding by simple casting, coating of a core, by injection, extrusion, thermoforming or drawing. In all these cases, molds, cores or dies are used with a shape specific to that of the element to be produced.

 In the very case. classic sand molding, each half-mold is made by compacting sand on a model. The latter being removed and the tap holes and vents made, the material, generally liquid metal, is poured and during demolding the mold is destroyed.

 These half-molds with their corresponding molding part, are now generally made of steel and form the die and the punch, between which the material is cast and pressed. The shape of the molding surfaces is obviously specific to each mold, in other words to an object to be molded corresponds a mold.

 These molds are currently made from relatively expensive materials and pose technical problems such as problems of relative expansion, the need for expensive machine tools ...

 In addition, an error in the design of the object and therefore of the model leads to considerable losses, when the manufacture of the molds is already advanced and consequently an additional cost of manufacture.

 The object of the invention is therefore to provide a mold, consisting of at least a part, the molding surface of which can be formed and adapted to a desired shape by means of a model in a simple manner and can be modified at will according to another model.

 To do this, the present invention provides a mold whose manufacturing cost is favorable and which allows thanks to the possibility of modifying the configuration of its molding surfaces to mold objects without significant investment. Thus it is possible to make molding tests from models which are possibly not yet developed.

 It is also possible with a single type of mold to produce objects of different shape, which is particularly advantageous in the case of manufacture in small series.

 In the case of mass production, once the final configuration has been obtained, by a particularly simple operation, the mold can be reinforced and fixed in this configuration.

 This mold allows the molding of liquid material cold or hot up to a temperature between about 250'C to 300 ~ C.

 Curing can be achieved or accelerated by baking using integrated heaters. No autoclave oven is therefore necessary.

 For this purpose, the mold according to the invention is of the type with at least two mold parts, to be superimposed or juxtaposed to form a molding imprint between them; this mold is remarkable in that a first part of the mold comprises a rigid frame and a molding element deformable by vacuum from an inactive position, the molding surface of this element taking the form of the molding imprint by wrapping of a model placed between the first mold part and a second mold part assembled with the first.

 In order to allow the molding of thermosetting materials, the first part of the mold may include a heating device integrated in the molding element.

 Preferably, in the inactive position, the molding surfaces are spaced from each other, the mold parts being assembled.

 To obtain these deformation properties, the molding element consists, according to a preferred embodiment, of an incompressible material per se, granular, delimited and contained between an internal elastic membrane. forming a molding surface and fixed to the inner edge of the frame and an outer elastic membrane attached to the other edge of the frame.

 According to a preferred embodiment, the mold according to the invention comprises at least two mold parts of identical constitution to the first part above.

 According to a variant, the first mold part described above can be associated with a rigid non-deformable mold part, for example planar.

 The invention is set out below in more detail with the aid of drawings representing only one embodiment.

 - Figure 1 is a partial cross-sectional view of a mold according to the invention in the inactive state.

 - Figures 2A to 2H are sectional views of the mold, the support plates not being shown, illustrating the steps of shaping the mold and molding an element from precut layers impregnated with plastic material by the commonly used method called. by draping.

 - Figures 3A to 3F are sectional views of the mold, the support plates not being shown, illustrating the steps of shaping the mold and molding an element by plastic injection.

 Figure 1 shows in detail a mold according to the invention.

 According to the example shown, the mold comprises two mold parts, namely an upper half-mold 1 and a lower half-mold 1 'of analogous and symmetrical constitution. These two half-molds 1, 1 ′ are connected to each other by superposition and for example nesting, a hydraulic lifting system which can complete the connection and the separation of these two half-molds. In order to obtain a good seal, the connecting surfaces of these half-molds have a silicone seal 3, 3 '.

 Each half-mold has a rigid frame forming the side walls 4, 4 ′, preferably metallic, for example made of steel. These side walls have on their inner side, at least one shoulder 2, 2 'whose function will be explained below.

 Each half-mold also has a plate 5, 5 'preferably perforated and acting as a foot for the machine with regard to the lower plate 5'.

 The molding elements A, A 'of the half-molds 1,1' are therefore of identical constitution and will now be described more precisely. The molding element A, A 'mainly comprises an incompressible and granular material 6, 6' delimited and contained between an internal elastic film 7, 7 'forming the molding surface and an external wall # 8, 8'. The elastic film 7, 7 'is fixed to the inner edge of the rigid frame 4, 4' and stretched between the four sides of the frame forming this edge. To do this, it is held in a groove made at the bottom of the shoulder 2, 2 'thanks to a seal 9, 9' preferably made of stiffened silicone.

 The outer wall 8, 8 preferably also consists of an elastic membrane and is also held in a groove in the rigid frame 4, 4 '. This groove is preferably located outside the frame, the plate 5, 5 ′ therefore cooperating with a seal 10, 10 ′ in silicone to lock the film 8; 8 ′ in position.

 According to a preferred embodiment, the elastic film 7, 7 ′ will be a polyvinyl acetate film or a silicone film. The film 8, 8 ′ will preferably be made of silicone. The granular material 6, 6 'meanwhile is preferably made of sand, dehydrated so as not to cause damage to the films 7, 7' and 8, 8 '.

 Thanks to the shoulders 2, 2 ', the films 7, 7' have a certain distance between them and therefore form a space 11.

 The mold also has vacuum deposition holes. Each frame comprises for this purpose at least one vacuum opening 12, 12 'opening into the sand zone 6, 6' and an opening 13, 13 'opening into the space 11 between the molding surfaces 7, 7' . The function of these different orifices will be explained later, when describing the preferred modes of use of the mold according to the invention.

 Each half-mold may also include at least one heating device, preferably an electrical resistance 14, 14 ′, generally controlled by a rheostat and intended for heating the mold, in the case of molding of material requiring cooking.

 Finally, the space 11 between the molding surfaces can be draped with a mold release envelope 15, preferably made of a mold release nylon which also allows the passage of air.

 Preferably, each half-mold will be symmetrical, more precisely at least two series of orifices 12, 12 'and 13, 13' will be arranged symmetrically, each on an opposite side of the rigid frame 4, 4 '.

 It is also possible to provide a thermal probe placed in the sand 6, 6 ′, in order to measure and control the temperature, the temperature of the sand being homogeneous.

 Preferably, the silicone membrane 8 continuously resists a temperature of approximately 250 μl and the films 7 of polyvinyl acetate at a temperature of approximately 300 ° C. The silicone seals withstand a temperature of around 300-C.

 As an indication but not limiting, the film 7 will be of a thickness of approximately 0.8 mm and the membrane 8 of a thickness of approximately 2 mm; the silicone seals will have a diameter of approximately 8 mm; the grain size of the sand will be chosen between 0.8 and 0.12 mm.

 FIGS. 2A to 2H show diagrammatically the different stages of shaping the mold and of molding an element from precut layers impregnated with plastic material by the process commonly called draping.

 This process is particularly suitable for the production of carbon fiber or composite material objects.

 The model is therefore placed in the open mold (Figure 2A) and the mold is closed (Figure 2B).

 First of all, the depression is produced by the orifices 13 and 13 ′ in the space 11 between the molding surfaces. The flexible membranes 7 and 7 'then conform to the shapes of the model. Then the depression is made in the sand 6, 6 'through the orifices 12, 12'. The sand will therefore first of all conform to the shape of the membranes 7 and 7 ′ and, due to the depression and its non-compressibility, become rigid and hard. This rigidity is achieved by adjusting to adequate depressions (Figure 2C).

 To be able to achieve the depression of the sand 6, 6 ′ the orifice 12 or 12 ′ or the corresponding vacuum setting duct must be provided with a filter or a valve preventing the passage of the sand.

 We thus obtained two half-molds with sufficiently rigid molding elements and by stopping the vacuum in the space 11, we can open the mold (Figure 2D) and extract the model.

 The draping molding according to this example can then be carried out in a conventional manner (FIG. 2E at 2H).

The lay-up is carried out in Figure 2E), the mold is closed (Figure 2F); thanks to the electrical resistors 14, 14 ′ the molding elements are heated and the cooking is carried out (FIG. 2G); the mold is then opened and the finished part extracted (Figure 2H).

 FIGS. 3A to 3F represent the stages of production in the case where an injection molding of a plastic material is carried out.

 In this case the model is preferably coated with delamination nylon put into a ball on each side of the model as can be seen in FIG. 3A. The mold is closed (FIG. 3B) and, as previously, the vacuum is produced in space 11 and then in the sand 6, 6 ′ (FIG. 3C).

 The vacuum is removed in space 11 and the mold is therefore open (FIG. 3D), the model can therefore be extracted as well as the delamination nylon which allows the creation of degassing bubbles and / or recesses allowing the casting of '' a surplus of material ensuring the correct filling of the imprint.

 Then the plastic M is injected on one side of the mold through the orifices 13, 13 'while on the other side the suction is again carried out in order to achieve a correct filling of the molding impression with evacuation of the air as the injection progresses (Figure 3E).

 After cooling, the injected plastic object is removed from the mold (Figure 3F).

 After the molding of an object, the mold according to the invention can be used again to mold an object of different shape. In fact, if the molding is carried out at room temperature, the depression of the vacuum in the sand 6, 6 'allows the return of the molding films 7, 7' in their inactive planar position. Another molding process can then be carried out.

 After a certain number of uses, and especially when the molding is carried out by heating, the film 7, 7 ′ may be deformed, become brittle and therefore it must be changed. In this case it is dismantled, and replacement films are put in place, these films being in the form of a silicone or polyvinyl acetate film stretched over a rigidified silicone frame constituted by the seal 9, 9 ' . These spare elements are easily fixed by clipping into the corresponding grooves.

 For mass production, once the molding surface 7, 7 'has been shaped according to the desired impression, a resin can be injected through the orifices 12, 12' in order to definitively harden the molding elements A and A '.

 The temperature can be adjusted automatically and / or computerized.

 For the production of relatively large molds and for the molding of particular shapes, the electrical resistances can be arranged to form compartmentalized heating zones and thus achieve modulation of the heating.

 The mold thus produced is in particular intended for molding thermosetting plastics, but it can obviously also be used for molding ceramic, plaster or any other material. Depending on the molded material, the composition, dimensions and strength of the molding elements will be studied to be compatible with this material.

 The mold described above is a preferred embodiment. According to the invention, it is possible to produce a mold in several mold parts, for example in eight parts of superimposed and juxtaposed molds, the molding impression being centered on the common top of these eight parts, which in this case , are comparable to a half-mold as described above, divided into four parts.

 It is also possible, in accordance with the invention, to associate a half-mold as described above, with a conventional non-deformable rigid mold part. For example, this second part of the mold may be a simple flat molding surface and in this case, the mold thus formed will be intended to produce flat basic objects. Possibly even, it is possible to use a conventional non-deformable molding surface comprising a molding imprint, in order to produce objects whose base is of determined shape.

 Any other combination of mold parts is possible and remains within the protective field of the present invention.

Claims (14)

 1) Mold intended for molding plastics, ceramics or other materials consisting of at least two parts of mold to be superimposed or juxtaposed to form a molding imprint between them, mold characterized in that a first part of mold (1 ) comprises a rigid frame (4) and a molding element (A) deformable by depression from an inactive position, the molding surface of this element taking the form of the molding imprint by wrapping a model put in place between the first mold part (1) and a second mold part assembled with the first.  2) Mold according to claim 1, characterized in that the first mold part (1) comprises a heating device integrated in the molding element (A).  3) Mold according to any one of the preceding claims, characterized in that in the inactive position the molding surfaces of the different parts are distant from each other, the mold parts being assembled.  4) Mold according to claim 3, characterized in that the first mold part comprises at least one orifice (13) opening near the inner edge of the frame and intended to communicate with the space (11) between the molding surfaces when the mold parts (1) are assembled.  5) Mold according to any one of the preceding claims, characterized in that the molding element comprises a material (6) incompressible in itself, granular, delimited and contained between the rigid frame, an internal elastic membrane (7) forming a surface. molding and fixed to one edge of the frame and an elastic outer membrane (8) fixed to another edge of the frame.  6) Mold according to claim 5, characterized in that the first mold part (1) comprises at least one orifice (12) opening out between the inner membrane and the outer membrane (7, 8) and intended for placing the vacuum in the granular material.  7) A mold according to any one of claims 5 and 6, characterized in that the granular material (6) is dehydrated sand.  8) A mold according to any one of claims 5 to 7 characterized in that the inner membrane (7) is a polyvinyl acetate film.  9) Mold according to any one of claims 5 to 7, characterized in that the inner membrane (7) is a silicone film.  10) Mold according to any one of claims 5 to 9, characterized in that the outer membrane (8) is a silicone film.  11) Mold according to any one of claims 5 to 10, characterized in that the membranes (7, 8) are locked to the rigid frame (4) in grooves arranged dansocelui-ci thanks to silicone seals.  12) Mold according to any one of claims 5 to 11, characterized in that the first mold part (1) comprises a perforated plate (5) blocking the outer membrane (8) and being able to act as a foot.  13) Mold according to any one of the preceding claims, characterized in that the second part of the mold is of identical constitution to the first part.  14) Mold according to any one of claims 1 to 12, characterized in that the second part of the mold is a rigid element.