Molding core

Abstract

Molding core. Pressurizable molding core (1), to be inserted into a mold (61), comprising: - a flexible outer shell (2) intended to be filled and / or pressurized internally by a pressurized fluid; - a reinforcement (3) extending inside the outer shell (2) to maintain it in a predefined shape at rest, compatible with its insertion and extraction from the mold (61). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Molding core Technical field

[0001] The present invention relates to the molding of parts made of polymer material. In particular, the invention relates to a core for molding hollow parts having an undercut, as well as a method for manufacturing such parts. Prior art

[0002] To mold parts made of polymer material having an undercut cavity, it is known to manufacture several demoldable by-products, then to assemble these by-products together. Beyond the significant time required to assemble the by-products, the part obtained has a significant number of weak points at the junctions of the by-products. In addition, in the case where a part made of composite material must be produced, this method does not allow for continuity of the fibers at the junctions of the by-products, which increases the weakness of these parts.

[0003] It is also known to use an inflatable bladder which, when inflated, forms the cavity during molding and allows simple demolding by deflating the bladder. These bladders are, however, complex and expensive to produce, and cannot withstand the pressures and temperatures required for thermocompression transformation of polymer or thermoplastic composite materials. In addition, to manufacture a part from a composite material, the fibers must first be positioned in the mold, which is sometimes complex or even impossible.

[0004] There are still elastic cores made from the assembly of pieces of calendered silicone and raw silicone in a loaf, which are then crosslinked in an oven or autoclave in half-molds. Such cores have a limited lifespan due to the fragility of the junctions and are not capable of withstanding high pressures and temperatures. In addition, the cores have reliefs at the junctions of the parts, which can leave traces on the parts produced or introduce differences in consolidation of the material to be transformed. Statement of the invention

[0005] There is a need to manufacture parts made of polymer material or composite materials comprising undercut cavities in a simple manner and which are of good mechanical and visual quality. Summary of the invention

[0006] The present invention meets this need thanks to, according to one of its aspects, a pressurizable molding core, to be inserted into a mold, comprising:

[0007] - a flexible outer envelope intended to be filled and / or pressurized internally earlier by a fluid;

[0008] - a frame extending inside the outer casing to hold it in a predefined shape at rest, compatible with its insertion and extraction from the mold.

[0009] The use of a flexible outer casing allows a change of shape during filling and / or pressurization, this shape being able to form the undercut cavity. In addition, after manufacturing the part and emptying and / or depressurizing the outer casing, the core can be removed from the part directly or by elastic deformation of the outer casing. The core extraction operation can therefore be carried out simply and in a single operation.

[0010] Furthermore, thanks to the fact that the frame holds the outer casing in a shape that facilitates handling of the core, in particular by an operator or a robot, and insertion of the core into the mold, the core according to the invention makes it possible to simplify the molding operation and makes it repeatable on a production line. Indeed, the outer casing has a certain rigidity before molding thanks to the frame and offers a shape at rest that is substantially identical between two successive moldings.

[0011] The resting shape and the reinforcement make it easier to functionalize the part to be molded by positioning, for example, reinforcing elements on the core, in particular fibers. In particular, the resting shape and the reinforcement make it possible to deposit a textile on the core to produce a part made of composite material.

[0012] The core is suitable for reuse. Frame

[0013] The frame may be metallic, ceramic, polymer or composite, preferably metallic.

[0014] The frame is preferably rigid.

[0015] Alternatively, the frame may comprise at least two portions hinged together. This makes it possible to give an additional degree of freedom to the core. Said at least two portions may be rigid.

[0016] The frame may comprise an assembly of profiles.

[0017] The frame may have dimensions compatible with its insertion into the outer casing. In particular, the frame has dimensions smaller than those of the outer casing.

[0018] The armature may comprise a material suitable for being heated by induction, for example steel, copper and / or carbon fibers.

[0019] The frame may include an internal conduit allowing the circulation of fluid. This may facilitate the filling and / or pressurization of the envelope. exterior during molding, especially when the space between the outer shell and the frame is small. Fluid distribution is then faster and more homogeneous.

[0020] Preferably, the internal conduit comprises at least one inlet and a plurality of outlets, which makes it possible to distribute the fluid more homogeneously in the casing. Outer casing

[0021] The outer casing may comprise at least one part in permanent contact with the frame, in particular when at rest.

[0022] The outer casing may comprise at least one retaining stop configured to retain the reinforcement in the outer casing, in particular when the core is present in the mold and / or during the deposition of a functional layer.

[0023] When the outer casing is at rest, the armature may be fixed relative to the outer casing, in particular by being axially blocked between the bottom of the casing and said at least one retaining stop.

[0024] Alternatively, when the outer casing is at rest, a non-zero clearance may be present between the armature and the outer casing. This clearance allows slight mobility of the armature in the outer casing, which may facilitate the insertion of the core into the mold by slight movements of the armature.

[0025] When the largest dimension of the outer envelope is less than 2 m, this clearance may be between 5 mm and 100 mm, in particular between 5 mm and 60 mm.

[0026] In particular, the clearance can be determined as a function of the shape of the outer envelope, in particular as a function of the presence, or absence, of undercuts.

[0027] The outer envelope may have a variable thickness chosen according to the pressure field that one wishes to exert on the material present between the core and the mold during molding.

[0028] Variations in the thickness of the outer casing can also make it possible to control, in a predefined manner, the deformation of the outer casing when put under pressure.

[0029] The thickness variations may be local, and occupy a proportion of the total external surface of the envelope, for example less than 50%, or even 30% or 10%.

[0030] The outer envelope may include a thinning which will increase its deformability and the counter-pressure exerted by the outer envelope on the material present between the core and the mold, which will locally limit the thickness and / or increase the density of material on the part at this level.

[0031] Conversely, a local thickening will locally reduce the deformability of the envelope and in particular reduce the counter-pressure exerted on the material present between the core and the mold by the outer envelope at the level of the thickening, which will locally increase the thickness and / or reduce the density of material on the room at this level.

[0032] The outer casing may have a thickness of between 0.1 mm and 200 mm.

[0033] When the largest dimension of the outer envelope is less than 2 m, the outer shell can have a thickness between 0.5 and 40 mm.

[0034] The outer envelope may have dimensions at least equal to, in particular greater in at least one direction, than those of the cavity defined by the part to be manufactured. In particular, the dimension of the outer envelope in the direction of the axis of the opening may be greater than that of the part to be manufactured along this axis.

[0035] The outer surface of the outer casing may be smooth.

[0036] Alternatively, the outer surface may include reliefs, for example with hollows and / or ribs. This may make it possible to modify the appearance of the manufactured part, for example for aesthetic or technical reasons to functionalize the part or even stiffen it in certain places.

[0037] For example, the outer surface of the outer casing may include a hollow to accommodate a foam. In this case, the local thickness at the hollow is advantageously increased to reduce the back pressure exerted on the material present between the core and the mold at the hollow and facilitate the expansion of the foam.

[0038] For example, the outer surface of the outer casing may include ribs allowing the evacuation of porosities and / or air trapped in the material to be thermocompressed by creating a preferential air circulation channel to a chosen zone, for example an orifice in the mold and / or a joint plane or other.

[0039] The outer casing may define a cavity to be pressurized, so as to apply greater counter-pressure during thermocompression.

[0040] The outer casing may include an opening for injecting the pressurizing fluid, opening in particular into this cavity.

[0041] The outer casing may comprise a collar around the injection opening, this collar having in particular a function of sealing and / or mechanical retention of the core in the mold so as to form a molding cavity. This cavity corresponds to the space between the outer casing and the mold.

[0042] The outer casing may comprise on an inner surface, at the opening, at least one axial rib, in particular a plurality of axial ribs, for example in a crenellated pattern. The use of at least one axial rib makes it possible to limit the risk of pinching of the opening which would prevent the filling and / or emptying of said cavity.

[0043] The outer casing may comprise an elastomer, in particular having a thermal resistance greater than 250°C, preferably chosen from elastomers, in particular thermoplastics or hot vulcanizable silicones.

[0044] The outer casing may include a suture at a release slot, used during the manufacture of the casing.

[0045] The outer casing may include a surface marking configured to produce an imprint on the part manufactured during molding. Such an imprint may be used to identify that the part was produced by a core according to the invention, or even a given core, for example identified by a number.

[0046] The core may comprise a single outer envelope.

[0047] The outer casing is advantageously a single piece, in particular manufactured by thermocompression. This facilitates handling of the core and improves its lifespan.

[0048] The outer casing may be formed from a single material, in particular a silicone. Facility

[0049] The invention also relates, according to another of its aspects, in combination with the above, to an installation for the manufacture by thermocompression of a part made of polymer material, comprising a core as defined above and a mold into which the core is inserted to define the thermocompression cavity. This mold comprises, for example, at least two mold parts assembled together.

[0050] The mold may include orifices allowing the escape of air contained in the material to be transformed, in particular due to the degassing of certain materials, and / or the densification and / or consolidation of the materials. Process for manufacturing a core

[0051] The invention also relates, according to another of its aspects, in combination with the above, to a method of manufacturing a core as defined above, comprising:

[0052] - the manufacture of the entire outer casing in a core mold in a single step, in particular thermocompression;

[0053] - inserting the frame into the outer casing after demolding.

[0054] The use of a single thermocompression step to manufacture the outer casing makes it possible both to limit production time and also to have a single-piece outer casing, which gives it significant mechanical strength.

[0055] In addition, the one-piece appearance of the outer casing makes it possible to manufacture a part which bears little or no marks related to the manufacture of the outer casing.

[0056] Finally, manufacturing by thermocompression allows for good material health, particularly homogeneous. Indeed, thermocompression allows for the use of a non-crosslinked polymer resin and for it to be completely crosslinked at the time of manufacturing. shape of the outer envelope.

[0057] The core thus manufactured, in particular due to the mechanical qualities of the outer envelope, can be used many times.

[0058] The material of the outer casing may be chosen from elastomers, in particular thermoplastics or hot-vulcanizable silicones.

[0059] The method may include demolding the outer casing through at least one slot made during molding on the outer casing or made before demolding by local cutting.

[0060] When the slot must be made before demolding by local cutting, the molding can form a surface relief on the outer casing, the local cutting being made according to the surface relief.

[0061] The shape of the ends of the slot can be configured to limit, or even prevent, the propagation of cracks.

[0062] The insertion of the frame can be carried out through this slot.

[0063] The method may comprise, after insertion of the reinforcement into the outer casing, a suture of the slot, in particular using a local addition of material, in particular a material identical to that used to manufacture the outer casing, in particular an elastomer, preferably a raw silicone vulcanized hot in an oven.

[0064] Alternatively, the armature is inserted through the opening in the outer casing. In this case, it is not necessary to provide a slot in the outer casing for this purpose.

[0065] Method of manufacturing a part by thermocompression

[0066] The invention also relates, according to another of its aspects, in combination with the above, to a method for manufacturing a part at least partially made of polymer material and comprising a cavity, in particular an undercut, the method comprising the following steps:

[0067] - inserting between the shells of a mold in the open state a core according to the invention, such as as previously defined;

[0068] - close the mold by bringing the shells together;

[0069] - consolidate the material between the mold wall and the core, the outer shell being filled and / or pressurized internally by a fluid during consolidation;

[0070] - polymerizing the polymer material so as to form the part;

[0071] - depressurize and / or empty, at least partially, the core;

[0072] - open the mold to demold the part from the mold, and remove the core of the part. The manufacturing the part using the core according to the invention is easy to implement thanks to the ease of insertion and extraction of the core. This allows reproducibility of the process, compatible with mass production, particularly at reasonable costs.

[0073] After depressurization of the core, the shape of the core may prevent its removal from the part cavity. In this case, the core may be removed from the part cavity by elastic deformation of the outer shell.

[0074] When the pressure (relative to atmospheric pressure) of the fluid in the outer casing during consolidation is low, for example less than 1 bar, or even zero, the opening step can be carried out before the depressurization and / or emptying step. Indeed, in such a case, the manufactured part will not be damaged by the force due to the pressure of the outer casing in the absence of counter-pressure from the mold.

[0075] Conversely, when the pressure of the fluid in the outer casing during consolidation is high, for example greater than 1 bar, the opening step is preferably carried out after the depressurization and / or emptying step. Indeed, in such a case, the manufactured part could be damaged otherwise by the pressure force of the outer casing.

[0076] The method may comprise, prior to inserting the core into the mold, a step of applying a functional layer to the core. This operation is facilitated by the fact that the core comprises a reinforcement, which limits the deformations of the outer envelope during its handling. The reinforcement also allows reproducibility of the application of the functional layer.

[0077] The functional layer may comprise reinforcing fibers, the manufactured part then comprising a composite formed by the polymer material and the reinforcing fibers.

[0078] The reinforcing fibers may be long fibers in particular in the form of a textile, for example a fabric or a knit.

[0079] The application of the functional layer comprising fibers can be done by filament winding, by draping or by threading a textile structure onto the core, preferably by threading a textile structure onto the core, in particular in the form of a sock.

[0080] The reinforcing fibers may be chosen from the group consisting of carbon fibers, glass fibers, aramid fibers, ceramic fibers, fibers of plant origin, in particular flax fibers, polymer fibers, and a combination thereof.

[0081] In one embodiment, the reinforcing fibers are made of several materials, in particular several polymeric materials. The reinforcing fibers may be made of self-reinforced polypropylene (SrPP).

[0082] The functional layer may comprise a functionalization accessory chosen from the group consisting of small parts, for example metallic or polymer, optical fibers or electronic elements, such as sensors and / or LEDs.

[0083] Before the consolidation step, the method may include an application step of at least one layer of the polymer material in the mold.

[0084] Alternatively or additionally, the functional layer applied to the core may comprise at least one part made of polymer material.

[0085] During consolidation, the relative pressure inside the envelope can be between 0 and 25 bars, better between 2 and 25 bars, in particular between 10 and 20 bars.

[0086] During consolidation, the mold and / or the polymer material may be heated, in particular to a temperature above 200°C.

[0087] The polymer material may be thermoplastic or thermosetting.

[0088] The thermoplastic polymer material may be selected from the group consisting of polyamide (PA), polyethylene (PE), polypropylene (PP), polyetherimide (PEI), polyethylene terephthalate (PET), thermoplastic polyurethane (TPU) and mixtures thereof.

[0089] When the outer casing comprises a material having a thermal resistance greater than 380°C, the thermoplastic polymer material may further be chosen from the group consisting of polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyterephthalate and mixtures thereof.

[0090] The thermosetting polymer material may be selected from the group consisting of polyepoxide, vinylester (VE), crosslinked polyurethane (PUR), unsaturated polyester (UP), and mixtures thereof. Brief description of the drawings

[0091] The invention may be better understood by reading the detailed description which follows, non-limiting examples of its implementation, and by examining the attached drawing, in which

[0092] [Fig.l] illustrates, in longitudinal section, schematically, an example of a core according to the invention,

[0093] [Fig.2] illustrates, in perspective, partially, a part of the core of [Fig.l],

[0094] [Fig.3] illustrates, in longitudinal section, schematically, a stage of a example of a method of manufacturing a core according to the invention,

[0095] [Fig.4] illustrates, in a bottom view, schematically, a step in the method of manufacturing a core according to the invention,

[0096] [Fig.5] illustrates, in longitudinal section, schematically, a step of depositing a functional layer of an example of a method of manufacturing a part according to the invention,

[0097] [Fig.6] illustrates, in longitudinal section, schematically, a step of inserting a core into a mold of an example of a method of manufacturing a part according to the invention,

[0098] [Fig.7] is an enlargement showing detail VII of [Fig.6] after closing the mold,

[0099] [Fig.8] is an enlargement showing detail VIII of [Fig.6],

[0100] [Fig.9] is a view similar to [Fig.6] in which the mold is closed and the core is pressurized,

[0101] [Fig. 10] illustrates, in longitudinal section, schematically, a step of extracting a part from an example of a method of manufacturing a part according to the invention,

[0102] [Fig. 11] illustrates, in longitudinal section, schematically, another example of a method of manufacturing a part according to the invention,

[0103] [Fig. 12] illustrates, in longitudinal section, schematically, another example of core according to the invention,

[0104] [Fig. 13] illustrates, in longitudinal section, schematically, another example of core according to the invention,

[0105] [Fig. 14] illustrates, in longitudinal section, schematically, another example of core according to the invention, and

[0106] [Fig. 15] illustrates, in longitudinal section, schematically, another example core according to the invention. Detailed description

[0107] In the remainder of the description, elements that are identical or have identical functions bear the same reference sign. For the sake of brevity in this description, they are not described with reference to each of the figures, only the differences between the embodiments being described.

[0108] In the figures, the actual proportions have not always been respected, for the sake of clarity.

[0109] Figures 1 and 2 illustrate an example of a core 1 to be inserted into a thermocompression molding mold according to the invention.

[0110] The core 1 comprises an outer envelope 2, intended to be filled and / or pressurized internally by a pressurizing fluid, for example a gas, in which an armature 3 extends.

[0111] The outer casing 2 is for example made of silicone.

[0112] The outer casing 2 forms an inner cavity 5 configured to receive the pressurizing fluid and comprising an opening 4.

[0113] As illustrated in [Fig.2], the opening 4 may have, in cross section, a substantially rectangular section.

[0114] The thickness of the outer envelope 2 can be variable.

[0115] For example, the outer envelope 2 comprises lateral thicknesses 10 of thickness el at least twice greater than the thickness e bordering the thickening 10.

[0116] The outer envelope 2 also comprises a local thickening 11 on a base of maximum thickness e2 at least twice greater than the thickness bordering the thickening 11.

[0117] The frame 3, which is metallic in this example, maintains the outer casing 2 in a predefined shape at rest. In this example, at rest, the outer casing 2 has an elongated shape along an axis Z.

[0118] The frame 3 is for example formed from different assembled profiles, giving the assembly a general shape tapering towards the end 16 where the opening 4 opens.

[0119] The frame 3, as illustrated, is in contact with the bottom 11 when the outer casing 2 is at rest. The part of the frame 3 in contact with the shoulder 11 may be flat.

[0120] The frame 3 may also be in contact at its end 16 facing the opening 4 with retaining stops in the form of internal ribs 15 arranged at the opening 4, as illustrated in FIGS. 1 and 2.

[0121] In this example, the outer envelope 2 comprises several ribs 15 arranged on two large opposite faces 30. Each large face 30 may comprise three ribs 15 facing each other as visible in [Fig.2].

[0122] The large faces 30 are connected to each other by small faces 31 which may be devoid of ribs.

[0123] Each rib 15 has a flank at its end opposite the opening 4 which can define a shoulder 17, extending in a plane substantially perpendicular to the axis Z. The internal face 18 of each rib 15, facing the axis Z, can be inclined radially outwards in the direction of the opening 4.

[0124] The frame 3 may comprise projections 19 resting on the shoulders 17 and a central part 20 spaced from the projections 19 and connected to them, the central part 20 coming into contact with the internal faces 18 of the ribs 15 near the shoulders 17.

[0125] Thus, the armature 3 is axially blocked between the bottom 11 and the ribs 15 when the outer casing 2 is at rest.

[0126] The outer casing 2 also comprises, around the opening 4, a collar 25, the function of which will be described later.

[0127] The collar 25 defines a shoulder 26, extending substantially perpendicularly relative to the outer casing 2, and an inclined flank 27 extends obliquely relative to the shoulder 26.

[0128] The outer casing 2 may also include a suture 35, for example at the level of the bottom 11, which coincides with a demolding slot.

[0129] The core 1 can be manufactured according to the method described below and illustrated in Figures 3 and 4.

[0130] In a first step, illustrated in [Fig.3], the outer casing 2 is manufactured by thermocompression, for example of a silicone resin, in a mold 40.

[0131] The mold 40 comprises two shells 41 and 42 forming between them a cavity 43 and a rigid core 45, held between the shells 41 and 42 by tabs 46.

[0132] The legs 46 allow good positioning of the core 45 between the shells 41 and 42.

[0133] Then, the material is thermocompressed between the shells 41 and 42 and the core 45 to form the outer envelope 2.

[0134] After polymerization, the mold 40 is opened and the outer casing 2, in which the core 45 is located, is extracted.

[0135] The core 45 is then removed from the outer casing 2 through a demolding slot 47, such as for example that illustrated in view a) of [Fig.4], if necessary by elastically deforming the outer casing 2.

[0136] The slot 47 may be formed during molding by one of the legs 46 of the core 45.

[0137] The slot 47 can extend rectilinearly in a direction F over a length Lf greater than 50% of the width L of the outer envelope 2.

[0138] The slot 47 may have round holes at its ends 50 limiting the propagation of cracks.

[0139] After extracting the core 45, an armature 3 is inserted into the outer casing 2, by introducing it through the slot 47.

[0140] The slot 47 is then sutured by an addition of material, which may be identical to the material used elsewhere to form the envelope. Thus, the outer envelope 2 is a single piece and has few traces of manufacturing.

[0141] Alternatively, when the shape of the outer casing allows it, the core 45 is extracted from the outer casing 2 through the opening 4 of the outer casing 2, no slot being produced by the mold.

[0142] As a further variant, as illustrated in view b) of [Fig.4], the molding can form a surface relief 471 on the outer casing 2 making it possible to indicate where to make the local cut to form the slot 47.

[0143] The relief 471 can extend in a rectilinear manner over a length Lfl greater than 50% of the width L of the outer envelope 2.

[0144] An example of a method for manufacturing a part P made of polymer material comprising an undercut cavity according to the invention is illustrated in Figures 5 to 10.

[0145] In a first step, illustrated in [Fig.5], a functional layer 60, for example in the form of a sock, is threaded onto core 1.

[0146] In this example, the functional layer 60 comprises a fabric of long carbon fibers. The threading operation is easily carried out by an operator, or even a robot, thanks to the frame 3 which holds the outer casing 2 and limits its deformations.

[0147] In this example, the functional layer 60 is threaded through the bottom 11 of the core 1, that is to say the part opposite the opening 4.

[0148] In a second step, illustrated in Figures 6 to 8, the core 1 is placed in a mold 61.

[0149] The mold 61 comprises a first shell 62 and a second shell 63 which form between them, when the mold 61 is closed, a cavity 64 allowing the core 1 to be received.

[0150] The cavity 64 has an opening 65, intended to receive the end of the core 1 comprising the opening 4. When the mold 61 is closed, the opening 65 is closed by a plug 68, as illustrated in the enlargement of [Fig.7].

[0151] The opening 65 can open into the bottom of a counterbore 66 against which the shoulder of the collar 25 can come to bear.

[0152] The plug 68, when mounted on the mold 61, can press on the end of the outer casing by a wall 67, and can comprise a hollow beak 69 which penetrates into the opening 4 to come into contact with the frame 3.

[0153] Thus, the plug 68 makes it possible to block the core 1 in the mold 61 and to ensure the sealing of the cavity 64.

[0154] As illustrated in [Fig.6], a layer 58 of polymeric, thermoplastic or thermosetting material is positioned in the cavity 64. The material is for example a hot-vulcanizable silicone.

[0155] The walls 70 opposite the shells 62 and 63 may have a recess 71 delimiting along the Z axis a first volume VI and a second volume V2, as illustrated in the enlargement of [Fig.8].

[0156] The first volume VI extends between the recess 71 and the opening 65.

[0157] The second volume V2 occupies the remaining volume of the cavity 64.

[0158] The recess 71 makes it possible to close the space intended for thermocompression, and thus to delimit the molding zone corresponding to the second volume V2. The zone corresponding to the volume V1 is not intended to receive the material to be molded but to allow support against the mold 61 of the core 1 during thermocompression.

[0159] Then, in a new step illustrated in [Fig.9], the outer casing 2 is pressurized using a fluid injected through an orifice 75 in the spout 69. This pressurization makes it possible to inflate the outer casing 2 and to deform it into a predefined molding shape.

[0160] As illustrated in this figure, the pressurization of the envelope can cause a break in contact between the frame 3 and the thickened bottom 11 of the outer envelope 2.

[0161] The polymer material 58 is then thermocompressed in the cavity 4 between the walls 70 and the outer envelope 2 in the second volume V2.

[0162] Thanks to the thickenings 10 and 11, the consolidation pressure field which is applied to the material can be controlled to obtain the desired geometric characteristics for the part.

[0163] During thermocompression, the fibers of the functional layer 60 are also impregnated.

[0164] The polymer is then consolidated and polymerized, for example by heat transmitted by the mold 61.

[0165] Once the part P is consolidated, as illustrated in [Fig.10], the core 1 is depressurized and then the mold 61 is opened.

[0166] Part P has an undercut cavity 76.

[0167] The shape of the core, in the example illustrated, is such that once depressurized, it can be removed from the cavity 76 of the part obtained without elastic deformation of the outer casing 2.

[0168] The part P produced is a part made of composite material comprising reinforcing fibers from the functional layer 60, and a polymer matrix.

[0169] Of course, the invention is not limited to the example which has just been described.

[0170] The outer casing 2 may have a different shape at rest, for example spherical, ovoid, parallelepiped, generally U-shaped or L-shaped in longitudinal section, or a combination of these.

[0171] During the manufacture of the part P, the core 1 can be removed from the cavity 76 by elastic deformation of the outer casing 2, as illustrated in [Fig. 11].

[0172] In the left part a) of [Fig.l 1], the core 1 is pressurized. In the middle part b) of this figure, the core 1 is depressurized but still present in the part P. In the right part c), the core 1 is being extracted from the cavity 76 of the part P with elastic deformation of the outer casing 2.

[0173] In the variant illustrated in [Fig. 12], the outer envelope 2 has a constant thickness e, except at the level of three local thinnings 100 whose thickness Ea is less than 50% of the thickness e.

[0174] When molding with core 1 of [Fig.12], the consolidation pressure exerted on the material between the mold and core 1 will be greater at the local thinnings 100, than on the rest of core 1.

[0175] Furthermore, still on the core 1 illustrated in [Fig. 12], a clearance J is present between the bottom 101 and the frame 3. This clearance is for example less than 10 mm.

[0176] In the variant illustrated in [Fig. 13], the outer casing 2 has hollows 110, configured to house a polymer foam.

[0177] The local thickness Ec at the level of the hollows 110 is greater than the thickness e outside the hollows 110, in order to reduce the back pressure at the level of the hollows 110 during molding and to facilitate the development of the polymer foam there.

[0178] The outer casing 2 also comprises a marking 115, for example in the form of a relief such as a mark and / or an identification code. This marking 115 makes it possible to form an imprint in the manufactured part, for example to authenticate it.

[0179] In the variant illustrated in [Fig. 14], the outer casing 2 has a tapered shape extending along a longitudinal axis Y. The frame 3 also has a tapered shape extending along this axis.

[0180] The space Es between the frame 3 and the outer casing 2 is small here, for example less than 5 mm.

[0181] To facilitate the filling and / or pressurization of the outer casing 2, the frame 3 comprises an internal conduit 119 comprising a fluid inlet 120 and a plurality of outlets 125 distributed homogeneously along the frame 3.

[0182] In the variant illustrated in [Fig. 15], the frame 2 comprises two portions 150 connected to each other by an articulation 150. This makes it possible to give an additional degree of freedom to the core 2. The two portions 150 can be rigid.

[0183] The articulation 150 may be a ball joint, possibly a finger joint or a pivot.

Claims

Claims

1. Pressurizable molding core (1), to be inserted into a mold (61), comprising: - a flexible outer casing (2) intended to be filled and / or pressurized internally by a fluid; - a frame (3) extending inside the outer casing (2) to maintain it in a predefined shape at rest, compatible with its insertion and extraction from the mold (61).

2. Core (1) according to claim 1, in which the outer casing (2) comprises at least one part in permanent contact with the armature (3).

3. Core (1) according to one of the preceding claims, the outer casing (2) comprising at least one retaining stop (15) configured to retain the reinforcement (3) in the outer casing (2), in particular when the core (1) is present in the mold (61) and / or during the deposition of a functional layer.

4. Core (1) according to the preceding claim, in which, when the outer casing (2) is at rest, the armature (3) is fixed relative to the outer casing (2), in particular by being axially blocked between the bottom of the outer casing (2) and said at least one retaining stop (15).

5. Core (1) according to one of claims 1 and 2, in which, when the outer casing (2) is at rest, a non-zero clearance (J) is present between the armature (3) and the outer casing (2).

6. Core (1) according to any one of the preceding claims, in which the outer envelope (2) has a variable thickness (e; el; e2; Ea; Ec) chosen as a function of the pressure field that one wishes to exert on the material present between the core and the mold during molding.

7. Core (1) according to any one of the preceding claims, in which the outer casing (2) comprises an opening (4) for injecting the pressurizing fluid, the outer casing (2) comprising a collar (25) around the injection opening (4), this collar (25) having in particular a function of sealing and / or mechanical retention of the core (1) in the mold (61) so as to form a molding cavity.

8. Core (1) according to the preceding claim, in which the envelope outer (2) comprises on an inner surface, at the level of the opening (4), at least one axial rib (15).

9. Core (1) according to any one of the preceding claims, wherein the outer surface of the outer casing (2) comprises reliefs.

10. Core (1) according to any one of the preceding claims, in which the outer envelope (2) comprises an elastomer, having in particular a thermal resistance greater than 250°C, preferably chosen from elastomers, in particular thermoplastics or hot-vulcanizable silicones.

11. Core (1) according to any one of the preceding claims, comprising a single outer casing (2) in one piece, in particular manufactured by thermocompression.

12. Core (1) according to any one of the preceding claims, in which the frame (3) comprises an internal conduit (119) allowing the circulation of fluid comprising at least one inlet (120) and a plurality of outlets (125).

13. A core (1) according to any preceding claim, wherein the outer shell (2) comprises a surface marking (115) configured to produce an imprint on the manufactured part during molding.

14. Core (1) according to any one of the preceding claims, in which the frame (2) comprises at least two portions (150) articulated together.

15. A method of manufacturing a core (1) according to any one of the preceding claims comprising: - manufacturing the entire outer casing (2) in a core mold (40) in a single thermocompression step; - inserting the armature (3) into the outer casing (2) after demolding.

16. Method according to the preceding claim, the material of the outer casing (2) being chosen from elastomers, in particular thermoplastics or hot vulcanizable silicones.

17. Method according to claim 15 or 16, comprising the demolding of the outer casing (2) from the core mold (40) through at least one slot (47), in particular made during molding on the outer casing (2) or made before demolding by local cutting.

18. A method according to the preceding claim, wherein when the slit (47) must be carried out before demolding by local cutting, the molding forms a surface relief (471) on the outer casing (2), the local cutting being carried out according to the surface relief (471).

19. Method according to one of claims 16 to 18, in which the insertion of the armature (3) is carried out through this slot (47).

20. Method according to the preceding claim, comprising, after insertion of the reinforcement into the outer casing (2), a suture of the slot (47), in particular using a local addition of material, in particular an elastomer, preferably a raw silicone vulcanized hot in an oven.

21. Method according to claim 15, the outer casing (2) comprising an opening (4) for injecting the pressurizing fluid, the armature (3) being inserted through the opening (4) of the outer casing (2).

22. Method for manufacturing a part (P) at least partially made of polymer material comprising a cavity (76), in particular an undercut, the method comprising the following steps: - inserting between the shells (62; 63) of a mold (61) in the open state a core (1) according to any one of claims 1 to 14; - closing the mold (61) by bringing the shells (62; 63) together; - consolidating the material between the wall (70) of the mold (61) and the core (1), the outer casing (2) being filled and / or pressurized internally by a fluid during consolidation; - polymerizing the polymer material so as to form the part; - depressurizing and / or emptying, at least partially, the core (1); - opening the mold (61) to demold the part (P) from the mold (61), and removing the core (1) from the part (P).

23. Method according to the preceding claim, comprising, prior to the insertion of the core (1) into the mold (61), a step of applying a functional layer (60) on the core (1).

24. Method according to the preceding claim, in which the functional layer (60) comprises reinforcing fibers, the manufactured part (P) then comprising a composite formed by the polymer material and the reinforcing fibers, in which the reinforcing fibers are long fibers in particular in the form of a textile.

25. Method according to the preceding claim, in which the application of the functional layer (60) comprising fibers is carried out by filament winding, by draping or by threading a textile structure on the core (1), preferably by threading a textile structure onto the core (1), in particular in the form of a sock.

26. A method according to any one of claims 22 to 25, wherein, before the consolidation step, the method comprises a step of applying a layer (58) of the polymer material in the mold (61).

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