Tool for moulding rotationally symmetrical parts with circumferential compacting from the inner face of a preform

Abstract

The invention relates to a mould (10) comprising a base (30), an annular belt (40), a cover and a core (50) comprising a central shim (60) and a set of removable guide shims (70) and closure shims (80) each forming a sector of an annular disc. The central shim (60) has an inclined outer radial face that flares downwards and the removable shims each have an inclined ramp that matches the shape of the inclined face and is intended to bear against the latter. A preform (20) is compacted between the outer radial face of the removable shims (30, 40) and the inner radial face of the belt. The core (50) comprises n guide shims (70) and n closure shims (80), with n ≥ 2, each closure shim (80) being located between two closure guide shims (80). The mould also comprises a device for radially immobilising the removable shims.

Description

[0001]Tooling for molding revolution parts with circumferential compaction from the internal face of a preform TECHNICAL FIELD OF THE INVENTION The technical field of the invention is that of molding revolution parts in composite material by resin transfer. The present invention relates to a tooling for molding such parts and comprising a base, a cover and a set of shims coming into compacting support on a preform positioned inside a belt and intended to be impregnated with resin. TECHNOLOGICAL BACKGROUND OF THE INVENTION For resin transfer molding, it is known to use a mold comprising a central core and a peripheral belt positioned on a base. When the mold is closed by a cover,the belt and the core delimit a hollow molding volume in which a preform can be impregnated with resin. The preform is usually formed of fibers and needs to be compacted before resin injection. When molding revolution parts, circumferential compaction of the preform can be carried out from its internal face. In this case, the core is usually composed of several shims which are placed against each other by sliding them radially and horizontally in the plane of the base, compacting the preform locally each time. When a shim is thus placed, it comes into contact with the preform before being in contact with the adjacent shim(s), which can cause the preform to be pinched between the shims and / or the shims to fold or crease the preform. Before injecting the resin into the mold, however, it is necessary to ensure that the preform is neither creased nor folded,nor jammed by the shims. There is therefore a need for a mold capable of carrying out circumferential compaction from the internal face of a preform and which is not likely to cause pinching of the preform while also ensuring that the preform is neither creased nor folded by the shims. SUMMARY OF THE INVENTION The invention offers a solution to the problems mentioned above, by providing a mold comprising two types of shim to be placed in a defined order so that when a shim is placed between two others,it first comes into contact with these before coming to bear on the preform. These shims are put in place radially for radial compaction from the inside to the outside. They can also be put in place at an angle from the top of the mold for radial compaction from the inside to the outside and axial compaction from the top to the bottom. One aspect of the invention relates to a mold for producing a part of revolution of axis Y-Y' by molding, comprising a base extending along a main plane P perpendicular to the axis Y-Y', an annular-shaped belt extending along a plane parallel to the plane P, a core and a cover extending along a plane parallel to the plane P,said mold being such that: - the core comprises a central wedge and a set of guide wedges and removable closing wedges each forming a sector of an annular disc on the Y-Y' axis; - the guide wedges and the closing wedges each have two lateral faces provided at the interface located between an adjacent guide wedge and closing wedge; - the central wedge has a lower face, and an inclined external radial face which widens towards the lower face; - the guide wedges and the closing wedges each have an inclined ramp of a shape complementary to the inclined external radial face; and - the core comprises n removable guide wedges and n removable closing wedges, with n ≥ 2. A first holding and compacting of the preform is advantageously carried out by the installation of the guide wedges, which make it possible to prevent the preform from being creased or folded. Then,the placement of the closing wedges between two guide wedges, with a radial movement outwards possibly combined with a vertical movement from top to bottom, makes it possible to finalize the holding and the circumferential compaction of the preform. The sliding of the lateral faces of the closing wedges along the lateral faces of the adjacent guide wedges advantageously makes it possible to guide the placement of the closing wedges and to finalize the compaction of the preform without the latter being pinched between the wedges. The mold according to the invention thus allows complete forming of the preform, by circumferential compaction from its internal face, without pinching it. Furthermore, the increase in the number of wedges provides two technical advantages, namely better management of the expansion, because the more n increases, the more the risk of wrinkling of the fibers of the preform decreases, and easier handling of the wedges,each being lighter. The cost of the tooling and the implementation time increasing with n, we therefore optimize n by seeking a certain balance taking these positive and negative points into account. According to one aspect of the invention, in the closed position of the mold, the belt is supported on the base, the core is centered on the Y-Y' axis, the cover is supported on the belt and on the core, each closing wedge is located between two guide wedges, and the inclined ramp of the guide wedges as well as the inclined ramp of the closing wedges are supported against the inclined external radial face of the central wedge. According to another aspect of the invention, the mold comprises a device for radially immobilizing the guide wedges and the closing wedges. This radial immobilizing device prevents the axial displacement of said removable wedges, in particular outwards. According to an additional aspect of the invention,the radial immobilization device comprises an annular guide structure provided on an upper face of the central wedge and shaped with a complementary shape provided on a lower face of each of the guide wedges and the closing wedges. This type of radial immobilization device makes it possible in particular to index the radial position of the wedges, while allowing their introduction from above in an inclined manner. According to another aspect of the invention, the guide structure has a triangular-shaped section. Such a shape makes it possible in particular to gradually guide the wedges during their installation to their final molding position. According to an additional aspect of the invention, in a plane parallel to the plane P, the two lateral faces of the closing wedges diverge by an angle α relative to the axis Y-Y',α being between 0° and 5° and preferably substantially equal to 4°. The presence of the angle α makes it possible to ensure permanent contact between the guide wedges and the removable closing wedges during their movement. During this movement, the cover pushes the removable closing wedges, which in turn push the removable guide wedges. Thus, during the compaction of the preform by the guide wedges then the closing wedges, the fibers of the preform do not have the possibility of becoming wedged between two adjacent wedges. According to one aspect of the invention, in a plane perpendicular to the plane P, the two lateral faces of the closing wedges converge at an angle β towards a lower face of the closing wedges,β being between 5° and 10° and preferably substantially equal to 8°. Such an angle facilitates the introduction of the closing wedges between two guide wedges for the vertical component of their movement. This angle β is only necessary when axial compaction of the preform is desired at the same time as radial compaction. According to another aspect of the invention, the inclined external radial face of the central wedge is circular, which in particular makes it possible to freely position and move the guide wedges around the central wedge. According to an additional aspect of the invention, in the closed position of the mold, the lateral faces of the closing wedges are parallel to the lateral faces of the guide wedges, which in particular provides a satisfactory seal between two adjacent wedges. According to one aspect of the invention, the lateral faces of the guide and closing wedges are flat,which simplifies in particular their design and their installation. According to another aspect of the invention, the guide wedges are identical to each other and the closing wedges are identical to each other, which makes it possible in particular to reduce the manufacturing costs of the two types of wedges and to make them interchangeable. Another aspect of the invention relates to a molding method for producing a part of revolution in composite material by impregnating a preform with resin and using a mold as described above,which method comprises the following steps: - placing the base and the central wedge; - placing the preform; - placing the belt and compacting the preform by an internal radial face; - placing the guide wedges by sliding the inclined ramp of the guide wedges against the inclined external radial face of the central wedge and compacting the preform between the guide wedges and the belt; - placing the closing wedges by sliding the inclined ramp of the closing wedges against the inclined external radial face of the central wedge, each closing wedge being located between two adjacent guide wedges, and compacting the preform between the closing wedges and the belt; - placing the cover on the belt and the central core,the belt and the core delimiting a hollow molding volume; - injection of resin in liquid form into the hollow molding volume. The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES The figures are presented for information purposes only and in no way limit the invention. [Fig. 1] is a perspective view of a preform and a central wedge placed on a base of a mold according to an exemplary embodiment of the invention. [Fig. 2] is a view similar to [Fig. 1], where the mold guide wedges are placed. [Fig. 3] is a view similar to [Fig. 1],where the mold closing wedges are put in place. [Fig. 4] is a partial vertical sectional view illustrating the placement of a belt on a base equipped with a preform and a central wedge of a mold according to an exemplary embodiment of the invention. [Fig. 5] is a view illustrating the placement of a mold guide wedge on the elements of [Fig.4]. [Fig. 6] is a partial vertical sectional view of a complete mold according to an exemplary embodiment of the invention in the closed molding position. [Fig.7] is a view illustrating the placement of a closing wedge on the elements of [Fig.4]. [Fig.8] is a top view of a closing wedge of a mold according to an exemplary embodiment of the invention. [Fig. 9] is a view of the external radial face of the closing wedge of [Fig.8]. DETAILED DESCRIPTION Unless otherwise specified, the same element appearing in different figures has a single reference. By convention, in this application,when referring to the mold according to the invention, by upper, lower, above and below we refer to the mold as shown in the drawings. Similarly, by vertical we refer to a direction along an axis extending perpendicularly to the main plane in which the base of the mold extends. In the figures, the Y-Y' axis is vertical. Finally, by inside we refer to a direction directed towards the center of the mold, by outside we refer to an opposite direction. Similarly, by the expression "closed position of the mold", we mean a configuration of a mold where all the removable parts are assembled in a sealed manner around the preform, said mold being ready to receive an injection of liquid resin. The mold 10 according to the invention makes it possible to produce a part of revolution with the Y-Y' axis in composite material by impregnating a preform 20 with resin. The preform 20 shown in [Fig. 4] to [Fig. 7], sometimes also referred to as a reinforcement,usually comprises a fibrous structure, the fibers of which may be pre-impregnated. As shown in [Fig.4] to [Fig.7], the mold 10 comprises a base 30, a belt 40, a core 50 and a cover 90. In the closed position of the mold 10, the belt 40 rests on the base 30, the core 50 is centered on the axis Y-Y', and the cover 90 rests on the belt 40 and on the core 50. All these elements are preferably rigid. They are preferably made of steel, but the choice of manufacturing material depends in particular on the expected geometric precision, the coefficient of friction between the shims 70, 80 with respect to the angles α and β to allow the movement of said shims, the conditions of transformation of the injected resin (temperature, pressure, sealing,etc.) and the expected lifetime of the mold. The base 30 extends along a main plane P perpendicular to the axis Y-Y' (see [Fig. 1] to [Fig. 3]). It serves in particular as a support for the other elements of the mold 10 and closes the lower part of the mold 10. It is preferably in the form of a substantially flat disc having a lower face 38 and an upper face 39. The belt 40 is annular in shape and extends along a plane parallel to the plane P. It has a lower face 48, an upper face 49, an external radial face 44 and a circular internal radial face 45 intended to come into compacting support against the preform 20 (see [Fig.4] to [Fig.7]). The belt 40 may be in several parts, for example in three sectors of 120° to facilitate demolding. The core 50 is characterized in that it comprises several different shims 60, 70, 80. These shims 60, 70, 80 are preferably single-piece,as shown in [Fig.1] to [Fig.3], but they can also be in several parts. The cover 90 extends along a plane parallel to the main plane P and serves in particular to close the upper part of the mold 10. It is preferably in the form of a substantially flat disc having a lower face 98 and an upper face 99. The core 50 comprises a central wedge 60 and a set of removable wedges comprising at least two removable guide wedges 70 and two removable closing wedges 80. The core 50 comprises as many guide wedges 70 as closing wedges 80 (see [Fig.3]). The central wedge 60 has a lower face 68, an upper face 69 and an inclined external radial face 65, forming a sliding ramp,which flares radially outwards towards the lower face 68. The inclined external radial face 65 of the central wedge 60 is preferably circular (see [Fig. 4] to [Fig. 7]). The central wedge 60 is preferably removable. Its centering can be achieved in different ways, all very conventional. In [Fig. 4] to [Fig. 7], the complementary shape of the central wedge 60 with the base 30 ensures its centering. The guide wedges 70 are preferably identical to each other and the closing wedges 80 are preferably identical to each other. The guide wedges 70 and closing wedges 80 each form a sector of an annular disc. When they are assembled against each other,the guide 70 and closing 80 wedges form an annular disc centered on the axis Y-Y', the circular external radial face 110 of which is intended to come into compacting support against the preform 20 (see [Fig. 1] to [Fig. 3]). The guide 70 and closing 80 wedges each have a lower face 78, 88, an upper face 79, 89 and two lateral faces 71, 72, 81, 82, preferably flat and provided at the interface located between two adjacent removable wedges 70, 80. In the closed position of the mold 10, each closing wedge 80 is located between two guide wedges 70 and the guide 70 and closing 80 wedges together form the aforementioned annular disc. Within this disc, each lateral face 71, 72 of a guide wedge 70 is in contact against a lateral face 82, 81 of a closing wedge 80 and preferably parallel to the latter. The surface of each removable wedge 70,80 in contact with the preform preferably covers a substantially identical sector, for example approximately 45° in the case of four guide wedges 70 and four closing wedges 80. The guide wedges 70 and closing wedges 80 each have an inclined ramp 75, 85 of a shape complementary to the inclined external radial face 65 and designed to slide and bear against it when they are placed in the mold 10 (see [Fig. 5] and [Fig. 7]). This inclined 75, 85 is preferably provided on the lower face 78, 88 of the guide 70 and closing 80 wedges, at the level of their internal radial face 74, 84. As can be seen in [Fig.8], considered in a plane parallel to the plane P, the two lateral faces 81, 82 of the closing wedges 80 diverge by an angle α relative to the axis Y-Y',α being between 0° and 5° and preferably substantially equal to 4°. This angle α meets the “radial” compacting requirement. As can be seen in [Fig. 9], considered in a plane perpendicular to the plane P, the two lateral faces 81, 82 of the closing wedges 80 converge at an angle β towards a lower face 88 of the closing wedges 80, β being between 5° and 10° and preferably substantially equal to 8°. This angle β meets the “axial” compacting requirement. The mold 10 further comprises a radial immobilization device 120 for the removable wedges 70, 80 intended to prevent axial displacement of the removable wedges 70, 80, in particular outwards (see [Fig. 1] to [Fig. 3]). According to a preferred embodiment shown in [Fig. 1] to [Fig. 7], the radial immobilization device 120 comprises an annular guide structure 127, in relief or in hollow,provided on the upper face 69 of the central wedge 60 and cooperating with a complementary shape 77, 87, respectively hollow or raised, provided on the lower face 78, 88 of each of the guide wedges 70 and closing wedges 80 (see [Fig.4]). The guide structure 127 preferably has a triangular-shaped section. In the figures, the guide structure 127 is in relief while the complementary shape 77, 87 of each removable wedge 70, 80 is hollow. The reverse is possible. The shape of the external radial face 110 of the annular disc formed by the guide wedges 70 and closing wedges 80 defines at least partially the internal shape of the revolution part to be produced, while the shape of the internal radial face 45 of the belt 40 defines the external shape of the revolution part made of composite material obtained. The latter can for example be cylindrical, conical, truncated, barrel-shaped or half-barrel-shaped,but must have at least one open upper or lower face to allow its extraction from the core 50. The belt 40 is preferably a single piece in the case where the external shape of the part to be molded includes a strong draft. In the case where the external shape of the part to be molded is more complex, in particular by the presence of undercuts, the belt 40 is preferably in several parts. It then comprises: an external belt, completed with one or more shims. The part to be molded can for example be any part having a shape of revolution and requiring geometric control on its internal and external faces,such as found in or around a turbomachine. A preferred example of producing a composite material revolution part by impregnating a preform 20 with resin and using a mold 10 according to the invention comprises the following steps: - positioning the base 30 and the central wedge 60; - positioning the preform 20; - positioning the belt 40 and compacting the preform 20 by the internal radial face 45; - positioning the guide wedges 70 by sliding the inclined ramp 75 of the guide wedges 70 against the inclined external radial face 65 of the central wedge 60 and compacting the preform 20 between the guide wedges 70 and the belt 40; - installation of the closing wedges 80 by sliding the inclined ramp 85 of the closing wedges 80 against the inclined external radial face 65 of the central wedge 60, each closing wedge 80 being located between two adjacent guide wedges 70,and compacting the preform 20 between the closing wedges 80 and the belt 40; - placing the cover 90 on the belt 40 and the central core 50, the belt 40 and the core 50 delimiting a hollow molding volume 100; - injecting resin in liquid form into the hollow molding volume The belt 40 is preferably placed before the removable wedges 70, 80 because it serves as a guide for them in its upper part. The tangential contact between the belt 40 and the removable wedges 70, 80 prevents the pinching of fibers between these parts. Depending on their mass and the production rate to be maintained, the removable wedges 70, 80 can be placed manually or by means of a lifting device. After curing the resin, for example by polymerization, heating and / or cooling, and removal of the cover 90, the removable shims 70, 80, and the belt 40,the composite material part can be removed from the mold 10. In [Fig.4] to [Fig.7] illustrating different stages of the molding, the presence of an optional, preferably annular, internal shaping wedge 130 will be noted, which can be positioned inside the mold 10, for example on the base 30 and preferably between the central wedge 60 and the belt 40, and on which the preform 20 is positioned so that the external face 134 of the internal wedge 130 gives its internal shape to the composite material part during molding. This internal wedge 130 can be in one piece or in several parts.,

Claims

CLAIMS

1. Mold (10) for producing a part of revolution of axis (Y-Y') by molding, comprising a base (30) extending along a main plane P perpendicular to the axis (Y-Y'), a belt (40) of annular shape extending along a plane parallel to the plane P, a core (50) and a cover (90) extending along a plane parallel to the plane P, said mold (10) being characterized in that: - the core (50) comprises a central wedge (60) and a set of removable guide wedges (70) and closing wedges (80) each forming a sector of an annular disc on the axis (Y-Y'); - the guide wedges (70) and the closing wedges (80) each have two lateral faces (71, 72, 81, 82) provided at the interface located between an adjacent guide wedge (70) and closing wedge (80); - the central wedge (60) has a lower face (68),and an inclined external radial face (65) which flares towards the lower face (68); - the guide wedges (70) and the closing wedges (80) each have an inclined ramp (75, 85) of a shape complementary to the inclined external radial face (65); and - the core (50) comprises n removable guide wedges (70) and n removable closing wedges (80), with n ≥ 2.

2. Mold (10) according to claim 1, characterized in that in the closed position of the mold (10), the belt (40) is supported on the base (30), the core (50) is centered on the axis (Y-Y'), the cover (90) is supported on the belt (40) and on the core (50), each closing wedge (80) is located between two guide wedges (70), and the inclined ramp (75) of the guide wedges (70) as well as the inclined ramp (85) of the closing wedges (80) are supported against the inclined external radial face (65) of the central wedge (60).

3. Mold (10) according to claim 1 or 2,characterized in that it comprises a radial immobilization device (120) for the guide wedges (70) and the closing wedges (80).

4. Mold (10) according to any one of the preceding claims, characterized in that the radial immobilization device (120), comprises an annular guide structure (127) provided on an upper face (69) of the central wedge (60) and shaped with a complementary shape (77, 87) provided on a lower face (78, 88) of each of the guide wedges (70) and the closing wedges (80).

5. Mold (10) according to any one of the preceding claims, characterized in that, in a plane parallel to the plane P, the two lateral faces (81, 82) of the closing wedges (80) diverge by an angle α relative to the axis (Y-Y'), α being between 0° and 5° and preferably substantially equal to 4°.

6. Mold (10) according to any one of the preceding claims, characterized in that, in a plane perpendicular to the plane P, the two lateral faces (81, 82) of the closing wedges (80) converge at an angle β in the direction of a lower face (88) of the closing wedges (80), β being between 5° and 10° and preferably substantially equal to 8°.

7. Mold (10) according to any one of the preceding claims, characterized in that the inclined external radial face (65) of the central wedge (60) is circular.

8. Mold (10) according to any one of the preceding claims, characterized in that the lateral faces (71, 72, 81, 82) of the guide wedges (70) and closing wedges (80) are planar.

9. Mold (10) according to any one of the preceding claims, characterized in that the guide wedges (70) are identical to each other and the closing wedges (80) are identical to each other.

10. Molding method for producing a part of revolution in composite material by impregnating a preform (20) with resin and using a mold (10) according to any one of the preceding claims, characterized in that said method comprises the following steps: - positioning the base (30) and the central wedge (60); - positioning the preform (20); - positioning the belt (40) and compacting the preform (20) by an internal radial face (45) of the belt (40);. - placing the guide wedges (70) by sliding the inclined ramp (75) of the guide wedges (70) against the inclined external radial face (65) of the central wedge (60) and compacting the preform (20) between the guide wedges (70) and the belt (40); - placing the closing wedges (80) by sliding the inclined ramp (85) of the closing wedges (80) against the inclined external radial face (65) of the central wedge (60), each closing wedge (80) being located between two adjacent guide wedges (70), and compacting the preform (20) between the closing wedges (80) and the belt (40); - placing the cover (90) on the belt (40) and the central core (50), the belt (40) and the core (50) delimiting a hollow molding volume (100); and - injecting resin in liquid form into the hollow molding volume (100).

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