Method for manufacturing a pipe made of thermoformable foam

Abstract

The invention relates to a method for manufacturing a pipe made of thermoformable foam, comprising the following steps: a) inserting at least one sheet (10) of thermoformable foam into a shaping mould (20) provided with lips (21 A, 21 B) that are configured to engage with one another, the shaping mould being pre-installed in or on a tool that is capable of closing and opening the lips, the at least one sheet having two side edges (11 A, 11 B) that connect a first end edge to a second end edge; b) closing the lips of the shaping mould by means of the tool so as to pre-form the at least one sheet into the shape of a pipe in which the side edges thereof are joined together; and c) heating the at least one sheet, with its shaping mould, to a temperature suitable for welding the side edges and for thermoforming the pipe.

Description

Description TITLE: PROCESS FOR MANUFACTURING A THERMOFORMABLE FOAM CONDUIT Technical field of the invention

[0001] The present invention relates to a method for manufacturing a thermoformable foam duct and the installation implementing this method. The duct thus obtained is used in particular for the circulation of an air flow within an aircraft. Technological background

[0002] Generally, existing air circuit ducts in aircraft are made with composite materials, particularly based on fibers held in a resin. These composite materials have the advantage of having excellent mechanical characteristics, for example in terms of rigidity or mechanical resistance, while being lightweight. They can also be coupled with materials used as thermal insulation, for example insulating foams. However, for certain applications, particularly for air ducts, the mechanical characteristics are of less importance. In recent years, we have therefore seen the appearance of foam ducts, which are flexible by nature, particularly lightweight and also provide suitable thermal insulation. These foam ducts have, in particular thanks to their flexibility, the advantage of being easier to install, less fragile and able to adapt to their environment as needed.

[0003] There are different manufacturing methods for foam ducts.

[0004] For example, document EP-B1-2814660 describes a foam conduit and its manufacturing method which consists of giving a cylindrical shape to a foam sheet before joining the lateral edges of the sheet by gluing, that is to say by the use of an adhesive deposited between the lateral edges.

[0005] Document WO-A1-2008 / 156505 describes a thermoplastic foam conduit, based on polyvinylidene fluoride (PVDF) for example, and its manufacturing process. This manufacturing process consists of inserting a thermoplastic foam sheet into a former comprising a cylindrical mandrel and partitions extending around the mandrel, the sheet being inserted between the mandrel and the partitions. In particular, the sheet is wound around the mandrel so that the The side edges of the sheet overlap, preforming the duct. The overlapping side edges of the sheet and the duct thus preformed are heated and pressed by the partitions so as to weld the edges of the sheet and thermoform the duct. Alternatively, a process is also proposed consisting of placing two sheets of thermoplastic foam flat in a former, heating and then creating a vacuum in a mold to conform the sheets to the shape of the former.

[0006] Document EP-B1-445592 also describes a thermoplastic foam conduit and its manufacturing method which consists of inserting two preheated foam sheets into a former, closing the former so as to weld the lateral edges of the sheets together before injecting a pressurized fluid between the sheets so as to give them the shape of the former and thus form a conduit.

[0007] The above-mentioned foam duct manufacturing processes can be expensive and / or complex to implement.

[0008] Also, an objective of the invention is therefore to propose an improved method for obtaining a foam conduit which does not have at least one of the aforementioned drawbacks. Summary of the invention

[0009] A method for manufacturing a thermoformable foam conduit is therefore proposed, comprising the following steps: a) inserting at least one thermoformable foam sheet inside a former provided with lips configured to cooperate with each other, the former being pre-installed in or on a tool capable of closing and opening the lips, the at least one sheet having two lateral edges connecting a first end edge to a second end edge; b) closing the lips of the former by means of the tool, so as to preform the at least one sheet in the form of a conduit in which its lateral edges are joined; and c) heating the at least one sheet with its former to a temperature suitable for ensuring welding of the lateral edges and thermoforming the conduit.

[0010] Thus, thanks to the invention, a simplified and rapid shaping of the foam sheet(s) to form a conduit is ensured. Indeed, on the one hand, the simple closing of the former allows the sheet(s) to be preformed into a conduit, and, on the other hand, the thermoformable property of the foam allows the conduit to retain its shape thanks to heating, which limits the constraints at the welding level for example. In addition, the heating step simultaneously allows the conduit to be thermoformed but also the lateral edges of the sheet(s) to be welded.

[0011] The method according to the invention may comprise one or more of the following characteristics, taken in isolation from each other or in combination with each other: - the conformer is removable; - step c) is carried out in an oven or stove; - the method comprises, after step c), a step consisting of receiving an adhesive tape on at least one external welding line formed by welding the side edges and at the end edges so as to reinforce the conduit; - which thermoformable foam is selected from polyvinylidene fluoride (PVDF), polyphenylsulfone (PPSU), polyetherimide (PEI), polyether sulfone (PESU) or polyethylene terephthalate (PET); - in step b), the lips of the conformer are kept closed using at least one fixing means; - the method comprises, after step c), a step consisting of dismantling the at least one fixing means; - the conformer is made of metal, metal alloy or a composite material; - the method comprises, prior to step c), and after step b), a step consisting of mounting at least one wedge at at least one end edge of the preformed conduit, the wedge having a predefined cross-sectional shape, so that the conduit adopts in cross-section the predefined shape of the wedge; - the section of the wedge is oblong or ellipsoidal in shape;

[0012] The invention also relates to an installation for implementing the method for manufacturing a thermoformable foam conduit as described above, the installation comprising at least: a former provided with lips configured to cooperate with each other, a tool capable of closing and opening the lips of the former, a heating system; the former being pre-installed in or on the tool capable of closing and opening the lips of the former.

[0013] The installation, according to the invention, may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: the conformer is removable; the installation comprises at least one fixing means capable of keeping the lips closed; the heating system is an oven or a stove. Brief description of the figures

[0014] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which:

[0015] Figure 1 shows a schematic flat view of a thermoformable foam sheet,

[0016] Figure 2 represents a schematic perspective view of a straight duct, in particular formed from at least one thermoformable foam sheet according to Figure 1,

[0017] Figure 3 represents a schematic perspective view of a conduit having a curvature relative to its longitudinal axis, conduit in particular formed from two sheets of thermoformable foam,

[0018] Figure 4A shows a schematic cross-sectional view of one embodiment of a conformer according to the invention, particularly when the conformer contains a thermoformable foam sheet and the conformer is open,

[0019] Figure 4B shows a schematic cross-sectional view of the conformer of Figure 4A, particularly when the conformer is closed,

[0020] Figure 5A shows a schematic cross-sectional view of another embodiment of a conformer according to the invention, in particular when the conformer contains two thermoformable foam sheets and the conformer is open,

[0021] Figure 5B shows a schematic cross-sectional view of the conformer of Figure 5A, particularly when the conformer is closed,

[0022] Figure 6 represents a block diagram of the manufacturing process according to the invention,

[0023] Figure 7 represents a partial schematic perspective view of the shaper according to the invention, in particular when a wedge is mounted at least one end edge of the preformed conduit. Detailed description of the invention

[0024] In the following, reference is made to a thermoformable foam conduit C. The term "conduit" should be understood as designating a generally tubular device allowing the conveyance of a fluid and also allowing this fluid to be isolated from an environment external to the conduit. "Conduit" is also understood to mean a constituent element of an assembly which can form a circuit or a network.

[0025] Figure 1 shows a sheet 10 made of thermoformable foam, shown flat in a state considered to be initial, that is to say before any shaping to obtain a conduit C, shown in Figure 2. In other words, the sheet 10 is the raw material of a conduit C. This sheet 10 comprises a first lateral edge 11A and a second lateral edge 11B, each of its two lateral edges 11A, 11B connects a first end edge 12A to a second end edge 12B.

[0026] Figure 2 shows an example of a thermoformable foam conduit C obtained at the end of the manufacturing according to the invention, from at least one thermoformable foam sheet 10 as shown in Figure 1. In the example of Figure 2, the conduit C is straight, that is to say that the conduit is substantially parallel to its longitudinal axis X, and is formed from a single foam sheet 10. Thus, the first lateral edge 11A and the second lateral edge 11B of the sheet 10 are welded together, and an external weld line and an internal weld line are then formed on the conduit C. In another embodiment, not shown, the straight conduit C can be formed from several sheets 10, for example two sheets 10, 10'. Thus, the first lateral edge 11A of a first sheet 10 is welded with the second lateral edge 11B' of a second sheet 10', while the second lateral edge 11B is welded with the first lateral edge 11A' of the second sheet 10'. In other words, there are two welds and, for each weld, an external weld line and an internal weld line are then formed on the conduit C.

[0027] Figure 3 shows an example of a thermoformable foam duct C obtained at the end of the manufacturing according to the invention and having a curvature relative to the longitudinal axis X' of the duct C. A curved duct C can be formed from at least two sheets 10, 10' of thermoformable foam. In a case with two sheets 10, 10', the first lateral edge 11A of a first sheet 10 is welded with the second lateral edge 11B' of a second sheet 10', while the second lateral edge 11B is welded with the first lateral edge 11A' of the second sheet 10'. Two weld lines S, S' are then formed on the duct C. Although not shown, a curved duct C can be formed from more than two sheets 10, 10', for example four, consequently increasing the number of weld lines. A conduit C formed with more than two sheets 10, 10' allows the creation of more complex geometries of the conduit C.

[0028] Furthermore, a curved conduit C means that the internal part of the curvature is shorter than the external part. Also, the first sheet 10, positioned at the internal part of the curvature, is of smaller dimension than the dimension of the second sheet 10', then positioned at the external part of the curvature. The term "dimension" can for example designate the distance separating each lateral edge 11A, 11B and / or the distance separating each end edge 12A, 12B of each of the sheets 10, 10'. Advantageously, the sheets 10, 10' are pre-cut.

[0029] Advantageously, the material making up the thermoformable foam of each sheet 10 is chosen in a non-limiting manner from polyvinylidene fluoride (PVDF), polyphenylsulfone (PPSU), polyetherimide (PEI), polyether sulfone (PESU) or even polyethylene terephthalate (PET).

[0030] The manufacture of a thermoformable foam C-duct as described above can be done using a dedicated installation.

[0031] This installation comprises a former 20 which is provided with lips 21A, 21B configured to cooperate with each other. The installation also comprises a tool capable of closing and opening the lips 21A, 21B of the former 20, the former 20 being pre-installed in or on this tool. The installation also comprises a heating system.

[0032] Advantageously, the conformer 20 is removable. In other words, the conformer 20 can be placed in the installation tooling and can also be removed therefrom, whether it is open or closed with at least one sheet 10 of thermoformable foam inside.

[0033] The conformer 20 may be a single piece, as illustrated in Figures 4A and 4B, or may comprise two parts, as illustrated in Figures 5A and 5B.

[0034] When the shaper 20 is in two parts, a first part is provided with lips 21 A, 21 B configured to cooperate with the lips 21 A', 21 B' of the second part. Alternatively, not shown, the two parts of the shaper 20 may be non-symmetrical.

[0035] The former 20 may be made of a metallic material, a metallic alloy, for example steel, or a composite material, for example based on carbon fibers embedded in an epoxy resin. All these materials have the advantage of having a thermal conductivity capable of improving the quality of the thermoforming.

[0036] In the particular case of a conformer 20 made of a material other than metal or metal alloy, it is preferred that the conformer 20 comprises two parts.

[0037] The lips 21 A, 21 B, 21 A', 21 B' of the shaper 20 can be held together using at least one fixing means 40. This fixing means 40 can be, in a non-limiting manner, a screw / nut system or a clamp.

[0038] The heating system is configured to allow even temperature distribution.

[0039] The heating system can be, for example, an oven or a stove.

[0040] Furthermore, the heating system may be external. That is, it is not included in the same frame as the closing / opening tooling of the conformer 20.

[0041] Reference is now made to Figure 6 showing a block diagram of the process 100 for manufacturing a thermoformable foam conduit.

[0042] In a step 110, at least one sheet 10 of thermoformable foam is inserted into a former 20 as described above. This former 20 is furthermore pre-installed in or on a tool capable of closing and opening the lips 21 A, 21 B of the former 20.

[0043] In a step 120, the lips 21 A, 21 B of the former 20 are closed by means of the tooling. In this way, the at least one sheet 10 is preformed in the form of a conduit C in which its lateral edges 11 A, 11 B are joined. It is understood that the section of the preformed conduit C is then, by default, substantially circular.

[0044] A first example of a shaper 20 comprising at least one sheet 10 of thermoformable foam is shown in FIGS. 4A and 4B. In this embodiment, the shaper 20 is in a single piece. In the example of FIGS. 4A and 4B, a single sheet 10 is inserted inside the shaper 20. It is understood that the orientation or position of the sheet 10 shown in the example of FIGS. 4A and 4B is non-limiting and given by way of illustration. Advantageously, the first lateral edge 11A and the second lateral edge 11B are distant from the lips 21A, 21B of the shaper 20, and for example placed substantially opposite the lips 21A, 21B of the shaper 20.

[0045] When the former 20 is closed, the thermoformable foam sheet 10 is constrained by the former 20 and adopts the shape of the latter, which is that of the conduit C. Once the former 20 is closed, that is to say once the lip 21 A and the lip 21 B of the former 20 cooperate with each other, the first lateral edge 11 A and the second lateral edge 11 B of the sheet 10 are joined, as visible in FIG. 4B. It is understood that more than one foam sheet 10 can be used with this configuration.

[0046] The embodiment of Figures 4A and 4B is preferred for shaping a straight conduit C, i.e. without curvature along the longitudinal axis X of the conduit C.

[0047] Another example of a former 20 comprising at least one sheet 10 of thermoformable foam is shown in Figures 5A and 5B. In this embodiment, the former 20 is in two parts. In the particular case of Figures 5A and 5B, two sheets 10, 10' are inserted inside the former 20. It is understood that the orientation or position of the sheets 10, 10' shown in the example of Figures 5A and 5B is non-limiting and given by way of illustration. When the former 20 is closed, the sheets 10, 10' of thermoformable foam are constrained by the former 20 and adopt the shape of the latter, which is that of the conduit C.Once the former 20 is closed, that is to say once the lip 21 A of each part of the former 20 cooperates with the lip 21 B of the other part of the former 20, the first lateral edge 11 A and the second lateral edge 11 B of a first sheet 10 are respectively attached to the second lateral edge 11 B' and to the first lateral edge 11 A' of the second sheet 10', as visible in FIG. 4B. It is understood that fewer or more than two sheets 10, 10' of thermoformable foam can be used with this configuration.

[0048] The embodiment of Figures 5A and 5B may be particularly useful for manufacturing a conduit C describing a curve along its longitudinal axis X', as described above.

[0049] In a step 122, optional and able to be carried out after step 120, the lips 21 A, 21 B of the former 20 are kept closed using at least one fixing means 40. In this way, the shaping of the at least one sheet 10 is improved by limiting the risks of unwanted opening of the former 20.

[0050] When the shaper 20 is in a single part, the at least one fixing means 40 is advantageously a clamp, as visible in FIG. 4B.

[0051] When the conformer 20 is in two parts, the at least one fixing means 40 is advantageously a screw / nut assembly, as seen in FIG. 5B.

[0052] At a step 124, taking place after 122 and when the former 20 is removable, the former 20 can be removed from the tooling.

[0053] In an optional step 126, which may take place after any one of steps 120, 122 or 124, a shim 30 is mounted at least at one end edge 12A, 12B, and preferably at each end edge 12A, 12B. Figure 7 shows this shim 30, once mounted, which has a predefined shaped section. In In particular, the predefined shape of the section of the shim 30 may be oblong or ellipsoidal. In this way, with the shim installed, the section of the conduit C will take the shape of the section of the shim. It is understood that this shim makes it possible to adapt the shape of the section of the conduit C as required, in particular when a circular section is not desired. The shim 30 is intended to remain mounted at the designated end edge until the conduit C is removed from the former 20, once the conduit C has been thermoformed. It is understood that carrying out step 126 requires access to at least one of the end edges 12A, 12B. In other words, the tooling provides at least one access to these end edges 12A, 12B, in particular when step 126 is carried out directly following any one of steps 120 or 122, that is to say when the shaper 20 is not removable.

[0054] At a step 130, taking place after any one of steps 120, 122, 124 or 126, the former 20 containing the at least one preformed sheet 10 is heated in a heating system. The heating is carried out at a temperature suitable for ensuring welding of the lateral edges 11 A, 11 B of the sheet 10 and thermoforming the conduit C. Advantageously, the thermoformable foam is heated so as to approach the melting temperature of the material chosen to form the conduit C. In this way, a quality weld and a final shape after returning to room temperature can be obtained. On the other hand, the heating temperature must not be too high so as not to pass into the molten state, which would cause the chosen material to lose its foam state.

[0055] When the conformer 20 is removable, it can be placed in a heating system external to the installation. This heating system can be an oven or a drying oven.

[0056] In a step 132, after step 130, carried out if the optional step 122 has been implemented, the at least one fixing means 40 keeping the lips 21 A, 21 B of the conformer 20 closed is dismantled.

[0057] At a step 140, the conduit C is removed from the former 20 after opening the latter using the tooling.

[0058] At a step 150, after removing the conduit C from the former 20, an adhesive tape may advantageously be applied at least in part to the external weld line marking the junction of the side edges 11A, 11B. An adhesive tape may also be applied to each of the end edges 12A, 12B. The application of an adhesive tape makes it possible to reinforce the conduit.

[0059] It is clear that the process as described above allows for the improvement of the shaping of the thermoformable foam sheet(s) to form a conduit. This is both simplified and faster. Indeed, on the one hand, the mere closing of the former allows the sheet(s) to be preformed into a conduit, and, on the other hand, the thermoformable property of the foam allows the conduit to retain its shape thanks to heating, which limits the stresses at the welding level for example. In addition, the heating step simultaneously allows the conduit to be thermoformed but also the lateral edges of the sheet(s) to be welded together.

[0060] Another advantage is that it allows the shaping of conduits of different shapes, such as straight or curved conduits, for example.

[0061] It has also been found that with such a manufacturing process, the loss of material due to manufacturing is reduced or substantially identical to more expensive manufacturing processes. Indeed, the thermoformable foam sheet inserted into the conformer is the raw material directly shaped. Thus, the ratio of the mass of the raw product, i.e. the thermoformable foam sheet, to the mass of the final product, i.e. the duct, is close to 1. In other words, there is almost no loss of material.

Claims

Demands [1] A method for manufacturing a thermoformable foam conduit (C) comprising the following steps: a) inserting at least one thermoformable foam sheet (10) inside a former (20) having lips (21 A, 21 B) configured to cooperate with each other, the former being pre-installed in or on a tooling suitable for closing and opening said lips, said at least one sheet having two lateral edges (11 A, 11 B) connecting a first end edge (12 A) to a second end edge (12 B); b) closing the lips of the former by means of the tooling, so as to pre-form said at least one sheet into the form of a conduit in which its lateral edges are joined; and c) heating said at least one sheet with its former to a suitable temperature to ensure welding of said lateral edges and thermoforming the conduit. [2] Method according to claim 1, wherein the former is removable. [3] A method according to any one of claims 1 or 2, wherein step c) is carried out in an oven or a drying oven. [4] A method according to any one of claims 1 to 3, comprising, after step c), a step of receiving adhesive tape on at least one external weld line formed by welding the lateral edges (11A, 11B) and at the end edges (12A, 12B) so as to reinforce the conduit (C). [5] A method according to any one of claims 1 to 4, wherein the thermoformable foam is selected from polyvinylidene fluoride (PVDF), polyphenylsulfone (PPSU), polyetherimide (PEI), polyethersulfone (PESU) or polyethylene terephthalate (PET). [6] A method according to any one of claims 1 to 5, wherein, in step b), the lips of the conformer are held closed using at least one fastening means (40). [7] Method according to claim 6, comprising, after step c), a step consisting of dismantling said at least one fastening means (40). [8] A method according to any one of claims 1 to 7, wherein the former (20) is made of metal, metal alloy or composite material. [9] Method according to claim 8, comprising, prior to step c) and after step b), a step consisting of mounting at least one shim (30) to at least one end edge (12A, 12B) of the preformed conduit (C), the shim having a predefined shape section, so that the conduit adopts in section the predefined shape of said shim. [10] Method according to claim 9, wherein the section of the wedge (30) is oblong or ellipsoidal in shape. [11] Installation for implementing the process for manufacturing a thermoformable foam conduit (C) according to any one of claims 1 to 11, comprising at least: a former (20) having lips (21 A, 21 B) configured to cooperate with each other, a tooling suitable for closing and opening the lips of the former, a heating system; the former being pre-installed in or on the tooling suitable for closing and opening the lips of the former. [12] Installation according to claim 12, wherein the former (20) is removable. [13] Installation according to any one of claims 12 or 13, comprising at least one fastening means suitable for keeping the lips (21 A, 21 B) closed. [14] Installation according to any one of claims 12 to 14, wherein the heating system is an oven or a drying oven.

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