Mandrel for a machine for bending a double-wall pipe, associated bending machine and associated method

Abstract

A mandrel (2) for a bending machine (1), extending along a mandrel axis (M), the mandrel (2) being configured to be inserted from upstream to downstream in a pipe, the pipe having an outer tube in which an inner tube is mounted, the mandrel (2) comprising - an external member (21) configured to extend into an intermediary space, - an internal member (22) mounted in the external member (21) and configured to extend into the inner tube; the external member (21) comprising an external body (210) and at least one row (R1-R3) of balls (4) that is positioned in a downstream continuation of the external body (210), the row (R1-R3) of balls (4) being connected to the external body (210) by a connection system (5) such that the balls (4) can extend into the intermediary space of the pipe portion that is to be bent.

Description

Mandrel for a double-wall pipe bending machine, bending machine and associated process

[0001] The present invention relates to the field of pipes intended to be mounted in a fluid circuit of an aircraft, for example, in a fuel circuit. More specifically, the invention relates to a mandrel for a machine for bending a double-walled pipe.

[0002] In an aircraft, a fluid circuit comprises a plurality of pipes mechanically and fluidically connected to each other. In a known manner, each pipe comprises an inner tube and an outer tube, for transporting fluids. Such a pipe is commonly referred to as a "double-walled pipe". A double-walled pipe makes it possible, for example, to limit fuel leaks in the event of damage to the inner tube, particularly in risk areas such as a hot zone for fuel or liquid leaks in areas containing electrical devices, for example.

[0003] When circulating the fluid in the fluid circuit, each pipe is pressurized, causing radial and longitudinal forces to appear. In addition, there may be areas with a temperature differential between the exterior, and therefore the outer tube, and the fluid circulating in the inner tube, also causing forces to appear. Also, it is necessary to maintain a regular spacing between the inner tube and the outer tube to allow the inner tube to expand without risking damage.

[0004] When assembling a fluid circuit, the pipes each have a predetermined profile to follow, for example, the curvatures of the aircraft structure or to bypass equipment. To achieve this, each pipe can be curved locally; this is called bending.

[0005] To bend a double-walled pipe, both pipes must be shaped at the same time and positioned precisely relative to each other. This allows for a predefined, regular spacing to be maintained between the walls of the inner pipe and the walls of the outer pipe along the entire length of the pipes.

[0006] In the prior art, it is known to insert a flexible sleeve into the space between the inner tube and the outer tube in order to transmit the bending forces from the outer tube to the inner tube during bending. However, such a sleeve cannot be removed after bending and remains in place after the fluid circuit is mounted on the aircraft, significantly increasing the mass of the fluid circuit, which is not desirable in an aeronautical environment in which mass constraints are significant. In addition, the flexible sleeve occupies the space between the inner tube and the outer tube which is intended to collect any fuel leaks.

[0007] Also known from document US2010018599A1 is a method for manufacturing a double-walled pipe, in which a filler material, for example corundum, is introduced between the inner tube and the outer tube to temporarily fill the space between the tubes during the bending operation and allow them to be shaped. The filler material is then removed after bending in a practical manner. The implementation of the steps of filling, bending and removing the filler material are time-consuming to implement, which presents a disadvantage. Also known from patent application JP2007319904A is a mandrel for manufacturing a double-walled pipe which comprises an inner body and an outer body comprising a plurality of external elements.

[0008] The invention thus aims to eliminate at least some of these drawbacks by proposing a machine for bending a double-walled pipe which is simple and reliable, while ensuring that the mass of the fluid circuit is limited. PRESENTATION OF THE INVENTION

[0009] The invention relates to a mandrel for a bending machine extending along a mandrel axis, the mandrel being configured to be inserted from upstream to downstream into a pipe having a portion to be bent, the pipe having an outer tube in which an inner tube is mounted so as to form a pipe having a double wall, an intermediate space being defined between the inner tube and the outer tube, the mandrel comprising:An external member configured to extend into the intermediate space,An ​​internal member, mounted in the external member, configured to extend into the inner tube,The external member comprising an external body and at least one row of balls positioned in a downstream extension of the external body,The row of balls being connected to the external body by a connecting system so that the balls can extend into the interposed space of the portion of the pipeline to be bent in order to guide the deformation of the external tube in said portion to be bent during a bending operation.

[0010] Thanks to the invention, the balls advantageously allow the bending forces to be transmitted to the inner tube of the pipeline in a controlled manner. The balls can move conveniently in the interposed space while remaining close to each other thanks to the connection system. Thus, any concentration of stresses in the portion to be bent is avoided. The combined presence of an internal member and an external member also allows the forces on the inner tube to be controlled. The mandrel ensures a regular spacing between the inner tube and the outer tube, which is advantageous when using the pipeline. In addition, several consecutive bends can be carried out by moving the mandrel in a practical manner in order to form a pipeline following the curvatures of the aircraft structure. Finally, the mandrel is removed from the pipeline after bending and no member remains permanently in the pipeline.The operation and mass of the pipeline are therefore not penalized.

[0011] In one aspect, the balls of a ball row are uniformly distributed around the mandrel axis. This allows for uniform spacing to be maintained during the transmission of bending forces.

[0012] According to one aspect, the external member comprises at least two rows of balls, preferably between 2 and 4, being spaced longitudinally along the axis of the mandrel. This makes it possible to achieve uniform and homogeneous bending suitable for the aeronautical field.

[0013] In one aspect, the connecting system comprises a plurality of lines for connecting the at least one row of balls to the outer body. The balls are thus connected along the mandrel axis but remain free to move.

[0014] According to one aspect, the external member comprises at least one traction member associated with at least one line for exerting a traction force towards the external body. This makes it possible to adapt the position of the balls during bending between the internal side and the external side of a bend. This makes it possible to keep the rows grouped together, and allows each line to adapt its longitudinal length to the length of the portion to be bent, which is longer on the outside of the bend than on the inside.

[0015] According to one aspect, the connecting system comprises at least one connecting ring in which the balls of the same row are mounted. The connecting ring makes it possible to ensure positioning of the balls of the same row, in particular, by ensuring a uniform spacing.

[0016] According to one aspect, the connecting ring is mounted in translation on the lines of the connecting system so as to adapt the spacing of the at least one row of balls relative to the external body during bending. Thus, the spacing between the rows adapts dynamically during bending.

[0017] According to one aspect, the internal member comprises a rigid internal body terminated at its downstream end by a flexible portion. This advantageously makes it possible to guide the deformation of the inner tube. According to one aspect, the flexible portion comprises a plurality of slats. According to one aspect, the flexible portion comprises an alternation of slats and tenons in order to allow controlled inclination of the slats during bending.

[0018] In one aspect, the flexible portion extends opposite the at least one row of balls such that the balls and the flexible portion together guide the deformation of the inner tube of the portion to be bent during a bending operation. The support is thus uniform in the inner tube and in the interposed space.

[0019] In one aspect, the flexible portion has a longitudinal length equal to + / - 10% of the longitudinal length of the at least one row of balls.

[0020] In one aspect, the mandrel includes a mounting foot configured to connect to a mandrel holder of a bending machine.

[0021] The invention also relates to a bending machine comprising a mandrel holder on which is mounted a mandrel as presented previously, a guide member and a bending member configured to move a portion of the pipe in order to deform it against the guide member.

[0022] The invention also relates to a method for bending a pipe having a portion to be bent by means of a bending machine comprising a mandrel as presented previously, the pipe having an outer tube in which an inner tube is mounted, an intermediate space being defined between the inner tube and the outer tube, the pipe comprising a first rectilinear portion extending along a first axis, a second rectilinear portion extending along a second axis, the bent portion connecting the first rectilinear portion to the second rectilinear portion, the first axis and the second axis being the same, the bending method comprising steps consisting of:Introducing the mandrel into the pipe, the outer member extending into the intermediate space, the inner member extending into the inner tube, the balls of the outer member extending into the portion to be bent,andBending the portion of the pipe to be bent by keeping the first rectilinear portion fixed and moving the second rectilinear portion, the balls guiding the deformation of the outer tube in said portion to be bent.,

[0023] In a particular aspect, the pipes of the pipeline are made of thermoplastic material. The method is particularly advantageous for such pipes which are, by nature, more fragile than metal pipes. PRESENTATION OF FIGURES

[0024] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0025] This is a schematic representation of a straight double-walled pipeline before bending.

[0026] This is a schematic representation of a double-walled pipe after bending.

[0027] This is a schematic representation of a straight pipe in a bending machine before bending.

[0028] This is a schematic representation of the pipeline after bending.

[0029] This is a schematic representation of a side sectional view of a bending mandrel according to one embodiment.

[0030] This is a close-up schematic representation of the.

[0031] This is a partial schematic representation of a connecting ring.

[0032] The is a schematic representation of a longitudinal sectional view of the bending mandrel positioned in a portion to be bent.

[0033] The is a schematic representation of a longitudinal sectional view of the bending mandrel positioned in the portion to be bent after bending.

[0034] This is a schematic representation of a longitudinal sectional view of a bending mandrel according to another embodiment positioned in a portion to be bent.

[0035] This is a schematic representation of a longitudinal sectional view of the bending mandrel after bending.

[0036] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0037] The invention will be presented for the bending of a double-walled pipe, hereinafter referred to as "pipe" for the sake of clarity and conciseness. Such a pipe 3 is intended to be mounted in a fluid circuit of an aircraft, for example a fuel circuit.

[0038] With reference to the, the pipeline 3 comprises an outer tube Te and an inner tube Ti, mounted in the outer tube Te. The inner tube Ti and the outer tube Te are concentric and form the double wall of the pipeline 3. Before its bending, each tube Te, Ti extends rectilinearly along a longitudinal axis X. Subsequently, the terms inner and outer are defined radially with respect to the longitudinal axis X. An intercalary space EI is defined between the inner tube Ti and the outer tube Te. This intercalary space EI must remain substantially constant despite the presence of bent portions.

[0039] The inner tube Ti has an inner surface Ti1 and an outer surface Ti2 which is opposite the inner surface Ti1. Similarly, the outer tube Te has an inner surface Te1 and an outer surface Te2 which is opposite the inner surface Te1. Preferably, each tube Ti, Te has a circular cross-section but it goes without saying that any cylindrical cross-section could be suitable. Preferably, each tube Ti, Te is made of a metallic material. Such a material is liable to be damaged during bending. One of the objectives of the present invention is to carry out controlled bending in order to avoid any damage leading to scrapping.

[0040] Following a bending operation, as illustrated in, the pipe 3 comprises a first rectilinear portion P1 extending along a first axis X1, a second rectilinear portion P2 extending along a second axis X2 and a curved portion PC connecting the first rectilinear portion P1 to the second rectilinear portion P2. A bending angle α is defined as the angular difference between the axes X1, X2 as shown in.

[0041] Referring to Figures 3 and 4, there is shown a bending machine 1 according to an embodiment of the invention for bending the pipe 3 presented previously.

[0042] In this example, the bending machine 1 comprises a mandrel holder 10 on which a mandrel 2 is mounted, a guide member 11 and a bending member 12 configured to move a portion of the pipe 3 in order to deform it against the guide member 11.

[0043] The guide member 11 is known to those skilled in the art and is preferably in the form of an anvil, called a “bending stone”, having a profile adapted to the bending to be carried out. The profile is for example curvilinear. In this example, the guide member 11 has an imprint to cooperate with the external surface of the outer tube Te of the pipeline 3. It goes without saying that this could be different.

[0044] Similarly, the folding member 12 is known to those skilled in the art and is preferably in the form of an arm controlled, for example, hydraulically. Preferably, the folding member 12 comprises an imprint for cooperating with the outer surface of the outer tube Te of the pipeline 3. It goes without saying that this could be different.

[0045] Still with reference to Figures 3 and 4, the mandrel holder 10 comprises a proximal end 10b and a distal end 10a adapted to receive a mandrel 2 in order to move it precisely in the pipe 3 along the longitudinal axis X. In this example, the bending machine 1 further comprises a controllable movement module 13 which is connected to the proximal end 10b of the mandrel holder 10 in order to move the mandrel 2 precisely and repeatably in a portion PC of the pipe 3 to be bent. This is particularly advantageous for carrying out bends with high rates in an automated manner. It nevertheless goes without saying that the mandrel holder 10 could be moved manually.

[0046] With reference to the, there is shown an embodiment of a mandrel 2 according to the invention. The mandrel 2 extends along a mandrel axis M oriented from upstream to downstream on the. The mandrel 2 comprises, in this example, a mounting foot 20 located upstream and intended to be connected to the mandrel holder 10, in particular, at its distal end 10a.

[0047] The mandrel 2 has axial symmetry along the mandrel axis M so as to cooperate with a pipe 3 having axial symmetry in order to carry out bending independently of its angular orientation.

[0048] According to the invention, with reference to Figures 5 and 6, the mandrel 2 comprises an external member 21 configured to extend into the intermediate space EI () and an internal member 22, mounted in the external member 21 along the mandrel axis M, configured to extend into the inner tube Ti (). The external member 21 has a shape complementary to the intermediate space EI and the internal member 22 has a shape complementary to the inner cavity of the inner tube Ti. Also, the internal member 22 has an outside diameter smaller than the inside diameter of the external member 21.

[0049] Still with reference to the, the internal member 22 comprises a rigid internal body 220 terminated at its downstream end by a flexible part 23. In this example, the rigid internal body 220 is in the form of a cylindrical part, preferably solid. For example, the rigid internal body 220 has a diameter De slightly smaller than the diameter of the inner tube Ti. The length of the rigid internal body 220 is variable and depends on the length of the pipe 3 and the longitudinal position of the portion to be bent PC. The rigid internal body 220 is made of a rigid material. For example, the rigid internal body 220 is made of steel.

[0050] Still with reference to the, the flexible part 23 comprises a plurality of strips 231 in order to limit the deformations of the inner tube Ti in the portion to be bent PC. For this purpose, each strip 231 has a diameter De slightly smaller than the diameter of the inner tube Ti. In particular, the strips 231 have a diameter equal to that of the rigid inner body 220.

[0051] Preferably, the lamellae 231 have a longitudinal thickness defined along the mandrel axis M. In this example, the lamellae 231 are spaced from each other along the mandrel axis M by a non-zero spacing distance. This advantageously allows the lamellae 231 to tilt relative to the mandrel axis M so as to match the shape of the portion to be bent PC during bending. Preferably, the lamellae 231 all have the same shape.

[0052] In order to connect together the different strips 231 of the flexible part 23 while allowing them to tilt, the flexible part 23 comprises an alternation of strips 231 and tenons 232. Each tenon 232 is connected at its end to a strip 231. Each tenon 232 has a section, in particular a diameter, smaller than the diameter of a strip 231. Preferably, a connecting bar connects all of the strips 231, the tenons 232 corresponding to the portions of the connecting bar positioned between two adjacent strips. Preferably, the strips 231 are stacked on top of each other along the mandrel axis M. It goes without saying that the flexible part 23 could be formed differently. The tenons 232 allow the slats 231 to be spaced apart by the same spacing distance in order to provide uniform support while increasing flexibility.

[0053] In this example, the slats 231 are made of a material resistant to contact pressure and resistant to scratches, for example a thermoplastic or a steel treated to improve its hardness. For example, the slats 231 are made of treated steel.

[0054] With reference to the, the flexible portion 23 extends over a longitudinal length L23 along the mandrel axis M which is adapted to the length of the portion to be bent PC. For example, the longitudinal length L23 is between 10 and 40% of the length of the portion to be bent PC.

[0055] In this example, three slats 231 are shown, but it goes without saying that their number can vary. Preferably, the number of slats 231 is between 1 and 4.

[0056] The flexible part 23 advantageously allows the deformation of the inner tube Ti to be followed during bending. It allows the forces on the inner tube Ti to be supported while protecting it from unwanted deformations.

[0057] Still with reference to the, the external member 21 comprises an external body 210, and several rows R1-R3 of balls 4 positioned in a downstream extension of the external body 210 along the mandrel axis M.

[0058] In this example, the outer body 210 is in the form of a hollow cylindrical part. For example, the outer body 210 has an outer diameter slightly smaller than the diameter of the outer tube Te, and an inner diameter slightly larger than the outer diameter of the inner tube Ti (). The length of the outer body 210 is variable and depends on the length of the pipe 3 and the position of the portion to be bent PC. Preferably, the length of the outer body 210 is equal to the length of the rigid inner body 220. The outer body 210 is made of a rigid material. For example, the outer body 210 is made of steel. The outer body 210 has a radial thickness Er slightly smaller than the distance separating the outer surface Ti2 of the inner tube Ti from the inner surface Te1 of the outer tube Te, advantageously allowing the insertion of the outer body 210 into the intermediate space EI.

[0059] In this example, the mandrel 2 has three rows of balls R1-R3 but it goes without saying that their number could be different. Preferably, the number of rows R1-R3 is between 1 and 4.

[0060] The rows R1-R3 of balls 4 are spaced longitudinally along the mandrel axis M and connected to each other by a connecting system 5. In other words, the mandrel comprises a connecting system 5 for connecting the rows of balls R1-R3 to the external body 210. With reference to the, the rows R1-R3 are spaced apart by a non-zero spacing distance D4. The rows R1-R3 extend over a longitudinal length L4. Each row of balls R1-R3 extends in a plane, specific to each row of balls R1-R3, perpendicular to the mandrel axis M.

[0061] Preferably, the flexible part 23 extends opposite the balls 4, and the longitudinal length L23 of the flexible part 23 is equal to + / - 10% of the longitudinal length L4.

[0062] With reference to the, the balls 4 of a row of balls R1-R3 (here the row R3) are distributed uniformly and circumferentially around the mandrel axis M. Preferably, the diameter of the balls 4 is equal to + / -10% of the radial thickness Er of the external body 210, so as to be able to be inserted into the intermediate space EI while providing sufficient counter-force to the external tube TE during bending.

[0063] The connecting system 5 is connected to the external body 210 so that the balls 4 can extend into the intermediate space EI of the portion to be bent PC of the pipe 3 in order to guide the deformation of the outer tube Te in said portion to be bent PC during a bending operation.

[0064] According to one embodiment, illustrated in this example in the, the connecting system 5 comprises a plurality of lines W1, W2 for connecting the balls 4 of different rows R1-R3 to each other. Before bending, the lines W1, W2 extend parallel to the mandrel axis M. The connecting system 5 is connected to the downstream end of the external body 210. With reference to the, only two lines W1, W2 are shown, each comprising three balls 4.

[0065] Preferably, the lines W1, W2 are independent of each other so as to allow a relatively unconstrained movement of the balls 4 in the intermediate space EI as will be presented later. In other words, the connecting system 5 comprises a plurality of lines W1, W2 which are flexible and allow them to move relative to each other, each line W1, W2 being flexible and capable of deforming.

[0066] Preferably, the connecting system 5 is made of a thermoplastic material. Preferably, with reference to la and la, each ball 4 is mounted in the connecting system 5 according to a ball joint. For this purpose, the connecting system comprises a plurality of connecting rings 51-1, 51-2, 51-3 associated respectively with each row of balls R1-R3. Each connecting ring 51-1, 51-2, 51-3 comprises a plurality of elementary cages 52 in which the balls 4 are respectively mounted. The balls 4 can advantageously roll in the elementary cages 52. Each connecting ring 51-1, 51-2, 51-3 is connected to at least one line W1-W2 so as to connect each connecting ring 51-1, 51-2, 51-3 to the external body 210. With reference to the, the connecting ring 51-3 comprises a plurality of elementary cages 52 connected to each other. In this example, the connecting ring 51-3 is connected by four lines W1-W3 spaced 90° apart to the external body 210.The connecting ring 51-3 advantageously comprises four openings arranged between the elementary cages 52 to allow the passage of the lines W1-W3.

[0067] According to another aspect of the invention, the balls 4 are integral with a line of the connecting system 5 and are directly connected to it. Preferably, the connecting system 5 comprises as many lines as there are balls 4 in the same row R1-R3.

[0068] According to another aspect of the invention, the connecting system 5 is in the form of a peripheral grid in which the balls 4 of the different rows R1-R3 are mounted. In other words, the connecting system 5 comprises lines W1, W2 which are connected to each other. For example, the connecting system 5 has a cylindrical net shape which is flexible.

[0069] According to one embodiment of the invention, shown in Figures 10 and 11, the external member 21 comprises a traction member associated with each line W1, W2 to exert a traction force towards the external body 210. This makes it possible to dynamically adapt the length of each line W1, W2 according to the type of bending. Preferably, the traction member is in the form of a spring.

[0070] With reference to Figures 10 and 11, the outer body 210 comprises a housing 211 at its downstream end. The housing 211 extends longitudinally along the mandrel axis M. A plurality of springs 212 extending longitudinally along the mandrel axis M are positioned in the housing 211. Each line W1, W2 extends partly in the housing 211 through a spring 212. According to another aspect, the external body 210 comprises as many housings 211 as lines W1, W2, each housing 211 then comprising a spring 212. Each line W1, W2 is mechanically linked by its upstream end to a line stop 213 free to move in the housing 213, but retained downstream by one of the springs 212. This advantageously allows each line W1, W2 to adapt its longitudinal length L4 to the length of the portion to be bent PC, which is longer on the outside of the bend than on the inside, as shown in.The spacing distance D4 is in this case variable and is adapted to the curvature of the curved portion PC.

[0071] With reference to the, the mandrel 2 is configured to be inserted into the pipe 3 along the longitudinal axis X. In practice, the external member 21 is configured to be inserted into the intermediate space EI between the inner tube Ti and the outer tube Te. The external member 21 matches the internal surface Te1 of the outer tube Te and the external surface Ti2 of the inner tube Ti while the internal member 22 is configured to match the internal surface Ti1 of the inner tube Ti. Before bending, the mandrel axis M coincides with the longitudinal axis X when the mandrel 2 is inserted into the pipe 3.

[0072] An example of implementation of a method for bending a pipe 3 having a portion to be bent PC by means of the bending machine 1 illustrated in figures 3 and 4 will now be presented.

[0073] In this example, with reference to the, the mandrel 2 is connected to the mandrel holder 10 of the bending machine 1. The pipe 3 is positioned in the bending machine 1 so as to have its portion to be bent PC in the vicinity of the guide member 11. The pipe 3 is in this example rectilinear. The pipe 3 is preferably positioned automatically by the bending machine 1.

[0074] With reference to the, the pipe 3 comprising a first rectilinear portion P1 extending along a first axis X1, a second rectilinear portion P2 extending along a second axis X2, the portion to be bent PC connecting the first rectilinear portion P1 to the second rectilinear portion P2. Before bending, the axes X, M, X1, X2 are merged.

[0075] With reference to the, the bending method comprises a step consisting of introducing E1 the mandrel 2 into the pipe 3. In practice, the mandrel 2 is introduced along the longitudinal axis X into the first rectilinear portion P1 until reaching the portion to be bent PC as illustrated in the and in the.

[0076] As shown in detail in the, the external member 21 extends into the intermediate space EI and the internal member 22 extends into the inner tube Ti. The balls 4 of the external member 21 and the flexible part 23 extend into the portion to be bent PC. The bodies 210, 220 advantageously make it possible to push the balls 4 and the flexible part 23 during insertion. The connecting system 5 is flexible and allows positioning of the balls 4 with little stress in the intermediate space EI. As a result, the balls 4 are positioned in a substantially homogeneous manner for any bending angle.

[0077] With reference to the, the bending method comprises a step consisting of bending E2 the portion to be bent PC of the pipe 3 by keeping the first rectilinear portion P1 fixed and moving the second rectilinear portion P2. With reference to the, during bending, the bending member exerts a force on the second rectilinear portion P2 to deform the portion to be bent PC against the guide member 11 to obtain a predetermined bending angle α1, here, of the order of 90°. For the sake of brevity, the portion to be bent and the bent portion are both referenced PC.

[0078] During deformation, with reference to the, the mandrel 2 supports the forces to allow controlled bending. In particular, the balls 4 guide the deformation of the outer tube Te in the portion to be bent PC while the flexible part 23 of the internal member 22 guides the deformation of the inner tube Ti in the portion to be bent PC. The connection system 5 makes it possible to connect the balls 4 while providing great flexibility.

[0079] During deformation, the lamellae 231 allow orientation in order to avoid deformation of the inner tube Ti during bending. The diameter of the inner tube Ti advantageously remains constant. Similarly, the balls 4 allow a constant distance to be maintained between the inner tube Ti and the outer tube Te while moving during bending in order to distribute the forces evenly when the intermediate space EI deforms. Thus, the balls 4 allow the stresses applied to the outer tube Te to be transmitted in a controlled manner to the inner tube Ti which is supported by the flexible part 23. Any involuntary deformation, linked to an excessive uncontrolled force, can thus be avoided. The distance between the tubes Ti, Te remains the same as before bending, and the integrity of the pipe 3 is thus advantageously preserved. Thanks to the mandrel 2, bending can be carried out at any bending angle α1.

[0080] The flexibility of the flexible portion 23 advantageously makes it possible to provide a counter-force to the wall of the inner tube Ti in the portion to be bent PC. The inclination of the lamellae 231 follows the shape of the inner tube Ti, making it possible to provide a homogeneous counter-force to the inner wall Ti1. The balls 4 extend in a similar manner in the portion to be bent PC of the intermediate space EI between the inner tube Ti and the outer tube Te, to guide the deformation of the outer tube Te by providing a counter-force in a homogeneous manner, in particular thanks to the identical spacing distance between each row R1-R3 of balls 4. The number of lamellae 231 and balls 4 is adapted to avoid any concentration of forces during bending.

[0081] The mandrel 2 can then be easily removed from the pipe 3 by simply acting on the mandrel holder 10. The connecting system 5 advantageously makes it possible to move the balls 4 during removal. The same mandrel 2 can advantageously be positioned in another portion to be bent PC. This advantageously reduces the time required to carry out a plurality of bends in the same pipe 3.

[0082] The bending of a double-walled pipe 3 by using a mandrel 2 according to the invention is carried out in a manner similar to bending a single-walled pipe, and advantageously makes it possible to obtain a similar bending rate. The insertion of the mandrel 2 into the cylindrical pipe 3 advantageously makes it possible to provide a counter-force on the walls of the Ti, Te tubes and thus to support the pipe 3 during bending to protect it from deformation. This is particularly advantageous for a thermoplastic pipe which is more fragile than a traditional metal pipe.

[0083] Thanks to the invention, it is advantageous to maintain a regular spacing between the tubes of a pipeline 3 while carrying out different types of bending to follow the curvatures of the structure of the aircraft. Following the bending, no element remains in a curved portion PC, which avoids penalizing the circulation of fluid in the intermediate space EI or increasing the mass.

Claims

Mandrel (2) for a bending machine (1) extending along a mandrel axis (M), the mandrel (2) being configured to be inserted from upstream to downstream into a pipe (3) having a portion to be bent (PC), the pipe (3) having an outer tube (Te) in which an inner tube (Ti) is mounted so as to form a pipe (3) having a double wall, an intermediate space (EI) being defined between the inner tube (Ti) and the outer tube (Te), the mandrel (2) comprising:An external member (21) configured to extend into the intermediate space (EI),An internal member (22), mounted in the external member (21), configured to extend into the inner tube (Ti),The external member (21) comprising an external body (210) and at least one row (R1-R3) of balls (4) positioned in a downstream extension of the external body (210),The row (R1-R3) of balls (4) being connected to the external body (210) by a connecting system (5) so that the balls (4) can extend into the intermediate space (EI) of the portion to be bent (PC) of the pipeline (3) in order to guide the deformation of the external tube (Te) in said portion to be bent (PC) during a bending operation., Chuck (2) according to claim 1, wherein the balls (4) of a row of balls (R1-R3) are distributed uniformly around the chuck axis (M). Chuck (2) according to one of claims 1 to 2, in which the connecting system (5) comprises a plurality of lines (W1, W2) for connecting the at least one row of balls (R1-R3) to the external body (210). Mandrel (2) according to claim 3, in which the external member (21) comprises at least one traction member (212) associated with at least one line (W1, W2) for exerting a traction force towards the external body (210). Mandrel (2) according to one of claims 1 to 4, in which the connecting system (5) comprises at least one connecting ring (51-1, 51-2, 51-3) in which the balls (4) of the same row (R1, R2, R3) are mounted. Mandrel (2) according to claims 3 and 5 taken in combination, the connecting ring (51-1, 51-2, 51-3) being mounted in translation on the lines (W1-W3) of the connecting system (5) so as to adapt the spacing of the at least one row of balls (R1-R3) relative to the external body (210) during bending. Mandrel (2) according to one of claims 1 to 6, in which the internal member (22) comprises a rigid internal body (220) terminated at its downstream end by a flexible part (23). Mandrel (2) according to claim 7, in which the flexible part (23) extends opposite the at least one row (R1-R3) of balls (4) so ​​that the balls (4) and the flexible part (23) together guide the deformation of the inner tube (TI) of the portion to be bent (PC) during a bending operation. Bending machine (1) comprising a mandrel holder (10) on which is mounted a mandrel (2) according to one of claims 1 to 8, a guide member (11) and a folding member (12) configured to move a portion of the pipe (3) in order to deform it against the guide member (11). Method for bending a pipe (3) having a portion to be bent (PC) by means of a bending machine (1) comprising a mandrel (2) according to one of claims 1 to 8, the pipe (3) having an outer tube (Te) in which an inner tube (Ti) is mounted, an intermediate space (EI) being defined between the inner tube (Ti) and the outer tube (Te), the pipe (3) comprising a first rectilinear portion (P1) extending along a first axis (X1), a second rectilinear portion (P2) extending along a second axis (X2), the bent portion (PC) connecting the first rectilinear portion (P1) to the second rectilinear portion (P2), the first axis (X1) and the second axis (X2) being the same, the bending method comprising steps consisting of:Introducing (E1) the mandrel (2) into the pipe (3), the external member (21) extending into the intercalary space (EI), the internal member (22) extending into the inner tube (Ti),the balls (4) of the external member (21) extending into the portion to be bent (PC), andBending (E2) the portion to be bent (PC) of the pipe (3) by keeping the first rectilinear portion (P1) fixed and moving the second rectilinear portion (P2), the balls (4) guiding the deformation of the external tube (Te) in said portion to be bent (PC)., Bending method according to claim 10, in which the tubes (Ti, Te) of the pipeline (3) are made of metallic material.

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