EP3579990B1 - Electrohydraulic forming device - Google Patents

Electrohydraulic forming device Download PDF

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Publication number
EP3579990B1
EP3579990B1 EP18703599.3A EP18703599A EP3579990B1 EP 3579990 B1 EP3579990 B1 EP 3579990B1 EP 18703599 A EP18703599 A EP 18703599A EP 3579990 B1 EP3579990 B1 EP 3579990B1
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EP
European Patent Office
Prior art keywords
electrode
peripheral electrode
peripheral
central electrode
electrohydroforming
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EP18703599.3A
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German (de)
French (fr)
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EP3579990A1 (en
Inventor
Gilles Avrillaud
Julien DEROY
Romain PECQUOIS
Pierre THOUET
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ADM28 SARL
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ADM28 SARL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
    • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
    • B21D26/06—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves
    • B21D26/12—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure by shock waves initiated by spark discharge

Definitions

  • the present invention relates to an electrohydroforming device.
  • Electrohydraulic forming deforms a blank of material against a mold by applying dynamic pressure. To this end, an electric discharge is generated between at least two electrodes placed in a chamber filled with liquid, for example water. An electric arc is then formed between the two electrodes causing a high temperature gradient and vaporization of the liquid. A pressure wave, also commonly called a “shock wave”, travels at high speed and presses the blank of material against the mold. Electrohydraulic forming is particularly advantageous in comparison with other forming processes since it allows to have a reduced springback and to obtain etching-type details and / or sharp angles and / or local elongations before breakage improved on the parts to be formed.
  • Electrohydraulic or electrohydroforming forming has drawbacks.
  • One of the disadvantages of electrohydroforming is that the electrodes wear out quickly. As a result, the distance between the electrodes increases and the electric discharge is less strong. The efficiency of electrohydroforming decreases.
  • the electrodes are replaced regularly. The replacement of the electrodes generates additional maintenance costs and involves a reduction in the production rate following a temporary immobilization of the device.
  • the document US4,068,514 describes an electrohydroforming device comprising a central electrode extending in a longitudinal direction and a peripheral electrode formed by the wall of the forming chamber surrounding the central electrode. Since the wear of the peripheral electrode is distributed over a larger area, the distance between the electrodes varies less than with a device in which two electrodes, most often conical, are placed face to face and whose active parts are therefore very localized.
  • the electrodes can therefore be used longer without the efficiency of the electrohydroforming, and in particular the pressure generated by the shock wave, being affected.
  • replacing an electrode involves changing the entire electrohydroforming chamber, which generates higher maintenance costs than for other devices of the prior art and temporary immobilization of the device to replace the electrode. longer electrode.
  • the present invention aims in particular to overcome the drawbacks of the aforementioned prior art.
  • each peripheral electrode is separate from said body.
  • the use of a peripheral electrode separate from the body partly forming the electrohydroforming chamber makes it possible to reduce the size of the peripheral electrode to be changed and the immobilization time of the device when changing electrodes. , thus reducing maintenance costs.
  • the at least one peripheral electrode protrudes from the body, allowing better control of where the discharge occurs and increasing the efficiency of electrohydroforming.
  • the at least one peripheral electrode is supported by an electrode holder.
  • an electrode holder makes it possible to reduce the size of the peripheral electrode to be changed and to simplify the replacement of the peripheral electrode.
  • the electrode holder can also act as a blank holder. A compact and easy to assemble electrohydroforming device is thus obtained.
  • the device comprises a single peripheral electrode and at least one central electrode.
  • the electrohydroforming device may include several pairs of central and peripheral electrodes associated with one or more molds. It is thus possible to produce several parts in parallel or a large part by implementing several electric discharges in parallel.
  • the electrohydroforming chamber is formed by a body and the end of the peripheral electrode.
  • the electrohydroforming chamber is then closed by the blank of material to be deformed. This embodiment is advantageous because it is easy to machine and assemble.
  • a blank of material is held between the end of the peripheral electrode and the mold.
  • a compact and easy to assemble electrohydroforming device is thus obtained.
  • the end of the peripheral electrode can comprise a shoulder in which the blank of material is housed. The peripheral electrode then acts as a blank holder and allows the blank to be held material against the mold.
  • the device comprises a blank holder arranged between the end of the peripheral electrode and the mold.
  • the device further comprises a mold support which makes it easier to change the mold depending on the part to be formed.
  • the central electrode is surrounded for part of its length by an electrical insulator.
  • the body is in electrical contact with the central electrode and further comprises an electrical insulator intended to insulate the peripheral electrode from the central electrode.
  • the body When the central electrode is surrounded over part of its length by an electrical insulator, the body is easier to machine and assemble than when the body includes the electrical insulator intended to insulate the peripheral electrode from the central electrode.
  • the body further comprises a cavity partly forming the electrohydroforming chamber and the electrical insulator at least partly forming a side wall of said cavity.
  • the electrical insulator constitutes the side wall of the cavity.
  • the insulator located on the side wall is less stressed than when it surrounds the central electrode and forms a part the bottom wall of the cavity.
  • the end of the peripheral electrode and the mold are in electrical contact and subjected to a first electrical potential, the central electrode being subjected to a second electrical potential.
  • the central electrode and the mold When the peripheral electrode and the mold are in electrical contact, optionally via a mold support and / or a blank holder, the central electrode being moreover isolated, it is easy to generate the discharge electric by connecting the central electrode or the body, if it is in electrical contact with the central electrode, to one of the terminals of a pulse voltage generator and by connecting one of the elements to the electrical contact of the peripheral electrode to the other terminal of the pulse voltage generator.
  • the design of the electrohydroforming device is therefore easier since the electrical connections with the terminals of the high-voltage pulse generator are not necessarily established at the level of the central and peripheral electrodes.
  • the figure 1A shows a first embodiment of an electrohydroforming device according to the invention.
  • the electrohydroforming device 100 comprises an electrohydroforming chamber 110, a central electrode 120 and a peripheral electrode 130.
  • the central electrode 120 extends in a longitudinal direction XX 'and has a first end 122 disposed inside the device. the electrohydroforming chamber 110.
  • the peripheral electrode 130 has an end 132 disposed at a distance from and around the end 122 of the central electrode 120.
  • the end 132 of the peripheral electrode 130 extends in a transverse plane relative to said central electrode 120, that is to say in the plane perpendicular to the axis XX '.
  • the electrohydroforming device 100 also comprises a body 140 and a mold 150.
  • the body 140 comprises an internal cavity 142 and is crossed by the central electrode 120.
  • the internal cavity 142 of the body forms, with the end 132 of the peripheral electrode 130, the electrohydroforming chamber 110.
  • the electrohydroforming chamber 110 is intended to be filled with a liquid, for example water, and is closed by a blank of material 160 to be deformed.
  • the blank of material 160 is pressed against the mold 150 and deforms against the mold 150 under the action of a shock wave propagating in the electrohydroforming chamber 110.
  • the shock wave is generated following the application. of a high voltage electrical pulse between the electrodes 120 and 130 and the generation of an electrical discharge between the electrodes.
  • the electric discharge causes the formation of an electric arc, an increase in temperature and the vaporization of the liquid causing the creation of the shock wave.
  • part of the end 132 of the peripheral electrode 130 surrounds the lower end 122 of the central electrode 120.
  • An electric arc is preferably created between two zones 124 and 134, called active parts. , the central electrode 120 and the peripheral electrode 130 respectively.
  • an electric arc is preferably created between two different points of the external surface 125 of the active part 124 of the central electrode 120 and of the internal surface 135 of the active part 134 of the peripheral electrode 130 corresponding to the shortest path between the central electrode 120 and the peripheral electrode 130, respectively.
  • each electrode wears out locally at different points distributed over the external surface 125 of the active part 124 of the central electrode 120 and on the internal surface 135 of the active part 134 of the peripheral electrode 130.
  • the wear of the peripheral electrode being distributed over a larger area, the distance between the electrodes varies less than with a device of the prior art in which two electrodes, most often conical, are placed face to face and the active parts of which are therefore very localized.
  • the electrodes can therefore be used longer without the efficiency of the electrohydroforming, and in particular the pressure generated by the shock wave, being affected.
  • section of the central electrode is not necessarily constant along its longitudinal axis XX 'as illustrated by example with reference to figure 2 .
  • section of the electrode is not necessarily axisymmetric.
  • the blank of material 160 is held against the mold 150 by the peripheral electrode 130 ( figure 1A ).
  • the peripheral electrode 130 also comprises, on its lower face, a shoulder in which the material blank 160 can be housed.
  • the peripheral electrode 130 then acts as a blank holder and makes it possible to hold the material blank. 160 against the mold 150.
  • the electrohydroforming device 100 further comprises an electrode holder 136 supporting the peripheral electrode 130.
  • the electrode holder 136 is arranged between the mold 150 and the body 140. It comprises on its lower face a shoulder in which the blank of material 160 can be housed. and on its upper face a housing adapted to accommodate the peripheral electrode 132.
  • the electrode holder 136 therefore also acts as a blank holder to hold the blank of material 160 against the mold 150.
  • an additional part 280 can be used to act as a blank holder and to hold the blank of material to be deformed against the mold as illustrated with reference to figure 2 , for example.
  • the electrode holder 136 does not have a shoulder on its underside.
  • the body 140, the peripheral electrode 130 and the mold 150 are in electrical contact with one another when they are made of a conductive material such as steel, or any other alloy. metallic.
  • an electrical insulator 115 surrounds the central electrode 120 over at least part of its length, in particular over the part of the central electrode 120 housed in the body 140.
  • the central electrode 120 is therefore electrically isolated from the peripheral electrode 130, even if the body 140 is in electrical contact with the peripheral electrode 130.
  • the central electrode 120 can therefore be subjected to a first electric potential by connecting it to one of the terminals of a high voltage pulse generator 170 and by connecting the body 140, the peripheral electrode 130 or the mold 150 to the other terminal of the pulse generator high voltage 170.
  • This embodiment of the invention is particularly advantageous because it is easy to machine and to assemble.
  • the mold 150 can be made in one piece or be fixed to an additional part called the mold support, thus making it easier to change the mold depending on the part to be formed.
  • the central electrode can be fixed in the electrohydroforming device by various means. It can, for example, be held using an additional part (not shown) electrically insulated from the body.
  • the assembly formed by the mold and the peripheral electrode is movable relative to the body comprising the central electrode and the body is preferably fixed.
  • the peripheral electrode is then fixed to the mold.
  • the mold is mounted on the plate of a press and the peripheral electrode is fixed directly to the body.
  • the material blank is held between the peripheral electrode and the mold when the mold is held against the peripheral electrode using the press.
  • peripheral electrode is easily accessible and can be easily changed.
  • the figure 2 shows a second embodiment of an electrohydroforming device according to the invention.
  • the electrohydroforming device 200 is similar to that shown with reference to figure 1A in that it also comprises an electrohydroforming chamber 210, a central electrode 220, a peripheral electrode 230, a body 240 and a mold 250.
  • the electrohydroforming device 200 further comprises an additional part 280 acting as a blank holder.
  • the device further comprises an electrode holder 232 on which the peripheral electrode 230 is fixed.
  • the body 240 further comprises an electrical insulator 215 positioned, no longer between the body and the central electrode as illustrated with reference to figures 1A and 1B , but for example, on the lower part of the body 240.
  • the electrical insulator 215 constitutes the side wall 243 of the cavity 240 partly forming the electrohydroforming chamber 210. In other variants embodiment, the electrical insulator 215 may form only part of the side wall.
  • the central electrode 220 and the upper part 241 of the body 240 are then in electrical contact and the upper part 241 of the body 240, for example, can be connected to a first terminal of the high voltage pulse generator 270.
  • the peripheral electrode 230, the electrode holder 232, the blank holder 280 and the mold 250 are in electrical contact and the peripheral electrode 230 is connected to a second terminal of the high voltage pulse generator 270 through the electrode holder 232, the clamp blank 280 or of the mold 250 thus causing an electric discharge between the central electrode 220 and the peripheral electrode 230.
  • the shock wave thus generated propagates in a plane perpendicular to this discharge.
  • part of the shock wave propagates towards the bottom wall 244 and impacts this wall, which can damage it. Since the insulation is located on the side wall, it is therefore less stressed, which reduces its risk of damage.
  • the body 240 comprises a cavity 242 and that the side wall 243 and the bottom wall 244 can have different shapes adapted to better containment of the pressure waves towards the blank of material to be deformed.
  • the bottom wall 244 can be inclined so as to better reflect the shock waves towards the blank of material to be deformed.
  • the active part 224 of the central electrode 220 and the active part 234 of the peripheral electrode 230 are not necessarily of constant and / or axisymmetric section as illustrated with reference to figure 2 .
  • electrohydroforming devices have only one central electrode and one peripheral electrode.
  • the electrohydroforming device may include several pairs of central and peripheral electrodes associated with one or more molds. It is thus possible to produce several parts in parallel or a large part by implementing several electric discharges in parallel.
  • FIGS. 3A to 3D illustrate more particularly the active parts of central and peripheral electrodes seen in section along a plane (YY ', ZZ') perpendicular to the longitudinal axis XX 'of a central electrode.
  • the active part 301 of the central electrode is circular in shape and the active part 302 of the peripheral electrode has the shape of a circular ring.
  • the active parts 303, 305, 307 of several central electrodes are of rectangular section, preferably with rounded corners, and aligned in a common direction ZZ 'at the center of a ring of rectangular shape forming the active part 308 of the electrode corresponding device.
  • the active parts 309, 311 of several central electrodes are of elliptical section and aligned in a common direction ZZ 'at the center of an elliptical shaped ring forming the active part 312 of the corresponding peripheral electrode.
  • the active parts 313, 314, 315, 316 of four central electrodes are of square rectangular section, preferably with rounded corners, and are arranged inside a square-shaped ring forming the active part 317 of the electrode corresponding device.
  • peripheral electrodes described here are formed in one piece.
  • the peripheral electrodes comprise different separate sections intended to be placed opposite each central electrode in order to generate discharges. These different sections therefore include the active parts of the peripheral electrode. The costs of replacing the peripheral electrodes are thus reduced by replacing only certain sections. It will be noted that other geometric shapes can also be used provided that the distance between the external surface of the active part of the central electrode considered and the internal surface of the active part of the neighboring peripheral electrode is substantially equidistant over at minus a portion of the surfaces of the active parts considered in the plane.
  • the section of the active parts of the electrodes can be constant or vary according to their longitudinal direction represented by the axis XX 'on the figures 1A , 1B and 2 .
  • an electrohydroforming device allows the electrohydraulic forming of blanks of material with a peripheral electrode partially surrounding a central electrode, the peripheral electrode being separate from the body forming part of the chamber. electrohydroforming.
  • the electric discharge is therefore distributed over the periphery of the active parts of the electrodes.
  • the peripheral electrode which has a larger contact surface, wears out more slowly.
  • the distance between the electrodes varies little, which makes it possible to maintain the efficiency of the electrohydroforming while keeping a pressure generated by the electric discharge substantially constant.
  • the peripheral electrode can advantageously easily be changed when the electrohydroforming device is opened to place the material blank, the peripheral electrode being separate from the body and the material blank. being preferably placed between the peripheral electrode and the mold.
  • the central electrode can be moved along its longitudinal axis in order to present to the peripheral electrode a less degraded active part.
  • the present invention is not limited to the various embodiments described and illustrated and to the variants mentioned, but it also relates to the embodiments within the reach of a person skilled in the art within the framework of the claims below.

Description

Arrière-plan de l'inventionBackground of the invention

La présente invention concerne un dispositif d'électrohydroformage.The present invention relates to an electrohydroforming device.

Objet et résumé de l'inventionPurpose and summary of the invention

Le formage électrohydraulique, également appelé électrohydroformage, permet de déformer un flan de matière contre un moule par application d'une pression dynamique. A cet effet, on génère une décharge électrique entre au moins deux électrodes placées dans une chambre remplie de liquide, par exemple de l'eau. Un arc électrique est alors formé entre les deux électrodes provoquant un gradient de température élevé et la vaporisation du liquide. Une onde de pression, aussi communément appelée « onde de choc », se déplace à grande vitesse et vient plaquer le flan de matière contre le moule. Le formage électrohydraulique est particulièrement avantageux en comparaison avec les autres procédés de formage puisqu'il permet d'avoir un retour élastique réduit et d'obtenir des détails de type gravure et/ou des angles vifs et/ou des allongements locaux avant rupture améliorés sur les pièces à former.Electrohydraulic forming, also called electrohydroforming, deforms a blank of material against a mold by applying dynamic pressure. To this end, an electric discharge is generated between at least two electrodes placed in a chamber filled with liquid, for example water. An electric arc is then formed between the two electrodes causing a high temperature gradient and vaporization of the liquid. A pressure wave, also commonly called a “shock wave”, travels at high speed and presses the blank of material against the mold. Electrohydraulic forming is particularly advantageous in comparison with other forming processes since it allows to have a reduced springback and to obtain etching-type details and / or sharp angles and / or local elongations before breakage improved on the parts to be formed.

Le formage électrohydraulique ou électrohydroformage présente cependant des inconvénients. L'un des inconvénients de l'électrohydroformage est que les électrodes s'usent rapidement. De ce fait, la distance entre les électrodes augmente et la décharge électrique est moins forte. L'efficacité de l'électrohydroformage diminue. Afin de pallier à cet inconvénient, les électrodes sont remplacées régulièrement. Le remplacement des électrodes engendre des coûts supplémentaires de maintenance et implique une baisse de la cadence de production suite à une immobilisation temporaire de l'appareil.Electrohydraulic or electrohydroforming forming, however, has drawbacks. One of the disadvantages of electrohydroforming is that the electrodes wear out quickly. As a result, the distance between the electrodes increases and the electric discharge is less strong. The efficiency of electrohydroforming decreases. In order to overcome this drawback, the electrodes are replaced regularly. The replacement of the electrodes generates additional maintenance costs and involves a reduction in the production rate following a temporary immobilization of the device.

Le document US4 068 514 décrit un dispositif d'électrohydroformage comprenant une électrode centrale s'étendant selon une direction longitudinale et une électrode périphérique formée par la paroi de la chambre de formage entourant l'électrode centrale. L'usure de l'électrode périphérique étant répartie sur une plus grande surface, la distance entre les électrodes varie moins qu'avec un dispositif dans lequel deux électrodes, le plus souvent coniques, sont placées face à face et dont les parties actives sont de ce fait très localisées.The document US4,068,514 describes an electrohydroforming device comprising a central electrode extending in a longitudinal direction and a peripheral electrode formed by the wall of the forming chamber surrounding the central electrode. Since the wear of the peripheral electrode is distributed over a larger area, the distance between the electrodes varies less than with a device in which two electrodes, most often conical, are placed face to face and whose active parts are therefore very localized.

Les électrodes peuvent donc être utilisées plus longtemps sans que l'efficacité de l'électrohydroformage, et notamment la pression générée par l'onde de choc, soit affectée. Cependant, le remplacement d'une électrode implique le changement de la totalité de la chambre d'électrohydroformage ce qui engendre des coûts de maintenance plus élevés que pour les autres dispositifs de l'art antérieur et une immobilisation temporaire de l'appareil pour remplacer l'électrode plus longue.The electrodes can therefore be used longer without the efficiency of the electrohydroforming, and in particular the pressure generated by the shock wave, being affected. However, replacing an electrode involves changing the entire electrohydroforming chamber, which generates higher maintenance costs than for other devices of the prior art and temporary immobilization of the device to replace the electrode. longer electrode.

La présente invention vise notamment à pallier aux inconvénients de l'art antérieur précités.The present invention aims in particular to overcome the drawbacks of the aforementioned prior art.

À cet effet, la présente invention propose un dispositif d'électrohydroformage d'un flan de matière comprenant :

  • une chambre d'électrohydroformage,
  • au moins une électrode dite électrode centrale s'étendant selon une direction dite longitudinale et comportant une première extrémité disposée à l'intérieur de la chambre d'électrohydroformage, et
  • au moins une électrode dite électrode périphérique électriquement isolée de chaque électrode centrale, présentant une extrémité disposée à distance et autour de l'extrémité d'une électrode centrale, ladite extrémité s'étendant dans un plan transversal par rapport à ladite électrode centrale,
  • un corps muni d'un alésage pour l'introduction de chaque électrode centrale dans la chambre d'électrohydroformage, la chambre d'électrohydroformage étant en partie formée par ledit corps, et
  • un moule.
To this end, the present invention provides an electrohydroforming device for a material blank comprising:
  • an electrohydroforming chamber,
  • at least one electrode called the central electrode extending in a direction called longitudinal and having a first end disposed inside the electrohydroforming chamber, and
  • at least one electrode called the peripheral electrode electrically insulated from each central electrode, having one end disposed at a distance from and around the end of a central electrode, said end extending in a plane transverse to said central electrode,
  • a body provided with a bore for the introduction of each central electrode into the electrohydroforming chamber, the electrohydroforming chamber being partly formed by said body, and
  • a mold.

En outre, chaque électrode périphérique est distincte dudit corps.In addition, each peripheral electrode is separate from said body.

Selon l'invention, l'utilisation d'une électrode périphérique distincte du corps formant en partie la chambre d'électrohydroformage permet de réduire la taille de l'électrode périphérique à changer et le temps d'immobilisation du dispositif lors du changement d'électrodes, réduisant ainsi les coûts de maintenance.According to the invention, the use of a peripheral electrode separate from the body partly forming the electrohydroforming chamber makes it possible to reduce the size of the peripheral electrode to be changed and the immobilization time of the device when changing electrodes. , thus reducing maintenance costs.

Dans une forme de réalisation, l'au moins une électrode périphérique est en saillie par rapport au corps, ce qui permet de mieux contrôler l'endroit où se produit la décharge et d'augmenter l'efficacité de l'électrohydroformage.In one embodiment, the at least one peripheral electrode protrudes from the body, allowing better control of where the discharge occurs and increasing the efficiency of electrohydroforming.

Dans une forme de réalisation, l'au moins une électrode périphérique est supportée par un porte-électrode.In one embodiment, the at least one peripheral electrode is supported by an electrode holder.

L'utilisation d'un porte-électrode permet de réduire la taille de l'électrode périphérique devant être changée et de simplifier le remplacement de l'électrode périphérique. De manière avantageuse, le porte-électrode peut aussi faire office de serre-flan. On obtient ainsi un dispositif d'électrohydroformage compact et facile à assembler.The use of an electrode holder makes it possible to reduce the size of the peripheral electrode to be changed and to simplify the replacement of the peripheral electrode. Advantageously, the electrode holder can also act as a blank holder. A compact and easy to assemble electrohydroforming device is thus obtained.

Dans une forme de réalisation, le dispositif comporte une unique électrode périphérique et au moins une électrode centrale.In one embodiment, the device comprises a single peripheral electrode and at least one central electrode.

Il peut être avantageux d'utiliser plusieurs électrodes centrales associées à une unique électrode périphérique, notamment dans le cas de pièces à former de grandes dimensions. En réalisant plusieurs décharges électriques simultanées ou différées à différents endroits, il est possible de réaliser un formage électrohydraulique plus homogène ou plus progressif ou plus profond qu'avec un dispositif d'électrohydroformage de l'art antérieur. Dans d'autres formes de réalisation, le dispositif d'électrohydroformage peut comporter plusieurs paires d'électrodes centrales et périphériques associées à un ou plusieurs moules. Il est ainsi possible de réaliser plusieurs pièces en parallèle ou une grande pièce en mettant en œuvre parallèlement plusieurs décharges électriques.It may be advantageous to use several central electrodes associated with a single peripheral electrode, in particular in the case of parts to be formed of large dimensions. By carrying out several simultaneous or delayed electric discharges at different places, it is possible to carry out an electro-hydraulic forming that is more homogeneous or more progressive or deeper than with an electrohydroforming device of the prior art. In other embodiments, the electrohydroforming device may include several pairs of central and peripheral electrodes associated with one or more molds. It is thus possible to produce several parts in parallel or a large part by implementing several electric discharges in parallel.

Dans une forme de réalisation, la chambre d'électrohydroformage est formée par un corps et par l'extrémité de l'électrode périphérique. La chambre d'électrohydroformage est alors fermée par le flan de matière à déformer. Cette forme de réalisation est avantageuse car facile à usiner et à assembler.In one embodiment, the electrohydroforming chamber is formed by a body and the end of the peripheral electrode. The electrohydroforming chamber is then closed by the blank of material to be deformed. This embodiment is advantageous because it is easy to machine and assemble.

Dans une forme de réalisation,un flan de matière est maintenu entre l'extrémité de l'électrode périphérique et le moule. On obtient ainsi un dispositif d'électrohydroformage compact et facile à assembler. De manière avantageuse, l'extrémité de l'électrode périphérique peut comprendre un épaulement dans lequel vient se loger le flan de matière. L'électrode périphérique fait alors office de serre-flan et permet de maintenir le flan de matière contre le moule.In one embodiment, a blank of material is held between the end of the peripheral electrode and the mold. A compact and easy to assemble electrohydroforming device is thus obtained. Advantageously, the end of the peripheral electrode can comprise a shoulder in which the blank of material is housed. The peripheral electrode then acts as a blank holder and allows the blank to be held material against the mold.

Dans une variante de réalisation, le dispositif comprend un serre-flan disposé entre l'extrémité de l'électrode périphérique et le moule.In an alternative embodiment, the device comprises a blank holder arranged between the end of the peripheral electrode and the mold.

Dans une forme de réalisation, le dispositif comporte en outre un support de moule qui permet de changer plus facilement le moule en fonction de la pièce à former.In one embodiment, the device further comprises a mold support which makes it easier to change the mold depending on the part to be formed.

Dans une forme de réalisation, l'électrode centrale est entourée sur une partie de sa longueur par un isolant électrique.In one embodiment, the central electrode is surrounded for part of its length by an electrical insulator.

Dans une autre variante de réalisation, le corps est en contact électrique avec l'électrode centrale et comprend en outre un isolant électrique destiné à isoler l'électrode périphérique de l'électrode centrale.In another variant embodiment, the body is in electrical contact with the central electrode and further comprises an electrical insulator intended to insulate the peripheral electrode from the central electrode.

Lorsque l'électrode centrale est entourée sur une partie de sa longueur par un isolant électrique, le corps est plus facile à usiner et à assembler que lorsque le corps comprend l'isolant électrique destiné à isoler l'électrode périphérique de l'électrode centrale.When the central electrode is surrounded over part of its length by an electrical insulator, the body is easier to machine and assemble than when the body includes the electrical insulator intended to insulate the peripheral electrode from the central electrode.

Avantageusement, le corps comporte en outre une cavité formant en partie la chambre d'électrohydroformage et l'isolant électrique forme au moins en partie une paroi latérale de ladite cavité. De manière particulièrement avantageuse, l'isolant électrique constitue la paroi latérale de la cavité.Advantageously, the body further comprises a cavity partly forming the electrohydroforming chamber and the electrical insulator at least partly forming a side wall of said cavity. Particularly advantageously, the electrical insulator constitutes the side wall of the cavity.

Une partie de l'onde de choc se propageant en direction de la paroi de fond de la cavité où débouche l'électrode centrale, l'isolant situé sur la paroi latérale est moins sollicité que lorsqu'il entoure l'électrode centrale et forme en partie la paroi de fond de la cavité.Part of the shock wave propagating in the direction of the bottom wall of the cavity where the central electrode opens, the insulator located on the side wall is less stressed than when it surrounds the central electrode and forms a part the bottom wall of the cavity.

Dans une forme de réalisation, l'extrémité de l'électrode périphérique et le moule sont en contact électrique et soumis à un premier potentiel électrique, l'électrode centrale étant soumise à un second potentiel électrique.In one embodiment, the end of the peripheral electrode and the mold are in electrical contact and subjected to a first electrical potential, the central electrode being subjected to a second electrical potential.

Lorsque l'électrode périphérique et le moule sont en contact électrique, éventuellement par l'intermédiaire d'un support de moule et/ou d'un serre-flan, l'électrode centrale étant par ailleurs isolée, il est aisé de générer la décharge électrique en reliant l'électrode centrale ou le corps, s'il est en contact électrique avec l'électrode centrale, à l'une des bornes d'un générateur de tension impulsionnel et en reliant l'un des éléments au contact électrique de l'électrode périphérique à l'autre borne du générateur de tension impulsionnel. La conception du dispositif d'électrohydroformage est donc plus aisée puisque les connexions électriques avec les bornes du générateur impulsionnel haute-tension ne sont pas nécessairement établies au niveau des électrodes centrales et périphériques.When the peripheral electrode and the mold are in electrical contact, optionally via a mold support and / or a blank holder, the central electrode being moreover isolated, it is easy to generate the discharge electric by connecting the central electrode or the body, if it is in electrical contact with the central electrode, to one of the terminals of a pulse voltage generator and by connecting one of the elements to the electrical contact of the peripheral electrode to the other terminal of the pulse voltage generator. The design of the electrohydroforming device is therefore easier since the electrical connections with the terminals of the high-voltage pulse generator are not necessarily established at the level of the central and peripheral electrodes.

Brève description des dessinsBrief description of the drawings

Des détails et avantages de la présente invention apparaitront mieux de la description qui suit, faite en référence aux dessins annexés sur lesquels :

  • la figure 1A représente une vue en coupe d'un dispositif d'électrohydroformage selon une première forme de réalisation de l'invention,
  • la figure 1B représente une vue en coupe d'un dispositif d'électrohydroformage selon une variante de réalisation,
  • la figure 2 représente une vue en coupe d'un dispositif d'électrohydroformage selon une seconde forme de réalisation de l'invention,
  • les figures 3A, 3B, 3C et 3D représentent une vue en coupe des parties actives de différentes électrode centrales et périphériques selon différentes variantes de réalisation.
Details and advantages of the present invention will become more apparent from the description which follows, made with reference to the accompanying drawings in which:
  • the figure 1A shows a sectional view of an electrohydroforming device according to a first embodiment of the invention,
  • the figure 1B shows a sectional view of an electrohydroforming device according to an alternative embodiment,
  • the figure 2 shows a sectional view of an electrohydroforming device according to a second embodiment of the invention,
  • the figures 3A, 3B, 3C and 3D show a sectional view of the active parts of different central and peripheral electrodes according to different variant embodiments.

Description détaillée de plusieurs modes de réalisation de l'inventionDetailed description of several embodiments of the invention

La figure 1A représente une première forme de réalisation d'un dispositif d'électrohydroformage selon l'invention. Le dispositif d'électrohydroformage 100 comprend une chambre d'électrohydroformage 110, une électrode centrale 120 et une électrode périphérique 130. L'électrode centrale 120 s'étend selon une direction longitudinale XX' et comporte une première extrémité 122 disposée à l'intérieur de la chambre d'électrohydroformage 110. L'électrode périphérique 130 présente une extrémité 132 disposée à distance et autour de l'extrémité 122 de l'électrode centrale 120. L'extrémité 132 de l'électrode périphérique 130 s'étend dans un plan transversal par rapport à ladite électrode centrale 120, c'est-à-dire dans le plan perpendiculaire à l'axe XX'.The figure 1A shows a first embodiment of an electrohydroforming device according to the invention. The electrohydroforming device 100 comprises an electrohydroforming chamber 110, a central electrode 120 and a peripheral electrode 130. The central electrode 120 extends in a longitudinal direction XX 'and has a first end 122 disposed inside the device. the electrohydroforming chamber 110. The peripheral electrode 130 has an end 132 disposed at a distance from and around the end 122 of the central electrode 120. The end 132 of the peripheral electrode 130 extends in a transverse plane relative to said central electrode 120, that is to say in the plane perpendicular to the axis XX '.

Le dispositif d'électrohydroformage 100 comprend également un corps 140 et un moule 150. Le corps 140 comporte une cavité interne 142 et est traversé par l'électrode centrale 120. La cavité interne 142 du corps forme, avec l'extrémité 132 de l'électrode périphérique 130, la chambre d'électrohydroformage 110.The electrohydroforming device 100 also comprises a body 140 and a mold 150. The body 140 comprises an internal cavity 142 and is crossed by the central electrode 120. The internal cavity 142 of the body forms, with the end 132 of the peripheral electrode 130, the electrohydroforming chamber 110.

La chambre d'électrohydroformage 110 est destinée à être remplie d'un liquide, par exemple de l'eau, et est fermée par un flan de matière 160 à déformer. Le flan de matière 160 est plaqué contre le moule 150 et se déforme contre le moule 150 sous l'action d'une onde de choc se propageant dans la chambre d'électrohydroformage 110. L'onde de choc est générée suite à l'application d'une impulsion électrique à haute tension entre les électrodes 120 et 130 et la génération d'une décharge électrique entre les électrodes. La décharge électrique entraine la formation d'un arc électrique, une augmentation de température et la vaporisation du liquide provoquant la création de l'onde de choc.The electrohydroforming chamber 110 is intended to be filled with a liquid, for example water, and is closed by a blank of material 160 to be deformed. The blank of material 160 is pressed against the mold 150 and deforms against the mold 150 under the action of a shock wave propagating in the electrohydroforming chamber 110. The shock wave is generated following the application. of a high voltage electrical pulse between the electrodes 120 and 130 and the generation of an electrical discharge between the electrodes. The electric discharge causes the formation of an electric arc, an increase in temperature and the vaporization of the liquid causing the creation of the shock wave.

Dans la forme de réalisation décrite ici, une partie de l'extrémité 132 de l'électrode périphérique 130 entoure l'extrémité 122 inférieure de l'électrode centrale 120. Un arc électrique se crée préférentiellement entre deux zones 124 et 134, appelées parties actives, de l'électrode centrale 120 et de l'électrode périphérique 130 respectivement. Après chaque décharge électrique, un arc électrique se crée préférentiellement entre deux points différents de la surface externe 125 de la partie active 124 de l'électrode centrale 120 et de la surface interne 135 de la partie active 134 de l'électrode périphérique 130 correspondant au plus court chemin entre l'électrode centrale 120 et l'électrode périphérique 130, respectivement. Ainsi, chaque électrode s'use localement en différents points répartis sur la surface externe 125 de la partie active 124 de l'électrode centrale 120 et sur la surface interne 135 de la partie active 134 de l'électrode périphérique 130. L'usure de l'électrode périphérique étant répartie sur une plus grande surface, la distance entre les électrodes varie moins qu'avec un dispositif de l'art antérieur dans lequel deux électrodes, le plus souvent coniques, sont placées face à face et dont les parties actives sont de ce fait très localisées. Les électrodes peuvent donc être utilisées plus longtemps sans que l'efficacité de l'électrohydroformage, et notamment la pression générée par l'onde de choc, soit affectée.In the embodiment described here, part of the end 132 of the peripheral electrode 130 surrounds the lower end 122 of the central electrode 120. An electric arc is preferably created between two zones 124 and 134, called active parts. , the central electrode 120 and the peripheral electrode 130 respectively. After each electric discharge, an electric arc is preferably created between two different points of the external surface 125 of the active part 124 of the central electrode 120 and of the internal surface 135 of the active part 134 of the peripheral electrode 130 corresponding to the shortest path between the central electrode 120 and the peripheral electrode 130, respectively. Thus, each electrode wears out locally at different points distributed over the external surface 125 of the active part 124 of the central electrode 120 and on the internal surface 135 of the active part 134 of the peripheral electrode 130. The wear of the peripheral electrode being distributed over a larger area, the distance between the electrodes varies less than with a device of the prior art in which two electrodes, most often conical, are placed face to face and the active parts of which are therefore very localized. The electrodes can therefore be used longer without the efficiency of the electrohydroforming, and in particular the pressure generated by the shock wave, being affected.

On notera par ailleurs que la section de l'électrode centrale n'est pas forcément constante le long de son axe longitudinal XX' comme illustré par exemple en référence à la figure 2. En outre, la section de l'électrode n'est pas forcément axisymétrique.It will also be noted that the section of the central electrode is not necessarily constant along its longitudinal axis XX 'as illustrated by example with reference to figure 2 . In addition, the section of the electrode is not necessarily axisymmetric.

Le flan de matière 160 est maintenu contre le moule 150 par l'électrode périphérique 130 (figure 1A). A cet effet, l'électrode périphérique 130 comprend également, sur sa face inférieure, un épaulement dans lequel peut être logé le flan de matière 160. L'électrode périphérique 130 fait alors office de serre-flan et permet de maintenir le flan de matière 160 contre le moule 150.The blank of material 160 is held against the mold 150 by the peripheral electrode 130 ( figure 1A ). For this purpose, the peripheral electrode 130 also comprises, on its lower face, a shoulder in which the material blank 160 can be housed. The peripheral electrode 130 then acts as a blank holder and makes it possible to hold the material blank. 160 against the mold 150.

Dans une variante de réalisation représentée sur la figure 1B, le dispositif d'électrohydroformage 100', de structure similaire à celle du dispositif représenté en référence à la figure 1A, comporte en outre un porte-électrode 136 supportant l'électrode périphérique 130. Le porte-électrode 136 est disposé entre le moule 150 et le corps 140. Il comprend sur sa face inférieure un épaulement dans lequel peut être logé le flan de matière 160 et sur sa face supérieure un logement adapté pour accueillir l'électrode périphérique 132. Le porte-électrode 136 fait donc également office de serre-flan pour maintenir le flan de matière 160 contre le moule 150.In an alternative embodiment shown in figure 1B , the electrohydroforming device 100 ', similar in structure to that of the device shown with reference to figure 1A , further comprises an electrode holder 136 supporting the peripheral electrode 130. The electrode holder 136 is arranged between the mold 150 and the body 140. It comprises on its lower face a shoulder in which the blank of material 160 can be housed. and on its upper face a housing adapted to accommodate the peripheral electrode 132. The electrode holder 136 therefore also acts as a blank holder to hold the blank of material 160 against the mold 150.

Dans d'autres variantes de réalisation, une pièce supplémentaire 280 peut être utilisée pour faire office de serre-flan et maintenir le flan de matière à déformer contre le moule tel qu'illustré en référence à la figure 2, par exemple. Dans ce cas, le porte-électrode 136 ne comporte pas d'épaulement sur sa face inférieure.In other variant embodiments, an additional part 280 can be used to act as a blank holder and to hold the blank of material to be deformed against the mold as illustrated with reference to figure 2 , for example. In this case, the electrode holder 136 does not have a shoulder on its underside.

On remarquera par ailleurs que le corps 140, l'électrode périphérique 130 et le moule 150 sont en contact électrique l'un avec l'autre lorsque ceux-ci sont constitués d'un matériau conducteur tel que l'acier, ou tout autre alliage métallique. Dans la forme de réalisation décrite ici, un isolant électrique 115 entoure l'électrode centrale 120 sur une partie de sa longueur au moins, notamment sur la partie de l'électrode centrale 120 logée dans le corps 140. L'électrode centrale 120 est donc isolée électriquement de l'électrode périphérique 130, même si le corps 140 est en contact électrique avec l'électrode périphérique 130. L'électrode centrale 120 peut donc être soumise à un premier potentiel électrique en la reliant à l'une des bornes d'un générateur impulsionnel haute tension 170 et en reliant le corps 140, l'électrode périphérique 130 ou le moule 150 à l'autre borne du générateur impulsionnel haute tension 170. Cette forme de mise en œuvre de l'invention est particulièrement avantageuse car facile à usiner et à assembler.It will also be noted that the body 140, the peripheral electrode 130 and the mold 150 are in electrical contact with one another when they are made of a conductive material such as steel, or any other alloy. metallic. In the embodiment described here, an electrical insulator 115 surrounds the central electrode 120 over at least part of its length, in particular over the part of the central electrode 120 housed in the body 140. The central electrode 120 is therefore electrically isolated from the peripheral electrode 130, even if the body 140 is in electrical contact with the peripheral electrode 130. The central electrode 120 can therefore be subjected to a first electric potential by connecting it to one of the terminals of a high voltage pulse generator 170 and by connecting the body 140, the peripheral electrode 130 or the mold 150 to the other terminal of the pulse generator high voltage 170. This embodiment of the invention is particularly advantageous because it is easy to machine and to assemble.

On notera que le moule 150 peut être constitué d'un seul tenant ou être fixé sur une pièce supplémentaire appelée support de moule, permettant ainsi de changer plus facilement le moule en fonction de la pièce à former.It will be noted that the mold 150 can be made in one piece or be fixed to an additional part called the mold support, thus making it easier to change the mold depending on the part to be formed.

On notera que les différents éléments constitutifs du dispositif d'électrohydroformage décrits ici sont fixés entre eux à l'aide de vis et que des joints peuvent être utilisés afin d'étanchéifier la chambre d'hydroformage, notamment au niveau de l'électrode centrale, de l'électrode périphérique et du moule par exemple. De tels moyens sont à la portée de l'homme du métier et ne sont pas décrits avec plus de détails ici par soucis de simplification.It will be noted that the various constituent elements of the electrohydroforming device described here are fixed together using screws and that gaskets can be used in order to seal the hydroforming chamber, in particular at the level of the central electrode, of the peripheral electrode and of the mold for example. Such means are within the reach of those skilled in the art and are not described in more detail here for the sake of simplification.

On notera par ailleurs que la façon dont est maintenue l'électrode centrale dans le corps n'est pas représentée. L'électrode centrale peut être fixée dans le dispositif d'électrohydroformage par différents moyens. Elle peut, par exemple, être maintenue à l'aide d'une pièce supplémentaire (non représentée) isolée électriquement du corps.It will also be noted that the way in which the central electrode is held in the body is not shown. The central electrode can be fixed in the electrohydroforming device by various means. It can, for example, be held using an additional part (not shown) electrically insulated from the body.

De manière avantageuse, afin de pouvoir placer le flan de matière entre l'électrode périphérique et le moule, l'ensemble formé par le moule et l'électrode périphérique est mobile par rapport au corps comprenant l'électrode centrale et le corps est de préférence fixe. L'électrode périphérique est alors fixée sur le moule. Ainsi, il n'est pas nécessaire de déplacer les conducteurs d'amenée du courant reliés au corps lorsque l'on change le flan de matière à déformer.Advantageously, in order to be able to place the blank of material between the peripheral electrode and the mold, the assembly formed by the mold and the peripheral electrode is movable relative to the body comprising the central electrode and the body is preferably fixed. The peripheral electrode is then fixed to the mold. Thus, it is not necessary to move the current supply conductors connected to the body when changing the blank of material to be deformed.

Dans une variante de réalisation, le moule est monté sur le plateau d'une presse et l'électrode périphérique est fixée directement sur le corps. Le flan de matière est maintenu entre l'électrode périphérique et le moule lorsque le moule est maintenu contre l'électrode périphérique à l'aide de la presse.In an alternative embodiment, the mold is mounted on the plate of a press and the peripheral electrode is fixed directly to the body. The material blank is held between the peripheral electrode and the mold when the mold is held against the peripheral electrode using the press.

On notera que dans les dispositifs d'électrohydroformage décrits ici et dans la présente demande, l'électrode périphérique est facilement accessible et peut être facilement changée.It will be noted that in the electrohydroforming devices described here and in the present application, the peripheral electrode is easily accessible and can be easily changed.

La figure 2 représente une deuxième forme de réalisation d'un dispositif d'électrohydroformage selon l'invention. Le dispositif d'électrohydroformage 200 est semblable à celui représenté en référence à la figure 1A en ce qu'il comprend également une chambre d'électrohydroformage 210, une électrode centrale 220, une électrode périphérique 230, un corps 240 et un moule 250. Contrairement au dispositif d'électrohydroformage représenté en référence à la figure 1A, le dispositif d'électrohydroformage 200 comprend en outre une pièce supplémentaire 280 faisant office de serre-flan. Le dispositif comprend en outre un porte-électrode 232 sur lequel est fixée l'électrode périphérique 230. Le corps 240 comprend en outre un isolant électrique 215 positionné, non plus entre le corps et l'électrode centrale comme illustré en référence aux figures 1A et 1B, mais par exemple, sur la partie inférieure du corps 240. Dans la forme de réalisation illustrée ici, l'isolant électrique 215 constitue la paroi latérale 243 de la cavité 240 formant en partie la chambre d'électrohydroformage 210. Dans d'autres variantes de réalisation, l'isolant électrique 215 peut ne former qu'une partie de la paroi latérale. L'électrode centrale 220 et la partie supérieure 241 du corps 240 sont alors en contact électrique et la partie supérieure 241 du corps 240, par exemple, peut être reliée à une première borne du générateur impulsionnel haute tension 270. L'électrode périphérique 230, le porte-électrode 232, le serre-flan 280 et le moule 250 sont en contact électrique et l'électrode périphérique 230 est reliée à une seconde borne du générateur impulsionnel haute tension 270 par l'intermédiaire du porte-électrode 232, du serre-flan 280 ou du moule 250 provoquant ainsi une décharge électrique entre l'électrode centrale 220 et l'électrode périphérique 230. L'onde de choc ainsi générée se propage dans un plan perpendiculaire à cette décharge. Ainsi, une partie de l'onde de choc se propage vers la paroi de fond 244 et vient impacter cette paroi, ce qui peut l'endommager. L'isolant étant situé sur la paroi latérale, celui-ci est donc moins sollicité, ce qui diminue son risque d'endommagement.The figure 2 shows a second embodiment of an electrohydroforming device according to the invention. The electrohydroforming device 200 is similar to that shown with reference to figure 1A in that it also comprises an electrohydroforming chamber 210, a central electrode 220, a peripheral electrode 230, a body 240 and a mold 250. Unlike the electrohydroforming device shown with reference to figure 1A , the electrohydroforming device 200 further comprises an additional part 280 acting as a blank holder. The device further comprises an electrode holder 232 on which the peripheral electrode 230 is fixed. The body 240 further comprises an electrical insulator 215 positioned, no longer between the body and the central electrode as illustrated with reference to figures 1A and 1B , but for example, on the lower part of the body 240. In the embodiment illustrated here, the electrical insulator 215 constitutes the side wall 243 of the cavity 240 partly forming the electrohydroforming chamber 210. In other variants embodiment, the electrical insulator 215 may form only part of the side wall. The central electrode 220 and the upper part 241 of the body 240 are then in electrical contact and the upper part 241 of the body 240, for example, can be connected to a first terminal of the high voltage pulse generator 270. The peripheral electrode 230, the electrode holder 232, the blank holder 280 and the mold 250 are in electrical contact and the peripheral electrode 230 is connected to a second terminal of the high voltage pulse generator 270 through the electrode holder 232, the clamp blank 280 or of the mold 250 thus causing an electric discharge between the central electrode 220 and the peripheral electrode 230. The shock wave thus generated propagates in a plane perpendicular to this discharge. Thus, part of the shock wave propagates towards the bottom wall 244 and impacts this wall, which can damage it. Since the insulation is located on the side wall, it is therefore less stressed, which reduces its risk of damage.

On notera que, comme dans la figure 1A, le corps 240 comprend une cavité 242 et que la paroi latérale 243 et la paroi de fond 244 peuvent avoir différentes formes adaptées à un meilleur confinement des ondes de pression vers le flan de matière à déformer. Par exemple, la paroi de fond 244 peut être inclinée de façon à mieux réfléchir les ondes de choc vers le flan de matière à déformer.Note that, as in figure 1A , the body 240 comprises a cavity 242 and that the side wall 243 and the bottom wall 244 can have different shapes adapted to better containment of the pressure waves towards the blank of material to be deformed. For example, the bottom wall 244 can be inclined so as to better reflect the shock waves towards the blank of material to be deformed.

On notera également que la partie active 224 de l'électrode centrale 220 et la partie active 234 de l'électrode périphérique 230 ne sont pas forcément de section constante et/ou axisymétrique comme illustré en référence à la figure 2.It will also be noted that the active part 224 of the central electrode 220 and the active part 234 of the peripheral electrode 230 are not necessarily of constant and / or axisymmetric section as illustrated with reference to figure 2 .

Dans les formes de réalisation décrites en référence aux figures 1A, 1B et 2, les dispositifs d'électrohydroformage ne comportent qu'une électrode centrale et qu'une électrode périphérique.In the embodiments described with reference to figures 1A , 1B and 2 , electrohydroforming devices have only one central electrode and one peripheral electrode.

Dans d'autres formes de réalisation, le dispositif d'électrohydroformage peut comporter plusieurs paires d'électrodes centrales et périphériques associées à un ou plusieurs moules. Il est ainsi possible de réaliser plusieurs pièces en parallèle ou une grande pièce en mettant en œuvre parallèlement plusieurs décharges électriques.In other embodiments, the electrohydroforming device may include several pairs of central and peripheral electrodes associated with one or more molds. It is thus possible to produce several parts in parallel or a large part by implementing several electric discharges in parallel.

Dans le cas de pièces à former de grandes dimensions, il peut être avantageux aussi d'utiliser plusieurs électrodes centrales associées à une unique électrode périphérique. En réalisant plusieurs décharges électriques simultanées ou différées à différents endroits, il est possible de réaliser un formage électrohydraulique plus homogène ou plus progressif ou plus profond.In the case of parts to be formed of large dimensions, it may also be advantageous to use several central electrodes associated with a single peripheral electrode. By carrying out several simultaneous or delayed electric discharges at different places, it is possible to achieve a more homogeneous or more progressive or deeper electro-hydraulic forming.

Différentes formes d'électrodes et différentes dispositions d'électrodes centrales sont illustrées en référence aux figures 3A à 3D.Different shapes of electrodes and different arrangements of center electrodes are illustrated with reference to figures 3A to 3D .

Les figures 3A à 3D illustrent plus particulièrement les parties actives d'électrodes centrales et périphériques vues en coupe selon un plan (YY', ZZ') perpendiculaire à l'axe longitudinal XX' d'une électrode centrale.The figures 3A to 3D illustrate more particularly the active parts of central and peripheral electrodes seen in section along a plane (YY ', ZZ') perpendicular to the longitudinal axis XX 'of a central electrode.

Dans la figure 3A, la partie active 301 de l'électrode centrale est de forme circulaire et la partie active 302 de l'électrode périphérique a la forme d'un anneau circulaire.In the figure 3A , the active part 301 of the central electrode is circular in shape and the active part 302 of the peripheral electrode has the shape of a circular ring.

Dans la figure 3B, les parties actives 303, 305, 307 de plusieurs électrodes centrales sont de section rectangulaire, de préférence à coins arrondis, et alignées selon une direction commune ZZ' au centre d'un anneau de forme rectangulaire formant la partie active 308 de l'électrode périphérique correspondante.In the figure 3B , the active parts 303, 305, 307 of several central electrodes are of rectangular section, preferably with rounded corners, and aligned in a common direction ZZ 'at the center of a ring of rectangular shape forming the active part 308 of the electrode corresponding device.

Dans la figure 3C, les parties actives 309, 311 de plusieurs électrodes centrales sont de section elliptique et alignées selon une direction commune ZZ' au centre d'un anneau de forme elliptique formant la partie active 312 de l'électrode périphérique correspondante.In the figure 3C , the active parts 309, 311 of several central electrodes are of elliptical section and aligned in a common direction ZZ 'at the center of an elliptical shaped ring forming the active part 312 of the corresponding peripheral electrode.

Dans la figure 3D, les parties actives 313, 314, 315, 316 de quatre électrodes centrales sont de section rectangulaire carrées, de préférence à coins arrondis, et sont disposées à l'intérieur d'un anneau de forme carrée formant la partie active 317 de l'électrode périphérique correspondante.In the 3d figure , the active parts 313, 314, 315, 316 of four central electrodes are of square rectangular section, preferably with rounded corners, and are arranged inside a square-shaped ring forming the active part 317 of the electrode corresponding device.

Les électrodes périphériques décrites ici sont formées d'une seule pièce. Dans une variante de réalisation, les électrodes périphériques comportent différents tronçons séparés destinés à être mis en regard de chaque électrode centrale pour générer des décharges. Ces différents tronçons comprennent donc les parties actives de l'électrode périphérique. On diminue ainsi les coûts de remplacement des électrodes périphériques en ne remplaçant que certains tronçons. On notera que d'autres formes géométriques peuvent également être utilisées pour peu que la distance entre la surface externe de la partie active de l'électrode centrale considérée et la surface interne de la partie active de l'électrode périphérique avoisinante soit sensiblement équidistante sur au moins une portion des surfaces des parties actives considérées dans le plan.The peripheral electrodes described here are formed in one piece. In an alternative embodiment, the peripheral electrodes comprise different separate sections intended to be placed opposite each central electrode in order to generate discharges. These different sections therefore include the active parts of the peripheral electrode. The costs of replacing the peripheral electrodes are thus reduced by replacing only certain sections. It will be noted that other geometric shapes can also be used provided that the distance between the external surface of the active part of the central electrode considered and the internal surface of the active part of the neighboring peripheral electrode is substantially equidistant over at minus a portion of the surfaces of the active parts considered in the plane.

Comme discuté précédemment en référence à la figure 2, la section des parties actives des électrodes peut être constante ou varier selon leur direction longitudinale représentée par l'axe XX' sur les figures 1A, 1B et 2.As discussed previously with reference to the figure 2 , the section of the active parts of the electrodes can be constant or vary according to their longitudinal direction represented by the axis XX 'on the figures 1A , 1B and 2 .

Les diverses formes de réalisation d'un dispositif d'électrohydroformage décrites ci-dessus permettent le formage électrohydraulique de flans de matière avec une électrode périphérique entourant en partie une électrode centrale, l'électrode périphérique étant distincte du corps formant en partie la chambre d'électrohydroformage. La décharge électrique est donc distribuée sur la périphérie des parties actives des électrodes. L'électrode périphérique, qui possède une plus grande surface de contact, s'use plus lentement. Ainsi, la distance entre les électrodes varie peu, ce qui permet de maintenir l'efficacité de l'électrohydroformage en gardant une pression générée par la décharge électrique sensiblement constante. Toutefois, lorsque les électrodes doivent être changées, l'électrode périphérique peut, de manière avantageuse, facilement être changée lorsque le dispositif d'électrohydroformage est ouvert pour placer le flan de matière, l'électrode périphérique étant distincte du corps et le flan de matière étant préférentiellement placé entre l'électrode périphérique et le moule. De manière avantageuse, l'électrode centrale peut être déplacée selon son axe longitudinal afin de présenter à l'électrode périphérique une partie active moins dégradée.The various embodiments of an electrohydroforming device described above allow the electrohydraulic forming of blanks of material with a peripheral electrode partially surrounding a central electrode, the peripheral electrode being separate from the body forming part of the chamber. electrohydroforming. The electric discharge is therefore distributed over the periphery of the active parts of the electrodes. The peripheral electrode, which has a larger contact surface, wears out more slowly. Thus, the distance between the electrodes varies little, which makes it possible to maintain the efficiency of the electrohydroforming while keeping a pressure generated by the electric discharge substantially constant. However, when the electrodes are to be changed, the peripheral electrode can advantageously easily be changed when the electrohydroforming device is opened to place the material blank, the peripheral electrode being separate from the body and the material blank. being preferably placed between the peripheral electrode and the mold. Advantageously, the central electrode can be moved along its longitudinal axis in order to present to the peripheral electrode a less degraded active part.

La présente invention ne se limite pas aux différentes formes de réalisation décrites et illustrées et aux variantes évoquées mais elle concerne également les formes de réalisation à la portée de l'homme du métier dans le cadre des revendications ci-après.The present invention is not limited to the various embodiments described and illustrated and to the variants mentioned, but it also relates to the embodiments within the reach of a person skilled in the art within the framework of the claims below.

Claims (13)

  1. Electrohydraulic forming device (100; 100'; 200) forming a blank of material (160; 260) comprising:
    - an electrohydraulic forming chamber (110; 210),
    - at least one so-called central electrode (120; 220; 301, 303, 305, 307, 309, 311, 313, 314, 315, 316) extending in a so-called longitudinal direction (XX') and comprising a first end (122) arranged inside the electrohydraulic forming chamber (110; 210),
    - at least one so-called peripheral electrode (130; 230; 302, 308, 312, 317) electrically insulated from each central electrode (120; 220; 301, 303, 305, 307, 309, 311, 313, 314, 315, 316), having an end (132) arranged at a distance from and around the end (122) of a central electrode (120; 220; 301, 303, 305, 307, 309, 311, 313, 314, 315, 316), said end (132) extending in a transverse plane (YY', ZZ') relative to said central electrode (120; 220; 301, 303, 305, 307, 309, 311, 313, 314, 315, 316),
    - a body (140; 240) provided with a bore for introducing each central electrode (120; 220; 301, 303, 305, 307, 309, 311, 313, 314, 315, 316) into the electrohydraulic forming chamber (110; 210), the electrohydraulic forming chamber (110; 210) being partially formed by said body (140; 240), and
    - a mould (150; 250),
    characterised in that each peripheral electrode (130; 230; 302, 308, 312, 317) is separate from said body (140; 240).
  2. Device (100; 100'; 200) according to claim 1, characterised in that the at least one peripheral electrode (130; 230; 302, 308, 312, 317) is protruding relative to the body (140; 240).
  3. Device (100'; 200) according to claim 1 or 2, characterised in that the at least one peripheral electrode (130; 230; 302, 308, 312, 317) is supported by an electrode holder (136; 232).
  4. Device (100, 100'; 200) according to one of the preceding claims, characterised in that the device (100; 200) comprises a single peripheral electrode (130; 230; 302, 308, 312, 317) and at least one central electrode (120; 220; 301, 303, 305, 307, 309, 311, 313, 314, 315, 316).
  5. Device (100; 100'; 200) according to one of the preceding claims, characterised in that the electrohydraulic forming chamber (110; 210) is formed by a body (140; 240) and by the end (132) of the peripheral electrode (130).
  6. Device (100; 100') according to one of the preceding claims, characterised in that the central electrode (120) is surrounded over a portion of the length thereof by an electrical insulator (115).
  7. Device (200) according to one of claims 1 to 5, characterised in that the body (240) is in electrical contact with the central electrode (220) and further comprises an electrical insulator (215) for insulating the peripheral electrode (230) of the central electrode (220).
  8. Device (200) according to claim 7, characterised in that the body (240) further comprises a cavity (242) partially forming the electrohydraulic forming chamber (210) and in that the electrical insulator (215) forms at least partially a lateral wall (243) of said cavity (242).
  9. Device (200) according to claim 8, characterised in that the electrical insulator (215) constitutes the lateral wall (243) of the cavity (242).
  10. Device (100; 200) according to one of the preceding claims, characterised in that the device (100; 200) further comprises a mould support.
  11. Device (100; 200) according to one of the preceding claims, characterised in that the blank of material (160; 260) is held between the end (132) of the peripheral electrode (130; 230) and the mould (150; 250).
  12. Device (200) according to one of the preceding claims, characterised in that the device (200) comprises a blank holder (280) arranged between the end of the peripheral electrode (230) and the mould (250).
  13. Device (100; 200) according to one of the preceding claims, characterised in that the end (132) of the peripheral electrode (130; 230) and the mould (150; 250) are in electrical contact and subject to a first electric potential, the central electrode (120; 220) being subject to a second electric potential.
EP18703599.3A 2017-02-08 2018-02-08 Electrohydraulic forming device Active EP3579990B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1751053A FR3062586B1 (en) 2017-02-08 2017-02-08 ELECTROHYDROFORMING DEVICE
PCT/EP2018/053214 WO2018146216A1 (en) 2017-02-08 2018-02-08 Electrohydraulic forming device

Publications (2)

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EP3579990A1 EP3579990A1 (en) 2019-12-18
EP3579990B1 true EP3579990B1 (en) 2020-10-14

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EP18703599.3A Active EP3579990B1 (en) 2017-02-08 2018-02-08 Electrohydraulic forming device

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US (1) US11338346B2 (en)
EP (1) EP3579990B1 (en)
JP (1) JP7083176B2 (en)
CN (1) CN110582360B (en)
FR (1) FR3062586B1 (en)
WO (1) WO2018146216A1 (en)

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4068514A (en) * 1976-07-12 1978-01-17 Viktor Nikolaevich Chachin Device for electrohydraulic die-forging
RU2060077C1 (en) * 1992-09-02 1996-05-20 Волгоградский государственный технический университет Method of electrohydraulic pulse deformation of tubular blanks
JP4944322B2 (en) * 2001-09-26 2012-05-30 本田技研工業株式会社 Method for manufacturing hollow member
US7802457B2 (en) 2008-05-05 2010-09-28 Ford Global Technologies, Llc Electrohydraulic forming tool and method of forming sheet metal blank with the same
US8567223B2 (en) * 2009-09-21 2013-10-29 Ford Global Technologies, Llc Method and tool for expanding tubular members by electro-hydraulic forming
FR3000909B1 (en) * 2013-01-11 2015-05-15 Adm28 S Ar L METHOD, TOOLING AND PRESS FOR FORMING A PIECE
FR3013243B1 (en) * 2013-11-15 2016-01-01 Adm28 S Ar L ELECTRO-HYDROFORMING DEVICE
TW201600310A (en) * 2014-06-17 2016-01-01 Univ Nat Kaohsiung 1St Univ Sc Drawing die provided with slant blank clamping surface
FR3031054B1 (en) * 2014-12-29 2017-01-27 Adm28 S Ar L ELECTRO-HYDROFORMING DEVICE WITH OPTIMIZED CHAMBER
CN104785605B (en) * 2015-03-31 2017-04-19 西北工业大学 Electro-hydraulic forming device for pipe fitting and forming method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

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Publication number Publication date
WO2018146216A1 (en) 2018-08-16
US20200001344A1 (en) 2020-01-02
JP2020506809A (en) 2020-03-05
CN110582360B (en) 2020-12-04
EP3579990A1 (en) 2019-12-18
FR3062586B1 (en) 2020-02-28
FR3062586A1 (en) 2018-08-10
CN110582360A (en) 2019-12-17
US11338346B2 (en) 2022-05-24
JP7083176B2 (en) 2022-06-10

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