Classifications

• • 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 electro-hydroforming device.
• Electro-hydroforming devices are increasingly used for the production of mechanical parts. Indeed, these forming devices make it possible to obtain parts of relatively complex appearance while controlling production costs. For example, the automotive and aerospace industries use such devices.
• a hydroforming process is a process of manufacture by deformation. It allows the plastic deformation of a metal part of a relatively small thickness. To achieve this deformation, a fluid is used which, when pressurized, allows the deformation of said piece on a mold. Several techniques are used to pressurize the fluid.
• electro-hydroforming process One of the processes used is a so-called electro-hydroforming process. This process is based on the principle of an electric discharge in the fluid stored in a tank. The amount of electrical energy released generates a wave whose propagation in the fluid is very fast and allows the plastic deformation of the mechanical part against the mold. To do this, electrodes positioned in the fluid released an electric charge stored in energy storage capacities.
• the deformation of the part is proportional to the volume of water displaced during the explosion generated by the electric arc.
• a step of emptying the tank is necessary after each explosion to recover the formed part.
• US Pat. No. 7,437,787 discloses an electro-hydroforming device in which a membrane is used to retain two volumes of liquid.
• a device adapted to generate a high voltage pulse is coupled to electrodes to create a shock wave in one of the liquid volumes.
• the shock wave thus generated is transferred through the membrane to the other volume of liquid for deforming a piece against a mold. Thanks to the use of the membrane separating the two volumes of liquid, only the volume of liquid in which the part to be deformed is to be emptied during a change of room, which improves productivity.
• the workpiece is protected from particles from electrode wear.
• such a device is of relatively complex design because composed of at least three parts.
• the strength of the membrane directly affects the reliability of the device.
• the use of the membrane allows only a simple transmission of the shock wave.
• the present invention therefore aims to provide an electro-hydroforming device of relatively simple design that is to say preferably comprising only two parts with improved reliability compared to devices of the prior art.
• the present invention advantageously provides an electro-hydroforming device having a controlled manufacturing cost while complying with the standards in force.
• the part to be formed is protected from the particles resulting from the wear of the electrodes, which makes it possible to obtain parts with a desired surface state.
• the present invention proposes an electro-hydroforming device comprising a mold with an upper part and a lower part, an enclosure having a first zone, a second zone, a mold cavity positioned in the second zone and electrodes. having electrode ends positioned in the first zone, characterized in that a piston is movably mounted in translation in a sealed conduit and separates the first zone from the second zone of the enclosure.
• the piston may have first complementary guide means second guide means of the conduit.
• the guide means have three ribs for limiting to one the degrees of freedom of the piston.
• the second guide means have three grooves, thus making it possible to optimize displacements in translation of the piston in the conduit.
• the piston has a first face having a flat shape and directed towards the mold cavity.
• the piston may have a first face having a shape selected from the set of concave and convex shapes and directed towards the mold cavity.
• the piston has a second face adapted to the shape of the chamber and directed towards the first zone.
• the piston has for example a second face having a shape selected from the set of concave and convex shapes and directed towards the first zone.
• the conduit may have a stop adapted to hold the piston.
• a spring can be positioned between the piston and the abutment to improve the reproducibility of details on parts to be deformed. Indeed, thanks to the presence of the spring, the piston is reduced to a determined altitude and identical after each emptying of the mold.
• FIG. 1 is a schematic cross-sectional schematic view of an electro-hydroforming device according to the present invention
• FIG. 2 is a simplified schematic view corresponding to the figure 1 in another position
• FIG. 3 is an enlarged and simplified schematic view of a detail of embodiment of another embodiment of the invention.
• Figure 4 shows different forms of pistons.
• FIG. 1 is a schematic representation of an electro-hydroforming device 2 comprising a mold 4 having an upper part 6, a lower part 8, an enclosure 10, a conduit 12, a mold cavity 14 positioned in the lower part. 8 and electrodes 16.
• Such an electro-hydroforming device 2 can be arranged on a frame
• the upper part 6 of the mold 4 is in the embodiment shown in the drawing placed above the lower part 8 of the mold 4.
• the lower part 8 is fixed to the upper part 6 by means of, for example, tightening (not shown in the figures).
• the mold 4 (comprising the upper part 6 and the lower part 8) is composed of a high density material such as a metal or a metal alloy.
• the enclosure 10 has a first zone 18, a second zone 20 and the conduit 12. As illustrated in FIG. 1, the enclosure 10 has a first wall 22 having a shape of revolution with respect to an axis AA 'and is example of cylindrical shape with a determined diameter.
• the enclosure 10 also has a second wall 24 of frustoconical shape connected to the first wall 22 and the other to the conduit 12.
• the chamber 10 is also adapted to receive in the first zone 18 of the ends 26 of the electrodes 16.
• the electrodes 16 are high voltage electrodes (several tens of kV). These are here maintained perpendicular to the axis of revolution A-A '( Figure 1).
• an insulating sleeve 28 is used.
• the electrodes 16 also have an inter-electrode gap adjustable and modifiable which makes it possible to control a tripping of an electric arc between them.
• an electrical storage device (not shown in the figures) adapted to store a sufficient amount of electrical energy to generate at least one electric arc between the electrodes 16.
• a pulse generator (not shown in the figures) is coupled to the energy storage device.
• the pulse generator and the electrical storage device being known to those skilled in the art, they are not presented in the present description.
• the duct 12 has a cylindrical circular shape and has a determined length sufficient to allow displacements of a piston 30 corresponding to the deformation to be made to a part placed facing the mold cavity 14.
• duct 12 is also adapted to the mold cavity 14.
• the lower part 8 receives the mold cavity 14 which defines the final shape to be given to the part 32 that it is desired to achieve by Electro-Hydro-Forming (EHF).
• EHF Electro-Hydro-Forming
• the mold cavity 14 may have, depending on the complexity of the shape of the part 32 to deform a large form factor with details of great accuracy.
• the lower portion 8 may comprise a pipe (not shown in the figures) coupled to means for evacuating (not shown in the figures) to eliminate any presence of air between the piece 32 and the mold cavity 14
• a pipe not shown in the figures
• means for evacuating not shown in the figures
• the piston 30 is movably mounted in translation in the duct 12 with sealing and forms the separation between the first zone 18 and the second zone 20 of the enclosure 10.
• the first zone 18 is filled with a first fluid and the second zone 20 is filled with a second fluid.
• the first fluid and the second fluid are water.
• the water contained in the first zone 18 is isolated from the water contained in the second zone 20 of the enclosure 10.
• particles torn from the ends 26 of the electrodes 16 are stopped by the piston 30 and do not reach the piece 32.
• the first zone 18 and the second zone 20 vary depending on the positioning of the piston 30 in the leads 12.
• the piston 30 is for example made of a material identical to the material of the mold 4.
• the piston 30 has a diameter identical to the diameter of the conduit 12.
• piston 30 is movably mounted in translation in the conduit 12 thus allowing translational movements along the axis of symmetry AA 'of a first position (Figure 1) to a second position ( Figure 2).
• sealing means such as, for example, elastic rings 38 positioned between the piston 30 and the conduit 12.
• FIG. 3 represents a partial sectional view of the electro-hydroforming device 2 with the two elastic rings 38.
• the latter may comprise grooves (not shown in the figures) of shape and depth adapted to receive and maintain the elastic rings 38 which form a seal between the piston 30 and the duct 12.
• the conduit 12 comprises at least one groove (not shown in the figures) and that the piston 30 has at least one rib.
• the groove of the duct 12 is adapted to cooperate with the rib of the piston 30.
• the piston 30 may comprise three equi-distributed ribs around the piston 30, and the duct 12 may comprise three equi-distributed grooves, the ribs being placed opposite the grooves.
• the piston 30 has a single degree of freedom and the forces are better distributed during the transition from the first position (Figure 1) to the second position ( Figure 2) which improves the life of the electro-hydroforming device 2.
• the latter has a stop 40 as illustrated in FIG. 3.
• the stop 40 is positioned on a lower part of the duct 12.
• this stop 40 also prevents the piston 30 from exiting and / or falling out of the conduit 12 when the second zone 20 of the enclosure 10 is drained.
• a spring (not shown in the figures) can be used.
• the spring is for example positioned on an outer edge of a first face 42 of the piston 30 and bears on the abutment 40. The spring then makes it possible to return the piston 30 to its first position after a process step of EHF of the piece 32 placed in the mold cavity 14.
• the passage from the first position to the second position of the piston 30 as previously described in the description is achieved by the propagation of a first wave generated by an electric arc at the level of the electrodes 16.
• the first wave thus generated propagates in the first wave.
• zone 18 perpendicular to the axis AA 'to the piston 30 and more precisely to a second face 44 of the piston 30.
• the first wave presents an energy which depends inter alia on the power of the electric arc.
• the displacement of the piston 30 in the duct 12 makes it possible to transfer almost all the energy of the first wave to the water contained in the second zone 20 giving rise to a second wave.
• the second wave thus created propagates towards the mold cavity 14 in order to deform the piece 32 disposed thereon.
• an electro-hydroforming device 2 with the piston 30 positioned in the duct 12 to isolate the first zone 18 of the second zone 20 enables the quality of the part 32 to be improved.
• a relatively small amount of material is torn off from the electrodes and forms particles which fall into the fluid, in this case water. These particles once torn fall by gravity on the piston 30 and do not reach the piece 32 unlike devices of the prior art which comprise a single volume of fluid.
• the use of the piston 30 in the duct 12 to isolate the water contained in the first zone 18 of the water contained in the second zone 20 advantageously makes it possible to reduce the time required for the filling and emptying of the water. water contained in the second zone 20.
• the movement of the piston 30 from its first position to its second position is without resistance and can thus be achieved in a relatively short time, for example less than a millisecond, which allows to obtain a rapid deformation of the piece 32 and thus obtain a better deformation of the piece 32.
• the second face 44 of the piston 30 may have, for example, a concave shape and the first face 42 of the piston 30 may have a convex shape (FIG. 4d). .
• the propagation of the second wave in the lower part 8 is optimized improving the deformation quality of the part 32 after deformation.
• the first face 42 may have a greater or smaller radius of curvature.
• the selected radius of curvature it is possible to improve the focusing of the second wave on the part 32 in order to optimize its deformation.
• the first face 42 and the second face 44 may also have other shapes as illustrated in Figures 4a to 4c with more or less significant curvatures to optimize the deformation of the piece 32.
• the piston 30 may have a shape rectangular to avoid any rotations in the conduit 12.
• first face 42 is of a shape adapted to the deformation to be made on the piece 32 and the second face 44 is of a shape adapted to the shape of the first zone 18.
• the present invention therefore provides an electro-hydroforming device comprising a mold having an enclosure with a conduit and a piston positioned in said conduit and a mold cavity.
• the mold proposed here is composed only of two parts facilitating its assembly and limiting its cost of manufacture.
• the use of the piston in the conduit to separate a first zone from a second zone makes it possible to limit the volume of fluid to be emptied between two manufacturing phases and to improve the productivity gain.
• the manufacturing time of a part corresponds to the time required to position a part on the mold cavity, fill the chamber with fluid, close the chamber and trigger an electric arc before the fluid is emptied.
• the particles torn from the electrodes during the triggering of the electric arc do not fall on the workpiece which allows not to alter the quality.

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• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Pistons, Piston Rings, And Cylinders (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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ID=53200045

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Citations (4)

Family Cites Families (24)

• 2014
  • 2014-12-29 FR FR1463412A patent/FR3031055B1/fr not_active Expired - Fee Related
• 2015
  • 2015-12-29 JP JP2017552238A patent/JP6666926B2/ja active Active
  • 2015-12-29 EP EP15823172.0A patent/EP3240650B1/fr active Active
  • 2015-12-29 CN CN201580075203.XA patent/CN107530755B/zh active Active
  • 2015-12-29 US US15/540,941 patent/US20170355007A1/en not_active Abandoned
  • 2015-12-29 WO PCT/EP2015/081381 patent/WO2016107888A1/fr not_active Ceased

Patent Citations (4)

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