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.
• hydroforming parts manufacturing processes have been used in many industries. Indeed, thanks to the evolution of these manufacturing processes, it is now possible to obtain mechanical parts of relatively complex shape with competitive production costs.
• the automotive and aerospace industries use such technologies.
• a hydroforming process is a process of manufacture by deformation. It allows the plastic deformation of metal parts of relatively small thickness. To achieve this deformation, it is used a fluid that when pressurized allows the deformation of said piece on a mold. Several techniques are used to pressurize the fluid.
• 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 shock wave whose propagation in the fluid is very fast and allows the plastic deformation of the mechanical part against the mold. Electrodes positioned in the fluid thus make it possible to release the electric charge stored in energy storage capacities.
• US Patent 6591649 discloses an electro-hydroforming device.
• the latter comprises a vessel adapted to contain a fluid, a part to be deformed, a set of electrodes coupled to an electrical energy storage device adapted to generate a shock wave.
• This shock wave of relatively high power, can generate during production phases, failure problems on some parts of the electroforming device.
• US Pat. No. 3,214,950 discloses an apparatus for deforming metal sheets and preformed parts under the effect of a shock in water.
• the deformation is effected by pressure using shock waves transmitted by water on the workpiece to be deformed in a vacuum space of a hollow mold.
• the device includes a water container embedded in the ground, a hollow mold as well as a support frame for an explosive charge.
• the water reservoir further comprises a wall composed of U-shaped flanges held together by means of a band at their upper ends and cast in concrete at their lower ends.
• a lower part of the tank is covered with an absorbent material. The use of U-shaped flanges poured into the concrete thus makes it possible to secure the device during the explosion.
• the electrodes, the mold and the part to be deformed are generally positioned at the bottom of the tank and thus immersed in the fluid.
• the operator it is necessary for the operator to change the part to be formed in a liquid environment.
• the present invention therefore aims to provide an electro-hydroforming device for improving production gains for the manufacture of parts.
• the present invention aims to provide an electro-hydroforming device having a reliability and an improved life compared to devices of the prior art.
• the proposed device will of course preferably comply with the standards in force and retain the characteristics required for industrial applications.
• it will be easy to use and will have a competitive manufacturing cost.
• the present invention provides an electro-hydroforming device comprising a frame, a tank, a discharge chamber with at least one electrode device and a lid.
• this electro-hydroforming device further comprises a movable enclosure comprising the lid, a mold connected to the lid by support means, a forming chamber and the discharge chamber, said chamber being movable between a first position wherein the vessel is closed by the lid and a second position in which the discharge chamber and the forming chamber are out of the vessel.
• this geometry also advantageously makes it possible to have a liquid and therefore pressure waves situated on the top of the part to be formed, which makes it possible to have the liquid in contact with the part to be formed, without having to make the empty between the workpiece and the liquid.
• An advantageous embodiment of the invention provides that first damping means are placed between the clamping discs and the cover. In this way, the effect of the propagation of the shock wave in the fluid on the different parts of the device is decreased.
• second damping means are placed between the support means and a mold support mold.
• the third damping means are placed between the cover and the tank and thus allow a significant improvement in the service life of such a device.
• the first damping means, the second damping means and the third damping means are resilient blocks, preferably made of rubber.
• the discharge chamber comprises at least one paraboloid shaped reflector.
• the set of reflectors may for example be conical, flat or ellipsoid.
• the forming chamber is associated with means for depressurizing.
• the support means comprise three legs distributed at 120 °.
• a distance between the cover and the mold is adjustable thus allowing to modulate the power to which the piece to be deformed will be subjected.
• FIG. 1 is a schematic isometric view of an electro-hydroforming device according to the present invention
• FIG. 2 is an enlarged cross-sectional detail view of the device illustrated in FIG. 1 in another position;
• FIG. 3A is a front view of the device of FIG. 1 in the position of FIG. 2,
• Figure 3B is a front view of the device of Figure 1 in a third position
• Figure 4 is a view corresponding to the view of Figure 2 for an alternative embodiment of the present invention.
• an electro-hydroforming device Such a device comprises a frame 2 adapted to support a tank 4.
• the electro-hydroforming device of the invention comprises a mobile chamber 6, an electrical energy storage device and an electric pulse generator. two not shown in the figures.
• the electrical energy storage device coupled to the electric pulse generator makes it possible, according to a determined strategy, to trigger an electric discharge process in a liquid stored in the tank 4 in order to structure a part to form 5. This process will be presented in more detail. details later.
• the frame 2 is adapted to support the tank 4. This can be in an embodiment attached to the frame 2 by means of fixing systems regularly distributed around the tank 4.
• the frame 2 can be made of a metal or a metal alloy such as iron or hardened steel.
• the frame 2 is of parallelepipedal shape and of suitable dimensions to be able to support the tank 4.
• the frame 2 is disposed on a base 8.
• This base 8 may be metal or any other material allowing the frame 2 to be placed on said base 8 for example not to damage the ground where the device is installed.
• the base 8 also comprises two fastening systems (not shown in the figures) adapted to allow the attachment of a gantry 10.
• the gantry 10 comprises at least two vertical elements 12 and 14 and at least one horizontal element 16.
• the vertical elements 12 and 14 are adapted to allow the displacement along an axis x ( Figure 1) of the horizontal element 16.
• Figure 1 Figure 1 of the horizontal element 16.
• the vertical element 14 (FIG. 1) comprises a complementary fastening system (not shown in the figures) intended to cooperate with a fixing system of the base 8 in order to fix the vertical element 14 on the base 8.
• the element vertical 14 also comprises a carriage 18 for moving the horizontal element 16 along the x axis.
• the carriage 18 comprises two locations adapted to receive respectively a first toothed rod 20 and a second toothed rod 22.
• the carriage 18 comprises at least one motor, a power supply and control device of said motor and a toothed wheel (not shown in the figures).
• the power supply and control device is adapted to deliver electrical energy to the motor to rotate the toothed wheel in one direction or in the opposite direction according to a specific strategy.
• the teeth of the toothed wheel are placed in grooves of the first toothed rod 20 so that when the motor is activated the carriage 18 slides along the first toothed rod 20 along the x axis.
• a second motor with its control system as presented above is arranged on the second toothed rod 22.
• the vertical element 12 comprises a carriage whose characteristics are identical to those of the carriage 18.
• This embodiment has been given by way of example, other embodiments of the displacement means can be realized as for example a system of hydraulic cylinders.
• the carriage 18 comprises an orifice 181 adapted to receive an axis 182.
• the carriage 18 comprises rotation control means (not shown in the figures).
• the rotation control means comprise for example a motor and a gear.
• the rotation control means are adapted to allow the rotation of the horizontal element 16 along the y axis according to the direction of rotation of the motor. To do this, teeth of the gear are interposed with teeth made at the periphery of the axis 182 thus allowing the rotation of the horizontal element 16.
• the horizontal element 16 is in the form of a beam with at its ends two bearings each receiving an axis 182.
• the horizontal element 16 is adapted to support the movable enclosure 6 by means of a suitable fastening system.
• FIG. 2 shows a detailed sectional view of the electroforming device. This comprises the vessel 4, the mobile enclosure 6 having a lid 26, closure means 28, support means formed by three legs 30, 31, 32, a mold 362 and a forming chamber 364.
• the tank 4 is adapted to receive and contain a fluid, which fluid is preferably water.
• a fluid which fluid is preferably water.
• the tank 4 is made of a sufficiently resistant material to be able, on the one hand, to contain the water stored therein and, on the other hand, to withstand the shocks or explosions generated during electric discharges into the water.
• the tank 4 is made of metal such as steel.
• the tank 4 is preferably circular in shape with a bottom whose diameter is in line with the dimensions of the parts to be formed.
• the circular shape of said tank allows an optimal distribution of the shock wave in the tank 4 during the electric discharge and thus allows an increase in the service life of the tank 4.
• the vessel 4 comprises at least one verification window (not shown in the figures) allowing the operator to verify the correct positioning of the workpiece 5 before the process is started.
• the tank 4 comprises the closing means 28 which are adapted to hold the cover 26 on the tank 4. These closing means 28 can be made using flanges as shown in FIGS. 1 and 2.
• the lid 26 is adapted to cover the tank 4 during the process of forming a sheet. It may be made of a material identical to that of the tank 4. It may be made in one or more parts and in one or more materials or alloys compatible with the specification of said electro-hydroforming device.
• the lid 26 carries on the one hand an electrode device 42 on its face intended to be oriented towards the tank 4 and on the other hand connecting means for fixing the lid 26 and thereby the mobile enclosure 6 to the element horizontal 16.
• the electro-hydroforming device may comprise a seal 263 also acting damping means.
• This seal 263 is placed on an edge of the lid 26, which is in other words the zone of contact between the lid 26 and the tank 4.
• the seal 263 is made of a material making it possible to obtain good sealing performance and damping, for example synthetic material, preferably flexible.
• the leg 30 is preferably in the form of a cylindrical rod (FIG. 2) having at one end a tapping for receiving a screw 38 and at its other end a head 302 adapted to hold a mold support 361 carrying the mold 362.
• the length of the leg 30 is adapted so that the mold 362 is at a predetermined distance from the bottom of the discharge chamber 344.
• the three legs are distributed at 120 °.
• the stability as well as the robustness of the mobile enclosure 6 are improved.
• the discharge chamber 344 comprises the electrode device 42 adapted to generate, according to a determined strategy, an electric arc in the water stored in the tank 4.
• the discharge chamber 344 comprises also at least one set of reflectors of preferentially paraboloid shape adapted to guide the pressure waves towards the workpiece to be formed during a discharge of an electric arc in the fluid. This embodiment substantially improves the finish of the formed part.
• the set of reflectors may be conical, flat or elliptical.
• the electrode device 42 has at least one set of two electrodes. These are preferably placed on each side of an axis of symmetry A-A 'and at a determined distance allowing the generation of an electric arc in the water. In another embodiment, at least two sets of two electrodes are used. Advantageously, this embodiment allows equivalent electric power (with respect to a set of two electrodes) to obtain a deflagration wave in the more homogeneous fluid and thus makes it possible to obtain a better finish of the formed part.
• the electrode device 42 and the associated connectors are known to those skilled in the art they will not be presented in detail here.
• the mold 362 is disposed on a mold support 361.
• the mold support 361 is preferably of circular shape with a diameter sufficient to accommodate the mold 362.
• the mold support 361 has three holes of diameter adapted to allow the passage of the legs 30, 31, 32.
• the mold 362 is attached to the mold support 361 using for example screws.
• the mold 362 comprises an internal channel system 365 coupled to a pumping device (not visible in the figures) making it possible to obtain a desired vacuum under the part to be formed 5 in the forming chamber 364.
• the mold 362 is preferably circular in shape and comprises an enclosure corresponding to the part to be formed.
• the forming chamber 364 corresponds to the space between the mold 362 and the workpiece 5.
• the fixing device 363 is positioned opposite the mold 362 and makes it possible to hold the part to be formed in the desired position 5 and also to seal the forming chamber 364.
• the ring 363 is fixed to
• the material of the ring 363 is preferably identical to the mold material 362.
• it can be inserted between the mold 362 and the workpiece 5 and between the workpiece 5 and the ring 363 at least one flexible material seal such as synthetic material.
• the distance between the workpiece 5 and the cover 26 is adapted so that the energy delivered by the electric discharge provided by the electrode device 42 in the liquid allows in a single step to obtain the desired shape on the piece to be formed.
• wedges 400, 401, 402 are placed between the clamping discs 301, 305, 307 and the cover 26.
• insert several spacers in order to get the desired distance.
• the electroforming device of the invention makes it possible to significantly optimize production times between two plate forming operations.
• a movable enclosure 6 adapted to be in a first position in which the tank 4 is closed by the cover 26 and in a second position where the movable chamber 6 is outside the tank 4 giving access to the mold 362.
• the first position is shown in Figure 3A.
• the mobile chamber 6 is positioned in the tank 4 until the cover 26 of the mobile chamber 6 is in contact with the tank 4 and more precisely with the seal 263.
• the tank 4 is previously filled with water to a certain level.
• the electrical energy storage device coupled to the electrical pulse generator allows the electric discharge in a liquid stored in the tank 4 through the electrode device 42 to structure (depending on the mold 362) the workpiece 5
• the discharge chamber 344 placed in front of the mold 362 makes it possible to obtain a very good finish and a very good rendering of the part to be formed 5.
• the second position is shown in Figure 3B.
• the mobile enclosure 6 is positioned thanks to the gantry 10 and the associated displacement means outside the vessel 4.
• the mold 362 is positioned outside the vessel 4.
• the discharge chamber 344 is out water contained in the tank 4 and allows the operator a simplified installation (or replacement) of the workpiece.
• the mobile enclosure 6 is inclined with the aid of the gantry 10 and its displacement means in order to evacuate the residual water.
• the handling time between two parts forming steps is reduced and moreover, the change of the parts to be formed on the mold 362 is simplified.
• the cost of production, but also the quality, of the parts obtained are improved.
• first damping means 44, 48, 54 for reducing the impact of the shock waves. on the mobile speaker 6 and thus increase the life of the device.
• These first damping means 44, 48, 54 are placed between the clamping discs 301, 305, 307 and the cover 26 (FIG. 4).
• the first damping means 44, 48, 54 are preferably in the form of a ring with an outer diameter, for example equal to the diameter of the clamping discs 301, 305, 307 and an inside diameter adapted to the diameter of the legs 30, 31, 32
• the first damping means 44, 48, 54 have a thickness sufficient to allow the partial or total damping of the shock wave generated by the device through the water contained in the tank 4.
• second damping means 46, 50, 56 placed between the mold support 361 and the heads 302, 320, 322 of the legs 30, 31, 32 are used here.
• the second damping means 46, 50, 56 are also in the form of a ring with an outside diameter, for example equal to the diameter of the heads 302, 320, 322 and an inside diameter adapted to the diameter of the legs 30, 31, 32. L
• the thickness of the second damping means 46, 50, 56 is sufficient to allow partial or total damping of the shock wave.
• the first damping means 44, 48, 54 and the second damping means 46, 50, 56 may for example be composed of synthetic material. However, any other material or structure for damping the shock wave can be used.
• the seal 263 is also used as damping means.
• damping means 263 FIG. 4 whose thickness is sufficient to partially or totally absorb the residual energy during propagation of the wave in the water contained in the tank 4.
• the first damping means 44, 48, 54, the second damping means 46, 50, 56 and the third damping means 263 alone or combined allow, by attenuating it, a slight movement between the cover 26 (which carries the electrodes 42) and the mold support 361 (which contains the mold 362). Part of the shock energy is thus dissipated by said damping means instead of being fully absorbed by the structure.
• the present invention thus proposes to have an electro-hydroforming device with suspended enclosure. Thanks to the two positions of the mobile enclosure allowing simplified access to the forming chamber, the handling time is significantly reduced, thus making it possible to optimize the production costs.
• the electro-hydraulic pressure that propagates in the tank is important and can in some cases cause damage to the various parts of the device. It is possible, thanks to the damping means, to reduce the impact of the shock wave on the various parts of the device and thereby increase the life of the electro-hydroforming device.

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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)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2013
  • 2013-11-15 FR FR1361218A patent/FR3013243B1/fr not_active Expired - Fee Related
• 2014
  • 2014-11-14 WO PCT/IB2014/066045 patent/WO2015071869A1/fr active Application Filing
  • 2014-11-14 CN CN201480064631.8A patent/CN105828970A/zh active Pending
  • 2014-11-14 US US15/035,987 patent/US9937547B2/en active Active
  • 2014-11-14 JP JP2016531065A patent/JP6678104B2/ja active Active
  • 2014-11-14 EP EP14821844.9A patent/EP3068557B1/de active Active

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