EP3068557A1

EP3068557A1 - Electrohydraulic forming device

Info

Publication number: EP3068557A1
Application number: EP14821844.9A
Authority: EP
Inventors: Gilles Avrillaud; Eran PLAUT; Hervé PERONNET
Original assignee: ADM28 SARL
Current assignee: ADM28 SARL
Priority date: 2013-11-15
Filing date: 2014-11-14
Publication date: 2016-09-21
Anticipated expiration: 2034-11-14
Also published as: JP2016538135A; US9937547B2; WO2015071869A1; CN105828970A; FR3013243B1; EP3068557B1; JP6678104B2; FR3013243A1; US20160271676A1

Abstract

An electrohydraulic forming device comprising a framework (2), a tank (4), a movable enclosure (6) comprising a cover (26), a mould (362) connected to the cover (26) by supporting means (30, 31, 32), a forming chamber (364) and a discharge chamber (344) having at least one electrode device (42), said enclosure being movable between a first position in which the tank (4) is closed by the cover (26) and a second position in which the discharge chamber (344) and the forming chamber (364) are outside the tank (4).

Description

ELECTRO-HYDROFORMING DEVICE

The present invention relates to an electro-hydroforming device. Over the past decade, 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. For example, 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. To protect the tank from shocks, 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.

In order to generate the shock wave, 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. Thus, with each change of part, 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. In addition, 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. Advantageously, it will be easy to use and will have a competitive manufacturing cost.

For this purpose, 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.

According to the present invention 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.

Thanks to the two positions of the mobile chamber, it is possible to access the workpiece without emptying the fluid stored in the tank. So the time of production is improved. In addition, 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.

In order to further reduce the impact of the shock wave on the device, second damping means are placed between the support means and a mold support mold.

In order to optimize the service life of the device, 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.

In order to optimize the damping of the shock wave, the first damping means, the second damping means and the third damping means are resilient blocks, preferably made of rubber.

In order to optimize the deformation of the part, it is important to control and guide the shock wave thus created. To do this, the discharge chamber comprises at least one paraboloid shaped reflector.

Depending on the need, the set of reflectors may for example be conical, flat or ellipsoid.

In addition, in order to maintain the workpiece in a stable position and as close as possible to the mold, the forming chamber is associated with means for depressurizing.

During the creation and propagation of the shock wave, the stability of the device is very important to avoid any deformation or inadvertent breakage of certain parts. To do this, the support means comprise three legs distributed at 120 °.

Finally, to control and optimize the deformation of the part, 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.

Details and advantages of the present invention will become more apparent from the description which follows, given with reference to the appended schematic drawing in which:

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, and

Figure 4 is a view corresponding to the view of Figure 2 for an alternative embodiment of the present invention.

Those skilled in the art recognize in Figure 1 an electro-hydroforming device. Such a device comprises a frame 2 adapted to support a tank 4. In addition, 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. In an exemplary embodiment, 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. In order to not weigh down the description and knowing that the vertical element 12 and the vertical element 14 are structurally identical only the vertical element 14 will be detailed in the following description.

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. In an exemplary embodiment, the carriage 18 comprises two locations adapted to receive respectively a first toothed rod 20 and a second toothed rod 22.

In an exemplary embodiment, 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.

In another embodiment, a second motor with its control system as presented above, is arranged on the second toothed rod 22.

It is noted that 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. In addition, 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.

Figure 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. To do this, 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. . In an exemplary embodiment, the tank 4 is made of metal such as steel.

In addition, 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. Advantageously, 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.

In another embodiment, 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.

In the embodiment shown in FIG. 2, the cover

26 has three holes of diameter adapted to allow the passage of the three legs 30, 31, 32. The latter are each fixed to the cover 26 by means of clamping discs 301, 305, 307 and screws 38, 40, 60 .

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.

For reasons of safety of machines and men, 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 three legs 30, 31, 32 being identical, only the leg 30 will be described. 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.

In a preferred embodiment, the three legs are distributed at 120 °. Thus, 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. However, depending on the complexity of the workpiece 5, 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 (connecting the electrode device 42 to the pulse generator) 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. In addition, 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. In addition, 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.

In an alternative embodiment, 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.

Advantageously, 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. Indeed, the strong deflagration causes a shock wave that moves in the fluid very rapidly in a few milliseconds (1 ms = 10 ^"3 s) and causes a plastic deformation of the workpiece.

Advantageously, in order to optimize the deformation of the plate by means of the electro-hydroforming process, it is possible to adjust the distance between the mold 362 and the cover 26. To do this, wedges 400, 401, 402 (Figure 2) are placed between the clamping discs 301, 305, 307 and the cover 26. In order to precisely adjust the distance between the mold 362 and the cover 26 it is possible in a variant embodiment to insert several spacers in order to get the desired distance.

As explained at the beginning of the description, the electroforming device of the invention makes it possible to significantly optimize production times between two plate forming operations. To do this, it is proposed 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. Here 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. It is understood that the tank 4 is previously filled with water to a certain level. In addition, it is possible to complete the level of the water in the tank 4 before positioning the mobile chamber 6 in the first position. Once the lid 26 is fixed to the tank 4 by means of the fixing means 28, the electro-hydroforming process can then be performed. 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 Advantageously, 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. Here, the mobile enclosure 6 is positioned thanks to the gantry 10 and the associated displacement means outside the vessel 4. Thus, the mold 362 is positioned outside the vessel 4. In this position, the discharge chamber 344 is out water contained in the tank 4 and allows the operator a simplified installation (or replacement) of the workpiece.

Advantageously, in order to eliminate all the residual water in the forming chamber 36, the mobile enclosure 6 is inclined with the aid of the gantry 10 and its displacement means in order to evacuate the residual water.

Advantageously, thanks to the electro-hydroforming device as presented, 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. Thus, the cost of production, but also the quality, of the parts obtained are improved.

In order to optimize and improve the service life of certain parts of the electro-hydroforming device, a preferred embodiment provides 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 In addition, 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.

In order to optimally attenuate the shock wave, 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.

It is recalled that the seal 263 is also used as damping means. Thus, there are third 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.

Advantageously, it is possible to partially or totally combine the first damping means 44, 48, 54, the second damping means 46, 50, 56 and the third damping means 263 presented above. Indeed, each of these means acts on a vertical component (Figure 1, axis AA ') of the shock wave. 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. This makes it possible to reduce the stresses generated during the discharge in the rooms. Therefore, it is possible to reduce the masses and thus to have a reduced size system, more easily / quickly manipulated and of reduce costs.

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. In the electro-hydroforming process, or in another method involving electrohydraulic discharge, 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.

The present invention is not limited to the embodiments described above by way of non-limiting examples and the shapes shown in the drawing and the other variants mentioned but it relates to any embodiment within the reach of the skilled person within the scope of the claims below.

Claims

An electro-hydroforming device comprising a frame (2), a tank (4), a discharge chamber (344) with at least one electrode device (42) and a lid (26), characterized in that it furthermore has a movable enclosure (6) comprising the cover (26), a mold (362) connected to the cover (26) by support means (30, 31, 32), a forming chamber (364) and the discharge chamber (344), said chamber being movable between a first position in which the tank (4) is closed by the cover (26) and a second position in which the discharge chamber (344) and the forming chamber ( 364) are out of the tank (4).

2. electro-hydroforming device according to claim 1, characterized in that first damping means (44, 48, 54) are placed between clamping discs (301, 305, 307) and the cover (26). .

3. electro-hydroforming device according to one of claims 1 or 2, characterized in that second damping means (46, 50, 56) are placed between the support means (30, 31, 32) and a mold support (361) of the mold (362).

4. Electro-hydroforming device according to one of claims 1 to

3, characterized in that third damping means (263) are placed between the cover (26) and the tank (4).

Electro-hydroforming device according to one of claims 1 to

4, characterized in that the first damping means (44, 48, 54), the second damping means (46, 50, 56) and the third damping means (263) are elastic blocks, preferably in rubber.

Electro-hydroforming device according to one of claims 1 to

5, characterized in that the discharge chamber (344) comprises at least one paraboloid shaped reflector.

7. Electro-hydroforming device according to one of claims 1 to 6, characterized in that the forming chamber (364) is associated with depression means.

8. electro-hydroforming device according to one of claims 1 to 7, characterized in that the support means (30, 31, 32) comprise three legs spread at 120 °.

9. Electro-hydroforming device according to one of claims 1 to 8, characterized in that the distance between the cover (26) and the mold (362) is adjustable.