Support and machining method for a bipolar plate of an electrolyzer stack.

Abstract

Support and machining method for a bipolar plate of an electrolyzer stack. The present invention relates to the construction of certain parts of an electrolyzer stack and a tool intended to support such parts during their machining. The tool according to the present invention is characterized by the presence of a double-plate support thanks to which it is possible to avoid having to turn the blank during machining. Figure for the abstract: 4

Description

Title of the invention: Support and machining method for a bipolar plate of an electrolyzer stack. Technical field

[0001] The present invention relates to the technical field of dihydrogen electrolysis and more particularly to certain parts of an electrolyzer stack. More specifically, the present invention relates to the construction of certain parts of an electrolyzer stack and a tool intended to support such parts during their machining. Technological background

[0002] A membrane electrolysis device generally comprises a stack (called an electrolyzer stack) of electrolytic cells within which the water electrolysis reaction is carried out. The electrolytic cells are assembled electrically in series and fluidically in parallel. Referring to Figures 1 to 3, an electrolytic cell 10 comprises, in order, a bipolar plate 11, a space 125 surrounded by an intermediate frame (or simply interlayer) 12, a first electrode 131, in this case a cathode, a membrane 14, a second electrode 132, namely an anode, a second space 125 surrounded by an intermediate frame 12 and a second bipolar plate 11.The space (sometimes also called the electrode chamber) surrounded by the interlayer 12 is intended for the circulation of the electrolyte and the electrolysis gases and allows, thanks to the circulation of the electrolytic fluid, the arrival of the reactants (water and hydroxide ions) at the surface of the electrodes 131 and 132. The interlayer 12 is generally metallic and provides a low resistivity path for the electric current between each bipolar plate 11 and the electrode 131 or 132 attached to it. The electrodes 131, 132 are generally made of doped metal, for example nickel, but other conductive metals can also be used. The membrane 14 (also called a diaphragm or porous separator) provides electrical insulation between the two electrodes 131, 132 as well as the transport of protons or hydroxide ions from one electrode to the other while being impervious to electrolysis gases.The bipolar plates 11 (also called current collector) have the function of supplying the current and evacuating the gases from the electrolytic cell 10. The materials of the bipolar plates 11 must therefore have a sufficient level of electrical conductivity and good chemical inertia with respect to the fluids present in the electrolytic cell 10 (electrolyte, acid, gas). The most common bipolar plates 11 are made of graphite, conductive composite material or metal (for example stainless steel). The bipolar plates 11 . are generally equipped with grooves or reliefs to facilitate the evacuation of gases. The electrolyte (alkaline water solution) from a supply pipe 15 is introduced into the space 125 through a supply opening 121 in the spacer 12, the resulting electrolyte / gas mixture is extracted from the space 125 through a second extraction opening 1221 or 1222 made in the spacer 12. When it is the space 125 arranged between the bipolar plate 11 and the cathode 131, the electrolyte / gas mixture extracted through the extraction opening 1221 is essentially composed of dihydrogen, H2, gas and the mixture is discharged into the extraction pipe 161. When it is the space 125 arranged between the anode 132 and the bipolar plate 11, the electrolyte / gas mixture extracted through the extraction opening 1222 is mainly composed of gaseous oxygen, O2, and the mixture is discharged into the extraction pipe 162.The extraction pipes 161 and 162 conduct the electrolyte / gas mixture to separate degassing devices (not shown) allowing the dihydrogen and dioxygen to be recovered respectively. In the space 125, either the electrodes 131, 132 are against the bipolar plate 11, or a metal net, preferably made of nickel, is placed between the bipolar plate 11 and the electrodes 131, 132.

[0003] The electrolyser stack therefore comprises a stack of such electrolytic cells 10, the bipolar plate 11 terminating the first electrolytic cell 10 constitutes the start of the following electrolytic cell 10. Thus, the bipolar plate 11 of the first electrolytic cell 10 (upstream of the following one) has a higher potential than that of the bipolar plate 11 of the second electrolytic cell 10 (downstream of the preceding one) and consequently, its surface in contact with the space 125 adjoining the cathode 131 plays the role of anode 132. Conversely, the surface of the bipolar plate 11 in contact with the space 125 adjoining the anode 132 plays the role of cathode 131.

[0004] Within the electrolyser stack, the elements coming into contact with the electrolyte are subjected to a particularly corrosive environment and can undergo significant corrosion, quickly making them unfit for use. In addition, any roughness or surface imperfection of these elements is a potential source of gas leakage, particularly dihydrogen. These two problems are solved by electrolytic nickel plating these parts. However, this electrolytic nickel plating requires that the element has been machined perfectly.

[0005] Among the elements subjected to such conditions, the bipolar plate is particularly important insofar as it plays a major role in the operation of the electrolyser stack. It is therefore imperative that the nickel layer deposited on the bipolar plate is perfectly homogeneous. To this end, the bipolar plate is machined so as to present the most perfect surface (smooth, free of roughness) possible. This machining is carried out by milling and / or turning a rough part (called rough stock). The rough stock is generally cut from a billet. The rough stock is placed flat on a support so that its upper face, opposite the support, is accessible to the machining tools. After machining the accessible face of the rough stock, it is turned over on the support, leaving its other face accessible to the machining tools. This conventional technique is extremely time-consuming and tedious for the operator who must turn the rough stock in a dangerous environment.

[0006] It would therefore be desirable to provide a solution allowing the machining of a blank intended to provide a bipolar plate which allows a part to be machined quickly while avoiding the problems linked to the difficulty and danger of the blank turning operation. Summary of the invention

[0007] The invention which is the subject of the present patent application aims to solve this technical problem. To achieve this, it is proposed according to a first aspect of the invention to use a machining support comprising a lathe with an axis of revolution, a false table arranged on the lathe in a plane orthogonal to the axis of revolution of the lathe and a support for one or more blanks, the support comprising an upper plate and a lower plate arranged in planes parallel to each other and orthogonal to the axis of revolution of the lathe. The machining support according to the invention has the following characteristics:

[0008] - the upper face of the false table is provided with a plurality of means coupling for cooperating with coupling means of the lower plate of the support;

[0009] - the upper face of the false table is provided with a plurality of zero points;

[0010] - the lower plate and the upper plate of the support are connected by a jack whose height is variable, one of the two plates being movable in translation along the axis of the lathe relative to the other, for example, this jack can be arranged centrally and be coaxial with the axis of the lathe;

[0011] - the upper plate is provided with a plurality of internal fixed supports distributed at the periphery of the upper plate, each of the internal fixed supports being provided with an internal clamping cylinder, said internal clamping cylinder allows the rough material to be machined to be held in a neutral position and also plays the role of anti-vibration;

[0012] - the lower plate is provided with a plurality of external fixed supports distributed at the periphery of the lower plate, each of the external fixed supports being provided with an external clamping cylinder.

[0013] The rough workpiece of the present invention is generally made of steel or one of its alloys and is cut from a billet, but it can also be forged or bent and then welded. It can be in any shape, generally it is in the form of a ring whose outer diameter can be between 700 and 2500 mm and the inner diameter between 500 and 2200 mm and with a thickness between 7 and 20 mm.

[0014] A false table is a support receiving the machining support whose position and dimensions are perfectly known and thus making it possible to create a very precise reference for the machining support. It is commonly called a “zero point interface”. The false table of the invention can be presented in different configurations. Generally, it has a circular shape corresponding to the lathe and can be coupled to it without involving manual connection or adjustment.

[0015] Unlike the devices of the prior art (known for example from documents FR3099072, FR2950276, FR3078911) which at best comprise a support for the rough, the device according to the invention comprises a support comprising two plates. This particular configuration allows three operating positions of the machining support: a first position, called high, dedicated to a first machining operation thanks to the upper plate movable relative to the lower plate, a second position called low, dedicated to the second machining operation thanks to the fixed lower plate and a third position, called intermediate allowing the transfer of the rough to one or other of the machining positions. The transfer of the rough from the upper plate to the lower plate, and vice versa, can be fully automated thanks to the vertical movement of the upper plate along the axis of rotation of the lathe by means of the central jack.The advantage of having the high and low positions is that it allows machining on both sides of a first end of the blank without being hindered by the upper plate and on both sides of the second end of the blank without being hindered by the lower plate without having to carry out a blank turning operation.

[0016] According to a preferred embodiment of the invention, a circle defined by the rotation of the false table around the axis of revolution R has a diameter of between 1200 and 2500 mm.

[0017] According to another advantageous embodiment, the coupling means between the false table and the lower plate of the support consist of studs cooperating with holes. Advantageously, the false table is provided with studs cooperating with holes in the lower plate of the support.

[0018] According to an advantageous embodiment of the invention, the upper face of the false table is provided with at least 5 zero points, preferably at least 10 zero points. The number of zero points is fixed so that the quantity makes it possible to meet a limit holding force (depending on the masses and dynamics involved), a zero point being placed in the center of the false table. This point helps to ensure precise positioning between the false table and the support.

[0019] According to an advantageous embodiment of the invention, the jack is fitted with a protective shell to prevent chips produced during the machining of the rough material from damaging the jack. This jack can be central and coaxial with the axis of the lathe.

[0020] According to another preferred embodiment of the invention, the lower plate is fixed and the upper plate is movable relative to the lower plate. In particular, the upper plate can move in translation along the axis of rotation of the lathe.

[0021] According to another preferred embodiment of the invention, the plurality of external fixed supports are distributed regularly around the periphery of the lower plate. According to another preferred embodiment of the invention, the plurality of internal fixed supports are distributed regularly around the periphery of the upper plate. In other words, the fixed supports are distributed angularly at regular intervals around the periphery of the plate, both for the lower plate and for the upper plate.

[0022] According to an advantageous variant of the invention, the upper plate is provided with vibration attenuation means, preferably radial vibration attenuation means and axial vibration attenuation means. Advantageously, a clamping cylinder is arranged on the axial vibration attenuation means. In this way, the workpiece can be pressed against the vibration attenuation means via the cylinder.

[0023] According to a second of its aspects, the invention relates to a machining method.

[0024] According to the invention, this method comprises the following steps carried out in order:

[0025] a) providing a machining support as defined above;

[0026] b) bring the upper plate into the high position and open all the internal clamping cylinders;

[0027] c) depositing the crude oil on at least two, preferably at least three internal fixed supports of the upper plate; the internal fixed supports thus ensure the centering of the crude oil thanks to an expansion of the internal jacks which will therefore maintain the crude oil by pressure;

[0028] d) close the internal clamping cylinders on the internal fixed supports of the upper plate;

[0029] e) open the external clamping cylinders on the external fixed supports of the lower plate;

[0030] f) machining a first end of the rough work;

[0031] g) lowering the upper plate to the low position so that the partially machined blank rests on the external fixed supports of the lower plate;

[0032] h) open all the internal clamping cylinders of the upper plate and deactivate all the vibration attenuation means and their cylinders;

[0033] i) close the external clamping cylinders of the lower plate;

[0034] j) machining a second end of the blank opposite the first machined end;

[0035] k) open the external clamping cylinders of the lower plate;

[0036] 1) open all the internal clamping cylinders of the upper plate so that the raw material machined rests on the fixed internal supports of the upper plate;

[0037] m) raise the upper plate to the high position;

[0038] n) extract the machined raw material.

[0039] According to a particular embodiment of the invention, the raw material is a bipolar plate.

[0040] Because the process ends with the upper plate being brought into the upper position and all the internal clamping cylinders being open, the machining support is ready to receive a new blank for machining without any loss of time.

[0041] Advantageously, step c) is carried out by a robot. Preferably, the robot is moved away from the machining area before the start of machining step f).

[0042] Advantageously, steps h) and i) can be carried out simultaneously.

[0043] According to an advantageous embodiment, a robot is used for the step of extracting the machined bipolar plate.

[0044] Advantageously, the machining steps f) and / or j) are carried out simultaneously on both faces of the machined end of the blank.

[0045] According to an advantageous embodiment, a machining tool such as that described in the patent application filed on the same day in the name of the same applicant companies can be used for machining. Brief description of the figures

[0046] The invention will now be described by means of figures which have no other purpose than to illustrate the present invention. These figures schematically represent:

[0047] [Fig-1] [Fig.l] is a prior art electrolytic cell;

[0048] [Fig.2] [Fig.2] is a prior art insert;

[0049] [Fig.3] [Fig.3] is a stack of electrolytic cells of the prior art;

[0050] [Fig.4] [Fig.4] is a machining support according to the invention;

[0051] [Fig.5] [Fig.5] is a blank to be machined to provide a bipolar plate;

[0052] [Fig.6] [Fig.6] is a first machining phase;

[0053] [Fig.7] [Fig.7] is a second machining phase;

[0054] [Fig.8] [Fig.8] is a bipolar plate after machining. Description of the embodiments

[0055] [Fig. 4] shows a machining support 200 according to the invention. This machining support 200 comprises a lathe 400 with an axis of revolution R, a false table 300 arranged on the lathe 400 in a plane orthogonal to the axis of revolution R and a support 201 for a blank 170 illustrated in [Fig. 5]. A circle defined by the rotation of the false table 300 around the axis of revolution R would have a diameter between 1200 and 2500 mm. The support 201 comprises a lower plate 500 and an upper plate 600 arranged in planes parallel to each other and orthogonal to the axis of revolution R. The upper face of the false table 300 is provided with a plurality of coupling means 301 for cooperating with coupling means 501 of the lower plate 500 of the support 201. In this [Fig. 4], the coupling means consist of three studs 301 of the false table 300 cooperating with as many holes 501 of the lower face of the lower plate 500 of the support 201. Thus, the support 201 can be removably attached to the false table 300. The support 201 and the false table 300 comprise coupling means for connecting the pneumatic and hydraulic supplies (not shown).According to a variant of the invention, these coupling means for connecting the power supplies can be the coupling means 301 and 501. The upper face of the false table 300 is provided with a plurality of zero points 302. The upper face of the false table 300 is shown provided with ten zero points 302, one of the ten zero points being arranged in the center of the false table 300.

[0056] The lower plate 500 and the upper plate 600 of the support 201 are connected by a jack 401 whose height is variable, the lower plate 500 is fixed and the upper plate 600 is movable relative to the lower plate 500. Here, the jack is central and coaxial with the axis R. The central jack 401 is protected by a protective shell 402 preventing machining chips from damaging the central jack 401.

[0057] The lower plate 500 is provided with a plurality of external fixed supports 502 distributed at regular intervals around the periphery of the lower plate 500, each of the external fixed supports 502 being provided with an external clamping cylinder 503. Similarly, the upper plate 600 is provided with a plurality of internal fixed supports 601 distributed at regular intervals around the periphery of the upper plate 600, each of the internal fixed supports 601 being provided with an internal clamping cylinder 602.

[0058] It can also be seen that the upper plate 600 is provided with radial vibration attenuation means 603 and axial vibration attenuation means 604. Clamping cylinders 602 are arranged on the axial vibration attenuation means 604.

[0059] [Fig. 5] shows a blank 170 to be machined. The blank 170 has a portion which will be called the first end 171 and another, opposite the first, which will be called the second end 172. These two portions 171, 172 are separated by a stopping distance 175 set by the operator according to the machining requirements of the bipolar plate 11. The bipolar plate 11 machined from the blank 170 has been shown by transparency. [Fig. 8] shows the bipolar plate 11 fully machined.

[0060] We will now describe by means of figures 6 and 7 the method for machining a bipolar plate 11 from the blank 170 by means of the machining support 200 described previously.

[0061] The machining support 200 is prepared to receive the rough work 170 by bringing the upper plate 600 into the high position by activating the jack 401 and opening all the internal clamping jacks 602.

[0062] The blank 170 is then deposited on at least two, preferably at least three, internal fixed supports 601 of the upper plate 600. The internal fixed supports 601 ensure the centering of the blank 170 by interlocking the internal diameter of the blank and the diameter of the fixed support. Thus, the blank 170 is stabilized in the machining support 200 by its weight. The blank 170 can be deposited by means of an automaton or robot (not shown). The internal clamping cylinders 602 are then closed on the internal fixed supports 601 of the upper plate 600. The external clamping cylinders 503 are also opened on the external fixed supports 502 of the lower plate 500.

[0063] A first end 171 of the blank 170 is then machined up to a stopping line or distance 175. The machining can be carried out by any machining tool 700, for example a ravaging milling cutter. The two accessible faces 173 and 174 of the blank 170 can be machined simultaneously.

[0064] Once this first portion 172 of the blank 170 has been machined, the upper plate 600 is lowered to the low position, for example by deactivating the jack 401 which descends under the effect of its weight, so that the partially machined blank 170 now rests on the external fixed supports 502 of the lower plate 500. It is advisable to ensure that the upper plate 600 has indeed lowered to the low position before moving on to the next step. A delay of one or more seconds can therefore be applied in order to avoid any handling errors.

[0065] All the internal clamping cylinders 602 of the upper plate 600 are then opened and all the vibration attenuation means 603, 604 and their internal clamping cylinders 605 are deactivated. The external clamping cylinders 503 of the lower plate 500 are then closed.

[0066] The second end 172 opposite the first end 171 of the blank 170 which has already been machined can then be machined. The machining can be carried out by any machining tool 700, for example a ravaging milling cutter. The two accessible faces 173 and 174 of the blank 170 can then be machined simultaneously.

[0067] At this stage, after the machining operation, the thickness of the bipolar plate 11 is thinner than that of the blank 170 initially deposited on the machining support 200. This is why, in order to avoid generating stresses in the bipolar plate 11, the latter rests on the internal clamping cylinders 602 arranged on the upper plate 600.

[0068] The external clamping cylinders 503 of the lower plate 500 are opened, then all the internal clamping cylinders 602 of the upper plate 600 so that the machined bipolar plate 11 now rests on the internal fixed supports 601 of the upper plate 600. The upper plate 600 is raised to the high position by activating the cylinder 401 before extracting the machined bipolar plate 11.

[0069] Because the process ends with the upper plate 600 being brought into the high position and all the internal clamping cylinders 602 being open, the machining support 200 is ready to receive a new blank 170 for machining without any loss of time.

[0070] It was thus possible to carry out the machining of the bipolar plate 11 without ever having to carry out a step of turning the blank 170.

[0071] Reference to figures

[0072] 10 Electrolytic cell

[0073] 11 Bipolar plate

[0074] 12 Intercalary

[0075] 121 Electrolyte supply opening

[0076] 1221 Electrolyte / dihydrogen mixture extraction opening

[0077] 1222 Electrolyte / dioxygen mixture extraction opening

[0078] 123 Flared section of the opening

[0079] 125 Space

[0080] 131 Electrode (cathode) [0081 ] 132 Electrode (anode)

[0082] 14 Membrane

[0083] 15 Electrolyte supply line

[0084] 161 Electrolyte / dihydrogen mixture extraction pipe

[0085] 162 Electrolyte / dioxygen mixture extraction pipe

[0086] 170 Gross

[0087] 171 First end of the crude

[0088] 172 Second end of the crude

[0089] 173 Upper face of the rough

[0090] 174 Underside of the rough

[0091] 175 Stopping distance

[0092] 200 Machining support

[0093] 201 Support for crude

[0094] 300 Fake table

[0095] 301 Coupling means (plot)

[0096] 302 Zero point

[0097] 400 Tour

[0098]

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] 401 Cylinder 402 Cylinder protection shell 500 Lower plate 501 Coupling means (hole) 502 Outer fixed support 503 Outer clamping cylinder 600 Upper plate 601 Inner fixed support 602 Inner clamping cylinder 603 Radial vibration attenuation means 604 Axial vibration attenuation means 605 Inner clamping cylinder 700 Machining tool

Claims

Claims

1. Machining support (200) comprising a) a lathe (400) with an axis of revolution R; b) a false table (300) arranged on the lathe (400) in a plane orthogonal to the axis of revolution R; and c) a support (201) for one or more blanks (170), wherein, - the support (201) comprising a lower plate (500) and an upper plate (600) arranged in planes parallel to each other and orthogonal to the axis of revolution R; - the upper face of the false table (300) is provided with a plurality of coupling means (301) for cooperating with coupling means (501) of the lower plate (500) of the support (201); - the upper face of the false table (300) is provided with a plurality of zero points (302); - the lower plate (500) and the upper plate (600) of the support (201) are connected by a jack (401) whose height is variable, one of the two plates (600) being movable in translation along the axis R relative to the other (500);- the lower plate (500) is provided with a plurality of external fixed supports (502) distributed around the periphery of the lower plate (500), each of the external fixed supports (502) being provided with an external clamping cylinder (503); and - the upper plate (600) is provided with a plurality of internal fixed supports (601) distributed around the periphery of the upper plate (600), each of the internal fixed supports (601) being provided with an internal clamping cylinder (602).;

2. Machining support (200) according to claim 1, in which the jack (401) is central and coaxial with the axis R.

3. Machining support (200) according to one of claims 1 or 2, in which a circle defined by the rotation of the false table (300) around the axis of revolution R has a diameter between 1200 and 2500 mm.

4. A machining support (200) according to any one of claims 1 to 3, wherein the coupling means between the false table (300) and the lower plate (500) of the support (201) are made up of studs (301) cooperating with holes (501).

5. Machining support (200) according to claim 4, in which the false table (300) is provided with studs (301) cooperating with holes (501) of the lower plate (500) of the support (201).

6. Machining support (200) according to any one of claims 1 to 5, wherein the upper face of the false table (300) is provided with at least 5 zero points (302), preferably at least 10 zero points (302), one zero point (302) being arranged in the center of the false table (300).

7. Machining support (200) according to any one of claims 1 to 6, in which the jack (401) is fitted with a protective shell (402).

8. A machining support (200) according to any one of claims 1 to 7, wherein the lower platen (500) is fixed and the upper platen (600) is movable relative to the lower platen (500).

9. Machining support (200) according to any one of claims 1 to 8, wherein the plurality of external fixed supports (502) are regularly distributed around the periphery of the lower plate (500).

10. Machining support (200) according to any one of claims 1 to 9, wherein the plurality of internal fixed supports (601) are regularly distributed around the periphery of the upper plate (600).

11. Machining support (200) according to any one of claims 1 to 10, wherein the upper plate (600) is provided with vibration attenuating means (603, 604), preferably radial vibration attenuating means (603) and axial vibration attenuating means (604).

12. Machining support (200) according to claim 11, in which a clamping cylinder (602) is arranged on the axial vibration attenuating means (604).

13. A method for machining a blank (170) comprising the following steps in order: a) providing a machining support (200) according to any one of the preceding claims; b) bringing the upper plate (600) into the high position and opening all the internal clamping cylinders (602); c) depositing the blank (170) on at least two, preferably at least three internal fixed supports (601) of the upper plate (600); d) closing the internal clamping cylinders (602) on the internal fixed supports (601) of the upper plate (600); e) opening the external clamping cylinders (503) on the external fixed supports (502) of the lower plate (500); f) machining a first end (171) of the blank (170); g) lowering the upper plate (600) to the low position so that the partially machined blank (170) rests on the external fixed supports (502) of the lower plate (500); h) opening all the internal clamping cylinders (602) of the upper plate (600) and possibly deactivating all the vibration attenuation means (603, 604) and their cylinders (605) if these are present; i) closing the external clamping cylinders (503) of the lower plate (500); j) machining a second end (172) of the blank (170) opposite the first machined end (171); k) opening the external clamping cylinders (503) of the lower plate (500);1) open all the internal clamping cylinders (602) of the upper plate (600) so that the machined blank (170) rests on the internal fixed supports (601) of the upper plate (600); m) raise the upper plate (600) to the high position; n) extract the machined blank (170).;

14. A method according to claim 13 wherein step c) is performed by a robot and wherein the robot is moved away from the machining support (200) before step f).

15. A method according to claim 13 or 14 wherein steps h) and i) are carried out simultaneously.

16. Method according to any one of claims 13 to 15, in which the machining steps f) and / or j) are carried out simultaneously on both faces of the end (171, 172) of the machined blank (170).

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