Tool and method for milling a blank for providing a bipolar plate

Abstract

According to a first of its aspects, the invention relates to a milling tool (700) for machining a blank (170) intended to provide certain parts of an electrolyzer stack, for example a bipolar plate (11). It comprises at least two separate milling heads (701, 702) each provided with a cutting tool (703, 704), the milling heads (701, 702) being configured to be operated on either side of the blank (170) to be milled, and a support element (705) provided with two arms for supporting the milling heads (701, 702) and provided with means (706) for coupling to a robot arm.

Description

Description Title of the invention: Tool and method for milling a blank intended to provide a bipolar plate 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 machine such parts by milling. 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 are also suitable. 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 provided with grooves or reliefs promoting 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 comes to 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 comes to the space 125 arranged between the anode 132 and the bipolar plate 11, the electrolyte / gas mixture extracted through the extraction opening 1222 is essentially composed of gaseous dioxygen, 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) making it possible to recover the dihydrogen and the dioxygen 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 electrolyzer stack therefore comprises a stack of such electrolytic cells 10, the bipolar plate 11 terminating the first electrolytic cell 10 constitutes the beginning of the next electrolytic cell 10. Thus, the bipolar plate 11 of the first electrolytic cell 10 (upstream of the next) has a higher potential than that of the bipolar plate 11 of the second electrolytic cell 10 (downstream of the previous 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 electrolyzer stack, the elements that come into contact with the electrolyte are subjected to a particularly corrosive environment and undergo significant corrosion, making them quickly 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 operating on these parts with electrolytic nickel plating. 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 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 a rough part (called rough part). Since the rough part does not have an axis of revolution, turning is not an appropriate option. The rough part is generally cut from a billet. The rough part is placed flat on a support so that its upper face, opposite the support, is accessible to the milling tools. After milling the accessible face of the rough part, it is turned over on the support, leaving its other face accessible to the milling tools.This conventional technique is extremely time-consuming and arduous for the operator who has to turn the blank in a hazardous environment. Document DE-A1 -102021104821 describes such a technique. Documents EP- A1 -4015119, KR 10-2020-0029698, W0-A1 -2022-194317, US-A-5778746 and FR-A- 2125227 mainly describe turning tools that are not suitable for machining a blank.

[0006] It would therefore be desirable to provide a solution enabling the milling of a blank intended to supply certain parts of an electrolyser stack, for example a bipolar plate, which allows a part to be milled quickly while avoiding the problems linked to the difficulty and danger of the blank turning operation. Summary of the invention

[0007] The invention that is the subject of this patent application aims to solve this technical problem. To achieve this, it is proposed to use a milling tool capable of machining the upper and lower faces of a blank without having to be moved from one surface to the other.

[0008] The blank to be milled of the present invention is generally made of steel or one of its alloys and is generally cut from a billet, but, depending on the requirements, it can also be forged or bent and then welded. It is in any shape allowing for example to provide a bipolar plate after milling. Generally, it is in the form of a ring with an external diameter between 700 and 2500 mm and an internal diameter between 500 and 2200 mm and with a thickness between 7 and 20 mm.

[0009] Milling is a manufacturing process where the removal of material in the form of chips generally results from the combination of two movements: the rotation of the cutting tool, on the one hand, and the advancement of the part to be milled on the other. Milling is carried out by a machine tool (the milling machine) which can produce all types of shapes, even complex ones, using a milling cutter.

[0010] The milling tool according to the invention makes it possible to machine a blank intended to provide a bipolar plate. It comprises at least two separate milling heads each provided with a cutting tool, the milling heads being configured to be operated on either side of the blank to be machined and a support element provided with two arms for supporting the milling heads provided with means for coupling to a robot arm.

[0011] According to one embodiment, the support element of the milling tool has two arms on either side of a plane of symmetry. For example, the support element is configured in a U-shape. Thus, it is possible to engage the support element on either side of the blank so that the blank is arranged between the two arms of the support element and therefore between the milling heads which thus have access to the faces of the blank to machine them. Generally, the gap between the two branches of the support element is at least 5 mm, preferably at least 10 mm.

[0012] Advantageously, the coupling means are configured to allow the transmission of energy for the activation of the milling head, preferably to allow the transmission of pneumatic or electrical energy for the activation of the milling head.

[0013] For the purposes of the invention, any type of cutting tool is used, although it is preferred to use a head with removable inserts. These inserts have different shapes (triangular, rhombic, rectangular, square, round, etc.), and are mounted on a head having a housing for the insert and a clamping system (generally by screw or flange) to accommodate the insert(s). Carbide inserts make it possible to Milling with very high speeds, they have among other advantages, due to their interchangeability, a short tool repair time. The inserts are provided or not with a coating, which is intended to improve the performance of the tool by providing additional resistance to wear and heat. Such inserts and / or their coating are for example made of carbide, nitride, carbonitride, for example titanium.

[0014] According to a second of its aspects, the invention relates to a milling method.

[0015] According to the invention, this method comprises the following steps carried out in order:

[0016] (a) provision of a milling support;

[0017] (b) holding the workpiece in such a way that two of its faces to be milled to provide a bipolar plate are accessible to a milling tool;

[0018] c) milling a first face of the rough;

[0019] d) milling a second face of the blank opposite the first milled face;

[0020] e) extraction of the milled bipolar plate.

[0021] Because the blank is held in such a way that two of its faces to be milled to provide a bipolar plate are accessible to a milling tool, no time is lost in turning the blank. Because of the presence of milling heads on either side of the blank, one face and then the other can be milled successively without wasting time in passing a milling tool from one face of the blank to the other.

[0022] According to an advantageous embodiment, a robot is used for the step of extracting the milled bipolar plate.

[0023] According to an advantageous embodiment, the support used to hold the rough during milling operations is that described in French patent application 23 / 13025 filed in the name of the same applicants. Brief description of the figures

[0024] 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:

[0025] [Fig. 1] Figure 1 a prior art electrolytic cell;

[0026] [Fig. 2] Figure 2 is a prior art insert;

[0027] [Fig. 3] Figure 3 is a stack of prior art electrolytic cells;

[0028] [Fig. 4] Figure 4 is a milling tool according to the invention;

[0029] [Fig. 5] Figure 5 is a blank to be machined to provide a bipolar plate;

[0030] [Fig. 6] Figure 6 is a first phase of milling;

[0031] [Fig. 7] Figure 7 is a second milling phase;

[0032] [Fig. 8] Figure 8 is a bipolar plate after milling. Description of the embodiments

[0033] 4, 6 and 7 respectively show schematically a milling tool 700 for a blank 170 intended to provide a bipolar plate 11 in accordance with the present invention. According to the invention, it can be seen that this milling tool 700 comprises two separate milling heads 701 and 702, each provided with a cutting tool 703 and 704. The milling heads 701 and 702 are configured to be operated on either side of the blank 170 to be machined. The tool further comprises a support element 705 provided with two arms for supporting the milling heads 701 and 702 and is provided with coupling means 706 to a robot arm (not shown). In Figure 4, it can also be seen that the support element 705 has two arms arranged on either side of a plane of symmetry. In particular, Figure 4 shows a support element configured in a U shape.Thus, the rough 170 can be arranged between the two arms of the support element 705 and its upper 174 and lower 173 faces are accessible to the milling heads 701 and 702.

[0034] The support element 705 supports the two milling heads 701 and 702, which are each provided with a cutting insert 703 and 704.

[0035] Also seen in this figure 4 are the coupling means 706 to a robot arm (not shown) making it possible to hold and move the milling tool 700 during the milling operations. The coupling means 706 are configured to allow the transmission of pneumatic or electrical energy for the activation of the two milling heads 701 and 702.

[0036] Figure 5 shows a blank 170 to be machined. The blank 170 has a portion that will be called the first end 171 and another, opposite the first, that will be called the second end 172. These two portions are separated by a stopping distance 175 set by the operator according to the milling requirements of the bipolar plate 11. The bipolar plate 11 milled from the blank 170 is shown by transparency. Figure 8 shows the bipolar plate 11.

[0037] 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 milling tool 700 described previously.

[0038] The 600 milling support is prepared to receive the 170 rough.

[0039] The 170 rough is then placed on the 600 milling support.

[0040] A first end 171 of the blank 170 is then milled (said first end 171 does not rest on the milling support 600, in other words it is suspended in a vacuum) up to a stopping line or distance 175. The milling is carried out by means of the milling tool 700 described above. The two accessible faces 173 (upper face) and 174 (lower face) of the blank 170 can be milled respectively by means of the milling heads 701 and 702.

[0041] The milling of the two faces 173, 174 of this first end 171 of the blank 170 having been carried out, the partially machined blank 170 is transferred onto the support 500 where the upper 173 and lower 174 faces of a second end 172 are then accessible (said second end 172 does not rest on the milling support 500, in other words it is suspended in a vacuum).

[0042] The second end 172 opposite the first end 171 of the blank 170 which has already been milled can then be milled. This is done using the milling tool 700 described above. The two accessible faces 173 (upper face) and 174 (lower face) of the blank 170 can then be milled respectively using the milling heads 701 and 702 before extracting the bipolar plate 11.

[0043] 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 rough 170.

[0044] Figure reference

[0045] 10 Electrolytic cell

[0046] 11 Bipolar plate

[0047] 12 Intercalary

[0048] 121 Electrolyte supply opening

[0049] 1221 Dihydrogen electrolyte mixture extraction opening

[0050] 1222 Oxygen electrolyte mixture extraction opening

[0051] 123 Flared section of the opening

[0052] 125 Space

[0053] 131 Electrode (cathode)

[0054] 132 Electrode (anode)

[0055] 14 Membrane

[0056] 15 Electrolyte supply line

[0057] 161 Electrolyte / dihydrogen mixture extraction pipe

[0058] 162 Electrolyte / dioxygen mixture extraction pipe

[0059] 170 Brut

[0060] 171 First end of the crude

[0061] 172 Second end of the crude

[0062] 173 Upper face of the rough

[0063] 174 underside of the rough

[0064] 175 Stopping distance

[0065] 500 Milling support for rough

[0066] 600 Milling support for rough

[0067] 700 Milling Tool

[0068] 701 Milling head

[0069] 702 Milling head

[0070] 703 Cutting insert

[0071] 704 Cutting insert

[0072] 705 Milling head support

[0073] 706 Means for coupling the support to a robot arm

Claims

CLAIMS

1. Milling tool (700) for a blank (170) intended to provide a bipolar plate (11) comprising a) at least two separate milling heads (701, 702) each provided with a cutting tool (703, 704), the milling heads (701, 702) being configured to be operated on either side of the blank (170) to be machined and b) a support element (705) provided with two arms for supporting the milling heads (701, 702) and provided with coupling means (706) to a robot arm.

2. Milling tool (700) according to claim 1, wherein the coupling means (706) are configured to allow the transmission of energy for the activation of the milling head (701, 702).

3. Milling tool (700) according to claim 2, wherein the coupling means (706) are configured to allow the transmission of pneumatic or electrical energy for the activation of the milling head (701, 702).

4. A milling tool (700) according to any preceding claim, comprising two milling heads (701, 702) and wherein the support member (705) has two arms on either side of a plane of symmetry.

5. The milling tool (700) of claim 4, wherein the support member (705) is configured in a U-shape.

6. Milling tool (700) according to any one of the preceding claims wherein at least one of the milling heads (701, 702) is provided with a head (703, 704) with removable inserts.

7. Milling tool (700) according to the preceding claim in which the removable insert is made of carbide, nitride, carbonitride of metal, for example titanium.

8. A method of milling a blank (170) intended to provide a bipolar plate (11) a) providing a milling support (600); b) holding the blank (170) in such a way that two of its faces (173, 174) to be milled to provide a bipolar plate (11) are at least partially accessible to a milling tool (700) as defined in any one of the preceding claims; c) milling a first face (173) of the blank (170); c) milling a second face (174) of the blank (170) opposite the first milled face (173); d) extracting the milled bipolar plate (11).

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