Tool and machining process for a blank intended to produce a bipolar plate

Abstract

Tool and method for machining a blank intended to provide a bipolar plate. According to a first aspect, the invention relates to a machining 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 machining heads (701, 702), each equipped with a cutting tool (703, 704), the machining heads (701, 702) being configured to be operated on either side of the blank (170) to be machined, and a support element (705) equipped with two arms for supporting the machining heads (701, 702) and provided with coupling means (706) for coupling to a robotic arm. Figure for the abstract: 4

Description

Title of the invention: Tool and method for machining a blank to produce 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 for machining such parts. Technological background

[0002] A membrane electrolysis device generally comprises a stack (called an electrolyzer stack) of electrolytic cells within which the electrolysis reaction of water is conducted. The electrolytic cells are electrically connected in series and fluidically connected in parallel. With reference to Figures 1 to 3, an electrolytic cell 10 comprises, in order, a bipolar plate 11, a space 125 surrounded by an intercalated frame (or simply intercalated) 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 intercalated frame 12, and a second bipolar plate 11.The space (sometimes also called the electrode chamber) enclosed by the interlayer 12 is designed for the circulation of the electrolyte and electrolysis gases. Through the circulation of the electrolytic fluid, the reactants (water and hydroxide ions) reach the surface of 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. Electrodes 131 and 132 are generally made of doped metal, for example, nickel, but other conductive metals are also suitable. The membrane 14 (also called the diaphragm or porous separator) provides electrical insulation between the two electrodes 131 and 132 and allows the transport of protons or hydroxide ions from one electrode to the other while remaining impermeable to electrolysis gases.The bipolar plates 11 (also called current collectors) serve to supply current and vent gases from the electrolytic cell 10. The materials of the bipolar plates 11 must therefore possess sufficient electrical conductivity and good chemical inertness 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). Bipolar plates 11 are generally equipped with grooves or raised features to facilitate gas venting. The electrolyte (alkaline water solution) from a supply line 15 is introduced into space 125 through a supply opening 121 in the spacer 12. The resulting electrolyte / gas mixture is extracted from space 125 through a second extraction opening 1221 or 1222 in the spacer 12. When space 125 is located between the bipolar plate 11 and the cathode 131, the electrolyte / gas mixture extracted through the extraction opening 1221 consists primarily of gaseous dihydrogen, H2, and is discharged into the extraction line 161. When space 125 is located between the anode 132 and the bipolar plate 11, the electrolyte / gas mixture extracted through the extraction opening 1222 consists primarily of dioxygen, O2, gaseous and the mixture is discharged into extraction pipe 162.Extraction pipes 161 and 162 carry the electrolyte / gas mixture to separate degassing devices (not shown) allowing the recovery of dihydrogen and dioxygen respectively. In space 125, either the electrodes 131, 132 are against the bipolar plate 11, or a metallic mesh, 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 at the end of the first electrolytic cell 10 constituting 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 adjacent to the cathode 131 acts as an anode 132. Conversely, the surface of the bipolar plate 11 in contact with the space 125 adjacent to the anode 132 acts as a cathode 131.

[0004] Within the electrolyzer stack, the components in contact with the electrolyte are subjected to a particularly corrosive environment and undergo significant corrosion, quickly rendering them unusable. Furthermore, any surface roughness or imperfection on these components is a potential source of gas leakage, particularly hydrogen gas. These two problems are solved by electrolytic nickel plating these parts. However, this electrolytic nickel plating requires that the component be machined perfectly.

[0005] Among the components subjected to such conditions, the bipolar plate is particularly important as it plays a major role in the operation of the electrolyzer stack. It is therefore imperative that the nickel layer deposited on the bipolar plate be perfectly homogeneous. To this end, the bipolar plate is machined to present the most perfect (smooth, free of roughness) surface possible. This machining is carried out by milling and / or turning. of a rough workpiece (called a blank). The blank is usually cut from a billet. The blank 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 blank, it is turned over on the support, leaving its other face accessible to the machining tools. This conventional technique is extremely time-consuming and arduous for the operator, who must turn the blank over in a hazardous environment. Document DE-A1-102021104821 describes such a technique.

[0006] It would therefore be desirable to provide a solution for machining a blank intended to supply certain parts of an electrolyzer stack, for example a bipolar plate, which would allow for rapid machining of a part while eliminating the problems associated with the difficulty and danger of turning the blank over. Summary of the invention

[0007] The invention which is the subject of this patent application aims to solve this technical problem. To achieve this, it is proposed to use a machining tool, in particular 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 workpiece 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 that allows, for example, a bipolar plate to be produced after machining. Generally, it is in the form of a ring with an outer diameter between 700 and 2500 mm and an inner diameter between 500 and 2200 mm, and a thickness between 7 and 20 mm.

[0009] Milling is a manufacturing process where material removal 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 advance of the workpiece, on the other. Milling is performed by a machine tool (the milling machine) which makes it possible to create all types of shapes, even complex ones, using a milling cutter.

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

[0011] According to one embodiment, the support element of the machining 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 workpiece so that the workpiece is positioned between the two arms of the element. support and therefore between the machining heads which thus have access to the faces of the stock for machining. Generally, the gap between the two arms 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 machining head, preferably, to allow the transmission of pneumatic or electrical energy for the activation of the machining head.

[0013] In the context of the invention, any type of cutting tool can be used, although a head with interchangeable inserts is preferred. These inserts have various shapes (triangular, rhombic, rectangular, square, round, etc.) and are mounted on a head that has a housing for the insert and a clamping system (generally by screw or flange) to hold the insert(s). Carbide inserts allow machining at very high speeds and, among other advantages, due to their interchangeability, offer a short tool changeover time. The inserts may or may not be coated, with the coating intended to improve tool performance by providing additional resistance to wear and heat. Such inserts and / or their coatings are made, for example, of carbide, nitride, carbonitride, or titanium.

[0014] According to a second aspect, the invention relates to a machining process.

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

[0016] a) providing a machining support;

[0017] b) maintaining the raw material in such a way that two of its faces to be machined to provide a bipolar plate are accessible to a machining tool;

[0018] c) machining of a first face of the raw material;

[0019] d) machining of a second face of the blank opposite to the first machined face;

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

[0021] Because the blank is held in such a way that two of its faces, which must be machined to provide a bipolar plate, are accessible to a machining tool, no time is lost turning the blank over. Due to the presence of machining heads on both sides of the blank, one face and then the other can be machined successively without losing time moving a machining 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 machined bipolar plate.

[0023] According to an advantageous embodiment, the support used to hold the raw material during machining operations is that described in the patent application filed on the same day in the name of the same applicants. Brief description of the figures

[0024] The invention will now be described by means of the figures, which serve no other purpose than to illustrate the present invention. These figures schematically represent:

[0025] [Fig-1] The [Fig.1] an electrolytic cell of the prior art;

[0026] [Fig.2] The [Fig.2] is an intercalary of the prior art;

[0027] [Fig.3] The [Fig.3] is a prior art electrolytic cell stack;

[0028] [Fig.4] The [Fig.4] is a machining tool according to the invention;

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

[0030] [Fig.6] The [Fig.6] is a first machining phase;

[0031] [Fig.7] The [Fig.7] is a second machining phase;

[0032] [Fig.8] The [Fig.8] is a bipolar plate after machining. Description of the implementation methods

[0033] Figures 4, 6, and 7, respectively, schematically represent a machining tool 700 for a blank 170 intended to produce a bipolar plate 11 according to the present invention. According to the invention, this machining tool 700 comprises two separate machining heads 701 and 702, each equipped with a cutting tool 703 and 704. The machining 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 equipped with two arms for supporting the machining heads 701 and 702 and is provided with coupling means 706 for coupling to a robotic arm (not shown). Figure 4 also shows 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 raw material 170 can be placed between the two arms of the support element 705 and its upper face 174 and lower face 173 are accessible to the machining heads 701 and 702.

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

[0035] Figure 4 also shows the coupling means 706 to a robotic arm (not shown) for holding and moving the machining tool 700 during machining operations. The coupling means 706 are configured to allow the transmission of pneumatic or electrical energy for activating the two machining heads 701 and 702.

[0036] Figure 5 represents a blank 170 to be machined. The blank 170 has a portion, referred to as the first end 171, and another, opposite the first, referred to as the second end 172. These two portions are separated by a stop distance 175, fixed by the operator according to the machining requirements of the bipolar plate 11. The bipolar plate 11, machined from the blank 170, is shown in transparency. Figure 8 shows the bipolar plate 11.

[0037] We will now describe, using Figures 6 and 7, the process for machining a bipolar plate 11 from the raw material 170 using the machining tool 700 described previously.

[0038] The machining support 600 is prepared to receive the blank 170.

[0039] The raw material 170 is then placed on the machining support 600.

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

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

[0042] Machining can then proceed to the second end 172 opposite the first end 171 of the blank 170, which has already been machined. This is carried out using the machining tool 700 described above. Machining of the two accessible faces 173 (upper face) and 174 (lower face) of the blank 170 can be performed respectively using the machining 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 proceed with a turning step of the raw material 170.

[0044] Figure reference

[0045] 10 Electrolytic cell

[0046] 11 Bipolar plate

[0047] 12 Divider

[0048] 121 Electrolyte supply opening

[0049] 1221 Extraction opening for the dihydrogen electrolyte mixture

[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 channel

[0058] 162 Electrolyte / dioxygen mixture extraction channel

[0059] 170 Gross

[0060] 171 First end of the crude

[0061] 172 Second end of the crude

[0062] 173 Upper face of the crude

[0063] 174 lower face of the crude

[0064] 175 Stopping distance

[0065] 500 Machining support for the raw material

[0066] 600 Machining support for the raw material

[0067] 700 Machining tool

[0068] 701 Machining head

[0069] 702 Machining head

[0070] 703 Cutting plate

[0071] 704 Cutting plate

[0072] 705 Machining head support

[0073] 706 Means of coupling the support to a robotic arm

Claims

Demands

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 means for coupling (706) to a robotic 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 permit the transmission of pneumatic or electrical energy for the activation of the milling head (701, 702).

4. Milling tool (700) according to any one of the preceding claims, comprising two milling heads (701, 702) and in which the support element (705) has two arms on either side of a plane of symmetry.

5. Milling tool (700) according to claim 4, wherein the support element (705) is configured in a U-shape.

6. Milling tool (700) according to any one of the preceding claims in which 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. Method for 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 of a first face (173) of the raw material (170); c) milling of a second face (174) of the blank (170) opposite the first milled face (173); d) extraction of the milled bipolar plate (11).

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