Tool and method for machining a blank intended to provide a bipolar plate

Abstract

Tool and method for machining a blank intended to provide a bipolar plate. According to a first of its aspects, 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 provided 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) provided with two arms for supporting the machining heads (701, 702) provided with coupling means (706) to a robot arm. Figure for the abstract: 4

Description

Title of the invention: Tool and method for machining 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. 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 line 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 line 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 essentially composed of dioxygen, 02, gaseous 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) for recovering 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 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 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 layer of nickel 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. of a raw part (called rough). The rough is generally cut from a billet. The rough 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, 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 in a dangerous environment. Document DE-A1-102021104821 describes such a technique.

[0006] It would therefore be desirable to provide a solution allowing the machining of a blank intended to provide certain parts of an electrolyser stack, for example a bipolar plate, which allows a part to be machined quickly while avoiding the problems linked to the difficulty and danger of the operation of turning the blank. 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 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 rough workpiece of the present invention is generally made of steel or one of its alloys 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 machining. Generally, it is in the form of a ring whose outer diameter is between 700 and 2500 mm and the inner 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 machined on the other hand. 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 machining tool according to the invention makes it possible to machine a blank intended to provide a bipolar plate. It comprises at least two separate machining heads each provided 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 provided with two arms for supporting the machining heads provided with means for coupling to a robot 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 blank so that the blank is arranged between the two arms of the support element. support and therefore between the machining heads which thus have access to the faces of the rough material 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 machining head, preferably, to allow the transmission of pneumatic or electrical energy for the activation of the machining 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 allow machining at very high speeds; they have, among other advantages, due to their interchangeability, a short tool repair time. The inserts may or may not be provided 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, carbo-nitride, for example titanium.

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

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

[0016] a) providing a machining support;

[0017] b) holding the blank 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 a first face of the rough work;

[0019] d) machining a second face of the rough material opposite 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 to be machined to provide a bipolar plate are accessible to a machining tool, no time is lost in turning the blank. Because of the presence of machining heads on either side of the blank, one face and then the other can be machined successively without wasting time in passing 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 rough during the 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 figures which have no other purpose than to illustrate the present invention. These figures schematically represent:

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

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

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

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

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

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

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

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

[0033] Figures 4, 6 and 7 respectively show schematically a machining 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 machining tool 700 comprises two separate machining heads 701 and 702, each provided 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 provided with two arms for supporting the machining heads 701 and 702 and is provided with coupling means 706 to a robot arm (not shown). In [Fig. 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, [Fig. 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 machining heads 701 and 702.

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

[0035] Also seen in this [Fig.4] are the coupling means 706 to a robot arm (not shown) for holding and moving the machining tool 700 during the machining operations. The coupling means 706 are configured to allow the transmission of pneumatic or electrical energy for the activation of the two machining heads 701 and 702.

[0036] [Fig. 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 machining requirements of the bipolar plate 11. The bipolar plate 11 machined from the blank 170 is shown by transparency. [Fig. 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 machining tool 700 described previously.

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

[0039] The rough work 170 is then deposited on the machining support 600.

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

[0041] Once the two faces 173, 174 of this first end 171 of the blank 170 have been machined, the partially machined blank 170 is transferred to 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 machining 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 machined can then be machined. This is carried out using the machining tool 700 described above. The two accessible faces 173 (upper face) and 174 (lower face) of the blank 170 can be machined 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 carry out a step of turning the blank 170.

[0044] Reference to figures

[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 Opening for extracting the dioxygen electrolyte mixture

[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]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] 170 Stock 171 First end of stock 172 Second end of stock 173 Upper face of stock 174 Lower face of stock 175 Stop distance 500 Machining support for stock 600 Machining support for stock 700 Machining tool 701 Machining head 702 Machining head 703 Cutting insert 704 Cutting insert 705 Support for machining heads 706 Means for coupling the support to a robot arm

Claims

Claims

1. Machining tool (700) for a blank (170) intended to provide a bipolar plate (11) comprising a) at least two separate machining heads (701, 702) each provided 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 b) a support element (705) provided with two arms for supporting the machining heads (701, 702) and provided with coupling means (706) to a robot arm.

2. A machining tool (700) according to claim 1, comprising two machining heads (701, 702) and wherein the support element (705) has two arms on either side of a plane of symmetry.

3. The machining tool (700) of claim 2, wherein the support member (705) is configured in a U-shape.

4. A machining tool (700) according to any preceding claim, wherein the coupling means (706) are configured to enable transmission of energy for activation of the machining head (701, 702).

5. Machining tool (700) according to claim 4, wherein the coupling means (706) are configured to allow the transmission of pneumatic or electrical energy for the activation of the machining head (701, 702).

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

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

Images