Electrolytic polishing apparatus and electrolytic polishing method

Abstract

This invention provides an apparatus and method for electrolytically polishing the inner surface of a container tank. [Solution] First, a unit electrode is constructed. The electrode plate has a predetermined length in the inner circumferential direction of the container tank, with a curve corresponding to the curvature of the inner circumference, and a predetermined width in the axial direction. A gripping device rotatably grips the electrode shaft, which is positioned axially at the center of the container tank. An arm has its rear end fixed to the gripping device and supports the electrode plate at its tip. Casters are fixed to the outer circumference of the electrode plate so that the electrode plate can move circumferentially on the inner surface of the container tank, and maintain insulation between the electrode plate and the inner surface of the container tank. Next, multiple unit electrodes are arranged along the axial length of the container tank. In this state, electrolytic polishing is performed with the unit electrodes immersed in the electrolyte, and once partial electrolytic polishing is complete, the container tank is rotated.

Description

[[Technical Field]]

[0001] The present invention relates to an electrolytic polishing apparatus for the inner circumferential surface of a container tank used for liquid transportation, and an electrolytic polishing method using the same. [[Background Art]]

[0002] With the miniaturization of semiconductors, containers for storing IPA (isopropyl alcohol) used in semiconductor cleaning are now required to have a metal elution amount in units of ppm or less.

[0003] The amount of metal elution from stainless steel containers used for storage or transportation of IPA, particularly from the inner surface in contact with IPA, is the subject of discussion herein. In order to reduce the amount of metal elution from the inner surface of the stainless steel container, it is preferable to electrolytically polish the inner surface of the container in contact with IPA. Although electrolytic polishing of a stainless steel container with a capacity that can be held by hand is relatively easy even on the inner surface, no technology for electrolytic polishing the inner surface of a container tank used for transportation by trucks or ships has been proposed to date. Japanese Patent No. 5190012 discloses a bathtub frame for electrolytically polishing the inner surface of a vertical tank. Further, Japanese Patent No. 6231879 discloses a jig that covers a part of a surface to be polished with a transparent cover, holds an electrolytic solution in a space between the transparent cover and the surface to be polished, and can finally complete the entire electrolytic polishing while partially polishing a work surface having a large area. [[Prior Art Documents]] [[Patent Documents]]

[0004] [[Patent Document 1]] Japanese Patent No. 5190012 [[Patent Document 2]] Japanese Patent No. 6231879 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0005] Transporting large quantities of IPA requires container tanks used for liquid transport by ship or truck. Since these container tanks have a relatively large inner diameter of around 2 meters or more, electrolytic polishing would require a large amount of electrolyte if the tanks were filled with electrolyte, making it impractical.

[0006] Furthermore, while the container tank is large enough for a person to stand and move around inside, the loading and unloading of materials is done through a manhole. This manhole is only a few tens of centimeters in diameter, which is sufficient for loading and unloading liquids, but it is not possible to bring in large equipment.

[0007] The apparatus disclosed in the above-mentioned Patent No. 5190012 is designed for vertical, relatively large-diameter tanks and is therefore large in scale. Consequently, the equipment used is large in scale, making it difficult to transport through the manhole.

[0008] While it is possible to polish the inner surface in sections using the jig described in Patent No. 6231879, the inner surface of a container tank has a considerable surface area, making it a time-consuming process.

[0009] This invention was proposed in view of the above-mentioned conventional circumstances, and provides a method for electropolishing the inner surface of a container tank in a relatively short time, and a jig used in this method. [Means for solving the problem]

[0010] The present invention relates to an apparatus and method for polishing the inner surface of a container tank, which has both ends of a cylindrical body closed with lids.

[0011] <Inner surface polishing device> Polishing the inner surface of a container tank requires an electrode device that combines the following unit electrodes.

[0012] First, the unit electrode is configured as follows.

[0013] The electrode plate has a predetermined length in the inner circumferential direction of the container tank, with a curve corresponding to the curvature of the inner circumference, and a predetermined width in the axial direction. The gripping device rotatably grips the electrode axis, which is positioned axially at the center of the container tank.

[0014] The rear end of the arm is fixed to the gripping device, and the tip supports the electrode plate. Casters are fixed to the outer circumference of the electrode plate so that the electrode plate can move circumferentially on the inner surface of the container tank, and insulation is maintained between the electrode plate and the inner surface of the container tank.

[0015] The electrode device has a configuration in which multiple unit electrodes are arranged along the axial length of the container tank on an electrode axis positioned axially at the center of the container tank. <Method for polishing the inner surface> The procedure for polishing the inner surface of the container tank using the aforementioned electrodes is as follows.

[0016] An electrode shaft is stretched along the axis of the container tank. Multiple unit electrodes are assembled on the electrode shaft to form an electrode device, corresponding to the length of the container tank. An electrolyte solution is filled to the container tank to the extent that the electrode plates constituting the unit electrodes are submerged.

[0017] The inner circumferential surface of the portion filled with the electrolyte is electropolished by applying a voltage of appropriate polarity between each electrode plate and the container tank.

[0018] Furthermore, the container tank is rotated by a predetermined angle so that the unpolished portion of the inner surface of the container tank is positioned downwards, and the electrode plate is positioned above the unpolished portion. The unpolished portion positioned downwards is then electropolished. The rotation of the container tank and the electropolishing of the unpolished portion are then repeated until the entire inner surface of the container tank is polished. [Brief explanation of the drawing]

[0019] [Figure 1] Front view of the liquid stopper plate. [Figure 2] Side view of the liquid stopper plate. [Figure 3] Partial enlarged view of Fig. 1. [Figure 4] Partial enlarged view of Fig. 1. [Figure 5] Figure showing the polished state of the wave-eliminating rib. [Figure 6] Front view of the unit electrode. [Figure 7] Side view of the unit electrode. [Figure 8] Plan view of the unit electrode. [Figure 9] Front view of the shaft support. [Figure 10] Side view of the shaft support. [Figure 11] Side view showing a state where a container tank is placed on a roller base. [Figure 12] Front view of Fig. 11. [Figure 13] Figure showing the state of the weir pipe. MODE FOR CARRYING OUT THE INVENTION

[0020] The present invention provides a jig for polishing the inner surface (the inner surface of the lid and the inner circumferential surface) of a container tank, and a method using the jig. As described above, since the manhole of the container tank has a size of several tens of centimeters, the members constituting the liquid stopping plate and the electrode device described below need to have a size that allows them to be carried into the container tank through the manhole.

[0021] <Liquid stopping plate> Fig. 1 is a front view of a liquid stopping plate used when electrolytically polishing the inner surface of the lid of the container tank, Fig. 2 is a side view, and Figs. 3 and 4 are partial enlarged views of Fig. 1.

[0022] First, a wheel-shaped liquid stopping plate 1 is constructed in the container tank as follows. Multiple spokes 10 of a predetermined length are fixed radially from a central axis 11. Each spoke 10 is designed so that its diameter can be adjusted. For example, in the example shown in Figure 1 (enlarged view of Figure 3), spoke tubes 13 with nuts 14 attached to their ends are rotatably inserted into multiple spoke shafts 12 fixed radially at equal angular intervals from the central axis 11. A threaded rod 15 is screwed onto the nut 14, and by rotating the nut 14, the threaded rod 15 extends and retracts, thereby forming a single spoke 10.

[0023] A receiving plate 17 is fixed to the tip of the aforementioned threaded rod 15, and each receiving plate 17 receives a retaining plate 18 that forms a ring corresponding to the inner circumference of the container tank 100. Multiple (for example, four) retaining plates 18 are connected together to form a ring corresponding to the inner circumference of the container tank 100.

[0024] Of course, a clearance sufficient to withstand the expansion and contraction of the threaded rod 15 is provided at the joint of each retaining plate 18.

[0025] A sealing material 19 is applied to the outside of the retaining plate 18 of the wheel body formed in this way, and a cover material 20 is applied to the circular surface of the wheel body. A notch is provided in a part of the circumference of the cover material 20 and used as a work window 21. The functions of the sealing material 19 and the cover material 20 will be described later.

[0026] On the semicircular surface opposite to the work window 21 (the lower side if the work window side is considered the upper side), a semicircular electrode 22 is attached to the semicircular portion on the outside (electrolyte side) of the cover material 20, in contact with the cover material 20, and is immersed in the electrolyte that fills the liquid reservoir space 102 formed when the wheel body is installed on the inner surface of the container tank 100 as described below. Therefore, naturally, the sealing material 19 and the cover material 20 will be liquid-tight with respect to the electrolyte that fills the liquid reservoir space 102. The semicircular electrode 22 can take the form of a mesh or strips combined in a grid pattern, and can be attached to the outside of the cover material 20 by means of hanging it from a hook fixed to the cover material 20.

[0027] <Method for polishing the inner surface of the lid> First, the container tank is designed to rotate in order to perform the following tasks. Figure 11 is a side view of the container tank mounted on a roller stand, and Figure 12 is a front view. Figures 11 and 12 themselves are diagrams used to explain the polishing of the inner surface, which will be described later.

[0028] The roller stand 200 has a structure in which two sets of rollers 202 are fixed front to back on a base 201 with a predetermined distance between them from left to right.

[0029] In the above state, first, the necessary components are brought into the container tank 100 through the manhole 104, and the liquid stop plate 1 is assembled parallel to the inner surface 101i of the lid 101, maintaining a predetermined distance from the inner surface 101i of the lid 101.

[0030] At this time, with the semicircular electrode 22 facing downwards (with the work window 20 facing upwards), the sealant 19 is firmly pressed against the inner surface of the container tank 100 via the retaining plate 18 using the nut 14 to ensure liquid tightness. This creates a liquid reservoir space 102 between the inner surface 101i of the lid of the container tank 100 and the liquid stopper plate 1.

[0031] Next, the electrolyte is filled into the liquid reservoir space 102. The amount of electrolyte to be filled is not particularly limited, but in order to reduce the number of rotation operations of the container tank 100 as described below, it is desirable to fill it to slightly above halfway. Therefore, the semicircular electrode 22 will be about half the size of the liquid stopper plate 1, and the work window 21 of the cover material 20 will be located above the halfway point of the liquid stopper plate 1.

[0032] With the electrolyte filling the liquid reservoir space 102 as described above, the appropriate polarity and voltage are applied between the semicircular electrode 22 and the container tank 100 to electropolish the portion immersed in the electrolyte. At this time, the work window 21 serves as a passage for the power supply cable to the semicircular electrode 22 and as a discharge hole for the generated gas.

[0033] The portion not immersed in the electrolyte in the above process becomes the unelectrolyzed portion. Therefore, first, the electrolyte is drained, and the container tank 100 itself is rotated 180° on the roller stand 200. Next, as in the above process, the nuts 14 on each spoke 10 of the liquid stopper plate 1 are loosened to position the semicircular electrode 22 downwards. Then, the electrolyte is filled in and the unelectrolyzed portion is electrolyzed.

[0034] This means that the inner surface 101i of one lid has been polished. The inner surface of the other lid can be polished using the same procedure.

[0035] <Method for polishing wave-breaking ribs> If waves generated by vibrations during transport in a container tank 100 are left untreated, they may interfere with the movement of trucks and ships. Therefore, some container tanks 100 have a structure in which wave-dissipating ribs are provided at least once in the middle of the axial direction (often in the center). These wave-dissipating ribs have a structure in which annular members protrude inward in a rib-like manner from the inner circumferential surface of the container tank 100.

[0036] Figure 5 shows the process of polishing the wave-breaking rib 106 using the liquid-stopping plate.

[0037] First, the liquid stopper plates 1 are fixed on both sides of the wave-dissipating rib 106, maintaining a predetermined distance between them, with the work window 21 facing upwards (and the semicircular electrode 22 facing downwards). The electrolyte is filled into the liquid reservoir space formed between the two liquid stopper plates 1. A voltage of the appropriate polarity is applied between the container tank 100 and the liquid stopper plates 1 to polish the portion of the wave-dissipating rib that is submerged in the electrolyte (up to slightly above the halfway point).

[0038] Furthermore, the electrolyte is drained, the container tank 100 is rotated 180°, and the two liquid stop plates 1 are rotated and repositioned so that the semicircular electrodes 22 are positioned on the lower side, and then the electrolyte is filled and polished.

[0039] This also allows the wave-breaking ribs 106 that protrude into the interior of the container tank 100 to be polished.

[0040] <Inner surface polishing device> As described above, the inner surfaces 101 of the lids at both ends of the container tank 100 and the wave-breaking ribs have been polished, but the remaining inner circumferential surface 103 also needs to be polished.

[0041] To polish the inner surface, it is necessary to construct an electrode device having an electrode plate with a curvature along the inner surface 103.

[0042] Figure 6 is a front view of a unit electrode (hereinafter referred to as a unit electrode) that constitutes the electrode device, Figure 7 is a side view thereof, and Figure 8 is a top view thereof.

[0043] The electrode device described above consists of a collection of unit electrodes, as described below.

[0044] The electrode plate 31 is a plate-shaped conductor, such as a copper mesh or strip, arranged in a grid pattern as shown in Figure 8, having a predetermined length in the circumferential direction of the inner circumference of the container tank 100 with a curve corresponding to the curvature of the inner circumference, and a predetermined width in the axial direction (a width that takes into account the diameter of the manhole 104 (for example, 40 cm)).

[0045] Casters 32 are fixed to the outer circumference of the electrode plate 31, allowing the electrode plate 31 to move circumferentially on the inner surface of the container tank, while the casters 32 maintain insulation between the electrode plate 31 and the inner surface of the container tank 100. The electrode plate 31 is supported by arms 33 on an electrode shaft 50 positioned axially in the center of the container tank 100.

[0046] Specifically, radial arms 33 are raised from the center of both circumferential ends of the electrode plate 31. Meanwhile, an electrode shaft 50 (described later) is passed axially through the center of the inside of the container tank 100. A gripping member 34 is rotatably attached to the electrode shaft 50, and the two arms 33 are fixed to the gripping member 34.

[0047] This constitutes the formation of the unit electrode 30.

[0048] To polish the entire inner surface of the container tank 100, it is necessary to configure the electrode device 3 described below.

[0049] Figure 9 is a front view of the axial support that supports the electrode axis of the electrode device, and Figure 10 is a side view.

[0050] First, the radial wheel body used in the liquid stopper plate 1 is composed of 12 spokes spaced at 30° intervals, but here, as shown in Figure 9, an axle support 40 is constructed with 4 spokes 10 spaced at 90° intervals. The configuration of each spoke 10 is exactly the same as the spokes used in the liquid stopper plate 1, so a detailed description is omitted here.

[0051] The retaining plate 18 and sealing material 19 used in the liquid-stopping plate 1 are not necessary, but a backing plate 42 is required between the receiving plate 17 and the inner circumferential surface 103 of the container tank 100 to protect the inner circumferential surface 103. The contact area of ​​the backing plate 42 with the inner circumferential surface 103 should be reduced, for example, by making the contact portion linear, to prevent the generation of unelectrolyzed areas.

[0052] Furthermore, a shaft hole 41 is provided at the center of the central axis 11 to which each spoke 10 is attached, into which the electrode shaft 50 described below is fitted. With the electrode shaft 50 passed through the shaft hole 41, the nuts 14 on the spokes 10 are adjusted to fix the shaft support 40 radially at both ends (or where necessary) of the container tank 100, and the electrode shaft 50 is stretched axially within the container tank 100.

[0053] In other words, the electrode shaft 50 is fixed in a position that coincides with the axis of the container tank 100. In this state, multiple electrodes 30 of the aforementioned unit are attached to the electrode shaft 50 rotatably along the entire axial direction using the gripping member 33, and the electrode device 3 is formed as shown in Figures 11 and 12.

[0054] Furthermore, due to the size of the manhole 104, the length of the electrode shaft 50 that can be brought into the container tank 100 may be limited, and multiple electrode shafts 50 may be required to cover the axial length of the container tank 100. In this case, a number of shaft supports 40 corresponding to the number of electrode shafts 50 will be required. <Method for polishing the inner surface> First, as described above, the electrode shaft 50 is stretched across the axial support 40 fixed near both walls of the container tank 100.

[0055] Multiple unit electrodes 30 are attached along the electrode axis 50, extending along the entire axial direction, to constitute the electrode device 3.

[0056] Next, the electrolyte is filled to a depth such that the electrode plates 31 constituting the unit electrode are submerged. A voltage of appropriate polarity is applied between each electrode plate 31 and the container tank 100 to electrolytically polish the inner circumference of the portion filled with the electrolyte.

[0057] Furthermore, the container tank 100 is rotated by a predetermined angle so that the un-electrolyzed portion is positioned on the lower side. At this time, the gripping member 34 is rotatable with respect to the electrode axis 50, and the electrode plate 31 moves relative to the inner circumferential surface of the container tank 100 via the caster 32. Consequently, as the container tank 100 rotates, the electrode plate 31 is positioned above the unpolished portion, and naturally the electrolyte accumulates in the position of the un-electrolyzed portion.

[0058] Next, the unpolished portion located on the lower side is electropolished. The rotation of the container tank 100 and the electropolishing of the unpolished portion are repeated until the entire inner circumference of the container tank 100 is polished.

[0059] <Procedure for polishing the entire interior> The usual procedure is to polish the inner surface 101i of the lid, and if there are wave-removing ribs 106, then polish the wave-removing ribs 106, followed by the inner circumferential surface 103.

[0060] When the inner surface 101i of the lid is polished, the liquid stopper plate 1 is fixed to the inner circumferential surface 103, which is 10 to 20 cm away from the inner surface 101i of the lid, so that a portion of the inner circumferential surface is polished. Therefore, by installing the shaft support 40 on the polished portion of the inner circumferential surface, it does not interfere with the polishing of the inner circumferential surface. Even if the shaft support 40 is installed on the unpolished portion, as described above, the contact area between the backing plate 42 and the inner circumferential surface 103 can be reduced to minimize the occurrence of un-electrolyzed areas.

[0061] Furthermore, a manhole 104 is always present in the container tank 100. Figure 13 shows the state of electrolytic polishing of the manhole area.

[0062] The portion of manhole 104 may be a polishing position, or a position where electrolyte solution is filled even if it is not a polishing position. In this case, a damming pipe 60 having a diameter equal to that of manhole 104 and a height greater than or equal to the height of the electrolyte solution to be filled is inserted into the manhole 104.

[0063] A flange 61 with a diameter larger than the diameter of the manhole 104 is formed at the rear end of the damming pipe 60, so that the inserted damming pipe 60 does not get stuck in the manhole 104.

[0064] With this configuration, if liquid-tightness is ensured between the entrance of the manhole 104 and the flange 61, liquid leakage will not occur even if the portion of the manhole 104 overlaps with the portion filled with electrolyte.

[0065] The unit electrodes 30 are positioned to avoid the manhole 104, and the avoided portion cannot be electrolyzed as is. Therefore, a configuration is adopted in which a conductor is extended from an adjacent unit electrode 30 to the portion of the inner surface of the container tank where no unit electrode 30 is directly above.

[0066] This allows for electrolytic polishing of areas where the unit electrode 30 is not present through the extended conductor, thus avoiding the occurrence of unpolished areas. [Explanation of symbols]

[0067] 1. Liquid stopper plate 3 Electrode device 10 spokes 11 Center axis 12 spoke axle 13 spoke tubes 14 nuts 15 threaded rods 17 Receiving plate 18. Pressing plate 19. Sealant 20 Cover material 21 Work window 22 Semicircular electrodes 30 unit electrodes 31 Electrode plate 32 casters 33 Arms 34 Gripping member 40 shaft support 41 Shaft hole 42 backing plate 50 Electrode axis 60 Damming pipe 61 Flange 100 container tanks 101 Lid 101i Lid inner surface 102 Liquid storage space 103 Inner surface 104 Manhole 106 wave-reducing ribs 200 Roller Stand 201 Foundation 202 Laura

Claims

1. A unit electrode that constitutes an electrode device for polishing the inner circumferential surface of a container tank whose ends are closed with lids, An electrode plate having a predetermined length in the inner circumferential direction corresponding to the curvature of the inner circumference of the container tank, and a predetermined width in the axial direction, A gripping device that rotatably grips an electrode shaft positioned axially at the center of the container tank, An arm whose rear end is fixed to the gripping device and whose tip supports the electrode plate, The electrode plate is fixed to the outer circumference so that it can move circumferentially on the inner surface of the container tank, and a caster is provided to maintain insulation between the electrode plate and the inner surface of the container tank. A unit electrode for polishing the inner surface of a container tank, characterized by having the following features.

2. An electrode device comprising a plurality of unit electrodes according to claim 1 arranged along the axial length of the container tank on an electrode axis axially positioned in the center of the container tank.

3. In a method for polishing the inner surface of a container tank whose ends are closed with lids, The steps include stretching an electrode shaft along the axis of the container tank, The steps include: assembling a plurality of unit electrodes according to claim 1 on the electrode shaft in a manner corresponding to the length of the container tank to form an electrode device; The steps include filling the electrolyte with an amount sufficient to immerse the electrode plates constituting the unit electrode, The steps include: applying a voltage of appropriate polarity between each electrode plate and the container tank to electrolytically polish the inner surface of the portion filled with the electrolyte; A method for polishing the inner surface of a container tank, characterized by comprising [a specific component].

4. Furthermore, the container tank is rotated by a predetermined angle so that the unpolished portion of the inner circumferential surface of the container tank is positioned downwards and the electrode plate is positioned above the unpolished portion. The step of electropolishing the unpolished portion located on the lower side, The steps of rotating the container tank and electrolytically polishing the unpolished portion are repeated until the entire inner circumference of the container tank is polished. A method for polishing the inner circumferential surface of a container tank according to claim 3, comprising the following:

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