Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1994-08-31
1995-12-19
Valentine, Donald R.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204224R, 204DIG7, C25D 1700
Patent
active
054765773
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for the electrolytic deposition of metal on the metal strips forming the cathode, preferably steel strips, in accordance with the introductory part of claim 1.
A device of said type is known, in which for the prevention of irregular and excessive deposition of the metal on a metal strip to be galvanized, provision is made in the gap between each two parallel, plate-like anodes for edge masks having a U-shaped cross section, which masks, with their two shanks extending parallel with each other, such shanks being suitably set up transversely to the direction of the strip, enclose the edge zones of the metal strip to be coated, and thus screen off said zones against the electrical field, so that the deposition occurring in the respective edge zones of the metal strip is not stronger than the other deposition on the strip. Said edge masks are made of an insulating material, preferably of plastic material. In view of the relatively large anode plates, said plastic masks with a U-shaped cross section have a length of up to two meters and are, therefore, relatively unstable, corresponding to the small gap between the strip and the anodes, so that only relatively small shank widths can be formed. It is necessary in practical life to coat in strip refining plants strip charges with different widths of the strips. After the strips of a certain widths--which, as a rule, run off coils--have been treated, it is, therefore customary to weld the next strip to the end. Such next strip may have a different width. For the purpose of adapting the screening of the edge zone to the next-following strip to be coated, the edge masks can be set up transversely to the direction of the strip. When the next-following strip is inserted between the two shanks of the edge masks, the zone of transition of the strip with the break in width causes problems in this connection. Since the shanks of the edge masks have only a relatively short length, it happens that the next-following strip will not "thread" itself between the two shanks but is guided between the outer side of a shank and the adjacent anode, which can destroy the edge masks and damage the anodes. However, the width of the shanks of the known edge masks cannot be enlarged, as this will make the edge mask too unstable. In addition, the electrolyte flows through the gap between the anodes still at a relatively high rate, whereby a pressure difference is caused between the inside and the outside of each mask shank due to differences in flow pressure, such pressure difference subjecting the shank to an inwardly directed pressure. Therefore, shanks with low stiffness, if excessively long, are forced inwardly and thereby narrow the clear spacing between the shanks. With the known masks with the relatively short shanks, there is the additional risk that the sheets to be coated knock in an undesirable way against the inside of the shanks or against the bridge of the masks due to their tolerances in guidance and because of uneven spots, and thus may even damage or destroy the masks. Therefore, only masks with a small outside dimension can be used in the narrow gap, which amounts to about between 20 mm to 50 mm. It is not possible to visually monitor the masks in the device from the outside.
The object of the invention is to enhance on a device of the type specified above the edge masks in order to particularly assure the screening in a deposition process after changing from one strip to another of a different width.
The object of the invention is solved on a device of the type specified above, such device being characterized in that the shanks of each edge mask rest against the anodes with elastic prestress.
If edge masks according to the invention are correspondingly arranged between the anodes, it is possible due to the predetermined elastic prestress to realize substantially greater widths of the shanks of the edge mask made of suitably insulating material because on the one hand, by having the shanks rest against the anodes under elastic prestress,
REFERENCES:
patent: 2974097 (1961-03-01), Ramirez et al.
patent: 3399130 (1968-08-01), Lovekin
patent: 3537971 (1970-11-01), Green
patent: 4784740 (1988-11-01), Murakami et al.
Patent Abstracts of Japan, vol. 10, No. 120, Dec. 5, 1985.
May Hans J.
Schnettler Roland
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