Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1995-05-09
1997-04-08
Gorgos, Kathryn
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204206, 205130, 205137, 205138, 205152, C25D 1700, C25D 502
Patent
active
056183917
DESCRIPTION:
BRIEF SUMMARY
This is a 371 of PCT/93/0105 filed Oct. 22, 1993.
The invention relates to a device for electrolytically coating one side of metal strips, in which the metal strips to be coated are contactingly guided around a rotating cathodic current roller, and a partially cylindrical, insoluble anode is arranged approximately concentrically around the current roller with a spacing from the latter, whereby the electrolyte flows through the spacing.
In such a device, which is known from U.S. Pat. No. 3,900,383, the unit comprising the current roller, the metal strip to be coated, the latter looping around said roller by about 180.degree., and the partly cylindrical anode arranged with a spacing from said roller is completely immersed in an electrolyte bath in a tub. The continous contacting of the metal strip to be coated, particularly a very thin strip, has the advantage that voltage drops are avoided because the electrical field develops exclusively between the concentrically arranged anode and the cathodic current roller or metal strip resting against the latter. However, the drawback with said known device is the risk of coating the current roller in the lateral zones not covered by the metal strip to be coated. In addition, there is the risk of electrolyte entering between the current roller and the metal strip, leading to undesirable coatings. Particularly in connection with very thin strips, for example metal foils, it is not possible to design the width of the current roller smaller than the width of the strip, because the support of the latter would be missing in that case. Also, with such a design, the projecting lateral strip would again be used for conducting current. This would result in voltage drops and thus heating of the strip in the edge zones.
If the strip width is smaller than the roller width, the protruding zone of the roller is galvanized. Since strips and foils of varying width are coated in such installations, the rollers would have to be exchanged according to the width of the strip.
Also, a device of the type specified above is known from EP-OS 0 125 707, in which the electrolyte is exclusively guided within the spacing (gap) between the partly cylindrical anode and the cylindrical cathodic current roller, while maintaining a turbulent forced flow.
In this case too, there is the risk of undesirable coating of the current roller, which obviously comes into contact with the electrolyte. The electrolyte is admitted via an inlet tube extending across the total width of the current roller. With such an arrangement, the electrolyte can obviously exit from the gap between the anode and the current roller also on the face side and pass into a container arranged underneath. Therefore, the risk that electrolyte may enter between the metal strip to be coated and the current roller exists in this case as well.
The problem of the invention consists in proposing a device of the type specified above, in which it is assured that the electrolyte does not come into contact with the surface of the current roller.
The problem of the invention is solved with a device of the type specified above, which device is characterized in that provision is made for seals between the section of the strip guided on the current roller and the anode, such seals being installed in each case within the zone of the edge of the strip in the axially parallel direction. In this way, the space of the electrolyte is limited to the width of the strip, so that wetting of the current roller with electrolyte is avoided. In adaptation to the given width of the metal strip to be coated, the sealing can be installed on both sides of the strip, with a nearly uncoated zone of the edge of the strip remaining, which, however, is separated in the manufacture of such strips in any case.
The invention also comprises the proposal of lubricating the sealing side with blocking water against the section of the strip guided on the current roller, with the intention to prevent any electrolyte that may pass through the sealing from coming into contact with
REFERENCES:
patent: 2044415 (1936-06-01), Yates
patent: 3483098 (1969-12-01), Kramer
patent: 3900383 (1975-08-01), Austin et al.
patent: 4132617 (1979-01-01), Noz
patent: 4582583 (1986-04-01), Laverty
patent: 5069762 (1991-12-01), Modrowski et al.
Derwent and JAPIO abstracts and Fig. 4 of JP05279892 (Kurusu Ryozaburo) Oct. 26, 1993.
May Hans J.
Schnettler Roland
Gorgos Kathryn
Noguerda Alexander
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