Title of Invention

APPARATUS FOR METAL COATING OF BANDS BY ELECTROPLATING

Abstract

An apparatus for metal coating of bands by electroplating, with a band running through an acidic electrolyte enriched with a metal, the apparatus including at least one insoluble anode extending parallel to the band and divided, in a running direction of the band, in a plurality of separate anode strips insulated from each other, an arrangement for feeding current to each separate anode strip for precipitating the metal from the electrolyte, with the current flowing from a respective anode strip to the band which forms a cathode, whereby the metal is precipitated onto a band surface, and elements for supplying each anode strip with protective current the voltage of which is so selected that formation of cathode regions on anode strips, which are not supplied with the precipitation current, is prevented.

Full Text

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for metal coating of bands by electroplating, with a band running through an acidic electrolyte enriched with a metal. The apparatus includes at least one insoluble anode extending parallel to the band and divided, in a running direction of the band, in a plurality of separate anode strips insulated from each other, and means for feeding current to each separate anode strip for precipitating the metal from the . electrolyte, ,with the current flowing from a respective anode strip to the band which forms the cathode. 2. Description of the prior art Usually, the anodes of such apparatuses are wider than a band to be coated in the apparatus. As a rule, for metal coating of the band, only those anode strips are supplied with current which are located either above or below the band. As a result, the anode strips, which are supplied with current, can be subjected to corrosion. The danger of corrosion is particularly great for the NYLIB1/615236/1 anode strips which are arranged immediately adjacent to the anode strips which are supplied with current and on which both cathode and anode regions are formed. In the cathode regions of the anode strips, which are supplied with current, hydrogen is generated. The hydrogen can penetrate in the anode strips, in particular into the anode strips formed of titanium. In order to maintain a controlled and uniform current density at the cathode/article intended to be plated and in order to achieve a desired controlled uniform plating thereof USP5049246 discloses an apparatus for electroplating or materials, comprising an electrolytic processing bath, plural first electrodes in said bath and at least one second electrode in said bath and power supply means for supplying time multiplexed power to said electrodes. This power supply 20 (see figure 1 of USP5049246) is coupled by conductors 22, 23, to the respective groups of anodes that are respectively supported from the electrically conductive support bars 15, 16, as illustrated in figure 1. The power supply 20 provides a voltage between the cathode 14 and one group of anode 13a-13c at one period of time and between cathode 14 and the other group of anodes 13d-13f at a different period of time. This time multiplexing behavior of the power supply 20 shall ensure uniform plating. USP5049246 does not disclose a band running through the electrolyte. Hence there is no anode divided in a running direction of the band in a plurality of separate anode strips with insulating means separating the anode strips from each other. Furthermore USP5049246 fails to disclose means for supplying each anode strip with protective current which is adapted to supply select voltage to prevent formation of cathode regions on the anode strips and which protective current constitutes from about 3% to about 10% of the precipitation current. USP4681665 relates to a process and an apparatus for electrochemical treatment of the surface of metal products within a cell containing an electrolyte. The cell comprises a plurality of electrodes positioned along its walls and forming at least four groups of electrodes. Current is passed through the electrodes for developing successively along the length of the cell an anodic group, a none-charged group, a cathodic group and a non-charged group spaced apart irom each other. With reference to figure 3 this disclosure becomes clear. The four groups of electrodes (22,23,24 and 25) are distributed along the cell. At a time t the cathodes 22 and 24 are connected to the positive and negative poles of an electrical generator so as to produce cathodic and anodic zones in their respective vicinities and the electrodes 23 and 25 are not supplied with power so as to separate the cathodic and anodic zones. By sliding the power supply locations in the direction indicated by the arrow 26 in figure 3 the cathodic and anodic zones arc displaced along the product whereby the entire surface of the product is successively swept by zones of opposite polarities. USP4681665 does not disclose an apparatus for metal coating with a band forming the cathode, while the anode extending parallel to tlie band is separated in anode strips insolated from each other. USP4681665 discloses a plurality of electrodes, which from time to time work as a cathode or anode. Furthermore USP4681665 does not disclose providing separate means for supplying each anode sfrip with protective current which is adapted to supply select voltage to prevent formation of cathode regions on the anode strips, and which protective current constitutes from about 3 % to about 10 % of the precipitating current. Actually USP4681665 does not even remotely suggest providing such means for supplying a protective current. The teaching of USP 4681665 suggests providing at least 2 groups of electrodes, which are separated, by none-charged groups. There is no hint to provide any protective current in these non-charged groups. US 4,240,881 referred to as, the object of USP4240881 was to provide means for controlling the plating thickness of a metal strip which passes through an a electrochemical plating line. In order to optimize the plating thickness (USP 4240881) considers not only the precipitating current but also the band speed and the band dimensions. The precipitating or plating current for an optimal thickness is determined based on the band dimensions and speed. To automate this determination the electrodes are controlled with plating rectifiers so that the total current is correctly provided which permits to achieve appropriate plating thickness. The control circuitry provides for delivery of the plating current but not for generating a protective current. In consequence USP 4240881 discloses a plating control system and not a corrosion prevention system as disclosed by the present invention. In particular the control system of USP 4240881 is not designed for producing in addition to the plating current also a protective current, which according to the present invention is substantially smaller (3 %-10 %) than the plating (precipitating) current. Accordingly, an object of the present invention is to provide, in an apparatus of the type described above, means which would prevent the danger of corrosion is anode strips, the supply of precipitation current to which is interrupted. SUMMARY OF THE INVENTION This and other objects of the present invention, which will become apparent hereinafter, are achived by providing means for supplying each anode strip with protective current the voltage of which is so selected that the formation of cathode regions on the anode sfrips, to which the supply of the current for precipitation of metal from the electrolyte is interrupted, is prevented. The feeding of the protective current prevents the formation of the cathode regions on all of the anode strips. The protective current is so selected that practically no metal precipitation takes place on the anode strips to which the current supply is interrupted, and particularly, no edge growth on the band occur. To meet these requirements, the amount of the protective current is so selected that it constitutes from 3% to 10% of the precipitation current. The protective current supply means can be formed, with small technical expenditures, from current resistors which connect adjacent anode strips. An additional advantage of this verv simple solution consists in that even the outer anode strips, which are not supplied with current for precipitating the metal from electrolyte and which are spaced from the last of the anode strips supplied with the precipitation current, are subjected to the action of the protective current. The spacing corresponds, to the drop of the voltage gradient. Therefore, the outer anode strips can be exposed to as small as possible protective current. Therefore, the present invention provides an apparatus for metal coating of bands by electroplating, with a band running through an acidic electrolyte enriched with a metal, the apparatus comprising at least one insoluble anode extending parallel to the band and divide-in a running direction of the band, in a plurality of separate anode strips, means for insulating the separate anode strips from each other; means for feeding precipitation current to each separate anode strip for precipitating the metal from the electrolyte, wherein insulating regions between the anode strips are adapted for interrupting the precipitating current, with the current flowing from a respective anode strip to the band which forms a cathode, so that the metal is precipitated onto a band surface; and means for supplying each anode strip with protective current, the supplying means being adapted for supplying select voltage to prevent formation of cathode regions on the anode strips, wherein the protective current supplying means comprises electrical resistors which directly connect adjacent anode strips, and wherein the protective current constitutes from 3 % to 10 % of the precipitation current. The invention, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: The drawings show: Fig. 1 a schematic view illustrating the formation of an electrical field in an apparatus according to the present invention during electroplating of a band; and Fig. 2 a schematic view illustrating the supply of a protective current in the apparatus shown in Fig.l. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The arrangement for forming an electric field shown in Fig. 1 consists of a plurality of separate anode strips 5a, 5b arranged above and below a treated band 2. The separate anode strips 5a, 5b are separated from each other by insulation strips 6a, 6b which protect over the upper surfaces of the anode strips 5 a, 5b in a direction toward the passing band. As shown in Fig.2, each separate anode strip is connected by a respective switch 8 with a rectifier (not shown) which supplies to the anode strip 5 current for precipitating the metal from the electrolyte 1 onto the surface of the band 2 (precipitation current). As shown in Fig.2, three of the switches 8 are closed. The closed switches are associated with those anode strips which are arranged opposite the surface of the band 2 which is not shown in Fig. 2. At the adjacent anode strips, the switches of which are open, current overshooting, shown in Fig.l, takes place, without supply of the protective current according to the present invention. As a result, there are arranged, side by side, anode strips subjected to the action of the precipitation current and not subjected to the precipitation current. Thereby, cathode and anode regions are formed on the anode strips 5. In the cathode region, hydrogen is formed which can penetrate in the anode strips, which are formed of titanium, and lead to corrosion. Basically, the cathode and anode regions can be formed on all of the anode strips which are not subjected to the precipitation current. As further shown in Fig2, the supply of the protective current takes place via resistors 11 which connect adjacent anode strips. As a result of the series connection of the resistors 11, the fiirther outer anode strips 5, which are not subjected to the action of the precipitation current, are also protected against a possible corrosion. Though the present invention was shown and described with references to the preferred embodiments, various modifications thereof will be apparent to those skilled in the art and, therefore, it is not intended that the invention be lunited to the disclosed embodiments or details thereof WE CLAIM;- 1. An apparatus for metal coating of bands (2) by electroplating, with a band running through an acidic electrolyte (1) enriched with a metal, the apparatus comprising at least one insoluble anode extending parallel to the band (2) and divided, in a running direction of the band, in a plurality of separate anode strips (5a,5b), means for insulating (6a,6b) the separate anode strips from each other; means for feeding precipitation current to each separate anode strip for precipitating the metal from the electrolyte, wherein insulating regions between the anode strips are adapted for interrupting the precipitating current, with the current flowing from a respective anode strip (5a, 5b) to the band (2) characterized in that the band forms a cathode, so that the metal is precipitated onto a band surface; and means for supplying each anode strip with protective current, the supplying means being adapted for supplying select voltage to prevent formation of cathode regions on the anode strips, wherein the protective current supplying means comprises electrical resistors (11) which directly connect adjacent anode strips (5a, 5b), and wherein the protective current constitutes from 3 % to 10% of the precipitation current. 2. An apparatus for metal coating of bands by electroplating, with a band running through an acidic electrolyte enriched with a metal, the apparatus comprising at least one insoluble anode extending parallel to the band and divided, in a running direction of the band, in a plurality of separate anode strips; means for insulating the separate anode strips from each other; means for feeding precipitating current to each separate anode strip for precipitating the metal from the electrolyte, wherein insulating regions between the anode strips are adapted for interrupting the precipitating current, with the current flowing from a respective anode strip to the band, characterized in that the band forms a cathode, so that the metal is precipitated onto a band surface; and means for supplying each anode strip with protective current, the supplying means being adapted for supplying select voltage to prevent formation of cathode regions on the anode strips, wherein the protective current supplying means has a plurality of switches associated with respective anode strips for controlling current flow thereto, and wherein the protective current constitute from 3 % to 10 % of the precipitation current. 3. The apparatus as claimed in claim 2, comprises at least one power source for supplying protective current. 4. The apparatus as claimed in claim 2, comprises a recitifier having a current controller connected with each of the anode strips and a control range of which provides for supplying the anode strips with both the protective current and the current for precipitating the metal from the electrolyte onto the band surface.

Documents:

943-mas-1999 abstract-duplicate.pdf

943-mas-1999 abstract.pdf

943-mas-1999 claims-duplicate.pdf

943-mas-1999 claims.pdf

943-mas-1999 correspondence-others.pdf

943-mas-1999 correspondence-po.pdf

943-mas-1999 description (complete)-duplicate.pdf

943-mas-1999 description (complete).pdf

943-mas-1999 drawings-duplicate.pdf

943-mas-1999 drawings.pdf

943-mas-1999 form-1.pdf

943-mas-1999 form-19.pdf

943-mas-1999 form-26.pdf

943-mas-1999 form-3.pdf

943-mas-1999 form-5.pdf

943-mas-1999 others.pdf

943-mas-1999 petition.pdf