Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Forming nonmetal coating
Reexamination Certificate
1999-07-01
2001-07-17
Enad, Elvin (Department: 2834)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Forming nonmetal coating
C310S049540
Reexamination Certificate
active
06261437
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an anode for batch anodizing of a length of metallic conductor wire. More specifically, the invention relates to an anode for generating an electrically insulating oxide layer on the surface of a wire length of electric conductor wire of metal by anodizing, wherein the anode is immersed into an electrolyte. The invention also relates to a process for batch anodizing of a wire length of metallic conductor wire, in which such an anode is utilized, an insulated conductor wire with an electrically insulating surface layer by batch anodizing according to the invented anodizing process, and an electric device having one or more such insulated conductor wires which have been provided with an electrically insulating surface layer by batch anodizing.
2. Discussion of the Background
An electric device such as a cable, a transformer, a generator, a motor, etc., has at least one current carrying and voltage-carrying metallic body, hereinafter in this document referred to as a conductor. Certain high-voltage electric devices include conductors which have a large number of conductor wires of a more slender dimension, referred to in this document as strands. The strands are composed, for example laid, into parts of strands, windings or coils in generators and other electric machines. The voltage difference between the laid strands is low but the laid strands are still often insulated relative to one another.
According to the prior art, single-wire conductor wires which, as strands, are laid into coarser conductors, included in high-voltage devices, are insulated preferably by organic insulating materials, such as thermoplastic resins, waxes or varnishes. However, organic insulating materials have a poor capacity to withstand influence in severe environments. For example, they have a low temperature resistance and they must often be applied in relatively thick layers. The organic insulations also give rise to drawbacks and costs when recycling/recovering consumed or rejected conductor material since they have to be taken care of or destructed separately from the metallic conductor wire. For use in severe environments such as at high temperatures, under vacuum, in chemically aggressive environments or in environments involving a high fire hazard, it is known to use inorganic insulating materials such as insulating materials based on glass fibre or mica, which are usually wound onto the conductor wire. Further, it is known to insulate aluminum wire or aluminum-coated copper wire with a surface layer of aluminum oxide by anodic oxidation, anodizing. To obtain an oxide layer with a suitable structure and adhesion for the use described above, a treatment cycle is required which cannot be realized by way of a continuous electrochemical process but requires a batch process. A problem in this connection is to arrange a wire of a wire length sufficient for a coil- in an electric high-voltage device. The wire length in a coil usually amounts to between a few two hundred meters and a few kilometers. The wire must in its entirety be connected to the positive pole of a current source in such a way that the potential difference is minimized over the long wire length. The wire, which preferably has a diameter of 1 to 5 mm, must usually be supported and kept in such a way that essentially the whole surface may be anodized.
SUMMARY OF THE INVENTION
It is an object of the invention to suggest an anode which has a holder suitable for anodizing, in one batch, a conductor wire with a wire length of 100 meters to 10 kilometers.
It is also an object of the invention to suggest an anodizing process for batch anodizing of a conductor wire, an anodized conductor wire manufactured by way of this process, as well as an electric device having one or more such anodized wires.
The above is achieved by way of an anode which is adapted for batch anodizing of a wire length, includes the wire to be anodized and a holder for supporting and holding the conductor wire, during the anodizing, in such a way that essentially the whole surface of the conductor wire can be anodized, whereby, according to the invention, the wire is spirally wound onto the holder and the holder has at least three guide cams with guide slots in which the spirally wound wire is fixed. Preferably, the guide slots are formed such that the contact surfaces between the holder and the wire are minimized essentially into point contacts. The guide slots of the guide cams hold the spiraled conductor wire such that all the turns are separated by a space. By this space between each turn and by the contact surfaces between holder and wire having been minimized, it is ensured that essentially the whole envelope surface of the conductor wire is anodized and that a homogeneous oxide layer is generated. The wire and the holder are immersed into an electrolyte during the anodizing, and the wire is connected at both its ends to the positive pole of a current source. The wire includes, at least in an outer layer, aluminum or copper which during the anodizing is oxidized into an oxide layer with good adhesion, a suitable structure and a thickness of less than 15 &mgr;m, preferably less than 10 &mgr;m. This ensures the workability without the oxide layer being damaged or flaked and a sufficient electrical insulation for the limited potential difference between two strands included in the same winding or coil in a high-voltage electric machine. In certain embodiments, the wire is a solid wire of some of these metals or of an alloy based on aluminum or copper, and in other embodiments a wire with a core of a first metal or alloy coated with a layer including aluminum or copper; the core may, of course, include aluminum or copper. That is to say, a core of aluminum may be coated with a copper layer, a core of copper with an aluminum layer or a core of copper or aluminum be coated with an alloy comprising copper and aluminum, respectively, where the content of the coating differs from the content of the core. Preferably, during anodizing of a batch of metal wire, a conductor wire with a wire length of 100 meters to 10 kilometers is wound onto the holder. The invention has proved to be exceedingly suitable for anodizing conductor wire with a diameter of 0.1 to 6 mm, preferably 1 to 5 mm.
The guide cams are preferably made of an electrically conducting material such as aluminum, copper or titanium. Under certain conditions, it is also suitable to connect both holder and wire ends to the positive pole of the current source.
In a preferred embodiment, the holder includes a central shaft and three bars, oriented parallel to the shaft and fixed to the central shaft by way of radially oriented arms. The bars are arranged with guide slots or with guide cams fixed to the bars.
An anode as described above is preferably suitable for use during a batch anodizing where the electrochemical, thermal or other parameters are varied during the process cycle, or during a batch anodizing which goes on for such a long time that a process where the wire is continuously drawn through the anodizing bath is not suitable.
Depending on the electrochemical conditions prevailing in the electrolytic bath, either the whole holder is made of an electrically conducting material and connected as an anode to the positive pole of the current source, or only the guide cams fixed to the bars are made of an electrically conducting material and connected as an anode to the positive pole of the current source. In the latter case, the guide cams are electrically insulated from the supporting parts of the holder. The electrolyte may contain other metal ions or anions, which during the oxidation are included in the oxide layer and act in a stabilizing way thereon or improve the adhesion to the underlying metal or in certain cases change the surface properties of the oxidized conductor wire, which surface properties facilitate water rejection, the application of polymer-based surface layers outside oxide layers, etc. The contents of such additiv
Hernnaes Bo
Imrell Torbjorn
Kalldin Hans-Olof
Asea Brown Boveri AB
Enad Elvin
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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