This application is a 35 U.S.C. 371 National Stage application of International application PCT/EP00/01490 filed Feb. 23, 2000.
The invention relates to an apparatus and a method for treatment, cleaning and/or heating in particular, of electrically conductive continuous material during the movement in direction of extension thereof.
A known apparatus of this kind is used for soft-annealing the wire material prior to a method step for diameter reduction of the wire material by transformation by means of drawing of the wire material. Furtheron, the known apparatus is used for cleaning the wire material prior to being coated with an insulating material in order to permit good adhesion of the insulating material which e.g. is applied by varnishing. The known apparatus includes an annealing furnace formed as tube through which the continuous material is transferred. The tube e.g. is heated by resistance heating and by radiation or convection transmits heat to the continuous material moved therethrough, for soft-annealing the latter. Furtheron, during said heating impurities vaporize on the surface of the continuous material and this cleaning effect can be supported in that in the furnace a particular gas atmosphere, e.g. steam, is maintained.
For achieving a desired heating of the wire material, said wire material has to dwell a given period of time in the furnace. If the moving speed of the continuous material is to be increased for increasing the throughput of the apparatus, the length of the apparatus has to be increased correspondingly. An advantage of the known apparatus thus lies in its increased spatial requirement as well as the increase energy demand for heating the furnace with increased throughput.
It is the object of the present invention to create an apparatus for treatment of continuous material of the above-described kind, which permits efficient treatment also in case of increased moving speeds of the continuous material.
In accordance with the present invention an apparatus for treatment of electrically conductive continuous material during its movement through the apparatus in its direction of extension is provided for which includes an electrode arrangement disposed with a distance to the continuous material and at least partly encompassing it. A gas discharge chamber located between the continuous material and the electrode arrangement is filled with reaction gas. Furtheron, a contact means is available for generating an electrical contact with the moving continuous material and by applying an electrical voltage between the contact means and the electrode arrangement a gas discharge can be produced in the gas discharge chamber. This gas discharge generates a plasma in the gas discharge chamber, i.e. electrically charged particles are formed there.
As the continuous material contacted through the contact means herein acts as electrode itself, a portion of the electrically charged particles generated in the reaction gas and accelerated by the voltage directly impinges on the continuous material and exerts the treating effect thereon. Thus, this bombardment with charged particles, of the continuous material can e.g. cause cleaning of the surface of the continuous material and/or heat the continuous material in total.
The apparatus in accordance with the present invention preferably is used for soft-annealing metallic wire material, copper wire in particular, prior to a drawing step for reducing the diameter of the wire material and/or for cleaning the surface of the wire material prior to a coating step for coating the wire material with an insulating material and/or for heating the wire material in total prior to the coating step.
The electrode arrangement preferably comprises a cylinder geometry through which the continuous material extends essentially axially and in straight line. By this an electrode arrangement essentially completely encompassing the continuous material is made available such that a gas discharge uniform about the continuous material in circumferential direction and thus uniform treatment of the material from all sides is achievable. Furtheron, by corresponding dimensioning of the length of the cylinder geometry an intensity of the treatment, harmonized with the moving speed of the continues material through the apparatus can be adjusted.
A pressure deviating from the ambient pressure, of the reaction gas in the gas discharge chamber preferably is adjustable for better control of the gas charge, when a container encompassing the gas discharge chamber in essentially gas-proof manner is provided for. The continuous material enters this container in its movement through the apparatus through an entry lock and exits through an exit lock. The entry lock and/or the exit lock, respectively, provides sufficient sealing function between the container and the moving continuous material and is to permit passage of the continuous material with as low friction as possible.
If the continuous material is a wire, the entry lock and/or the exit lock can be formed by drawing plate as usually used for wire drawing. Such a drawing plate also is referred to as drawing die or drawing hole. The internal diameter therein is harmonized to the outer diameter of the wire such that on one hand essentially no gap exists between the wire and the drawing plate and on the other hand friction between the wire and the drawing plate is as low as possible such that essentially also no reduction of the outer diameter of the wire is effected by deformation during passage through the drawing plate.
In order to preventing ambient air to enter the gas discharge room through the entry lock or the exit lock, respectively, preferably a protective gas chamber is provided for which is limited to the reaction chamber by the entry lock or the exit lock, respectively. Hereby it can be guaranteed that through the respective lock only harmless protective gas enters the gas discharge room. The gas pressure in the protective gas chamber may be lower than in the gas discharge chamber. Preferably, however, the pressure there is higher and the entry of ambient air into the protective gas chamber itself can then be prevented if the pressure there is higher than standard pressure.
The trailing protective gas chamber which the continuous material enters after treatment can also be provided for cooling of the treated continuous material. Then, the protective gas existing in the protective gas chamber preferably is cooled itself and/or preferably is under increased pressure for intensivation of heat transfer from the continuous material.
Furtheron, for cooling of the treated continuous material a liquid bath, a water bath in particular, can be provided for into which the continuous material enters directly after treatment in the gas discharge chamber. Preferably, however, the treated continuous material enters the liquid bath after passage through the trailing protective gas chamber, entry of liquid of the liquid bath through the exit lock into the gas discharge chamber to a far extent being avoidable thereby.
For making available a gas discharge as defined as possible, preferably a gas supply for supply of the reaction gas with a given gas composition into the gas discharge chamber is provided for. Preferably, however, at least part of the supplied gas amount is supplied to the protective gas chamber where it acts as protective gas. Thereafter, the gas moves from the protective gas chamber to the container through the entry or exit lock, respectively, for acting as reaction gas there. This embodiment permit a particularly friction-free dimensioning of the entry and exit locks, respectively, without foreign gases entering the gas discharge chamber.
The amount of gas supplied to the gas discharge chamber preferably is adjustable, namely in dependence on a signal of a gas pressure sensor detecting the pressure in the gas discharge chamber.
The pressure in the gas discharge chamber can furtheron by lowered below the ambient pressure by pumping-down using a vacuum pump.
The reaction gas preferably includes argon and/or nitrogen and/or air.
A simple embodiment of the container and the electrode arrangement is possible when the electrode arrangement itself is part of the gas-proof container. Preferably, the electrode arrangement then is formed as metal tube forming a part of the gas-proof container wall.
The electrode arrangement preferably includes a plurality of partial electrodes at least partly also encompassing the continuous material, which in direction of extension of the material are disposed adjacent to one another and electrically mutually insulated. Thereby, a separate gas discharge can be generated between each individual partial electrode and the continuous material, this permitting to act against non-homogeneities in the intensity of treatment along the length of the electrode arrangement.
The current provided by means of a current source, for the gas discharge preferably is dimensioned such that the gas discharge is a glow discharge. Herein it is preferred that the voltage provided by the current source is a direct voltage such that the electrode arrangement is switched as anode and the continuous materialxe2x80x94as cathode. Thereby the gas ions generated in the gas discharge in the plasma impinge on the continuous material and thus cause a particularly intense treatment.
For adjusting the treatment of the continuous material to a desired intensity, preferably a temperature sensor is provided for which detects the temperature of the continuous material as directly as possible after treatment. The current provided for the gas discharge, by the current source then is adjusted, regulated in particular, in dependence on the detected temperature.
A particularly uniform treatment of the continuous material can be achieved in that vibrations of the continuos material with respect to the electrode arrangement are dampened by means of a attenuation means provided therefor.