Electric heating – Metal heating – For bonding with pressure
Reexamination Certificate
2000-05-08
2002-10-01
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
For bonding with pressure
C219S085150, C219S085220, C219S086900
Reexamination Certificate
active
06459064
ABSTRACT:
The invention relates to a method for assembling electroconductive parts by electric current heating, a device for its implementation as well as its use.
Until now, electroconductive components, particularly hollow bodies, such as long, closed profiles or big, massive parts that are difficult for electrodes to contact from the underside could be assembled often only through thermal assembly with filler metal, soldering material, or the like.
A disadvantage of this thermal assembly method is that the heat needed for assembly cannot be placed precisely. The parts to be assembled are therefore heated up more than is necessary for the pure assembly process of welding or soldering, and the parts partially lose their dimensional accuracy, or the material suffers a disadvantageous structural deformation (for example, in work-hardened parts that originate from cold forming method, like the internal high-pressure metal forming method explained below in detail. In extreme cases, the preformed part to be assembled loses its shape and a part of its firmness.
Spot welding with laser picker or the like also has other disadvantages.
The internal high pressure process as such is known. Under the mentioned internal pressure method or even the internal high pressure method, the word method is understood as that which was described in the lndustrieanzeiger No. 20, dated Mar. 9, 1984 or even in the “Metallumformtechnik”, ID/91 edition, page 15 ff: A. Ebbinghaus: Aviation Type Precision Work Pieces, produced through internal high-pressure metal forming “or Werkstoff und Betrieb” 123 to 243: A. Ebbinghaus: “Economic Construction with internal high-pressure metal formed Precision Pieces” or “Werkstoff und Betrieb” 122, (1991), 11, (1989), page 933 to 938. To avoid repetition, reference will subsequently be made to the disclosure of these publications in full. The method was previously used for the manufacture of hollow parts of various shapes, such as for the manufacture of constructed camshafts to fasten cams to a tube, for the manufacture of hollow camshafts, for the manufacture of steering axles, as well as for the manufacture of vehicle frame parts.
It delivers highly precise, cold-formed parts that have experienced a cold hardening during the shaping and whose fibre run, as determined in the course of a microscopic observation of the ground sections, essentially corresponds to the run of the outer contours of the shaped part. As a result, these parts are very sturdy or light in relation to their strength.
In order to avoid the disadvantageous heating up, particularly of such types of work-hardened whole parts, resistance welding could also be used because the current used there for welding heats up precisely between two or several electrodes, said electrodes of one polarity being called “welding electrodes” and the electrodes of the opposite polarity being called counterelectrodes. One-sided indirect welding, in which a material with very good conductivity (counter copper
1
) is placed under the sheet metals to be assembled, has the disadvantage in that the welding current is prone to shifting, so that welding points are created at points totally different from the desired locations. Such as method for impulse welding, in which the welding electrodes are supplied from one side to the parts for assembly,
Furthermore, problems with the achievable welding deposits often occurred with large equipment, all the more the bigger the parts to be welded, the earlier the shunt wounds could occur.
It is therefore the task of the invention to create a method for assembling parts through resistance welding, which can also be used for parts that are easily accessible only from one side.
The task is solved according to the invention through a method for assembling electroconductive parts by heating by means of electric current, in which electrodes of different polarity are supplied from the same side of the parts to be assembled and touch at least one of the parts to be assembled, current is applied to the electrodes, and in such a manner, the conductive parts are heated and assembled through the current flowing from one electrode to the other through the parts to be assembled.
Advantageous developments are in the dependent claims.
To increase the welding deposits, a certain amount of force can be applied to the surfaces/parts to be assembled, thereby improving the electrically capable contact and allowing higher welding current to flow. In the process, the parts may fuse partially or completely in the heated up area, or welding material or solder may be placed for smelting.
As the expert in the field of electrical welding engineering knows, the electrodes can be cooled in a known manner. When superconductive materials, such as special ceramic, are used, the electrodes may of course be cooled appropriately through liquid helium or nitrogen.
The parts may also be assembled by using electroconductive soldering material between the parts, thereby involving a soldering procedure.
In the process, one may be surrounded by one or several counterelectrodes surrounding the same, or the counterelectrodes may enclose the central electrode in a ring shape, or two counterelectrodes, between which the central electrode is placed, may be used.
In cases where the underside of the parts for assembly is accessible, it may be advantageous to place under the electroconductive parts for assembly, on the surface of the compound arrangement opposite the electrodes, a counter material of greater electroconductive capacity than the parts for assembly, in order to improve the current passage through the parts for assembly.
If the parts for assembly exhibit differing electroconductivity, it is preferable to make the conductivity of the part, which is not in contact with the electrodes, higher than that of the part that is contacted by the electrodes.
It is useful to develop, in at least one of the parts for assembly, an opening for the penetration of an electrode and to make contact only with the object behind it so that through this electrode, a potential other than the one to be placed on the upper part can be placed on the lower part, so that current flows between the two, and if necessary, soldering material as well, and this is heated locally for welding/soldering. If the material thickness permits, it makes sense to perform the procedure in such a way that an opening for penetration of one electrode be made, for example, through drilling, stamping, cutting, or the like, before applying of the electrodes.
A device according to the invention for performing the procedure according to any one of the previous claims shows at least two adjacently arranged electrodes, which are insulated from one another and are movable from the same parts towards the parts for assembly; and a power supply for applying high voltage/intensity of current of varying potential to the electrodes of different polarity.
At the same time, this device may comprise a facility for creating openings suitable for the passage of internal electrodes and insulated against the contact with the opening walls.
It is useful for the device to also comprise during the assembly a device for exerting pressure on the electroconductive parts to be assembled because, with better contact between the two parts, the current can flow better through the same. This device may, for instance, be formed by one or several electrodes, but if the underside of the electroconductive parts to be assembled is accessible, it may also comprise the conductive counterpart (“copper back-up bar”), which then interacts with the electrodes.
The electrodes may be shaped in such a way that the counter electrode at least partially encloses the central electrode. Several counterelectrodes, which at least partially enclose a central electrode between them, may also be provided. There may be an insulation material between the electrodes of different polarity.
For instance, an electrode may be shaped as a hollow body, for example, as a hollow cylinder, in which the counterelectrode is axially movable, in such
Cooke Colleen
Magna IHV Gesellschaft fur Innenhochdruck
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