Electric heating – Metal heating – For bonding with pressure
Patent
1984-12-17
1985-09-24
Shaw, Clifford C.
Electric heating
Metal heating
For bonding with pressure
219 5622, 219119, B23K 1100
Patent
active
045434620
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a method for establishing a galvanic contact between an insulated work piece and welding electrodes; the subsequent welding of this work piece whereby at least one of the electrodes has a heating current loop which is connected to the working area of the electrode as a supply and return whereby a potential difference can be applied through this loop in the heating or in the stripping phase; and an electrode arrangement for the execution of such, and its use.
PRESENT STATE OF TECHNOLOGY
From the Japanese Pat. Nos. 45-15 856 and 49-3 380, a construction is known in which heating current flows before the welding operation. By a decrease in the cross section of the loop conductor, the latter will be correspondingly higher in resistance in its working area in order to ensure the necessary heat in the heating process. The problem arising from the technique described here is that, although advantageous in its use of the same conductor arrangement for the conduction of the heating current and for the conduction of the welding current, the reduced cross section of the conductor (for the heating operation) can lead to undesirable high heating of the electrode during the welding operation.
DESCRIPTION OF THE INVENTION
The present invention serves to alleviate the above-mentioned disadvantage, and to prevent thereby unwanted heating of the electrode in the welding operation as occurs in the type of method previously mentioned. This is achieved by applying an equal potential to the two conductors of the loop, thereby changing them to parallel welding current conductors.
It is now also possible to take a temperature measurement of the electrode in the working area, which the considerable significance if the welding is to take place corresponding to the transfer resistance between electrode and welding piece, since the electrode is heated only slightly due to its own conductor resistance in the welding operation. Preferably, after the temperature is measured, a switch from the heating to the welding operation takes place and the welding operation is controlled or adjusted.
An electrode arrangement for the execution of the described method distinguishes itself in that at least one electrode is constructed as a loop with a current supply to the working area and a return line, and in that welding current connections are provided for both conductors.
Preferably, the electrode has along its working area a portion with a higher resistance for the heating current, the portions bordering on this sides of the working area having a low resistance so that the welding current thereby flows mostly through the portion with the relatively low resistance. Therefore it is ensured that the welding current flows only minimally through the provided portion of increased resistance for the heating operation, i.e., mostly directed to the left and right of this area of the work piece.
A simple design form of the electrode, achieved for use in the mentioned method, is to make it U-shaped. Preferably it is formed such that the U base forms the working area so that it has a reduced cross section in the middle area and in the side areas an enlarged cross section. The reduction of electrode heating in its working area, during the welding process, results in the possibility that on the electrode a thermal sensor can be provided directly on its working area, the output signal of which, especially in the welding operation, represents the temperature of the actual welding operation and not the entire welding current-related electrode heating. The mentioned arrangement is used preferably for spot or aperture welding, especially for micro-spot or micro-aperture welding, and if need be, for soldering, especially micro-soldering.
BRIEF DESCRIPTION OF THE FIGURES
The invention is described in the following with the aid of figures. Shown are:
FIG. 1 a schematic representation of two common aperture welding electrodes on a work piece, with applied welding current,
FIG. 2 a representation similar to FIG. 1 for spot weldin
REFERENCES:
patent: 3263059 (1966-07-01), Rzant
patent: 3418444 (1968-12-01), Ruehlemann
Rossell Electronique SA
Shaw Clifford C.
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