Electric heating – Metal heating – By arc
Patent
1997-05-02
1999-06-01
Shaw, Clifford C.
Electric heating
Metal heating
By arc
219 5622, 219 8518, 219 8522, B23K 9167
Patent
active
059085681
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method and a device for contacting the winding wire of a coil to a connecting pin by an end section of the winding wire being wound around an end section of the connecting pin using a plurality of turns, the connecting pin then being brought into contact with a fluxless soft solder and the latter finally being fused at a soldering temperature under a protective gas by feeding heat in a contactless fashion.
In order to avoid the undesired fluxes and solder baths in the production of relay coils, EP-0 651 407-A1 proposes a connection by means of a soft solder which is fused in a fluxless fashion under a protective gas. A proposed, preferred method is an arc/inert-gas soldering, which is analogous to the already known WIG welding (tungsten/inert-gas welding), and in which the connecting pin itself is not being fused together with the winding wire as in the case of the welding method, but the arc is dimensioned such that only the soft solder is liquefied. In this way, the thermal loading is significantly reduced for the coil former and the winding wire.
In the case of the WIG soldering described there, the arc is struck between the connecting pin and a counter-electrode. However, in this process problems could arise whenever, for example in the case of coils for miniature relays, connecting pins are used whose thickness is much less than 1 mm, that is to say 0.2 to 0.4 mm, for example. Such connecting pins can be contacted only with difficulty because of the correspondingly small coil dimension and their own cross-section. Under some circumstances the pins are even no longer capable of conducting the minimum current of, for example, 1A which can be generated in the case of customary WIG current sources.
SUMMARY OF THE INVENTION
The aim of the present invention is thus a further development of the WIG arc soldering such that it is also possible to solder coil connections with the smallest dimensions in a simple way and with minimum thermal loading.
According to the invention, this aim is achieved by means of a method of the type mentioned at the beginning when the wound end section of the connecting pin is arranged in the vicinity of two electrodes having their points opposite one another, and an arc is struck between the two electrodes with the strength and duration of the are being matched to the fusing of the soft solder.
Thus, the invention operates by using a so-called non-transferred arc in the case of which the arc is struck not on the connecting pin itself, but between two electrodes separated therefrom, with the result that the soft solder is fused by the radiant heat. The connecting pin itself is thus not contacted at all and, because it does not participate in the striking of the arc, it also does not require the pin to be adjusted to a precise spacing from a counter-electrode. The two electrodes themselves are set once at the correct spacing from one another and connected to the power supply, while the connecting pins of the individual coils only need to be brought close to the two electrodes while passing through before the arc is struck again. It is expedient for the end of the connecting pin to be brought between the two electrode points such that the end is approximately flush with the connecting line between the electrode points. The electrodes themselves can be at an angle to one another which can reach from approximately 0.degree. (electrodes parallel) up to 180.degree. (electrodes flush in a line). It has proved to be expedient to arrange the electrodes at an angle of approximately 130.degree. to one another.
In the known method in accordance with EP-0 651 407-A1, the soft solder is provisionally applied, for example, by short-term immersion of the connecting pins in a solder bath, and then fused once again by the arc in a further operation. There is thus a need for two operations, the solder growing cold in the meantime and also being subjected in the process to oxidation, albeit slight. It is proposed in another exemplary embodimen
REFERENCES:
patent: 2425090 (1947-08-01), Eitel et al.
patent: 2903559 (1959-09-01), Wempe
patent: 4039801 (1977-08-01), Foerster et al.
patent: 4237365 (1980-12-01), Lambros et al.
patent: 4404456 (1983-09-01), Cann
Dittmann Michael
Vojta Erich
Shaw Clifford C.
Siemens Aktiengesellschaft
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