Electric heating – Metal heating – Wire – rod – or bar bonding
Patent
1993-12-03
1995-09-19
Shaw, Clifford C.
Electric heating
Metal heating
Wire, rod, or bar bonding
21912164, B23K 9167
Patent
active
054517362
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a welding process for connecting a preferably insulated winding wire of a coil to a terminal, including a metal sleeve being slipped over the terminal and the winding wire attached to the latter, and the metal sleeve, the terminal and the winding wire then being welded to one another under inert gas. The invention relates, furthermore, to a metal sleeve for use in this process.
2. Description of the Related Art
A preferred field of use of the present invention is coils for electromagnetic relays or similar switchgear. The windings of these coils consist, as a rule, of lacquer-insulated copper wires, a heat resistant lacquer insulation for the winding wires being necessary for use under relatively high thermal load. For contacting the winding ends with corresponding terminals, it has hitherto largely been customary to solder the stripped winding wire to the terminals. In addition to a complicated process technology in terms of the soldering baths and handling, the disadvantage of this soldering process is that the fluxes used for such process, in so far as they cannot be removed completely, can subsequently generate contact-impairing vapors in the switchgear.
Moreover, it is also already known to contact winding wires and terminals by means of a welded joint. In conventional welding processes, however, there is the risk that the copper alloys of the winding wires or of the terminals will become brittle and therefore be in danger of breaking. German Patent Application 39 11 027 has consequently already proposed a process of the type mentioned in the introduction, in which an arc-welding process is carried out under inert gas, a metal sleeve being welded over the terminal and the wound-on wire. This relates, however, to a sleeve which is open at both ends and which is slipped over the terminal as far as the anchor location of the terminal in the base body and is then also pressed onto the base body. There is a risk, here, that the wound-on winding wire will be pulled in an undesirable way and possibly be pinched between the metal sleeve and base body, thus resulting in the risk of subsequent breakage, for example in the event of temperature changes.
SUMMARY OF THE INVENTION
An object of the invention is, therefore, to improve the inert gas welding process mentioned in the introduction, with the use of a metal sleeve, in such a way that the sleeve is to be handled and positioned on the terminal as simply as possible, without the winding wire being subjected to mechanical stress in the region between the base body and terminal.
This is achieved, according to the invention, in that use is made of a metal sleeve in the form of a cap having an at least partially closed end, which sleeve is placed onto the free end of the terminal, and in that the cap is melted on from its closed end.
As a result of the use of a metal sleeve in the form of a cap or of a thimble, this metal sleeve, after being placed onto the free end of the terminal, remains seated on the end portion of this terminal, without additional measures, so that the winding wire disposed in the angular region between the base body and terminal is not additionally tensioned by the end edge of the cap. Since the cap, in order to be placed on more easily, must have a larger diameter than the terminal together with the wound-on winding wire end, it can be advantageous, before the welding step, to pinch this cap at its side regions against the terminal by means of a pincer-like device. This pincer-like device can at the same time form an electrical connection if the TIG-welding or plasma-arc welding process is used.
Instead of the arc-welding processes, other fusion-welding processes, such as laser-beam welding, can be employed. However, at all events, as already presupposed in the introduction, inert gas is blown, preferably in the axial direction, onto the closed cap end to be welded, in order to prevent embrittlement and scaling of the welded joint.
The metal cap employed for
REFERENCES:
patent: 3539762 (1970-11-01), Swengel, Sr. et al.
patent: 3610874 (1971-10-01), Gagliano
patent: 3703623 (1972-11-01), Swengel, Sr.
patent: 3795786 (1974-03-01), Chanowitz
patent: 4039801 (1977-08-01), Foerster et al.
patent: 4530563 (1985-07-01), Brzezinski
patent: 4966565 (1990-10-01), Dohi
Fiedler Arthur
Sollner Hans-Jurgen
Vojta Erich
Shaw Clifford C.
Siemens Aktiengesellschaft
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