Electric heating – Metal heating – By arc
Patent
1989-08-23
1990-09-11
Shaw, Clifford C.
Electric heating
Metal heating
By arc
219136, B23K 924
Patent
active
049565419
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a current nozzle for a MIG- and MAG-welding burner, comprising a nozzle body having an orifice for the passage of a welding wire.
FIG. 1 shows the structural principle of a MIG- and MAG-burner generally used at present. FIGS. 2 and 3 are sectional views of the welding current nozzles (0.1 and 0.2) of a conventional MIG- and MAG-burner. Hereinafter, the term MIG and MAG describing a welding practice is replaced by the term MIG only.
What is problematic and requires a lot of maintenance is particularly the point where the welding current is transmitted from the body of a burner to the welding wire. As known in the art, in MIG-welding the additive wire serves also as an electrode, i.e. it conducts the welding current from a burner to a body being welded. The additive wire is passed from a reel through a nozzle, the wire rubbing a current nozzle through the intermediary of an internal straight central surface. After unwinding it from a wire reel, the additive wire is straightened in awire-forwarding device and, due to its thinness (diameter of solid wire from 0.6 mm to 1.6 mm), the wire is quite flexible, so even though the end of a burner is bent to an angle of 30.degree. to 45.degree. approximately 100 mm upstream of the nozzle, the wire is guided concentrically to a current nozzle. If a current nozzle is made small or narrow, the wire may easily be subjected to an excessive axial load in a wire-forwarding device and thus the wire might buckle.
Furthermore, in an elongated worn-out orifice the current transfer point varies since the contact point is not structurally directed at any particular section in a current nozzle and, in addition, the magnetic forces occurring at least when welding on steels can cause a lateral movement of the wire; thus the passage of welding current to the actual heat delivery point becomes unstable. Although the modern welding machines are provided with sophisticated current regulation equipment, still, as transfer resistance increases, a welding machine first supplies too low a welding current and, after the adjustment, it easily supplies too high a voltage and therefore too high a transient welding current. This leads to blow-through and spatters and also otherwise to a faulty welding result. This is the case especially with a worn-out current nozzle. In short-term welding work, the presently available nozzle has exhibited poor ignitability whereby, e.g. in robotized welding, there will be no joint at all or it will be of poor quality. The increased welding voltage readily heats a wire in the nozzle so that the wire melts, breaks and gets stuck in the nozzle orifice. This interrupts the work and the welder must remove the wire or replace the current nozzle.
Particularly in robot-automated production, the current nozzle disturbances are quite detrimental and further, due to increased welding voltage, there will occur so-called cold flow welding fault; a joint is apparently of good quality but in reality a joint is poor or does not exist at all. A welding problem occurring this way is avoided by frequent replacements of a current nozzle and production must be cut off for those.
An object of the invention is to eliminate or at least to reduce the above problems. In view of fulfilling this object, the invention is characterized by comprising means for automatically turning a welding wire and a nozzle orifice eccentrically relative to each other as a function of the wearing of a nozzle orifice.
An advantage offered by an apparatus of the invention is that the welding current can be conveyed to an additive wire, serving as an electrode and slidably forwarded to a welding point, as near the electric arc as possible.
The invention will now be described with reference made to the accompanying drawings, in which:
FIG. 1 shows the structural principle of a conventional MIG/MAG-burner,
FIGS. 2-3 show conventional nozzles of a MIG/MAG-burner in a sectional view,
FIG. 4 is a sectional view of a first embodiment of an apparatus of the invention,
FIG. 5 is a sect
REFERENCES:
patent: 3116408 (1963-12-01), Turbett et al.
patent: 3826888 (1974-07-01), Garfield et al.
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