GB930211A - Initiation and maintenance of power-welding arcs - Google Patents

Abstract

930,211. Arc - torches. AIR REDUCTION CO. Inc. March 25, 1960 [April 27, 1959], No. 10744/60. Class 39 (3). [Also in Group XXII] A thermionic arcing electrode in a welding torch is pre-heated by internal resistance heating to facilitate striking the arc. The electrode may be consumable or non-consumable. In one arrangement, Fig. 1, a tungsten electrode 1 is supported in a gas nozzle 2 to which a shielding gas such as argon, helium, hydrogen, nitrogen or mixtures thereof is supplied through a conduit 3. The electrode 1 is divided lengthwise into two parts separated by insulating material 4 except at the arc-supporting terminal portion where the parts are conductively joined together. The material 4 may be a thin film of aluminium oxide or a silicate and may contain a material for bonding the electrode parts together, a flux for facilitating the fused union between the electrode parts or an electron-emitting material. Heating current is supplied by a transformer 5 and may be made adjustable. A source 11 of welding current and a source 14 of sparking voltage are connected between the mid-point 17 of the secondary winding of transformer 5 and a workpiece 10 via the contacts 15 of a contactor 16. In an alternative arrangement, Fig. 2, one part of the divided electrode 20 is connected to one welding circuit conductor 19 and the other part is connected through a switch 21 and an adjustable resistor 22 to the other welding circuit conductor 23 which is connected to the workpiece 24. In one position of the switch 21 welding current passes through both parts of the electrode 20 in parallel. In the switch position shown the welding current is confined to one part of the electrode. In the other switch position a heating circuit is completed through both parts of the electrode in series and resistor 22. Suitable holders for supporting and supplying heating and welding current to the divided electrode are described (Figs. 4 and 5, not shown). If the parts of the divided electrode are very small they may be mounted in an adaptor extension of the electrode holder (Figs. 6-8, not shown). Fig. 9 shows an arrangement employing a solid electrode 75 in place of a divided electrode. Heating current is supplied to the part of the electrode between a collet clamp 78 and a pair of jaws 76 attached to the body portion 77 which is insulated from the clamp 78 by members 781 and 79.