Patent GB-367695-A (GB)
Title: Improvements in and relating to arc welding
IPC: B23K9/073
Filed: 1931-06-29
Abstract: 367,695. Arc welding systems. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Chapman, V. J. ; 25, Lakewood Avenue, and Stephens, R. M. ; 122, State Street, both in Schenectady, New York, U.S.A.) June 29, 1931, No. 18772. Convention date, June 30, 1930. [Class 39 (iii).] In an arc welding system the electrode feeding means is operated by a motor connected to a substantially constant voltage supply circuit through a reversing switch and a vibratory regulator which are connected to be responsive to arc voltage and control the speed and direction of rotation of the motor. If a generator of the type described in Specification 159,374 be employed, a source of constant voltage and the welding current can both be obtained therefrom. The welding electrodes 1, 2 are connected to such a generator 5, whose characteristic is suitably modified as by means of reactance 6 and resistance 7. A feed motor 8, preferably shunt wound, is connected through speed reduction gearing to feed rolls 9 engaging the electrode 1, and to the generator 5 through a reversing switch 10, of the double pole double throw type controlled by a coil 12 across the electrodes, and a vibratory regulator 11, having a resistance 15 which may be shorted by closure of the contacts 16, 17 due to excitation of the coil 18. This coil is connected across the electrodes and is in series with a variable resistance 21. The field of the feed motor 8 is connected across the generator 5 and is at all times fully excited. When the welding circuit is energized, switch 10 moves to its upper position and contacts 16, 17 engage, the motor 8 being connected to the generator 5 so that it operates at constant speed. If the electrodes touch, the coils 12, 18 are shorted, and the switch 10 and regulator 11 assume the positions shown, whereby the feed motor reverses its direction of motion to withdraw the electrode 1. When the voltage drop across the arc attains a predetermined value, coils 12, 18 are sufficiently energized to return switch 10 and regulator 11 to their original positions. The motor again functions to feed the electrode 1. If the arc voltage becomes too great, due to too slow feeding, contacts 16, 17 close, and the full voltage of the generator 5 is applied to the motor increasing its speed. When the desired arc length is obtained, the voltage falls so that contacts 16, 17 separate, thereby inserting resistance 15 in series with the motor. Whether the circuit of the armature 28 is completed through the contacts 16, 17 or the resistance 15 depends on the adjustment of the spring 22 and the resistance 21. The motor may be connected to a source of substantial voltage, say 60 volts, and a high resistance armature circuit can therefore be used. In case of a change of welding current or electrode size it is desirable to change the gear reduction between motor 8 and feed rolls 9. The resistance 15 may be entirely omitted, which is equivalent to using an infinite resistance, or other controlling means such as a condenser, an impedance or a combination of any of these may be used. The field circuit of the motor may be similarly controlled instead of the armature circuit.