Patent GB-831580-A (GB)
Title: Improvements in or relating to arc welding apparatus
IPC: B23K9/12
Filed: 1957-08-22
Abstract: 831,580. Welding by fusion. WESTINGHOUSE ELECTRIC CORPORATION. Aug. 22, 1957 [Sept. 14, 1956], No. 26524/57. Class 83 (4). [Also in Group XXXVII] In consumable electrode arc welding apparatus having control means controlling the electrode feeding speed, the control means includes a resistor/capacitor network adapted to produce a predetermined signal to effect a gradual decrease in the speed prior to the end of the welding operation. An electrode Z is fed through a carbon dioxide shielding water-cooled torch by a motor supplied from A.C. mains AL1, AL2, through a thyratron ITU, and is supplied with current from terminal 11 on a supply unit having a threephase transformer and rectifier. A composite potential may be applied between the grid 55 and cathode 53 of the thyratron including an alternating component derived from a phase-shift network, a directcurrent component derived from a timing network N and a direct-current component depending on the current supplied to the motor and the drop across the armature. With the electrode spaced from the work and with the circuit contacts in the positions shown a button SA is pressed to energize a relay ITD which closes its contacts 21, 23 thus locking in the relay ITD and energizing solenoids SW, SG to allow cooling water and shielding gas to flow to the torch and energizing relay ICR to close its contact 14 to supply potential across the electrode and work. Pressing button SA and closing of contact 21 also energizes arid locks in relay 2CR which closes contacts 25, 27, 29 and opens contact 31. The motor circuit is closed by contact 29 and the electrode is fed towards the work at a speed determined by the setting of rheostat P4 in the control circuit for the thyratron extending now from grid 55, the phase-shift network potentiometer P3 and potentiometer P1, potentiometer P4, contacts 45, 41, line AL2, contact 29, armature A and cathode 53. The capacitor IC in the network N is charged through a rectifier 1RX when the contact 25 closes. When the electrode contacts the work an arc is struck and relay 3CR in the electrode lead is energized to close its contacts 15, 17, thus energizing relay 5CR which opens its contact 41. The thyratron control circuit now extends from grid 55, potentiometer P3, potentiometer P1, potentiometer P2, resistor R5, line AL2, contacts 17 or 29, armature A and cathode 53. Prior to the end of the welding operation the button SO is pressed to de-energize relays ITD and 2CR; contact 21 opens but contact 23 is time delayed so that current, gas and water continue to flow. Contacts 25, 27, 29 open and contact 31 closes so that charging of capacitor IC stops and it discharges through resistors R9, R1, R3, R5 to decrease the conductivity of the thyratron to slow down the motor until the arc is interrupted. If inert gas is used the switch SWB is placed in its position IG to connect a resistor RB across the armature prior to the end of the welding operation rather than applying the control forming the subject of the present invention. The supply unit may be of the constant potential or constant current type. The electrode may be manually jogged into its correct start position by pressing the button SI momentarily.