GB772896A - Improvements in arc voltage regulating circuits in consumable electrode welding - Google Patents

Abstract

772,896. Automatic arc welding control systems. SOC. L'AIR LIQUIDE, SOC. ANON. POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES G. CLAUDE. Dec. 14, 1954 [Dec. 18, 1953], No. 36229/54. Class 38 (4). [Also in Group XL (c)] In a D.C. arc welding system in which the electrode is fed by a non-reversible servomotor in accordance with the amplified difference between the arc voltage and a reference voltage, the gain of the amplifier is increased as the error signal increases. In one embodiment, Fig. 1, the voltage between the electrode 1 and workpiece 4 is opposed by a reference source 10. A portion of the resultant is tapped off at 7a and applied via an integrating network 13, 13a to control a triode 11 which forms part of the cathode load of a push-pull oscillator 19, 20 and so controls the amplitude of oscillation. The controlled output of the oscillator is rectified at 26 to provide a D.C. control signal to a thyratron control represented at 29 for a D.C. electrode feed motor 3. It is stated that hydraulic or pneumatic motors may replace the electric motor. To obtain the non-linear gain characteristic, the triode 11 is shunted by a triode 32 normally biased to cut-off, which conducts when the error signal increases beyond the cut-off point. In a second embodiment, Fig. 4, a portion of the arc voltage tapped off a potentiometer 73 is compared with a reference 76 and the resulting error signal is converted to A.C. by a synchronous vibrator 74. The A.C. error signal is amplified by a variable mu tetrode 54, the output of which is rectified at 65 and applied to the feed motor control 29. The tetrode 54 is biased by a battery 49 opposed by the output of a rectifier 55. This output is derived from a second vibrator 81 in accordance with the difference between a portion of the arc voltage tapped off a second potentiometer 73 and a second reference voltage 82. The gain of the amplifier is thus increased for signals which are above or below the value determined by the second reference source.