Patent GB-767689-A (GB)
Title: "improvements relating to electric arc welding systems"
Inventor: NEEDHAM JAMES CHRISTOPHER
IPC: B23K9/073
Filed: 1953-03-25
Abstract: 767,689. Automatic arc control systems; supply systems for welding arcs. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION. June 15, 1954 [March 25, 1953], No. 8290/53. Class 38 (4). In an automatic arc-welding system in which the consumable electrode is fed at a preset and nominally constant rate, the length of the arc being maintained substantially constant by the inherent characteristics of the supply circuit the arc voltage is compared with a reference voltage and the supply is additionally controlled to maintain the arc voltage constant. In the D.C. embodiments the arc is supplied from a D.C. generator G, Fig. 2, having a separately excited (or alternatively, shunt excited) field F, an opposing series field SF to provide the required drooping characteristic, and a control field C supplied from an exciter G<SP>1</SP> controlled by a winding C<SP>1</SP> in accordance with the difference between arc volts and the voltage of a reference source P. In a first modification, Fig. 1 (not shown), the exciter is omitted, and the main generator is controlled directly by the winding C<SP>1</SP>. In a second modification, Fig. 10, the main field F of the generator is controlled by a rheostat Gx actuated by a reversible motor Sm connected across the arc in series with an opposing reference source P. In a third modification, Fig. 11 (not shown), an amplifying exciter supplies the reversible motor of Fig. 10, the field of the exciter being across the arc in series with the reference source. In a fourth modification, Fig. 12 (not shown), the reversible motor of Fig. 10 is controlled by a polarized relay across the arc in series with the reference source. In a fifth modification, Fig. 4, an auxiliary generator Ga is connected in parallel (or, it is stated, in series) with the main generator, and the control field Ca of the auxiliary generator is across the arc in series with the reference source. In a sixth modification, Fig. 5 (not shown), the controlled generator of Fig. 4 is replaced by a level compounded generator (or, it is stated, a battery). In a seventh modification, Fig. 6, the main generator is again shunted by a level compounded generator Ga and the main generator field F is controlled by a reversible servomotor Sm, controlled by a relay RF in the anode circuit of one valve of a double triode V<SP>1</SP>, V<SP>2</SP> which compares the arc voltage with a neon reference source. In one A.C. embodiment, Fig. 3 (not shown), the arc is supplied from a transformer via a saturable reactor which is controlled by the resultant of the rectified arc voltage and a reference voltage. In a modification, Fig. 7 (not shown), in which the arc is re-ignited each cycle, as disclosed in Specification 705,164, the point of re-ignition is controlled in accordance with the difference between arc voltage and a reference voltage. (It is also stated that the image of the arc may be projected on to a photo-cell or bolometer, the output of which is amplified and used in an unspecified manner to control the power source.) Specification 767,688 also is referred to.