Method and apparatus for electric arc and analogous welding under

Abstract

Signals which contain components that vary with the lateral position of an electric welding instrument as it travels along a weld path between opposite work pieces are obtained from the arc or other heat source and are first processed to remove confusing or nonsignificant components. The processed signals are then compared or combined with each other, or with other signals of predetermined value, to obtain outputs which can be used to determine or control the lateral position or movement of the welding instrument along the weld path. Specifically, in electric arc welding of metals, signals from an electrical characteristic at the arc, such as arc current, which include a component indicative of lateral position of the welding instrument with respect to one or more sidewalls, are first filtered and processed to remove undesirable components. Under control of separate timing signals, the processed signals so obtained are sampled to derive and hold peak values indicative of extreme lateral positions of the instrument as it moves from side to side of its main travel path. By using deliberately timed control signals, these peak values are compared with each other, and/or combined or compared with other signals of known value, to obtain as output the desired position-control signals. The latter are used to indicate, control and/or to change an extreme lateral position of the instrument either by correcting its centerline of main travel and/or by modifying the width or amplitude of its lateral reciprocation.