PURPOSE: To control at high precision even if relative position of molten pool level and strap is slightly deviated, without being affected by weaving, by cooling the detection medium when controlling the relative position of molten pool level and strap from the temperature changes in the detection medium in the passage of the sliding strap.
CONSTITUTION: Detection medium, such as water, being supplied from a pipe 5 runs through a detection medium passage 4 which penetrates through a sliding strap 1 in the widthwise direction, and, in this process, receives thermal effects proportional to the distance from the molten pool level. Then, the detection medium is discharged from pipe 6, and transmits the temperature due to thermal effects to an indicated temperature regulator 10. Consequently, cooling water is fed into a cooling water passage 7 from a pipe 8 to cool the detection medium running through the passage 4 continuously, and is discharged from a pipe 9. When a temperature higher than the set point is transmitted, the temperature regulator 10 issues a signal, and a motor 11 accelerates the welding head elevation speed. When the detection medium temperature is lowered, the speed returns to the standard elevation speed. To the contrary, if the relative distance above is too long, the operation goes reversely.
SUGIYAMA TADATERU
SAITOU MASAO
