PURPOSE: To stop the turning rollers for pushing up the pipe in a correct position even if their mounting is inadequate and prevent the breakage of the welding apparatus by having the safety ascending limit of the turning rollers detected by a vertical tracing detector.
CONSTITUTION: When an up command enters a drive unit 13, turning rollers are moved upward. Then, a pipe 1 detaches from conveying rollers 3 and keeps ascending by being held by turning roller device 6. The signal of the transmission part 24 of a vertical tracing detector 21 is inputted to the drive unit 13 which in turn stops the turning roller device 6 in that position. Next, the rollers of the turning roller device 6 are revolved to dispose the groove right above or right below. When welding is started, the transmission parts 25, 26 transmit upper threshold and lower threshold and therefore the welding head is elevated by an elevating motor 17 within these ranges. At the upper limit of the turning roller device 6, a limit switch 15 actuates.
NAGASHIMA HITOSHI
KOJIYOU KAZUNOBU
OOKUBO NORIMASA
HASHIMOTO KENICHIROU
NIPPON KOKAN KK