Flynn & Frishauf
Method for rotationally positioning a welded steel pipe in response to a seam section thereof and an apparatus for positioning the same
 Disclosed is an apparatus for rotationally positioning a welded steel pipe in response to a seam section thereof which comprises a driving means for subjecting the welded steel pipe to a high speed-normal rotation and low speed-counter rotation about its axis, a detecting signal-generating means including an AC bridge circuit, a sensor disposed close to the surface of the welded steel pipe, a differential amplifier and a synchronous detector, to produce, when the welded steel pipe makes a high speed-normal rotation, a negative peak voltage signal and in succession a positive peak voltage signal in response to the seam section of the welded steel pipe and to produce, when the welded steel pipe makes a low speed-back rotation. a positive peak voltage signal and in succession a negative peak voltage signal in response to said seam section, a first Schmitt circuit for producing an output when the level of said detecting signal has exceeded the zero level, a second Schmitt circuit for producing an output when the level of said detecting signal has exceeded a positive specified level, a flip-flop circuit set in response to the rising operation of the second Schmitt circuit output and reset in response to the falling operation of the first Schmitt circuit output, a monostable multivibrator for producing an output pulse signal having a prescribed time width in response to the falling operation of the flip-flop circuit output, and means for controlling said driving means for said welded steel pipe so that when the monostable multivibrator has produced an output pulse signal during said high speed-normal rotation, the welded steel pipe is changed-over from the high speed-normal rotation to the low speed-back rotation; and when the monostable multivibrator has produced an output pulse signal during said low speed-counter rotation, the welded steel pipe is promptly stopped. 
Nippon Kokan Kabushiki Kaisha
G G G G
G01N G05D G01N G01B
inventional inventional inventional inventional
Toshihiro Katsujiro Akihiko
Mori Watanabe Nishisaka