| 摘要 |
PROBLEM TO BE SOLVED: To prevent circumferential variance of depth and width dimensions of an annular groove and spiral deviation by rotating a face plate, dies, copying rolls and an air cylinder along an outer peripheral direction of a steel pipe by means of an electric motor. SOLUTION: A steel pipe 1 is fixed and pressed with dies 10 having copying rolls 11, thus making it possible to form an annular groove in the outer surface of the steel pipe 1 at a constant dimension regardless of roundness of the steel pipe 1. Since a face plate 14 is rotated with the steel pipe 1 fixed, a good annular groove can be formed regardless of the extent of bending in the longitudinal direction of the steel pipe. In order to press down the dies 10 and the copying rolls 11 onto the outer surface of the steel pipe, an air cylinder 15 is installed to the face plate 14. The face plate 14 is rotated by the electric motor 19 via face plate rotating bearings 20 and gears. It is, therefore, possible to form annular grooves on the outer surface of the steel pipe efficiently and accurately regardless of the roundness of the steel pipe 1.
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