PURPOSE: To execute easily and quickly bending without generating a flaw and a wrinkle on the inside surface of a pipe by elongating a mandrel to the radial direction, moving a pipe to be worked to the axial direction in a state that a pipe expanding force is applied, and bending it.
CONSTITUTION: A mandrel 2 is inserted so as to be positioned in a bending part of a pipe 1 to be worked by a hydraulic cylinder 23. A pipe expanding force is applied to the pipe 1 by supplying a pressurized fluid into an enclosed space 17 from a pressurized fluid path 19 and elongating a cylindrical body 12 to the radial direction. The pipe 1 is pressed against a bending die 3 and a metallic strap 6 by a fixed table 5, and the pipe is rotated in the direction as indicated with an arrow by holding the tip part by the bending die 3 and a clamping die 4. In that case, a mandrel position detecting bar 21 is fixed to a holding tool 20 by a clamp 22, and movement of the pipe 1 is detected through a displacement meter 26 by the mandrel position detecting bar 21. By an output of this displacement 26, an oil pressure is supplied to the hydraulic cylinder 23, the mandrel 2 is moved to the axial direction at the same speed as that of the pipe 1, and the mandrel 2 is bent in accordance with a bending of the pipe 1.
MARUOKA KUNIO
KAWAGUCHI SATORU
