| 摘要 |
An object of the present invention is to provide a bending method for a multi-layered pipe according to which a multi-layered pipe can be bent while maintaining a stable gap between an inner pipe and an outer pipe and between outer pipes. In this method, an inside mandrel is inserted into the inner pipe of the multi-layered pipe, a tubular outside mandrel is inserted into the annular space between the inner pipe and outer pipe, the multi-layered pipe is clamped to a bending die by a clamping die, the multi-layered pipe is held at the rear of a bending portion of the multi-layered pipe by a pressure die and a crease-removing die, and the multi-layered pipe is bent by causing the clamping die to revolve around the bending die. An annular outside mandrel having at least three slits formed in the distal end thereof along generating lines is used as the outside mandrel, and the clamping die is caused to revolve around the bending die with the outside mandrel and inside mandrel protruding toward the distal end of the multi-layered pipe from a bending start point.
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