Method of manufacturing corrugate tube and molding apparatus thereof

摘要

There is disclosed a technique characterized by the following steps. An axial load is applied from both ends of a primary tube while locally heating the primary tube by use of a high frequency coil in the peripheral direction, and the heated portion is thereby bulged. The application of load is stopped almost concurrently with termination of the heating process. The heated portion is forcibly cooled with a cooling liquid, thus molding one crest. Then the primary tube and the high frequency coil are relatively moved. The next crest is formed by repeating the foregoing steps. Such operations are consecutively repeated in the axial direction of the primary tube, thereby obtaining a corrugate tube formed with crests having a large amount of bulge and a small pitch.