| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of longitudinal shrinkage when a tube shrinks by expanding the diameter of the tube by putting a plurality of rotating rolls into the tube and expanding the space between the rotating rolls while the tube is rotated around the plurality of rotating rolls to thereby expand the diameter of the tube. SOLUTION: In a diameter expanding device having a fixed rotating roll 1 whose rotating shaft is fixed and a movable rotating roll 2 movable in parallel so as to vary the space with the fixed rotating 1, the rotating rolls 1 and 2 are inserted through a tube to be diametrically expanded and the tube 3 is rotated around the rotating rolls 1, 2 by means of a tube rotating means. In synchronism with this, the space between thr rotating rolls 1, 2 is expanded through the parallel movement of the movable rotating roll 2, and the tube 3 is extended in a circumferential direction and is diametrically expanded. This eliminates a risk of the tube being imparted a longitudinal tension when the tube is diametrically expanded, and since the tube is fixed while it is being expanded only in the circumferential direction, it is possible to obtain a shrinkable tube that does not shrink in the longitudinal direction when it shrinks. |
