To provide a tubular body expanding and contracting method for forming a tubular body which has a polygonal cross section shape, in which the ratio of ridge parts to valley parts is large, and in which the sectional shape is not fixed, but is changed in each part.
The tubular body expanding and contracting method includes a step of providing a stock tube (Step S1), a step of providing a die (Step S2), a step of applying an internal pressure to the stock tube (Step S3), a valley part forming step (Step S4), and a ridge part forming step (Step S5). In the die providing step (Step S2), a die movably divided into a plurality of sections in the radial direction of the stock tube and having die ridge parts and die valley parts, is provided. In the valley forming step (Step S4), valley parts are formed in the stock tube by the die ridge parts while closing the die. In the ridge part forming step (Step S5), the internal pressure of the tube with the valley parts formed therein is increased after closing the die, and ridge parts are formed in the stock tube by the die valley parts.
MINAMIYAMA HIDEO
TUBE FOMING CO LTD
JP2000343141A | 2000-12-12 | |||
JP2007015543A | 2007-01-25 | |||
JP2004255445A | 2004-09-16 | |||
JPH11226662A | 1999-08-24 | |||
JPH0890097A | 1996-04-09 |