To improve the accuracy of the outward shape of a formed article by jointly using an elastic core made of rubber inside a stock tube to eliminate the bending buckling generated inside the bending during the bending forming when the hydraulic pressure is applied to the stock tube to perform the bending.
Elastic cores 2a, 2b made of rubber, etc., are inserted in a stock tube 1, the hydraulic pressure P1 is applied thereto, an upper die 3 is lowered and the stock tube 1 is bent between the upper die and a lower die 4. The hydraulic pressure P1 generates the tensile force in the stock tube 1 to suppress generation of the buckling deformation. In addition, the individual and rigid elastic cores 2a, 2b made of rubber, and the dies 3, 4 suppress generation of the buckling deformation of the stock tube 1. The movement in the axial direction of the elastic cores 2a, 2b made of rubber, etc., is restricted by a jig. The elastic cores 2a, 2b made of rubber, etc., are split so as to easily take out the cores from the formed article.
OSANAWA TAKASHI
YOSHITOMI YUJI
TANAKA SHINJI
SATO TOSHIMI
UCHINUMA YOSHIAKI
KUROKAWA TAKEO
