| 摘要 |
PURPOSE:To make a bulging under a small pressure and to obtain a uniform thickness by making preliminary forming of bulged lines on the internal circumference near at least one side of bulged part of a pipe material, pushing the bulged lines with a push lever, compressing it with the push lever toward the bulged part and making bulging by liquid pressure. CONSTITUTION:Bulged lines 5, 5 in the circumference direction are formed preliminarily by beads 4, 4 on the internal circumference near a bulged site 1B of the pipe material 1. Then, the preliminarily formed pipe material 1 is put in a forming die 2 composed of an upper and a lower die 2A, 2B, the push levers 8, 8 are inserted from both ends of the forming die 2, compression surfaces 6A, 6A at the ends of compression axial parts 6, 6 are brought into contact with the sides of the bulged lines 5, 5 of the pipe material 1. When the push levers 8, 8 are forced in the direction of an arrow as pressure liquid is pressed in through flow channels 3A, 3A, the bulged part 1A is formed after the forming die 2. Simultaneously, the material of the pipe material 1 is moved to the bulged site 1B by loading compression force with the push levers 8, 8 to smoothly form the bulged part 1A.
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