| 摘要 |
PURPOSE:To expand a brach pipe having the same diameter as that of a base pipe without dividing the base pipe into two, by specifying a punch shape, when executing the expanding by a press drawing by a semi-spherical punch. CONSTITUTION:As for a punch 21, its sectional shape is semi-elliptical, and a shaft diameter E in the longitudinal direction is length which adds a spring-back portion 2alpha to a diameter (equal to that of a base pipe) A of a desired branch pipe. On the other hand, a shaft diameter F in the short axis direction meeting at a right angle with the shaft diameter E is made shorter than the base pipe diameter by about 50-100mm., so that the punch 21 can be inserted into the base pipe. The punch 21 has a shape divided into half by a horizontal shaft in the iongitudinal direction as to a rotating elliptical body of long and short shaft diameters E, F, and the upper part of a shaft 22 of its upper face center part is supported by a ram 25 provided with a rotating mechanism 24. A die 28 provided with a branch pipe forming hole 27 is fixed to the outside of a branch pipe forming part of a base pipe 26, the punch 21 is inserted from a branch hole of the base pipe, the ram 25 is drawn up by rotating it, the edge of the branch hole is deformed along the die 28, and a branch pipe lead part 30 is formed. |
