JPS57115931A - Method for manufacturing spherical flexible pipe joint - Google Patents

Abstract

PURPOSE: To closely insert an inner tube into an outer shell tube to slide movably, and to improve the accuracy of the spherical flexible joint, by swelling out the outer shell tube which is swell-formed by extruding with upper and lower forming dies while affecting high liquid pressure in the blank material of inner tube, and holding the outer shell tube with the inner tube forming die, and swelling out said blank material in the outer shell tube.

CONSTITUTION: An upper forming die 17 is lifted and removed from a guide cylinder 13 and a blank pipe 10' is inserted into a space between a projected part 15_a of an end plug 15 and a lower forming die 16, and then, an upper end plug 21 is lowered until it contacts with the upper end of the blank pipe 10'. Then, a liquid pressure is introduced into the blank pipe 10' from a liquid pressure introducing path 14 and, at the same time, the blank pipe 10' is compressed in the direction of the axis by lowering the upper forming die 17 until a space 25 disappears. The blank pipe 10' is expanded toward the inner surface of spherical cavities 16_a and 17_a of the upper and lower forming dies 16 and 17. After the blank pipe 10' is expanded, its end part and a part of the spherical part are cut off, and thus, a formed outer shell tube 10 is obtained. Then, the outer shell tube 10 is inserted into a lower forming die 26 together with a blank pipe for inner tube 11'. Thereafter, the blank pipe 11' is spherically expanded toward the inner wall of the spherical part 10_a of the outer shell tube, and thus, a spherical flexible pipe joint in which the inner tube 11 is joined to the outer shell tube 10 is obtained.

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