| 摘要 |
PROBLEM TO BE SOLVED: To prevent a pipe from buckling, cracking or being pinched. SOLUTION: Bulging molds 1 and 2 are axially split into two pieces respectively from the specified positions of semicircular-arc-shaped recesses 1a and 2a for forming an expanded portion in a diameter. At least the center portions of the recesses la and 2a for forming the expanded portion are circumferentially split into a multitude of parts, with split portions a-b of the split molds 11, 12, 21 and 22 as boundaries, and those parts engage with each other axially whereby the center portions of the recesses la and 2a for forming the expanded portion are formed into a pair of circular comb-teeth-shaped sections composing the inner faces of the recesses la and 2a for forming the expanded portion. Both open ends of the pipe 5 are stopped up by forcing and fitting core bars 3 and 4 into the pipe 5, and in the bulging molds 1 and 2, a high-pressure liquid is supplied into the pipe 5 through a hydraulic pressure feeding slot 3a formed in the axis of the core bar 3. The pipe 5 is made to closely touch with the inner wall faces of the recesses 1b and 2b for forming the expanded portion formed with the pair of the circular comb-teeth-shaped sections 1c and 2c in the intermediate portions of the bulging molds 1 and 2 by axially pressing the split molds 11, 12, 21 and 22 themselves by a specified pressing means so that the specified expanded portion 5b is formed. COPYRIGHT: (C)2006,JPO&NCIPI
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