To provide a bulging method and a bulging device, wherein prevention of leakage of pressure liquid, and high speed and high accuracy of tube expansion molding are attained and thereby the occurrence of variation of products is prevented.
By applying the liquid pressure of the pressure liquid L to the sealing part 140 on the side in the direction of forming in the direction from a rod 30 to a tube stock 2, the sealing part 140 is made possible to follow up the bulging of the tube stock 2. Thus, at least a part of the sealing part 140 is constantly made to be in close contact with the tube stock 2. The interval between the mutual sealing parts 140, 150 is set to the distance of at least two peaks of the bellows shape 11 of a die 10. The length in the axial direction of the sealing part 150 on the opposite side of the direction of forming is set to the distance of at least one peak of the bellows shape of the die 10. Consequently, the sealed part 150 is constantly made to be in close contact with either of the flat part of the tube stock 2 and the formed valley part 2B of the tube stock.
HORI IZURU
JP2001321841A | 2001-11-20 | |||
JP3042969B | ||||
JPS5039271A | 1975-04-11 | |||
JPS5677024A | 1981-06-25 |
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