| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of forming by which a bellows tube the outside diameter of which is a small diameter (about 4-7 mm, for example) and which is excellent in pressure withstanding strength is formed with high accuracy. SOLUTION: The method of forming the bellows tube from a metallic round tube by press working comprises: (1) a first step where a workpiece of the metallic round tube is inserted between an outer die having annular projected lines on the inner side face and an inner die having projected lines on the outer side face and a corrugated shape is preformed on the tube wall of the workpiece by expanding the inner die in the direction of the outer die; (2) a second step where the pleat portions of the preformed workpiece are clamped from the upper and lower parts with plate members and the pitch intervals between the corrugated shapes are compressed; (3) a third step where trough portions of the corrugated shape of the workpiece which are formed in the second step is held with a divided punch and the diameter is reduced to the aimed inside diameter by moving the divided punch from the outside in the radial direction toward the center. COPYRIGHT: (C)2009,JPO&INPIT
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