PURPOSE: To improve the pressure resistivity and durability of a product by forming a U-type shevron part and straight tubular part in advance, then compressing by adding an internal pressure to the blank material tube, and thereafter exerting a high pressure to an inside of the tube.
CONSTITUTION: As a first step, a blank material tube 10 is formed by a forming machine provided with a group of split dies for bellows, and a blank material tube 10 consisting of a U-type shevron part 10a and a straight tubular part 10b crossing in perpendicular to the foot is produced, then the blank material tube 10 is inserted to a collector forming machine composed of a hydraulic pressure generating unit 20, a core metal 30, a press 40, and by exerting a specified internal pressure to the inside of the tube, the tube 10 is compressed towards an axial direction. Then, as the third step, the hydraulic pressure generating unit 20 is switched over to the high pressure, and a specified high pressure is exerted into the tube 10 for a prescribed period of time. By means of this method, an idealistic curved surface is formed on the shevron part and the side wall part of the bellows. And accordingly, the pressure resistivity and durability of the bellows tube are improved.
KAMAOKU AKIO
OGASAWARA HIROMITSU
NAKANO MITSUAKI
| JPS5987931A | 1984-05-21 | |||
| JPS5656733A | 1981-05-18 |