| 摘要 |
<p>A bellows having at least its internal surface consisting of a mirror surface polytetrafluoroethylene, obtained by melting-pressure molding into a bellows form. In particular, the bellows is obtained by inserting a core in the inside of either a cylindrical or beaker-shaped preform of polytetrafluoroethylene, or a cutting wrought or blow molded polytetrafluoroethylene bellows; carrying out fusion pressure bonding with the use of, for example, a special metal mold; and drawing out the core, optionally followed by welding. The special metal mold consists of multiple movable outer piece dies and the same number of back-push outer piece dies.The movable outer piece dies and back-push outer piece dies are alternately disposed, and while sliding, narrow the circle made thereby to thereby accomplish fusion pressure bonding of molding.Thereafter, the movable outer piece dies and back-push outer piece dies are detached to thereby expand the molding. Simultaneously, mechanical force is applied to thereby expand a flange portion. The core is taken out, optionally followed by welding. Thus, a bellows can be obtained.</p> |
