| 摘要 |
<p>PURPOSE:To manufacture bellows, on the inner peripheral face of which beads running in the direction of the axis center line of the bellows are provided and consequently which has excellent bending strength and the like, by a method wherein concavities are formed on the outer peripheral face of an inner pipe for extrusion in the method to manufacture the bellows by blow-molding extruded tube in an endless molding tool. CONSTITUTION:Tube 4 is extruded from an annular port 3 made by an outer pipe 2 and an inner pipe 1 with a plurality of concavities 8. Said extruded tube 4 is blow-molded in an endless rotatable molding tools 6 consisting of molding units 7A, on the inner peripheral face of each of which corrugated tongued-and-grooved face is made, in order to be turned into bellows 13. Because the concavities 8 are provided on the inner pipe for extrusion, the bellows, on the inner peripheral face of which beads 9 are provided, is obtained. The bead 9 improves the bending strength of the belows and, in addition, is available for the insertion of cable or the like. Further, because the concavities are made on the outer peripheral face of the inner tube, the working of the mold, or of the inner pipe 1, is easy.</p> |
