| 摘要 |
<p>A variable cross section extruding die comprises a die (24) for varying an area of an extrusion molding hole (31) provided movably in a direction perpendicular to a direction in which a molding material is extruded for extrusion of the molding material and a mandrel (27) provided in the extrusion molding hole in such a manner as to freely move back and forth in the above extruding direction and having a tapered portion (27B) on its outer circumferential portion tapered such that the outer diameter thereof gets gradually smaller from one of the back and forth directions to the other. With this variable cross section extruding die, while a molding material is being pressed against the die (24), the die is moved such that the configuration of the extrusion molding hole (31) is deformed, and the tapered portion of the mandrel (27) is moved in and out of the extrusion molding hole, whereby a tubular molded article is extruded whose outside and inside diameters vary along its longitudinal direction.</p> |
