| 摘要 |
PURPOSE:To eliminate affection extending to deterioration in strength and accuracy in thickness of a joining surface, by a method wherein bridges supporting a core mandrel are provided more than one, which are inclined by a predetermined angle to a radial axial line extending in a radius direction from the external circumferential surface of the core mandrel. CONSTITUTION:A core mandrel 23 is fitted with a screw to a bridge block 25 having a bridge 24. The bridge 24 is constituted of at least more than one piece of the same, which is inclined by a predetermined angle alpha to a radial axial line extending in a radius direction from the external circumferential surface. Therefore, as for molten materials obtained by dividing by a material flow path 26, as joining parts at an inside diametral surface and outside diame tral surface deviate each other like outlets 27, 28 when the molten materials are extruded through the outlet 26, joining strength is high and nonuniformity in thickness is also few. As for the bridge 24, the more the same becomes in number, the thinner thickness can be made and uniformity in thickness is favor able extending over the whole circumference of a cylindrical molded article. |
