| 摘要 |
PURPOSE:To permit the efficient change of a material in blow molding, by a method wherein the new material, different from the old material, is supplied into a space between a mandrel and a blow head, thereafter, the extruding stroke of a plunger is divided into a plurality of times to effect extruding operation intermittently. CONSTITUTION:In the case of changing an oil material to a new material, the material 8, different from the old material and employed for the extrusion of this time, is supplied into a space 2, thereafter, a plunger cylinder 6 is operated intermittently so as to divide the extruding stroke of a plunger 7 into a plurality of times whereby the extrusion of the material 8 is effected intermittently by the plunger 7. According to this constitution, the thick part 9a and the thin part 9b of a parison 9, extruded from a slit 4, are formed alternately. Influences, enlarging the effect of the change of the material immediately after extrusion, are repeated by the intermittent extruding operations of the plunger 7, which is described above. Accordingly, the change of the material may be performed effectively and remarkable reduction in the using amount of the material as well as the time, which are necessitated for the change of the material, may be achieved. |
