| abstract |
The invention addresses the problem of reducing fluctuations, in the circumferential direction, of the height of the leading edges of the middle layer in a preform in an injection molding device for test tube-shaped preforms in which a middle layer is laminated in a base substance layer of the main resin so that the middle layer is divided into parts in the circumferential direction. The main means of the invention for solving the problem are: to configure the nozzle so as to dispose three cylindrical layer-forming paths, an inner flow path and an outer flow path that form the base substance layer and a middle flow path that forms the middle layer, and to dispose longitudinal blocking rib pieces, which stand parallel to each other in the circumferential direction and cross the flow path, on the downstream end of the middle flow path to divide the flow path into a prescribed number of flow paths in the circumferential direction by the longitudinal blocking rib pieces; and to configure the nozzle to adjust the flow behavior of the middle layer resin in the middle flow path by the positioning of the longitudinal blocking rib pieces in the circumferential direction so that the height difference between the highest end and lowest end of the leading edges of the middle layer that emerge in the preform is reduced. |