| 摘要 |
PURPOSE:To improve the moldability, by a method wherein the forward part further to the middle part of the gate side of the runner for the gate is made smaller in its diameter than that of the cross section at the point where a main runner crosses with the former. CONSTITUTION:The gate runner 14 is provided in the center of a hot bush 19, and heaters 20 for heating the gate runner 14 are provided on the outer sides of the hot bush 19. The diameter of the forward end 14a of the gate runner 14 adjacent to a gate 16 is smaller than that of the cross section of the gate runner 14 that is in communication with the main runner 13, so that the rate of the material passing through the forward end becomes faster, and therefore the moldability is improved. In the communicated section of the runners 12, 14 a valve rod bush 18 is provided making the material not to stagnate in a corner part D, and the end face of the bush 18 facing the gate runner 14 has a helical shape that facilitates helical movement of the material flowing from the main runner 13. Consequently, the molded item has not weld line, thereby improving, the apparance and the mechanical properties. |
