| 摘要 |
PURPOSE:To prevent the enlargement of a ring for preventing back-flow, by absorbing the pressure of injection by providing a smaller diameter part at the nozzle side of the ring for preventing back-flow and forming a circular space between its outer peripheral surface and the inner surface of a cylinder. CONSTITUTION:At the outer peripheral surface of the smaller diameter part 21 of a ring 6 for preventing back-flow, there is formed a screw groove 23 having the same tortional direction as the screw groove 13 of a screw itself 4. Thereby an annular space is provided between the outer peripheral surface of the ring 6 for preventing back-flow and the inner surface of a cylinder. Therewith when a screw is revolved in plasticizing process, a resin residing in the annular space 22 between the smaller diameter part 21 and the cylinder 1 is discharged to the space 12 at the side of the nozzle by the carrying function of the screw groove. Accordingly it is possible to prevent the enlargement of the diameter of the ring for preventing back-flow because injection pressure is applied to both of inner and outer surfaces of the ring for preventing back- flow. |
