| 摘要 |
PROBLEM TO BE SOLVED: To shorten a molding cycle and to prevent molding inferiority and the seizing of a resin by providing a non-return ring to the periphery of a screw head, and allowing a screw to advance while allowing flights to retreat apparently in an injection process. SOLUTION: A non-return ring 28 is provided to the periphery of the columnar part 26 of a screw head 27. When a screw 12 is allowed to advance by driving an injection motor in an injection process, a weighing motor is driven to rotate the screw 12 in a reverse direction to allow flights 23 to retreat apparently. Therefore, the screw 12 advances but the resin in grooves 24 retreats. In this case, since the non-return ring 28 is set to a cutting-off position and the holes 28a, 29a thereof are cut off, the resin in front of the screw head 27 does not flow back toward a flight part 21. By this constitution, suck-back is dispensed with by a simple process and, in the succeeding weighing process, no irregulality is generated in the amt. of the resin in front of the screw head 27. |
