| 摘要 |
PURPOSE:To prevent a white stream streak, gas cavity, burn, black streak or the like, by providing a screw body with gas release holes which communicate with an opening in a cylinder in rotation but are shut off by a screw head in forward movement. CONSTITUTION:A screw head 2 is moved forth relatively to a screw body 3 by its forward rotation so that the screw head is engaged with an annular projection 12. At that time, a gap 17 corresponding to the distance of the relative forward movement of the screw head 2 in an opening is defined between the top 5 of the screw head 2 and the contact surface of the screw body 3 on the screw head, and gas relase holes 15 are connected to an opening in a cylinder 1 to feed a synthetic resin into the cylinder. A produced gas is sucked and discharged by a vacuum pump or the like through the gas release holes 15, a fitting section 10 and a communication hole 16. Then, the rotation of the screw 4 is stopped so that the molten resin stored in front of the screw head 2 is injected through a nozzle 18. |
