| 摘要 |
PURPOSE:To prevent a melted resin from staying and adhering near a vent hole and being deteriorated and to perform venting positively, by arranging, near a screw in a heating cylinder, a vent-blocking preventive screw whose diameter is a little smaller than the inner diameter of a vent cylinder. CONSTITUTION:A very small clearance is kept between the outer circumference of a helical blade 9 and the inner surface of a vent cylinder in such an extent that a gas can pass through the clearance but a melted resin 4 cannot pass through it. Therefore, the gas generated from the melted resin 4 in a heating cylinder 1 is sucked into the vent cylinder 5 and is discharged via a discharge pipe 10 by a suction apparatus. Since the rotation and axial movement of a molding screw 2 are intermittently repeated, the melted resin 4 is every time raised, but as the raised resin is pushed down together with other melted resin 4 into the heating cylinder 1, the resin would not stay near the lower end opening section of the vent cylinder 5 and would not be deteriorated. |
