| 摘要 |
PURPOSE:To discharge involved air without increasing back pressure by blocking a hopper and a heating cylinder from the atmosphere excepting the leading end of the heating cylinder in which a molten molding material is injected and providing an air vent hole connected to a vacuum source to the hopper or the communication passage of the hopper and the heating cylinder. CONSTITUTION:An air vent hole 5 is formed to a hopper base 4 and connected to a vacuum pump. A hopper 7 is separated into chambers 9, 10 by a central partition wall 8 and the molding materials received in the chambers 9, 10 are alternately supplied in a screw 2 by changing over a change-over valve 11. Valves 12, 13 are provided to the air vent hole 5 and air vent valves 15, 17 are provided to hopper lids 14, 15. When the molding material is supplied to the screw 32 from the chamber 9, the change-over valve 11 is changed over and the valve 12 is opened while the air vent valve 16 is closed. Air seals 18, 20 are arranged between the hopper 7 and the hopper lids 14, 15 and between the heating cylinder 1 and the screw 2 while the molding material in a molten state is present at the leading end of the screw 2 to seal the hopper and the heating cylinder from the outside and, therefore, the hopper and the screw grooves can be held to low pressure. |
