| 摘要 |
PURPOSE: To increase even the extrusion amt. of a resin material low in melt tension and to enhance productivity by providing an air ring above a molding die in concentric relation to an annular emitting orifice and providing a pressure chamber above the annular air blowoff port for cooling a resin bubble provided to the inner peripheral surface thereof. CONSTITUTION: A tubular resin bubble 50 is extruded from the extrusion lip (annular emitting orifice) of a spiral die 3. Lower and upper air rings 11, 12 are provided to the external cooling apparatus 10 provided to the upper part of the die 3 and the lower air ring 11 is continued to the die 3 in the vicinity of the outside of the extrusion lip 3a thereof and has an air lip (annular air blowoff port) 11a. A pressure chamber 21 consisting of lower, middle and upper stage pressure chambers 21a, 21b, 21c is provided to the inner peripheral surface of the lower stage air ring 11. Cooling air A blown out of the lower stage air lip 11a is reduced in flow velocity within the pressure chambers 21a-21c without disturbing air flow to flow in a second pressure chamber 22 along with the cooling air A blown out of the upper stage air lip 12a. |
