| 摘要 |
PURPOSE:To make it possible to regulate the height of a frost line to an arbitrary desired position, by providing a ring shaped perforated cylinder on the inside lip of the slit of a cooling medium chamber or inside the lip. CONSTITUTION:The molten tube 5 extruded from a ring shaped die 1 is preliminarily cooled in the space 6 consisting of a ring shaped cooling medium chamber 2 and a ring shaped perforated cylinder 4. A part of the cooling medium blown off toward the cylinder 4 from the lip of the cooling medium chamber 2 through a slit 3 passes through the cylinder 4 to be met with air flowed in from a joint plate 7 and further met with the cooling medium flowing outside the cylinder 4 in a space 11. The cooling medium, of which the velocity is increased through the gap 12 between the adjusting ring 10 provided to the upper part of a ring shaped unperforated cylinder 8 and the tube 5, performs the final cooling of the tube 5 while the tube 5 is abruptly expanded by Venturi effect to form a frost line 13. By this method, by adjusting the height of the frost line to a desired position, a tubular film can be stably prepared. |
