| 摘要 |
PURPOSE:To reduce thickness irregularity, color irregularity at the time of the addition of pigment and transparency irregularity by sufficiently diffusing just the slight irregularity in the speed of cooling air in a double ring shaped blow-off cooling ring, by providing a ring shaped barrier plate or the ring shaped barrier wall and/or a ring shaped buffer groove at the specific position is said ring. CONSTITUTION:Cooling air reaching a ring shaped air distribution chamber 4 enters a first ring shaped air blow-off passage 18 through an air passing hole 11 and successively passes through a ring shaped barrier chamber 16 and a ring shaped barrier chamber 17 to be formed into a uniformized cooling air stream having a good pressurized air amount while this air stream is blown off form a first ring shaped air blow-off port 19 to preparatorily cool the molten tube 2 extruded from an extrusion die 1 at first. Similarly, cooling air coming through the ring shaped air blow-off passage 20 and passes through ring shaped barrier walls 14, 15 to be reduced in its wind velocity irregularity and final cooling is performed by cooling air blown off from a second ring shaped air blow-off port 21. |
