| 摘要 |
An extruder die head, such as a blown film head, comprises an internal cylindrical mandrel and an outer concentric jacket enveloping the mandrel to provide an annular channel that communicates with a die slit. To avoid slit-like gaps between the central mandrel and the concentric jacket, where the polymer melt can accumulate and degrade resulting in flaws in the extruded polymer, the mandrel is made with an integral outwardly extending flange-like foot. At least one supply line for molten polymer, such as a set of boreholes communicating with helical grooves in the outer cylindrical face of the mandrel, is connected to the annular channel in the area adjacent the flange- like foot. A ring is shrunk onto the mandrel against to the foot, under a level of predetermined tension which seals the slit between the mandrel and the jacket, and which avoids the effects of differential thermal expansion. The cylindrical jacket is mounted sealingly onto the ring.
|
