External cooling ring for an annular extrusion die, especially a blown film die

摘要

A cooling ring (3) for cooling an extruded thermoplastic tube emerging from an annular die, comprises an opening facing the tube (2) divided into individual nozzle orifices(4), each of which is linked by a connecting channel to two distribution channels (5,6) whose separate air flows are at different temperatures. Directional control valves (15,20) can be independently controlled to produce a stepless mixture of cooling air flowing from both distribution channels (5,6) into the distribution channel.