| 摘要 |
Apparatus for cooling tubular plastic films extruded from a film blowing head. Air cooling means consisting of co-axial pipes extending axially through the film blowing head supply the cooling and inflating air and withdraw the same from the inflated parison. Vertically inner cooling rings are disposed substantially concentrically to the axis of the parison downstream of the annular extrusion die orifice of the blowing head. The inner cooling rings define nozzle gaps and have air guiding surfaces, which face the wall of the parison and are convexly curved in a longitudinal section of the inner cooling rings and during the operation of the apparatus are swept by the cooling air blown out of said nozzle gaps. An outer cooling air jet concentrically surrounds the extruded parison and serves to blow air in a direction which is approximately parallel to the direction of travel of the parison. The inner cooling rings are concentric to the parison. A telescopic inner pipe is provided and includes axially spaced annular gaps serving to withdraw the cooling and inflating air. The outside diameter of the lowermost internal cooling ring is substantially as large as the inner diameter of the annular extrusion die orifice. The diameters of the inner cooling rings progressively decrease in an upward direction so that the parison will assume an upwardly tapering, frustoconical shape having a small included angle before it is inflated. |
