Apparatus for the production of blown foils or films of thermoplastic

A foil-blowing apparatus for a thermoplastic synthetic resin material, said apparatus comprising:

• a blowing head formed with an annular orifice issuing a tube of thermoplastic synthetic resin material and blowing same to form a substantially vertical foil balloon from said material extending from a neck and having a transition region between said neck and said balloon, said transition region terminating at a frost line of the balloon;
• a calibration basket surrounding said foil balloon above said frost line;
• flattening means vertically spaced from said head for closing said balloon and flattening foil thereof into a coilable web;
• external cooling means in said transition region and comprising at least one cooling nozzle crown surrounding said transition region and formed with nozzles training jets of cooling air against said transition region;
• and
• means for eliminating foil thickness errors and including means for detecting thickness of the blown foil and means responsive to the detected thickness for adjusting positions of said nozzles in at least one of the vertical direction and the radial direction relative to said transition region in response to the detected thickness, the cooling nozzle crown being subdivided into nozzle segments which are adjustable independently from one another by said means for adjusting, each of said nozzle segments being provided with at least one of said nozzles.