Method and apparatus for producing thermoplastic tubing

Claim 1

IN APPARATUS FOR PREPARING SELF-SUSTAINING PLASTIC FILM INCLUDING MEANS TO ANNULARY EXTRUDED A MOLTEN THERMOPLASTIC IN THE FORM OF SEAMLESS TUBING, MEANS SPACED TO INFLATE THE TUBING TO A PREDETERMINED DIAMETER INTERMEDIATE THE EXTRUSION MEANS AND THE FLATTENING MEANS, THE IMPROVEMENT WHICH COMPRISES MEANS FOR ENVELOPING THE FLATTENING MEANS ANS THE TUBING FROM SAID EXTRUSION MEANS TO SAID FLATTENING MEANS WITHIN A CONFINED AREA, MEANS FOR ANNULARY IMPINGING A STREAM OF CHILLED GAS ON THE TUBING IN THE VININITY OF THE POINT OF EXTRUSION, MEANS FOR SUPPLYING A STREAM OF CHILLED G AS TO SAID CONFINED AREA BETWEEN SAID EXTRUSION MEANS AND SAID FLATTENING MEANS TO LOWER THE AMBIENT TEMPERATURE OF SUCH AREA, AND MEANS FOR CIRCULATING BOTH STREAMS PF CHILLED GAS THROUGH SAID CONFINED AREA SUCH THAT SAID CHILLED GAS WHOLLY ENVELOPES THE TUBING TO AND INCLUDING THE POINT OF FLATTENING, TO MAINTAIN THE SOLIDIFICATION POINT OF THE TUBING IN CLOSE PROXIMITY TO THE POINT OF EXTRUSION.