Apparatus for simultaneously extruding and cooling tubular film

Claim 1

APPARATUS COMPRISING AN EXTRUDER ADAPTED TO EXTRUDE MOLTEN THERMOPLASTIC POLYMER IN THE FORM OF A TUBULAR FILM DOWNWARDLY THROUGH AN ANNULAR ORIFICE; A SUBSTANTIALLY CYLINDRICAL MANDREL AFFIXED TO SAID EXTRUDER COAXIAL WITH AND APPROXIMATELY THE SAME DIAMETER AS SAID ANNULAR ORIFICE, SAID MANDREL HAVING A RECESS EXTENDING CIRCUMFERENTIALLY AROUND ITS UPPER EXTREMITY; MEANS FOR CONTINUOUSLY DELIVERING A COOLING LIQUID TO SAID RECESS; MEANS FOR DRAWING THE FILM DOWNWARDLY OVER SAID MANDREL WHEREBY THE FILM CONTACTS THE COOLING LIQUID AND IS THEREBY COOLED AND SOLIDIFIED; A SECOND RECESS EXTENDING CIRCUMFERENTIALLY AROUND THE PERIPHERY OF THE MANDREL AT A POINT BENEATH THE FIRST-NAMED RECESS; SEPARATE MEANS FOR APPLYING VACUUM TO SAID SECOND RECESS FOR REMOVING COOLING LIQUID BY ASPIRATION FROM BETWEEN THE FILM AND MANDREL; A THIRD RECESS EXTENDING CIRCUMFERENTIALLY AROUND THE PERIPHERY OF SAID MANDREL AT A POINT BENEATH THE SECOND RECESS; AND MEANS FOR APPLYING VACUUM TO SAID THIRD RECESS TO CREATE A GAS-TIGHT SEAL BETWEEN THE FILM AND THE MANDREL.