Apparatus for production of tubular blown foils of polyvinyl chloride interpolymers

Claim 1

4. IN APPARATUS FOR PRODUCTION OF A TUBULAR FOIL, A FIRST CHAMBER WITH A FORWAEDLY DIRECTED ANNULAR ORIFICE, A BLASTING HEAD POSITIONED CENTERALLY WITHIN AND SMALLER THAN SAID ANNULAR ORIFICE, MEANS FOR FORCING A PLASTIC MASS THROUGH SAID ORIFICE AND ABOUT SAID BLASTING HEAD IN THE FORM OF A TUBE, GAS EGRESS PASSAGE MEANS EXTENDING LONGITUDINALLY THROUGH SAID BLASTING HEAD, GAS INGRESS PASSAGE MEANS EXTENDING LONGITUDINALLY THROUGH SAID BLASTING HEAD, A SECOND ENLARGED CHAMBER EXTENDING FORWARDLY FROM SAID FIRST CHAMBER, A GAS SUPPLY CONDUIT PROJECTING FORWARDLY FROM SAID BLASTING HEAD CONCENTRICALLY WITHIN SAID TUBE, SAID CONDUIT SERVING AS AN EXTENSION OF SAID INGRASS PASSAGE MEANS, MEANS FOR CIRCULATING GAS THROUGH SAID ENLARGED CHAMBER AND ABOUT THE OUTSIDE OF SAID TUBE, A MANTLE WITH AN INTERNAL CYLINDRICAL WALL PROJECTING FORWARDLY FROM SAID ENLARGED CHAMBER OPPOSITE SAID ANNULAR ORIFICE, AND MEANS TO MAINTAINN SAID WALL AT A CONTROLLED, PREDETERMINED TEMPERATURE.