Variable orifice extrusion die

Claim 1

A DIE STRUCTURE FOR THE EXTRUSION OF TUBULAR THERMOPLASTIC FILM WHEREIN SAID STRUCTURE PROVIDES A VARIABLE DIAMETER DIE ORIFICE, COMPRISING IN COMBINATION, A DIE BODY; A PRIMARY PASSAGEWAY DEFINED IN SAID BODY, SAID PASSAGEWAY HAVING AN INLET END, AND A DISCHARGE END INCLUDING AN OUTWARDLY IN STEM AND A HEAD, ADAPTED TO BE A MANDREL, INCLUDING A STEM AND A HEAD, ADAPTED TO BE MOUNTED IN CONCENTRIC RADIALLY SPACED RELATION TO SAID PASSAGEWAY WALLS, THEREBY LIMITING SAID PASSAGEWAY TO AN ANNULAR FORM; SAID MANDREL HEAD HAVING A FIRST RIGHT FRUSTO-CONICAL PORTION, SUBSTANTIALLY MATCHED WITH SAID PASSAGEWAY CONICALLY FORMED PORTION, JOINED TO SAID STEM IN AN INVERTED POSITION, AND A SECOND RIGHT FRUSTO-CONICAL PORTION JOINED TO SAID FIRST HEAD PORTION AT THEIR LARGER BASE ENDS, SAID SECOND HEAD PORTION BEING DISPOSED ENTIRELY BEYOND SAID PRIMARY PASSAGEWAY; A FIRST DIE RING MOUNTED ON SAID DIE BODY AT THE DISCHARGE END OF SAID ANNULARLY LIMITED PRIMARY PASSAGEWAY, CONCENTRIC THEREWITH, SAID FIRST DIE RING HAVING AN INNER PERIPHERAL SURFACE PORTION SHAPED TO MATCH AN OUTER PERIPHERY SURFACE PORTION OF SAID MANDREL DISPOSED BEYOND SAID PRIMARY PASSAGEWAY DISCHARGE END, AND RADIALLY SPACED FROM SAID MANDREL SURFACE PORTION, THEREWITH TO DEFINE A CONTINUING SECONDARY PASSAGEWAY PORTION AND AN ANNULAR DIE ORIFICE; AND A PLURALITY OF ADDITIONAL DIE RINGS SUCCESSIVELY AND SERIALLY CONNECTED ON SAID FIRST DIE RING AND ON EACH OTHER THEREAFTER, EACH OF SAID ADDITIONAL RINS BEING REMOVABLY CONNECTED TO ONE ANOTHER,EACH SAID ADDITIONAL RING HAVING A TAPERED, CONICAL INNER SURFACE AREA ANGULARLY MATCHED TO A SPECIFIC PORTION OF SAID MANDREL SECOND HEAD PORTION, AND PROVIDING THEREWITH A CONTINUATION OF SAID SECONDARY PASSAGEWAY, AND A DISCHARGE ORIFICE; WHEREIN, WHEN SAID ADDITIONAL RINGS ARE SERIALLY MOUNTED ON SAID FIRST DIE RING AND AN EACH OTHER, SAID RINGS VARIABLE DETERMINE THE OUTER DIAMETER OF SAID DISCHARGE ORIFICE IN A DESCENDING ORDER, AND WHEN SERIALLY REMOVED DETERMINE SAID ORIFICE DIAMETER IN AN ASCENDING ORDER.