Annular extrusion die with back pressure control

Claim 2

An extrusion die for making tubing, parisons, and the like, comPrising in combination A. a die adapted for mounting in face to face engagement with the face of a prechosen extruder, said die adapter defining therewithin a generally centrally located passageway. B. an annular spider means adjoining said die adapter, and having radially extending supporting fingers, C. an elongated die body means circumferentially adjoining said spider means through said supporting fingers, said die body defining therewithin an elongated cavity having a flared crosssectionally circular entrance portion and a terminal, cylindrical land portion, said land portion having a predetermined ratio of the length thereof to the diameter thereof, D. elongated mandrel means supported by said spider means and continuously extending within said cavity in radially spaced relationship to said die body to define in combination with said spider means a passageway between said mandrel and said die body means and between said entrance portion and the end of said land portion, said passageway being annular in cross section except in the region of said spider means where the apertures between said supporting finger interconnect with said passageway, E. said die body means and said mandrel means in combination between said spider means and said land portion defining convergence in said passageway, F. a choke ring demountably seated on said mandrel means on either said mandrel means or on said die body means between said spider means and said land portion and adapted to reduce circumferentially the cross section of said passageway to a predetermined extent, said choke ring being reversible in position said choke ring being assymetrical as respects a hypothetical centerplane extending through said choke ring perpendicularly to the axis thereof, G. shoulder means defined in either said mandrel means or said die body means and adapted for so seating said choke ring thereon, as the case may be, H. the interrelationship between said choke ring and said convergence in said passageway being such that the radial distance between said choke ring and the opposed wall of said passageway has either one of two different values depending upon which way said reversable choke ring is so seated, and I. mounting means adapted to maintain said die adapter, said spider means, said die body means, said mandrel means, and said choke ring in fixed, predetermined relationship to one another and further adapted to permit at least partial disassembly and reassembly of said mandrel means and said die body means to an extent necessary for mounting and demounting said choke ring from said shoulder means.

Claim 3

The die of claim 1 wherein, in said mandrel means and said spider means, A. said mandrel means continuously extends from a position adjacent, but axially spaced from, the passageway in said die adapter to said annular orifice to define a circumferentially continuous, axially extending passageway forwardly of said spider, and B. said mandrel means in combination with said spider provides a plurality of axially extending, circumferentially spaced apertures interconnecting said passageways on either side of said spider.

Claim 4

The die of claim 1 wherein said spider means has an integral nose extending into the passageway of said die adapter.

Claim 5

The die assembly of claim 1 wherein said die body comprises a die barrel and a mounting ring in axially adjacent relationship to one another and said choke ring is seated therebetween.

Claim 6

The die body of claim 1 wherein said mandrel includes a melt shaping portion forwardly of said spider as respects the direction of melt flow therethrough and said choke ring is seated on said shaping portion adjacent said spider.

Claim 7

An annular extrusion die for making tubing, parisons, and the like when in combination with a single screw extruder, said die being adapted to control back pressure, comprising in combination A. a die adapter adapted for mounting in face to face Engagement with the face of the barrel of a single screw extruder, said die adapter defining therewithin a generally funnel-shaped interior having a mouth portion and a neck portion, with said neck portion being adapted to be adjacent said barrel face, said funnel-shaped interior being generally coaxial with the screw of said extruder. B. an annular spider means adjoining said die adapter adjacent said mouth portion, and having radially extending supporting fingers, C. an elongated die body means generally circumferentially adjoining said spider means through said supporting fingers, said die body defining therewithin an elongated cavity having a flared cross-sectionally circular entrance portion and a terminal, cylindrical land portion, said land portion having a predetermined ratio of the length thereof to the diameter thereof, said cavity being generally coaxial with said screw, D. mandrel means supported by said spider means generally adapted to be coaxial with said screw and continuously extending within said die body means from said spider means to the end of said land portion in radially spaced relationship to said die body, E. said mandrel means and said spider means in combination defining within said elongated cavity a passageway between said mandrel and said die body means extending from a position axially adjacent said neck portion to the end of said land portion, said passageway being annular in cross section except in the region of said spider means, F. said spider means further providing between said supporting fingers thereof a plurality of axially extending circumferentially spaced apertures interconnecting said passageway, G. said die body means and said mandrel means in combination between said spider means and said land portion defining convergence in said passageway, H. channel means defined in said mandrel means and adapted to interconnect with exterior conduit means extending through said spider means normally and further adapted for circulation of temperature regulating fluid therethrough, I. heater means circumferentially located exteriorly about at least a portion of the combination comprising said die adapter, said spider means and said die body means, and adapted to regulate the temperature thereof, J. a choke ring demountably seated in either said mandrel means or in said die body means between said spider means and said land portion and adapted to reduce the cross section of said passageway, said choke ring being assymetrical as respects a hypothetical centerplance extending through said choke ring perpendicularly to the axis thereof, said choke ring being reversably seatable as so demountably seated, K. shoulder means defined in either said mandrel means or said die body means and adapted for so seating said choke ring thereon, as the case may be, L. the interrelationship between said choke ring and said convergence in said passageway being such that the radial distance between said choke ring and the opposed wall of said passageway has either one of two difference values depending upon which way said reversable choke ring is so seated, and M. mounting means adapted to maintain said die adapter, said spider means, said die body means, said mandrel means, and said choke ring is fixed, predetermined relationship to one another and further adapted to permit at least partial disassembly and reassembly of said mandrel means and said die body means to an extent necessary for seating and unseating said choke ring.

Claim 8

An annular extrusion die for making tubing, parisons, and the like when in combination with a single screw extruder, said die being adapted to control back pressure, comprising in combination A. a die adapter adapted for mounting in face to face Engagement with the face of the barrel of a single screw extruder, said die adapter defining therewithin a generally funnel-shaped interior having a mouth portion and a neck portion, with said neck portion being adapted to be adjacent said barrel face, said funnel-shaped interior being generally coaxial with the screw of said extruder. B. an annular spider means adjoining said die adapter adjacent said mouth portion, and having radially extending supporting fingers, C. an elongated die body means generally circumferentially adjoining said spider means through said supporting fingers, said die body defining therewithin an elongated cavity having a flared cross-sectionally circular entrance portion and a terminal, cylindrical land portion, said land portion having a predetermined ratio of the length thereof to the diameter thereof, said cavity being generally coaxial with said screw, D. mandrel means supported by said spider means generally adapted to be coaxial with said screw and continuously extending within said die body means from said spider means to the end of said land portion in radially spaced relationship to said die body, E. said mandrel means and said spider means in combination defining within said elongated cavity a passageway between said mandrel and said die body means extending from a position axially adjacent said neck portion to the end of said land portion, said passageway being annular in cross section except in the region of said spider means, F. said spider means further providing between said supporting fingers thereof a plurality of axially extending circumferentially spaced apertures interconnecting said passageway, G. said die body means and said mandrel means in combination between said spider means and said land portion defining convergence in said passageway, H. channel means defined in said mandrel means and adapted to interconnect with exterior conduit means extending through said spider means normally and further adapted for circulation of temperature regulating fluid therethrough, I. heater means circumferentially located exteriorly about at least a portion of the combination comprising said die adapter, said spider means and said die body means, and adapted to regulate the temperature thereof, J. a choke ring demountably seated in either said mandrel means or in said die body means between said spider means and said land portion and adapted to reduce the cross section of said passageway, said choke ring being assymetrical as respects a hypothetical centerplance extending through said choke ring perpendicularly to the axis thereof, said choke ring being reversably seatable as so demountably seated, K. shoulder means defined in either said mandrel means or said die body means and adapted for so seating said choke ring thereon, as the case may be, L. the interrelationship between said choke ring and said convergence in said passageway being such that the radial distance between said choke ring and the opposed wall of said passageway has either one of two difference values depending upon which way said reversable choke ring is so seated, and M. mounting means adapted to maintain said die adapter, said spider means, said die body means, said mandrel means, and said choke ring is fixed, predetermined relationship to one another and further adapted to permit at least partial disassembly and reassembly of said mandrel means and said die body means to an extent necessary for seating and unseating said choke ring.