Tubular extrusion apparatus

A side-fed tubular extrusion die comprising:

• a sidewall defining the exterior of said die, an inlet orifice in said sidewall for introducing a molten resin into said die, a first chamber located interiorly of said inlet orifice and extending circumferentially of said die so that the longitudinal extent of said chamber forms a C-shape, said inlet orifice communicating with said C-shaped first chamber at a point intermediate the ends thereof, said C-shaped first chamber receiving a molten resin introduced through said inlet orifice, a second toroidal-shaped chamber located interiorly of said die, an interior die wall separating said first and second chambers, a plurality of openings provided in and spaced along said interior die wall and oriented in a substantially axial direction of said die, said openings interconnecting said first and second chambers to allow said second chamber to receive a molten resin from said first chamber, and an extrusion gap defined by a mandrel positioned coaxially within said die and an interior die sidewall coaxial with said mandrel, said extrusion gap receiving molten resin from said second toroidal-shaped chamber.

A side-fed tubular extrusion die comprising:

• a sidewall defining the exterior of said die, an inlet orifice in said sidewall for introducing a molten resin into said die, a first at least partly toroidal-shaped chamber located interiorly of said die in communication with said inlet orifice for receiving a molten resin introduced through said inlet orifice, a second toroidal-shaped chamber located interiorly of said die, an interior die wall separating said first and second chambers, a plurality of openings provided in and spaced along said interior die wall, said openings having respective lengths which progressively decrease from an opening closest to said inlet orifice to an opening farthest removed therefrom, said openings interconnecting said first and second chambers to allow said second chamber to receive a molten resin from said first chamber, and an extrusion gap defined by a mandrel positioned coaxially within said die and an interior die sidewall coaxial with said mandrel, said extrusion gap receiving molten resin from said second toroidal-shaped chamber.