Patent ID: 7713047

Claim:
An extrusion apparatus for making a multilayer article, the extrusion apparatus having a first end and a second end and a flow direction going from the first end to the second end, the extrusion apparatus comprising: a central mandrel having an axis; a plurality of discs where each disc surrounds the central mandrel, the plurality of discs including: a first pair of discs including a first disc and a second disc, the first disc having a central cone-shaped portion extending toward the second end and the second disc having a cone-shaped portion into which the cone-shaped portion of the first disc fits such that a gap exists between the two cone-shaped portions to form a polymer flow channel, a second pair of discs including a third disc and a fourth disc, the third disc having a central cone-shaped portion extending toward the second end and the fourth disc having a cone-shaped portion into which the cone-shaped portion of the third disc fits such that a gap exists between the two cone-shaped portions to form a polymer flow channel, wherein the plurality of discs and the central mandrel define a cylindrical flow channel, and wherein the second disc and the third disc together define a gap creating a polymer flow channel having a portion that is perpendicular to the axis of the mandrel and wherein the perpendicular portion abuts the cylindrical flow channel; and a thickness of at least one of the discs in the flow direction is about one inch or less.