| 摘要 |
The coextrusion die assembly receives a first and a second plasticized material flow which it forms into a layered, cylindrically tubular flow. An inlet block (100) receives the first material flow axially and the second material flow radially. A manifold block (200) forms the first material flow into a cylindrical flow and divides the second material flow into eight equal flow portions. A spider structure (300) has a first plurality of apertures (302-308) which pass the first material flow and eight second apertures (330-344) which receive the eight second material flow portions from the manifold. Each of the eight second spider apertures has a relatively small upstream opening and fans peripherally outward into a continuous cylindrical downstream region. A non-linear restriction means (440-454) provides a greater restriction in longitudinal alignment with the center of each of the second apertures and a less restrictive region therebetween. The nonlinearity of the nonlinear restrictive region is the inverse of anticipated axial velocity gradients in the second material flow such that it averages out any velocity gradients in the second material flow.
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