Patent ID: 8936460
Filing Date: 2015-01-20
Classification: B29C,B29L

Abstract:
1. An extrusion head comprising: a spider having radially extending webs for supporting a central mandrel; a high volume reservoir mounted to the spider on a downstream side of the spider and the radially extending webs, the central mandrel extending into the high volume reservoir, the high volume reservoir having an axially straight annular conduit with a long length L, an inner diameter ID and an outer diameter OD with a large size difference between the ID and OD, forming an OD to ID ratio over 2:1 with a large constant annular gap G therebetween; and a set of dies mounted downstream of the high volume reservoir, whereby the high volume reservoir reduces pressure and promotes homogenization of molten polymer flowing therethrough before reaching the set of dies, in combination with the long length L, and the OD to ID ratio over 2:1 with the large annular gap C of the annular conduit, the high volume reservoir being configured to provide sufficient volume, length, radial space and pressure drop for allowing movement of molten polymer radially between the inner diameter ID and the outer diameter OD for mixing in the radial direction for reducing spider lines formed in the molten polymer by the radially extending webs.