An electrically operated apparatus and method for altering the flow resistance experienced by a thermoplastic passing through a flow channel using one or more thermal valves having a short response time is described. The extrudate configuration of thermoplastic emerging from one or more extrusion orifices...http://www.google.com/patents/US6238613?utm_source=gb-gplus-sharePatent US6238613 - Apparatus and method for thermoplastic extrusion
