Extrusion strip die for thermoplastic sheet

Claim 1

A strip die for the extrusion of high melt viscosity thermoplastic materials into sheets comprising a pair of spaced die sections including a relatively thin broad channel of generally flat configuration therebetween including means for laterally distributing thermoplastic melt therein, an inlet into which molten thermoplastic resin may be fed for delivery to the channel, a pair of lips through which the thermoplastic melt can be extruded in generally sheet-like configuration, and valving means including a plurality of individually adjustable laterally contiguous segments for varying the spacing of the channel in transverse increments, each of said segments including one flat face oriented substantially parallel to the path of travel of the advancing melt stream and one inclined flat face oriented at an acute angle with respect to said advancing melt stream, said inclined faces lying in substantially a single plane, and means for adjusting each of said segments along corresponding axes parallel to said plane so that only parallel inclined faces confront the advancing melt stream while said first mentioned flat faces define channel walls to effect streamlined flow of the melt stream with a smooth profile conforming substantially to the channel configuration as the valve segments are interposed therein.