Screw extruder for the continuous extrusion of thermoplastic materials

A screw extruder for the continuous extrusion of thermoplastic materials, comprising:

• (a) a main extruding screw rotatably mounted in a housing therefor, said thermoplastic material being fed to and mixed by said main extruder screw, said housing defining an outlet feed passage at the bottom of said main screw;
• (b) a first cylindrical chamber extending transversely to the axis of said main screw and communicating with said outlet feed passage;
• (c) a first transverse screw mounted in said first cylindrical chamber, said screw having conveying screw lands formed thereon which extend laterally outwardly from said outlet feed passage so as to convey said material laterally away from said feed passage to an outer end of said chamber;
• (d) means adjacent said first cylindrical chamber for cooling said material as it is mixed and laterally conveyed;
• (e) a second cylindrical chamber extending transversely to the axis of said main screw and spaced from said first chamber, said second chamber communicating with an extrusion outlet orifice positioned generally below said outlet feed passage;
• (f) a second transverse screw mounted in said second chamber and having screw lands formed thereon which extend laterally outwardly from said extrusion outlet orifice, the pitch of said screw lands being such as to convey material delivered to an outer end of said second cylindrical chamber toward said outlet orifice;
• (g) means adjacent said second cylindrical chamber for cooling said material as it is mixed and conveyed toward said outlet orifice, and
• (h) connecting passage means intercommunicating the outer ends of said first and second cylindrical chambers,
• whereby said material is thoroughly mixed and conveyed from said main extruding screw, laterally outwardly through said first chamber, through said connecting passage means and said second chamber to said outlet orifice.