Improvements in extruder screws

摘要

An extruder has a barrel 1 with screw section 9 of large diameter and coarse pitch and screw section 10 of smaller diameter and finer pitch, both separately rotatable therein in the same sense to move material from solid inlet 6c to melt outlet 8c. Sections 9 and 20 are separate, coaxial screws having either separate gear control from a single motor, or separate motor drives through motors 4, 5 separately controlled by gearboxes 20, 21 respectively. Thus feed section 6 of the barrel, fed through orifice 6c with non-uniform scrap polymer is controlled separately from metering section 8 feeding outlet 8c whereby non-uniformity of feed does not overload the extruder. Separate control can be effected by feedback of pressure signals to the motors or gearboxes. End seal 19 can be water cooled.