Backflow valve in extruder head - sealing ring moves backwards to close polymer flow when screw moves forwards

摘要

A backflow valve on the screw head of an extruder has a moving pressure ring located between front and back stop faces and sliding on its outer face along the barrel wall. On its inner face it has a gap for polymer to flow through, and it has a sealing surface for the back stop face. At the front of the pressure ring the gap is closed by a backflow valve device.. Design is simple and quick acting. No loss of material occurs even if its viscosity is low and hence provides constant shot weight.