Flow channel cross-section varying mechanism for an extrusion process comprises a thin flexible inner wall which is not persuaded and whose wall can be varied over a larger area

摘要

At least part of the flow channel wall comprises an elastically deformable sleeve (2) with a wall thickness of /- 1 mm and local deformation of the sleeve is effected by an external control member (3) to produce profile changes in the extruded product. Independent claims are also included for: (a) a process in which the wall thickness at points on an extruded hose is varied by local deformation of a thin sleeve (2) during the extrusion; (b) a hose extrusion process in which the wall thickness is measured after leaving the die and compared with a set value stored in a computer which automatically adjusts the control members (3) and hence the sleeve; (c) a process for multilayer hose production where several independent layers are brought together before the end of the flow channel in which the thickness of one layer is periodically varied or the individual layers are selectively measured at a position and the computer then adjusts the control members and hose thickness.