seen and device for framstellning of plastror with cirkuler tversektion, including an outer row and an inner row

摘要

An apparatus for forming a plastic pipe having a circular cross-section and elongated longitudinal channels in the pipe wall is disclosed. A mass of synthetic plastic material is pressed through an annular space defined by inner and outer annular supports, the annular space having a plurality of spaced pin supports concentrically disposed therein and regulating the quantity of material flow through the annular space, depending on the shape of the pin supports, by selectively moving the walls of the annular supports closer to each other. In a particularly advantageous embodiment, either the wall of the inner annular support or the wall of the outer annular support, or both, are moved closer to each other in the area between adjacent pin supports.