Abstract: The present disclosure is directed to a centering device for shaping tools for extrusion presses, wherein an outer mandrel together with an inner mandrel define a through gap for plastic extrusion material which device has a plurality of centering members supported on the outer mandrel which are distributed over the periphery of a radial plane and which are adjustable in the radial direction and which are constructed in the form of push rods guided for radial displacement. Each push rod (6,106) has associated therewith an individually adjustable drive, an adjustable lever (7,107) supported for pivoting on the outer mandrel and which are actuable by means of a tightening device (8,108) and form a transmission gear for applying the tightening force.

Abstract: 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.

Abstract: Method and extruder for manufacturing plastic pipes provided with longitudinal channels in its wall. Before the extrusion nozzle of the extruder, the stream of plastics to be extruded for forming the pipe is subdivided into two concentric annular streams flowing through two annular division channels formed by means of a dividing member being retained by only a breaker in the outer division channel, the other division channel forming a free passage between the channel inlet and the outlet.