Mixer block for feeding melt from an extruder to an extruder has a ring of outer channels flowing to inner outlets and a ring of inner channels flowing to outer outlets

摘要

The block separates an extruded melt flow into several flows passing through channels (36, 38, 40; 41, 42, 44). Melt flows which are radially outermost at the inlet side are diverted during passage through the block so that they become the innermost flows at the outlet end. Conversely the inner melt flows at the inlet become the outer flows at the outlet end. Inlets (24, 26, 28, 30, 32, 34) of a first group of channels (36, 38, 40) surround inlets (46, 48, 50, 52, 54, 56) of a second group of channels (41, 42, 44). Inlets of the first group of channels form a ring around the inlets of the second channel group and outlets of the second group of channels form a ring surrounding outlets of the first channel group. Each inlet and outlet has a trapezium cross-section with circular arc bases. Inlets and outlets surrounded by the outer rings form circles and each inlet or outlet has a triangular cross-section with an outer shank following a circular arc. All channels run along a straight path at an angle to the block axis (58). Channels may have a different cross-section to that of their inlets and outlets. The block has between 6 and 18, preferably 12 channels and forms an insert in an extrusion die and/or extruder. Channels may comprise three or more sections each with a long axis at 0-45[deg] to the block axis.