Nozzle assembly for plastic extrusion press - has heated duct with separate and interchangeable component contg. nozzle orifice

摘要

The extrusion nozzle assembly is for a plastic extrusion press. It comprises a flow duct (2) through which the plastic passes to the nozzle orifice (9) and means, such as an electric heating coil in an annular space (4) around the duct wall (1), to heat the plastic as it passes through the duct. The orifice is arranged in a separate component (10) connected (14,15) with the duct, e.g. by a screw connection. The duct may be formed by the bore of a cylindrical tube (1) co-axially arranged in an outer housing (3) having an inward flange (8) at the end with a bore to centralise a collar (11) provided on the component (10). The arrangement permits the inner duct wall and the nozzle orifice to be independently, and thus accurately, machined. It facilitates cleaning of duct and orifice, enables installation of different-size nozzle orifices and permits coating the inner duct wall and/or orifice, e.g. with PTFE. It further absorbs differential thermal expansion between duct wall (1) and housing (3) (seal ring 13).