Nozzle assembly for extruding a synthetic-resin tube

Abstract

A nozzle assembly for extruding a tube has an outer housing sleeve having an inner surface centered on an axis and having an axially forwardly directed front end and a core formed of attached-together front, intermediate, and rear core ports. The front core part lies within the sleeve at the front end thereof and forms with the inner housing surface an annular axially forwardly open extrusion passage. The intermediate core part lies within the sleeve axially behind the front core part and is formed with a pair of grooves opening radially outward into the passage and each defined by a respective annular rear face extending generally perpendicular to the axis, a respective annular front face confronting the rear face and extending generally perpendicular to the axis, and a heart-shaped annular surface axially bridging the respective faces, facing radially forward, and having a portion forming a radially forwardly directed point. The rear core part lies within the sleeve axially behind the intermediate core part and axially rearwardly closes the passage. At least one feed passage in the rear and intermediate core parts serves for feeding a mass to be extruded under pressure to the grooves at locations therein generally diametrally opposite the respective points. Each of the grooves has its region of greatest radial depth at the respective location and the feed passage opens radially into the grooves.