Improvements relating to a process and means for improving the transverse strength of tubes produced under pressure by ring-shaped nozzles

摘要

A fibrous plastic mass of animal or vegetable origin is extruded from an annular nozzle inside which it is pressed through annular channels of increasing diameters and expanded in a transverse direction before extrusion as an artificial tube. The mass may be shaped initially in the extrusion device in a cylindrical portion having an annular channel of small diameter and expanded in a further annular channel of larger diameter. Advantageously the distance between the walls of this further channel may be gradually increased. The further portion of the annular channel may have the shape of a frustum of a cone or may be dome-shaped. As shown, the extrusion device may be formed from two bodies 1 and 2 provided with a central bore and joined together by threaded engagement. A core 3 of smaller diameter is arranged within the bore and is secured by a thread and nut to body 2. Adjusting screws 5 maintain the core centrally, thus forming a cylindrical channel 6. A forked pipe 11 supplies the plastic material through channels 7, 8, 9 and 10 (formed by grooves in one body and walls in the other) to the cylindrical channel 6. A hemi-spherical dome-shaped member 15 is secured to body member 1 and forms with the dome-shaped member 12, which is attached to the core 3, the extension of the annular channel 6. This gap 16 may increase in width as it approaches the extrusion orifice.