초록 ▼

The twin-nozzle extrusion head in accordance with the invention includes basically three axially spaced but radially overlapping annular housing members, together establishing two nozzle gaps and a first and a middle one of the two members are provided with annular feeder ducts for these nozzles. Ea

The twin-nozzle extrusion head in accordance with the invention includes basically three axially spaced but radially overlapping annular housing members, together establishing two nozzle gaps and a first and a middle one of the two members are provided with annular feeder ducts for these nozzles. Each of these ducts has on its exit side a baffle ring wherein one baffle ring is effective on its radially inner surface while the second baffle ring is effective on a radially outer surface of larger diameter. These surfaces are nonround in a particular determined manner to establish nonuniform gap width related directly to the location of feed ducts for the annular channels, generally, the gaps are wider in locations away from a proximity of such feed ducts. The nozzle gaps are both frustoconical of different steepness and terminate in a common plane. The nozzles are particularly provided for disposing an adhesive on top of a steel pipe and a polyethylene coating and envelope on top of the adhesive.

대표청구항 ▼

Twin nozzle extrusion head for depositing two layers in superimposed relationship upon a pipe comprising: a first annular housing member having a first annular channel and duct means for feeding the channel; a second annular housing member being disposed generally and in axially displaced relationsh

Twin nozzle extrusion head for depositing two layers in superimposed relationship upon a pipe comprising: a first annular housing member having a first annular channel and duct means for feeding the channel; a second annular housing member being disposed generally and in axially displaced relationship to the first member; a first removable but unadjustable baffle member interposed between the first and second members and having a radially, inwardly directed, non-round, throttling surface, deviating from a circular contour, for providing a narrow annular exit gap from the annular channels; the non-round baffle surface facing a round exit gap to provide therewith a gap varying in width in azimuthal direction, with a smaller gap width adjacent the duct means; the first and the second members defining a straight frusto-conically shaped extruder nozzle duct extending from said exit gap in slanting relation towards a nozzle exit; the second member having a second annular channel and duct means, the channel being of larger diameter than the first channel means; a third annular housing member disposed in axially spaced relation to the second member, the second and third members together defining a second extrusion nozzle terminating close to said first nozzle duct; and a second removable but unadjustable baffle ring interposed between the second and the third members and having a radially outwardly directed, non-round throttling surface of larger diameter than the throttling surface of the first baffle ring, for providing a narrow gap betwen the second annular duct and the second nozzle gap; the second nozzle gap having a round surface facing the non-round surface of the second ring to provide therewith a gap varying in width in azimuthal direction, with smaller dimensions adjacent the duct means in the second member.