Manufacture of helical turbulence-inducing members

摘要

An extruder 20 has an outlet 26 fitted with a rotary nozzle 34 formed with a slit orifice to extrude a flat plastics strip which emerges downwardly. In operation the nozzle is rotatingly driven, so as to twist the strip into a helical configuration which is cooled and solidified by a water bath 42 where it passes around the guide rollers 44 and 46. The twisted strip is advanced by a drawing device 48 and wound on a reel 52. When cut into lengths the twisted strip forms turbulence-inducing members for insertion into e.g. domestic radiators. The member may be extruded from a nozzle slit comprising a single diametral arm, or a plurality of radial arms (36).