Helically convoluted plastics tube mfr. - by helically winding a wire over a plastics tube on an undersized non-rotatable mandrel

摘要

Helically convoluted plastics tube is made by locating a plastics tube over a slightly radially undersized non-rotatable mandrel and passing the mandrel through a head which helically winds a wire under tension about the plastics tube. The wire impresses convolutions into the plastics tube, which are retained either by cold or hot setting. To form convolutions of small pitch the wire wound tube may be axially compressed upon the mandrel before setting. Compression may be effected by clamps slidable along the mandrel or by locating a stretched spring over the mandrel prior to applying the tube and after winding with wire allowing the spring to contract. The method is partic. useful in making pressure hose or electrical conduit, the wire being retained on, or removed from, the tube.