Method of reinforcing flattened tubular film with tape layers

摘要

A flattened tube of continuous film is opened up by being fed over a mandrel which is floatingly disposed within the tube. As the tube is passing over the mandrel, which serves as a backing, a layer of reinforcing tapes is helically wound thereabout and fixed thereto, whereafter the tube is flattened again. Each side of the tube is then successively provided with a layer of parallel further reinforcing tapes which are anchored by a plastics covering layer that is extruded thereon and pressed thereto.