METHOD OF AND MEANS FOR FORMING AND SEALING HELICALLY WOUND TUBES

摘要

A strip (1) adapted to form a tube by helically winding and having a series of longitudinal ribs (2) upstanding from a base on the strip and transversely spaced thereon in which one rib (4) has a bulbous end portion (9) and another has a bulbous longitudinal socket (5) to form interengaging means when helically wound, all or some ribs optimally defining a hollow (20) whereby limited lateral stretch at the join and ribs is permitted. The hollow (5 or 20) can be closed by a flap (16). In various embodiments the ribs take a number of forms. In most cases all ribs are hollow and of substantially rectangular or semicylindrical shape to give a corrugated external form. A panel formed by winding a strip to helical form and splitting the strip longitudinally and straightening it at least partially to form a draining wall is also described and claimed.