| 摘要 |
Longitudinally extending identifying strips (24) of polyethylene, are distributed around the circumference, on the surface of a steel pipe (17) or like elongate article sheathed with polyethylene, the sheating of which is formed by simultaneous extrusion of a tubular foil (19) of ethylene copolymer serving as contact adhesive and of a tubular polyethylene foil (24) lying over it, using an extruder head with two ring channels (6,11) from which the foils are extruded. The labelling strips are applied in the longitudinal direction during the extrusion process, by delivery into the extrusion channel (11) of the tubular foil (24), at an extrusion pressure greater than that of the tubular foil, via an extruder head inlet (20), ring channel (21), and openings (23) into the channel (11). <IMAGE> |
