plastic piping, and method and device for manufacture of plastic pipes

摘要

1278332 Welding; moulding pipes KAMPHUIS KUNSTOFFEX NV 29 Aug 1969 [4 Sept 1968] 43119/69 Headings B5A and B5K [Also in Division F2] A method and apparatus are described for making a pipe, e.g. a sewer pipe, from a plastics strip having a cross-section with one or more projections which form helical ribs when the strip is helically wound and welded or cemented along the helical seam to form the pipe, the seam running between adjacent ribs. In a preferred embodiment the strip (Fig. 2) is produced by extrusion, and the projection is a hollow trapezoid, with the shorter parallel side 2 on the outside of the pipe, to prevent the projection ribs from bending over during the making of the pipe, or when subsequently under load, and the sum of the thicknesses of parallel wall 1 and 2 being substantially equal to the thickness of web 5. Sides 6 of the strip may be bevelled to form a channel to facilitate welding or the edging portions of web 5 may be formed into complementary ribbed and grooved sections (Fig. 4, not shown), those on adjacent turns engaging one another as the pipe is wound, the overlapping portions each being half the thickness of the remainder of web 5. After extrusion the strip may be passed into a cooled vacuum shaper of helical internal profile, and thus directed into a helical path, and formed into a pipe, the turns being welded together as the pipe leaves the shaper. Alternatively the strip may be wound on a mandrel and the turns joined together before the pipe thus formed is fed through a vacuum shaper in which the projections and seams are given finishing treatment. The seaming may be carried out by hot air directed by nozzles, by high-frequency or ultrasonic welding, or a weld filler strip may be inserted into the then V-shaped groove formed by the chamfered edges. Alternatively the edges are butt-welded. A synchronized saw may be provided to cut the pipe into lengths.