| 摘要 |
1,124,656. Double walled pipes. POLVANEDERLAND N.V. 13 Sept., 1965 [14 Sept., 1964], No. 38957/65. Heading F2P. A tube has an inner wall 1, an outer wall 2 and webs extending spirally about the axis of the tube. The webs may be straight or curved and vertical or inclined radially, forming the sides of a geometrical figure. The tube is made from an extruded plastics strip similar to that in Fig. 1 by winding the strip spirally on a mandrel and securing the webs of adjacent turns together with adhesive or by heat welding. Overlaps as at 4 and 7 may be provided which, when wound, lie in rebates as at 5 and 6. Alternatively, snap fastening joints which interlock may be formed along either edge of each strip (Fig. 4, not shown). |
