GB803260A - Method of and means for making strengthened pipes or other articles from plastic or other material - Google Patents

Abstract

803,260. Moulding tubes and rods. FRENKEL, M. S. Feb. 8, 1955 [Feb. 17, 1954; Nov. 9, 1954], Nos. 4719/54 and 32388/54. Class 87(2). A screw-threaded member, in which the crosssectional areas of the grooves of the thread vary inversely with the radial clearance between the member and a co-axial member, may be used either as an extrusion screw for extruding tubes or rods or as the outer component of a sizing die. In Fig. 1, the screw-threaded member is shown as an extrusion screw 10 rotating within a cylinder 11. The screw is a four start thread having a zero depth at the entry 14 increasing to a maximum through the section 15 and then decreasing to zero depth again through the section 16. Longitudinal ribs 18 may be provided on the member 11 to prevent the material from rotating with the screw at the exit end 17. Passages may be provided in the outer member or the screw may be hollow, see Fig. 2 (not shown), for the circulation of steam. Air or other gases are allowed to escape through the outer member 11. In a modification, Fig. 6 (not shown), the mean diameter of the screw may increase only slightly. In a further modification, Fig. 10, a tube may be formed from three heated strips of Z or U-section which may contain a reinforcement by winding the strip 41 about a stationary mandrel 40 by means of a rotating tool 42 having a thread 44 having members 45 which acts to heat the strips by friction. A spring-urged plate 46 applies axial pressure to the strip. The formed tube may pass through a further rotating tool 48 also provided with an internal thread 50. This tool may rotate in the opposite direction to the tool 42. The strip may be pre-heated by passing it about a shaft 52 having friction members 56. In another modification, Fig. 12, two rotating tools 63, 62, each having friction heating elements 67 form a tube having two layers. The first friction heating element 67 of the ring 62 is bent at right angles at 73 to heat the adjacent surfaces of the tube. Alternatively, Fig. 13 (not shown) the strips may be preheated by passing them through two rotating tools. As shown in Fig. 14, a pipe may be expanded by passing it over a mandrel 82 by means of a rotating tool having an internal thread 87. As shown in Fig. 15, a pipe 92 which may come from an extruder 91 is sized by passing it between a mandrel 93 and a rotating ring 94 having an internal thread 98. The ring may be heated at 108. A wire reinforcement 102 may be introduced through a channel 104.