GB874241A - Method of and apparatus for manufacturing a tubular synthetic plastic product - Google Patents

Abstract

874,241. Making reinforced synthetic plastic tubes. FOOD MACHINERY & CHEMICAL CORPORATION. Sept. 16, 1958 [Sept. 16, 1957], No. 29640/58. Class 99(2). A synthetic plastic tube formed with a plurality of superposed layers 29, 30 of resinimpregnated material is supported by and slidably moved along a rigid mandrel 10 to a zone 17 where it is supported by fluid under pressure whilst curing takes place. The tube comprises a layer 28 of polyvinyl chloride and the layers 29, 30 may be of resin-impregnated glass fibre, nylon, sisal or cotton. A stationary mandrel 10, e.g. of aluminium, has an upper tubular portion 10a, a reduced diameter portion 10b, and a lower cylindrical portion 10c. The annular space 17 is supplied with fluid e.g. air or oil under pressure from a pipe 15. Fluid is pressure regulated by a valve 19 and is heated by a heater H in the pipe 15 or by a heating coil H1 on the mandrel portion 10b. The sliding of the tube over the mandrel is facilitated by pressurized air supplied from a pipe 21 through the lateral passages 20. The mandrel portion 10d adjacent a heated curing zone 18 is cooled by water flowing through the chamber 24 by means of the inlet pipe 25 and the discharge pipe 26. The tube is pulled downwards along the mandrel by the mechanism 33. Sealing rings 27, fitted into the mandrel portion, 10c seal the annular space 17 and form the inside of the tube just before final curing. The liner 28 is formed longitudinally or as shown by helically wrapping a ribbon 34 of a thermoplastic material, e.g. polyvinyl chloride, with the overlapping edges forming a seal 44 which is sealed by the heated iron 46. Longitudinally disposed glass fibres 55 are passed through a bath of liquid resin 57 and then applied to the layer 28 to form layer 29. Glass fibre strands forming the layer 30 are helically wound over the layer 29 after passing through the liquid resin bath 71. After the tube is completley formed it is drawn through the heated zone 18 between electric heaters 31 wherein the resin is cured whilst the tube is subjected to the internal fluid pressure in the annular space 17. Whilst within the curing zone the tube is contacted by a spring-loaded rotatable wiper device 92 which smooths the partially-cured outer surface of the tube. The apparatus may also be arranged for horizontal operation.