Patent GB-771590-A (GB)
Title: Improvements in manufacture of plastic pipe
IPC: D02G3/36
Filed: 1955-11-17
Abstract: 771,590. Reinforced plastic pipes. GANAHL, C. DE. Nov. 17, 1955 [Feb. 21, 1955], No. 32950/55. Class 99(2), In a method of manufacturing a pipe wherein glass fibres are drawn from a spool and through a liquid resin composition to thoroughly impregnate the fibres with the resin, the resin - impregnated fibres being then wound upon a mandrel in a number of layers and the resulting glass - fibre-reinforced plastic pipe being removed from the mandrel after the resin has been treated to cause setting thereof while the pipe is on the mandrel, the back tension of the fibres is maintained at the minimum practical value required to draw the fibres from the spools and through the resin. That tension is in any event sufficiently low so that the fibres are only loosely compacted in a radial direction on the mandrel and are free to accommodate shrinkage of the resin in a radial direction equivalent to substantially the full volumetric shrinkage thereof that occurs upon setting of the resin. The apparatus for making the pipe comprises a mandrel 10 advanced upwardly along the axes of a number of parallel, axially aligned, rotatable. annular tables 11 on each of which are mounted a number of supply spools 12 of multi filament glassfibre rovings or yarns 13. As.the mandrel moves upwardly at least one of the tables rotates in a clockwise direction so that the rovings are applied to the mandrel in the form of a helix having a righthand pitch, and at least one of the tables is rotated in a counter-clockwise direction so that the rovings are applied in the form of a helix having a left-hand pitch. A third table is maintained stationary so that a layer of rovings is applied longitudinally of the mandrel. The rate at which the mandrel is advanced upwardly is co-ordinated with the rate of rotation of the tables and number and thickness of the rovings. The rovings are drawn from the spools in groups of, for example, twelve parallel rovings, and are preheated by a heating device 15 prior to immersion by a device 16 in annular, dip pans 17 containing uncured liquid polyester resin composition and disposed on the tables 11. Dip pans. Each of these is formed by inner and outer rings 18, 20 and a base plate 19, Fig. 3, the ring 18 resting on a support column 21 of the table 11 and relative movement, of the pan, column and a collar 22 secured to the underside of the Ting 18 is prevented by screws 24. Secured to the collar are a number of circumferentially spaced channel members 25 extending radially from the outer surface of the ring to a heater support ring 26 and contacting the under side of and thus supporting the. plate 19. Resting on the ring 26 are heater support channels 27 each pivoted at the inner end thereof on a pin 28 secured to the plate 19; secured to each channel 27 is a U-shaped heater support bracket 30 provided with two bracket arms 31 extending inwardly over the ring 20. The channel 27 also supports a vertical post 32 the lower end of which rests in one of a series of holes 33 in the channel and the upper end of which engages an eye member 34 on the bottom surface of the heating device 15. Heating devices. A heating capacity is provided which ensures preheating of the rovings to a temperature above 200‹ F., and preferably in the range of from 400‹F. to about 800‹F., so that the rovings are at a temperature above 120‹ F. at the time of immersion in the plastic composition to en sure thorough penetration of the composition into the interstices of the rovings. Tach device 15 comprises upper and lower electrically-heated elements 35, 36, Fig. 3, slightly separated from each other to permit free movement of the rovings therebetween, the inner elements being supported by a horizontal pin 38 which in turn is supported in open-ended slots 39 in the arms 31 of the bracket 30. The outer end of the device is supported by the post 32. A bar 37 at the lower end of the device guides the rovings to the immersion device 16. The devices are adjustable to accommodate a number of arrangements of spools and rovings and sizes of pipes to be manufactured and are held in an established position by a set screw 40. Immersion devices. An immersion device, which may incorporate an ultrasonic vibrator to ensure thorough impregnation of the rovings, is associated with each heating device 15, and comprises an upper and lower row of low-friction rollers 42, Fig. '3, providing a serpentine path of travel for the rovings and mounted in centrepoint bearing screws 43 in the side frames of the device, a large-diameter flanged guide roller 44 which receives the rovings from the guide bar 37 of the device 15 and directs those rovings on to the first of the rollers 42, and a large-diameter floating roller 46 supported on the flanges of the roller 44 and on corresponding flanges of an idler roller 47. The device rests on the plate 19 of the pan 16 and is pivoted on a guide pin 48 to permit the device to move in an arcuate path, and is locked in the desired position by a nut 51 engaged on a stud 49 fixed to the plate 19 and extending through an arcuate slot 50 in the base of the device. An adjustable altitude control ring 52, under which the rovings pass, is mounted on the guide pins 48 which together with a number of uniformly, circumferentially spaced pins 53.serve as an azimuth control for the rovings. The complete pipe is stripped from the mandrel after the resin has been cured.