Patent GB-780677-A (GB)
Title: Improvements in or relating to process and apparatus for making reinforced plastic bars, tubes and like elongated stock
IPC: B29C35/14
Filed: 1955-05-13
Abstract: 780,677. Moulding fibre-resin rods, tubes &c. THOMPSON FIBER GLASS CO., H. I. May 13, 1955, No. 13892/55. Class 87(2). [Also in Group XI] An elongated fibrous body is impregnated with thermosetting liquid resin and pulled through a shaping die formed of an electricallyinsulating material having a low dielectric loss factor, and the resin is set by dielectric heating as the body passes through the die. Fibres 10, Fig. 2, are pulled from spools 14 by pulling clamps 26, 27 and pass through a resin bath 15, through an apertured plate 19 fixed to the bath, and into and through a shaping and curing die 21, where the resin is polymerized to a hard condition by high-frequency dielectric heating. The die 21 comprises a block of polytetrafluoroethylene, glass, steatite, forsterite, quartz, polystyrene foam or other material having a low loss factor. This block has conduits 33, Fig. 6, through which the resin-coated fibres pass, and the conduit entrances 34 are flared. (In a modification the conduits may be formed as tubular inserts within the block). The block is surrounded by an aluminium &c. holder 37 which forms the earth electrode of the H.F. heater, the other electrode being a silver-plated brass member 39 disposed within the block. The effective length of the annular heating zone thus formed may be varied by shifting the electrode 39 axially. The electrode 39 and die-holder 37 may be cooled by air from a fan, or cooling passages may be formed in the electrode or adjacent the die holder to receive liquid coolant. After the resultant fibre-reinforced rods 11 (or tubes, channel-sections or I-sections) pass through the pulling clamps 26, 27 they are cut off by a saw 46 mounted on a rolling carriage 47. When a tube 11a, Fig. 25, is being formed the electrical lead 44c to the inner electrode 39c, and the mechanical support 44d for that electrode, are positioned in advance of the inner and outer polytetrafluoroethylene dies 21c, 21d, so that the resin-impregnated fibre separates as it passes these members and re-forms in the shape of a tube before it enters the annular space 33c. The resin may be polyester, phenolic, diallyl phthalate, silicone or epoxy. The fibre may be loose roving, loosely spun or woven as a tape or sleeving or cloth, and may be glass, nylon or jute. The two pulling clamps 26, 27 Figs. 11, 13 and 14, alternately advance, grasp and pull with an action overlapping in time, in the manner of pulling a rope with two hands. not hand-over-hand but with one hand constantly behind the other. The leading clamp 26 comprises a box-like housing 90 which is slid to and fro on stationary bars 50 by two cams 64 (only one can be seen in the drawings) which act through levers 65. The sides 91 of the housing have forwardly-convergent wedge guides 95, 96 within which slide side extensions 100, 102 of two clamping jaws 97, 98 which surround the reinforced-fibre rods 11. The jaws are normally urged towards the closed position (leftwards) by light springs 109 acting through levers 105, 107, 108. At the beginning of a cycle of operation of clamp 26, the jaws are in the position shown in Fig. 13. As the jaws begin their rearward (rightward) pulling stroke they do not at first grip the rods 11 because they are moving more slowly than the rods, but permit the rods to slide through them (the rods being pulled at this time by the similarlyconstructed-and-operated clamp 27). When, however, clamp 27 slows down, the speed of clamp 26 equals and for an instant exceeds that of the rods and the jaws 97, 98 frictionally engage the rods and slide forwardly (leftwards) in the guides 95, 96 so that the jaws clamp tightly on the rods and pull them along. When clamp 26 slows down for the leftward recovery stroke the other clamp takes over the pulling and rightward pressure on the jaws moves them in their guides so as to loosen their grip and permit the rods to slide between them.