Patent GB-986882-A (GB)
Title: Improvements in joints for pipes or like members made of resin
Inventor: BAKER WILLIAM ANDREW
IPC: B29C65/48
Filed: 1960-05-03
Abstract: 986,882. Pipe joints. BRISTOL AEROPLANE PLASTICS Ltd. Aug. 3, 1961 [May 3, 1960; Nov. 29, 1960], Nos. 15571/60 and 41006/60. Headings F2G and F2P. In a method of joining together two pipes of synthetic resin, a spigot on one pipe 4 having an electrical resistance wire wound round it is inserted into a socket on the other pipe 2 and into a position in which the spigot and socket define between them an annular space of small but finite width, the space being bounded by annular seals but having inlet and outlet openings, and a fluid resin is injected into the space until it is filled, the resin then being cured by heating by passing a current through the resistance wire so that the resin bonds the spigot and socket together. As shown, the socket has an internal shoulder to limit inward movement of the spigot, the latter being provided with a groove for a rubber sealing ring 14 and helical grooves for reception of the wire 30. The pipes have flanges 10, 12 the axial gap between which is sealed by an annular rubber band 20, and a resin inlet hole 22 for injection of resin into the space 23 is provided in the socket, while the flange 12 is formed with air outlet hole or holes 24; the holes are closed by rubber bungs 26, 28, that for the hole 22 being in the form of a cup having a slit in the bottom thereof and acting as a non-return valve for resin supplied through a hose to a nozzle pressed into the cup. The flanges are held together temporarily by clamps 18. In making the pipes, prefabricated " olives " of moulded resin reinforced with fibre, e.g. epoxy resin and chopped acrylic fibre, are placed on a mandrel on to which and the olives is wound a layer of resin-impregnated acrylic fibre tape, layers of resin-impregnated glass rovings to form the main structure of the pipes and an outer layer of resin-impregnated acrylic fibre tape; the " olives " which form the shoulder 8 and outer end of the spigot are frusto-conical in form; alternatively, the " olives " are built up on the mandrel as a preliminary to helically winding the remainder of the reinforcing fibres on the mandrel. In modifications, (a) the spigot and socket are tapered and a sealing ring is lodged in a groove in the external surface of the spigot, (b) the sealing ring 14 is replaced by a sealant injected into a space divided from the annular space 23 by a shoulder on the spigot, and (c) the pipes 44, 46 have the ends reduced in diameter and are provided with tapering grooves 50, an inner sleeve 40 being positioned to cover the grooves and flanges 52 and the grooves being filled with sealant 48 which is injected through holes 54 in the sleeve until it escapes from the ends of the sleeve or, alternatively, the sealant is confined by sealing rings or shoulders on the pipe ends and vent openings are provided in the sleeve; an outer sleeve 42 is held in position by pads 62 and short rubber sleeves which close the annular space for the resin may act as non-return vent valves, or the resin is confined by sealing rings, or shoulders and vent holes, subsequently closed by bungs, are provided in the sleeve.