GB1135213A - Improvements in or relating to manufacture of moulded articles - Google Patents

Abstract

1,135,213. Moulding cable sheaths or dielectrics. H. M. POSTMASTER GENERAL. 10 Dec., 1965, No. 52668/65. Heading B5A. Polyethylene dielectric is reinstated by the moulding thereof between joined inner conductors (3, 4) (Figs. 1 and 2, not shown), and unjoined outer conductors (5, 6), of two coaxial telecommunication cables (1, 2), by enclosing the unjoined dielectric within a longitudinally split mould (7) with the moulding space loaded with polyethylene string, slugs, tape, granules or split cylindrical pre-cast form, whereby the mould (7) is heated by an electric heating element and molten polyethylene is injected under pressure, from suitable apparatus connected to the mould, to complete filling of the mould (7), and the pressure is maintained until the moulding has cooled. After joining the outer conductors (5, 6) the polyethylene sheath is completed between the cable outer sheaths (9, 10) by repeating the process or by using a polyethylene sheath to cover most of the length and joining this at either end by a similar moulding process, using a shorter mould. The mould (7) is water cooled at either end (7a) and is provided with cooling fins (7b). Suitable portable injection moulding apparatus is mounted about a collar 23 located between a stainless steel injection barrel 24 on an electrically heated barrel extension 25. Curved legs 20 are pivotally connected at 21 to a collar extension bracket 22 and loaded by springs 28 connected to stub axles 26 projecting on either side of the collar 23 providing an over centre action to hold the legs 20 in either the full line moulding position when the legs 20 may be inserted into support tubes, or a retracted position shown in dotted lines. The injection part of the apparatus is mounted about a pair of guide rods, e.g. 33, connected at one end to a plate 34 and pivotally at the other end to the stub axles 26 whereby, with the injection piston 39 fully retracted, a stepped 47 and chamfered 49 open end of the bore of barrel 24 allows the injection ram 40 to be pivoted on the rods 32, 33 to a vertical position to permit loading of the barrel 24. The ram is slidably mounted in a bearing block 37 at one end and is fixed at the other end to a thrust plate 36 slidable along the guide rods 32, 33 under the action of a manually operated screw 41 which engages within the ram 40 and which is formed with a disc 43 and fixedly carries a collar 44 between which is located a pressure plate 35 slidable on the rods 32, 33 against loading springs 45, 46 which are supported on the plate 34 whereby moulding pressure is developed by compression of the springs when the piston 39 is advanced to push the charge through the nozzle 50. The moulding pressure developed may be measured by the position of pressure plate 35 along a right hand scale of a graduated rod 38 and the position of the piston head 39 in the bore of the barrel 24 is indicated by the position of thrust plate 36 along a left hand scale on the rod 38.