GB711967A - Improvements in or relating to the manufacture of metal cable sheaths - Google Patents

Abstract

711,967. Sheathing cables. BRITISH INSULATED CALLENDER'S CABLES, Ltd. May 29, 1952 [May 30, 1951], No. 12758/51. Class 83 (4) Extruding; drawing; rolling.-In a method of extruding cable sheaths of lead, lead-rich alloy or aluminium the internal and external surfaces of the extruded sheath are simultaneously operated upon to displace metal from the wall areas of greater thickness than the nominal thickness to areas of less than the nominal thickness thereby reducing inequalities in the wall thickness' of the sheath. Apparatus for carrying out the method comprises a die box 1 consisting of upper and lower parts 2, 3, recessed to form a bore into which is positioned a tubular mandrel 4 which forms an annular chamber 6 into which a pair of passages 7 lead from an opening 8 in the upper part of the die box. The front end of the mandrel carries an externally conical point 9 which co-operates with an outer die 10 to form an annular extrusion orifice. The die is retained and adjusted by a ring 12 positioned by wedge bolts (not shown). The point 9 of the mandrel has a tubular extension or internal gauging member 15 which projects beyond the die and terminates in an external conical surface 16 which co-operates with a stationary external gauging member 21 mounted on the die box to exert a squeezing action on the portions of the extruded sheath wall that are of greater thickness than the nominal. The gauging members 15, 21 form an annular orifice of gradually diminishing diameter. The member 21 is held in place by a frame 24 and laterally adjusted by bolts 26. Correct spacing between the gauging surfaces 16, 23 is ensured by shims 27. The temperature of the member 21 is regulated by coolers 28. The member 21 may be given a rotary motion in which - case it is housed within a sleeve, 29, Fig. 3, rotatably supported in ball and roller bearings in' a stationary sleeve 33. The front end of the sleeve 29 carries a gear wheel 35. The outer member may consist of two or more shoes 41, Fig. 4, on shanks 40 housed in grooves 39 in a disc 36 having a toothed rim 37 said disc being rotatably mounted on the die box. The shoe shanks are slidably held in the grooves by a cover plate 42 adjustably bolted to the disc 36. Frustoconical rollers 48, Fig. 5, may take the place of the shoes 41. These rollers are set in a cage 49 and are driven by engagement with a conical face 56 on a driving sleeve 57 supported in a bearing 58 housed in the die box and driven by a gear wheel 59 mounted on the sleeve. The rolls and their bearings are lubricated by bitumen fed through passages 61 and 62. Adjustment between member 15 and the rolls is effected by the use of thrust pads 54 and axial adjustment of the sleeve 57. As the rolled sheath 64 emerges from the sleeve 57 a sinking die 63 reduces the sheath in diameter to fit the cable core 18. When sheathing a cable the cable core 65, Fig. 6, is fed from a reel 66 and passed through a sheathing press 67 and gauging device 69 after which the sheathed cable is allowed to form a loop between the gauging device and a sinking die 70 through both of which it is drawn by a capstan 71 and then wound on a reel 72. A jockey roller 73 rides on the loop and as it rises and falls due to fluctuations in the delivery speed of the sheathed cable from the gauging device it adjusts the speed of the motor 74 driving the capstan 71 by means of a regulator 75. The extruded sheathing may be cooled by an air blast or water spray and also lubricated before entering the gauging device. Specification 644,690 is referred to.