GB894075A - Improvements in insulated cable - Google Patents

Abstract

894,075. Electric cables. ANACONDA WIRE & CABLE CO. Oct. 31, 1960 [Dec. 29, 1959], No. 37326/60. Class 36. An electric cable having a plurality of tubular conducting layers surrounding the core formed by providing pairs of wrapping tapes with conductive coatings on adjacent sides only, is characterized in that the conductive coatings do not extend to the edge of the insulating strips, but leave margins, which form insulating gaps between the edges of the coating on consecutive turns of one tape, the gaps being bridged by the conductive coating of the other tape. In the cable of Fig. 1, the conductor assembly 11 is first surrounded by an uncoated insulating layer 19, of paper, polyethylene, polyethylene terephthalate or rubber, possibly saturated with oil. Alternatively a tape with its conducting coating facing the conductor, may be used. Gaps 14 are left between consecutive turns to prevent the tapes buckling when the cable is bent. A second layer of tape 12 is formed having a thin conducting layer 15 of aluminium or other metal or non-metal foil, bonded to the tape 12 by an adhesive 16, or applied as a spray or by evaporation methods in vacuo, and covering only part of the tape, leaving insulating margins 17, 18. A third layer of tape 22 is wound having a part-covering layer of conducting material 15, but with the conductive coating towards the conductor 11, and so positioned that the non-conductive gaps 14 are bridged, and the conductive coatings of the two layers of tape combine to form a continuous conductive cylindrical layer. This process can be repeated, forming a second conductive layer, or an intermediate layer of non-conducting strip can be wound (Fig. 2, not shown) to increase the length of the leakage path 24. A discontinuity can be formed in a conductive layer, by furnishing the outward facing conductive tape with a non-conductive portion extending slightly more than once round the cable, and wrapping round this an inwardlyfacing conductive tape with a smaller non- conductive portion, positioned above the adjacent non-conductive regions of the two consecutive turns of the inner tape (Fig. 5, not shown).