Patent GB-973211-A (GB)
Title: Electric tape cables
IPC: H05B3/16
Filed: 1959-12-11
Abstract: 973,211. Heating cables. P. EISLER. Dec. 12, 1960 [Dec. 11, 1959], No. 42253/59. Heading H5H. [Also in Division H1] A flat strip cable, which may be a heating cable, comprises a plurality of flat conductors, each enveloped in a separate prefabricated sheath, the sheaths being joined together but the conductors being free from adhesion to the sheaths over at least a major portion of their length. The conductors are preferably of crimped foil of copper, aluminium, brass, steel, lead, cupro-nickel, or nickel-chrome and the insulating sheaths of nylon, polythene, P.V.C., P.T.F.E., or polyester, polycarbonate or polypropylene film, or asbestos, glass fibre or quartz fibre tapes, or neoprene. Each crimped conductor 11 (Figs. 1 and 2) is enveloped in a sheath 12, the overlapping edges of which may be joined by adhesive or by heat treatment, the sheaths being similarly secured to an insulating layer 13. The face of the cable opposite the layer 13 may have a pressure-sensitive adhesive layer 14 covered during storage by a layer 15 for example of crepe paper. The insulating layer 13 may be on either or both faces of the cable and may itself be provided with the pressure-sensitive adhesive. The insulating layer 13 may be omitted if the outer overlapping portion of each sheath 12 is made long enough to overlap a neighbouring sheath, to which it is secured (Figs. 3, 4 and 5, not shown). The individual foil conductors may alternatively be sandwiched between two layers of thermoplastic insulation, heated cutting tools separating the necessary width of insulation and sealing the top and bottom layers at both edges of the conductor or at one edge only, the other being folded (Figs. 8-11, not shown). For convenience of making junction or terminal connections, the conductor strip may be pleated transversely at intervals, before covering with the insulating wrapping, so that when the insulation is cut near a pleat a connecting element may be inserted in the fold of the pleat (Figs. 12 and 13, not shown). In order to strengthen the cable a filament may be secured throughout the length of the cable between the overlapping edges of the insulation 12 (Fig. 14, not shown). When used as a heating tape, a meander pattern is obtained by slotting a wide strip of foil 71, as shown in Fig. 21. A strip of insulating film is then located along the length of the tape below each longitudinal row of slots, and having the plane of the insulating film perpendicular to the plane of the foil 71. The upper edge of the insulating strip is cut away so as to avoid the " bridges " between the ends of the slots. Thus, if the foil and insulation are moved along in a gradually converging manner, the insulation will rise through each slot and as they pass a blade member 73, the projecting portions of the insulation are folded flat, as shown, and stuck together by heat or adhesive. The insulation inserted in a slot may be one, two, or three layers thick and suitable ways of achieving this are described (Figs. 17-20, not shown). The insulation may be in the form of a single wide film pleated into longitudinal folds corresponding with each line of slots, the folds being suitably castellated to avoid the " bridges " (Figs. 15 and 16, not shown). When the insulation employed is asbestos, glass fibre, or quartz fibre, tape, the sealing medium used is a refractory cement which sets as a thin brittle layer. The enveloped conductors are then taken round small rollers in order to break the cement layer into narrow flakes and so maintain the flexibility of the cable. Specifications 900,516 and 900,519 are referred to.