Patent GB-538014-A (GB)
Title: Safety core insulators
IPC: H01B17/12
Filed: 1939-10-13
Abstract: 538,014. Insulators. AUSTIN, A. O. Oct. 13, 1939, No. 27838. [Class 36] An insulator comprises an elongated loop having a layer formation and formed of fibrous material held together with a resilient binder. In Fig. 1, an insulating jacket 10, of circular or other section, is held between heads 11, gaskets 13 being provided to retain insulating oil &c., and an insulating tension link 14, in the form of a flat loop, has slits 16 to receive flat eyes 15 threaded to the heads 11, and provided with enlarged inner ends 20, keepers 17, with lateral lugs 18, being inserted in the eyes 15 to retain the link 14 ; in place of the slots 16, two separate links 14 may be provided. Shields 23, electrically connected to the heads 11 through eyes 15, may be provided to prevent electrical discharges. In Fig. 4, a link 24 of smaller section is held to one head by a U-bolt 27 and to the other by a pin 28 ; inter-locking sectional insulation 35, Fig. 6, and sand &c. may be introduced to reduce the amount of filling liquid required. In Fig. 7, the link 41 is strained by an eye 42 with a threaded end 44 passing through an expansion chamber 40 for the filling medium, a shield 49 and ground joints 43 or gaskets being provided. In Fig. 8, a horizontal insulator has a lateral expansion chamber 50, and a link or links 53, 54, held between a pin 57 carried by a forked bolt 55 and an oval pin 61. The links may be formed of canvas &c. treated with "Bakelite" (Registered Trade Mark) wound on a flat mandrel and cured in a vulcanizing &c. press. In Fig. 10, a mandrel 65, with pins 66 for engagement with driving mechanism for winding has divisions 67 to enable its length to be varied, while a mandrel 68 has separate ends 69 and springs 70 to place the fabric under tension ; the mandrels are placed between heated platens 71, 72, 73, and rams 74 to bind the fabric. The fabric may have its strongest threads lengthwise and a wide link may be initially made and subdivided into narrow links. A mandrel may be wrapped with a treated cord, and separate links may be formed by using platens with grooves. To equalize stress, each link may be in layers with slip surfaces formed as by inserting wax or waxed paper between the layers ; further, the effective length of the mandrel may be reduced during wrapping and also the tension may be increased, or the fabric &c. of the inner layers may be made more elastic than that of the outer layers, as by providing kinks in longitudinal threads &c. In Figs. 11 and 14, a link is formed by winding fabric 137 on a mandrel comprising main sections.138, 139, a wedge 140, and end pieces 141 guided by dowels 163 and bearing on spiral springs 165, all held together by side plates 142 in turn held between ears 143, 144, on drive gears 146, 147, pins 145 preventing longitudinal movement ; gears 146, 147, are driven by a belt 152 and pinions 148, and effective length of the outer turns is reduced by slightly withdrawing the wedge 140 from time to time, as by a threaded member 157 engaging a nut which is relatively rotated through a clutch 160 or belt 161 driving gears 159, or by a brake 162 controlling the gear 159. Tension is applied to the fabric by friction rolls or by a weight 169 connected by cable 168 to a gripping yoke 167, the tension varying as the weight is lifted from liquid in a container 172 ; the rate of increase of the tension may be varied by shaping the weight or said container. During wrapping, the fabric is heated as by radiant heaters, hot air blasts, operating in a heated chamber or by steam-heated rollers 173 carried by hinged arms 174. After wrapping, the wedge 140 may be forced in to stretch the layers. The link mandrel may be grooved as in Fig. 14, the finished link then having a similar form. Gas under pressure may be used instead of liquid in the insulator jacket, or together with oil &c. which will harden or polymerize.