Patent GB-1406341-A (GB)
Title: Cable joining devices
IPC: H02G15/02
Filed: 1973-09-26
Abstract: 1406341 Stress relief element for H.T. coupling G & W ELECTRIC SPECIALTY CO 26 Sept 1973 [28 Sept 1972] 45103/73 Heading H2E A stress relief element 69, Fig. 8a, comprises a first portion 121 of a compressible elastomer and having electrically conductive properties, a second portion 127 of higher dielectric strength than the first and a third portion 129 comprising a compressible elastomer and having electrically conductive properties. The three portions may be bonded together or formed as a unitary moulding. In an alternative embodiment (Fig. 10, not shown) the interface 123 bends back on itself (133) near the outer surface of the element. The outer surface of the element is very slightly tapered. Portions 127 and 129 may be made from a closed-cell sponge with a semi-conductive coating 125 of a silicone resin thereon or the entire portion is rendered conductive by impregnation with carbon particles. The sponge may be a silicone resin or copolyethylenepropylene optionally fluorinated. Portion 127 is made from a higher density sponge or a solid material. The stress relief element 69 is used in a cable connector, Fig. 2, with the first portion 121 in contact with the shield layer 45 of a high power cable 27, the second portion 127 in contact with the dielectric insulation of the cable and the third portion 129 in contact with a crimped metal terminal 79 enclosing the conductor 57 of the cable 27 and a conductive coating 55 on an insulating housing 29. Terminal 79 is joined to another terminal 79a by bolt 95 through a metal spacer 93 using a nut and a spring washer 101. The conductive coating 55 of the housing 29 continues around the cross-bore of the housing and conductive caps 89, 89a are provided for the bolt head and nut. Insulating sealing caps 87, 87a and gaskets 91, 91a are held in place by four bolts, the caps having a conductive outer coating. The housing 29 has an outer coating 47 of tin except between ridges 137 where an isolated circumferential conductive layer (157, Fig. 4, not shown) is provided. A castellated threaded clamp 63 holds a housing 65 in place, the housing having a terminal 61 for a ground line and securing a conductive elastomeric sealing sleeve 67. Three or four cables may be joined using the arrangement above (Fig. 16, not shown), a strap being placed across the grounding terminals 61 if the cables are adjacent, to prevent electromagnetic displacement. Alternatively the arrangement may be used to terminate cables at a three-phase switch (Figs. 17 to 19, not shown). The terminal posts having grooves (217) terminating conductive surface coatings (219) and thus giving regions of low dielectric stress. A voltage test point, Fig. 11, is provided on the outer surface of the housing 29 by a circumferential conductive band 157 having an insulating sleeve 143 and a metal clip 147 thereon. A metal pin 139 making contact with band 157 is used to test the potential on the conductive layer 55 within the housing by a capacitative effect. When not in use the pin 139 is covered by a conductive elastomeric cap 151 which touches the clip 147 which is grounded by an earth wire. The clip 147 is rotatable about the housing 29.