Abstract: Long lengths of a heat-shrinkable sleeve for use in splicing electrical cables and the like are manufactured by providing an elongated impermeable core having a smooth outer surface, extruding an elongated sleeve around and in contact with the core, the sleeve having a smooth inner surface conforming to the outer surface of the core, and effecting an initial expansion of a portion of the sleeve to a larger diameter in an expansion zone so that the sleeve separates from the core and leaves a space between the sleeve and core. A fluid is introduced into the space under pressure via a fitting at the downstream end of the sleeve while continuously advancing the sleeve and core through the expansion zone. To begin the process, a permeable core is used, and the sleeve is extruded around and in contact with the permeable core.

Abstract: A joint structure for covering a joint between cables is provided in which an insulation structure extends over and beyond cut back ends of insulation layers of the cables, but terminates at a distance ahead of cut back ends of insulation shield layers of the cables. The insulation structure of the joint structure includes a multi-layered, heat shrinkable tube with its ends beveled or "feathered". In assembling the joint, the tube is positioned to overlie the cable conductors and the insulation layers of the cables and is shrunk thereover so as to terminate at a distance from the cut back ends of the insulation shield layers of the cables. The heat shrinkable tube can be manufactured with feathered edges, so that no additional time or labor is required to shape the sleeve when the joint is assembled. The joint structure also includes a semiconductive conductor shield member applied in successive convoluted layers over the exposed conductors of the joint prior to application of the heat shrunk tube.

Abstract: Voltage stress control cones for high voltage cable terminations are produced by premolding and radially expanding to mechanically prestress. The mechanically prestressed premolded cone is slipped over the insulation of a cable end and heat relaxed to shrink tightly over the cable. The cone is fabricated from cross-linkable polyethylene or other cross-linkable polymeric material having substantially the same electrical and thermal characteristics as the cross-linked polymeric insulation of the cable. A semiconductive layer of cross-linked polymeric material provides the transition between the insulation of the cone and the semiconductive insulation shield of the cable.

Abstract: The insulation shield in a power cable having thick polymeric insulation is constructed of a metallic layer radially spaced from but in electrical communication with an inner semiconducting layer by an intervening helical wrap of a semiconducting or high dielectric constant longitudinal structurally resiliently compressible substantially shape recoverable element. Various elements are described, both hollow and solid, with and without one flat longitudinal surface, and of both monolithic plastic and composite plastic and metal construction.

Abstract: Long lengths of a heat-shrinkable sleeve for use in splicing electrical cables and the like are made in a continuous process. The sleeve is formed around a permeable core, and the core and sleeve are advanced together in an axial direction, the leading end of the advancing sleeve being hermetically sealed. The core and sleeve pass through a heating station, thereby heating a portion of at least the sleeve, and a fluid is introduced under pressure into the core, thereby internally pressurizing the sleeve to effect a radial expansion of the heated portion thereof. The core and sleeve then pass through a cooling station, thereby cooling the expanded sleeve to stabilize it. A stress graded compound also for use in splicing electrical cables and the like is made by heating a dimethyl silicone liquid to remove entrapped gas and mixing the liquid with a silicone carbide powder having a particle size capable of passing through a 400 mesh screen.

Abstract: An improved method and apparatus for fabricating insulated cables, particularly polymeric insulated electrical power cables, resistant to the formation and growth of electrochemical trees is disclosed. Internal pressure on the conductor side of the cable is maintained lower than the external pressure on the outer surface of the insulation during extrusion. Extrusion pressure higher than the external pressure results in expansion of the insulation following extrusion. This expansion or swelling reduces the number and size of cracks and voids which are precursors of electrochemical trees. In addition, pressure curing the extruded, insulated cable with a curing medium above its melting point followed by gradual gradient cooling under internal pressure and higher external cooling fluid pressure to around room temperature optimizes the resistance of the cable to nucleation and growth of electrochemical trees.

Abstract: Long lengths of a heat-shrinkable sleeve for use in splicing electrical cables and the like are made in a continuous process. The sleeve is formed around a permeable core, and the core and sleeve are advanced together in an axial direction, the leading end of the advancing sleeve being hermetically sealed. The core and sleeve pass through a heating station, thereby heating a portion of at least the sleeve, and a fluid is introduced under pressure into the core, thereby internally pressurizing the sleeve to effect a radial expansion of the heated portion thereof. The core and sleeve then pass through a cooling station, thereby cooling the expanded sleeve to stabilize it. A stress graded compound also for use in splicing electrical cables and the like is made by heating a dimethyl silicone liquid to remove entrapped gas and mixing the liquid with a silicone carbide powder having a particle size capable of passing through a 400 mesh screen.

Abstract: A method and apparatus for retarding electrochemical tree-type decomposition of polyolefin electrical insulation by saturating the insulation with a liquid having high resistivity and a low dielectric constant. The insulation of cables which have already been in service is dried prior to being saturated with the liquid. One embodiment of the invention provides a continuing supply of liquid to the cable after it has been buried underground.