Electric cables

Claim 1

A method of producing an electric cable by means of a cablesheathing head, which includes the steps of: feeding a cable core into a cable-sheathing head, extruding a polyolefin material into the said head so that said polyolefin material embraces said core to form a tubular-formed sheath therefor, feeding bundles of unimpregnated glass fibers free from any adherence means into said head so that the bundles are embedded in and mechanically connected to the tubular-formed sheath material at angularly spaced locations circularly distributed about the axis of the core, said glass fibers being arranged to permit ducted gathering thereof into a pre-compressed bundle of minimum cross section prior to introduction in said head, effecting a preliminary compacting of the fibers in each of said bundles within said head, subjecting each bundle to underpressure for removing the air entrained with the fibers in the respective bundle, supplying the sheath material so as to provide additional compacting of the fibers, maintaining said compacting by a shrinkage exerted during contraction when the sheath material quickly cools to harden at atmospheric pressure after leaving said head, and forming radially extending undulations in each bundle to thereby improve the mechanical connection of a bundle within the polyolefin.

Claim 2

A method of producing an electric cable by means of a cablesheathing head, which includes the steps of: feeding a cable core into a cable-sheathing head, extruding a polyolefin material into the said head so that said polyolefin material embraces said core to form a tubular-formed sheath therefor, feeding bundles of unimpregnated glass fibers free from any adherence means into said head so that the bundles are embedded in and mechanically connected to the tubular-formed sheath material at angularly spaced locations circularly distributed about the axis of the core, said glass fibers being arranged to permit ducted gathering thereof into a pre-compressed bundle of minimum cross section prior to introduction in said head, effecting a preliminary compacting of the fibers in each of said bundles within said head, subjecting each bundle to underpressure for removing the air entrained with the fibers in the respective bundle, supplying the sheath material so as to provide additional compacting of the fibers, maintaining said compacting by a shrinkage exerted during contraction when the sheath material quickly cools to harden at atmospheric pressure after leaving said head, and forming radially extending undulations in each bundle to thereby improve the mechanical connection of a bundle within the polyolefin.

Claim 3

A method of producing an electric cable by means of a cable-sheathing head, which includes the steps of: feeding a cable core into a cable-sheathing head, extruding a polyolefin material into the said head so that said polyolefin material embraces said core to form a tubular-formed sheath therefor, feeding bundles of unimpregnated glass fibers free from any adherence means into said head so that the bundles are embedded in and mechanically connected to the tubular-formed sheath material at angularly spaced locations circularly distributed about the axis of the core, said glass fibers being arranged to permit ducted gathering thereof into a pre-compressed bundle of minimum cross section prior to introduction in said head, effecting a preliminary compacting of the fibers in each of said bundles within said head, subjecting each bundle to underpressure for removing the air entrained with the fibers in the respective bundle, supplying the sheath material so as to provide additional compacting of the fibers, maintaining said compacting by a shrinkage exerted during contraction when the sheath material quickly cools to harden at atmospheric pressure after leaving said head, and forming radially extending undulations in each bundle to thereby improve the mechanical connection of a bundle within the polyolefin.

Claim 4

A method of producing an electric cable by means of a cable-sheathing head, which includes the steps of: feeding a cable core into a cable-sheathing head, extruding a polyolefin material into the said head so that said polyolefin material embraces said core to form a tubular-formed sheath therefor, feeding bundles of unimpregnated glass fibers free from any adherence means into said head so that the bundles are embedded in and mechanically connected to the tubular-formed sheath material at angularly spaced locations circularly distributed about the axis of the core, said glass fibers being arranged to permit ducted gathering thereof into a pre-compressed bundle of minimum cross section prior to introduction in said head, effecting a preliminary compacting of the fibers in each of said bundles within said head, subjecting each bundle to underpressure for removing the air entrained with the fibers in the respective bundle, supplying the sheath material so as to provide additional compacting of the fibers, maintaining said compacting by a shrinkage exerted during contraction when the sheath material quickly cools to harden at atmospheric pressure after leaving said head, and forming radially extending undulations in each bundle to thereby improve the mechanical connection of a bundle within the polyolefin.

Claim 5

A method of producing electrical cables for power transmissions and telecommunications, which includes the steps of: providing a cable containing at least one insulated electric conductor, extruding around said cable a polyethylene cable sheath, so embedding in said polyethylene cable sheath bundles of unimpregnated glass fibers free from any adherence means but capable of being associated in the form of single and double yarns in the respective bundle and so relatively spacing said bundles concentrically about said cable that each bundle is enveloped by the minimum quantity of sheath material needed to generate compressive stress by shrinking sufficiently to cause a mechanical connection between the enveloping polyethylene sheath and the bundles of glass fibers to form, precondensing the bundles in preliminary narrowing means while they are being formed, removing ballast air contained in said bundles by subjecting thereof to underpressure and prodUcing a packed and condensed association of glass fibers in each bundle while maintaining said compaction by the shrinkage pressure when the polyethylene sheath quickly cools after having been extruded, and forming undulations of the bundles in a direction longitudinally of said cable to improve anchorage in said polyethylene sheath of the element of the glass fibers which are to take up the tensile load.

Claim 6

A method of producing electrical cables for power transmissions and telecommunications, which includes the steps of: providing a cable containing at least one insulated electric conductor, extruding around said cable a polyethylene cable sheath, so embedding in said polyethylene cable sheath bundles of unimpregnated glass fibers free from any adherence means but capable of being associated in the form of single and double yarns in the respective bundle and so relatively spacing said bundles concentrically about said cable that each bundle is enveloped by the minimum quantity of sheath material needed to generate compressive stress by shrinking sufficiently to cause a mechanical connection between the enveloping polyethylene sheath and the bundles of glass fibers to form, precondensing the bundles in preliminary narrowing means while they are being formed, removing ballast air contained in said bundles by subjecting thereof to underpressure and prodUcing a packed and condensed association of glass fibers in each bundle while maintaining said compaction by the shrinkage pressure when the polyethylene sheath quickly cools after having been extruded, and forming undulations of the bundles in a direction longitudinally of said cable to improve anchorage in said polyethylene sheath of the element of the glass fibers which are to take up the tensile load.