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US 2003/0070831 A1Published application
Communications cable
OwnerMartin Frederick Arthur Hudsoninventor
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OwnerMartin Frederick Arthur Hudsoninventor
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The invention provides a communications cable comprising a plurality of cores (4) through which communications signals can be transmitted, each core comprising a metallic conductor (6) surrounded by a close-fitting sleeve (8) of insulating material which is substantially free of halogenated polymers, the insulating material having a permittivity of no greater than 3, and comprising an outer layer (8′″) of a non-foamed polymer surrounding a layer (8″) of foamed polymer, the outer layer (8′″) containing a fire retardant, the layer of foamed polymer optionally surrounding a layer (8′) of non-foamed polymer, and wherein the region of the insulating material immediately adjacent the metallic conductor (6) contains no fire retardant metal hydroxide and/or carbonate filler; an outer cable sheath (16) disposed radially outwardly of and surrounding the cores, the outer cable sheath (16) constituting a fire protection layer and being formed from an extrudable polymer containing a fire retardant material such as a metal hydroxide and/or carbonate filler; and optionally a metallic or metallised screening layer disposed between the cores and the outer cable sheath; but provided that no additional fire protection layer is disposed between the cores and the outer cable sheath (16).
A communications cable comprising a plurality of cores through which communications signals can be transmitted, each core comprising a metallic conductor surrounded by a close-fitting sleeve of insulating material which is substantially free of halogenated polymers, the insulating material having a permittivity of no greater than 3, and comprising an outer layer of a non-foamed polymer surrounding a layer of foamed polymer, the outer layer containing a fire retardant which is substantially halogen free, the layer of foamed polymer optionally surrounding a layer of non-foamed polymer, and wherein the region of the insulating material immediately adjacent the metallic conductor contains no fire retardant metal hydroxide and/or carbonate filler;
A communications cable according to any one of the preceding claims wherein the maximum flame propagation distance of the cable, as measured by American National Standards Institute test ANSI UL 910, is less than 152 cm beyond an initial test flame.
A communications cable according to any one of the preceding claims wherein the peak optical density of the smoke produced by the cable, as measured by American National Standards Institute test ANSI UL 910, is less than 0.5 and the average optical density of the smoke is 0.15 or less.
A communications cable according to any one of the preceding claims which is unscreened.
A communications cable according to any one of the preceding claims wherein the insulating material surrounding each metallic conductor comprises a radially inner foam layer and a radially outer non-foamed layer.
A communications cable according to any one of the preceding claims wherein the outer non-foamed layer contains a metal hydroxide and/or metal carbonate fire retardant.
A communications cable according to any one of the preceding claims wherein the insulating material of the core is a polyolefin such as polyethylene or polypropylene.
A communications cable according to any one of the preceding claims wherein the cores are arranged in the form of one or more twisted pairs or quads.
A communications cable according to any one of the preceding claims wherein a screening layer is interposed between the cores and the outer cable sheath.
Dependencies are inferred from the claim text.