GB2262646A - Improvements in cables. - Google Patents

Improvements in cables. Download PDF

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Publication number
GB2262646A
GB2262646A GB9126799A GB9126799A GB2262646A GB 2262646 A GB2262646 A GB 2262646A GB 9126799 A GB9126799 A GB 9126799A GB 9126799 A GB9126799 A GB 9126799A GB 2262646 A GB2262646 A GB 2262646A
Authority
GB
United Kingdom
Prior art keywords
cable
plastics
sheath
transmission package
fire
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9126799A
Other versions
GB9126799D0 (en
GB2262646B (en
Inventor
Mark James Parry
Andrew Eliot Pierce
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nortel Networks Ltd
Original Assignee
Northern Telecom Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Northern Telecom Ltd filed Critical Northern Telecom Ltd
Priority to GB9126799A priority Critical patent/GB2262646B/en
Publication of GB9126799D0 publication Critical patent/GB9126799D0/en
Publication of GB2262646A publication Critical patent/GB2262646A/en
Application granted granted Critical
Publication of GB2262646B publication Critical patent/GB2262646B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/29—Protection against damage caused by extremes of temperature or by flame
    • H01B7/295—Protection against damage caused by extremes of temperature or by flame using material resistant to flame
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/29—Protection against damage caused by extremes of temperature or by flame
    • H01B7/292—Protection against damage caused by extremes of temperature or by flame using material resistant to heat

Landscapes

  • Insulated Conductors (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

A limited fire hazard cable comprises a transmission package 11 contained in a protective sheath 13. The sheath comprises a plastics, e.g. a zero halogen polyolefin, incorporating a fibrous refractory filler. In a fire situation the refractory fibres support the charred remains of the plastics and provide a heat insulating barrier between the fire and the transmission package. <IMAGE>

Description

IMPROVEMENTS IN CABLES This invention relates to telecommunications cables and in particular to cables having limited fire hazard (LFH) properties.
Limited fire hazard cables are cables which, in the event of a fire generate considerably less toxic fumes than conventional PVC sheathed cables. A number of sheathing materials which reduce the fumes or smoke hazard have been described. A particular problem with telecommunications cables is that of ensuring that the cable retains it telecommunications function in the event of a fire. One approach to this problem is described in our co-pending application No. 90 18617.2 which describes a cable construction in which an annular duct is provided to allow the escape of combustion products. An alternative approach is to sheath the cable with a refractory insulating material, but cables of this type are relatively expensive to manufacture as they generally require nonstandard manufacturing equipment.
The object of the present invention is to minimise or to overcome this disadvantage.
According to the invention there is provided a limited fire hazard telecommunications cable, including a transmission package enclosed in a plastics sheath, wherein said sheath incorporates a refractory fibre filler adapted to provide a thermally insulating support structure when the plastics sheath is thermally degraded by response Z a heat source.
Advantageously the plastics comprises a zero halogen polyolefin and the fibres comprise a glass, a ceramic or carbon fibre. It will be understood that the term zero halogen relates to materials that are substantially halogen free.
During a fire, the fibre filler supports the charred remains of the sheath so as to form a stable insulating barrier between the fire and the transmission package.
An embodiment of the invention will now be described with reference to the accompanying drawing in which the single figure is a crosssectional view of a limited fire hazard (LFH) cable.
Referring to the drawing, the cable comprises a transmission package 11, e.g. a plurality of paired insulated conductors 12 enclosed in a protective plastics sheath 13, this sheath providing a thermally insulating barrier in the event of a fire. The transmission package 11 may also incorporate optical elements.
In some applications a metal tape (not shown) may be provided between the transmission package and the plastics sheath.
Typically the plastics sheath comprises a zero halogen polyolefin filled with alumina. The sheath material further incorporates from 2 to 10 percent by weight of a fibrous refractory material such as glass, ceramic or carbon fibres. These fibres are of relatively short length e.g. 2 to 4 mm, and have an aspect ratio of 100 to 500. The fibres are compounded with the plastics material which is then extruded on to the transmission package via a conventional extruder.
In the event of a fire the plastics content of the surface of the sheath is burned away to expose the refractory fibres. The fibres provide support for the charred remains of the plastics material. In addition, the porous matrix provided by the fibres provides an effective heat insulating barrier between the cable transmission package and the heat source, thus inhibiting damage to the transmission package.

Claims (6)

1. A limited fire hazard telecommunications cable, including a transmission package enclosed in a plastics sheath, wherein said sheath incorporates a refractory fibre filler adapted to provide a thermally insulating support structure when the plastics sheath is thermally degraded by response to a heat source.
2. A cable as claimed in claim 1 wherein said refractory filler comprises glass, ceramic or carbon fibres.
3. A cable as claimed in claim 1 or 2, wherein said fillers comprise 2 to 10 weight percent of the plastics sheath.
4. A cable as claimed in claim 1, 2 or 3, wherein said fibres are from 2 to 4 mm in length and have an aspect ratio of 100 to 500.
5. A cable as claimed in any one of claims 1 to 4 wherein the plastics comprises a zero halogen polyolefin.
6. A limited fire hazard cable substantially as described herein with reference to and as shown in the accompanying drawing.
GB9126799A 1991-12-18 1991-12-18 Improvements in cables Expired - Fee Related GB2262646B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9126799A GB2262646B (en) 1991-12-18 1991-12-18 Improvements in cables

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9126799A GB2262646B (en) 1991-12-18 1991-12-18 Improvements in cables

Publications (3)

Publication Number Publication Date
GB9126799D0 GB9126799D0 (en) 1992-02-19
GB2262646A true GB2262646A (en) 1993-06-23
GB2262646B GB2262646B (en) 1995-11-08

Family

ID=10706426

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9126799A Expired - Fee Related GB2262646B (en) 1991-12-18 1991-12-18 Improvements in cables

Country Status (1)

Country Link
GB (1) GB2262646B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7298957B2 (en) 2005-07-11 2007-11-20 Gift Technologies, Lp Method for controlling sagging of a power transmission cable

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4225649A (en) * 1978-09-27 1980-09-30 The Flamemaster Corporation Fire retardant composition and cables coated therewith
US4598018A (en) * 1983-10-13 1986-07-01 Galileo Electro-Optics Corp. Insulating high temperature wire
EP0373757A2 (en) * 1988-12-14 1990-06-20 Associated Electrical Industries Limited Fire-resistant electrical insulator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4225649A (en) * 1978-09-27 1980-09-30 The Flamemaster Corporation Fire retardant composition and cables coated therewith
US4598018A (en) * 1983-10-13 1986-07-01 Galileo Electro-Optics Corp. Insulating high temperature wire
EP0373757A2 (en) * 1988-12-14 1990-06-20 Associated Electrical Industries Limited Fire-resistant electrical insulator

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7298957B2 (en) 2005-07-11 2007-11-20 Gift Technologies, Lp Method for controlling sagging of a power transmission cable

Also Published As

Publication number Publication date
GB9126799D0 (en) 1992-02-19
GB2262646B (en) 1995-11-08

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20011218