US3557301A - Sheathing of electrical cables - Google Patents

Sheathing of electrical cables Download PDF

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Publication number
US3557301A
US3557301A US719352A US3557301DA US3557301A US 3557301 A US3557301 A US 3557301A US 719352 A US719352 A US 719352A US 3557301D A US3557301D A US 3557301DA US 3557301 A US3557301 A US 3557301A
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US
United States
Prior art keywords
sheath
core
layer
corrugations
composition
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.)
Expired - Lifetime
Application number
US719352A
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English (en)
Inventor
Paolo Gazzana Priaroggia
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.)
Pirelli and C SpA
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Pirelli SpA
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Publication date
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Publication of US3557301A publication Critical patent/US3557301A/en
Assigned to SOCIETA' PIRELLI S.P.A., A COMPANY OF ITALY reassignment SOCIETA' PIRELLI S.P.A., A COMPANY OF ITALY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INDUSTRIE PIRELLI S.P.A.
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Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/0009—Apparatus or processes specially adapted for manufacturing conductors or cables for forming corrugations on conductors or cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/22—Sheathing; Armouring; Screening; Applying other protective layers
    • H01B13/24—Sheathing; Armouring; Screening; Applying other protective layers by extrusion
    • H01B13/245—Sheathing; Armouring; Screening; Applying other protective layers by extrusion of metal layers
    • 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
    • H01B7/18—Protection against damage caused by wear, mechanical force or pressure; Sheaths; Armouring
    • H01B7/20—Metal tubes, e.g. lead sheaths
    • H01B7/201—Extruded metal tubes
    • 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
    • H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B9/00—Power cables
    • H01B9/06—Gas-pressure cables; Oil-pressure cables; Cables for use in conduits under fluid pressure
    • H01B9/0611—Oil-pressure cables

Definitions

  • the present invention relates to electric cables of the type having a core, an intermediate layer or an insulating composition. and an outer metallic sheath. More particularly, the invention relates to electric cables for power transmission which have an outer metallic sheath that is corrugated and to a process for sheathing said cables.
  • a typical method of insulating electric power cables is to surround the conductors with layers of paper that have been impregnated with an insulating composition such as a very thick oil or an oil mixed with suitable resinous material.
  • an insulating composition such as a very thick oil or an oil mixed with suitable resinous material.
  • such cables have generally been covered with a protective extruded metal sheath made. for example, of lead or aluminum. Lead has been used for a long time due to its malleability and its ability of being extruded easily.
  • Aluminum is preferred to lead because of its considerably better mechanical qualities, its low specific gravity, its good resistance to vibration, and its lower electric resistance.
  • aluminum sheaths as compared with lead sheaths, have less flexibility. That is, the aluminum sheath is less able to be subjected to substantial bending without being damaged.
  • the corrugating operation has generally been carried out so as to provide a ratio between the depth and the pitch of the corrugation which is greater-than 1:7, the depth ofthe corrugations falling within a range of between 2.5 and 7.25 millimeters.
  • the term depth means one-half of the value of the difference between the maximum diameter and the minimum diameter of the sheath.
  • Atmospheric air or gases can be trapped in such zones, and in course of time this can give rise to deleterious consequences with regard to the dielectric characteristics of the insulation.
  • portions of the impregnating composition forming part of the insulation on the core can separate from the core and fall into the zones. This reduces the insulation at such points and adversely affects the ability of the cable to withstand the electric gradient when the cable is placed into use.
  • a proposed solution to eliminate the voids or nonimpregnated zones involves admitting the impregnating composition, after the corrugating operation, into the space between the sheath and the cable core by means of a pump or injecting device.
  • this procedure does not permit complete filling of the nonimpregnated zones due to the high viscosity of the composition and the resistance it encounters in its passage along the space between the sheath and the core.
  • an electric cable insulated with paper impregnated with an insulating composition and provided with a corrugated metal sheath which is free from the aforementioned drawbacks.
  • an electric cable comprising a core, an intermediate layer of an insulating composition, and an outer metallic sheath, the sheath being sinusoidally corrugated with a minimum diameter at least one millimeter larger than the outside diameter of the core and with the depth of the corrugations in the range of between 0.5
  • the expression -sinusoidally corrugated refers to a corrugation which in longitudinal section has a profile whose curvature varies between constant positive and negative values.
  • a further object in accordance with the present invention, is the provision of a process for fabricating electric cables of the aforementioned type, said process comprising the steps of passing the core through an extruder and extruding thereon the metal sheath while introducing the composition under pressure between the core and the sheath, and corrugating the extruded sheath with the core in situ such that the final dimensions fall within the ranges indicated above.
  • FIG. 1 is a generally diagrammatic view of the equipment necessary to practice the process of the present invention.
  • FIG. 2 is a fragmentary longitudinal sectional view of the resultant cable produced by the apparatus shown in FIG. 1.
  • l is a conventional extruder for extruding aluminum sheaths and 2 is a cooling jacket intended to cause a drop in the temperature of the sheath immediately upon its leaving the extruder. Cooling of the sheath within the jacket 2 may be accomplished by means ofa water spray.
  • the cable core can be supplied from a revolving platform, not visible in the figure, on which it is supported in coils.
  • the core 3 enters the extruder 1 after passing through a small tank 4, connected to the entrance to the extruder and filled with impregnating composition.
  • the tank 4 is always used during the covering of cables of the aforesaid type with a smooth sheath in order to restore, prior to entry of the core into the extruder, the quantity of impregnating composition which has dropped from the core during its stay on the revolving platform and on the way from the latter to the extruder.
  • the cable core Downstream of the extruder the cable core, now covered with the aluminum sheath 5, passes through a conventional corrugating device 6 which imparts to it a helical corrugation having a sinusoidal profile as best seen in FIG. 2,
  • a conventional corrugating device 6 which imparts to it a helical corrugation having a sinusoidal profile as best seen in FIG. 2,
  • the corrugating step such that the ratio between the depth 1 and the pitch p of the corrugations lies between 1:15 and 1:25
  • the cable remains highly flexible even though all of the regions 7 are completely filled with the insulating composition.
  • an object of the present invention is to provide a process for sheathing cables of the type having a core insulated with paper impregnated with an insulating composition and covered with a corrugated metal sheath.
  • An important feature of the process is that the application of the metal sheath is carried out under a pressure head of the composition contained in the tank 4, thereby filling the entire space between the sheath and the cable core.
  • the insulating papers may be easily torn, with a consequent damage to the insulating characteristics of the cores themselves It is believed that this may be due to the fact that. on account of the considerable depth of the corrugations. the initial diameter of the aluminum sheath. and therefore. the quantity of composition contained in the space 8. must be increased. The subsequent corrugation which. owing to its depth, causes about a 50 percent reduction in the volume enclosed in the space 8, gives rise to a considerable return flow of the composition. The composition is at a relatively low temperature. having been cooled during its passage through the jacket 2. and its viscosity is such that its return flow is hindered or prevented. As a consequence. the papers can be torn and distortion or rupture of the sheath can occur.
  • a cable core 50 millimeters in diameter, was covered with an aluminum sheath.
  • the applicable dimensions were:
  • corrugation pitch p 25 millimeters
  • the sheaths constructed in accordance with the present invention avoid thedrawbacks generally encountered heretofore in the corrugating operation. In fact. owing to the reduced extent of the corrugations, which can be produced in a simple and easy manner, a smaller quantity of aluminum is required. thereby reducing the total cost of the cable.
  • An electric cable comprising a core having a conductor surrounded by a layer of insulation, an outer metallic sheath surrounding said core and an insulating composition intermediate said layer and said outer metallic sheath.
  • said sheath being sinusoidally corrugated with a minimum interior diameter at least 1 millimeter larger than the outside diameter of said layer and with thedepth of the corrugations in the range of between 0.5 and 1.5 millimeters and the ratio of said depth to the pitch of said corrugations in the range of 1:25 to 1:15.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacturing Of Electric Cables (AREA)
  • Insulated Conductors (AREA)
US719352A 1967-05-23 1968-04-08 Sheathing of electrical cables Expired - Lifetime US3557301A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT1639067 1967-05-23

Publications (1)

Publication Number Publication Date
US3557301A true US3557301A (en) 1971-01-19

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ID=11148848

Family Applications (1)

Application Number Title Priority Date Filing Date
US719352A Expired - Lifetime US3557301A (en) 1967-05-23 1968-04-08 Sheathing of electrical cables

Country Status (3)

Country Link
US (1) US3557301A (no)
DE (1) DE1996553U (no)
FR (1) FR1549940A (no)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3745232A (en) * 1972-06-22 1973-07-10 Andrew Corp Coaxial cable resistant to high-pressure gas flow
US3754094A (en) * 1971-01-25 1973-08-21 Kabel Metallwerke Ghh Cable with welded corrugated metal sheath
US3766309A (en) * 1970-07-14 1973-10-16 P Calzolari Electric cable with corrugated metallic sheath
US3885088A (en) * 1973-05-23 1975-05-20 Pirelli Fully-filled telephone cable with improved screen
US3943271A (en) * 1974-05-06 1976-03-09 General Cable Corporation Extruded solid dielectric high voltage cable resistant to electro-chemical trees
US4216645A (en) * 1977-06-06 1980-08-12 Aktieselskabet Nordiske Kabel-Og Traadfabriker Wound cable and apparatus for forming cables
US4631392A (en) * 1984-07-13 1986-12-23 Raychem Corporation Flexible high temperature heater
US5760334A (en) * 1996-07-24 1998-06-02 Alcatel Kabel Ag & Co. Metallic sheath for an electric cable and method of making the same
US20020074328A1 (en) * 2000-10-19 2002-06-20 O'connor Jason Heating cable
US20130175079A1 (en) * 2010-09-16 2013-07-11 Yazaki Corporation Shield member for conducting path and wire harness
US20150107873A1 (en) * 2013-10-21 2015-04-23 Dekoron Wire & Cable LLC Flexible armored cable
US9171659B2 (en) * 2012-09-14 2015-10-27 Abb Research Ltd Radial water barrier and a dynamic high voltage submarine cable for deep water applications
US20190190245A1 (en) * 2016-05-13 2019-06-20 Nkt Hv Cables Gmbh Joint, Termination Or Cross-Connection Arrangement For A Cable And Method For Providing A Joint, Termination Or Cross-Connection Arrangement
US20190237215A1 (en) * 2018-01-26 2019-08-01 Hitachi Metals, Ltd. Insulated Wire

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0780848B1 (de) 1995-12-18 2002-12-18 Felten & Guilleaume Kabelwerke GmbH Gasaussendruckkabel

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2817363A (en) * 1952-10-31 1957-12-24 Pirelli General Cable Works Corrugated aluminium tube and electric cable employing the same as a sheath
US2870792A (en) * 1956-03-07 1959-01-27 Pirelli General Cable Works Metal tubes or metal sheaths of electric cables
US2890263A (en) * 1952-11-18 1959-06-09 Hackethal Draht & Kabelwerk Ag Coaxial cables
US2995616A (en) * 1961-08-08 Nicolas
US3287490A (en) * 1964-05-21 1966-11-22 United Carr Inc Grooved coaxial cable
US3394400A (en) * 1965-10-22 1968-07-23 Andrew Corp Corrugated sheath coaxial cable with water-sealing barriers and method of making same

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2995616A (en) * 1961-08-08 Nicolas
US2817363A (en) * 1952-10-31 1957-12-24 Pirelli General Cable Works Corrugated aluminium tube and electric cable employing the same as a sheath
US2890263A (en) * 1952-11-18 1959-06-09 Hackethal Draht & Kabelwerk Ag Coaxial cables
US2870792A (en) * 1956-03-07 1959-01-27 Pirelli General Cable Works Metal tubes or metal sheaths of electric cables
US3287490A (en) * 1964-05-21 1966-11-22 United Carr Inc Grooved coaxial cable
US3394400A (en) * 1965-10-22 1968-07-23 Andrew Corp Corrugated sheath coaxial cable with water-sealing barriers and method of making same

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3766309A (en) * 1970-07-14 1973-10-16 P Calzolari Electric cable with corrugated metallic sheath
US3754094A (en) * 1971-01-25 1973-08-21 Kabel Metallwerke Ghh Cable with welded corrugated metal sheath
US3745232A (en) * 1972-06-22 1973-07-10 Andrew Corp Coaxial cable resistant to high-pressure gas flow
US3885088A (en) * 1973-05-23 1975-05-20 Pirelli Fully-filled telephone cable with improved screen
US3943271A (en) * 1974-05-06 1976-03-09 General Cable Corporation Extruded solid dielectric high voltage cable resistant to electro-chemical trees
US4216645A (en) * 1977-06-06 1980-08-12 Aktieselskabet Nordiske Kabel-Og Traadfabriker Wound cable and apparatus for forming cables
US4631392A (en) * 1984-07-13 1986-12-23 Raychem Corporation Flexible high temperature heater
US5760334A (en) * 1996-07-24 1998-06-02 Alcatel Kabel Ag & Co. Metallic sheath for an electric cable and method of making the same
US20020074328A1 (en) * 2000-10-19 2002-06-20 O'connor Jason Heating cable
US6680465B2 (en) * 2000-10-19 2004-01-20 Heat Trace Ltd Heating cable
US20130175079A1 (en) * 2010-09-16 2013-07-11 Yazaki Corporation Shield member for conducting path and wire harness
US10004166B2 (en) * 2010-09-16 2018-06-19 Yazaki Corporation Shield member for conducting path and wire harness
US9171659B2 (en) * 2012-09-14 2015-10-27 Abb Research Ltd Radial water barrier and a dynamic high voltage submarine cable for deep water applications
US20150107873A1 (en) * 2013-10-21 2015-04-23 Dekoron Wire & Cable LLC Flexible armored cable
US9576702B2 (en) * 2013-10-21 2017-02-21 Dekoron Wire & Cable LLC Flexible armored cable
US20190190245A1 (en) * 2016-05-13 2019-06-20 Nkt Hv Cables Gmbh Joint, Termination Or Cross-Connection Arrangement For A Cable And Method For Providing A Joint, Termination Or Cross-Connection Arrangement
US11201458B2 (en) * 2016-05-13 2021-12-14 Nkt Hv Cables Ab Joint, termination or cross-connection arrangement for a cable and method for providing a joint, termination or cross-connection arrangement
US20190237215A1 (en) * 2018-01-26 2019-08-01 Hitachi Metals, Ltd. Insulated Wire

Also Published As

Publication number Publication date
FR1549940A (no) 1968-12-13
DE1996553U (de) 1968-11-14

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Legal Events

Date Code Title Description
AS Assignment

Owner name: SOCIETA PIRELLI S.P.A., PIAZZALE CADORNA 5, 20123

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:INDUSTRIE PIRELLI S.P.A.;REEL/FRAME:003847/0084

Effective date: 19810101