US3916078A - Skid wire for pipe type electric cables - Google Patents

Skid wire for pipe type electric cables Download PDF

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Publication number
US3916078A
US3916078A US505964A US50596474A US3916078A US 3916078 A US3916078 A US 3916078A US 505964 A US505964 A US 505964A US 50596474 A US50596474 A US 50596474A US 3916078 A US3916078 A US 3916078A
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US
United States
Prior art keywords
skid
pipe
wire
metal
surrounded
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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
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US505964A
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English (en)
Inventor
Paolo Gazzana Priaroggia
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Pirelli and C SpA
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Pirelli SpA
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Publication of US3916078A publication Critical patent/US3916078A/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
    • 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
    • H01B7/22—Metal wires or tapes, e.g. made of steel
    • H01B7/226—Helicoidally wound metal wires or tapes

Definitions

  • ABSTRACT A pipe type electric cable in which the core comprising a central conductor surrounded by insulation which, in turn, is surrounded by a conductive screen, is received within a fluid-tight metal tube and is separated from and conductively connected to the inner surface of the pipe by one or more skid wires wound around the screen, each of which skid wires comprises one or more metal cords extending longitudinally of the skid wire and surrounded by a semi-conductivesynthetic resin which prevents contact of the cords with the inner surface of the pipe.
  • the present invention relates to pipe type electric cables, especially for high voltages, which comprise a core including a central conductor surrounded by one or more layers of insulation and an outer electrostatic screen, a helically wound wire or wires, known in the art as skid wires, and surrounding the electrostatic screen a fluid-tight, rigid metal tube or pipe loosely receiving the core with the skid wires therearound.
  • Such cables do not-have a sheath integral with, or tightly surrounding, the insulation or electrostatic screen of the core.
  • the skid wires serve, during the laying or installation operations, as well as during the thermal cycles, to mechanically protect the cable core. In addition, they assist in reducing the possibility of abrasion of the inner surface of the pipe during installation, and they conductively interconnect the electrostatic screen of the core with the pipe.
  • skid wires four main types, namely:
  • Bare metal skid wires of good conductivity and preferably made of copper, bronze, brass, zinc, stainless steel or aluminum.
  • Skid wires of dielectric or insulating material such as a highly resistant synthetic resin, usually linear polyethylene or nylon.
  • the metal skid wires set forth in (l) hereinbefore have a high friction coefficient. Therefore, they cause substantial abrasion of the inner surface of the pipe, and this causes problems, for example, in the use of aluminum pipes as the outer pipe.
  • the employment of aluminum pipe would be of substantial interest because, by using such pipes, the losses due to eddy currents, with the same core, would be much lower than with iron tubes and, therefore, a greater current carrying capacity would be obtained.
  • such metal skid wires limit the maximum core length which can be drawn in a pipe, when it is taken into account that the whole drawing strain is transferred to the core conductor.
  • Dielectric skid wires of the type described in (2) hereinbefore find use only in very special cases, but not with metal pipes, because they do not provide the necessary electrical interconnection of the electrostatic screen of the core with the pipe.
  • Such dielectric skid wires have, moreover, the disadvantage that they do not offer a sufficient mechanical resistance to the longitudinal stresses occurring during drawing and, therefore, they are subjected to rupturing and to consequent pulling out of the broken portions.
  • Dielectric skid wires of the type described in (3) hereinbefore obviously have a greater friction coefficient than polyethylene or nylon and, therefore, there is always the risk of undesirable abrasion of the inner surface of the pipe.
  • skid wires of the type described in (4) hereinbefore provide thenecessary electrical interconnection between the screen of the core and the pipe, the metal parts extending from the surface of the skid wire cause the undesirable effects of a high friction coefficient on the inner surface of the pipe.
  • said composite skid wires are difficult to manufacture, because of the difficulties encountered in finding a resin of low friction coefficient which is able to firmly adhere to the metal.
  • One object of the present invention is that of eliminating the disadvantages encountered with cables comprising conventional skid wires and at the same time, to provide cables comprising skid wires which may be easily manufactured.
  • the core of the cable is provided with skid wires which have a low friction coefficient, which provide very good electrical contact between the electrostatic screen of the core and the pipe, and which provide substantial resistance to the longitudinal drawing strains which occur during the installation of the core in the pipe.
  • the object of the present invention is an electric cable of the pipe type, provided with one or more skid wires helically wound up on the electrostatic screen of the core, characterized in that each skid wire is constituted by an elongated element of synthetic resin made semi-conductive by means of an appropriate filler and one or more metallic cords surrounded by the resin and extending for the full length of said element.
  • FIG. 1 is a perspective view, partly in section, of a pipe cable constructed in accordance with the invention
  • FIG. 2 shows, in enlarged scale, a perspective view of aportion of the skid wire of the cable shown in FIG. 1;
  • FIG. 3 is a longitudinal section of the skid wire shown in FIGS. 1 and 2 and is taken along the line 3-3 indicated in FIG. 2.
  • FIG. 1 illustrates a screened cable core 10 laid in a pipe ll.
  • the core 10 comprises a central stranded conductor l2, surrounded by a first conductive screen 13 which, in turn, is surrounded by layers of insulation 14.
  • the insulation 14 is surrounded by a second conductive, electrostatic screen 15.
  • the screen 15 is of the conventional type, namely, is constituted by a metallic tape wound helically around the insulation 14.
  • skid wires 16 and 17 are wound helically around the electrostatic screen 15. Although two skid wires 16 and 17 have been shown, it will be apparent to those skilled in the art that the number of the skid wires applied can be different, for example, greater than two or only one skid wire. In case only one skid wire is used, said skid wire, for a given size of core 10, preferably will be applied at a pitch corresponding to one half of the pitch normally employed when two skid wires are used.
  • each skid wire 16 and 17 is constituted by a tape or elongated element 18 of synthetic resin which is made semi-conductive by means of appropriate fillers.
  • the synthetic resin is high density polyethylene (friction coefficient on metal 0.25), polyvinyl chloride (friction coefiicient on metal 0.36) or nylon (friction coefiicient on metal 0.l9 0.20).
  • the filler used to make the synthetic resin semiconductive preferably is carbon black.
  • Three metal cords 19, 20 and 21, extend longitudinallyof the element 18 and are completely embedded in, or surrounded by, the resin of the element 18 so that the cords 19, 20 and 21 cannot engage the inner surface of the pipe 11.
  • steel is preferred asthe metal for the cords 19, 20 and 21, because of its strength, other metals may be used.
  • the cords 19, 20 and 21 run parallel to each other and are spaced apart from one another from one end of the skid wire to the other.
  • the number of cords may be different from three and, for example, only one steel cord or more than three cords could be used.
  • Each skid wire 16 and 17 can have the shape indicated in FIG. 2, namely, can be D-shaped in crosssection.
  • the skid wire 16 has a surface 22 of semiconductive resin which contacts the electrostatic screen 15 of the core 10.
  • Said surface 22 is substantially flat but, if desired, can beconcave which permits it to adhere better to the electrostatic screen 15.
  • the lower surface 23 of the skid wire 16, also of semiconductive synthetic resin, is rounded so as to provide the conventional D-shape, but it could have another appropriate shape.
  • the surface 23 could be a flat surface, and, if desired, the skid ,wire 16 could rectangular in cross-section.
  • the skid wires 16 and 17 can be the same or different, provided that their maximum thickness s (FlGQ3) is the same.
  • skid wires 16 and 17 are very easy, since it consists in the mere extrusion of the synthetic resin 18, chosen as desired and appropriately loaded, on the steel cord or cords 19, 20 and 21 to be embedded.
  • skid wires 16 and 17 Owing to the low friction coefficient of such skid wires 16 and 17, at the most preferably about 0.20 (dynamic friction coefficient on metals), with respect to the friction coefficient of "the skid wires of the prior art, which, as an average ranges from 0.5 to 0.6, the core can be easily drawn into the pipe 11 during installation, and can freely slide in the pipe 11 during thermal cycles, without causing significant abrasion of the inner surface 23 of the pipe 11.
  • the semi-conductive characteristic of the loaded synthetic resin of the elongated element 18 ensures a good conductive connection' between the screen and the pipe 11;
  • the resistivity of the resin should be at least 1000 ohms/m. and, preferably, is in the range from l000-l0,000 ohms/m.
  • cords l9, 20'and 21 embedded-in theresin element l8 cooperate with the latter by taking the longitudinal stresses exerted 'on the skid wires16 and 17 during drawing in operations for laying the core 10 in the P p
  • An electric cable member for a pipe type cable comprising an electric conductor surrounded by insulation, a conductive screen around said insulation, and at least one skid wire wound around and in contact with said screen, said skid wire comprising at least one metal wire extending longitudinally of said skid wire for the length thereof and surrounded by a semi-conductive synthetic resin.
  • said semi-conductive synthetic resin is a resin selected from the group consisting of high density polyethylene, polyvinyl chloride and nylon loaded with carbon black.
  • skid wire comprises at least three stranded extending longitudinally of said skid wire for the length thereof and surrounded by a semi-conductive synthetic resin.

Landscapes

  • Ropes Or Cables (AREA)
  • Insulated Conductors (AREA)
  • Shaping Of Tube Ends By Bending Or Straightening (AREA)
US505964A 1973-10-12 1974-09-16 Skid wire for pipe type electric cables Expired - Lifetime US3916078A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT30035/73A IT995803B (it) 1973-10-12 1973-10-12 Cavo elettrico in pipe perfezionato

Publications (1)

Publication Number Publication Date
US3916078A true US3916078A (en) 1975-10-28

Family

ID=11228906

Family Applications (1)

Application Number Title Priority Date Filing Date
US505964A Expired - Lifetime US3916078A (en) 1973-10-12 1974-09-16 Skid wire for pipe type electric cables

Country Status (8)

Country Link
US (1) US3916078A (xx)
JP (1) JPS5066788A (xx)
AR (1) AR200943A1 (xx)
BR (1) BR7407945D0 (xx)
CA (1) CA1006931A (xx)
GB (1) GB1448607A (xx)
IE (1) IE39937B1 (xx)
IT (1) IT995803B (xx)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0139166A2 (en) * 1983-08-23 1985-05-02 Sumitomo Electric Industries Limited Optical fiber cable
US4783576A (en) * 1987-10-01 1988-11-08 Pirelli Cable Corporation High voltage gas filled pipe type cable
US20050007290A1 (en) * 2001-02-15 2005-01-13 Integral Technologies, Inc. Low cost omni-directional antenna manufactured from conductive loaded resin-based materials
US20050078050A1 (en) * 2001-02-15 2005-04-14 Integral Technologies, Inc. Low cost antenna devices comprising conductive loaded resin-based materials with conductive wrapping
US20080289854A1 (en) * 2007-05-21 2008-11-27 Powers Wilber F Pushable Cable
US20080289855A1 (en) * 2007-05-21 2008-11-27 Southwire Company Pushable Cable
US20090107719A1 (en) * 2007-10-24 2009-04-30 Powers Wilber F Pushable Cable
CN110544558A (zh) * 2019-09-04 2019-12-06 俞园芳 拖拉电缆结构

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2516747A (en) * 1945-08-29 1950-07-25 Okonite Callender Cable Co Inc Fluid impregnated electric cable
US2615074A (en) * 1947-08-02 1952-10-21 Gen Cable Corp Cable pulling eye and method of making the same
US2665328A (en) * 1947-07-23 1954-01-05 Gen Cable Corp Oil-impregnated electric power cable with flow-limiting tapes
US3047652A (en) * 1960-10-06 1962-07-31 Anaconda Wire & Cable Co Pipe-type cable core with armor tape reinforcing
US3080446A (en) * 1961-05-16 1963-03-05 Anaconda Wire & Cable Co High voltage cable
US3579863A (en) * 1969-06-19 1971-05-25 Martin H Mcgrath Vip jacket under skid wire of paper power cables
US3594492A (en) * 1969-09-30 1971-07-20 Gen Cable Corp Pipe-type cable systems with reduced ac losses
US3621110A (en) * 1969-04-01 1971-11-16 Gen Cable Corp Field impregnated extra high voltage cable system
US3673307A (en) * 1971-04-21 1972-06-27 Gen Cable Corp Pipe type cables with improved skid wire protection

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4926081B1 (xx) * 1970-11-05 1974-07-05

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2516747A (en) * 1945-08-29 1950-07-25 Okonite Callender Cable Co Inc Fluid impregnated electric cable
US2665328A (en) * 1947-07-23 1954-01-05 Gen Cable Corp Oil-impregnated electric power cable with flow-limiting tapes
US2615074A (en) * 1947-08-02 1952-10-21 Gen Cable Corp Cable pulling eye and method of making the same
US3047652A (en) * 1960-10-06 1962-07-31 Anaconda Wire & Cable Co Pipe-type cable core with armor tape reinforcing
US3080446A (en) * 1961-05-16 1963-03-05 Anaconda Wire & Cable Co High voltage cable
US3621110A (en) * 1969-04-01 1971-11-16 Gen Cable Corp Field impregnated extra high voltage cable system
US3579863A (en) * 1969-06-19 1971-05-25 Martin H Mcgrath Vip jacket under skid wire of paper power cables
US3594492A (en) * 1969-09-30 1971-07-20 Gen Cable Corp Pipe-type cable systems with reduced ac losses
US3673307A (en) * 1971-04-21 1972-06-27 Gen Cable Corp Pipe type cables with improved skid wire protection

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0139166A2 (en) * 1983-08-23 1985-05-02 Sumitomo Electric Industries Limited Optical fiber cable
EP0139166A3 (en) * 1983-08-23 1987-07-15 Sumitomo Electric Industries Limited Optical fiber cable
US4966434A (en) * 1983-08-23 1990-10-30 Sumitomo Electric Industries, Ltd. Optical fiber cable
US4783576A (en) * 1987-10-01 1988-11-08 Pirelli Cable Corporation High voltage gas filled pipe type cable
US7230572B2 (en) * 2001-02-15 2007-06-12 Integral Technologies, Inc. Low cost antenna devices comprising conductive loaded resin-based materials with conductive wrapping
US20050078050A1 (en) * 2001-02-15 2005-04-14 Integral Technologies, Inc. Low cost antenna devices comprising conductive loaded resin-based materials with conductive wrapping
US20050007290A1 (en) * 2001-02-15 2005-01-13 Integral Technologies, Inc. Low cost omni-directional antenna manufactured from conductive loaded resin-based materials
US7317420B2 (en) * 2001-02-15 2008-01-08 Integral Technologies, Inc. Low cost omni-directional antenna manufactured from conductive loaded resin-based materials
US20080289854A1 (en) * 2007-05-21 2008-11-27 Powers Wilber F Pushable Cable
US20080289855A1 (en) * 2007-05-21 2008-11-27 Southwire Company Pushable Cable
WO2008144689A1 (en) * 2007-05-21 2008-11-27 Southwire Company Pushable cable
US7915531B2 (en) 2007-05-21 2011-03-29 Southwire Company Pushable cable
US8222525B2 (en) 2007-05-21 2012-07-17 Southwire Company Pushable cable
US20090107719A1 (en) * 2007-10-24 2009-04-30 Powers Wilber F Pushable Cable
CN110544558A (zh) * 2019-09-04 2019-12-06 俞园芳 拖拉电缆结构

Also Published As

Publication number Publication date
IE39937B1 (en) 1979-01-31
IE39937L (en) 1975-04-12
GB1448607A (en) 1976-09-08
CA1006931A (en) 1977-03-15
AR200943A1 (es) 1974-12-27
BR7407945D0 (pt) 1975-09-16
JPS5066788A (xx) 1975-06-05
IT995803B (it) 1975-11-20

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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