Electric power cables

Details Electric power cables Electric power cables

1999-04-21

2001-04-10

Kincaid, Kristine (Department: 2831)

Electricity: conductors and insulators

Conduits, cables or conductors

Insulated

C174S12000C, C174S1060SC

Reexamination Certificate

active

06215070

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to electric power cables of the kind having at least one metallic conductor, usually a conductor screen of semiconductive material, and insulation all enclosed in an earth screen comprising wires or narrow tapes and an external sheath comprising polymeric material which will usually (but not necessarily) form the exposed surface of the cable.
In most environments, it is desirable, if not essential, that the sheath is more effectively watertight than can be achieved with polymeric material alone, and attempts have thus been made to follow the practice used in communications cables of including a metal/plastics laminate foil beneath the main body of the sheath, so as to become bonded to it, normally when the main polymeric body is extruded. It is difficult, with such structures, to design a sheath in which the laminate foil remains intact when the cable is subjected to the impact tests specified by Standards Authorities and customers, as the laminate tends to be driven into the gaps between the wires or tapes of the screen and to split along resulting crease lines.
SUMMARY OF INVENTION
The cable in accordance with the present invention is characterised by a sheath construction comprising a first extruded polymeric layer which encloses the earth screen of the cable without filling the gaps between the components thereof (the wires or strips), a second extruded polymeric layer enclosing the first and between them and bonded to both of them a moisture barrier laminate comprising a metal foil layer coated on each of its major faces with a polymeric material compatible with the material of the extruded layer it contacts.
Preferably the extruded polymeric layers are of the same material, or at least adhesively compatible materials, and the both faces of the laminate are coated with a single polymeric material which is the same as or compatible with the material(s) of the extruded layers, so that the laminate may self-bond where its edges overlap.
More specifically, we prefer that the two extruded layers of the sheath and the coating on each face of the laminate are all of polyethylene, or alternatively all of polyvinyl chloride or all of an “LSF” composition based on ethylene-vinyl acetate copolymer or an ethylene-propylene rubber (in each case with conventional additives).
The laminate is preferably longitudinally applied, but could be helically lapped if desired.
Preferably the insulation of the cable is of a polymeric material, such as crosslinked polyethylene or ethylene-propylene rubber, and in this case the conductor screen is preferably of carbon-loaded polymeric material and the earth screen preferably includes an inner layer of carbon-loaded conductive polymeric material, in addition to the wires or strips of metal.
Preferably the gaps between the wires or strips of the earth screen are waterblocked by applying water-swellable tapes under and/or over them, or in other known ways. Preferably at least one semiconductive water-swellable tape is applied under the wires or tapes and at least one insulating water-swellable tape over the top of them. A waterblocking tape applied over the wires or tapes may facilitate ensuring that the first extruded layer of the sheath does not fill the gaps between them. Other suitable tapes could be used for this purpose if desired.
Because the laminate is bonded to both the adjacent extruded polymeric layers, no water leakage path is formed adjacent either of its faces and the laminate is given strong and resilient mechanical support, while the inner extruded layer can deform under impact to penetrate (temporarily at least) between the wires or tapes of the earth screen to absorb impact with minimal distortion of the laminate.


REFERENCES:
patent: Re. 36307 (1999-09-01), Marin et al.
patent: 3321572 (1967-05-01), Garner
patent: 4125739 (1978-11-01), Bow
patent: 4145567 (1979-03-01), Bahder et al.
patent: 4256921 (1981-03-01), Bahder
patent: 4533789 (1985-08-01), Katz
patent: 4703134 (1987-10-01), Uematsu
patent: 4731504 (1988-03-01), Achille et al.
patent: 4986372 (1991-01-01), Ganssle
patent: 5010209 (1991-04-01), Marciano-Agostinelli et al.
patent: 5043538 (1991-08-01), Hughey, Jr.
patent: 5082719 (1992-01-01), Arroyo
patent: 5146046 (1992-09-01), Arroyo et al.
patent: 5170010 (1992-12-01), Aldissi
patent: 5249248 (1993-09-01), Arroyo et al.
patent: 5281757 (1994-01-01), Marin et al.
patent: 5293001 (1994-03-01), Gebs
patent: 5300733 (1994-04-01), Uematsu
patent: 5373100 (1994-12-01), Arroyo et al.
patent: 5486648 (1996-01-01), Chan et al.
patent: 5614269 (1997-03-01), Hoskins et al.
patent: 5756159 (1998-05-01), Hoskins et al.
patent: 0 209 899 (1987-01-01), None
patent: 1035564 (1953-04-01), None
patent: 1485130 (1966-06-01), None
patent: 2465301 (1979-09-01), None
patent: 2538941 (1984-07-01), None
patent: 632657 (1949-11-01), None
patent: 1136912 (1968-12-01), None
patent: 0410307 (1992-02-01), None
patent: WO 98/14960 (1998-04-01), None

Affiliated with

Also associated with

Rating

Electric power cables does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Electric power cables, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electric power cables will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2500845