Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Reexamination Certificate
1999-06-10
2001-09-11
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
Reexamination Certificate
active
06288340
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns an electrical conductor cable for transmitting information. It also concerns a method of manufacturing a cable of this kind.
2. Description of the Prior Art
Nowadays information is transmitted via electrical cables comprising a large number of conductors and at very high frequencies. The increased frequencies and the increased number of streams of information to be transmitted in parallel on separate conductors leads to the necessity of providing effective insulation between the various electrical conductors assembled together in the same cable. The risk of crosstalk increases with the number of conductors and the frequency. Crosstalk is the result of information transmitted on one conductor being radiated toward another conductor.
The information is usually transmitted by pairs of conductors and the pairs are insulated and/or shielded from each other to prevent crosstalk, or near-end crosstalk.
The most usual solution to the problem of shielding each pair of conductors is to wrap a metal or metalized tape around each pair in a helix, the cable being formed by assembling the shielded pairs into a common protective sheath. Shielding the pairs individually is slow and difficult. To connect the resulting cable the individual shields of the pairs must be removed to obtain access to the conductors, which makes the connection operation, which is usually carried out on site, difficult.
To overcome these drawbacks, document FR-2 738 947 proposes a cable in which the electrical shields of the various conductors, in particular the pairs, comprise a central member with radial fins separating the pairs from each other and partially shielding each pair and a peripheral shield around the central member and the pairs, the peripheral shield completing the shielding of each pair. However, the fins of the central member form stiffener ribs and a cable made this way is unsuitable for many applications in which the cable needs to be flexible. Also, a cable equipped with a central member of the above kind is not easy to manufacture as it necessitates an extrusion operation.
The invention provides a flexible cable having good insulation between conductors, pairs or quads and which is also particularly simple to manufacture and use.
SUMMARY OF THE INVENTION
To this end, the present invention proposes a cable for transmitting information including a set of conductors or pairs or quads of conductors insulated from each other to limit crosstalk between the conductors, pairs or quads and at least two metalized longitudinal flexible tapes separating the conductors, pairs or quads and applied around each conductor, pair or quad by virtue of twisting or torsion of the cable.
It has been found that the longitudinal tapes largely wrap around each pair by virtue of twisting or torsion of the cable and the shielding obtained is therefore more effective than simple compartmentalization.
Also, the cable is more flexible than with cruciform compartmentalization and simpler and faster to manufacture.
In the case of a non-twisted cable, the torsion necessary for the tapes to wrap around each pair can be small. It can also be obtained in a virtually natural fashion by winding the cable onto a spool, or unwinding it therefrom, during manufacture.
The tapes are preferably folded so that each conductor, pair or quad is shielded by a double thickness of tape.
In one embodiment of the invention, each tape is folded along a longitudinal line, the two sections on respective opposite sides of the longitudinal fold are pressed together and each is extended by an end section comprising the longitudinal edges of the tape, which end sections are pressed against the corresponding end sections of the other tape.
In this way, the center sections of the two tapes and the end sections of a tape pressed against the corresponding end sections of the other tape form four flexible walls and therefore delimit four compartments into which the conductors, pairs or quads are inserted. Each of the flexible walls wraps around the conductor, pair or quad by virtue of twisting or torsion of the cable.
The longitudinal folding line can be central, so that the four longitudinal sections of each tape have the same length, or offset relative to a central folding line, so that the four longitudinal sections of each tape have different widths.
The invention applies to a cable having any number of conductors, pairs or quads insulated from each other.
In one embodiment, at least one of the two tapes, or each tape, can be formed of a composite material comprising an insulative support onto which a metal is deposited. The composite tape is made of “Aluster”, for example, i.e. polyester insulation covered with aluminum.
The tapes can be shaped at the same time as the conductors, pairs or quads are laid in the resulting compartments, laying obviously being effected downstream of shaping.
Other features and advantages of the invention will become apparent from the following description of particular embodiments of the invention given with reference to the accompanying drawings.
REFERENCES:
patent: 1389143 (1921-08-01), Kempton
patent: 2538019 (1951-01-01), Lee
patent: 3911200 (1975-10-01), Simons et al.
patent: 4453031 (1984-06-01), Justiss
patent: 5789711 (1998-08-01), Gaeris et al.
patent: 5969295 (1999-10-01), Boucino et al.
patent: 0 529 607 A1 (1993-03-01), None
patent: 2 120 836 A (1983-12-01), None
Nexans
Nguyen Chau N.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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