Electricity: conductors and insulators – With fluids or vacuum – Conduit or cable end structure
Patent
1996-01-22
1998-02-03
Sough, Hyung S.
Electricity: conductors and insulators
With fluids or vacuum
Conduit or cable end structure
174 23R, 174 75B, H02G 1523, H02G 1525
Patent
active
057147159
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention generally relates to sealing the ends of multiple conductor electrical cables, and more particularly to a cable end seal for use when splicing or terminating a cable having an oil-impregnated layer as part of the dielectric system.
BACKGROUND OF THE INVENTION
Electrical cables, such as those used for telephone lines, high voltage lines, cable television, etc., can develop faults or breaks in the line due to manufacturing defects, misuse or environmental factors. Faults occur both in underground and aerial cables. Rather than replacing an entire section of such a cable, it is expedient to expose a portion of cable, repair the fault, and place an enclosure about the connection. Splicing of electrical power cables is similarly useful in the connection of successive cable sections, and in the termination of such cables.
One of the earliest constructions for these cables, particularly for underground power cables, consists of a lead jacket surrounding one or more conductors, with a layer of insulative, oil-impregnated paper placed between the lead jacket and the conductors. Although most modern underground cables now have extruded dielectric (plastic) coverings, with no fluid inside, there are still substantial amounts of the paper-insulated lead covered cables ("PILC") in use. A problem thus arises when a PILC cable needs to be repaired or terminated, due to the deleterious effects caused by the egress of the oil or other dielectric fluid.
U.S. Pat. No. 5,374,784, assigned to the assignee of the present invention and incorporated herein by reference, offers an approach to accomplishing a cable end seal by providing an elastomeric, pre-stretched tube adapted to be placed around the exposed end of the PILC cable, directly in contact with the oil-impregnated paper, and a heat recoverable tubular sleeve which is adapted to completely surround and confine the elastomeric tube. The heat recoverable sleeve mechanically restricts the elastomeric tube, preventing the elastomeric tube from swelling which, in turn, precludes absorption of the oil. A complete oil seal is thus achieved with only two layers in the joint, and without the need for oil-resistant mastics, sealing resins, or metal clamps. In another approach disclosed in U.S. Pat. No. 5,408,047, which is also owned by the assignee of the present invention and incorporated herein by reference, the heat-recoverable sleeve is replaced by epoxy-impregnated restricting tape which accomplishes the purpose of preventing the elastomeric tube from swelling.
The above-described patent is directed specifically to single-conductor cables. It is desirable to extend and adapt the oil-stop concept to cables having multiple conductors.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a cable end seal at an end of a cable having a number of conductors and oil-impregnated, electrically insulative layers surrounding each conductor, the cable end seal comprising an oil stop overlying the insulative layer of each cable conductor, the oil stop including an elastomeric layer adjacent to the insulative layer and means for restricting the elastomeric layer overlying the elastomeric layer, an elastomeric inner boot having a glove-like shape including a generally cylindrical body, a single opening at one end of the body and multiple openings corresponding in number to the number of cable conductors at the other end of the body, the inner boot being applied to the cable such that the cable conductors exit one through each of the multiple openings and the multiple openings engage the oil stop of each conductor, and the single opening is directed toward the intact cable, preferably an oil restraining material disposed within the inner boot for at least temporarily preventing egress of oil from the cable, preferably a mold surrounding and radially spaced from the cable, an elastomeric outer boot having a glove-like shape including a generally cylindrical body, a single opening at one end of the body and multiple o
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patent: 2195933 (1940-04-01), Marlborough et al.
patent: 2962542 (1960-11-01), Witt
patent: 4865890 (1989-09-01), Erlichman
patent: 5183966 (1993-02-01), Hurtado et al.
patent: 5374784 (1994-12-01), Wentzel
patent: 5408047 (1995-04-01), Wentzel
3M Brochure: Cellpack Working Instructions; 3M Electrical Products Division, CH-5610 Wohlen/Switzerland: Tenaga Nasional Berhad, West Malaysia; M8E065--Apr. 1992.
Ackland Gordon Lawrence
Garcia-Ramirez Rafael
Hutchinson Ted Flynn
Sundhararajan Srinivasan
Griswold Gary L.
Kirn Walter N.
McNutt Matthew B.
Minnesota Mining and Manufacturing Company
Nguyen Chau N.
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