US3378627A - Adaptors for terminating devices in high voltage power cables - Google Patents

Description

April 16, 1968 R. P. ALDIGHIERI ADAPTORS FOR TERMINATING DEVICES IN HIGH VOLTAGE POWER CABLES Filed April 16, 1965 INVENTOK I RUDOLPH P. ALDIGHIERI ATTORNEY United States Patent 3,378,627 ADAPTORS FOR TERMINATING DEVICES IN IHGH VOLTAGE POWER CABLES Rudolph P. Aldighieri, Long Valley, N.J., assignor to Elastic Stop Nut Corporation of America, Union, N.J., a corporation of New Jersey Filed Apr. 16, 1965, Ser. No. 448,716 4 Claims. (Cl. 17473) ABSTRACT OF THE DISCLOSURE A bedding tape adaptor for enabling the use of cable terminating devices of the type ordinarily designed for concentric neutral cables in terminating high voltage power cables of the type having an electrically conductive bedding tape wrapped around the insulation which surrounds the conductor of the cable, the adaptor being in the form of a relatively thin-walled tubular member of electrically conductive ela-stomeric material which is readily dilatable so as to be easily slipped over the bedding tape for effectively securing the end of the tape against the insulation and providing a relatively firm foundation including an external cylindrical surface for receiving a complementary cylindrical bore of the terminating device in watertight electrical contact therewith.

This invention relates to bedding tape adaptors, and more particularly to such adaptors for high voltage shielded power cables to terminate the same in such a manner as to render them corona free, and also to drain any leak-age cur-rent or voltage which has accumulated on the shield to ground.

One type of high voltage power cable comprises a metallic conductor surrounded by insulation, and wrapped by an electrically conductive bedding tape of graphite impregnated cloth drawn tightly down against the insulation so that no air exists between the bedding tape and the insulation. Above this bedding tape is applied a layer of a conducting metallic shield drain such as copper tape or screen, covered by a jacket for external protection of the cable. In order to terminate such cable, it is necessary to terminate both the bedding tape and the metallic shield drain above the insulation so as to be stepped back a considerable distance from the end of the insulation.

At the location where the bedding tape ends, it has been found in the past extremely difiicult to keep the bedding tape tight against the insulation and preclude the establishment of an air void between the bedding tape and the insulation. It is also necessary when terminating a shielded cable, to provide a means of stress relief at the point at which the bedding tape or the shield or both have their ends.

Various expedients have been provided to accomplish thisstress relief. However, these devices are made for a particular type of cable known as concentric neutral, and to use these devices for stress relief on cables having a bedding tape requires the provision of adaptors.

It is therefore an important object of the present invention to provide .an adaptor which will enable the standard line of connectors and stress relief cones which are made for concentric neutral cables to be applied without change in size or configuration to cables of the type having a bedding tape and metallic lead jackets. Another object is to provide such adaptors which will positively hold the bedding tape termination against the insulation in such a manner that it will preclude any air from being trapped between the insulation and the bedding tape. A further object is to provide a unit which can be carried by a workman and applied to the cable in the field in a minimum of time, effort and inconvenience. This 3,378,627 Patented Apr. 16, 1968 application involves minimum skill to assemble, since it requires substantially no taping.

According to the invention, the adaptor comprises a tube of electrically conductive material slid over the bedding tape toward the cut back end of the conductive metal shield. The bedding tape is then unwound until it reaches the trailing end of the tube, Where it is cut off, or folded over the adaptor.

In the drawings:

FIGUREI is a vertical axial section through a cable end provided with an adaptor constructed according to the preferred embodiment of the present invention; and

FIGURE 2 is a similar view of a modified form of the same.

The cable shown comprises a metallic wire conductor 10, which may be solid or stranded, having a covering of insulation 12, which is preferably a solid tube molded thereon. Wrapped around the insulation is a bedding tape 14 of semiconductive mate-rial, such as graphite impregnated cotton cloth, which is drawn tight down against the insulation so that no air exists between the electrically conductive bedding tape and the insulation, so as to form an electrostatic shield for the cable.

The bedding tape 14 is preferably covered with a conductive metallic shield drain 16, preferably of copper tape or screen wrapped around the bedding tape 14. The copper tape 16 drains the voltage accumulating on long runs of bedding tape. A protective jacket is usually applied over the copper shield drain. The protective jacket 18 is cut back as at 22 to expose the copper shield 16, which is then unwound back to the line 28 to expose the bedding tape 14. Between the line 28 and the jacket end 22, a conductor 30 is connected to the copper shield 16 to lead to a ground connection.

An adaptor is provided, which comprises a tube 24 of electrically conductive rubber having an annular shoulder 26. The bore of the tube 24 is of a diameter to make a snug -fit with the outside of the bedding tape 14. The bore 25 of the tube 24 is lubricated and passed over the end of the conductor 10 and insulation 12 to slide onto and over the bedding tape 14, advancing the shoulder 2-6 toward the jacket end 22, while the trailing end of the tube passes-the insulation end 20. The bedding tape 14 is then unwound until it reaches the trailing end of the tube 24, where the bedding tape is cut off, or folded back over the outside of the trailing end of the adaptor.

A terminating device in the form of a stress relief cone is provided comprising an inner cone 32 of an insulating elastomeric material, having a central bore 34 of a diameter to slide over, but tightly grip, the insulation 12 in waterproof contact. An outer cone 36 of electrically conductive material, also elastomeric, is secured to the inner cone 32 by molding. This outer cone has a central bore 38 of the same diameter and function as the bore 34. The outer cone has a sleeve 40 with an enlarged bore 4-2 to snugly receive the adaptor tube 24 in waterproof and electrical contact. The insulation 12 is cut back as at 20 to bare the end of the conductor 10. Other terminating devices such as electrical connectors with the same style of stress relief configuration may also be mounted upon the adaptor.

In the form shown in FIGURE 2, the bedding tape 14 is covered by a conductive jacket 44 of metallic lead. The adaptor 46 is a tube of conductive rubber having an enlarged sleeve portion 48 to receive the terminal rim 50 of the lead jacket in waterproof contact. The bedding tape and the lead jacket can both be cut off in the same plane, and the interior of the sleeve 48 is undercut to form an inwardly tapering shoulder 52 for contacting the bedding tape 14. Axial thrust in applying the sleeve 48 increases the contact with the bedding tape 14 to a land contacting the lead jacket rim 50. It also may be desirable to mount the adaptor above the bedding tape as was done in the cable used in FIGURE 1. The stress relief cone shown in FIGURE 1 is applied, with the adaptor tube 46 received in the sleeve 40 in waterproof and electrical contact.

What is claimed is:

1. A cable termination for a high voltage power cable of the type having an electrically conductive bedding tape surrounding the cable insulation, said termination com prising a terminating device having a sleeve of electrically conductive elastomeric material with a resiliently dilatable cylindrical bore having an internal diameter considerably larger than the outside diameter of the bedding tape, and a bedding tape adapt-or including a relatively thin-walled tubular member of electrically conductive elastomeric material having an inside diameter and an outside diameter, the relative normal dimensions of the inside diameter of the tubular member and outside diameter of the bedding tape being such that the inside diameter of the tubular member is resiliently dilated and grips the bedding tape to secure the terminal end thereof void free against the cable insulation and the relative normal dimensions of the outside diameter of the tubular member and the inside diameter of the bore in the terminating device being such that the bore is resiliently dilated and grips the tubular member to make electrical connection with the bedding tape through the tubular member, the relative dimensions of the inside and outside diameters of the tubular member defining a Wall thickness in said member which renders the inside diameter thereof so readily resiliently dilatable as to enable passage of the entire length of the tubular member over the bedding tape.

2. The adaptor of claim 4 wherein the tubular member has an internal undercut groove between said internal cylindrioal surface of enlarged diameter and said inside diameter of the tubular member, said undercut groove establishing an inwardly tapering shoulder for intimately contacting the terminal end of the bedding tape with said shoulder resiliently deformed to establish a land engaging at least a portion of the terminal rim of the jacket to assure that all air is excluded from between the bedding tape and the insulation and any air trapped within the tubular member in the vicinity of the bedding tape is confined within the undercut groove, surrounded by electrically conductive materials.

3. A bedding tape adaptor for enabling the termination of a high voltage power cable of the type having a bedding tape surrounding the cable insulation and a jacket of electrically conductive material surrounding the bedding tape, said adaptor comprising a relatively thin-walled tubular member of electrically conductive elastomeric 4 material having an inside diameter and an outside diam eter, the relative normal dimensions of the inside diameter of the tubular member and the outside diameter of the cable insulation being such that .the inside diameter of the tubular member must be resiliently dilated to grip the insulation and secure the tubular member thereon in water proof contact therewith with a first portion of the tubular member in electrical contact with the bedding tape, and an enlarged further portion provided with an undercut groove forming an inwardly tapering shoulder for int-imately contacting the terminal end of the bedding tape with said shoulder resiliently deformed to establish a land engaging at least a portion of the terminal rim of the jacket to assure that all air excluded from between the bedding tape and the insulation and any air trapped within the tubular member in the vicinity of the bedding tape is confined within the undercut groove, surrounded by electrically conductive materials.

4. A bedding tape adaptor for enabling the termination of a high voltage power cable of the type having a bedding tape surrounding the cable insulation and a jacket of electrically conductive material surrounding the bedding tape, said adaptor comprising a relatively thin-walled tubular member of electrically conductive elastomeric material having an inside diameter and an outside diameter, the relative normal dimensions of the inside diameter of the tubular member and the outside diameter of the cable insulation being such that the inside diameter of the tubular member must be resiliently dilated to grip the insulation and secure the tubular member thereon in waterproof contact therewith with a first portion of the tubular member in electrical contact with the bedding tape, and an externally flanged second portion at the end of the tubular member furthest from the terminal end of the cable, said externally flanged second portion having an internal cylindrical surface of enlarged diameter receiving and engaging the outside diameter of said jacket when the inside diameter of the tubular member grips the cable insulation and said first portion of the tubular member is in electrical cont-act with the bedding tape.

References Cited UNITED STATES PATENTS OTHER REFERENCES Blume, Ger-man printed application, lished Sept. 24, 1959.

LARAMIE E. ASKIN, Primary Examiner.

1,065,910, pub-

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