US1672821A - Submarine cable core and insulation therefor - Google Patents

Description

June 5, 1928.

c. MARTELL SUBMAR'INE CABLE 001m AND INSULATION THEREFOR Filed Oct. 1924 Patented June 5, 1928.

'. NI ED STATES ra'nzurornca.

CHARLES MARTELL, F CICERO, ILLINOIS, 'ASSIGNOR TO WESTERN ELECTRIC COM- IPANY, INCORPORATED, 01 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SUBMARINE CABLE CORE AND INSULATION THEREFOR.

Application filed October 7, 1924. Serial No. 742,142.

This invention relates to an improved submarine cable core, particularly of the continuously loaded type, and an improved in sulation for such cores.

5 The materials usually employed for insulating deep sea cables are gutta-percha and balata. Gutta-percha is to be preferred to balata for durability and long life. It oxidizes very slowly, is substantially non-water absorbent, and as a result will last for a very long length of time. Balata oxidizes more rapidly and its useful life as an insulation is considerably less than that of guttapercha. Balata, however, has better electri- 5 cal characteristics than gutta-percha, and electrical impulses can be transmitted more quickly through a conductor insulated With balata than through a conductor insulated with gutta-percha. Submarine cableinsulation is often made from a mixture giving better electrical characteristics than gutta- Eercha and at the same time greater duraility than balata. Hence, durability is sacrificed to obtain better electrical characteristics. Moreover, the price of. gutta-percha is considerably higher than that of other types of insulation materials. Other socalled gum exudates of the samegrade are in general much less expensive than guttapercha. It is, therefore, desirable from a cost standpoint to utilize wherever possible chelaper grades of plastic insulating materia s. 7

An object of the invention is to produce' an improved subn'larine cable core. Another object is to produce an inexpensive, durable and efiicient insulation for electrical conductors. I

The invention comprises an insulation 40 consisting of alternate laminations of guttapercha and a plastic materialhaving better electrical characteristics, and in its preferred form two laminations of gutta-perclaa and one lamination of balata, one layer of the gutta-percha being adjacent to the conductor, and the other forming the outside shell of the insulation with the layer of balata lying between the two layers of -gutta-, percha.

In the attached drawings,

Fig. 1 is a fragmentary side elevation of submarine cable core, embodying theinvention, and

-. patent to G. W. Elmen, N 0. 1,586,884, issued June 1, 1926. Adjacent to the loading ma-' terial 11 and entirely surrounding it is a layer of gutta-percha 12, and surrounding the layer of gutta-percha 12 is a layer of balata 13. Adjacent to'the balata 13 and comprising the outer shell of insulation is another layer of gutta-percha 14.

The invention as embodied in the drawings may take a variety of forms. For instance, the number of laminations need not be limited to three, but may be any number which might be required, depending upon the conditions or circumstances in which the core is to be used. It is desirable, however, to have a layer of guttapercha next to the conductor because of a slight acid content in balata which may in time cause a corrosion of the metallic conductor or loading material as the case may be. It is also deiirable on account of the physicalproperties of gutta-percha that the outside layer or lamination be of that substance. In the preferred form of the invention the layers of gutta-percha are made no thicker thanv is required to insure durability, the balance of the insulation being balata. In a desirable composite insulation of this preferred type the two layers of gutta-percha. taken together are of-about the same thickness as the single layer of balata interposed between them.

The advantage of this type of insulation 1 tioned by the total power losses in the di-- electric, is lower. An insulation ofguttapercha and balata produced according to this invention and in which the proportion corrode the conductor.

'longerlife, is to of the two materials is about equal, has a conductance at 24 C. of about 6 micromhos per nautical mile at 900 cycles; while an insulation of pure gutta-percha has a conductance of from to 50 micromhos per nautical mile under the same conditions. Gutta-percha, however, on account of its be preferred to balata for economical purposes. As an example, a submarine cable'in which the conductor is insulated exclusively with balata would in a relatively shorter time than in the case of gutta-percha be unfit for use because the balata would deteriorate, principally by oxidation. and the acid in the balata would This would cause a very great retardation in the speed at which messages couldbe. transmitted from end to end of thecablc and would ultimately cause a breaking down of the entire cable.

The price of balata, however, is comparatively low, a satisfactory grade of guttaand decomposition or of the insulation where percha as a general rule being at times as much as two or even three times as high. The lack of economy in the use of pure balata for insulation as mentioned above, is due to the. shorter life of such material as compared to gutta-percha, due to its more rapid disintegration. The initial cost is low, and by means of the present invention the low initial cost of balata is taken advantage of, deterioration of the balata avoided by means of protective layers of gutta-percha as herein disclosed.

It is not absolutely necessary that balata be used as one of the materials which will go to make up an insulation produced according to this invention. which has better electrical characteristics than gutta-percha maybe employed. Furthermore, it it is desirable to lower the cost the electrical reare' not so exacting, a material quirements 7 better electrical characteristics having no than. gutta-percha but which is cheaper in price may be employed instead of the balata. However, from the standpoint of all-around Any materialadaptability, balata is to be preferred for use in this manner.

\Vhat is claimed is:

1. An insulation for electrical conductors comprising a layer of balata, and a layer of gutta-percha.

2. An insulation for electrical conductors comprising a layer of balata, and a layer of gutta-percha, the layer of balata being thicker than the layer of gutta-percha.

3. An insulation for electrical conductors comprising a plurality of layers of balata and gutta-pcrcha, and so arranged that the desirable characteristics of each material is utilized.

4. An. insulation for electrical conductors comprising alternate layers of balata and gutta-percha.

5. Au insulation for electrical conductors comprising a layer of balata positioned between two layers of gutta-percha.

6. A submarine cable comprising -a conductor, and an insulation consisting of a thick layer of balata interposed between relatively thin layers of gutta-percha.

7. A submarine cable'comprising-a conductor, a magnetic loading material associated therewith, sisting of alternate layers of and balata.

8. A submarine cable comprising a conduetor, a magnetic loading material associated therewith, and an insulation congutta-percha sisting of a thick layer of balata interposed between relatively thin layers of gutta insulation for electrical conductors I In witness whereof, I hereunto subscribe my name this 18th day of September, 1924/ CHARLES MARTELL.

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