US1762255A - Method of plugging cables - Google Patents

Description

June 10, 1930.

c. E. BALDWIN METHOD OF PLUGGING CABLES Filed Sept. 1, 1928 1 [III] III 1 III I 11) INVENTOR' CEBalmmJm A'ITORN EY Patented June 10, 1930 UNITED STATES PATENT OFFICE CHARLES E. BALDWIN, OF STANHOPE, NEW JERSEY, ASSIGNOR T AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK METHOD OF PLUGGING- CABLES Application filed September 1, 1928. Serial No. 303,624.

This inventionrelates to cables, and more particularly to arrangements for plugging a cable in order to prevent the flow of gas through the cable durin pressure tests.

In certain cases of ca le testing it is desirable that gas pressure be maintained in order that mechanical defects, such as holes in the sheath, may be detected and in order to prevent the entrance of water which m'might otherwise occur before the defects could be located and repaired. \Vhen gas pressure is used for such purposes it is, of course, necessary or at least desirable to seal the cable at two or more points to prevent the flow of gas along the cable or the escape of gas at the terminals-that is, to confine the gas to the cable section under test. Various gas-tight plugs for this purpose have been used or suggested, the esscntial'idea upon which these plugs have been based is that of filling a cable sleeve with molten wax, the single sleeve being placed over the cable at a place where a short section of the sheath has been removed. Such plugs have notbeensatisfactory, chiefly for the reason that the wax, upon cooling, shrinks away from the inner surface of the sleeve and small leakage paths are formed over which the gas passes to other sections of the cable.

The applicants arrangement for plugging a cable against the flow of gas therethrough is based in part upon the idea of filling a sleeve with molten wax but has important novel features and important advantages over any plugging arrangement heretofore suggested and known to the applicant. Thus, it is to be understood that the applicant claims as his invention not the broad 40 idea of employing wax to seal a cable section but the novel method indicated by the followingillustrative description and claimed hereinbelow.

The principal object of this invention is the provision of gas-tight plugging arrangements which do not permit slight leakage of gas over small aths between the wax and the enclosing lea', thus giving satisfactory sealing even in the case of relatively high pressures.

Another object of the invention is the provision of gas-tight plugging arrangements which permit of satisfactory construction and application in the field.

In general, the applicant plugs a cable against the flow of gas therethrough by removing a short section of the cable sheath, wiping a lead sleeve over the opening, filling this sleeve with molten wax, cutting a transverse strip from the sleeve, wipin a second and larger lead sleeve over the first sleeve and filling the outer sleeve with moltenwax.

The invention will be more clearly understood when the following detailed description is read with reference to the accompanying drawing, of which Figure 1 shows in longitudinal section a cable plugged at one point in accordance with the invention, and Figs. 2, 3 and 4 indicate the various earlier steps of the applicants method.

\Vith reference to the details of the drawings, there is shown a cable having an on veloping sheath 1 and a plurality of conductors 2'. When it is desired to seal the cable against the flow of gas through the section shown, the sheath 1 is removed over a short length of the cable, say about ten inches. (See Fig. 2.) Preferably, the conductors 2 are separated as indicated to per- -mit the wax to penetrate and fill the interstices. The ends of the cable sheath which bound the gap should be slightly flared in order to prevent the cutting of or other damage'to the conductors. Assuming that the cable has a diameter of approximately 2 inches, care should be taken in the separating of the cable conductors that the extended diameter of the group of. conductors be slightly less than, say, four inches. A

four iuch split sleeve 3 having a length ofv about 14 inches is now placed over the opening in the cable sheath.

(.See Fig. 3.) This sleeve should be lined with a layer of wrapping paper or similar material, as indicated 1n the drawing, in order that the conductors 2 may not come in contact with the sleeve 3. This layer of paper may be regarded as replacing the ordinary cable bandage. The sleeve 3 is wiped in place as shown, and a small filling hole 8 is then made through the lead of the sleeve and through the paper lining. In addition a vent hole 9 is made through the sleeve and lining. Wax heated to approximately 375 F. is poured over the sleeve and over the cable for about two feet on either side of the sleeve for the purpose of heating the cable and the sleeve. With the cable and the sleeve thoroughly heated, wax at a temperature of about 300 F. is poured through the opening in the sleeve by means of a funnel. During this operation the sleeve and the neighboring portionof the cable should be kept hot. When no more Wax can be poured through the opening the sleeve is allowed to. cool.

A transverse band of about four inches, including the area through which the filling and vent holes were pierced, is now carefully cut out of the middle of the sleeve 3, as indicated in the drawing (see Fig. 4), the out being carried through the paper lining but care being taken that the wax (not shown) is not cut. A second sleeve 4 considerably larger than the sleeve 3six inches in diameter, for instaneeand having a length of approximately 20 inches is now placed over the sleeve 3 and wiped in place, as indicated in the drawing. Three small holes 5, 6 and 7 are made in this outer sleeve 4:. A grease fitting is placed in the hole 6, and through the other hole 5 wax at a temperature of 350 F. is poured into the outer sleeve. The opening 7 serves as a vent hole. When no more wax can be added by the pouring method, the sleeve 4 is allowed to cool and the filling and vent openings 5 and '7 are sealed with solder. Wax at. about 250 F. is then forced into the sleeve through the opening 6 with a grease gun until the operation of the gun indicates that considerable pressure has been created in the sleeve. Then the grease fitting is re- I .moved and the opening 6 is sealed.

It will be understood from an examination of the above description that the outer sleeve 4 is in eiiect a reservoir from which molten wax is forced into the inner sleeve 3 and into any voids which may exist between the cable conductors 2 and the enveloping sheath 1 and sleeve 3. \Vhen the wax in the outer sleeve 4 cools it shrinks tightly about the cable and the inner sleeve 3, and the cable is satisfactorily plugged against the flow of gas.

While approximate measurements have been indicated in the above description of the cutting of the sheath 1 and the placing over the cable of the sleeves 3 and 4 this is, of course, merely for the purpose of illustration. In general, it is to be understood that, while the invention has been specifically described as embodied in a certain form and as applied to a certain type of cable, this description does not limit either the scope or the application of the invention.

The true limitations are to be found by an examination of the appended claims.

What is claimed is:

1. The method of plugging a cable against the flow of gas therethrough which consists in removing a short section of the cable sheath, wiping a sleeve over the open section of the cable, filling the sleeve with a sealing compound, removing the middle section of the sleeve, wiping an outer sleeve on the cable over the first sleeve and filling the outer sleeve with a sealing compound.

2. The method of plugging a cable against the flow of gas therethrough, the cable comprising a plurality of insulated conductors and an enveloping sheath, which consists in removing-a short section of the sheath, separating the conductors, wiping a sleeve over the open section of the cable, filling the sleeve with a'sealing compound, removing the middle section of the sleeve, wiping an outer sleeve on the cable over the first sleeve and filling the outer sleeve with a sealing compound.

In testimony whereof, I have signed my name to this specification this 30th day of 4 August, 1928.

' CHARLES E. BALDWIN.

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