US3678175A

US3678175A - Deformable casing joining cable ends

Info

Publication number: US3678175A
Application number: US85469A
Authority: US
Inventors: Edoardo Appiani; Alberto Felici
Original assignee: Pirelli SpA
Current assignee: Pirelli and C SpA
Priority date: 1969-12-09
Filing date: 1970-10-30
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18
Also published as: ES164260U; GB1295723A; FR2072211A5; ES164260Y; DE2059667A1

Abstract

Casing for protecting joined cable ends surrounded by variable volume insulation which is of maximum cross-section at its center and tapers to a smaller size at its ends and which has longitudinally extending corrugations to permit it to expand and contract and thereby follow the volume variations of the insulation.

Description

United States Patent Appiani et a]. [451 July 18, 1972 [s41 DEFORMABLE CASING JOINING 174/76, 88 R, 21 R CABLE ENDS [56] References Cited [72] Inventors: Edoardo Appiani, Milan; Alberto Felici,

Monza, both of Italy FOREIGN PATENTS OR APPLICATIONS [73] Assignee: Pirelli Societa- Per Azioni Centro Plrelli, 397,539 8/ I933 Great Britain ..l74/l3 Milan, Italy Filed: O 1970 Primary ExammerDarrell L. Clay Appl. No.: 85,469

Foreign Application Priority Data FieldofSearch l74/l3, 12 R, 89,91-93,

Attorney-Brooks, Haidt & Haffner 57] ABSTRACT Casing for protecting joined cable ends surrounded by variable volume insulation which is of maximum cross-section at its center and tapers to a smaller size at its ends and which has longitudinally extending corrugations to permit it to expand and contract and thereby follow the volume variations of the insulation.

10 Claims, 3 Drawing Figures Patented July 18, 1972 INVENTOES fl-7% HTTO was DEFORMABLE CASING JOINING CABLE ENIB The present invention concerns an improved casing for restoring the-continuity of the sheath of a power or control cable and is installed over an insulated cable joint protected with insulating compositions which vary their volume, in consequence of thermal or chemical-physicalactions, from the moment of the joint installation to its coming into service. The casing, by varying its shape, follows the volume variations of said insulating compositions.

It is known that, when joints are made in sheathed cables, the cable insulation is locally destroyed and the electrical or mechanical continuity of the sheath is interrupted. Both must therefore be restored .before the cable is put into operation. Therebuilding of the sheath is carried out by disposing around the joint, in such a way as to cover its central portion, a sleeveshaped casing, having tapered ends, the end openings of which have a size slightly greater than the outer diameter of the cable sheath to which they are welded or joined.

The cable insulation, appropriately rebuilt over the joint, is protected with an insulating composition supplied to the interior of the casing through a suitable pouring inlet.-

Insulating compositions of various kinds, in particular, hotpouring or cold-pouring compositions, are used for this purpose.

Hot-pouring compositions, which at room temperature are in a solid or highly viscous state, must be fluidized by heating in order to permit pouring thereof and to cause it to penetrate into all recesses of the casing, as well as to permit an easy filling of the latter. After its pouring, the compositions cools and consequently shrinks. The cooling, for the most widely used compositions, is carried out for a time period variable as a function of the involved volumes and of the physical characteristics of the material and in any case, it lasts several hours. During the cooling time, the interior of the casing must remain accessible for refilling purposes, which is intended to eliminate mainly the space left free within the casing after shrinkage of the composition in order to avoid, inside the joint when in service, the presence of undesired air bubbles or hollow spaces, which would impair the performance of the joint and hence, the cable.

If cold-pouring insulating compositions are used for filling the casing, these undergo an exothermic reaction, so that initially they beat up and expand, and after the reaction, the poured composition cools and consequently shrinks.

, In order to prevent said volume variations from producting air bubbles or hollow spaces inside the joint, it is necessary to carry out, even with the cold pouring compositions, a final preparation phase, postponed for several hours, during which the joint must remain accessible.

The need of maintaining the joint accessible in the interval of some hours between the initial preparation of the joint and its being placed in service is technically disadvantageous. Such need prolongs the total time necessary for the joint installation and consequently delays the placing of the cable into service. If the cable is laid underground, which is the most frequent situation, the trench must be left open for a long time, depriving large built-up areas of primary utilities or excluding traffic from important highways.

The present invention aims at providing'an improved casing for power and control cables having conductive or insulating sheaths, which obviates the above indicated disadvantages and does not require refilling operations, or other operations required by the need of eliminating air bubbles or hollow spaces inside the joint in the time interval between the initial installation and the coming into service of joints prepared with insulating compositions subject to volume variations due to thermal or chemical-physical actions.

More precisely, the object of the present invention is an improved casing for restoring the continuity of the covering sheath of a power or control cable over a joint protected with insulating compositions subject to volume variations from the moment of the joint installation to its coming into service,

characterized in that the body of said casing is at least partially provided with longitudinal corrugations able to facilitate and to orient its deformation and its consequent variation of capacity, the median longitudinal section of said body having a main central portion of maximum transverse size and two lateral portions tapered to a size slightly greater than the size of the sheaths of the two joined cable lengths.

The enclosed sheet of drawing illustrates by way of example a preferred, practical embodiment of the invention, in which drawing: I

FIG. 1 is a side elevation view of a preferred embodiment of the casing according to the invention assembled on the joint of a cable having a metallic covering sheath; I

FIG. 2 is the cross-sectional view taken along the line A--A indicated in FIG. 1 before the insulating composition of the hot-pouring type is poured into it; and

FIG. 3 represents the same cross-section shown in FIG. 2, after the pouring and the shrinkage of the hot-pouring insulating composition.

As shown in FIG. 1, the two cable lengths l0 and 10" are connected by means of a joint enclosed within the casing 14, whose body is preferably made of lead or of another conductive material, and is secured to the metal sheaths of the cable lengths l0 and 10" by

welds

12, 12" at the casing end openings l3, 13'', respectively.

The casing 14 is constituted by two half-shellsl4' and 14", respectively, a lower one and anupper one. The lower halfshell 14 is provided on its longitudinal edges with two L- shaped seats 15' and 15" (see FIGS. 2 and 3), the inner por tions of which receive, during the assembling, the

corresponding edges

16, 16" of the upper half-shell 14".

A pouring inlet 17, provided with a lid 18, is provided in the central portion of the half-shell 14". The two half-shells 14' and 14" are secured together by welds l9 and 19', such as, lead or solder, effected along the longitudinal contact zones between the seats 15' and 15" and the edges 16' and 16'.

The body of the casing 14 can be divided longitudinally into three positions, namely: a main central portion 20 of substan tially rectangular shape, as viewed from the side, and two oppositely tapered lateral portions 21' and 21" of trapezoidal shape, the smaller bases of which are slightly greater than the diameter of the metallic sheaths covering the two cable lengths to be joined.

In the preferred embodiment illustrated in the figures, the main central portion 20 can be inscribed in a cylinder, and the two lateral portions 21' and 21" can be inscribed in truncated cones tapered towards their

corresponding entry openings

13 and 13".

The body of the casing 14 is provided with longitudinal corrugations 22 which extend along the whole main central portion 20 and are prolonged at 22 and 22" in the lateral por-

v tions

21 and 21" along the generatrices of the corresponding circurmcribed frustum of cone, but interrupted at a predetermined distance from the two

openings

13 and 13".

After the casing is assembled on the joint, an insulating composition, solid at room temperature, is poured into the casing 14 for instance, at high temperature, until the composition overflows the opening 17. Then, the casing is tightly closed with the lid 18, sealed at 23, and at this time, normal conditions can be reestablished inside the joint between the two cable lengths l0 and 10" by carrying out further operations outside the joint, such as by closing the trench immediately afterwards. In the meantime the composition cools, with corresponding shrinkage, and creates a depression inside the tightly closed casing. The outer atmospheric pressure acting on the casing 14, whose deformability is facilitated and oriented by the longitudinal corrugations, compels the casing itself to adhere to the composition and to follow the volume variations of the latter, passing therefore from the configuration 24 to the service configuration 24' (see FIG. 3).

Even if cold-pouring compositions are used, the composition is poured, as described above, until the composition overflows the casing with respect to the pouring inlet 17; then, the lid 18 is closed and tightly sealed at 23. The exothermic reaction which takes place in the insulating composition causes an initial expansion which, acting on the corrugated walls, increases the capacity of the casing and equalizes it to the volume of the therein contained insulating composition. When the reaction is over, the insulating composition begins to cool and to shrink, and this variation is followed by the casing wall subjected to the outer atmospheric pressure.

It will be understood by those skilled in the art that the details of construction of the present invention can be varied as necessary. For example, the conductive or insulating casing could be built up with a different number of sections or with differently located joints between sections and the longitudinal corrugations could be discontinuous or alternate or could be formed of combinations of channels and projections different from the regular, sinusoidal corrugations illustrated by way of example. Also the cross-section of the theoretical area in which the portions of the casing are circumscribed could be other than circular. Another form is, for example, an ellipse or a polygon.

What is claimed is:

1. An electric cable joint between a pair of cable sections, said cable sections each having a conductor surrounded by a sheath and said joint comprising an interconnection between the conductors of said sections, a casing enclosing said interconnection and extending longitudinally of said joint from the sheath of one cable section to the sheath of the other cable section, said casing being substantially unbroken in the longitudinal direction and comprising a hollow central portion of maximum cross-section greater than that of the sheaths of said sections and that of said interconnection, and at opposite ends thereof, having a pair of hollow, tapered, end portions forming a continuation thereof, each end portion having an end opening smaller than the cross-section of said central portion and each surrounding and joined to one of the sheaths of a cable section, and void-free solid insulation within said casing and surrounding said interconnected cable sections, said casing being in complete contact with said insulation with no void spaces therebetween, said casing being provided with a plurality of longitudinally extending corrugations disposed peripherally of at least said central portion thereby pemiitting said casing to expand and contract in volume and outwardly with respect to said conductors.

2. A joint as set forth in claim 1 wherein said casing is made of conductive material.

3. A joint as set forth in claim 1 wherein the central portion of the joint has a generally circular cross-section and where the end portions have the shape of truncated cones.

4. A joint as set forth in claim 3 wherein said corrugations extend the full length of said central portion and along at least part of the lengths of said end portions.

5. A joint as set forth in claim 4 wherein said corrugations terminate at points spaced from the end openings.

6. A joint as set forth in claim 5 wherein said casing is made of conductive material.

7. A joint as set forth in claim 5 wherein at least the major portion of the periphery of the casing is corrugated.

8. A joint as set forth in claim 1 which comprises a plurality of parts which interconnect along longitudinally extending seams.

9. A joint as set forth in claim 8 which comprises a further opening in one of said portions and a cover for said further opening.

10. A cable joint as set forth in claim 1 wherein said sheaths and said casing are made of metal and said sheaths are secured to the ends of said casing with an electrically conductive connection therebetween.

Claims

1. An electric cable joint between a pair of cable sections, said cable sections each having a conductor surrounded by a sheath and said joint comprising an interconnection between the conductors of said sections, a casing enclosing said interconnection and extending longitudinally of said joint from the sheath of one cable section to the sheath of the other cable section, said casing being substantially unbroken in the longitudinal direction and comprising a hollow central portion of maximum cross-section greater than that of the sheaths of said sections and that of said interconnection, and at opposite ends thereof, having a pair of hollow, tapered, end portions forming a continuation thereof, each end portion having an end opening smaller than the cross-section of said central portion and each surrounding and joined to one of the sheaths of a cable section, and void-free solid insulation within said casing and surrounding said interconnected cable sections, said casing being in complete contact with said insulation with no void spaces therebetween, said casing being provided with a plurality of longitudinally extending corrugations disposed peripherally of at least said central portion thereby permitting said casing to expand and contract in volume and outwardly with respect to said conductors.