US1981612A - Cable - Google Patents

Description

P. H. CHASE Nov. 20, 1934.

CABLE Filed Jan. 17, 1929 FIG.

Patented Nov. 20, 1934 UNITED STATES,

PATENT OFFICE This invention relates to cables, and with regard to certain more specific features toimpregnated electric cable, preferably for high voltages.

6 Among the several objects of the invention may be noted the provision of a simple and improved method of constructing a cable to. relieve or equalize hydrostatic pressures within the sheath; the provision of improved separated gas filled l expansion devices or units within the cable for controlling the internal pressure due to temperature and other changes; the provision of a cable construction of the class described which minimizes the formation of-voids therein; and 18 the provision within a cable of the class described for compensating the pressures caused by the relative expansion and contraction of the parts of the cable. Other objects will be in part obvious and in part pointed out hereinafter.

Q0 The invention accordinglycomprises the elements and combinations of elements, features of construction and operation, arrangements of parts, steps and sequence of steps, which are exemplified in the'structure hereinafter described and the scope or application of which is indicated in the following claims.

In the accompanying drawing in which is illustrated several embodiments of the invention,

Fig. 1 is a trimetric view of a section of threeconductor cable, certain portions being broken away to show the invention;

Fig. 2 is a cross section of the cable of Fig. 1;

Fig. 3 is a cross section, similar to Fig. 2,

Similar reference characters indicate corre-- sponding parts throughout the several views of the drawing. V 7

Referring now more particularly to Fig. 1, the

cable conductors are designated by numeral 1 and the insulation bynumeral 2. Laid in one or more of the lateral and/or central spaces 6 between the insulated conductors is a series of separate, self-contained, convoluted tubes or containers or flexible bellows or units-4, having closed ends and peripheral ridges to provide the convolutions, which units are each so constructed of thin, flexible metal, for example copper, that the length, and therefore the volume, is capable of substantial change, as a consequence of the (ill movement of the walls of the containers. This movement or expansion is primarily longitudinal but there is also' some lateral expansion. Over these hollow containers 4 may be applied a retaining or protecting tape 5, which may be made of paper or metal or of other suitable material. This protecting tape 5 is laid on helically. Such lateral or central spaces as are occupied in'part by the tubes 4 may be completely filled with the usual fillers. An outer lead sheath 3 completes thestructure.

Figs. 4 and 5 show in end and side section and projection one of the containers or peripherally convoluted tubes 4, preferably though not necessarily of circular cross-section. The end section and projection of the container 4 as will be seen in Fig. 4, is peripherally of generally heartshaped or triangle-shaped cross section which more nearly conforms to the space ordinarily occupied by the lateral fillers in the cables and so therefore afiords a greater volumetric change fora given change in length of the flexible bellows.

The units 4 shown in Figs. 1 to 8 comprise a series of separate, longitudinally expansible bellows or tubes, which contain fluids of gaseous form, which fluids may, if desired, be of nature which would ordinarily adversely affect the insulation of the cable if in contact therewith or interspersed therein. It is apparent that through the usage of a gas such as air, for example, for filling the hollow tubes or units, the internal hydrostatic pressure in the cable is made susceptible of control. Further, it is apparent that this control of hydrostatic pressure is quickly responsive to changed conditions and is largely independent of the degree of viscosity or fluidity of the cable impregnating compound. The hollow units maybe used in a cable which has oil or compound-filled passages in or adjacent to the insulation or conductor. g

The adjacent ends of the containers may be close together or may be separated appreciable distances, depending for example upon the mobility of the impregnating compound, the extent of equalization of pressure desired along the cable and the volumetric capacity of the containers.

Variations of hydrostatic pressure within a cable are largely determined by the relative temperatures and coefiicients of expansion of the conductor, insulation, compound and outer sheath. As the conductor, solid insulation and impregnating compound or oil are substantially incompressible, the resultant pressure from their expansion ordinarily is exerted on the outer sheath. Where this is composed of lead, permanent stretching of the sheath may be caused.

Conversely, when the cable cools the internal hydrostatic pressure will be lower than under corresponding conditions before the sheathha'd stretched. The resulting low internal pressures may result in the rapid deterioration and ulti mate failure of the insulation, due to the formation of voids and ionization therein under electrical stress. The utilization of my hollow gasfilled tubes afiords a means and method of controlling or regulating the hydrostatic pressure within predetermined limits and thereby contributes to minimize the stretching of the outer sheath, the formation of voids and the destruction of the insulation. i

As the temperature of the different parts of the cable changes and when there is a difference in the rate of expansion of those parts, the pressure upon the walls of the hollow containers changes and if there is an excess external'pressure, such as for example when the cable is heating, the hollow tubes 4 decrease in length and thus limit the pressure exerted upon the outer sheath.

Conversely, in case there is a decrease of pressure external to the hollow tubes, such as, for example, when the cable is cooling, the hollow tubes increase in length and compensate for the shrinkage of the compound and other parts and thus prevent the pressure from decreasing to values which would cause the formation of voids. It will be seen from the above that inasmuch as the gaseous fiuid is inherently compressible, that expansion and contraction may take place independently as determined by' the conditions existing along or adjacent each of the independent hollow tube sections or containers.

Each hollow tube section or container of the desired cross-sectional area, after being filled with the desired gas at the desired pressure, is closed so that the space occupied by the tube is determined by the pressure and temperature oi. the cable parts adjacent thereto.

The gas filled hollow tubes in each section of cable constitute a number oi relatively small separate closed containers and thus closely localize the extent of damage or'loss oi fluid in the event r of a leak or rupture of the walls 01' one of the hollow tubes.

It is apparent that two or more series of hollow tubes may be used in case a greater range 01 volumetric capacity is desired.

The portions of the lateral and central spaces 6 not occupied by the tubes 4, may be filled with the usual filler'materials such as'shown by the stippling in Figs. 2, 3, and 8, or left open for the storage and/or passage 01' the impregnating compound or oil.

Fig; 8 illustrates expansible, convoluted containers 4 of circular cross section, carried in the center 20 of the conductor 1, in a cable of the hollow-conductor type.

The separate gas-filled hollow tubes or containers may be assembled together, for example as illustrated in Figs. 1, 2, 6, '7, and 8, by means oi. wire spacing cages 8, made up of wires 9, so they form a chain or series of tubes or containers for application in the lateral and central spaces through protecting tubes.

along the insulated conductors or for drawing Fig. 7 shows an end sectional view of a convoluted container and the wires 9 of Fig. 6. The cages are somewhat longer than the containers to permit endwise expansion.

The cages 8, as in the case of Figs. 6 to 8, are likewise applicable to the triangular cross section bellows elements 4 of Figs. 4 and 5, and are thus illustrated in position in the cable in Figs. 1 and 2. However, as indicated in Fig. 3, the triangular bellows 4 are advantageous in themselves, not requiring the presence of the cages 8 'or their utility.

It is also to be understood in this invention that lead cable of the class described is usually laid in lengths or sections which are joined together at suitable splices. These sections are usually many feet in length. It is a characteristic of this invention that the equalizing, hollow tubes or. units are much shorter than the cable sections.

In view of the above, it willbe seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. The cable comprising a conductor, substantially incompressible insulating material surrounding the conductor which material expands with increasing temperature, a sheath surrounding said conductor and insulating material, and a series of hollow containers within the sheath. said hollow containers being held in linked cages 1 to form at least one chain, said cages protecting the containers.

2. The cable comprising a hollow conductor. substantially incompressible insulating material surrounding the conductor which material expands with increasing temperature, a sheath around the conductor and insulating material. and a series of substantially longitudinally e!- pansible bellowswithin said hollow conductor, cages respectively surrounding the bellows and being longer than the same to permit longitudinal expansion and means linking the cages.

3. The cable comprising a conductor, substantially incompressible insulating material surrounding the conductor, said material expanding with increase in temperature, a sheath surrounding said conductor and said material, a series of hollow containers within the sheath, and cages holding said hollow containers, said cages protecting the containers.

4. The cable comprising a conductor, substantially incompressible insulating material surrounding the conductor, said material expanding with increase in temperature, a sheath surrounding said conductor and said material, a series of hollow longitudinally expansible containers within the sheath, and cages holding'said hollow containers, said cages protecting the containers, and said cages being 01 a size adapted to permit appreciable expansion 01' said containers therein.

5. The cable comprising a conductor, substantially incompressible insulating material surrounding the conductor, said material expanding with increase in temperature, a sheath surbut without the conductor, and cages holding said hollow containers, said cages protecting the containers.

6. The cable comprising a conductor, substan- I tially incompressible insulating material surrounding the conductor, said material expanding with increase in temperature, a sheath surrounding said conductor and said material, a series of hollow longitudinally expansible approximately triangular containers within the sheath but without the conductor, and cages holding said hollow containers, said cages protecting the containers, and said cages being of a size adapted to permit appreciable expansion of said containers therein.

1. The cable comprising a conductor, substantially incompressible insulating material surrounding the conductor, said material expanding with increase in temperature, a sheath surrounding said conductor and said material, a series of longitudinally expansible hollow containers within the sheath and within the conductor, and cages holding said hollow containers, said cages protecting the containers.

8. The cable comprising a conductor, substantially incompressible insulating material surrounding the conductor, said material expanding with increase in temperature, a sheath surrounding said conductor and said material, a series of hollow longitudinally expansible containers within the sheath and within the conductor, and cages holding said hollow containers, and. said cages protecting the containers, said cages being of a size adapted to permit appreciable expansion of said containers therein.

9. The cable comprising a plurality of conductors, substantially incompressible insulating material surrounding the conductors, said material expanding with increasing temperature, a sheath surrounding the conductors and said material, said conductors having lateral spaces therebetween of approximately triangular form, and a series of expansible and compressible hollow bellows containers of approximately triangular form in said lateral spaces.

10. The cable comprising a plurality of conductors, substantially incompressible insulating material surrounding the conductors, said material expanding with increasing temperature, a sheath surrounding the conductors and said material, said conductors having spaces therebetween of approximately triangular form and a series of expansible and compressible hollow bellows containers of approximately triangular form in said spaces.

PHILIP H. CHASE.

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