US2120088A - Armored conductor - Google Patents

Description

June 7, 1938. CARLSON 2,120,088

ARMORED CONDUCTOR Filed April 19, 1934 lhv ehcof": Geokge CaHsoh,

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Patented June 7, 1938 ARMORED CONDUCTOR George Carlson, Bridgeport, Conn, assignor to General Electric Company, a corporation New York Application April 19, 1934, Serial No. 121,310 Claims. (Cl. 173-267) This invention relates generally to armored electrical cables and it is directed more particularly to the improvement of the construction of armored cables provided with insulated conduc- 5 tors and with an uninsulated ground return con-' ductor.

It is an object of this invention to prevent kinking of the ground return conductor while the conductors 'of the cable are being twisted and armored.-

It is a further, object of this invention to prevent movement of the uninsulated ground return conductor relatively to the armor when the cable is installed invertical ms.

Other objects of the invention will become apparent upon reference to the following detailed description and to the drawing in which Fig. 1 illustrates the construction of a cable accordingv to the present invention; Fig. 2 illus- 0 trates the manner oi building up the diameter of the uninsulated ground return conductor of the cable; and Fig. 3 illustrates the construction of a modified cable according to the invention.

Referring now to the drawing, a metallic 25 sheath or armor l encloses two insulated'conductors 2 and 3 which are twisted with an uninsulated conductor 4. The sheath or armor .l is formed of a spirally wound metal strip having the usual construction'of interlocking turns, as

30 shown in the'drawing.

Each of the insulated conductors 2 and I is provided with an outer insulating cover I which may be a rubber and braid insulation or may be formed from any other insulation material pre- 35 ferred. The uninsulated conductor 4 is wound ith spiral turns of paper or other suitable fibrous material 8 for the purpose of building up the diameter of this oonductor'so that it is substantially the same overall diameter as that 40 of the insulated conductors I and I. Preferably, the conductor 4 is wound with a single strand of the paper or fibrous material and this strand is wound in spiral turns spaced from one another so as to leave bare or uncovered portions I at 45 intervals along the length of the conductor and having a longer pitch than the pitch of the interlocking turns of the armor. It is to be understood, however, that any desired number of strands of the paper or fibrous material may be used as a winding for the conductor 4 and that these strands may be wound in spaced spiral turns having any desired pitch. The strands are first twisted or transversely crumpled and then they are wound about the conductor 4 in a directionoppositetothedirectioninwhichthisconductor is to be twisted with the. insulated conductors 2 and 3. Instead of twisting strands of paper or fibrous material about the uninsulated conductor 4, a cord having a diameter sufiicient to build up the diameter of the conductor 5 4 to substantially the same overall diameter as the insulated conductors 2 and 3 may be twisted about this conductor. The uninsulated conductor 4, when thus wound, is twisted with the insulated conductors 2 and 3 and then the metal 10 sheath or armor l is tightly disposed about the twisted conductors. In the cable, as thus constructed, the uninsulated conductor 4 makes con-' tact with the convolutions or inner surface of the armor i at the spaced portions 1 along its 15 length, thus providing the armored cable with alternative ground returns through the armor l or through the uninsulated conductor 4.

A modified construction for another cable exemplifying the invention is shown in Fig. 3. Referring to this figure,'the insulated conductors 8 and 9, provided with braided insulation coverings I, are twisted with an uninsulated conductor l0 and all of the conductors are covered by a spirally locked metal armor II. The uninsulated conductor III comprises a hemp core II, or a core fabricated from any suitable fibrous material, and a suitable number of metal strands l8 twisted 0n the core. The metal strands are of a suitable diameter to build up the diameter of the uninsulated conductor ill to substantially the same diameter as that of the insulated conductors I and I and are twisted on the core in spiral turns having a pitch shorter than the turns of the armor. In this cable, the metal strands I: of the uninsulated conductor it make contact with the convolutions or inner surface of the armor I I, thus providing the cable with alternative ground returns through the armor or through the uninsulated conductor.

In the ordinary armored cable, provided with insulated conductors and an uninsulated ground return conductor, the uninsulated ground return conductor has a lesser diameter than the insulated conductors, and consequently kinking of the uninsulated conductor occurs when the conductors oi! the cables are being twisted and armored. The present-invention provides means for preventing the kinking of the uninsulated conductor in a cable of this type during either 5 of the operations mentioned by building up the diameter of this conductor until it is substantially the same as the diameter of the insulated conductors. This may be done either by wind-' ing this conductor with strands of paper or fibrous material, as shown in Fig. l, or-by providing this conductor with a core of suitable fibrous material and winding on the core metal strands, as shown in Fig. 3.

Another disadvantage of the ordinary armored cable in which the uninsulated conductor has a lesser diameter than the other conductor or conductors of the cable is that the uninsulated conductor tends to slip relatively to the armor when the cable is installed in vertical runs. This slippage is caused by the fact that the convolutions or turns of the armor do not press with as much force against the uninsulated conductor as they do against the insulated conductor or conductors, and consequently there is insufilcient friction between the armor and uninsulated conductor to prevent this slippage. When the uninsulated conductor slips relatively to the armor, the weight of the uninsulated conductor is supported by the terminal connection (not shown) at the upper end of the vertical run, thereby placing an undesirable strain on these connections which may ultimately lead to a broken connection. The present invention evercomes this disadvantage of the ordinary cable by building up the diameter of the uninsulated conductor until it is substantially the sameas that of the insulated conductor whereby the convolutions or turns of the armor press with equal force against the uninsulated ground return conductor and the insulated conductors and suincient friction is therefore set up between the turns of the armor and the uninsulated conductor to prevent slippage of the conductor relatively to the armor.

The invention therefore provides means for preventing kinking of the uninsulated ground return conductor of an armored cable, when the conductors of the cable are being twisted together or armored, by building up the diameter of the uninsulated ground return conductor until it is substantially the same as the diameter of the insulated conductors of the cable. The invention further provides means for preventing slipconductors and an uninsulated conductor, means associated with said uninsulated conductor for building up the overall diameter of said conductor to substantially the same overall diameter as that of the insulated conductors, said insulated and uninsulated conductors being wound spirally I together with the built-up uninsulated conductor resting in one of the valleys between the twisted insulated conductors, and a metal armor substantially completely enclosing said conductors and having a plurality of interlocked turns clamping the uninsulated conductor with sufllcient force to prevent said uninsulated conductor from slipping relatively to the armor.

2. A cable comprising a plurality of insulated electrical conductors twisted with an uninsulated electrical conductor said uninsulated conductor interlocked spiral turns clamping the covered portions of the uninsulated conductor with sufiicient force to prevent slippage oi the uninsulated conductor relatively to the armor.

3. A cable comprising a plurality of insulated electrical conductors twisted with an uninsulated electrical conductor said uninsulated conductor having a lesser diameter than the overall diameter of each of the insulated conductors, a fibrous material wound in a long pitch spiral on the uninsulated conductor ior building up the overall diameter of said uninsulated conductor to substantially the same overall diameter as that of the insulated conductors, said built-up uninsulated conductor resting in one of the valleys between the twisted insulated conductors, and a metal armor substantially completely enclosin said conductors, said armor comprising a plurality of interlocked spiral turns which have a shorter pitch than the winding on said uninsulated conductor and which clamp the covered portions of the uninsulated conductor with suflicient force to prevent said conductor from slipping relatively to the armor.

4. A cable comprising a plurality of insulated electrical conductors twisted with an uninsulated electrical conductor said uninsulated conductor having a core of fibrous material and metal strands, spirally wound on said core, for building up the overall diameter oi. said conductor to substantially the same overall diameter as that of each of the insulated conductors said uninsulated conductor resting in one of the valleys between the twisted insulated conductors and a spiral interlocked metal armor substantially completely enclosing said conductors and clamping the uninsulated conductor with sufllcient force to prevent said uninsulated conductor from slipping relatively to the armor.

5. A cable comprising a plurality of insulated electrical conductors twisted with an uninsulated electrical conductor said uninsulated conductor having a core of fibrous material and metal) strands, spirally wound with a short pitch on said core, for building up the overall diameter of the uninsulated conductor to substantially the same overall diameter as that of each of the insulated conductors said uninsulated conductor resting in one of the valleys between the twisted insulated conductors, and a metal armor of interlocked spiral turns, having a longer pitch than that of the metal strands substantially completely enclosing said conductors, the turns of said armor clamping the uninsulated conductor with sufllcient force to prevent said conductor from slipping relatively to the armor.

GEORGE CARLSON.

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