US3448204A - Electric power cable - Google Patents

Description

June 3, 1969 R, J, PERRONE ETAL 3,448,204

ELECTRIC POWER CABLE Filed'MarCh ll, 1968 PRIOR ART 1N fm/'1014s' R .J. PERRON E O. E. JORE United States Patent U.S. Cl. 174-115 5 Claims ABSTRACT 0F THE DISCLOSURE Flat power cables, used -in hard service, such as powering mining machines, have flat, grounding-conductor, spacer assemblies, with extruded coverings, between the insulated conductors.

BACKGROUND OF THE INVENTION Our invention relates to insulated cables with dissimilar or auxiliary conducting elements and particularly to flat tough, flexible portable cables of the type that can be repeatedly taken up on reels and dragged over the ground. Such cables are typically used to carry power to mining machines and, for such use, are known as mining machine cables.

It has been known to make such cables with the insulated conductors parallel, as in Patent 2,455,773, and with flat grounding wires, reinforced by fabric breaker strips between the conductors as in Patent 2,689,268. A commercially successful 3-conductor mining machine cable that has proven very satisfactory in hard service is constructed flat with the two end conductors having D- shaped insulation and the center conductor with a square insulation. In the two divisions between the insulated conductors there are disposed bare (in the sense of being uninsulated), stranded grounding conductors that have been rolled flat. When the flat cable is considered in a horizontal position the flat grounding conductors are vertical. These grounding conductors are not as wide as the power conductor insulation and at both edges of each of the grounding conductors there are square or rectangular rubber or plastic positioning spacers. The spacers keep the stranded grounding conductors centered, and it has been found that they must be square or rectangular to be retained in position during assembly. In this known cable nylon fabric breaker strips are laid flat on both sides of each grounding conductor, making four breaker strips in all. The assembly so far described is covered with a nylon open web braid and then paid into an extrusion machine where a tough synthetic rubber jacket is applied over it.

While cables constructed in the manner described have performed well they have been difficult to make because of the need for fabric nylon breaker strips, the care required in handling of the square spacers to keep them from twisting and, particularly, because of the difliculty of paying the complex assembly of thirteen elements into the braider. It has been found that round spacers cannot be retained in their proper positions in this assembly.

SUMMARY The diiculty of producing mining machine cables has been reduced with no sacrifice, and even an improvement, in performance and the simplicity of manufacture has been greatly increased by the cable of our present invention. Our new flexible electric cable comprises a plurality, usually two or three, insulated power-carrying conductors laid in flat, parallel arrangement, with a thick, tough jacket surrounding them. It also comprises at least one uninsulated flat grounding conductor positioned, within the jacket, between two of the insulated conductors and parallel to them, and dielectric positioning spacers laid against the edge of each grounding conductor. A positioning spacer is laid against each edge of each grounding conductor. A thin continuous extrusion of synthetic polymer, preferably nylon 1-l0 mils thick, surrounds each grounding conductor and the positioning spacer or spacers, forming a grounding-conductor-spacer assembly directly adjacent to the insulated conductors.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 shows a perspective, with elements exposed, of a prior art cable.

FIGURE 2 shows a perspective, with elements exposed, of an embodiment of the cable of our invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Prior list Since it is diflicult to understand the nature of our invention without a detailed consideration of the prior art, a very 4brief description of present practice is herein given.

In FIGURE 1 a known type of mining machine cable is indicated generally by the numeral 10. It has 3 conductors 11, of flexibly stranded copper encased, respectively, in thick walls lof insulation 14, 15, 16'. Between each pair of insulated conductors there is positioned an uninsulated flat grounding conductor, a conductor 17 :being positioned between the conductors 11 and 12, and a conductor 18 `between the conductors 12 and 13. The conductor 17 is protected by 2 square rubber positioning spacer strips 19, 20v and the conductor 18 by two strips 21, 22. These spacer strips must be square or rectangular in section since it has been established that round strands will work out of position during assembly or use of the cable. Woven nylon breaker strips 23, 24 separate the conductor 17 from the insulated conductors 11 and 12, respectively, and identical breaker strips 26, 27 separate the conductors 18 from the respective insulated conductors 12 and- 13. These strips 23, 24, 26, 27 are essential to prevent destruction, under flexing, of the grounding conductors 17, 18. The whole 5-conductor assembly (3 insulated and 2 grounding) is covered by an open nylon braid 28 over which is extruded a jacket 29 of neoprene or other tough material. Considering the live conductors 11, 12, 13, 17, 18; four positioning spacers 19, 20, 21, 22; and four Ibreaker strips 23, 24, 26, 2,7 it will 'be seen that a complex assembly of thirteen unconnected units must be paid into a braiding machine to apply the braid 28.

=In our improved cable, indicated generally by the numeral 30 of FIGURE 2, three flexibly stranded copper conductors 31, 32, 33 are insulated respectively with heavy walls of insulation 34, 35, 36. The insulated conductors are separated .by grounding- conductor assemblies 37, 38 constructed as follows. A flat grounding conductor 39 of very flexible construction has assembled with it, against it edges, continuous elongated extruded positioning spacers 41, 42 of a material such as polyvinyl chloride, neoprene, nylon vor the like. The strand 39 is made in a known manner by rolling a hunched strand of copper wires, or it may tbe braided, within the scope of our invention. The positioning spacers 41, 42 are round in section as opposed to the strips 19, 20 since, as shall be seen, they are firmly held in position. It will be understood that an important saving is effected by the use of round, rather than square positioning spacers since no special precautions are necessary to keep them from twisting. In production there is les-s scrap and the operation can proceed much faster with less operator attention with the use of our round spacers,

but these are only possible because of an extrusion 43 of nylon that we have applied over the grounding-strand spacer assembly. This extrusion is very thin, preferably 3 to 5 mils, or at the extremes 1-10l mils in thickness. Prior to our invention it had not been found possible to substitute lilrns of nylon for the woven strips 23, 24, because in the strenuous service for which mining machine cables are intended, the film would buckle and fold, eventually causing a failure in the grounding conductor. A nylon braid 44 is applied over the assembly of the conductors 31, 32, 33 similar to the braid 28 but instead of having to pay thirteen separate elements into the braider we have to pay only ve, the three conductors 31, 32, 33 and the two grounding wire assemblies 37 and 38. In addition we have eliminated the slow operation of weaving the strips 23, Z4, 264 and 27 in favor of a high-speed ex-` trusion of the coverage 43 on the assembly 37 and its equivalent on the assembly 38. v

The cable of FIGURE 2 having walls 34, 35, 36 formed of neoprene, extrusion 43 of nylon, and a jacket of neoprene was found to perform well as a mining machine cable. Other known conductor insulations and jacketing materials may, however, be used within the scope of our invention, as may extrusions 43 of materials other than nylon such as polypropylene, polyvinyl chloride, poly vinylidene fluoride, and polyethylene. Although the cable 30 that has been described has three power conductors ,and two grounding-conductor assemblies it will be understood that other embodiments of our invention may have two power conductors with one grounding conductor assembly or four power conductors with three groundingconductor assemblies, etc.

We have invented a new and useful cable of which the foregoing description has been exemplary rather than denitive and for which we desire an award of Letters Patent as defined in the following claims.

We claim:

1. A flexible electric power cable comprising (A) a plurality of insulated power-carrying conductors laid in at, parallel arrangement,

(B) a thick, tough jacket surrounding said insulated conductors,

(C) at least one uninsulated flat grounding conductor positioned within said jacket between two of said insulated conductors and parallel thereto,

(D) two dielectric positioning spacers laid against the edges of said grounding conductor,

(E) -a thin continuous extrusion of synthetic polymer surrounding said grounding conductor and said spacer strand, forming a grounding-conductor, spacer assembly directly adjacent tosaid insulated conductors.

2. The cable of claim 1 comprising three insulated power-carrying conductors and two grounding-conductor, spacer assemblies.

3. The cable of claim 1 comprising dielectric positioning spacers against both edges of said grounding conductor, said extrusion surrounding said grounding conductor and said positioning spacer.

4. The cable of claim` 1 wherein said extrusion cornprises nylon.

5. The cable of claim 1 wherein said extrusion is between one and ten mils thick.

References Cited UNITED STATES PATENTS LEWIS H. MYERS, Primary Examiner.

E. A. GOLDBERG, Assistant Examiner.

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