US3805667A

US3805667A - Braided rope

Info

Publication number: US3805667A
Application number: US00227682A
Authority: US
Inventors: K Orser
Original assignee: Columbian Rope Co
Current assignee: Columbian Rope Co
Priority date: 1970-08-21
Filing date: 1972-02-18
Publication date: 1974-04-23
Anticipated expiration: 1991-04-23

Abstract

A plurality of strands are plaited together to form a rope. Each strand includes a plurality of yarns which are enclosed within a tubular braided cover and lie substantially parallel to the axis of the cover. An electrical conductor runs longitudinally within each of the strands.

Description

United States Patent 1191 Orser [451 Apr. 23, 1974 BRAIDED ROPE [75] lnventorz Keith L. Orser, Auburn, NY.

[73] Assignee: Columbian Rope Company, Auburn,

[22] Filed: Feb. 18, 1972 [21] Appl. No.: 227,682

Related US. Application Data [63] Continuation-impart of Ser. No. 65,965, Aug. 21,

1970, abandoned.

[52] US. Cl 87/6, 87/7, 87/8, 174/122, 174/124 [51] Int. Cl. D04c 1/12, l-lOlb 7/04, HOlb 7/18 [5 8] Field of Search 87/5-8; 174/120-124 [56] References Cited UNITED STATES PATENTS 1,718,920 6/1929 Frederickson 87/6 X 3,036,490 5/1962 Mullen et a1 87/6 3,090,277 5/1963 Schmittmann 87/6 X FOREIGN PATENTS OR APPLICATIONS 1,014,591 12/1965 Great Britain 87/8 19,907 1904 Great Britain 87/6 389,162 6/1908 France 87/8 Primary Examiner-John Petrakes Attorney, Agent, or Firm-Browne, Beveridge De- Grandi & Kline [5 7] ABSTRACT A plurality of strands are plaited together to form a rope. Each strand includes a plurality of yarns which are enclosed within a tubular braided cover and lie substantially parallel to the axis of the cover. An electrical conductor runs longitudinally within each of the strands.

12 Claims, 2 Drawing Figures ATENTEI] APR 2 3 I974 YARNS LIE SUBSTANTLALLY PARALLEL T0 AXIS OF STRANDS 4.

FIG. 2

INVENTOR KEITH L. ORSER ATTORNEYS BRAIDED ROPE This is a continuation-in-part of my earlier application Ser'. No. 65,965 filed Aug. 21, 1970, now abandoned.

This invention relates to a rope having unusually high strength and characteristics which enable it to function properly while passing over sheaves, drums, capstans and the like. Further, the rope has elongation characteristics which make it particularly suitable for carrying electrical conductors of the type used for mooring oceanographic buoys.

For centuries, it has been common to manufacture cord'age products such as rope by twisting together a plurality of subunits to form a larger unit.

The basic unit in rope is a yarn which may be formed of staple fibers held together by twisting or continuous filaments which are twisted together. Yarns may be plied by twisting three of them together, and a plurality of single or plied units are then twisted together to form a strand. Strands may then be twisted together to form the rope. Each twisting operation is normally performed in a direction opposite to the preceding twisting operation, and'factors such as diameters, fiber characteristics and intended usage are considered in deter-v mining the suitable amount of twist. If the laid rope is properly balanced, the resulting product is strong, flexible-and able to maintain its integrity in use. However, under some conditions, it has been found that even properly balanced laid rope possesses a natural tendency to twist or untwist when suspending a weight, and there are occasions where laid ropes kink, hockle or form loops which at least causes serious inconvenience and probable local weakness.

A prior effort to overcome the disadvantages of conventional laid rope and to provide more flexibility is represented by a product sold under the trademark PLl-MOOR made by Columbian Rope Company, the assignee of the present invention. This construction is achieved by plaiting an even number of twisted strands together, in contrast to conventional twisting operations. ,Fou'r pairs of strands are used, with half of the pairs being twisted in one direction and half in the other direction, with the plaiting operation being performed in a direction opposite to its twist. Such rope is completely neutral, having no predisposition to twist or turn in either direction, and no tendency to kink or hockle.

The PLLMOOR rope discussed above, althoughideal for many purposes, also suffers in loss in fiber strength utilization and increases in elongation over that of its fiber because of the multiplicative effects of twist on twist.

Briefly, the reason why the twisted structure possesses the disadvantages expressed above is that each of the units in the strand forms a helical path which lies at a certain angle, termed helix angle, with respect to its axis. This has a twofold effect on thebreaking length or the strength of a rope of a given weight.

First. the contribution which the stress in a subunit makes to the stress'in the unit in which it lies is the product of its straight tensile strength and the cosine of the helix angle; therefore, there is a loss in overall strength which increases with the helix angle which depends on amounts of twist and size of unit. This effect is multiplicative since there is a loss from a single end to the single ply yarn, from the single yarn to the three ply yarn, from the three ply yarn to the strand and then from the strand to the rope. The reduced strength due to twist in any unit is the ratio of the length of the unit in helical form to its straight length. This ratio is the cosine of the helix angle. The overall reduced tensile strength is the product of the ratios or cosines of subunits and also of the laid or plaited rope. it is also the ratio of the rope length to the length of the smallest subunit. In ropes of conventional construction an individual element such as a filament may be 50 percent or more longer than the rope so that the strength of the rope may be less than 50 percent of the combined strength of the elements therein. Accordingly, only a percentage of the potential fiber strength is utilized in the rope.

A second effect of twist is that the weight of each unit per given length is increased over the sum of the weights of the subunits comprising it by the ratio of their lengths. This effect is likewise multiplicative, so that the weight of the finished rope per unit length is greater than the sum of the weights of the individual filaments comprising it by the product of the individual unit length ratios, which is the ratio of the length of a filament to the length of the finished rope.

Thus, this ratio not only reduces the strength of the rope, but increases its weight at the same time, so that it must be applied twice in considering the reduction in the strength of arope of a given weight caused by the twist in its various elements. In other words, when it is necessary to have a rope of given strength characteristics, the weight per unit length of a conventional rope is much greater than of a rope constructed according to this invention.

Prior to this invention, there have been ropes typified by the product sold under the trademark NOLARO by the assignee of this invention which enclose a plurality of parallel members in an extruded jacket. The parallel elements are most often loosely twisted yarns of continuous synthetic filaments which produce a high strength to weight ratio. Unfortunately, this product is unsuited for many applications in that it lacks the requisite flexibility and in larger sizes are stiff and suffer a stress concentration when bent through a small radius as around a sheave, drum or capstan because the path of the outer parallel elements is somewhat larger than that of the inner ones. Such usage also tends to flatten the structure. A few years before arriving at the present invention, applicant's assignee sought to overcome these shortcomings by forming twisted and plaited rope with strands of the extrusion-jacketed NOLARO rope. Three-strand twisted ropes and eight strand plaited ropes were made using conventional rope manufacturing machinery. The resulting products exhibited some improvement, but were still considered to be too stiff for many uses.

It now has been discovered that the. use of a textile covering for each of the plaited strands will provide the essential handleability of the rope, while providing a rope with a superior breaking length. According to present invention, the rope is formed of strands each of which includes a more flexible braided cover which encloses a plurality of units such as yarns which extend substantially parallel to the central axis of the tubular cover. The strands are plaited together in order to form a rope which avoids or minimizes the disadvantages outlined above which are inherent in previously known rope construction.

It has been found that this invention provides a rope which combines the desirable features of high strength to weight ratio, low elongation, flexibility, good handling properties, abrasion resistance and good wearing qualities. The product does not have a tendency to kink, hockle or loop, it has a very much improved strength to weight ratio, its elongation is relatively low and it is suited to many practical uses. One such use is in the mooring of oceanographic buoys where it is necessary to have electrical conductors extending through the rope from submerged sensing devices to a radio transmitting device on the buoy. The conductors carry signals which indicate oceanographic or other information which is transmitted to a monitoring station. The low elongation characteristics of rope made according to this invention will minimize the danger of breakage of the electrical conductor, and avoids the tendency of the conductor to work its way radially out of the strand of the rope when the rope is subjected to varying tensile forces.

The rope of this invention has a further advantage of affording a reliable visible warning when there is an impending loss of strength due to abrasive wear. This warning is given when the braided strand covering wears through, indicating that any further wear will occur in the load-bearing fibers which constitute the core of the strand. The visibility of such a warning may be improved by making the cover and the core of materials which have different colors.

A preferred embodiment of rope construction ac cording to the invention is' illustrated in the accompanying drawings wherein FIG. 1 is a side elevational view of the rope and FIG. 2 is a cross sectional view thereof taken along the line 2-2.

In the drawings, it will be seen that the rope 2 is formed of eight strands 4 which are plaited together in pairs so that each pair of strands runs together throughout the rope structure.

Each ofthe strands 4 has a core 6, formed ofa plurality of yarns 8 which are held together by a tubular cover 10 which preferably is braided. The illustrated braided cover 10 may have a large helix angle and contribute little to the tensile strength of the construction but principally serves to hold the yarns together. The cover may also be designed to make a contribution to tensile strength. Preferably the weight of the tubular cover is no greater than about percent of the weight of the strand excluding the conductor. Where high rope strength is the objective, the ratio of the weight of the cover to the weight of the strand should be as low as possible; however, where abrasion resistance is a prime consideration, the corresponding relative thickness and weight of the cover may be increased to about 45 percent for nylon and about 40 percent for Dacron and still retain an advantage in strength to weight over contiqnal sqn ttucti nst The core itself is formed of a plurality of yarns which extend substantially parallel to the axis of the cover 10. Each individual yarn may possess a twist, preferably slight in the order to about 0.5 0.8 turns per inch to facilitate their handling during manufacturing operations. The twist of the fibers within the core should be such that the length of any section of the'strand is at least 99 percent of the length of a major portion, i.e. at least 50 percent, of the fibers which form that section.

For large rope sizes where the overall diameter is greater than 2.5 inches, it is desirable to give a very slack twist (about 0.6 to 0.9 turns per foot, preferably about 0.8 turns per foot) to the bundle of parallel yarns prior to applying the braid which holds them together. This makes the resulting rope sufficiently flexible to bend around bobbin barrels and pulleys of small diameter without distorting the braided jacket. This amount of twist is significantly less than the twist of 2.5 to 4.0 turns per foot used for conventional rope construction.

Extending centrally within each of the strands, there may be one or more insulated electrical conductors 12 which preferably is of the type described in U.S. Pat. No. 2,456,015. The low elongation characteristics of this rope structure reduces the danger of tensile failure of the electrical conductor 12 and reduces its tendency to work its way out of the structure, but most important, the braided cover positively contains the conductor and prevents it from popping out to the surface where it might be damaged by abrasion, etc. as is characteristic in conventional rope structures.

The strands are typically plait'ed together using a Herzog P36 or similar plaiting machine in substantially the same manner used for the previously-discuseed PLI-MOOR construction, to provide the desired pick lengths.

The rope is preferably made of continuous nylon or polyester fibers such as Dacron; however, it may be made of any textile fibers used in rope construction such as rayon, polypropylene and the like. Many fiber combinations are possible. The cover may be of a different material from the core. Both core and cover can consist of more than one material. In some instances, it may be desirable to form the cover 10 of a material having special properties such as abrasion or heat resistance much superior to the core material, or to form the core from a less dense and more buoyant material than the cover. A core may include yarns of different textile fibers given different degrees of twist. For example, a buoyant rope may be made by using nylon and polypropylene core yarns, with the polypropylene yarns being given a greater twist than the nylon yarns, whereby both types of yarns will contribute to the strength of the rope and will have similar elongation-atbreak properties;

To demonstrate the advantages of rope constructed according to the invention, experiments were conducted to compare physical characteristics with ropes of standard eight-strand plaited (Pli-Moor) and ropes of the construction of this invention. The results of this testing are presented in the following table:

3,805,667 1 5 6 TABLE Continued Additional samples were made and tested, using the Nylon Dam, improved construction in both nylon and Dacron in order to ascertain the relative characteristics of ropes Ph'MOOr New made from these materials. in the case of the nylon Basic Y 5 ropes, the core is formed of 39 parallel yarns, each (number denier)..... 6x2520 7 2s20 l6 l100 2l 1l00 formed of 2520 demer DuPont 707 nylon glven gwist turns per inch for handleability. The parallel yarns were "55:5 2.3 2A 8 passed through a braiding machine which applied the 3 ply yarn cover. The braiding machine had 32gtrriers, each of g gg'g g 10 which was supplied with three ends of 840 denier nyp g 33 lon. The braider provided 16.5 picks per inch. Ropes Length ratio 5, 6 and 7 were tabilized by preshri ki th i h t Singles/1 end 985 997 975 997 water. In 100 feet of strand, the conductor weighed 3 ply/singles... .955 1.0 .955 1.0 0.675 lbs., the core weighed 5.30 lbs. and cover iggg g g gx: g2 -2 weighed 1.1 1 lbs. The core of the Dacron samples had Rope/end 32 yarns per strand, each yarn being made of 21 ends (P oduct of I of 1,100 denier Dacron 67 made and sold by the Duratios) .68 .84 .67 .847

- Pont Company of Wilmington, Delaware. The cover :Excludes weight of conductor. h was formed in a braider having 32 carriers, each supto sggllpgutllated excluding weight of conductor which contributes little plying two ends of 1,100 denier Dacron 67. The com ductor 12 is a special elastic insulated conductor having a resistance equal to No. 22 AWG. Each strand has It will be seen from the table that the nylon rope aca weight of 7.66 pounds per hundred feet, with the concording to this invention is about 25 percent lighter ductor contributing 0.57 pounds, the core contributing than the standard nylon PLI-MOOR construction (in 25 6.2 pounds and the covercontributing 0.89 pounds. the order of about 0.23 lbs/ft. less in the improved con- The total breaking strength of an individual strand was struction). Despite the lighter weight, the breaking in excess of 11,000 pounds. Seven different test samstrength of the improved construction is greater, and ples are described in the following table:

TABLE 2 Rope i 2 s 4 s 6 7 8* Material Dacron/ Dacron Dacron Dacron Nylon Nylon Nylon Nylon Nylon Pick length (in.) 5.75, dry 6.7, dry 8.6, dry 5.75, dry; 5.33, dry; 6.38, dry; 8.0, dry; 4 m.

' or wet. or wet. or wet. 5.54, 5.54 5.57, 8.4, wet. 1 wet Circumference (in.)..., wet 3%,,d Lbs/100 ft. (total) dry..... .2 Lbs/100 ft. (fiber only) dry. .3 21.8. 11 181 !QUHQPQWUEQUQPQ (in.) dry. v, i N

*Rope of this invention having a braided cover of 2 X 1100-17 ppi Dacron 67 and a core of 3-28 X 2520 Nylon 718.

the breakinglength which is the product'of the break- The testing of these ropes, both in wet and dry condiing strength (expressed in pounds) and the rope weight tions, produced the following results: (expressed in feet per pound) is considerably higher (about percent higher). The table also shows a simi- 5O lar increase in breaking length for the Dacron rope. M; TABLE3 Although breaking length is defined above, perhaps clarification of its significance is needed. Briefly, breaking length provides a method of comparing ropes Percent Breaking of different weights, sizes, strengths and materials. T0 55 Moisture elongation strength Breaking one experienced in the art, the increases in breaking 9 f fi i'f'f m flwi (in length shown in Table 1 are extremely significant. 212 70,000 103,000 An explanation for these improved results may be 20 74,400 found in the description of the length ratios in the pregiggg ceding table where it will be seen that for any given 16.8 95,400 155,000 15.0 94,000

length of one unit (units may be ends, singles, plys, strands or rope), the next smaller subunits have a greater length. The length of the PLl-MOOR rope, both in the case of nylon and Dacron, is only about 68 6 percent of the length of the fibers therewithin, contrasted to a figure of about 84 percent for improved rope made according to this invention.

Comparative abrasion tests were made with a variety of typical 1 inch diameter standard ropes made in U.S. of different materials and combinations thereof including laid three strand, plaited eight strand and double ing length of about 70,000 ft. This test data not only shows the superiority which rope of this invention has over typical previous rope constructions in abrasion resistance but also clearly shows its superiority in breakbraid, and a 1 inch diameter rope made as per this in- 5 ing length.

vention. The strand of the invented rope consisted of h b i of these tests, i ill b appreciated b a substantlally f Core of X 2520 yp 718 those skilled in the art that this rope does indeed have DuPont nylon Welghmg 0-0165 lbs-KL enclosed y 3 characteristics which are superior to prior ropes for tubular brald of 322 X 1,100 DuPont 67 Dacron at many li i 7 p elg mg 0 007.3 lbs/ft The bialded (fever was 10 its strength to weight ratlo ls much hlgher than for applled by a conventional Butt bralder. Elght such d strands were plaited in pairs to form a rope 3 3/32 inch other Known construction Its wet and abrasion Circ., 4 7/16 inch pitch. having a strand to rope ratio reslstance is unexpectedly .good and supenor to of 13 5/12 and a weight of 0.218 lbs/ft. In the abrasion other ropes and Superior to has Substan tially lower elongatlon than conventlonal stranded test, the newly lnvented rope moved longltudlnally l5 12-14 inches while under 628 lbs. tension back and ropes Electrical c9ndu.ct(.)rs can i readily i forth over an AlSiMg surface until the braided jacket li and i m ln.ziddltlon It has the flex]- was just barely worn through. it was found that 1,182 blllty f other handlmg qualmes "f apcycles accomplished this on wet r0pe An attempt was pllcatlons. Thls unexpectedly superlor comblnatlon of made to subject Standard ropes of the Same Size and characteristics results from a novel comblnatlon of eleferent materials in standard constructions to this same mems of construcnon disclosed In this apphcanon' number of wet abrasive cycles under the same load the Obviously, the illustrated construction may be modltravel distance. The complete test data is shown in fled within the spirit of the invention to achieve the de- Table 4 which follows: sirable result and characteristics attributable to this im- TABLE 4 Nominal Breaking breaking Wet strength Percent strength strength Nominal Breaking abrasion after wet retained ea. Type rope Material (lbs) ft/lb. length (ft) cycles abrasion of2 Av/2 *1214 28,250 100 Rope of thls lnventlon Dacron cover nylon core 28,000 4.65 130,000 82 24,350 93.5

- 1182 17,500 80 Pl|-Moor Dacron 22,000 3.3 72,500{ 1185 12,500 68.5

. 1022 0 0 Pll-Moor s. Duo-Syn 14,000 3.7 52,000 1023 0 0 Pli-Moor Duo-Syn 15,000 4.28 65,000{ 3% g g} 0 255 0 0 Pll-Moor Nylon 25,000 3.8 95,000 442 0 0 Pl -Moor Polypro 14,000 5.5 77,000 g g} 0 1182 16,700 76 a strand Dacron 22,000 3.3 72,500{ 82 18500 so 1182 10,600 76 a strand s. Duo-Syn 14,000 3.7 52,000 1182 M00 74 1182 6,700 3 strand Duo-Syn 15,000 4.28 65,000 "82 3,950 2 35.5

692 0 0 3 strand Nylon 22,000 3.8 95,000 785 0 0 197 0 0 3 strand Polypro 14,000 5.5 77,000 273 0 0 *200 395 0 0 Double concentrlc brald Nylon 28,000 4.0 112,000 346 0 0 "337 998 0 0 Double concentrlc brald Nylon/Polypro 25,000 4.0 100,000 375 891 0 0 1182 20.800 75 Double concentrlc brald Polyester/Polypro 28,000 3.56 100,000 l 182 26.100 84.3

Cycles to wear through outer braid without damage to core yarns. Second identical specimen were through and did slight damage to core it will be noted that 1 inch rope according to this invention retained an average of 94 percent of its original strength while eight of the other'ropes tested, including some containing as much polyester, were completely through. The other five ropes did not wear through but lost more strength. With a 10 percent greater loss in strength, the rope having a polyester braid over a multipro braid had a breaking length of only 100,000 ft. compared with about 128,000 ft. for the rope of this invention. The 1 inch polyester three strand rope and plaited rope are much heavier and have a lower breaksaid strands being formed of a plurality of core yarns enclosed within a tubular braided cover of textile fibers, a major portion of the core yarns in the strand lying substantially parallel to the longitudinal axis of the cover, said strands being plaited together to form the rope structure, the weight of the tubular braided cover being no greater than about 20 percent of the combined weight of the cover and the yarns, and, for any longitudinal portion of the rope, the length of a strand being at least 99 percent of the length of a major portion of the yarns therein.

2. A rope according to claim 1 wherein there are only four pairs of strands with the strands in each pair running together and being plaited to the other pairs of strands.

3. A rope according to claim 2 wherein at least some of said strands have an electrical conductor extending longitudinally therewithin.

4. A rope consisting essentially of a plurality of interengaged strands which are plaited together; each of said strands including a plurality of fibers and a tubular braided cover of textile material surrounding the fibers to maintain the integrity of the strand, a length of the strand being at least 99 percent of the length of the major portion of the fibers therewithin, the weight of the tubular braided cover being no greater than about 20 percent of the combined weight of the cover and the fibers.

5. A rope according to claim 4 wherein there are only four pairs of strands with the strands in each pair running together and being plaited to the other pairs of strands.

6. A rope according to claim 5 wherein at least some of said strands have an electrical conductor extending longitudinally therewithin.

7. A rope comprising four pairs of strands engaged by having the strands in each pair running together and being plaited to the other pairs of strands, each of said strands being formed of a plurality of core yarns and a cover, said core yarns being substantially parallel to the axis of their respective strand, and each said cover being a tubular cover of textile yarns braided together to surround the core yarns of the respective strand, the weight of said cover being no greater than about of the combined weight of the core yarns and cover.

8. A rope having low elongation characteristics for transmission of electrical signals, said rope comprising a plurality of strands, each of said strands being formed of a plurality of core yarns enclosed within a tubular braided cover of textile fibers, a major portion of the core yarns in the strand lying substantially parallel to the longitudinal axis of the cover to impart low elongation characteristics to the strand, at least some of said strands including an electrical conductor which extends longitudinally therewithin parallel to the core yarns whereby the braided cover positively contains the electrical conductor and prevents its from popping out to the surface of the rope, said strands being plaited together to form the rope structure.

9. A rope comprising four pairs of strands engaged by having the strands in each pair running together and being plaited to the other pairs of strands, each of said strands being formed of a plurality of core yarns and a cover, said core yarns being substantially parallel to the axis of their respective strand, and each said cover being a tubular cover of textile yarns braided together to surround the core yarns of the respective strand, the weight of saidcover being no greater than about 30 percent of the combined weight of the core yarns and cover.

10. A rope comprising a plurality of strands, each of said strands being formed of a plurality of core yarns enclosed within a tubular braided cover of textile fibers, a major portion of the core yarns in the strand lying substantially parallel to the longitudinal axis of the cover, said strands being plaited together to form the rope structure, at least some of the strands having an electrical conductor extending longitudinally therewithin.

11. A rope comprising a plurality of strands, each of said strands being formed of a plurality of core yarns enclosed within a tubular braided cover of textile fibers,,a major portion of the core yarns in the strand lying substantially parallel to the longitudinal axis of the cover, said strands being plaited together to form the rope structure, the weight of the tubular braided cover being no greater than about 20 percent of the combined weight of the cover and the yarns.

12. A rope consisting essentially of a plurality of interengaged strands which are plaited together; each of said strands including a plurality of fibers and a tubular braided cover of textile material surrounding the fibers to maintain the integrity of the strand, a length of the strand being at least 99 percent of the length of a major 'portion of the fibers therewithin, at least some of the strands having an electrical conductor extending longitudinally therewithin.

Claims

1. A rope comprising a plurality of strands, each of said strands being formed of a plurality of core yarns enclosed within a tubular braided cover of textile fibers, a major portion of the core yarns in the strand lying substantially parallel to the longitudinal axis of the cover, said strands being plaited together to form the rope structure, the weight of the tubular braided cover being no greater than about 20 percent of the combined weight of the cover and the yarns, and, for any longitudinal portion of the rope, the length of a strand being at least 99 percent of the length of a major portion of the yarns therein.

7. A rope comprising four pairs of strands engaged by having the strands in each pair running together and being plaited to the other pairs of strands, each of said strands being formed of a plurality of core yarns and a cover, said core yarns being substantially parallel to the axis of their respective strand, and each said cover being a tubular cover of textile yarns braided together to surround the core yarns of the respective strand, the weight of said cover being no greater than about 20% of the combined weight of the core yarns and cover.

9. A rope comprising four pairs of strands engaged by having the strands in each pair running together and being plaited to the other pairs of strands, each of said strands being formed of a plurality of core yarns and a cover, said core yarns being substantially parallel to the axis of their respective strand, and each said cover being a tubular cover of textile yarns braided together to surround the core yarns of the respective strand, the weight of said cover being no greater than about 30 percent of the combined weight of the core yarns and cover.

11. A rope comprising a plurality of strands, each of said strands being formed of a plurality of core yarns enclosed within a tubular braided cover of textile fibers, a major portion of the core yarns in the strand lying substantially parallel to the longitudinal axis of the cover, said strands being plaited together to form the rope structure, the weight of the tubular braided cover being no greater than about 20 percent of the combined weight of the cover and the yarns.

12. A rope consisting essentially of a plurality of interengaged strands which are plaited together; each of said strands including a plurality of fibers and a tubular braided cover of textile material surrounding the fibers to maintain the integrity of the strand, a length of the strand being at least 99 percent of the length of a major portion of the fibers therewithin, at least some of the strands having an electrical conductor extending longitudinally therewithin.