US3035476A - Braided cord - Google Patents

Description

K. L. FOGDEN May 22, 1962 BRAIDED CORD Filed Feb. 23, 1961 United States Cordage Works, Boston, Mass., a corporation of Massachusetts Filed Feb. 23, 1961, Ser. No. 91,252 4 Claims. (Cl. 87-9) This invention relates generally to cordage, and is more particularly concerned with a braided cordage construction which has unusually high resistance to snagging and abras-ion, together with excellent strength characteristics.

In certain applications for cord or rope lines, the resistance of the line to snagging and abrasion is as important as its breaking strength. Lines that are used with Winches, purse lines for commercial fishing operations, and drop hammer lines are but a few examples of instances where high abrasion resistance is particularly important. For such applications, braided cord comprising a large number of exposed strands has certain advantages over ordinary twisted rope because of its relatively smooth surface. In addition, with a braided construction it is possible to make use of a core of one kind of material which is noted for its strength, and a 'cover of another kind of material, which, although not as strong as the core material, nevertheless has especially good resistance to the elements and to abrasion. The double-braided cord disclosed in the applications of Arthur F. Chace, Ir., Serial No. 2,188, filed January 13, 1960, now abandoned, and Serial No. 85,309, led January 27, 1961, entitled Braided Cordage, both assigned to the same assignee as the present invention, is made this Way, the same being comprised of a hollow braided core of a higher elongation material, such as a high elongation nylon or equivalent material, and a cover of lower elongation material, such as a low elongation Daeron or equivalent material, braided over the core.

It is an object of the present invention to further enhance the snag and abrasion resistance qualities of braided cordage lWithout detracting in any way from its other attributes.

Other and further objects and advantages of the invention will become apparent from the following detailed description of a presently preferred embodiment thereof, wherein reference is made to the accompanying drawing, in which FIG. 1 is an elevation of a double braided cord, the cover being partly broken away for purposes of illustration;

FIG. 2 is an elevation of the component strands of the cover;

FIG. 3 is an elevation of the component strands of the core;

FIG. 4 is a sectional View taken on line 4 4 of FIG. l; and

FIG. 5 is a diagrammatic view of a portion of the cord of FIG. 1 illustrating the orientation of the cover filaments.

With reference now to the illustrative embodiment of the invention shown in the drawing, the invention has been illustrated in connection with a double-braided cord having a core element 2 and a cover element 4. The core 2 is comprised of higher elongation ilaments such as higher elongation filaments o-f nylon, polyvinyl alcohol or The cover 4 is made of unplied ends 10 having no twist or only a negligible degree of twist, such as a manu facturers twist. The ends 1t) consist of lower elongation lilaments of lower elongation than those of the core, such as Daeron or other lower elongation ilaments.

In the embodiment shown, twelve such Daeron ends 10 are twisted together to `form a strand 12 and two such strands v1.2 are Wound parallel to each other for each carrier used in braiding the cover 4 over the core 2. That is, each strand 12 of the cover 4 has associated with it another strand ot like character which describes the same convolutions throughout the braid. Each such pair of strands constitutes a double strand 12', of which there are twenty in the cover. For a i716 diameter cord of the selected embodiment, the size of each of the ends 10 which are twisted together to form a cover strand 12, is 1100 denier.

To realize optimum strength from the cord, the core strands are loosely braided together and the cover strands are tightly braided together. As a res-ult of the loose braiding of the `core strands, the core increases in length und'er load less than it would with a tighter braid. On the other hand the tight braiding of the cover causes it to increase in length under load to a greater extent than it would with a looser braid. What I mean by a tight braid, for the cover, is a Ibraid Ihaving a pick ratio in the range 2 to 5 inclusive, and what I mean by a loose braid for the core, is la braid having a pick ratio in the range 6 to l5, inclusive. Within these limits, the core and cover undergo approximately equal increase in length under load so that they work together. When the cover has a pick ratio within the range 2.7 to 5 inclusive and the core has a pick ratio in the range 6-8, inclusive, with the cover contri-buting approximately half the bulk of the cord, still another highly desirable feature of cord constructed in accordance with the invention is that it can be spliced.

As applied herein to a braided element, the term pick ratio meansthe number of picks per revolution of the braider divided by the number of picks per inch of length of the cord times the diameter in inches of the braid. For a hollow braid of eight strands, as in the core of the selected embodiment, each revolution of the braider produces four picks. Hence, the pick ratio for an eight strand braid is i PD and for a twenty-strand braid, as described herein for the cover, Ithe pick ratio is wherein F is the pick ratio, P is the number of picks per inch measured lengthwise of the braid, and D is the braid diameter in inches, all measurements being taken with the cord under the standard tension of 200 D2 pounds, where D again is the diameter of the cord in inches.

According to the present invention, the amount of twist used in forming the ends 10 into a cover strand 12 is such that the helical angle of the filaments is substantially equal and opposite to the helical angle of the strands 12 when braided into the cord. In consequence, in the completed cord, the portions of the filaments on the surface of the cord are so disposed as to be substantially aligned with the axis of the cord. I have found that when a cord so constructed is passed through a chock or otherwise moved axially while in fractional contact with some other object, substantially less friction is produced as a result of this disposition of the filaments of the ends 10 and there is substantially less tendency for the individual laments to snag, thereby prolonging the life of the cord.

To accomplish this result with the cord so far described, one-half of all the double strands 12 (each composed of two strands 12) to be used in making the cover have their ends 10 twisted together in one direction about 2.9 turns per inch, While the other half of the double strands have their ends twisted the same amount but in the opposite direction. The helical angle, 0, of the cover strands for which this amount of twist is adapted to compensate is 42 (referred to the cord axis) and may be found from the formula Jcan 0:5;-

F being the pick ratio of the cover.

In braiding the cover, the strands which have their ends twisted in one direction are braided into the cover along a helix of one hand and the other half, which have their ends twisted in the opposite direction, are braided into the cover along a helix of the opposite hand. In each case, the direction or hand of the helix of each strand is such as to bring the portions of the iilaments on the surface of the cord substantially into parallelism with the cord axis.

Although the invention has been described in connection with a double-braided cord, those skilled in the art will appreciate that it is also applicable to cord with a parallel center and even to single-braided cord. The invention is applicable to all hollow braided cord of four strands and up and the number of strands per carrier or the number of carriers per strand may be modied, as to either core or cover. Also it will be recognized that the amount of twist employed in forming a group of ends into a cover strand can be varied at will to match the particular helical angle of the cover strands. Therefore, the invention should not be deemed to be limited to the details of what has been described herein by way of example but rather it should be deemed to be limited only by the scope of the appended claims.

What is claimed is:

1. A cord construction especially adapted to resist snagging and abrasion, comprising a core of ends arranged in strands that are braided together to form an interlocked bundle, and a cover of ends essentially composed of filaments, the ends of the cover being arranged in strands that are braided together over said core, each of said ends in a said cover strand being disposed at a helical angle within the strand that is equal and opposite tothe helical angle of said strand in the cord whereby the portions of the laments at the surface of the cord extend substantially parallel to the axis of the cord.

2. A cord construction especially adapted to resist snagging and abrasion, comprising a core of higher elongationV ends arranged in strands that are braided together to form an interlocked bundle, and a cover of ends composed essentially of lower elongation iilarnents, the ends of the cover being arranged in strands that are braided together over said core, each of said cover ends in a said cover strand being disposed at a helical angle in the strand that is equal and opposite to the helical angle of the strand in the cord, whereby the portions of the laments at the surface of the cover extend substantially parallel to the axis of the cord.

3. A cord construction especially adapted to resist snagging and abrasion comprising a core of ends arranged in strands that are braided together to form an interlocked bundle, and a cover of ends composed of filaments, said ends of the cover being arranged in groups of strands that are braided together over said core, the strands in each of said groups being disposed side by side throughout the braid, and each of said ends in a said group being disposed at a helical angle in the strand which is equal and opposite to the helical angle of the strands of the group in the cord, whereby the portions of the filaments at the surface of the cord extend substantially parallel to the axis of the cord.

4. A cord construction of high tensile strength and especially adapted to resist snagging and abrasion, comprising a core of ends of higher elongation filaments arranged in strands that are braided together to form an interlocked bundle, said core braid having a pick ratio in the range 6 to l5, and a cover of ends composed of filaments of lower elongation than said core filaments, said cover ends being arranged in strands that are braided together over said core, said cover braid having a pick ratio in the range 2 to 5, each of said ends in a said cover strand being disposed at a helical angle within the strand that is equal and opposite to the helical angle of said strand in the cord, whereby the portions of the filaments at the surface of the cord extend substantially parallel to the axis of the cord.

References Cited in the iile of this patent UNITED STATES PATENTS 1,373,632 Phelps Apr. 5, 1921 2,195,592 Jones Apr. 2, 1940 FOREIGN PATENTS 18,422 Great Britain 1895 512,217 Italy Ian. 29, 1955

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