|Publication number||US3145525 A|
|Publication date||Aug 25, 1964|
|Filing date||Nov 23, 1962|
|Priority date||Nov 23, 1962|
|Publication number||US 3145525 A, US 3145525A, US-A-3145525, US3145525 A, US3145525A|
|Inventors||Remo J Laureti|
|Original Assignee||Wall Rope Works Inc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (10), Classifications (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
.Aug. 25, 1964 R. J. LAURETI ROPES OF SYNTHETIC FIBERS Filed Nov. 23 1962 F I G. 4.
F l G. 2.
REMO J. LAURETI BY a w i/flrz ATTORNEYS United States Patent 3,145,525 RGPES 0F SYNTIETIC FIBERS Remo .l. Laureti, Moerestown, N.J., assignor to Wall Rope gvorks, Inc, Beverly, NJ., a corporation of New ersey Filed Nov. 23, 1962, Ser. No. 239,420 8 Claims. (Cl. 57-140) This invention relates to ropes of synthetic fibers, and particularly to ropes formed to a major extent of polypropylene.
The advantages of rope made of polypropylene are well recognized. They are characterized by light weight, chemical inertness so that they are proof against rotting and deterioration due to chemicals normally encountered in use, they do not absorb water, have little stretch, and have high tensile strength. However, they have the drawback, particularly for maritime uses, especially towing, that they tend to stick to timber heads and bitts so that when stressed they move in rapid jerks resulting in rapid deterioration. The deterioration has been ascribed to the generation of heat in these rapid jerking movements, polypropylene having -a rather low melting or softening point so that the surface fibers are destroyed. Following up this theory, it has been proposed to form the strands of a largely polypropylene rope with an outer layer of yarns including a substantial number of synthetic yarns of higher melting point material. Higher melting point yarns selected for this purpose have been typified by nylon. Polyester and cellulose fiber yarns have also been proposed, all of these having higher melting points than polypropylene.
But these materials have various disadvantages typified by nylon which has been found to be the best. Nylon has a high coefiicient of friction with respect to wood or iron, and must be carefully lubricated with special lubricants which will not be removed by immersion in water. Nylon is also water-absorbent and shrinks when exposed to water, and its ultimate elongation and tensile strength vary greatly with its moisture content. Accordingly, nylon is not compatible with polypropylene yarns. This incompatibility is also true with respect to polyester and polypropylene yarns.
It is the general object of the present invention to provide rope which may be regarded as of the polypropylene type in that, most desirably, its constitution is mainly of polypropylene, which rope has substantially all the desirable qualities of polypropylene rope but does not have its tendency to stick.
A further object of the invention is to provide a polypropylene type of rope which requires no lubricant.
In brief, in accordance with the invention, the rope is provided at least at its exterior with a substantial proportion of polyethylene fibers. Polyethylene is light in weight and less expensive as compared with nylon and polyester. But these are not its major advantages over nylon and polyester. One of its advantages is that it may be made completely compatible with polypropylene in its elastic properties. Both polypropylene and polyethylene may be produced with varying elastic properties; but the ranges of these are, or can be made, very similar, and for any polypropylene there may be chosen a polyethylene of substantially the same elastic properties. Polyethylene, furthermore, has elastic properties which are independent of exposure to moisture, the same being true of polypropylene.
Its outstanding advantage utilized in accordance with the invention is that it has a relatively low coeflicient of friction with wood or steel, much less so than either nylon or polyester; and not only in itself but in combination with polypropylene it provides adequate low friction characteristics for a rope. While not as strong as polypropylene, nylon or polyester, it has sufficiently high strength that, when it forms a relatively minor constituent of the complete rope there is little dilference in strength between the composite rope and a pure polypropylene rope.
Through its use, a polypropylene type rope, by which is meant a rope having the general characteristics of an all polypropylene rope by reason of a major polypropylene content, may be provided which does not have the sticky characteristic leading to destruction of the rope as described above. Whereas this problem has been solved in one way by the proposal referred to, i.e., by sheathing polypropylene rope with yarns having higher melting point but requiring lubrication to lessen friction to a satisfactory degree, the same problem is solved in accordance with the present invention by making use of the lubricating qualities of polyethylenes. In the solution in accordance with the invention, added lubricant is entirely unnecessary. The result, furthermore, is achieved without taking into consideration any matter of melting points. In fact, as noted, polyethylenes compatible with polypropylenes have lower melting points than the polypropylenes. Stated briefly, the troubles encountered by reason of heat generation are overcome by prevention of the generation of heat by lowering the effective friction and providing for smooth sliding between the rope and the bitts or the like about which it is trained.
As will appear, the effective utilization of polyethylene may be achieved in various fashions, all substantially equally effective, which provide a substantial polyethylene content at the exterior of the rope.
The general objects of the invention together with others relating to details, will be apparent from the following description, read in conjunction with the accompanying drawing in which:
FIGURE 1 is a side elevation of one form of poly propylene type rope provided in accordance with the invention;
FIGURE 2 is a transverse section taken on the plane indicated at Z-2 in FIGURE 1, the showing being diagrammatic;
FIGURE 3 is an elevation of diagrammatic type illustrating a ply which may be used in forming a rope in another embodiment of the invention; and
FIGURE 4 is a relatively enlarged cross-sectional view showing the composition of a yarn which may be used in a further embodiment of the invention.
Referring first to the modification illustrated in FIG- URES 1 and 2, a rope 2 is illustrated as formed of laid strands 4 each formed of plies generally indicated at 6, formed of twisted yarns. From the geometric standpoint, the rope illustrated is merely typical, the invention not being concerned with or limited to the particular arrangement of yarns, plies, or strands. As will be evident to those versed in this art, the invention is quite universally applicable irrespective of the particular geometric nature of the rope. However, for purposes of description of the invention, a particular rope is illustrated which from the geometric structural standpoint is conventional. Because of confusion in terminology, the makeup of such a rope may be briefly described. The basic elements are fibers or filaments, these two terms being used rather interchangeably, except that fibers is the usual designation when natural staple fibers of limited length are used, and filaments is more generally used in speaking of artificial materials, such as those with which we are here concerned, which are drawn into continuous filaments of indefinite length.
The fibers or filaments are then formed into yarns by twisting, this term being equivalently referred to, at times, as threads or singles yarns. The yarns just referred to are then twisted to form what are known as plied yarns, ply yarns, or, simply, plies. Another equivalent term sometimes used is cords, but this term is more aptly used with reference to plied yarns twisted together.
The plied yarns or plies or sometimes cords in the stricter sense referred to are then formed into strands. While strands contain twisted. plied yarns or cords, they generally have special structure: the component plies or cords are not merely arbitrarily twisted but are arranged in generally concentric layers, so that there is a distinct layer of plies at the exterior of each strand. The plies of this outer layer of a strand are of particular interest herein.
The strands are then laid into rope, there being, usually, three strands in a rope. With the foregoing preliminary discussion, it will now be seen, with particular reference to FIGURE 2, that the plies, generally referred to as 6, are associated in the strands in this layer fashion. In the specific arrangement illustrated, it may be considered that the plies of all layers of a strand except the outermost are formed of polypropylene. It is the outermost layer of plies which will now be primarily discussed. The outermost layer is shown as formed of alternating plies of two sets of different compositions. The plies 8 of one set are formed of yarns It) of polypropylene. The plies I2 of the other set are formed of yarns 14 of polyethylene.
The rope just described is highly satisfactory in showing no tendency to stick on bitts or other members about which it is trained. This is apparently due to the fact that its surface presents only small separated areas of polypropylene to the area with which the rope makes contact and in the direction of lengthwise movement of the rope as slipping occurs. Bounding each small presented area of the polypropylene is either polyethylene or the interruption of contact occasioned by the curvature of the strands into the troughs or grooves between them. It must, of course, be remembered that in actual use when the rope is trained about an object and under load what would be essentially only point or line contacts (in unloaded condition) are very considerably fiattened so that area contacts actually exist. the fact that any elemental area of contact presenting polypropylene to the other surface is quite limited and bounded at least in part by surface areas of polyethylene which have the low friction aspect previously described, the situation is essentially as if the rope was lubricated.
While in FIGURES 1 and 2 the polypropylene and polyethylene plies alternate, it is quite satisfactory to lessen the proportionate amount of polyethylene in the exterior layer of a strand by having in this layer a polyethylene ply as every third ply or every fourth ply, the others being of polypropylene. The same situation is presented of having the polypropylene presented on the surface of the rope in only relatively small separated areas.
The structure may also involve an excess of polyethylene plies over polypropylene plies in the outer layer of a strand; e.g. there may be two or more plies of polyethylene per ply of polypropylene, and, in the limit, all of the plies of the outer layer may be of polyethylene.
With any of the aforementioned constructions it will be noted that the major cross-section of the rope is polypropylene. Accordingly, the rope exhibits, so far as flexibility, strength and other characteristics are concerned, those of an all polypropylene rope. The polyethylene content is only a relatively minor percentage of the whole and, in itself, has properties of strength at least approaching those of polypropylene so that there is little loss of strength of the rope as compared with one consisting only of polypropylene.
The same principles of preventing sticking and of lubrication may be achieved in other fashions. One of these is illustrated in FIGURE 3 in which a ply 16 is formed by twisting two yarns 18 of polypropylene with one yarn 20 of polyethylene. Such plies 16 may form all of the plies of the outer layer of each strand. Under these Apparentlyconditions there is again the interruption of continuity of the polypropylene presented at the surface of the rope, the continuity of the areas of polypropylene being broken up by areas of polyethylene. In this arrangement the individual areas of polypropylene average as greater than in the rope first described. The composite plies such as 16 may alternate with plies of polypropylene in the outer layer of each strand. It will be evident that plies may also involve two or more yarns of polyethylene and one of polypropylene.
Still another modification may be used as illustrated in FIGURE 4 which shows a ply 22 in which the individual yarns 24 are made up of filaments of polypropylene 26 and polyethylene 28 twisted together. In the formation of these yarns actual layering is not achieved, the filaments being arranged essentially at random and twisted together. The proportion of polyethylenefila ments 28 to polypropylene filaments 26 may vary from, for example, about 1:5 to 1:1, or more. As will be immediately evident, therefore, because of the rather random distribution, quite small areas of the two yarns are presented at the surface of the ply. The plies 22 thus produced may be incorporated in the strand in the outer layer of plies thereof with the special plies 22 of the mixed filaments alternating with plies of polypropylene as in the case of FIGURE 1, the mixed plies taking the place of the all-polyethylene plies 12. The result of absence of sticking qualities and of effective lubrication still results. The mixed plies 22 may form all of the outer layer of each strand.
It will be evident, of course, that the yarn 20 of FIG- URE 3 may be of the type shown at 24 in FIGURE 4. Obviously there are other combinations which may be used introducing adequate amounts of polyethylene into the surface layers of the strands.
The proportion of polyethylene to polypropylene in the outermost layer of a strand depends entirely upon the use to be made of the rope. Where very heavy loadsare expected to be encountered, the proportion of polyethylene to polypropylene may be high, as 1:1 to 1:2. On the other hand if minor loads are involved orless aspects of rubbing are expected, the proportion of polyethylene to polypropylene presented by the outer layer of plies of the strand may be less. What is to be avoided, however, is the possibility that large areas of propylene without interruption by polyethylene might be presented at the rope surface.
It will be evident that the invention is applicable to ropes in which the polypropylene and/ or the polyethylene filaments may be blended with other filaments, natural or artificial, which may be used in rope construction; nevertheless the protection of the polypropylene filaments by the polyethylene filaments may be achieved as already described.
In summary, the rope may be said to be formed, at least in part, of polypropylene and polyethylene filaments and comprising a plurality of strands, each strand being formed of an outer layer of plies and interior plies, the interior plies being formed primarily of polypropylene, and the outer layer of each strand presenting exteriorly of the rope one or more polypropylene areas interrupted by areas of polyethylene and presenting to a curved surface engaged under stresses by the rope areas of both polypropylene and polyethylene. In the case of the rope shown in FIGURES 1 and 2, the polypropylene areas of a strand are presented by the individual polypropylene plies which are separated by polyethylene plies. In the case of a rope formed using the plies of FIGURE 3, the corresponding areas are provided by the exposed surfaces of the two types of yarns. In this case, assuming plies such as shown at 16 alternate with plies formed solely of polypropylene, the polypropylene presented area is continuous in the sense that in a picture of the rope a line could be continuously drawn through adjacent polypropylene yarns; but theoverall area is still interrupted at close intervals by polyethylene, so that a surface engaged by the rope under tension would have both polypropylene and polyethylene areas presented on it. In the case of the use of yarns of mixed filaments, the areas thus presented are much smaller. The overall aspect is that sufficient polyethylene is close to any polypropylene region so as to produce the lubricating effect which has been described, preventing the stacking of the polypropylene.
Further, as already described, the entire outer layer may consist of polyethylene, the interior layers comprising, largely, polypropylene.
It will be obvious from the foregoing that variations may be made in details of application of the invention without departing therefrom as defined in the following claims.
What is claimed is:
1. A rope of polypropylene and polyethylene filaments comprising a plurality of strands, each strand being formed of an outer layer of plies and interior plies, the interior plies being formed primarily of polypropylene, and the outer layer of each strand presenting exteriorly of the rope one or more polypropylene areas interrupted by areas of polyethylene and presenting to a curved surface engaged under stress by the rope areas of both polypropylene and polyethylene.
2. A rope according to claim 1 in which the outer layer of each strand is formed of plies primarily of polypropylene interspersed with plies containing polyethylene.
3. A rope according to claim 1 in which the outer layer of each strand is formed of plies primarily of polypropylene interspersed with plies of polyethylene.
4. A rope of polypropylene and polyethylene filaments comprising a plurality of strands, each strand being formed of an outer layer of plies and interior plies, the interior plies being formed primarily of polypropylene, and the outer layer of each strand presenting exteriorly of the rope at least some areas of polyethylene and at least some areas of polypropylene to a curved surface engaged by the rope under stress.
5. A rope comprising a plurality of strands, each strand being formed of an outer layer of plies and interior plies, said interior plies being formed primarily of polypropylene, said outer layer of plies containing at least one yarn primarily of polypropylene and at least one yarn primarily of polyethylene.
6. A rope comprising a plurality of strands, each strand being formed of an outer layer of plies and interior plies, said interior plies being formed primarily of polypropylene, said outer layer containing plies having at least one yarn of mixed polypropylene and polyethylene filaments.
7. A rope comprising a plurality of strands, each strand being formed of an outer layer of plies and interior plies, said interior plies being formed primarily of polypropylene, all of said plies of said outer layer of each strand containing polyethylene.
8. A rope comprising a plurality of strands, each strand being formed of an outer layer of plies and interior plies, said interior plies being formed primarily of polypropylene, all of said plies of said outer layer of each strand being formed of polyethylene.
References Cited in the file of this patent V UNITED STATES PATENTS 2,591,628 Snyder Apr. 1, 1952 2,804,745 Foster Sept. 3, 1957 3,026,669 Stanton Mar. 27, 1962 3,043,086 Hood July 10, 1962
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|US6279305||Jun 6, 1995||Aug 28, 2001||Wells Lamont Industry Group, Inc.||Knittable yarn and safety apparel|
|US6826898||Apr 19, 1995||Dec 7, 2004||Wells Lamont Industry Group||Knittable yarn and safety apparel|
|USRE38136 *||Aug 12, 1999||Jun 10, 2003||Supreme Elastic Corporation||Cut resistant support yarn suitable for wrapping with an additional yarn covering|
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|Cooperative Classification||D07B1/02, D07B2205/201, D07B2201/2041, D07B2201/2036|