US2438864A - Rope - Google Patents

Description

March 30, 1948.

S. A. REED ROPE I Filed Jan. 10, 1945 Izwezaoa Sifephezz uilleeol,

Patented 1M". r

3 UNITED STATES PATENT OFFICE aims acre Stephen A. Read, Duxbury, Mass, on... to Plymouth Cordage Company, North Plymouth, M8l8., a corporation of Massachusetts Application January 10, 1945, Serial No.- 572,107

- 4 Claims. (01. 51-144) This invention relates to improvements in rope. More particularly it relates to rope strands in which the filamentary elements that carry thetensile stresses occupy the whole cross section of the strand. Among such, it relates especially to strands so large that it is impracticable to make all of the yarns-be of equal length by arranging them all in one circular course, as can be done in small ropes having only a few yarns per strand.

The invention isiherein illustratively described as it may be applied in hard fibre rope, of which manila and sisal are examples; but the invention is not limited to this, being applicable with other yarns can have equal length or, at choice, at least will be more nearly equal than in a conventional construction; and (2) has them organized so that the rope is of all-around-utility-up to accepted standards of good performance. It is notable that (3) it combines in one strand these two ideals, equal lengths and all-around utility, and, beyond that, (4) is round to surpass former rope performance standards in some characteristics.

The two requirements, that the rope be of allaround-utility, and that all .yams be of equal length, have hitherto appeared incompatible for a rope so large that some yarns in each strand are surrounded by other yarns. The problem of making a rope or strand that should embody both of these ideals has seemed insoluble.

In large ropes hitherto known, having inner yarns shorter than the outer or cover yams which surround them, the full strength of all of the yarns is never available. The shorter yarns become taut, and may break, before the full stretch. and strength, of the longer yarns in the same strand have been realized. This deficiency has long been known, especially in ropes that have w had usage enough to disturb the original twist.

Various efforts have been made to avoid this defeet; but every large strand construction proposed for making all yarns be of equal length, sofar as I am aware, has made a rope which is lacking in some other property that is considered essential in a good rope of all-around utility. Among such faults are, in one case, that it is impracticable to col] the rope, and that the 'rope can only be reeled. In another, that the rope is not stable, and kinks develop when the rope is back twisted. In another, that the surface fibres are so loosely held that the rope does not have satisfactory re- 2 sistance to surface abrasions. Cure of the last mentioned fault has been attempted by wrapping each strand with a sheet or cover yarns; but thissacriiices the ideal of having all yarns be equal in length.

The said ideal, that all yarns be of equal length, can be realized'in a small rope, ii the strand is made without a center yarn--i. e., if the yarns being thus deformed and positioned in the same ,strand, around the same axis. Theoretically the sector mightbe extended outward .to make a larger yarn, but the practical necessity that all fibres be bound, tightly enough to withstand abrasion at the surface of the rope, limits the practicable size of the individual yarn. From the combined effects of these two limitations, ofsize and of number, it results that in commercial manufacture good practice permits the putting of eleven yarns of sector shape into such a strand; and it is not considered industrially practicable to attempt to make the strand have more than twelve yarns thus arranged. Attempts to make large strands on this pattern by augmenting the,

sizeof the individual yarns, arranged in a single course, abutting each other at the axis, have proven unsatisfactory because in yarns of larger size the rope has insuiiicient resistance to abrasion unless its twist is made so short that the 'efiiciency and utility of the rope are reduced.

The principal field of utility of the invention therefore lies among ropes which are so large that in present customary practice each strand has some yarns which are surrounded by other yarns.

For illustrating the invention thev drawing shows in Figure 1 such a strand having '72 yarns, and in Figure 2 another having 128 yarns.

In a 72-yarn strand of present day approved ordinary construction; having'a diameter of 'one inch, for assembly with two similar strands .to make a three-strand ropeof two inches diameter, good industrial practice might arrange the 7 "l2 yarns of equal size in an, outside single-thick circular course of 33 yarns, covering an intermediate single-thick circular coursehaving 24 yarns, within which wouldbe a group of 15 yarns. One or more of these 15 would lie at the axis.

surrounded by the remainder of the 15. In such an arrangement the'greatest number of yarns having equal length is 33. These would constitute only 45.8 per cent of the whole number.

But the invention, as illustratively described,

might divide the whole seventy-two into nine groups of eight yarns each, each group being individually twisted. These nine independently twisted groups of yarns are organized into (1) a cylindrical core, comprising one of the groups; and (2) a single circular course of eight groups surrounding that core. Thus 64 yarns have lengths precisely equal, being 88.8 per cent of the whole; and the remaining eight yarns can be made to have lengths which equal the lengths of the 64, actually or approximately, by forming the core group with shorter pitch.

In each particular group the conventional machinery of manufacture operating under industrial conditions makes all of the yarns of the group substantially equal to each other in length. Actual or approximate equality of length of core yarns with yarns that surround them is attained by forming the core group with more turnsper unit length of strand than each surrounding group has in the same length of strand.

The 128 yarns of the other illustrative strand are divided into (1) a single core group of eight; (2) a surrounding circular course of five groups of eight yarns each; and (3) a circular cover course of ten groups of eighteach. The 80 yarns of the cover course make 62.5 per cent of the whole number of yarns precisely equal in length; each of the 40 yarns in the intermediate course of five groups may be made to have length equal to that of the yarns in the outer course, by forming each of those five groups with a little shorter pitch than the outer groups have; and the yarns of the core group can be made to equal all of the others in length by giving them a still shorter pitch, thus making all yarns be so nearly equal in length that, under severe stress, with resulting stretch, every yarn may be expected to come under strain and be contributing practically its full strength, before the first one of those yarns breaks.

As will be seen in each illustration, the group at the core has its yarns standing in sector shape; but the cross section of each other group is a truncated sector; and the cross section of each component individual yarn in those other groups is a sector somewhat deformed.

In each group having truncated sector shape, the truncating surface acts as a base for the group, affording a helical surface of substantial width resting on a firm core surface at a distance from the axis of the strand. If this positive interior support were omitted from the strand, and so it were attempted to make every group in a single circle of groups be a sector extending to the axis, without there being a cylindrical group at the axis, it would be so very difficult to control the forming of the strand, in manufacture, that the irregular product would not be acceptable. In the absence of a firm core support, there is a strong tendency to form a central hollow; and the compression under which a strand is formed tends to force one or more of the groups into this hollow, thus producing inequality of length. Also, in such a construction, the range of sizes that could be made is limited.

The invention avoids the above manufacturing limitations and operating difiiculties. It achieves a rope structure having yarns of equal length; having stability of strand structure; one which can be made in an unlimited range of large sizes; and one which is of atype that is practicable for industrial use even when made with a long lay such as will give extra flexibility and will have still greater ultimate strength because of the low torsion.

By the construction herein described, approximately the full strength of every constituent fibre or other elemental filament will be utilized before breakage of any yarn will occur. The diflerences of loading angles of the individual equal-length yarns have been found inconsequential. The rope thus made has good handling qualities, including impossibility of being kinked, and has the novel property of retaining its tensile strength when back twisted; has good resistance to abrasion, by having its surface fibres well bound; and is a rope of good allaround utility. It is obvious that it can be made in many variations as to the size of strand, and as to the size, number, arrangement and component material of yarns.

It is intended that the patent shall cover, by suitable expression in the appended claims, whatever features of patentable novelty exist in the invention disclosed.

In the 72-yarn strand of Figure l, the central group III is made of eight yarns l2 twisted together; and each of the remaining eight groups 20 comprises eight yarns 22, twisted together. The latter groups 20 stand in helixes around the core group [0 which is approximately a cylindrical body having each component yarn a sector in cross section. -But each group 20 in the surrounding course stands deformed from the roundness which it may have had transitorily while the strand was being formed being a truncated sector whose truncated surface rests on one-eighth portion of the cylindrical surface of the core I0, and fills one-eighth of the course of groups which surround that core. The shaping of each individually twisted group as a truncated sector occurs as the strand is being formed under tension, and may be assisted if desired by passing the group of yarns which constitute it through a tube whose shapeapproximates that of the truncated sector. Similar pre-shaping tubes may be used if desired for the individual yarns as they are formed into their several groups 20. All yarns that are in the same course of groups around the core are equal to each other in twist; and they are equal to each other in their pitch, and length, in their several helical paths into and out of the general mass of the strand.

The actual pitch in the individual yarns and in the groups is a matter for selection by the designer. of the rope; but for embodying the invention the group ID that. constitutes the core will be twisted so that this group I0 has shorter pitch than the group 20. Thus, it can be chosen that in a iven length of strand the helical positions of the yarns in the core shall have a pitch that will make their lengths equal to the lengths of yarns in those groups 20 which surround the core. However, it is found that practical benefit of the invention is had even when this equality of length is only approximated. Test has shown that when such a strand is under stress the core does not rupture until a proportion of the breaking strain has been reached which is well above what is considered to be a safe working load.

The following specific example is illustrative:

24s yarns with a twist of 2.60 inches per turn.

Aroundthis were eight 7-thread similar groups of 24s yarns each with a twist 01' 2.75 inches per turn, all groups totalling63 yarns and every group being twisted in the same direction. The yarns l2 in the core group III were 5.8" long per turn of the strand, being 94.6%. of the length 6.13" of the approximately equal yarns 22 in the cover group 20. The whole strand was twisted with 5.60" per turn. If the twist of the core had been a little tighter, the relation between the length of the core yarns and the length of the yarns in the groups around the core wouldhave been one of precise equality; but by test and by experimental use this rope was'found to attain satisfactorily the above stated objects and benefits, including tensile strength, elongation, and satisfactory handling. No kinking or distortion was producible by back twisting; and the loss of after turn resulting from throwing turns out of the rope did not affect the strength of the rope. although in regular rope of current standard types the strength is reduced considerably by a throwing out of turns; and kinking always results from a back twisting, with subsequent tensile weakness at the location of the kink The organizing of the yarns with all having equal lengths and with their twists. all in the same direction prevents the arising of length difierentials between outer and inner yarn in thestrand, when such a rope is back-twisted.

The organizing of the strand as a whole into a two-yarn-thick outer course of units. each unit consisting of eight yarns twisted together-a bale-rope" eonstruction--surrounding a halo rope core unit, makes a combination in which the sizes of the bale rope units prevent the occurrence of inter-unit spaces large enough to permit the tangling of any one unit between two whose large number of yarns is accommodated by arranging themfin successive twisted-group courses around the core.

Figure 2 represents a core group of eight yarns 32 twisted as a. cylinder at the axis, surrounded by a course of five groups 40 of eight' yarns 42 each, each group 40 being formed as a truncated sector with the truncated surface based on the central core 30; and around this course of groups 40 is a course of ten roups 50 of eight yarns 52, each, each group 50 bein formed as a truncated sector with its truncated surface based on the courseot groups ll within this outer course. In this construction no element is distorted much from its normal rotundity; and the groups 30, 40 and ill each can have a degree of twist that will make its yarns have ter have less pitch than those of the'yarns 52' in the groups 50 in the outer course. Also, the

7 groups 40 themselves may stand with less pitch in the strand than the groups 50 around them.

Thus equality of length of all yarns is appreached-in a strand structure which is inhe ently stable. y

If it be ,illustratively assumed that Figure 2 with its 128 yarns represents a strand for a threestrand hard fibre rope of eight inch circumferothers such as occurs in kinking. This latter mentioned feature of the organization indeed modifies'the first mentioned, so that for practical purposes the objects of the invention are attained without extreme precision in attaining the equality of lengths of yarns. In the construction having two-yam-thick twisted units formed in a. course surrounding a two yarn thick core there is in any event a closer approach to equality of length of yarns than in the conventional strand first above described, for the helical axis of each yarn in the core unit, and the length of each such yarn, is longer than that of a. yarn lying straight at the axis of the strand; and the length oi. each yarn in an outer unit is shorter than if it were 1 always on the surface of the strand as all yarns are in the outer course of a conventional large strand. Therefore the designer of a rope embodying the invention has a field of choice as to the extent to which he will shorten the twist of; the core unit in order to make the length of the yarns approach actual precise equality with the length of outer yarns, knowing that in any event his rope will be stable against kinking and his ence, having diameter of two and five-eighths inches, with a strand diameter of 11 inches, or

1.3125", the inner course will have diameter .8125"; and the core .333". Further illustratively assuming that this strand is made with a pitch of one turn in 8.37 inches, this makes the length of the helical axis of each outmost group 50 be r 9.03 inches. Assuming; further that the pitch in each of these outside groups is initially 3 inches, there are 3.01 turns of each outmost group in one turn of the-strand. The removing of one 7 by turn from the group when the strand is laid into rope will leave a residual twist of 2.01 turns in each outmost group 50, which therefore will then have a pitch of 4.44 inches, instead of the original 3 inches; and the length of each yarn in the'0ut-' most groups 50 will be 9.05 inches for each turn of the strand.

In the inner course having forty yarns divided intofive' groupslil, by a similar analysis, the initial length of the helical axis of each group is 8.58 inches. Assuming each of these groups to have originally a pitch of 1% inches makes 3.9 residual turns of the axis of the group in one turn of the strand, and a residual pitch of 2.20

inches; and this makes every yarn in the group 40 havea length of 9.009 inches.

For the core group, the axial length isthe same as the length of one turn of the strand, 8.37

inches. Assuming an original'pitch for the core group of 1 /2 inchesthere are 5.58 turns of the core group in one turn of the strand, which, when the strand is laid into rope becomes 4.58 residual equal in length, within less than 0.5% difference;

and the remaining interior eight yarns differ less than 1% from those in the course which surrounds them. By a re-designing, with slight differ slightly in pitch, but this has been found.

to have no consequential effect in limiting the utility of the rope.

Considering that for manila rope the elongation at breaking stress is of the order of 15-18%, and that, when tensile stress on a rope has made a strong radial compression of the inner yarns, there is a binding effect of friction between fibres, it is evident that when under heavy load every yarn in the rope of this illustrative example would contribute its full strength.

The total number of yarns which are to be in each strand can be chosen at will, and can be divided into such groups as will conveniently serve to make a balanced strand. Groups of yarns that are in a course together should each have the same number of yarns, or equivalent volume but groups that are in different courses may differ in their content of yarns. However, if the number of yarns is too large the middle of the group may have a hollow, or may have a yarn enclosed there, which would make an inequality of length of its yarns.

If made of glass, nylon or other synthetic multifilamentarymaterial, its structure may be substantially the same as is above illustrated for hard fibre. If mono-filaments are used, each one or more of such that takes the place of a yarn should be of a quality such that, at the moment when the strand is formed, it is deformable from rotundity into a shape approaching those illustrated for yarns.

In the construction thus described fora large strand, 1. e., a strand so large that some yarns are enclosed and surrounded by other yarns, the surface fibres can be well bound, to resist abrasion, by using yarns of conventional small sizes, as 18's or 24's or smaller. All yarns in a rope made of such strands will have stretch characteristics practically equal, because the lengths of inside and outside yarns are practically equal. And in that rope all kink-causing dislocation of yarns is inhibited by their being grouped and twisted in large units, of eight or whatever number is chosen; and dislocation of units is inhibited by the combination in which (a) each outer unit covers so large a fraction of the surface of the course or core within it, with the potential spaces that theoretically might be made between units being both few and small; whil (b) the units that would have to be forced into such an opening, if a kink were to be formed, are relatively very large; and (c) the development of a dif-= ferential of lengths inside the strand is so small, because'of the equality of lengths and of directions of twist. The rope therefore can be made in a great variety of sizes, and may. at choice, have tight twist for firmness, or long lay for flexibility and strength. when in use this rope can be coiled as well as reeled; can be back-twisted at will; without kink or loss of strength; and when put to extreme tensile duty can utilize substantially all of the strength of every yarn beforebreakage of any yarn will occur.

'I claim as my invention:

1. A rope strand consisting of spun yarns which carry the tensile stresses of the strand and occupy the whole cross section of the strand and are so many in number that some of them are surrounded by others of them, characterized in that each of these yarns is equal to each other of them in length; and in that the whole number of these yarns is divided into groups, each of these roups being twisted on its own axis in form for every yarn of that particular group to meet every other yarn of that group at the axis of the group, the said groups severally constituting units in the strand, formed with one of those group units constituting a core located at the axis of the strand,

surrounded by every other said group; every yarn group which surrounds another yarn group being longer, in a given length of strand, than is that group which it surrounds in that same length of strand, but having longer twist-pitch about its own axis than the twist-pitch of the said surrounded group; -those said group units which are most distant from the axis of the strand constituting the exterior Wearing surface of the strand;

whereby the strand combines equality of lengths of all yarns with flexibility and stability of the strand.

2. A rope strand consisting of spun yarns as in claim 1, further characterized in that the said unit groups of yarns which surround the core group are organized in two courses; the first of which courses surrounds and rests upon the core, being an interior course; and the second said course is at the exterior surface of the strand, surrounding and resting on the first course; each unit group in the second course being wound helically around the first course and being longer, in a given length of strand, than are the unit groups in the first course in the same length of strand.

3. A rope strand consisting of spun yarns as in claim 1, further characterized in that all of the unit groups other than the core group are arranged in a single course of unit groups surrounding and resting upon the said'core group, this course being at the exterior surface of the strand.

4. A rope strand consisting of spun yarns as in claim 1, further characterized in that said constituent yarns are all approximately equal to each other in size and in character of twist.

STEPHEN A. REED.

REFERENCES CITED The following references are of record. in the file of this patent UNITED STATES PATENTS Switzerland May 1 1935

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