US2055037A - Rope - Google Patents

Description

c. MacKlNNoN 2,055,037

ROPE

sept. 22, 1936.

2 Sheets-Sheet l Filed July l5, 1955 In vani/074 sept. 22, 1936. C. 'MaCKINNON 2,o55;o37

ROPE

Filed Ju'ly 13, 1935 2 Sheets-Sheet 2 dfi-www@ Patented sept. 22, 1936 UNITED STATES ROPE Charles MacKinnon, Plymouth, Mass., assignor to Plymouth Cordage Company, North Plymouth, Mass., a corporation of Massachusetts Application July 13, 1935, Serial No. 31,217

strands together lays a rope.

Ordinary ropes have lsuccessive reversals of direction of twist, as between yarns, strands'and 15" rope. The particular direction in which an element stands spun, formed, or laid, in the completed rope, is herein called the lfore-twist direction of the particular element concerned; and

the opposite is its back-twist direction, being its y' direction of untwisting. Tension on the rope tends to untwist the rope, i. e. to untwist the group of strands; but, because of the said reversal of direction of twist as between strands and rope, 4this twists the more tightly each individual strand of the group; and these harden until flu nally the untwisting of the rope is stopped by their balancing resistance. This balancing of twists is normal and is the characteristic feature by which a rope holds itself' together. But, be-

yond this balance, the applying of an external and excessive untwlsting force to the rope as Ya whole, sometimes called back-twisting, or the introducing of back turns, tends to derange the internal structure of the rope, because kinks, nubs and loops `form within the strands, and bulge or burst out of them more or less; and this has the general eifect that the utility of the rope becomes impaired, its limit of tensile strength reduced, and its working life shortened. 'I'he introducing of back-turns can be avoided by expert handling and skilful attention, 'but many who handle rope arel inexpert or careless; and these evil effects a`re encountered more or less in ordinary handling of rope, especially when that 45 handling is such that turns of the twist are forcibly taken out, as may happen in looping a rope around a bit or cleat, in capstan work, or in coiling. A sizeable rope of nest quality will sometimes be wrecked in a few days of use, by failure f' of men to observe the `precautions which will prevent its being back-twisted.

l It is an object of the present invention to produce a rope which may in general have the attributes of a rope of ordinary type, but will'be un- 55 injured by such inexpert or careless back-twistgether forms a strand; and the twisting of,

(Cl. 117-52) l ing as a'rope is likely to experience in ordinary use.

Among the many efforts which have been made to avoid or overcome this difliculty, -one with which I have had'successful experience provides 5 a septum barrier that inhibits the protruding of yarn kinks, IiiE formed, keeping each in its own part of the rope. 'Ihis finds its greatest utility in ropes of large size, butis not so advantageously applicable in a small rope. It is therefore another object of the present invention to provide an anti-kink device which can conveniently be built into ropes of relatively small size. The invention accomplishes this for ropes of any size, large or small, having inside yarns, by so organizing the yarns in the strands that the tendency toward the forming of kinks is inherently forestalled and counteracted, and kinks are much reduced if not entirely prevented.

In one' desirable embodiment, my. invention would lay the rope with its iinal twist reverse to that of each strand; and would have formed each strand with twist in direction reverse to the direction of twist of its own exterior yarns; and yarns would fill the strand solidly, each in a helix about the axis of the strand, all as is customary; but the yarns in each strand would vary .among themselves in direction of twist and in degree of twist, the exterior or cover yarns of the strand being well twisted; and those yarns standing nearer the axis of strand having degrees of twisting which individually are progressively less in the mathematical sense, step by step, from one course to another, until at the axis the yarns stand well twisted in direction reverse to that of the exterior yarns. lThe particular eifect which vthe invention seeks is attained in highest degree in a rope structurevin `which the yarns are relatively large, as compared with customary practice regarding the size of yarns, so lthat the helixes of bres which make up the several yarns are as large as may be found advisable after weighing the disadvantages which in other respects attend the use of large yarns.

The making of a rope whose yback-twisting would not form kinks has been an aspiration of rope makers for a very long time; but the reactions, conflicts, shiftings `of stresses and changes of relations which occur within a v'rope when it is put into a state of strain are so abstruse and confusing that no one hitherto, so far as I am aware, has known the art herein set forth of mastering the kinking evil,how to apply this art with certainty and at will to ropes of various specifications. Therefore, to perpetuate beneflcial advantage of this art I make the following description, setting forth the best modes in which I have contemplated applying the principle.

Each strand of an "ordinary or conventional rope structure has a multiplicity of well twisted yarns,-for example fty or sixty, or considerably less-filling solidly the cross-section of the strand. One, or a few, of theseyarns lies along the axis of the strand; a few lie in a course next to and surrounding those axial yarns; and others lie in courses successively farther from the axis. Each course constitutes a cylindrical sheath which constricts all yarns within it. Each yarn in each course is a helix about the axis of the strand. It is a common practice that all helixes of the strand are formed in the same direction of turn about the axis; but sometimes the outer course or courses of yarns run around in direction of turn opposite to the directionof those within. In either arrangement, in a section of strand having a given length, a yarn at the axis has approximately the same length which the axis of the strand has; the yarns immediately surrounding -that yarn each have a little greater length; and

so on, progressively outward, those yarns which run around the axis at a substantial distance from it having, in any given section of strand, a substantially greater individual linear extent than do those in this same section near the axis.

The explanation-of the invention can now begin to be seen. The length of each yarn is a function of the pitch andthe diameter of its helix,v the pitch being the length of axis along which a single convolution of the helix extends. If that said section of strand should be twisted more tightly,for'example, so that one could see by looking at its surface yarns that another half convolution had been introduced,each of those surface yarns would have been drawn to a steeper angle to the axis, and all would have shorter pitch. As the actual length of each yarn remains unchanged, each yarn could not extend as far as it did along the axis. Each sheath of yarns would have become shorter in its coverage of yarns within it, as well as coming to constrict them more tightly.

The extent of shortening of sheath would. be

greatest for those yarns which are located at the surface of the strand, for at that distance from the axis each added convolution of yarn requires more length of yarn than is required by a convolution added at a location near the axis.

When a rope is back-twisted the whole of'the individual strand experiencesthe lsame degree of angular turning, inner yarns like outer yarns; but the consequent shortening of the axial extent of the outer yarns is greater than the simultaneous shortening of axial extent of the innerv yarns.

Thus an internal disorganization is promoted, an endwise thrust, of yarns near the axis relative to yarns which surround them. This has to be executed under confused conditions yof constric-j tion and friction, which resist it. Flexibility and changing curvature of the rope yarns tend to -make a. `mobile condition somewhat akin to a condition oi'- flux, within the rope, in spite of the tightening pressure; the incompressibility of matter asserts itself; and when the thrust has become Strong enough the central elements of the rope find some place to bend laterally, between the surrounding yarns, so as to dispose their growing excess of length, in a loop whose extrusion gives relief. Upon cessation of back-twisting, thev extruded disorganized matter does not readily resume its proper location. It is held by friction,

and by the presence of local stabilities of twist known as kinks; and if ythe back-twisting has been severe enough no manipulation is practicable to restore the inaccessible interior parts of the rope to proper form for doing normal work.

The invention provides a combination of helixes that gives a measure of relief within the strand. It causes the inner yarns individually to shorten themselves, when the outer helixes of yarns shrink because of a tighter twisting of the strand as a whole.

This is accomplished by initially building the strand with the fibres of those yarns which are at and near its axis having their helixes as large as is feasible, and by having those bre helixes turn in the direction in which all of the yarn helixes turn in the strand. 'I'he axial yarns being yarns twisted in one direction, yarns surrounding them concentrically. standing in other courses progressively further from the axis, may be successively of twist diminished, reversed, and increased in reverse direction, the outside yarns having individual twist opposite to that twist with which the assemblage as a whole is being formed as a strand. Strands thus formed may then be twisted into rope, laid with reversal of twist, in the usual way.

With this construction, and assuming the rope to be in its normal condition of internal balance of stresses and parity of relations of its several parts, any back-twisting of the rope will twist each strand more tightly; and the outer yarns therein will tend to make the outer portion of the strand have a shorter linear length, as with conventional ropes hitherto; but that same twisting which shortens and tightens the strand will simultaneously put more turns into the helixes of fibres in the yarns near the axis, and this will harden and shorten each of those yarns. Thereby to an extent the interior parts of the strand are shortened simultaneously with the shortening of the outer zone of the strand, thus to an extent reducing the difference and disparity of lengthwise thrust, as between successive courses, which has heretofore resulted in the formation of loops or kinks.

The correction accomplishedbythe invention is not fully described by the foregoing, because the assumed back-twisting of a rope, with consequent tighter twisting of each strand, involves also ameasure of untwisting of each yarn whose individual twist is opposite to the twist of itsA strand. -Therefore, with the shrinkage in length of exterior yarn helixes, the bre helixes which compose each of those yarns experience a lengthening which reduces the extent of that vshrinkage of those yarn helixes. At the same time the interior yarn helixes are undergoing a super-shortening, as above described, because of the sho ening of their fibre helixes. Therefore, with t e described diversity and locations of individual twists of yarns, the elements cooperate so as to convert Athe normal disparity of shrinkages into a sub-disparity, and thus to minimize and defer the eifort of interior yarns to protrude.

Because of the inevitable difference in diameter, betweenv the mean helix of 4fibres in one individual yarn and the mean helix of the course of yarns in which that yarn lies, the differential of length of a yarn, resulting from its individual change of twist when the' twist of strand is changed, is not of the same order as is that difference of length 'of strand surface which is produced by the same twisting of the strand. 'I'herefore a structure embodying the invention may4 not 75 compensate for the whole of the described disparity. However, it does more than diminish the disparity as above. explained, for in addition the beneficial .effect is compounded. That harder twisting of the inner yarns which makes them shorter also tends to make them occupy less diameter, and thus to permit the courses of yarns which surround them to settle to a smaller diameter, and therefore to extend themselves to a vgreater length,which further reduces the amount of their shortening and of the disparity. In considering the ultimate result one must remember also the characteristic mobility which always exists to some extent inside a rope. Taking this into account, the frontier limit of in-A jurious back-twisting. can be made so remote, by proper designon the principles of the invention, that it is not likely to be reached in the ordinary experience of a rope.

When the ldescribed gradation of twist of individual yarns extends through several courses, as in Figure l, it produces in the midst of the strand an intermediate zone wherein are spun yarns whose twist is less hard. These can adjust their shape so as to lill more perfectly all available crannies of space; and this makes it more dicult for the harder twisted units at the axis to ilnd f a crevice through which they can extrude themselves..

Details may be simplified, especially in a small rope, by making the gradation have. only one step,all of the yarns surrounded by the cover course having individual hard or soft twist in the direction opposite to that of the cover yarns. The rope would then be made by forming the whole strand with twist opposite to that of the cover yarns; and by laying the desired number of strands together with twist opposite to that of diametric location ofl the cylinder at which 'the change from one twist to the other occurs; they A identity of the direction in which interior yarns were spun, in the making of the yarn, with the direction in which the exterior yarns in the strand are formed, in the making of the strand.;l and the having of all yarns formed in like direction in the making of the strand, opposite to the twist of strands together in the rope. Best results are attained when the yarns of the exterior course individually have twist contrary to thatin which the strand is formed', and all yarns individually have large cross-section, and their fibre helixes have short pitch. Y

fI'he reason why a major elimination of kinking tendency is favored by the use of individual yarns which are large, as compared with spun yarns heretofore used in ordinary practice, is that a change of twist of strand imparts to the mean fibre helix of any yarn in it a greater change of length of helix than the mean bre'? helix of a smaller yarn of equal length, in that strand, would experience per equal angular extent of twist. And, further, according to the invention. changes of length of libre helixes in the yarns cooperate with changes of length'of yarn helixes in the strand to minimize the disparity,- decreasing the shrinking of helixes in the cover yarns and increasing the shrinkage of helixes of core yarns.

Rope is madelwith its surface yarns in small or medium sizes because of better appearance and durability in use. Hence the practical relation may be defined for such ropes by saying that for better anti-kinking elect the interior spun yarns, twisted like the strand, are of sizes larger than the exterior yarns. But whenever a ylarge size is permissible, Ifor the exterior'yarnsy of a particular rope, the tendency of that rope to kink when back-twisted will be still less if also the exterior yarns are of large size.I This is because larger cover yarns have greater tendency to extend their length, and so to reduce the net contraction of the exterior helix, upon the occurrence of the back-twisting.

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 accompanying drawings:

Figure 1 shows a rope embodying the. invention, with the end of one strand disclosing a cross-section of the strand; and with the end of another strand laid open which discloses gradation of twists of the individual yarns, from course to course;

Figure 2 is another embodiment of the invention, being a strand having a core and a single cover course of yarns;

Figure 3 is another embodiment of the invention, being a strand with a cover course of yarns smaller than those within.

Figure 4 is a theoretical diagram showing, for

lva strand of a conventional rope, without bene- The drawings illustrate modes of applying the invention to ropes of three varieties of specilcation. In Figure 1 the rope I 0 isof right lay and each of its three strands I l is an assemblage of a multiplicity of yarns arranged in courses 20, 22, 24, 26 formed to the left.l As thus'far described the rope is of ordinary and conventional construction, and each course may have, its own individual pitch as illustrated in Figure 1, or all the courses together may be formed as a group all having the same pitch as is indicated in 4Figures 2 and 3, both types being heretofore known. But a departure from ordinaryconstruction is found in the individuality' of twist of the yarns. The outmost yarns are of rm right twist, being those in the outer course 20; and step by step toward the' center the hardness of 'right twist diminishes until, at' the axis, it becomes a firm left twist in 'yarns 26.

Obviously the construction might be reversed in all respects, with equivalent eiect; also variations may be made in number and size of yarns and mixtures -of sizes and in other details of arrangement on general principles of' lrope construction, according as the designer ot the rope may choose'for serving his purpose and according to the sizeor other specification for the rope in general, as the invention does not depend upon the rope being of any particular lay or construction, in other respects than those herein particularly set forth. Thus Figure 2 illustrates application of the invention to a smaller rope, of `fine yarns wherein, for example, each strand of half inch diameter has 'a core of about one quarter inch diameter, with ve yarns in the core and twenty in the cover, all in. the core being of hard or soft left twist individually and all in the cover being individually of firm right twist, and all of both twists, core and cover, as an assemblage, being formed into the strand by twisting all at the same pitch to the left.' To make a complete rope three strands such as this would be laid together with right twist.

In Figure 3 a strand is illustrated in which the cover yarns 40 are of ordinary size, for example, 18s, about one eighth inch diameter, but the interior yarns 46 are of larger size, and all are of the same pitch; but the individual yarns at the surface are of right twist and the yarns under the surface course are individually of left twist, as is indicated by the short oblique lines 4l and 41 thereon showing the directions in which the fibres run.

In the strand forming process, when the yarns are assembled under tension and twist, they become distorted from the rotundity produced by their initial twisting, and settle together to ll the strand solidly in shapes like fragments of sectors as indicated; but notwithstanding this distortion and the further distortion by the forming of the yarn-into a helix in the strand, and still further by the making of the strand helical in the rope, the fibres in any individual yarn may for purposes of the invention be considered to lie approximately in helixes. And when the length of any single complete3 convolution of a yarn o'r nbre helix is compared with the length of a single convolution of another helix having\ equal pitch, and overlying the same part of the axis, it can be seen that the length of single convolu- `tion is greater for that yarn or fibre whose helix,

considered in cross section, has the greater per- Inspection of this confirms that the throwing of an additional convolution into a strand, Where there are helixes both of larger and of smaller diameter, causes helixes having large diameter to undergo 'greater change of length of helical formation, i. e. length of sheath, than do the helixes having small diameter, because, for the larger, the added convolution embodies a greater length of line; and more of the actual length of the yarn or bre constituting the helix is thus put into the circling part of the helix; leaving less for its progression along the axis. In computing for this demonstration it is sufcientto use round numbers and approximate ilgures; and it helpful to make' a rigid postulate thatthe diameter of the helix and that the lengths of the yarns in the helix which is being examined remain unchanged. The

actual change in length of that yarn,l and its effect, may be considered separately. The effect of introducing a convolution depends upon its pitch and upon the length of section into which it is introduced, but for a one-eighth inch helix at the axis the effect would be to change the length of helix only a few hundredths of an inch.

The operation of the invention can be visualized to an extent by considering the conditions of internal strain which tend toward the making of interior bulges and the bursting forth of kinks, and how the invention reduces these strains. Attention is directed especially in Figures 4 and 5 to the body of material at the axis of the strand, and the body of material comprising the surface course of the strand; the change of length which each of these bodies tends to experience;l and the disparity between their changes of length.

Figure 4 is a theoretical diagram illustrating the invention by showing strains which tend toarise within each strand upon the back-twisting of a rope of conventional structure, all of the yarns beng formed in like direction within the strand. Figure 4 assumes that a section of strand, initially in a normal state of internal stresses, initially has one of its ends at a plane indicated by the dotted positions 40,42, 44, 46; the other end in a parallel plane for example, six feet away, each being squarely cross-cut; and makes other incidental assumptions hereinbefore indicated which do not seriously affect the main relations which are under consideration. The dotted lines show the initial position; and the full lines show the changes of position which tend to accur when one additional convolution of twist is introduced into thisv section.

Assuming the pitch of yarns in the outmost course of the strand to have been initially fourI and one-half inches, and other yarns to have had pitch about as the drawings would indicate if the external surface of the outmost course had a diameter of one inch; and assuming that the yarnends remain unmoved at the remote end (not shown in the drawing) of this six foot section, so that the whole shrinkage is accumulated at the end which is seen in Figure 4, the diagram of Figure 4 can be made. This can be done by computing the length of any one convolution of yarn before and after the introduction of the additional convolution to the section of strand, knowing that the actual length of that section of yarn revmains unchanged, although the total number of convolutions therein changes; then nding the new pitch, conforming to the new length of convolution, the diameter remaining unchanged; and then nding the new total length of helix, the new number of convolutions therein being known. Comparison of this with the initialI length of helix shows the contraction experienced by the helix which expresses the location of that particular yarn; 'Ihe change of length of each yarn has then to be found by similar method, for the introduction of the convolution to the strand as a whole applies to each element in the strand.

The pitch' of the fibre helixes, and the diameter of helixes of bres in the particu`ar yarn being taken, at a proper value, assuming either the external diameter of the yarn or a mean diameter `of lbre helixes, a computation can be made similarly to ascertain the distance by which the helix of bresin that yarn tends to lengthen or shorten, and this may be considered to be a measure of the tendency of the yarn itself to extend or to shrink in length. For this computation the working value for perimeter and diameter of vthe fibre helix may be found by assuming the diameter of yarn to be that of a circular yarn having the same area wh'ich the yarn actually has in crosssection,-a value which is known because the sizes of yarns are commonly named by their area, to wit, by stating the number of themv that can be contained in a tube of known cross-sectional area,-onehalf inch, in diameter.

'Ihe helical course of the axis of the yarn in the strand will ordinarily be a negligible factor in determining the change of length of yarn; and

so it will also for determining whether the effect will be pro-kinking or anti-kinking', but if it be desired to measure the extent to which a lengthening or shortening of the yarn affects the shortening of axis of that helix in which the-'yarn lies, account should be taken of the pitch of the axis of that yarn relative to the axisy of the .helix in which the yarn lies, in order to determine the value of its projection on said axis of the helix in which the yarn lies.

y Figure 4, being a diagram thus made on the basis of the assumptions stated, shows that, in

order to re-establish the initial state of stressesr between fibres, yarns and courses ofyarns, the ends of the yarns of the outer course must recede approximately to the position 40'; and that the ends of the yarns in the other courses must move approximately to the'A positions 42', N and 46'. Thus the addition of a convolution to the strand,'by its excessive shortening of the outer helixes, makes the inner helixes relatively much longer than the 'outmost helix 40.

In actuality neither end of the strand section moves as represented. f The generated tendency to excess of interior lengths is distributed through the section, in slips, strains and stresses :of various sorts, and becomes expressed in tighter compressions; in adjustments of internal relations with other yarns; and, if the stress is sumcient, in a lateral bursting out of some of the interior parts in loops and kinks. The introducing of a second additional convolution of twist would more than double the distress caused bythe first.

Figure 4 represents a strand having yarn` sizes and arrangement similarto those of Figure l, except that it isa conventional strand not embodying `the invention.

' terior material and length of exterior material illustrates how a rope can have interior yarns. and yet have the internal stresses and strains of backtwisting relatively small. They may indeed be made so small, by design in accord with principles of the invention, that the rope is both easy to handle, and is immune from damage caused by such mishandling as rope ordinarily experiences..

For the exterior yarns, which have to maintain appearance, resist abrasions and to resist the extrusion` of kinks, there has been universal recognition that firm-twisted yarns of size 18's are customary and suitable, and that it is better not to use a larger size. But, with the invention,

it appears practicable that both interior and exterior yarns may be 6s or larger., with advantage and with the saving of cost which is attendant. Being three times the size of 18s they shorten and lengthen more than do the smaller yarns, in case of super-twisting, and so, when set interioriy, they both reduce the tendency for kinks to form. and they make the extrusion of kinks more diiiicult because of the larger size; and when set exteriorly, their greater lengthening power further reduces the need for their function of resisting kinking extrusion, without failing in their l0 function of providing a practicable wearing surface if the precaution is taken to have them hard twisted.

As regards pitch, the va'rlti-kinking effects of the invention are greatest when the rope contains the feature that the pitch of the interior yarns is as short as is feasible, one benefit of which is that with shorter pitch a greater retraction is` experienced upon the adding of a convolution. This construction is illustrated in Figure 1, where 20 the pitch of yarns nearer the axis is progressively less than the pitch of yarns more remote.

I claim as my invention:

1. A rope of spun yarns formed into strands that are twisted together to make the rope, com- 25 prising a combination wherein all of the yarns of a strand are formed in like direction of twist; each yarn of the strand being individually twisted, and theindividual twists of the inner yarns of the strand are in the said direction in which the yarns are formed, whereby a tendency to a shortenlng and hardening of the fibre helixes of the inner yarns accompanies any tighter twisting of the strand; 5

2. A rope of spun yarns formed into strands that are twisted together to make the rope, comprising a combination wherein' all of the yarns in a strand are formed in like direction of twist; each yarn of the strand being individually twisted, and the individual twists of the inner yarns of 40 the strand are in the said direction in which the yarns are formed, and the twists of the bres constituting outer yarns are contrary, whereby tendencies to a shortening of the fibre helixes of v the inner yarns and a lengthening of the fibre helixes of the outer yarns accompany any tighter twisting of-the strand. f

3. An anti-kinking construction 'of spun yarns into a ropestrand wherein a multiplicity of spun yarns lie in a plurality of courses of yarns formed in helixes, the helixes of one course surrounding the helixes of another course; and wherein the fibres spunl in the yarns'lie in helixes; all helixes of yarns having twist in a common direction; and all helixes of fibres in yarns of the inmost helix having twist in that same direction; and 4all helixes of bres in yarns in the exterior helix having twist in the contrary direction, whereby, when a change-of twist in the strand as a whole occurs, disparity ofv contraction of helixes in the 00 several courses is minimized. y y

4. An anti-kinking construction ofy spun yarns as in claim 3, in which there are one or more helixes of yarns intervening between said inmost and said exterior helixes of yarns, in which in- 65 tervening yarns the fibres stand in helixes having twist of a degree intervening between the twists of fibre-helixes in said inmost and in said exterior yarns.

5. A rope of spun yarns formed into strands 'l0 that are twisted together to make the rope, comprising a combination wherein all of the yarns in each strand are formed in like direction of twist; each strand having exterior yarns and interior yarns; and each of the said exterior yarns having 'l5 individual twist contrary to said forming direction; and each interior yarn having twist individually in the said direction of forming.

6. A rope of spun yarns formed into strands that are twisted together to make the rope, `comprising a combination wherein all of the yarns in each strand are formed in like direction of twist; each strand having exterior yarns and interior yarns; and each of the said exterior yarns having individual twist contrary to said forming direction; and some of the interior yarns having twist individually in the said direction of forming; the exterior yarns individually having size of a character well suited for resisting abrasion, and the interior yarns which are twisted in the forming direction individually having a larger size, whereby they have a character better suited for shortening their several helixes when the strand is super-twisted. I

7. A rope of spun yarns formed into strands that are twisted together to make the rope, comprising a combination wherein al1 of thev yarns in each strand are formed in like direction of twist; each strand having exterior yarns and interior yarns; and each of the said exterior yarns having individual twist contrary to said forming direction; and each interior yarn having twist individually in the said direction of forming; the rope being of a type in which yarn sizes 18s or smaller are suitable for all purposes except anti-kinking, but the rope actually being one in which both interior and exterior yarns are individually 6s or larger, whereby the anti-kinking quality of the rope is enhanced as compared with what this quality wouldl be if the same'total volume'of spun yarns which compose the rope were made up in sizes of 18s or smaller.

8. A rope of spun yarns formed into strands that are twisted together to make the rope, comprising a combination wherein the yarns lie in a plurality of courses, all formed in like direction of twist in a strand, and the pitch with which the yarns are thus formed is shorter for yarns which stand nearer the axis than it is for yarns which stand more remote from the axis; and the twists of the fibres constituting said yarns which stand nearer the axis being in the said direction in which the yarns are formed, whereby a tendency to a shortening and hardening of the nbre helixes of said yarns nearer the axis accompanies any tighter twisting of the strand.

9. An anti-kinking construction of spun-yarns into strands, and of those strands into rope, wherein, in each strandthe fibres of the inmost group of yarns stand spun, in their several yarns, in the fore-twist direction of the forming of their cover yarns in the strand, or in such near proximity thereto that a. substantial back-twisting of the rope as a whole would fore-twist them thus; each course of yarns intervening between said inmost group and the exposed cover yarns standing formed in the same said direction, or in the said near proximity thereto, which direction also is the back-twist direction of the rope; the exposed fibres of the cover yarns standing spun with pitch, in theirindividual yarns, which is less than the ptch in which those yarns stand formed in the completed strand.

CHARLES MACKINNON.

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