US3022566A - False twisted yarn beam - Google Patents

Description

1962 c. E. DANIELS ET AL 3,022,566

FALSE TWISTED YARN BEAM Filed Feb. 11, 1958 2 Sheets-Sheet 1 FIG I 5 s 1 a e 72 W W 21 E1 0 I I '0 1. H fi [7 A a 2 '5 FIG. 2 I I6 1 1 18 n l6 INVENTOR5 CHARLES WARD, NIELS NATHA NIEL NVER YETH ATTORNEY Feb. 27, 1962 c. E. DANIELS ETAL 3,022,566

FALSE TWISTED YARN BEAM 2 Sheets-Sheet 2 Filed Feb. 11, 1958 FIGS? FIG.

FIG. IO

83 R L O E m WD D m M E S E L R A H C NATHANIEL CONVERS WYETH ATTORNEY United States Patent 3,022,566 FALSE TWKSTED YARN BEAM Charles Edward Daniels, Wilmington, and Nathaniel Convers Wyeth, Hockessin, Del., assignors to E. I. du

Pont de Nemours and Company, Wilmington, DeL, a

corporation of Delaware Filed Feb. 11, 1958, Ser. No. 714,549 6 Claims. (Cl. 28-78) This invention relates to yarn winding and packaging, and has particular reference to beaming continuous multifilament Zero-twist yarn. More specifically, this inven tion relates to a novel and useful process for continuously twisting such yarn during beaming, and to the novel beam package produced thereby.

Yarn, thread, fibers, and the like filamentary structures are conveniently packaged and transported on beams. Such beams are prepared by simultaneously winding with slight traversing a plurality of yarn ends maintained in a spaced, parallel, coplanar relationship, i.e., as a warp sheet onto a beam, a single large core or a yarn package support provided with suitable end flanges. Beams ordinarily may contain on the order of one hundred or more yarn ends, and upwards to many hundreds of pounds of yarn. A beam may be used by the consumer as received to provide the warp for weaving (loom beam) or as a single supply package for large-scale twisting, plying, and the like textile operations (supply beam). In either case, the use of the beam enables the handling and transporting of large quantities of yarn with but a minimum of singleend operations.

Yarn is wound onto a beam at essentially Zero helix angle since the traverse stroke during beaming normally is no greater than the yarn-to-yarn spacing in the warp eing beamed. To insure that individual filaments in the yarn bundles do not become trapped, entangled, or broken due to overlap with the filaments of adjacent or subsequently wound yarn, i.e., to insure that the yarn can be unwound (backwound) from the beam, it is necessary to apply 'a certain amount of twist to the individual yarn ends prior to beaming. This producer twist is required in order to maintain the unity of the yarn bundle, and is applied at relatively low levels (nominally about 0.5 turn per inch) as compared to consumer twist, which may range upwards to several turns per inch. Yarn containing such producer twist does not form the so-called filament ringers (filament wraps on the beam) because any potential trapped or tangled filaments are broken and pulled along by the parent yarn during backwinding. However, without such twist, breaks which occur during backwinding lead to the formation of ringers, which, in turn, cause considerable yarn waste and may lead to the eventual interruption of the backwinding operation. Therefore, it is required in every beaming operation that the individual yarn ends be twisted or receive an equivalent treatment prior to beaming, not to facilitate preparation of the beam, which is no problem, but to permit the yarn to be backwound therefrom, which indeed is a real problem.

Although twisting insures the formation of a backwindable beam, such twisting has involved much additional yarn handling, and is costly in terms of time and equipment required. Moreover, the mechanics of twisting and the additional handling often result in lower yarn quality. Finally, since the consumers twist demands vary widely depending upon the end use of the yarn, and since the presence of the costly initial producer twist in the yarn may render such subsequent twisting nonuniform, thereby affecting the fatigue and load-carrying ability of the yarn, there has been a need for means to beam yarn without prior twisting (i.e., means which would permit beaming zero-twist or as-spun yarn directly into a backwind- "ice able package). By zero-twist yarn is meant yarn having no substantial process twist, excluding the omnipresent slight twist in the yarn resulting from normal handling (e.g., twist resulting when removing yarn from a stationary package) which for all practical purposes is negligible. Despite the need, however, no satisfactory method for preparing backwindable beams of zero-twist yarn is known to the art.

That the problem of beaming zero-twist yarn has been recognized is shown by Bradshaw (US. 2,224,665), who

discloses that slashing (sizing) such yarn prior to beaming results in a backwindable beam. The slashing, in this case, serves in a manner similar to twisting, by binding the separate filaments of the yarn into a coherent bundle. However, the slashing operation may entail as much additional handling and equipment as does twisting, is timeconsuming, and requires that the sized yarn be rigorously dried prior to beaming, since otherwise the yarn bundles stick together. Further, the size on the yarn often must be removed at some subsequent stage of handling by the consumer. Karns (US. 2,324,584), seeking to avoid the need for either twisting or slashing, proposed to traverse a single thread along the length of the beam so as to separate the successive windings on the beam. During backwinding, the traverse thread serves to break out trapped and tangled filaments, thereby avoiding the formation of ringers.

ing and subsequent handling, which is the crux of the problem of beaming Zero-twist yarn. Moreover, the breaking-out process often leads to yarn of unacceptable quality containing an excessive number of broken filamerits.

Recently, the problem of. beaming zero-twist yarn has arisen anew. Technological advances in the textile art have led to improved and higher speed production of yarn, requiring rapid, continuous yarn packaging opera tions. For example, many benefits derive from spinning and drawing nylon yarn in a coupled operation, prior to initial packaging. It would be highly desirableto beam directly from such a spinning package, without having to divert the yarn to a twisting or slashing operation. Recent advances in apparatus design have made spin beaming (i.e., packaging yarn on a beam immediately as it is formed) a feasible operation save for the need for twisting. It is apparent that many improvements in the con tinuous production of yarn would derive from a suitable process for beaming zero-twist yarn, and would enable beaming much of the current zero-twist yarn production presently being sold on single-end packages.

One object of this invention is to provide a backwind able beam wound from a warp of continuous multifilament yarn, the separate yarn ends having substantiall zero net twist therein.

A further object is a process for beaming continuous muitifilarnent yarn having substantially zero net twist therein, the beam so produced being backwindable with: out incurring tangled or trapped filaments, and without the formation of filament ringers.

A still further object is a backwinda'ble beam of a warp of continuous multifilament yarn, the separate yarn ends having a periodic, reversing, i.e., alternating (false) twist preferably throughout theentire length.

Yet another object is a process for backwinding from a beam to supply a warp of continuous multifilarnent yarn, the separate yarn ends having substantially zero net.

twist therein. These and other objects, together with means for accomplishing these objects, will appear hereinafter.

The objects of this invention are accomplished in general by continuously subjecting individual ends of a warp of continuous multifilarnent zero-twist yarn to the However, Karns method does not eliminate trapped and tangled filaments during package 3 action of a false twister, imparting thereto'a periodically reversing (i.e., alternating twist) of average twist level of at least about 0.4 turn per inch, and immediately thereafter winding such a warp onto abeam. in the usual manner and at usual beaming speeds. In a preferred embodiment, individual zero-twis't'yarns of a warp are subjected to intermittent pneumatic unidirectional twisting with air so as topro'duce a warp with'indiv'idual ends having from about 0.4 to'qabout. 0.8 average turn per inch of alternating twist at a period length of from about 4 to about 16 feet while winding at a yarn tension of from about 30 to about 60 grams. There results a novel and useful loom or supply beam containing'a warp of yarn,

the individual ends of which have substantially zero net twist, which may be backwound with either removal or retention of the alternating twist applied thereto by the process of the present invention. Such a beam may be backwound without incurring tangled or trapped yarn filaments, and without the formation of objectionable filament ringers.

The'invention will be more clearly understood by rcference to the attached drawings.

7 FIGURE 1 shows a schematic view of an apparatus useful in the practice of the present invention.

FIGURE 2 shows in schematic section an apparatus useful for twisting yarn pneumatically.

FIGURE 3' shows an end view of the apparatus of FIGURE 2.

FIGURE 4 shows an enlarged, schematic partial section of the apparatus ofFIGURE 2 taken alongthe sertion line aaf.

FIGURES- shows a sectional viewof several pneumatic twisters together with fluid supply means suitably ar ranged for use in beaming. FIGURE 54 shows a fluid supply regulator useful with the apparatus of FIGURE 5. FIGURE, 6 shows a side elevation of one apparatus useful for twisting yarn mechanically. 7

FIGURE 7 shows a left-end view of the; apparatus of FIGURE 6,

FIGURE 8 is a sectional view of another apparatus useful for twisting yarn mechanically.

FIGURE 9 shows a left-end view (rotated 90 counterclockwise) of theapp aratus of FIGURE 8. I

FIGURES 10 and 11. show in enlarged schematic section other pneumatic twisters suitable for use in the present invention.

"FIGURE 12 shows graphically the lengthwise variation in twist along the lengthof a segment of yarn prepared in accordance with this invention.

Referring to FIGURE 1, there is shownschematically a' conventional; beaming apparatus modified to include false twisting means for carrying out the process of the instantv invention. In operation, a plurality of. yarn. ends indicated at 1 (from a source not shown): is led over the guide 2, which1may be a pinboard, an eyelet board, or other suitable guiding means. At. this point, the individual, yarn ends. are combined at form a warp sheet. The. warp sheet is passed. about vibration control and delivery rolls at 3 andv then through separator guide (a pin board, comb, grooved rolls,.-or the like), eyelet guide 6, then twisting means 8 where each yarn is false a twisted. Downstream'from the twister Stheyarns pass through an eyeletguide 7. Eyelet guides 6 and 7 are 'rnounted on eyelet boards located approximately the same distance upstream anddownstream, respectively, from thetwister 8, and serve tocenterlthe yarn in the twister and'to control lateral fluctuations of the individual yarns in the warp sheet. The twisted yarns then encounter traverse comb 9 and are thereby traversed over idler roll and onto beam 11, the lay of the warp being controlled by the presser roll 15. Beam 11 is ofv conventional design, having a barrel portion 12 and a flange 13 mounted at either extremity to control and contain the yarn bulldup, indicated at 14. Excluding the twisttermed hereinafter equilibriumtwisting.

URE l is conventional and individual components may be altered, added, or even removed, inaccordance with accepted beaming practice. The yarn supply means (not shown) may be packages mounted in a conventional creel, or may consist of a number of spinning machines, whereby as-spun yarn is forwarded directly to the beam without intervening discontinuous process steps.

Utilizing the apparatus of FIGURE 1, the yarn 1 passing from the supply means'to beam 11 is false twisted, that is, twisted in opposite directions upstream and downstream from the twister. 'Downstream twist is trapped on the beam while upstream twist of equal amount but opposite direction is accumulated. If such twisting continues, the point is rapidly reached where the upstream twist is accumulated to an extent sufficient to counteract the twisting torque of the twister, resulting in either the winding of Zero-twist yarn onto the beam or complete breakdown of the yarn line. Such a condition will be In order that the upstream twist may reach the beam, the torque of the twister must be relieved or otherwise overcome. Three important methods are available for permitting the periodic alternation of twist in the yarn being packaged and which avoid the condition of equilibrium twisting.

The simplest method of applying periodically alternating twist to a running yarn line according to this invention comprises intermittent application of twisting. Thus, after the upstream twist has, accumulated to a predetermined extent, the twister torque may be reduced or eliminated to allow some or all of the accumulated upstream twist to pass downstream and onto the beam. Suchan intermittent twist-no-twist action, when suitably timed with respectto yarn speed permits the winch ing and packaging of yarn having good uniformity of twist period and level, with dwell at twist reversal points (i.e., points ofzero twist) being at aminirnum. The intermittent application (pulsating) of unidirectional twist is preferred for the purposes of the present invention.

Periodically alternating twist may also be applied to a running'yarn line according to this invention by intermittently applying twisting in opposite directions. Such a method is more desirable, however, because less sensitive to timing of the twist cycles. These two methods are applicable to either mechanical or pneumatic twisting. When. employing pneumatic twisting, periodically. alternating twist may be applied to arunning yarn line with constant unidirectional application of twisting byfperiodically varying the tension in the yarn. After upstream twist has accumulated to the desired extent, the tension on the yarn line is increased, thereby permitting some ofthe upstream twist to: pass through the twister and downstream onto the beam. The efiectiveness of this and uniformity of the product so produced;

FIGURE 12 shows graphically the lengthwise variation in twist along the length of a segment of yarn twisted in accordance with thisinventiomwherein ordinate 05 indicates level of S twist and ordinate 02. indicates level a of .the Z twist at any point along the yarn length, i.e.,

the abscissaoL. At the initiation of twisting (at 0), the S twist level rises rapidly'to a maximum a, then, approaching equilibrium twisting, falls off towards b. Twisting is stopped or reversed at b, allowing the up stream accumulation of twist to pass downstreamand onto the beam. Such practice results in Z twist rising to its maximum twist level at c, then, again approaching equilibrium twisting, falling off towards d, at which point twisting in the 8 direction is initated, and the process commencng at o is repeated. By suitable variation of processing conditions, the curve of FIGURE 12 can be made to assume a variety of proportions, and, of course, need not be symmetrical.

FIGURES 2 and 3 show section and end views respectively of a representative pneumatic twister suitable for use in this invention. This twisting means comprises cylindrical yarn passageway 1618, with enlarged exhaust section 16, beveled section 17, and twisting section 18, the latter being tangentially intercepted by the fluid conduit 19 in a plane normal to the axis of the yarn passageway. In operation, fluid passing through conduit 19 intercepts the yarn 1 in twisting section 13 and imparts thereto a crank twisting action. The path of the high velocity twisting fluid in the twister is indicated by arrows in FIGURE 4. By periodically interrupting the supply of the fluid to the twister, intermittent unidirectional application of twist described in the fore going is achieved. With reference to FIGURE 12, fluid is supplied to the twister during passage of a segment of yarn having length o-b. Fluid supply is interrupted for a yarn length bd. Enlarged exhaust section 16 of the twister 3 serves to facilitate the release of exhaust twisting fluid with minimum interaction with the yarn. Beveled section 17 serves to guide the yarn into twisting section 18, and serves to minimize yarn damage. The length of yarn twisting section 18 should not be less than its diameter, and preferably, the total length of the yarn passageway will be about six times its diameter for optimum twisting. Further, the ratio of the area or" the yarn twisting-section 18 to the area of the fluid conduit 19 may vary from about 4:1 to about :1, but is preferably 6:1. Ratio of the diameter of the yarn to the diameter of the twisting section 18should be from about 1:2 to about 1:10, and is preferably about 1:4. The yarn twist-section 18 and the fluid conduit 19 are preferably cylindrical in shape, as shown, but either or both may be other than circular in cross section and neither need be uniform in area or cross-sectional form throughout its length. It is readily apparent that many variations of the twister from the representation shown in FIGURE 2 are possible.

Air at room temperature is a suitable fluid for twisting yarn in accordance with the preferred practice of this invention. However, other fluids or liquids substantially inert to the yarn, such as carbon dioxide, nitrogen and the like may be utilized if desirable, and such fluid may be heated or refrigerated as desired, so long as such a temperature is not deleterious to the yarn being twisted. Air is the preferred twisting fluid, and will be referred to herein for illustrative purposes as representative of all such twisting fluids. Steam may also be employed.

In FIGURE 5, an arrangement is shown whereby several pneumatic twisters are employed in a side-by-side relationship for use in beaming in accordance with PIG- URE 1. FIGURE 5 shows several twisters 18 mounted in a single block 8, which is securely attached to the manifold means 21. Manifold means 21 contains an enlarged fluid supply pipe from which a plurality of fluid ducts 22 communicate with the fluid conduit 19 of each twister. If desired, either or both the fluid duct 22 and the fluid conduit 19 may be outwardly beveled at eir respective points of contact to facilitate alignment. in operation, fluid from an external source (not shown) is supplied at either or both ends of the fluid supply pipe 6 constant source of fluid by utilizing the apparatus of FIGURE 5a, which consists of a tubular valve means 20a adapted to be rotatably mounted in the fluid supply pipe 29 of FIGURE 5 so that each of the openings 22a may rotate into alignment with the corresponding fluid ducts 22 in manifold 21. Openings 22a are cut about half of the way around the circumference of the tubular valve means 20a, and are of about the same or slightly greater width than the diameter of the fluid duct 22. In operation, the tubular valve means 2% is caused to rotate at a predetermined rate in the fluid supply pipe 20 of the manifold 21. Fluid from a constant source is supplied at either or both ends of the tubular valve 29a. When an opening 22a of the tubular valve Zita rotates into an open position with respect to the corresponding fluid conduit 22, fluid passes through the said duct 22 and the conduit 19, thereby twisting the yarn passing thorugh the twister 18. Fluid is supplied during about one-half of each cycle of rotation to each twister, hence twist alternation is controlled and maintained uniform. Since the twisting or open cycle of each opening 22a partically overlaps that of an adjacent opening, fluid is consumed at a constant rate during operation. Otherwise, if all twisters operate simultaneously, there exists the possibility of insufficient supply of fluid to those twisters located farthest from the source of supply. However, where an adequate supply of fluid is assured, all twisters may be operated simultaneously with equal eflicacy. 'It is obvious that the individual twisters may be operated in or out-of phase with respect to adjacent twisters and that they'may even twist in opposite directions. 7 Many varieties of manii'olding may also be employed. For large-scale twisting operations, involving a large number of individual twisting elements, it is often preferred to employ several blocks of twisters, rather than a single block carrying all of the twisters. In any such apparatus, twist level and uniformity across the warp sheet is dependent on and requires an adequate and reasonably constant supply of fluid. Fluid supply should be suitably synchronized with the beamer so that twisting ceases when the beaming is stopped for any reason.

Twisting in accordance with this invention, whether it be intermittent unidirectional or alternately in opposite directions, leads to yarn having segments of twist in one direction, each positioned between two segments 'containing the opposite twist. All segments will usually contain about the same length of yarn, and about the same amount of absolute twist. The net twist in the yarn is essentially zero, that is, the total -8 twist'is equal to the total Z twist. The resulting yarn is called an alternating twist yarn.

The parameters used to define such an alternating twist yarn are the twist period, maximum twist, and average twist. Twist period or cycle length is the distance along the threadline that contains complete sections of both S and Z twist. A length of yarn containing twist in but one direction (8 or Z) is described as the increment length of twist. The average twist level is defined as the absolute numerical average of twist per unit length, taken over a representative sample length of yarn (several twist periods), regardless of twist direction. Maximum twist is the largest amount of twist (in turns per inch) encountered in an S or Z twist section. The three parameters are interrelated by the generality that maximum twist approaches the average twist value as period increases, i.e., the curve of FIGURE 12 tends to flatten at longer periods. In FIGURE 12, the twist period is the length of segment 0d; increment level of twist is the length of segments ob and bd; maximum twist is indicated at a or c, and average twist is given by dotted line oL'.

Yarn may also be twisted in accordance with this invention by utilizing mechanical means. In FIGURES 6-7 are shown mechanical twister 23 mounted in reversibly driven rotating sleeve 25, and having machined therein helical yarn guide 24 adapted to receive a yarn end and characterized by having yarn entry and exit sections located coaxially with respect to twister 23 but axially displaced therebetween. In operation, yarn passing through the rotating twisters enters the helical guide, is

versing the direction of rotation of sleeve 25. This may be accomplished by positioning the twister assembly betweentwo belts being driven in opposite directions, and by suitably shifting the twister assembly so that it is alternately being driven by the one belt and then the other. Surprisingly, such practice permits rapid twist reversal and minimum reversal dwell even at operating speeds up to about 20,000-r.p.m.

An alternate mechanical twister suitable for use in the present invention is seen in FIGURES 8-9, wherein are shown views of a twister consisting of fixed member 26 and shifting member 27, both mounted coaxially within driven cylindrical sleeve 28. Members 26 and .27 each contain a portion of yarn passageway 29 which may contain suitable bushings to resist abrasion by the running yarn and at the same time protectthe yarn from damage. Each of members 26 and 27 contained rounded rectangu- .lar slots 31a and 315, respectively, which cooperate in serving as a guide for pin 32. The apparatus is shown with pin32 in the disengaged position with respect to yarn 1. Pin 32 can be shifted into the yarn line by urging'shifting member 27 into fixed member 26 (moving 27 to the right). Such shifting causes pin 32 to move from position- A to position B in FIGURE 9. In operation, the entire twister assembly rotates unidirectionafly by, e.g., a belt drive frictionallycontacting sleeve 28. The shifting member 27 is periodically shifted into fixed member 26, causing yarn being alternately twisted (pin 32 engaging =yarn line) and being allowed to pass the twister without twisting (pin 32.in the disengaged position), i.e., permitting. the

upstreamaccumulation of twist to pass downstream and onto the beam. Shifting'member 27 is conveniently level is the most important of the three in this invention. in that its value determines the back-windability of. the

beam. An average twist level of at least about 0.4 turn per inch has been found critical in the practice of'this invention. Below that value, twist periodicity becomes difiicult to control, andjfilarnent ringers appear on the beam during back winding. Where it is desirable that twist be completely removed during backwinding less than about 0.8 turn per inch average twist has been found to be desirable since otherwise twist removal may be incomplete, leading to twist variation in the consumer-twisted product. Such variable twist may affect the fatigue and load-bearing properties of the yarn, especially in the case of supply beams of yarn to be used in' industrial applications (e.g., tire cord). The optimum and hence preferred average twist level is about 0.6 turn per inch, which permits most efficient. backwinding with substantially complete twist removal. Where twist is to be retained during backwinding, as in a loom beam, average twist level may range upwards to 30 turns per inch or more, as desired. Such high levels of twist are quite practical using any one of several species of pneumatic twisters, which are capable of twisting at rates in excess of one million revolutions per minute. capable of imparting more than 66 turns of twist per inch at yarn speeds of 500 yards per minute, at normal oper-- ating efiiciency.

The value of the twist period? also governs to an appreciable extent the operability of the beam during backwinding as well as the extent of retentionor removal of. Accordingly, the twist period should be such that twist. twist is accumulated in the yarn being wound during beaming, but so that it either may be removedtor retained during backwinding.

In operations wherein complete removal of twist during backwinding is desired, a twist period of from about 4 evident that twist cancellation or removal occurs when spring-loaded and thereby; maybe directly shifted by use of a cam of suitable profile. The pin'32 should be com-' posed of a material capable of resisting" the wear induced by repeated shifting and contact with the running yarn,

but, of course, such compositions should not abrade the yarn. Several such twister assemblies may be located within a single driven belt, and preferably are positioned in a staggered relationshipwith respect to one another to. provide ,warp twisting. at the usual yarn-to-yarn spacing. Such considerations also apply to the helical guide to the absence of moving or rotating parts and minimum yarn contact-(no yarndegradation) is practically insta11-- taneous in its action, and is very economicfl to operate. Moreover, such twisters are readily adaptable tooperate on extremely close centers, as required in warp twisting. and when the "twister conforms to the operable and/or preferreddimensions as indicated hereinabove, uniform and reproducible twisting is obtained. 7

The parameters most usefulin describing the alternating twist in the individual yarn ends in the warp, as wound on the beam, are the twist period, the average level of twist{ and the maximum level of twist. Average twist ever sections of yarn having segments of twist in opposite directions are freely suspended. In operations wherein retention of twist is desired, longer periods may be employed to advantage. Accordingly, at a given rate of twisting, an increase in the twist period causes the twist distribution curve of FIGURE 12 to flatten, which results in a proportionate increase in the length of the reversal sections, i.e., segments on the said curve having effectively zero twist. If such regions are permitted to become overly extended, the above-mentioned difliculties common to zero-twist yarn'may be encountered. In view of these potential difiiculties, it is desirable to'avoid extremes in period length, or, alternatively, increase theaverage level of twist. Another equally suitable procedure which. avoids the problem of extended reversal points is outof phase. twisting, such as results from utilizing the fluid supply regulator of FIGURE 5a, which assures that the yarn windings will not have their respective reversal points wound adjacent to one another.

When utilizing a mechanical twister in the process of thisinvention, the average twistlevel imparted to the running yarn line is a straightforward function of the rate of twister rotation since such devices are. relatively insensitive to yarntension, and incur substantially no slippage given yarn, the average level of alternating twist imparted to the yarn line depends on three factors: yarn speed, yarn For example, the twister of FIGURE 2 is When utilizing any given pneumat1c twister (fixed dimensions), and'when twisting any tension, and rate of twisting, which, for the sake of the present discussion may be expressed in terms of fluid supply, e.g., air pressure. When twisting at constant cycle timing and air supply, the yarn speed, of course, determines the length of the segment of yarn over which twist is applied during any given twist cycle, and hence determines the average twist level. The yarn tension also governs the average twist level, since the yarn must be axially displaced before twisting is initiated. By increasing the tension on the yarn line, such displacement is resisted. Finally, the air pressure applied to the twister determines the rate of twisting and, therefore, the average level of alternating twist in any given segment of yarn during the twist cycle.

Tension and air pressure are interdependent variables, i.e., an increase in one decreases the effect of the other, and conversely. At constant tension, the relationship between average twist level, expressed in terms of turns per unit length, with respect to air pressure applied to the twister is substantially linear, hence to increase the average twist level, all other factors being the same, an increase in air pressure is sufiicient.

For either mechanical or pneumatic twisting, the twist period depends mainly upon the duration of twisting. By duration of twisting is meant the twisting relationship which exists during any one twisting cycle, and which is related to the yarn speed and the time of twisting during the twisting cycle, i.e., the time interval during which the twister is twisting in a given direction. Thus, the duration of twisting determines the length of the yarn segment over which twist of a given direction is accumulated, and hence also determines the twist period except during conditions of equilibrium twisting. During equilibrium twisting, of course, zero-twist yarn is packaged. To avoid packaging g zero-twist yarn, the cycle during which the twister operates (in intermittent unidirectional twisting) should be adjusted to less than that required to establish an equilibrium twisting condition. Although there exists no theoretical upper limit for the twist period, there is a practical upper limit, which is determined by the distance between the twister and the first upstream snubbing guide. A snubbing guide tends to inhibit the further upstream accumulation of twist. Therefore, twist is confined to the yarn segment between such a snubbing guide and the twister, and since only a certain amount of twist may be accumulated before the upstream twist counter torque becomes equal to the applied twister torque (at initiation of equilibrium twisting), the upper limit of the period is limited.

The nature of the process of this invention makes certain demands upon the associated beaming equipment. As mentioned, an alternating twist is trapped or conlined by a snubbing-type guide, e.g., pinch rolls, nip rolls, and the like. Twist ordinarily cannot pass either upstream or downstream from such a guide, certainly not in a continuous manner as required for the present purposes. That twist which does pass such a snubbing guide does so in an uncontrolled and intermittent fashion, and at rather high levels which are subsequently distributed over long lengths of zero-twist yarn, and are thereby rendered ineffectual. Accordingly, such guides as the yarn may encounter in the vicinity of the twister, and particularly downstream therefrom should be of the non-snubbing variety, such as eyelet guides, comb guides, and freely rotating idler rolls. The roll 19 in FIGURE 1 is of such freely rotating operation. Upstream from the twister, the location of the first snubbing guide determines the maximum twist period. Referring to FIGURE 1, the vibration control and delivery rolls 3 serve in that capacity. V

The alternate twist yarn of this invention may be backwound in such a manner as to remove or retain twist, as required by the consumer. In the case of supply beams, e.g., to be used in the preparation or" tire cord, substantially complete twist removal is usually desirable. In

the case of a loom or warp beam, the presence of a certain amount of residual twist may be highly desirable, or in some cases required. Accordingly, the wound-yarn parameters of average twist level and twist period should be adjusted, keeping in mind the possible end uses.

Twist is removed during backwinding by either of two methods. Twist is removed if the free suspended length of yarn during backwinding or any subsequent textile operation is allowed to achieve or exceed the twist period. By free suspended length is meant the length of running yarn tensioned between two suubbing-type guides, e.g., between the package and a snubbiug guide. If shorter portions of the yarn are freely suspended, twist removal is incomplete, e.g., about half of the alternating twist is removed when an increment length of yarn is freely suspended. The relationship between twist removal and suspended length is, for all practical purposes, a linear one. In addition, since twist is contained by snubbing guides, as indicated earlier, when such a guide is encountered during backwinding, twist will tend to accumulate and be concentrated upstream from such a guide. Twist of the opposite direction will also be trapped, hence twist cancellation then occurs. Accordingly, by suitable positioning of snubbing guides with respect to the beam during backwinding, twist removal may be accomplished. It is evident that in either method of twist removal, some twist may be retained. Yet for every section of twist that is not removed, there will subsequently occur passage of the twist of the opposite direction, leading to eventual complete twist cancellation. in either method of removing twist, the completeness and efiiciency of such twist removal is enhanced by utilizing increased yarn tensions during backwinding.

if it is desirable that twist be retained during backwinding, it is obvious that both of the above-mentioned conditions are to be avoided. Therefore, to retain twist during backwinding or any subsequent textile operation, the free suspended length of yarn should be kept as low as possible, and the use of snubbing guides or the like means avoided. The retention of twist may be further assurred by utilizing a higher average twist level initially, or by increasing the period, or both. Twist may also be set" by twisting the yarn in the plastic state (via heat or residual solvent), followed by cooling or by slashing the as-twisted yarn. The most desirable method to insure residual twist retention is to increase the average twist level. This is accomplished in pneumatic twisting by increasing the air flow. Increasing the average twist level is preferred over increasing the period, since by the latter method the reversal length between segments containing twist in opposite directions increases. Such exaggerated sections of yarn having little or no twist are subject to the same difficulties during backwinding as is zero-twist yarn. It is preferred, therefore, that the over-all twist period be about from 4 to 16 feet in order to minimize segments having zero twist in the separate yarns in the warp.

One of the most important process variables effecting the practice of the present invention is yarn tension. Suiiicient tension is required during winding to maintain the stability and spacing of the separate yarn ends in the warp Sheet, and to insure acceptable package formation on the beam. However, excessive tension inhibits the effect of action of the pneumatic twister, and insufficient tension permits rolling together of adjacent yarn lines, due at least in part to the upstream and downstream flutter induced by the exhaust gases from the twister. Moreover, it is required that the tension be uniform across the warp, which is partly controlled by the diametrical uniformity of the vibration control and delivery rolls indicated at 3 and of the idler roll 10 in FIGURE 1. The yarn line tension should be suflicient to insure that the yarn is reasonably centered in the pneumatic twister during winding and twisting. Accordingly, it is preferred that yarn tensions from about 30 grams to about 60 Tenn.) eyelets.

' may be necessary in the case of beaming at very close yarn-to-yarn spacing in the warp. The present considerations apply to warp spacings of about one-fourth to onehalf of an inch. Tension values are reported at the beam unless otherwise indicated. The yarn suppliedfrom the creel is usually at about 30 'to 45 grams tension. The vibration control-delivery roll system (indicated at 3,

FIGURE 1) adds about 5 grams tension, hence the upstream yarn tension is about 35 to 50 grams, which results in yarn being'supplied from the twister to the beam at about 45-60 grams tension. It is preferred that the minimum values of tension within these ranges be em ployed wherever possible, consistent with warp and yarnline stability.

' In the preparation of warp or loom beams, it is usually preferred that such beams be prepared via section beams, as is well known in the art ofpackaging and winding. Thus, several section beams containing 500 or more yarn ends can be used to prepare warp beams containing several thousand individual yarn ends. Of course, when using the apparatus of this invention to prepare beams at very close yarn-to-yarn spacings in the warp, i.e., at high end densities, blocks of twisters may be disposed in a horizontal and vertical staggered array, permitting twist ing of a 'very large number'of ends without requiring an unduly large or bulky apparatus. Bythis procedure, a warp containing or more ends per inch is easily beamed according to the instant invention. 7

The process of this invention is illustrated by the following examples.

EXAMPLE 1 The process of this invention is carried out utilizing the apparatus of FIGURE 1 '(Cocker Beamer Model SD-49,-supplied by Cooker Machine and Foundry Co.,

Such measurements are averaged without regard to direction of twist. These measurements are precise to about 0.05 turn per inch (t.p.i.). The period length is determined by actual measurement of the distance between points of twist reversal in the yarn immediately as removed from' the beam. The results of these determinations are summarized in Table I.

The results of these tests show the linear relationship between air pressure (fluid supply) and. average twist level, and the critical dependence of operability on the average twist level. About 0.4 t.p.i. of average alternatnig twist is necessary to prepare'a backwindable beam. Referring to the curve of FIGURE 12, the yarn from Test AD has a period length of 6 feet (0d), maximum 8 twist (twister on) of about 0.9 t.p.i. (a), maximum 2 "twist (twister ofi) of about 0.82 t.p.i. .(c), and su Gastonia, NC.) equipped with the pneumatic twister of FIGURES 2-3arranged in 16 blocks, 11 twisters per block, according to FIGURE 5. The dimensions ofthe individual twisters are as follows:

Length Diameter,

inches Exhaust section 16 0.24 inch each.-. Beveled section 17 60 bevel Twister section 18 Fuid (air) conduit 19 Tot 0.875 inch 'The upstream guide 6 and the downstream guide ,7 are both located about 6 inches from the twister block, and contain Al Si Mag (American Lava Corp, Chattanooga, The twister operates on an on-ofi cycle, i.e., by the intermittent application of unidirectional twist. Each complete cycle is of the same duration, about 4.1 cycles/second, hence twisting is efiected for periods of 0.12 second duration. Since the yarn speed is 500 y.p.m., such a twisting cycle determines a period length of about 6 feet. The twisted yarn :ends in 'the warp sheet are traversed onto the beam at grams tension, the traverse stroke being about 4521116111. After V winding, the beam is backwound. During backwinding, the average level of twist is determined, the periodicity checked, and the behavior (operability) during backwinding is noted. The average level of twist is determined by measuring the twist contained a in 24 successive 6-inch lengths of yarn immediately as removed from the beam.

stantially no dwell at the reversal point b. Air is supplied to the twister from o to b, and is cut off from b to d, i.e., the twisting cycle is adjusted to change precisely at the point of initiation of equilibrium twisting, thereby avoiding that condition. When the twisting cycle time is increased, there results sections of yarn having zero twist between the segments of yarn containing twist, i.e., there results exaggerated twist reversal points. When the twisting cycle time is reduced, the curve of FIGURE 12 assumes a saw toot contour.

EXAMFLE 2 The mechanical twister of FIGURES 76-7 is utilized with the apparatus of FIGURE 1 to beam 176 ends of 840 denier, filament poly(hexamethylene adipamide) yarn, supplied from a creel at 35-40 grams tension. The twisters are positioned between two belts driven in opposite directions. During contact with either belt, the twister rotates at l8,000 revolutions per minute (r.p.m.). The twister contacts either belt for 0.25 second, then is immediately shifted to the other belt for the same contact time. Theyarn isbeamed at 500 y.p.m., hence the twist period is about 12 feet, at an average level of twist or" 0.5 t.p.i. Such a beam is fully operable during backwinding, twist periodicity is uniform, andsubstantially no filament ringers are formed.

EXAMPLE 3 Beams prepared according to Examples 1, 2, or 3 are backwound to supply conventional downtwisting apparatus. Each yarn end is passed from the beam via guide means through drop-type tension rolls serving each twisting position, thence to the ring and associated traveler and onto a conventional twister package (pirn) mounted The beam so prepared is on a rotating spindle. The shortest beam-to-tension roll (a form of snubbing guide) distance is about feet. Twist removal is substantially complete up to about 0.6 t.p.i., above which, however, twist removal becomes progressively less complete, as evidenced by twist variation in the downtwisted product. For example, when the average residual twist in the yarn is about 0.2 t.p.i. of alternating twist, the net twist variation in the downtwisted product is at once about 0.4 t.p.i., which occurs in addition to the twist variability which normally occurs in the downtwister package (pirn). Such twist variation is highly detrimental to the performance characteristics of the yarn in demanding industrial applications, e.g., in tire cord. However, by increasing the average twist level to above about 0.8 t.p.i., some twist retention occurs. Retention of twist may be highly desirable in many applications, e.g., in textile uses. Progressively more twist retention occurs as the average twist level is further increased.

The process of this invention has been illustrated by intermittent unidirectional twisting (Examples 1 and 3) and intermittent two-directional twisting (Example 2). Though less desirable, it is also possible to apply an alternating twist to a running yarn line with the application of unidirectional twisting by periodically varying the yarn tension, speed, the twister speed, or the upstream guide distance. Moreover, such twisting may be accomplished by utilizing upstream setting means, i.e., by employing plasticizing agents (e.g., heat or solvent) upstream from the twister so that the yarn is twisted while in the plastic or semi-plastic state. Upon passing such setting means, the yarn becomes set in the twisted configuration. Twistsetting also occurs on the beam when a dry-spun yarn (e.g., cellulose acetate) containing residual solvent is packaged, since such a yarn is twisted while in the semi-plastic state. Eventual evaporation of the residual solvent leads to twist setting. Twist which has been set may be relieved by increasing the yarn tension during backwinding. Twist may be releasably held by slashing.

Many species of mechanical or pneumatic twisters may be employed in carrying out the process of this invention. For example, in FIGURES l0 and 11 are shown variations of the pneumatic twister of FIGURE 2 which are useful in the warp twisting applications. In FIGURE is shown the twister 8 having twisting section 18 and fluid conduit 19 as in FIGURE 2. A yarn string-up slot 33 is out throughout the length of the twister 8. In operation, air entering through conduit 19 serves to screen the string-up slot, so that the twister operates at full efliciency. This twister is ideally suited for spin-beaming where rapid string-up and continuous operation are prerequisites. In FIGURE 11 is shown the twister 8 having twisting section 18, fluid conduit 19, and the additional fluid conduit 34. In operation, air enters the twister 8 alternately through fluid conduit 19 and fluid conduit 34. Operation is similar to that of the mechanical twister in Example 2, i.e., resembles intermittent unidirectional twisting through one-half of the twisting cycle; during completion of the cycle, fluid enters the twister through the opposite fluid conduit, thereby positively applying twist of the opposite direction onto the yarn being packaged. The twister of FIGURE 11 has an additional advantage, namely, that twisting in any given direction may be carried out for longer times before the initiation of an equilibrium twisting condition. Fluid supply may be provided to the twister of FIGURE 11 by use of rotary valve means, or by suitable modification of the apparatus of FIGURES 55a.

The process of this invention is applicable to any continuous multifilament yarn, such as poly(hexarnethylene adipamide), poly(e-caprolactam), or other polyamides, polyesters, such as poly(ethylene terephthalate), poly- (acrylonitrile), or its copolymers, and other polyacrylates, regenerated cellulose (rayon) or protein, cellulose acetate, poly(vinyl chloride or acetate), poly(vinylidene cyanide or chloride), any suitable copolymers of the foregoing materials, glass and many other fiber-forming compositions. Yarn prepared from such compositions may contain 2 or more filaments per yarn bundle, and the total denier of such a yarn bundle may range upwards to several thousand or more grams. When warp twisting extremely large or small yarn bundles, twister dimensions may be adjusted for optimum twisting. Such yarns may contain any of the usual textile additives, e.g., titanium dioxide as a delustrant or copper chloride/ potassium iodide as an anti-oxidant, and may be finished in accordance with accepted practice.

The process of this invention is applicable to any packaging operation, but it is most useful in those cases where two or more yarn ends are simultaneously wound onto a common package core. Difiiculties in backwinding zerotwist yarn become most pronounced whenever such yarn is wound at reduced hel x angles; hence in lieu of either true twisting or slashing, the practice of this invention becomes an essential prerequisite to good backwindability whenever several yarn ends are wound at such reduced helix angles. Of course, the mternate twist in the packaged yarn may be regular or irregular with respect to twist period and average level, so long as the average level does not fall below about 0.4 t.p.i., and may contain reasonable lengths of zero-twist yarn at the reversal points. It is noted that the yarn cross section becomes circular as the twist level increases, and individual filaments in the yarn bundle tend to spread into a band or ribbon at segments of zero twist. Accordingly, at close yarn-to-yarn spacings in the warp, the length of such zerotwist yarn segments, relative to the length of the twisted segments, should be minimized.

The practice of the present invention is of obvious advantage in the various handling operations of continuous multifilament zero-twist yarn, particularly for the replacement of the discontinuous operation of true twisting yari s prior to beaming. The beam prepared by this invention is backwindable with or without twist removal, and the formation of filament ringers is avoided. In accordance with a preferred embodiment utilizing pneumatic twisting, beaming may be carried out rapidly (200-600 y.p.m. or more) and continuously with a minimum of added investment or operating costs. Yarn quality is undirninished. Further advantages inherent in the practice of this invention will readily occur to those undertaking its practice. Pneumatic false twisting apparatus and methods which may be used are disclosed in application Serial No. 598,135, filed July 16, 1956, by Breen and Sussrnan, now US. Patent No. 3,009,309.

The claimed invention:

1. A Warp beam wound with a warp sheet of a large number of essentially parallel continuous multifilarnent yarn ends under tension, having a yarn-to-yarn spacing of less than about one-half inch between the individual yarn ends in the warp winding, each of said individual yarns consisting of a single bundle of filaments having maintained therein solely by being trapped on the beam from about 0.4 to about 0.8 average turn per inch of releasable alternating twist at a period length of from about 4 to about 16 feet as the essential means for maintaining sufficient unity of the filament bundle to provide a beam which backwinds without entangling of filaments and without the formation of filament ringers, the beam being backwindable into a warp with substantially complete removal of the alternating twist by merely providing a free suspended length greater than said period length.

2. A backwindable beam as defined in claim 1 wherein the separate yarn ends have substantially zero net twist therein.

3. A beam as defined in claim 2 which backwinds to supply a warp of continuous multifilament yarn wherein the separate yarn ends have substantially zero twist.

4. A backwindable beam as defined in claim 1 wherein the alternating twist in the individual yarns is out of phase with that of adjacent yarns so that twist reversal points are separated by twisted portions of intermediate yarns 2,702,982 Guyot Mar. 1, 1955 across the warp winding. 2,741,893 Vandamme et a1; Apr. 17, 1956 5. A baekwinda'ole beam as defined'in claim 1 wherein 2,751,747 Burleson June 26, 1956 thereis less thw one-half inch of traverse in the wound 2,778,187- Leath et all Ian. 22, 1957 yam, 5 2,813,393 Kingsburg et a1. Nov. 19, 1957 6. A backwindable beam as defined in claim, 1 wherein 2,846,839, Billion Aug. 12, 1958' the yarn is tire yarn having aboutt0.6 turn per inch of 2,846,840 Billion AugQ12, I958 releasable alternating twist at a period length of about 2,863,280 Ubbelohde Dec. 9, 1958 6 feet to provide an efiective supply beamfor multi-end 2,909,028 Comer et a1. Oct.'2(), 1959 2 true twisting into uniformlytwisted tire cord. I 10 2,952,116 Burleson Sept. 13, 1960 References Cited in the file of this patent FOREIFHTI PATENTS UNITED STATES PATENTS 355,447 Great Brrtam Aug. 27, 1931' 2,370,899 Wildbore Mar. 6, 1945 i

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