[1]United States Patent Office 32022@566 3,022,566 FALSE IIVISTED YAP-,N BEAM Charles Edward Daniels, Wilmington, and Nathaniel Convers Wyeth, Hockessin, Del., assignors to E. 1. du Pont de Nemours and Company, Wilmington, Del. a corporation of Deaware Filed Feb. 11, 1958, Ser. No 714,549 6 CUms. " i8) (Cl. 28- 'T@his invention relates to yarn winding and packa,- irg, and has particular reference to beaming continuous multifilament zerotwist yam. More specifir-ally, this inv,-nt;on relates to a novel and usefiil process for contl:nliously twistin- such yarn during beanin.- I and to the novel beain packaae p-oduced thereby. Ylm, thread, fibers, and th-- like filamentary struct,,ires are conveniently packaged and transported on beams. Si-7-,h beams are prepared by s,.'multancously ivinding v,-.th slighttraversing a plurality of yam ends maiptained in a s-oaced. parallel, coplanar relat;onship, i.e., as a warp sheet onto a '@cam. a sin,-le large core or a yai-n package support provided with suitable end flanges. Beai@ns ordinarily may contai-,i on the order of one hiindred or more yam ends, and upwards to many hundreds ol, pounds of yard. A beam may be used by the consliner -a-. received to provide the @varp for weailing (loom beam) ox as a sin.-le s,jp,oly package for large,-scale twisting, plying, and the like te,- ,Lile operations (si,@i3ply bear-q) In either case the us.- of the beam enables the handiiii.a and transporting of large quantiti,-s of yarn with but a minimum of sin.-leend operations. Yarn is woind o-,ito a beani at e.,sentially 2ero helix angle since the trav,-rse stroke during beanin.- normally is no greater than the yarn-to@yarn spacir-g in @,he warp being beamed. To insure that individual filaments in the yarn bundles do not become trapped, @entangled, or broken due to overlap wil,h the filaments of adjacent or subsea-aently wound yam, i.e., to insure that th.- yam enn be unwound (ba--@,wound) from the beam, it Is necessary to appiy'a cei-ta;.l amount of twist to the individual yam ends prior to beaming. This "producer 'Lwist" is reciuired in order to mairtain. the unity of the yarn bundle, and is appli@-d at relativeiy low levels (noni:lnally about 0.5 turn per inch) as com.Dared to '@consumer twist," which may rangd upwards to several turns per inch. Yarn cc@ntainin.- such "Produc-@r twist" does not form the so-called filam-Int "rin.-ers" (filament wraps on the beam) because any potential trapped or tanaled filaments are broken and pulled along by the parent yarn during backwi.-.ding. However, without such twist, breaks wh;ch occur durinback,@,,ir.din.- lead to the formation of "ringers," which, in turn, cai-ise considerable yarn waste and may lead to the eventual interraption ol' the backwinding operat;on. Therefore, it is required in every beaming operation that the individual yarn ends be t,,visted (>r r@--ceiv-- an etaivalent treatm@-nt prior to beaming, not to facilitate preparatig@i of the beam, which is no problem, but to permit the yarn to be backwound theref@-om, which indeed is a real pro'olem. Although twisting insures the L'ormation of a bac'Kviin'able beam, such l,wistin.- has involved much additional yarn handlin,-, and ;s costly in terrns of tiine and equipment required. Moreover, the mechanics of twistip,_a and the additional handling often result in lower yarn qdality. Finally, since the consumer's tvi-st demands vary widely dependi-@ig iipon the end use of the yarn, and since the presence of the costly initial "producer twist" in the yarn may render such subsequent tnvisting nonuniforin. thereby affectin.- the fati.-L,.e and load-carryin.- ability of the yarn, there has been a need for means to beam yarn without prior twisting (i.e., means which would permit beami-.ig zero-@.wist or as-spun yarn directly into a backwindPatented Feb. 27, 1962 2 ,ble package). By "zero-t,,vist" yam is meant yain havin.- no substantial process twist, excluding the omnipresent sli-ht twist in the yam resulti-@ig from normal handling @e.g., twist res-alling when removing yarn Lrom a stationary package) which for all practical -ourpgses is negli 'ble. Despite the need, however no sa.'isfactory 91 method for preparing backwitidable beams of zero-twist yarn is known to the ar-t. That the problem of beaniing zero-tviist yarn has been 10 reco,-nized is shown by Bradshaw (U.S. 2,224,665), who discloses that slashing (sizing) such yarn pr;or to beamirig results in a backwindable beam. The slashing, in this case, serves in a manner sim;lar to twisting, by binding the separate filaments of the yarn into a coherenl bundle. 15 Hoviever, th.- slashing operation may entail as mtich additiunal handlin.- and equipment as does tivisting, is t imeconsdillin-. and requires that the sized yarn be rigorously dried prior to beariing, since otherwise the yar@i bundles stick to-ether. Further, the size on the yarn often must 20 be ren-ioved at some subsequent stage of handl;ng by the consumer. Karns (U.S. 2,324,5'4), seekir@g to avoid the 0 need for either twisting or slashing, proposed to traverse a sin.- le thread along the length of the beam so as to separate the successive windings on the beam. Diiring 25 backivinding, the traverse thread serves to break out trapped and tangled filaments, thereby avoiding the formation (>f ringers. Howeier. Karns' method does not te trapp d and tangled filaments durin@ packag-. elimina e ;11.- and subs-,quent handling, -vvhich is the crux of the 30 pi-oblem of beaming zero-twist yarn. Moreover, . the "breaking-out" process often leads to yarn of unaccel)table quality containing an excessive number of broken fil.aments. ReceTitly, the problem of. beamin-g zero-twist yarn has 35 aris-.n anew. Technolo.-ical advances in the textile art have led to improved and higher speed production of yarn, requiring rapid, continuous yarn packaging opera-: tion . For example, i-nary benefits derive from spinnin.aiid drawing nylon yarii in a coupled operation, pror to 40 initial packaging. It would be highly desirable to beam directly from such a spinning package, wit,hout having to divert the yam to a twistin.- o.- slashing operation. Recent advances in apparatus design have made st)in beaming (i.e., packaging yarn on a beam immediate as it is 45 formed) a feasible operation save for the nee for twisti-@i-g. It is appardnt that many improvements in the coptinuous production c@,' yai-n would der:ive from a suitable, process for beaming zero-twist yarn, and would enable b-.amin,@ much of the current zero-twist yam productioq presently being sold on single-end pa.-kages. One object of this in7,,ention is to provide a backwindable beam wound from a warp of coiitin-aous mult@.filament yam, the separate yai-n ends having sifostantially zero net twist .herein. 55 A further object is a process for beamin.- contituous rquItifilament yarn having substa-@itially zero net twist therein, the beam so producedbeing bacl,,Yvin(iable with-, out incurring tangled or trapped filaments, and without the formation of filament ringers. 60 A still further object is a backwinda-ble beam of a warp of continuous multifilament yam, the separate yarn ends havin.- a periodic, reversing, i.e., @alternatirg (false) twist pre'lerablv throughout the entire length. Yet another o'Z)ject is a process for backwinding from 65 a beam to siipply a warp of continuous multifilmm--nt yarn, 'Lhe separate yarri ends ha@,,in.- substantially zero nettwist therein. Th,-se :and other objects, to,.aether with means for accomniishing these ob-jects, ,vill appear here.nafter. 70 i-he objects of this inveiition are accoriiplished in general by continuously subjecting individual ends of a warp of continuous multifilarr@ent zero-tvist yarn to the
[2]action of a fals.- twister, impart-ing therelo a periodically rev,-rsin.- (i.e., alternating twist) of average twist level of at least about 0.4 turn per inch, and imniediately th.reafter winding stich a Nvarp onto a b,-am. in the usual ma-@iner and at usual beamin.a sp.-eds. In a preferred embodiment, individualzero-twist.- yarns of a v@,arp are subjected to intermittent pneumatic un.idirectionalt@vis'Lin- Nvith air so as to produce a warp with@individual ends having from about 0.4 to aboiit 0.8 average tum per inch of @alternating twist at a period length of from ibout 4 to about 16 feet while wind:,.-.g at a yarn tensio-@i of from about 30 to about 60 grams. There resul'Ls a novel and us.-ful loom or supply beam containin.@ a viarp of yarn, the individual ends of which have su-bstantially zero net tw;st, which may be backwound wit'@l either removal or retention of the alternating twist applied thereto by tne process of the present invention. Such a beam may b-@ backwound without incurring tangled or trapped yarn filaments, and Avithout the formation of objectionable filament ringers. The inven'lion will be more cl-l-rly understood by reference to tho attached drawings. FIGURE 1 shows a schematic view of an apparatus useful in the practice of t@ie present irvention. FIGURE 2 @hows in schematic sec'cion an apparatus useflil for twisting yarn pneumatically. FIGURE 3 shows an end view of the apparatus of FIGURE 2. FIGURE 4 shows an enlp-rged schematic partial section of the apparatus of I FIGUR@ 2 taken along th-. sertion line a-a',. FIGURE. 5 shows a sectional view, of several preumatic twister s tooether with fluid supply means uitably ar-, rqnged for use in beaming. FIGURE 5a shows a fluid supply regulatbr u@eful witli the apparatus o" FIGU@RE 5 FIGURE 6 shows a side, elevation of one apparati-is useful for twi@ting yarn mechanically. FIGURE 7 shows a left-end view o'L the: apparatus of FIGURE 61. FIGURE 8 is a sectional view of another apparatus useful for twisting @am. mechanically. FIGURE 9 shows a left-end,vieiv (rotated 9G' counterclo6kwise) of the ap paratus of FIGU 8. -FIGURES 10 and Il- show in enlarged schematic c -s suitable, for use n present invention. FIGURE 12 shows graphically the len-thwise variation in, tnvist along the length of a segment of yarn preRpred in accordance with this invenlion. R--ferring to FIBURF, 1, there is shown@ scheiiiaticallv a- conventional beaming ap paratus modified to include fa.Ise twisting means for carryin- o@,it the process of the instant. invention. In operation,. a plurality of yarn. ends indical,ed at I (from a source not, show-ii) is led over the, guide 2, @.,,,bich -nav be a pin@ board, an eyelet board, or other suitable guiding means. At. this po:.nt, the@ inoiviotial@@yarn ends@are comb,@'"-ed at form a warp sh.-6t.T'he warp sh-eet is pa--,sed. about vibration control and delivery rolls at 3 and@ then through g eparator guide 5 (a pin board comb, grooved rolls,. or the like) eyelet - I guide 6, th,-n twisting means, 8 where each yarn is false twisted. Downstream from, the t,@vister 8 the- yarns p ass through an eyelet guide 7. Eyelet guides 6 and 7- are mounted on eyelet boards located api)roximately the sa nie distance upstream and downstream-, respectively, from the twister 8, and serve to center the yarn in the twister and to control lateral fluctuations of the individual y,,,rns in the warp sheet. The tnvisted yarns then encounter traverse comb 9 and are thereby tra-vers--d over idler roll 10 and onto beam 11, th e lav of the warp bein.- controlled by the presser roll 15. Beam 11 is of, conventional design, having a barrel portion 12 and a flange 13 mounted at either extremity to co@trol and cont'aiii the yarn buildup, iiadicated- at 14. Excluding the twistse tion 6thei pneumatic twister i the ing and associated guidin.- nieans, the- apparatus of FIG-URE I is conventional and individual components may be @-Itered, added, or even removed, in accordance with accepted beaming practice. 'Me yarn supply means (not shown) may be packages m@o-Linted in a conventional creel, or may consist of a number of spinning r4iachines, whereby as-spun yarn is forwarded directly to the beam without i-@itervening discontinlious process steps@ Utilizing the apparatus of FIGURE 1, the yarn I pass10 ing from the supply means to beam 11 is false twisted, that is, twisted in opposite airections upstream and downstream from the twister. : Downstream twist is trapped on the beam,-wh-lie upstream twist of equal amount but opposite direction is accumulated@ If such tv,7i-sting con15 tinues, the point is rapidly reached @vhere the upstream t,@;:Ist is accumulated to an extent sufficient to counteract the twistin.- torque of the twister, resulting in either the winding of zero-twist yarn onto the beam or corrplete breakdown of the yarn I;ne. Such a cor@dition will be 20 termed hereinafter "equilibriurr@ twistin-.." In order that the upstream t-wist may reach the b,,am, the torque of the twister must be relieved or other@viq-e overcom.-. Tbree important methods are available for perw-ittin-. the periodic alternation of twist in the yarn being pack25 aged ar.,d which avoid the coidition of equilibrium twistin,-. The simplest method of app'lying per,.odically alternatin.@ twist to a runn@n@, yarn line accordin-, to this invention comprises intermittent ai)i)lication of twisting. 30 -ihus, after the upstrea@--c. twist has, acc@amulated, to a predeiermined extent, the i%-vister torqu-. may be reduced or 61iminated to . aflow sorle or all of the accumulated upstream twist t6 pass downstream and on,,O the beam. Si,-ch an interm,.ttp-nt "twist-no-t-,,,,ist" action, ,@ilien su-it35 ably li med with respect to yarn specd perniits the win ing and packaging of yarn having good uniformity of twist period and level, w;th dwell at t,@ilist reversal t)oints (i.e., points of zero twis") be'm,- at a m;niniutn. The hitermittent application (pulsating) of unidirect:.onal twist 40 is preferred for the T)Urposes. of the present invention. Periodically alternating tnvist may ai'so be applied to a rannir@g yar@i line according to this invention by iiitermittently applying tvvisting in opposite directions Such a method is more desirable, however, because less sensi45 tive to timing of the twist cycles. These two methods arpapplicable to either mechanical or pneumatic twislin-NN'hen. employing pneumalic tviisting, periodically, alternating tnvist may be applied to a,running yarn lir@e with constant unidirectional ipplication of twisting by peri50 odicallv varying the tension in the yarn. After upstream twist j@as accumulated to the desired exte-@it, the tension on the yarn line is increased, thereby perrm ting some of the tipstream twist to. pass through the twister and downstream onto the beam. The effectiveness of t'@iis: 55 method is dependent upon the range,,of tension vatiation, its period with iespec', to the yarn, speed, and the effect of varying tensio-Ti on the twister. Each of th@, three above-mentioned methods has particular utihty for certain applicafions. @Ho-,vever, the most v.-rgatile of (30 th-,se meth6ds is intermittent unidirect@'@onal t 'sting due wi to simplicity of apparatus, applicabitity to both pneurnatic and riiecham'cal twisting ease of operation under a wide variety of conditions of Yarn speed and tension, and uniformity of the prod I uct so: prodlced; 65 FIGUR-P 12 shokvs graphically the lengthwise variation in twist along the@ length of a segment of yarn tmisted@ in accordance withthis@invention,,wherein ordinate OS indicates level of S twist and ordindte oZ indicates lei'll of th-- Z twist at anY point along the yarn length, 70 the abscissa oL. At the initiation of twisting (at o), th-- 8 twist level@ rises rapidly to a maximum a then, approaching equilibrium t,,visting, falls off towards h. Twisting is stopped or reversed at b, allowing the upstream accumulation of twist to pass downstreani and 75 onto the,beam. Such pra-ctice results in Z twist rising
[3]3,022,566 to its maximum t@vist level at c, then, a-,ain approachin.a equilibrium tivistin.-, fahing off towards d, at which point tnvistin.- in the S direc@--ion is initated, a-,id th.- process commencn.- at o is repeated. By slitable varia@Lion of processina conditiors, the ciirve of FIGLTPE 12 can be made to assume a variel,l of proportions, and of course, need not be synimetrical. FIGURES 2 and 3 show ceciion apd end vieivs respectively of a represertative pneumatic twister suitable for use in this i-@ivention. Tnis twistin,- means comprises 1( cylindrical yarn passaqeway 16-19, with enlarged exhaust sectirn 16, bev,-led section 17, aiid twistinscetion 18, the latter b-.:in,- t,,in.aentially inter-,epted by the ffuid conduit 19 in a p,tane normal to tile axis of the yarn passageway. In opp-ration, iluid rassing through 15 conduit 19 intercepts the yarn I in tnvisting section 18 and imparts thereto a crank tviistinl- action. The path of the high velocity twistina, fluid in the tiiiister is indicated by arrows in FIGURE 4. By periodically interruptina the supply of the ffuid to the twister, intermittent 20 unidirectional applicatioti of twist described in the foregoing is achieved. With reference to FIGURE 12, R-aid is suppl@ed to the tw;ster dur@.ng passa.-e of a se.-ment of yarn havin-, len-,th a--b. Fluid supply is interj-upted for a yarn len.-th b-d. Enlarged ex'aaust section 16 of the 2.5 twister 8 s2i-ves to facilitate the release of exhaust twistin@ fluid with m:@@mum interaction with the yarn. Beveled section IL7 serv,-s to .-uide the yarn into twistin.- section 18, and serves to minimize yarn damage. The length of yarn tviisting section IS should not be less than 3ij its dia.-neter, and preferably, the total le:i.-th 4o@,' the yam passa.-ew-@y will be abotit six 'imes its diameter for c@,Dtimum tv@isLin-. furth@-r, the ratio of the area of -Cr-c yarn twistin,@@section IS to 'Lhe elrea of the iiuid condu-'@t ]Lg may vary from abolit 4:'@ to about 10:1, b,,it is pref@>5 er,-ably 6: 1. Ratio of the diameter of the varn to the diam.-ter of the twistin.@ section 1.8 should be from about 1:2 to about 1:10, and is pref,-rably about 1:4. yarn twist-section 18 and the fluid co-..iduit 19 are preferably cylindrical in shap--, as showi,., buL either or both 40 may be other than circular in cross section and neither need be uniforra in area or cross-sectional form@ throL,,-hout its length. It is read@'@ly apparent that many variations of the twister from the representat@,on shown in FIGURE 2 are possible. 45 Air at rcom temperatare is a s-,iltable fiuid for twisting . yarn in accordance wi@Lh the preferred practice of th:s invention. However, other fluids or liqlids sLLbstantially inert to the yarn, sleh as carbon dioxille, nillro--en and the like may be utilized if desirable, and sucn fluid may 50 be heated or refrigerated as desired, so lon.a as such a temperature is not deleterious to the yarn bein.- tw;sted. Air is the preferred t,,visting fluid, and will be referred to herein for illust-ative purposes as representative ol all such twistin- fluids. Steam may also be employed. 55 e In FIGURE D, an arrangement is shown whereby several pneuma,ic twisters are employed ;.n a side-by-side relationship for use in bearxiing in accordance viith FIGURE 1. FIGURE 5 shows several twisters 18 mo@,inted in a sin.-le bloc'@@ 8, which is securely attached to the 60 manii'Old means 21. Manifold means 21 contai-is an enlarged fluid supply pipe 20 from wi%ich a plurality of fluid ducts 22 communicate with the fluid conduit 19 of each twister. I'l desired, either or both the fluid duct 22 and the fluid conduit 19 may be ol-i',wardly beveled at 65 th.-@r resp---ctive points of contact to f-acilitate alignmen". ,in op.-ration, fluid from an external source (not shown) is supplied at either or both ends of the fi-aid supply pi-ae 20, thence to the individlal twisters via ',he fluid duct 22 70 and the fluid conduit 19. The external fillid supply is an intermittent source in accordance with the preferr,-d means of un;directional intermittent twistin.-. Such an intermittert supply of fluid to the individual twisters may be secured from a 75 6 constant source of Ril-id by utilizing the apparati-is of FIGURE 5a, whi@-h consists of a tubular valve means 20a adapted to be rotatably mounted in the fluid supply pipe 20 of FIGURE 5 so that each of the openir.-gs 22a nt may rotate i o ali;.,Dment with the correspondin- iquid ducts 22 in manifold 21. Openin. -s 22a are cut about half of the way around the circumfer-.,ree oL' th.- tubular valve means 20a, and are of about the same or sli-htly greater width than th,- diameter ol' the fl@,iid d,,ict 22. In operation, the tubular valve means 20a is caused to rotate at a predetermined rate iii the fluid supply pipe 20 of the manifold 21. Fluid from a constant so-arce is suppeed at either or both ends of the tulular val@Ve 20a. When an openin.- 22a of the tubular valve 20a rotates into an "open" position with respect to the corresponding fluid conduit 22, j9-uid passes through the said duct 22 and the conduit 19, thereby twisting the yarn passing thorugh the twister 18. Fluid is suppl,.ed d@,iring about one-h@iif of each cycle of rotation to each tw,.ster, hence twist altematio-ti is controlled and maint?diied uni@lorm. S:@lace the taistipg or "op-,n" cycle of each openina 22o partically overlaps tnat of an adjacent openir@g, fluid is consumed at a constant rate during operation. Otherwise, if all twisters operate siniultaneously, there exists the possibility of insufficient stipply of fl@did to those twisters located farthest from the source of supply. However, where an adcouate supply of fluid is assured, all twisters may be operated simul@taneously with equal efficacy. It is obvious that the individual tv@isters may be operated in or out-of ptiase with res@i)ect to -.djacent twisters and that they may e-v.-n twist in op-cos;te dirce-' tions. Manv varie@lies of manii'O'idiig may also,be employed. For large-s@cale t@,vistin.@ operat;ons, involvin,@ a large number of individual twisting elements, it is Ofte.,i preferred to employ several blocks of twisters. rather than a sin,-le block carryin--, all of the tviisters. Ir. any slich -.pparatLis, twist level and uniformity across the warp sheet is dependent on and requir.-s an adequate and reasonably constant supply of flu'@d. Fluid supp'@y should be siiitably synchronized with the beamer so that twisting ceases Nvhen the beaming is stodped for any reason. Twisting in accordance with :Lhis invention, whether it be intermittent unidirectional or alternately in 6pposite --iirections, leads to yarn having segments of twist in one direction, each positioied between twb segments containIn' 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 ydrn is essentially zero. that is, the total @S twist is equal to the total Z twist. The r--sulting yarn is called an alternating twist yarn. The parameters used to defi-ne such an alternating twist yarn are the "twist per,.od," "maximum twist," and "avera.ae twist." "Twist period" or cycle len,@th is the distance alon.- the threadline that contains conplete sections of both S and Z t@vist. A length of yarn containing twist in but one direction (S or Z) is described as the increment lenglh of - twist. The "avera.ae twi,s'L" level is defined as the absolute numerical avera-e of twist per unit len-,th, taken over a representative sample length of yarn (several twist periods), regardless of twist direction. "Maximum tnvist" is the laraest amount of twist (in turns per inch) encountered in an 8 or z twist section. The three parameters @are interrelated by the generality that maximum ist approaches the average twist value as period intw creases, i.e., the curve of FIGLTRE 12 tends to "flatten" at -longer periods. In FIGURE 12, the tw,.'st period is the length of segment od; "increment level of twist" is the length of seaments ob and bd-I "maximum twist" is indicated at a or c, and "average twist" is given by dotted line o'L'. Yarn may also be twisted in accordance with this invention by utilizing mechanical means. In FIGLTRES 6-7 are shown mechanical twister 23 mounted in reversibly driven rotating sleeve 25, and having machined there-
[4]in helical yarn guide 24 adapted to rec@-ive a yarn:end and characte.rized by having yarn entry and exit sections located coaxially with respect to twister 23 but axially displn@eed therebet@xeen. In operal-on, yarn passing thrbugh the rotating twisters enters the helical guide, is 5 axiahy displaced while traversing the guide and exits the helical guide on its original axis, and is thereby subjected to a crank twisting action analogous to that imparted by the pneur@iatic t,,&,ister of FIGURE 6@ Twister 23 may be removed from the driven sic--ve 25 to facilitate yam string10 up. Alternation of twist is &ffected, by periodically reversing the direction o'L rotation -of sleeve 25. This may be accomplished by posit;oiin,- the twister assembly between, two belts being driven in opposi@.e directions, and by suitably shifting the t@vister assembly so that it is 15 alternately being driven by the one belt and then the other. Surprisingly, such p.-actice permits rapid twist reversal and rnimmum reversal dwell even at operating sp--eds up to about 20,000 r.p.m. A,n alternate mechanical twister slitable for use in the 20 present invention is seen in FIGURES 8-9, wherein are sho-,vn v-iews of a tivister consistin.- of fixed member 26 and shiftivig member 27, both mo-anted coaxiahy within driven cylindrical sleeve 28. Members 26 and,27 each contain a portion of yarn passageway 29 which may con25 tain suitable bushings to resist abrasion by the running yarn and at the same time protect the yarn from damage. Each of members 26 and 27 contained rou@ided rectangular slots 31a and 3!o, respecti-,rely, which cooperate in serving as a guide For pin 32. The app@aratus is shown 30 with pin 32 in the disenga,@ed position with respect to yam 1. Pin 32 can be shifted into the yarn line by tirging shifting member 27 into fi--ed member 26 (moving 27 to the rigbt). Such shif@ting causes pin 32 to move from position A to position B in FIGURE 9. In operation, the eniire 35 t,@vister assembly. rotates unidl:rectional]v by,. e.g., a bel@t drive frictionally contacting sleeve 28. The shifting member 27 is periodically shifted into fi--ed member 26, causing the pin 32 to alternately engage and disengage the moving yarn 1. The effect is entirely analo,-ous t-o the action 40 o,f an intermittent unidirectl:onal pneumatic twister, the @.-arn 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., pern-iitting@ the upstream accumulation of twist to pass downstream and 45 ,onto the beam., Shifting member 27 is conveniently . @prin,--Ioaded @and@ thereby may be directly shifted by use of @a cam of suitable profile. The pin 32 should be composed of a material ckdable of resistin- the wear induc,-d by repeated shifting and contact w-ith the running, yarn,, 50 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 relationship with respect to one another to, provide v,,arp twisting, at the usual yarn-to-yarn spac- 55 ing. Such considerations also apply to the helical guide twister of FIGURE 6@ Of course, when usin.-, either ,t,,Yister in a ri)altip'e installation, adjacent twisters need: n,ot twist in the same, direction@ nor need they. be in phase. it is@@preferred- for the purposes of this invention tO 60 apply alternating twist to the yams in the warp bye utilizing the pneumatic twister described hereinabove. Such an apparatus is inexpensive, requires little maintenance due to the absence of moving or rotating parts and minimum yarn contact (no yarn degradation) is practicahy instan-@ 65 taneous in i+,S action, and is very economical to operate. Moreover, such twisters are readily adaptable - to-operate on extremely close centers@ as reqi@red in warp twisting@ and when the -twister conforms to the operable and/or preferred_ dimensions as indicated hereinabove, unifonn 70 and reproducible twisting is obtained. The parameters most useful@ in describing the - altemating tivist in the individual yam ends in the warp, as wound on the beam, are the "twist period," the "average level of lev6l is the most important of the three in tlbs invention in that its value deterrrines the back-windability of. the beam. An average twist level of at least about 0.4 tum per inch has been found critical in the practice of this ir@vention. Below that value, twist periodicity becomes difficult to control, and filament rin.-ers appear on the beam during backwinding. A)'Vh.-re it is desirable that twist be con-ipletely removed during backwinding less than about 0.8 turn per inch average t,@vist 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 loadbearing properties of ,he 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 'Ewisl@ level is about 0.6 tum per inch, which permits most efficient backviinding with substant@Ially complete twist removal. Vlhere twistis to be retained during backwinding, as in a loom beam, average 'Livist level may range upwards to 30 turns per inch @or mor-1, as desired. Such hi.-h levels of twist are quite practical using any one o s-verat species of pneumatic twisters, whic'ii are capable rk twisling at rates in excess of one million revolutions per minute. For exa@nple, the twister of FIGURE 2 is capable of imparting more than 60 turns of twist per inch at yarn speeds of 500 yards per minute, at normal operating effl-.iency. -Lhe value of 'the "twist period" also governs to an appreciable extent the operability of the beam dur@ing backwindin.- as well as the extent of retention or removal oftwist. Accordingly, the twist period should be such that t w -@'S I t is accumulated in the yarn being wound during, beaming, but so that it either may be removed or retained during backwinding. I,,- operntions wherein complete removal of twist during backwindini: is desired'. a twist period of from about 4 feet to aoout 16 feet has been found satisfactory, with a period of about 6 feet being preferred. Of. course, any twist cycle may be employ.-d, but it has been found that 'ne 6-foot period best suits the distances encountered in conventional beaming equipment and in b@ckwinding facilities most commonly used by the consumer. It is evident that twist cancellation or removal occurs whenever sections of yam havin.- segments of twist in opposite directions are freely suspended. In operations wherein retention of twist is desired, longer periods may be employed to advanta,@e. Accordingly, at a given rate of twisting, an increase in the twist period causes the twist distribution curve of F IGURE 12 to '@Ratten," 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 belcome overly extended, the aoove-mentioned difficulties common to zero-twist yarn may be encountered. In view o,4 these potential difficulties, it is desirable to avoid extremes in period length, or, alternatively, increase the. average level of tnvist. Another equally suitable procedure Vnich@ a-,,oids the problem of bxtended reversal points is "out of phase" twisi'mg, slch as results from ii@ilizinc. the fluid supply regulator of FIGURE 5a, which assures that the yarn windin,-s will not have their respective reversal points wound adjacent to one another. Whe-n utilizing a mechanical twister in the process Of this invention, the average twist level imparted to the runring yarn line is -a straightforward function of the rate of *,wister rotation since such devices are relatively inse-@isitive to yarn,tension, and incur substantially no shppage during normal op,-ration. When employing a pneumatirtwister in the process of this invention, a number of interrelatedvariables, stich as twister design, twister fluid and supply, yarn tensio a an n nd denier, d the like, determine the average twist level. When utilizing any g-lven pneumatic twister (fixed dimensions), and when twisting any liven yarn, the average level of alternating twist imparted twist," and the level of twist." Averae twist 75 to the yarn line depend s on three factors: y a r n s p e e d , y a r n
[5]9 tension, and rate of twisting, which, for the sake of th-present discussion -.-iay be expressed in terms of fluid supply, e.,-., air pressure. Wien twisting at constant cycle timin- and air supply, the yarn speed, of course, determills the length of the segment of yarn over which twis t is appl,ed during any given twist cycle, and hence determines the av.-rage twist 1--vel. The yarn t-,ns-lon also governs the P-Vera.@e t,@,iist level, since the yarn must be axially displaced bei'Ore twisinl- is initiated. By increasin- the ter-sion on the yarn line, such displacement is relisted. Finally, the air pressure applied to the t@v-.Ster determines the ra,e of twistin- and, therefore, the average level of alternatin.- twist in any given se.-ment of yarn duri-.ig the tviist cycl,-. @ension and air pressure are interdependent variables i.e., aia inereas,- ;.n one decreases the eflect of th,- olher: and coiaversely. At cor@stant iension, the relationsh,@-D between average wist level, express@-d in terms of turns pp-r unit lenth, w-@'th respect to air pressure applied to the twister is substantially linear, hence to increase the avera,-e twist level, ail other facto.@s being the sam.-, an increase in air pressure is sufficient. o.- ei@her mechanical or pieumati@ t-,vistin-, the twist pe-T-iod depends ma:inly upon the di-@ration @of twisting. By "durat-@'on of twisting" is meant the twisting relationship which exists during any one twisting cycle, and which is related to the yarn specd and the time of tnvisting durlig the *Nvisting cycle, i.e., the time int,- rval during which the twister is tviist-in.- in a givendirectioil. Thus, the duration of twistin- deterniincs the length of the yarn segment over which tnvist of a given direction is accumulated, and hence also determ-ines the twis" period except during conditions of eciuilibrium tivisting. During equilibrium t-wisting, of course, zero-tviist yarn ;s packa-ed. To avoid packa.-ing og zero-twist yarn, the cycle Y-,,ring which the tivister operates (in intermittent unidirectional tnvistng) should be adjusted to less than that required to establish an ecuilil.-ii'm twistin.- condit:ion. Although there exists no t@eoretical upper lim;t for th,- twist period, there is a pract;cal upper which is determined by the d,@'stance between the t,,vister and the first upstream sr@ubbinguide. A snubbin@ guide tends to inhibit the further udstream aecumulat@.on of twist. Therefore, twist is confined to the yarn se,@ment betiv-,en such a snubbing guid-. and the ti,vister, and since on"y a certain amount of *,Nvist may be accum,,Iated beiore @h)e upstream tviist counter torqu-. becomes equal t(> the applied tivister torque (at init@atio-.i of equilibriumtivisting), the upper Iiinit of the period is Em,'ted. @he nature of the process of this :@nvention makes certain demar.,ds upon @,he - ssociated bea-rning equipment. As meniiored, an alternating tviist is "trapped" or conf.;ncd by a snubbin.--type -i-@ide, e.g., pinch rolls, nip rolls, and the L-ke. Twist ordinar@:ly can-iot pass either ups'Lr,-am or downstream from s@,ich a -uide, certainly not in a continuous manner as required for the present purpos.-s. That twist which does pass such a snubbin@ gu'de does so in an unco-ritrolled and inter@nittent fashion, and at rather high l@vels which are subs,-qu.-n',Iy distributed over lon.- lergths of zero-twist yarn, and are thereby rendered ineffec',i-lal. Accordi-igly, such -,Uides as the yarn may en-counter in the vic,'@nity of tne twister, an-d particularly downstream therefrom should be of the non-snubbinvari.-ty, such as eyelet -u:ldes, comb giiides, and freely rotati-.i.- id'@er rolls. The roll 10 in FIGURE 1 is of such freely rotatinoperation. LTpstream from the twister, the lo.-ation of the firs" snubbing g-aide det-- rmi-Ties the maximum twist period. Referripg to FIGUPt7-- 1, the vibvation control and d-.Iivery rolls 3 serve in that capacity. Th.- alternate twist ya@-n of this invention may be back-wo,and i-.1 such a manner as to remove or re-ain twist, as r,-qu;rcd by the consumer. -(n the case of s-apply beams, e.g., to be Lised in the prepar--tion of tire coi7d, substanti-LIIY cor.-P.ete tiv,@st removal is usually desirable. In 3,022,566 10 the case of a loom or warp b.-am, the presence o a certain amount of residual twist may be highly desirable, or in some cases required. Accordiiigly, the wound-yarn parameters of avera,-e twist level and twist period should in. -n be adjusted, keep' - i mind the possible end uses. Twist is removed during backwinding by either of two methods. Tviist is removed if the free suspended length of yarn during backivindiig or any subsequent textile operation is allowed to achieve or exceed the twist period. 10 @y "free suspended len.-th" is meant tl-.e length of runiiin.@ yarri tensioned between two snubbing-type guides, e.,-., between the package and a snubbing guide. If shorter portions of th,- yarn are freely suspended, twist removal is incomplete, e.g., about half of the alternating twist is removed wher@ an ineremen', length of yarn is freely 15 s!ispend,-d. The relalionship between twist removal and suspended !en,-th is, for all practical purposes, a linear one. In addition, since twist is contained by snubbing -uides, as indica-ed earlier, 'when such a guide is encoun20 tered during backwind,.ng, 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 positionin.- of snubb@'.ng -uides w@th respect to the beam dur25 ing backwinding, tw;st removal may be accomplished. It is e@@,ident that in -it'@er method of twist removal, some twist -.iay be relained. Yet for every section of twist that is not removed, there will subsequently occur passa.-c of the twist of the onposite direction, leading to even30 tuai complete twist cancellation. In either method of removin.- twist, the corjrpleteness and efficiency of such twist removai is enhanced by utilizing increased yarn tensions dliring backwinding. If il is desirable that tviist be retained during back35 winding, it is obviotis that both ol' the above-mentioned cond:itions are to be avoided. Therefore, to retain twist duritig baelwitiding or aiiy subsequ,-nt textile operation, the @'.-ce suspended lergth of yarn should be kept as low as possible, and the use of snubbing guides or the like 40 means avoided. TLe retention of twist may be flrther assurred by ut-ilizin.- a higher average twist level initially, or by increasi--,.@ the p@-riod, or both. Twist may also be "set" by twisting the yarn in Llie plastic state (via heat or residual solvent), followed by cooling or by slashin.a the 4-- as-twisted yarn. The most desirabl@e met!iod to insure residual twist retention is to increase the average twist level. This is accompl-ished in pneumatic twisting by inereasin.- the air flow. Increasing th@- average tviist level is preferred over increasing the period, since by the lat50 @ler method the reversal length between segments containin-, twist in opposite directions increases. Such exaggerated sectio-ils of yarn hav'nlittle or no twist are sub;ect to th,- sam,- difficulties durin.a backnvinding as is zero-twist yarn. It is pre@'-,rred, therefore, that the over-all twist 5,5 per,od be about from 4 to 16 feet in order to minimize se,a@-nents having zero twist in the separate yarns in the warp. One of th- most important process variables effecting the practice of the present invention is yarn tension. ro Sui-neient tension is required durin.- windin.- to maintain the stab,:Iity ar-ld si)acing of the separate yarn ends in the warp sh,-et,. and to insure acceptable package formation on the beam. However, excessive tension inhibits the eff.-ct of action of the pneumatic twister, a,.qd insufficient 65 tension pei7mits "roll;-,ig together" of adjacent yarn lines, due at least in part to the upstream and downstream flutter -indiieed by the exhai-ist gases from the twister. Moreover, it is required that the tension be uniform across fn.- warp, which is partly controlled by the diametrical 70 unii.Ormity of the vibration control and delivery rolls indicated at 3 and of the idler roll 10 in FIGURE 1. The yarn line tens;on should be sufficient to insure that the ya,-n is reasonably cen'Lered in tie pneumatic twister during windin.a and twisting. Accordingly, it is preferred 75 that yarn tenslons from about 30 grams to about 60
[6]3,022,566 grams be employed during the practice of the invention, altbough satisfactory windin.- has been accorqplish,-d Ls@@ng @lensions as low as 10 --ams or Iess. HigL@er tensions Tnay be necessary in the case of beaming at-very close yarn-to-yarn spacin.- in the warp. T.,ie present cons@,dcra- 5 tions apply to wa.-p spacin,@s of about onefourth to oichalf of an inch. Tension val,,,;es are reported at the beam uriless oth--rwis-. @'.nd-@eated. The yarn supplied Lrom the creel is usually at about 30 to 45 grams tension. The - vibration control-delivery roll system (indicated at 3, 10 FIGURE 1) adds about 5 grams tension, hence the upstream yarn tension is about 35 to 50 grams, which results in yarn bein.- sLv lied from the twister to the beam - p at about 45-60 -rams tension. It is preferred that the minimum values of tension viithin these ranges be em- 15 ployed wherever possible, consis*,,,nt with warp and yarnline stability. In the preparation of warp or loom beams, it is usuaily preferred that such b,-@ams be prepared via section bean-@s, as is well known in the art of,packagin.- and winding. 20 nus, several section beams con' aining 500 or more yarn ends can be used to prepare warp beams containing several thousand individual yarn ends. Of course, when ,usin.a the apparatus of this invention to prepare b.- ams at very close yarn-to-yarn spacings in the warp, i@e., at hi.-h 25 end densities, blocks of twisters may be disposed in a hdn'zonta', and vertical staggered array, permitting twisting of a very large number of ends without requiring an unduly lar.-c or bulky apparatus. By this procedure, a wa@r-p containing 10 or more ends per inch is easily @30 beamed according to the instant invention. The process of this invention is illustrated by the folloiving examples. EXAMPLE1 35 The process of this invention is carried out utilizing the apparatus of FIGURE I (Cocker Beamer Model SD-49, -supplied by Cocker Machine and Foundry Co" Gastonia, N.C.) equipped wi-Lh the pneumatic twister of FIGURES 2-3 arranged in 16 blocks, 11 twisters per 40 block, -according to FIGURE 5. The dimensions of the individual twisters are as follows ilengih Diameter iiaches 45 Exhaust se.@tion 16 ---------------------- 0.24 inch each --- 0.1.10 Beveled section 17 ----------------------- 601 bevel -------- ------- @.- -o -5 -o Twister section IS --------- -------------- 0.245 incb ------- Fuid (air) conduit 19 -------------------- ------------------ 0.020 Total ------------------------------------- 0.875 inch ------- ------------ 50 Compressed air is the twisiing fluid employed, and is siipplied at varying pressure as indicated hereinbelow. A warp sheet of 176 ends of 840.denier, 140 filament T)oly(hexamethylene adipamide) yarn supplied from a creel at 35 gram tension is beamed at 500 yards per minute 55 y.p@m.) ' The yam-to-yarn spacing in the warp is 0.31 inch, and the tviisters are lo-cated on 0.31 inch centers. T'he upstream -uide 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, 60@ Tenn.) eyelets. Tb6 twister operates on an "onoff-" cycle, i.e, by the intermittent application of unidirectional twi'st. Each complete cycle is of the same duration, about 4.1 cycles/second, hence twisting is effected for periods of 0.12 second duration. Since the yarn speed is 500 y.p.m., such a twistin.- i@,yele determines a 65 period len.-th of about 6 feet. The twisted yarn @ends in the warp sheet are traversed ont6 the beam at 45 grams tensibn, the traverse stroke being about 7/32 -inch. After winding, the beam is backwound. During backwinding, 70 the average level of tnvist is determined, the periodicity checked, and the behavior - (operability) during backwiiiding is noted. The average level of twist is determined by - measuring the twist contained in 24 successive 6-inch lengths of yarn immediately as removed froni the beam- 75 12 Stic;h measarements are av@@raged without regard to dir,-ction of twist. T'hese measurements are precise to abo--t 0.05 turn per inch (t.p.i.). The period len@-th is determined by a@-tual measurement of the distance bet-vveen points of tvvist reversal in the yarn immed@ately as removed from the beam. The results of these determinations are summarized in Table l@ Tt7ble I Air pres- Ave.@a@@e Test S17to twist level, Operability P.S.i.i. t.p.i. AA--- 3 0. '@> Poor-hi,@bly variable t,.vist 13eriorli,,ity, many riugers fo,-med ddring bacl,- winding, poor yarn quality. A]3--- 6 0.3 Fair-var-lable tivi-t reriodicity, several ring,,rs noted during ba6kwinding AC --- 0 0.4 Good-ver'y few ringers good per'od control. AD --- 13.4 0.56 Exceilent-no ringers, uniform tivist periodicity. AP --- 18 07 Do. AP --- 21 0'83 Do. The results of these tests show the linear relationship between air pressure (fluid supply) and average twist level, and the critical d--Pendence of operability on ihe average twist level. About 0.4 tp.i. of avera,-e alternatni-, twist is n-.cessary to prepare a back,,vindable bea-n. Rej'erring to the curve of FIGURE 12, the yarn from Test AD has a period length of 6 feet (od), maximum S twist (twister "on") of about 0.9:t.p.i. (a), maximum Z twist (twister "off") of about 0.82 t.p.i. .-(c), a-od substaiitially no dwell at the re,@ersal point b. Air is siipplied to the twister from 0 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 tivi.sting, thereby avoiding that condit-lon. When the twisting cycle tirre is increased, there restilts seeL,'Ons of yarn having z,,ro twist between the segments of yarn containing twist, i.e., there results exag,-erated twist reversal - poirits. V,7hen the t@.visting cycle time is reduced, the curve of FIGURE 12 assumes a "saw tooth" cont<)ur. EXAMPLE 2 The niechanical- twister of FIGURES 6-7 is utilized -vvith the apparatus of FIGURE I to beam 176 ends of 840 denier, 140 filament poly(hexamethylelic adipamide) yarn, sur)plied from a creel at 35- 40 grams tension. The twisters are positioned between two belts driven in opposite directions. During contact with either belt, t@lie twister rotates at 18,000 revoluti-ons per minute (r.p.m.). The tivister co@itacts either belt for 0.25 second, fiien is immedl:at-.Iy shifted to the otner belt for the same contact time. The-yq@rn is beamed at 500 v p.m.. hence the twl@st period is abo@at 12 fe-.t, at an average level of t,,vst of 0.5 t.p' i. Such a beai-n is flilly oper.able during bacl-ivindi,:ig, twist periodicity is uniform, and.substantiahy no fdm-nent ringers are formed@ EXAMPLE 3 i The mechanicdl twister of FIGURES 8-9 ig util;zed n the apparatus of FIGURE I to bearn 11 ends of 840 denier, 140 filament poly (hexarqethylene adipamide) yar-@i, si@,nplied from a creel at 35- 40@grams tension. The indiiidual twisters are driven at a constant 18.-000 rp.r@i., and slifted at 0.25 second - intervals. The yam is beame,-'L at 500 y.p.m., he.,ice the tw-st peiiod is about 1-7 feet, at a p average tnvist level of 0.5 t.p.i. The beam so prepared is fully backwindable. - EXAMPLE 4 Beams prepared according to Examples 1, 2, or 3 are backv@'oland to supply conveiitional downtwisting apparatus. Each yarn end is passed from the beam via guide m.-ans throu,@h drop-type tension rolls serving each twisting position, thence to the ring and associe@ed "rav.-ler and o@ito a conventional twister packa,@e (pirn) mounted
