Drafting and Twisting Processes in

Open-end Spinning Machine MS-400 By TeiryoKojima, Kozo Susamiand Masaaki Tabata, Members,TMSJ Basedon the Journal of the Textile Machinery Society of Japan, Proceedings, Vol. 21, No. 11, p. 737(1968); Vol. 25, No. 9, p. 623(1972) Abstract

The most characteristic features of the open-end spinning compared to the ring spinning are in the drafting and twisting mechanism. In the present paper, some discussion will be made on the analysis of the drafting and twisting processes in MS-400 open-end spinning and their relation to the properties of its spun yarn. The mechanical characteristics of MS-400 are; (1) Roller drafting device (2) Ejector for fiber separation (3) Special eyelet, a yarn guide attached to the axis of the drum. These mechanisms make MS-400 a suitable spinning machine for man-made fibers. In the first part of this paper, the behaviour of fibers in the ejector separated into individ uals from a fiber bundle by the air stream will be considered. The discussion will be extended on the degree of fiber separation and the state of fibers, such as straightness at the outlet of the ejector. The second part deals with some mathematical analysis of the process of fiber collection in the drum and its self-doubling effect on the yarn irregularity. It is shown that the self-doubling effect is extremely useful for decreasing the yarn irregularity of short wave length and for improving the blend uniformity of fibers in the yarn. In the third part, the effect of the eyelet equipped in the drum is considered. The eyelet is shown to have a great influence on the yarn strength and on the end down in spinning. In the last part, a brief mention will be made on the spinning features obtained by the practical production in MS-400.

KEY WORDS: DRAFTING,TWISTING, OPEN END SPINNING

1. Introduction Principal processes of spinning machines consist of draft ing, twisting and winding. If fiber properties are being fixed, yarn qualities are mostly governed by fiber motion in drafting and twisting processes, although these processes are quite different in open-end spinning from those in ring spinning; this characterizes the yarn property produced by open-end spinning. In this report, discussion will be made on drafting and twisting processes in the open-end spinning machine MS-400 and their relation to the yarn properties. Also the characteristics of the open-end spun yarn will be considered. Toray Industries Inc. carried on the study of open-end spinning in cooperation with 1-iowa Machinery Ltd. for several years, and developed MS-400; it belongs to a drum type spinning machine, as schematically shown in Fig. 1, A sliver is fed to 4-line double apron drafting system (1), and passes through an ejector (2) into which compressed air (6) is fed through a valve (10). A fiber bundle is separated to single fibers, and they are sent to a drum (3) rotating in Fig. 1 Main constitution of MS-400

8 Journal of The Textile Machinery Society of Japar high speed, and then twisted by the rotation of the drum (3) where relative to delivery rollers (4), forming a yarn which is F0=C(Va-V0)2 wound in a cheese (14) on a winding drum (5). F=C(Va-V)2 The most characteristic processes of yarn formation in Vd=V0/Va MS-400 are the separation of a fiber bundle in the ejector and the fiber motion in the drum; these characteristics will be discussed in the following chapters.

2. Separation of Fiber Bundle by Ejector-Air Draft

Fig. 3 Relation between distance and flying speed V of a fiber

Fig. 3 shows the variation of the fiber speed calculated by Fig. 2 Constitiuton of the ejector the above equation, indicating that a fiber in the ejector gets nearly the same velocity as air at few centi-meters Fig. 2 shows a schematic diagram of an ejector, which distant from the nip point of front rollers. This distance is consists of two parts; nozzle and diffuser. Fibers sent from extremely shorter than that anticipated. However, the front rollers of the drafting device are fed into the ejector friction between neighboring fibers in the bundle acts on through the nozzle. Compressed air is fed into an air the fiber in the ejector, adding to air force, causing a slightly chamber and is gushed out through the alley between the longer distance until the fiber gets the same velocity as air. nozzle and the diffuser, causing a sucking air stream in the Nevertheless, an ejector 1.5 times longer than the fiber nozzle. The fiber bundle is separated by the air-friction be length would be enough to separate a fiber bundle. tween fibers and air stream in the nozzle. Now, considering the state of fibers separated with the We shall consider the variation of the flying speed of a ejector, the performance of fiber esparation is very im single fiber supplied in the ejector from front rollers of the portant not only in MS-400 but also in any other open-end drafting device, in order to guess the process of the fiber machines: it directly influences upon both the evenness of bundle separation. The following symbols are adopted[1]: and the breakage of yarns. It is desirable to get uniform x= Distance from the nip point of front rollers to separation of fibers in the ejector. But the degree of fiber the trailing end of a fiber at time t. separation is dependent on the properties of raw materials, m= Mass of a fiber. quality of fiber bundles, ability of the ejector and air V= Flying speed of a fiber at time t. pressure supplied to it, etc. The relation among them is too Va=Air speed in the ejector. complicated to make a theoretical analysis, and experi When a fiber was placed in air stream and its one end was mental observation would be reasonable. connected to a strain meter, the air resistance of the fiber Figs. 4 and 5 show photographs of fibers flowing from was proportional to (air speed)2. This suggests that the air the ejector to the drum in spinning condition. They are resistance acting on a moving fiber should be proportional taken with a camera equipped with 75mm telescope lens, to (relative speed between the fiber and air)2. So, the fiber 20mm ring, film of ASA 400 (Kodak), and flash time of motion after the release from the nip point of front rollers 12 micro-second. In Fig. 4, four fibers are shown supplied is: simultaneously to the drum. In Fig. 5, a single fiber is presented. By this way, the behavior of fibers moving from the ejector to the drum was observed to estimate the uni where C=const. formity of fiber separation from 1,000 frames of photo When the initial speed of the fiber is Vo (equal to the sur graphs. face speed of front rollers of the drafting device), the fiber Fig. 6 shows an example of the relation between the speed Vat an arbitrary position x is given by: number of fibers in a frame of the photographs (horizontal axis) and its frequency (vertical-axis). No fibers in a frame means the occurrence of "open-end" there. The distri

Vol. 20 No. 1 (1974) 9 Fig. 6 Relation between number of fibers per frame of photos and its frequency

celerated in the air stream and supplied to the drum at the velocity equal to air velocity. So the degree of fiber sepa ration can be estimated by the average number of fibers Fig. 4, Fig. 5 Photograph of hbers flowing trom the supplied to the drum, which could be calculated from ejector to the drum in spinning bution in Fig. 6 almost follows Poisson distribution. As suming the number of fibers be n and its frequency be f, an Table 1 shows the average fiber speed V and the average average number of fibers n can be expressed by number n•Œ of fibers with different kinds of fibers having the staple length of 51 mm. It can be seen that the higher the

air pressure, the better the fiber separation. But the air which n can be considered the average fiber density in the air flow blowing from the ejector to the drum. When the Table 1. Degree of Fiber Separation yarn take-up speed is Vy and the number of fibers in the yarn cross-section is ny which is determined by both the yarn count and the fiber denier, the average fiber speed V supplied from the ejector to the drum is calculated by

The calculated speed is almost equal to the air speed blow ing from the ejector to the drum which can be experi mentally measured. This shows that fibers are fully ac

Table 2. Content of Hook Fibers after Separation (%)

10 Journal of The Textile Machinery Society of Japan pressure supplied to the ejector should not be raised ex cessively, because if the fiber speed exceeds the surface speed of the drum, the fiber arrangement and its straight ness are disturbed. Comparing the materials of fibers used, the degrees of fiber separation of polyester or polyester rayon blended are worse than those of polypropylene or polyacrylonitrile. Table 2 shows the fiber-hook observed on photographs mentioned above. Fibers used are polyester, polyacrylo Fig. 8 Relative motion of the peeling point A and nitrile, nylon and polyester-rayon blended of 51mm staple the supplying point B length. In any case, the amount of total hook-fibers is only two to three percent. This fact suggests that the ejector can Fig. 8, the supplying point of the sub-yarn B is rotating at straighten the fibers supplied from the drafting device. the velocity v clockwise and the peeling point of the layers of the sub-yarn A is rotating at the velocity w anti-clock 3. Fiber Motion on Drum-Collecting Process and Self wise (it is rarely rotating clockwise). When the circumfer doubling Effect ence of the collecting surface is I and the peeling point A meets with the supplying point B at time t=0 on the point Fibers laid on the inside of the drum by air flow are P (it is decided as the original point), the time r for A to

subjected to a doubling operation. The web on the drum is meet with B next, is given by, jointed to a twisted yarn, which is then removed by take-up wƒÑ+ƒËƒÑ=l ...... (1) rollers. The surface speed of the inside wall of the drum is then perhaps 100 to 300 times higher than that of take-up rollers. ƒÑ=l/(w+ƒË) ...... (2)

Thus the draft ratio at this stage is fractional i.e. 1/100 to And the distance d from the meeting point to the original 1/300. A self-doubling effect is caused by the fractional point is draft ratio, resulting in an extremely uniform yarn. ?? =wƒÑ=wl/(w+ƒË)=1/(ƒË/w+l) ...... (3)

The effect of self doubling, which was already reported =1/(Q+1), ...... (4)

qualitatively by Rohlona et al[2], will be considered mathe where matically as follows. The number of fibers supplied to the ƒË/ w=Q

drum by air flow is so small that the flow continuity of Fig. 9 shows the layers of the sub-yarns on the collecting fibers is practically interrupted. However, assuming a con surface of the drum at time ƒÑ. tinuous flow of fibers, we call it a sub-yarn for convenience When the supplying point B goes over the peeling point sake. The sub-yarn is wound on the inside of the drum, A, the newly supplied sub-yarn is divided at that point; more exactly on the collecting surface. one part of the sub-yarn supplied before is peeled by the Fig. 7 shows layers of the sub-yarns on the drum. When advance of the peeling point but the other of the sub-yarn the surface speed of the take-up roller is w, the peeling which will be supplied after, will make new layers on the speed of the bundle from the collecting surface is equal to collecting surface. And thus the sub-yarn is repeatedly w. When the surface speed of the collecting surface of the divided and deposited on the collecting surface. The di drum is v, it is equal to the supplying speed of the sub-yarn vided length of the sub-yarn is given by, to the drum. In fact, the fiber supplying inlet to the drum is ƒËƒÑ=ƒËl/(w+ƒË)=1Q/(Q+1) ...... (5)

fixed and the drum is rotating, but it would be convenient or for simplicity to consider reversely: the drum is fixed and ƒËƒÑ =1-wƒÑ=1- ?? ...... (6) the fiber supplying inlet is rotating. In this case as shown in The time for the peeling point to come back to the origi

nal point P is 1/w. As the drum speed is ƒË/l, the revolution

Fig. 9 Layers of sub-yarns on the collecting surface at time t=Ą Fig. 7 Layers of sub-yarns deposited on the drum

Vol. 20 No. 1 (1974) 11 Fig. 10 Positions of deviding points of sub-yarns

number of the drum during that time is

ƒË/l•E1/w=ƒË/w=Q

That is equal to the revolution number of the supplying Fig. 12 Positions of devided sub-yarns on the spun yarn point. As mentioned above, Q (=ƒË/w) layers of the sub yarn are deposited on the point P, when the peeling point A comes back again to the original point P. This process does And the position xi+k corresponding with Milk is not change, even if the original point may be taken any xi+k=-y+i¥1+k¥1 ...... (8)

place on the collecting surface. Therefore, on the peeling where x-axis is put on the lengthwise axis of the sub-yarn

point, Q layers of the sub-yarns are always deposited and and the original point of x-axis is the leading end of the

then those are collected, peeled, twisted and spun out as a sub-yarn. As the doubling number of the sub-yarns is Q, yarn. We call this a self-doubling effect. The number Q of k in eq.(8) has values from 0 to (Q-1). Then, when the the self-doubling in the open-end spinning system of drum thickness of the sub-yarn is S(x), the thickness of yarn type is decided by the ratio of the surface speed of the drum S(y) within the region (i-1)4•…y•ƒi ?? is to the take-up speed, ƒË/w.

As shown in Fig. 10, the sub-yarn is divided in the length IQ/(Q+1) and the divided sub-yarns are deposited in the For simplicity, the sub-yarn delivered to the drum may be distance of 4=l/(Q+1) on the collecting surface. Then the assumed to have the sinusoidal thickness irregularity of sub-yarn is placed in the spun yarn as shown in Fig. 11, in wave-length 2 and relative amplitude a, as follows: which, i and i•Œ show the divided points of the sub-yarn. i

shows the leading end of the divided piece number (i+1) of the sub-yarn and i•Œis the trailing end of the divided piece From eqs. (9) and (10), the thickness of yarn S(y) is: number i. It should be noticed that, in Fig. 10 the leading end of the sub-yarn is in the left hand and in Fig. 11 the

leading end of the spun yarn is in the right hand. while We put y-axis on the length wise axis of the yarn and

assume the thickness of the yarn at y as S(y). It is clear that S(y) is the sum of the thickness of the sub-yarns at y, as Then, eq.(11) is re-arranged: shown in Fig. 11. Next, we may calculate S(y). Now, the original point of y-axis is the leading end 0 of the first divided piece of the sub-yarn (Fig. 11). To clear the variance of the thickness within short If ƒÎl•áƒÉ, then sin So, eq.(13) can be ex. ranges, we consider it within (i-1) ?? •ƒy•… ?? . In Fig. 12, pressed as when we put points Mi, Mi+i,...for each sub-yarns at y, the position xi on the sub-yarn corresponding with the po sition Mi is where xi=i(l- ?? )+(i ?? -y)=-y+il ...... (7)

As the draft ratio in the fiber opening device of open-end

spinning machines is very large, the wave-length of sinu

soidal thickness irregularity of the sub-yarns is long . Then, we may consider ƒÎl•á2. So, eq.(14) shows that the spun

yarn has also the sinusoidal thickness irregularity of wave length ), and relative amplitude aA within the region of

Fig. 11 Positions of deviding points of sub-yarns (i-l) ?? •ƒy•…i ?? . on the spun yarn In order to know the thickness of yarn S(y) in wide

12 Journal of The Textile Machinery S ociety of Japan Fig. 14 Evenness of spun yarns

equipped with an eccentric roller drafting device. The same count yarn was also spun in a ring spinning machine

equipped with the same drafting device, using the same roving. The fiber used was polypropylene staples of 1.5 denier and 38mm length. The front top roller was 29.1mm

in diameter and 0.52mm in eccentricity. The draft ratio Fig. 13 Relation between A and 1Q/ă between the front and second rollers was 20.0. In this case,

l Q/ă was 1.75, A being 0.14. Fig. 14 shows the evenness range, we may calculate S(y) when y= ?? , 2 ??, 3 ??, curves of spun yarns. As can be seen from it, periodic Putting y=i ?? , amplitude irregularity of about 18% was observed in the

ring spun yarn, whilst there was scarcely any in the yarn

produced with the open-end spinning machine. Successive then ly, experiments were made using some front top rollers -Y+il=-y+(Q+1)y=Q¥u ...... (17) with different eccentricity, but periodic irregularity was Thus eq.(14) is changed to scarcely observed. Self-doubling is very effective for not only making a uniform yarn in lengthwise but making a uniform blend of fibers in the yarn. Because Q layers of sub-yarns are de where y= ?? , 2 ?? , 3 ?? ...... ,i ?? ...... posited on the inside wall of the drum, this has the same As mentioned above, we can see that the spun yarn as a effect as the doubling of Q slivers in roller drafting. When whole has the sinusoidal thickness irregularity of wave different fibers are blended, the greater the number of length ƒÉ/Q and relative amplitude aA. If Q is very large and doubling, the more uniform the blend of fibers in the yarn. 1/Q is very small, eq.(18) may be considered to show the The theoretical number of total doubling is said to be more true variation of yarn thickness S(y) in whole yarn length. than the average number of fibers in the yarn cross section.

Using eqs.(14) or (18), the sinusoidal thickness irregu So, in conventional spinning, several separate doubling larity of wave-length ă and relative amplitude a, existing in processes are necessary. But in open-end spinning this is sub-yarns is changed to the sinusoidal thickness irregulari not so, because doubling effect corresponding with dou ty of relative amplitude aA due to the self-doubling effect bling number Q (=v/w) is given by self-doubling. For in the drum. As shown in eq.(l 5), A is always smaller than example, the number of self-doubling is nearly equal to

1. Then, the relative amplitude of sinusoidal thickness ir 140 when the drum diameter is 6 cm, the drum speed being regularity in spun yarns is always smaller than that in sub 30,000 rpm, the take-up speed being 40m/min; this is

yarns. equivalent to the doubling of 140 times. For this reason, in Fig. 13 shows the relation between A and lQ/ă. It can be open-end spinning, usually the blending in preparing pro

seen that A (decreasing ratio of irregularity amplitude) cess is not necessary. To demonstrate this effect, yarns of decreases with increase of lQ/ă, and that it becomes very 26's cotton count were produced by feeding two rovings to small when lQ/2 is greater than 1. This means that the both a ring and an open-end spinning machine. The two

periodic irregularity or irregularity factor of short wave rovings were of polyester staple fibers, 1.5 denier and length existing in sub-yarns or fiber bundles supplied to the 38mm length, one roving being white and the other dyed drum, is almost diminished to zero. This self-doubling black. Fig. 15 shows photographs of the cross sections of effect is the most characteristic feature in open-end spinn yarns produced by both methods; it is clear that the yarn ing. produced by open-end spinning has an extremely uniform In order to illustrate the effect of self-doubling as de fiber blend. The value of Q in this experiment was about scribed above, a yarn of 24's (English cotton count) was 140. spun in an open-end spinning machine MS-400 especially Self-doubling effect of an open-end spinning machine

Vol. 20 No. 1 (1974) 13 The drum of MS-400 has two actions; one is "re collection" of separated fibers to predetermined thickness, and the other is "twisting" of the re-collected fiber bundle to form a yarn. As the re-collection was discussed in the previous chapter, we may now consider the fiber behavior in twisting. In the conventional ring spinning machine, the fleece fed from front rollers is nipped tightly between rollers on its trailing end, and twisted under rather high tension caused by ballooning of the yarn. On the other hand, in the open-end spinning machine, the web deposited on the collecting surface of the drum is peeled and twisted. There (a) ring spun yarn (b) open-end spun yarn fore, the end of the yarn now being twisted is maintained Fig. 15 Photographs of cross sections of yarns only by the frictional force between the web and the MS-400 was discussed above. This effect is generally char collecting surface (caused by centrifugal force acting on acteristic in a drum-type open-end spinning machine. So, the web) and by the friction acting between fibers. This the yarn produced on MS-400 has extremely uniform force is very small, but the tension acting on the yarn being thickness nearly equal to a random sliver because of self twisted is also small. It can be said that a ring spun yarn is doubling. twisted under high tension with its trailing end nipped As shown in the experiment mentioned in the previous tightly, while an open-end spun yarn is twisted under lower chapter, a sliver is not always separated into individual tension with its trailing end nipped loosely. For this reason, fibers in the opening device, and a part of fibers is supplied a ring spun yarn has tight construction, but an open-end to the drum in groups. Then, strictly speaking, it can be spun yarn is soft and bulky. In open-end spinning, fiber said that the spun yarn is composed of collection of fiber slip occurs more easily in twisting. So in extreme case of groups (a single fiber being considered a group having one open-end spinning, fibers in outer layers of the yarn remain fiber). Using Tabata's theory[3,4], the relative variance in outer layers extending lengthwise and fibers in inner C2(S) of the spun yarn of thickness S is expressed by layers remain in inner layers. Also twist numbers of fibers c2(S)=k{l+c2(k)}/S in outer layers differ from those in inner layers. where S is the average thickness of the spun yarn, k the There are unusual groups of fibers distinguishing the number of fibers in groups, k the average of k, c2(k) the appearance of open-end spun yarns from that of ring spun relative variance of k. And. yarns. As shown in Fig. 16, some fibers G may be taken off relative variance=(variance)/(mean)t. from the thin end of the web lying on the collecting surface, As the relative variance given in the above equation is, in and some fibers may be blown to the portion H of the yarn strict meaning, the relative variance of the number of fibers already formed. These fibers form a coil of fine helical in a yarn cross section, the relative variance of yarn thick pitch around the parent yarn and they are called bridging ness must be obtained by adding it the effect of single fiber fibers. The number of these fibers is affected by the design thickness irregularity. of the drum and can be decreased in some degree by adopting an adequate position of the ejector outlet against The above equation shows that the smaller k or ct(k), the drum or using a separator insulating the yarn from the the better the evenness of spun yarn thickness. Therefore, supplied fibers. The longer the circumference of the col it is desirable that the fiber opening device separates the lecting surface or the shorter the staple length, the less the fiber bundle as fully as possible into individual fibers, and number of the bridging fibers. also that the fiber opening device does not hurt or cual fibers. As seen in Table 2, the value k is slightly samller than 2 in case of MS-400 in good condition. This value is near to that measured before by Tabata about group behavior of fibers in ring spinning machines[5]. This shows that the superior uniformity of spun yarns produced by MS-400 depends mainly on the fact that it has extremely few periodic irregularity of short wave length, compared with conventional machine.

4. Fiber and Yarn Behavior in Twisting

4-1. Behavior of Fibers Fig. 16 Unusual groups of fibers

14 Journal of The Textile Machinery Society of Japan surface of the eyelet B, when the yarn end A moves. Be havior of the yarn in this stage is similar to that of the

friction type false twisting machine.

For example, in the friction type false twisting machine

shown in Fig. 19, the rotation of a friction ring B•Œ corre sponding with B in Fig. 18 rotates the yarn which touchs

B•Œ. When there is no slip between the yarn and the friction ring, the yarn at B•Œ rotates with ƒÁB•Œ/ƒÁy turns during 1

revolution of the friction ring, where rB' is the radius of

the friction ring and ƒÁY is that of the yarn. Therefore, when

(upper) good yarn (below) bad yarn the rotating speed of the friction ring is V•Œ, the false twisting Fig. 17 Yarn appearance speed is V•Œ-ƒÁB•Œ/ƒÁy. In the stable state of false twisting, a yarn is twisted only in the region A•ŒB•Œ(before the friction ring), and untwisted in the region B•ŒC•Œ(after the friction Fibers G and H except those normally taken off and ring). The twist density of the yarn fed with velocity W•Œ, twisted, can scarcely contribute to yarn strength, but spoil in the region A•ŒB•Œ, is (V•Œ/ W•Œ) x(ƒÁB•Œ/ry) yam appearance. Fig. 17 shows good and bad open-end Actually, there is some slip between the friction ring and yarns. The good yarn looks like a ring spun yarn; the bad the yarn. Assuming k (0•ƒk•ƒ1) be a constant expressing yarn is quite different in appearance, having many fibers the degree of slip, the false twisting speed U•Œ is equal to coiled around the outer layer of the yarn. kV•ŒƒÁB•Œ/r, and the twist density of the yarn in the region 4-2. False Twisting Action of Eyelet A•ŒB•Œis equal to k(V•Œ/W•Œ) (ƒÁB•Œ/ƒÁY).In Fig. 18, the eyelet B In this chapter, the eyelet may be considered which is fixed and the yarn is moving on the inner surface of the touches the yarn taken from the drum (Fig. 18, B). Its eyelet B. It is dissimilar to Fig. 19, but false twisting of the shape, material, surface finish and contact angle ƒÆ with the yarn is similar to Fig. 19. Then in open-end spinning, the yarn are important and exert much influence upon the yarn yarn in the region AB is given a false twist caused by quality and the yarn breakage during spinning. friction atainst the eyelet B, in addition to true twist given In Fig. 18, the yarn end A moves on the circle which the by the drum rotation; the twist density of the yasn in this collecting surface describes due to the rotation of the drum, region is given by and the yarn between A and C is given a true twist (its (V/W)+k(V/W)(ƒÁB/ƒÁY)=(V/W)(1+k. ƒÁB/ƒÁY), direction being z twist in Fig. 18). Twist density of the yarn between B and C is equal to that of the yarn spun out, where V is the drum speed and W is the take up speed of

whilst that between A and B is not so. This is because, the yarn.

false twist occurs due to the rolling of the yarn on the inner A constant k is affected by friction between the yarn and the eyelet B, contact angle between both, yarn tension and

yarn rigidity; the greater the k, the higher the twist density. Therefore in this case, the web deposited on the collecting surface of the drum is taken off more easily and yarn

breaks during spinning decrease, but contrarily the yarn

quality is spoiled. The eyelet should be chosen carefully in its material, shape and contact angle of the yarn. Though the eyelet of MS-400 machine is fixed, a rotatable eyelet can be considered. For example, the eyelet fixed to the

drum will have scarcely false twisting effect, but that rotat

ing to reverse direction against the drum will have a greater false twisting effect.

Fig. 20 shows the measuring device of false twist density, U/W. As shown in Fig. 18, actually the yarn is rotating on

the fixed eyelet and taken off downward, but in this device, a yarn (1) is only running downward by rollers (7), and the

eyelet rotates to reverse direction aginst the drum with the same velocity as the drum. In Fig. 20, a yarn (1) is unwound

Fig. 18 False twisting Fig. 19 False twisting action of from a cone cheese, running through the snail guide (2), action of eyelet the false twisting machine in a disk tensioner (3) and the eyelet (4), and taken-off with friction type delivery rollers (7). The eyelet (4) is fixed on the upper end

Vol. 20 No. 1 (1974) 15 Table 3. Yarn qualities produced with MS-400

Fig. 21 False twist number U/W (turn/25 mm)

different eyelets. The yarn used was polyester rayon blended of 30's (English cotton count). Its blending ratio was 65/35 and the twist number was 19.2 turns/25mm. Same yarn Fig. 20 Measuring device of false twist number U/W was used in the measurement of frictional coefficient. The greater the frictional coefficient, the greater the false twist of the tube (5), which is driven by a driving belt (6). number U/W. Therefore, it is suggested that the twist The yarn (1) touches a twist-measuring device (8), density of the yarn in the drum can be raised by using the which has a rotor (9) supported with pivot, which has eyelet with high frictional coefficient, and that yarn-breaks little resistance against rotation, and whose rotation is decrease even if the true twist number determined by the proportional to that of the yarn (1). The rotor (9) has ratio of the drum speed to the take-up speed is lowered. eight holes, through which a ray from a light source (10) is Fig. 22 shows an example of spinning condition when cast to a photo-electric element (11) at the time when a several eyelets with different frictional coefficients are used. hole comes on the line connecting the light source (10) and End-down index is the number such as the least end-down the photo-electric element (11), which is connected to a is taken as a unit, yarn strength index being such as the degital-counter (12). Then, the rotation of the yarn (2) highest yarn strength is taken as a unit. The yarn used was driven by the friction force between the yarn and the the same as that in Fig. 21. The greater the frictional co eyelet (4), is delivered to the rotor (9) of the twist-measuring efficient, the less the end-down during spinning and the device (8), and the number proportional to the rotation of lower the yarn strength. The reason of the former phe the yarn is expressed on the degital-counter (12). nomenon was discussed already, and the latter is caused by Fig. 21 shows the relation between the false twist number the yarn damage during yarn-passing through the eyelet U/W (vertical axis) and the frictional coefficient of yarn having high frictional coefficient. In fact, when the eyelet against the eyelet (horizontal axis), measured with several having high frictional coefficient is used, a lot of powder is

16 Journal of The Textile Machinery Society of Japan After time dt, the variance of twist number ?? N1 between A and B may be written as

...... (19) Then

When U is constant, by integrating the above equation we have:

Assuming N1=0 at t=0, then

Therefore ...... (20)

Eq.(20) shows that the twist density of the yarn in the region AB is (V+U)/Win stable state (t being infinite). Fig. 22 End-down and yarn strength when different Next, the twist density of the yarn in the region BC may eyelets are used be considered. Similary as above mentioned, the variance of twist number 4N2 of the yarn in the region BC after the deposited in the drum, which is recognized to be fine pieces time ??t, is: of fibers by observating through a microscope. As mentioned above, the role of the eyelet is not only to lead out a yarn formed in the drum, but to raise the twist Substituting eq.(20) into eq.(21) density of the yarn in the drum by false twist given by friction between the eyelet and the yarn. The higher the When U is constant, frictional coefficient of the eyelet, the more the twist density of the yarn, and the more stable spinning condition with a low true twist number. But the eyelet with high frictional Assuming N2=O at t=0, eq.(22) is changed to coefficient sometimes hurts the yarn passing on it. There fore, in selecting the eyelet, these contradictory effects should be considered to suit for the spinning condition and where raw material used. 4-3. Variance of Twist Density of Spun Yarns False twisting discussed before acts not only in MS-400 but in all the drum-type open-end spinning machines, such The twist density of the yarn in the region BC is V/Win as BD-200. This effect is useful for decreasing yarn-breaks stable state (t being infinite). Namely, if the false twisting and for stabilizing spinning. But in case that false twisting speed U is constant, twist densities of yarns in the region speed varies, the twist density of the yarn varies too. This AB and BC have respectively constant number, (V+U)/W problem may be considered mathematically as follows. and V/U in stable state, giving the spun yarn a constant The following symbols are adopted (see Fig. 18). twist. V,W: defined before, But in case when the false twisting speed U varies by, for l1=Yarn length between A and B. example, unstable yarn touch with the eyelet, twist densi l2=Yarn length between B and C. ties of yarns in the region AB and BC vary too, and the Nl=Twist number of yarn existing between A and spun yarn becomes uneven. For simplicity, the false twist B at time t. ing speed U may be assumed to have sinusoidal irregularity N2=Twist number of yarn existing between B and C such as: at time t. U=a+b sinwt ...... (24) - U=False twist number per unit time given by the Putting eq.(24) into eq.(19), we have: friction between eyelet B and yarn. (the rotating direction of yarn in false twist is reverse to that given by rotation of the drum) C1, C2 =integral constants.

Vol. 20 No. 1 (1974) 17 where

As the second term in the right hand side of the above equation diminishes in stable state,

Also, from eqs.(21) and (24):

where

Fig. 23 Full spinning process including MS-400

As the third and forth terms reduce to zero in stable state,

Eq.(28) shows the twist density of the yarn in the region BC and it is equal to that of yarn spun out. Therefore, the ratio of the amplitude of the periodic irregularity of spun yarn's twist density to that of false twisting speed b is expressed as:

This value is always less than one. But in case of using the eyelet with extremely high frictional coefficient and of spin

ning with low twist, the variance of twist density of yarn Fig. 24 MS-400 during spinning shown in eq.(28) may be extremely large. In that case, the yarn structure becomes uneven, and the yarn strength is extremely weak. To prevent this trouble, the eyelet used should be selected to suit for raw material and spinning condition, and it is effective to shorten the distance l1, from the collecting surface of the drum to the eyelet, and to ex tend the distance 12 from the eyelet to the take-up rollers, as shown by eq.(29).

5. Production of Yarn with MS-400

In preceding chapters, drafting and twisting processes have been considered basically. In this chapter, practical production using MS-400 will be mentioned briefly. We, Toray Ind. Inc., started yarn production with MS 400 in our Seta plant in 1968, and have acquired considera ble experience during these five years. Fig. 23 shows full spinning process including MS-400; drawing is two passages and roving process is excluded. Sliver cans supplied to MS-400 can contain 20 pounds. Fig. 25 Automatic yarn piecing machine

18 Journal of The Textile Machinery Society of Japan the piecing part and knotts the end of the yarn being spun out from the drum with the end of the yarn unwound from the cheese by using a knotter. As the result, the spun yarn has no slub made at piecing. Rewinding is scarcely needed, but only partial cheeses produced at machine-breaks or yarns used for special fabrics are rewound. At the present time, pure acrylic yarns and polyester yarns and polyester-rayon blended yarns are being spun. Fibers used have 1.5 to 2 denier and these staple lengths are 38,44 and 51mm. The qualities of these spun yarns are shown in Table 3; these yarns are uniform, bulky and soft with little hairiness and knots. Utilizing these properties, greater parts of these spun yarns are used in knitting.

6. Conclusion The most characterystic processes of open-end spinning, Fig. 26 Auto-Doffer particularly in MS-400, compared with ring spinning are fiber separating, recollecting and twisting. These charac terize the open-end spun yarn. In this paper, these matters were considered. Specialized points of MS-400 from other open-end spinning machines are to use air stream for fiber separating and to use the special eyelet for stabilizing the yarn formation in the drum. Therefore, MS-400 can make the yarn with longer staple fibers, and the produced yarn has good parallelism, low twists and high tenacity as ring spun yarns. These results reported in this paper may give some suggestions to the research which will be widely done in future.

Literature cited Fig. 27 Sideview of a spinning room [1] M. Tabata, et al.; J. Text. Mach. Soc. Japan, 25, 623 (1972) The drum of MS-400 rotates at 30,000 to 37,000 r.p.m. [2] M. Tabata, K. Susami; ibid, 21, 737 (1968) during spinning. Yarn count being spun is Nm 24 to 68 [3] M. Tabata, S. Ishikawa; J. Text. Mach. Soc. Japan, (see Figs. 24 and 25). To reduce labor, auto-doffers and 13, 454 (1957) automatic yarn piecing machines are running (Figs. 26 and [4] M. Tabata, S. Ishikawa; J. Text. Mach. Soc. Japan, 27). The yarn piecing machine pieces a broken yarn by 11, 447 (1958) using an already prepared yarn, takes off the slub made on [5] M. Tabata; ibid, 11, 678 (1958)

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