US3449900A - Twist retention yarn guide and method of uptwisting yarn - Google Patents

Description

June 17, 1969 c w ELDRIDGE ET AL 3,449,900

TWIST RETENTION YARN GUIDE AND METHOD OF UPTWISTING YARN Filed Nov. 25, 1966 Sheet of 2 June 17, 1969 c. w. ELDRIDGE ET AL 3,449,900

TWIST RETENTION YARN GUIDE AND METHOD OF UPTWISTING YARN Sheet i of 2 Filed Nov. 25, 1966 United States Patent US. Cl. 57--59 4 Claims ABSTRACT OF THE DISCLOSURE The yarn passing from the supply package of a delivery twist system such as an uptwister is in the form of a rotating loop called a balloon. In order to minimize air drag on the rotating loop and to produce stable balloons in which filament separation is eliminated, the invention provides for concentrating in the portion of the yarn forming the balloon, a relatively high degree of twist. In the illustrated embodiment, the yarn is bent sharply over a narrow edge of a guide located beyond the end of the supply package. This serves to restrain the passage of twist over the guide edge, so that the twist level in the portion of the yarn forming the balloon builds up to a value greater than the twist level in the yarn beyond the guide.

This invention relates to the twisting of yarns. It is concerned particularly with a method and apparatus for so controlling a continuous multifilament yarn passing from the supply or delivery package of a delivery twist machine as to stabilize the balloon and reduce filament separation.

In the production of multifilament yarn it frequently is desirable to impart twist to the assembly of individual filaments in an operation separation from the operations associated with the extrusion and collection of the filaments. This separate twisting operation ordinarily should be one that can be carried out at a high production rate for economic reasons. Also, it is desirable that the quality of the yarn not be adversely affected by the conditions existing in the twisting step.

Various types of equipment have been employed heretofore in imparting the desired twist to the multifilament yarns. Delivery twist systems (e.g., uptwisters), receiving twist systems (e.g., downtwisters), and combination delivery twist and receiving twist systems (e.g., up/down- .twisters) have all been used. The combination systems are particularly advantageous from the standpoint of achieving high production, in that part of the twist may be applied at the uptwist station and the remainder applied at the downtwist station without an intermediate winding or packaging operation. For example, where a zero-twist yarn is to be given two turns per inch, one turn per inch may be introduced by the uptwister and one turn per inch by the downtwister. However, in using uptwisting techniques for this type of service, either alone or in combination with downtwisting, some difiiculties have been encountered.

A typical uptwister apparatus setup includes a power driven upright spindle for supporting and rotating a supply package wound with the yarn to be twisted. A guide is disposed above the spindle for guiding the yarn leaving the package periphery, and yarn feeding means, such as driven feed rolls or a yarn takeup, removes the yarn through the guide.

The length of yarn between the supply package and the guide rotates rapidly about the supply package axis during operation, forming what is known as a balloon. The operational stability necessary for the production of uniformly high quality yarn can be achieved only when the balloon configuration is that generated by a single loop of yarn rotating as a unit about the spindle axis. Balloon instability, as reflected by the formation of multi-neck balloon configurations, is detrimental and is often accompanied by separation from each other of the individual filaments making up the portion of the multifilament yarn in the balloon.

Balloon shape in uptwisting is very nearly independent of spindle speed, and the necessary constraints for establishing and maintaining stable balloons must be derived from sources other than speed control. Moreover, in providing a constant restraining force for the rotating loop at the supply package, the yarn tension must not be allowed to increase to a value high enough to adversely affect yarn quality.

This limitation upon tension is particularly troublesome in connection with uptwist systems; Even when such a system is operating in the desired manner, the yarn tension is likely to be higher than that developed in a properly designed downtwist system operating at a comparable production rate. The tension in uptwisting is caused primarily by air drag and is approximately proportional to the square of the spindle speed, whereas in downtwisting the tension is established to a large extent by the friction between the ring and the traveler.

Since the necessity of maintaining a high production rate makes it impractical to reduce significantly spindle speed and since the air drag forces inevitably develop substantial tension in the yarn, the techniques employed for balloon stabilization in an uptwist system cannot be such as to add materially to the tension developed in the yarn if the total tension is to be held to an acceptable level. For example, flyer tension systems have been proposed, but these have been found unsuitable in some instances because the frictional element caused excessive tensions.

Accordingly, it is an object of this invention to provide an improved method and apparatus which will permit uptwisting operations to be carried out eificiently, without the development of excessive yarn tensions and without producing unstable balloons or filament separation phenomena tending to reduce yarn quality.

Another object of the invention is to provide, in a delivery twist system, a novel method of and means for retaining in the balloon portion of the yarn drawn from a supply package a twist level substantially higher than the twist level in the yarn at the output end ofthe system.

In accordance with the invention, the distribution along the yarn of the twist inserted during a delivery twist operation is controlled so as to concentrate the twist in the portion of the yarn forming the balloon. By restraining the passage of twist through the guide at the upper end of the balloon, the effective twist level in the balloon is increased sufficiently to bind the filaments into a unit which rotates about the spindle axis with minimum air drag. Filament separation is avoided and, because of the reduced air drag, there is virtually no tendency toward balloon instability.

Control over twist distribution is achieved, in a preferred embodiment of the invention, by sharply bending the yarn over a narrow guide surface as the yarn passes out of the balloon. The guide surface is quite smooth but has a very short radius of curvature, and there is a substantial change in the direction of yarn movement as it passes over the guide surface. In this arrangement the guide surface holds back or restrains the passage of twist sufficiently to establish the desired twist distribution pattern referred to above. Moreover, yarn tension is maintained at an acceptable low level, because the contact area between the yarn and the guide surface is so small that substantial friction loads are not developed.

A more complete understanding of these and other features and advantages of the invention will be gained from a consideration of the following detailed description of an embodiment illustrated in the accompanying drawings, in which:

FIGURE 1 is a schematic view illustrating an up/downtwist process in which the invention has been applied;

FIGURE 2 is a plan view of a twist retaining guide assembly constructed in accordance with the invention and used in the process illustrated in FIGURE 1;

FIGURE 3 is a side elevational view of the twist retaining guide assembly of FIGURE 2, with a yarn being shown passing therethrough;

FIGURE 4 is a vertical cross-sectional view taken along the line 4-4 in FIGURE 2.

Processes of the type illustrated in FIGURE 1 are applicable to a variety of twisting operations. However, it will be helpful to refer specifically here to the use of the process in the production of one hundred and fifty denier, forty filament, bright cellulose acetate yarn having a twist of about two turns per inch in the Z direction from an asspun yarn.

A supply package 2 containing the as-spun yarn is positioned upon and rotated by a power driven spindle 4. The package 2 is of conventional construction and is sometimes referred to as a metier package. It includes a barrel (not shown) having flanges 6 and 8 thereon, and the as-spun yarn is wound on the barrel in the Zone between the flanges 6 and 8. The maximum diameter of the body of yarn on a full package is, as indicated in FIG- UR-E 1, usually greater than the diameter of the upper flange 6.

The yarn 10 from the supply package 2 is passed through guide means 12 located directly above the spindle 4 and is led away through guide means 14 and '16- to a pair of driven feed rolls 18 and 20. The feed rolls 18 and 20 nip and positively advance the yarn 10 at a speed corresponding to the surface speed of the rolls.

As the spindle 4 and the feed rolls 1 8 and 20 are rotated, the yarn 10 is drawn off the package 2 and twist is inserted into the yarn. The length of yarn extending between the periphery of the package 2 and the guide means 12 is in the form of a loop that rotates about the axis of the spindle 4 at a rate somewhat higher than the rate of rotation of the package 2. The path followed by this whirling loop, designated 22 in FIGURE 1, is the socalled balloon.

The twist inserted into the yarn 10 by the uptwisting operation is determined by the rate of rotation of the spindle 4 and the surface speed of the feed rolls 18 and 20. For example, if the spindle 4 makes one revolution during the time interval required for the feed rolls 18 and 20 to advance the yarn through a distance of one inch, the twist inserted in the yarn would be one turn per inch.

From the feed rolls 18 and 20, the yarn 10 passes through a guide 24 disposed above a downtwist spindle 26, thence through a conventional traveler guide carried by a ring 28 for free rotation about the axis of the spindle 26, and then onto a take-up package 30. The spindle 26 is power driven and serves to rotate the package 30 to impart additional twist to the yarn 10 and wind the yarn onto the package. In this embodiment, the twist imparted to the yarn in the downtwist step is in the same direction, and preferably in substantially the same amount, as the twist imparted by the uptwist step of the process. The total twist inserted into the yarn is, of course, the sum of the twists imparted by the two steps.

The guide means 12 and 14 are part of an assembly shown in greater detail in FIGURES 2, 3 and 4. Both are carried by a rod member 32, one end portion 34 of which is mounted upon the twisting machine.

In the illustrated embodiment, the guide means 12 includes a bent Wire element 36 and a contact element 38 affixed by suitable means 40 to a portion of the wire element 36. The wire element 36 may be a steel wire having a diameter of 0.092 inch, and it preferably is hardened and chrome plated to provide a surface having a mirror finish. The contact element 38 is a Wear resistant insert of metal or some suitable ceramic material, such as aluminum oxide, and its surface also should be quite smooth and free from blemishes. Epoxy cement may be used, as indicated at 40, to secure the insert 38 onto the wire element 36, and it is preferable that the epoxy cement fill all of the spaces between the proximate surfaces of the insert 38 and the wire element 36 so as to securely bound the parts together.

The top of the guide element 38 is provided with a V or U shaped yarn receiving notch 42 of suflicient size to accommodate the yarn being processed. For example, in a guide suitable for use in connection with the processing of denier multifilament yarn, the notch may have a depth of about & inch. The yarn-contacting edge of the notch 42 should be thin or narrow and should curve in the direction of yarn movement over the guide surface. For example, the radius of curvature of the yam-contacting edge of the notch 42 may be in the range from about 0.003 inch to about 0.012 inch and preferably is on the order of 0.004 inch.

The wire element 36 of the guide means 12 serves not only to support the insert 38 but also to guide the yarn 10 into the notch 42 of the insert 38 in the desired manner. Its configuration should additionally be such as to facilitate threading of the guide means.

One end 44 (FIGURE 4) of the wire element 36 is butted against the bottom surface of the rod 32 and soldered or otherwise affixed rigidly thereto. A first portion of the Wire element extends from the end 44 downwardly, then laterally, and then upwardly again in a first vertical plane at right angles to the length of the support rod 32 to form a flat-bottom loop 46 for supporting the insert 38. Continuing, the wire element 36 is bent back upon itself in the same transverse plane to form a front yarn-guiding loop 48 extending beneath the loop 46 as shown in FIGURE 4. At the remote end of the loop 48, a bight portion 50 of the wire guide element 36 extends for a short distance along the length of the support rod 32 and is soldered or otherwise secured thereto. Then the wire element 36 extends downwardly again to form a second yarn-guiding loop 52, the lower portion of which is substantially identical to the lower portion of the first yarn-guiding loop 48. The wire element then extends rearwardly and upwardly as indicated at 54 to join a terminal portion 56 that is soldered or otherwise secured to the bottom of the support rod 32.

The spacing between the first and second yarn-guiding loops 48 and 52 must be sufiicient to permit passage of the yarn 10 therebetween. However, these loops 48 and 52 should be close enough together to guide the yarn to the notch '42 in the guide element 38 along a path lying substantially in a vertical plane. For example, a spacing of about inch has been found to be suitable in connection with the processing of 150 denier yarn.

'It will be observed from FIGURE 2 that the loops 48 and 52 are not connected together at the lateral margin of the guide means 12 remote from the support rod 32. In threading the guide means, a portion of the yarn may be moved laterally into the space between the loops 48 and 52 and then dropped into place within the notch 42 in the guide element 38.

The guide means 14 includes an element 58 of pigtail configuration connected to a depending front end portion 60 of the support rod 32 through a flexible plastic tube 62-. The element 58 preferably is formed of some suitable wear resistant material such as aluminum oxide ceramic or tungsten carbide. As shown in FIGURE 2 of the drawings, the support rod 32 is bent laterally somewhat between the two guide means 12 and .14 so as to dispose the pigtail element 58 in alignment with the notch 42 in the guide element 38. This permits the yarn to be drawn across the edge of the notch 42 along a path extending '5 in a vertical plane at right angles to the vertical plane containing the yarn-contacting edge of the notch.

The relative vertical positions of the guide means 12 and 1 4 are indicated in FIGURE 3. It is necessary that the yarn undergo a sharp change in direction as it moves toward and then away from the notch 42 in the guide element 38. The angle of the direction change should be in the range from 85 to 125, and angles of from about 95 to about 105 have been found to be particularly desirable. This preferred relationship may be established by disposing the pigtail guide element 58 at a level beneath the yarn-contacting portion of the guide element 38.

The illustrated yarn guide assembly is of a construction that permits it to be used in operations for inserting twist in either the S or the Z direction, so that the machine setup changes involved in changing direction of twist are minimal. The guide assembly also is inexpensive and requires little maintenance due to the absence of moving or rotating parts.

This relatively high twist in the balloon portion of the yarn results from the restraints offered by the yarn guiding system of this invention against the passage of twist over the edge of the guide element 38. As a yarn bent sharply over a narrow edge is drawn lengthwise over that edge, there is a tendency for the twist to be redistributed along the length of the yarn, with the turns accumulating in the portion of the yarn leading to the edge. However, the energy stored in the yarn by the twisting action cannot accumulate indefinitely in a short length of yarn, and when the energy level in the balloon portion of the yarn reaches a value sufiicient to overcome the forces applied at the edge of the guide, twist will move past the guide. Thus a dynamic balance is achieved after a short time interval. Thereafter, twist moves past the guide 38 at the same rate that additional twist is inserted into the yarn, and in the dynamically stable twist distribution pattern, the twist level in the balloon portion of the yarn is high as compared with the twist level in the portion of the yarn beyond the guide. The difference in twist levels before and after the guide is suggested schematically in FIGURE 3.

The relatively high twist, e.g. at least about 4-6 t.p.i., in the balloon binds the filaments into a unit which resists air drag forces on single filaments. Filament-to-filament irregularities are therefore avoided and yarn defects are minimized.

The improvements in yarn quality resulting from the use of the invention are most pronounced in that portion of the yarn uptwisted from a full supply package. For example, Whereas the number of faults per unit length in the initial portion (e.g. approximately the first 40,000 yards from a supply pack-age containing about 125,000 yards) of a yarn uptwisted in the conventional manner from a four-pound supply of as-spun 150 denier, 40 filament, bright cellulose acetate yarn was very much higher than in the terminal portion of the yarn, the number of faults per unit length in a comparable yarn uptwisted in accordance with the invention is uniformly low throughout the length thereof.

Moreover, it has been established that the reduction in fault counts resulting from employment of the invention is not accompanied by adverse effects upon yarn physical properties. For example, the tensile properties of comparable yarns processed respectively in a system employing the conventional yarn guide and in a system embodying a twist retaining yarn guide in accordance with the invention were found to be substantially the same.

In this connection, it should be pointed out that use of the twist-retaining yarn guide does not materially raise the level of yarn tension during uptwisting. The yarn-contacting surface of the guide element 38 is smooth, and the yarn passes thereover with little drag being developed.

Also, the tension attributable to air drag on the yarn in the balloon is reduced by the compacting effect of the additional twist in this portion of the yarn. No ditficulty has been experienced in maintaining yarn tension within safe limits, e.g. twenty grams for a 150 denier, 40 filament, bright cellulose acetate yarn.

Of course, the guide element 3 8 should be kept clean and free of yarn waste. Some tendency toward accumulation of waste has been observed, but an effective degree of control over this potential source of yarn defects can be achieved simply by assuring that the guide element is free of waste at the start of each twisting cycle, that is, at the time when a new supply package is placed on the uptwist spindle.

What is claimed is:

1. In an uptwisting process in 'which a multifilament yarn is drawn from a supply package through a guide in such a way as to form a balloon about an end of the package, the improvement which comprises bending the yarn through an angle of from about to about over a narrow edge as the yarn passes away from said guide and out of said balloon to restrain the passage of twist over said edge and cause twist to accumulate in the portion of the yarn in the balloon, said edge being a curved edge having a radius of curvature of from about 0.0003" to about 0.012".

2. A process according to claim 1 wherein said supply package is wound with as-spun continuous multifilament cellulose acetate yarn.

3. A process according to claim 2 wherein said yarn is composed of about forty filaments and has a weight of about one hundred and fifty denier, and wherein the tension of the yarn during processing does not exceed about 20 grams.

4. In an uptwisting apparatus of the type having a driven spindle for receiving and rotating a supply package of yarn to be twisted and yarn feeding means for withdrawing yarn from said package, the improvement which comprises an element positioned above the free end of said spindle and having a narrow upper edge, and guide means for causing the yarn to undergo a sharp change in direction as it passes over said edge, said guide means including surface portions for confining the yarn approaching said edge to a path lying substantially in a vertical plane and including surface portions beyond said edge for contacting the yarn at a location below and laterally spaced from said edge.

References Cited UNITED STATES PATENTS 2,944,382 7/ 1960 Batty et al. 57-62 2,947,136 8/1960 Arridge et al. 57-62 XR 2,451,919 10/ 1948 Clarkson. 2,843,998 7/1958 Schlums 57-59 2,946,176 7/ 1960 Higgins 57-62 2,976,671 3/1961 Steen. 2,981,048 4/1961 Burnell 57-62 3,069,837 12/1962 Olson 28-72 XR 3,153,891 10/1964 Kissler 28-72 XR 3,330,104 7/1967 Dunwoody 57-106 XR 794,427 7/1905 Schmutz 57-60 2,080,918 5/1937 Honig 57-60 3,014,337 12/1961 Pim 57-60 3,016,679 1/ 1962 Rakhorst 57-60 XR FOREIGN PATENTS 132,242 7/1910 Germany.

DONALD E. WATKINS, Primary Examiner.

US. Cl. X.R.

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