US3890422A - Method of drawing yarn using a plurality of separator rolls with each driven roll - Google Patents

Abstract

A plurality of skewed freely rotating separator rolls associated with a driven yarn forwarding roll are positioned so that each handles one wrap of a multi-wrap threadline arrangement around the driven roll. The yarn or threadline contacts the surface of the driven roll in wraps of at least 150* in the first and last contacts with the driven roll and at least 30* on each intermediate contact.

Description

O United States Patent 1 in] 3,890,422 Livingston 1 June 17, 1975 METHOD OF DRAWING YARN USING A 2.956.330 10/1960 Pam 264/290 N PLU OF SEPARATOR ROLLS WITH 2,988,866 6/1961 Kleekamm et a1. 264/290 T l FQWICT et a1 1 1. 3,400,194 9/1968 Boone et a1... 264/290 T [75] Inventor: Richard Donnan Livingston, 3,471,608 10/1969 Schippers....,........i.......... 264/290 R Seaford, Del.

[73] Assignee: E. l. du Pont de Nemours &

' Primary Exammer-R0bert F. White Company Wilmington Assistant Examiner.1ames B. Lowe [22] Filed: Apr. 26, 1974 [21] Appl. No.: 464,368

Related US. Application Data 57] ABSTRACT [63] Continuation-in-part of Ser. No. 387,049, Aug. 9,

1973, abandoned.

A plurality of skewed freely rotating separator rolls [52] US, Cl 264/290 R; 23/713; 264/D 73; associated with a driven yarn forwarding roll are posi- 425/131 17 tioned so that each handles one wrap of a multi-wrap 511 Int. Cl. B291: 17/02 headline arrangement around the driven roll. The [58] Field of S h 264/290 210 F D[(} 73; yarn or threadline contacts the surface of the driven 23 713; 425/ 1(] 17 131 153 roll in wraps of at least 150 in the first and last contacts with the driven roll and at least 30 on each [56] References Cited intermediate contact.

UNITED STATES PATENTS 2,883,733 4/1959 Notarbartolo el al. 28/713 3 Claims, 3 Drawing Figures PATENTEDJUH 17 I975 SHEET FIG- FIG-

r1 mu PATENTEDJUN17 ms -,890.422

SHEET 2 FIG-3 1 METHOD OF DRAWING YARN USING A PLURALITY OF SEPARATOR ROLLS WITH EACH DRIVEN ROLL CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part of my copending application Ser. No. 387,049, filed Aug. 9, I973 and now abandoned.

BACKGROUND OF THE INVENTION This invention concerns processing of polymeric fila ments and threads, more particularly, means for positively controlling the elongation of such synthetic threads, especially when multiple threads are processed simultaneously.

Synthetic filaments and yarns are usually stretched after solidification to increase their tenacity, stretching usually being accomplished by driven rolls running at different speeds. Various means have been employed to prevent slippage of the yarn on driven rolls, such as employing a series of driven rolls or an elastomer coated second roll. The least expensive method is usually a freely rotating roller located at a distance from and approximately parallel to the driven roller so that the yarn may be wrapped more than once on the driven roller. However, subsequent wraps of the yarn must not touch previous ones if abrasion and entangling are to be avoided. To accomplish this separation of sebsequent wraps, the axis of the separator roll is either canted or skewed with relation to the axis of the driven roll, canted meaning that the axes of the two rolls intersect when extended and skewed meaning that the axes are not parallel and do not intersect. Cant is usually undesirable because the distance between the two rolls varies along their length, requiring the yarn to stretch or retract, and yarns tend to slide erratically on the inclined roll surfaces. Skewed rolls, however, do not have these disadvantages if the yarn is positioned where the distance between the two axes is least. On the other hand, when very long skewed rolls are employed, as when a single yarn is wrapped many times or when a large number of parallel yarns are handled simultaneously, it can be seen that the distance between the axes of two skewed rolls can be substantially greater than the minimum distance at the end of the rolls. Thus, when a large number of parallel yarns are handled simultaneously, the yarns on the extreme ends have a much greater tendency to slide or scuff than those at the middle. When such instability occurs, filaments may be transferred from one multifilament yarn to another, giving finished yarns with the wrong number of filaments. In addition. such instability results in broken filaments and in variable degrees of drawing of the yarn.

When yarns are stretched between two rolls driven at different speeds, it is particularly important that slippage be minimized at each roll; therefore, the yarn should have a maximum possible degree ofwrap on the roll which it is leaving and the roll which it is approaching. This is particularly important in so-called two-stage drawing where the yarn is partially drawn in a firstdrawing stage and is drawn the remainder of its ultimate draw in a second stage. The properties, such as dyeability, of the final product having a certain total draw may be quite different depending upon the proportion of draw taken in the first and second stages. Therefore, it is important that all yarns of a multiple bundle should be in stable contact with each roll so that all are treated equally and uniformly with minimum abrasion,

A particular problem of using multiple wraps on a single separator roll can be seen where undrawn yarn coming from the spinning operation is wrapped several times around a single separator roll associated with a driven feed roll. The tension in the filaments from the spinning operation is low whereas the tension in the yarn leaving the feed roll is high as it enters the first draw zone. This high tension generally results in slippage of the last wrap so that the yarn on the last wrap of the separator roll tends to move forward while the yarn on the first wrap of the separator roll coming from the spinning operation tends to lag. Thus, the yarn at opposite ends of the separator roll subjects the roll to conflicting tendencies and the separator roll speed may; vary erratically depending upon the degree of slippage and yarn stability. Such conflicting tendencies are particularly damaging when yarn passes over such a separator roll before its first contact with or after its last contact with the driven roll.

SUMMARY OF THE INVENTION In a method for drawing synthetic yarn that includes passing substantially undrawn yarn in multiple spaced surface wraps around a driven feed roll and a plurality of associated separator rolls, then passing the yarn in multiple spaced wraps around a driven draw roll and its associated separator rolls while maintaining the yarn between the feed and draw rolls at drawing tension, all rolls being of constant diameter, the axis of said separator rolls being skewed with respect to the axis of said driven rolls, the improvement comprising: passing the yarn in multiple wraps around the driven rolls while contacting each of their associated separator rolls only once, therebeing one wrap on the driven roll for each associated separator roll. The yarn or a band of parallel yarns is centered on the separator roll at or near the point of closest approach of the axis of the separator roll to the axis of the driven roll. Yarn contacts a separator roll only after its first contact with a driven roll and before its last contact therewith. Preferably, the yarn or yarns wrap at least on the surface of the driven roll at the first and last contacts therewith and at least 30 on each intermediate contact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows synthetic yarn passing from spinning through two stages of drawing according to the method of the invention.

FIG. 2 is the right-hand side view of FIG. 1. FIG. 3 is an alternate embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, multiple yarns 13, each consisting of a number of polymeric filaments, are extruded from spinnerets in spinning block 14 and are solidified before they reach guides 15 and 16 which keep the yarns separated from each other but closely spaced as they approach positively driven feed roll 17. The yarns contact feed roll 17 for an average wrap of about and then pass via path 1 to freely rotating separator roll 18 which is skewed to advance the yarns as they approach feed roll 17 via path 2. They contact feed roll 17 for about 55 of wrap and then pass via paths 3 and 4 around skewed separator roll 19 and back to feed roll 17. They contact feed roll 17 for about 35 of wrap and then pass via paths 5 and 6 around skewed separator roll 20 and back to feed roll 17. They contact feed roll 17 for slightly more than 180 of wrap and then pass via path 7 to first draw roll 21 which is positively driven at a faster rate than feed rool 17 so that the yarns are partially drawn under drawing tension maintained between the two. The yarns contact first draw roll 21 for about l60 of wrap and then pass via paths 8 and 9 around freely rotating skewed separator roll 22 and back to first draw roll 21. Here they wrap about 30 and pass via paths l and 11 around skewed separator roll 23 and back to first draw roll 21. They wrap on roll 21 for slightly more than I80 and then pass via path 12 to a pair of second draw rolls 24 which are positively driven at a faster rate than first draw roll 21. The yarns are drawn additionally between first draw roll 21 and second draw rolls 24.

Since the speed at which filaments are removed from the spinneret is governed by the feed roll, it is important that maximum contact be maintained between the yarn and feed roll during its first contact. The arrangement of the invention permits an average wrap of at least 150 around the feed roll at its first contact. The arrangement also allows a wrap of at least I80 on the last wrap before the first draw zone. The provision of an intermediate separator roll 19 permits the first and last separator rolls to be located in positions providing high degrees of wrap. However, high degrees of wrap are not necessary on intermediate contacts between the yarn and driven roll as, for example, between paths 2 and 3 and paths 4 and 5. It has been found that wraps of at least 30 are desirable to prevent wandering of the yarns at such intermediate contacts.

An additional advantage of the roll arrangement shown in FIGS. 1 and 2 is that the yarn progresses in a single rotational direction, i.e., clockwise, while being wrapped around the driven rolls and their associated separator rolls. A person stringing up such a machine can proceed more rapidly and with less chance of error if all wraps are made in the same direction,

If separator roll 19 is positioned so that yarn goes directly from separator roll 18 to 19 or separator roll 19 to 20 without contacting the driven roll, the yarns become unstable. This may be partly caused by the fact that such pairs of rolls may have opposite skews.

However, FIG. 3 shows one method of minimizing such problems. In this alternative embodiment multiple yarns contact feed roll 17 for an average wrap of about I70 and then pass via path 1' to freely rotating separator roll 25 which is skewed to advance the yarns as they approach feed roll 17 via path 2'. They contact feed roll 17 for about 100 of wrap and then pass via path 3 to separator roll 26. The yarns then pass via path 4 to separator roll 27 and then back to feed roll 17 via path They contact feed roll 17 for about 180 of wrap and then pass via path 6' to first draw roll 21 driven at a faster rate than feed roll 17. The yarns Contact first draw roll 21 for about l60 of wrap and then pass via path 7' to separator roll 28. From roll 28 they pass via path 8' to separator roll 29 and then via path 9' to first draw roll 21. They wrap on roll 21 for about [60 and then pass via path 10' to second draw rolls (not shown).

Scuffing and instability of the yarns is minimized in the arrangement of FIG. 3 because the yarns have a greater degree of wrap on feed roll 17 between paths 2' and 3' than between paths 2 and 3 of FIG. 1, and because the yarns need to advance axially along feed roll 17 only one band width in traversing paths 3', 4 and 5' and, therefore, the skew angles of rolls 26 and 27 can be smaller than those for rolls l9 and 20 of FIG. 1.

Individual separator rolls for each wrap of yarn allow the yarn to seek its preferred speed. Thus, the elongation which the yarn may undergo in changing from the low tension in the spinning zone to the high tension of the draw zone can take place without affecting other portions of the yarn path. Similarly, when going from the first draw zone to the second draw zone in which the tension is higher, the yarn speeds may be slightly different between paths 8 and 9 and paths l0 and 11 due to controlled and minimized slippage.

It has been found that when large changes in tension and elongation in synthetic yarn occur, as in drawing the yarn, slippage or rolling of yarn on a driven roll may be minimized through use of this invention.

Other arrangements of separator rolls than those shown in the drawings may fall within the present invention. For example, if the arrangement of other machine elements in FIG. 1 were such that yarn path 7 leaving feed roll 17 were in a 10 oclock direction, sep arator rolls 19 and 20 could be spaced between rolls 17 and 18 on a line between their centers.

What is claimed is:

1. In a method for drawing synthetic yarn that includes passing substantially undrawn yarn in multiple spaced surface wraps around a driven feed roll and a plurality of associated separator rolls, then passing the yarn in multiple spaced wraps around a driven draw roll and its associated separator rolls while maintaining the yarn between the feed and draw rolls at drawing tension, all rolls being of constant diameter, the axis of said separator rolls being skewed with respect to the axis of said driven rolls, the improvement comprising: passing the yarn in multiple wraps around the driven rolls while contacting each of their associated separator rolls only once, therebeing one wrap on the driven roll for each associated separator roll.

2. The method of claim I, the first and last wraps on each driven roll being at least with each intermediate wrap being at least 30".

3. The method as defined in claim 1, said yarn contacting each separator roll once at the point of nearest approach of the axis of the separator roll to the axis of the associated driven roll.

Claims (3)

1. In a method for drawing synthetic yarn that includes passing substantially undrawn yarn in multiple spaced surface wraps around a driven feed roll and a plurality of associated separator rolls, then passing the yarn in multiple spaced wraps around a driven draw roll and its associated separator rolls while maintaining the yarn between the feed and draw rolls at drawing tension, all rolls being of constant diameter, the axis of said separator rolls being skewed with respect to the axis of said driven rolls, the improvement comprising: passing the yarn in multiple wraps around the driven rolls while contacting each of their associated separator rolls only once, therebeing one wrap on the driven roll for each associated separator roll.

2. The method of claim 1, the first and last wraps on each driven roll being at least 150*, with each intermediate wrap being at least 30*.

3. The method as defined in claim 1, said yarn contacting each separator roll once at the point of nearest approach of the axis of the separator roll to the axis of the associated driven roll.

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