US2987869A

US2987869A - Yarn crimping apparatus and methods

Info

Publication number: US2987869A
Application number: US700518A
Authority: US
Inventors: Norman E Klein
Original assignee: Milliken Research Corp
Current assignee: Deering Milliken Research Corp; Milliken Research Corp
Priority date: 1957-12-03
Filing date: 1957-12-03
Publication date: 1961-06-13
Anticipated expiration: 1978-06-13

Description

June 13, 1961 N. E. KLEIN 2,987,869

YARN CRIMPING APPARATUS AND METHODS Filed Dec. 3. 1957 INVENTOR. NORMAN E. KLEIN Eva/$5M ATTORNEY 2,987,869 YARN CRIMPING APPARATUS AND METHOD Norman E. Klein, Pendleton, S.C., assignor to Bearing Milliken Research Corporation, Oconee, S.C., a corporation of Delaware Filed Dec. 3, 1957, Ser. No. 700,518 13 Claims. (Cl. 57-34) This invention relates to novel methods and apparatus for the production of torsionally stressed thermoplastic yarns which tend to kink and curl when in an untensioned condition.

Torsionally stressed thermoplastic yarns which tend to kink or curl are well known in the art and are widely employed because of their elastic nature for a variety of purposes. They can be prepared by any number of well known processes, but the process which is presently most widely employed consists of highly twisting an end of yarn, setting the twist, for example, by means of heat and thereafter untwisting the yarn. The thus treated yarn forms into loops and curls, when in an untensioned condition, in an effort to relieve the torsional stresses created by the heatsetting and twisting operations. The twisting and untwisting of the yarn in a process of this nature can be accomplished by the insertion of a true twist followed by a down twisting operation or it can be accomplished by applying a false twist to a section of a running length of yarn and heatsetting the twist before it is removed.

The false twist method of producing a torsionally stressed yarn has the advantage that the yarn need be handled a fewer number of times and the advantage of a relatively high production rate, but has the disadvantage of requiring complicated apparatus not generally suitable for other use in the textile industry. Prior to this invention, the false twist method has generally required a rapidly rotating member, journaled at either end, which is provided with a central yarn passage for the yarn and means within the passage to force the yarn to rotate with the rotating member. One of these rotating members has been required for each strand of yarn being processed and, of course, there is also required a system of pulleys, belts or the like for driving each of the rotating members. Even though the method is faster than the true twist procedure, it will be apparent to those skilled in the art that the speed of rotation of a member such as described above must be relatively slow and this means that a large number of units and a considerable expenditure of power will be'necessary for the production of yarn in quantity. i

It is an object of this invention to provide novel methods and apparatus for the production of torsionally stressed yarns which overcome the disadvantages of prior art methods and apparatus.

It is another object of the invention to provide apparatus for the production of torsionally stressed yarns which apparatus is simple in design, inexpensive to manufacture and economical to operate.

It is still another object of the'invention to provide apparatus for producing crimped or curly yarn by the false twist procedure at a rate far in excess of that heretofore possible.

It is a further object of the invention to provide a method for simultaneously processing two strands of yarn wherein each of the strands acts to insert false twist into the other.

The above as well as other objects of the invention are accomplished by an apparatus wherein two or more ends of'yarn under approximately equal tensions are wrapped several turns about each other and thereafter separated and collected at substantially equal linear velocities. It has been found that this single operation can result in 'nited States atent a high degree of false twist being inserted into each of the yarn ends, and if the yarn ends are heated while they are in a highly twisted condition and are then allowed to cool or are cooled before they are untwisted, an appreciable torsional stress is imparted in untwisting the yarns so that they subsequently assume a highly convoluted linear configuration when in a substantially tensionless condition.

The invention is operable with any thermoplastic yarn which is capable of having a twist heat-set therein. Typical examples of suitable yarns are cellulose acetate, ny- =lon, polyester yarns such as that sold under the trademark Dacron, and acrylic yarns such as those sold under the trade-marks of 'Acrilan and Orlon. The invention is best employed with continuous filament yarns but if desired can frequently be employed to advantage with spun yarns. It has also been found that best results are obtained with monofilamentary strands such as 15 denier monofilament yarn but again the invention can also be employed with multifilamentary strands. The invention can be employed with yarns of any total denier but is preferably employed with smaller yarns, for example below about denier. The maximum amount of twist that can normally be inserted by the new method is approximately one turn of twist per VEJnD length of yarn, where D is the diameter of the yarn, and it will, therefore, be apparent that if the diameter of the yarn is large, twist per unit length will be low.

One preferred form of apparatus for performing the new method of the invention will now be described with reference to the accompanying drawing which is a schematic view in perspective. The illustrated apparatus is suitable for simultaneously processing only two ends of yarn but it will become apparent that the apparatus might be readily modified to handle three or more ends.

With reference to the drawing in greater detail, there is illustrated a pair of yarn supply packages 10 and 11, in each instance containing a supply of yarn. Yarn ends 12 and 13 are passed from the supply packages 10 and 11 through a pair of pigtail guides 14 and 15, positioned axially of the yarn supply packages, which permits the yarn to be readily withdrawn from the packages in an over-end manner.

Means are preferably provided for placing the yarn ends 12 and 13 under substantially equal tensions and in this instance is illustrated as comprising a driven roll 17 about which each of the yarn ends 12 and 13 may be wrapped one or more turns. The roll 17 is carried by a shaft 18 which in turn is rotated by means of a sprocket 19 and a block chain 20. Chain 20 runs about a second sprocket 21 on a shaft 22 which in turn is driven by an electrical motor 23 or by any other suitable source of power through a belt 24. Shaft 22 serves as a driving means for a pair of conventional yarn takeup devices in this instance illustrated as comprising a pair of rolls '25 and 26 carried by the shaft 22 and engaging the yarn surfaces on a pair of

takeup spools

27 and 28. As will be apparent to those skilled in the art, this results in the yarn being collected at a uniform velocity regardless of the diameter of the yarn on the takeup package, and if the roll-s 25 and 26 are of the same diameter, yarn will be collected by spool 27 at substantially the same rate as by spool 23. A conventional transverse mechanism 29 is schematically illustrated and is for the purpose of winding the yarn evenly on the takeup packages.

The yarn ends from supply means 10 and 11 may be under very low tensions since little resistance is met in removing the yarns in an over-end manner, and to additionally tension the yarn ends to an extent that they do not slip over the surface of roll 17, there is provided a pair of pretensioning devices 40 and 41. The tensioning 3 devices 40 and 41 are illustrated as being of the disc type, but may be of any conventional design or construction.

The illustrated arrangement, having a feed roll ar.

ranged for rotation ate constant rate with respect to the takeup rolls, is extremely advantageous for use with yarns, such as nylon, which shrink an appreciable degree when heated. The speeds of rotation can be. such that the peripheral velocity of roll 17 is slightly, for example 1 to in excess of the peripheral velocity of rolls and 26, since the yarn will shrink to remove any slack that might otherwise result, and under such conditions it will be found that the tension in the yarn is a characteristic of the specific yarn being employed and of the temperature applied. In other words, the tension in a strand of nylon yarn being fed by roll 17 to spool 28 will be substantially identical to the tension in a strand of nylon yarn being fed from roll 17 to spool 27 if the temperature applied to both yarns is substantially equal and if the degree of overfeed is not in excess of about 10. With yarns that do not tend to shrink upon heating, an overfeed arrangement cannot be employed and roll 17 must have .a peripheral velocity substantially equal to or slightly less than that of

rolls

25 and 26. In fact, with yarns of this type it isgenerally advantageous to employ tension regulating means of a more conventional type. Almost any conventional type of tension regulating device or even some types of simple tensioning devices can be employed since it is not necessary that the yarns be under identical tensions and the tensions in the strands may operatively difier as much as 10% or more. With some types of yarn supply means it is even possible to dispense with supplementary tensioning means entirely since the supply means will deliver the yarn ensd under tensions which sufficiently approximate each other to give operative results. It is, however, generally advantageous to employ supplemental tension regulating means so that the two yarn ends are under as nearly the same tensions as possible since otherwise, when the two ends are twisted together, the end having the higher tension will serve more or less as a core for the end under a lower tension. This not only lessens the degree of frictional contact to an extent that may permit an objectionable degree of slippage, but can also result in more twist being inserted in one strand than in the other so that the two yarns, after processing, do not have comparable activities.

Positioned between the roll 17 and the transverse member19 are four yarn

guide idler pulleys

30, 31, 32 and 33 positioned with respect to each other so as to form the corners of an elongated rectangle. These pulleys may be supported in any suitable manner and are, therefore, indicated only schematically in the drawing. Positioned in substantially the same plane as the pulleys to 33 is a plate member 34- preferably made of a heat conducting metal or the like and which has a polished upper face suitable for slideably engaging a strand of yarn. The plate 34 is adapted to be cooled by means of a con duit 35 carried by its lower face and through which may be circulated a cooling fluid or the like. Also lying in substantially the same plane as pulleys 30 to 33 and positioned between pulleys 3t) and 31 and plate 34 is a second plate indicated by the reference numeral 36. The plate 36 is also preferably made of metal or other heat conducting material and has a smooth upper face for slidably engaging a plurality of strands of yarn. The plate 36 is adapted to be heated by any suitable means such as by an electrical resistance unit carried on its lower face and supplied with power from any suitable source, not illustrated, by means of conductors 37.

In operation, the yarn ends 12 and 13 are lead from supply packages 10 and 11 through guides 14 and 15 to 'pretensioning means '40 and =41 and are thereafter passed one or more turns around feed roll 17. The two ends of yarnare then passed about

guide pulleys

30 and 31 and twisted together for a plurality of turnsas indicated'be- 4 tween the

reference numerals

38 and 39. The two ends are then separated, passed about

guide pulleys

32 and 33 and over the transverse means 29 to takeup

spools

27 and 28. Plates 3-6 and 34 are then brought to the desired temperatures and motor 23 is-energized to result in the two strands of yarn being drawn through theapparatus and collected on rolls 27 and 2d.

The plying together of the two ends of yarn causes them, in effect, to roll over each other as they are moved through their respective linear paths and this results in the yarn ends being individually twisted at the point 33 and then being untwisted as they are separatedat the point 39. In other words, the yarn ends are individually twisted between the point 39 and the pulleys-30 and 31, as well as being twisted about each other between the pointsSS and 39. if plate 36 is at a sufiiciently high temperature, the twist in the

yarn'between pulleys

30 and 31 and point 33 is heat-set therein so that the yarn normally tends to twist when in a relaxed conditon and since the yarn is cooled belowa heat-setting temperature by the time it reaches the point 339., .removal of the twist at this point torsionally stresses both yarn ends. Therefore, the yarn collected onpackages 27 and 28 will tend .to kink, cur-l or loop when it is removed therefrom and relieved of tension even though it maybe in a substantially untwisted condition.

In View of the above discussion, it will be apparent that the yarn ends .may be heated at any point in their linear paths where they are in a highly twisted condition if sufficient time is allowed for cooling before the ends reach the point where they are separated. However, the illustrated arrangement, wherein the yarn are heatedwell in advance of the point of mutual contact, is preferred since this allows more time for cooling than would be available if the yarns were, for example, heated at a point intermediate the

points

38 and 39 and, in'addition, better contact of the yarn with the heater element-is obtained. it is likewise not generally advantageous to have a heater element or the like in contactwith the yarns at the exact point at which they are brought together, since this might interfere with the twistingof :the individual ends.

The degree of twist inserted into the individual yarn ends depends upon the number of turns per unit length with which the two ends are plied together between the poins 38' and 39 and this in turn depends upon the diameter of the yarn ends, upon the angle between the yarn ends as they are brought'together, the angle between the yarn ends as they separate and, to some extent, upon the tension employed. With yarn of a given diameter, the most convenient means of increasing or decreasing the degree of twist inserted in the individual ends comprises increasing or decreasing the angles between the yarn ends at the point where they come together and/or separate. This can readily be accomplished in the embodiment illustrated by increasing or decreasing the number of turns with which the ends are plied together or more satisfactorily by increasing the distance between

pulleys

30 and 31 and/or the distance between the pulleys 3'2 and 331. Generally, the distances between the two sets of pulleys should be adjusted so that the angles between the two ends as they approach and as they separate are, in each instance, between about 30 and but a very low degree of twist is desired, the angles may in each instance be as small as about 10, and ifa-very'high degree of twist is desired, the angles maybe as large as or even in some instances.

The number of turns that the yarn should be twisted together between the

points

38 and 39 .is not critical, but should be at least a sufiicient number of turns toelimimate, to a large extent, slippage between the two ends of yarn. Twisting the yarns together for two turns will generally give operative results if the; yarns are under a relatively high tension, for-example l to 2Igms. per denier, but :as a general 111181116 yarn should be twisted together for at least aboutlO to 15 :ormore turns. There is no upper limit as to the number of turns-that may b employed in twisting the two yarn ends together, but as a general rule there is no advantage in twisting the two yarns together more than about 20 to 30 turns.

The minimum tension under which the yarns should be placed depends upon the size of the yarn and the number of turns which the yarns are twisted together. The yarns should be under sufiicient tension to insure adequate frictional contact between each other and to prevent kinking of the yarns at the point where they are highly twisted and yet the tension should not be so high as to stretch the yarns. As a general rule it can be said that operative limits run from about 0.01 gm. per denier to about 1 to 4 gms. per denier with the preferred range being from about 0.05 to 0.6 gms. per denier.

The temperature of the plate 36 necessary for adequate heat-setting of the yarns is a function of the type and size of the yarns being processed, of the width of the strip, and of the linear velocity of the yarn. Of course, the important consideration is that the yarn reach a proper heat-setting temperature and, as is well known, various types of yarns require difierent temperatures for a reasonable degree of heat-setting to be efiected. With nylon yarns, it is generally preferable to make certain that the yarns reach a temperature of at least about 160 F. and preferably a temperature of about 240 F. or higher. On the other hand, the yarns should not be heated above their sticking temperature since if heated above this temperature they tend to stick to the heating plate. The sticking temperature for nylon is about 450 F. so that this is an operative upper limit for nylon yarns and as a general rule, it is not advantageous to heat nylon yarns above about 380 F. Inasmuch as heat-setting of yarns is such a common practice and is a procedure familiar to those skilled in the art, a proper temperature for other types of yarn will be readily apparent from the above discussion or can be readily determined by routine tests.

The temperature of plate 34 is not critical and indeed it the yarn speeds are slow enough, for example below about 25 to 50 yards per minute, the yarn will cool sutficiently to give good results even though plate 34 is eliminated and the yarn is allowed to cool by open contact with the atmosphere. With very high yarn speeds, however, it is possible that the yarn ends may reach the point 39 while still at a temperature sufiiciently high to result in loss of some of the tendency to twist previously imparted and for this reason the plate 34 should be employed with such yarn speeds and retained at a temperature to result in the yarn being cooled, before it reaches the point 39, below a point at which it loses its tendency to twist. By the use of a cooling plate and a very eifective heating means, linear yarn speeds up to 500 yards per minute, or even higher, can be achieved. For nylon yarns the temperature at which the yarn will retain, to a large extent, its tendency to twist is in the vicinity of 160 F. so that the plate 34 should be designed to insure that the yarn will be below this temperature by the time it reaches point 39. A corresponding temperature for other types of yarn will be readily apparent to those skilled in the art or can be determined by routine tests.

The elasticity or activity of yarns prepared according to this invention can be materially increased by subjecting the same to a heat treatment while they are under such a low tension that they are free to contract. This operation can, if desired, be postponed until after Weaving or knitting, and it is generally more convenient to heat treat the yarn in fabric form.

Having thus described my invention, what I desire to claim and secure by Letters Patent is:

1. An apparatus for processing yarn comprising in combination a plurality of yarn supply means to supply separated ends of yarn, a plurality of yarn takeup means for collecting separated ends of yarn at substantially equal rates, whereby when yarn ends from said supply means are plied together a plurality of turns, separated and thereafter collected by said takeup means, a false twist is inserted into each of said yarns, and yarn heating means to heat each of said yarn ends in an area where they are in an individually twisted condition and spatially separated trom each other. 4

2. Apparatus for processing yarn comprising in combination a pair of yarn supply means to supply two separated ends of yarn, a pair of yarn takeup means for collecting two separated ends'of yarn at substantially equal rates, means for placing said yarns under approximately equal tension prior to their being collected by said takeup means, whereby when two yarn ends are passed from said supply means to the tensioning means, twisted a plurality of turns about each other and are thereafter collected by said takeup means, a false twist is inserted into each of said yarns, and yarn heating means to heat the twisted yarn ends between said tensioning means and the point at which said yarn ends operatively come into contact with each other.

3. Apparatus according to claim 2 wherein said tensioning means comprises a driven feed roll for delivering an equal length of said two yarns to said takeup means.

4. Apparatus according to claim 2 including means to cool said yarns at the point where they are in mutual contact.

5. Apparatus for simultaneously processing two running lengths of yarn comprising in combination means to supply two yarn ends and to transport the same under tension over linear paths at substantially equal linear velocities, first and second pairs of separated yarn guide means positioned within the paths of said yarn ends, and yarn heating means for heating said two yarn ends while they are spatially separated, said heating means being positioned between said first pair of yarn guide means and a point equidistant from said two pairs of yarn guide means, whereby the two yarn ends, when passing from said first pair of yarn guide means, wrapping several turns about each other and thereafter separating to pass to said second pair of yarn guide means, act upon each other to result in the yarn ends being twisted between the point of mutual contact and said first pair of yarn guide means, and said twist is heat-set by said yarn heating means.

6. Apparatus for simultaneously processing two running lengths of yarn comprising in combination means to supply two yarn ends and to transport the same under tension along linear paths at substantially equal linear velocities, first guide means positioned in the yarn paths of said yarn ends to maintain said yarn ends separated one from the other at a first point in their line of travel, second guide means, spaced from said first guide means, to maintain said yarn ends separated one from the other at a second point in their line of travel, whereby when said ends are twisted a plurality of turns about each other between said first and second points, the yarn ends act upon each other to insert false twist, and heating means positioned in the paths of said yarn ends between said first guide means and the point where the yarn ends are operatively in mutual contact.

7. A method for simultaneously imparting a tendency to curl, kink and loop to a pair of thermoplastic yarn ends being transported through linear paths at substantially equal velocities which method comprises separating said yarn ends at a first and at a second point in their line of travel, passing said ends a plurality of turns about each other in an area intermediate said first and second points, retaining said yarn ends under approximately equal tensions between said first and second points, whereby the yarn ends acting upon each other in said area of mutual contact causes a false twist to be inserted into each of said yarn ends, heating said yarn ends in the portions of their respective yarn paths immediately preceding the area of mutual contact and while they are in a twisted condition, and subjecting said yarn ends to cooling conditions to cool the same below a heat-setting temperature 7 at the point where their mutual contact with each other is rmi ated- 8- A 1, e hod a c rding to claim 7 wherein sa yarns are twisted together for ,from about 10 to 25 turns.

9. A method according to claim 8 wherein said there moplastic yarns are nylon, said yarns are retained under equal tensions of approximately 0.2 to 1.0 gm. per denier, the twisted yarns are heated to a temperature of at least about 240 F. preceding the point at which they are in mutual contact, and said yarns are cooled to a temperature of not more than about 160 F. before their mutual Contact is terminated.

10. A method according to claim 7 wherein said yarn ends are positively fed into said portions of their respective yarn paths where they are heated, at a linear rate in excess of that at which they are withdrawn from said portions of their yarn paths to thereby permit the yarns to contract'upon being heated.

11. Apparatus for simultaneously processing two running ends of yarn comprising in combination means to supply two ends of yarn, first guide means to retain said two ends of yarn in spaced relationship with respectto each other, second guide means to retain said ends of yarn in spaced relationship with respect to each other, a. contact yarn heater, to heat said two yarn ends by conduction, disposed in intermediate yarn flow relationship with respect to said first and second guide means, the positional relationship of said contact yarn heater and said guide means being such that said two ends of yarns can be passed a plurality of turns about each other between said first and second guide means so that each of said ends is individually false twisted and said contact yarn heater heats said two yarn ends only in an area where they are spatially separated from each other, and the twist is heat-set thereinby passage of said two ends of yarn into effective heating relationship with said contact Cit yarn heater, yarn advancing means, disposed in intermediate yarn flow relationship with respect to said supply means and saidfirst guide means, to positively advance ea h f s id en of Ya n at an equal an s stant y constant first linear rate, means disposed in subsequent yarn flow relationship with respect to said second guide means to positively advance each of said ends of yarn at an equal and substantially constant second linear rate which is less than said first linear rate, whereby the tension in each of said ends of yarn between said first and second guide means is determined primarily by the thermal contraction characteristics of said yarns.

12. Apparatus according to claim 11 including yarn cooling means to cool said two yarn ends in an area between said two guide means where said two yarnends are in mutual contact.

13. Apparatus according to claim 11 wherein said means to advance said yarn ends at a second selected linear rate comprises a pair of constant linear rate yarn collecting means.

References Cited in the file of this patent UNITED STATES PATENTS 2,76l,272 Vandamme Sept. 4, 1956 2,890,568 Willens June 16, 19-59 FOREIGN PATENTS 1,072,786 France Mar. 17, 1954 1,076,599 France Apr. 21, 1954 1,120,046 France Apr. 9, 19-56 OTHER REFERENCES Moncrieff: Artificial Fibers, copyright 1954, page '270, John Wiley and Sons, Inc, New York. (Copy in Division 21.)