US3807162A - Covered elastic yarn - Google Patents

Abstract

The present invention relates to a covered elastic yarn with an elastic thread as a core yarn, and a continuous thermoplastic multifilament thread as a sheath yarn, wherein the respective filaments forming said covered elastic yarn are respectively tangled with each other to retain flux form, and at the same time to form the sheath-core system, and said sheath yarn wraps the outer periphery of said core yarn but is reversed irregularly and intermittently in said direction, and said sheath yarn and said core yarn are substantially twistless.

Description

United States Patent [191 Tsujita et al. I

[ 1 Apr. 30, 1974 COVERED ELASTIC YARN Inventors: Yasuo Tsujita; Toshihiko Kimura,

both of Otsu; Shigeji Yamashita, Shiga-ken; Kazuo Yuki; Hiroshi Asami, both of Ot'su, all of Japan Assignee: Toray Industries, Inc., Tokyo, Japan Filed: Ma 17, 1971 Appl. N0.: 143,940

Foreign Application Priority Data May 18, 1970 Japan 45-41579 US. Cl. 57/152, 57/157 TS, 57/163 Int. Cl D02g 3/32 Field of Search 57/34 HS, 12, 152, 163, 57/157 TS References Cited UNITED STATES PATENTS 11/1966 Rapuza 57/152 3,393,505 7/1968 Reid et a1. 57/152 3,447,296 6/1969 Chidgey et al.... 57/34 HS 3,460,338 8/1969 Morrison 57/ 163 3,540,204 11/1970 Tanaka et a]. 57/163 Primary Examiner.lohn Petrakes [57] ABSTRACT The present invention relates to a covered elastic yarn with an elastic thread as a core yarn, and a continuous thermoplastic multifilament thread as a sheath yarn, wherein the respective filaments forming said covered elastic yam are respectively tangled with each other to retain flux form, and at the same time to form the sheath-core system, and said sheath yarn wraps the outer periphery of said core yarn but is reversed irregularly and intermittently in said direction, and said sheath yarn and said core yarn are substantially twistless.

6 Claims, 15 Drawing Figures mmmmsomm 3.807162 SHEEI 1 (1F 3 PRIOR ART Fig. I

PRIOR ART Fig.2

lNV EN TORS YASUO TSUJITA, TOSHIHIKO KIMURA, SHIGEJI YAMASHITA,

KAZUO YUKI 0nd HIROSHI ASAMI ATTORNEYS.

PATENTEDAPR 30 m4 SHEET 2 OF 3 [NVENTORS YASUO TSUJITA, TOSHIHIKO KIMURA, SHKSEJI YAMA KAZUO YUKI and HIROSHI ASAMI SH ITA ATTORNEYS.

rmmzmmu m4 SHEET 3 0F 3 INVENTORS. YASUO TSUJITA,TOSHIHIKO KIMURA, SHIGEJI YAMASHITA, KAZUO YUKl 0nd HIROSHI ASAMI ATTORNEYS.

1 COVERED ELASTIC YARN BACKGROUND OF THE lNVENTlON:

This invention relates to a novel elastic yarn and to a method of making this yarn.

The yarn according to this invention is a covered yarn wherein a multi-filament, continuous filament thread as a sheath yarn wraps a core yarn in such a manner that said multi-filament thread wraps round said elastic thread, and said core yarn and said sheath yarn are substantially twistless.

In conventional covered elastic yarns which are generally used at present core spun yarn or rubber yarn or polyurethane elastic fiber yarn is used as the elastic core yarn and other filament yarn or spun yarn is twisted around said cores, or said yarns are associated and twisted thereon.

In addition, elastic yarn such as rubber yarn or polyurethane elastic filament yarn is used as the core in the convection of ejected fluid, and other filament yarns are tangled therewith, or elastic yarn and thermoplastic filament yarn are associated, and the associated yarns are crimped in twisting-heat setting-untwisting type method so called ltallian type" (twister) to produce over-untwisting yarn, While, the conventional covered elastic yarns have excellent characteristics, they have the following drawbacks.

First of all, in the case of single or double covered yarn prepared either in such a manner that non-elastic yarn wound on a bobbin mounted on a rotating hollow spindle is wound onto the rubber or polyurethane elastic core filament as that filament is drawn through the spindle,'or in another case of single covered yarn prepared in such a manner that non-elastic sheath yarn and rubber or polyurethane elastic core filament yarn are twisted under tension in a ring twister, considerably excellent covering property can be obtained but it is necessary to carry out appropriate thermal setting for power down and the setting of twisting torque because of the high torque attributable to the twisting operation. Other problems include excessive stretch power, and, in addition, there is a limitation to the speed spindle; in the experimental calculation of the productivity of fine yarn (total denier 90 denier), there is no such a case that the processing speed should go beyond m/min even when the number of revolutions of the spindle is adjusted to be 10,000 rpm, and the number of twists is adjusted to be 500 turns/m.

On the other hand, in addition to the above given drawbacks, there is a drawback that crimped yarn such as wooly yarn to be used as covering yarn must be separately prepared.

In addition, in the case of the conventional sheathcore type bulked elastic yarn prepared in such a manner that polyurethane elastic filament yarn and other filament yarn are passed through ejected fluid convection, wherein the other filaments are disturbed around said polyurethane elastic filament yarn to be tangled the, covering yarn is not twisted, and therefore the tangling property thereof is poor, and not satisfactory, and there is a fear that the core yarn may be exposed, and at the same time the cost of air is expensive. In addition to these drawbacks, as above, this process has a remarkable over-all drawback in the cost of labor attributable to the complicated processes, and the cost of processing is therefore high.

On the other hand, in the case of over twisted yarn produced from the associated elastic yarns and thermoplastic filament yarns by using the Italian type twister, the covering property is excellent but in view of the ordinary twisting process which is required in this case, the productivity thereof is-not more than that of single covered yarn; at the same time, the number of processes is increased, and the cost of production is high, and therefore over-twisted yarn produced by the Italian type twister is not practical.

Thus, there is no twistless covered elastic yarn although there are those conventional covered elastic yarns having actual twists, or poor tangling property caused by fluidal convection.

it is a principal object of this invention to remove the above mentioned drawbacks of the prior arts, and to provide a novel covered elastic yarn having fast elasticity and remarkably excellent covering property.

It is another object of this invention to provide a method for producing the above mentioned novel convered elastic yarn.

in order to attain the above described objects of this invention,. the present invention has the following structure.

This invention relates to a covered elastic yarn comprising an elastic thread as a core yarn and a multifilament continuous filament thread as a sheath yarn, wherein the respective filaments forming said covered elastic yarn are tangled to retain the fluxability and at the same time to form sheath-core stage, and said sheath yarn wraps the outer periphery of said core yarn, and is reversed intermittently and irregularly in said direction, and said sheath yarn and said core yarn are substantially twistless.

The present invention is explained more in detail in the following paragraphs;

The yarn of this invention is produced by using elastic thread having remarkably high elongation and recovery, such as rubber yarn or polyurethane filament yarn, as the core yarn. Said core yarn may be a monofilament but it is preferable to use a plural number of associated filaments, i.e., multi-filament; as a matter of course it is most preferable that the number of filaments should be great.

The reason for this is that the tangling property of core yarn against sheath yarn increases as the number of filaments in the core yarn increases.

On the other hand, as the above mentioned elastic yarn, crimped yarn or such elastic yarn having shrinkability attained by chemicals can be used.

On the other hand, as said sheath yarn, a crimped yarn composed of multi-filament yarn composed of thermoplastic filaments can be used.

Said sheath yarn covers and is twisted around said core yarn, and the core yarn is placed almost in the centre of said covering elastic yarn, and in regard to the direction of twisting of said sheath yarn, said sheath yarn is twisted in such a direction that said sheath yarn is twisted with random interval and intermittently in the lengthwise direction of said covered elastic yarn, and either filaments themselves forming said sheath or the filaments forming said sheath yarn and said core yarn are mutually tangled to retain fluxability.

Sometimes, it is possible to partially melt the filaments forming s'aid sheath-yarn in order to improve the fluxability further.

When thermoplastic synthetic yarn is used as the core yarn, random untwisting or slight crimping can be observed intermittently in the same manner as in the case of said sheath yarn.

In such a structure as described above, it is possible for said sheath yarn to be more excellently tangled against said core yarn.

For a better understanding of the nature of this invention, reference should be had to the following detailed description of specific embodiments thereof, when read in conjunction with the accompanying drawings forming a part thereof, wherein;

FIG. 1 (A) is a model schematic view of a length of conventional covered elastic yarn, in its fully, or nearly fully, elongated condition.

FIG. I (B) is a model schematic view of a length of the yarn of FIG. 1 (A) contracted further than in FIG. I (A).

FIG. 2 (A) is a model schematic view of a length of covered elastic yarn prepared by conventional falsetwisting method, in its fully, or nearly fully elongated condition. FIG. 2 (B) is a model schematic view of a length of the yarn of FIG. 2 (A) contracted further than in FIG. 2 (A).

FIG. 2 (C) is a model schematic view of a length of the yarn of FIG. 2 (B) further twisted.

FIG. 3 (A) is a model schematic view of a length of the yarn in accordance with this invention, in its fully, or nearly fully elongated condition.

FIG. 3 (B) is a model schematic view of a length of the yarn of FIG. 3 (A) contracted further than in FIG. 3 (A).

FIG. 4 (A) is an enlarged cross sectional view of the yarn of FIG. 2 (A);

FIG. 4 (B) is an enlarged cross sectional view of the yarn of FIG. 2 (B); I

FIG. 5 (A) is an enlarged cross sectional view of the yarn of FIG. 3 (A);

FIG. 5 (B) is an enlarged cross sectional view of the yarn of FIG. 3 (B).

FIG. 6 (A) is a schematic view of false-twisting apparatus which, shown partially in cross section, which can be used to make the yarn in accordance with the present invention.

FIG. 6 (B) is a vertical sectional view of a guide in the apparatus shown in FIG. 6 (B). I

FIG. 7 (A) is a schematic view, partially in cross section, of modified false twisting apparatus which can be used to make the yarn in accordance with this invention.

FIG. 7 (B) is a vertical sectional view of a star-wheel type pulley usable for FIG. 8 (A).

Referring first to FIG. 1 (A), FIG. 1 (A) is a model schematic view of the covered elastic yarn twisting two yarns (2) and (21) on the core yarn (l) by a conventional spinning machine or a conventional twister, in elongated state. FIG. 1- (B) is a model schematic view of the covered elastic yarn of FIG. 1 (A) contracted by 30 percent.

As is apparent from FIG. 1 (A), the filaments of the sheath yarns (2), (2') of the covered yarn are regularly twisted and therefore the covering property of the covered elastic is remarkably excellent, but since the filaments composing the covered yarns (2), (2') are controlled by twisting, the space occupied by said filaments becomes narrower, and the bulkiness thereofis deteriorated, and this is accounted to be a drawback.

FIG. 2 (A) is a model schematic view of a covered yarn under tension prepared by simply associating and conventional false-twisting the core yarn (1) and the covering yarns (2), (2') and FIG. 2 (B) shows a model schematic view of the same yarn shown in FIG.'2- (A) contracted by 30 percent.

As is apparent from FIG. 2 (8), the core yarn (I) and the covering yarns (2), (2) have no twist at all, and it is very bulky but there is no contact of the filaments composing the core yarn and the covering yarn (See FIG. 4 described below).

Therefore, the covering property is very poor, and the core yarn and the covering yarn can be separated by a slight external effect when the covered yarn passes through a guide or tensioner, and the separated core yarn and the covering yarn are not restored to their original state, and this is accounted to be a serious drawback.

Therefore additional twisting is required after the false twisting or pre-twisting is required before the twisting.

FIG. 2 (C) shows the form of the yarn after the above mentioned additional twisting or pre-twisting. Theincrease of the number of processes in making this yarn, and its poor bulkiness are accounted to be drawbacks.

FIG. 3 (A) and FIG. 3 (B) show the covered elastic yarns obtained in accordance with the present invention in comparison with the covered elastic yarns obtained in accordance with the prior arts.

FIG. 3 (A) shows the covered elastic yarn of the present invention under tension in the same manner as in FIG. 1 (A) and FIG. 2 (A), and FIG. 3 (B) shows said yarn contracted by about 30 percent.

FIG. 3 (B) is a model schematic view of the structure which makes use of the merits of the yarns of FIG. 2 (B) and FIG. 1 (B), so as to compensate for the respective drawbacks thereof.

In other words in the yarn structure of FIG. 3 (B), the filaments composing the sheath yarn (2), (2) covering the core yarn (l), are reversed in the twisting direction at random intervals.

Point (a) of FIG. 3 (A) and FIG. 3 (B) shows the twist reversing point of said filaments.

The above described phenomena are demonstrated by all of the filaments forming the sheath yarn, and therefore the covered elastic yarn as a whole has remarkably excellent covering property, and at the same time, the filaments forming thesheath yarn have almost no contact against the core filaments attributable to twisting because the filaments forming the core yarn and sheath yarn are substantially twistle'ss, and therefore excellent bulkiness can be attained.

In addition, a covered elastic yarn of FIG. 2 (A), (B), produced in accordance with a conventional falsetwisting method is covered with the covering yarn not being closely adhered on the elastic yarn (l) as is apparent from FIG. 4 (A), (B), while in a covered elastic yarn produced in acccordance with the present invention, as is apparent from FIG. 5 (A), (B), the thermoplastic continuous multifilament thread is partially laid in the elastic thread (1) in such a manner that the thermoplastic continuous multifilament thread is inserted into said elastic thread.

Therefore, the yarn of the present invention has remarkably excellent fluxability, and the slipping-off of the core yarn (l) is less against tension and pulling, and the covering property is not at all deteriorated.

Namely, in accordance with this invention, an elastic thread is released from the package thereof under tension, and a thermoplastic continuous multi-filarnent thread and said elastic thread are associated, and thus associated, the thermoplastic continuous multifilament and the elastic thread are passed through the fluxing guide, and are arranged in such a manner that said elastic thread can become the core and that said multi-filament thread can wrap said elastic thread, and the thus obtained fluxed and associated yarns are then supplied into a false twisting machine, to carry out a twisting, heat setting and untwisting process.

The method of the present invention is explained in more detail in the following paragraphs.

In supplying elastic thread and thermoplastic multifilament thread simultaneously to the same false twisting machine, the relation of said elastic thread and thermoplastic multi-filament thead is such that the filaments of said thermoplastic multifilament thread are arranged in such a manner that the elastic thread can.

be wrapped by said filaments, and the covered elastic yarn thus obtained has elastic thread within the fiber flux of the crimped thermoplastic multi-filaments by means of false twisting, and the elastic thread is covered with the crimped multi-filament, and therefore the two cannot be easily separated.

Moreover, in regard to the covered elastic yarn thus obtained, the elastic thread as the core yarn and the filaments forming the sheath yarn are substantially untwisted, and the generation of torque and kink can be hardly observed.

In regard to the determination of the temperature at which the false twisting is carried out in accordance with the present invention, it is a matter of course that temperature should be adjusted to be sufficient to fix the desirable crimping of the thermoplastic multifilament to be used as the sheath thread, but it is necessary that the kind of elastic thread used as the core yarn should be taken into consideration.

For example, when an elastic thread which is subject to thermal deterioration (such as natural rubber) is used, the temperature at which false twisting is carried out must be adjusted to be low so as not to-damage the elastic thread, or said elastic thread must be protected by the sheath thread, and therefore it is a matter of course that the conditions such as the kind of the sheath thread, temperature and the number of twisting turns should be taken into consideration.

On the other hand, when a thermoplastic elastic thread, such as polyurethane fibers, is used as the core yarn and the elastic thread is supplied under a high tension or high elongation in a high temperature zone, the elongation of the covered elastic yarn product is less; on the contrary, when the elastic thread is supplied under less tension or at low elongation, the elongation of the covered elastic yarn product is larger.

Conversely, when the elastic thread is supplied under a high tension or at high elongation, in a low temperature zone, the elongation of the covered elastic yarn becomes larger while if the elastic thread is supplied under a low tension or at low elongation, the elongation of the covered elastic yarn product becomes small. Therefore, in accordance with the method of the present invention, it is possible to select the tension of the core yarn elastic thread and the temperature at which false twisting is carried out to meet the object of this invention.

Furthermore, it is possible to select the temperature at which false twisting is carried out in such a manner that the fibers forming the sheath strand can be partially melted and adhered to each other.

In addition, when polyurethane elastic yarn, as the core yarn, is subjected to the false twisting treatment at a temperature in the neighbourhood of the melting point of the core yarn, i.e. if the heat-setting of the false twisting is carried out at a temperature ranging from lC to 200C, or more preferably at C, the polyurethane elastic yarn is softened, and, in addition, the twists attributable to the false twisting is generated on the surface of said polyurethane elastic yarn, and therefore the fibers forming said sheath strand are laid into the concave portions produced by the twisting of said elastic yarn.

Therefore, the covering property of the covered elastic yarn which can be obtained as described above, can be further improved, and at the same time the migration of said sheath thread cannot be brought about by the external frictional force.

What is important in the method of the present invention is that in supplying the elastic thread as the core yarn and the thermoplastic multi-filaments thread as the sheath yarn to the same false twisting machine, the filaments forming the thermoplastic multi-filaments should be parallelly arranged in such a manner as to rap the core yarn.

The above mentioned arrangement determines the superiority of the covering property of the covered elastic yarn of this invention.

In order to arrange the respective filaments to be supplied to the false twisting zone, it is necessary that the relation of the respective threads, at the time when they are supplied, be sufficiently taken into consideration.

First of all, in order to place the elastic thread in the center, said elastic thread should be supplied under tension, to prevent the free slipping-off thereof, and furthermore the multi-filament thread should be supplied under low tension to wrap said elastic thread.

When the respective threads are supplied in such a manner as described above, the fibers which are to become sheath form the outer side, and' the elastic thread which is to become the core thread is placed in the center.

In the above described embodiment, it is necessary to have a gude for fluxing the thread, i.e. a U or V shaped yarn guide or a star-wheel type pulley guide having a U or V shaped concave portion on the periphery thereof to arrange the filaments in the neighbourhood of the twist-starting point, and to prevent, from that point backward the twisting of the fluxed threads which abruptly starts, beyond that point, using a nip roller guide to define that point.

In other words, in the present invention, the elastic thread and non-elastic thread are directly introduced into a false twisting machine after they have been associated, but it is necessary to keep said elastic thread and non-elastic thread in the associated state for a predetermined time, and said elastic thread is introduced into the center of said non-elastic thread by the above mentioned treatment.

Therefore, a U or V shaped guide is preferable.

In other words, in accordance with the present invention, said core yarn and said sheath yarn are doubled,

and thereafter, the doubling state is retained for a predetermined distance, while a tension difference is maintained therebetween in a yarn introducing zone of a false-twisting aparatus, in which the yarn is falsetwisted while the backward travel of twist is controlled, and thereby said core yarn is sufficiently placed into said sheath yarn.

FIG. 6 and FIG. 7 are diagrams showing the embodiments of apparatus for carrying out the process and for making the product of the present invention.

In FIG. 6 (A), the elastic thread which is positively released from the package (3) thereof by the roller (4), is supplied to a pair of feed rollers (6) of the false-twisting machine while being subjected to tension.

On the other hand, the thread (8) which is released from package (7) of the thermoplastic multi-filament yarn which becomes the sheath yarn passes through the guide (9), and is supplied to the feed roller (6) of the false-twisting machine, and is associated with the elastic thread (5).

The elastic thread (5) supplied by the feed rollers (6), and the continuous multi-filament thread (8) are arranged by the grooved guide (10) having a V shaped groove in the lateral cross section perpendicular to the running direction of said threads (5) and (8) in such a manner that said thread (5) is arranged within the central portion of said continuous multi-filament thread (8). Said elastic thread (5) and continuous multifilament thread (8) are then subjected to false twisting by means of the false twisting spindle (l3), and the twisted portion thereof is thermally set by means of the heater (12), and when said threads have passed through said spindle (13), they are untwisted, and are drawn out by a pair of delivery rollers (14), and said threads pass through the guide (15), and are taken up i into a package (17) by means of a take up device such as drum type winder.

In other words, the false twisting is perfectly stopped by a nip roller (11), and the two threads keep their associated state between the feed roller (6) and nip roller (11). This prevents twist from travelling backward to grooved guide (10) or said feed rollers (6) so that the state of core-sheath of the two threads is not destroyed thereby.

FIG. 6 (B) is a diagram showing the cross sectional form of. grooved guide (10) in the plane perpendicular to the running direction of the threads (5), (8), and

said elastic thread (5) is arranged into the central portion of said continuous multi-filament thread (8) in said groove.

On the other hand, FIG. 7 is a diagram showing a modified form of the apparatus of FIG. 6 (A), (B). In FIG. 7 (A), the elastic thread (5) released by the positive feed-roller (4) from the package (3) thereof is elongated by a predetermined degree between said feed roller (4) and delivery roller (14).

Said elastic thread (.5) is associated with the thermoplastic multi-filament thread (8) released from the package (7) thereof in an almost tensionless state, and is supplied into the star-wheel type pulley (18).

FIG. 7 (B) is a cross sectional view of said star-wheel pulley across the center of said star-wheel type pulley, Said star-wheel type pulley is light and is rotated in the running direction of the threads (5), (8) on shaft (20) by contacting with the threads.

The peripheral portion (21) of said pulley (as seen in FIG. 7 (B)) has a shaped groove that helps said two threads take on a sheath-core form without adding high tension to said continuous multi-filament thread which becomes sheath thread by using said pulley and said elastic thread (5) arranged in the central portion of said continuous multi-filament thread (8) therein.

Further, in FIG. 6 (A), a pin nip rollers (11) is provided in order to prevent the travelling of the twist of the false-twisting machine during the false twisting process, but when a pair of the nip rollers (11) is used, there is a fear that the sheath-core arrangement of the threads (5), (8) attained by the groove guide (10), may be upset thereby.

On the other hand, the star wheel type pulley as is shown in FIG. 7 (A) is rotated along with the running of the threads (5), (8), and therefore it is not necessary to use such a pair of nip rollers (11) as is shown in FIG.

6 (A) because there is no fear that the twist of the false twisting machine may arrive at the entrance portion of the groove (21) of said pulley (l8), and only the guide (19) for converting the running direction suffices.

As described so far in the foregoing paragraphs, the respective threads (5), (8) associated in the sheathcore state, are taken up on the package (17) after they are subjected to the process for twising-heatsettinguntwisting.

The covered elastic yarn thus obtained is an elastic yarn having remarkably strong covering property, and the covering cannot be destroyed even if it is used over and over again, and partial exposure of the core yarn thereof can be hardly observed, and the cover elastic yarn has a very uniform shape in the lengthwise direction thereof.

In addition, when the thermoplastic filaments are slightly melted and adhered by raising the temperature of the heater of the false twisting machine, it is needless to mention here that faster covering can be attained and the covering becomes more compact.

The covered elastic yarn of the present invention has almost the same processiability as the ordinary crimped yarns, and it is possible to adjust the crimping degree by adjusting the temperature of the heater of the falsetwisting machine and the stretch power thereof is almost the same as that of the thermally set single covered yarn, or core spun yarn.

Since the covered elastic yarn of the present invention is twistless yarn, snarls and kinks are not easily formed in the yarn of this invention when compared with the conventional single covered yarn to say nothing of the conventional false twisted crimped yarn.

Thus, the hank reeling property, hank dyeing property, hank winding property, cone-up property, preparing property for weaving, and preparing property for knitting of the covered elastic yarn of the present invention are the same as or more excellent than those of the conventional false twisted crimped yarn or single covered yarns.

The woven or knit fabrics obtained from the covered elastic yarn of the present invention can present the soft touch of wooly yarn by crimping process of the thermoplastic filaments and twistless covering process into the elastic filament yarn attained thereby, without being controlled by twist thereof, and has a special appearance as woven or knit goods.

The covered elastic yarn of the present invention can be directly used for producing the ordinary knit goods,

longitudinally stretchable woven fabric and, laterally stretchable woven fabric, without employing any heat setting process or twisting process, and this is accounted to be an advantage of the present invention.

In particular, in the ease of the longitudinally stretchable woven fabric, it is possible to omit sizing process by using the covered elastic yarn prepared by slightly melting and adhering the thermoplastic filaments at the time when false twistin is carried out.

When the covered elastic yarn of the present invention is used for knit goods, there is a remarkable advan tage that the yarn having the same stretch power as that of the conventional thermoplastic yarn can be directly woven from the cheese of the false-twisted yarns since in accordance with the prior art, the covered elastic yarn is used by thermally setting the same in most cases.

In addition, the processing speed of the covered elastic yarn of the present invention isfrom to 10 times the speed of the conventional yarns, and it is apparent that the present invention can greatly'reduce the cost of production.

On the other hand, the method of this invention can be easily worked out directly on the conventional false twisting machine, or by a simple improvement of the conventional devices, and the operation required for working out the method of thisinvention is hardly different from that of the conventional methods.

The following are the examples to further illustrate the present invention.

The method for measuring the elongation and covering property, and coefficient of feeding asdescribed in the following examples of the present invention are explained below;

I. METHOD FOR MEASURING ELONGATION The yarn of the present invention was wound on the periphery of a 50 cm frame for 10 times, and thermal treatment was carried out with 60C hot water for 30 minutes.

After having dried the yarn for 24 hours, 40 g a weight of par a yarn was suspended thereon for 30 seconds, and the length I was read. Thereafter, the load was removed, and the yarn was left out to be shrunk for 20 seconds, and then a weight of 0.16 g par a yarn was suspended thereon for 30 seconds, and the length I, was read.

Elongation =1, -l,/l, X I00 10 zqmsrnoo FOR MEASURING THE COVERING PROPERTY A weight of 40 g was suspended on the yarn of the present invention for 30 seconds, and the length of cm was marked on the yarn, and thereafter the weight was removed, and then the yarn was left out to be shrunk for I20 seconds, and then, a weight of 0.5 g was suspended thereon so to separate the core yarn and the sheath yarn thereof.

The length l, of the yarn with the weight hanging down is read.

Covering property 50 [J50 X I00 3. DETERMINATION AND COEFFICIENT OF FEEDING Coefficient of Feeding (Peripheral speed of feed roller Peripheral speed of delivery roller/Peripheral speed of delivery roller) X 100 4. DEFINITION OF POLYURETHANE ELASTIC THREAD USED IN RESPECTIVE EXAMPLES A polyurethane elastic thread 40 denier-I filament used in the following examples and comparative examples is a monofilament in which six polyurethane elastic filaments are coalesced, and a polyurethane elastic thread denier-I filament is a monofilament in which 18 polyurethane elastic filaments are coalesced.

EXAMPLES I, 2, AND 3,

1. Examples l and 2 A polyurethane elastic thread 40 denier-l filament elongated by 3.5 times of the original length thereof and Nylon-6, 70 denier-34 filaments being tensioned by 0.1 g were associated with each other, and thereafter the associated filaments were supplied'into the apparatus embodiment as shown in FIG. 6. (A), (B), and treated under conditions as shown in items EX-l and Ex-2 of Table-1.

The resultsas shown in items EX-l and EY-Q ofTable-2 were obtained.

2. Examples 3 On the other hand, a polyurethane elastic thread 40 denier-1 filament elongated 2.8 times the original length thereof and Nylon-6, 70 denier-34 filaments being tensioned by 1.0g were associated with each other, and thereafter the associated filaments were supplied into the apparatus embodiment as shown in FIG. 6. (A), (B) and treated under conditions as shown in item EX-3 of Table-l.

The results as shown in item Ex-3 of Table-2 were obtained.

TABLE 1 EX-1 EX-Z EX-3 Materials:

Polyurethane thread (denier-filament) 40- 1 40-1 40- I Nylon-6 multi filament (denier-filament) 70-34 70-34 70-34 Conditions of processing:

Elongating degree of elastic thread (times) 3.5 3.5 2.8 Doubling tension of Nylon-6 multi-filament (g)... 0.l 0.1 1.0 Existence of a grooved guide Yes Yes Yes Coefficient of feeding of processing (percent) 1 2 I Number of rotations of false-twisting spindle (r.p.m)..... 20 X 10* 20 X 10 20 X 10 Number of false-twisting (turns/meter) 3600 3600 3600 Temperature of heater (C) I I80 Length of heater (mm)......... 900 900 900 Tension of twisting (g) 7 7 7 Tension of untwisting (g) l4 I6 20 Number of true twist (turns/meter) 0 0 0 3: Considerations As is apparent from EX-l and EX-2 of Table-2, the

*Cl value: It is based on the rule ofJlS.

covered elastic yarns of the present invention, in the production of which there is a relatively large difference between the tension of the polyurethane elastic thread and that of the Nylon-6 multifilament, and heat-setting of the false-twisting is carried out at a temperature ranging from 180C to.

200C, have excellent covering property, because the respective filaments of Nylon-6 are adhered to the outer surface of the polyurethane elastic thread.

On the other hand, the covered elastic yarn in accordance with Example-3, produced with only slight differential tension between the polyurethane elastic thread and the Nylon-6 multi-filament and with heat-setting of the false-twisting at a temperature lower than 180 "C, i.e., [70C, has poor covering property, because the respective filaments of Nylon-6 are generally not adhered to the outer surface TABLE 2 EX-1 EX-2 EX-3 Number of filaments of Nylon-6z Multi-filament adhered to-polyurethane elastic thread (number/an optional cross section of the covered elastic yarn) 22 16 Multi-filament not adhered to polyurethane elastic thread (number! an optional cross section of the covered elastic yarn) l2 18 34 Covering property (percent):

Weight of 0.5g... 97 87 12 E ght Qfl-Ofi "he. ,2 94 80 0 Clz Coefficient of cry of el y (percent). 54 58 60 Coefficient of elongation (percent)... I79 I91) I)! Index of torque ,L l 8 Existence of the twisting mass produced by rubbing motion Yes Yes Ycs 6f the polyurethane elastic thread.

EXAMPLES 4 AND 1. Example 4 A polyurethane elastic thread denier-1 filament elongated by 3.6 times the original length thereof and Nylon-6, denier-24 filaments, under 0.2

grams tension, were. associatedwith each other,

and thereafter the associated filaments were sup- TABLE 3 EX-4 EX-S Materials:

Polyurethane thread (denier-filament) 40-] 40-] Nylon-6 multi filament (denier-filament) 70-24 70-24 Conditions of processing:

An elongating degree of elastic thread (times)..... 3.6 I 3.6 Doubling tension of Nylon-6 multi-filament (g) 0.2 0.2 Ratio of tension between an entry and an exit of the star-wheel type grooved guide L06 Existence of a grooved guide Yes Yes Coefiicient of feeding of processing (percent)... 1 Number of rotations of false-twisting spindle (rpm). 20 X 10 20 X 10 Number of false-twisting (turns/meter) 3.300 3,300 Temperature of heater (C).... Length of heater (mm) 900 900 Tension of twisting (5).. l2 1 I Tension of untwistint; (g) 22 20 Number of true twist (turns/meter) 0 0 TABLE 4 EX-4 EX-5 A number of filaments of Nylon-6:

Multi-t'ilament adhered to polyurethane elastic thread (number/an optional cross section of the covered elastic yarn) 14 i0 Multi-filament not adhered to polyurethane elastic thread (number/an optional cross section of the covered elastic yarn) 10 I4 Covering property (percent):

Weight of 0.5g 1 00 98 Weight of 2.0g 99 96 Cl:* Coefficient of recovery of elasticity (percent).. 57 58 Coefficient of elongation (percent) 147 15] Index of torque 9 8.2 Existence of the twisting mass produced by rubbing motion None None 7 *CI value: It is based on the rule ofJlS.

3. Considerations 7 As is apparent from items of EX-4 and EX-5 of Table-4, the covered elastic yarn of the present invention can be obtained by either apparatus emboditween said polyurethane elastic thread and Nylon-6 multi-filament thread, when a weight of 0.5 g was suspended thereon.

As is apparent from the foregoing description, in the ment as shown in FIG. 6 or as shown in FIG. 7. But 5 present invention, the method in accordance with Exthe coveringproperty of the covered elastic yarn of ample-4 is more excellent than that in accordance with Example 4, produced with the apparatus embodi- Example-5. ment of FIG. 7 which is provided with a star-wheel TABLE 5 type guide, IS more excellent than that of the covered elastic yarn of Example 5 produced with the i Examples x apparatus embodiment of FIG. 6 which is provided 2:232: 1 E with a simple grooved guide. x. o.; cm 0 cm In both examples mentioned, it may seem as if there i? 3'3 3"; a is only a slight difference between the covering propx, 0 cm 0.3 cm erty of Example-4 and Example-5, but actually there is 5 cm 0 X 0.54 cm 1.98 cm a five fold difference In the mean value of the length m 4mm, differential used in calculating covering property cove-fins l00= 9.0 48.0/50.0 100= 96.0 defined herein rim to the descri tion of Exam le 1 Empeny p p p X: arithmetical mean value As a matter of fact, m the covered elastic yarn produced in accordance with Example-4, as shown in Table-S, all of the five samples showed little tendency to permit slipping-off between said polyurethane elastic EXAMPLES 6 AND 7 thread and Nylon-6 multi-filament thread, when a A polyurethane elastic thread denier-l filament weight of 0.5g was suspended thereon. and Nylon-6, 70 denier-24 filaments were treated On the other hand, in the covered elastic yarn pro- 25 under conditions as shown in items EX-6 and EX-7 of duced in accordance with Example-5, as shown in Ta- Table-6 with the apparatus embodiment as shown in ble-S, one of five samples showed about 20% (about FIG. 7, and thereby the effects as shown in items EX-6 9.4 cm) of slipping of par length of cm thereof beand EX-7 of Table-8. were obtained.

M HTAEIE E EX-6 EX-7 Materials:

Polyurethane thread (denier-filament) 40-1 40-1 Nylon-6 multi filament (denier-filament) -24 70-24 Conditions of processing:

Elongating degree of elastic thread (times) Doubling tension of N ylon-6 multi-filament (g) 3.6 2.2 Ratio of tension between entry and exit of the star-wheel type grooved guide. 1.08 I .95 Existence of a grooved guide Yes Yes Coefficient of feeding if processing (percent)...... Number of rotations of false-twisting spindle (r.p.m.). 20X 10 20X 10 Number of false-twisting (turns/meter) 3400 3400 Temperature of heater (C) I Length of heater (mm) 900 900 Tension of twisting (g) I3 28 Tension of untwisting (g) 24 39 Number of true twist (tums/meter 0 0 ""TAiiLE? EX-6 EX-7 Number of filaments of Nylon-6:

Multi-filament adhered to polyurethane elastic thread (number/an optional cross section of the covered elastic yarn) l2 0 Multi-filament not adhered to polyurethane elastic read (number/an optional cross section of the covered elastic yarn) I2 24 Covering property (Percent):

Weight of 0.5g 89 0 Weight of 2.0g '83 0 CI:* Coefficient of recovery of elasticity (percent).. 6] 63 Coefficient of elongation (percent) 162 I702 Index of torque 7 r 7 Existence of the twisting mass produced by ru bing motion None None CI value: Based on the rule ofJlS.

EX-S EX-9 EX-IO EX] 1 EX-IZ Materials:

Polyurethane thread (denier-filament) 70-l 70-] 70-1 70-1 70-1 Nylon-6 multi filament (denier-filament) 70-24 70-24 70-24 70-24 70-24 Conditions of processing:

Elongating degree of elastic thread (times) 3.6 3.6 3.6 3.6 3.6 Doubling tension of Nylon-6 multi-filament (g).. 0.2 0.2 2.0 2.0 2.0 Ratio of tension between an entry and an exit of the star-wheel type grooved guide 1.14 Existence of a grooved g u ide. Yes None None None None Coefficient of feeding of processing (percent) 1 1 I 1 Number of rotations of false-twisting spindle 7 7* (rpm) 20X 10 20 X 10 20 X10 20 X10" 20 X 10 Number of false-twisting (tums/meter)..... 3,300 3,300 2,300 2,300 2,300 Temperature of heater (C) 195 195 I50 150 190 Length of heater (mm) 900 900 900 900 900 Tension of twisting (g) 16 '14 14 14 Tension of untwisting (g)..... 32 32 v 28 28 28 Number of true twist (turns/meter)... 0 0 300 0 0 As is apparent from the foregoing discussion a starwheel type grooved pulley is used in both Exampleo 20 and in Example 7 however, the covered elastic yarn in accordance with Example-6, in which the temperature of heat setting of false-twisting is the same as that of conventional false twisting methods has a small covering property. Therefore, in order to obtain a covered elastic yarn having excellent covering property, it is preferable that a temperature of the heat setting of false-twisting, as is in Example-6, is higher than that of conventional false-twisting methods.

EXAMPLES 8,9, 10,11 AND 12 1. Examples 8 and 9 A polyurethane elasticthread 70'denier-l filament elongated by a 3.6 times the original length thereof and Nylon-6, 70 denier-24 filaments under 0.1g tension were associated with each other, and thereafter ther respective associated filaments were supplied to apparatus of the type shown in FIG. 6 and FIG. 7 and treated under conditions as shown in items EX-8 and EX-9 of Table-8. 40

The results as shown in items EX-8 and EX-9 of Table-9 were obtained.

As is apparent from the foregoing discussion, the

covering property of the covered elastic yarn of Example 8 produced with the apparatus embodiment of FIG. 7 is better than that of the covered elastic yarn of Example 9 produced the apparatus embodiment of FIG. 6.

2. Example 10 On the other hand, threads used in Examples8 and 5 9 were treated by a conventional method.

The conventional method used (as taught in Japanese Patent Publication No.255l l/67) comprises a first step of associating said elastic thread with said thermoplastic multi-filament thread, a second step of pro-twisting said associated threads, a third. step of twisting said threads in the direction opposite to that of the original twist-heat settingand'untwisting said threads in the same direction as that of the original twist. I

Conditions of treatment of the present example are shown in item EX-9 of Table-8 and the effects thereof are shown in item EX-9 of Table-9. As is apparent from the above result, the covered elastic yarn produced in accordance with Example-l0 has practically no rubbing resistance and forms a twist-' ing mass in the longitudinal direction thereof directly after it was rubbed, because it is twisted slightly.

The covering property of said yarnof the present example has somewhat similar property to that of the yarn of the present invention.

The reason for said effect is that some of the original twist imparted by the pre-twisting process is retained after twisting-heat setting-untwisting.

However, in said covered elastic yarn, the elastic thread and the thermoplastic multi-filament thread are not substantially twistless as in the present invention.

Furthermore, in the present example, the covered elastic yarns treated without any pre-wisting process are not always'the same in covering property as the above mentioned result as is apparent from the following examples (Examples 11 and 12).

3. Example 11 The covered elastic yarn of this example was obtained by the method of Example 10', but without any pre-twisting.

In the covered elastic yarn of this example, the elastic thread and thermoplastic multi-filament were substantially twistless, but the covering property thereof was very poor as is apparent from item EX-ll of Table-9.

Furthermore, the covering properties of 38 (with a weight of 0.5g) and 34 (with a weight of 2.0g) seem to indicate some degrees of covering property, but

, as a matter of fact, the yarn obtained by this example is of almost no practical value, because the portions covered therefor uncovered with said thermoplastic multi-filament were randomly distributed along the longitudinal direction of said yarn.

4. Example 12 Furthermore, to make sure of the result reported in Example 11, the method of Example 11 was repeated, but at a heatsetting temperature in the vicinity of Examples 8 and 9. As the result, a covering property of the covered elastic yarn of this example was more excellent than that of Examplefl 1,. but the covering property thereof was not completely perfect, and the coefficient of recovery of elasticity was lower than that of Examples 10 and l l.

TABLE 9 EX-8 EX-9 EX-lO EX-l l EX-l2 Number of filaments of Nylon-6:

Multi-filament adhered to polyurethane (numberlan optional cross section of the covered elastic yarn) 13 8 0 0 Multi-filament not adhered to polyurethane .elastic thread (number/an optional cross section of the covered elastic yarn) 1 l 16 24 24 24 Covering property (percent):

Weight of0.5g 100 81 100 38 71.6 Weight of 2.0g 99 76 98.5 34 63.5 Cl Coefficient of recov'erity of elasticity (percent). 62 59 6I 64 l Coefficient of elongation (percent) 167 163 159 I72 143 Index of torque 9 9 l2 8 6 Existence of the twisting mass produced by ru ing motion 1. None None None None None *Cl value: It is based on the rule of .IIS.

elastic thread, the wrapping direction thereof being reversed at irregular intervals in the longitudinal direction of said elastic threads, and

5. said thermoplastic multi-filament thread and said elastic thread being substantially twistless.

2 A covered elastic yarn according to claim 1,

wherein said filaments of said thermoplastic multifilament thread are partially adhered to said elastic thread along the longitudinal direction thereof.

3. A covered elastic yarn, according to claim 1, wherein said centrally disposed elastic thread consists of a thermoplastic material.

4. A covered elastic yarn, according to claim 1, wherein said centrally disposed elastic thread consists of a multi-filament yarn.

5. A covered elastic yarn, according to claim 1, wherein said centrally disposed elastic thread consists of an essentially monofilament yarn formed by coalescing a thermoplastic multi-filament yarn.

6. A covered elastic yarn, according to claim 5, wherein said filaments of said thermoplastic multifilament thread disposed about said elastic thread are partially adhered to said elastic thread along the length thereof.

Claims (9)

1. A covered elastic yarn comprising, 1. two filament groups consisting of a thermoplastic multifilament thread and an elastic thread, 2. said elastic thread being larger in diameter than the filaments forming said thermoplastic multi-filament, 3. said elastic thread being positioned in a central portion of the filaments of said thermoplastic multi-filament thread, said filaments being distributed about said central portion and closely adjacent thereto, 4. respective filaments of said thermoplastic multi-filament thread being wrapped spirally around said elastic thread, the wrapping direction thereof being reversed at irregular intervals in the longitudinal direction of said elastic threads, and 5. said thermoplastic multi-filament thread and said elastic thread being substantially twistless. CM,2Ered elastic yarn according to claim 1, wherein said filaments of said thermoplastic multi-filament thread are partially adhered to said elastic thread along the longitudinal direction thereof.

2. said elastic thread being larger in diameter than the filaments forming said thermoplastic multi-filament,

3. said elastic thread being positioned in a central portion of the filaments of said thermoplastic multi-filament thread, said filaments being distributed about said central portion and closely adjacent thereto,

3. A covered elastic yarn, according to claim 1, wherein said centrally disposed elastic thread consists of a thermoplastic material.

4. A covered elastic yarn, according to claim 1, wherein said centrally disposed elastic thread consists of a multi-filament yarn.

4. respective filaments of said thermoplastic multi-filament thread being wrapped spirally around said elastic thread, the wrapping direction thereof being reversed at irregular intervals in the longitudinal direction of said elastic threads, and

5. said thermoplastic multi-filament thread and said elastic thread being substantially twistless. 2 A covered elastic yarn according to claim 1, wherein said filaments of said thermoplastic multi-filament thread are partially adhered to said elastic thread along the longitudinal direction thereof.

5. A covered elastic yarn, according to claim 1, wherein said centrally disposed elastic thread consists of an essentially monofilament yarn formed by coalescing a thermoplastic multi-filament yarn.

6. A covered elastic yarn, according to claim 5, wherein said filaments of said thermoplastic multi-filament thread disposed about said elastic tHread are partially adhered to said elastic thread along the length thereof.

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