The present invention relates to spinning technology for the production of a singles ring yarn. The invention is particularly concerned with a method and apparatus that utilize a false twist device with two false twisting points to yarns between double belts and incorporate them in the conventional ring spinning machine to improve yarn properties and fabric performance as well as the efficiency of false twist and ease of operation. The false twist efficiency for yarn and thus the property of the final singles ring yarn can be controlled, resulting in yarns with reduced residual torque and twist. This invention further relates to a solution to problems of yarn appearance deterioration peculiar to yarns produced using the double false twisting techniques of the present invention. This solution is particularly necessary for producing finer yarns count as well as yarns for high-quality products.
Twisting is an important step of short fiber spinning. In this process, the yarns are twisted and transformed to attain sufficient strength, wear resistance and smoothness. However, as a negative effect, a large amount of residual torque or twist liveliness is also brought about in the yarns simultaneously. Such twist liveliness of the yarns significantly influences the quality of the resulting products. For example, if yarns with twist liveliness are used for knitting, loops of the fabric will lose their balance because of the residual torque in the yarns. In order to attain the natural structure with the minimum energy condition, the loops tend to rotate to release the internal torsion stress. As a result, one end of the loops will tilt and protrude from the fabric surface, while the other end will stay inside the fabric. Such deformation of the loops will increase the spirality of the fabric, i.e., a deformation similar to the rib effect, which should be prevented to the greatest extent possible. Thus, the balancing of torque inside the yarns is particularly important.
Staple yarns are made from a large quantity of fibers bonded by the friction between the fibers. Hence, the residual torque of the yarns or the spirality of the fabric is mainly affected by the friction-related characteristics of the fibers, such as the type and cross-sectional shape of the fibers, the polymerizing manner of the fibers and the internal structure of the yarns, etc.
First of all, different types of fibers have a different modulus and cross sectional shape, thus leading to different degree of stress in the yarns. In cotton/polyester blended yarns, increasing the ratio of polyester will enhance the twist liveliness of rotor and ring yarns, but heat setting can improve the spirality of the resultant fabrics.
This is because polyester has a higher modulus than cotton, and said two types of fiber have different cross sectional shapes.
Next, different yarn structures have a different distribution of stress. Experimental results, such as Barella and Manich in the Textile Research Journal, Vol. 59, No. 12, 1989, Lord and Mohamed in the Textile Research Journal, Vol. 44, No. 7, 1974 and Sengupta, and Sreenivasa in the Textile Research Journal, Vol. 64, No 10, 1994 showed that, friction spun yarns (DREF-II) have the largest residual torque and trend of deformation in the priority sequence followed by ring yarns, rotor yarns and air-jet yarns. It is generally agreed that singles ring yarns are composed of a plurality of uniformly enveloped concentric helical threads, while fiber migration is a secondary feature. Hence, when the ring yarns are reverse-twisted, their strength will gradually decreases to zero, by then the yarns will be all dispersed. In relation to ring yarns, unconventional spinning systems produce yarns with core-sheath structures, such as rotor spinning yarn, air jet spinning yarn and friction spinning yarns. The packing density of said yarns is uneven and mainly characterized by partial entanglement and entrapment of the fibers.
In addition, many factors can affect the degree of movement freedom of the loops of the fabric and also the final spirality of the fabric. Said factors include fabric structure, parameters of the knitting machine, and the fabric relaxation and fabric setting due to finishing. All the aforesaid factors affecting the spirality of fabric were reported in detail by Lau and Tao in the Textile Asia, Vol. XXVI, No. 8, 1995. As with other materials, the residual torque of the yarns can be reduced or eliminated using different methods. In the past several decades, a variety of torque balancing methods have been developed. According to the basic theory, they can generally be split into two categories: permanent processing methods and physical torque balancing methods.
Permanent setting methods mainly accomplish the purpose of releasing residual torque by transforming the elastic torsional deformation into plastic deformation. The method mainly relates to a variety of setting techniques for material, such as thermal setting, chemical processing and wet setting etc. In the Textile Research Journal, Vol. 59, No. 6, 1989, Araujo and Smith have proved that for air-jet and rotor yarns, the heat setting of singles cotton/polyester blended yarns can effectively reduce the residual torque of the yarn. However, in relation to natural fibers such as cotton or wool, permanent setting is more complicated. It may involve steaming, hot water and chemical processing (such as mercerization in the case of cotton yarns and treatment with sodium bisulphite in the case of the wool yarns). In addition, in relation to natural yarns, setting cannot completely eliminate the residual torque of the singles yarns, and may also cause damage to the yarns.
Compared with permanent processing, physical torque balancing is a purely mechanical processing technique. The main point of the method is to fully utilize the structure of the yarns to balance the residual torque generated in different yarns while maintaining the elastic deformation characteristic of the yarns. Currently in the industry, separate machines are required to achieve torque balancing of the yarns, hence the cost is higher. The method comprises plying two identical singles yarns with a twist equal in magnitude but in the opposite direction or feeding two singles yarns with twist of the same magnitude but in opposite direction into the same feeder.
Recently, some new torque balancing methods for yarns also emerged in the Textile Research Journal, Vol. 65, No. 9, 1995, Sawhney and Kimmel described a series spinning system for processing torque-free yarns. The inner core of said yarns is formed by processing with an airjet system while outside the core is enwrapped with crust fibers similar to DREF-III yarns. In the Textile Research Journal, Vol. 62, No. 1, 1992, Sawhey etc. have suggested a method of processing ring cotton crust/polyester inner core yarns. Said yarns accomplish balancing by utilizing core yarns with opposite twisting direction from synthetic yarns, or applying heat processing on the polyester portion of said yarns. However, it is readily seen that the machines and processing techniques related to the aforesaid method are generally more complicated.
In the Textile Research Journal, Vol, 57, No. 10, 1997, Tao has processed the layer structure of the inner core-crust of rotor yarns to generate torque-free singles yarns, but said technique is not suitable for ring yarns.
In addition, U.S. Pat. No. 6,860,095 B2, filed by Tao et al. discloses a method of producing torque-free singles ring yarns. According to this patent application, a draft fiber is divided into a plurality of sub-assemblies of fibers. Each sub-assembly of fibers first attains an individual twist value during a false twisting, and then are twisted together to form the final yarns. The false twisting is controlled such that balancing of the internal torque of the final yarns is achieved. Furthermore, U.S. Pat. No. 7,096,655 B2 filed by Tao et al. discloses a method and apparatus for producing a singles ring yarn. In this method, a false twist device rotates at a first speed for twisting the fibers. Immediately after the first twisting step, a joint twist of the second twist in the same direction as the first twist and a third twist in a reversed direction is supplied to the preliminary yarn for producing final singles ring yarn. Moreover, the ratio of the first speed to the second speed is controlled for controlling the residual torque in the final singles ring yarn.
The aforementioned patents present the method and apparatus for singles ring yarn. However, the abovementioned patent application is more appropriate for torque-free singles ring yarn production in the laboratory scale. The yarn piecing-up and doffing process are not completely able to meet the practical requirements of large scale production in the textile industry. Furthermore, the spinning end-breakage when using ordinary cotton and the cost of investment and maintenance need to be further reduced for wide adoption in commercial application. In order to overcome the above shortcomings, two twisting points, instead of one twisting point, are adopted for the yarn false twisting to obtain the high false twist efficiency in this invention. In addition, the ratio of the velocity of the belt to the delivery speed of the yarn is controlled and the wrapping angle of the yarn on the belts is adjusted in order to obtain the desired properties of the final singles ring yarn.
Therefore, it is an objective of the present invention to provide an improved method and apparatus for producing singles ring yarns. The method and apparatus have the actual advantages of easy yarn piecing-up and doffing process, low spinning end breakage when using ordinary fibers and low cost of investment and maintenance. The method is thus not only able to meet the commercial requirements of the large-scale production in the textile industry but also possesses high false twist efficiency. Instead of one twisting point, two twisting points are adopted for the yarn false twisting to improve the false twist efficiency. Also, the false twist efficiency is controlled such that the desirable lower residual torque as well as other yarn properties can be achieved. Accordingly, a ratio of the velocity of the belt to the delivery speed of the yarn is controlled and the wrapping angle of the yarn on the belts is adjusted in order to obtain the desired property of the final singles ring yarn.
Another object of the invention is to provide a technique to solve the problems of appearance deterioration observed on yarns which are produced using low-twist and low-torque technologies, such as the double false twisting techniques disclosed in the present application. While those low-twist and low-torque methods are capable of producing satisfactory results in low-end products, they can cause appearance deterioration of the yarns, for example, unsatisfactory high numbers of neps, thick and thin places will present a problem in high-quality yarn products (see Table 1).
According to an aspect of present invention, a method for producing singles ring yarns is as follows.
A first high twist is imparted to a strand of traveling fibers emerged from the front-drafting-roller nip with the upper belt of a false twist device for producing a preliminary singles yarn, wherein the belt travels at a velocity for twisting the fibers and thus the strength of fiber strand is enhanced at the spinning triangle when a low twist level is adopted in the final singles yarn. Immediately after the false twisting step by the upper belt served as the first twisting point, a joint twist of a second twist in the same direction is imparted to the preliminary singles yarn for the production of a final singles ring yarn, wherein the second false twist is applied by running of the lower belt on the yarn. The rotating traveler imparts the yarn twist which will propagate upward to the false twist points. Then the final singles yarn was drawn onto the take-up package. The upper and lower belts run at the same speed but opposite direction.
Controlling a ratio of the velocity of the belts to the delivery speed of the yarn and the wrapping angle of the yarn on the belts can control the false twist efficiency for yarn and thus the yarn properties.
According to another aspect of present invention, an apparatus for producing singles ring yarns is as follows.
The upper belt of a false twist device traveling at the speed of the belt imparts a first high twist to a strand of traveling fibers emerged from the front-drafting roller nip such that a preliminary singles yarn is produced. The lower belt of a false twist device traveling at the same speed as the upper belt imparts a second twist in the same direction as the first twist to a preliminary singles yarn emerged from the upper belt such that a further preliminary singles yarn is produced. A rotatable take-up package onto which the final singles yarn is drawn imparts a third twist in the same direction as the first twist and second twist to a preliminary singles yarn such that final singles yarn is produced. The strength of the fiber strand is enhanced at the spinning triangle when a low twist level is adopted in the final singles yarn.
The ratio of the speed of the belts to the delivery speed of the yarn can be controllable and the wrapping angle of the yarn on the belts is adjustable such that the false twist efficiency and the yarn property can be adjusted.
According to a further aspect of the present invention, there is provided an apparatus for producing singles ring yarns with lowered residual torque and a reduced number of neps, which comprises a compact spinning device and a false twist device capable of producing two separate false twisting points. In operation, a traveling nascent strand of fibers is first running through the compact spinning device in the spinning triangle and then through the false twist device to be false twisted twice at two twisting points separately. The compact spinning device has a known effect of reducing hairiness of the yarn. It is not a part of the present invention by itself, and can be any known devices which are commercially available or customarily made with ordinary skill in the art, or to be made by technologies developed in future as long as they can achieve the similar technical effects as a compact spinning device as it is understood by a person of ordinary skill in the art. Currently, the preferred compact spinning device is a suction drum or suction tube.
Similarly, the false twist device is not part of the present invention by itself and can be any known devices which can be fitted to the spinning apparatus and create two separate false twisting points on a traveling yarn when it leaves the spinning triangle. Although, to the knowledge of the present inventors, such twisting device is not commercially available at the present time, the present disclosure provides sufficient information so that a person of ordinary skill in the art can make a double false twisting device for practicing the present invention. Among several embodiments of double-twisting devices and techniques disclosed herewith, the currently preferred one is the endless circular belt design as depicted in
According to a further aspect of the present invention, there is provided a method for reducing residual torque in singles ring yarns for producing high-quality yarns or fine count yarns. The method comprises (a) compacting the traveling yarn in the spinning triangle and (b) double false twisting it outside the spinning triangle.
The preferred device for effecting the contacting step is a suction drum and the preferred device for effecting the double false twisting step is a single endless belt which twists the yarn twice with a upper part and a lower part of the belt, respectively. With this belt twisting design, the preferred speed of belt is 6-68 m/min and the speed ratio between the belt and the yarn traveling is 0.3-3.4. The preferred wrapping angle of the yarn on the belt is 15-60°. Of course, based on the operating principles disclosed herein, a person of ordinary skill in the art may find other parameters that can also produce satisfactory results.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be made to the drawings and the following description in which there are illustrated and described preferred embodiments of the invention.
Immediately after the false twist step by the lower belt 113 serving as the second twisting point, a joint twist of a forth twist in the same direction as the first twist and second twist, and a fifth twist in the reversed direction are imparted to the preliminary singles yarn for the production of a final singles ring yarn 104, wherein the forth twist is produced by a rotatable take-up package 121 onto which the final singles yarn is drawn, wherein the fifth twist results in correspondence to the second twist by a running of the lower belt 113 on the yarn. Then the yarn 104 proceeds to a yarn guide 115, and then further to the bobbin 121. The yarn 104 becomes wound on the bobbin 121 via a traveler 117 moving on a ring rail 119.
As shown in
Furthermore, in the exemplary embodiment, there are two false twisting points of a false twist device by the travelling upper belt and lower belt for the yarn. The false twist efficiency for the yarn depends on the friction between the yarn and the surface of the upper belt and lower belt, and the ratio of the speed of the belts to the delivery speed of the yarn. The residual torque and other yarn properties of the final singles ring yarn are controlled by controlling the friction between the yarn and the surface of the upper belt and lower belt, and the ratio of the speed of the belts to the delivery speed of the yarn.
The belt can be driven by a conveyor belt 209 having two or more pulleys 207, whereby at least one of the pulleys 207 is attached to a motor 211. The motor 211 is controlled by suitable electronics such as inverters 213. The motor 211 has the capability to drive the conveyor belt and further drive the double belts with a controllable ratio of the speed of the belts to the delivery speed of the yarn predetermined by the desired impartation of false twist and thus the resultant amount of residual torque as well as other yarn performance properties in the final singles ring yarn.
An additional yarn guide 110 installed above the upper belt 111 for each spindle is used to control the yarn movement during the spinning. The positioning of the yarn guide 110 should be carefully arranged in the installation. Excess amount of friction between yarn guide and yarn results in the yarn breakage while insufficient amount of false twist results in poor yarn strength. Several belt guides 203, installed on the both sides of the double belts 111 and 113, and several pressuring discs 201, installed on upper and lower sides of the belts 111 and 113, are used to control the belts' movement, as well as adjust the geometric interrelationships of the yarn and the upper belt and lower belt and the tension of the belts. Through the belt guides 203, pressurizing discs 201 and the wheels 205, the belts are maintained in a stable condition with predetermined tension.
The use of the double false-twisting technique according to the present invention alone may be sufficient for producing reasonable quality yarns. This double false-twisting technique has achieved the following effects: (1) improving the yarn structures substantially in terms of fiber packing density and fiber configuration. For example, the central packing density can reach as high as 90%, and the average inclination angle of fibers can be reduced by 30-40%. (2) reducing yarn hairiness by at least 50% from what is achievable by compact spinning which is a more complicated, more expensive process; (3) reducing yarn residual torque by 40% or more; (4) reducing yarn twist by 20% or more yet keeping the same yarn strength, which means increasing productivity of yarn spinning by 20% or more; and (5) enhancing yarn and fabric softness significantly. While in the present invention, the double-belt twister (implemented as a single endless belt) depicted in
For producing finest quality yarns or yarns for high-quality products, it was subsequently discovered that the double-twisting technique disclosed above in the present invention alone was not sufficient because significant numbers of neps, thick and thin places are present in the yarns, as shown in the Table 1. Hence, the appearance of the yarn deteriorates and is not acceptable in high-quality products. This necessitated further efforts in the present invention to solve the problem. Consequently, various preferred embodiments were developed as shown in
Table 1 shows comparative results of the yarn properties made by the embodiments with and without tucking the long fiber ends prior to entering the false twisting zone. Two trials were conducted with the same set of parameters except that the first trial was using the spinning apparatus with the linear and open false twisting device alone (i.e., the upper and lower belt of a single endless belt shown in
As it can be seen from the results that the improvement brought about by the combination was dramatic in terms of neps reduction: the Neps (140%) was reduced from 1245 to 185. In almost every respects of yarn properties, the combination produced improvement.
Thus, with the addition of a compact spinning device, an effective solution is provided in the present invention to produce high-quality yarns with low residual torque, low twisting, low hairiness and low rate of neps. This solution is unexpected and outside of conventional thinking. Given the fact that the double-twisting device of the present invention is regarded a less-expensive replacement for a compact spinning device (i.e., the double-twisting device can achieve the same or better effect in reducing yarn hairiness with less cost as the compact spinning device), it would not make sense to put these two devices in a sequence because of added installation and operational costs. Indeed, for general purposes of producing lower-end or coarse count yarns, the double-twisting technique alone would be an adequate replacement for a more expensive setup with the compact spinning device. However, in the present invention, it was surprisingly discovered that combination use of both the compact spinning device and a double false twisting device can have an unexpected effect of solving the problem (i.e., the presence of neps, thick and thin places in the yarn) introduced by the double-twisting technique. The improvement brought by the combination is of such a degree which justifies the extra cost of adding a compact spinning device to the double-twisting technique of the present invention, particularly for producing high-quality yarns and fine count yarns.
While there have been described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes, in the form and details of the embodiments illustrated, may be made by those skilled in the art without departing from the spirit of the invention. The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.
This application is a continuation-in-part (CIP) application of patent application Ser. No. 12/222,133, filed on Aug. 4, 2008, now abandoned, the disclosure of which is incorporated herein by reference in its entirety for all purposes.
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Number | Date | Country | |
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Child | 13343723 | US |