Draft roller, spinning unit, and spinning machine

The front top roller (20) includes a fiber contacting portion (30) and a reduced-diameter portion (31). The fiber contacting portion (30) has a substantially uniform outer diameter. The reduced-diameter portion (31) is provided at both ends of the fiber contacting portion (30) in an axial direction, and is formed with an outer diameter smaller than an outer diameter of the fiber contacting portion (30). The fiber contacting portion (30) has a width (W1) in an axial direction of 18 mm and the outer diameter (D1) of 30 mm. An outer diameter (D2) of the reduced-diameter portion (31) is 25 mm.

CROSS REFERENCE

The present application claims the benefit of JP-2011-146765 filed on Jun. 30, 2011, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention mainly relates to a shape of a draft roller arranged in a spinning machine.

BACKGROUND OF THE INVENTION

A spinning machine includes a spinning device adapted apply a twist to a fiber bundle to produce a spun yarn. The spinning machine also includes a draft device adapted to draft the fiber bundle (stretch the fiber bundle). The draft device sandwiches the fiber bundle (or the sliver) with a rotating draft roller pair and transports the fiber bundle to stretch the fiber bundle into an appropriate fiber width, and to supply the fiber bundle to the spinning device.

In this type of draft device, the draft roller rotates at high speed, and thus airflow (accompanying airflow) is generated along an outer peripheral surface of the draft roller. This accompanying airflow is known to greatly influence yarn quality. Therefore, conventionally, attempts have been made to devise a shape of the draft roller to reduce an adverse effect by the accompanying airflow. Such a draft roller is described in Japanese Unexamined Patent Publication Nos. 7-126926 (Patent Document 1), 2010-163702 (Patent Document 2), and 2005-113274 (Patent Document 3).

Patent Document 1 discloses a front top roller in which an effective roller width is narrowed to about a half or more of a standard width. In other words, a step is provided on an outer periphery of the front top roller disclosed in Patent Document 1. In Patent Document 1, according to such a configuration, the drafted fiber bundle is not influenced by the accompanying airflow and cotton fly is hardly moved to both sides of the front top roller.

In Patent Document 2, a step formed on a front top roller (referred to as gap L in Patent Document 2) is preferably greater than or equal to 1 mm and smaller than or equal to 3 mm. However, Patent Document 2 does not disclose about other specific dimensions of the step.

In this regard, according to Patent Document 3, in high speed spinning exceeding 300 m/min (experiment was conducted at specifically 350 m/min in Patent Document 3), a dimension of a step of a front roller (referred to as gap B in Patent Document 3) is suitably 1.5 mm. In Patent Document 3, drawbacks occur even if the step of the front roller is too narrow or too wide.

As described above, when forming the step on the front top roller, it is known that the step of 1.5 mm is the most suitable. As pointed out in Patent Document 3, drawbacks occur even if the dimension of the step is too high or too low. Therefore, the dimension of the step of the front top roller is not ventured to be set to other than 1.5 mm.

The front top roller of the draft device is generally made of rubber. With such a rubber roller, a portion that makes contact with the fiber bundle (central portion in an axial direction) tends to wear and become recessed through use. That is, the rubber front top roller is a consumable. However, if the front top roller is discarded with minor wear, an operation cost of the spinning machine increases. Thus, attempts have been made to abrade a surface of the worn-out front top roller into a smooth state (state in which the recess is eliminated) so that the front top roller can be reused.

Meanwhile, since the outer diameter of the front top roller becomes smaller with the abrasion of the surface of the front top roller, the step formed on the front top roller becomes smaller. As a result, yarn quality degrades. Therefore, in view of the quality of the spun yarn to be produced, a minimum diameter of the usable front top roller is set and the reuse of the front top roller, which outer diameter has become smaller than the minimum diameter, needs to be prohibited. Thus, the conventional front top roller cannot be repeatedly abraded and used for a long period of time.

Patent Document 3 assumes a spinning speed of at least 300 m/min as “high speed spinning”, but due to further improvement in the spinning speed of recent years, the spinning speed may exceed 400 m/min. Therefore, a rotation speed of the draft roller is becoming higher in recent years than at the time of the application of Patent Document 3, and an influence of the accompanying airflow on the yarn quality is also assumed to have changed. Therefore, the shape of the draft roller assumed as optimum in the above patent documents may not be optimum in the current high speed spinning (spinning speed of around 400 m/min). In other words, there is still room for improvements to improve the shape of the draft roller to enhance the yarn quality.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a draft roller in which degradation of yarn quality is reduced.

According to a first aspect of the present invention, a draft roller suitable for drafting a fiber bundle includes a fiber contacting portion and a reduced-diameter portion. The fiber contacting portion has a substantially uniform outer diameter. The reduced-diameter portion is provided at both ends of the fiber contacting portion in an axial direction, and is formed with an outer diameter smaller than the outer diameter of the fiber contacting portion. The fiber contacting portion has a width in an axial direction of 18 mm and the outer diameter of 30 mm. The outer diameter of the reduced-diameter portion is 25 mm.

Since a step formed by the fiber contacting portion and the reduced-diameter portion is 2.5 mm, the draft roller has a margin in the step as compared to the conventional draft roller (step of 1.5 mm). Therefore, even if the fiber contacting portion is abraded and the step becomes small, an influence on the yarn quality is smaller than the conventional draft roller. As a result, since the number of times of abrasion can be increased with the above draft roller than the conventional draft roller, the draft roller can be used for a longer period of time, and an operation cost can be reduced.

In the above draft roller, after abrading the outer peripheral surface of the fiber contacting portion, a step formed by an outer peripheral surface of the fiber contacting portion and an outer peripheral surface of the reduced-diameter portion is preferably at least 1.5 mm.

Since the step is made greater than the conventional draft roller, the draft roller according to an embodiment of the present invention can allow the abrasion of the fiber contacting portion while the step is greater than at least the conventional draft roller (a step of 1.5 mm). If the fiber contacting portion is excessively abraded, a thickness of a rubber of the fiber contacting portion becomes thin and a force of gripping the fiber bundle is lowered, which may cause the degradation in the yarn quality. However, according to the structure described above, the step of at least 1.5 mm can be ensured. Therefore, the yarn quality can be maintained.

According to a second aspect of the present invention, a draft roller suitable for drafting a fiber bundle includes a fiber contacting portion and a reduced-diameter portion. The fiber contacting portion has a substantially uniform outer diameter. The reduced-diameter portion is provided at both ends of the fiber contacting portion in an axial direction, and is formed with an outer diameter smaller than the outer diameter of the fiber contacting portion. A step of at least 1.5 mm is formed by an outer peripheral surface of the fiber contacting portion and an outer peripheral surface of the reduced-diameter portion after abrasion of the outer peripheral surface of the fiber contacting portion.

Since the above draft roller has a larger margin in abrading the fiber contacting portion than the conventional draft roller (a step of 1.5 mm), the number of times of abrasion of the fiber contacting portion can be increased. Accordingly, the draft roller can be used for a longer period of time, and the operation cost can be reduced.

The draft roller is structured such that the outer diameter of the reduced-diameter portion is 25 mm, and the outer diameter before the abrasion of the fiber contacting portion is 30 mm.

Since the step formed by the fiber contacting portion and the reduced-diameter portion is 2.5 mm, the draft roller has a margin in the step as compared to the conventional draft roller (a step of 1.5 mm). Therefore, even if the fiber contacting portion is abraded and the step becomes small, the influence on the yarn quality is smaller than the conventional draft roller. As a result, since the above draft roller can be abraded more times than the conventional draft roller, the draft roller can be used for a longer period of time, and the operation cost can be reduced.

In the above draft roller, the fiber contacting portion and the reduced-diameter portion are preferably connected by a taper portion.

According to such a structure, when abrading the outer peripheral surface of the fiber contacting portion with a grinding machine, the draft roller can be more easily brought close to a grinding stone from the axial direction, and an abrasion operation can be smoothly carried out.

According to a third aspect of the present invention, a spinning unit includes a draft device adapted to draft a fiber bundle, and a spinning section adapted to spin a fiber bundle drafted by the draft device at a spinning speed of at least 400 m/min. The draft device includes a draft roller adapted to draft the fiber bundle by rotating. The draft roller includes a fiber contacting portion and a reduced-diameter portion. The fiber contacting portion has a substantially uniform diameter. The reduced-diameter portion is provided at both ends of the fiber contacting portion in an axial direction, and is formed with an outer diameter smaller than the outer diameter of the fiber contacting portion. A step of 2.5 mm is formed by an outer peripheral surface of the fiber contacting portion and an outer peripheral surface of the reduced-diameter portion.

Since the step of 2.5 mm is formed as described above, there is a margin in the step as compared to the conventional draft roller (a step of 1.5 mm). Therefore, even if the fiber contacting portion is abraded and the step becomes small, the influence on the yarn quality is smaller than the conventional draft roller. As a result, since the above draft roller can be abraded more times than the conventional draft roller, the draft roller can be used for a longer period of time, and the operation cost can be reduced. Furthermore, in the draft roller having the step of 2.5 mm as described above, the number of yarn defects can be reduced compared to the conventional draft roller in the high speed spinning in which the spinning speed is at least 400 m/min.

In the above spinning unit, the fiber contacting portion preferably has a width in an axial direction of 18 mm and an outer diameter of 30 mm, and the reduced-diameter portion preferably has an outer diameter of 25 mm.

In the draft roller arranged in the spinning unit, the number of yarn defects can be reduced as compared to the conventional draft roller, particularly in the high speed spinning in which the spinning speed is at least 400 m/min.

In the above spinning unit, the draft device includes a plurality of rollers adapted to draft the fiber bundle and arranged along a transportation direction of the fiber bundle. The draft roller is a front top roller arranged most downstream in the transportation direction in the draft device.

In the draft device, the rotation speed of the roller becomes higher at the downstream. Therefore, since the front top roller arranged most downstream rotates at a very high speed, the influence of the accompanying airflow is large and wear is also severe. Accordingly, the structure of the draft roller described above is applied to the front top roller so that an effect of increasing the number of times of abrasion as well as reducing the number of yarn defects can be suitably achieved.

According to a fourth aspect of the present invention, a spinning machine including a plurality of spinning units described above is provided.

In such a spinning machine, since the draft roller having a usable period longer than the conventional draft roller is adopted in each spinning unit, the operation cost of the entire spinning machine can be reduced. In the high speed spinning of at least 400 m/min, by adopting the draft roller having a step (step of 2.5 mm) greater than the conventional draft roller in each spinning unit, the influence of the accompanying airflow is less likely to be received, and consequently, a variation in yarn quality for each spinning unit can be reduced and the quality of the produced spun yarn can be maintained uniform.

According to a fifth aspect of the present invention, there is provided a spun yarn manufacturing method for manufacturing a spun yarn by applying a twist to a fiber bundle drafted by a draft roller. The draft roller includes a fiber contacting portion and a reduced-diameter portion. The fiber contacting portion has a substantially uniform outer diameter. The reduced-diameter portion is provided at both ends of the fiber contacting portion in an axial direction and is formed with an outer diameter smaller than the outer diameter of the fiber contacting portion. Spinning is performed while gradually changing a step formed by an outer peripheral surface of the fiber contacting portion and an outer peripheral surface of the reduced-diameter portion from 2.5 mm to 1.5 mm.

If the outer peripheral surface of the fiber contacting portion begins to be recessed by wear, the outer peripheral surface of the fiber contacting portion is abraded to reduce the outer diameter, so that the outer peripheral surface of the fiber contacting portion is in a smooth state and the draft roller can be reused. Although the step of the outer peripheral surface of the roller is gradually reduced through such abrasion, the yarn quality can be prevented from degrading by having the step within the range described above.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A fine spinning machine (spinning machine) according to one embodiment of the present invention will be described with reference to the drawings. A fine spinning machine1as a spinning machine illustrated inFIG. 1includes a plurality of spinning units2arranged in line, a yarn joining cart3, a blower box80, and a motor box5.

As illustrated inFIG. 1, each spinning unit2includes a draft device7, a spinning device (spinning section)9, a yarn accumulating device12, and a winding device13, arranged in this order from upstream to downstream. “Upstream” and “downstream” respectively refer to upstream and downstream in a travelling direction of a fiber bundle and a yarn at the time of spinning. Each spinning unit2is adapted to spin a fiber bundle8fed from the draft device7by the spinning device9to produce a spun yarn10, and the spun yarn10is wound by the winding device13into a package45. Each spinning unit2is set so as to produce the spun yarn10at a spinning speed of at least 400 m/min.

The draft device7is arranged in proximity to an upper end of a housing6of the fine spinning machine1. The draft device7drafts (stretches the fibers) of a sliver (material of the fiber bundle)15supplied from a sliver case (not illustrated) through a sliver guide (not illustrated) until a predetermined width is obtained.

The draft device7includes a plurality of draft rollers. Two draft rollers as one set form a draft roller pair. The draft device7of the present embodiment is a so-called four line draft device including four draft roller pairs, i.e., a back roller pair including draft rollers16and66, a third roller pair including draft rollers17and67, a middle roller pair including draft rollers19and69, and a front roller pair including draft rollers20and70, arranged in this order from the upstream.

In each draft roller pair, a draft roller on a front side of the fine spinning machine1is referred to as a top roller, and a draft roller on a rear side of the fine spinning machine1is referred to as a bottom roller. The top rollers are, in the order from the upstream, a back top roller16, a third top roller17, a middle top roller19provided with an apron belt18made of rubber, and a front top roller20. The bottom rollers are, in the order from the upstream, a back bottom roller66, a third bottom roller67, a middle bottom roller69provided with an apron belt68made of rubber, and a front bottom roller70.

Outer peripheral surfaces of the top rollers16,17, and20are made of rubber. Since the outer peripheral surface of the top roller is made of rubber, the outer peripheral surface of the top roller can be caused to elastically make contact with the sliver15, and each draft roller pair can firmly sandwich the sliver15. Each top roller16,17,19,20is supported via a bearing (not illustrated) and the like in a freely rotatable manner with an axis line thereof as a center.

Each bottom roller66,67,69,70is a roller made of metal, and is rotatably driven with an axis line thereof as the center by a driving source Mot illustrated). In each draft roller pair, the top roller and the bottom roller are arranged to face each other. The draft device7includes an urging unit (not illustrated) adapted to urge each of the top rollers16,17,19, and20towards the opposing bottom rollers66,67,69, and70, respectively. The outer peripheral surface of the top roller16,17,19, and20is thereby pushed against the outer peripheral surface of the bottom roller66,67,69, and70, respectively. When the bottom rollers66,67,69, and70are rotatably driven, the top rollers16,17,19, and20opposing and contacting thereto also rotate accompanying the rotation of the bottom rollers66,67,69, and70.

The draft device7sandwiches the sliver15between the rotating top rollers16,17,19, and20and the bottom rollers66,67,69, and70, and transports the sliver15towards the downstream. The draft device7is structured such that the rotation speed becomes faster towards the draft roller pair on the downstream. Therefore, the fiber bundle8(or the sliver15) is stretched (drafted) while being transported between the draft roller pair and the draft roller pair. A degree to which the fiber bundle8is drafted can be changed by appropriately setting the rotation speed of each of the bottom rollers66,67,69, and70, and thus the fiber bundle8can be drafted into a desired fiber width.

The spinning device9is arranged immediately downstream of the front roller pair. The fiber bundle8drafted by the draft device7is supplied to the spinning device9. By supplying the fiber bundle8drafted to a predetermined width to the spinning device9, the spun yarn10of a desired yarn count (thickness) can be spun by the spinning device9.

The spinning device9applies a twist to the fiber bundle8supplied from the draft device7to produce the spun yarn10. In the present embodiment, an air-jet spinning device which uses whirling airflow to apply the twist to the fiber bundle B is adopted. This type of spinning device can also perform high speed spinning of at least 400 m/min. As illustrated inFIG. 3, the spinning device9mainly includes a nozzle holder35, a hollow guide shaft body23, and a fiber guide (fiber guiding section)22.

A spinning chamber26is formed between the nozzle holder35and the hollow guide shaft body23. The nozzle holder35is provided with an air ejecting nozzle27for ejecting air into the spinning chamber26. The fiber guide22is provided with a yarn introducing port21for introducing the fiber bundle8into the spinning chamber26. The air ejecting nozzle27is configured to eject the air into the spinning chamber26to generate whirling airflow. The fiber bundle8supplied from the draft device7is guided into the spinning chamber26by the fiber guide22having the yarn introducing port21. In the spinning chamber26, the fiber bundle8is swung around the periphery of the hollow guide shaft body23by the whirling airflow, and the twist is applied to produce the spun yarn10. The twisted spun yarn10is passed through a yarn passage29formed at an axial center of the hollow guide shaft body23, and fed to an outside of the spinning device9from a yarn exit (not illustrated) on the downstream of the hollow guide shaft body23.

A needle-like guide needle22ais arranged in the yarn introducing port21, and a tip of the guide needle22ais arranged towards the spinning chamber26. The fiber bundle8introduced from the yarn introducing port21is guided into the spinning chamber26so as to be wound around the guide needle22a. Accordingly, a state of the fiber bundle8introduced into the spinning chamber26can be stabilized. Furthermore, since the fiber bundle8is guided so as to be wound around the guide needle22a, even if a twist is applied to the fiber in the spinning chamber26, the twist is prevented from being propagated to the upstream of the fiber guide22. Accordingly, the twist applied by the spinning device9is prevented from influencing the draft device7. However, the guide needle22amay be omitted, and a downstream end of the fiber guide22may function as the guide needle22a.

The winding device13is arranged downstream of the spinning device9. The winding device13includes a cradle arm71supported to be swingable about a supporting shaft73. The cradle arm71can rotatably support a bobbin48for winding the spun yarn10.

The winding device13includes a winding drum72and a traverse device75. The winding drum72is adapted to be driven while making contact with an outer peripheral surface of the bobbin48or an outer peripheral surface of the package45formed by winding the spun yarn10around the bobbin98. The traverse device75includes a traverse guide76capable of engaging the spun yarn10. The winding drum72is driven by an electric motor (not illustrated) while reciprocating the traverse guide76by a driving unit (not illustrated). The package45making contact with the winding drum72can be rotated, and the spun yarn10can be wound into the package45while being traversed.

As illustrated inFIG. 1andFIG. 2, the yarn joining cart3includes a splicer (yarn joining device)43, a suction pipe44, and a suction mouth46. When yarn breakage or yarn cut occurs in a spinning unit2, the yarn joining cart3travels on a rail41to the relevant spinning unit2and stops. The suction pipe44sucks and catches a yarn end fed from the spinning device9while being swung vertically with a shaft as the center and guides the yarn end to the splicer43. The suction mouth46sucks and catches a yarn end from the package45supported by the winding device13while being swung vertically with a shaft as the center and guides the yarn end to the splicer43. The splicer43joins the guided yarn ends.

The yarn accumulating device12is arranged between the spinning device9and the winding device13. As illustrated inFIG. 2, the yarn accumulating device12includes a yarn accumulating roller14, and an electric motor25for rotatably driving the yarn accumulating roller19.

The yarn accumulating roller14can have a prescribed amount of the spun yarn10wound around an outer peripheral surface thereof to temporarily accumulate the spun yarn10. The yarn accumulating device12rotates the yarn accumulating roller14at a predetermined rotation speed with the spun yarn10wound around the outer peripheral surface of the yarn accumulating roller14to pull out the spun yarn10from the spinning device9at a predetermined speed and transport the spun yarn10towards the downstream. Since the spun yarn10is temporarily accumulated on the outer peripheral surface of the yarn accumulating roller14, the yarn accumulating device12can function as one type of buffer. Accordingly, a drawback (e.g., slackening of the spun yarn10or the like) when a spinning speed in the spinning device9and a winding speed in the winding device13do not match for some reason can be resolved.

A yarn clearer (yarn quality measuring instrument)52is arranged at a position between the spinning device9and the yarn accumulating device12. The spun yarn10spun by the spinning device9is passed through the yarn clearer52before being wound by the yarn accumulating device12. The yarn clearer52monitors the travelling spun yarn10with a capacitance sensor (not illustrated), and when a yarn defect of the spun yarn10(area where abnormality is found in thickness or the like of the spun yarn10) is detected, the yarn clearer52transmits a yarn defect detection signal to a unit controller (not illustrated). The yarn clearer52may perform monitoring with an optical sensor instead of a capacitance sensor.

Upon receiving the yarn defect detection signal, the unit controller immediately cuts the spun yarn10with a cutter57, stops the draft device7, the spinning device9, and the like, and also stops the winding in the winding device13. The unit controller transmits a control signal to the yarn joining cart3to cause the yarn joining cart3to travel to front of the relevant spinning unit2. The yarn joining cart3guides the yarn end from the spinning device9and the yarn end from the package45to the splicer43with the suction pipe44and the suction mouth46, respectively, and carries out a yarn joining operation by the splicer43. According to such a yarn joining operation, the yarn defect is removed, and the winding of the spun yarn10into the package45can be resumed. The cutter57may be omitted, and the spun yarn10may be cut as if being torn off by stopping the driving of the draft device7while continuing the driving of the winding device13.

The front top roller20arranged in the draft device7will be described in detail below.

As described above, since the rotation speed becomes faster for the draft roller pair located downstream in the draft device7, the rotation speed of the front roller pair which is the draft roller pair arranged most downstream (the front top roller20and the front bottom roller70) becomes very fast. Thus, the accompanying airflow generated in proximity to the front roller pair also becomes very strong, and an influence of the accompanying airflow on the yarn quality also becomes large. In the draft device7according to the present embodiment, in order to reduce the influence of the accompanying airflow generated in proximity to the front roller pair rotating at high speed, a step is formed on the outer peripheral surface of the front top roller20.

Specifically, as illustrated inFIG. 4andFIG. 5, the front top roller20includes a fiber contacting portion30formed in a circular column shape having a substantially uniform outer diameter, and a reduced-diameter portion31formed in a circular column shape having an outer diameter smaller than the fiber contacting portion30at both ends of the fiber contacting portion30in an axial direction. A taper portion32is formed between the fiber contacting portion30and the reduced-diameter portion31. As described above, since the front top roller20includes the fiber contacting portion30and the reduced-diameter portion31having an outer diameter smaller than the fiber contacting portion30, the front top roller20have a step formed by an outer peripheral surface of the fiber contacting portion30and an outer peripheral surface of the reduced-diameter portion31(indicated with reference numeral L1inFIG. 4andFIG. 5).

The outer peripheral surface of the fiber contacting portion30of the front top roller20makes contact with the outer peripheral surface of the front bottom roller70arranged facing the front top roller20. Accordingly, as illustrated inFIG. 4, the front roller pair can sandwich the fiber bundle8between the fiber contacting portion30and the front bottom roller70. A gap is formed between the reduced-diameter portion31and the front bottom roller70.

Next, a description will be made on the accompanying airflow generated in proximity to the front top roller20. As described above, when the front bottom roller70facing the front top roller20is rotatably driven, the front top roller20rotates accompanying the rotation of the front bottom roller70. Therefore, the front top roller20and the front bottom roller70rotate in opposite directions to each other. Thus, as illustrated inFIG. 6, accompanying airflow90generated by the rotation of the front top roller20and accompanying airflow91generated by the rotation of the front bottom roller70become airflows opposing each other, and collide near an entrance to the front roller pair of the fiber bundle8.

The collided accompanying airflows90and91become airflows flowing in a direction parallel to a roller shaft of the front top roller20and the front bottom roller70(hereinafter simply referred to as axial direction), and flow towards the ends of the front top roller20and the front bottom roller70in the axial direction (i.e., flow so as to spread outward). When reaching the end of the fiber contacting portion30in the axial direction, the accompanying airflow passes through the gap formed between the reduced-diameter portion31and the front bottom roller70and flows in a direction parallel to the travelling direction of the fiber bundle8. In this manner, the flow of the accompanying airflow flowing in the axial direction can be released through the gap formed between the reduced-diameter portion31and the front bottom roller70.

As described above, by forming the step L1on the outer peripheral surface of the front top roller20, the gap can be formed between the front top roller20and the front bottom roller70, and the accompanying airflow generated by the rotation of the front top roller20can be released. As a result, since the flow of the accompanying airflow flowing in the axial direction weakens, the fibers of the fiber bundle8can be suppressed from spreading in the axial direction by the accompanying airflow, and the yarn quality can be prevented from being degraded.

In the present embodiment, the step L1of the front top roller20is formed by scraping a normal cylindrical rubber roller. The fiber contacting portion30, the reduced-diameter portion31, and the taper portion32are formed as an integrated rubber member. However, the entire front top roller20is not required to be made of rubber, and only the outer peripheral surface is required to be made of rubber. For example, in the present embodiment, as illustrated inFIG. 5, a metal tubular body34is arranged on an inner side of the front top roller20. Accordingly, rigidity of the front top roller20can be ensured. The front top roller20according to the present embodiment is provided with a bearing (not illustrated) between the metal tubular body34and a rotation shaft36, and the front top roller20can be supported in a freely rotatable manner with respect to the rotation shaft36.

Next, a description will be made on the wear and abrasion of the front top roller20.

As described above, since the outer peripheral surface of the front top roller20is made of rubber, the front top roller20wears with use and the shape changes. In the following description, in order to distinguish from the worn-out front top roller20, a state before wear (and abrasion) (i.e., shape of the new front top roller20) is referred to as “initial state”.

The wear of the front top roller20will be more specifically described below. If the front top roller20is continuously used, the outer peripheral surface of the fiber contacting portion30making contact with the fibers starts to wear. The outer peripheral surface of the fiber contacting portion30is not uniformly in contact with the fiber bundle8, and the central portion in the axial direction of the fiber contacting portion30is mainly in contact with the fiber bundle8. Therefore, if the front top roller20is continuously used, an axial central part of the fiber contacting portion30wears and is recessed. If the axial central part of the fiber contacting portion30is recessed, a gripping force of the fiber bundle8weakens between the outer peripheral surface of the fiber contacting portion30and the outer peripheral surface of the front bottom roller70, which becomes a cause of degradation in the yarn quality.

Therefore, conventionally, the outer peripheral surface of the worn-out front top roller20is abraded to a smooth state (state in which the recess is eliminated) so that the front top roller20can be reused. An abrasion device50therefor is illustrated inFIG. 7.

The abrasion device50is configured as one type of grinding machine. Specifically, the abrasion device50includes a rotating grinding stone51, a roller holding section53, and a roller driving section54. The roller holding section53holds the rotation shaft36of the front top roller20. The roller holding section53can move in a direction parallel to an axial direction of the front top roller20. The roller driving section54includes a driving roller55which makes contact with the outer peripheral surface of the front top roller20. The driving roller55is rotatably driven by a motor (not illustrated). When the driving roller55is rotatably driven, the front top roller20making contact with the driving roller55can be rotated.

In the abrasion device50, the roller holding section53gripping the rotation shaft36of the front top roller20is moved towards the grinding stone51rotating at high speed from an axial direction of the rotation shaft36. In this manner, the fiber contacting portion30of the front top roller20is caused to make contact with the grinding stone51, and the outer peripheral surface of the fiber contacting portion30is abraded. When the driving roller55is rotatably driven, the front top roller20is rotated about the rotation shaft36, and the outer peripheral surface of the fiber contacting portion30can be uniformly abraded.

Since the taper portion32is formed on the front top roller20of the present embodiment, the fiber contacting portion30can be caused to smoothly make contact with the grinding stone51. If the taper portion32is not formed (when cross-sectional contour of a connecting portion of the fiber contacting portion30and the reduced-diameter portion31is a right angle), the grinding stone51may get caught at the step of the front top roller20when the front top roller20is moved towards the grinding stone51, and the abrasion may not be smoothly carried out. Since the taper portion32is formed between the fiber contacting portion30and the reduced-diameter portion31, the front top roller20of the present embodiment can cause the fiber contacting portion30to smoothly make contact with the grinding stone51.

Problems that may arise from the abrasion will be briefly described below.

As described above, the conventional front top roller typically has a dimension of the step of 1.5 mm. Patent Document 3 describes that defects arise if the step is smaller than 1.5 mm. If the fiber contacting portion of the conventional front top roller (step of 1.5 mm) is abraded, it is apparent that the step becomes smaller than 1.5 mm. In other words, the yarn quality degrades as more abrasion is carried out in the conventional front top roller (step of 1.5 mm). Thus, in the conventional front top roller, the number of times the abrasion can be carried out for reuse is small, and consequently, life of the front top roller is short.

A reason why the yarn quality degrades as the step becomes smaller will be described below. If the step L1becomes small, the gap formed between the front top roller20and the front bottom roller70becomes narrow, and the effect of releasing the accompanying airflow through the gap weakens. As a result, the fibers are easily disturbed by the accompanying airflow, which may degrade the yarn quality. Reduction in the step L1means that a thickness of the rubber at a portion of the fiber contacting portion30is reduced. Therefore, the force of gripping the fiber bundle8with the fiber contacting portion30and the front bottom roller70weakens and the yarn quality degrades.

A shape of each section of the front top roller20of the present embodiment will be specifically described below.

The front top roller20of the present embodiment is structured as below in view of the problems of the conventional front top roller having a step of 1.5 mm. The front top roller20has a step L1of 2.5 mm in the initial state. Since the step of the initial state is greater than the conventional front top roller (step of 1.5 mm), a margin for abrading the outer peripheral surface of the front top roller20can be provided, and the life of the front top roller20can be lengthened.

Specifically, in the initial state, the fiber contacting portion30of the front top roller20according to the present embodiment has a width W1of 18 mm, and an outer diameter D1of 30 mm. A width W2of the reduced-diameter portion31is 6 mm, on each left and right side, and an outer diameter D2is 25 mm. That is, a difference (D1-D2) between the outer diameter D1of the fiber contacting portion30and the outer diameter D2of the reduced-diameter portion31is 5 mm in the initial state. Therefore, the step L1formed by the outer peripheral surface of the fiber contacting portion30and the outer peripheral surface of the reduced-diameter portion31is 2.5 mm in the initial state. A width W3of the taper portion32in the axial direction is 1 mm on each end of the fiber contacting portion30.

Therefore, with the step L1of the front top roller20as 2.5 mm in the initial state, the margin for scraping the outer peripheral surface of the fiber contacting portion30can be ensured 1 mm more than the conventional front top roller (a step of 1.5 mm). This is because even if the outer peripheral surface of the fiber contacting portion30of the front top roller20of the present embodiment is scraped by 1 mm (even if the outer diameter D1of the fiber contacting portion30is reduced by 2 mm), the step of 1.5 mm, which is the same as the conventional front top roller, can be ensured. In other words, if the step L1after the outer peripheral surface of the fiber contacting portion30is abraded is greater than or equal to 1.5 mm, the front top roller20of the present embodiment can be continuously used. The use of the front top roller20may, of course, be continued even if the step L1after the abrasion becomes smaller than 1.5 mm, but this is not recommended since the quality of the spun yarn10may degrade.

Therefore, the manufacturing method of the spun yarn10by the fine spinning machine1of the present embodiment is as described below.

First, an operator of the fine spinning machine1attaches the (new) front top roller20in the initial state to the spinning unit2. At this time, the step L1of the front top roller20is 2.5 mm. Under this state, the spun yarn10is produced at the spinning speed of at least 400 m/min. As the spinning is continued, the fiber contacting portion30wears and is recessed. After the fiber contacting portion30is worn out to a certain degree, the operator once detaches the worn-out front top roller20from the spinning unit2and abrades the outer peripheral surface of the fiber contacting portion30with the abrasion device50. Accordingly, the outer diameter D1of the fiber contacting portion30is reduced, and the step L1becomes smaller.

If the step L1of the front top roller20after the abrasion is greater than or equal to 1.5 mm, the operator attaches the abraded front top roller20to the spinning unit2and continues to produce the spun yarn10by the high speed spinning of a spinning speed of at least 400 m/min. If the step L1of the front top roller20after the abrasion is smaller than 1.5 mm (if the fiber contacting portion30is worn out to the limit), the yarn quality degrades if such a front top roller20is used, and thus, the relevant front top roller20is discarded.

As described above, in the fine spinning machine1of the present embodiment, the spun yarn10is produced while repeating the use and abrasion of the front top roller20. That is, the fine spinning machine1of the present embodiment is performing spinning while gradually changing the step L1of the front top roller20from 2.5 mm to 1.5 mm. By manufacturing the spun yarn10with such a manufacturing method, the degradation in the yarn quality can be suppressed while abrading and reusing the front top roller20.

Meanwhile, as disclosed in Patent Document 3, it is known that drawbacks arise if the step is greater than 1.5 mm in the high speed spinning in which the spinning speed is at least 300 m/min. Thus, conventionally, a roller having a step larger than 1.5 mm has not been used. In other words, from conventional common knowledge, the front top roller20of the present embodiment (a step of 2.5 mm) may be considered as an impractical draft roller.

The spinning speed of about 350 m/min was a limit in the high speed spinning when Patent Document 3 was filed. However, the spinning speed is further increasing in recent years, and the spinning speed of around 400 m/min has become popular, and thus the spinning speed of at least 400 m/min may be set. If the spinning speed increases, the rotation speed of the front top roller20also increases, and thus the accompanying airflow generated at the periphery of the front top roller20also changes. Therefore, the experimental result described in Patent Document 3 may not be applied to the fine spinning machine1of the present embodiment (spinning speed of at least 400 m/min).

Experiments have been conducted to compare the conventional front top roller (a step of 1.5 mm) and the front top roller20(a step of 2.5 mm) of the present embodiment in high speed spinning at about 400 m/min (spinning speed of at least 350 m/min). The conventional front top roller is, specifically, a roller in which the fiber contacting portion30has the outer diameter D1of 30 mm, the width W of 18 mm, and the reduced-diameter portion31has the outer diameter D2of 27 mm.

Contents of the experiments will be specifically described below. A plurality of spinning units2adopting the conventional front top roller (a step of 1.5 mm) and a plurality of spinning units2adopting the front top roller of the present embodiment (a step of 2.5 mm) are prepared. In each spinning unit2, high speed spinning of around 400 m/min (spinning speed of at least 350 m/min) is carried out, and the number of yarn defects of the produced spun yarn10is measured. An average value of the number of yarn defects detected in the spun yarn10produced by the plurality of spinning units2is calculated, and such an average value becomes the measurement result. The measurement result is illustrated inFIG. 8andFIG. 9. As the number of measured yarn defects is smaller, the spun yarn10has higher quality.

The measurement of the yarn defect can be carried out after the package45is formed, by measuring the spun yarn10wound into the package45with a dedicated measuring device (a yarn defect measuring device). The yarn defect of the spun yarn10can be measured in real time during the spinning with the yarn clearer52arranged in each spinning unit2. In the experiments, data is acquired with both the yarn clearer52and the yarn defect measuring device, and thus both results are illustrated in graphs for reference. The yarn clearer52arranged in the spinning unit2of the present embodiment differs from the yarn defect measuring device in the measuring method of the spun yarn10, and thus the measurement results differ. The measurement result by the yarn clearer52and the measurement result by the yarn defect measuring device match in overall tendency of the data, and thus explanation will not be separately made for each data in the present specification.

InFIG. 8toFIG. 13, A1, B1, and C1are names of category indicating types of yarn defects categorized by a known CLASSIMAT (registered trademark) test. The CLASSIMAT test continuously measures thickness unevenness of the yarn, and categorizes the yarn by a degree of thickness and length. For example, an A1defect refers to the thickness unevenness in which the thickness falls within a range from the average (100%) to 150%, and the length is 1 cm at a maximum. A B1defect refers to the thickness unevenness in which the thickness falls within a range from the average (100%) to 150%, and the length is from 1 cm to 2 cm. A C1defect refers to the thickness unevenness in which the thickness falls within a range from the average (100%) to 150%, and the length is from 2 cm to 4 cm. The vertical axis of the graph ofFIG. 8toFIG. 13indicates the detected number of the yarn defects of A1, B1, and C1.

In the experiments illustrated inFIG. 8andFIG. 9, in order to verify a difference according to the type of fiber, experiments are conducted for each of a case where the spun yarn of a yarn count Ne30 is spun with the fibers of Rayon 100% (FIG. 8A), a case where the spun yarn of the yarn count Ne30 is spun with the fibers of polyester (PE) 100% (FIG. 8B), a case where the spun yarn of the yarn count Ne30 is spun with the fibers of card cotton (CD) 100% (FIG. 9A), and a case where the spun yarn of a yarn count Ne45 is spun with the fibers of polyester 65% and cotton 35% (PC65/35) (FIG. 9B).

As is apparent fromFIG. 8andFIG. 9, the quality of the spun yarn10produced using the front top roller20of the present embodiment (a step of 2.5 mm) is not inferior to the quality of the spun yarn10produced using the conventional front top roller (a step of 1.5 mm). That is, the spun yarn10produced using the front top roller20of the present embodiment has less number of yarn defects than the spun yarn10produced using the conventional front top roller. In other words, in the fine spinning machine1adopting the front top roller20of the present embodiment, the quality of the spun yarn10is improved.

Therefore, it became apparent for the first time from the experiments that the front top roller20having a step of 2.5 mm, which was conventionally considered as impractical, is actually effective at the spinning speed of around 400 m/min. In particular, the above effects can be obtained with the high speed spinning of at least 400 m/min, which is becoming popular in recent years. Therefore, the front top roller20of the present embodiment (a step of 2.5 mm) not only increases the number of times in which abrasion can be carried out and lengthening the life, but also improves the yarn quality.

The experiment results illustrated inFIG. 10andFIG. 11will be described below.

The above experimental results are the average values of the results of measuring the spun yarn10produced with the plurality of spinning units2. However, even when the average yarn quality is satisfactory, if a spun yarn of unsatisfactory quality is produced in a specific spinning unit, only the yarn of unsatisfactory quality greatly stands out in a final fabric product. Therefore, in the fine spinning machine1, it is important to not only improve the average quality of the produced spun yarn10, but also to suppress the variation in quality among the plurality of spinning units2.

Experiments have been conducted to examine the variation in the yarn quality among the plurality of spinning units2. The results are illustrated inFIG. 10andFIG. 11.

First, experiments on the conventional front top roller (a step of 1.5 mm) will be described. In the experiments, eight spinning units2adopting the conventional front top roller (a step of 1.5 mm) are prepared, and the spun yarn10of the yarn count Ne40 are produced with the fibers of Rayon 100% at the spinning speed of around 400 m/min in each spinning unit2.FIG. 10AandFIG. 11Aillustrate the number of yarn defects in the produced spun yarn10for every spinning unit2.

As is apparent from the figures, when using the conventional front top roller having a step of 1.5 nm, the quality of the spun yarn10produced in each spinning unit2varies. For example, in the data ofFIG. 10A, the spun yarn10produced in the spinning unit2indicated as “UNIT6” has the most number of yarn defects (bad yarn quality).

At the conventional spinning speed (about 300 m/min), the yarn quality did not greatly vary among the plurality of spinning units2. Therefore, problems rarely arose even with the conventional front top roller having a step of 1.5 mm. However, as the spinning speed becomes faster to the spinning speed of around 400 m/min in recent years, the yarn quality tends to easily vary among the plurality of spinning units2, as illustrated inFIG. 10AandFIG. 11A. This is because since the rotation speed of the front top roller20becomes faster at high speed spinning, and the accompanying airflow is easily disturbed, the yarn quality is easily influenced by the slight individual difference or the like of each spinning unit2.

The front top rollers of the eight spinning units2, to which the experiments ofFIG. 10AandFIG. 11Awere conducted, were replaced with the front top roller20of the present embodiment (a step of 2.5 mm), and then conducted similar experiments. The results are illustrated inFIG. 10BandFIG. 11B.

As is apparent fromFIG. 10BandFIG. 11B, when the front top roller20of the present embodiment (a step of 2.5 mm) is adopted, the variation in the yarn quality among the plurality of spinning units2is reduced as compared to a case where the conventional front top roller (a step of 1.5 mm) is adopted (FIG. 10AandFIG. 11A). If the front top roller20having a step of 2.5 mm is used, the gap for releasing the accompanying airflow can be sufficiently ensured between the relevant front top roller20and the front bottom roller70, and the accompanying airflow is less likely to be disturbed. As a result, the influence of the individual difference of each spinning unit2hardly appears, and the variation in the yarn quality is assumed to be suppressed.

As described above, according to the front top roller20of the present embodiment, the variation in the yarn quality among the plurality of spinning units2that may occur at the spinning speed of around 400 m/min can be reduced. In particular, it was found that the above-described effects can be obtained in the high speed spinning of at least 400 m/min, which is becoming popular in recent years.

The experimental results ofFIG. 12andFIG. 13will be described below.

The above experimental results are results of using the front top roller20of the initial shape. However, when the outer peripheral surface of the front top roller20is abraded as described above, the outer diameter D1of the fiber contacting portion30is reduced and the step L1becomes smaller, and hence the reduction of the step L1is assumed to influence the yarn quality. Experiments were thus conducted to measure the influence on the yarn quality by reducing the outer diameter D1of the fiber contacting portion30of the front top roller20.

Specifically, for the conventional front top roller (the outer diameter D2of the reduced-diameter portion is 27 mm) and the front top roller of the present embodiment (the outer diameter D2of the reduced-diameter portion31is 25 mm), a plurality of front top rollers20in which the outer diameter D1of the fiber contacting portion30is reduced by 0.3 mm from the initial shape (30 mm) are prepared. Specifically, the front top rollers of D1=30 mm, 29.7 mm, 29.4 mm, 29.1 mm, and 28.8 mm were prepared for each of the conventional front top roller (the outer diameter D2of the reduced-diameter portion is 27 mm) and the front top roller of the present embodiment (the outer diameter D2of the reduced-diameter portion is 25 mm). Then, each front top roller was set in the spinning unit2, and the spun yarn10was produced at the spinning speed of around 400 m/min.

FIG. 12AandFIG. 13Aillustrate the number of yarn defects in the spun yarn10, where the spun yarn of the yarn count Ne40 was produced using each front top roller with the fibers of Rayon 100%. As illustrated inFIG. 12AandFIG. 13A, in the conventional front top roller (the outer diameter D2of reduced-diameter portion is 27 mm), the number of yarn defects increases (the yarn quality degrades) as the outer diameter D1of the fiber contacting portion becomes smaller from the initial shape (30 mm). This means that, in the conventional front top roller (a step of 1.5 mm in the initial shape), the yarn quality degrades as the outer peripheral surface of the fiber contacting portion is abraded.

In the front top roller20of the present embodiment (the outer diameter D2of the reduced-diameter portion is 25 mm), although the outer diameter D1of the fiber contacting portion30is reduced from the initial shape (30 mm), the number of yarn defects hardly increased. This means that in the front top roller20of the present embodiment (a step of 2.5 mm in the initial shape), even if the outer peripheral surface of the fiber contacting portion30is abraded, the yarn quality does not degrade as much as the conventional front top roller (a step of 1.5 mm in the initial shape).

In other words, since the step L1of the front top roller20of the present embodiment is larger than the conventional front top roller (a step of 1.5 mm in the initial shape), even if the step L1is reduced by abrasion, the influence on the yarn quality caused by the reduction in the step L1is smaller than the conventional front top roller. Since the degradation in the yarn quality by the abrasion is small, the front top roller20of the present embodiment can be continuously used without any problems even after the abrasion. (However, as described above, the yarn quality degrades if the step L1is smaller than 1.5 mm. Therefore, the front top roller20of the present embodiment can be used without any problems only if the step L1after the abrasion is greater than or equal to 1.5 mm.)

FIG. 12BandFIG. 13Billustrate the results of producing the spun yarn10of the yarn count Ne30 with the fiber of combed cotton 100% under the same conditions as described above. As is apparent fromFIG. 12BandFIG. 13B, in this case as well, even if the outer diameter D1of the fiber contacting portion30is reduced from the initial shape (30 mm), the number of yarn defects hardly increased with the front top roller20of the present embodiment. In other words, even when producing the spun yarn10of cotton 100%, the front top roller20of the present embodiment can be used without any problems.

However, as is apparent from comparingFIG. 12AandFIG. 12B, the effect in improving the yarn quality through the use of the front top roller20of the present embodiment is greater in producing the spun yarn10of Rayon 100%. This is because the Rayon fibers are more flexible than the cotton fibers and are more easily subjected to the influence of the accompanying airflow, and hence the influence of the change in the shape of the front top roller20is large. Therefore, by using the front top roller20of the present embodiment when spinning flexible fibers such as Rayon, in particular, the effects of the present invention to reduce the degradation in the yarn quality by abrasion can be more effectively achieved.

As described above, the front top roller20of the present embodiment includes the fiber contacting portion30and the reduced-diameter portion31. The fiber contacting portion30has a substantially uniform outer diameter. The reduced-diameter portion31is provided at both ends of the fiber contacting portion30in the axial direction, and is formed with the outer diameter smaller than that of the fiber contacting portion30. The fiber contacting portion30has the width W1in the axial direction of 18 mm, and the outer diameter D1of 30 mm. The outer diameter D2of the reduced-diameter portion31is 25 mm.

Since the step L1formed by the fiber contacting portion30and the reduced-diameter portion31is 2.5 mm, the front top roller20has a margin in the step as compared to the conventional front top roller (a step of 1.5 mm). Therefore, even if the fiber contacting portion30is abraded and the step L1becomes small, the influence on the yarn quality is smaller than the conventional front top roller. As a result, since the front top roller20of the present embodiment can be abraded more times than the conventional front top roller, the front top roller20can be used for a longer period of time, and the operation cost can be reduced. Furthermore, in the high speed spinning in which the spinning speed is around 400 m/min, the number of yarn defects can be reduced with the front top roller20having the step of 2.5 mm as compared to the conventional front top roller.

After the outer peripheral surface of the fiber contacting portion30is abraded, the front top roller20of the present embodiment has a step L1of greater than or equal to 1.5 mm.

Since the step is made greater than the conventional front top roller, the front top roller20of the present embodiment can allow the abrasion of the fiber contacting portion30while the step is greater than at least the conventional front top roller (a step of 1.5 mm). If the fiber contacting portion30is excessively abraded, the thickness of the rubber of the fiber contacting portion30becomes thin and the gripping force of the fiber bundle8is lowered, which may become a cause of degradation in yarn quality. However, according to the above structure, the step of at least 1.5 mm can be ensured. That is, the space of at least 1.5 mm can be ensured for releasing the accompanying airflow even after the abrasion, and the degradation in yarn quality can be prevented.

In the front top roller20of the present embodiment, the fiber contacting portion30and the reduced-diameter portion31are connected by the taper portion32.

Therefore, when abrading the cuter peripheral surface of the fiber contacting portion30with the abrasion device50, the front top roller20can be allowed to be more easily moved towards the grinding stone51from the axial direction, and the abrasion operation can be smoothly carried out.

The spinning unit2of the present embodiment includes the draft device7adapted to draft the fiber bundle8and the spinning device9adapted to spin the fiber bundle8drafted by the draft device7at the spinning speed of at least 400 m/min. The draft device7includes the front top roller20adapted to draft the sliver15by rotating.

In the spinning unit2of the present embodiment, the draft device7includes a plurality of rollers for drafting the fiber bundle8in the transportation direction of the fiber bundle8. The structure of the present invention is applied to the front top roller20arranged most downstream of the draft device7.

In the draft device7, the rotation speed becomes higher in the roller located downstream. Therefore, since the front top roller20arranged most downstream rotates at a very high speed, the influence of the accompanying airflow is large and the wear is also severe. The structure of the present invention is thus applied to such a front top roller20, and the effects of increasing the number of times in which abrasion can be carried out and reducing the number of yarn defects can be more suitably achieved.

The fine spinning machine1of the present embodiment includes a plurality of spinning units2.

In the fine spinning machine1, the front top roller20of which the usable period is longer than the conventional front top roller is adopted in each spinning unit2, and thus the operation cost of the entire fine spinning machine1can be reduced. Furthermore, in the high speed spinning of at least 400 m/min, by adopting the front top roller20having a step (a step of 2.5 mm) larger than the conventional front top roller in each spinning unit2, the influence of the accompanying airflow is less likely to be received. As a result, the variation in the yarn quality for each spinning unit2can be reduced, and the quality of the produced spun yarn10can be maintained uniform.

In the fine spinning machine1of the present embodiment, the spun yarn10is manufactured with a method of carrying out spinning while gradually changing the step L1from 2.5 mm to 1.5 mm.

If the outer peripheral surface of the fiber contacting portion30begins to be recessed by wear, the outer peripheral surface of the fiber contacting portion30is abraded to reduce the outer diameter. The outer peripheral surface of the fiber contacting portion30can be made in a smooth state and the front top roller20can be reused. Therefore, although the step on the outer peripheral surface of the front top roller20is gradually reduced through abrasion, the yarn quality can be prevented from degrading by having the step within the range described above.

The preferred embodiments of the present invention have been described above, but such a structure can be modified as below.

In the embodiments described above, the description has been made on the spinning unit2having a structure of pulling out the spun yarn10from the spinning device9by the rotating yarn accumulating roller14. However, the structure is not limited thereto, and for example, the spun yarn10may be pulled out from the spinning device9by sandwiching the spun yarn10with two rollers arranged facing each other and rotating the rollers.

In the embodiments described above, the structure in which the step is provided on the front top roller20has been adopted, but the structure of the present invention may be applied to any one of the plurality of draft rollers arranged in the draft device7. In particular, by applying the structure of the present invention to the draft rollers16,17, and20, which outer peripheral surface is made of rubber, the effect of the present invention of preventing degradation in the yarn quality caused by abrasion of the outer peripheral surface can be suitably achieved.

The taper portion32may be omitted.