EP1602756A2

EP1602756A2 - Method and apparatus for manufacturing special yarn

Info

Publication number: EP1602756A2
Application number: EP05011036A
Authority: EP
Inventors: Yutaka Shinozaki
Original assignee: Toyota Industries Corp
Current assignee: Toyota Industries Corp
Priority date: 2004-05-24
Filing date: 2005-05-20
Publication date: 2005-12-07
Anticipated expiration: 2025-05-20
Also published as: JP2005336627A; JP4333477B2; CN100398712C; CN1702206A; EP1602756B1; EP1602756A3; ES2591238T3

Abstract

A motor (18), which drives a pair of front rollers (17) of a draft part (16), is controlled such that the rotation speed of the pair of front rollers is decreased from a reference speed (N0) to a decelerated speed (N1) and thereafter increased to the reference speed based on a designed thickness profile (DP) including a slub length (L). The yarn length (La) spun while the rotation speed of the pair of front rollers is increased from the decelerated speed to the reference speed is computed in advance. When the rotation speed of the pair of front rollers is decreased from the reference speed to the.decelerated speed, the motor is controlled such that the rotation speed of the pair of front rollers is increased at a point in time at which the yarn length spun from when the rotation speed of the pair of front rollers is started to be decreased reaches a value obtained by subtracting the yarn length computed in advance from the slub length of the designed thickness profile. Therefore, a special yarn that accurately conforms to the designed thickness profile is manufactured.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a method and an apparatus for manufacturing a special yarn, and more specifically to a method and an apparatus for manufacturing a special yarn having an actual thickness profile corresponding to a designed thickness profile.

A special yarn, which is referred to as slub yarn or a fancy yarn, is known in the prior art. The thickness of the slub yarn is not constant and includes reference thickness portions (no-slub portions) and large diameter portions (slub portions), which are thicker than the reference thickness portions. The basic structure of the spinning frame used for manufacturing the slub yarn is the same as that of the ring spinning frame, and the spinning frame includes a pair of front rollers and a group of back rollers, which can independently change the rotation speed, at a draft part. When manufacturing the slub yarn, at first, the thickness profile including the slub thickness, the slub length, and the slub pitch of a desired slub yarn is designed. Then, based on the designed thickness profile, the rotation speed of either the pair of front rollers or the group of back rollers is changed by a control section to manufacture the special yarn having the actual thickness profile corresponding to the designed thickness profile (for example, see Japanese Laid-Open Patent Publication No. 62-199821).

Assume that slub yarn SY are manufactured by changing the rotation speed of the pair of front rollers based on a designed thickness profile DP shown in Fig. 6. In this case, at the slub starting position of the designed thickness profile DP, the rotation speed of the pair of front rollers is started to be decreased. The rotation speed of the pair of front rollers is decreased at a predetermined deceleration slope A1 from a reference speed (original speed) N0 to a predetermined speed N1. Thereafter, at a point in time when the spinning time of the length corresponding to the slub length L of the designed thickness profile DP has elapsed from when the rotation speed of pair of front rollers is started to be decreased, the rotation speed of the pair of front rollers is started to be increased. The rotation speed of the pair of front rollers is increased to the reference speed N0 at a predetermined acceleration slope A2. Furthermore, the rotation speed of the pair of front rollers is started to be decreased again at a point in time when the spinning time of the length corresponding to the slub pitch P of the designed thickness profile DP has elapsed from when the rotation speed of the pair of front rollers is started to be increased.

In the prior art, when designing the thickness profile including the slub thickness; the slub length; and the slub pitch, the time required for the acceleration or the deceleration of an adjustable-speed motor which drives the pair of front rollers or the group of back rollers is not taken into consideration. Therefore, even if manufacturing is performed based on the designed thickness profile DP of Fig. 6, the slub length of the actually obtained slub yarn SY is equal to "L + La", which is longer than the slub length L of the designed thickness profile DP by a yarn length La spun during acceleration of the adjustable-speed motor, and the slub pitch of the actually obtained slub yarn SY is equal to "P - La", which is shorter than the slub pitch P of the designed thickness profile DP by the yarn length La as shown in Fig. 6. Thus, the thickness profile of the actually obtained slub yarn SY is not equal to the designed thickness profile.

A method for manufacturing slub yarn is known that changes the rotation speed of not only either the pair of front rollers or the group of back rollers, but the rotation speeds of both the pair of front rollers and the group of back rollers simultaneously to increase the slub thickness. However, in this case, until part of a fleece located between a nip point of the pair of front rollers and the distal ends of middle aprons of the group of back rollers at a point in time when the rotation speed of the group of back rollers is changed pass through the nip point, the slub portion having the target thickness does not appear. Therefore, the thickness profile of the slub yarn obtained through this method is not equal to the designed thickness profile.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a method and an apparatus for manufacturing a special yarn that enables manufacturing a special yarn that accurately conforms to a designed thickness profile.

To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a method is provided for manufacturing a special yarn, which has an actual thickness profile corresponding to a designed thickness profile, by changing the rotation speed of a pair of front rollers or a group of back rollers of a draft part from a reference speed to a predetermined speed, and thereafter returning the rotation speed to the reference speed based on the designed thickness profile including a slub length. The pair of front rollers and the group of back rollers are driven by different motors. The method includes computing, in advance, a yarn length spun while the rotation speed of the pair of front rollers or the group of back rollers is returned from the predetermined speed to the reference speed, and when the rotation speed of the pair of front rollers or the group of back rollers is changed from the reference speed to the predetermined speed, controlling the corresponding motor such that the rotation speed of the pair of front rollers or the group of back rollers the rotation speed of which has been changed is started to be returned at a point in time at which a yarn length spun from when the rotation speed is started to be changed reaches a value obtained by subtracting the yarn length computed in advance from the slub length of the designed thickness profile.

The invention provides another method for manufacturing a special yarn, which has an actual thickness profile corresponding to a designed thickness profile, by changing the rotation speed of a pair of front rollers and a group of back rollers of a draft part from a reference speed to a predetermined speed respectively, and thereafter returning each rotation speed to the reference speed based on the designed thickness profile including a slub length. The pair of front rollers and the group of back rollers are driven by different motors, and the group of back rollers includes a pair of middle rollers equipped with aprons. A point in time at which the rotation speed of the group of back rollers is started to be changed is set to be earlier than a point in time at which the rotation speed of the pair of front rollers is started to be changed, a point in time at which the rotation speed of the group of back roller is started to be returned is set to be earlier than a point in time at which the rotation speed of the pair of front rollers is started to be returned, and the time from the point in time at which the rotation speed of the group of back rollers is started to be changed to the point in time at which the rotation speed of the pair of front rollers is started to be changed and the time from the point in time at which the rotation speed of the group of back rollers is started to be returned to the point in time at which the rotation speed of the pair of front rollers is started to be returned conform to the time required for a fleece to move the distance from the distal ends of the aprons to a nip point of the pair of front rollers.

Further, the present invention provides an apparatus for manufacturing a special yarn that includes a draft part and a control section. The draft part includes a pair of front rollers and a group of back rollers. The pair of front rollers and the group of back rollers are driven by different motors. The control section includes a storing section, which stores a designed thickness profile including a slub length. The control section controls the corresponding motor to change the rotation speed of the pair of front rollers or the group of back rollers from a reference speed to a predetermined speed, and thereafter returning the rotation speed to the reference speed based on the designed thickness profile stored in the storing section. The control section further includes a computation section, which computes a yarn length spun while the rotation speed of the pair of front rollers or the group of back rollers is returned from the predetermined speed to the reference speed. When the rotation speed of the pair of front rollers or the group of back rollers is changed from the reference speed to the predetermined speed, the control section controls the corresponding motor such that the rotation speed of the pair of front rollers or the group of back rollers the rotation speed of which has been changed is started to be returned at a point in time at which a yarn length spun from when the rotation speed is started to be changed reaches a value obtained by subtracting the yarn length computed by the computation section from the slub length of the designed thickness profile.

The present invention provides another apparatus for manufacturing a special yarn that includes a draft part and a control section. The draft part includes a pair of front rollers and a group of back rollers. The pair of front rollers and the group of back rollers are driven by different motors. The group of back rollers includes a pair of middle rollers equipped with aprons. The control section including a storing section, which stores a designed thickness profile including a slub length. The control section controls the corresponding motor to change the rotation speed of the pair of front rollers and the group of back rollers from a reference speed to a predetermined speed respectively, and thereafter returning each rotation speed to the reference speed based on the designed thickness profile stored in the storing section. The control section sets a point in time at which the rotation speed of the group of back rollers is started to be changed to be earlier than a point in time at which the rotation speed of the pair of front rollers is started to be changed, and a point in time at which the rotation speed of the group of back roller is started to be returned to be earlier than a point in time at which the rotation speed of the pair of front rollers is started to be returned, and the time from the point in time at which the rotation speed of the group of back rollers is started to be changed to the point in time at which the rotation speed of the pair of front rollers is started to be changed and the time from the point in time at which the rotation speed of the group of back rollers is started to be returned to the point in time at which the rotation speed of the pair of front rollers is started to be returned conform to the time required for a fleece to move the distance from the distal ends of the aprons to a nip point of the pair of front rollers.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

the upper part of Fig. 1 is a schematic diagram of a designed thickness profile according to a first embodiment of the present invention;

the middle part of Fig. 1 is a graph showing the fluctuation pattern of the rotation speed of a pair of front rollers according to the first embodiment;

the lower part of Fig. 1 is a schematic diagram of slub yarn manufactured based on the designed thickness profile of the upper part of Fig. 1;

Fig. 2 is a diagram illustrating a special yarn manufacturing apparatus according to the first embodiment;

the upper part of Fig. 3(a) is a graph showing the fluctuation pattern of the rotation speed of a pair of middle rollers of a special yarn manufacturing apparatus according to a second embodiment of the present invention;

the lower part of Fig. 3(a) is a graph showing the fluctuation pattern of the rotation speed of a pair of front rollers of the special yarn manufacturing apparatus;

the upper part of Fig. 3(b) is a graph showing the fluctuation pattern of the rotation speed of a pair of middle rollers of a special yarn manufacturing apparatus according to the prior art;

the lower part of Fig. 3(b) is a graph showing the fluctuation pattern of the rotation speed of a pair of front rollers of the special yarn manufacturing apparatus according to the prior art;

Fig. 4 is a schematic diagram illustrating the relationship between the pair of front rollers and the pair of middle rollers;

the upper part of Fig. 5 is a schematic diagram of a designed thickness profile according to a third embodiment of the present invention;

the middle part of Fig. 5 is a graph showing the fluctuation pattern of the rotation speed of a pair of middle rollers according to the third embodiment;

the lower part of Fig. 5 is a schematic diagram of slub yarn manufactured based on the designed thickness profile of the upper part of Fig. 5;

the upper part of Fig. 6 is a schematic diagram of designed thickness profile according to the prior art;

the middle part of Fig. 6 is a graph showing the fluctuation pattern of the rotation speed of the pair of front rollers according to the prior art; and

the lower part of Fig. 6 is a schematic diagram of slub yarn manufactured based on the designed thickness profile of the upper part of Fig. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described with reference to Figs. 1 and 2.

Fig. 2 shows a special yarn manufacturing apparatus according to a first embodiment. The manufacturing apparatus manufactures special yarn, which is slub yarn in the first embodiment, having a predetermined thickness profile by changing the rotation speed of a pair of front rollers. The manufacturing apparatus of Fig. 2 has basically the same configuration as a ring spinning frame, and more specifically, includes spindles 1 rotated by a spindle drive system. The spindle drive system includes a drive pulley 3, which is driven by a first motor 2, a driven pulley 4, a tangential belt 5, which is wound about the pulleys 3, 4. The first motor 2 is an adjustable-speed motor driven via an inverter 6 and includes a rotary encoder 2a. A rotatable line shaft 7 is located along a row of spindles. The line shaft 7 is provided with lifting units 10 (only one of the lifting units 10 is shown in Fig. 2) which lift and lower a ring rail 8 and a lappet (not shown). The lifting units 10 are located at predetermined intervals. The ring rail 8 includes a ring 8a, which permits running of a traveller T, and the lappet includes a snail wire 9.

Each lifting unit 10 includes a screw gear 11, which is rotatably secured to the line shaft 7, and a nut body 13, which is engaged with the screw gear 11. Each nut body 13 is screwed to a screw portion 12a, which is located below the corresponding one of poker pillars 12 for supporting the ring rail 8. The line shaft 7 is coupled to a drive shaft of a servo motor, which is a second motor 14 in the first embodiment, via a gear mechanism (not shown). When the drive shaft of the second motor 14 is rotated forward or in reverse, the ring rail 8 is lifted or lowered accordingly. The above configuration is basically the same as the corresponding configuration of the apparatus disclosed in Japanese Laid-Open Patent Publication No. 2-277826. The second motor 14 includes a rotary encoder 14a, and the second motor 14 is controlled via a servo driver 15. The line shaft 7, the lifting units 10, the poker pillars 12 configure a lifting drive system.

A draft part 16 includes a pair of front rollers 17 (only a bottom roller is shown in Fig. 2) and a group of back rollers including a pair of middle rollers 19 (only a bottom roller is shown in Fig. 2) and a back bottom roller 21. The pair of front rollers 17 is coupled to a third motor 18, which is a servo motor and an adjustable-speed motor. The pair of middle rollers 19 is coupled to a fourth motor 20, which is a servo motor and an adjustable-speed motor. The third motor 18 and the fourth motor 20 each include rotary encoders 18a, 20a. The back bottom roller 21 is coupled to the pair of middle rollers 19 via a gear train 22. Therefore, the pair of front rollers 17 and the group of back rollers are driven by separate adjustable-speed motors. The pair of middle rollers 19 is equipped with aprons 19a. A gear 17a, which rotates integrally with the pair of front rollers 17, is secured to one end of the pair of front rollers 17. A sensor S1, which outputs a pulse signal in accordance with rotation of the pair of front rollers 17, is located in the vicinity of the gear 17a.

A control section 23, which controls the first to

fourth motors

2, 14, 18, 20, includes a computation section, which is a central processing unit (CPU) 24 in the first embodiment. The control section 23 further includes a program memory 25, a storing section, which is a working memory 26 in the first embodiment, an input section 27, an input interface 28, an output interface 29, and first to fourth motor drive circuits 30 to 33. The CPU 24 is connected to the

rotary encoders

2a, 14a, 18a, 20a, the sensor S1, and the input section 27 via the input interface 28. The CPU 24 is further connected to the inverter 6 via the output interface 29 and the first motor drive circuit 30, and to the servo driver 15 via the output interface 29 and the second motor drive circuit 31. The CPU 24 is further connected to the third motor 18 via the output interface 29, the third motor drive circuit 32, and a servo driver 34, and to the fourth motor 20 via the output interface 29, the fourth servo motor drive circuit 33, and a servo driver 35.

The CPU 24 operates based on a predetermined program data stored in the program memory 25. The program memory 25 is a read only memory (ROM) and stores the program data and various data necessary for executing the program data. The program data stored in the program memory 25 includes a control program for the first motor 2 and the second motor 14 during winding-up operation, and a program that calculates an acceleration time Ta, a deceleration time Td, and a yarn length La spun during the acceleration time Ta, which are described later, and controls the third motor 18 to change the rotation speed of the pair of front rollers 17 based on these information. The various data stored in the program memory 25 includes: data regarding the spindle rotation speed during the normal operation, the rotation speed of the third motor 18, the rotation speed of the fourth motor 20, and the lifting and lowering speed of the ring rail 8, which correspond to the spinning condition such as types of fiber to be used, the count of the no-slub portion of the desired slub yarn, and the draft ratio; a deceleration slope A1 and an acceleration slope A2, which are described later; a computing equation for computing the rotation speed of the pair of front rollers 17 that should be set for obtaining the desired slub thickness.

The working memory 26 is a random access memory (RAM) and temporarily stores data from the input section 27 and the result of the computation performed by the CPU 24. The working memory 26 includes a backup power source (not shown).

The input section 27 is used for inputting the spinning condition data such as the designed thickness profile of the desired slub yarn, the count of the no-slub portion of the desired slub yarn, the spindle rotation speed when spinning the no-slub portion, the lift length, and the chase length.

One example of the designed thickness profile of the slub yarn is shown in the upper part of Fig. 1. A designed thickness profile DP shown in Fig. 1 includes the slub length L, which is the length of a slub portion S the diameter of which is larger than a no-slub portion Y0, the slub thickness D, which is the thickness of the slub portion S, the distance between the adjacent slub portions S, that is, the slub pitch P, which is the length of the no-slub portion Y0. The slub thickness D is the percentage of the thickness of the slub portion S to the thickness of the no-slub portion Y0. For example, if the thickness of the slub portion S is 1.5 times the thickness of the no-slub portion Y0, the slub thickness D is 150%, and if the thickness of the slub portion S is twice the thickness of the no-slub portion Y0, the slub thickness D is 200%.

The CPU 24 computes, based on the slub thickness D of the designed thickness profile DP stored in the working memory 26, the rotation speed of the pair of front rollers 17 required during spinning of the slub portion S, that is, a decelerated rotation speed N1 (rpm) by the following equation (1). In the equation (1), N0 represents the rotation speed of the pair of front rollers 17 required during spinning of the no-slub portion Y0, that is, a reference rotation speed (rpm). N1 = 100(N0/D)

Subsequently, the CPU 24 computes the deceleration time Td, which is the time required for the rotation speed of the pair of front rollers 17 to decrease from the reference rotation speed N0 to the decelerated rotation speed N1, using the computed decelerated rotation speed N1 and the predetermined deceleration slope A1 by the following equation (2). The CPU 24 further computes the acceleration time Ta, which is the time required for the rotation speed of the pair of front rollers 17 to increase from the decelerated rotation speed N1 to the reference rotation speed N0, using the decelerated rotation speed N1 and the predetermined acceleration slope A2 by the following equation (3). Td = |N1 - N0|/A1 Ta = |N1 - N0|/A2

Subsequently, the CPU 24 computes the average rotation speed NE (rpm) of the pair of front rollers 17 during the deceleration time Td and the acceleration time Ta. Then, the CPU 24 computes the yarn length Ld spun during the deceleration time Td using the average rotation speed NE according to the following equation (4). In the same manner, the CPU 24 computes the yarn length La spun during the acceleration time Ta using the average rotation speed NE according to the following equation (5). In the equations (4) and (5), d represents the outer diameter (mm) of each roller of the pair of front rollers 17. Ld = Td × d × π × NE/60 La = Ta × d × π × NE/60

The operation of the special yarn manufacturing apparatus of Fig. 2 will now be described. Before operating the manufacturing apparatus, the spinning condition is entered in the control section 23 via the input section 27. The spinning condition to be entered includes the designed thickness profile DP of the desired slub yarn, the count of the no-slub portion of the slub yarn, the spindle rotation speed during spinning of the no-slub portion, the lift length, the chase length, and the like.

When the manufacturing apparatus is activated, the first to

fourth motors

2, 14, 18, 20 are controlled in accordance with commands from the control section 23. The CPU 24 computes the rotation speed of the first to

fourth motors

2, 14, 18, 20 based on output signals from the

rotary encoders

2a, 14a, 18a, 20a. Then, the CPU 24 outputs command signals for driving the spindle drive system, a draft part drive system, and the lifting drive system in sync at a predetermined speed corresponding to the spinning condition. The command signals are transmitted to the inverter 6 and the

servo drivers

15, 34, 35 via the output interface 29 and the first to fourth motor drive circuits 30 to 33. As a result, the spindle drive system, the draft part drive system, and the lifting drive system are independently driven in sync, and yarn Y supplied from the draft part 16 is wound up by a bobbin B via the corresponding snail wire 9 and the traveller T.

The CPU 24 computes the number of rotations of the pair of front rollers 17, that is, the spun yarn length based on output signals from the sensor S1. Furthermore, when spinning the slub portion S, the CPU 24 computes the rotation speed of the pair of front rollers 17 required during spinning of the slub portion S, that is, the decelerated rotation speed N1 based on the desired thickness of the slub portion S according to the equation (1) Then, based on the computation result, the CPU 24 computes the deceleration time Td, which is the time required for the rotation speed of the pair of front rollers 17 to decrease from the reference rotation speed N0 to the decelerated rotation speed N1 at the predetermined deceleration slope A1, according to the equation (2), and the acceleration time Ta, which is the time required for the rotation speed of the pair of front rollers 17 to increase from the decelerated rotation speed N1 to the reference rotation speed N0 at the predetermined acceleration slope A2, according to the equation (3). Based on the computation results, the CPU 24 further computes the yarn length La spun during the acceleration time Ta according to the equation (5).

The CPU 24 outputs a deceleration command to the third motor 18 during the deceleration time Td from when the rotation speed of the pair of front rollers 17 is started to be decreased. Simultaneously, the CPU 24 computes the spun yarn length from when the rotation speed is started to be decreased based on the output signal of the sensor S1. The CPU 24 outputs an acceleration command to the third motor 18 at the point in time TFas at which the yarn length spun from when the rotation speed is started to be decreased reaches a value (L - La) obtained by subtracting the yarn length La from the slub length L of the designed thickness profile DP. As a result, the rotation speed of the pair of front rollers 17 returns to the reference rotation speed N0 in the acceleration time Ta, and formation of the slub portion S is completed. The length of the slub portion S formed as described above conforms to the slub length L of the designed thickness profile DP. Hereafter, by repeating formation of the slub portion S and formation of the no-slub portion Y0, slub yarn SY is spun.

The first embodiment provides the following advantages.

(1) The CPU 24 calculates the yarn length La spun during the acceleration time Ta, which is the time required for the rotation speed of the pair of front rollers 17 to be increased from the decelerated rotation speed N1 to the reference rotation speed N0. Then, the CPU 24 controls the third motor 18 such that the rotation speed of the pair of front rollers 17 is started to be increased at the point in time at which the yarn length spun from when the rotation speed of the pair of front rollers 17 is started to be decreased reaches the value (L - La) obtained by subtracting the yarn length La from the slub length L of the designed thickness profile DP. Therefore, the slub length L and the slub pitch P of the actually obtained slub yarn SY accurately conform to the slub length L and the slub pitch P of the designed thickness profile DP.

(2) The slub portion S can be formed by changing the rotation speed of the pair of middle rollers 19 instead of the rotation speed of the pair of front rollers 17 as in the first embodiment. However, in this case, even if the rotation speed of the pair of middle rollers 19 is increased to reduce the draft ratio, due to the influence of the fleece (fiber bundles) located between the distal ends of the aprons 19a of the pair of middle rollers 19 and the nip point of the pair of front rollers 17, the slub portion S, especially the slub portion S the slub length of which is as short as some tens of millimeters is not clearly formed. Contrarily, in the first embodiment, since the slub yarn having the predetermined thickness profile is manufactured by changing the rotation speed of the pair of front rollers 17, the slub portion S the slub length L of which is short is also clearly formed.

(3) The deceleration slope A1 when the rotation speed of the pair of front rollers 17 decreases from the reference rotation speed N0 to the decelerated rotation speed N1 and the acceleration slope A2 when the rotation speed of the pair of front rollers 17 increases from the decelerated rotation speed N1 to the reference rotation speed N0 are constants. This facilitates computation of the deceleration time Td and the acceleration time Ta. A second embodiment of the present invention will now be described with reference to Figs. 3(a) to 4. The second embodiment differs from the first embodiment in the control method of the draft part 16. More specifically, the second embodiment differs from the first embodiment in that the rotation speeds of both the pair of front rollers 17 and the pair of middle rollers 19 are changed instead of changing the rotation speed of the pair of front rollers 17. The rotation speeds of both the pair of front rollers 17 and the pair of middle rollers 19 are changed to further increase the slub thickness. The mechanical configuration of a special yarn manufacturing apparatus according to the second embodiment is the same as the manufacturing apparatus of Fig. 2. Accordingly, differences from the first embodiment will mainly be discussed below, and explanations of components that are like or the same as the components of the first embodiment are omitted.To obtain the draft ratio that enables forming a thicker slub portion S, changing the rotation speed of the pair of front rollers 17 might be insufficient. Therefore, in the second embodiment, the rotation speed of the pair of front rollers 17 when spinning the slub portion S is set lower than the rotation speed of the pair of front rollers 17 when spinning the no-slub portion Y0, and the rotation speed of the pair of middle rollers 19 when spinning the slub portion S is set higher than the rotation speed of the pair of middle rollers 19 when spinning the no-slub portion Y0.However, if the rotation speeds of the pair of front rollers 17 and the pair of middle rollers 19 are simultaneously changed at the slub starting point of the designed thickness profile DP as shown in Fig. 3(b), the slub portion S having the desired thickness does not appear immediately after changing the rotation speeds. This is because, even if the rotation speeds of both the pairs of

rollers

17, 19 are simultaneously changed, the draft ratio of the fleece F supplied from the nip point NP will not become the desired value until all the fleece F (see Fig. 4) located between the nip point NP of the pair of front rollers 17 and the distal ends of the aprons 19a of the pair of middle rollers 19 at the point in time when the rotation speed is changed passes through the nip point NP. Therefore, when the distance between the nip point NP of the pair of front rollers 17 and the distal ends of the aprons 19a of the pair of middle rollers 19 is referred to as the distance Lm (mm), the difference corresponding to the distance Lm is generated from when the rotation speeds of both the pairs of

rollers

17, 19 are simultaneously changed until the slub portion S having the desired thickness appears. In the second embodiment, as shown in Fig. 3(a), the point in time TMas at which the rotation speed of the pair of middle rollers 19 is started to be increased is set to be earlier than the point in time TFds at which the rotation speed of the pair of front rollers 17 is started to be decreased. Furthermore, the point in time TMds at which the rotation speed of the pair of middle rollers 19 is started to be decreased is set to be earlier than the point in time TFas at which the rotation speed of the pair of front rollers 17 is started to be increased. The time period from the point in time TMas at which the rotation speed of the pair of middle rollers 19 is started to be increased to the point in time TFds at which the rotation speed of the pair of front rollers 17 is started to be decreased, and the time period from the point in time TMds at which the rotation speed of the pair of middle rollers 19 is started to be decreased to the point in time TFas at which the rotation speed of the pair of front rollers 17 is started to be increased conform to the time required for the fleece F to move the distance Lm from the distal ends of the aprons 19a (downstream ends) to the nip point NP of the pair of front rollers 17.The CPU 24 performs substantially the same control as the first embodiment regarding the pair of front rollers 17. On the other hand, regarding the pair of middle rollers 19, the CPU 24 computes the rotation speed of the pair of middle rollers 19 required when spinning the slub portion S, that is, an accelerated rotation speed NB1 (rpm). Then, the CPU 24 computes an acceleration time TMa, which is the time required for the rotation speed of the pair of middle rollers 19 to increase from a reference rotation speed NB0 (the rotation speed of the pair of middle rollers 19 required when spinning the no-slub portion Y0) to the accelerated rotation speed NB1, using the computed accelerated rotation speed NB1 and a predetermined acceleration slope B1 according to the following equation (6). Furthermore, the CPU 24 computes a deceleration time TMd, which is the time required for the rotation speed of the pair of middle rollers 19 to be decreased from the accelerated rotation speed NB1 to the reference rotation speed NB0 using the accelerated rotation speed NB1 and a predetermined deceleration slope B2 according to the following equation (7). TMa = |NB1 - NB0|/B1 TMd= |NB1 - NB0|/B2Subsequently, the CPU 24 computes the average rotation speed NMe of the pair of middle rollers 19 during the acceleration time TMa and the deceleration time TMd. Then, using the average rotation speed NMe, the CPU 24 computes the time TaLm required for spinning a yarn having the length that is the same as the distance Lm during the acceleration time TMa and the time TdLm required for spinning a yarn having the length that is the same as the distance Lm during the deceleration time TMd.The CPU 24 changes the rotation speeds of the pair of front rollers 17 and the pair of middle rollers 19 based on the designed thickness profile DP. At this time, the CPU 24 sets the point in time TMas at which the rotation speed of the pair of middle rollers 19 is started to be increased to be earlier than the point in time TFds at which the rotation speed of the pair of front rollers 17 is started to be decreased by the time TaLm, and the point in time TMds at which the rotation speed of the pair of middle rollers 19 is started to be decreased to be earlier than the point in time TFas at which the rotation speed of the pair of front rollers 17 is started to be increased by the time TdLm. As a result, the slub portion S having the desired thickness is started to be formed from when the rotation speed of the pair of front rollers 17 is started to be decreased, and formation of the slub portion S is completed at the point in time when increasing the rotation speed of the pair of front rollers 17 is completed. Therefore, the slub yarn SY having the slub length L and the slub pitch P that accurately conform to the designed thickness profile DP is obtained.The second embodiment provides the following advantages in addition to the advantages (1) and (3) of the first embodiment.

(4) In the second embodiment, the rotation speeds of the pair of front rollers 17 and the pair of middle rollers 19 are changed based on the designed thickness profile DP to manufacture the slub yarn having the predetermined thickness profile. When changing the rotation speeds of both the pairs of

rollers

17, 19, the point in time TMas at which the rotation speed of the pair of middle rollers 19 is started to be increased is set to be earlier than the point in time TFds at which the rotation speed of the pair of front rollers 17 is started to be decreased by the time TaLm, and the point in time TMds at which the rotation speed of the pair of middle rollers 19 is started to be decreased is set to be earlier than the point in time TFas at which the rotation speed of the pair of front rollers 17 is started to be increased by the time TdLm. The time TaLm and the time TdLm are the time required for the fleece F to move the distance Lm from the downstream ends of the aprons 19a of pair of middle rollers 19 to the nip point NP of the pair of front rollers 17. Therefore, the slub portion (large diameter portion) S having the desired thickness is started to be formed from the point in time at which the rotation speed of the pair of front rollers 17 is started to be decreased, and formation of the slub portion S is completed at the point in time when increasing the rotation speed of the pair of front rollers 17 is completed. Therefore, the slub yarn SY is obtained that has the slub length L and the slub pitch P that accurately conform to the designed thickness profile DP.

(5) The acceleration slope B1 when the rotation speed of the pair of middle rollers 19 is increased from the reference rotation speed NB0 to the accelerated rotation speed NB1 and the deceleration slope B2 when the rotation speed of the pair of middle rollers 19 is decreased from the accelerated rotation speed NB1 to the reference rotation speed NB0 are constants. This simplifies computation of the acceleration time TMa and the deceleration time TMd.

A third embodiment of the present invention will now be described with reference to Fig. 5. The third embodiment differs from the first embodiment in the control method of the draft part 16. More specifically, the third embodiment differs from the first embodiment in that the rotation speed of the group of back rollers including the pair of middle rollers 19 is changed instead of the rotation speed of the pair of front rollers 17. The mechanical configuration of a special yarn manufacturing apparatus according to the third embodiment is the same as the manufacturing apparatus of Fig. 2. Accordingly, differences from the first embodiment will mainly be discussed below, and explanations of components that are like or the same as the components of the first embodiment are omitted.

The CPU 24 computes the acceleration time TMa, which is the time required for the rotation speed of the pair of middle rollers 19 to increase from the reference rotation speed NB0 to the accelerated rotation speed NB1, and the deceleration time TMd, which is the time required for the rotation speed of the pair of middle rollers 19 to be decreased from the accelerated rotation speed NB1 to the reference rotation speed NB0. The CPU 24 further computes the yarn length Ld spun during the deceleration time TMd.

At first, the rotation speed of the pair of middle rollers 19 is increased in the acceleration time TMa from the reference rotation speed NB0 to the accelerated rotation speed NB1 by the acceleration slope B1. Then, the rotation speed of the pair of middle rollers 19 is started to be decreased at the point in time when the yarn length spun from when the rotation speed is started to be increased reaches a value (L-Ld) obtained by subtracting the yarn length Ld from the slub length L of the designed thickness profile DP. Then, the rotation speed of the pair of middle rollers 19 returns to the reference rotation speed NB0 in the deceleration time TMd, and formation of the slub portion S is completed. The length of the slub portion S formed as described conforms to the slub length L of the designed thickness profile DP.

The ring spinning frame generally estimates the point in time of full bobbin based on the integrated value of the rotation speed of the pair of front rollers 17, prepares for doffing in accordance with the point in time, and retracts a cleaning device that travels along the spinning frame such that the cleaning device does not hinder doffing. Therefore, if the slub portion S is formed by changing the rotation speed of the pair of front rollers 17 to change the draft ratio, estimation of the point in time of full bobbin is difficult. Therefore, preparation for doffing and retraction of the cleaning device are hindered. However, in the third embodiment, since the slub portion S is formed by changing the rotation speed of the pair of middle rollers 19, estimation of the point in time of full bobbin is not difficult as in the prior art.

Furthermore, when the rotation speed of the pair of front rollers 17 is changed, the number of twists varies if the rotation speed of the spindles 1 is constant. Therefore, in a case where variation of the number of twists is not preferable, the rotation speed of the spindles 1 also needs to be changed in accordance with the change of the rotation speed of the pair of front rollers 17. This complicates the control. However, when the slub portion S is formed by changing the rotation speed of the pair of middle rollers 19, the rotation speed of the spindles 1 does not need to be changed to prevent variation of the number of twists.

The embodiments may be modified as follows.

The designed thickness profile DP may be entered by an operator through directly entering the slub length L, the slub thickness D, and the slub pitch P using the input section 27, or through selecting and determining one of the designed thickness profiles DP stored in the program memory 25 using the input section 27.

The designed thickness profile DP may include a combination of the slub length L, the slub thickness D and the slub pitch P determined using a random number table from a set of the slub lengths L, a set of the slub thicknesses D, and a set of the slub pitches P stored in the program memory 25. In other words, the designed thickness profile DP may be produced using the set of the slub lengths L, the set of the slub thicknesses D, the set of the slub pitches P, which are stored in the program memory 25, and the random number table.

The deceleration slope A1 and the acceleration slope A2 of the pair of front rollers 17 do not need to be constants, but may be variables that vary in accordance with the thickness of the slub portion S. The acceleration slope B1 and the deceleration slope B2 of the pair of middle rollers 19 do not need to be constants, but may be variables that vary in accordance with the thickness of the slub portion S. In these cases, the shape of both ends of the slub portion S can be adjusted.

The deceleration slope A1 and the acceleration slope A2 of the pair of front rollers 17 may be changed in accordance with whether the type of the fiber used is cotton or synthetic fiber. The acceleration slope B1 and the deceleration slope B2 of the pair of middle rollers 19 may also be changed in accordance with whether the type of the fiber used is cotton or synthetic fiber. Even if the slub portion S having the same thickness is formed, the roller pressures of the pair of front rollers 17 and the group of back rollers differ depending on the type of the fiber used such as cotton or synthetic fiber. More specifically, the roller pressures are reduced when cotton is used, and a load applied to a motor that drives the rollers is small as compared to a case where synthetic fiber is used. When a large load is applied to the motor, the motor accelerates slowly and decelerates promptly. Therefore, depending on whether the type of fiber used is cotton or synthetic fiber, the appropriate speed change slope when controlling the third motor 18 to change the rotation speed of the pair of front rollers 17 differs, and the appropriate speed change slope when controlling the fourth motor 20 to change the rotation speed of the pair of middle rollers 19 differs. Thus, depending on whether the type of fiber used is cotton or synthetic fiber, the deceleration slope A1, B2 and the acceleration slope A2, B1 are preferably different. If the relationship between the thickness of each of slub portions S with different thicknesses and the speed change slope appropriate for the slub thickness D of the slub portion S is calculated in advance, the speed change slope appropriate for the slub portion S with any thickness is calculated by a proportional calculation.

The absolute values of the deceleration slope A1 and the acceleration slope A2 of the pair of front rollers 17 may be the same. Furthermore, the absolute values of the acceleration slope B1 and the deceleration slope B2 of the pair of middle rollers 19 may be the same.

Instead of coupling the pair of middle rollers 19 to the back bottom rollers 21 with the gear train 22, the pair of middle rollers 19 and the back bottom rollers 21 may be driven by separate adjustable-speed motors. In this case, even if the rotation speed of the pair of middle rollers 19 is changed as in the second embodiment and the third embodiment, and the slub thickness D is great, the fleece F is smoothly supplied from the pair of middle rollers 19.

When the slub thickness D of the designed thickness profile DP is greater than or equal to a predetermined value (for example 200%), the slub portion S may be formed by changing the rotation speeds of both the pair of front rollers 17 and the pair of middle rollers 19, and when the slub thickness D is less than the predetermined value, the slub portion S may be formed by changing the rotation speed of one of the pair of front rollers 17 and the pair of middle rollers 19. This facilitates the control as compared to a case where the rotation speeds of both the pair of front rollers 17 and the pair of middle rollers 19 are changed regardless of the slub thickness D.

When forming the slub portion S by changing the rotation speeds of both the pair of front rollers 17 and the pair of middle rollers 19, as in the prior art, the rotation speed of the pair of front rollers 17 may be started to be increased at the point in time when the yarn length spun from when the rotation speed of the pair of front rollers 17 is started to be decreased reaches the slub length L of the designed thickness profile DP. However, increase of the rotation speed of the pair of middle rollers 19 is set to be earlier than when the rotation speed of the pair of front rollers 17 is started to be decreased by the time required for the fleece F to move the distance Lm from the downstream ends of the aprons 19a to the nip point NP, and starting of decreasing the rotation speed of the pair of middle rollers 19 is set to be earlier than when the rotation speed of the pair of front rollers 17 is started to be increased by the time required for the fleece F to move the distance Lm from the downstream ends of the aprons 19a to the nip point NP. In this case also, the slub portion S having the desired thickness is started to be formed from the point in time at which the rotation speed of the pair of front rollers 17 is started to be decreased, and formation of the slub portion S is completed at the point in time at which increasing of the rotation speed of the pair of front rollers 17 is completed.

If the rotation speed of the pair of front rollers 17 is not changed when forming the slub portion S, the spindles 1 and the pair of front rollers 17 may be driven by the same motor.

Claims

A method for manufacturing a special yarn (SY), which has an actual thickness profile corresponding to a designed thickness profile (DP), by changing the rotation speed of a pair of front rollers (17) or a group of back rollers (19) of a draft part (16) from a reference speed (N0, NB0) to a predetermined speed (N1, NB1), and thereafter returning the rotation speed to the reference speed based on the designed thickness profile (DP) including a slub length (L), wherein the pair of front rollers and the group of back rollers are driven by different motors (18, 20), the method being characterized by:

computing, in advance, a yarn length (La, Ld) spun while the rotation speed of the pair of front rollers or the group of back rollers is returned from the predetermined speed to the reference speed, and when the rotation speed of the pair of front rollers or the group of back rollers is changed from the reference speed to the predetermined speed, controlling the corresponding motor such that the rotation speed of the pair of front rollers or the group of back rollers the rotation speed of which has been changed is started to be returned at a point in time at which a yarn length spun from when the rotation speed is started to be changed reaches a value obtained by subtracting the yarn length computed in advance from the slub length of the designed thickness profile.
The method according to claim 1, characterized in that the special yarn is manufactured by changing the rotation speed of the pair of front rollers.
The method according to claim 1, characterized in that the special yarn is manufactured by changing the rotation speed of the group of back rollers.
A method for manufacturing a special yarn (SY), which has an actual thickness profile corresponding to a designed thickness profile (DP), by changing the rotation speed of a pair of front rollers (17) and a group of back rollers (19) of a draft part (16) from a reference speed (N0, NB0) to a predetermined speed (N1, NB1) respectively, and thereafter returning each rotation speed to the reference speed based on the designed thickness profile including a slub length (L), wherein the pair of front rollers and the group of back rollers are driven by different motors (18, 20), and the group of back rollers includes a pair of middle rollers (19) equipped with aprons (19a), the method being characterized in that:

a point in time (TMas) at which the rotation speed of the group of back rollers is started to be changed is set to be earlier than a point in time (TFds) at which the rotation speed of the pair of front rollers is started to be changed, a point in time (TMds) at which the rotation speed of the group of back roller is started to be returned is set to be earlier than a point in time (TFas) at which the rotation speed of the pair of front rollers is started to be returned, and the time from the point in time at which the rotation speed of the group of back rollers is started to be changed to the point in time at which the rotation speed of the pair of front rollers is started to be changed and the time from the point in time at which the rotation speed of the group of back rollers is started to be returned to the point in time at which the rotation speed of the pair of front rollers is started to be returned conform to the time required for a fleece (F) to move the distance (Lm) from the distal ends of the aprons to a nip point (NP) of the pair of front rollers.
The method according to claim 4, characterized by computing, in advance, a yarn length (La) spun while the rotation speed of the pair of front rollers is returned from the predetermined speed to the reference speed, and when the rotation speed of the pair of front rollers is changed from the reference speed to the predetermined speed, controlling the corresponding motor such that the rotation speed of the pair of front rollers is started to be returned at a point in time at which a yarn length spun from when the rotation speed of the pair of front rollers is started to be changed reaches a value obtained by subtracting the yarn length computed in advance from the slub length of the designed thickness profile.
An apparatus for manufacturing a special yarn (SY), the apparatus being characterized by:

a draft part (16), which includes a pair of front rollers (17) and a group of back rollers (19), and the pair of front rollers and the group of back rollers are driven by different motors (18, 20); and

a control section (23), the control section including a storing section (26), which stores a designed thickness profile (DP) including a slub length (L), wherein the control section controls the corresponding motor to change the rotation speed of the pair of front rollers or the group of back rollers from a reference speed (N0, NB0) to a predetermined speed (N1, NB1), and thereafter returning the rotation speed to the reference speed based on the designed thickness profile stored in the storing section, the control section further includes a computation section (24), which computes a yarn length (La, Ld) spun while the rotation speed of the pair of front rollers or the group of back rollers is returned from the predetermined speed to the reference speed, and when the rotation speed of the pair of front rollers or the group of back rollers is changed from the reference speed to the predetermined speed, the control section controls the corresponding motor such that the rotation speed of the pair of front rollers or the group of back rollers the rotation speed of which has been changed is started to be returned at a point in time at which a yarn length spun from when the rotation speed is started to be changed reaches a value obtained by subtracting the yarn length computed by the computation section from the slub length of the designed thickness profile.
An apparatus for manufacturing a special yarn (SY), the apparatus being characterized by:

a draft part (16), which includes a pair of front rollers (17) and a group of back rollers (19), the pair of front rollers and the group of back rollers are driven by different motors (18, 20), and the group of back rollers includes a pair of middle rollers (19) equipped with aprons (19a); and

a control section (23), the control section including a storing section (26), which stores a designed thickness profile (DP) including a slub length (L), wherein the control section controls the corresponding motor to change the rotation speed of the pair of front rollers and the group of back rollers from a reference speed (N0, NB0) to a predetermined speed (N1, NB1) respectively, and thereafter returning each rotation speed to the reference speed based on the designed thickness profile stored in the storing section, the control section sets a point in time (TMas) at which the rotation speed of the group of back rollers is started to be changed to be earlier than a point in time (TFds) at which the rotation speed of the pair of front rollers is started to be changed, and a point in time (TMds) at which the rotation speed of the group of back roller is started to be returned to be earlier than a point in time (TFas) at which the rotation speed of the pair of front rollers is started to be returned, and the time from the point in time at which the rotation speed of the group of back rollers is started to be changed to the point in time at which the rotation speed of the pair of front rollers is started to be changed and the time from the point in time at which the rotation speed of the group of back rollers is started to be returned to the point in time at which the rotation speed of the pair of front rollers is started to be returned conform to the time required for a fleece (F) to move the distance (Lm) from the distal ends of the aprons to a nip point (NP) of the pair of front rollers.
The apparatus according to claim 7, characterized in that the control section further includes a computation section (24), which computes a yarn length (La) spun while the rotation speed of the pair of front rollers is returned from the predetermined speed to the reference speed, and when the' rotation speed of the pair of front rollers is changed from the reference speed to the predetermined speed, the control section controls the corresponding motor such that the rotation speed of the pair of front rollers is started to be returned at a point in time at which a yarn length spun from when the rotation speed of the pair of front rollers is started to be changed reaches a value obtained by subtracting the computed yarn length from the slub length of the designed thickness profile.