A method for spinning and starting a roving on a rotor spinning machine

Abstract

The application belongs to the technical field of spinning and relates to a rotor spinning doffing and piecing method. After rotor spinning doffing, cotton feeding is stopped, and a piecing action is performed after replacing the empty tube. The piecing action includes piecing cotton feeding and seed yarn into the rotor. During piecing, piecing combination fibers are mixed and wound with the seed yarn in the rotor to form piecing yarn. After rotor spinning doffing, the rotor is not cleaned, and the piecing combination fibers are composed of the fibers remaining in the rotor after rotor spinning doffing and the fibers fed in by piecing cotton feeding. The application can greatly reduce the doffing and piecing time under the premise of ensuring the quality of the joint and the uniformity of the yarn, thereby improving the overall production efficiency of the rotor spinning.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of spinning, and relates to a rotor spinning doffing and piecing method. BACKGROUND

[0002] Rotor spinning is the most mature and widely used spinning technology after ring spinning. Compared with ring spinning, rotor spinning mainly reflects the application of semi-automatic splicing technology.

[0003] Currently, when full package yarn replacement and empty tube piecing are performed in rotor spinning, the following steps are usually performed: first, open the spinning machine to clean the rotor (if there is residual fiber in the rotor, a significant thick spot will be formed at the piecing position, thereby affecting the quality of the initial section of the yarn); then close the spinning machine; and finally perform the yarn leading splicing. However, this piecing process involves multiple operation links such as opening, cleaning, closing, and piecing of the spinning machine, and the process is relatively complicated, which leads to the extension of the piecing time and thus adversely affects the production efficiency.

[0004] For example, the automatic piecing method disclosed in the patent application with the application publication number CN118932559A performs the doffing and piecing process in the following steps: first, reverse the feed roller and apply the brake to the rotor, then open the spinning machine to clean the rotor and then close it, then reverse the yarn leading roller, feed the yarn into the rotor through the yarn leading tube, at this time the feed roller is usually in a stationary state, after the yarn enters the condensing groove of the rotor, the yarn leading roller stops reversing and remains stationary, finally the feed roller starts feeding the cotton, after reaching the set amount of cotton feeding, the yarn leading roller is turned to forward rotation to lead the yarn with stable yarn outwards, thereby completing the entire piecing process.

[0005] A small number of existing technologies also attempt to complete piecing without opening the spinning machine. For example, the automatic piecing method based on regulating the length of the tail yarn to realize rotor spinning disclosed in the patent application with the application publication number CN118814324A performs piecing without opening the spinning machine by combining the length of the tail yarn with the residual fiber in the rotor when the yarn is broken due to temporary stop or power failure. However, this method is only applicable to the piecing of yarn broken due to temporary stop or power failure and cannot be widely applied.

[0006] Therefore, it is necessary to develop a new rotor spinning doffing and piecing method to shorten the time of doffing and piecing and improve the production efficiency of doffing and piecing while ensuring the uniformity of the yarn and the quality of the splicing. SUMMARY

[0007] The present application aims to solve the problems existing in the prior art and provide a rotor spinning doffing and piecing method.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0009] A cup spinning open-end spinning and piecing method, after cup spinning open-end spinning, cotton feeding is stopped, and piecing action is performed after replacing the empty tube, the piecing action includes piecing cotton and seed yarn entering the cup, during piecing, piecing combination fibers are mixed and entangled with the seed yarn in the cup to form piecing yarn (the initial section of normal spinning), the cup is not cleaned after cup spinning open-end spinning, and the piecing combination fibers are composed of the fibers remaining in the cup after cup spinning open-end spinning and the fibers fed by the piecing cotton.

[0010] As a preferred technical solution:

[0011] The cup spinning open-end spinning and piecing method as described above, the piecing cotton and the seed yarn enter the cup at the same time.

[0012] The cup spinning open-end spinning and piecing method as described above, the piecing cotton speed is the same as the normal spinning cotton feeding speed.

[0013] The cup spinning open-end spinning and piecing method as described above, the piecing cotton feeding amount w is as follows:

[0014] w = [1 - (c1-α t ) / c1×c2]×π×D×T t / (1000×1000);

[0015] In the formula, the unit of w is g;

[0016] D is the diameter of the condensation groove of the cup, in mm;

[0017] T t is the target number of the spun yarn, in tex, and the value range is [14, 118];

[0018] c1 is a constant, α t is the twist factor of the spun yarn, c2 is a constant, and the values of c1, α t , and c2 are related to T t ; when 14≤T t ≤20, the value of c1 is 390, the value of α t is 350~380, and the value of c2 is 0.7~0.9; when 20<T t ≤28, the value of c1 is 370, the value of α t is 330~360, and the value of c2 is 0.7~0.8; when 28<T t ≤59, the value of c1 is 330, the value of α t is 300~320, and the value of c2 is 0.5~0.7; when 59<T t ≤118, the value of c1 is 300, the value of α tThe value of c2 is 0.3-0.5.

[0019] The spinning rotor speed is 30000-120000 rpm.

[0020] The spinning rotor speed is 30000-120000 rpm.

[0021] The single-spindle yarn-dropping spinning head time is 1-2 s.

[0022] The yarn-diameter of the joint part is 1.05-1.2 times the diameter of the spun yarn, and the length of the joint part is 4-8 mm.

[0023] The principle of the application is as follows:

[0024] In the full-tube state or the active yarn-dropping state during the rotor spinning, when the feed roller stops feeding cotton, the yarn will not be immediately broken, but will enter a gradual breaking process synchronously with the stop of the feed roller, because the feed roller still holds part of the fibers, and part of the fibers remain in the combing cavity of the combing roller. In this process, the yarn-drawing roller continuously rotates outward to draw the yarn, and as the fiber stock in the rotor gradually decreases due to continuous consumption, the diameter of the drawn yarn also gradually decreases, until the fiber stock is insufficient to support the yarn structure, and the final breakage occurs. Experimental data shows that the diameter of the yarn breakage position (yarn tail) is related to the twist factor and the target count of the spun yarn, the thicker the spun yarn, the larger the target count, the greater the proportion of the diameter of the yarn at the breakage position to the diameter of the target yarn, and as the twist factor of the spun yarn increases, the proportion also increases accordingly. After the yarn is completely broken, part of the fibers that are not drawn will remain in the condensing groove of the rotor, and the mass of the remaining fibers is related to the count and twist of the target yarn.

[0025] Based on the above phenomenon, in the yarn-dropping spinning process, the spinning device is not opened, cleaned, closed, etc., the spinning device remains closed, the rotor does not perform a brake action, and the rotor remains in high-speed operation, the fibers in the condensing groove of the rotor are retained, and according to the proportion of the amount of fibers remaining in the condensing groove of the rotor to the target count of the spun yarn, when the head end of the spinning head enters the condensing groove of the rotor, the amount of fibers in the condensing groove is consistent with the amount of fibers required for the target count of the spun yarn. Under this condition, the yarn-drawing roller can continuously draw the yarn without stopping, and directly restore the normal spinning state. Specifically, the application sets w = [1-(c1-α t ) / c1×c2] ×π×D×T t / (1000×1000), and the derivation process of the formula is as follows:

[0026] When the rotor spinning is falling spinning, the fiber amount left in the condensation groove of the rotor in the action of step (1) is related to the count and twist of the spun yarn. The experimental data shows that the fiber amount left in the condensation groove of the rotor w1=c2×(c1-α t ) / c1×π×D÷1000×T t ÷1000

[0027] Therefore, when the operation of step (2) is performed without opening the spinning machine for rotor cleaning, in order to ensure that the yarn fineness of the spinning position is consistent with the count T t of the spun yarn, when the yarn fineness of the spinning position is consistent with the count T t of the spun yarn, the fiber amount in the condensation groove of the rotor is w2=π×D×T t / (1000×1000), and the fiber amount in the condensation groove of the rotor needs to be supplemented w=w2-w1=[1-(c1-α t ) / c1×c2]×π×D×T t / (1000×1000).

[0028] Advantages

[0029] The rotor spinning spinning process provided by the application can directly perform the yarn leading spinning without performing the traditional steps of opening, cleaning and closing the spinning machine, can greatly reduce the falling spinning spinning time, and can avoid the formation of thick spots or thin spots in the spinning position, so as to ensure that the joint quality is excellent and the uniformity of the spun yarn is good. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a structural schematic view of the spinning device adopted by the application;

[0031] Among them, 1 is a spinning yarn, 2 is a feed roller, 3 is a rotor, 4 is a condensation groove, and 5 is a yarn leading roller. DETAILED DESCRIPTION

[0032] The application will be further described below in combination with specific embodiments. It should be understood that these embodiments are only used for illustrating the application and are not used for limiting the scope of the application. In addition, it should be understood that after reading the content taught by the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0033] The following is the relevant performance detection method of each embodiment and comparative example:

[0034] (1) Single spindle falling spinning spinning time: after the falling spinning is completed and the empty tube is replaced, the time is started to be counted, and the time when the spinning is successfully spun is completed.

[0035] (2) The diameter of the yarn at the joint part is a multiple of the diameter of the spun yarn: the joint part is cut off, the cutting length is 5 mm, the sampling times are 10, the average mass is m1, and the unit is g; the normal spinning part is also cut off and sampled in the same way, and the average mass is m2, and the unit is g; the diameter of the yarn at the joint part is a multiple of the diameter of the spun yarn = m1 / m2.

[0036] (3) The length of the joint part: the joint part is photographed and processed to measure its length.

[0037] Example 1

[0038] A rotor spinning open-end spinning and piecing method, using a spinning device as shown in Figure 1 After rotor spinning open-end spinning, the cotton feeding is stopped, the empty tube is replaced, and the piecing action is performed. The piecing action includes piecing cotton feeding (using feeding roller 2) and seed yarn entering rotor 3. Piecing cotton feeding and seed yarn entering rotor 3 are performed simultaneously. The piecing cotton feeding speed is the same as the normal spinning cotton feeding speed. During piecing, the piecing combination fiber is mixed and wound with the seed yarn in rotor 3 to form piecing yarn 1, which is drawn out by yarn guide roller 5;

[0039] After rotor spinning open-end spinning, the rotor 3 is not cleaned, and the piecing combination fiber is composed of the fiber remaining in the rotor 3 after rotor spinning open-end spinning and the fiber fed by the piecing cotton feeding;

[0040] The speed of rotor 3 is 30000 rpm;

[0041] The piecing cotton feeding amount w is as follows:

[0042] w = [1-(c1-α t ) / c1×c2]×π×D×T t / (1000×1000)=0.023;

[0043] In the formula, the unit of w is g;

[0044] D is the diameter of the condensation groove 4 of the rotor 3, the unit is mm, D is 65;

[0045] T t is the target number of the spun yarn, the unit is tex, T t is 118;

[0046] c1 is a constant 300, α t is the twist factor of the spun yarn, α t is 270, and c2 is a constant 0.4.

[0047] The average time of the single spindle doffing and piecing is 2s, the diameter of the pieced yarn is 1.2 times of the diameter of the spun yarn, and the average length of the pieced part is 8mm.

[0048] Comparative Example 1

[0049] A rotor spinning doffing and piecing method, which is different from that of Example 1 only in that the doffing and piecing method described in the prior art CN118932559A is used.

[0050] The average time of the single spindle doffing and piecing is 6s.

[0051] Compared with Example 1, the average time of the doffing and piecing of Comparative Example 1 is doubled, because the doffing and piecing method of Comparative Example 1 needs to perform the actions of opening, cleaning and closing the spinning device, which greatly increases the average time of doffing and piecing, which is not conducive to saving the doffing and piecing time.

[0052] Comparative Example 2

[0053] A rotor spinning doffing and piecing method, which is basically the same as that of Example 1, and the only difference is that the cotton feeding amount w of the feed roller 2 is w = π × D × T t / (1000×1000).

[0054] The diameter of the pieced yarn is 1.6 times of the diameter of the spun yarn.

[0055] Comparing Example 1 with Comparative Example 2 can see that if only the rotor is not cleaned and the cotton feeding amount of the piecing is not adjusted at the same time, the pieced yarn will have obvious thick spots.

[0056] Example 2

[0057] A rotor spinning doffing and piecing method, which stops feeding after doffing, replaces the empty tube and performs the piecing action, which includes the piecing feeding (using the feed roller) and the seed yarn entering the rotor, the piecing feeding and the seed yarn entering the rotor are performed at the same time, the piecing feeding speed is the same as the normal spinning feeding speed, and the piecing combination fiber is mixed and wound with the seed yarn in the rotor during piecing to form the pieced yarn, which is drawn out by the drawing roller;

[0058] The rotor is not cleaned after doffing, and the piecing combination fiber is composed of the fiber remaining in the rotor after doffing and the fiber fed by the piecing feeding;

[0059] The rotation speed of the rotor is 50000rpm;

[0060] The cotton feeding amount w of the piecing feeding is as follows:

[0061] w = [1-(c1-α t) / c1 x c2] x π x D x T t / (1000 x 1000) = 0.008;

[0062] wherein the unit of w is g;

[0063] D is the diameter of the condenser tank 4 of the rotor 3, in mm, D is 45;

[0064] T t T is the target number of the spun yarn, in tex, T t is 59;

[0065] c1 is a constant 330, a t a is the twist factor of the spun yarn, a t is 310, and c2 is a constant 0.6.

[0066] When the final doffing is performed, the average time of single spindle doffing is 1 s, the diameter of the yarn at the joint part is 1.05 times the diameter of the spun yarn, and the average length of the joint part is 4 mm.

[0067] Example 3

[0068] A rotor spinning doffing and piecing method, after the doffing of the rotor spinning, the feeding of the cotton is stopped, and the piecing action is performed after the empty tube is replaced. The piecing action includes the piecing feeding (using a feed roller) and the seed yarn entering the rotor. The piecing feeding and the seed yarn entering the rotor are performed simultaneously, the piecing feeding speed is the same as the normal spinning feeding speed, and during the piecing, the piecing combination fiber is mixed and wound with the seed yarn in the rotor to form a pieced yarn, which is drawn out by a yarn guide roller;

[0069] After the doffing of the rotor spinning, the rotor is not cleaned, and the piecing combination fiber is composed of the fiber remaining in the rotor after the doffing of the rotor spinning and the fiber fed by the piecing feeding;

[0070] The rotation speed of the rotor is 100000 rpm;

[0071] The feeding amount w of the piecing feeding is as follows:

[0072] w = [1 - (c1 - a t ) / c1 x c2] x π x D x T t / (1000 x 1000) = 0.002;

[0073] wherein the unit of w is g;

[0074] D is the diameter of the condenser tank 4 of the rotor 3, in mm, D is 32;

[0075] T t T is the target number of the spun yarn, in tex, T t is 21;

[0076] c1 is a constant 370, and a t is a twist factor of the spun yarn, and a t is 350, and c2 is a constant 0.7.

[0077] When the final doffing is performed, the average time of the single spindle doffing is 1.5s, the diameter of the yarn at the joint part of the yarn produced is 1.1 times the diameter of the spun yarn, and the average length of the joint part is 5mm.

[0078] Example 4

[0079] A rotor spinning doffing and starting method, after the rotor spinning doffing, the cotton feeding is stopped, and the starting action is performed after the empty tube is replaced. The starting action includes starting feeding (using a feed roller) and seed yarn into the rotor. The starting feeding and the seed yarn into the rotor are performed simultaneously. The starting feeding speed is the same as the normal spinning feeding speed. During the starting, the starting combination fiber is mixed and wound with the seed yarn in the rotor to form the starting yarn, and the starting yarn is drawn out by the yarn guide roller;

[0080] After the rotor spinning doffing, the rotor is not cleaned, and the starting combination fiber is composed of the fiber remaining in the rotor after the rotor spinning doffing and the fiber fed by the starting feeding;

[0081] The rotation speed of the rotor is 120000rpm;

[0082] The feeding amount w of the starting feeding is as follows:

[0083] w = [1 - (c1 - a t ) / c1 x c2] x π x D x T t / (1000 x 1000) = 0.001;

[0084] In the formula, the unit of w is g;

[0085] D is the diameter of the condensation groove 4 of the rotor 3, and the unit is mm. D is 28;

[0086] T t is the target number of the spun yarn, and the unit is tex. T t is 14;

[0087] c1 is a constant 390, and a t is a twist factor of the spun yarn, and a t is 360, and c2 is a constant 0.8.

[0088] When the final doffing is performed, the average time of the single spindle doffing is 1.8s, the diameter of the yarn at the joint part of the yarn produced is 1.08 times the diameter of the spun yarn, and the average length of the joint part is 7mm.

[0089] Example 5

[0090] A cup spinning doffing and piecing method, after cup spinning doffing, cotton feeding is stopped, and piecing action is performed after replacing the empty tube, the piecing action includes piecing feeding (using a feed roller) and seed yarn into the cup, piecing feeding and seed yarn into the cup are performed simultaneously, the piecing feeding speed is the same as the normal spinning feeding speed, during piecing, piecing combination fibers and seed yarn are mixed and wound in the cup to form piecing yarn, and the piecing yarn is drawn out by a yarn guide roller;

[0091] After cup spinning doffing, the cup is not cleaned, and piecing combination fibers are composed of fibers remaining in the cup after cup spinning doffing and fibers fed by piecing feeding;

[0092] The rotation speed of the cup is 80000 rpm;

[0093] The piecing feeding amount w is as follows:

[0094] w = [1 - (c1-α t ) / c1 × c2] × π × D × T t / (1000 × 1000) = 0.003;

[0095] In the formula, the unit of w is g;

[0096] D is the diameter of the condensation groove 4 of the cup 3, in mm, D is 35;

[0097] T t is the target number of the spun yarn, in tex, T t is 29;

[0098] c1 is a constant 330, α t is the twist factor of the spun yarn, α t is 310, and c2 is a constant 0.6.

[0099] When the final doffing piecing is performed, the average time of single spindle doffing piecing is 1.5 s, the diameter of the yarn at the joint part of the prepared yarn is 1.15 times the diameter of the spun yarn, and the average length of the joint part is 6 mm.

[0100] Example 6

[0101] A cup spinning doffing and piecing method, after cup spinning doffing, cotton feeding is stopped, and piecing action is performed after replacing the empty tube, the piecing action includes piecing feeding (using a feed roller) and seed yarn into the cup, piecing feeding and seed yarn into the cup are performed simultaneously, the piecing feeding speed is the same as the normal spinning feeding speed, during piecing, piecing combination fibers and seed yarn are mixed and wound in the cup to form piecing yarn, and the piecing yarn is drawn out by a yarn guide roller;

[0102] The fiber of the spinning head combination is composed of the fiber remained in the rotor after the rotor spinning and the fiber fed by the spinning head;

[0103] The rotating speed of the rotor is 45000 rpm;

[0104] The feeding amount w of the spinning head cotton is as follows:

[0105] w = [1- (c1-α t ) / c1×c2]×π×D×T t / (1000×1000) =0.003;

[0106] In the formula, the unit of w is g;

[0107] D is the diameter of the condensing tank 4 of the rotor 3, in mm, D is 54;

[0108] T t is the target number of the spun yarn, in tex, T t is 20;

[0109] c1 is a constant 390, α t is the twist factor of the spun yarn, α t is 350, and c2 is a constant 0.8.

[0110] When the final spinning head is dropped, the average time of the single spinning head is 1.7 s, the diameter of the yarn at the joint part is 1.07 times of the diameter of the spun yarn, and the average length of the joint part is 5 mm.

[0111] Example 7

[0112] A rotor spinning spinning head method, after the rotor spinning, the feeding of the cotton is stopped, the empty tube is replaced, and the spinning head action is performed, the spinning head action includes the spinning head cotton (using the feed roller) and the seed yarn entering the rotor, the spinning head cotton and the seed yarn enter the rotor at the same time, the speed of the spinning head cotton is the same as the normal spinning feeding speed, and the spinning head combination fiber is mixed and wound with the seed yarn in the rotor to form the spinning head yarn, and the yarn is drawn out by the yarn guide roller;

[0113] The fiber of the spinning head combination is composed of the fiber remained in the rotor after the rotor spinning and the fiber fed by the spinning head cotton;

[0114] The rotating speed of the rotor is 40000 rpm;

[0115] The feeding amount w of the spinning head cotton is as follows:

[0116] w = [1- (c1-α t ) / c1×c2]×π×D×T t(1000 x 1000) = 0.004;

[0117] wherein the unit of w is g;

[0118] D is the diameter of the condenser 4 of the rotor 3, in mm, D is 48;

[0119] T t is the target number of the spun yarn, in tex, T t is 28;

[0120] c1 is a constant 370, a t is the twist factor of the spun yarn, a t is 340, and c2 is a constant 0.8.

[0121] The average time of the single spindle doffing and starting is 1.8 s, the diameter of the yarn at the joint part is 1.1 times of the diameter of the spun yarn, and the average length of the joint part is 7 mm.

[0122] Example 8

[0123] A rotor spinning doffing and starting method, after the rotor spinning doffing, the cotton feeding is stopped, the empty tube is replaced, and the starting action is performed, the starting action includes the starting cotton feeding (using a feed roller) and the seed yarn entering the rotor, the starting cotton feeding and the seed yarn entering the rotor are performed simultaneously, the speed of the starting cotton feeding is the same as the normal spinning cotton feeding speed, during the starting, the starting combination fiber is mixed and wound with the seed yarn in the rotor to form the starting yarn, and the starting yarn is drawn out by a yarn guide roller;

[0124] After the rotor spinning doffing, the rotor is not cleaned, and the starting combination fiber is composed of the fiber remaining in the rotor after the rotor spinning doffing and the fiber fed by the starting cotton feeding;

[0125] The rotation speed of the rotor is 35000 rpm;

[0126] The cotton feeding amount w of the starting cotton feeding is as follows:

[0127] w = [1 - (c1 - a t ) / c1 x c2] x π x D x T t (1000 x 1000) = 0.011;

[0128] wherein the unit of w is g;

[0129] D is the diameter of the condenser 4 of the rotor 3, in mm, D is 60;

[0130] T t is the target number of the spun yarn, in tex, T t is 60;

[0131] c1 is a constant 300, a t is the twist factor of the spun yarn, a t is 270, and c2 is a constant 0.4.

[0132] The average time for single spindle doffing and piecing was 1.2 seconds, the diameter of the yarn at the joint portion was 1.13 times the diameter of the spun yarn, and the average length of the joint portion was 6 mm.

Claims

1. A method for generating yarn heads in rotor spinning, wherein after doffing in rotor spinning, cotton feeding is stopped, and after changing to an empty tube, a yarn head generation action is performed. The yarn head generation action includes feeding cotton and introducing seed yarn into the rotor. During yarn head generation, the yarn head bonding fibers and seed yarn are mixed and wound together inside the rotor to form a yarn head. The method is characterized in that... If the rotor is not cleaned after doffing, the raw yarn fibers are composed of fibers remaining in the rotor after doffing and fibers fed in during the raw yarn feeding process. The cotton feeding amount (w) for newborns fed cotton is as follows: w=[1-(c1-α t ) / c1×c2]×π×D×T t / (1000×1000); In the formula, the unit of w is g; D is the diameter of the condensation tank of the rotating cup, in mm; T t The target yarn count is expressed in tex, with a value range of [14, 118]. c1 is a constant, α t c1 is the twist coefficient of the spun yarn, c2 is a constant, and c1 and α are... t The values ​​of c2 and c2 are both related to T. t Relevant; when 14≤T t When ≤20, the value of c1 is 390, α t The value of c is 350~380, and the value of c2 is 0.7~0.9; When 20 <T t When ≤28, the value of c1 is 370, α t The value of c is 330~360, and the value of c2 is 0.7~0.8; when 28 <T t When ≤59, the value of c1 is 330, α t The value of c is 300~320, and the value of c2 is 0.5~0.7; when 59 <T t When ≤118, the value of c1 is 300, α t The value of c is 250~290, and the value of c2 is 0.3~0.

5.

2. The method for doffing and yarn raising in rotor spinning according to claim 1, characterized in that, The cotton and seed yarn are fed into the rotor simultaneously.

3. The method for doffing and yarn raising in rotor spinning according to claim 1, characterized in that, The feeding speed of raw cotton is the same as the normal cotton feeding speed during spinning.

4. The method for doffing and yarn raising in rotor spinning according to claim 1, characterized in that, D is 28~65mm.

5. The method for doffing and yarn raising in rotor spinning according to claim 1, characterized in that, The rotation speed of the rotor is 30,000 to 120,000 rpm.

6. A method for doffing and yarn raising in rotor spinning according to any one of claims 1 to 5, characterized in that, When the yarn starts to grow back, the time for a single spindle to start growing back is 1 to 2 seconds.

7. A method for doffing and yarn raising in rotor spinning according to any one of claims 1 to 5, characterized in that, The diameter of the yarn at the splice is 1.05 to 1.2 times the diameter of the spun yarn, and the length of the splice is 4 to 8 mm.

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