A method for online monitoring of the elasticity change of three-dimensional crimped fibers

Abstract

The present application belongs to the technical field of performance test, and discloses a method for online monitoring elasticity change of three-dimensional crimped fiber, which comprises the following steps: in the process of producing multiple batches of silk cakes, first, online monitoring the expansion coefficient A of the first batch of silk cakes in the winding forming process, and drawing the relation curve between the expansion coefficient A and time; taking the relation curve between the expansion coefficient A and time obtained after the production of the first batch of silk cakes is completed as the original curve; then, in the winding forming process of the subsequent batches of silk cakes, online monitoring the expansion coefficient B of the subsequent batches of silk cakes in the winding forming process respectively, and comparing the expansion coefficient B with the expansion coefficient A in the original curve; when the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than a preset value at the same time, it is judged that the elasticity of the three-dimensional crimped fiber has changed, otherwise, the elasticity of the three-dimensional crimped fiber has no change. The present application can realize online monitoring elasticity change of three-dimensional crimped fiber.

Description

Technical Field

[0001] This invention belongs to the field of performance testing technology and relates to a method for online monitoring of elasticity changes in three-dimensional crimped fibers. Background Technology

[0002] Elastic fiber is a functional fiber that can quickly recover its original shape after being stretched and released by external force. Its elasticity mainly comes from its special molecular structure and physical form. Three-dimensional crimped fiber is an elastic fiber with a permanent three-dimensional crimped structure formed by bicomponent composite spinning or asymmetric cooling process. Its crimped form exists simultaneously in the X, Y, and Z spatial directions, giving it high bulkiness, excellent resilience, and warmth retention properties.

[0003] Changes in fiber elasticity significantly impact the style of finished fabrics; therefore, ensuring fiber elasticity stability is crucial during fiber production. Existing technologies, such as FZT 50058-2022 "Test Method for Elasticity Properties of Bicomponent Composite Filaments of Synthetic Fibers," determine elasticity changes during production by testing the elasticity of fibers within the filament cake. However, monitoring in subsequent processes suffers from significant lag, and relies solely on sampling rather than comprehensive monitoring. For example, only the surface filaments of the filament cake are examined to determine the overall elasticity. This makes it impossible for existing technologies to detect changes in fiber elasticity in a timely manner and to guarantee fiber elasticity stability throughout the production process.

[0004] Therefore, it is of great significance to study a method for online monitoring of fiber elasticity changes in order to solve the problems existing in the current technology. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art and to provide a method for online monitoring of elastic changes in three-dimensional crimped fibers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for online monitoring of elasticity changes in three-dimensional crimped fibers involves monitoring the expansion coefficient A of the first batch of fibers during the winding process when producing multiple batches of fiber cakes, and simultaneously plotting the relationship curve between the expansion coefficient A and time. The curve obtained after the first batch of fibers is produced is used as the original curve. Then, during the winding process of subsequent batches of fibers, the expansion coefficient B is monitored online, and compared with the expansion coefficient A in the original curve. If the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than a preset value at the same time, it is determined that the elasticity of the three-dimensional crimped fiber has changed; otherwise, the elasticity of the three-dimensional crimped fiber remains unchanged.

[0008] Wherein, the expansion coefficient = the maximum height of the yarn cake in real time during the winding process / the displacement of the lateral displacement device.

[0009] During the winding process, the fibers reciprocate left and right under the lateral displacement device of the winding machine, spiraling and winding themselves from small to large. During winding, the fibers are initially straight. After winding, the tensile stress is gradually released, and under the elastic recovery force of the fibers, each loop of fiber on the coil shrinks and becomes shorter. Utilizing the shape memory effect, the fibers transform from a straight state to a three-dimensional spiral coil. This transformation from a two-dimensional to a three-dimensional form increases the space occupied, theoretically expanding outwards. However, in the winding process, the bottom fibers of the coil are supported by the paper tube, while the surface fibers are compressed by the machine pressure. Therefore, the material deforms in the direction of least resistance, i.e., in the axial direction of the coil, resulting in a bulge. Furthermore, because the surface fibers are in contact with the pressure rollers of the machine, and the bottom fibers are in contact with the paper tube, these fibers are easily constrained by friction, making axial horizontal expansion difficult. Since the fibers in the middle layer are far from the pressure rollers and paper tube, they are less affected by friction and expand more freely in the axial horizontal direction, ultimately forming the largest "bulge" in the radial middle layer of the coil.

[0010] During the elastic recovery process, the fibers in the yarn cake generate tremendous cohesive force, which exerts normal pressure on the inner fibers, much like an object being "clutched." During winding, as the diameter of the yarn cake increases, the normal pressure increases, the inner fibers are pressed deeper, and the protrusions become larger.

[0011] During the winding process, when the elasticity of the fiber decreases, its ability to transform from a two-dimensional to a three-dimensional form weakens, resulting in a decrease in the cohesive force exerted by the less elastic fiber on the yarn cake, thus reducing the length of the increased protrusion. Conversely, when the elasticity of the fiber increases, its ability to transform from a two-dimensional to a three-dimensional form strengthens, increasing the cohesive force exerted by the more elastic fiber on the yarn cake, thus increasing the length of the increased protrusion. Therefore, there is a relationship between protrusion and elasticity; all other things being equal, the greater the elasticity of the fiber, the larger the protrusion.

[0012] This invention, by plotting the relationship curve between the expansion coefficient A and time, reveals the changing pattern of the protrusions during the winding of the first batch of yarn cakes. When producing the second batch of yarn cakes, if the obtained curve of the expansion coefficient B versus time differs from the curve corresponding to the first batch, and the absolute value of the difference exceeds a preset value, it indicates a change in elasticity. This could be due to elastic fluctuations in the fibers during the production of the first batch, or it could be due to changes in the elasticity of the fibers in the second batch. The cause of elasticity fluctuations may be: if one spinning station in the same spinning chamber stops, the melt does not flow, causing the melt residence time at the other station to increase, resulting in viscosity changes and elasticity changes. If the stopped station is reopened, the viscosity at the other station gradually recovers, and the elasticity returns to normal.

[0013] If the elasticity of the fibers does not change during the production of the first batch of silk cakes, and the curves corresponding to the third and subsequent batches of silk cakes are different from those corresponding to the first batch of silk cakes, and the absolute value of the difference exceeds the preset value, it indicates that the elasticity of the batch of silk cakes has changed.

[0014] As a preferred technical solution:

[0015] The method for online monitoring of elastic changes in three-dimensional crimped fibers as described above includes an online monitoring device and a PLC controller.

[0016] The online monitoring device includes an infrared sensor; the infrared sensor is used to monitor the maximum height of the yarn cake in real time during the winding process.

[0017] The online monitoring device is connected to the PLC controller. The PLC controller receives the information sent by the online monitoring device and plots the relationship curve between the expansion coefficient and time. After the first batch of silk cakes is produced, the relationship curve between the expansion coefficient A and time is used as the original curve. The expansion coefficient B is compared with the expansion coefficient A in the original curve to determine whether the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value.

[0018] The method for online monitoring of elastic changes in three-dimensional crimped fibers as described above, wherein the online monitoring device further includes a fixed block A, a fixed block B, a connecting rod A, and a connecting rod B;

[0019] There are multiple infrared sensors, which include infrared transmitters and infrared receivers;

[0020] Infrared emitters are arranged in a row to form an infrared emitter group, which is horizontally fixed on fixed block A.

[0021] The infrared receivers are arranged in a row to form an infrared receiver group, and the infrared receiver group is horizontally fixed to the fixed block B;

[0022] Fixed block A is fixedly connected to the winding machine via connecting rod A; fixed block B is fixedly connected to the winding machine via connecting rod B;

[0023] The length direction of the infrared transmitter group and the infrared receiver group is the same as the length direction of the spindle of the winding machine;

[0024] The length of the infrared emitter assembly is the same as the length of the paper tube on the spindle, and it is aligned with one of the paper tubes on the spindle.

[0025] On the vertical plane perpendicular to the spindle shaft, the infrared rays emitted by the infrared emitter are tangent to the paper tube on the spindle shaft.

[0026] This design allows for the real-time monitoring of the maximum height of the wire cake during the winding process, while eliminating interference from the paper tube. The maximum height of the wire cake during winding is calculated as follows: (Number of infrared receivers not receiving signals + 1) × Spacing between two adjacent infrared lines. To improve measurement accuracy, the spacing between adjacent infrared lines should be as small as possible. Using infrared sensors to monitor length is an existing technology, such as the DeepVision ZDC0640Z1-2.

[0027] As described above, in an online monitoring method for the elastic change of three-dimensional crimped fibers, the distance between the infrared rays in two adjacent infrared sensors is denoted as a; the preset value is ≥ a / displacement of the lateral displacement device, and the preset value is < 2a / displacement of the lateral displacement device. a is the minimum length that the online monitoring device can monitor. Therefore, the preset value is ≥ a / displacement of the lateral displacement device, and in order to improve the accuracy of monitoring elastic changes, the preset value is < 2a / displacement of the lateral displacement device.

[0028] In the method described above for online monitoring of elastic changes in three-dimensional crimped fibers, the spacing between the infrared rays in two adjacent infrared sensors is 0.1 mm.

[0029] The method for online monitoring of elastic changes in three-dimensional crimped fibers as described above, wherein the device used in the method for online monitoring of elastic changes in three-dimensional crimped fibers further includes a display;

[0030] The display is electrically connected to the PLC controller, and the PLC controller sends the plotted curve of the expansion coefficient versus time to the display.

[0031] The method for online monitoring of elasticity changes in three-dimensional crimped fibers as described above, wherein the device used in the method for online monitoring of elasticity changes in three-dimensional crimped fibers further includes an alarm device;

[0032] The alarm device is electrically connected to the PLC controller; when the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value at the same time, the PLC controller controls the alarm device to sound an alarm.

[0033] Beneficial effects:

[0034] This invention enables online monitoring of the elasticity changes of three-dimensional crimped fibers by comparing the relationship curves of the expansion coefficient versus time for different batches with the relationship curve of the first batch of yarn cakes. Attached Figure Description

[0035] Figure 1 This is a front view of the infrared transmitter and infrared receiver of the present invention.

[0036] Figure 2 Top view of the infrared transmitter and infrared receiver of the present invention;

[0037] Figure 1 and Figure 2 The dashed lines in the diagram represent infrared radiation and are for illustrative purposes only.

[0038] Among them, 1-infrared transmitter, 2-infrared receiver, 3-infrared light, 4-winding machine, 5-silk cake, 6-paper tube, 7-fixed block A, 8-fixed block B, 9-connecting rod A, 10-connecting rod B. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0040] A method for online monitoring of elasticity changes in three-dimensional crimped fibers, the specific process of which is as follows:

[0041] When producing multiple batches of silk cakes, the expansion coefficient A of the first batch of silk cakes is monitored online during the winding and forming process, and the relationship curve between the expansion coefficient A and time is plotted at the same time.

[0042] The curve showing the relationship between the expansion coefficient A and time obtained after the first batch of yarn cakes is produced is used as the original curve. Then, during the winding and forming process of subsequent batches of yarn cakes, the expansion coefficient B of each subsequent batch of yarn cakes is monitored online and compared with the expansion coefficient A in the original curve. If the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value at the same time, it is determined that the elasticity of the three-dimensional crimped fiber has changed; otherwise, the elasticity of the three-dimensional crimped fiber has not changed. Wherein, the expansion coefficient = the maximum height of the yarn cake in real time during the winding and forming process / the displacement of the lateral displacement device.

[0043] The device used in the above-mentioned method for online monitoring of elastic changes in three-dimensional crimped fibers, such as... Figure 1 , Figure 2As shown, it includes an online monitoring device, a PLC controller, a display, and an alarm device;

[0044] The online monitoring device includes an infrared sensor, a fixed block A7, a fixed block B8, a connecting rod A9, and a connecting rod B10;

[0045] Infrared sensors are used to monitor the maximum height of the yarn cake 5 in real time during the winding and forming process; there are multiple infrared sensors, including an infrared transmitter 1 and an infrared receiver 2.

[0046] Infrared emitters 1 are arranged in a row to form an infrared emitter group, and the infrared emitter group is horizontally fixed on the fixing block A 7;

[0047] Infrared receivers 2 are arranged in a row to form an infrared receiver group, and the infrared receiver group is horizontally fixed to the fixing block B8;

[0048] Let a be the distance between infrared rays 3 in two adjacent infrared sensors, where a is 0.1 mm;

[0049] Fixed block A7 is fixedly connected to winding machine 4 via connecting rod A9;

[0050] Fixed block B8 is fixedly connected to winding machine 4 via connecting rod B10;

[0051] The length direction of the infrared transmitter group and the infrared receiver group is the same as the length direction of the spindle of the winding machine 4; the length of the infrared transmitter group is the same as the length of the paper tube 6 on the spindle, and it is aligned with one of the paper tubes 6 on the spindle; on the vertical plane perpendicular to the spindle, the infrared rays 3 emitted by the infrared transmitter are tangent to the paper tube 6 on the spindle.

[0052] The PLC controller is connected to the online monitoring device. After receiving information from the online monitoring device, the PLC controller plots the relationship curve between the expansion coefficient and time. The curve of the relationship between the expansion coefficient A and time obtained after the first batch of silk cakes is produced is used as the original curve. The expansion coefficient B is compared with the expansion coefficient A in the original curve to determine whether the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value. The preset value is ≥ a / displacement of the lateral displacement device and < 2a / displacement of the lateral displacement device.

[0053] The display is electrically connected to the PLC controller, and the PLC controller sends the plotted curve of the expansion coefficient versus time to the display for display.

[0054] The alarm device is electrically connected to the PLC controller; when the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value at the same time, the PLC controller controls the alarm device to sound an alarm.

[0055] To verify the accuracy of the above method for online monitoring of the elasticity changes of three-dimensional crimped fibers, this method was used to monitor the elasticity changes of three-dimensional crimped fibers during the winding of elastic fibers into a filament cake. The specific process is as follows:

[0056] PET chips with an intrinsic viscosity of 0.45 dL / g and PBT with an intrinsic viscosity of 1.20 dL / g are dried and then melt-extruded in their respective screw extruders. After passing through their respective melt pipes, spinning boxes, and metering pumps, they enter the composite spinneret assembly for distribution. Finally, they are extruded from their respective spinneret orifices on the spinneret and bonded together to form a "dumbbell" shaped monofilament cross-section structure. After being heated by hot rollers, stretched, heat-set, and wound, a PET / PBT three-dimensional crimped composite fiber with a specification of 83 dtex / 48f is obtained.

[0057] The process parameters for preparing three-dimensional crimped composite fibers are as follows: the temperatures of the first to fifth zones of the screw extruder for PET are 272℃, 273℃, 275℃, 278℃, and 273℃, respectively; the temperatures of the first to fifth zones of the screw extruder for PBT are 242℃, 245℃, 247℃, 243℃, and 241℃, respectively; the box temperature of PET is 275℃, and the box temperature of PBT is 245℃; the temperature of the first hot roller is 80℃, the temperature of the second hot roller is 145℃, the draw ratio is 1.91, and the spinning speed is 4200m / min.

[0058] When producing 50 batches of PET / PBT three-dimensional crimped composite fibers using the above method, the elasticity changes of the three-dimensional crimped fibers will be monitored using the online monitoring method described above.

[0059] First, the curve showing the relationship between the expansion coefficient A and time obtained in the first batch was used as the original curve. Then, the expansion coefficient B of the second batch was compared with the expansion coefficient A in the original curve. It was found that under the same time, the absolute value of the difference between the expansion coefficient B and the expansion coefficient A was less than the preset value (0.0023). Therefore, it can be concluded that the elasticity of the three-dimensional crimped fiber in the first and second batches did not change.

[0060] In subsequent batches during the winding process, the expansion coefficient B was compared with the expansion coefficient A in the original curve, and the expansion coefficient-time relationship curve was plotted. It was found that in the production of batches 19, 34, and 48, at the same time, the absolute value of the difference between the expansion coefficient B and the expansion coefficient A was greater than the preset value, and the alarm was triggered. The changes in these three batches are as follows:

[0061] Batch 19: During the production process of this batch, the PLC controller calculated that when the yarn cake reached the 83-minute mark, the expansion coefficient B was 1.0816, while the expansion coefficient A of the original curve at that time was 1.0851. The absolute value of the difference between the two exceeded the preset value. At this time, the PLC controller activated the alarm device. After discovering the alarm, the workshop technicians checked the expansion coefficient-time relationship curve on the display and found that the curve gradually deviated from the original curve starting from the 83-minute mark. Elasticity tests were conducted on the three-dimensional crimped composite fibers produced in the abnormal stage and found that the crimp shrinkage rate measured according to the FZ / T 50058-2022 standard "Test Method for Elastic Properties of Two-Component Composite Filaments of Synthetic Fibers" was only 27% (the crimp shrinkage rate of normal three-dimensional crimped composite fibers is 32%±1.5%). Then, the abnormal yarn cake was switched downgraded.

[0062] After the above problem occurred, the technicians investigated and found that the connection of the heating signal line in the fifth zone of the PBT screw was loose due to screw vibration. The actual temperature of the fifth heating zone was 285℃, exceeding the displayed set temperature of 41℃. The overheating caused the PBT melt temperature to rise and the viscosity to decrease. When it was compounded with PET melt, the cross-section of the composite fiber was deformed and the elasticity was reduced. After the cause was found and the problem was resolved, the monitoring data of the next batch was tracked to confirm whether the elasticity had returned to normal.

[0063] Batch 34: During the production of this batch, the PLC controller calculated that when the yarn cake reached the 259th minute, the expansion coefficient B was 1.1552, while the expansion coefficient A of the original curve at that time was 1.1586. The absolute value of the difference between the two exceeded the preset value, and the PLC controller activated the alarm device. After discovering the alarm, the workshop technicians checked the expansion coefficient-time relationship curve on the display and found that the curve gradually deviated from the original curve starting from the 259th minute. Elasticity tests were conducted on the three-dimensional crimped composite fibers produced in the abnormal stage and found that the crimp shrinkage rate measured according to the FZ / T 50058-2022 standard "Test Method for Elastic Properties of Synthetic Fiber Bicomponent Composite Filaments" was only 29% (the crimp shrinkage rate of normal three-dimensional crimped composite fibers is 32%±1.5%). Then, the abnormal yarn cake was switched downgraded.

[0064] After the above problems occurred, the technicians investigated and found that it was due to an abnormality in the hot roller motor. The draw ratio of the first and second hot rollers decreased from 1.91 to 1.75. After the draw ratio changed, the orientation crystal structure of the two components changed, resulting in a change in the difference in thermal shrinkage rate and reduced elasticity. After the technicians found the cause and fixed it, they switched the abnormal yarn cake to a lower grade and continued to track the monitoring data of the next batch to confirm whether the elasticity had returned to normal.

[0065] Batch 48: During the production process of this batch, the PLC controller calculated that when the yarn cake reached the 156th minute, the expansion coefficient B was 1.1218, while the expansion coefficient A of the original curve at that time was 1.1184. The absolute value of the difference between the two exceeded the preset value, and the PLC controller activated the alarm device. After discovering the alarm, the workshop technicians checked the expansion coefficient-time relationship curve on the display and found that the curve gradually deviated from the original curve starting from the 156th minute. The elasticity test of the three-dimensional crimped composite fiber produced in the abnormal stage was carried out and it was found that the crimping shrinkage rate measured according to the FZ / T 50058-2022 "Test Method for Elastic Properties of Synthetic Fiber Bicomponent Composite Filament" standard was 34% (the crimping shrinkage rate of normal three-dimensional crimped composite fiber is 32%±1.5%). Then, the abnormal yarn cake was switched downgraded.

[0066] After the above problem occurred, the technicians investigated and found that the temperature of the second hot roller was 145℃, but due to the blockage of the oil fume pipe of the second hot box, the temperature inside the hot box was too high. This caused the orientation and crystal structure of the two components to change, resulting in a change in the difference in thermal shrinkage rate and increased elasticity. After the technicians found the cause and fixed it, they switched the abnormal yarn cake to a lower grade and continued to track the monitoring data of the next batch to confirm whether the elasticity had returned to normal.

[0067] As can be seen from the above, the present invention can realize online monitoring of the elastic changes of three-dimensional crimped fibers.

Claims

1. A method for online monitoring of elastic changes in three-dimensional crimped fibers, characterized in that, When producing multiple batches of yarn cakes, the expansion coefficient A of the first batch of yarn cakes is monitored online during the winding process, and the relationship curve between the expansion coefficient A and time is plotted simultaneously. The relationship curve between the expansion coefficient A and time obtained after the first batch of yarn cakes is produced is used as the original curve. Then, during the winding process of subsequent batches of yarn cakes, the expansion coefficient B of the subsequent batches of yarn cakes is monitored online, and the expansion coefficient B is compared with the expansion coefficient A in the original curve. When the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value at the same time, it is determined that the elasticity of the three-dimensional crimped fiber has changed; otherwise, the elasticity of the three-dimensional crimped fiber has not changed. Wherein, the expansion coefficient = the maximum height of the yarn cake in real time during the winding process / the displacement of the lateral displacement device.

2. The method for online monitoring of elastic changes in three-dimensional crimped fibers according to claim 1, characterized in that, The apparatus used in the method for online monitoring of elastic changes in three-dimensional crimped fibers includes an online monitoring device and a PLC controller; The online monitoring device includes an infrared sensor; the infrared sensor is used to monitor the maximum height of the yarn cake in real time during the winding process. The online monitoring device is connected to the PLC controller. The PLC controller receives the information sent by the online monitoring device and plots the relationship curve between the expansion coefficient and time. After the first batch of silk cakes is produced, the relationship curve between the expansion coefficient A and time is used as the original curve. The expansion coefficient B is compared with the expansion coefficient A in the original curve to determine whether the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value.

3. The method for online monitoring of elastic changes in three-dimensional crimped fibers according to claim 2, characterized in that, The online monitoring device also includes fixed block A, fixed block B, connecting rod A, and connecting rod B; There are multiple infrared sensors, which include infrared transmitters and infrared receivers; Infrared emitters are arranged in a row to form an infrared emitter group, which is horizontally fixed on fixed block A. The infrared receivers are arranged in a row to form an infrared receiver group, and the infrared receiver group is horizontally fixed to the fixed block B; Fixed block A is fixedly connected to the winding machine via connecting rod A; fixed block B is fixedly connected to the winding machine via connecting rod B; The length direction of the infrared transmitter group and the infrared receiver group is the same as the length direction of the spindle of the winding machine; The length of the infrared emitter assembly is the same as the length of the paper tube on the spindle, and it is aligned with one of the paper tubes on the spindle. On the vertical plane perpendicular to the spindle shaft, the infrared rays emitted by the infrared emitter are tangent to the paper tube on the spindle shaft.

4. The method for online monitoring of elastic changes in three-dimensional crimped fibers according to claim 3, characterized in that, Let a be the distance between the infrared rays in two adjacent infrared sensors; the preset value is ≥ a / displacement of the lateral displacement device, and the preset value is < 2a / displacement of the lateral displacement device.

5. The method for online monitoring of elastic changes in three-dimensional crimped fibers according to claim 4, characterized in that, The distance between the infrared rays in two adjacent infrared sensors is 0.1 mm.

6. The method for online monitoring of elastic changes in three-dimensional crimped fibers according to claim 5, characterized in that, The apparatus used in the method for online monitoring of elastic changes in three-dimensional crimped fibers also includes a display. The display is electrically connected to the PLC controller, and the PLC controller sends the plotted curve of the expansion coefficient versus time to the display.

7. The method for online monitoring of elastic changes in three-dimensional crimped fibers according to claim 6, characterized in that, The apparatus used in the method for online monitoring of elastic changes in three-dimensional crimped fibers also includes an alarm device; The alarm device is electrically connected to the PLC controller; when the absolute value of the difference between the expansion coefficient B and the expansion coefficient A is greater than the preset value at the same time, the PLC controller controls the alarm device to sound an alarm.

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