Tension detection device for knitwear production and working method

Abstract

The application discloses a tension detection device for knitted shirt production and a working method, which comprises a rectangular machine shell with an open design on the front end face, rectangular feed ports and discharge ports symmetrically arranged on the left and right sides of the machine shell, a protective auxiliary unit installed at the opening of the front end face of the machine shell, a mounting frame installed in the machine shell, a tension detection unit, a positioning unit, a double-sided cleaning unit for cleaning the surface of the yarn, a signal processing unit, an operation control unit, and an output execution unit adapted to the original system of the knitting equipment. The application adopts non-contact detection, is suitable for high-end knitting production, has multiple anti-interference designs, perfectly adapts to harsh working conditions in the knitting workshop, has a modular design, each unit can be freely disassembled and assembled, has a double-sided cleaning design, impurities on the surface of the yarn can be completely removed, has a multi-station design, has high detection precision and small error, is suitable for all kinds of products and all scenes, covers the whole knitting industry chain, and realizes full-process closed-loop linkage, so that the production automation level is improved.

Description

Technical Field

[0001] This invention belongs to the field of yarn processing tension detection technology, and in particular relates to a tension detection device and its working method for knitwear production. Background Technology

[0002] Knitwear is a type of garment made by using knitting needles to form loops from yarn, which are then linked together. It is characterized by its soft texture, good elasticity, and excellent breathability. In the production process of knitwear, the yarn tension is a core parameter determining the quality of the finished product: excessive tension can easily lead to tearing and breakage of high-elasticity yarns, while insufficient tension can cause loop slack, fabric defects, and dimensional errors in the finished garment. Currently, circular knitting machines / flat knitting machines generally have 12-120 yarn feeds, and high-speed knitting speeds can reach over 30 rpm, which places extremely high demands on the detection of yarn tension.

[0003] To solve the above problems, existing technologies have proposed a variety of contact yarn tension detection schemes: (1) such as the tension detection device for knitwear disclosed in CN218349992U, which uses a threaded rod to rotate and push the moving seat, and uses a spring to pull the slide cylinder, which in turn drives the round rod to press down the knitwear fabric. The tension value is read by observing the position of the scale groove on the metal rod on the slide cylinder. This scheme relies on visual observation of the scale groove, which makes it difficult to achieve accurate quantitative detection; (2) such as the tension detection device for knitwear production disclosed in CN214277703U, whose mechanical structure applies force to the shirt fabric instead of manual pulling force, and the pressure sensor reacts in real time. The tension condition replaces the visual observation of the shirt fabric deformation, improving detection efficiency and accuracy. This scheme adopts a large yarn wrap angle (≥30°) design, which increases the contact area between the yarn and the detection roller to improve the stability of tension acquisition. However, it will cause yarn stretching deformation and surface fiber wear, eventually leading to problems such as yarn breakage and fabric pilling. If the wrap angle is reduced to reduce wear, there will be problems of tension component loss and a significant decrease in detection accuracy. The two cannot be taken into account at the same time. (3) For example, a wool sweater yarn tension detection device disclosed in CN217807998U can be conveniently disassembled from wool sweater yarn textile equipment by means of the matching setting of the pre-installed mechanism. To facilitate the disassembly and maintenance of the wool sweater yarn tension testing device, a brushing mechanism is provided on the side wall surface of the machine plate on both sides of the auxiliary wheel. The wool sweater yarn tension testing device can remove impurities such as lint from the surface of the wool sweater yarn by means of the brushing mechanism. This solution can only clean one side of the yarn and cannot meet the need for double-sided cleaning; (4) As disclosed in CN120721483A, a knitted fabric tension testing device is provided. This solution uses guide rails, rail sleeves and base plate to drive multiple clamps to move laterally. The gear set and micro motor are used for precise positioning. Multiple clamp sets can be preloaded with different samples and automatically switch to the testing mode during testing. The workstation eliminates the manual disassembly and assembly steps. The position sensor automatically identifies the position of the fixture, realizing seamless connection of the detection process and improving the detection efficiency by more than 50%. However, the integration is high and the related components are difficult to disassemble, making it inconvenient to maintain and replace them separately. In addition, the existing technology has also proposed a non-contact tension detection scheme: (1) such as the non-contact yarn tension detection system and method disclosed in CN108796710A. This scheme can measure the yarn tension value in the spinning process in a non-contact manner during the continuous operation of the spinning machine. However, impurities such as fly hair and dust in the detection environment will block the detection components such as laser / photoelectric lens, thus causing the detection to fail.(2) As disclosed in CN110160694B, a non-contact yarn tension detection system and its detection method can measure the yarn tension during spinning in a non-contact manner without generating additional pressure or deformation on the yarn. However, when the yarn linear density is uneven, the ambient airflow interference is large, or the yarn is running at low speed, the vibration characteristics measured by a single frequency detection may not be obvious, resulting in inaccurate frequency extraction.

[0004] Therefore, in response to the above problems, the tension testing device and working method for knitwear production proposed in this solution are of great significance. They can achieve high-precision, non-contact, multi-station testing, and have strong resistance to environmental interference. They can clean the yarn surface lint from both sides and the components can be disassembled. Summary of the Invention

[0005] This invention provides a tension testing device and its working method for knitwear production. The tension testing process involves no physical contact with the yarn, eliminating friction and wear, thus completely solving the damage problem caused by traditional contact testing to high-end, easily damaged yarns such as silk, cashmere, and ultra-fine denier spandex. It avoids fabric defects caused by yarn fuzzing and breakage, significantly improving the finished product quality and yield of high-end knitwear. Specifically designed for knitwear production scenarios, it employs an optical anti-interference design using PWM modulated light and a narrow-band filter to thoroughly filter out stray light from the workshop environment. A dual-isolation power supply design (analog and digital) isolates the device from electromagnetic interference from the machine motor and frequency converter. A dustproof air-blowing design addresses the industry pain point of fly hair obstructing the light path. The protective auxiliary unit, tension testing unit, and positioning unit can all be disassembled individually for long-term maintenance or replacement after malfunction, without requiring the entire device to be scrapped. A double-sided cleaning unit allows for simultaneous cleaning of lint and other impurities adhering to the upper and lower surfaces of the yarn before and after testing, eliminating the need for flipping or repeated cleaning operations and avoiding cleaning dead zones. This technology not only improves efficiency but also significantly enhances cleaning effectiveness. Multiple photoelectric transmitting and receiving modules simultaneously collect frequency data from multiple positions on the yarn surface, allowing for the calculation of multiple sets of tension data. By comparing these data sets and averaging them, more accurate data can be obtained, greatly reducing detection errors. A programmable gain amplifier circuit allows for flexible adjustment of the signal amplification factor, adapting to all types of knitting yarns, from ultra-fine denier filaments to coarse wool yarns. It is compatible with all types of knitting equipment, including circular knitting machines, flat knitting machines, seamless underwear machines, and sock machines. It can be installed independently or integrated into a multi-line array layout, accommodating batch retrofitting of new and old knitting equipment. It not only enables real-time tension detection and abnormal alarms but also allows direct connection to the knitting equipment's native shutdown control circuit via optocoupler isolation relays, significantly shortening the response time for yarn breakage / tension over-limit, thus preventing long stretches of defective products. Simultaneously, it can be linked with the yarn feeding mechanism to achieve closed-loop automatic tension adjustment, ensuring coil uniformity from the source, improving fabric weight and density consistency, and reducing manual adjustment costs. In summary, this technology solves the problems mentioned in the background.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] The present invention provides a tension detection device for knitwear production, comprising a rectangular housing with an open front end, rectangular feed inlets and outlets symmetrically arranged on the left and right sides of the housing, a protective auxiliary unit installed at the opening on the front end of the housing, a mounting frame installed inside the housing, a tension detection unit for detecting yarn tension, a positioning unit for positioning yarn span, a double-sided cleaning unit for cleaning the yarn surface, a signal processing unit, a calculation and control unit, and an output execution unit adapted to the native system of the knitting equipment.

[0008] The protective auxiliary unit includes a rectangular cover plate for sealing the casing, an air inlet on the front end of the cover plate, a hollow rectangular air chamber fixed on the rear end of the cover plate, and two sets of air outlets on the surface of the air chamber.

[0009] The tension detection unit includes several photoelectric emitting modules and photoelectric receiving modules symmetrically distributed above and below the yarn. Each photoelectric emitting module includes a modulation light source, a collimating lens group, and a PWM modulation drive circuit fixed above the mounting frame. Each photoelectric receiving module includes a PIN-type photodetector, a focusing lens group, a narrowband filter, and a low-noise IV-to-transimpedance amplifier fixed below the mounting frame.

[0010] The positioning unit includes mounting seats symmetrically fixed on the left and right sides of the mounting frame, wheel axles fixed on the front end face of each mounting seat, and upstream and downstream yarn guiding ceramic wheels coaxially and parallelly mounted on the two wheel axles.

[0011] The double-sided cleaning unit includes two pairs of rectangular fixing plates symmetrically fixed above and below the inlet and outlet, two pairs of rectangular cleaning plates symmetrically distributed between each pair of fixing plates, and rectangular cleaning brushes installed on the opposite surfaces of each pair of cleaning plates.

[0012] The signal processing unit is sequentially electrically connected to a programmable gain amplifier circuit, a second-order Butterworth bandpass filter circuit, and a hysteresis comparator and shaper circuit.

[0013] The computation control unit uses an industrial-grade MCU or FPGA chip with a built-in advanced hardware counter.

[0014] The output execution unit includes a display terminal, an audible and visual alarm module, an optocoupler isolation relay group, and an RS485 industrial communication interface.

[0015] Furthermore, the number of modulation light sources in the photoelectric transmitting module is the same as the number of photodetectors in the photoelectric receiving module, and they are equidistantly linearly distributed along the top and bottom of the mounting frame, respectively, and the central axes of each modulation light source and each photodetector coincide with each other.

[0016] Furthermore, the collimating lens group in the photoelectric emitting module and the focusing lens group in the photoelectric receiving module each include a plurality of collimating lenses and a plurality of focusing lenses that are linearly distributed at equal intervals. The number of collimating lenses and focusing lenses is the same as the number of modulation light sources and photodetectors. Each collimating lens and each focusing lens is located directly below and directly above each modulation light source and photodetector, respectively. The narrowband filter in the photoelectric receiving module is located between the focusing lens group and the yarn below, and its area covers each focusing lens.

[0017] Furthermore, support frames for supporting the housing are fixedly connected to both sides of the bottom of the housing. A base for fixing the support frame is fixedly connected to the bottom of the support frame. The base has threaded holes for inserting fasteners. The length and width of the housing and the cover plate are equal. A pair of first positioning seats and a pair of second positioning seats are symmetrically distributed on the top and bottom of the housing and the cover plate, respectively. A first positioning hole is opened on the surface of the first positioning seat. A first screw with the same diameter as the first positioning hole is fixedly connected to the second positioning seat. The central axis of each first screw and each first positioning hole coincides with each other. A first nut that mates with each first screw is threaded onto each first screw.

[0018] Furthermore, the two sets of air outlets are symmetrically distributed vertically, and each set of air outlets is equidistantly linearly distributed along the long side of the air guide chamber. The height of each set of air outlets is flush with that of each photoelectric transmitting module and each photoelectric receiving module. The length and width of the air guide chamber correspond to the length and width of the inner wall of the housing, respectively. A rectangular sealing groove is formed on the side wall of the air guide chamber, and a sealing ring is fixedly installed in the sealing groove. The sealing ring is rectangular, and its width and thickness correspond to the width and depth of the sealing groove, respectively.

[0019] Furthermore, the side of the mounting bracket is C-shaped, and a second screw is fixedly connected to the four corners of its rear end face. A second nut that mates with the second screw is threaded onto the second screw. The rear end face of the housing has four second positioning holes, the same number as the second screw and with the same diameter as the second screw. The central axis of each second positioning hole coincides with the central axis of each second screw.

[0020] Furthermore, the shaft of the wheel axle is provided with an external thread and a stop block is fixedly connected thereto, and the shaft of the wheel axle is threadedly connected with a third nut that mates with it. The upstream yarn guiding ceramic wheel and the downstream yarn guiding ceramic wheel are respectively located between the stop block and the third nut on each wheel axle, and the upstream yarn guiding ceramic wheel and the downstream yarn guiding ceramic wheel are coaxial with the feed inlet and the discharge outlet, respectively.

[0021] Furthermore, each cleaning plate has a pair of guide rods fixedly connected to one side of the plate near the fixing plate, and a rectangular slot is formed on the other side. Each fixing plate has a pair of guide holes with the same diameter as the guide rods on its surface. The top of each guide rod passes through the corresponding guide hole and is fixedly connected to a connecting block. Each guide rod has a spring wound around its body. The top and bottom of the spring are fixedly connected to the fixing plate and the cleaning plate, respectively. The length and width of the cleaning brush and the slot are respectively equal, and the thickness of the cleaning brush is greater than the depth of the slot.

[0022] A method for operating a tension detection device for knitwear production, implemented using the aforementioned tension detection device, includes the following steps:

[0023] S1. Pre-configuration of testing benchmark: The yarn to be tested is fed into the machine housing from the feed port on one side and out from the discharge port on the other side. It passes around the upstream and downstream guide rollers in the positioning unit. Through the rigidly fixed positioning mechanism, a free yarn segment with a fixed length of L is constructed on the yarn conveying path of the knitting equipment. The linear density ρ of the yarn to be tested is pre-entered into the calculation control unit to complete the configuration of testing benchmark parameters.

[0024] S2, Modulated light path projection: Each photoelectric emission module is activated, and the PWM modulation signal output by the operation and control unit drives the modulation light source to emit modulated light of a preset wavelength. The light is converted into a parallel fine beam by the collimating lens group and projected vertically to various positions of the free yarn segment to form a stable detection light path.

[0025] S3. Vibration light signal conversion: During the operation of the knitting equipment, the free yarn segment generates a transverse vibration at its natural frequency under the action of tension. The yarn vibration periodically changes the light-blocking area of ​​the detection light path, causing the light flux received by each photoelectric receiving module to generate a periodic change synchronized with the yarn vibration frequency. Each photoelectric receiving module converts the light flux change into an alternating initial electrical signal in real time.

[0026] S4. Signal preprocessing: The signal processing unit performs IV conversion, programmable gain amplification, bandpass filtering and hysteresis shaping on the initial electrical signal in sequence to filter out noise interference caused by ambient light in the knitting workshop and machine vibration, and outputs a standard square wave signal that corresponds exactly to the yarn vibration frequency.

[0027] S5. Equal Precision Frequency Acquisition: The operation and control unit uses a built-in hardware counter to perform equal precision frequency measurement on the standard square wave signal to obtain the real-time natural vibration frequency f of the free yarn segment;

[0028] S6. Real-time tension calculation: The calculation and control unit substitutes the pre-configured yarn linear density ρ, the fixed length of the free yarn segment L, and the real-time acquired vibration frequency f into the string vibration tension calculation formula to calculate the dynamic tension value T of the yarn in real time. The string vibration tension calculation formula is as follows:

[0029] T=4·ρ·L 2 ·f 2

[0030] In the formula, T is the real-time tension of the yarn in cN, ρ is the linear density of the yarn in tex, L is the fixed length of the free yarn segment in m, and f is the natural vibration frequency of the yarn in Hz.

[0031] S7. Result Output and Linkage Control: The calculation and control unit outputs the real-time tension value to the display terminal, and compares the real-time tension value with the preset upper and lower tension thresholds and the yarn breakage judgment threshold. When the tension value exceeds the threshold range or the vibration frequency signal is detected to disappear, the control signal is immediately sent to the knitting equipment through the output execution unit.

[0032] S8. Compare multiple sets of data to reduce errors: Multiple photoelectric emission modules and photoelectric receiving modules can simultaneously collect multiple position frequencies on the yarn surface to calculate multiple sets of tension data. By comparing multiple sets of data and taking their average value, more accurate data can be obtained, thereby reducing detection errors.

[0033] The present invention has the following advantages over the prior art:

[0034] (1) Non-contact testing is adopted, which is suitable for high-end knitting production: the tension testing process has no physical contact with the yarn, no friction and no wear, which completely solves the problem of damage to high-end fragile yarns such as silk, cashmere and superfine denier spandex caused by traditional contact testing, avoids fabric defects caused by yarn pilling and yarn breakage, and greatly improves the finished product quality and yield of high-end knitwear.

[0035] (2) Multiple anti-interference design, perfectly adapted to the harsh working conditions of the knitting workshop: For the knitting production scenario, the optical anti-interference design of PWM modulated light + narrow band filter is adopted to completely filter the stray light in the workshop environment; the analog and digital dual isolation power supply design is adopted to isolate the electromagnetic interference of machine motors and frequency converters; the dustproof blowing design is adopted to solve the industry pain point of flying flowers blocking the light path.

[0036] (3) Modular design, each unit can be disassembled and assembled at will: the protective auxiliary unit, tension detection unit and positioning unit can be disassembled separately so that they can be maintained separately after long-term use or replaced separately after failure, without scrapping the entire device;

[0037] (4) Double-sided cleaning design, thorough removal of impurities on yarn surface: The double-sided cleaning unit can clean the lint and other impurities adhering to the upper and lower surfaces of the yarn simultaneously before and after inspection, without the need to flip or repeat the cleaning operation. This not only avoids the generation of cleaning dead corners, but also greatly improves the cleaning efficiency.

[0038] (5) Multi-station design, high detection accuracy and small error: Multiple photoelectric emission modules and photoelectric receiving modules can simultaneously collect multiple position frequencies on the yarn surface to calculate multiple sets of tension data. By comparing multiple sets of data and taking their average value, more accurate data can be obtained, thereby greatly reducing the detection error.

[0039] (6) Full category and full scenario adaptation, covering the entire knitting industry chain: Through the programmable gain amplifier circuit, the signal amplification factor can be flexibly adjusted to adapt to all categories of knitting yarns from ultra-fine denier filament to coarse wool yarn; it is compatible with all categories of knitting equipment such as circular knitting machines, flat knitting machines, seamless underwear machines, and sock machines. It can be installed independently on a single line or integrated in a multi-line array layout to adapt to the batch transformation of new and old knitting equipment;

[0040] (7) Full-process closed-loop linkage to improve the level of production automation: It can not only realize real-time tension detection and abnormal alarm, but also directly connect to the original shutdown control circuit of the knitting equipment through optocoupler isolation relay, greatly shortening the response time of yarn breakage / tension over-limit, so as to avoid the generation of long-segment defective products; at the same time, it can link the yarn feeding mechanism to realize closed-loop automatic tension adjustment, ensuring the uniformity of the coil from the source, improving the consistency of fabric weight and density, and reducing the cost of manual adjustment.

[0041] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a front structural diagram of a tension detection device for knitwear production according to the present invention;

[0044] Figure 2 This is a schematic diagram of the back structure of a tension detection device for knitwear production according to the present invention;

[0045] Figure 3 This is a schematic diagram of the front structure of the casing in this invention;

[0046] Figure 4 This is a schematic diagram of the back structure of the housing in this invention;

[0047] Figure 5 This is a schematic diagram of the front structure of the tension detection unit in this invention;

[0048] Figure 6 This is a schematic diagram of the back structure of the tension detection unit in this invention;

[0049] Figure 7 This is a schematic diagram of the upstream and downstream yarn guiding ceramic wheels in this invention;

[0050] Figure 8This is a top view of the upstream and downstream yarn guiding ceramic wheels in this invention;

[0051] Figure 9 This is a front structural diagram of the protective auxiliary unit in this invention;

[0052] Figure 10 This is a schematic diagram of the rear structure of the protective auxiliary unit in this invention;

[0053] Figure 11 This is an internal cross-sectional view of the protective auxiliary unit in this invention;

[0054] Figure 12 This is a schematic diagram of the sealing ring structure in this invention;

[0055] Figure 13 This is a schematic diagram of the structure of the double-sided cleaning unit in this invention;

[0056] Figure 14 This is a side view of the double-sided cleaning unit in this invention;

[0057] Figure 15 This is a schematic diagram of the cleaning brush in this invention;

[0058] Figure 16 This is a circuit connection block diagram of a tension detection device for knitwear production according to the present invention.

[0059] The attached diagram lists the components represented by each number as follows:

[0060] 1. Machine housing; 2. Feed inlet; 3. Discharge outlet; 4. Mounting bracket; 5. Cover plate; 6. Air inlet; 7. Air guide chamber; 8. Air outlet; 9. Modulation light source; 10. Collimating lens group; 11. Photodetector; 12. Focusing lens group; 13. Narrow band filter; 14. Mounting base; 15. Wheel axle; 16. Upstream yarn guide ceramic wheel; 17. Downstream yarn guide ceramic wheel; 18. Fixing plate; 19. Cleaning plate; 20. Cleaning brush ; 21. Support frame; 22. Base; 23. First positioning seat; 24. Second positioning seat; 25. First positioning hole; 26. First screw; 27. First nut; 28. Sealing groove; 29. ​​Sealing ring; 30. Second screw; 31. Second nut; 32. Second positioning hole; 33. Stop block; 34. Third nut; 35. Guide rod; 36. Slot; 37. Guide hole; 38. Connecting block; 39. Spring. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] In the description of this invention, it should be understood that the terms "relative", "one end", "inner", "lateral", "end", "both ends", "both sides", "front", "one end face", "the other end face", etc., which indicate orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention.

[0063] Please see Figure 1-16 As shown, a tension detection device for knitwear production according to the present invention includes a rectangular housing 1 with an open front face, a rectangular feed port 2 and a feed port 3 symmetrically opened on the left and right sides of the housing 1, a protective auxiliary unit installed at the opening on the front face of the housing 1, a mounting frame 4 installed inside the housing 1, a tension detection unit for detecting yarn tension, a positioning unit for positioning yarn span, a double-sided cleaning unit for cleaning the yarn surface, a signal processing unit, a calculation and control unit, and also includes an output execution unit adapted to the native system of the knitting equipment.

[0064] In this embodiment, the circular knitting machine is a 34-inch 32-gauge single-sided circular knitting machine with a rotation speed of 30 rpm. The yarn being tested is 40Ne pure cotton knitting yarn with a linear density ρ = 14.6 tex. The preset normal tension range is 8~12 cN, and the yarn breakage judgment threshold is a vibration frequency signal disappearance time ≥ 10 ms.

[0065] The protective auxiliary unit includes a rectangular cover plate 5 for sealing the housing 1, an air inlet 6 opened on the front end face of the cover plate 5, a hollow rectangular air guide chamber 7 fixed on the rear end face of the cover plate 5, and two sets of air outlets 8 opened on the surface of the air guide chamber 7.

[0066] The tension detection unit includes several photoelectric emitting modules and photoelectric receiving modules symmetrically distributed above and below the yarn. Each photoelectric emitting module includes a modulation light source 9, a collimating lens group 10, and a PWM modulation drive circuit fixed above the mounting frame 4. The modulation light source 9 is a semiconductor laser with a wavelength of 650nm or an infrared light-emitting diode with a wavelength of 850nm / 940nm. The control terminal of the PWM modulation drive circuit is electrically connected to the PWM output pin of the operational control unit, and the power output terminal is electrically connected to the modulation light source 9. The PWM modulation drive circuit outputs a modulation signal of a preset frequency to drive the modulation light source 9 to emit light. The collimating lens group 10 converts the divergent light source into a parallel narrow beam with a spot diameter ≤0.5mm to ensure detection accuracy. Each photoelectric receiving module includes a PIN-type photodetector 11, a focusing lens group 12, a narrowband filter 13, and a low-noise IV-to-transimpedance amplifier fixed below the mounting frame 4. The center wavelength of the narrowband filter 13 is perfectly matched with the light source wavelength of the photoelectric emitting module. The system is configured to allow only modulated light from the light source to pass through, thus blocking stray light from the workshop environment. In this embodiment, the ultra-fine denier filament uses an 850nm low-power (5mw) infrared light-emitting diode, and the coarse wool / cotton yarn uses a 650nm semiconductor laser (10mw). The PIN photodetector 11 is adapted to model S1223-01 (response time 1ns). The narrowband filter 13 has a half-bandwidth of 8nm and an optical density OD of 4. The focusing lens group 12 can focus the emitted light onto the receiving surface to improve sensitivity. The photodetector 11 is a PIN photodiode, and its signal output terminal is electrically connected to the input terminal of the IV-to-transimpedance amplifier to convert the received light flux change into an alternating current signal. The response wavelength range of the photodetector 11 is 400~1000nm, and the response time is ≤10ns. The IV-to-transimpedance amplifier is built using the OP07 low-noise operational amplifier from Analog Devices, with a feedback resistor of 1MΩ, which can convert nA-level photocurrent into mV-level voltage signal.

[0067] The positioning unit includes mounting seats 14 symmetrically fixed on the left and right sides of the mounting frame 4, axle 15 fixed on the front end face of each mounting seat 14, and an upstream yarn guide ceramic wheel 16 and a downstream yarn guide ceramic wheel 17 coaxially and parallelly mounted on the two axle 15. The distance between the upstream yarn guide ceramic wheel 16 and the downstream yarn guide ceramic wheel 17 is a fixed value L, which can form a positioning reference for the unconstrained free yarn segment and prevent yarn axial movement and span offset. In this embodiment, the free yarn segment length L ranges from 50 to 100 mm, of which 80 to 100 mm is suitable for circular knitting machines and 50 to 70 mm is suitable for flat knitting machines / sock machines; the diameter of the yarn guide ceramic wheel is 20 to 30 mm, the groove shape is U-shaped (groove width 0.5 to 5 mm, suitable for yarns of different linear densities), and the ceramic wheel material is 95% alumina ceramic.

[0068] The double-sided cleaning unit includes two pairs of rectangular fixing plates 18 symmetrically fixed above and below the inlet 2 and outlet 3, two pairs of rectangular cleaning plates 19 symmetrically distributed between each pair of fixing plates 18, and rectangular cleaning brushes 20 installed on the opposite surfaces of each pair of cleaning plates 19.

[0069] The signal processing unit is sequentially connected to a programmable gain amplifier circuit, a second-order Butterworth bandpass filter circuit, and a hysteresis comparator shaping circuit. The input of the programmable gain amplifier circuit is electrically connected to the output of the IV-to-IV conversion transimpedance amplifier, and its control terminal is electrically connected to the operational control unit via an SPI bus. The output of the hysteresis comparator shaping circuit is electrically connected to the hardware counter pin of the operational control unit. The IV-to-IV conversion circuit converts the weak current signal output by the photodetector 11 into a voltage signal. The programmable gain amplifier circuit adjusts the amplification factor according to the yarn type. The passband of the bandpass filter circuit is 50Hz-2000Hz (matching the vibration frequency range of knitted yarn). The shaping circuit converts the noisy sine wave signal into a standard square wave signal. The programmable gain amplifier circuit 401 uses a PGA113 chip, and its amplification factor is adjustable from 100 to 2000 times. It is electrically connected to the operational control unit via an SPI bus; in this embodiment, the amplification factor is set to 500 times. The passband of the bandpass filter circuit is 50Hz-2000Hz, matching the vibration frequency range of pure cotton yarn. The hysteresis comparator shaping circuit... The circuit uses an LM393 voltage comparator to convert the noisy sine wave signal into a standard square wave signal, which is then output to the arithmetic control unit. The signal processing unit is installed inside the housing 1, adjacent to the photoelectric transmitter and receiver modules (the specific installation location is not shown in the figure), to minimize the analog signal transmission distance and avoid decreased detection accuracy due to electromagnetic interference and signal attenuation in the workshop. Specifically, the signal processing unit can be installed on the rear end face inside the housing 1, at a distance ≤10cm from the photoelectric module. Shielded twisted-pair cable is used for wiring. The layer is single-ended grounded (grounding resistance ≤ 4Ω). The connection interface between the signal processing unit and the arithmetic control unit is a GPIO port, and the signal transmission level standard is 3.3VTTL. In the second-order Butterworth bandpass filter circuit, the resistors are 1kΩ / 2kΩ metal film resistors, and the capacitors are 0.1μF / 0.01μF ceramic capacitors. The amplification factor matching rules for the programmable gain amplifier circuit are: ultra-fine denier filament (amplification factor 1000-2000 times), pure cotton yarn (500-800 times), and coarse wool yarn (100-300 times).

[0070] The operation and control unit uses an industrial-grade MCU or FPGA chip with a built-in advanced hardware counter to complete equal-precision frequency acquisition, tension calculation, threshold comparison, and full-process logic control. In this embodiment, the operation and control unit uses an STM32F103RCT6 industrial-grade MCU with four built-in advanced hardware timers. The gate time is set to 200ms, and the frequency measurement error is ≤0.1%. The MCU has a built-in operation module that calculates the tension value in real time using the string vibration formula to complete the threshold comparison and logic control. The operation and control unit is installed in a location with low electromagnetic interference, stable power supply, and easy debugging and maintenance, away from the high-voltage components of the machine (the specific installation location is not shown in the figure). At the same time, the wiring distance to each signal processing unit is ensured to be uniform. The gate time adjustment rules for different vibration frequencies are: 50-500Hz (gate time 200ms) and 500-2000Hz (gate time 100ms). The sampling rate of the hardware counter is 10kHz, and the interrupt trigger condition is triggered by the rising edge of the square wave signal.

[0071] The output execution unit includes a display terminal, an audible and visual alarm module, an optocoupler-isolated relay group, and an RS485 industrial communication interface. The control terminal of the optocoupler-isolated relay group is electrically connected to the IO pins of the arithmetic control unit, and the contact terminals are respectively connected to the shutdown control circuit and the yarn feeding mechanism control circuit of the knitting equipment. The RS485 industrial communication interface is connected to the PLC main control system of the knitting equipment. The optocoupler-isolated relay group includes two independent relays. The normally open contact of the first relay is connected in series to the emergency shutdown control circuit of the knitting equipment, and the normally open contact of the second relay is connected to the yarn feeder speed control circuit of the knitting equipment. This is used to realize the shutdown alarm for tension over-limit / yarn breakage, as well as the closed-loop automatic tension adjustment linked with the yarn feeding mechanism. In this embodiment, the audible and visual alarm module includes a red LED indicator and a buzzer, which triggers an alarm when the tension exceeds the limit. The first normally open contact of the optocoupler isolation relay group is connected in series to the emergency stop control circuit of the circular knitting machine, and the normally open contact of the second relay is connected to the yarn feeder speed control circuit of the circular knitting machine. The RS485 industrial communication interface is connected to the PLC main control system of the circular knitting machine to realize tension data upload and remote parameter configuration. The output execution unit is connected to the native control circuit nearby, which is convenient for human-machine interaction and safe and reliable operation. Different sub-components are installed separately according to function (the specific installation position is not shown in the figure), which takes into account both control reliability and operation convenience. The contact capacity of the optocoupler isolation relay is 5A / 220VAC. The stop control circuit is a normally open contact, and the yarn feeder speed control circuit is a normally closed contact. The linkage response time is ≤50ms. The relay action delay parameter and the communication protocol with the PLC of the knitting equipment are Modbus-RTU.

[0072] In this embodiment, the number of modulation light sources 9 in the photoelectric emission module and photodetectors 11 in the photoelectric receiving module are the same, and they are equidistantly linearly distributed along the top and bottom of the mounting frame 4, respectively. The central axes of each modulation light source 9 and each photodetector 11 coincide with each other. Multiple photoelectric emission modules and photoelectric receiving modules can simultaneously collect multiple position frequencies on the yarn surface to calculate multiple sets of tension data. By comparing multiple sets of data and taking their average value, more accurate data can be obtained, thereby greatly reducing detection errors. In this embodiment, the number of photoelectric emission modules and photoelectric receiving modules is 4-8 sets (adapting to the conventional multi-station layout for knitted yarn detection), and the spacing along the mounting frame 4 is 10-15mm. When analyzing and processing multiple sets of data, the 3σ criterion is used to remove abnormal data that deviate from the mean by 3 times the standard deviation, and then the average value of the remaining valid data is taken. During detection, all photoelectric emission modules are synchronously triggered by the PWM signal of the calculation control unit to ensure the time consistency of multi-station data acquisition and avoid errors caused by time differences.

[0073] The collimating lens group 10 in the photoelectric emitting module and the focusing lens group 12 in the photoelectric receiving module each include a number of collimating lenses and a number of focusing lenses that are linearly distributed at equal intervals. The number of collimating lenses and focusing lenses is the same as the number of modulation light sources 9 and photodetectors 11. Each collimating lens and each focusing lens is located directly below and directly above each modulation light source 9 and photodetector 11, respectively. The narrow-band filter 13 in the photoelectric receiving module is located between the focusing lens group 12 and the yarn below, and its area covers each focusing lens. The positions of each collimating lens and focusing lens correspond one-to-one with the positions of each modulation light source 9 and photodetector 11, so as to ensure that the light source output by each photoelectric emitting module is first converted into a parallel narrow beam by the collimating lens group 10 and then focused onto the corresponding photoelectric receiving module.

[0074] The bottom of the housing 1 is fixedly connected to two support frames 21 on both sides. A base 22 is fixedly connected to the bottom of each support frame 21. The base 22 has threaded holes for inserting fasteners, such as screws. The device is fixed in a designated position by the fasteners and the threaded grooves pre-drilled on the fixing surface. The length and width of the housing 1 and the cover plate 5 are equal. A pair of first positioning seats 23 and a pair of second positioning seats 24 are symmetrically distributed on the top and bottom of the housing 1 and the cover plate 5, respectively. The surface of the first positioning seat 23 has a first positioning hole 25, and the second positioning seat 24 is fixedly connected to a first positioning hole 25. The first screws 26 with the same diameter of positioning holes 25 are all aligned with the central axis of each first screw 26 and each first positioning hole 25. Each first screw 26 is threaded with a first nut 27 that mates with it. When the cover plate 5 is placed on the opening at the front end of the housing 1, it can completely overlap with the opening. Each first screw 26 can be aligned and pass through the corresponding first positioning hole 25. At this time, the first nut 27 is threaded onto each first screw 26 and tightened. The cover plate 5 and the protective auxiliary unit can be firmly fixed to the housing 1. By unscrewing the first nut 27, the cover plate 5 and the protective auxiliary unit can be removed from the housing 1 for individual maintenance or replacement.

[0075] The two sets of air outlets 8 are symmetrically distributed vertically. Each set of air outlets 8 is linearly distributed at equal intervals along the long side of the air guide chamber 7, and each set of air outlets 8 is flush with the height of each photoelectric emitting module and each photoelectric receiving module. The length and width of the air guide chamber 7 correspond to the length and width of the inner wall of the housing 1, respectively. A rectangular sealing groove 28 is formed on the side wall of the air guide chamber 7, and a sealing ring 29 is fixedly installed in the sealing groove 28. The sealing ring 29 is rectangular, and its width and thickness correspond to the width and depth of the sealing groove 28, respectively. An external air pump can be connected through the air inlet 6 to introduce air into the air guide chamber 7 through the air inlet 6. After entering the air guide chamber 7, the air is blown through the two sets of air outlets 8 to each photoelectric emitting module and each photoelectric receiving module, so as to continuously sweep the detection optical path area. This effectively prevents impurities such as fly shavings and dust from obstructing the light path. When the cover plate 5 is fixed at the opening on the front face of the housing 1, the air guide chamber 7 can be inserted and fitted against the inner wall of the housing 1. At this time, the cover plate 5 can shield and seal the housing 1 to isolate ambient light interference. At the same time, the sealing ring 29 can fill the gap between the air guide chamber 7 and the inner wall of the housing 1 to further improve the sealing effect of the cover plate 5. In this embodiment, the housing 1, cover plate 5, and air guide chamber 7 are all made of aluminum alloy with an IP65 protection rating. The working air pressure of the air pump is 0.05-0.1MPa, the air flow rate of the air outlet 8 is 0.5-1L / min, the diameter of the air outlet 8 is 0.5mm, and the direction of the blowing airflow is parallel to the detection light path and perpendicular to the yarn vibration direction to avoid the airflow directly acting on the yarn and causing vibration interference.

[0076] The mounting bracket 4 has a C-shaped side, and two second screws 30 are fixedly connected to the four corners of its rear end face. Two second nuts 31 are threaded onto the second screws 30. The rear end face of the housing 1 has four second positioning holes 32, the same number as the second screws 30, with the same diameter as the second screws 30. The central axis of each second positioning hole 32 coincides with that of each second screw 30. After the mounting bracket 4 is placed into the housing 1 and fits against the inner rear end face of the housing 1, each second screw 30 can be aligned and pass through the corresponding second positioning hole 32. At this time, the second nuts 31 are threaded onto each second screw 30 and tightened, which can fix the mounting bracket 4 together with the tension detection unit and the positioning unit inside the housing 1. By unscrewing the second nuts 31, the mounting bracket 4 together with the tension detection unit and the positioning unit can be removed from the housing 1 for individual maintenance or replacement of the relevant components.

[0077] The axle 15 has an external thread and a stop 33 is fixedly connected to it. A third nut 34 is also threaded onto the axle 15. The upstream guide roller 16 and the downstream guide roller 17 are located between the stop 33 and the third nut 34 on each axle 15, respectively. The upstream guide roller 16 and the downstream guide roller 17 are coaxial with the inlet 2 and the outlet 3, respectively. A through hole with the same diameter as the axle 15 is opened at the center of both the upstream guide roller 16 and the downstream guide roller 17. When the axle 15... 5. After passing through the through holes in the centers of the upstream yarn guide ceramic wheel 16 and the downstream yarn guide ceramic wheel 17, the third nut 34 can be threaded onto the wheel shaft 15 and tightened until the third nut 34 is tightly fitted against one end face of the upstream yarn guide ceramic wheel 16 and the downstream yarn guide ceramic wheel 17, so as to rigidly fix the upstream yarn guide ceramic wheel 16 and the downstream yarn guide ceramic wheel 17. At the same time, the upstream yarn guide ceramic wheel 16 and the downstream yarn guide ceramic wheel 17 can be limited by the mutual cooperation between the stop block 33 and the third nut 34 to prevent them from axially shifting.

[0078] Each cleaning plate 19 has a pair of guide rods 35 fixedly connected to one side of the plate near the fixing plate 18, and a rectangular slot 36 formed on the other side. Each fixing plate 18 has a pair of guide holes 37 with the same diameter as the guide rods 35 on its surface. The top of each guide rod 35 passes through the corresponding guide hole 37 and is fixedly connected to a connecting block 38. A spring 39 is wound around the body of each guide rod 35, and the top and bottom ends of the spring 39 are fixedly connected to the fixing plate 18 and the cleaning plate 19, respectively. The length and width of the cleaning brush 20 and the slot 36 are respectively equal, and the thickness of the cleaning brush 20 is greater than the depth of the slot 36. When one end of the yarn passes through the feed port 2 into the machine housing 1 and the other end passes through the discharge port 3, each pair of cleaning plates 19 can be attached to the upper and lower surfaces of the yarn under the elastic reset action of the spring 39. As the yarn moves continuously during the operation of the knitting equipment, the lint and other impurities attached to the upper and lower surfaces of the yarn can be brushed away by the cleaning brush 20, thereby achieving the cleaning of the yarn. Double-sided cleaning eliminates the need for flipping or repeated cleaning, avoiding dead corners and significantly improving cleaning efficiency. The cleaning brush 20 can be inserted into and fitted into the slot 36 for fixation. After prolonged use, the cleaning brush 20 can be removed from the slot 36 for regular cleaning. In this embodiment, the spring 39 has an elastic coefficient of 0.5-2 N / mm. The bristle material of the cleaning brush 20 is: nylon soft bristles (Shore A20-30) for high-end yarns (silk / cashmere), and pig bristles (Shore A40-50) for regular yarns (cotton / polyester). The contact pressure between the cleaning brush 20 and the yarn is 0.1-0.3 N, precisely controlled by the compression of the spring 39 (compression 5-10 mm). For high-end, easily damaged yarns, the cleaning brush can be replaced with an electrostatic cleaning roller (made of anti-static silicone material) to remove impurities from the yarn surface through electrostatic adsorption, thus completely avoiding physical friction between the bristles and the yarn.

[0079] A method for operating a tension detection device for knitwear production, implemented using the aforementioned tension detection device, includes the following steps:

[0080] S1. Pre-configuration of detection benchmark: The yarn to be tested is fed into the inlet 2 on one side of the machine housing 1 and out of the outlet 3 on the other side. It passes over the upstream guide roller 16 and the downstream guide roller 17 in the positioning unit respectively. Through the rigidly fixed positioning mechanism, a free yarn segment with a fixed length of L is constructed on the yarn conveying path of the knitting equipment. The linear density ρ of the yarn to be tested is pre-entered into the calculation control unit to complete the configuration of detection benchmark parameters.

[0081] S2, Modulated light path projection: Start each photoelectric emission module, drive the modulation light source 9 to emit modulated light of preset wavelength through the PWM modulation signal output by the operation control unit, convert it into a parallel fine beam through the collimating lens group 10, and project it vertically to various positions of the free yarn segment to form a stable detection light path;

[0082] S3. Vibration light signal conversion: During the operation of the knitting equipment, the free yarn segment generates a transverse vibration at its natural frequency under the action of tension. The yarn vibration periodically changes the light-blocking area of ​​the detection light path, causing the light flux received by each photoelectric receiving module to generate a periodic change synchronized with the yarn vibration frequency. Each photoelectric receiving module converts the light flux change into an alternating initial electrical signal in real time.

[0083] S4. Signal preprocessing: The signal processing unit performs IV conversion, programmable gain amplification, bandpass filtering and hysteresis shaping on the initial electrical signal in sequence to filter out noise interference caused by ambient light in the knitting workshop and vibration of the machine casing 1, and outputs a standard square wave signal that corresponds exactly to the yarn vibration frequency.

[0084] S5. Equal Precision Frequency Acquisition: The operation and control unit uses a built-in hardware counter to perform equal precision frequency measurement on the standard square wave signal to obtain the real-time natural vibration frequency f of the free yarn segment;

[0085] S6. Real-time tension calculation: The calculation and control unit substitutes the pre-configured yarn linear density ρ, the fixed length of the free yarn segment L, and the real-time acquired vibration frequency f into the string vibration tension calculation formula to calculate the dynamic tension value T of the yarn in real time. The string vibration tension calculation formula is as follows:

[0086] T=4·ρ·L 2 ·f 2

[0087] In the formula, T is the real-time tension of the yarn in cN, ρ is the linear density of the yarn in tex, L is the fixed length of the free yarn segment in m, and f is the natural vibration frequency of the yarn in Hz.

[0088] S7. Result Output and Linkage Control: The calculation and control unit outputs the real-time tension value to the display terminal, and compares the real-time tension value with the preset upper and lower tension thresholds and the yarn breakage judgment threshold. When the tension value exceeds the threshold range or the vibration frequency signal is detected to disappear, the control signal is immediately sent to the knitting equipment through the output execution unit.

[0089] S8. Compare multiple sets of data to reduce errors: Multiple photoelectric emission modules and photoelectric receiving modules can simultaneously collect multiple position frequencies on the yarn surface to calculate multiple sets of tension data. By comparing multiple sets of data and taking their average value, more accurate data can be obtained, thereby reducing detection errors.

[0090] The circuits, electronic components, and chip modules involved in this invention are all existing technologies, which can be fully implemented by those skilled in the art, and need not be elaborated upon. The content protected by this invention does not involve improvements to the software and methods.

[0091] All standard parts used in the application documents can be purchased from the market. All components in this application document can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art. The electrical components mentioned in this document are all electrically connected to the external main controller and power supply, and the main controller is a conventional known device that can play a control role.

[0092] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A tension detection device for knitwear production, characterized in that, It includes a rectangular housing (1) with an open front face, rectangular feed inlets (2) and discharge outlets (3) symmetrically opened on the left and right sides of the housing (1), a protective auxiliary unit installed at the opening on the front face of the housing (1), a mounting bracket (4) installed inside the housing (1), a tension detection unit for detecting yarn tension, a positioning unit for positioning yarn span, a double-sided cleaning unit for cleaning yarn surface, a signal processing unit, a calculation and control unit, and an output execution unit adapted to the native system of the knitting equipment; The protective auxiliary unit includes a rectangular cover plate (5) for sealing the housing (1), an air inlet (6) opened on the front end face of the cover plate (5), a hollow rectangular air guide chamber (7) fixed on the rear end face of the cover plate (5), and two sets of air outlets (8) opened on the surface of the air guide chamber (7). The tension detection unit includes several photoelectric emission modules and photoelectric receiving modules symmetrically distributed above and below the yarn. Each photoelectric emission module includes a modulation light source (9), a collimating lens group (10), and a PWM modulation drive circuit fixed above the mounting frame (4). Each photoelectric receiving module includes a PIN-type photodetector (11), a focusing lens group (12), a narrowband filter (13), and a low-noise IV-to-transimpedance amplifier fixed below the mounting frame (4). The positioning unit includes mounting seats (14) symmetrically fixed on the left and right sides of the mounting frame (4), wheel axles (15) fixed on the front end face of each mounting seat (14), and upstream guide ceramic wheel (16) and downstream guide ceramic wheel (17) coaxially and parallelly mounted on the two wheel axles (15). The double-sided cleaning unit includes two pairs of rectangular fixing plates (18) symmetrically fixed above and below the feed inlet (2) and the discharge outlet (3), two pairs of rectangular cleaning plates (19) symmetrically distributed between each pair of fixing plates (18), and rectangular cleaning brushes (20) installed on the opposite surfaces of each pair of cleaning plates (19). The signal processing unit is sequentially electrically connected to a programmable gain amplifier circuit, a second-order Butterworth bandpass filter circuit, and a hysteresis comparator and shaper circuit. The computation control unit uses an industrial-grade MCU or FPGA chip with a built-in advanced hardware counter. The output execution unit includes a display terminal, an audible and visual alarm module, an optocoupler isolation relay group, and an RS485 industrial communication interface.

2. The tension detection device for knitwear production according to claim 1, characterized in that, The number of modulation light sources (9) in the photoelectric emission module is the same as the number of photodetectors (11) in the photoelectric receiving module, and they are equidistantly linearly distributed along the top and bottom of the mounting frame (4), respectively, and the central axes of each modulation light source (9) and each photodetector (11) coincide with each other.

3. The tension detection device for knitwear production according to claim 1, characterized in that, The collimating lens group (10) in the photoelectric transmitting module and the focusing lens group (12) in the photoelectric receiving module each include a number of collimating lenses and a number of focusing lenses that are linearly distributed at equal intervals. The number of collimating lenses and focusing lenses is the same as the number of modulation light source (9) and photodetector (11). Each collimating lens and each focusing lens is located directly below and directly above each modulation light source (9) and photodetector (11), respectively. The narrowband filter (13) in the photoelectric receiving module is located between the focusing lens group (12) and the yarn, and its area covers each focusing lens.

4. The tension detection device for knitwear production according to claim 1, characterized in that, The bottom sides of the housing (1) are fixedly connected to support frames (21) for supporting the housing (1). The bottom of the support frame (21) is fixedly connected to a base (22) for fixing the support frame (21). The base (22) is provided with threaded holes for inserting fasteners. The length and width of the housing (1) and the cover plate (5) are equal. The top and bottom of the housing (1) and the cover plate (5) are symmetrically distributed with a pair of first positioning seats (23) and a pair of second positioning seats (24). The surface of the first positioning seat (23) is provided with a first positioning hole (25). The second positioning seat (24) is fixedly connected with a first screw (26) with the same diameter as the first positioning hole (25). The central axis of each first screw (26) and each first positioning hole (25) coincides with each other. Each first screw (26) is threaded with a first nut (27) that matches it.

5. The tension detection device for knitwear production according to claim 1, characterized in that, The two sets of air outlets (8) are symmetrically distributed vertically. Each set of air outlets (8) is equidistantly linearly distributed along the long side of the air guide chamber (7). Each set of air outlets (8) is level with the height of each photoelectric transmitting module and each photoelectric receiving module. The length and width of the air guide chamber (7) are equal to the length and width of the inner wall of the housing (1). A rectangular sealing groove (28) is opened on the side wall of the air guide chamber (7). A sealing ring (29) is fixedly installed in the sealing groove (28). The sealing ring (29) is rectangular, and its width and thickness are equal to the width and depth of the sealing groove (28).

6. The tension detection device for knitwear production according to claim 1, characterized in that, The mounting bracket (4) has a C-shaped side, and a second screw (30) is fixedly connected to the four corners of its rear end face. A second nut (31) is threaded onto the second screw (30) and matches it. The rear end face of the housing (1) has four second positioning holes (32) with the same number as the second screw (30) and the same diameter as the second screw (30). The central axis of each second positioning hole (32) coincides with the central axis of each second screw (30).

7. The tension detection device for knitwear production according to claim 1, characterized in that, The shaft of the axle (15) is provided with an external thread and is fixedly connected to a stop block (33). The shaft of the axle (15) is threadedly connected to a third nut (34) that cooperates with it. The upstream yarn guide ceramic wheel (16) and the downstream yarn guide ceramic wheel (17) are respectively located between the stop block (33) and the third nut (34) on each axle (15). The upstream yarn guide ceramic wheel (16) and the downstream yarn guide ceramic wheel (17) are coaxial with the feed inlet (2) and the discharge outlet (3) respectively.

8. The tension detection device for knitwear production according to claim 1, characterized in that, Each cleaning plate (19) has a pair of guide rods (35) fixedly connected to one side of the fixed plate (18), and a rectangular slot (36) is opened on the other side. Each fixed plate (18) has a pair of guide holes (37) with the same diameter as the guide rods (35) on its surface. The top of each guide rod (35) passes through the corresponding guide hole (37) and is fixedly connected to a connecting block (38). Each guide rod (35) has a spring (39) wrapped around its body. The top and bottom of the spring (39) are fixedly connected to the fixed plate (18) and the cleaning plate (19) respectively. The length and width of the cleaning brush (20) and the slot (36) are respectively equal, and the thickness of the cleaning brush (20) is greater than the depth of the slot (36).

9. The working method of the tension detection device for knitwear production according to claim 1, characterized in that, The tension detection device for knitwear production as described in any one of claims 1-8 is used, comprising the following steps: S1. Pre-configuration of detection benchmark: The yarn to be tested is inserted into the feed port (2) on one side of the machine housing (1) and out through the discharge port (3) on the other side. It passes around the upstream guide roller (16) and the downstream guide roller (17) in the positioning unit respectively. Through the rigidly fixed positioning mechanism, a free yarn segment with a fixed length of L is constructed on the yarn conveying path of the knitting equipment. The linear density ρ of the yarn to be tested is pre-entered to the calculation control unit to complete the configuration of detection benchmark parameters. S2, Modulation light path projection: Start each photoelectric emission module, drive the modulation light source (9) to emit modulation light of preset wavelength through the PWM modulation signal output by the operation control unit, convert it into a parallel fine beam through the collimating lens group (10), and project it vertically to each position of the free yarn segment to form a stable detection light path; S3. Vibration light signal conversion: During the operation of the knitting equipment, the free yarn segment generates a transverse vibration at its natural frequency under the action of tension. The yarn vibration periodically changes the light-blocking area of ​​the detection light path, causing the light flux received by each photoelectric receiving module to generate a periodic change synchronized with the yarn vibration frequency. Each photoelectric receiving module converts the light flux change into an alternating initial electrical signal in real time. S4. Signal preprocessing: The signal processing unit performs IV conversion, programmable gain amplification, bandpass filtering and hysteresis shaping on the initial electrical signal in sequence to filter out noise interference caused by stray light in the knitting workshop environment and vibration of the machine casing (1) and outputs a standard square wave signal that is completely corresponding to the vibration frequency of the yarn. S5. Equal Precision Frequency Acquisition: The operation and control unit uses a built-in hardware counter to perform equal precision frequency measurement on the standard square wave signal to obtain the real-time natural vibration frequency f of the free yarn segment; S6. Real-time tension calculation: The calculation and control unit substitutes the pre-configured yarn linear density ρ, the fixed length of the free yarn segment L, and the real-time acquired vibration frequency f into the string vibration tension calculation formula to calculate the dynamic tension value T of the yarn in real time. The string vibration tension calculation formula is as follows: T=4·ρ·L 2 ·f 2 In the formula, T is the real-time tension of the yarn in cN, ρ is the linear density of the yarn in tex, L is the fixed length of the free yarn segment in m, and f is the natural vibration frequency of the yarn in Hz. S7. Result Output and Linkage Control: The calculation and control unit outputs the real-time tension value to the display terminal, and compares the real-time tension value with the preset upper and lower tension thresholds and the yarn breakage judgment threshold. When the tension value exceeds the threshold range or the vibration frequency signal is detected to disappear, the control signal is immediately sent to the knitting equipment through the output execution unit. S8. Compare multiple sets of data to reduce errors: Multiple photoelectric emission modules and photoelectric receiving modules can simultaneously collect multiple position frequencies on the yarn surface to calculate multiple sets of tension data. By comparing multiple sets of data and taking their average value, more accurate data can be obtained, thereby reducing detection errors.

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