A multi-light eye based sewing machine thread trimming control system

Abstract

The present application belongs to the technical field of sewing machines, and relates to a sewing machine thread trimming control system based on multiple light eyes, which comprises, arranged in sequence along the cloth feeding direction of the sewing machine: a first light eye for presser foot lifting control; a second light eye and a third light eye for combined control of pre-thread trimming; and the following control logic is adopted when the pre-thread is trimmed: when the cloth front edge blocks the second light eye, the controller starts timing T1; when the cloth front edge blocks the third light eye, the controller ends T1 timing and simultaneously starts timing T2; the controller judges whether the inequality T2>X*T1-Y is established according to preset parameters X and Y; when the inequality is established, the controller outputs a thread trimming signal to drive the scissors to perform a trimming action; wherein parameter X is a constant, and parameter Y is a time offset based on the response lag time of the equipment. The sewing machine thread trimming control system based on multiple light eyes provided by the present application can solve the problem of unstable thread trimming length caused by changes in actual sewing conditions.

Description

Technical Field

[0001] This invention belongs to the technical field of sewing machines and relates to a sewing machine thread cutting control system based on multi-eye. Background Technology

[0002] During the sewing process, the front and back edges of the fabric will form front and back braids, respectively. To ensure a neat appearance, the braids need to be trimmed cleanly after sewing.

[0003] Currently, fully automatic overlock sewing machines are generally equipped with automatic thread-cutting mechanisms based on photoelectric sensors. The conventional approach is to place a photoelectric sensor near the scissors. When the fabric leaves or blocks the photoelectric sensor, the light signal changes and is converted into an electrical signal. After receiving the signal, the controller controls the thread-cutting mechanism to perform the thread cutting action.

[0004] However, the above solution suffers from a long-standing technical problem that has remained unresolved: in actual sewing, the motor speed is not constant, and the stitch length is adjusted according to process requirements. Changes in both speed and stitch length alter the fabric's travel distance per unit time, but the timing of the thread-cutting mechanism triggered by the controller remains fixed or nearly fixed. This creates a fundamental contradiction—when the fabric travels quickly, a fixed delay means the fabric has already traveled further, resulting in a longer thread; when the fabric travels slowly, the thread-cutting mechanism activates before the fabric reaches the intended position. Existing overlock sewing machine thread-cutting mechanisms cannot effectively compensate for this through system parameter adjustments.

[0005] To address this issue, the industry has proposed several improvement solutions. For example, Jack Sewing Machine Co., Ltd. disclosed a thread-cutting control method and structure for overlock sewing in patent CN108823839A (publication date: November 16, 2018). This method, after the first and second sensors detect the edge of the fabric during the Mth sewing, obtains the current sewing parameters for the Mth sewing and calculates the compensation time accordingly. During the (M+1)th sewing, the thread-cutting drive source is controlled to operate based on this compensation time. The essence of this solution is to use historical data from the previous sewing to compensate for the timing of thread cutting in the next sewing.

[0006] However, the above solution has inherent flaws: when the working conditions of two adjacent sewing operations change abruptly—for example, the operator adjusts the speed or changes the sewing material to a different thickness, resulting in a change in the stitch length—the compensation time calculated based on the historical data of the old working conditions is no longer applicable to the new working conditions. Not only can it not effectively compensate, but it may also cause deviations in the timing of thread cutting, exacerbating the fluctuation in thread length. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a multi-eye sewing machine thread trimming control system, which can solve the problem of unstable thread trimming length caused by changes in actual sewing conditions.

[0008] To solve the above-mentioned technical problems, the objective of this invention is achieved through the following technical solution:

[0009] A multi-optical sewing machine thread trimming control system includes components arranged sequentially along the fabric feeding direction of the sewing machine:

[0010] The first light sensor is used for lifting and controlling the presser foot.

[0011] The second and third optical sensors are used to combine and control the cutting of the front braid;

[0012] The following control logic is used when the front braid is cut:

[0013] When the leading edge of the fabric blocks the second photodetector, the controller starts timing T1; when the leading edge of the fabric blocks the third photodetector, the controller ends timing T1 and starts timing T2 simultaneously.

[0014] The controller determines whether the inequality T2 > X × T1 - Y is true based on preset parameters X and Y.

[0015] When the inequality is true, the controller outputs a wire-cutting signal, driving the scissors to perform a cutting action;

[0016] Where parameter X is a constant, and parameter Y is a time offset based on the device response lag time.

[0017] As a further improvement of the present invention, the preset values ​​of parameters X and Y satisfy the following conditions: within the working range of rotation speed from 1000 rpm to 6000 rpm and needle pitch from 2 mm to 5 mm, the length of the thread end of the front braid after cutting is stable at 2 mm to 3 mm.

[0018] As a further improvement of the present invention, the parameter X ≤ 0.6.

[0019] As a further improvement of the present invention, the parameter Y ≥ 15ms.

[0020] As a further improvement of the invention, a fourth photoelectric eye is also included, which is used to control the shearing of the braid.

[0021] As a further improvement of the present invention, a control panel is also included, wherein a shortcut button is provided on the control panel. After entering the shortcut button, the length of the front braid can be adjusted by using the directional keys, and the controller automatically updates the values ​​of parameters X and / or Y according to the adjustment amount.

[0022] The present invention also provides a sewing machine, including any of the above-described multi-eye sewing machine thread cutting control systems.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention provides a multi-eye sewing machine thread-cutting control system, solving the problem of compensation mechanism failure when there are sudden changes in rotation speed or stitch length in existing technologies. This invention uses real-time measurement and calculation for each sewing operation, ensuring that the cutting timing depends solely on the current actual fabric feed speed, and can still accurately trigger the cut even during sudden changes in operating conditions. Actual measurements show that when X≤0.6 and Y≥15ms, within a wide operating range of 1000rpm to 6000rpm and 2mm to 5mm stitch length, the length of the front braid thread is consistently between 2mm and 3mm. This invention uses parameter Y to compensate for the response lag caused by the electromagnet's engagement time and mechanical transmission time, ensuring that the cutting signal is issued earlier than the theoretical cutting timing, guaranteeing that the actual cutting position matches the expected position. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the optical eye layout of the present invention;

[0026] Reference numerals: 1. Sewing machine; 2. First photoelectric sensor; 3. Second photoelectric sensor; 4. Third photoelectric sensor; 5. Fourth photoelectric sensor; 6. Cutting drive mechanism. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. See also: Figure 1 :

[0028] like Figure 1 As shown, the sewing machine thread-cutting control system based on photoelectric sensors provided by this invention has a first photoelectric sensor 2, a second photoelectric sensor 3, a third photoelectric sensor 4, and a fourth photoelectric sensor 5 arranged sequentially along the fabric feeding direction of the sewing machine 1. Each photoelectric sensor is electrically connected to a controller, and the controller is electrically connected to a cutter drive mechanism 6.

[0029] The first photodetector 2 is used to detect the leading edge of the fabric and control the lifting of the presser foot; the fourth photodetector 5 is used to detect the rear braid and control subsequent processing actions. The first photodetector 2 and the fourth photodetector 5 do not participate in the core control logic for cutting the front braid.

[0030] The cutting of the front brace is controlled by a combination of the second optical sensor 3 and the third optical sensor 4, and its control logic is as follows:

[0031] When the leading edge of the fabric blocks the second photon 3, the controller starts timing T1. When the leading edge of the fabric blocks the third photon 4, the controller ends timing T1 and simultaneously starts timing T2.

[0032] The controller determines whether the inequality T2 > X × T1 - Y is true based on preset parameters X and Y. When the inequality is true, the controller outputs a shearing signal to drive the shears to perform the shearing action.

[0033] In this context, parameter X is a constant, pre-calibrated based on the proportional relationship between L2 (the distance between the third photoelectric sensor 4 and the cutter) and L1 (the distance between the second photoelectric sensor 3 and the third photoelectric sensor 4). Parameter Y is a time offset based on the device response lag time, which includes the electromagnet engagement time and the mechanical transmission time. The existence of Y causes the wire cutting signal to be issued earlier than the theoretical wire cutting time, thereby offsetting the device response lag and ensuring accurate actual cutting position.

[0034] For example, under the conditions of a stitch pitch of 3mm and a rotation speed of 6000rpm: timing T1 begins after the leading edge of the fabric blocks the second photodetector 3; when the leading edge of the fabric blocks the third photodetector 4, T1 is measured to be approximately 54ms, and timing T2 is started simultaneously. With preset X=0.6 and Y=15ms, the calculated time is X×T1-Y=0.6×54-15=17.4ms. When timing T2 reaches 17.4ms, the inequality T2>17.4 is true, and the controller immediately outputs a cutting signal. Actual measurements show that under these conditions, the length of the thread end after cutting is approximately 3mm.

[0035] A key feature of this invention is that the timing data for T1 and T2 are derived from the current sewing process and do not rely on any historical data from previous sewing operations. Compared with existing technologies, this invention does not collect parameters from previous sewing operations, nor does it use previous data as the basis for calculating the timing of thread cutting in the current sewing operation. The control logic of this invention is real-time open-loop: the second photodetector 3 and the third photodetector 4 complete the measurement of T1 when the fabric passes through in the same instance, and T2 is then started timing in the same light-blocking event. The entire measurement-calculation-triggering chain is completed independently in the current sewing operation.

[0036] The adaptive principle of this real-time algorithm is as follows:

[0037] When the stitch length or rotation speed increases, the fabric feed speed increases, and the time T1 required for the leading edge of the fabric to pass through the fixed distance between the second photoreceptor 3 and the third photoreceptor 4 becomes shorter. Since X is a constant, the calculated result of X×T1-Y decreases accordingly, and T2 only needs a shorter time to reach the threshold, thus advancing the shearing timing. Conversely, when the stitch length decreases or the rotation speed decreases, the situation reverses, and the shearing timing is delayed.

[0038] Therefore, regardless of how the rotation speed and stitch length fluctuate during the sewing process, the cutting timing always adapts to the actual real-time feeding speed of the fabric, ensuring that the thread length remains basically stable.

[0039] To verify the above adaptive effect, this embodiment underwent extensive testing under various working conditions. Test results show that when the preset values ​​of parameters X and Y satisfy X≤0.6 and Y≥15ms, within a wide working range of rotation speeds from 1000rpm to 6000rpm and needle spacing from 2mm to 5mm, the length of the thread end of the front braid after cutting can be stably maintained within the range of 2mm to 3mm. Some test data are shown in the table below:

[0040] 6000 2 88 0.6 15 40 2 5000 2 107 0.6 15 50 2.5 4000 2 126 0.6 15 60 3 3000 2 165 0.6 15 85 3 2000 2 245 0.6 15 135 3 1000 2 485 0.6 15 278 3 6000 5 37 0.6 15 10 2 5000 5 42 0.6 15 12 2 4000 5 53 0.6 15 20 2.5 3000 5 70 0.6 15 20 2.5 2000 5 100 0.6 15 48 3 1000 5 198 0.6 15 105 3

[0041] As can be seen from the table above, T1 fluctuates significantly with changes in rotation speed and stitch length (ranging from 37ms to 485ms), but the T2 trigger threshold is dynamically adjusted accordingly after being automatically calculated by the algorithm, so that the thread length is always kept within a narrow range that has no impact on the sewing quality.

[0042] Furthermore, this invention provides a convenient user adjustment method. A shortcut button is provided on the control panel; after accessing this button, the user can directly adjust the front braid length using the arrow keys. The controller automatically updates the values ​​of parameters X and / or Y based on the adjustment, eliminating the need for the user to navigate through the internal parameter menu for item-by-item adjustments. This allows production line operators to quickly fine-tune the thread length when changing fabrics or adjusting processes, reducing the complexity of equipment setup.

[0043] This invention utilizes real-time measurement data from the second photocell 3 and the third photocell 4 during the current sewing process. It achieves real-time adaptive triggering through the inequality T2 > X × T1 - Y, eliminating the need to collect historical sewing parameters and remaining unaffected by sudden changes in operating conditions between adjacent sewing operations. The thread-cutting timing directly reflects the current actual fabric conveying speed. Furthermore, the user-friendly adjustment method further enhances the applicability to production lines.

[0044] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A multi-eye sewing machine thread trimming control system, comprising: sequentially arranged along the fabric feeding direction of the sewing machine: The first light sensor is used for lifting and controlling the presser foot. The second and third optical sensors are used to combine and control the cutting of the front braid; Its features are, The following control logic is used when the front braid is cut: When the leading edge of the fabric blocks the second photodetector, the controller starts timing T1; when the leading edge of the fabric blocks the third photodetector, the controller ends timing T1 and starts timing T2 simultaneously. The controller determines whether the inequality T2 > X × T1 - Y is true based on preset parameters X and Y. When the inequality is true, the controller outputs a shearing signal to drive the scissors to perform a shearing action; Where parameter X is a constant, and parameter Y is a time offset based on the device response lag time; The preset values ​​of parameters X and Y satisfy the following conditions: within the working range of rotation speed from 1000 rpm to 6000 rpm and needle pitch from 2 mm to 5 mm, the length of the thread end of the front braid after cutting is stable at 2 mm to 3 mm. The parameter X ≤ 0.6; The parameter Y ≥ 15ms; It also includes a control panel with a shortcut button. After accessing the shortcut button, the length of the front braid can be adjusted using the directional keys. The controller automatically updates the values ​​of parameters X and / or Y based on the adjustment amount.

2. The sewing machine thread trimming control system based on multi-optical sensors according to claim 1, characterized in that, It also includes a fourth photon, which is used to control the cutting of the braid.

3. A sewing machine, characterized in that, The sewing machine thread-cutting control system based on any one of claims 1-2 includes the one described in any one of claims 1-2.

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