Anti-nest thread trimming method based on linkage control of small-stitch-length seam starting and routing

Abstract

The invention provides an anti-nest thread trimming method based on linkage control of small-stitch-length sewing starting and thread bonding, which comprises the following steps: after a sewing starting instruction is received, an electric control unit controls a sewing machine to start sewing a first stitch, a second stitch,..., to an Nth stitch in a small-stitch-length sewing mode, a sewing starting stitch is formed on a fabric, and the sewing starting stitch does not enter a space between a pressing part and a middle needle plate of the sewing machine; the thread trimming driving source drives the main thread trimmer and the auxiliary thread trimmer to be meshed to cut off the thread end of the upper thread; then the main thread clamping device loosens the thread, and the bonding thread clamping device clamps the thread; the electric control unit controls the sewing machine to continue sewing at the target stitch length; when the take-up-lever moves downwards for paying off, the routing driving source drives the routing plate to swing for routing, and the routing plate draws back part of the upper thread on the fabric; when the take-up lever moves upwards to take up the thread, the main thread clamping device clamps the thread, the thread beating and clamping device loosens the thread, and the take-up lever continuously draws back a part of the upper thread on the fabric. According to the invention, the length of the residual thread end of the bird nest on the fabric after the anti-bird-nest trimming is effectively shortened, and a better anti-bird-nest effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of sewing machine technology, and in particular to a method for preventing bird nest thread cutting based on small stitch spacing start-up and stitch-setting linkage control. Background Technology

[0002] Currently, computerized flatbed sewing machines often create a clump of nest-like threads on the reverse side of the fabric when starting a seam. Mid- to high-end customers, as well as factories with certain requirements for sewing quality, require that the ends of the nest-like threads be cleaned up after sewing. This is especially true for garments made primarily of thin, elastic fabrics; the thinner the fabric, the higher the sensitivity to the nest-like threads.

[0003] To address this, some existing sewing machines are equipped with an anti-bird's nest thread-cutting mechanism. This mechanism clamps the thread end on one side of the needle during the initial stitching and cuts the thread end after a preset number of stitches (e.g., 2 or 3 stitches), thereby reducing the accumulation of bird's nest-like thread clumps on the fabric. Typically, the anti-bird's nest thread-cutting mechanism includes a rotatable movable blade, a thread-cutting motor that drives the movable blade, and a fixed blade and pressure plate, all of which are fixed in place. The movable blade has a thread-catching groove and a moving blade edge, while the fixed blade has a fixed blade edge. As the sewing machine begins its first stitch and the needle moves downwards, the thread-cutting motor drives the movable blade to rotate, causing the thread-cutting groove on the movable blade to rotate directly below the needle. The needle, carrying the top thread, passes downwards through the thread-cutting groove, and under the action of the rotary hook, the thread end on one side of the needle is pulled below the movable blade. Then, the needle moves upwards above the needle plate, and the thread-cutting motor drives the movable blade to rotate back, clamping the thread end between the movable blade and the pressure plate. The sewing machine continues to sew the set number of stitches (e.g., 2 or 3 stitches) to complete the weaving of the bobbin thread and the top thread, preventing the thread from fraying after subsequent cutting. Afterwards, the thread-cutting motor drives the movable blade to continue rotating, and the moving blade edge of the movable blade engages with the fixed blade edge of the stationary blade, cutting the thread end. Figure 1 As shown.

[0004] from Figure 1 It can be seen that after the thread end is cut, the length of the bird's nest-like residual thread remaining on the fabric = the thickness of the needle plate 10 + the distance from the engagement point A of the movable blade 20 and the fixed blade 30 below the needle plate 10 to the needle hole 101 on the needle plate 10 + the sewing distance L from the start of the stitch to the thread cut. The thickness of the needle plate 10 and the distance from the engagement point A of the movable blade 20 and the fixed blade 30 below the needle plate 10 to the needle hole 101 on the needle plate 10 are fixed by the mechanical structure. The sewing distance L from the start of the stitch to the thread cut is determined by the number of stitches sewn from the start of the stitch to the thread cut; for example, assuming the stitch length is 3mm and the thread is cut after 3 stitches, then the sewing distance L from the start of the stitch to the thread cut is 9mm. Obviously, the more stitches sewn from the start of the stitch to the thread cut, the larger the sewing distance L from the start of the stitch to the thread cut, and the longer the bird's nest-like residual thread remaining on the fabric.

[0005] Therefore, existing anti-bird's nest thread-cutting mechanisms, in order to avoid thread detachment after cutting, require at least the second stitch to interlace the top and bottom threads before cutting the thread. Some thin and slippery fabrics require at least three stitches to ensure that the thread will not detach after cutting. As a result, when cutting the top thread end, the fabric has already traveled 2-3 stitch lengths relative to the needle hole 101 on the needle plate 10, and the residual bird's nest thread end on the fabric will be correspondingly longer by 2-3 stitch lengths, failing to effectively achieve a shorter residual bird's nest thread end. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for preventing bird nests from being cut by stitches based on the linkage control of small stitch spacing and stitching, which effectively shortens the length of bird nest residual thread ends left on the fabric after the bird nests are cut.

[0007] To achieve the above objectives, the present invention provides a method for preventing bird nest thread cutting based on the linkage control of small stitch spacing start-up and stitching, the method comprising the following steps:

[0008] S1. The sewing machine is equipped with an electronic control unit, an anti-bird nest thread cutting mechanism, a thread-tapping mechanism, a main thread clamp, a first thread-releasing drive source connected to the main thread clamp, a presser foot, and a thread take-up lever that can move up and down reciprocally, wherein the thread take-up lever is provided with a first thread-passing hole;

[0009] The anti-bird nest wire cutting mechanism includes a wire cutting drive source, a main wire cutting blade connected to the wire cutting drive source, and an auxiliary wire cutting blade. The main wire cutting blade is provided with a hook groove and a main wire cutting edge, and the auxiliary wire cutting blade is provided with an auxiliary wire cutting edge.

[0010] The wire bonding mechanism includes a wire bonding drive source, a swingable wire bonding plate, a wire bonding clamp, and a second wire release drive source that is pulsatingly connected to the wire bonding clamp. The wire bonding drive source is pulsatingly connected to the wire bonding plate, and the wire bonding plate is provided with a second wire passage hole.

[0011] The presser foot includes a presser foot base plate, a needle groove that runs vertically through the presser foot base plate, and a material pressing part formed by the solid part of the presser foot base plate. The material pressing part and the needle groove are distributed back and forth along the feeding direction when the sewing machine is sewing forward.

[0012] The top thread in the sewing machine passes through the thread holder, the second thread guide hole, the main thread holder, and the first thread guide hole in sequence before entering the sewing machine needle.

[0013] The first wire loosening drive source, the wire cutting drive source, the wire punching drive source, and the second wire loosening drive source are all communicatively connected to the electronic control unit.

[0014] S2, The electronic control unit receives the sewing start command;

[0015] The electronic control unit controls the first wire release drive source to operate, causing the main wire clamp to clamp the wire;

[0016] S3. The electronic control unit controls the sewing machine to start sewing the first stitch, the second stitch, ..., up to the Nth stitch in the small stitch distance sewing mode, forming a starting stitch on the fabric. The starting stitch does not enter between the pressing part and the needle plate of the sewing machine.

[0017] During the first stitch, the electronic control unit controls the thread cutting drive source to extend and then retract the main thread cutting blade, so that the thread end on the side of the needle passes through the hook groove.

[0018] S4. The electronic control unit controls the wire cutting drive source to move the main wire cutting blade toward the auxiliary wire cutting blade, so that the main wire cutting blade and the auxiliary wire cutting blade engage to cut off the wire end.

[0019] S5. The electronic control unit controls the first wire release drive source to reset and controls the second wire release drive source to operate, causing the main wire clamp to release the wire and the wire clamp to clamp the wire.

[0020] S6. The electronic control unit controls the sewing machine to continue sewing at the target stitch length;

[0021] During the process of continuing to sew the first stitch, when the take-up lever moves down to release the thread, the electronic control unit controls the thread-knocking drive source to move, causing the thread-knocking plate to swing and kick the thread, and the thread-knocking plate pulls back a portion of the top thread on the fabric.

[0022] Subsequently, when the take-up lever moves upward to retract the thread, the electronic control unit controls the first thread release drive source to operate and controls the second thread release drive source to reset, causing the main thread clamp to clamp the thread and the thread-locking clamp to release the thread, and the take-up lever continues to pull back a portion of the surface thread on the fabric.

[0023] Further, step S3 includes the following steps:

[0024] S31. Before the sewing machine starts sewing the first stitch, or during the process of the sewing machine starting sewing the first stitch and the needle moving down, the electronic control unit controls the thread cutting drive source to move, and the thread cutting drive source drives the main thread cutting knife to move so that the hook groove is located directly below the needle.

[0025] S32. The electronic control unit controls the sewing machine to start the first stitch in the small stitch distance sewing mode. The needle moves down and passes through the needle groove and the hook groove. Under the action of the rotary hook in the sewing machine, the thread end on one side of the needle is brought to the bottom of the main thread cutter.

[0026] S33. The needle moves upward. After the needle moves upward from the main thread cutter, the electronic control unit controls the thread cutting drive source to move. The thread cutting drive source drives the main thread cutter to move. The main thread cutter pulls out at least a part of the thread end.

[0027] S34. The electronic control unit controls the sewing machine to start sewing the second stitch, the third stitch, ..., up to the Nth stitch in the small stitch distance sewing mode.

[0028] Further, in step S34, after any one of the second, third, ..., Nth stitches, a pre-pulling of the thread is performed: the electronic control unit controls the first thread release drive source to reset and controls the second thread release drive source to operate, causing the main thread clamp to release the thread and the thread-pulling clamp to clamp the thread; then, during the process of the thread take-up lever moving down to release the thread, the electronic control unit controls the thread-pulling drive source to operate, causing the thread-pulling plate to swing and pull back the top thread, so that the top thread between the main thread clamp and the fabric is taut;

[0029] After the pre-pulling is completed, the electronic control unit controls the first wire release drive source to operate and controls the second wire release drive source to reset, causing the main wire clamp to clamp the wire and the wire release clamp to release the wire.

[0030] Furthermore, in step S3, when the sewing machine is operating in the small stitch distance sewing mode, the absolute value of the current stitch distance of the sewing machine is no greater than 2.5mm.

[0031] Furthermore, in step S3, the electronic control module controls the sewing machine to start sewing from the first stitch to the Nth stitch by switching between forward and reverse stitches.

[0032] Furthermore, the wire bonding mechanism also includes a fixedly mounted wire guide plate, the housing of the second wire loosening drive source is fixedly connected to the wire guide plate, and the wire guide plate is provided with a third wire guide hole, a fourth wire guide hole and a fifth wire guide hole;

[0033] Along the axial direction of the main shaft in the sewing machine, the third thread guide hole is distributed on the side of the thread tensioner facing away from the main thread tensioner, and the fourth and fifth thread guide holes are both distributed on the side of the thread tensioner facing the main thread tensioner.

[0034] Along the vertical direction, the third wire passage hole is distributed on the upper side of the wire clamp, the fourth and fifth wire passage holes are both distributed on the lower side of the wire clamp, and the second wire passage hole is distributed between the fourth and fifth wire passage holes;

[0035] The thread in the sewing machine passes through the third thread guide hole, the thread clamp, the fourth thread guide hole, the second thread guide hole, the fifth thread guide hole, the main thread clamp, and the first thread guide hole in sequence before entering the sewing machine needle.

[0036] Furthermore, the stitching mechanism also includes a stitching link and a stitching drive shaft. The stitching link is reciprocally mounted inside the sewing machine housing, and the stitching drive source is connected to the stitching link and drives the stitching link to reciprocate.

[0037] The wire-punching plate includes a main body, a first wire-passing portion extending from the lower end of the main body, a first connecting plate extending from the side of the main body, and a second connecting plate extending from the end of the first connecting plate. The main body is rotatably mounted on a second wire-releasing drive source. The main body and the second connecting plate are parallel. The two ends of the wire-punching drive shaft are respectively fixed to the main body and the second connecting plate. The end of the wire-punching connecting rod away from the wire-punching drive source is rotatably mounted on the wire-punching drive shaft.

[0038] Furthermore, the wire bonding mechanism also includes a limiting screw, which is fixed to the first connecting plate;

[0039] Along the axial direction of the wire bonding drive shaft, the second connecting plate and the limiting screw are close to both sides of the wire bonding link.

[0040] Furthermore, both the thread-knocking drive source and the thread-releasing drive source are electromagnets, and both are fixedly installed on the sewing machine housing.

[0041] Furthermore, in step S1, the sewing machine is also equipped with a stitch length adjustment mechanism.

[0042] The stitch length adjustment mechanism includes a stitch length adjustment drive source and a feeding mechanism connected between the main shaft and the feed dog in the sewing machine. The stitch length adjustment drive source is connected to the feeding transmission component in the feeding mechanism that determines the stitch length of the sewing machine. The stitch length adjustment drive source is also connected to the electronic control unit.

[0043] In steps S3 and S6, the electronic control unit controls the output of the stitch length adjustment drive source to enable the sewing machine to sew in a small stitch length sewing mode or to sew at a target stitch length.

[0044] As described above, the method for preventing bird nest thread cutting based on the linkage control of small stitch spacing start-up and stitching in this invention has the following beneficial effects:

[0045] This application employs a small stitch spacing sewing mode to start the first stitch to the Nth stitch before cutting the anti-bird nest thread. During this process, a starting stitch is formed on the fabric. The small stitch spacing sewing mode can shorten the length of the starting stitch and prevent the starting stitch from being pressed down by the presser foot. Therefore, in the first stitch after cutting the anti-bird nest thread, it is permissible to pull back a portion of the top thread on the fabric by the thread take-up plate when the thread take-up lever is lowered, and to further pull back a portion of the top thread on the fabric by the thread take-up lever when the thread take-up lever is raised. Ultimately, this effectively shortens the length of the residual bird nest thread on the fabric after cutting the anti-bird nest thread, resulting in a shorter residual bird nest thread and a better anti-bird nest effect. Attached Figure Description

[0046] Figure 1This is a schematic diagram of the wire-cutting mechanism for preventing bird nests from falling and cutting off the wire ends.

[0047] Figure 2 This is a flowchart of the bird nest prevention thread cutting method based on small stitch pitch start-up and stitching linkage control in this application.

[0048] Figure 3 This is a schematic diagram of the assembly structure of the anti-bird nest thread-cutting mechanism, needle, presser foot, and needle plate in the sewing machine of this application.

[0049] Figure 4 for Figure 3 A schematic diagram showing the coordination of the main thread cutter, auxiliary thread cutter, and pressure plate. In this diagram, the hook groove of the main thread cutter is located directly below the needle.

[0050] Figure 5 This is a schematic diagram showing the installation of the thread-pressing mechanism and the main thread clamp on the sewing machine housing in the sewing machine of this application.

[0051] Figure 6 and Figure 7 These are schematic diagrams of the stitching mechanism of this application from different perspectives.

[0052] Figure 8 and Figure 9 This is a schematic diagram of the wire-punching plate in the wire-punching mechanism of this application from different perspectives.

[0053] Figure 10 This is a schematic diagram of the wire guide plate in the wire bonding mechanism of this application.

[0054] Figure 11 This is a schematic diagram of the wire-punching mechanism in the wire-punching state of this application. The wire-punching drive source and wire-punching linkage are omitted in this diagram.

[0055] Figure 12 This is a schematic diagram of the residual bird nest thread remaining on the fabric after the bird nest is cut, as described in this application.

[0056] Figures 13 to 16 This is a stitch path diagram showing the stitch length of different embodiments of this application where the first stitch to the N+Mth stitch is sewn before the bird nest is cut.

[0057] Component labeling: Needle plate 10, needle hole 101, main thread clamp 20, presser foot 30, presser foot base plate 31, needle groove 32, material clamping part 33, thread take-up rod 40, first thread hole 41, thread cutting drive source 51, main thread cutter 52, thread hook groove 521, main thread cutting blade 522, first thread clamping part 523, auxiliary thread cutter 53, auxiliary thread cutting blade 531, pressure plate 54, second thread clamping part 541, thread punching drive source 61, thread punching plate 62, second thread hole 621 622. Main body of the sewing machine, 623. First thread guide, 624. First connecting plate, 625. Second connecting plate, 63. Thread clamp, 64. Second thread release drive source, 65. Thread guide plate, 651. Third thread guide hole, 652. Fifth thread guide hole, 653. Second thread guide, 654. Third thread guide, 655. Fourth thread guide, 656. Thread punching link, 66. Thread punching drive shaft, 67. Limiting screw, 68. Sewing machine housing, 70. Needle, 80. Bird's nest residual thread end, 90. Detailed Implementation

[0058] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0059] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0060] It should also be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or may be connected to an intermediary component. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component through an intermediary component.

[0061] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0062] This application relates to the field of sewing machine technology, and in particular to a method for preventing bird nest thread cutting based on small stitch spacing start-up and stitch-setting linkage control.

[0063] like Figure 3 and Figure 5 As shown, the sewing machine includes a sewing machine housing 70 and a sewing machine base plate, both fixedly mounted; a main shaft rotatably supported in the sewing machine housing 70; a main motor installed in the sewing machine housing 70 and connected to the main shaft; a lower shaft rotatably supported in the sewing machine base plate; a rotary hook fixed to the end of the lower shaft; a needle plate 10; a needle bar mechanism; a presser foot mechanism; a feed dog; a feed dog; a feed dog lifting mechanism; a feed mechanism; and an electronic control module. All drive sources in the sewing machine (including motors, electromagnets, etc.) are communicatively connected to the electronic control module. For ease of description, the axial direction of the sewing machine main shaft is defined as the left-right direction, with the side of the main shaft facing the needle bar mechanism being the left direction; the horizontal direction orthogonal to the left-right direction is defined as the front-back direction, with the direction of fabric movement during forward sewing being the front direction; and the vertical direction orthogonal to the left-right direction is defined as the up-down direction. Based on this, the rotary hook is fixed to the left end of the lower shaft, which is drively connected to the main shaft. The needle bar mechanism is connected to the left end of the main shaft via a transmission connection. The needle bar mechanism has a needle 80 that can reciprocate up and down, and a thread take-up lever 40 that can reciprocate up and down. The end of the thread take-up lever 40 has a first thread hole 41 that passes through from left to right. The needle plate 10 is fixed to the left side of the sewing machine base plate. The needle plate 10 has a toothed groove that allows the feed dog to move, and a needle hole 101 that passes through from top to bottom, allowing the needle 80 to pierce vertically. The feed dog is fixed to the feed dog holder with screws. The main shaft is connected to the rear end of the feed dog holder via a feed dog lifting mechanism, driving the feed dog holder and feed dog to reciprocate up and down, performing the feed dog lifting action. The main shaft is connected to the front end of the feed dog holder via a feeding mechanism, driving the feed dog holder and feed dog to reciprocate back and forth, performing the feeding action. Of course, in other embodiments, an independent motor can be used to drive the lower shaft to rotate, and the feed dog lifting mechanism and feeding mechanism can also be driven by independent motors.

[0064] Furthermore, such as Figure 3As shown, the presser foot mechanism includes a presser foot bar and a presser foot 30 installed at the lower end of the presser foot bar. The presser foot 30 includes a presser foot base plate 31, a needle groove 32 provided in the presser foot base plate 31 and extending vertically, and a pressing part 33 formed by the solid part of the presser foot base plate 31. The needle groove 32 allows the machine needle 80 to puncture vertically. The pressing part 33 and the needle groove 32 are distributed back and forth along the feeding direction when the sewing machine is sewing forward. That is, the solid part distributed in front of the needle groove 32 constitutes the pressing part 33. When the sewing machine is sewing forward, the fabric moves forward toward the pressing part 33.

[0065] The present invention relates to a method for preventing bird nest thread cutting based on small stitch spacing start-up and stitching linkage control, which includes the following steps.

[0066] Step S1: The sewing machine is also equipped with an anti-bird's nest thread-cutting mechanism, a thread-tapping mechanism, a main thread clamp 20, and a first thread-releasing drive source that is connected to the main thread clamp 20. The first thread-releasing drive source is communicatively connected to the electronic control unit. In the initial state, the main thread clamp 20 is in the thread-releasing state.

[0067] like Figure 3 and Figure 4 As shown, the anti-bird nest thread-cutting mechanism includes a thread-cutting drive source 51, a main thread-cutting blade 52, a thread-cutting transmission assembly, and an auxiliary thread-cutting blade 53. The thread-cutting drive source 51 is connected to the main thread-cutting blade 52 via the thread-cutting transmission assembly. The main thread-cutting blade 52 is provided with a hook groove 521 and a main cutting edge 522, and the auxiliary thread-cutting blade 53 is provided with an auxiliary cutting edge 531. Preferably, the thread-cutting drive source 51 is a motor and is communicatively connected to an electronic control unit. The main thread-cutting blade 52 rotates. Both the main thread-cutting blade 52 and the auxiliary thread-cutting blade 53 are disposed on the outer periphery of the rotary hook. The auxiliary thread-cutting blade 53 can be a fixed blade fixed to the sewing machine base plate or a movable blade.

[0068] like Figures 5 to 7 As shown, the thread-knocking mechanism includes a thread-knocking drive source 61, a thread-knocking plate 62 that can swing left and right, a thread-knocking clamp 63, and a second thread-releasing drive source 64 that is pulsatorically connected to the thread-knocking clamp 63. The thread-knocking drive source 61 is pulsatorically connected to the thread-knocking plate 62 and drives the thread-knocking plate 62 to swing left and right. The lower end of the thread-knocking plate 62 is provided with a second thread-passing hole 621 that runs vertically through it. Both the thread-knocking drive source 61 and the second thread-releasing drive source 64 are pulsatorically connected to the electronic control unit. The thread-knocking clamp 63 is located on the upper right side of the main thread-passing clamp 20, and the main thread-passing clamp 20 is located on the lower right side of the take-up lever 40. The top thread drawn from the thread spool in the sewing machine passes sequentially through the thread-knocking clamp 63, the second thread-passing hole 621 of the thread-knocking plate 62, the main thread-passing clamp 20, and the first thread-passing hole 41 of the take-up lever 40 before entering the sewing machine needle 80. Initially, the wire clamp 63 is in the loose state, and the wire punch plate 62 is in the as-open state. Figure 6 The vertical position shown indicates that the punch plate 62 has not swung to the right.

[0069] Preferably, the main wire clamp 20 and the wire clamping device 63 have essentially the same structure, both including a wire clamping spindle that can move back and forth, a pair of wire clamping plates mounted on the wire clamping spindle, a wire clamping spring fitted on the wire clamping spindle, and an adjustment knob threaded onto the rear end of the wire clamping spindle. The wire clamping spindle of the main wire clamp 20 is driven by a first wire loosening drive source and moves back and forth by the first wire loosening drive source. The wire clamping spindle of the wire clamping device 63 is driven by a second wire loosening drive source 64 and moves back and forth by the second wire loosening drive source 64. The first wire loosening drive source and the second wire loosening drive source 64 are preferably both electromagnets. When the first wire loosening drive source is de-energized, the main wire clamp 20 is in the wire clamping state; when the first wire loosening drive source is energized and engaged, it drives the wire clamping spindle of the main wire clamp 20 to move backward, and the main wire clamp 20 is in the wire loosening state. When the second wire release drive source 64 is de-energized, the wire clamp 63 is in the wire-releasing state. When the second wire release drive source 64 is energized and engaged, it drives the wire clamping spindle of the wire clamp 63 to move forward, and the wire clamp 63 is in the wire-clamping state. The wire clamping spring abuts against the rear wire clamping plate and the adjusting knob. By rotating the adjusting knob, the compression of the wire clamping spring is adjusted, thereby adjusting the wire tension applied to the opposite wire by the pair of wire clamping plates.

[0070] Step S2, as follows Figure 2 As shown, when the electronic control unit receives the sewing start command, the electronic control unit controls the first loosening drive source to operate. The first loosening drive source is de-energized, causing the main wire clamp 20 to clamp the wire, while the wire clamp 63 remains in the loosening state.

[0071] In step S3, the electronic control unit controls the sewing machine to start sewing the first, second, ..., up to the Nth stitch in the small stitch distance sewing mode, thereby forming a starting stitch on the fabric. Because the first to Nth stitches are sewn with a small stitch distance, the fabric moves forward a short distance towards the presser foot 30's pressure plate 33, preventing the starting stitch from entering between the pressure plate 33 and the sewing machine's needle plate 10; that is, the starting stitch is not pressed down by the presser foot 30's pressure plate 33. Furthermore, during the first stitch, the electronic control unit controls the thread cutting drive source 51 to operate, causing the main thread cutter 52 to extend and then retract, so that the thread end on one side of the needle 80 passes through the hook groove 521. Preferably, in step S3, when the sewing machine is operating in the small stitch distance sewing mode, the absolute value of the current stitch distance is no greater than 2.5mm.

[0072] Specifically, step S3 preferably includes the following sub-steps.

[0073] Step S31: Before the sewing machine starts sewing the first stitch, or during the process of the sewing machine starting sewing the first stitch and the needle 80 moving down, the electronic control unit controls the thread cutting drive source 51 to operate. The thread cutting drive source 51 drives the main thread cutting knife 52 to rotate backward through the thread cutting transmission assembly, so that the hook groove 521 is located directly below the needle 80.

[0074] Step S32: The electronic control unit controls the sewing machine to start the first stitch in the small stitch distance sewing mode. The needle 80 moves down and the needle 80, carrying the top thread, passes through the needle groove 32 of the presser foot 30, the thread hole of the needle plate 10, and the hook groove 521 of the main thread cutter 52. Under the action of the rotary hook, the top thread end on one side of the needle 80 is brought to the bottom of the main thread cutter 52.

[0075] Step S33: The sewing machine begins to sew the first stitch. The needle 80 moves upward. After the needle 80 moves upward from the hook groove 521 of the main thread cutter 52, the electronic control unit controls the thread cutting drive source 51 to operate. The thread cutting drive source 51 drives the main thread cutter 52 to rotate forward through the thread cutting transmission assembly. During this process, the main thread cutter 52 pulls at least a portion of the top thread end out of the hook groove 521. At this time, the main cutting edge 522 of the main thread cutter 52 is close to the auxiliary cutting edge 531 of the auxiliary thread cutter 53, but they are not engaged. The main cutting edge 522 is located behind the auxiliary cutting edge 531.

[0076] Step S34: The electronic control unit controls the sewing machine to start sewing the second stitch, the third stitch, ..., up to the Nth stitch in the small stitch distance sewing mode, where N≥2.

[0077] Step S4: After the sewing machine has sewn the set number of stitches N, the electronic control unit controls the thread-cutting drive source 51 to operate. The thread-cutting drive source 51 drives the main thread-cutting blade 52 to continue rotating forward toward the auxiliary thread-cutting blade 53 through the thread-cutting transmission assembly, causing the main thread-cutting blade 522 and the auxiliary thread-cutting blade 531 to engage. The main thread-cutting blade 52 and the auxiliary thread-cutting blade 53 then engage and cut the thread end of the top thread, completing the anti-bird's nest thread cutting. Because the sewing machine has already interwoven the top and bottom threads during the second to Nth stitches, the thread will not come loose after the anti-bird's nest thread cutting. Furthermore, after the anti-bird's nest thread cutting, if... Figure 12 As shown, the length of the bird's nest residual thread 90 remaining on the fabric is equal to the thickness H of the needle plate 10, the distance L1 between the engagement position of the main thread cutter 52 and the auxiliary thread cutter 53 below the needle plate 10 and the needle hole 101 on the needle plate 10, and the sewing distance L2 from the start of the stitch to the thread cut. The sewing distance L2 is the distance the fabric is moved forward from the first stitch to the Nth stitch. Since the first stitch to the Nth stitch is done in a small stitch distance sewing mode, the distance the fabric is moved before the anti-bird's nest thread is cut is shortened, which also shortens the sewing distance L2 from the start of the stitch to the thread cut during this process, thereby shortening the length of the bird's nest residual thread 90 remaining on the fabric after the anti-bird's nest thread is cut.

[0078] Step S5: After the bird nest is cut, the electronic control unit controls the first wire loosening drive source to reset and controls the second wire loosening drive source 64 to operate, causing the main wire clamp 20 to loosen the wire and the wire clamp 63 to clamp the wire.

[0079] Step S6: The electronic control unit controls the sewing machine to switch to a sewing mode that matches the target stitch length, and the sewing machine continues sewing at the target stitch length; for example, controlling the sewing machine to continue sewing in the normal sewing mode until the sewing is finished; the stitch length corresponding to the normal sewing mode is usually +3mm or more. During the process of continuing to sew the first stitch (i.e., the N+1th stitch), when the take-up lever 40 moves down to release the thread, the electronic control unit controls the thread-laying drive source 61 to operate, causing the thread-laying plate 62 to swing to the right around the front-to-back extended axis to lay the thread, such as... Figure 11 As shown, during this process, the thread-pulling plate 62 pulls the top thread, thereby retracting a portion of the top thread from the fabric and further shortening the length of the residual bird's nest thread 90 left on the fabric after the anti-bird's nest thread is cut. Then, when the thread take-up lever 40 moves upward to retract the thread, the electronic control unit controls the first thread release drive source to operate and controls the second thread release drive source 64 to reset, causing the main thread clamp 20 to clamp the thread and the thread-pulling clamp 63 to release the thread. The upward movement of the thread take-up lever 40 further retracts a portion of the top thread from the fabric, further shortening the length of the residual bird's nest thread 90 left on the fabric after the anti-bird's nest thread is cut.

[0080] Therefore, this application uses a small stitch spacing sewing mode to start the first stitch to the Nth stitch before performing the anti-bird's nest thread cutting. During this process, a starting stitch is formed on the fabric. The small stitch spacing sewing mode can shorten the length of the starting stitch and prevent the starting stitch from being pressed by the pressing part 33 of the presser foot 30. In the first stitch after the anti-bird's nest thread cutting, it is permissible to pull back a portion of the top thread on the fabric by the thread take-up plate 62 when the thread take-up bar 40 moves down to release the thread, and then to pull back a portion of the top thread on the fabric by the thread take-up bar 40 when the thread take-up bar 40 moves up to take back the thread. With this setup, this application shortens the length of the residual bird's nest thread 90 left on the fabric after cutting the thread by using three points: first, shortening the sewing distance L2 from the first to the Nth stitch based on a small stitch pitch; second, when continuing to sew the N+1th stitch, first using the thread-beating plate 62 to swing back the thread and pull back the residual bird's nest thread 90 on the fabric; and third, using the thread take-up lever 40 to move up the thread and pull back the residual bird's nest thread 90 on the fabric. Compared to existing technologies, this application achieves a shorter residual bird's nest thread 90 on the fabric, resulting in a better bird's nest prevention effect.

[0081] Furthermore, the sewing machine is also equipped with a stitch length adjustment mechanism, which includes a stitch length adjustment drive source, a stitch length adjustment component, and the aforementioned feeding mechanism. The feeding mechanism includes a feeding shaft rotatably supported in the sewing machine base plate and extending laterally, a first feeding transmission component drivingly connected between the main shaft and the feeding shaft, and a second feeding transmission component drivingly connected between the feeding shaft and the feed dog. The first feeding transmission component has a stitch length adjustment seat rotatably supported in the sewing machine base plate. In the feeding mechanism, the swing angle of the stitch length adjustment seat corresponds one-to-one with the swing angle of the feeding shaft, determining the stitch length of the sewing machine. The stitch length adjustment drive source is drivingly connected to the feeding transmission component in the feeding mechanism that determines the stitch length of the sewing machine; that is, the stitch length adjustment drive source is drivingly connected to the stitch length adjustment seat through the stitch length adjustment component; or, the stitch length adjustment drive source is drivingly connected to the feeding shaft through the stitch length adjustment component; or, the stitch length adjustment drive source is directly connected to the feeding shaft. The stitch length adjustment drive source is communicatively connected to the electronic control unit.

[0082] Taking the stitch length adjustment drive source connected to the stitch length adjustment seat via a stitch length adjustment component as an example, when the stitch length adjustment drive source operates, it drives the stitch length adjustment seat to rotate around its axis of rotation by an angle through the stitch length adjustment component, changing the swing angle of the stitch length adjustment seat, thereby changing the stitch length of the sewing machine and realizing stitch length adjustment, as well as switching between forward and reverse sewing modes. In forward sewing machine mode, the stitch length of the sewing machine is a positive value, and the fabric is moved forward during sewing; the numerical value of the stitch length indicates the distance the fabric is moved forward for one stitch. In reverse sewing machine mode, the stitch length of the sewing machine is a negative value, and the fabric is moved backward during sewing; the absolute value of the stitch length indicates the distance the fabric is moved backward for one stitch. Furthermore, the structure of the stitch length adjustment mechanism itself is existing technology; for example, see the stitch length adjustment and reverse sewing control method for a sewing machine disclosed in Chinese invention patent application number 201910176598.2, and therefore will not be described further here. Based on this, in steps S3 and S6 above, the electronic control unit controls the output of the stitch length adjustment drive source to enable the sewing machine to sew in a small stitch length sewing mode or to sew at the target stitch length.

[0083] Further, in step S3, the electronic control module controls the sewing machine to start sewing from the first to the Nth stitches by switching between forward and reverse stitches. That is, it uses a small stitch pitch for back-and-forth sewing. Therefore, the first to the Nth stitches include at least one forward stitch and at least one reverse stitch. When sewing forward, the current stitch pitch of the sewing machine is no greater than 2mm; when sewing reverse, the absolute value of the current stitch pitch of the sewing machine is no greater than 2mm. Finally, when the sewing machine has sewn the set number of stitches N, the feeding distance L2 that the feeding mechanism drives the fabric to move is -2mm to 3mm, where -2mm means the fabric has moved backward by 2mm and 3mm means the fabric has moved forward by 2mm. In this way, it is more reliable to ensure that the starting stitch does not enter below the pressing part 33 of the presser foot 30, and the starting point of the top thread on the fabric is near the needle groove 32 of the presser foot 30 and near the needle hole 101 of the needle plate 10. At the same time, it further reduces the sewing distance L2 from the starting stitch to the thread cutting, thus better improving the bird nest prevention effect.

[0084] Furthermore, because this application uses a small stitch pitch to sew back and forth from the first to the Nth stitch, the thread between the main thread clamp 20 and the fabric will be loose. This is not conducive to shortening the length of the residual bird's nest thread 90 on the fabric after the thread is pulled out through steps S5 and S6 after the bird's nest prevention thread is cut. Based on this, in step S34, this application also performs pre-pulling after any one of the second, third, ..., Nth stitches, for example, after the third stitch, or after the fourth stitch. The pre-pulling action is as follows: the electronic control unit controls the first thread release drive source to reset and controls the second thread release drive source 64 to activate, causing the main thread clamp 20 to release the thread and the thread clamp 63 to clamp the thread; then, during the thread release process of the take-up lever 40 moving down, the electronic control unit controls the thread clamp drive source 61 to activate, causing the thread clamp plate 62 to swing to the right around the front-to-back extended axis to clamp the thread, and the thread clamp plate 62 pulls back the top thread, thereby tightening the top thread between the main thread clamp 20 and the fabric. After the pre-pulling is completed, the electronic control unit controls the first thread release drive source to activate and controls the second thread release drive source 64 to reset, causing the main thread clamp 20 to clamp the thread and the thread clamp 63 to release the thread. This application performs a pre-pulling action before the start of the sewing to prevent bird nests from being cut, so that the surface thread between the main thread clamp 20 and the fabric is taut. Then, after the start of the sewing to prevent bird nests from being cut, when the residual bird nest thread 90 is pulled back by swinging the thread plate 62 and when the residual bird nest thread 90 is pulled back by moving the thread take-up rod 40 upward, the residual bird nest thread 90 on the fabric can be shortened more reliably.

[0085] Furthermore, step S3 also includes the following sub-steps: S35, after the anti-bird's nest thread-cutting mechanism cuts the top thread end, the sewing machine continues to sew M-needles in a small stitch distance sewing mode, for example, continuing to sew 1-2 more stitches. Each M-needle includes at least one backstitch or at least one forward stitch, achieving 1-2 backstitches with a small stitch distance on top of the initial N stitches. This allows the remaining bird's nest thread end 90 under the fabric after the top thread end is cut to be wrapped inside, further shortening the length of the remaining bird's nest thread end 90 on the fabric and improving the anti-bird's nest effect. After cutting the top thread end, if the Nth stitch is a backstitch and is closer to the human side, the first stitch in the continued M-needles is preferably a forward stitch; if the Nth stitch is a forward stitch and is closer to the pressure plate 33 side, the first stitch in the continued M-needles is preferably a backstitch.

[0086] The following are four preferred embodiments of a sewing machine in a small stitch pattern where it starts with N stitches, cuts the thread, and then sews M stitches.

[0087] Example 1 of needle spacing route: Figure 13 As shown, start with N stitches: First stitch: 1mm straight stitch, second stitch: 1mm straight stitch; cut the thread end, the sewing distance L2 from the start of the stitch to the thread cut is 2mm; then sew M stitches: third stitch: 2mm backstitch, the thread guide 62 and the thread take-up lever 40 pull back the bird's nest residual thread end 90 on the fabric in succession, fourth stitch: 2mm straight stitch.

[0088] Example 2 of needle spacing route: Figure 14 As shown, start with N stitches: First stitch: 2mm straight stitch, second stitch: 1mm reverse stitch; cut the thread end, the sewing distance L2 from the start of the stitch to the thread cut is 1mm; then sew M stitches: third stitch: 1mm reverse stitch, the thread guide 62 and the thread take-up lever 40 pull back the bird's nest residual thread end 90 on the fabric in succession, fourth stitch: 2mm straight stitch.

[0089] Example 3 of needle spacing route: Figure 15 As shown, start with N stitches: First stitch: backstitch 1mm, second stitch: straight stitch 1mm; cut the thread end, the sewing distance L2 from the start of the stitch to the thread cut is 0mm; then sew M stitches: third stitch: backstitch 1mm, the thread guide 62 and the thread take-up lever 40 pull back the bird's nest residual thread end 90 on the fabric in succession, fourth stitch: straight stitch 1mm.

[0090] Example 4 of the needle spacing route: Figure 16 As shown, start with N stitches: First stitch: 1mm straight stitch, second stitch: 1mm reverse stitch; cut the thread end, the sewing distance L2 from the start of the stitch to the thread cut is 0mm; then sew M stitches: Third stitch: 1mm straight stitch, the thread guide 62 and the thread take-up lever 40 pull back the bird's nest residual thread end 90 on the fabric in succession, fourth stitch: 1mm reverse stitch.

[0091] Example 5 of stitch pattern: Starting stitch N: First stitch: 1mm straight stitch; Second stitch: 1mm straight stitch; Third stitch: 2mm backstitch, pre-pull thread; Fourth stitch: 2mm straight stitch, cut the thread end, the sewing distance L2 from starting stitch to cutting thread is 2mm; Then sewing M stitch: Fifth stitch: 1mm straight stitch, the thread guide 62 and the thread take-up lever 40 successively pull back the bird's nest residual thread end 90 on the fabric; Sixth stitch: 1mm backstitch.

[0092] Of course, in other embodiments, the N stitches set for the starting stitch are not limited to 2 stitches, but can be 3 stitches, 4 stitches, or other numbers of stitches; the absolute value of the stitch distance corresponding to each stitch in the first N stitches of the starting stitch is not limited to 1mm or 2mm, but can be 0.8mm, 1.2mm, 1.5mm, or 1.8mm. The M stitches set after the top thread end is cut are not limited to 2 stitches, but can be 1 stitch, 3 stitches, or other numbers of stitches.

[0093] Figures 13 to 16 In the stitch path diagram shown, the stitches should overlap, but to more clearly illustrate the N+M stitch method for starting a stitch, Figures 13 to 16 Arrange the needles separately; and... Figures 13 to 16 When the center is facing down, the material is fed forward during a straight seam; when it is facing up, the material is fed backward during a reverse seam.

[0094] Furthermore, such as Figure 6 and Figure 11 As shown, the stitching mechanism also includes a fixedly mounted thread guide plate 65. The thread guide plate 65 is preferably fixed to the rear end of the housing of the second thread release drive source 64. The second thread release drive source 64 is fixedly mounted on the sewing machine housing 70, so that the thread guide plate 65 is also fixedly mounted on the sewing machine housing 70. Figure 10 As shown, the upper right end of the wire guide plate 65 has a second wire guide portion 654 that bends upward and backward. The left side of the bottom of the wire guide plate 65 has a third wire guide portion 655 and a fourth wire guide portion 656 that both bend downward and backward. The second wire guide portion 654 has a through third wire guide hole 651, the third wire guide portion 655 has a through fourth wire guide hole 652, and the fourth wire guide portion 656 has a through fifth wire guide hole 653. The third wire guide hole 651 is located on the upper right side of the wire clamp 63, while the fourth and fifth wire guide holes 652 and 653 are located on the lower left side of the wire clamp 63, facing each other vertically. The second wire guide hole 621 is located between the fourth and fifth wire guide holes 652 and 653. Based on this, the thread in the sewing machine passes sequentially through the third thread guide hole 651, the thread clamp 63, the fourth thread guide hole 652, the second thread guide hole 621, the fifth thread guide hole 653, the main thread clamp 20, and the first thread guide hole 41 before entering the sewing machine needle 80. When the thread-feeding drive source 61 is not activated, the thread-feeding plate 62 is in its initial state, as... Figure 6As shown, the fourth wire guide hole 652, the second wire guide hole 621, and the fifth wire guide hole 653 are aligned from top to bottom; when the wire bonding drive source 61 drives the wire bonding plate 62 to swing to the right to bond the wire, as shown... Figure 11 As shown, the second wire guide hole 621 is located to the right of the fourth wire guide hole 652 and the fifth wire guide hole 653, and serves to take in the wire.

[0095] Furthermore, the thread-tapping drive source 61 is an electromagnet and is fixedly installed on the sewing machine housing 70. The preferred transmission connection structure between the thread-tapping drive source 61 and the thread-tapping plate 62 is as follows: Figure 6 and Figure 7 As shown, the stitching mechanism also includes a stitching link 66 extending left and right, and a stitching drive shaft 67 extending front and back. The stitching link 66 is installed inside the sewing machine housing 70 and can reciprocate left and right. The electromagnet core of the stitching drive source 61 is hinged to the right end of the stitching link 66. Figure 8 and Figure 9 As shown, the bonding plate 62 includes a main body 622, a first wire guide 623 extending downward and backward from the lower end of the main body 622, a first connecting plate 624 extending forward and backward from the left side of the main body 622, and a second connecting plate 625 extending rightward from the front end of the first connecting plate 624. The upper part of the main body 622 is rotatably mounted on a second wire release drive source 64. The main body 622 and the second connecting plate 625 are parallel. The rear end and front end of the bonding drive shaft 67 are fixed to the main body 622 and the second connecting plate 625, respectively. The left end of the bonding link 66, away from the bonding drive source 61, is rotatably mounted on the bonding drive shaft 67. The bonding drive source 61 is normally de-energized, at which time the bonding plate 62 is not bonding wire. When the wire bonding drive source 61 is energized and engaged, it drives the wire bonding link 66 to move to the right, thereby driving the wire bonding plate 62 to swing to the right through the wire bonding drive shaft 67, and the wire bonding plate 62 bonds the wire. After the wire bonding is completed, the wire bonding drive source 61 is de-energized and resets, the wire bonding link 66 moves to the left and resets, and the wire bonding plate 62 swings to the left and resets.

[0096] Preferably, such as Figure 6 and Figure 7 As shown, the wire bonding mechanism also includes a limiting screw 68, which is fixed to the first connecting plate 624. Along the axial direction of the wire bonding drive shaft 67, the second connecting plate 625 and the limiting screw 68 are close to both sides of the wire bonding link 66, which axially limits the left end of the wire bonding link 66 to prevent movement and improve transmission reliability.

[0097] Furthermore, such as Figure 3 As shown, the anti-bird nest thread-cutting mechanism also includes a pressure plate 54 fixed to the sewing machine base plate. Both the pressure plate 54 and the auxiliary thread-cutting blade 53 are fixedly located on the front side of the needle 80. The pressure plate 54 is also distributed on the outer periphery of the auxiliary thread-cutting blade 53. Figure 4As shown, the upper surface of the main wire cutter 20 is provided with a first wire clamping portion 523; as Figure 3 As shown, the pressure plate 54 is provided with a second thread clamping part 541. In the above step S33, when the main cutting blade 522 is close to the auxiliary cutting blade 531 and the two are not engaged, a thread clamping seam is formed between the first thread clamping part 523 and the second thread clamping part 541. The pulled-out head of the top thread is clamped in the thread clamping seam between the main cutting blade 52 and the pressure plate 54, preventing the head of the top thread from coming out.

[0098] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0099] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preventing bird nest thread cutting based on small stitch spacing start-up and stitch-setting linkage control, characterized in that: The method for preventing bird nests from cutting the wire includes the following steps: S1. The sewing machine is equipped with an electronic control unit, an anti-bird nest thread cutting mechanism, a thread-tapping mechanism, a main thread clamp, a first thread-releasing drive source connected to the main thread clamp, a presser foot, and a thread take-up lever that can move up and down reciprocally, wherein the thread take-up lever is provided with a first thread-passing hole; The anti-bird nest wire cutting mechanism includes a wire cutting drive source, a main wire cutting blade connected to the wire cutting drive source, and an auxiliary wire cutting blade. The main wire cutting blade is provided with a hook groove and a main wire cutting edge, and the auxiliary wire cutting blade is provided with an auxiliary wire cutting edge. The wire bonding mechanism includes a wire bonding drive source, a swingable wire bonding plate, a wire bonding clamp, and a second wire release drive source that is pulsatingly connected to the wire bonding clamp. The wire bonding drive source is pulsatingly connected to the wire bonding plate, and the wire bonding plate is provided with a second wire passage hole. The presser foot includes a presser foot base plate, a needle groove that runs vertically through the presser foot base plate, and a material pressing part formed by the solid part of the presser foot base plate. The material pressing part and the needle groove are distributed back and forth along the feeding direction when the sewing machine is sewing forward. The top thread in the sewing machine passes through the thread holder, the second thread guide hole, the main thread holder, and the first thread guide hole in sequence before entering the sewing machine needle. The first wire loosening drive source, the wire cutting drive source, the wire punching drive source, and the second wire loosening drive source are all communicatively connected to the electronic control unit. S2, The electronic control unit receives the sewing start command; The electronic control unit controls the first wire release drive source to operate, causing the main wire clamp to clamp the wire; S3. The electronic control unit controls the sewing machine to start sewing the first stitch, the second stitch, ..., up to the Nth stitch in the small stitch distance sewing mode, forming a starting stitch on the fabric. The starting stitch does not enter between the pressing part and the needle plate of the sewing machine. During the first stitch, the electronic control unit controls the thread cutting drive source to extend and then retract the main thread cutting blade, so that the thread end on the side of the needle passes through the hook groove. S4. The electronic control unit controls the wire cutting drive source to move the main wire cutting blade toward the auxiliary wire cutting blade, so that the main wire cutting blade and the auxiliary wire cutting blade engage to cut off the wire end. S5. The electronic control unit controls the first wire release drive source to reset and controls the second wire release drive source to operate, causing the main wire clamp to release the wire and the wire clamp to clamp the wire. S6. The electronic control unit controls the sewing machine to continue sewing at the target stitch length; During the process of continuing to sew the first stitch, when the take-up lever moves down to release the thread, the electronic control unit controls the thread-knocking drive source to move, causing the thread-knocking plate to swing and kick the thread, and the thread-knocking plate pulls back a portion of the top thread on the fabric. Subsequently, when the take-up lever moves upward to retract the thread, the electronic control unit controls the first thread release drive source to operate and controls the second thread release drive source to reset, causing the main thread clamp to clamp the thread and the thread-locking clamp to release the thread, and the take-up lever continues to pull back a portion of the surface thread on the fabric.

2. The method for preventing bird nests from cutting the wire according to claim 1, characterized in that: Step S3 includes the following steps: S31. Before the sewing machine starts sewing the first stitch, or during the process of the sewing machine starting sewing the first stitch and the needle moving down, the electronic control unit controls the thread cutting drive source to move, and the thread cutting drive source drives the main thread cutting knife to move so that the hook groove is located directly below the needle. S32. The electronic control unit controls the sewing machine to start the first stitch in the small stitch distance sewing mode. The needle moves down and passes through the needle groove and the hook groove. Under the action of the rotary hook in the sewing machine, the thread end on one side of the needle is brought to the bottom of the main thread cutter. S33. The needle moves upward. After the needle moves upward from the main thread cutter, the electronic control unit controls the thread cutting drive source to move. The thread cutting drive source drives the main thread cutter to move. The main thread cutter pulls out at least a part of the thread end. S34. The electronic control unit controls the sewing machine to start sewing the second stitch, the third stitch, ..., up to the Nth stitch in the small stitch distance sewing mode.

3. The method for preventing bird nests from cutting the wire according to claim 2, characterized in that: In step S34, after any one of the second, third, ..., Nth stitches, a pre-pulling of the thread is performed: the electronic control unit controls the first thread release drive source to reset and controls the second thread release drive source to operate, causing the main thread clamp to release the thread and the thread-pressing clamp to clamp the thread; then, during the process of the thread take-up lever moving down to release the thread, the electronic control unit controls the thread-pressing drive source to operate, causing the thread-pressing plate to swing and press the thread, and the thread-pressing plate to pull back the top thread, so that the section of top thread between the main thread clamp and the fabric is taut; After the pre-pulling is completed, the electronic control unit controls the first wire release drive source to operate and controls the second wire release drive source to reset, causing the main wire clamp to clamp the wire and the wire release clamp to release the wire.

4. The method for preventing bird nests from cutting the wire according to claim 1 or 2, characterized in that: In step S3, when the sewing machine is operating in the small stitch distance sewing mode, the absolute value of the current stitch distance of the sewing machine is no greater than 2.5mm.

5. The method for preventing bird nests from cutting the wire according to claim 1 or 2, characterized in that: In step S3, the electronic control module controls the sewing machine to start sewing from the first stitch to the Nth stitch by switching between forward and reverse stitches.

6. The method for preventing bird nests from cutting the wire according to claim 1, characterized in that: The wire bonding mechanism also includes a fixed wire guide plate, the housing of the second wire loosening drive source is fixedly connected to the wire guide plate, and the wire guide plate is provided with a third wire guide hole, a fourth wire guide hole and a fifth wire guide hole; Along the axial direction of the main shaft in the sewing machine, the third thread guide hole is distributed on the side of the thread tensioner facing away from the main thread tensioner, and the fourth and fifth thread guide holes are both distributed on the side of the thread tensioner facing the main thread tensioner. Along the vertical direction, the third wire passage hole is distributed on the upper side of the wire clamp, the fourth and fifth wire passage holes are both distributed on the lower side of the wire clamp, and the second wire passage hole is distributed between the fourth and fifth wire passage holes; The thread in the sewing machine passes through the third thread guide hole, the thread clamp, the fourth thread guide hole, the second thread guide hole, the fifth thread guide hole, the main thread clamp, and the first thread guide hole in sequence before entering the sewing machine needle.

7. The method for preventing bird nests from cutting the wire according to claim 1, characterized in that: The stitching mechanism also includes a stitching link and a stitching drive shaft. The stitching link is reciprocally mounted inside the sewing machine housing. The stitching drive source is connected to the stitching link and drives the stitching link to reciprocate. The wire-punching plate includes a main body, a first wire-passing portion extending from the lower end of the main body, a first connecting plate extending from the side of the main body, and a second connecting plate extending from the end of the first connecting plate. The main body is rotatably mounted on a second wire-releasing drive source. The main body and the second connecting plate are parallel. The two ends of the wire-punching drive shaft are respectively fixed to the main body and the second connecting plate. The end of the wire-punching connecting rod away from the wire-punching drive source is rotatably mounted on the wire-punching drive shaft.

8. The method for preventing bird nests from cutting the wire according to claim 1, characterized in that: The wire-punching mechanism also includes a limiting screw, which is fixed to the first connecting plate; Along the axial direction of the wire bonding drive shaft, the second connecting plate and the limiting screw are close to both sides of the wire bonding link.

9. The method for preventing bird nests from cutting the wire according to claim 1, characterized in that: Both the thread-knocking drive source and the thread-releasing drive source are electromagnets, and both are fixedly installed on the sewing machine housing.

10. The method for preventing bird nests from cutting the wire according to claim 1, characterized in that: In step S1, the sewing machine is also equipped with a stitch length adjustment mechanism. The stitch length adjustment mechanism includes a stitch length adjustment drive source and a feeding mechanism connected between the main shaft and the feed dog in the sewing machine. The stitch length adjustment drive source is connected to the feeding transmission component in the feeding mechanism that determines the stitch length of the sewing machine. The stitch length adjustment drive source is also connected to the electronic control unit. In steps S3 and S6, the electronic control unit controls the output of the stitch length adjustment drive source to enable the sewing machine to sew in a small stitch length sewing mode or to sew at a target stitch length.

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