Single-moving-cutter anti-nest thread trimming mechanism and control method thereof

Abstract

The invention provides a single-moving-cutter anti-nest thread trimming mechanism and a control method thereof.The single-moving-cutter anti-nest thread trimming mechanism comprises a fixed cutter, a rotatable movable cutter, a thread trimming driving source and a thread trimming driving assembly, the fixed cutter is provided with a fixed cutter edge, and the thread trimming driving source is in transmission connection with the movable cutter through the thread trimming driving assembly; the movable cutter is driven to rotate in the direction close to or away from the fixed cutter, a sewing starting thread hooking groove and a thread separating thread hooking groove are formed in the movable cutter, a machine needle in the sewing machine can penetrate through the sewing starting thread hooking groove, a movable cutting edge opening is formed in the surface, facing the fixed cutter, of the movable cutter, and the sewing starting thread hooking groove and the thread separating thread hooking groove are distributed in the same side of the movable cutting edge opening. According to the automatic thread cutting device, the same thread cutting driving source and the same set of movable cutter and fixed cutter are matched to achieve the purposes of preventing bird nests during sewing and thread cutting and automatic thread cutting after sewing, thread loosening during sewing is effectively avoided, and the stable effect of normal sewing without bird nest thread balls during sewing is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of sewing machines, in particular to a single-moving knife anti-bird nest thread cutting mechanism and a control method thereof. Background Art

[0002] A sewing machine is a machine that uses one or more sewing threads to form one or more stitches on fabrics to interweave or sew one or more layers of sewing materials. A sewing machine is mainly composed of a base (i.e., a machine housing and a bottom plate), a needle bar mechanism, a feed mechanism, a thread hook mechanism, a presser foot mechanism, a thread trimmer mechanism, and accessories. Through the reasonable coordination of the movements of each mechanism and the cyclic work, the sewing materials are sewn together.

[0003] In order to improve sewing efficiency, automatic thread cutting equipment is usually used in sewing equipment, which not only makes sewing smooth, but also reduces thread ends in clothes, improving the efficiency of subsequent finishing. However, during the sewing process, the existing cutter can only cut the stitches after the sewing process is completed, that is, it can only realize automatic thread cutting after sewing is completed, but cannot realize automatic thread cutting when sewing. Therefore, when sewing for the second time, a certain length of thread ends will be left on the machine needle, causing the thread ends to form bird's nest-shaped thread ends on the sewn clothes during the sewing process, affecting the quality of the entire clothes, thereby affecting the quality of the entire clothes. In order to ensure the quality of the clothes, the thread ends must be trimmed manually, which increases the labor intensity and affects production efficiency.

[0004] In the prior art, some sewing machines are equipped with a thread trimming mechanism that can capture the upper thread at the beginning of sewing. For example, the Chinese utility model patent with application number 201720787765.3 discloses a thread trimming structure of a sewing machine, which cuts off the captured thread after the sewing machine runs at a certain angle, and realizes the thread trimming function again after sewing is completed. However, since the thread-hooking position of the thread trimming structure is located between the movable blade edge and the fixed blade edge, after the needle leaves the needle plate surface, the control system immediately controls the motor to drive the knife to trim the thread, which can easily lead to the upper thread end not being interwoven too short during the beginning of sewing and the thread being derailed at the beginning of sewing. If the needle does not trim the thread after leaving the needle plate surface, subsequent sewing will be impossible. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a single-action knife anti-bird nest thread trimming mechanism, which is used for both seam start thread trimming and sewing end thread trimming, and can effectively prevent seam start thread derailment.

[0006] To achieve the above-mentioned purpose, the present invention provides a single-movable knife anti-bird nest thread-cutting mechanism, comprising a fixedly arranged fixed knife, a rotatable movable knife, a thread-cutting drive source, and a thread-cutting drive assembly, wherein the fixed knife is provided with a fixed knife cutting edge, the thread-cutting drive source is transmission-connected with the movable knife through the thread-cutting drive assembly, and drives the movable knife to rotate in a direction approaching or away from the fixed knife, a seam-starting thread-hooking groove and a thread-dividing thread-hooking groove are provided in the movable knife, the seam-starting thread-hooking groove allows a machine needle in a sewing machine to pass through, a movable blade edge is provided on the surface of the movable knife facing the fixed knife, and the seam-starting thread-hooking groove and the thread-dividing thread-hooking groove are distributed on the same side of the movable knife cutting edge.

[0007] Furthermore, a seam start line groove and a seam back line groove are provided on the surface of the movable knife facing the fixed knife. The seam start line groove is connected between the seam start line hooking groove and the movable blade mouth, and the seam back line groove is connected between the line dividing line hooking groove and the movable blade mouth.

[0008] Furthermore, the single-action knife anti-bird nest wire cutting mechanism also includes a fixedly arranged air suction pipe, and the air suction pipe has an air suction port that can be aligned with the seam starting wire hook groove and / or the seam starting wire containing groove.

[0009] Further, the thread trimming drive source is a motor; within the range of 360° rotation of the motor shaft of the thread trimming drive source, the thread trimming drive source has a thread trimming working area, and the thread trimming working area has an initial angle, a seam start and knife exit angle, a seam back knife exit angle, a seam start and knife return line angle and a thread trimming angle;

[0010] When the thread trimming driving source rotates to the seam start and knife exit angle, the seam start hooking groove is distributed directly below the machine needle;

[0011] When the thread trimming driving source runs to the rear-end knife exit angle, the thread dividing and hooking grooves are located directly below the machine needle;

[0012] When the thread trimming driving source runs to the seam start return knife clamp line turning angle, the surface thread on the surface of the movable knife is clamped, and the movable knife edge and the fixed knife edge are not engaged;

[0013] When the thread trimming driving source runs to the thread trimming angle, the moving knife edge is engaged with the fixed knife edge.

[0014] Furthermore, the thread trimming drive source is a motor; the thread trimming drive assembly includes a thread trimming shaft rotatably supported in the sewing machine bottom plate, a first transmission assembly transmission-connected between the thread trimming drive source and the thread trimming shaft, and a second transmission assembly transmission-connected between the thread trimming shaft and the movable knife.

[0015] Furthermore, the first transmission assembly includes a first thread trimmer crank fixed on the motor shaft of the thread trimmer drive source, a first thread trimmer connecting rod, and a second thread trimmer crank fixed on the thread trimmer shaft, and both ends of the first thread trimmer connecting rod are respectively hinged to the first thread trimmer crank and the second thread trimmer crank.

[0016] Furthermore, the second transmission assembly includes a third thread trimming crank fixed on the thread trimming shaft, a second thread trimming connecting rod, and a movable knife frame, the two ends of the second thread trimming connecting rod are respectively hinged to the third thread trimming crank and the movable knife frame, and the movable knife is fixed on the movable knife frame.

[0017] Furthermore, a first pressing portion is provided on the surface of the movable knife facing the fixed knife, and the first pressing portion is provided on a side of the movable blade opening facing the seam starting hook groove;

[0018] When the thread trimming driving source drives the movable knife to rotate toward the fixed knife so that the movable blade edge is close to the fixed knife blade edge and not engaged, the first thread pressing portion abuts against the fixed knife to form a first thread clamping seam for clamping the surface thread.

[0019] Furthermore, the single-movable knife anti-bird nest thread trimming mechanism also includes a fixedly arranged thread pressing plate, wherein the thread pressing plate, the fixed knife and the movable knife are arranged in sequence from the outside to the inside along the radial direction of the rotary hook in the sewing machine; a second thread pressing portion is arranged on the surface of the movable knife facing the fixed knife, and the second thread pressing portion is arranged on the side of the movable blade mouth facing away from the seam starting thread hook groove, and protrudes toward the thread pressing plate along the thickness direction of the movable knife;

[0020] When the thread trimming driving source drives the movable knife to rotate toward the fixed knife so that the movable blade edge is close to the fixed knife blade edge and not engaged, the second thread pressing portion can abut against the thread pressing plate to form a second thread clamping seam for clamping the surface thread.

[0021] The present application also provides a control method for the above-mentioned single-action knife anti-bird nest wire cutting mechanism, which comprises the following steps in sequence:

[0022] S1, configuring a controller so that the thread trimming drive source is communicatively connected with the controller;

[0023] S2, during the process of the first needle of the sewing machine moving down, or before the first needle of the sewing machine starts sewing, the controller controls the thread trimming drive source to operate, so that the movable knife rotates in the direction away from the fixed knife, until the movable knife rotates to the seam start and exit position, and the seam start hook groove rotates to the right below the needle;

[0024] S3, the first needle of the sewing machine moves down, and the needle carries the upper thread downward into the seam hook groove, and the upper thread end moves to the bottom of the movable knife under the action of the rotary shuttle in the sewing machine;

[0025] S4, the first needle of the sewing machine moves up, and when the needle passes through the seam start thread hook groove upward, the controller controls the thread trimming drive source to operate in the reverse direction, so that the movable knife rotates in the direction close to the fixed knife, until the movable knife rotates to the seam start return knife clamping position, then the seam start thread hook groove rotates with the upper thread end toward the fixed knife, the upper thread end is accommodated on the surface of the movable knife and is clamped, and the movable knife edge and the fixed knife edge are not engaged;

[0026] S5, the sewing machine continues to sew the set number of stitches;

[0027] S6, the controller controls the thread trimming drive source to continue to run in the reverse direction, so that the movable knife rotates in the direction close to the fixed knife, until the movable knife rotates to the thread trimming position, and the movable knife edge and the fixed knife edge bite to cut the upper thread end;

[0028] S7, sewing machine sewing normally;

[0029] S8, when the sewing machine needs to trim the thread after sewing, during the process of the needle moving up to sew the last stitch of the sewing machine, the controller controls the thread trimming drive source to operate, so that the movable knife rotates in the direction away from the fixed knife until the movable knife rotates to the knife exit position after sewing, and performs thread hooking and thread separation;

[0030] S9, the controller controls the thread trimming drive source to run in reverse, so that the movable knife rotates in the direction close to the fixed knife until the movable knife rotates to the thread trimming position, and then the thread dividing and hooking groove rotates with the upper thread and the lower thread toward the fixed knife, and the upper thread is accommodated on the surface of the movable knife, and the upper thread and the lower thread are cut by the engagement of the movable knife blade and the fixed knife blade.

[0031] As described above, the single-action knife anti-bird nest wire cutting mechanism and control method thereof according to the present invention have the following beneficial effects:

[0032] The present application controls the travel of the movable knife at the beginning of sewing and the end of sewing by controlling the thread cutting drive source to move different travels at the beginning of sewing and the end of sewing, thereby realizing the cutting of the upper thread end at the beginning of sewing and the cutting of the upper thread at the end of sewing, so as to achieve the purpose of preventing bird nests at the beginning of sewing and automatic thread cutting at the end of sewing by cooperating with the same thread cutting drive source and the same set of movable knives and fixed knives. In particular, when sewing is started, the thread cutting drive source drives the movable knife to drive the upper thread end to move toward the fixed knife but not engaged, and the upper thread end on the surface of the movable knife can be clamped, that is, the number of stitches is set before sewing and then the upper thread end is cut off, which effectively avoids the thread from being derailed at the beginning of sewing, realizes the stable effect of normal sewing without bird nests at the beginning of sewing, ensures the beauty of the stitches, and reduces the manual trimming of thread ends. In addition, the present application is a single movable knife structure, which is simple and easy to implement, low cost, easy to control, has high control accuracy, and improves the accuracy of thread cutting at the beginning of sewing and thread cutting after sewing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the assembly of the single-moving knife anti-bird nest thread cutting mechanism in the sewing machine in this application.

[0034] Figure 2 and Figure 3 This is a schematic diagram of the structure of the single-moving knife anti-bird nest wire cutting mechanism in this application at different viewing angles.

[0035] Figure 4a This is a schematic diagram of the structure of the movable knife embodiment 1 in the present application.

[0036] Figure 4b This is a schematic diagram of the structure of the second embodiment of the movable knife in this application.

[0037] Figure 4c This is a schematic diagram of the structure of the movable knife embodiment 3 in this application.

[0038] Figure 5 This is a schematic diagram of the movable knife and the fixed knife cooperating with the clamp wire in this application.

[0039] Figure 6a This is a schematic diagram of the movable knife and the wire pressing plate cooperating to clamp the wire in this application.

[0040] Figure 6b for Figure 6a Enlarged view of circle A.

[0041] Figure 7a This is a schematic diagram of the working angle of the thread trimming drive source in this application. Figure 1 , which corresponds to Figure 4a The movable knife embodiment one in the present invention.

[0042] Figure 7b This is a schematic diagram of the working angle of the thread trimming drive source in this application. Figure 2 , which corresponds to Figure 4b The movable knife embodiment 2 in the present invention.

[0043] Figure 8 This is a state diagram of the single-moving knife anti-bird nest thread cutting mechanism in this application when the seam is started and the knife is released.

[0044] Fig. 9 This is a state diagram of the single-moving knife anti-bird nest trimming mechanism in this application when starting to sew and returning to the knife clamp line.

[0045] Fig.10 This is a state diagram of the single-moving knife anti-bird nest thread cutting mechanism in this application when the knife is out after sewing.

[0046] Component number description

[0047] 10 Fixed knife

[0048] 101 Fixed blade edge

[0049] 20 movable knife

[0050] 21 Seam hook groove

[0051] 22 branch line hook groove

[0052] 23 Moving cutting edge

[0053] 24 Seam-forming duct

[0054] 25 Seam back wire slot

[0055] 26 First crimping section

[0056] 27 Second crimping section

[0057] 30 Thread trimming drive source

[0058] 40 Thread trimmer drive assembly

[0059] 41 Thread trimmer

[0060] 42 First trimmer crank

[0061] 43 First thread trimmer link

[0062] 44 Second trimmer crank

[0063] 45 Third trimmer crank

[0064] 46 Second thread trimmer link

[0065] 47 Moving tool holder

[0066] 50 Pressing plate

[0067] 60 Suction pipe

[0068] 70 Needle

[0069] 80 Base Plate

[0070] 90 Hook

[0071] 110 Positioning hook

[0072] 120 Motor bracket DETAILED DESCRIPTION

[0073] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0074] It should be noted that the structures, proportions, sizes, etc. drawn in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0075] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or may be indirectly connected to the other element through an intermediate element.

[0076] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0077] The present application relates to the technical field of sewing machines, and more particularly to a single-action knife anti-bird nest thread trimming mechanism, and a control method for the single-action knife anti-bird nest thread trimming mechanism. For ease of description, in the following embodiments, the definitions of various directions are as follows: the axial directions of the main shaft and the lower shaft in the sewing machine are defined as the left and right directions, and the left and right directions are the directions toward the head of the machine, and the right direction is the direction toward the tail of the machine. The rotary hook 90 in the sewing machine is fixed to the left end of the lower shaft, such as Figure 1 As shown in the figure, the direction in which the feeding mechanism drives the sewing material to move when the sewing machine is sewing is defined as the forward direction.

[0078] like Figures 1 to 3As shown, the single-action knife anti-bird nest thread trimming mechanism involved in the present application includes a fixed fixed knife 10, a rotatable movable knife 20, a thread trimming drive source 30, and a thread trimming drive assembly 40. The fixed knife 10 is provided with a fixed knife edge 101. The thread trimming drive source 30 is connected to the movable knife 20 through the thread trimming drive assembly 40 to drive the movable knife 20 to rotate in a direction close to or away from the fixed knife 10. In this embodiment, in the front-to-back direction, the fixed knife 10 is distributed on the rear side of the machine needle 70, and the fixed knife edge 101 is provided at the front end of the fixed knife 10, as shown in FIG. Figure 5 As shown; when the thread cutting drive source 30 drives the movable knife 20 to cut out through the thread cutting drive assembly 40, the movable knife 20 rotates forward and moves away from the fixed knife 10; when the thread cutting drive source 30 drives the movable knife 20 to return through the thread cutting drive assembly 40, the movable knife 20 rotates backward and approaches the fixed knife 10. The movable knife 20 and the fixed knife 10 are both arranged on the lower side of the bottom plate 80 and are both located on the outer peripheral side of the rotary hook 90, and the movable knife 20 is closer to the rotary hook 90 than the fixed knife 10, so the movable knife 20 is located on the lower side of the fixed knife 10. The rotary hook 90 is provided with a positioning hook 110 for limiting position.

[0079] like Figure 4a or Figure 4b As shown, the movable knife 20 is provided with a seam starting thread hook groove 21 and a line dividing thread hook groove 22. Both the seam starting thread hook groove 21 and the line dividing thread hook groove 22 penetrate the movable knife 20 along the thickness direction of the movable knife 20. The seam starting thread hook groove 21 allows the needle 70 in the sewing machine to pass through. A movable knife edge 23 is provided on the upper surface of the movable knife 20 facing the fixed knife 10. The seam starting thread hook groove 21 and the line dividing thread hook groove 22 are distributed on the same side of the movable knife edge 23, that is, they are both distributed on the rear side of the movable knife edge 23. Along the direction of the movable knife 20 moving away from the fixed knife 10 when the movable knife 20 is moving out of the knife, the seam starting thread hook groove 21, the line dividing thread hook groove 22 and the movable knife edge 23 can be arranged in the following two ways: one is as follows: Figure 4a As shown, in the first embodiment of the movable knife 20, along the direction of the movable knife 20 moving away from the fixed knife 10, the seam starting thread hooking groove 21, the line dividing thread hooking groove 22 and the movable knife edge 23 are successively distributed, that is, the seam starting thread hooking groove 21, the line dividing thread hooking groove 22 and the movable knife edge 23 are successively distributed from back to front; second, as Figure 4b As shown, in the second embodiment of the movable knife 20, along the direction of the movable knife 20 away from the fixed knife 10 when the movable knife 20 is moving out of the knife, the dividing line hooking groove 22, the seam starting line hooking groove 21 and the movable knife blade 23 are distributed in sequence, that is, the dividing line hooking groove 22, the seam starting line hooking groove 21 and the movable knife blade 23 are distributed in sequence from back to front.

[0080] The present application also provides a control method for the above-mentioned single-action knife anti-bird nest wire cutting mechanism, which comprises the following steps in sequence:

[0081] Step S1, configure the controller so that the thread trimming drive source 30 is connected to the controller for communication. At the same time, the main motor driving the main shaft in the sewing machine is also connected to the controller for communication. The left end of the main shaft drives the needle 70 to move up and down through the needle bar mechanism.

[0082] Step S2, when the sewing machine starts to sew the first stitch, the needle 70 first moves down and then moves up; during the process of the needle 70 moving down when the sewing machine starts to sew the first stitch, or before the needle 70 starts to sew the first stitch, the controller controls the thread trimming drive source 30 to operate, and drives the movable knife 20 to come out through the thread trimming drive assembly 40, so that the movable knife 20 rotates forward in the direction away from the fixed knife 10, until the movable knife 20 rotates to the seam start and knife out position, at this time, Figure 8 As shown, the seam start hook groove 21 rotates to the position directly below the machine needle 70. Preferably, when the sewing machine is turned on, or after the thread is trimmed at the end of the last sewing, the controller controls the thread trimming drive source 30 to operate, so that the movable knife 20 rotates to the seam start knife exit position, so that the seam start hook groove 21 has rotated to the position directly below the machine needle 70 before the sewing machine starts sewing the first needle 70.

[0083] Step S3, the first needle 70 of the sewing machine moves downward. Since the thread hook groove 21 is directly below the needle 70, the needle 70 carries the upper thread and penetrates downward into the thread hook groove 21. Under the action of the rotary shuttle 90 in the sewing machine, the end of the upper thread moves to below the movable knife 20.

[0084] Step S4, the sewing machine continues to sew the first stitch, and the needle 70 moves up; when the needle 70 passes upward from the seam starting thread hooking groove 21, the controller controls the thread trimming drive source 30 to operate in the reverse direction, and drives the movable knife 20 to return the knife through the thread trimming drive assembly 40, so that the movable knife 20 rotates backward in the direction close to the fixed knife 10, until the movable knife 20 rotates to the seam starting return knife clamping position, such as Fig. 9 As shown, the seam starting thread hook groove 21 rotates backward toward the fixed knife 10 with the surface thread end, and the surface thread end is accommodated on the surface of the movable knife 20 and is clamped; in particular, when the movable knife 20 is in the seam starting return knife clamping position, the movable knife edge 23 and the fixed knife edge 101 are not engaged, so the surface thread end on the surface of the movable knife 20 is clamped but not cut.

[0085] Step S5: The sewing machine continues to sew the set number of stitches, during which the moving blade 23 and the fixed blade 101 remain in a non-engaging state. Fig. 9 As shown, the upper thread end is always on the surface of the movable knife 20 and is clamped and not cut, thereby effectively preventing the thread from coming off.

[0086] Step S6, the controller controls the thread trimming driving source 30 to continue to run in the reverse direction, and drives the movable knife 20 to continue to return the knife through the thread trimming driving assembly 40, so that the movable knife 20 rotates backward in the direction close to the fixed knife 10, until the movable knife 20 rotates to the thread trimming position, at which time, the movable knife edge 23 and the fixed knife edge 101 bite, and the upper thread end on the surface of the movable knife 20 is cut off. So far, through steps S2 to S6, the seam start cutting thread prevention and bird nest prevention are realized.

[0087] Step S7: The sewing machine sews normally.

[0088] Step S8, when the sewing machine needs to trim the thread after sewing, during the process of the needle 70 moving up to sew the last stitch of the sewing machine, the controller simultaneously controls the thread trimming drive source 30 to operate, and drives the movable knife 20 to move out through the thread trimming drive assembly 40, so that the movable knife 20 rotates forward in the direction away from the fixed knife 10 until the movable knife 20 rotates to the position of the knife moving out after sewing, such as Fig.10 As shown, draw the lines and divide the lines.

[0089] Step S9, the controller controls the thread trimming drive source 30 to run in the reverse direction, and drives the movable knife 20 to return the knife through the thread trimming drive assembly 40, so that the movable knife 20 rotates backward in the direction close to the fixed knife 10, until the movable knife 20 rotates to the thread trimming position. During this process, the thread dividing and hooking groove 22 rotates with the upper thread and the lower thread toward the fixed knife 10, and the upper thread is accommodated on the surface of the movable knife 20; after the movable knife 20 rotates to the thread trimming position, the movable knife edge 23 engages with the fixed knife edge 101 to cut the upper thread and the lower thread. At this point, through steps S8 and S9, automatic thread trimming at the end of sewing is realized.

[0090] In the present application, the movable knife 20 is provided with a thread hooking groove 21 for starting the seam and a thread hooking groove 22 for dividing the thread, and then the controller controls the thread cutting driving source 30 to move different strokes at the beginning of the seam and at the end of sewing, so as to control the stroke of the movable knife 20 at the beginning of the seam and at the end of sewing. When starting the seam, the movable knife 20 first rotates forward to the position of the knife exiting the seam, then rotates backward with the upper thread end to the position of the knife clamping line at the beginning of the seam, and finally rotates backward to the thread cutting position after setting the number of stitches at the beginning of the seam, so as to cut the upper thread end at the beginning of the seam. When the thread is cut at the end of sewing, the movable knife 20 first rotates forward to the position of the knife exiting the seam after the seam, then rotates backward with the upper thread to the thread cutting position, so as to realize automatic thread cutting at the end of sewing. Therefore, the present application achieves the purpose of realizing the anti-bird nest of thread cutting at the beginning of the seam and automatic thread cutting at the end of sewing by cooperating with the same thread cutting driving source 30, and the same set of movable knives 20 and fixed knives 10.

[0091] In particular, when the thread is cut at the beginning of the seam, the thread cutting drive source 30 drives the movable knife 20 to drive the surface thread end to move toward the fixed knife 10 to the position of the knife clamping line at the beginning of the seam, and the surface thread end on the surface of the movable knife 20 can be clamped, but the movable knife edge 23 and the fixed knife edge 101 are not engaged, but after the number of stitches is set at the beginning of the seam, the thread cutting drive source 30 drives the movable knife 20 to drive the surface thread end to rotate backward to the thread cutting position for thread cutting, that is, the number of stitches is set at the beginning of the seam first and then the surface thread end is cut off, and the surface thread end is always clamped during the process of setting the number of stitches at the beginning of the seam, which effectively avoids the thread from being derailed at the beginning of the seam, and achieves the stable effect of normal seam starting without bird's nest thread balls at the beginning of the seam, ensures the beauty of the stitches, and reduces the manual trimming of thread ends. In addition, the present application is a single movable knife structure, which is simple and easy to implement, and has low cost; the controller only controls the movable knife 20 by controlling the thread cutting drive source 30, which is easy to control, has high control accuracy, and improves the accuracy of thread cutting at the beginning of the seam and after the seam.

[0092] Based on the need to clamp the upper thread end when cutting the thread at the start of the seam, the single-moving knife anti-bird nest thread cutting mechanism involved in the present application also includes a thread clamping unit. When the movable knife 20 is located at the thread clamping position of the seam start return knife, the thread clamping unit acts on the upper thread end on the surface of the movable knife 20 to clamp the upper thread end on the surface of the movable knife 20. In this embodiment, the thread clamping unit has the following two preferred embodiments.

[0093] Wire clamping unit embodiment 1: The wire clamping unit is formed by a movable knife 20 and a fixed knife 10. Figure 5 As shown, the movable knife 20 is provided with a first thread pressing portion 26 on the upper surface facing the fixed knife 10, and the first thread pressing portion 26 is provided on the rear side of the movable knife blade 23 facing the seam start hooking groove 21. When the thread trimming driving source 30 drives the movable knife 20 to rotate backward to the seam start return knife clamping position, the movable knife blade 23 is close to the fixed knife blade 101 but not engaged, the first thread pressing portion 26 abuts against the fixed knife 10, and forms a first thread clamping seam for clamping the upper thread end, then the thread clamping unit embodiment 1 is composed of the abutting first thread pressing portion 26 and the fixed knife 10.

[0094] Wire clamping unit embodiment 2: The wire clamping unit is formed by a movable knife 20 and a wire pressing plate 50. Figure 6a and Figure 6bAs shown, the single movable knife anti-bird nest thread trimming mechanism also includes a fixedly arranged thread pressing plate 50, and the thread pressing plate 50, the fixed knife 10 and the movable knife 20 are arranged in sequence from the outside to the inside along the radial direction of the rotary hook 90 in the sewing machine, and the thread pressing plate 50 is arranged on the upper side of the fixed knife 10, and the thread pressing plate 50 is fixed to the bottom of the bottom plate 80 by screws. A second thread pressing portion 27 is provided on the surface of the movable knife 20 facing the fixed knife 10, and the second thread pressing portion 27 is arranged on the front side of the movable knife edge 23 facing away from the seam hook groove 21, and protrudes upward toward the thread pressing plate 50 along the thickness direction of the movable knife 20, and the front end of the thread pressing plate 50 passes forward over the fixed knife edge 101 at the front end of the fixed knife 10. When the thread cutting drive source 30 drives the movable knife 20 to rotate backward to the seam start and return knife clamp line position, the movable knife edge 23 is close to the fixed knife edge 101 but not engaged, the second thread pressing portion 27 abuts against the thread pressing plate 50, and forms a second thread clamping seam for clamping the surface thread, then the thread clamping unit embodiment 2 is composed of the abutting second thread pressing portion 27 and the thread pressing plate 50.

[0095] Preferably, if Figure 4a or Figure 4b As shown, the upper surface of the movable knife 20 facing the fixed knife 10 is further provided with a seam start line groove 24 and a seam back line groove 25. The seam start line groove 24 is connected between the seam start line hook groove 21 and the movable knife edge 23, that is, the rear end of the seam start line groove 24 extends backward to the seam start line hook groove 21, and the front end extends forward to the movable knife edge 23; the seam back line groove 25 is connected between the line dividing line hook groove 22 and the movable knife edge 23, that is, the rear end of the line dividing line groove 25 extends backward to the line dividing line hook groove 22, and the front end extends forward to the movable knife edge 23. Both the seam start line groove 24 and the seam back line groove 25 play a guiding role. In the first embodiment of the movable knife 20, as shown in FIG. Figure 4a As shown, the thread groove 25 after sewing is the front section of the thread groove 24 for starting sewing, and the thread dividing and hooking groove 22 is arranged on the extension path of the thread groove 24 for starting sewing; when the thread is cut at the beginning of sewing, the thread groove 24 for starting sewing contains the upper thread end, and part of the upper thread end is also contained in the thread groove 25 after sewing which constitutes the front section of the thread groove 24 for starting sewing; when the thread is cut after sewing, the thread groove 25 after sewing contains the upper thread and the lower thread. In the second embodiment of the movable knife 20, as shown in FIG. Figure 4b As shown, the seam start thread accommodating groove 24 is the front section of the post-sewing thread accommodating groove 25, and the seam start thread hook groove 21 is arranged on the extension path of the post-sewing thread accommodating groove 25; when the seam start thread is trimmed, the upper thread end is accommodated in the seam start thread accommodating groove 24; when the thread is trimmed after sewing, the post-sewing thread accommodating groove 25 accommodates the upper thread and the lower thread, and a part of the upper thread and the lower thread are simultaneously accommodated in the seam start thread accommodating groove 24 constituting the front section of the post-sewing thread accommodating groove 25.

[0096] Furthermore, if Figures 4a to 4c As shown, the line-dividing and hooking groove 22 is an open groove opening to the left, and the seam-starting and hooking groove 21 can be an open groove or a closed groove; for example: Figure 4a and Figure 4b In the movable knife 20 shown, the seam starting and hooking groove 21 is a closed groove; Figure 4c In the movable knife 20 shown, the seam starting thread hooking groove 21 is an open groove opening toward the rear; in other embodiments, the seam starting thread hooking groove 21 can also be an open groove opening toward the left.

[0097] Furthermore, if Figure 2 and Figure 3 As shown, the single-action knife anti-bird nest thread trimming mechanism also includes a fixed suction pipe 60, which is fixed to the bottom of the base plate 80 by screws, and has a suction port that can be aligned with the seam start hooking groove 21 and / or the seam start containing groove 24, and the suction pipe 60 is connected to the air source generating device, and the air source generating device is in communication connection with the controller. In the process of seam start cutting and anti-bird nest, when the controller controls the thread trimming drive source 30 to drive the movable knife 20 to rotate forward, the controller also controls the air source generating device to start, so that a negative pressure thread suction action is generated at the suction port of the suction pipe 60; in this way, when the subsequent movable knife 20 drives the upper thread head to rotate backward to the position of the seam start return knife clamp line, the upper thread head in the seam start hooking groove 21 is just in the negative pressure area of ​​the suction port, so that the thread head end of the upper thread head is picked up; after the seam start cutting, the cut upper thread head is sucked away by the negative pressure of the suction port, so that the upper thread head is collected.

[0098] Preferably, if Figure 1 As shown, the fixed knife 10 is fixed to the bottom of the sewing machine bottom plate 80 by screws, so as to realize the fixed setting of the fixed knife 10. In this way, the fixed knife 10, the wire pressing plate 50 and the air suction pipe 60 can be fixed to the bottom of the bottom plate 80 by the same screw.

[0099] Furthermore, the thread cutting drive source 30 drives the movable knife 20 to rotate around the lower axis through the thread cutting drive assembly 40, that is, the rotation center of the movable knife 20 is the lower axis. Figure 2 and Figure 3 As shown, the thread trimming drive source 30 is a motor, preferably a stepping motor, and the thread trimming drive source 30 is fixed on the motor bracket 120, and the motor bracket 120 is fixed to the bottom of the bottom plate 80 by several screws. Of course, the thread trimming drive source 30 can also be directly fixed to the bottom of the bottom plate 80 by several screws.

[0100] Furthermore, if Figure 2 and Figure 3As shown, the thread trimming drive assembly 40 includes a thread trimming shaft 41 rotatably supported in the sewing machine bottom plate 80, a first transmission assembly drivingly connected between the thread trimming drive source 30 and the right end of the thread trimming shaft 41, and a second transmission assembly drivingly connected between the left end of the thread trimming shaft 41 and the movable knife 20. The thread trimming shaft 41 is parallel to the lower shaft, and the thread trimming shaft 41 is rotatably supported in the sewing machine bottom plate 80 through a shaft sleeve. The thread trimming drive source 30 drives the thread trimming shaft 41 to rotate through the first transmission assembly, and the thread trimming shaft 41 drives the movable knife 20 to rotate through the second transmission assembly.

[0101] Furthermore, if Figure 2 and Figure 3 As shown, the first transmission assembly includes a first thread trimmer crank 42 fixed on the motor shaft of the thread trimmer drive source 30, a first thread trimmer connecting rod 43, and a second thread trimmer crank 44 fixed on the right end of the thread trimmer shaft 41, and the two ends of the first thread trimmer connecting rod 43 are respectively hinged to the first thread trimmer crank 42 and the second thread trimmer crank 44. The second transmission assembly includes a third thread trimmer crank 45 fixed to the left end of the thread trimmer shaft 41, a second thread trimmer connecting rod 46, and a movable knife frame 47, and the two ends of the second thread trimmer connecting rod 46 are respectively hinged to the third thread trimmer crank 45 and the movable knife frame 47, and the movable knife 20 is fixed to the movable knife frame 47 by screws.

[0102] Furthermore, if Figure 7a or Figure 7b As shown, within the range of 360° rotation of the motor shaft of the thread trimming driving source 30, the thread trimming driving source 30 has a thread trimming working area P, and the thread trimming working area P has an initial angle α1, a seam start knife angle α2, a seam end knife angle α3, a seam start knife return angle α4 and a thread trimming angle α5. Figure 4a The first embodiment of the movable knife 20 shown in FIG. Figure 7a As shown, the initial angle α1, the thread trimming angle α5, the seam start return knife clamp angle α4, the seam end knife exit angle α3 and the seam start knife exit angle α2 are set in sequence, and the range of the thread trimming working area P is α1~α2. Figure 4b The second embodiment of the movable knife 20 shown in FIG. Figure 7bAs shown, the initial angle α1, the thread trimming angle α5, the seam start return knife clamping angle α4, the seam start exit knife angle α2 and the seam end exit knife angle α3 are set in sequence, and the range of the thread trimming working area P is α1 to α3. When the thread trimming driving source 30 runs to the seam start exit knife angle α2, the movable knife 20 rotates to the seam start exit knife position, and the seam start hooking groove 21 is distributed directly below the machine needle 70. When the thread trimming driving source 30 runs to the seam end exit knife angle α3, the movable knife 20 rotates to the seam end exit knife position, and the line dividing hooking groove 22 is distributed directly below the machine needle 70. When the thread trimming driving source 30 runs to the seam start return knife clamping angle α4, the movable knife 20 rotates to the seam start return knife clamping position, the surface thread in the seam start thread holding groove 24 is clamped, and the movable knife edge 23 and the fixed knife edge 101 are not engaged. When the thread trimming driving source 30 rotates to the thread trimming rotation angle α5 , the movable knife 20 rotates to the thread trimming position, and the movable knife edge 23 engages with the fixed knife edge 101 .

[0103] In summary, the working principle of the single-action knife anti-bird nest wire cutting mechanism involved in the present application is as follows, and takes the configuration of the movable knife 20 embodiment 1 and the wire pressing plate 50 as an example.

[0104] 1. The single-action knife anti-bird nest cutting mechanism is used for seam cutting to prevent bird nests, including the following steps:

[0105] A1. When the sewing machine is working, the main shaft rotates, and the first stitch is sewn, the controller controls the thread trimming drive source 30 to move synchronously, and the thread trimming drive source 30 rotates to the seam start knife exit angle α2, driving the movable knife 20 to rotate forward to the seam start knife exit position, so that the seam start hook groove 21 rotates to the bottom of the needle 70; or, before the sewing machine starts sewing the first stitch, the controller has controlled the thread trimming drive source 30 to rotate to the seam start knife exit angle α2, and the seam start hook groove 21 has rotated to the bottom of the needle 70. At the same time, the controller controls the air source generating device to generate a negative pressure thread suction action at the air suction port of the air suction pipe 60.

[0106] A2. The sewing machine starts sewing with the first needle 70 moving downward. After the needle 70 carries the upper thread downward through the sewing thread hook groove 21, the upper thread end on one side of the needle 70 is driven to the bottom of the movable knife 20 under the action of the rotary shuttle 90.

[0107] A3. The first needle 70 of the sewing machine moves up. After the needle 70 moves upward and away from the movable knife 20, the controller controls the thread cutting drive source 30 to rotate in the opposite direction from the seam start knife angle α2 to the seam start return knife clamp line angle α4. The movable knife 20 retreats backwards with the upper thread end to the seam start return knife clamp line position, and the thread pressing plate 50 and the second thread pressing part 27 of the movable knife 20 abut against each other, clamping the upper thread end in the seam start thread containing groove 24; the thread end of the upper thread end in the seam start thread containing groove 24 is just in the negative pressure area of ​​the air suction port, so that the thread end end is picked up; the movable knife edge 23 and the fixed knife edge 101 are in a non-engaged state, so the upper thread end is only clamped but not cut.

[0108] A4. After the sewing machine continues to sew the set number of stitches, the controller controls the thread trimming drive source 30 to continue to rotate in the opposite direction from the seam start return knife clamp line angle α4 to the thread trimming angle α5, and the movable knife 20 rotates backward with the upper thread end to the thread trimming position, and the movable knife edge 23 engages with the fixed knife edge 101 to cut off the upper thread end in the seam start thread groove 24. The cut upper thread end is sucked away and collected by the negative pressure of the suction port.

[0109] A5. The controller controls the thread trimming drive source 30 to continue to rotate in the opposite direction from the thread trimming angle α5 to the initial angle α1, and the movable knife 20 returns to its initial position. The controller controls the air source generating device to stop moving, and the suction pipe 60 disconnects the suction; thereafter, the sewing machine sews according to the set state.

[0110] 2. The single-action knife anti-bird nest thread trimming mechanism is used to trim the thread at the end of sewing, including the following steps:

[0111] B1. When the sewing machine sews the last stitch, during the upward movement of the needle 70, the controller controls the thread trimming drive source 30 to move synchronously. The thread trimming drive source 30 rotates to the post-sewing knife exit angle α3, driving the movable knife 20 to rotate forward to the post-sewing knife exit position, and the thread separation is achieved by the thread separation hooking groove 22.

[0112] B2. The controller controls the thread trimming drive source 30 to rotate in the opposite direction from the rear-sewing knife exit angle α3 to the thread trimming angle α5, and the movable knife 20 rotates backward with the upper thread and the lower thread to the thread trimming position, and the movable knife edge 23 engages with the fixed knife edge 101 to cut off the upper thread and the lower thread in the rear-sewing thread receiving groove 25.

[0113] Therefore, the single-action knife anti-bird nest wire cutting mechanism involved in the present application has the following advantages:

[0114] 1. The movable knife 20 is provided with a seam start hooking groove 21, a line dividing hooking groove 22, a seam start accommodating groove 24 and a post-sewing accommodating groove 25. The same set of movable knife 20 and fixed knife 10 cooperate to achieve two functions: seam start cutting to prevent bird nests and automatic thread cutting after sewing.

[0115] 2. After hooking the thread at the start of sewing, bring the upper thread end to the side of the needle 70 and wait. During the waiting process, always clamp the upper thread end, and then cut off the upper thread end after the set number of stitches for sewing. The waiting time for cutting the upper thread end is accurately controlled according to the set number of stitches, which can avoid the thread from coming off at the start of sewing and the formation of bird's nest thread balls at the start of sewing.

[0116] 3. Driven by stepper motor, the thread trimming is stable and reliable with low thread trimming noise.

[0117] In the above embodiment, the fixed knife 10, the movable knife 20, the wire pressing plate 50 and the suction pipe 60 are all arranged on the rear side of the needle 70; in other embodiments, the fixed knife 10, the movable knife 20, the wire pressing plate 50 and the suction pipe 60 can also be symmetrically arranged on the front side of the needle 70 along the central axis of the rotary shuttle, so that the movable knife 20 swings backward when it is extended and swings forward when it is returned.

[0118] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0119] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A single-moving knife anti-bird nest thread cutting mechanism, comprising a fixedly arranged fixed knife (10), a rotatable movable knife (20), a thread cutting drive source (30), and a thread cutting drive assembly (40), wherein the fixed knife (10) is provided with a fixed knife edge (101), the thread cutting drive source (30) is connected to the movable knife (20) through the thread cutting drive assembly (40), and drives the movable knife (20) to rotate in a direction close to or away from the fixed knife (10), characterized in that: The movable knife (20) is provided with a seam starting thread hooking groove (21) and a thread dividing thread hooking groove (22), the seam starting thread hooking groove (21) allows a needle (70) in a sewing machine to pass through, a movable knife edge (23) is provided on the surface of the movable knife (20) facing the fixed knife (10), and the seam starting thread hooking groove (21) and the thread dividing thread hooking groove (22) are distributed on the same side of the movable knife edge (23).

2. The single-action knife anti-bird nest wire cutting mechanism according to claim 1, characterized in that: The movable knife (20) is also provided with a seam start thread accommodating groove (24) and a seam end thread accommodating groove (25) on the surface facing the fixed knife (10); the seam start thread accommodating groove (24) is connected between the seam start thread hooking groove (21) and the movable knife edge (23); and the seam end thread accommodating groove (25) is connected between the thread separation thread hooking groove (22) and the movable knife edge (23).

3. The single-action knife anti-bird nest wire cutting mechanism according to claim 2 is characterized by: It also comprises a fixedly arranged air suction pipe (60), wherein the air suction pipe (60) has an air suction port which can be aligned with the seam starting line hooking groove (21) and / or the seam starting line containing groove (24).

4. The single-action knife anti-bird nest wire cutting mechanism according to claim 1, characterized in that: The thread trimming drive source (30) is a motor; within the range of 360° rotation of the motor shaft of the thread trimming drive source (30), the thread trimming drive source (30) has a thread trimming work area (P), and the thread trimming work area (P) has an initial rotation angle (α1), a seam start knife angle (α2), a seam end knife angle (α3), a seam start knife clamp angle (α4) and a thread trimming angle (α5); When the thread trimming driving source (30) rotates to the seam start and knife exit angle (α2), the seam start hooking groove (21) is distributed directly below the machine needle (70); When the thread trimming driving source (30) rotates to the rear-sewing knife exit angle (α3), the thread dividing and hooking groove (22) is distributed directly below the machine needle (70); When the thread trimming drive source (30) rotates to the seam start return knife clamp line rotation angle (α4), the surface thread of the movable knife (20) is clamped, and the movable knife edge (23) and the fixed knife edge (101) are not engaged; When the thread trimming driving source (30) operates to the thread trimming rotation angle (α5), the movable blade edge (23) engages with the fixed blade edge (101).

5. The single-action knife anti-bird nest wire cutting mechanism according to claim 1, characterized in that: The thread trimming drive source (30) is a motor; the thread trimming drive assembly (40) comprises a thread trimming shaft (41) rotatably supported in a sewing machine bottom plate (80), a first transmission assembly drivingly connected between the thread trimming drive source (30) and the thread trimming shaft (41), and a second transmission assembly drivingly connected between the thread trimming shaft (41) and a movable knife (20).

6. The single-action knife anti-bird nest wire cutting mechanism according to claim 5, characterized in that: The first transmission assembly comprises a first thread trimmer crank (42) fixed on the motor shaft of a thread trimmer driving source (30), a first thread trimmer connecting rod (43), and a second thread trimmer crank (44) fixed on the thread trimmer shaft (41), wherein two ends of the first thread trimmer connecting rod (43) are respectively hinged to the first thread trimmer crank (42) and the second thread trimmer crank (44).

7. The single-action knife anti-bird nest wire cutting mechanism according to claim 5, characterized in that: The second transmission assembly comprises a third thread trimming crank (45) fixed on the thread trimming shaft (41), a second thread trimming connecting rod (46), and a movable knife frame (47); two ends of the second thread trimming connecting rod (46) are respectively hinged to the third thread trimming crank (45) and the movable knife frame (47); and the movable knife (20) is fixed on the movable knife frame (47).

8. The single-action knife anti-bird nest wire cutting mechanism according to claim 1, characterized in that: A first thread pressing portion (26) is provided on the surface of the movable knife (20) facing the fixed knife (10), and the first thread pressing portion (26) is provided on a side of the movable knife edge (23) facing the seam starting thread hooking groove (21); When the thread trimming drive source (30) drives the movable knife (20) to rotate in a direction close to the fixed knife (10), so that the movable knife edge (23) is close to the fixed knife edge (101) and is not engaged, the first thread pressing portion (26) abuts against the fixed knife (10) to form a first thread clamping seam for clamping the surface thread.

9. The single-action knife anti-bird nest wire cutting mechanism according to claim 1, characterized in that: The sewing machine also comprises a fixedly arranged thread pressing plate (50), wherein the thread pressing plate (50), the fixed knife (10) and the movable knife (20) are arranged in sequence from the outside to the inside along the radial direction of the rotary shuttle (90) in the sewing machine; a second thread pressing portion (27) is provided on the surface of the movable knife (20) facing the fixed knife (10); the second thread pressing portion (27) is arranged on a side of the movable knife edge (23) facing away from the seam starting thread hook groove (21) and protrudes toward the thread pressing plate (50) along the thickness direction of the movable knife (20); When the thread cutting drive source (30) drives the movable knife (20) to rotate in a direction close to the fixed knife (10), so that the movable knife edge (23) is close to the fixed knife edge (101) and is not engaged, the second thread pressing portion (27) can abut against the thread pressing plate (50) to form a second thread clamping seam for clamping the surface thread.

10. A control method for the single-action knife anti-bird nest wire cutting mechanism according to claim 1, characterized in that: The following steps are included in sequence: S1, configuring a controller so that the thread trimming drive source (30) is in communication connection with the controller; S2, during the process of the first needle (70) of the sewing machine starting to sew downward, or before the first needle (70) of the sewing machine starting to sew, the controller controls the thread trimming drive source (30) to operate, so that the movable knife (20) rotates in a direction away from the fixed knife (10), until the movable knife (20) rotates to the sewing start and exit position, and the sewing start thread hook groove (21) rotates to the position directly below the needle (70); S3, the first needle (70) of the sewing machine moves downward, and the needle (70) carries the upper thread and passes downward into the sewing thread hook groove (21), and under the action of the rotary shuttle (90) in the sewing machine, the upper thread end moves to the bottom of the movable knife (20); S4, the first needle (70) of the sewing machine moves upward, and when the needle (70) passes through the sewing thread hook groove (21) upward, the controller controls the thread trimming drive source (30) to run in the reverse direction, so that the movable knife (20) rotates in the direction close to the fixed knife (10), until the movable knife (20) rotates to the sewing start return knife clamping position, then the sewing thread hook groove (21) rotates with the upper thread end toward the fixed knife (10), and the upper thread end is accommodated on the surface of the movable knife (20) and clamped, and the movable knife edge (23) and the fixed knife edge (101) are not engaged; S5, the sewing machine continues to sew the set number of stitches; S6, the controller controls the thread trimming drive source (30) to continue to run in the reverse direction, so that the movable knife (20) rotates in a direction close to the fixed knife (10), until the movable knife (20) rotates to the thread trimming position, and the movable knife edge (23) and the fixed knife edge (101) are engaged to cut the upper thread end; S7, sewing machine sewing normally; S8, when the sewing machine needs to trim the thread after finishing sewing, during the process of the needle (70) of the sewing machine sewing the last stitch moving upward, the controller controls the thread trimming drive source (30) to operate, so that the movable knife (20) rotates in a direction away from the fixed knife (10), until the movable knife (20) rotates to the knife exit position after sewing, and performs thread hooking and thread separation; S9, the controller controls the thread trimming drive source (30) to run in reverse, so that the movable knife (20) rotates in a direction close to the fixed knife (10), until the movable knife (20) rotates to the thread trimming position, and then the thread dividing and hooking groove (22) rotates toward the fixed knife (10) with the upper thread and the lower thread, and the upper thread is accommodated on the surface of the movable knife (20), and the upper thread and the lower thread are cut by the engagement of the movable knife edge (23) and the fixed knife edge (101).

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