Few-nest thread trimming control method

Abstract

The invention provides a few-nest thread trimming control method, which is characterized in that a few-nest thread trimming mechanism is configured, the few-nest thread trimming mechanism comprises an auxiliary cutter, a movable cutter and a thread clamping assembly, and the movable cutter is provided with a sewing thread trimming cutting edge, a sewing thread hooking groove and an avoiding needle passing groove; in the first stitch of sewing, a machine needle penetrates through the sewing thread hooking groove, and an upper thread end on one side of the machine needle is brought to the position below the movable cutter; a first needle for starting sewing moves upwards, a movable cutter moves to enable an avoiding needle passing groove to be located under the needle, and a thread clamping assembly clamps an upper thread end; when the sewing machine starts to sew a second needle, a third needle,..., to an Nth needle, an upper thread end is cut off in the process of starting to sew the Nth needle, when the take-up-lever moves upwards to a target position A, the movable cutter moves towards the auxiliary cutter, the starting thread cutting edge and the auxiliary cutter are meshed to cut off the upper thread end, and the target position A is the non-highest point position of the take-up-lever; the take-up-lever continues to move upwards, the upper thread below the sewing material is drawn back, the bottom thread is tightened, the length of the bird nest is reduced, and few bird nests are sewn more reliably.

Description

Technical Field

[0001] The invention relates to the technical field of sewing machines, in particular to a bird's nest-less thread trimming control method. Background Art

[0002] A flat-bed sewing machine is a sewing machine that can form lock stitches. It is widely used in various sewing process scenarios and can meet the needs of sewing various fabrics. However, in the process of forming the initial lock stitch, the flat-bed sewing machine often brings the bottom thread under the sewing material and is intertwined and entangled with the bottom thread. Since the lengths of the surface threads brought down are different, the range of intertwining and entanglement underneath is different. This feature is called a bird's nest in the industry. The bird's nest formed in the initial stage of sewing is unsightly and is not accepted by everyone, especially for clothing with high sewing quality requirements. At present, there are two ways to deal with the bird's nest in the initial stage of sewing on the market.

[0003] Method 1: Manual removal, but this method greatly increases the labor intensity of workers, has high labor costs, large investment costs, wastes a lot of time, and has low efficiency.

[0004] Method 2: using a bird's nest thread trimmer to cut the upper thread end when starting to sew. However, the existing bird's nest thread trimmer is very likely to cause the upper thread to separate after cutting the thread at the beginning of the sew, resulting in failure to form good stitches subsequently and reducing sewing quality.

[0005] Therefore, the technologies and methods for removing bird nests or reducing bird nests on the market currently cannot well meet the customers' requirements for sewing quality. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a thread trimming control method with less bird nests, which can not only achieve less bird nests in seam starting, but also reliably avoid the upper thread from falling off.

[0007] To achieve the above object, the present invention provides a method for controlling a wire cutting with less bird nests, which comprises the following steps in sequence:

[0008] S1. A bird's nest thread trimming mechanism is configured, wherein the bird's nest thread trimming mechanism comprises an auxiliary knife, a movable knife capable of moving toward or away from the auxiliary knife, and a thread clamping assembly, wherein the movable knife is provided with a seam-starting thread trimming edge, a seam-starting thread hooking groove and a needle-avoiding groove both of which allow the needle of the sewing machine to pass through;

[0009] S2, before the sewing machine starts sewing the first stitch, or during the process of the sewing machine needle moving down, the movable knife moves so that the sewing thread hook groove is located directly below the sewing needle;

[0010] S3, the sewing machine's first needle moves downward, the needle passes through the sewing thread hook groove, and under the action of the rotary shuttle in the sewing machine, the upper thread end on one side of the needle is brought to the bottom of the movable knife;

[0011] S4, the sewing machine starts to sew the first needle and moves up. After the needle moves upward out of the movable knife, the movable knife moves so that the avoidance needle groove is located directly below the needle. The movable knife pulls out at least a part of the upper thread end, and at the same time, the thread clamping assembly clamps the upper thread end;

[0012] S5, the sewing machine starts sewing the second stitch, the third stitch, ..., until the Nth stitch, the needle moves up and down in the avoidance needle groove, and cuts the upper thread end during the process of sewing the Nth stitch, N≥2;

[0013] When the sewing machine starts to sew the Nth stitch, the needle moves down from the avoidance needle groove, the rotary hook hooks the thread to form a surface thread loop, and the thread take-up lever in the sewing machine moves up to start thread collection;

[0014] When the thread take-up lever moves up to the target position A, the movable knife moves toward the auxiliary knife until the seam start cutting edge engages with the auxiliary knife to cut the upper thread end. The target position A is the non-highest point position of the thread take-up lever.

[0015] S6, the thread take-up rod continues to move upward, draws back the upper thread under the sewing material, and tightens the lower thread.

[0016] Furthermore, the less-bird-nest thread trimming mechanism further comprises a fixedly arranged air suction pipe, wherein the air suction pipe has an air suction port aligned with the movable knife and / or the rotary hook;

[0017] In the step S3, the air suction port sucks air to pick up the upper thread end on one side of the needle and the lower thread end on the rotary hook;

[0018] In the step S5, the cut ends of the upper thread are collected through the suction port.

[0019] Furthermore, the movable knife is also provided with a thread trimming edge after sewing, the air suction port is arranged along the axial direction of the rotary hook in the sewing machine toward the rotary hook, and the air suction port is also arranged below the upper end of the rotary hook; the less-bird's nest thread trimming control method also includes the following steps:

[0020] S7, when the sewing is finished and the thread needs to be trimmed, the movable knife moves towards the auxiliary knife, and the movable knife brings the bottom thread and the upper thread together to the auxiliary knife until the post-sewing thread trimming edge engages with the auxiliary knife to cut the upper thread and the bottom thread;

[0021] S8, the suction port sucks air to pick up the bottom thread end on the rotary hook, so that the bottom thread end is tilted downward and located on the path of the upper thread loop.

[0022] Furthermore, the thread cutting edge at the beginning of sewing and the thread cutting edge after sewing are the same common thread cutting edge.

[0023] Furthermore, the air suction port is arranged close to the escape side of the thread loop on the rotary hook.

[0024] Furthermore, the bird's nest-less wire cutting mechanism further comprises a fixedly arranged wire pressing plate, a first wire clamping portion is arranged on the surface of the movable knife, a second wire clamping portion is arranged on the wire pressing plate, and the first wire clamping portion and the second wire clamping portion constitute a wire clamping assembly;

[0025] In the step S4, a thread clamping seam is formed between the first thread clamping portion and the second thread clamping portion, and the upper thread end is clamped in the thread clamping seam.

[0026] Furthermore, a first wire clamping portion is provided on the surface of the movable knife, a third wire clamping portion is provided on the auxiliary knife, and the first wire clamping portion and the third wire clamping portion constitute a wire clamping assembly;

[0027] In the step S4, a thread clamping seam is formed between the first thread clamping portion and the third thread clamping portion, and the upper thread end is clamped in the thread clamping seam.

[0028] Furthermore, the needle avoidance groove is an empty area formed on the outer peripheral side of the movable knife.

[0029] Furthermore, the needle avoidance groove is arranged adjacent to the seam starting and cutting edge, and the outer edge of the movable knife is provided with a transition surface distributed between the needle avoidance groove and the seam starting and cutting edge, and the transition surface is a bevel or an arc surface.

[0030] Furthermore, the movable knife is rotatably mounted below the sewing machine bottom plate, and the auxiliary knife is fixedly arranged, or movably mounted below the sewing machine bottom plate, or rotatably mounted below the sewing machine bottom plate.

[0031] As described above, the bird nest-less wire cutting control method according to the present invention has the following beneficial effects:

[0032] Before the upper thread ends are cut off at the beginning of the seam, the present application will first set the number of stitches at the beginning of the seam, and during this process, the upper thread ends are clamped by the thread clamping assembly, which reliably prevents the upper thread from being derailed. In particular, when the upper thread ends are cut off during the Nth stitch of the seam, the present application is performed at a non-highest position when the thread take-up lever is raised. In this way, after the upper thread ends are cut off, the thread take-up lever continues to rise, and the upper thread cut off under the sewing material is pulled back, and the bottom thread is also tightened together. The bird's nest length is further reduced by pulling back the upper thread, and the seam with less bird's nests is more reliably achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a structural schematic diagram of the first embodiment of the bird's nest-less wire cutting mechanism of the present application.

[0034] Figure 2a to Figure 2f It is a structural schematic diagram of multiple embodiments of the movable knife in the first embodiment of the bird's nest wire cutting mechanism.

[0035] Figure 3 It is a structural schematic diagram of the auxiliary knife in the first embodiment of the bird's nest thread cutting mechanism.

[0036] Figures 4a to 4d This is a schematic diagram of the wire cutting process of the first embodiment of the bird's nest wire cutting mechanism.

[0037] Figure 5 Schematic diagram of the connection between the first thread trimming drive source and the movable knife in the first embodiment of the bird's nest thread trimming mechanism.

[0038] Figure 6 This is a schematic diagram of the thread suction at the air suction port after thread cutting at the end of sewing in Example 1 of the bird's nest thread cutting mechanism.

[0039] Figure 7 This is a schematic diagram of the thread suction at the air suction port when the thread is being cut at the beginning of the seam according to the first embodiment of the bird's nest thread cutting mechanism.

[0040] Figure 8 This is a structural schematic diagram of the second embodiment of the bird's nest-less wire cutting mechanism of the present application, which only shows the movable knife and the auxiliary knife.

[0041] Figures 9a to 9d It is a schematic diagram of the wire cutting process of the second embodiment of the wire cutting mechanism with less bird nest.

[0042] Fig.10 This is a structural schematic diagram of the third embodiment of the bird's nest-less wire cutting mechanism of the present application.

[0043] Fig.11 This is a structural schematic diagram of the fourth embodiment of the bird's nest-less wire cutting mechanism of the present application.

[0044] Fig.12 This is a structural schematic diagram of the fifth embodiment of the bird's nest-less wire cutting mechanism of the present application.

[0045] Fig.13 It is a structural schematic diagram of the first thread trimming cam in the fifth embodiment of the bird's nest thread trimming mechanism.

[0046] Component number description

[0047] 10 Needle

[0048] 20 Hook

[0049] 30 Auxiliary knife

[0050] 31 Third clamping part

[0051] 32 Auxiliary knife thread cutting blade

[0052] 33 The second knife lifts the wings

[0053] 40 movable knife

[0054] 41 Seam hook groove

[0055] 42 Common cutting edge

[0056] 43 branch slot

[0057] 44 Thread cutting and dividing tip

[0058] 45 Avoid the needle groove

[0059] 46 Blade edge bulge

[0060] 47 Drum through hole

[0061] 48 Transition surface

[0062] 49 Seam back wire slot

[0063] 410 Seam-forming duct

[0064] 411 First clamping part

[0065] 412 The First Wing of the Blade

[0066] 50 Sewing machine base

[0067] 51 Guide chute

[0068] 61 First thread trimming drive source

[0069] 62 Thread trimmer drive shaft

[0070] 63 First Trimming Crank

[0071] 64 First thread trimmer link

[0072] 65 Moving tool holder

[0073] 70 Suction pipe

[0074] 71 Air intake

[0075] 81 Second thread trimming drive source

[0076] 82 Second trimmer crank

[0077] 83 Second thread trimmer link

[0078] 84 First return spring

[0079] 91 Thread trimmer drive motor

[0080] 92 First thread trimming cam

[0081] 921 Seam start and thread trimming drive section

[0082] 922 thread trimming drive section after sewing

[0083] 93 Second thread trimming cam

[0084] 94 First transmission shaft

[0085] 95 First drive crank

[0086] 96 Second drive crank

[0087] 97 First Roller

[0088] 98 First transmission connecting rod

[0089] 99 First Tool Holder

[0090] 910 Second drive shaft

[0091] 911 Third Drive Crank

[0092] 912 Fourth Drive Crank

[0093] 913 Second Roller

[0094] 914 Second transmission connecting rod

[0095] 915 Second tool holder

[0096] 916 Second return spring

[0097] 917 Third return spring

[0098] 110 Bottom thread DETAILED DESCRIPTION

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The present application relates to the technical field of sewing machines, and more particularly to a method for controlling thread cutting with less bird nests. Figure 1 As shown, the sewing machine is equipped with a needle 10 that can reciprocate up and down, and a rotatable shuttle 20. In the following embodiments, the axial direction of the shuttle 20 is defined as the left-right direction, the extension direction of the needle 10 is defined as the up-down direction, the direction orthogonal to both the left-right direction and the up-down direction is defined as the front-back direction, and the front direction is the moving direction of the sewing material when the sewing machine is sewing.

[0104] The bird nest-less wire cutting control method involved in the present application comprises the following steps in sequence.

[0105] Step S1, configure the bird's nest wire cutting mechanism; Figure 1 As shown, the bird's nest wire cutting mechanism includes an auxiliary knife 30, a movable knife 40 that can move toward or away from the auxiliary knife 30, and a wire clamping assembly. Figure 2a As shown, the movable knife 40 is provided with a seam start cutting edge, a seam start hooking groove 41 and a needle avoidance groove 45 for allowing the sewing machine needle 10 to pass through. Figure 3 As shown, the lower surface of the auxiliary knife 30 is provided with an auxiliary knife thread cutting blade 32. Through the movement of the movable knife 40, the seam start hook groove 41 can be moved to the right below the sewing machine needle 10, or the avoidance needle groove 45 can be moved to the right below the sewing machine needle 10, or the seam start cutting edge can be engaged with the auxiliary knife thread cutting blade 32 of the auxiliary knife 30.

[0106] Step S2, before the sewing machine starts sewing the first stitch, or during the process of the sewing machine needle 10 moving downward when sewing the first stitch, the movable knife 40 moves so that the sewing thread hook groove 41 is located directly below the needle 10.

[0107] Step S3, the sewing machine starts sewing with the first needle 10 moving down, and the needle 10 passes through the sewing thread hook groove 41, as shown in FIG. Figure 4a As shown, under the thread hooking action of the rotary shuttle 20 in the sewing machine, the upper thread end on one side of the needle 10 is brought to the bottom of the movable knife 40, that is, to the vicinity of the rotary shuttle 20.

[0108] Step S4, the sewing machine starts sewing the first needle 10 and moves up. After the needle 10 moves upward out of the movable knife 40, the movable knife 40 moves so that the needle groove 45 is located directly below the needle 10. Figure 4c As shown, the movable knife 40 pulls out at least a portion of the upper thread end, and at the same time, the thread clamping assembly clamps the upper thread end.

[0109] Step S5, the sewing machine starts to sew the second stitch, the third stitch, ..., until the Nth stitch, the needle 10 moves up and down in the avoidance needle groove 45, and cuts the upper thread end during the sewing of the Nth stitch, N ≥ 2; when the sewing machine starts to sew the Nth stitch, the needle 10 moves down from the avoidance needle groove 45, and the needle 10 pierces from the avoidance needle groove 45 without interfering with the movable knife 40; then the rotary shuttle 20 hooks the thread to form an upper thread loop, and when the upper thread loop expands to the maximum, it will pass through the bottom of the shuttle case of the rotary shuttle 20, and then the thread take-up rod in the sewing machine moves up to start winding the thread, and the upper thread loop below gradually shrinks, and the upper thread is gradually lifted out of the track of the rotary shuttle 20; when the thread take-up rod moves up to the target position A, the target position A is the non-highest point position of the thread take-up rod, and the movable knife 40 moves in the direction close to the auxiliary knife 30, such as Figure 4d As shown, until the seam starting cutting edge engages with the auxiliary knife 30, the upper thread ends are cut off, thereby preventing the upper thread ends from being entangled to form a bird's nest.

[0110] Step S6, since the target position A is not the highest point of the thread take-up rod, after the upper thread end is cut off, the thread take-up rod continues to move upward to pull back the upper thread cut off under the sewing material, and at the same time tightens the bottom thread together, and further reduces the length of the bird's nest by pulling back the upper thread.

[0111] Therefore, before the upper thread ends are cut off at the beginning of the seam, the present application will first set the number of stitches at the beginning of the seam, and during this process, the upper thread ends are clamped by the thread clamping assembly, which reliably prevents the upper thread from being derailed. In particular, when the upper thread ends are cut off during the Nth stitch of the seam, the present application is performed at a non-highest position when the thread take-up lever is raised. In this way, after the upper thread ends are cut off, the thread take-up lever continues to rise, and the upper thread that has been cut off under the sewing material is pulled back, and the bottom thread is also tightened together. The bird's nest length is further reduced by pulling back the upper thread, and the seam with less bird's nests is more reliably achieved.

[0112] The following provides multiple embodiments of a less-bird-nest wire trimming mechanism.

[0113] Less-bird's-nest thread-cutting mechanism embodiment 1

[0114] like Figure 1 As shown, in the first embodiment of the less-bird's nest thread trimming mechanism, along the radial direction of the rotary hook 20, the movable knife 40 and the auxiliary knife 30 are distributed inside and outside, that is, the movable knife 40 is distributed on the lower side of the auxiliary knife 30. Figure 2a As shown, the movable knife 40 is also provided with a post-sewing thread cutting edge, and the thread cutting edge for starting the seam and the thread cutting edge for finishing the seam are the same common thread cutting edge 42, and the thread hooking groove 41 for starting the seam is distributed on the side of the common thread cutting edge 42 facing the auxiliary knife 30. When the sewing machine starts sewing, the common thread cutting edge 42 engages with the auxiliary knife 30 to cut the upper thread end; when the sewing machine finishes sewing, the common thread cutting edge 42 engages with the auxiliary knife 30 to cut the upper thread and the lower thread, thereby reliably realizing the automatic thread cutting at the beginning of the seam and the end of sewing. In addition, the present application sets the thread cutting edge for starting the seam and the thread cutting edge for finishing the seam as the same common thread cutting edge 42, which has a simple structure and is easy to implement. There is no need to additionally process the thread cutting edge on the existing movable knife, which can reduce the modification of the movable knife in the existing sewing machine, reduce the modification cost, and has strong versatility.

[0115] Furthermore, the first embodiment of the bird's nest thread trimming mechanism is a single movable knife and single fixed knife structure, that is, the movable knife 40 is rotatably mounted below the sewing machine bottom plate 50, and the rear end of the auxiliary knife 30 is fixed to the bottom of the sewing machine bottom plate 50 by screws, and the movable knife 40 is rotated forward and backward to achieve the movable knife 40 close to or away from the auxiliary knife 30. In the initial state, the movable knife 40 and the auxiliary knife 30 are distributed on both sides of the needle 10, the movable knife 40 is distributed on the front side of the needle 10, and the auxiliary knife 30 is distributed on the rear side of the needle 10.

[0116] Furthermore, if Figure 5 As shown, the first embodiment of the bird's nest thread trimming mechanism also includes a first thread trimming drive source 61, a thread trimming drive shaft 62 rotatably supported in the sewing machine base plate 50, a first thread trimming crank 63 fixed on the thread trimming drive shaft 62, a first thread trimming connecting rod 64, and a movable knife frame 65 rotatably supported in the sewing machine base plate 50. The first thread trimming drive source 61 is a motor, preferably a stepping motor. The first thread trimming drive source 61 is connected to the thread trimming drive shaft 62 to drive the thread trimming drive shaft 62 to rotate; the two ends of the first thread trimming connecting rod 64 are respectively hinged to the first thread trimming crank 63 and the movable knife frame 65, and the right end portion of the movable knife 40 is fixed to the movable knife frame 65 by screws, and two fixing holes are provided in the right end portion of the movable knife 40. When the first thread trimming drive source 61 drives the thread trimming drive shaft 62 to rotate, the first thread trimming crank 63 rotates together with the thread trimming drive shaft 62, and drives the movable knife holder 65 to rotate forward and backward through the first thread trimming connecting rod 64, and the movable knife 40 rotates forward and backward together with the movable knife holder 65, thereby driving the movable knife 40 to rotate backward to approach the auxiliary knife 30, or rotate forward to move away from the auxiliary knife 30.

[0117] Furthermore, based on the auxiliary knife 30 being arranged at the rear side of the movable knife 40, the seam hooking groove 41 is arranged at the rear side of the common thread cutting edge 42. Preferably, the movable knife 40 is an arc knife body, and the extension trajectory of the arc knife body is substantially consistent with the rotation trajectory of the movable knife 40. Figure 2a or Figure 2b As shown, the movable knife 40 is provided with a wire dividing groove 43 and a wire cutting dividing tip 44, the common wire cutting edge 42 and the wire cutting dividing tip 44 are respectively arranged at the front side and the rear side of the movable knife 40, and the wire dividing groove 43 is distributed between the common wire cutting edge 42 and the wire cutting dividing tip 44. When the thread is cut after sewing, the wire cutting dividing tip 44 and the wire dividing groove 43 work together to separate the bottom thread and the top thread.

[0118] Furthermore, there are many ways to set the seam starting and hooking groove 41 and the needle avoiding groove 45 on the movable knife 40, so that the movable knife 40 has multiple embodiments.

[0119] The movable knife 40 embodiment 1, as Figure 2a As shown, the movable knife 40 is provided with a protruding edge bulge 46 at the common thread cutting edge 42, and a bulge through hole 47 is provided in the edge bulge 46, which is a circular hole structure, and the front edge of the bulge through hole 47 constitutes the common thread cutting edge 42, and the bulge through hole 47 constitutes the seam starting hook groove 41. The avoidance needle groove 45 is an empty area formed on the front edge side of the movable knife 40, and the avoidance needle groove 45 is arranged adjacent to the seam starting hook groove 41. Preferably, the outer edge of the movable knife 40 is provided with a transition surface 48 distributed between the avoidance needle groove 45 and the common thread cutting edge 42, and the transition surface 48 is an inclined surface or an arc surface, and the transition surface 48 is smoothly transitioned and connected with the outer edge of the surrounding movable knife 40. After sewing and thread cutting are completed, the movable knife 40 rotates forward to reset, and during this process, the transition surface 48 will gently leave the bottom line aside to prevent the bottom line from being pulled. Along the circumference of the movable knife 40, the needle groove 45, the common thread cutting edge 42, the sewing thread hook groove 41 and the thread dividing groove 43 are distributed on the same circumference of the movable knife 40 and are distributed in sequence from front to back. In addition, a post-sewing thread accommodating groove 49 is provided on the upper surface of the movable knife 40, and the front and rear ends of the post-sewing thread accommodating groove 49 are respectively connected between the common thread cutting edge 42 and the thread dividing groove 43, and the post-sewing thread accommodating groove 49 is used to accommodate the upper thread and the lower thread when the thread is trimmed after sewing.

[0120] The movable knife 40 embodiment 2, as Figure 2bAs shown, the starting seam hook groove 41 is arranged away from the common thread cutting edge 42. The common thread cutting edge 42 is close to the front side of the movable knife 40, the starting seam hook groove 41 is close to the rear side of the movable knife 40, and the thread dividing groove 43 is distributed between the common thread cutting edge 42 and the starting seam hook groove 41. The movable knife 40 is provided with a protruding edge bulge 46 at the common thread cutting edge 42, and a through hole 47 penetrating up and down is formed in the edge bulge 46. The front edge of the through hole 47 constitutes the common thread cutting edge 42. The needle passing avoidance groove 45 is an empty area formed on the front edge side of the movable knife 40. Preferably, a starting seam thread accommodating groove 410 and a post-sewing thread accommodating groove 49 are formed on the upper surface of the movable knife 40. The front and rear ends of the starting seam thread accommodating groove 410 are connected between the common thread cutting edge 42 and the starting seam hook groove 41, and the front and rear ends of the post-sewing thread accommodating groove 49 are respectively connected between the common thread cutting edge 42 and the thread dividing groove 43. Since the common thread cutting edge 42, the thread dividing groove 43 and the starting seam hook groove 41 are arranged in sequence from front to back, the post-sewing thread accommodating groove 49 is a part of the starting seam thread accommodating groove 410. In the second embodiment of the movable knife 40, since the starting seam hook groove 41 is arranged away from the common thread cutting edge 42, during the process of cutting the thread end of the starting seam cross-section line, more thread ends of the surface thread can be drawn out to the upper surface of the movable knife 40, and these thread ends of the surface thread are accommodated in the starting seam thread accommodating groove 410.

[0121] The third embodiment of the movable knife 40, the difference from the first embodiment of the movable knife 40 is only that: as Figure 2c shown, the starting seam hook groove 41 is distributed between the through hole 47 of the bulge and the thread dividing groove 43. The starting seam hook groove 41 is arranged adjacent to the through hole 47 of the bulge. The starting seam hook groove 41 is a through groove penetrating up and down and is a closed groove structure. The starting seam hook groove 41 is not communicated with the through hole 47 of the bulge, and the starting seam hook groove 41 is a kidney-shaped hole extending in the front and rear directions.

[0122] The fourth embodiment of the movable knife 40, the difference from the third embodiment of the movable knife 40 is only that: as Figure 2d shown, the front end of the starting seam hook groove 41 extends forward to the rear end of the through hole 47 of the bulge, that is, the starting seam hook groove 41 is communicated with the through hole 47 of the bulge, and the two are combined into an integral structure.

[0123] The fifth embodiment of the movable knife 40, the difference from the third embodiment of the movable knife 40 is only that: as Figure 2e shown, the starting seam hook groove 41 is an open groove structure with an opening on the left side, and the left end of the starting seam hook groove 41 extends leftward to the left edge of the movable knife 40.

[0124] The sixth embodiment of the movable knife 40, the difference from the third embodiment of the movable knife 40 is only that: as Figure 2f shown, the starting seam hook groove 41 is a round hole.

[0125] Furthermore, in the six embodiments of the movable knife 40 described above, a first knife-lifting wing 412 extending backward is integrally provided on the right end side of the rear edge of the movable knife 40, which is used to lift the auxiliary knife 30 so that the movable knife 40 and the auxiliary knife 30 can better engage with each other. Of course, on the premise of ensuring that the movable knife 40 and the auxiliary knife 30 engage well, the first knife-lifting wing 412 may not be provided on the movable knife 40. Preferably, a second knife-lifting wing 33 is integrally provided on the side of the auxiliary knife 30, which is used to abut the movable knife 40 so that the movable knife 40 and the auxiliary knife 30 can better engage with each other. Of course, on the premise of ensuring that the movable knife 40 and the auxiliary knife 30 engage well, the second knife-lifting wing 33 may not be provided on the auxiliary knife 30.

[0126] Furthermore, the wire clamping assembly preferably has the following two modes.

[0127] Method 1: clamping the end of the upper thread by the movable knife 40 and the additionally arranged thread pressing plate. Based on this, the first embodiment of the bird's nest thread trimming mechanism also includes a fixedly arranged thread pressing plate; along the radial direction of the rotary hook 20, the thread pressing plate, the auxiliary knife 30 and the movable knife 40 are distributed in sequence from the outside to the inside; the upper surface of the movable knife 40 is provided with a first thread clamping portion 411, and the thread pressing plate is provided with a second thread clamping portion, and the first thread clamping portion 411 and the second thread clamping portion constitute a thread clamping assembly. In the above step S4, when the movable knife 40 moves to avoid the needle groove 45 and is located directly below the machine needle 10, a thread clamping seam for clamping the end of the upper thread is formed between the first thread clamping portion 411 and the second thread clamping portion. Preferably, the thread pressing plate can be fixed on the auxiliary knife 30, or it can be directly fixed on the bottom of the sewing machine bottom plate 50.

[0128] Method 2: clamp the upper thread end by the movable knife 40 and the auxiliary knife 30. Figure 3 and Figure 4c As shown, the upper surface of the movable knife 40 is provided with a first thread clamping portion 411, the lower surface of the auxiliary knife 30 is provided with a third thread clamping portion 31, the auxiliary knife thread cutting edge 32 of the auxiliary knife 30 is distributed on the rear side of the third thread clamping portion 31, and the first thread clamping portion 411 and the third thread clamping portion 31 constitute a thread clamping assembly. In the above step S4, when the movable knife 40 moves to avoid the needle groove 45 and is located directly below the machine needle 10, a thread clamping seam for clamping the upper thread end is formed between the first thread clamping portion 411 and the third thread clamping portion 31.

[0129] Furthermore, if Figure 1As shown, the first embodiment of the bird's nest thread trimming mechanism includes an air suction device, which includes an air source and an air suction pipe 70; the air source is installed on a fixed frame, or can be installed on the bottom plate of the sewing machine, or can be directly placed on the ground; one end of the air suction pipe 70 is connected to the air source, and the other end of the air suction pipe 70 is an air suction port 71, and the air suction port 71 is aligned with the movable knife 40 and / or the rotary shuttle 20. In the above step S3, the air suction port 71 sucks air to pick up the upper thread end on one side of the needle 10 and the lower thread end 110 on the rotary shuttle 20, so as to pre-capture the upper thread end and the lower thread end 110 when the upper thread end is cut off at the beginning of sewing. In the above step S5, the cut upper thread end is collected through the air suction port 71, so as to realize automatic collection after the upper thread end is cut off.

[0130] Furthermore, in this embodiment, if Figure 1 As shown, the air suction port 71 is arranged along the axial direction of the rotary hook 20 in the sewing machine toward the rotary hook 20, that is, the air suction port 71 is arranged on the left end side of the rotary hook 20, and the air suction port 71 is also arranged below the upper end of the rotary hook 20. Based on this, the less-bird nest thread trimming control method also includes the following steps:

[0131] Step S7, when the sewing is finished and the thread needs to be trimmed, the movable knife 40 moves towards the auxiliary knife 30, and the movable knife 40 brings the bottom thread and the upper thread together and approaches the auxiliary knife 30 until the thread trimming edge after sewing engages with the auxiliary knife 30, and the upper thread and the bottom thread are cut;

[0132] Step S8, the air suction port 71 sucks air to pick up the bottom thread end 110 on the rotary hook 20, so that the bottom thread end 110 is tilted downward and located on the path of the upper thread loop.

[0133] Preferably, the suction port 71 is arranged close to the escape side of the upper thread loop of the rotary hook 20, that is, in the front-to-back direction, the suction port 71 is close to the front side of the rotary hook 20, which is more conducive to the upper thread loop winding the lower thread.

[0134] The following describes the working principle of the less-bird's nest thread trimming mechanism embodiment 1 by taking the less-bird's nest thread trimming mechanism embodiment 1 configured with the movable knife 40 embodiment 1, the movable knife 40 and the auxiliary knife 30 cooperating to clamp the surface thread end, and the air suction port 71 being arranged on the left end side of the rotary hook 20 as an example.

[0135] 1.1. Before or at the same time as the first stitch is sewn, the movable knife 40 rotates backwards so that the thread hooking groove 41 is located directly below the needle 10; then, when the first stitch is sewn, the needle 10 moves downwards and the upper thread passes through the thread hooking groove 41 downwards. Figure 4aAs shown in FIG. 1 , under the thread hooking action of the rotary hook 20, the upper thread end on the side of the needle 10 is brought to the bottom of the movable knife 40, that is, to the vicinity of the rotary hook 20. In this process, the electronic thread clamp on the sewing machine can be turned on to more reliably bring the upper thread end on the side of the needle 10 to the bottom of the movable knife 40. At the same time, the air source is turned on, and the air suction port 71 of the suction device sucks the upper thread end and the lower thread end 110, as shown in FIG. Figure 4b in particular, the time point at which the suction device provides suction power shall not be later than the time when the hook 20 hooks the thread and brings the upper thread end to the bobbin case.

[0136] 1.2. The needle 10 starts sewing the first stitch. The needle 10 moves upward. After the needle 10 moves upward out of the sewing thread hook groove 41, the movable knife 40 rotates backward toward the auxiliary knife 30. Figure 4c As shown, until the first thread clamping part 411 of the movable knife 40 just contacts with the third thread clamping part 31 of the auxiliary knife 30, the two press and clamp the surface thread end, and at the same time, the avoidance needle groove 45 of the movable knife 40 is located directly below the machine needle 10.

[0137] 1.3. The sewing machine continues to sew the second and third stitches, and cuts the upper thread end in the process of forming a thread loop when the Nth stitch is set, where N ≥ 2. For example: the upper thread end is cut in the process of forming a thread loop when the second stitch is sewn, and the needle 10 for the second stitch moves down, and the needle 10 pierces through the needle groove 45 without interfering with the movable knife 40; then the rotary shuttle 20 hooks the thread to form an upper thread loop, and when the upper thread loop expands to its maximum, it will pass through the bottom of the shuttle case of the rotary shuttle 20, at which time the upper thread loop will come into contact with the upper thread end sucked by the air suction port 71; then the thread take-up rod begins to reel in the thread, and the upper thread loop at the bottom gradually shrinks, gradually lifting the upper thread out of the track of the rotary shuttle 20. When the thread take-up rod rises back to its non-highest point target position A, the movable knife 40 continues to rotate backward in the direction close to the auxiliary knife 30, such as Figure 4d As shown, until the common thread cutting edge 42 engages with the auxiliary knife 30, the upper thread ends are cut off, thereby preventing the upper thread ends from entangled to form a bird's nest, and the cut upper thread ends are sucked away by the suction port 71. After that, the thread take-up rod continues to rise, and the upper thread that has been cut off under the sewing material is pulled back, and the bottom thread is also tightened together, and the length of the bird's nest is further reduced by pulling back the upper thread. The specific process of cutting the upper thread ends in the process of forming the thread loop at the beginning of sewing is adjusted according to the achieved effect.

[0138] 1.4. After the seam start and thread cutting are completed, the movable knife 40 rotates forward away from the auxiliary knife 30 until it is reset; during this process, the bottom line passes through the transition surface 48 of the movable knife 40 without affecting the position and thread tension of the bottom line; the air source is closed, and the air suction port 71 stops sucking air.

[0139] 1.5. The sewing machine performs normal sewing.

[0140] 1.6. When the sewing is finished and the thread needs to be trimmed, the movable knife 40 rotates backward, and the trimming and dividing tip 44 first passes through the upper thread loop; as the movable knife 40 continues to rotate backward, the lower thread and the upper thread on the side to be trimmed slide into the dividing groove 43, and then the lower thread and the upper thread are accommodated in the post-sewing groove 49; when the common trimming edge 42 engages with the auxiliary knife 30, the upper thread and the lower thread are cut. After that, the movable knife 40 rotates forward until it is reset.

[0141] 1.7. The air source is turned on, and the air suction port 71 of the air suction device sucks the bottom thread end 110, causing the bottom thread end 110 to tilt to the lower left, as shown in FIG. Figure 6 As shown. In this way, when starting to sew next time, the lower thread end 110 tilted to the lower left is located on the path of the upper thread loop, which helps to bring up the bottom thread at the beginning of sewing and reduces the probability of not being able to bring up the bottom thread when starting to sew. In addition, when starting to sew, the air source is also in an open state, which makes it easy to suck the bottom thread end 110. The direction in which the bottom thread end 110 is sucked when starting to sew is consistent with the direction in which it is sucked after the thread is trimmed at the end of sewing. When the upper thread loop passes through this place, it is definitely easier to entangle the bottom thread, as shown in FIG. Figure 7 As shown, it helps to start sewing with the bottom thread.

[0142] In summary, the first embodiment of the thread cutting mechanism with fewer bird's nests has a simple structure, can reduce the length of the bird's nest and improve the sewing quality; it has a simple structure, low cost, strong durability, and does not occupy sewing space; it has strong versatility and can be well applied to the existing thread cutting structures on the market, so that they can achieve the effect of fewer bird's nests after modification; at the same time, it can also greatly reduce the probability of the seam starting belt not being able to raise the bottom line.

[0143] Example 2 of the less-bird-nest thread trimming mechanism

[0144] The difference between the second embodiment of the less-bird's-nest wire-cutting mechanism and the first embodiment of the less-bird's-nest wire-cutting mechanism is that: Figure 8 As shown, in the initial state, the movable knife 40 and the auxiliary knife 30 are distributed on the same side of the needle 10, which is the rear side in this embodiment, and the movable knife 40 and the auxiliary knife 30 are in a bite state. Therefore, the working principle of the second embodiment of the less-bird's nest thread trimming mechanism is described as follows.

[0145] 2.1. Before or at the same time as the first stitch is sewn, the movable knife 40 rotates forward. Figure 9a As shown, the thread hooking groove 41 is located directly below the needle 10; then, when the first stitch of the sewing needle 10 moves downward, the needle 10 carries the upper thread downward through the thread hooking groove 41, and under the thread hooking action of the rotary hook 20, the upper thread end on one side of the needle 10 is brought to the vicinity of the rotary hook 20. At the same time, the air source is turned on, and the air suction port 71 of the suction device sucks the upper thread end and the lower thread end 110.

[0146] 2.2, the machine needle 10 starts sewing the first stitch. The machine needle 10 moves upward. After the machine needle 10 moves upward out of the sewing thread hook groove 41, the movable knife 40 rotates backward toward the auxiliary knife 30. Figure 9b As shown, until the first thread clamping part 411 of the movable knife 40 just contacts the third thread clamping part 31 of the auxiliary knife 30, the two press and clamp the upper thread end, and at the same time, the needle avoidance groove 45 of the movable knife 40 is located directly below the needle 10. In addition, the time point when the movable knife 40 rotates backward toward the auxiliary knife 30 shall not be later than the time point when the needle 10 moves down to this position when the second stitch is sewn, so as to ensure that the needle 10 can pierce in the needle avoidance groove 45 when the second stitch is sewn.

[0147] 2.3. The sewing machine continues to sew the second and third stitches, and cuts the upper thread end during the process of forming a thread loop at the set Nth stitch, where N≥2; the specific process is the same as step 1.3 in the above-mentioned embodiment 1 of the less-bird's nest thread cutting mechanism.

[0148] 2.4. After the seam cutting is completed, the movable knife 40 is at its initial position; at the same time, the air source is closed and the air suction port 71 stops sucking air.

[0149] 2.5. The sewing machine performs normal sewing.

[0150] 2.6. Before the thread needs to be trimmed after sewing, and when the needle 10 is above the needle plate of the sewing machine, the movable knife 40 rotates forward away from the auxiliary knife 30, such as Fig.9c As shown, the movable knife 40 is rotated to the front side of the needle 10, waiting for the thread trimming after sewing. After that, when the sewing is finished and the thread needs to be trimmed, the movable knife 40 rotates backwards towards the auxiliary knife 30, and the thread trimming tip 44 first passes through the upper thread loop, and then the lower thread and the upper thread on the side to be trimmed slide into the thread dividing groove 43 and are accommodated in the thread accommodating groove 49 after sewing; when the common thread trimming edge 42 is engaged with the auxiliary knife 30, as shown in FIG. Figure 9d As shown, the upper thread and the lower thread are cut. After the thread cutting is completed after the seam, the movable knife 40 is also in its initial position, and the movable knife 40 does not need to be reset and remains in this position.

[0151] Example 3 of the less-bird-nest thread trimming mechanism

[0152] The difference between the third embodiment of the less-bird's nest thread trimming mechanism and the first embodiment of the less-bird's nest thread trimming mechanism is that the auxiliary knife 30 is assembled under the sewing machine bottom plate 50 so as to be movable forward and backward. Fig.10 As shown, the bird's nest thread trimming mechanism further includes a second thread trimming drive source 81, which is transmission-connected to the auxiliary knife 30 to drive the auxiliary knife 30 to translate forward and backward.

[0153] Furthermore, the second thread trimming drive source 81 is a motor, preferably a stepping motor, which is fixed on the bottom surface of the sewing machine bottom plate 50 and connected to the rear end of the auxiliary knife 30 through a drive transmission mechanism. In this embodiment, the drive transmission mechanism adopts a crank connecting rod mechanism; based on this, Fig.10 As shown, the third embodiment of the little bird's nest thread trimming mechanism also includes a second thread trimming crank 82 fixed on the motor shaft of the second thread trimming drive source 81, and a second thread trimming connecting rod 83. The two ends of the second thread trimming connecting rod 83 are respectively hinged with the second thread trimming crank 82 and the auxiliary knife 30. The second thread trimming drive source 81 drives the auxiliary knife 30 to move forward or backward through the second thread trimming crank 82 and the second thread trimming connecting rod 83. In other embodiments, the second thread trimming drive source 81 and the auxiliary knife 30 can also be connected through a gear mechanism or a synchronous pulley mechanism, and the second thread trimming drive source 81 can also be fixed on the housing of the sewing machine, or on the table, or on the oil pan.

[0154] Preferably, if Fig.10 As shown, a guide slot 51 extending straightly forward and backward is provided at the bottom of the sewing machine base plate 50, and the auxiliary knife 30 is movably assembled in the guide slot 51. Through the sliding guide cooperation of the two, the stability of the auxiliary knife 30 moving forward and backward is improved.

[0155] The working principle of the third embodiment of the less-bird's nest thread trimming mechanism is described as follows.

[0156] 3.1. Before or at the same time as the first stitch, the movable knife 40 rotates backwards to make the thread hooking groove 41 located directly below the needle 10; after that, when the first stitch is moved downwards, the needle 10 carries the upper thread downwards through the thread hooking groove 41, and under the thread hooking action of the rotary hook 20, the upper thread end on one side of the needle 10 is brought to the vicinity of the rotary hook 20. At the same time, the air source is turned on, and the air suction port 71 of the suction device sucks the upper thread end and the lower thread end 110.

[0157] 3.2. The needle 10 moves up when starting to sew the first stitch. After the needle 10 moves upward out of the sewing thread hook groove 41, the movable knife 40 rotates backward toward the auxiliary knife 30. The auxiliary knife 30 can remain stationary or move forward horizontally until the first thread clamping part 411 of the movable knife 40 just contacts the third thread clamping part 31 of the auxiliary knife 30, thereby achieving the effect of clamping the upper thread end; at the same time, the avoidance needle groove 45 of the movable knife 40 is located directly below the needle 10.

[0158] 3.3. The sewing machine continues to sew the second and third stitches, and cuts off the upper thread in the process of forming a thread loop at the set Nth stitch, N≥2; the specific process is the same as step 1.3 in the above-mentioned embodiment 1 of the less-bird's nest thread cutting mechanism. However, in this embodiment, when cutting off the upper thread, the movable knife 40 remains stationary and the auxiliary knife 30 moves forward; or, the movable knife 40 rotates backward and the auxiliary knife 30 remains stationary; or, the movable knife 40 rotates backward and the auxiliary knife 30 moves forward, so as to achieve the effect of the shared thread cutting edge 42 and the auxiliary knife 30 engaging and cutting off the upper thread.

[0159] 3.4. After the seam cutting is completed, the movable knife 40 and the auxiliary knife 30 are reset respectively; the air source is closed, and the air suction port 71 stops sucking air.

[0160] 3.5. The sewing machine performs normal sewing.

[0161] 3.6. When the sewing is finished and the thread needs to be trimmed, the movable knife 40 rotates backward, and the trimming thread dividing tip 44 first passes through the upper thread loop; as the movable knife 40 continues to rotate backward, the lower thread and upper thread on the side to be trimmed slide into the thread dividing groove 43, and then the lower thread and upper thread are accommodated in the post-sewing thread accommodating groove 49; the auxiliary knife 30 can remain stationary or move forward horizontally until the shared trimming edge 42 engages with the auxiliary knife 30, and finally the upper thread and lower thread are trimmed. Afterwards, the movable knife 40 and the auxiliary knife 30 are reset.

[0162] 3.7. The air source is turned on, and the air suction port 71 of the air suction device sucks the bottom thread end 110, causing the bottom thread end 110 to tilt to the lower left.

[0163] Example 4 of the less-bird-nest thread-cutting mechanism

[0164] The difference between the fourth embodiment of the less-bird's nest thread trimming mechanism and the third embodiment of the less-bird's nest thread trimming mechanism is that the type of the second thread trimming drive source 81 and the connection structure between the second thread trimming drive source 81 and the auxiliary knife 30 are different. Specifically, in the fourth embodiment of the less-bird's nest thread trimming mechanism, Fig.11 As shown, the second thread trimming drive source 81 is a cylinder or an electromagnet, which is fixed on the bottom surface of the sewing machine base plate 50; the rear end of the auxiliary knife 30 is directly installed on the end of the piston rod of the cylinder or the end of the iron core of the electromagnet, and the auxiliary knife 30 is directly driven forward or backward by the cylinder or the electromagnet, eliminating the need to directly set a drive transmission mechanism between the second thread trimming drive source 81 and the auxiliary knife 30.

[0165] In addition, when the second thread trimming driving source 81 is an electromagnet, as shown in FIG. Fig.11 As shown, a first reset spring 84 is sleeved on the iron core of the electromagnet, and two ends of the reset spring are respectively in contact with the shell and the iron core of the electromagnet for resetting the iron core.

[0166] The working principle of the fourth embodiment of the wire trimming mechanism with few bird nests is the same as the working principle of the third embodiment of the wire trimming mechanism with few bird nests, and will not be repeated here.

[0167] Example 5 of the less-bird-nest thread trimming mechanism

[0168] The difference between the fifth embodiment of the less-bird's nest thread trimming mechanism and the first embodiment of the less-bird's nest thread trimming mechanism is that the movable knife 40 and the auxiliary knife 30 are both rotatably mounted below the sewing machine bottom plate 50. Based on this, Fig.12 As shown, the fifth embodiment of the bird's nest thread trimming mechanism also includes a thread trimming drive motor 91, a first thread trimming cam 92, a second thread trimming cam 93, a first transmission mechanism, and a second transmission mechanism; the thread trimming drive motor 91 is fixed on the bottom plate, or the casing, or the oil pan of the sewing machine; the first thread trimming cam 92 and the second thread trimming cam 93 are both fixed on the motor shaft of the thread trimming drive motor 91, and the first thread trimming cam 92 and the second thread trimming cam 93 can be two separate cam components or can be combined into the same cam component; the first thread trimming cam 92 is connected to the movable knife 40 through the first transmission mechanism, and the second thread trimming cam 93 is connected to the auxiliary knife 30 through the second transmission mechanism.

[0169] like Fig.13 As shown, the outer peripheral surface of the first thread trimming cam 92 is provided with a thread trimming drive section 921 for starting stitching and a thread trimming drive section 922 for finishing stitching; when the sewing machine starts stitching, the thread trimming drive section 921 for starting stitching acts on the first transmission mechanism for controlling the thread trimming at the beginning of stitching; when the sewing machine finishes sewing, the thread trimming drive section 922 for finishing stitching acts on the first transmission mechanism for controlling the normal thread trimming at the end of sewing. In addition, when the thread trimming drive section 921 for starting stitching of the first thread trimming cam 92 acts on the first transmission mechanism, there is no power transmission between the second thread trimming cam 93 and the second transmission mechanism; when the thread trimming drive section 922 for finishing stitching of the first thread trimming cam 92 acts on the first transmission mechanism, there is power transmission between the second thread trimming cam 93 and the second transmission mechanism.

[0170] Furthermore, if Fig.12 As shown, the first transmission mechanism includes a first transmission shaft 94 rotatably supported in the sewing machine base plate 50, a first transmission crank 95 and a second transmission crank 96 respectively fixed at both ends of the first transmission shaft 94, a first roller 97 rotatably mounted on the outer end of the first transmission crank 95, a first transmission connecting rod 98, and a first tool holder 99, the first roller 97 is abutted against the outer peripheral surface of the first thread trimming cam 92, the two ends of the first transmission connecting rod 98 are respectively hinged to the second transmission crank 96 and the first tool holder 99, and the movable knife 40 is fixed on the first tool holder 99.

[0171] Furthermore, if Fig.12As shown, the second transmission mechanism includes a second transmission shaft 910 rotatably supported in the sewing machine base plate 50, a third transmission crank 911 and a fourth transmission crank 912 respectively fixed at both ends of the second transmission shaft 910, a second roller 913 rotatably mounted on the outer end of the second transmission crank 96, a second transmission connecting rod 914, and a second tool holder 915, the second roller 913 is abutted against the outer peripheral surface of the second thread cutting cam 93, the two ends of the second transmission connecting rod 914 are respectively hinged to the fourth transmission crank 912 and the second tool holder 915, and the auxiliary knife 30 is fixed on the second tool holder 915.

[0172] Preferably, the first transmission mechanism further includes a second return spring 916, which is sleeved on the first transmission shaft 94, one end of which is fixed, and the other end acts on the second transmission crank 96 to reset the movable knife 40. The second transmission mechanism further includes a third return spring 917, which is sleeved on the second transmission shaft 910, one end of which is fixed, and the other end acts on the fourth transmission crank 912 to assist in resetting the knife 30.

[0173] The working principle of the fifth embodiment of the less-bird's nest thread trimming mechanism is described as follows.

[0174] 4.1. Before or at the same time as the first stitch, the thread trimming drive motor 91 drives the first thread trimming cam 92 and the second thread trimming cam 93 to rotate, and the thread trimming drive section 921 of the first thread trimming cam 92 contacts and cooperates with the first roller 97, and drives the movable knife 40 to rotate backward through the first transmission mechanism, so that the thread hooking groove 41 for sewing is located directly below the needle 10; while the second thread trimming cam 93 is separated from the second roller 913, or the equal-diameter surface of the outer periphery of the second thread trimming cam 93 contacts and cooperates with the second roller 913, the second transmission mechanism does not move, and the auxiliary knife 30 remains stationary. Afterwards, when the needle 10 for sewing the first stitch moves downward, the needle 10 carries the upper thread downward through the thread hooking groove 41, and under the thread hooking action of the rotary hook 20, the upper thread end on one side of the needle 10 is brought to the vicinity of the rotary hook 20. At the same time, the air source is turned on, and the air suction port 71 of the suction device sucks the upper thread end and the lower thread end 110.

[0175] 4.2. The first stitch needle 10 moves up when sewing. After the needle 10 moves upward out of the sewing thread hook groove 41, the thread trimming drive motor 91 continues to drive the first thread trimming cam 92 and the second thread trimming cam 93 to rotate. The sewing thread trimming drive section 921 of the first thread trimming cam 92 continues to push the first roller 97, driving the movable knife 40 to continue to rotate backward, while the auxiliary knife 30 remains stationary until the first thread clamping part 411 of the movable knife 40 just contacts with the third thread clamping part 31 of the auxiliary knife 30, thereby achieving the effect of clamping the upper thread end; at the same time, the avoidance needle groove 45 of the movable knife 40 is located directly below the needle 10.

[0176] 4.3. The sewing machine continues to sew the second and third stitches, and cuts the thread end of the upper thread during the process of forming a thread loop at the set Nth stitch of starting sewing, where N≥2; the specific process is the same as step 1.3 in Embodiment 1 of the less-nest thread cutting mechanism above. However, when cutting the thread end of the upper thread, the movable knife 40 continues to rotate backward, and the auxiliary knife 30 remains stationary.

[0177] 4.4. After the starting-sewing thread cutting is completed, the movable knife 40 resets; the air source is closed, and the suction port 71 of the suction device stops sucking.

[0178] 4.5. The sewing machine performs normal sewing.

[0179] 4.6. When thread cutting is required at the end of sewing, the thread cutting drive motor 91 drives the first thread cutting cam 92 and the second thread cutting cam 93 to rotate. The post-sewing thread cutting drive section 922 of the first thread cutting cam 92 contacts and cooperates with the first roller 97, and drives the movable knife 40 to rotate backward through the first transmission mechanism; at the same time, the variable diameter section of the second thread cutting cam 93 contacts and cooperates with the second roller 913, and drives the auxiliary knife 30 to rotate forward through the second transmission mechanism; as the movable knife 40 rotates backward, first the thread cutting and thread separating tip 44 passes through the upper thread loop, then the bottom thread and the upper thread on the cut side slide into the thread groove 43 and are accommodated in the post-sewing thread groove 49, and finally the common thread cutting edge 42 bites with the auxiliary knife 30 to cut the upper thread and the bottom thread. After that, the movable knife 40 and the auxiliary knife 30 reset respectively.

[0180] 4.7. The air source is turned on, and the suction port 71 of the suction device sucks the bottom thread end 110, making the bottom thread end 110 tilt towards the lower left.

[0181] In summary, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0182] The above embodiments only illustratively explain the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for controlling wire cutting with less bird nests, Features: The following steps are included in sequence: S1. A bird's nest thread trimming mechanism is provided, wherein the bird's nest thread trimming mechanism comprises an auxiliary knife (30), a movable knife (40) capable of moving toward or away from the auxiliary knife (30), and a thread clamping assembly, wherein the movable knife (40) is provided with a seam-starting thread trimming edge, a seam-starting thread hooking groove (41) and a needle-avoiding groove (45) both of which allow a sewing machine needle (10) to pass through; S2, before the sewing machine starts sewing the first stitch, or during the process of the sewing machine needle (10) moving downward, the movable knife (40) moves so that the sewing thread hook groove (41) is located directly below the sewing needle (10); S3, the first needle (10) of the sewing machine moves downward, the needle (10) passes through the sewing thread hook groove (41), and under the action of the rotary shuttle (20) in the sewing machine, the upper thread end on one side of the needle (10) is brought to the bottom of the movable knife (40); S4, the first needle (10) of the sewing machine moves upward, and after the needle (10) moves upward out of the movable knife (40), the movable knife (40) moves so that the avoidance needle groove (45) is located directly below the needle (10), and the movable knife (40) pulls out at least a part of the upper thread end, and at the same time, the thread clamping assembly clamps the upper thread end; S5, the sewing machine starts sewing the second stitch, the third stitch, ..., until the Nth stitch, the machine needle (10) moves up and down in the avoidance needle groove (45), and cuts the upper thread end during the process of sewing the Nth stitch, N≥2; When the sewing machine starts to sew the Nth stitch, the machine needle (10) moves down from the avoidance needle groove (45), the rotary shuttle (20) hooks the thread to form a surface thread loop, and the thread take-up lever in the sewing machine moves up to start thread collection; When the thread take-up lever moves upward to the target position A, the movable knife (40) moves toward the auxiliary knife (30) until the seam start cutting edge engages with the auxiliary knife (30) to cut the upper thread end, and the target position A is the non-highest point position of the thread take-up lever; S6, the thread take-up rod continues to move upward, draws back the upper thread under the sewing material, and tightens the lower thread.

2. The bird nest-less wire cutting control method according to claim 1, Features: The less-bird-nest thread trimming mechanism further comprises a fixedly arranged air suction pipe (70), wherein the air suction pipe (70) has an air suction port (71) aligned with the movable knife (40) and / or the rotary hook (20); In the step S3, the air suction port (71) sucks air to pick up the upper thread end on one side of the needle (10) and the lower thread end (110) on the rotary hook (20); In the step S5, the cut ends of the upper thread are collected through the suction port (71).

3. The bird nest-less wire cutting control method according to claim 2, Features: The movable knife (40) is also provided with a thread trimming edge after sewing, the air suction port (71) is arranged along the axial direction of the rotary shuttle (20) in the sewing machine and toward the rotary shuttle (20), and the air suction port (71) is also arranged below the upper end of the rotary shuttle (20); the less-bird's nest thread trimming control method further comprises the following steps: S7, when the sewing is finished and the thread needs to be cut, the movable knife (40) moves towards the auxiliary knife (30), and the movable knife (40) brings the bottom thread and the upper thread together and approaches the auxiliary knife (30) until the post-sewing thread cutting edge engages with the auxiliary knife (30) to cut the upper thread and the bottom thread; S8, the suction port (71) sucks air to pick up the bottom thread end (110) on the rotary hook (20), so that the bottom thread end (110) is tilted downward and located on the path of the upper thread loop.

4. The bird nest-less wire cutting control method according to claim 3, Features: The thread cutting edge at the beginning of sewing and the thread cutting edge after sewing are the same common thread cutting edge (42).

5. The bird nest-less wire cutting control method according to claim 3, Features: The air suction port (71) is arranged close to the escape side of the thread loop on the rotary hook (20).

6. The bird nest-less wire trimming control method according to claim 1, Features: The less-bird's nest wire cutting mechanism also includes a fixedly arranged wire pressing plate, a surface of the movable knife (40) is provided with a first wire clamping portion (411), the wire pressing plate is provided with a second wire clamping portion, and the first wire clamping portion (411) and the second wire clamping portion constitute a wire clamping assembly; In the step S4, a thread clamping seam is formed between the first thread clamping portion (411) and the second thread clamping portion, and the upper thread end is clamped in the thread clamping seam.

7. The bird nest-less wire trimming control method according to claim 1, Features: The surface of the movable knife (40) is provided with a first wire clamping portion (411), the auxiliary knife (30) is provided with a third wire clamping portion (31), and the first wire clamping portion (411) and the third wire clamping portion (31) constitute a wire clamping assembly; In the step S4, a thread clamping seam is formed between the first thread clamping portion (411) and the third thread clamping portion (31), and the upper thread end is clamped in the thread clamping seam.

8. The bird nest-less wire cutting control method according to claim 1, Features: The needle avoidance groove (45) is an empty area formed on the outer peripheral side of the movable knife (40).

9. The bird nest-less wire trimming control method according to claim 8, Features: The needle avoidance groove (45) is arranged adjacent to the seam start cutting edge, and the outer edge of the movable knife (40) is provided with a transition surface (48) distributed between the needle avoidance groove (45) and the seam start cutting edge, and the transition surface (48) is an inclined surface or an arc surface.

10. The bird nest-less wire trimming control method according to claim 1, Features: The movable knife (40) is rotatably mounted below the sewing machine bottom plate (50), and the auxiliary knife (30) is fixedly arranged, or movably mounted below the sewing machine bottom plate (50), or rotatably mounted below the sewing machine bottom plate (50).

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