Sewing thread trimming control method

Abstract

The invention provides a sewing thread trimming control method, which is characterized in that a double-moving-cutter thread trimming mechanism and a control system are arranged in a sewing machine, and during anti-bird nest thread trimming during sewing, a main thread trimming cutter and an auxiliary thread trimming cutter are controlled to move towards a machine needle along a first direction so as to cut off a starting thread end captured by the main thread trimming cutter right below the machine needle; the thread trimming method comprises the following steps: firstly, controlling a main thread trimming knife to move along a first direction until a main knife cutting edge on the main thread trimming knife crosses a position under a machine needle, and then immediately controlling the main thread trimming knife to return along a second direction until the main knife cutting edge on the main thread trimming knife is positioned under the machine needle so as to complete thread trimming; afterwards, the main thread trimmer continues to return and reset in the second direction, so that the situation that the main thread trimmer stays at a certain position and the cutting edge of the main cutter is kept under the machine needle is avoided, and the time consumed by the main thread trimmer driving source to drive the main thread trimmer to move in the first direction firstly and then return to the initial position in the second direction to cut off the needle starting thread end is shortened. Therefore, the anti-nest thread trimming can be completed when the sewing machine is in a normal sewing speed state.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewing machines, in particular to a sewing thread trimming control method. BACKGROUND

[0002] After each sewing operation, a sewing machine leaves a piece of thread on one side of the needle, which forms the starting thread for the next sewing operation. As a result, the starting thread on one side of the needle forms a bird's nest-like thread on the garment during the next sewing operation, affecting the quality of the entire garment. In order to ensure the quality of the garment, the starting thread must be manually trimmed, increasing the intensity of manual labor and affecting production efficiency.

[0003] To address the above problems, most sewing machines on the market are equipped with a thread trimming mechanism to trim the starting thread on one side of the needle during the starting operation and to trim the bottom thread and the face thread at the end of the sewing operation, achieving starting thread protection against bird's nests and automatic thread trimming after sewing, improving the automation level of the machine, better improving sewing efficiency, and ensuring the quality of the garment.

[0004] For example, a single-action knife anti-bird's nest thread trimming mechanism disclosed in Chinese patent application No. 202311289444.7 is provided with a fixed knife and a rotatable movable knife. The movable knife has different strokes during the starting operation and the end of the sewing operation, achieving trimming of the starting thread and trimming of the face thread and the bottom thread at the end of the sewing operation. However, the thread trimming mechanism is a single-action knife structure and cannot trim the thread directly below the needle. The thread trimming position of the fixed knife and the movable knife is on one side below the needle, i.e., the sewing thread from the needle plate has an angle, resulting in a longer length of the residual thread on the sewing material after trimming.

[0005] For example, the double-action knife line cutting mechanism disclosed in Chinese patent application No. 202411329869.0 is provided with two rotatable line cutting knives, namely line cutting knife one and line cutting knife two. When the line is cut during the start sewing and after the sewing, the line cutting knife one and the line cutting knife two can engage the line right below the needle, achieving the effect of cutting short line ends. The control method during the start sewing usually includes the following steps: first, the line cutting knife one is driven to capture the needle thread; then, the line cutting knife one is withdrawn to stay on one side of the needle, and the line cutting knife two is also withdrawn to stay on the same side of the needle, waiting for the sewing machine to complete the set number N of stitches; then, the line cutting knife one is first extended, and its blade is stopped right below the needle, and then the line cutting knife two is extended, and the two engage the line right below the needle; finally, the line cutting knife two and the line cutting knife one are withdrawn in sequence. However, after the set number N of stitches is completed, the line cutting knife one needs to stay at the position where its blade is right below the needle before it is rotated, which causes the motor driving the line cutting knife one to stop and start again. The motor needs a certain amount of time to stop and start again, resulting in a slow rotation speed of the line cutting knife one after the line is cut and a long time required for the rotation, which leads to the need to control the sewing machine to slow down during this process, thereby reducing the downward speed of the needle when the N+1th stitch is sewn. Otherwise, the needle may be broken and the line cutting knife one may be damaged when the needle moves downward too fast and the line cutting knife one does not fully retract during the sewing of the N+1th stitch. SUMMARY

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a sewing line cutting control method to improve the rotation speed of the main line cutting knife during the start sewing and bird nest prevention line cutting, and to complete the start sewing and bird nest prevention line cutting at the normal sewing speed of the sewing machine.

[0007] To achieve the above-mentioned purpose, the present application provides a sewing line cutting control method, which is configured with a double-action knife line cutting mechanism and a control system in a sewing machine. The double-action knife line cutting mechanism includes a main line cutting knife and an auxiliary line cutting knife, which are movably arranged on the outer periphery of the rotating hook in the sewing machine, a main knife line cutting driving source connected with the main line cutting knife, and an auxiliary knife line cutting driving source connected with the auxiliary line cutting knife. The main knife line cutting driving source and the auxiliary knife line cutting driving source are both communicatively connected with the control system. The main line cutting knife is provided with a main knife blade and a through start sewing thread hooking groove, and the auxiliary line cutting knife is provided with an auxiliary knife blade. The sewing line cutting control method includes a start sewing and bird nest prevention line cutting control method.

[0008] The start sewing and bird nest prevention line cutting control method includes the following steps:

[0009] S1, before the sewing machine starts to sew the first needle, or during the process of the sewing machine moving the first needle downward, the control system controls the main knife driving source to act, drives the main knife to move in the first direction, and moves the thread hooking groove to the position directly below the needle;

[0010] S2, the sewing machine moves the first needle downward, and the needle passes through the thread hooking groove with the thread, and under the action of the rotating hook, the thread end on one side of the needle is driven to the position below the main knife;

[0011] S3, the sewing machine moves the first needle upward, after the needle moves upward from the main knife, the control system controls the main knife driving source to act reversely, drives the main knife to retreat to the outer side of the needle in the second direction opposite to the first direction, and the main blade and the auxiliary blade are not engaged, and the thread end remains in the thread hooking groove;

[0012] S4, the sewing machine continues to sew until the set number of needles is reached;

[0013] S5, the control system controls the main knife driving source to act, drives the main knife to move in the first direction, and the main blade moves to the position directly below the needle or the position near the position directly below the needle; then the control system controls the main knife driving source to act reversely, drives the main knife to retreat in the second direction, and the main blade moves to the position directly below the needle or the position near the position directly below the needle; at the same time, the control system controls the auxiliary knife driving source to act, drives the auxiliary knife to move in the first direction, and the auxiliary blade moves to the position directly below the needle or the position near the position directly below the needle, and the main blade and the auxiliary blade are engaged to cut the thread end in the position directly below the needle or the position near the position directly below the needle;

[0014] S6, the control system controls the main knife driving source and the auxiliary knife driving source to act reversely, the main knife driving source drives the main knife to retreat to the outer side of the needle in the second direction, and the auxiliary knife driving source drives the auxiliary knife to retreat to the outer side of the needle in the second direction.

[0015] Further, the double-action knife thread cutting mechanism further comprises a fixedly arranged air suction pipe and an air suction device connected with the air suction pipe, the air suction pipe and the auxiliary knife are arranged on the same side of the needle, the air suction pipe is aligned with the outer surface of the main knife away from the rotating hook, and the air suction device is in communication connection with the control system;

[0016] In the step S5, the control system controls the air suction device to act, so that the pipe opening of the air suction pipe forms a negative pressure; at the same time, when the main blade moves to the position directly below the needle in the first direction, the end of the thread end is pulled out of the thread hooking groove and is sucked into the air suction pipe, and the air suction of the air suction pipe keeps the thread end in a straight state.

[0017] Further, the double-action knife thread trimming mechanism further comprises a fixedly arranged thread pressing plate, the thread pressing plate is distributed on the outer side of the auxiliary thread trimming knife away from the main thread trimming knife; the thread pressing plate is fixedly provided with a plate thread pressing part, and the surface of the main thread trimming knife is provided with a knife thread pressing part;

[0018] In the step S3, after the main thread trimming knife is driven to retreat in the second direction by the main knife thread trimming driving source, a thread clamping gap is formed between the plate thread pressing part and the knife thread pressing part, and the thread end is clamped in the thread clamping gap.

[0019] Further, the plate thread pressing part is distributed on the inner side of the main thread trimming knife away from the rotating hook, and the knife thread pressing part protrudes outward from the outer surface of the main thread trimming knife away from the rotating hook.

[0020] Further, the plate thread pressing part is distributed on the inner side of the main thread trimming knife away from the rotating hook, and the knife thread pressing part protrudes outward from the outer surface of the main thread trimming knife away from the rotating hook.

[0021] Further, the thread pressing plate comprises a plate fixed part and a plate main body part integrally bent and extended from the plate fixed part, the plate fixed part is fixed to the sewing machine bottom plate, the plate main body part is distributed on the inner side of the main thread trimming knife away from the rotating hook, and the plate thread pressing part is integrally extended from the edge of the plate main body part in the rotating hook axial direction and is distributed on the same side of the plate main body part as the thread end hooking groove.

[0022] Further, the thread pressing plate further comprises a thread blocking part, and the thread blocking part is distributed on the inner side of the main thread trimming knife away from the rotating hook.

[0023] In the step S6, when the control system controls the main knife thread trimming driving source to act reversely to drive the main thread trimming knife to retreat to the outer peripheral side of the needle in the second direction, the face thread dividing groove is distributed on the upper side of the thread blocking part and is blocked by the thread blocking part.

[0024] Further, in the step S4, the sewing machine is in a small stitch length sewing mode.

[0025] Further, the double-action knife thread trimming mechanism further comprises a main knife thread trimming transmission assembly connected between the main knife thread trimming driving source and the main thread trimming knife, the main knife thread trimming transmission assembly comprises a first thread trimming crank, a first thread trimming connecting rod, a first thread trimming shaft rotatably supported in the sewing machine bottom plate, a second thread trimming crank and a third thread trimming crank both fixed on the first thread trimming shaft, a second thread trimming connecting rod, and a main knife holder rotatably assembled in the sewing machine bottom plate, the first thread trimming crank is connected with the main knife thread trimming driving source and is driven to rotate by the main knife thread trimming driving source, the two ends of the first thread trimming connecting rod are hingedly connected with the first thread trimming crank and the second thread trimming crank respectively, and the two ends of the second thread trimming connecting rod are hingedly connected with the third thread trimming crank and the main knife holder respectively.

[0026] Further, the double-action knife thread trimming mechanism further comprises a secondary knife thread trimming transmission assembly connected between the secondary knife thread trimming driving source and the secondary knife, the secondary knife thread trimming transmission assembly comprising a fourth thread trimming crank, a third thread trimming connecting rod, a second thread trimming shaft rotatably supported in the sewing machine base plate, a fifth thread trimming crank and a sixth thread trimming crank both fixed on the second thread trimming shaft, a fourth thread trimming connecting rod, and a secondary knife holder rotatably assembled in the sewing machine base plate, the fourth thread trimming crank being connected with the secondary knife thread trimming driving source and being driven to rotate by the secondary knife thread trimming driving source, the two ends of the third thread trimming connecting rod being hingedly connected with the fourth thread trimming crank and the fifth thread trimming crank respectively, the two ends of the fourth thread trimming connecting rod being hingedly connected with the sixth thread trimming crank and the secondary knife holder respectively.

[0027] Further, the end of the primary knife is provided with a knife tip, the primary knife is provided with a thread hooking groove and a bobbin thread separating groove on the two sides of the rotating hook axis respectively, and the outer peripheral edge of the primary knife has a bobbin thread sliding surface connected between the knife tip and the groove opening of the thread hooking groove, and a bobbin thread sliding surface connected between the knife tip and the groove opening of the bobbin thread separating groove.

[0028] The sewing thread trimming control method further comprises a post-sewing automatic thread trimming control method, the post-sewing automatic thread trimming control method comprising the following steps:

[0029] A1. After the last needle of the sewing machine is moved upward from the needle plate, the control system controls the primary knife thread trimming driving source to act, drives the primary knife to move in the first direction, and inserts the knife tip into the bobbin thread loop, so that part of the bobbin thread and the bobbin thread are slid into the thread hooking groove along the bobbin thread sliding surface, and the other part of the bobbin thread is slid into the bobbin thread separating groove along the bobbin thread sliding surface;

[0030] A2. The control system controls the primary knife thread trimming driving source to act reversely, drives the primary knife to retreat in the second direction, and moves the primary knife blade to the position right below or adjacent to the position right below the needle; at the same time, the control system controls the secondary knife thread trimming driving source to act, drives the secondary knife to move in the first direction, and moves the secondary knife blade to the position right below or adjacent to the position right below the needle, so that the primary knife blade and the secondary knife blade cut off the bobbin thread and the bobbin thread at the position right below or adjacent to the position right below the needle.

[0031] A3. The control system controls the primary knife thread trimming driving source to continue to act reversely, continues to drive the primary knife to retreat in the second direction to the outer peripheral side of the needle; at the same time, the control system controls the secondary knife thread trimming driving source to act reversely, drives the secondary knife to retreat in the second direction to the outer peripheral side of the needle.

[0032] Further, in the process of the feeding dog rising in the sewing machine, the control system controls the secondary knife thread trimming driving source to act, drives the secondary knife to move in the first direction in the steps S5 and A2.

[0033] As described above, the sewing thread cutting control method of the present invention has the following beneficial effects:

[0034] In this application, when cutting the thread at the start of a stitch to prevent bird nests, the main thread cutter and the auxiliary thread cutter are controlled to move towards the needle in a first direction to cut the starting thread captured by the main thread cutter at a position directly below or adjacent to the needle. First, the main thread cutter is controlled to move in the first direction until its main blade passes directly below the needle. Then, immediately, the main thread cutter is controlled to retract in a second direction until its main blade is directly below or adjacent to the needle, completing the thread cutting. Afterward, the main thread cutter... The thread cutter continues to retract and reset along the second direction, thus avoiding the main thread cutter from remaining in a certain position with its blade directly below the needle. This shortens the time required for the main thread cutter to move along the first direction and then retract to its initial position to cut the starting thread, achieving rapid reset of the main thread cutter after the initial thread cut. This reduces the impact on the sewing machine's starting speed, allowing the initial thread cut to be completed at normal sewing speeds. Therefore, this application achieves the effect of cutting short thread ends during the initial thread cut without significantly affecting the sewing machine's starting speed. It reliably completes the initial thread cut at high sewing speeds, preventing the needle from hitting the main thread cutter during the initial thread cut, effectively preventing needle breakage, blade damage, and other adverse phenomena, thus improving the initial sewing experience and sewing quality. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the sewing machine in Embodiment 1 of this application, which is equipped with a double-acting thread-cutting mechanism.

[0036] Figure 2 This is a schematic diagram of the structure of Embodiment 1 of the double-acting wire-cutting mechanism in this application.

[0037] Figure 3 for Figure 2 A schematic diagram showing the connection between the main wire cutting drive source and the main wire cutting blade.

[0038] Figure 4 for Figure 2 A schematic diagram showing the connection between the auxiliary wire cutting drive source and the auxiliary wire cutting blade.

[0039] Figure 5 for Figure 2 A schematic diagram of the structure of the main wire shearing blade.

[0040] Figure 6 for Figure 2 A schematic diagram of the structure of the medium-voltage line plate.

[0041] Figures 7a to 7c This is a schematic diagram illustrating the process of cutting the thread to prevent the bird's nest from being sewn, as described in the embodiment of the double-acting knife thread-cutting mechanism of this application.

[0042] Figure 8 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0043] Figure 9a The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0044] Figure 9b The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0045] Figure 10 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0046] Figure 11 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0047] Figure 12 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing. Figure 11 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0048] Figure 13 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing. Figure 12 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0049] Figure 14 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0050] Figure 15 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0051] Figure 16 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0052] Figure 17 The schematic diagram of the main thread cutting knife in the first embodiment of the double-acting knife thread cutting mechanism of the present application in the automatic thread cutting after sewing.

[0053] Explanation of reference numerals: control system 10, main thread cutter 20, main blade edge 21, thread starting hook 22, tip 23, thread separating hook 24, bobbin thread separating groove 25, bobbin thread sliding surface 26, thread sliding surface 27, post-threading thread cutter 28, thread starting thread cutter 29, auxiliary thread cutter 30, auxiliary blade edge 31, main cutter thread driving source 40, auxiliary cutter thread driving source 50, first thread cutter crank 61, first thread cutter link 62, first thread cutter shaft 63, second thread cutter crank 64, third thread cutter crank 65, second thread cutter link 66, main cutter holder 67, fourth thread cutter crank 71, third thread cutter link 72, second thread cutter shaft 73, fifth thread cutter crank 74, sixth thread cutter crank 75, fourth thread cutter link 76, auxiliary cutter holder 77, air suction pipe 80, thread presser plate 90, thread presser plate portion 91, plate fixing portion 92, plate main body portion 93, thread blocking portion 94, shuttle 110, sewing machine base plate 120, lower shaft 130, needle bar 140, needle 150. DETAILED DESCRIPTION

[0054] The present application is explained by specific embodiments below, and other advantages and effects of the present application can be easily understood by those skilled in the art from the contents disclosed in the specification.

[0055] It should be noted that the structures, proportions, sizes, etc. shown in the drawings of the specification are merely used to facilitate understanding and reading by those skilled in the art in connection with the contents disclosed in the specification, and are not used to limit the conditions under which the present application can be implemented, and therefore do not have technical significance. Any modification of the structure, change of the proportional relationship, or adjustment of the size, which does not affect the effects that can be produced by the present application and the purposes that can be achieved, should still fall within the scope of the technical content disclosed by the present application. Meanwhile, the terms such as "upper", "lower", "left", "right", "middle", and "one" used in the specification are merely used for clear description, and are not used to limit the scope in which the present application can be implemented, and the change or adjustment of the relative relationship, without substantially changing the technical content, is also considered as the scope in which the present application can be implemented.

[0056] It should also be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or a middle element can be present at the same time. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or can be indirectly connected to the other element through a middle element.

[0057] In addition, the descriptions involving "first", "second" and the like in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the protection scope claimed by the present application.

[0058] The present application relates to the technical field of sewing machines, in particular to a sewing thread trimming control method for the sewing machine.

[0059] The sewing machine is a plain sewing machine. As shown in Figure 1 and Figure 16 , the sewing machine mainly comprises a control system 10, a sewing machine housing and a sewing machine bottom plate 120 which are fixedly arranged, a main shaft rotatably supported in the sewing machine housing, a main motor installed in the sewing machine housing and driving the main shaft to rotate, a lower shaft 130 rotatably supported in the sewing machine bottom plate 120 and in transmission connection with the main shaft, a rotating hook 110 installed at the end of the lower shaft 130, a needle bar 140 movably supported in the sewing machine housing and in transmission connection with the main shaft, and a needle 150 installed at the lower end of the needle bar 140. The main motor, pedal, operation screen, sensors, structures and the like in the sewing machine are in communication connection with the control system 10. When the sewing machine is normally sewing, the needle bar 140 drives the needle 150 to move up and down reciprocally, the lower shaft 130 drives the rotating hook 110 to rotate, and the needle 150 and the rotating hook 110 cooperate to interweave the face thread and the bottom thread and form stitches, thereby completing sewing.

[0060] For the convenience of description, in the following embodiments, the directions are defined as follows: the axial direction of the rotating hook 110 in the sewing machine is defined as the left-right direction, the horizontal radial direction of the rotating hook 110 in the sewing machine is defined as the front-rear direction, and the vertical radial direction of the rotating hook 110 in the sewing machine is defined as the up-down direction; at the same time, the front direction is the moving direction of the cloth when the sewing machine is normally sewing. Based on this, the rotating hook 110 is fixed at the left end of the lower shaft 130, and the upper end of the needle bar 140 is in transmission connection with the left end of the main shaft.

[0061] Further, to realize the sewing thread trimming control method involved in the present application, as shown in Figure 1 and Figure 16 , a double-action knife thread trimming mechanism is further arranged in the sewing machine. As shown in Figure 1 and Figure 2As shown, the first embodiment of the double-acting knife thread trimming mechanism includes a main thread trimming knife 20 and an auxiliary thread trimming knife 30, both of which are movably arranged on the outer periphery of the rotating hook 110 in the sewing machine, a main knife thread trimming driving source 40 in driving connection with the main thread trimming knife 20, and an auxiliary knife thread trimming driving source 50 in driving connection with the auxiliary thread trimming knife 30; the main thread trimming knife 20 and the auxiliary thread trimming knife 30 can both rotate around the rotating hook 110 or can both translate; in this embodiment, the main thread trimming knife 20 and the auxiliary thread trimming knife 30 are both rotatably arranged on the outer periphery of the rotating hook 110, and the main thread trimming knife 20 and the auxiliary thread trimming knife 30 are arranged in sequence in a direction away from the rotating hook 110 in the sewing machine, i.e., the outer side of the rotating hook 110 is the main thread trimming knife 20, and the outer side of the main thread trimming knife 20 is the auxiliary thread trimming knife 30; the main thread trimming knife 20 is driven to rotate by the main knife thread trimming driving source 40, and the auxiliary thread trimming knife 30 is driven to rotate by the auxiliary knife thread trimming driving source 50; the main knife thread trimming driving source 40 and the auxiliary knife thread trimming driving source 50 are both in communication connection with the control system 10. In the initial state, the main thread trimming knife 20 and the auxiliary thread trimming knife 30 are respectively located at the initial positions, at which time, as shown in Figure 11 As shown, the main thread trimming knife 20 and the auxiliary thread trimming knife 30 are both distributed on the rear side of the needle 150.

[0062] Further, as shown in Figure 2 and Figure 5 the main thread trimming knife 20 is provided with a main knife cutting edge 21 and a thread starting hooking groove 22 distributed on the rear side of the main knife cutting edge 21; the thread starting hooking groove 22 penetrates the main thread trimming knife 20 along the thickness direction of the main thread trimming knife 20 and allows the needle 150 to pass through; in addition, the front end of the main thread trimming knife 20 is provided with a knife tip portion 23, the left side of the main thread trimming knife 20 is provided with a thread hooking groove 24, and the right side of the main thread trimming knife 20 is provided with a bobbin thread separating groove 25; the groove opening of the thread hooking groove extends to the left edge of the knife body portion to allow the bobbin thread and the bobbin thread to enter the thread hooking groove from the left side of the knife body portion; the groove opening of the bobbin thread separating groove 25 extends to the right edge of the knife body portion to allow the bobbin thread to enter the bobbin thread separating groove 25 from the right side of the knife body portion. Furthermore, the outer peripheral edge of the main thread trimming knife 20 has a bobbin thread and bobbin thread sliding surface 26 connected between the groove opening of the knife tip portion 23 and the thread hooking groove 24, and a bobbin thread sliding surface 27 connected between the groove opening of the knife tip portion 23 and the bobbin thread separating groove 25; the bobbin thread and bobbin thread sliding surface 26 is a part of the left edge of the knife body portion, and the bobbin thread sliding surface 27 is a part of the right edge of the knife body portion. The front end of the auxiliary thread trimming knife 30 is provided with an auxiliary knife cutting edge 31.

[0063] The sewing thread trimming control method disclosed in the present application includes a thread starting anti-bird nest thread trimming control method and a post-sewing automatic thread trimming control method. As shown in Figure 17 The thread starting anti-bird nest thread trimming control method includes the following steps.

[0064] S1, before the sewing machine starts to sew the first needle, or during the process of the sewing machine lowering the first needle, the control system 10 controls the main knife driving source 40 to act, drives the main knife 20 to rotate forward in the first direction counterclockwise, and drives the thread hooking groove 22 to rotate forward to the position directly below the needle 150, as shown in Figure 7a .

[0065] S2, the sewing machine lowers the first needle, as shown in Figure 7a , the needle 150 passes through the thread hooking groove 22 with the thread, and under the action of the rotating hook 110, the thread head on one side of the needle 150 is driven to the position below the main knife 20; the thread head on one side of the needle 150 is a section of thread formed on one side of the needle 150 after the last sewing is finished.

[0066] S3, the sewing machine raises the first needle, after the needle 150 moves upward from the main knife 20, the control system 10 controls the main knife driving source 40 to act reversely, drives the main knife 20 to rotate backward in the second direction clockwise, the second direction is opposite to the first direction, the main knife 20 retreats to the back side of the needle 150, but the main blade edge 21 and the auxiliary blade edge 31 are not engaged; this process makes a part of the thread head be pulled out upward, but the thread head still remains in the thread hooking groove 22, and the part of the thread head pulled out upward is on the upper surface of the main knife 20, as shown in Figure 7b .

[0067] S4, the sewing machine continues to sew until the set number of stitches is reached, such as 2 stitches, or 3 stitches, or other number of stitches, so that the thread and the bobbin thread are interlaced with each other to form stitches on the sewing material; during this process, the main blade edge 21 and the auxiliary blade edge 31 always remain in the state of not engaging as in step S3, so that the thread head is not cut off.

[0068] S5, after the set number of stitches is reached, the control system 10 controls the main knife driving source 40 to act, drives the main knife 20 to rotate forward in the first direction counterclockwise, in particular, the forward rotation of the main knife 20 makes the main blade edge 21 on it pass through the position directly below the needle 150 in the first direction, that is, the main blade edge 21 is distributed on the front side of the needle 150; then the control system 10 controls the main knife driving source 40 to act reversely, drives the main knife 20 to rotate backward in the second direction clockwise, and drives the main blade edge 21 to rotate backward to the position directly below the needle 150; at the same time, the control system 10 controls the auxiliary knife driving source 50 to act, drives the auxiliary knife 30 to rotate forward in the first direction counterclockwise, and drives the auxiliary blade edge 31 to rotate forward to the position directly below the needle 150; in this way, as shown in Figure 7cAs shown, the main blade edge 21 and the auxiliary blade edge 31 are engaged and cut the thread end at the position right below the needle 150. Alternatively, when the main blade edge 21 passes the position right below the needle 150, the main blade edge 21 is rotated backward to a position right behind the needle 150 but adjacent to the position right below the needle 150 by the backward rotation of the main blade cutter 20 controlled by the control system 10; meanwhile, the auxiliary blade edge 31 is rotated forward to a position right behind the needle 150 but adjacent to the position right below the needle 150 by the forward rotation of the auxiliary blade cutter 30 controlled by the control system 10; thus, the main blade edge 21 and the auxiliary blade edge 31 are engaged and cut the thread end at the position right behind the needle 150 but adjacent to the position right below the needle 150.

[0069] S6, the control system 10 controls the main blade cutter driving source 40 and the auxiliary blade cutter driving source 50 to rotate backward in the second direction, the main blade cutter driving source 40 drives the main blade cutter 20 to rotate backward in the second direction to retreat to the outer periphery of the needle 150, and the main blade cutter 20 retreats to its initial position; the auxiliary blade cutter driving source 50 drives the auxiliary blade cutter 30 to rotate backward in the second direction to retreat to the outer periphery of the needle 150, and the auxiliary blade cutter 30 retreats to its initial position. Thus, there is no physical part of the main blade cutter 20 and the auxiliary blade cutter 30 distributed right below the needle 150, and the main blade cutter 20 and the auxiliary blade cutter 30 will not interfere with the up-and-down movement of the needle 150, and the subsequent sewing machine can sew normally.

[0070] Obviously, firstly, this application automatically cuts off the starting thread when sewing, preventing bird's nests from forming on the fabric and improving sewing quality. Secondly, by cutting the starting thread directly below or near the needle 150, the remaining thread on the fabric is very short, reliably achieving the effect of cutting short thread ends and avoiding subsequent manual trimming of residual thread on the fabric. In particular, when cutting the thread at the start of the stitch to prevent bird nests, this application controls the main thread cutter 20 and the auxiliary thread cutter 30 to rotate counterclockwise forward toward the needle 150 in the first direction to cut the starting thread captured by the main thread cutter 20 at a position directly below or adjacent to the needle 150. First, the main thread cutter 20 is controlled to rotate counterclockwise forward in the first direction until its main blade edge 21 passes directly below or adjacent to the needle 150. Then, immediately, the main thread cutter 20 is controlled to rotate clockwise backward in the second direction until its main blade edge 21 is positioned at or adjacent to the needle 150. The thread cutter 20 is positioned directly below the needle 150, completing the initial stitch cutting. Afterward, the main thread cutter 20 continues to rotate clockwise in the second direction to return to its original position. This avoids the main thread cutter 20 remaining in a certain position, keeping the main blade edge 21 directly below the needle 150. This shortens the time required for the main thread cutter drive source 40 to drive the main thread cutter 20 to rotate forward and then backward to return to its initial position to cut the starting thread. This achieves rapid reset of the main thread cutter 20 after the initial stitch cutting, reducing the impact on the sewing machine's starting speed and enabling the initial stitch cutting to be completed at the normal sewing speed of the sewing machine. Therefore, this application can achieve the effect of cutting short thread ends to prevent bird nests during the start-up stitching process, without significantly affecting the start-up speed of the sewing machine. It can reliably complete the start-up stitching to prevent bird nests during the high-speed start-up stitching process, and avoid the needle 150 from hitting the main thread cutter 20 during the start-up stitching to prevent bird nests. This effectively prevents defects such as broken needles and damaged blades, and improves the start-up stitching experience and sewing quality.

[0071] Furthermore, the automatic thread trimming control method after sewing includes the following steps.

[0072] A1. After the last stitch is sewn, the needle 150 moves upward from the sewing machine needle plate, the control system 10 controls the main thread-cutting drive source 40 to operate, driving the main thread-cutting blade 20 to rotate counterclockwise forward in the first direction, such as... Figure 8 As shown, when the tip 23 of the main thread cutter 20 is inserted into the top thread loop, the left half of the top thread loop and the bottom thread slide along the bottom thread sliding surface 26 into the thread splitting groove 24, and the right half of the top thread loop slides along the top thread sliding surface 27 into the top thread splitting groove 25.

[0073] A2, the control system 10 controls the main knife line driving source 40 to act reversely, drives the main knife line cutter 20 to rotate back in the second direction clockwise, makes the main knife edge 21 rotate back to the position right below the needle 150; at the same time, the control system 10 controls the auxiliary knife line driving source 50 to act, drives the auxiliary knife line cutter 30 to rotate forward in the first direction counterclockwise, makes the auxiliary knife edge 31 rotate forward to the position right below the needle 150; thus, as shown in Figure 9a , the main knife edge 21 and the auxiliary knife edge 31 are engaged and cut the thread end of the needle 150. Alternatively, the control system 10 controls the main knife line driving source 40 to act reversely, drives the main knife line cutter 20 to rotate back in the second direction clockwise, makes the main knife edge 21 rotate back to the position right below the needle 150; at the same time, the control system 10 controls the auxiliary knife line driving source 50 to act, makes the auxiliary knife edge 31 rotate forward to the position right below the needle 150; thus, as shown in Figure 9b , the main knife edge 21 and the auxiliary knife edge 31 are engaged and cut the thread end of the needle 150.

[0074] A3, the control system 10 controls the main knife line driving source 40 to continue to act reversely, continues to drive the main knife line cutter 20 to rotate back in the second direction clockwise to the outer periphery side of the needle 150 until the main knife line cutter 20 rotates back to its initial position; at the same time, the control system 10 controls the auxiliary knife line driving source 50 to act reversely, drives the auxiliary knife line cutter 30 to rotate back in the second direction clockwise to the outer periphery side of the needle 150 until the auxiliary knife line cutter 30 rotates back to its initial position. Finally, the main knife line cutter 20 and the auxiliary knife line cutter 30 are reset to the initial positions as shown in Figure 11 .

[0075] Further, as shown in Figure 2 and Figure 3As shown, Embodiment 1 of the dual-action wire cutting mechanism further includes a main blade wire cutting transmission assembly connected between the main blade wire cutting drive source 40 and the main wire cutting blade 20. The main blade wire cutting drive source 40 is a motor, preferably a stepper motor. The main blade thread-cutting drive assembly includes a first thread-cutting crank 61, a first thread-cutting connecting rod 62, a first thread-cutting shaft 63 rotatably supported in the sewing machine base plate 120 and extending laterally, a second thread-cutting crank 64 and a third thread-cutting crank 65 both fixed to the first thread-cutting shaft 63, a second thread-cutting connecting rod 66, and a main blade holder 67 rotatably mounted in the sewing machine base plate 120. The first thread-cutting crank 61 is fixed to the motor shaft of the main blade thread-cutting drive source 40 and is driven to rotate by the main blade thread-cutting drive source 40. The two ends of the first thread-cutting connecting rod 62 are hinged to the first thread-cutting crank 61 and the second thread-cutting crank 64, respectively. The two ends of the second thread-cutting connecting rod 66 are hinged to the third thread-cutting crank 65 and the main blade holder 67, respectively. Thus, the main blade thread-cutting drive source 40 drives the main thread-cutting blade 20 to rotate counterclockwise forward and clockwise backward through the main blade thread-cutting drive assembly.

[0076] Furthermore, such as Figure 2 and Figure 4 As shown, Embodiment 1 of the double-acting thread-cutting mechanism further includes an auxiliary thread-cutting transmission assembly connected between the auxiliary thread-cutting drive source 50 and the auxiliary thread-cutting blade 30. The auxiliary thread-cutting drive source 50 is a motor, preferably a stepper motor. The auxiliary thread-cutting transmission assembly includes a fourth thread-cutting crank 71, a third thread-cutting connecting rod 72, a second thread-cutting shaft 73 rotatably supported in the sewing machine base plate 120 and extending laterally, a fifth thread-cutting crank 74 and a sixth thread-cutting crank 75 both fixed on the second thread-cutting shaft 73, a fourth thread-cutting connecting rod 76, and an auxiliary blade holder 77 rotatably mounted in the sewing machine base plate 120. The fourth thread-cutting crank 71 is connected to and driven to rotate by the auxiliary thread-cutting drive source 50. The two ends of the third thread-cutting connecting rod 72 are hinged to the fourth thread-cutting crank 71 and the fifth thread-cutting crank 74, respectively. The two ends of the fourth thread-cutting connecting rod 76 are hinged to the sixth thread-cutting crank 75 and the auxiliary blade holder 77, respectively. Thus, the auxiliary wire cutting drive source 50 drives the auxiliary wire cutting blade 30 to rotate counterclockwise forward and clockwise backward through the auxiliary wire cutting transmission assembly.

[0077] Furthermore, the main thread cutter 20 is located on the outer periphery of the rotary hook 110, and the auxiliary thread cutter 30 is located on the outer periphery of the main thread cutter 20; thus, the upper surface of the main thread cutter 20 is its outer surface, facing away from the rotary hook 110 and towards the auxiliary thread cutter 30; the lower surface of the main thread cutter 20 is its inner surface, facing towards the rotary hook 110 and away from the auxiliary thread cutter 30. Figure 5As shown, the outer surface of the main thread cutter 20 is also provided with a post-sewing thread-cutting receiving part 28 and a starting-sewing thread-cutting receiving part 29. The post-sewing thread-cutting receiving part 28 is connected between the main blade edge 21 and the parting thread hook groove 24, and the starting-sewing thread-cutting receiving part 29 is connected between the main blade edge 21 and the starting-sewing thread hook groove 22. Both the post-sewing thread-cutting receiving part 28 and the starting-sewing thread-cutting receiving part 29 are recessed structures on the outer surface of the blade body. When cutting the thread at the start of the sewing, the starting thread end led out from the starting-sewing thread hook groove 22 is received in the starting-sewing thread-cutting receiving part 29 and cut at the main blade edge 21. When cutting the thread at the end of sewing, the left half of the top thread and the bottom thread led out from the parting thread hook groove 24 are received in the post-sewing thread-cutting receiving part 28 and cut at the main blade edge 21. In addition, the bottom thread sliding surface 26 extends at an angle as it moves further away from the blade tip 23 and further away from the top thread sliding surface 27, while the top thread sliding surface 27 extends at an angle as it moves further away from the blade tip 23 and further away from the bottom thread sliding surface 26. That is, the bottom thread sliding surface 26 extends at an angle to the left rearward, and the top thread sliding surface 27 extends at an angle to the right rearward, which allows for better thread separation after sewing is completed.

[0078] Furthermore, in step S4, which involves cutting the thread at the start of the stitch to prevent bird nests, the sewing machine is in a small stitch pitch sewing mode, shortening the distance the fabric is moved forward during this process, thus shortening the length of the thread remaining on the fabric after the starting thread is cut. Of course, in other embodiments, in step S4, which involves cutting the thread at the start of the stitch to prevent bird nests, the sewing machine can also be in a regular sewing mode. In addition, in step S5, which involves cutting the thread at the start of the stitch to prevent bird nests, and in step A2, which involves automatic thread cutting after sewing, when the control system 10 detects that the feed dog in the sewing machine is rising, the control system 10 sends a command to the auxiliary thread cutting drive source 50 to drive the auxiliary thread cutting blade 30 to rotate forward in the first direction, thereby avoiding collision between the auxiliary thread cutting blade 30 and the feed dog.

[0079] Furthermore, such as Figure 2 and Figure 16 As shown, the first embodiment of the double-acting thread-cutting mechanism also includes a fixedly installed suction pipe 80 and a suction device connected to the suction pipe 80. The suction pipe 80 and the auxiliary thread-cutting blade 30 are both located behind the needle 150. The suction pipe 80 is aligned with the outer surface of the main thread-cutting blade 20. The suction device is communicatively connected to the control system 10. In step S5, which involves cutting the thread at the start of the stitch to prevent bird nests from falling, the control system 10 controls the suction device to create a negative pressure at the opening of the suction pipe 80. Simultaneously, when the main blade 21 rotates counterclockwise in the first direction and passes directly below the needle 150, the starting thread end is continuously pulled upwards from the starting thread hook groove 22 until the end of the starting thread end is completely pulled upwards from the starting thread hook groove 22. Under the action of the suction pipe 80, the end of the starting thread end is sucked into the suction pipe 80, as... Figure 7cAs shown, the suction of the suction pipe 80 keeps the stitcher thread straight, and more stably realizes the stitcher thread cutting anti-bird nest effect of the short stitcher thread.

[0080] Further, as shown in Figure 2 Embodiment 1 of the double-action knife thread cutting mechanism also includes a fixedly arranged thread pressing plate 90, which cooperates with the main thread cutting knife 20 to press the thread from the lower side of the main thread cutting knife 20. Based on this, as shown in Figure 6 and Figure 7b The thread pressing plate 90 includes a plate fixing part 92 and a plate main body part 93 integrally bent and extended from the plate fixing part 92. The rear end of the plate fixing part 92 is fixed to the bottom of the sewing machine bottom plate 120 by a screw, and the thread pressing plate 90 is fixed to the bottom of the sewing machine bottom plate 120. The plate main body part 93 is distributed on the lower side of the main thread cutting knife 20 facing the hook 110. The plate thread pressing part 91 integrally extends to the left from the left edge of the plate main body part 93 along the axis of the hook 110, and is distributed on the inner side of the main thread cutting knife 20. At the same time, the plate thread pressing part 91 is also distributed on the left side of the plate main body part 93. The inner surface of the main thread cutting knife 20 is provided with a knife thread pressing part, which is part of the smooth inner surface of the main thread cutting knife 20 and does not protrude downward. In step S3 involved in the stitcher thread cutting anti-bird nest thread cutting, after the main thread cutting knife 20 is driven by the main thread cutting knife driving source 40 to rotate back in the second direction clockwise, although the main thread cutting knife 20 and the auxiliary thread cutting knife 30 are not engaged, a thread clamping seam is formed between the plate thread pressing part 91 of the thread pressing plate 90 and the knife thread pressing part of the main thread cutting knife 20. The stitcher thread is clamped in the thread clamping seam, avoiding accidental disengagement of the stitcher thread during the process of setting the number of stitches.

[0081] In addition, as shown in Figure 6 The thread pressing plate 90 of Embodiment 1 of the double-action knife thread cutting mechanism is also provided with a thread blocking part 94, which is integrally provided at the front end of the plate main body part 93, and the plate main body part 93 is distributed on the inner side of the main thread cutting knife 20. In step S6 involved in the stitcher thread cutting anti-bird nest thread cutting, after the stitcher thread is cut, the main thread cutting knife 20 is driven by the main thread cutting knife driving source 40 to reset in the second direction, and as shown in Figures 11 to 13As shown, the thread distribution grooves 25 are distributed on the upper side of the thread blocking part 94 and are blocked by the thread blocking part 94; in the subsequent normal sewing process, the stopping position of the main thread cutter 20 is such that the thread distribution grooves 25 thereon are just distributed on the upper side of the thread blocking part 94 and are blocked by the thread blocking part 94, at this time, the thread guard plate 90 plays a role of preventing thread hanging: the thread blocking part 94 on the thread guard plate 90 blocks the bottom of the thread distribution grooves 25 of the main thread cutter 20 and blocks the thread distribution grooves 25 from below, so that the thread loop of normal sewing is blocked outside the thread distribution grooves 25 and the thread loop of normal sewing is prevented from entering the thread distribution grooves 25, thus eliminating the phenomenon of thread loop hanging in the thread distribution grooves 25 in the normal sewing process, so that the thread does not break due to thread hanging and the cloth does not shrink due to thread hanging, effectively improving the sewing performance.

[0082] The difference between the second embodiment of the double-action knife thread cutting mechanism and the first embodiment of the double-action knife thread cutting mechanism is that in the second embodiment of the double-action knife thread cutting mechanism, the thread guard plate 90 cooperates with the main thread cutter 20 to press the thread from the upper side of the main thread cutter 20. Based on this, as shown in Figure 14 and Figure 15 As shown, the thread guard plate 90 in the second embodiment of the double-action knife thread cutting mechanism only has the plate thread pressing part 91 and does not have the function of preventing thread hanging during normal sewing; the plate thread pressing part 91 is distributed on the outer side of the main thread cutter 20 and is arranged at the front end of the thread guard plate 90; the outer surface of the main thread cutter 20 is provided with a cutter thread pressing part protruding outward (i.e. upward) towards the plate thread pressing part 91.

[0083] In summary, taking the first embodiment of the double-action knife thread cutting mechanism as an example, the working principle thereof when starting sewing to prevent bird nest thread cutting is as follows.

[0084] Firstly, after the last sewing is finished and before the sewing machine starts sewing again, the needle 150 is located above the needle plate, and the control system 10 can control the main cutter thread driving source 40 to act again, so that the starting thread hooking groove 22 on the main thread cutter 20 is already rotated forward to the position directly below the needle 150 before the first needle of the sewing machine starts sewing, as shown in Figure 7a Alternatively, after the last sewing is finished and before the sewing machine starts sewing again, the main thread cutter 20 always stays on the rear side of the needle 150; when starting sewing, in the process of the first needle of the sewing machine moving downward, the control system 10 controls the main cutter thread driving source 40 to act, so that the starting thread hooking groove 22 on the main thread cutter 20 is rotated forward to the position directly below the needle 150, as shown in Figure 7a In this way, when the sewing machine starts sewing the first needle, the needle 150 passes through the starting thread hooking groove 22 with the thread downward.

[0085] Second, when the needle 150 is going up, the main thread cutter 20 rotates backward with the thread end of the needle to the suction pipe 80 until the tip of the main thread cutter 20 goes beyond the position directly below the needle 150; at this time, as shown in Fig. 6, the end of the thread end of the needle is clamped between the plate thread pressing part 91 of the thread pressing plate 90 and the thread pressing part of the main thread cutter 20 on the lower side of the main thread cutter 20, the thread end of the needle is accommodated in the thread end accommodating part 29 on the upper side of the main thread cutter 20, and the main blade edge 21 and the auxiliary blade edge 31 are not engaged. Figure 7b

[0086] Third, the sewing machine continues to sew the set number of stitches in the small stitch length sewing mode. Then, during the process of the needle 150 going up and the feed dog going up, the control system 10 controls the main thread cutter driving source 40 to act, first drives the main thread cutter 20 to rotate counterclockwise forward until the main blade edge 21 on the main thread cutter 20 goes beyond the position directly below the needle 150, during which the control system 10 controls the suction device to act, so that the suction pipe 80 has the thread suction action, and with the counterclockwise forward rotation of the main thread cutter 20, the end of the thread end of the needle clamped between the plate thread pressing part 91 of the thread pressing plate 90 and the thread pressing part of the main thread cutter 20 is released, and the end of the thread end of the needle is sucked into the suction pipe 80, as shown in Fig. 7, so that the thread end of the needle to the end of the thread end of the needle is in a straightened state. Figure 7c

[0087] Fourth, then, the control system 10 controls the main thread cutter driving source 40 to reverse act and controls the auxiliary thread cutter driving source 50 to act, drives the main thread cutter 20 to rotate backward and the auxiliary thread cutter 30 to rotate forward, the main blade edge 21 and the auxiliary blade edge 31 engage and cut the thread end of the needle at the position directly below the needle 150 or near the position directly below the needle 150, so that the thread end of the needle after the thread end cutting is in the shortest state.

[0088] Fifth, finally, the control system 10 controls the main thread cutter driving source 40 to continue to reverse act and controls the auxiliary thread cutter driving source 50 to reverse act, the main thread cutter 20 and the auxiliary thread cutter 30 are respectively reset to the initial positions as shown in Fig. 1. Figure 11

[0089] During the thread end cutting, the above control is realized, the main thread cutter 20 is driven to rotate forward in advance, the pressed thread end of the needle is quickly released, and the suction pipe 80 straightens and stretches the thread end of the needle; after the thread end cutting, the main thread cutter 20 can quickly move away from the center of the needle 150, so that the needle 150 is prevented from quickly moving downward to the main blade edge 21 and the tip of the main thread cutter 20 to cause the needle breakage and damage to the main thread cutter 20.

[0090] ​​​After that, the sewing machine is normal sewing. In the process of normal sewing, the main thread cutter 20 and the auxiliary thread cutter 30 are distributed on the back side of the needle 150, and the thread blocking part 94 on the presser foot 90 blocks the bottom of the thread separation groove 25 of the main thread cutter 20, so that the bottom of the thread separation groove 25 is closed, the thread loop of the normal sewing is blocked from entering the thread separation groove 25, and the phenomenon of thread hanging is greatly reduced.

[0091] After the sewing is finished, the working principle of the automatic thread cutting after sewing of the double-action cutter thread cutting mechanism embodiment one is as follows.

[0092] Firstly, the control system 10 controls the main cutter thread cutting driving source 40 to act, drives the main thread cutter 20 to rotate forward in the first direction counterclockwise, so that the thread separation hook groove 24 and the thread separation groove 25 are all distributed below the needle 150, or all pass through the position below the needle 150, so that the thread and the bottom thread are hung in the thread separation hook groove 24 and the thread separation groove 25, as shown in the figure. Figure 8 The control system 10 controls the reverse action of the main cutter thread cutting driving source 40 and the action of the auxiliary cutter thread cutting driving source 50, drives the main thread cutter 20 to rotate back, and drives the auxiliary thread cutter 30 to rotate forward, so that the main cutter blade edge 21 and the auxiliary cutter blade edge 31 are engaged and cut off the thread end at the position below or adjacent to the needle 150, so that the thread end of the thread after the sewing is cut off is in the shortest state. In Figure 9a the figure, the thread end is the shortest when the thread is cut off below the needle 150; but in Figure 9b the figure, the thread is cut off on the back side next to the needle 150, which can ensure that the length of the bottom thread is better and the stability of the thread cutting is better.

[0093] Secondly, after the thread and the bottom thread are cut off, the control system 10 controls the main cutter thread cutting driving source 40 to continue to act reversely, and controls the auxiliary cutter thread cutting driving source 50 to act reversely, so that the main thread cutter 20 rotates back to the position where the thread separation groove 25 is away from the thread blocking part 94 of the presser foot 90 by a certain distance X, as shown in the figure. Figure 10 Then, the main thread cutter 20 forms an opening between the thread separation groove 25 and the thread blocking part 94 of the presser foot 90, so that the thread on one side of the needle 150 can pass through the opening smoothly after the thread is cut off, and the thread will not be blocked when the sewing material is taken out. After the sewing material is taken out, the main thread cutter 20 is reset completely, as shown in the figure. Figure 11

[0094] As described above, the present application effectively overcomes the shortcomings in the prior art and has high industrial utilization value.

[0095] ​The above embodiments are only illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present application shall be covered by the claims of the present application.

Claims

1. A sewing thread cutting control method, comprising a double-acting knife thread cutting mechanism and a control system (10) configured in a sewing machine, the double-acting knife thread cutting mechanism comprising a main thread cutting knife (20) and an auxiliary thread cutting knife (30) both movably configured on the outer periphery of a rotary hook (110) in the sewing machine, a main knife thread cutting drive source (40) connected to the main thread cutting knife (20) in transmission, and an auxiliary knife thread cutting drive source (50) connected to the auxiliary thread cutting knife (30) in transmission, the main knife thread cutting drive source (40) and the auxiliary knife thread cutting drive source (50) both being communicatively connected to the control system (10), the main thread cutting knife (20) having a main blade edge (21) and a through-hole starting stitch hook groove (22), and the auxiliary thread cutting knife (30) having an auxiliary blade edge (31); the sewing thread cutting control method comprises a starting stitch anti-bird nest thread cutting control method; Its features are: The method for controlling thread cutting during seam opening to prevent bird nests includes the following steps: S1. Before the sewing machine starts the first stitch, or during the process of the sewing machine needle (150) moving down during the first stitch, the control system (10) controls the main blade thread cutting drive source (40) to move, driving the main thread cutting blade (20) to move along the first direction, so that the starting stitch hook groove (22) moves to directly below the needle (150). S2. When the sewing machine starts the first stitch, the needle (150) moves down and the needle (150) carries the top thread down through the starting stitch hook groove (22). Under the action of the rotary hook (110), the starting thread end on one side of the needle (150) is moved to the bottom of the main thread cutter (20). S3. The sewing machine needle (150) moves upward when starting the first stitch. After the needle (150) moves upward from the main thread cutter (20), the control system (10) controls the main thread cutter drive source (40) to reverse the action, causing the main thread cutter (20) to retract to the outer periphery of the needle (150) in a second direction opposite to the first direction, and the main blade edge (21) and the auxiliary blade edge (31) do not engage, and the starting thread end is kept in the starting stitch hook groove (22). S4. The sewing machine continues sewing until the set number of stitches is reached. S5. The control system (10) controls the main blade thread cutting drive source (40) to move, causing the main thread cutting blade (20) to move in the first direction, so that the main blade edge (21) passes directly below the needle (150) in the first direction; then the control system (10) controls the main blade thread cutting drive source (40) to move in the opposite direction, causing the main thread cutting blade (20) to retract in the second direction, so that the main blade edge (21) moves to directly below or near the needle (150). 0) The position directly below; at the same time, the control system (10) controls the auxiliary knife cutting drive source (50) to move, driving the auxiliary knife (30) to move along the first direction, so that the auxiliary knife edge (31) moves to the position directly below or near the needle (150), then the main knife edge (21) and the auxiliary knife edge (31) bite and cut the starting thread at the position directly below or near the needle (150); S6. The control system (10) controls the main cutter wire cutting drive source (40) and the auxiliary cutter wire cutting drive source (50) to move in opposite directions. The main cutter wire cutting drive source (40) drives the main cutter (20) to retract along the second direction to the outer periphery of the needle (150), and the auxiliary cutter wire cutting drive source (50) drives the auxiliary cutter (30) to retract along the second direction to the outer periphery of the needle (150).

2. The sewing thread cutting control method according to claim 1, characterized in that: The double-acting wire cutting mechanism also includes a fixed suction pipe (80) and a suction device connected to the suction pipe (80). The suction pipe (80) and the auxiliary wire cutting knife (30) are arranged on the same side of the needle (150). The suction pipe (80) is aligned with the outer surface of the main wire cutting knife (20) facing away from the rotary hook (110). The suction device is communicatively connected to the control system (10). In step S5, the control system (10) controls the suction device to operate, so that the inlet of the suction pipe (80) forms a negative pressure; at the same time, when the main blade (21) passes directly below the needle (150) in the first direction, the end of the starting thread comes out from the starting stitch hook groove (22) and is sucked into the suction pipe (80), and the suction of the suction pipe (80) keeps the starting thread in a taut state.

3. The sewing thread cutting control method according to claim 1, characterized in that: The double-acting wire cutting mechanism also includes a fixedly installed wire pressing plate (90), which is distributed on the outside of the auxiliary wire cutting blade (30) facing away from the main wire cutting blade (20); a plate pressing part (91) is fixedly provided on the wire pressing plate (90), and a blade pressing part is provided on the surface of the main wire cutting blade (20); In step S3, when the main cutter thread drive source (40) drives the main cutter thread cutter (20) to retract in the second direction, a thread clamping seam is formed between the plate pressing part (91) and the cutter pressing part, and the starting thread end is clamped in the thread clamping seam.

4. The sewing thread cutting control method according to claim 3, characterized in that: The plate pressing part (91) is distributed on the outside of the main cutting knife (20) facing away from the rotary hook (110), and the knife pressing part protrudes outward from the outer surface of the main cutting knife (20) facing away from the rotary hook (110).

5. The sewing thread cutting control method according to claim 3, characterized in that: The plate pressing part (91) is distributed on the inner side of the main cutting blade (20) facing the rotary hook (110), and the blade pressing part is provided on the inner surface of the main cutting blade (20) facing the rotary hook (110).

6. The sewing thread cutting control method according to claim 5, characterized in that: The presser plate (90) includes a plate fixing part (92) and a plate body part (93) integrally bent and extended from the plate fixing part (92). The plate fixing part (92) is fixed to the sewing machine base plate (120). The plate body part (93) is distributed on the inner side of the main thread cutter (20) facing the rotary hook (110). The plate presser part (91) extends integrally from the edge of the plate body part (93) along the axial direction of the rotary hook (110) and is distributed on the same side of the plate body part (93) as the starting stitch hook groove (22).

7. The sewing thread cutting control method according to claim 5, characterized in that: The pressure plate (90) also includes a wire-blocking part (94), which is distributed on the inner side of the main wire cutter (20) facing the rotary hook (110); In step S6, when the control system (10) controls the main cutter wire cutting drive source (40) to reverse and cause the main cutter wire cutting blade (20) to retract along the second direction to the outer periphery of the needle (150), the surface thread dividing groove (25) on the main cutter wire cutting blade (20) is distributed on the side directly above the wire blocking part (94) and is blocked by the wire blocking part (94).

8. The sewing thread cutting control method according to claim 1, characterized in that: In step S4, the sewing machine is in a small stitch distance sewing mode.

9. The sewing thread cutting control method according to claim 1, characterized in that: The double-acting thread-cutting mechanism further includes a main blade thread-cutting transmission assembly connected between the main blade thread-cutting drive source (40) and the main thread-cutting blade (20). The main blade thread-cutting transmission assembly includes a first thread-cutting crank (61), a first thread-cutting connecting rod (62), a first thread-cutting shaft (63) rotatably supported in the sewing machine base plate (120), a second thread-cutting crank (64) and a third thread-cutting crank (65) both fixed on the first thread-cutting shaft (63), and a second thread-cutting connecting rod (66). The machine includes a main blade holder (67) rotatably mounted in the sewing machine base plate (120), the first thread cutting crank (61) being connected to the main blade thread cutting drive source (40) and driven to rotate by the main blade thread cutting drive source (40), the two ends of the first thread cutting connecting rod (62) being hinged to the first thread cutting crank (61) and the second thread cutting crank (64) respectively, and the two ends of the second thread cutting connecting rod (66) being hinged to the third thread cutting crank (65) and the main blade holder (67) respectively.

10. The sewing thread cutting control method according to claim 1, characterized in that: The double-acting thread-cutting mechanism also includes an auxiliary thread-cutting transmission assembly connected between the auxiliary thread-cutting drive source (50) and the auxiliary thread-cutting blade (30). The auxiliary thread-cutting transmission assembly includes a fourth thread-cutting crank (71), a third thread-cutting connecting rod (72), a second thread-cutting shaft (73) rotatably supported in the sewing machine base plate (120), a fifth thread-cutting crank (74) and a sixth thread-cutting crank (75) both fixed on the second thread-cutting shaft (73), and a fourth thread-cutting connecting rod (76). The machine includes a fourth thread-cutting crank (71) connected to and driven by an auxiliary thread-cutting drive source (50), and an auxiliary blade holder (77) rotatably mounted in the sewing machine base plate (120). The second ends of the third thread-cutting connecting rod (72) are respectively hinged to the fourth thread-cutting crank (71) and the fifth thread-cutting crank (74). The second ends of the fourth thread-cutting connecting rod (76) are respectively hinged to the sixth thread-cutting crank (75) and the auxiliary blade holder (77).

11. The sewing thread cutting control method according to claim 1, characterized in that: The main thread cutter (20) has a tip (23) at its end. The main thread cutter (20) has a thread hook groove (24) and a surface thread groove (25) on both sides along the axis of the rotary hook (110). The outer peripheral edge of the main thread cutter (20) has a surface thread sliding surface (26) connecting the opening of the tip (23) and the thread hook groove (24), and a surface thread sliding surface (27) connecting the opening of the tip (23) and the surface thread groove (25). The sewing thread cutting control method also includes a post-sewing automatic thread cutting control method, which includes the following steps: A1. After the last stitch of the sewing machine needle (150) moves upward from the sewing machine needle plate, the control system (10) controls the main blade thread cutting drive source (40) to move, causing the main thread cutting blade (20) to move in the first direction, so that the tip of the blade (23) is inserted into the top thread loop. Then, part of the top thread and the bottom thread slide into the thread separating groove (24) along the top and bottom thread sliding surface (26), and the other part of the top thread slides into the top thread separating groove (25) along the top thread sliding surface (27). A2. The control system (10) controls the main blade cutting drive source (40) to reverse the action, causing the main blade (20) to retract along the second direction, so that the main blade edge (21) moves to a position directly below or near the needle (150); at the same time, the control system (10) controls the auxiliary blade cutting drive source (50) to move, causing the auxiliary blade (30) to move along the first direction, so that the auxiliary blade edge (31) moves to a position directly below or near the needle (150), then the main blade edge (21) and the auxiliary blade edge (31) bite and cut the surface line and the bottom line at the position directly below or near the needle (150); A3. The control system (10) controls the main cutter wire cutting drive source (40) to continue to reverse, and continues to drive the main cutter wire cutting blade (20) to retract along the second direction to the outer periphery of the needle (150); at the same time, the control system (10) controls the auxiliary cutter wire cutting drive source (50) to reverse, and drives the auxiliary cutter wire cutting blade (30) to retract along the second direction to the outer periphery of the needle (150).

12. The sewing thread cutting control method according to claim 11, characterized in that: In steps S5 and A2, during the process of the feed teeth rising in the sewing machine, the control system (10) controls the auxiliary cutter thread drive source (50) to move, causing the auxiliary cutter thread (30) to move along the first direction.

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