Thread trimming mechanism for a sewing machine and double needle sewing machine

Abstract

The invention relates to a thread trimming mechanism of a sewing machine and a double-needle sewing machine, comprising a fixed knife, a movable knife and a movable knife driving part, the movable knife is provided with a knife part through hole, the side edge of the upper end hole of the knife part through hole forms a movable knife blade, the movable knife driving part can drive the movable knife to move to an initial position and a sewing starting extension position, when the movable knife is in the sewing starting extension position, the knife part through hole is located directly below the needle of the sewing machine, when the movable knife moves to the initial position, the movable knife blade can engage with the fixed knife blade, further comprising a bobbin thread retaining spring, a thread clamping piece and a suction assembly, the bobbin thread retaining spring is arranged below the movable knife, when the movable knife is in the initial position, a bobbin thread retaining structure is formed between the bobbin thread retaining part and the bobbin thread retaining spring, the suction assembly is provided with a suction port capable of generating a suction effect, when the movable knife is in the initial position, the suction port is located below the knife part through hole; the thread clamping piece is arranged above the movable knife, when the movable knife is in the initial position, a bobbin thread retaining structure is formed between the bobbin thread clamping part and the thread clamping piece, the movable knife driving part comprises a thread trimming motor.

Description

Technical Field

[0001] This invention relates to the field of sewing machinery technology, specifically to a thread-cutting mechanism for a sewing machine and a double-needle sewing machine. Background Technology

[0002] In conventional double-needle sewing machines, the thread-cutting mechanism uses an electromagnet in conjunction with a thread-cutting cam to drive the moving blade back and forth, achieving the thread-cutting function. In this design, the stroke of the moving blade is fixed, and the trajectory of the thread-cutting cam directly determines the stroke of the moving blade's extension and retraction. See the appendix for the structure of a conventional thread-cutting mechanism in a double-needle sewing machine. Figure 1 As shown, the wire-cutting electromagnet is fixed on the base plate. When the wire-cutting electromagnet is energized and attracted, the ball bearings of the main rod assembly will be engaged in the groove of the wire-cutting cam. As the wire-cutting cam rotates, the moving blade drive slider is driven to slide back and forth through the main rod assembly and the intermediate transmission mechanism composed of multiple transmission components. The moving blade drive slider drives the moving blade 3 fixed on it to move back and forth. Therefore, the moving blade moves back and forth under the drive of the wire-cutting cam. After engaging with the fixed blade, it can cut the thread.

[0003] The principle of existing wire-cutting mechanisms is as follows: (See Appendix) Figure 1 and attached Figure 4 As shown, the moving cutter has a hook and a moving blade. When the moving cutter begins to retract in preparation to cut the thread, the top thread and the bottom thread are already hooked by the hook on the moving cutter. At this time, the top thread and the bottom thread are still a complete thread. When the thread above the moving blade of the moving cutter comes into contact with the fixed blade of the stationary cutter, the thread will be cut. After the thread is cut, the top thread on the outer side of the stationary blade connects to the fabric, the top thread on the inner side connects to the needle, and the bottom thread connects to the bobbin. The bottom thread is also held by the bottom thread clamp under the moving cutter to prevent it from falling off.

[0004] After trimming, existing double-needle sewing machines often leave long thread ends on the top thread. When starting a new stitch, these long ends tend to tangle and become intertwined with the bottom thread or the sewing material itself, forming a raised clump of thread, commonly known as a "bird's nest." This clump is not only unsightly, but if it's in close contact with the skin, it can cause itching and discomfort. Therefore, removing these "bird's nests" is a persistent challenge in the garment industry, especially with double-needle sewing machines. These machines have two rotary hooks, one on each side, and the existing bird's nest removal mechanisms of single-needle flatbed sewing machines cannot be used on double-needle machines. Furthermore, the limited space on double-needle sewing machines restricts installation space. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a thread cutting mechanism for a sewing machine and a double-needle sewing machine, which can make the fabric nest small and effectively prevent the problem of sewing threads coming loose at the start.

[0006] To achieve the above objectives, the present invention provides a thread-cutting mechanism for a sewing machine, comprising a fixed blade, a movable blade, and a movable blade drive unit. The movable blade is provided with a hook and a through hole. One edge of the upper opening of the through hole forms the blade edge of the movable blade. The movable blade drive unit can drive the movable blade to an initial position and a sewing start extension position. When the movable blade is in the sewing start extension position, the through hole is located directly below the sewing machine needle. When the movable blade moves from the sewing start extension position to the initial position, the blade edge of the movable blade engages with the blade edge of the fixed blade. The thread-cutting mechanism also includes a bobbin thread retaining spring, a thread clamping plate, and a suction assembly. The bobbin thread retaining spring is disposed below the movable blade, and the lower side of the movable blade... The device includes a bottom thread holding part, and when the moving blade is in the initial position, the bottom thread holding part and the bottom thread holding spring form a bottom thread holding structure for stabilizing the bottom thread. The adsorption assembly has an adsorption port and can generate a suction effect at the adsorption port. When the moving blade is in the initial position, the adsorption port is located below the through hole of the blade. The thread clamping piece is disposed on the upper side of the moving blade, and the moving blade has a top thread clamping part. When the moving blade is in the initial position, the top thread clamping part is located on the side of the through hole of the blade near the needle, and the top thread clamping part and the thread clamping piece form a top thread holding structure for stabilizing the top thread. The moving blade drive part includes a thread cutting motor and an intermediate transmission assembly, and the thread cutting motor is connected to the moving blade through the intermediate transmission assembly.

[0007] Furthermore, the moving blade moves linearly along the front-back direction of the sewing machine, and the through hole of the blade is a strip-shaped hole extending along the front-back direction.

[0008] Furthermore, it also includes a moving knife guide frame and a moving knife drive slider. The moving knife guide frame is fixed in the sewing machine. The moving knife guide frame is provided with a guide groove extending in the front-to-back direction. The moving knife drive slider is installed in the guide groove, and the moving knife is fixed on the moving knife drive slider.

[0009] Furthermore, the moving blade is also provided with a guide groove that connects the hook and the through hole of the blade.

[0010] Furthermore, it also includes a fixedly mounted support spring plate, which is supported on the underside of the baseline retaining spring.

[0011] Furthermore, the adsorption assembly includes a straw, the end of which forms an adsorption port.

[0012] The present invention also provides a double-needle sewing machine, comprising two rotary hooks and two needles, wherein the two rotary hooks work in conjunction with the two needles respectively, and further comprising the aforementioned thread-cutting mechanism, wherein there are two thread-cutting mechanisms, and the two thread-cutting mechanisms are respectively used for cutting the thread of the two needles.

[0013] Furthermore, the two wire-cutting mechanisms share a single wire-cutting mechanism.

[0014] Furthermore, the two thread-cutting mechanisms share an intermediate transmission assembly, which includes a rotating crank, a drive connecting rod, a first thread-cutting lever, a synchronizing connecting rod, a second thread-cutting lever, a first moving blade shaft, and a second moving blade shaft. The rotating crank is fixed to the output shaft of the thread-cutting motor. The first and second moving blade shafts are rotatably mounted in the sewing machine. The first thread-cutting lever is fixedly connected to the first moving blade shaft, and the second thread-cutting lever is fixedly connected to the second moving blade shaft. One end of the drive connecting rod is hinged to the rotating crank, and the other end is hinged to the first thread-cutting lever. Both ends of the synchronizing connecting rod are respectively hinged to the first and second thread-cutting levers. The first moving blade shaft is provided with a first swing arm connected to the moving blade of one thread-cutting mechanism, and the second moving blade shaft is provided with a second swing arm connected to the moving blade of the other thread-cutting mechanism.

[0015] Furthermore, the lengths of the synchronizing link and the driving link are adjustable.

[0016] As described above, the thread-cutting mechanism and double-needle sewing machine of the present invention have the following beneficial effects:

[0017] 1. An innovative method for solving the bird nest problem is provided, which realizes the function of sewing a small bird nest. When sewing, the top thread is shortened by a thread-cutting mechanism. The bird nest on the sewn material after sewing is smaller and more beautiful in appearance. This solves the problem that the original bird nest was too big and would cause discomfort when in contact with the human body, thus meeting the user's needs.

[0018] 2. It can effectively improve the sewing thread rate. Since the thread is held by the thread clamp and the moving blade after the sewing, the thread will not be pulled out of the fabric due to the movement of the thread take-up lever or the needle, thus avoiding the problem of the sewing thread coming loose.

[0019] 3. The thread-cutting motor has high controllability and can well control the timing of the moving blade, thus facilitating the operation of the sewing machine to achieve the actions of starting to sew small bird nests and cutting threads.

[0020] 4. The thread-cutting mechanism has a compact and reasonable structure. It does not use any bulky additional devices that would interfere with the user's operation or affect the replacement of the bobbin. It can drive two moving blades to move synchronously through a thread-cutting motor and an intermediate transmission component. The moving blades are mounted on the shuttle frame. Even if the user changes the needle position and moves the shuttle frame, the relative position of the rotary hook and the needle hooking the thread remains unchanged, so there is no need to adjust the position of the moving blades. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an existing wire-cutting mechanism.

[0022] Figure 2 This is a schematic diagram of the wire-cutting mechanism of the present invention.

[0023] Figure 3 for Figure 2 Enlarged view of circle A in the image.

[0024] Figure 4 This is a schematic diagram of the moving blade in this invention.

[0025] Figure 5 This is a schematic diagram of state one during the operation of the wire-cutting mechanism of the present invention.

[0026] Figure 6 This is a schematic diagram of state two during the operation of the wire-cutting mechanism of the present invention.

[0027] Figure 7 This is a schematic diagram of state three during the operation of the wire-cutting mechanism of the present invention.

[0028] Figure 8 This is a schematic diagram of state four during the operation of the wire-cutting mechanism of the present invention.

[0029] Figure 9 This is a schematic diagram of state five during the operation of the wire-cutting mechanism of the present invention.

[0030] Figure 10 This is a schematic diagram of state six during the operation of the wire-cutting mechanism of the present invention.

[0031] Figure 11 This is a schematic diagram of the surface line position during state six of the operation of the wire cutting mechanism of the present invention.

[0032] Figure 12 This is a schematic diagram of the starting stitch of the seam head in this invention.

[0033] Figure 13 This is a schematic diagram of the intermediate transmission component in this invention.

[0034] Explanation of icon numbers

[0035] 1. Rotary shuttle

[0036] 2. Fixed tool

[0037] 2a Fixed blade edge

[0038] 3. Cutting

[0039] 3a Hook

[0040] 3b Through hole in the cutting edge

[0041] 3C moving blade

[0042] 3D facet clamping part

[0043] 3e guide slot

[0044] 4. Wire-cutting cam

[0045] 5. Wire-cutting electromagnet

[0046] 6. Bottom-line holding spring

[0047] 7. Straws

[0048] 7a Adsorption port

[0049] 8. Wire clips

[0050] 9 Support spring sheet

[0051] 10 needle plate

[0052] 10a Adjusting Bolt

[0053] 11. Delivery of cloth teeth

[0054] 12 needles

[0055] 13. Side Dish

[0056] 14 Bottom Line

[0057] 15. Moving blade driven slider

[0058] 16 Moving tool guide bracket

[0059] 17 Wire cutting motor

[0060] 18. Turn the crank.

[0061] 19 Drive Linkage

[0062] 20th tangent lever

[0063] 21 First moving cutter axis

[0064] 22 Synchronous Link

[0065] 22a First shot

[0066] 22b Second shot

[0067] 23 Second Tangential Lever

[0068] 24 Second moving cutter axis

[0069] 24a Second Swing Arm

[0070] B. Start stitch head Detailed Implementation

[0071] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0072] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0073] See Figures 2 to 13 This invention provides a thread-cutting mechanism for a sewing machine, including a fixed blade 2, a movable blade 3, and a movable blade drive unit. The movable blade drive unit drives the movable blade 3 to move. The movable blade 3 is provided with a hook 3a, which is used to hook the top thread 13 and the bottom thread 14 during thread cutting. In the thread-cutting mechanism of this invention, the movable blade 3 is also provided with a blade through hole 3b. One side edge of the upper end of the blade through hole 3b forms the movable blade edge 3c. The movable blade drive unit can drive the movable blade 3 to move to the initial position and the starting sewing extension position. When the movable blade 3 is in the starting sewing extension position, the blade through hole 3b is located directly below the sewing machine needle 12. When the movable blade 3 moves from the starting sewing extension position to the initial position, the movable blade edge 3c can engage with the fixed blade edge 2a of the fixed blade 2. The thread cutting mechanism also includes a bottom thread holding spring 6, a thread clamping plate 8, and an adsorption assembly. The bottom thread holding spring 6 is located below the moving blade 3. The lower side of the moving blade 3 has a bottom thread holding part. When the moving blade 3 is in the initial position, the bottom thread holding part and the bottom thread holding spring 6 directly form a bottom thread holding structure for stabilizing the bottom thread 14. The adsorption assembly has an adsorption port 7a and can generate a suction effect at the adsorption port 7a. When the moving blade 3 is in the initial position, the adsorption port 7a is located below the blade through hole 3b. The thread clamping plate 8 is located on the upper side of the moving blade 3. The moving blade 3 has a top thread clamping part 3d. When the moving blade 3 is in the initial position, the top thread clamping part 3d is located on the side of the blade through hole 3b near the needle 12, that is, between the needle 12 and the blade through hole 3b. The top thread clamping part 3d and the thread clamping plate 8 form a top thread holding structure. The moving blade drive unit includes a thread cutting motor 17 and an intermediate transmission assembly. The thread cutting motor 17 and the moving blade 3 are connected through the intermediate transmission assembly.

[0074] The thread-cutting mechanism of this invention can be used in both double-needle and single-needle sewing machines. The thread-cutting mechanism works in conjunction with a needle 12 and a rotary hook 1. The thread-cutting motor 17 and the suction assembly are both controlled by the sewing machine's electronic control system. The thread-cutting mechanism can effectively achieve small-volume bird's nests and effectively prevents thread slippage during sewing. The specific working process and principle are as follows:

[0075] (1) Initial state before starting the seam, see Figure 5 As shown, at this time, the thread end of the top thread 13 is located on the needle 12, the moving blade 3 is in the initial position, the bottom thread retaining part is in contact with the bottom thread retaining spring 6, and a bottom thread retaining structure is formed between the two. The bottom thread 14 extending from the bobbin is held by the bottom thread retaining structure and kept stable.

[0076] (2) See Figure 6 To begin sewing, adjust the stitch length to be shorter than normal sewing stitch length. The sewing machine's electronic control system controls the thread-cutting motor 17, which drives the moving blade 3 from its initial position to the starting sewing extension position. The blade through-hole 3b is located directly below the sewing machine needle 12. At this time, the bobbin thread 14, which was originally held below the moving blade 3, may fall off the bobbin thread retaining spring 6 due to the movement of the moving blade 3. Therefore, the suction component is activated, and the suction port 7a generates negative pressure. The suction port 7a is also located directly below the bobbin thread 14. If the bobbin thread 14 falls off, it will be sucked up by the suction tube 7, ensuring it does not fall off and avoiding problems such as the sewing not starting. By controlling the action of the thread-cutting motor 17, the moving blade 3 can accurately reach the starting sewing extension position and maintain it for a period of time.

[0077] (3) See Figure 7 At this moment, the rotary hook 1 is hooking the thread. At this time, the needle 12 has descended to enter the through hole 3b of the moving knife 3. The face thread 13 on both sides of the hole of the needle 12 also enters the through hole 3b of the knife. At the same time, the tip of the rotary hook 1 passes through the thread loop of the face thread 13.

[0078] (4) See Figure 8 After the tip of the rotary hook 1 enters the thread loop 13, it continues to move and expand the thread loop 13. At this time, the needle 12 has moved upward to above the feed dog 11. On the one hand, the rotary hook 1 has a certain pulling force on the thread loop 13. On the other hand, the thread loop 13 is not a complete loop when the first stitch is started. Therefore, as the rotary hook 1 continues to move and the loop expands, the thread loop 13 breaks and the thread end of the thread 13 comes off the rotary hook 1. Finally, the thread end of the thread 13 passes through the through hole 3b of the blade 3 and stays below the blade 3.

[0079] (5) When the thread take-up lever is in the upward movement state, the sewing machine's thread take-up lever will pull out part of the top thread 13 from below the feed dog 11 until the thread take-up lever is at its highest point (i.e., the upper needle stop position), at which point the top thread 13 will no longer be pulled out. See [link to documentation]. Figure 9 As shown. Then the moving cutter 3 begins to retract, moving from the starting position back to the initial position. During the retraction, the moving cutter 3 drives the top thread 13 toward the fixed cutter 2, while the top thread 13 is continuously driven by the thread take-up lever.

[0080] (6) When the thread take-up lever moves to the upper stop needle position, the moving blade 3 completes the reset action and reaches the initial position. See below. Figure 10 and Figure 11 As shown, the moving blade 3c engages with the fixed blade 2a to cut the face thread 13. When the moving blade 3 reaches its initial position, the face thread holding part 3d on the moving blade 3 contacts the face thread clamping piece 8, forming a face thread holding structure between them. At this time, the face thread holding part 3d is located between the through hole 3b of the blade and the needle 12. Therefore, the part of face thread 13 connected to the needle 12 will be held by the face thread holding structure and will not fall off, while the cut face thread 13 will be sucked away by the suction port 7a located below the moving blade 3.

[0081] This completes the process of starting the first stitch. Through the above process, on the one hand, the length of the thread end of the top thread 13 on the needle 12 can be shortened, and the cut thread end has been sucked away by the suction port 7a and will not accumulate under the oil tray. On the other hand, after the top thread 13 is cut, the part of the top thread 13 connected to the needle 12 will be stably clamped by the thread clamping plate 8 above the blade 3 and will not fall off.

[0082] Then the double-needle sewing machine continues to run the second stitch. Since the top thread 13 on the needle 12 is held by the thread clamp 8 and the moving blade 3, the loop of thread after the rotary hook 1 hooks the thread continues to expand after the second stitch. Therefore, the top thread 13 can bring the bottom thread 14 onto the fabric to form a stitch. At the same time, because the top thread 13 has a short end, and the current stitch length can be smaller than the normal stitch length, the resulting bird's nest will be particularly small, only piling up at a small point, looking more like a close-knit stitch with a cut thread. Also, because the top thread 13 is held in place during the second stitch, it will not be pulled out of the fabric by the movement of the take-up lever, which effectively prevents the stitch from coming loose. See the starting stitch of the small bird's nest stitch. Figure 12 As shown, it resembles the state of finishing sewing and cutting the thread. Of course, even if the top thread 13 and the bottom thread 14 are intertwined and wrapped around each other, the bird's nest will not be very large because the length of the top thread 13 has been effectively shortened.

[0083] In the thread-cutting mechanism of this invention, during thread-cutting after normal sewing, the moving blade 3 extends below the needle 12, exceeding the starting sewing extension position by a certain distance to the thread-cutting extension position. Then, the blade retracts, hooking the top thread 13 and bottom thread 14 via the hook 3a to reach the fixed blade 2. The moving blade 3c and the fixed blade 2a then engage, completing the thread-cutting operation. After thread cutting, the bottom thread 14 extending from the rotary hook 1 is positioned below the moving blade 3 and held by the bottom thread holding structure formed by the bottom thread holding part and the bottom thread holding spring 6. The thread-cutting mechanism returns to its state before sewing, i.e., returns to its original position. Figure 5As shown, wait for the next stitching start. When the moving blade 3 cuts the thread, the suction component works, causing the suction port 7a to suck up slightly, preventing the cut thread 13 from not being sucked up during the bird's nest stitching start.

[0084] The thread-cutting mechanism of the present invention is driven independently by the thread-cutting motor 17 to move the moving blade 3. The stroke of the moving blade 3 is controllable. It can work with the bottom thread retaining spring 6, the thread clamping plate 8 and the adsorption component when sewing begins. It also works with the action of the sewing machine needle 12 and the thread take-up lever to cut and clamp the thread end of the top thread 13. It can effectively realize small-volume bird nests and effectively prevent the problem of thread detachment when sewing begins.

[0085] See Figures 2 to 13 The present invention will be further described below with reference to a specific embodiment:

[0086] In this embodiment, see Figure 3 and Figure 4 As a preferred design, the moving blade 3 moves linearly along the front-to-back direction of the sewing machine, and the blade through-hole 3b is a strip-shaped hole extending along the front-to-back direction. When used in a double-needle sewing machine, since the needle bar swings back and forth during sewing, the length of the blade through-hole 3b along the front-to-back direction is determined according to the working stitch length of the sewing machine and the range of the needle 12's back-to-back swing, to ensure that the needle 12 can smoothly enter the blade through-hole 3b when the first stitch is started, and that the needle 12 will not collide with the moving blade 3 when it swings back and forth.

[0087] In this embodiment, see Figure 2 and Figure 5 As a preferred design, the thread cutting mechanism also includes a moving knife guide frame 16 and a moving knife drive slider 15. The moving knife guide frame 16 is fixed on the shuttle frame of the sewing machine. The moving knife guide frame 16 is provided with a guide groove extending in the front-to-back direction. The moving knife drive slider 15 is installed in the guide groove. The moving knife 3 is fixed on the moving knife drive slider 15. The moving knife drive unit is connected to the moving knife drive slider 15 and can drive the moving knife drive slider 15 to move linearly back and forth in the guide groove to realize the knife extension and retraction.

[0088] In this embodiment, see Figure 4 As a preferred design, the moving blade 3 is also provided with a guide groove 3e that connects the hook part 3a and the through hole 3b of the blade part. When cutting the thread, the moving blade 3 retracts from below the needle 12 to the initial position, and the hook part 3a hooks the top thread 13 and the bottom thread 14 and moves toward the fixed blade 2. The top thread 13 and the bottom thread 14 will be located in the guide groove 3e, which plays a role in stabilizing the position of the top thread 13 and the bottom thread 14.

[0089] In this embodiment, see Figure 2 and Figure 4As a preferred design, the bottom thread retaining spring 6 is an elastic clamping piece. When the moving blade 3 moves, the bottom thread retaining spring 6 can make good contact with the lower side of the moving blade 3, ensuring stable clamping of the bottom thread 14. The wire cutting mechanism also includes a fixedly installed support spring plate 9, which supports the lower side of the bottom thread retaining spring 6 and can provide an upward elastic force to the bottom thread retaining spring 6, further ensuring that the bottom thread retaining spring 6 and the moving blade 3 can stably clamp the bottom thread 14.

[0090] In this embodiment, see Figure 2 and Figure 4 As a preferred design, the adsorption assembly includes a straw 7 and a suction component (not shown in the attached drawings). The end of the straw 7 forms an adsorption port 7a. The straw 7 is located below the supporting spring plate 9 and is inclined, while the adsorption port 7a is horizontal. The straw 7 is connected to the suction component. By suctioning air through the suction component, a negative pressure is generated at the adsorption port 7a, thereby achieving adsorption.

[0091] In this embodiment, see Figure 2 , Figure 3 and Figure 11 The clamping plate 8 is a thin, elastic sheet structure located below the needle plate 10 and fixed to the needle plate 10 by screws. An adjusting bolt 10a is screwed onto the needle plate 10. The adjusting bolt 10a is located above the clamping plate 8, and its lower end is used to abut against the clamping plate 8. The degree of deformation of the clamping plate 8 can be adjusted by adjusting the adjusting bolt 10a, that is, adjusting the contact pressure between the clamping plate 8 and the face thread clamping part 3d of the moving knife 3, thereby adjusting the clamping force on the face thread 13.

[0092] The present invention also provides a double-needle sewing machine, see [link to documentation]. Figure 1 It includes two rotary hooks 1 and two needles 12, with the two needles 12 arranged one in front of the other. The two rotary hooks 1 are located on the left and right sides of the two needles 12, respectively, and each rotary hook 1 works in conjunction with one needle 12. It also includes the aforementioned thread-cutting mechanism. Correspondingly, there are two thread-cutting mechanisms, each used for cutting the thread of one needle 12. That is, one thread-cutting mechanism works with one needle 12, and the other thread-cutting mechanism works with the other needle 12.

[0093] In this embodiment, preferably, see Figure 2 and, Figure 3 and Figure 13 The two wire-cutting mechanisms share a single moving blade drive unit, through which a wire-cutting motor 17 in the moving blade drive unit simultaneously drives the two moving blades 3 to move synchronously. In this embodiment, see... Figure 2 and Figure 13The intermediate transmission assembly includes a rotating crank 18, a drive connecting rod 19, a first tangent lever 20, a synchronous connecting rod 22, a second tangent lever 23, a first moving cutter shaft 21, and a second moving cutter shaft 24. The rotating crank 18 is fixed to the output shaft of the thread-cutting motor 17. Both the first moving cutter shaft 21 and the second moving cutter shaft 24 are rotatably mounted in the sewing machine. The first tangent lever 20 is fixedly connected to the first moving cutter shaft 21, and the second tangent lever 23 is fixedly connected to the second moving cutter shaft 24. The drive connecting rod... One end of 19 is hinged to the rotating crank 18 and the other end is hinged to the first tangential lever 20. The two ends of the synchronous connecting rod 22 are respectively hinged to the first tangential lever 20 and the second tangential lever 23. The first moving blade shaft 21 is provided with a first swing arm connected to the moving blade 3 of a wire cutting mechanism. The second moving blade shaft 24 is provided with a second swing arm 24a connected to the moving blade 3 of another wire cutting mechanism. Specifically, the first swing arm and the second swing arm 24a are both connected to the moving blade drive slider 15 where the moving blade 3 is located.

[0094] In this embodiment, when the moving blade drive unit is working, the wire cutting motor 17 drives the crank 18 to rotate, which in turn drives the first tangent lever 20 to rotate via the drive linkage 19. When the first tangent lever 20 rotates, it drives the first moving blade shaft 21 to rotate. The first moving blade shaft 21 drives the moving blade drive slider 15 containing one of the moving blades 3 to move via its first swing arm, thereby driving the moving blade 3 to move. At the same time, the first tangent lever 20 drives the second tangent lever 23 to rotate via the synchronous linkage 22. When the second tangent lever 23 rotates, it drives the second moving blade shaft 24 to rotate. The second moving blade shaft 24 drives the moving blade drive slider 15 containing the other moving blade 3 to move via its second swing arm 24a, thereby driving the moving blade 3 to move. This achieves synchronous movement of the two moving blades 3 in one moving blade drive unit.

[0095] In this embodiment, see Figure 13 As a preferred design, the drive linkage 19 is a telescopic rod with adjustable length. The synchronous linkage 22 includes a first rod 22a and a second rod 22b. The first rod 22a has a slotted hole, through which a bolt is threaded to the second rod 22b, thus fixing the first rod 22a and the second rod 22b in place. The first rod 22a is hinged to the first tangential lever 20, and the second rod 22b is hinged to the second tangential lever 23. Changing the position of the bolt in the slotted hole changes the effective working length of the synchronous linkage 22. By using the adjustable length synchronous linkage 22 and drive linkage 19, the lengths of the synchronous linkage 22 and drive linkage 19 can be adjusted according to the structure of the sewing machine and the working conditions of the moving blade 3, meeting various usage requirements and facilitating assembly.

[0096] In this invention, the thread-cutting motor 17 is a stepper motor, and the thread-cutting motor 17 is guaranteed to be at the same zero point during each assembly by a limit pin. The moving blade drive sliders 15 of the two thread-cutting mechanisms are both mounted on the shuttle frame where their corresponding rotary hooks 1 are located. The first moving blade shaft 21 and the second moving blade shaft 24 are also mounted in their corresponding shuttle frames. Even if the user changes the needle position and moves the shuttle frame, the relative position of the rotary hook 1 and the needle 12 hooking the thread remains unchanged, so there is no need to adjust the position of the moving blade 3.

[0097] As can be seen from the above, the thread-cutting mechanism and the double-needle sewing machine of the present invention have the following beneficial effects:

[0098] 1. An innovative method for solving the bird nest problem is provided, which realizes the function of sewing a small bird nest. When sewing, the top thread 13 is shortened by a thread cutting mechanism. The bird nest on the sewing material after sewing is smaller and more beautiful in appearance. This solves the problem that the original bird nest was too big and would cause discomfort when in contact with the human body, thus meeting the user's needs.

[0099] 2. It can effectively improve the sewing thread rate. Since the thread 13 after the sewing is held by the thread clamping plate 8 and the moving knife 3, the thread 13 will not be pulled out of the sewing material due to the movement of the thread take-up lever or the needle 12, thus avoiding the problem of sewing thread coming loose.

[0100] 3. The thread-cutting motor 17 has high controllability and can well control the timing of the moving blade 3, thus facilitating the operation of the sewing machine to achieve the actions of starting to sew small bird nests and cutting threads.

[0101] 4. The thread-cutting mechanism has a compact and reasonable structure. It does not use any large additional devices that would interfere with the user's operation or affect the replacement of the bobbin. It can drive two moving blades 3 to move synchronously through a thread-cutting motor 17 and an intermediate transmission assembly. The moving blades 3 are mounted on the shuttle frame. Even if the user moves the shuttle frame to change the needle position, the relative position of the rotary hook 1 and the needle 12 hooking the thread remains unchanged, so there is no need to adjust the position of the moving blades 3.

[0102] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0103] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A thread-cutting mechanism for a sewing machine, comprising a fixed blade (2), a movable blade (3), and a movable blade drive unit, wherein the movable blade (3) is provided with a hook (3a), characterized in that: The moving blade (3) is also provided with a blade through hole (3b). One side edge of the upper end of the blade through hole (3b) forms the blade edge (3c). The moving blade drive unit can drive the moving blade (3) to the initial position and the starting sewing extension position. When the moving blade (3) is in the starting sewing extension position, the blade through hole (3b) is located directly below the sewing machine needle (12). When the moving blade (3) moves from the starting sewing extension position to the initial position, the blade edge (3c) of the moving blade can engage with the fixed blade edge (2a) of the fixed blade (2). The thread cutting mechanism also includes a bottom thread holding spring (6), a thread clamping piece (8), and an adsorption assembly. The bottom thread holding spring (6) is located below the moving blade (3). The lower side of the moving blade (3) is provided with a bottom thread holding part. When the moving blade (3) is in the initial position, the bottom thread holding part and the bottom thread holding spring (6) form a bottom thread holding structure for stabilizing the bottom thread (14). The adsorption assembly is provided with an adsorption port (7a). It can generate a suction effect at the suction port (7a). When the moving knife (3) is in the initial position, the suction port (7a) is located below the through hole (3b) of the knife part; the clamping piece (8) is set on the upper side of the moving knife (3). The moving knife (3) is provided with a top thread clamping part (3d). When the moving knife (3) is in the initial position, the top thread clamping part (3d) is located on the side of the through hole (3b) of the knife part close to the needle (12). The top thread clamping part (3d) and the clamping piece (8) form a top thread holding structure for stabilizing the top thread. The moving knife drive part includes a cutting motor (17) and an intermediate transmission assembly. The cutting motor (17) and the moving knife (3) are connected through the intermediate transmission assembly. The moving knife (3) is also provided with a guide groove (3e) connecting the hook part (3a) and the through hole (3b) of the knife part; it also includes a fixedly installed support spring piece (9). The support spring piece (9) is supported on the lower side of the bottom thread holding spring (6).

2. The wire-cutting mechanism according to claim 1, characterized in that: The moving blade (3) moves linearly along the front-back direction of the sewing machine, and the through hole (3b) of the blade is a strip-shaped hole extending along the front-back direction.

3. The wire-cutting mechanism according to claim 1, characterized in that: It also includes a moving knife guide frame (16) and a moving knife drive slider (15). The moving knife guide frame (16) is fixed in the sewing machine. The moving knife guide frame (16) is provided with a guide groove extending in the front-back direction. The moving knife drive slider (15) is installed in the guide groove. The moving knife (3) is fixed on the moving knife drive slider (15).

4. The wire-cutting mechanism according to claim 1, characterized in that: The adsorption assembly includes a straw (7), the port of which forms an adsorption port (7a).

5. A double-needle sewing machine, comprising two rotary hooks (1) and two needles (12), wherein the two rotary hooks (1) cooperate with the two needles (12) respectively, characterized in that: It also includes a thread-cutting mechanism as described in any one of claims 1 to 4, wherein there are two thread-cutting mechanisms, and the two thread-cutting mechanisms are respectively used for thread-cutting work of two needles (12).

6. The double-needle sewing machine according to claim 5, characterized in that: The two wire-cutting mechanisms share a single moving blade drive unit.

7. The double-needle sewing machine according to claim 6, characterized in that: The two thread-cutting mechanisms share an intermediate transmission assembly, which includes a rotating crank (18), a drive connecting rod (19), a first thread-cutting lever (20), a synchronous connecting rod (22), a second thread-cutting lever (23), a first moving cutter shaft (21), and a second moving cutter shaft (24). The rotating crank (18) is fixed on the output shaft of the thread-cutting motor (17). The first moving cutter shaft (21) and the second moving cutter shaft (24) are rotatably mounted in the sewing machine. The first thread-cutting lever (20) is fixedly connected to the first moving cutter shaft (21). The second tangential lever (23) is fixedly connected to the second moving blade shaft (24). One end of the driving connecting rod (19) is hinged to the rotating crank (18) and the other end is hinged to the first tangential lever (20). The two ends of the synchronous connecting rod (22) are respectively hinged to the first tangential lever (20) and the second tangential lever (23). The first moving blade shaft (21) is provided with a first swing arm connected to the moving blade (3) of a wire cutting mechanism. The second moving blade shaft (24) is provided with a second swing arm (24a) connected to the moving blade (3) of another wire cutting mechanism.

8. The double-needle sewing machine according to claim 7, characterized in that: The lengths of the synchronizing link (22) and the driving link (19) are adjustable.

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