A sewing machine thread cutting mechanism based on a connecting rod transmission

Abstract

The present application relates to sewing machine technology field, concretely is a kind of sewing machine cutting mechanism based on connecting rod drive, including installation base plate and the linear guide rail slide mechanism being arranged in the lower right of installation base plate, the linear guide rail slide mechanism includes two guide rails being symmetrically arranged and the slider being limited between two the guide pressing plate and making reciprocating linear sliding, driving link is hinged on the slider, the upper end of the driving link is hinged with rocker, the rocker is triangular rocker structure, and the middle part of the rocker is rotatably connected to installation base plate.The present application is by setting the guide groove of different curvature on tool holder, cooperate driving pin sliding in guide groove to realize variable force arm output, can amplify input torque in the key stage of cutting line, simultaneously cooperate with the design that fixed blade edge is tangent to tool holder rotation track, ensure that cutting line direction is always orthogonal with sewing thread, effectively avoid bird's nest phenomenon, improve thread end cutting quality, reduce the high-frequency noise generated during work.

Description

Technical Field

[0001] This invention relates to the field of sewing machinery technology, specifically to a thread cutting mechanism for a sewing machine based on linkage transmission. Background Technology

[0002] The thread-cutting mechanism of a sewing machine automatically cuts the top and bottom threads after sewing by driving a moving blade and a fixed blade to perform relative shearing motion. Currently, existing thread-cutting mechanisms for sewing machines based on linkage transmission typically include a drive source, a cascaded linkage transmission chain, and a moving blade assembly and a fixed blade assembly at the execution end. The drive source usually uses a thread-cutting electromagnet or a main shaft cam pair, which drives the moving blade to reciprocate around its fixed axis through the cascaded linkage transmission chain, using the relative shearing force between the moving blade and the fixed blade to cut the thread.

[0003] While the aforementioned linkage-based tangential sewing method is widely used, it is prone to defects such as tangential trajectory deviation and excessively long thread ends during high-speed sewing above 4000 rpm or when sewing fabrics of alternating thicknesses. The main reason is that existing cascaded linkage transmission chains contain multiple rotating pairs. Under the alternating load of high-speed reciprocating operation, the mechanical clearance of each rotating pair is progressively amplified. When the transmission reaches the end of the actuator, this causes significant lateral oscillation and out-of-plane runout of the moving blade, leading to missed cuts, incomplete thread breakage, or hard blade wear. Furthermore, the motion curve of the moving blade exhibits continuous near-chordal vibration characteristics, lacking the necessary mechanical dwell range at critical tangential positions, resulting in high-speed instantaneous shearing. When the thread tension fluctuates instantaneously, the thread is prone to slippage before shearing, leading to extremely poor initial thread end consistency after cutting. Simultaneously, during high-speed reversal, traditional irregularly shaped linkage components, due to their large spatial span and uneven mass distribution, have a large moment of inertia relative to the rotation center, generating huge transient inertial impacts that easily accelerate fatigue wear of the hinged drive pins and bushings. These defects can seriously affect the quality of the thread ends in the sewn product, leading to problems such as bird's nest effect and high-frequency noise, reducing the high-speed thread cutting reliability of the sewing machine and the overall service life of the machine. Summary of the Invention

[0004] The purpose of this invention is to provide a sewing machine thread cutting mechanism based on linkage transmission, so as to solve the technical problems mentioned in the background art, such as large lateral swing and jump of the moving blade and severe inertial impact leading to accelerated wear when the existing thread cutting mechanism is running at high speed.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A thread-cutting mechanism for a sewing machine based on linkage transmission includes a mounting base plate and a linear guide slider mechanism disposed on the lower right side of the mounting base plate. The linear guide slider mechanism includes two symmetrically arranged guide rails and a slider constrained between the two guide rails and reciprocating linearly. A drive linkage is hinged to the slider, and a rocker arm is hinged to the upper end of the drive linkage. The rocker arm has a triangular rocker arm structure, and its middle part is rotatably connected to the mounting base plate. A drive pin is vertically mounted on the output end of the rocker arm. A knife holder is rotatably connected to the mounting base plate, and a guide groove is formed on the knife holder. The drive pin extends into the guide groove. A fixed knife is fixedly mounted on the mounting base plate, and a moving knife is provided on the side of the knife holder facing the cutting edge of the fixed knife. The cutting edge plane of the fixed knife is tangential to the rotation trajectory of the knife holder. Further, the guide groove includes a first groove segment and a second groove segment that are connected, and the radius of curvature of the second groove segment is greater than the radius of curvature of the first groove segment.

[0006] By setting a rotatable tool holder on the mounting base plate, and with the guide groove located on the cutting edge side of the tool holder facing the fixed blade, the space at the end of the tool holder's execution allows the drive pin to directly act on the extreme resistance generated by the thread shearing, thereby effectively improving the deformation-resistant shearing efficiency. The connected first and second groove sections within the guide groove, along with the moving blade on the side of the tool holder, allow the drive pin to rotate with the rocker arm during operation. This drives the power of the linear guide slider mechanism into the different-diameter trajectory of the guide groove. As the drive pin slides within the trajectory, it adjusts the swing curve and amplifies the input force arm. Subsequently, the moving blade rubs against the cutting edge plane of the fixed blade, achieving effective shearing and automatic cutting of the top and bottom threads.

[0007] Furthermore, the No. 1 and No. 2 slots are smoothly connected. In practical applications, if a rotating pair experiences problems such as increased clearance or lateral sway due to long-term use or high-speed reciprocating operation, the moving blade assembly does not need to disassemble the entire linkage transmission chain. It only needs to move the drive pin from the No. 1 slot to the No. 2 slot, which has a larger radius of curvature. This shortens the shearing completion time and reduces the maintenance costs of blade wear and missed cuts. At the same time, the tangential setting of the fixed blade cutting edge plane and the blade holder rotation trajectory allows for convenient orthogonal cutting of the thread along the optimal tangential direction when there are instantaneous fluctuations in thread tension or easy slippage of the thread end. This improves the thread end consistency performance of the entire cutting mechanism.

[0008] Preferably, the tool holder includes a mounting part, a connecting part, and an extension part. The connecting part is rotatably connected to the mounting base plate. The connecting part is cylindrical. The mounting part and the extension part are both located on the outer side wall of the connecting part. The mounting part is located on the opposite side of the extension part, and the mounting part and the extension part are asymmetrically arranged. The second groove section extends into the extension part, and the moving tool is fixedly mounted on the connecting part.

[0009] By setting an installation section and an extension section on the outer wall of the connecting part, and with the installation section and extension section being asymmetrically arranged, it is beneficial to the rigid transmission of high torque shearing force, and also facilitates the installation, disassembly, coaxial fine adjustment and replacement of the moving blade on the connecting part. In practical applications, if the moving blade is damaged or the cutting edge becomes dull due to long-term use or high-speed impact wear, the operator can easily replace it without disassembling the entire complex cascade linkage transmission chain, reducing maintenance costs and time. Furthermore, the second groove section extends into the extension section, which is beneficial to the nonlinear optimization of the overall dynamic tangential performance. Moreover, the configuration parameters of the installation section and the extension section can be selected according to actual needs. For example, high-rigidity and lightweight metal alloy materials can be used to further improve the lateral bending resistance transmission efficiency of the blade holder, thereby improving the dynamic operation performance of the entire sewing machine tangential mechanism and ensuring that the moving blade can operate stably under various harsh conditions such as high-speed sewing above 4000 rpm or sewing fabrics of alternating thicknesses.

[0010] Preferably, a transition section is provided at the junction of the first groove segment and the second groove segment, and the two ends of the transition section are tangent to the first groove segment and the second groove segment, respectively.

[0011] By setting a transition section at the junction of the first and second slot sections, the reciprocating trajectory of the drive pin in the guide groove is further optimized. The design of the two ends of the transition section being tangent to the first and second slot sections respectively allows the alternating load during the conversion of different radii of curvature to be buffered and transmitted more evenly in the tool holder guide groove, avoiding transient rigid impacts and deviation of the moving tool trajectory. The tangential connection between the two ends of the transition section and the front and rear slot sections ensures a tight and continuous rolling contact between the drive pin and the sidewall of the guide groove, which is conducive to the smooth and stepless transmission of the large tangential torque. It also facilitates the smooth connection and flexible reversal of the drive pin between two different variable arm strokes. In practical applications, if the tangential mechanism faces rapid return and reversal conditions during high-speed sewing at speeds greater than 4000 rpm or when sewing fabrics of alternating thicknesses, the operator can easily use this transition section to eliminate sudden changes in speed and acceleration during the operation of the drive pin without having to perform tedious dynamic balancing adjustments on the complex transmission chain components, thus reducing the fatigue wear cost and time of each articulated drive pin and bushing.

[0012] Preferably, the end of the first groove segment away from the second groove segment is provided with a first elastic column, and the end of the second groove segment away from the first groove segment is provided with a second elastic column.

[0013] By setting No. 1 and No. 2 elastic pillars at the ends of the guide groove, the kinetic energy of the drive pin during the instantaneous reversal at the limit stroke can be absorbed more evenly and converted into elastic potential energy. This avoids overshooting impact and hard impact wear of the cutting tool under high-frequency, high-speed alternating loads. The method of setting the elastic pillars at the extreme points at both ends of the groove section for interception and limiting not only ensures close and flexible contact between the drive pin and the guide groove at the end of the reciprocating limit stroke, which is beneficial to the reduction of transient inertial impact during reversal of the entire transmission chain, but also facilitates elastic compensation, micro-arcing, and flexible protection of the cutting tool at the critical tangential position and the initial reset position. In practical applications, if the tangential mechanism experiences stroke overshoot, lateral sway, or hard impact due to the amplification of accumulated clearance during high-speed reversal operation at speeds greater than 4000 rpm, the operator can easily use the physical deformation of the elastic pillars for efficient vibration absorption and reset without having to perform cumbersome mechanical speed reduction, shutdown for recalibration, or disassembly and repair of the entire cascade linkage transmission chain, thus reducing maintenance costs and time.

[0014] Preferably, a needle roller bearing is coaxially sleeved on the outer side wall of the drive pin, the needle roller bearing is disposed in the guide groove, the outer side wall of the needle roller bearing is in rolling connection with the side wall of the guide groove, and a lock nut is threadedly connected to the end of the drive pin away from the rocker arm.

[0015] By coaxially mounting a needle roller bearing on the outer wall of the drive pin, the contact resistance between the drive pin and the guide groove is further reduced, avoiding local overheating and severe wear of the groove wall due to high-pair friction. The threaded connection of a locking nut at the end of the drive pin away from the rocker arm ensures tight axial positioning between the needle roller bearing and the drive pin, which is beneficial for the rigid transmission of high torque tangential force. It also facilitates the installation, disassembly, and replacement of the needle roller bearing. In practical applications, if the needle roller bearing experiences fatigue spalling or increased clearance due to long-term high-speed operation or external impact loads, the staff can easily replace it, reducing maintenance costs and time.

[0016] Furthermore, the needle roller bearing and the locking nut are coaxially mounted on the drive pin, which increases the rolling load capacity and anti-axial off-center load capacity of the drive end, which is beneficial to the optimization of the overall dynamic transmission stiffness and efficiency. Moreover, the model of the needle roller bearing and the structure of the locking nut can be selected according to actual needs. For example, a full complement needle roller bearing with a high load capacity and an anti-loosening nut with a nylon locking ring can be used to further improve the transmission accuracy at the moment of reversal, thereby improving the high-speed cutting reliability and smooth performance of the entire sewing machine cutting mechanism based on linkage transmission, and ensuring that the moving knife can operate stably under various working conditions.

[0017] Preferably, the rocker arm is provided with reinforcing ribs, the reinforcing ribs are in the form of a grid, the reinforcing ribs are provided on the front plate surface of the rocker arm, and the reinforcing ribs extend from the middle part of the rocker arm to both ends of the rocker arm.

[0018] By setting reinforcing ribs on the front surface of the rocker arm, the overall structural torsional and bending stiffness of the rocker arm is further improved. The grid-like design of the reinforcing ribs allows the alternating loads and inertial stresses generated during high-speed reciprocating operation at speeds greater than 4000 rpm to be more evenly transmitted from the rocker arm surface to the entire load-bearing base, avoiding local stress concentration and bending vibration. The reinforcing ribs extend from the middle of the rocker arm to both ends, ensuring a tight and rigid connection between the rotation fulcrum and each power end, which is beneficial for the structural transmission of large torque tangential force arms. They also facilitate the use of grid gaps to significantly reduce the spatial mass distribution of the rocker arm's asymmetric structure, thereby reducing rotational inertia.

[0019] Furthermore, the reinforcing ribs extend from the middle of the rocker arm to both ends, making the power transmission channel and components of the rocker arm lighter and more rigid. This is beneficial for optimizing the overall resistance to transient inertial impact during high-speed reversal. At the same time, the configuration and specifications of the grid-like reinforcing ribs can be selected according to actual needs. For example, an alloy material with good fatigue resistance can be used for integrated die casting to further improve the efficiency of mechanical energy and stress transmission. This will enhance the high-speed tangential reliability and lifespan of the entire linkage-driven sewing machine tangential mechanism, ensuring that the moving blade can operate stably under various working conditions.

[0020] Preferably, a wear-resistant layer is sleeved on the inner sidewall of the guide groove, and an oil storage groove is provided on the inner sidewall of the wear-resistant layer, wherein the extension direction of the oil storage groove is the same as the trajectory direction of the guide groove.

[0021] By applying a wear-resistant layer to the inner wall of the guide groove, the surface hardness of the guide groove against rolling and sliding friction of the high-pair friction is further improved. The design of the oil reservoir extending in the same direction as the guide groove allows the lubricating oil to be more evenly conducted and wetted along the contact interface of the reciprocating drive pin, avoiding local dry friction and hard scratches on the groove wall under high-speed alternating load reversing conditions. The method of embedding the wear-resistant layer into the oil reservoir and fitting it within the guide groove ensures close contact between the wear-resistant layer and the guide groove substrate, which is beneficial for the rigid and stable transmission of large torque in the tangential direction of the variable arm, and also facilitates long-term storage, adaptive spreading, and micro-circulation replenishment of the lubricating oil film. Furthermore, the fact that the extension direction of the oil reservoir is the same as the trajectory direction of the guide groove improves the dynamic lubrication and wear protection capabilities of the high-pair friction pair throughout its entire stroke, which is beneficial for optimizing the overall tangential running accuracy and micro-friction resistance characteristics.

[0022] Preferably, the mounting base plate is provided with a mounting seat, the lower side of the fixed blade is fixedly connected to the lower side wall of the mounting seat, and the upper end of the mounting seat is threaded with an adjusting screw, the lower end of the adjusting screw extending to the upper end face of the fixed blade.

[0023] By installing a mounting base on the mounting plate, the overall mounting rigidity and three-dimensional positioning stability of the fixed blade assembly are further improved. This allows the dynamic reaction force borne by the fixed blade during high-torque shearing motion to be transmitted and distributed more evenly to the mounting plate, avoiding slight deviation or lateral jumping of the fixed blade due to high-frequency alternating impact. The upper end of the mounting base is threaded with an adjusting screw, and the lower end of the adjusting screw extends to the upper end face of the fixed blade. This ensures that the adjusting screw is tightly pressed against the upper end face of the fixed blade and axially rigidly locked, which is beneficial for maintaining the micron-level precision of the fit gap between the moving and fixed blade edges. It also facilitates the precise and stepless adjustment and calibration of the fixed blade preload and relative shearing plane. In practical applications, if the fixed blade or moving blade experiences edge wear, increased shearing gap, or incomplete thread breakage due to long-term continuous cutting, sewing of fabrics with alternating thicknesses, etc., the operator can easily adjust the pressure gap and compensate for wear by rotating the adjusting screw without disassembling the entire fixed blade holder or complex cascaded linkage transmission chain, reducing maintenance costs and time.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves variable lever arm output by setting guide grooves with different curvatures on the tool holder and sliding the drive pin in the guide grooves. This can amplify the input torque at the critical stage of cutting. At the same time, the design of the fixed blade edge being tangent to the rotation trajectory of the tool holder ensures that the cutting direction is always orthogonal to the seam, effectively avoiding the bird's nest phenomenon, improving the quality of thread cutting, and reducing the high-frequency noise generated during operation.

[0025] 2. By setting a tangential transition section at the junction of the first and second slot sections, and cooperating with the elastic buffer columns at both ends of the guide groove, the present invention can uniformly buffer the alternating load during the transition of different curvatures, eliminate the sudden changes in speed and acceleration during the operation of the drive pin, absorb the kinetic energy of the instantaneous reversal at the limit stroke, effectively avoid transient rigid impact, tool trajectory deviation and over-collision of the tool, reduce the fatigue wear of each transmission component, and extend the service life of the mechanism.

[0026] 3. This invention, through an asymmetrically arranged knife holder structure, combined with modularly installed moving knife and needle roller bearing assemblies, allows for replacement and adjustment without disassembling the entire cascaded linkage transmission chain when the moving knife or worn components are damaged. This reduces the maintenance difficulty and repair cost of the mechanism, and also facilitates the adjustment of component parameters for different sewing conditions, thus improving the adaptability of the mechanism.

[0027] 4. By setting a grid-like extended reinforcing rib on the rocker arm, setting a wear-resistant layer with an oil reservoir inside the guide groove, and setting a mounting seat with an adjusting screw on the fixed blade mounting side, this invention can not only improve the overall structural rigidity of the rocker arm, reduce the moment of inertia, and ensure the lubrication reliability of the transmission process, but also facilitate micron-level fine-tuning and compensation of the shearing gap between the fixed blade and the moving blade, further ensuring the tangential stability of the mechanism under harsh working conditions such as high-speed sewing and sewing of fabrics with alternating thicknesses. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the sewing machine thread cutting mechanism in the uncut state. Figure 2 This is a schematic diagram of the sewing machine thread cutting mechanism in the thread cutting state according to the present invention; Figure 3 This is a schematic diagram of the knife holder in the thread cutting mechanism of the sewing machine of the present invention; Figure 4 for Figure 3 Enlarged view of point A in the middle; Figure 5 This is a schematic diagram of the rocker arm in the thread-cutting mechanism of the sewing machine.

[0029] In the diagram: 1. Mounting base plate; 2. Guide rail; 3. Slider; 4. Drive linkage; 5. Rocker arm; 6. Drive pin; 7. Tool holder; 701. Guide groove; 7011. First groove section; 7012. Second groove section; 7013. Transition section; 702. Mounting part; 703. Connecting part; 704. Extension part; 8. Moving tool; 9. Fixed tool; 10. First elastic column; 11. Second elastic column; 12. Needle roller bearing; 13. Locking nut; 14. Reinforcing rib; 15. Wear-resistant layer; 1501. Oil reservoir; 16. Mounting base; 17. Adjusting screw. Detailed Implementation

[0030] Please see Figures 1 to 5 This invention provides a thread-cutting mechanism for a sewing machine based on linkage transmission, the technical solution of which is as follows: Please refer to a thread-cutting mechanism for a sewing machine based on linkage transmission. Figure 1 , Figure 3 and Figure 5The system includes a mounting base plate 1 and a linear guide slider mechanism located at the lower right of the mounting base plate 1. The linear guide slider mechanism includes two symmetrically arranged guide rails 2 and a slider 3 constrained between the two guide rails 2 and reciprocating linearly. A drive linkage 4 is hinged to the slider 3, and a rocker arm 5 is hinged to the upper end of the drive linkage 4. The rocker arm 5 has a triangular rocker arm structure, and its middle part is rotatably connected to the mounting base plate 1. A drive pin 6 is vertically mounted on the output end of the rocker arm 5. A needle roller bearing 12 is coaxially sleeved on the outer wall of the drive pin 6. A locking nut 13 is threaded to the end of the drive pin 6 away from the rocker arm 5. A tool holder 7 is rotatably connected to the mounting base plate 1, and a guide is provided on the tool holder 7. The guide groove 701 contains a needle roller bearing 12, the outer side wall of which is rolledly connected to the side wall of the guide groove 701. A mounting base 16 is provided on the mounting base plate 1. The lower side of the fixed blade 9 is fixedly connected to the lower side wall of the mounting base 16. An adjusting screw 17 is threadedly connected to the upper end of the mounting base 16. The lower end of the adjusting screw 17 extends to the upper end face of the fixed blade 9. A moving blade 8 is provided on the blade side of the tool holder 7 facing the blade edge of the fixed blade 9. The blade edge plane of the fixed blade 9 is tangent to the rotation trajectory of the tool holder 7. The guide groove 701 includes a first groove segment 7011 and a second groove segment 7012 that are connected. The radius of curvature of the second groove segment 7012 is greater than the radius of curvature of the first groove segment 7011.

[0031] Please see Figure 3 and Figure 4 The tool holder 7 includes a mounting part 702, a connecting part 703, and an extension part 704. The connecting part 703 is rotatably connected to the mounting base plate 1 and is cylindrical. The mounting part 702 and the extension part 704 are both located on the outer wall of the connecting part 703. The mounting part 702 is located on the opposite side of the extension part 704, and the mounting part 702 and the extension part 704 are asymmetrically arranged. The second groove segment 7012 extends into the extension part 704, and the moving tool 8 is fixedly mounted on the connecting part 703. A transition section 7013 is provided at the junction of the first groove segment 7011 and the second groove segment 7012. The two ends of the transition section 7013 are tangent to the first groove segment 7011 and the second groove segment 7012, respectively. A first elastic post 10 is provided at the end of the first groove segment 7011 away from the second groove segment 7012, and a second elastic post 11 is provided at the end of the second groove segment 7012 away from the first groove segment 7011. A wear-resistant layer 15 is fitted on the inner wall of the guide groove 701, and an oil storage groove 1501 is provided on the inner wall of the wear-resistant layer 15. The extension direction of the oil storage groove 1501 is the same as the trajectory direction of the guide groove 701. A reinforcing rib 14 is provided on the rocker arm 5. The reinforcing rib 14 is in the form of a grid and is provided on the front plate surface of the rocker arm 5. The reinforcing rib 14 extends from the middle part of the rocker arm 5 to both ends of the rocker arm 5.

[0032] It should also be noted that the thread-cutting mechanism based on linkage transmission in this embodiment is applied to automatic thread-cutting operations in industrial flatbed sewing machines, overlock sewing machines, or special high-speed sewing machines. The high-speed sewing spindle speed of the sewing machine is 4500–5500 r / min, and the thread-cutting response time of this mechanism is less than 50 ms, with a single work cycle between 0.08 and 0.12 s. This mechanism is suitable for thread tensions ranging from 0.5 to 3.5 N, enabling high-quality cutting of both thick and thin threads with significant thickness variations. The cutting surfaces between the fixed blade 9 and the moving blade 8 are ultra-precision ground, maintaining an initial shearing interference of 2–5 μm. Among them, the outer diameter of the cylindrical connecting part 703 is 18mm, the thickness of the mesh reinforcing rib 14 is 1.2mm, the Shore hardness range of the first elastic column 10 and the second elastic column 11 is between A80 and A90, and the adjusting screw 17 adopts the fine thread specification of M4×0.5mm, which can realize the fine adjustment of the cutting edge gap pressure of 0.5mm per turn, and ensure the structural rigidity of the mechanism components working together under ultra-high speed and alternating stress environment.

[0033] Working principle: Please refer to Figures 1 to 5 When sewing ends and a tangent signal is issued, the external drive source drives the linear guide slider mechanism to work. The slider 3 is confined between two guide pressure plates and slides linearly back and forth on the two guide rails 2 at a high frequency. The linear output torque of the slider 3 is transmitted to the triangular rocker arm 5 through the hinged drive linkage 4. Since the middle part of the rocker arm 5 is rotatably connected to the mounting base plate 1, the rocker arm 5 rotates back and forth around its central pivot point. During this process, the grid-like reinforcing ribs 14 on the front plate of the rocker arm 5 extend from the middle part of the rocker arm 5 to both ends of the rocker arm 5, forming a lightweight, high-rigidity power transmission channel. This significantly reduces the rotational inertia of the rocker arm 5, evenly transmits alternating loads and inertial stresses to the base, and eliminates the oscillation and fatigue micro-deformation caused by high-speed operation.

[0034] As the rocker arm 5 swings, the drive pin 6, vertically mounted on the rocker arm 5, drives the needle roller bearing 12 to slide within the guide groove 701 of the tool holder 7, thereby introducing the power of the linkage mechanism into the different-diameter trajectory of the guide groove 701. The needle roller bearing 12 is located within the guide groove 701 and is rolledly connected to the side wall of the groove. The wear-resistant layer 15 sleeved on the outer wall and the oil reservoir 1501 extending in the same direction along the trajectory of the guide groove 701 provide a long-term stored and self-adaptive lubricating oil film, which greatly reduces the contact resistance, evenly disperses the contact stress, and avoids local overheating and severe wear or hard scratches on the groove wall caused by high-frequency friction. When the drive pin 6 slides from slot 1 7011 to slot 2 7012, the transition section 7013 at the junction utilizes a design where both ends are tangent to slot 1 7011 and slot 2 7012 respectively. This eliminates abrupt changes in speed and acceleration during different curvature transitions, achieving flexible reversal and smooth connection of the drive pin 6 between different variable arm strokes, avoiding transient rigid impacts and trajectory deviations. Since the radius of curvature of slot 2 7012 is larger than that of slot 1 7011, when the drive pin 6 enters slot 2 7012, its transmission trajectory achieves nonlinear variable arm output, amplifying the input torque, improving deformation shearing efficiency, and shortening the shearing completion time.

[0035] At the moment of reversal at the extreme position of the stroke, the drive pin 6 touches the first elastic post 10 and the second elastic post 11 respectively. The elastic posts are set at the extreme points at both ends to intercept and limit the movement. By using their physical deformation, the reversal kinetic energy at the end of the extreme stroke is evenly absorbed and converted into elastic potential energy, which reduces the transient inertial impact of the reversal of the entire transmission chain. This provides a small dwelling range and flexible protection for the moving blade 8 at the critical tangential position and the initial reset position, avoiding overshoot impact and hard blade collision under high frequency and high speed alternating load.

[0036] Meanwhile, the blade holder 7 reciprocates on the mounting base 1 along with the cylindrical connecting part 703, driving the moving blade 8, which is fixedly mounted on the connecting part 703, to move towards the fixed blade 9. The moving blade 8 brushes against the cutting edge plane of the fixed blade 9, which is fixed on the mounting base 16. Since the cutting edge plane of the fixed blade 9 is strictly tangent to the rotation trajectory of the blade holder 7, the cutting direction is always orthogonal to the seam. Even when the seam tension fluctuates instantaneously and the thread ends are prone to slippage, the effective cutting of the top and bottom threads can be completed, eliminating the bird's nest phenomenon and improving the consistency of the thread ends.

[0037] In practical long-term applications, if the moving blade 8 or the fixed blade 9 experiences hard wear due to high-frequency heavy-load use, or if the cumulative clearance of the rotating joint amplifies, leading to a larger shearing gap and incomplete thread breakage, the operator does not need to disassemble and completely reconstruct the entire complex cascade linkage transmission chain. Instead, they can simply rotate the adjusting screw 17 at the upper end of the mounting base 16 to make fine adjustments on the upper surface of the fixed blade 9. This allows for quick adjustment of the position and preload of the fixed blade 9, fine-tuning of the clearance, and wear compensation. This reduces the maintenance difficulty, cost, and time of the mechanism, ensuring that the entire thread cutting mechanism can operate stably and reliably for a long time under various harsh sewing conditions.

[0038] The specific embodiment of the present invention has been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the embodiments described above. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and ideas of the present invention should still fall within the protection scope of the present invention.

Claims

1. A thread-cutting mechanism for a sewing machine based on linkage transmission, characterized in that, The system includes a mounting base plate (1) and a linear guide slider mechanism located on the lower right side of the mounting base plate (1). The linear guide slider mechanism includes two symmetrically arranged guide rails (2) and a slider (3) that is confined between the two guide rails and slides linearly back and forth. A drive link (4) is hinged to the slider (3), and a rocker arm (5) is hinged to the upper end of the drive link (4). The rocker arm (5) has a triangular rocker arm structure, and the middle part of the rocker arm (5) is rotatably connected to the mounting base plate (1). A drive pin (6) is vertically mounted on the output end of the rocker arm (5). The mounting base plate (1) has... A tool holder (7) is rotatably connected. A guide groove (701) is provided on the tool holder (7). The drive pin (6) extends into the guide groove (701). A fixed tool (9) is fixedly installed on the mounting base plate (1). A moving tool (8) is provided on the cutting edge side of the tool holder (7) facing the fixed tool (9). The cutting edge plane of the fixed tool (9) is tangent to the rotation trajectory of the tool holder (7). The guide groove (701) includes a first groove segment (7011) and a second groove segment (7012) that are connected. The radius of curvature of the second groove segment (7012) is greater than the radius of curvature of the first groove segment (7011).

2. The sewing machine thread cutting mechanism based on linkage transmission according to claim 1, characterized in that, The tool holder (7) includes a mounting part (702), a connecting part (703) and an extension part (704). The connecting part (703) is rotatably connected to the mounting base plate (1). The connecting part (703) is cylindrical. The mounting part (702) and the extension part (704) are both located on the outer side wall of the connecting part (703). The mounting part (702) is located on the opposite side of the extension part (704). The mounting part (702) and the extension part (704) are asymmetrically arranged. The second groove section (7012) extends into the extension part (704). The moving tool (8) is fixedly mounted on the connecting part (703).

3. A sewing machine thread cutting mechanism based on linkage transmission according to claim 2, characterized in that, A transition section (7013) is provided at the junction of the first slot segment (7011) and the second slot segment (7012), and the two ends of the transition section (7013) are tangent to the first slot segment (7011) and the second slot segment (7012) respectively.

4. A sewing machine thread cutting mechanism based on linkage transmission according to claim 2, characterized in that, The first groove segment (7011) is provided with a first elastic column (10) at the end away from the second groove segment (7012), and the second groove segment (7012) is provided with a second elastic column (11) at the end away from the first groove segment (7011).

5. A sewing machine thread cutting mechanism based on linkage transmission according to claim 1, characterized in that, A needle roller bearing (12) is coaxially sleeved on the outer side wall of the drive pin (6). The needle roller bearing (12) is located in the guide groove (701), so the outer side wall of the needle roller bearing (12) is in rolling connection with the side wall of the guide groove (701). A locking nut (13) is threadedly connected to the end of the drive pin (6) away from the rocker arm (5).

6. A sewing machine thread cutting mechanism based on linkage transmission according to claim 5, characterized in that, The rocker arm (5) is provided with reinforcing ribs (14), which are in the shape of a grid. The reinforcing ribs (14) are located on the front plate of the rocker arm (5) and extend from the middle part of the rocker arm (5) to both ends of the rocker arm (5).

7. A sewing machine thread cutting mechanism based on linkage transmission according to claim 6, characterized in that, The inner wall of the guide groove (701) is fitted with a wear-resistant layer (15), and the inner wall of the wear-resistant layer (15) is provided with an oil storage groove (1501). The extension direction of the oil storage groove (1501) is the same as the trajectory direction of the guide groove (701).

8. A sewing machine thread cutting mechanism based on linkage transmission according to claim 1, characterized in that, The mounting base plate (1) is provided with a mounting seat (16). The lower side of the fixed blade (9) is fixedly connected to the lower side wall of the mounting seat (16). The upper end of the mounting seat (16) is threaded with an adjusting screw (17). The lower end of the adjusting screw (17) extends to the upper end surface of the fixed blade (9).

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