Needle plate thread trimming mechanism of sewing machine

Abstract

The utility model belongs to the technical field of sewing machines. The problem that in the prior art, a thread end of a trimming thread is long, and a nest-shaped disordered thread lump is easily formed on sewn clothes is solved. The needle plate thread trimming mechanism of the sewing machine is provided, the sewing machine comprises a machine base, a thread pressing piece, a rotating shuttle shaft and a needle plate with a needle falling hole, the thread pressing piece, the rotating shuttle shaft and the needle plate are arranged on the machine base, the needle plate thread trimming mechanism comprises a movable cutter which is arranged on the outer side of the rotating shuttle shaft in a sleeving mode and can swing up and down around the rotating shuttle shaft, and a thread hooking groove is formed in the movable cutter. The needle plate thread cutting mechanism further comprises a thread cutting groove formed in the needle plate, the thread cutting groove faces the thread pressing piece and is located between the needle falling hole and the thread pressing piece, one end of the thread cutting groove is communicated with the needle falling hole, and the other end of the thread cutting groove is communicated with the thread hooking groove. And a trimming blade is arranged on the groove wall at the other end of the trimming groove. The thread trimming mechanism has the advantage that the thread trimming effect that the thread trimming end is shorter can be achieved through the thread trimming mechanism.

Description

Technical Field

[0001] This utility model belongs to the field of sewing machine technology and relates to a needle plate thread cutting mechanism for a sewing machine. Background Technology

[0002] The thread-cutting mechanism of a sewing machine is mainly used to precisely cut the thread at the end of the sewing process. For example, Chinese patent literature discloses a thread-cutting structure, a thread-cutting method, and sewing machine application number: 202211259726.8. The thread-cutting structure includes a rotary hook and a thread-cutting mechanism. The thread-cutting mechanism includes a drive blade, which has a moving blade thread-separating tip, a first thread-separating edge, a second thread-separating edge, a moving blade thread-receiving groove, a moving blade cutting edge, and a bottom thread-separating opening. The thread-cutting structure also includes a thread-separating hook fixedly mounted to the drive blade. The thread-separating hook has a hooking tip, which is distributed on the inner circumference of the drive blade and on the side of the bottom thread-separating opening away from the moving blade thread-receiving groove. There is a thread-passing space between the hooking tip and the drive blade, and a thread-separating receiving groove between the hooking tip and the bottom thread-separating opening, which communicates with the thread-passing space.

[0003] The above-mentioned thread-cutting mechanism has the following shortcomings during use: After the previous sewing is finished and the thread is cut, a certain length of the top thread will remain on one side of the needle. This top thread forms the starting thread. However, because the starting thread is relatively long, it is very easy for it to form a bird's nest-shaped mess of threads on the sewn garment when sewing again, which greatly affects the quality of the sewn garment. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a needle plate thread-cutting mechanism for sewing machines. The technical problem this invention aims to solve is how to achieve a shorter thread-cutting effect through this mechanism.

[0005] The objective of this utility model can be achieved through the following technical solutions:

[0006] A needle plate thread cutting mechanism for a sewing machine. The sewing machine includes a machine base and a pressure plate, a rotary hook shaft, and a needle plate with a needle drop hole, all respectively disposed on the machine base. The needle plate thread cutting mechanism includes a movable blade fitted outside the rotary hook shaft and capable of swinging up and down around the rotary hook shaft. The movable blade has a thread hook groove. The pressure plate can press against the upper edge of the thread hook groove. The needle plate thread cutting mechanism also includes a thread cutting groove formed on the needle plate. The thread cutting groove is formed facing the pressure plate and located between the needle drop hole and the pressure plate. One end of the thread cutting groove is connected to the needle drop hole, and the groove wall at the other end of the thread cutting groove has a thread cutting blade.

[0007] When the sewing machine makes its first stitch, the needle, carrying the thread, passes downwards through the hook groove on the moving blade. Then, the needle moves upwards. As the needle moves upwards to above the needle plate, the moving blade, carrying the thread in the hook groove, swings downwards towards the pressure plate. The pressure plate of this sewing machine's thread-cutting mechanism presses against the upper edge of the hook groove of the moving blade, clamping the thread end. The downward swing of the moving blade moves the thread at the needle drop hole along the thread-cutting groove to the vicinity of the thread-cutting blade. Then, as the fabric moves forward, it moves forward synchronously with the thread, causing the thread between the fabric and the moving blade to be tightened and cut at the thread-cutting blade. This achieves thread cutting at the needle plate. Compared to the traditional thread cutting method where the moving blade and the fixed blade contact each other or both moving blades contact each other, the thread end is cut shorter, ensuring that the starting thread end remaining on the fabric is very short. This allows the thread-cutting mechanism to achieve a shorter thread end cutting effect.

[0008] In the needle plate thread-cutting mechanism of the aforementioned sewing machine, the thread-cutting groove is Z-shaped or L-shaped. This causes the needle drop hole and the thread-cutting blade to be offset along the front-rear direction of the machine base. This not only prevents the top thread from accidentally touching the thread-cutting blade and being cut during sewing, but also ensures that the top thread between the fabric and the moving blade is tightened and cut at the thread-cutting blade. In addition, the Z-shaped or L-shaped thread-cutting groove is also easy to manufacture.

[0009] In the needle plate thread-cutting mechanism of the sewing machine described above, the thread-cutting blade is inclined from top to bottom away from the needle drop hole. This ensures that the orientation of the thread-cutting blade is perpendicular to the direction of fabric travel, guaranteeing that the thread between the fabric and the moving blade can be smoothly cut after being tightened at the thread-cutting blade.

[0010] In the needle plate thread cutting mechanism of the sewing machine described above, the surface of the upper edge of the thread hook groove is uneven. This creates a friction surface (preferably a toothed surface) on the upper edge of the moving blade thread hook groove, allowing the pressure plate to better contact the moving blade surface and clamp the thread end, preventing the thread end from coming loose.

[0011] In the needle plate thread-cutting mechanism of the sewing machine described above, the bends in the thread-cutting groove walls are all rounded. This prevents the thread from accidentally being cut due to contact with the groove wall.

[0012] In the needle plate thread cutting mechanism of the sewing machine described above, the machine base includes a mounting base, the thread pressing plate is strip-shaped, one end of the thread pressing plate is fixed to the mounting base, and the other end of the thread pressing plate is a free end that can press against the upper edge of the hook groove. This allows the thread pressing plate to better press against the upper edge of the hook groove of the moving blade to clamp the thread end.

[0013] In the needle plate thread cutting mechanism of the sewing machine described above, the machine base includes a rotating base that can swing up and down around the rotary hook shaft. The thread pressing plate is formed by bending a strip of metal. The thread pressing plate includes a straight section parallel to the rotary hook shaft and an arc-shaped section that protrudes to the side relative to the straight section. The curvature of the arc-shaped section matches the curvature of the upper surface of the moving blade. The straight section is fixed to the rotating base, and the end of the arc-shaped section away from the straight section is the thread pressing end that abuts against the moving blade. As the sewing machine makes its first stitch, the needle, carrying the thread, passes downwards through the hook groove on the moving blade. Then, the needle moves upwards. When the needle reaches above the needle plate, the moving blade, carrying the thread within the hook groove, swings downwards. Simultaneously, the pressure plate swings upwards around the shuttle axis until it presses against the upper edge of the hook groove on the moving blade, clamping the thread end. Then, the pressure plate and moving blade swing downwards in sync, moving the thread at the needle drop hole along the thread cutting groove to the vicinity of the cutting blade, tautning the thread. The fabric then moves forward... The needle plate moves forward synchronously with the taut thread and is cut directly at the cutting blade, thus achieving thread cutting at the needle plate. In addition, the thread is taut before cutting, which makes the thread cutting mechanism achieve a shorter thread end. The pressure plate of the above structure is relatively simple to manufacture, which can reduce manufacturing costs. Since the curvature of the arc segment matches the curvature of the upper surface of the moving blade, it can ensure that the pressure plate and the moving blade can fit tightly together during the pressure process, forming an effective pressure force and avoiding pressure failure.

[0014] In the needle plate thread cutting mechanism of the sewing machine described above, the machine base is further provided with a limiting structure for restricting the up-and-down swing of the rotating seat. An elastic element is connected between the rotating seat and the machine base. Under the action of the elastic element, the rotating seat can swing upward around the shuttle shaft and abut against the limiting structure. The moving blade has a pushing part, and the rotating seat has a resisting part. When the pressure plate presses against the upper edge of the hook groove, the pushing part on the moving blade can overcome the elastic force of the elastic element and push the resisting part to drive the rotating seat to swing downward synchronously around the shuttle shaft. During thread cutting, the moving blade first swings upward to below the needle plate, and the needle, carrying the thread, passes downward through the hook groove on the moving blade. Then, the needle moves upward, and when it reaches above the needle plate, the moving blade, carrying the thread in the hook groove, swings downward towards the pressure plate, allowing the pressure plate to press against the upper edge of the hook groove on the moving blade to clamp the thread end. At this time, the pushing part on the moving blade abuts against the abutting part on the rotating seat. Subsequently, the moving blade continues to swing downward, and the pushing part on the moving blade overcomes the elastic force of the elastic element and pushes the abutting part, causing the rotating seat to swing downward synchronously around the rotary hook axis, thus achieving... The pressure plate can press against the upper edge of the moving knife's hook groove to clamp the thread end. The pressure plate and the moving knife swing downward synchronously, which can also drive the thread located at the needle hole to move along the cutting groove to the vicinity of the cutting blade and make the thread taut. Then, when the fabric moves forward, it can move forward synchronously with the taut thread and be cut directly at the cutting blade, thus achieving thread cutting at the needle plate. After the thread cutting is completed, the moving knife swings upward to reset, and then the rotating seat swings upward to reset under the action of the elastic element (the pressure plate resets synchronously with the rotating seat). That is, the thread cutting is driven by a single driving element.

[0015] In the needle plate thread-cutting mechanism of the aforementioned sewing machine, the rotating seat has an arc-shaped groove centered on the axis of the rotary hook shaft. The abutment part is the groove wall of the arc-shaped groove, and the pushing part is a positioning post disposed on the blade holder of the moving blade and arranged parallel to the rotary hook shaft, with the positioning post embedded in the arc-shaped groove. This allows the pushing part on the moving blade to overcome the elastic force of the elastic element and push the abutment part, thereby causing the rotating seat to swing downwards synchronously around the rotary hook shaft when the pressure plate presses against the upper edge of the hook groove.

[0016] In the needle plate thread-cutting mechanism of the sewing machine described above, a limiting seat is fixedly connected to the rotating base. The limiting seat has a strip-shaped groove perpendicular to the shuttle shaft. The limiting structure includes a bolt fixed to the machine base, which passes through the strip-shaped groove. The limiting seat can move relative to the bolt when the rotating base swings up and down. When the groove walls at both ends of the strip-shaped groove abut against the bolt, the bolt limits further movement of the limiting seat. That is, when the lower end of the strip-shaped groove abuts against the bolt, the rotating base is at its downward swing limit position; when the upper end of the strip-shaped groove abuts against the bolt, the rotating base is at its upward swing limit position, thus making the up-and-down swing position of the rotating base more precise. Alternatively, the limiting structure can also employ limiting posts parallel to the shuttle shaft at the machine base located at the extreme positions of the rotating base's up-and-down swing, using these limiting posts to limit further swing of the rotating base.

[0017] Compared with existing technologies, the advantages of the needle plate thread cutting mechanism of this sewing machine are as follows: The pressure plate of the needle plate thread cutting mechanism can press against the upper edge of the moving knife hook groove to clamp the thread end. By swinging the moving knife downward, the thread at the needle hole is moved along the thread cutting groove to the vicinity of the thread cutting blade. Then, when the fabric moves forward, it can move forward synchronously with the thread, so that the thread between the fabric and the moving knife is tightened and cut at the thread cutting blade, thereby achieving thread cutting at the needle plate. This ensures that the starting thread end remaining on the fabric is very short, and the thread cutting mechanism achieves a shorter thread end cutting effect. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the needle plate thread cutting mechanism of the sewing machine in use in Embodiment 1.

[0019] Figure 2 This is an exploded view of the needle plate thread cutting mechanism of the sewing machine in use in Embodiment 1.

[0020] Figure 3 This is a schematic diagram of the needle plate of the sewing machine in Embodiment 1, viewed from below.

[0021] Figure 4 This is a schematic diagram of the needle plate thread cutting mechanism of the sewing machine in Embodiment 1, viewed from above after the moving blade swings upward (the needle drop hole and part of the thread cutting groove are indicated by dashed lines as they are obscured by the moving blade).

[0022] Figure 5 This is a three-dimensional structural diagram of the moving blade of the needle plate thread cutting mechanism of the sewing machine in Embodiment 1.

[0023] Figure 6 This is a three-dimensional structural diagram of the needle plate of the needle plate thread cutting mechanism of the sewing machine in Embodiment 2.

[0024] Figure 7 This is a three-dimensional structural diagram of the needle plate of the needle plate thread cutting mechanism of the sewing machine in Embodiment 3.

[0025] Figure 8 This is a three-dimensional structural diagram of the thread-pressing plate of the needle plate thread-cutting mechanism of the sewing machine in Embodiment 3.

[0026] Figure 9 This is a partial three-dimensional structural diagram of the needle plate thread cutting mechanism of the sewing machine in Embodiment 4 after the needle plate has been removed.

[0027] Figure 10 This is a partial three-dimensional structural diagram of the needle plate thread cutting mechanism of the sewing machine in Embodiment 4 after removing the needle plate and moving blade.

[0028] Figure 11 This is a three-dimensional structural diagram of the moving blade of the needle plate thread cutting mechanism of the sewing machine in Embodiment 4.

[0029] In the diagram, 1 is the machine base; 2 is the pressure plate; 2a is the straight section; 2b is the arc section; 2b1 is the pressure end; 3 is the rotary hook shaft; 4 is the needle plate; 4a is the needle drop hole; 4b is the thread cutting groove; 4b1 is the thread cutting blade; 5 is the moving blade; 5a is the thread hooking groove; 5b is the pushing part; 6 is the rotating seat; 6a is the abutment part; 7 is the elastic element; 8 is the limiting structure; 9 is the limiting seat; 9a is the strip groove; 10 is the arc groove; and 11 is the mounting base. Detailed Implementation

[0030] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0031] Example 1

[0032] A needle plate thread-cutting mechanism for a sewing machine, as shown in the reference. Figure 1-5The sewing machine includes a base 1 and a pressure plate 2, a rotary hook shaft 3, and a needle plate 4 with a needle drop hole 4a respectively disposed on the base 1. The needle plate thread cutting mechanism includes a movable blade 5 mounted on the outside of the rotary hook shaft 3 and capable of swinging up and down around the rotary hook shaft 3. The movable blade 5 has a thread hook groove 5a. The thread pressure plate 2 can press against the upper edge of the thread hook groove 5a. The needle plate thread cutting mechanism also includes a thread cutting groove 4b opened on the needle plate 4. The thread cutting groove 4b is opened towards the pressure plate 2 and is located between the needle drop hole 4a and the pressure plate 2. The thread cutting groove 4b is Z-shaped. One end of the thread cutting groove 4b is connected to the needle drop hole 4a. The groove wall at the other end of the thread cutting groove 4b has a thread cutting blade 4b1. In this embodiment, the base 1 preferably includes a mounting base 11, the pressure plate 2 is strip-shaped, one end of the pressure plate 2 is fixed to the mounting base 11, and the other end of the pressure plate 2 is a free end that can press against the upper edge of the hook groove 5a.

[0033] Reference Figure 1 , Figure 2 and Figure 3 Specifically, the wire-cutting blade 4b1 is inclined from top to bottom in a direction away from the needle hole 4a.

[0034] In this embodiment, the surface of the upper edge of the hook groove 5a is preferably uneven, and the turns of the groove wall of the shearing groove 4b are all rounded.

[0035] The following section explains the working principle of the thread-cutting mechanism of this sewing machine:

[0036] Before the sewing machine starts sewing the first stitch, the moving blade 5 moves upward, so that the end of the hook groove 5a on the moving blade 5 near the needle drop hole 4a moves directly below the needle. Alternatively, during the process of the sewing machine starting to sew the first stitch and the needle moving downward, the moving blade 5 moves simultaneously, so that the end of the hook groove 5a on the moving blade 5 near the needle drop hole 4a moves directly below the needle.

[0037] The sewing machine makes its first stitch, with the needle carrying the thread downwards through the hook groove 5a on the moving blade 5. Then, the needle moves upwards. When the needle reaches above the needle plate 4, the moving blade 5, carrying the thread in the hook groove 5a, swings downwards towards the pressure plate 2. This allows the pressure plate 2 to press against the upper edge of the hook groove 5a on the moving blade 5, clamping the thread end. As the moving blade 5 continues to swing downwards (during which the pressure plate 2 and the moving blade 5 maintain the clamped thread end), the downward swing of the moving blade 5 also drives the thread in the hook groove 5a... The thread at the needle hole 4a moves along the thread cutting groove 4b to the vicinity of the thread cutting blade 4b1. Then, as the fabric moves forward, it can move forward synchronously with the thread, so that the thread between the fabric and the moving blade is tightened and cut at the thread cutting blade 4b1. This achieves thread cutting at the needle plate 4. Compared with the traditional thread cutting method where the moving blade and the fixed blade are in contact or the double moving blades are in contact, the thread end is shorter. This ensures that the starting thread end remaining on the fabric is very short, enabling the thread cutting mechanism to achieve a shorter thread end cutting effect.

[0038] Example 2

[0039] This embodiment is basically the same in structure and principle as Embodiment 1, the difference being: (Refer to...) Figure 6 The wire cutting groove 4b is L-shaped, and one end of the wire cutting groove 4b is connected to the needle drop hole 4a, while the wire cutting blade 4b1 is provided on the groove wall at the other end.

[0040] Example 3

[0041] This embodiment is basically the same in structure and principle as Embodiment 1, the difference being: (Refer to...) Figure 7 and Figure 8 The base 1 includes a rotating seat 6, which can swing up and down around the rotary shuttle shaft 3, and the pressure plate 2 is fixedly connected to the rotating seat 6. Specifically, the pressure plate 2 is formed by bending a strip of metal sheet. The pressure plate 2 includes a straight section 2a arranged parallel to the rotary shuttle shaft 3 and an arc-shaped section 2b protruding to the side relative to the straight section 2a. The curvature of the arc-shaped section 2b matches the curvature of the upper surface of the moving blade 5. The straight section 2a is fixedly connected to the blade holder 6, and the end of the arc-shaped section 2b away from the straight section 2a is the pressure end 2b1 that abuts against the moving blade 5.

[0042] When the sewing machine makes its first stitch, the needle, carrying the thread, passes downward through the hook groove 5a on the moving blade 5. Then, the needle moves upward. When the needle moves upward to above the needle plate 4, the moving blade 5 swings downward with the thread in the hook groove 5a. At the same time, the pressure plate 2 swings upward around the shuttle shaft 3 until it presses against the upper edge of the hook groove 5a of the moving blade 5 to clamp the thread end. Then, the pressure plate 2 and the moving blade 5 swing downward synchronously, causing the thread at the needle drop hole 4a to move along the thread cutting groove 4b to the vicinity of the thread cutting blade 4b1, making the thread taut. Then, when the fabric moves forward, it can move forward synchronously with the taut thread and be cut directly at the thread cutting blade 4b1, thus achieving thread cutting at the needle plate 4. In addition, the thread is taut before cutting, so the fabric can be moved forward a shorter distance to achieve thread cutting, thereby enabling the thread cutting mechanism to achieve a shorter thread end cutting effect.

[0043] Example 4

[0044] This embodiment is basically the same in structure and principle as Embodiment 1, the difference being: (Refer to...) Figure 8 , Figure 9 and Figure 10 The base 1 is also provided with a limiting structure 8 for restricting the up-and-down swing of the rotating seat 6. An elastic element 7 is connected between the rotating seat 6 and the base 1. Under the action of the elastic element 7, the rotating seat 6 can swing upward around the shuttle shaft 3 and abut against the limiting structure 8. The moving blade 5 has a pushing part 5b, and the rotating seat 6 has a resisting part 6a. When the pressure plate 2 presses against the upper edge of the hook groove 5a, the pushing part 5b on the moving blade 5 can overcome the elastic force of the elastic element 7 and push the resisting part 6a to drive the rotating seat 6 to swing downward synchronously around the shuttle shaft 2.

[0045] Reference Figure 9 , Figure 10 and Figure 11 Furthermore, the rotating seat 6 is provided with an arc-shaped groove 10 centered on the axis of the rotary shuttle shaft 3, the abutting part 6a is the groove wall of the arc-shaped groove 10, and the pushing part 5b is a positioning post arranged on the tool holder of the moving knife 5 and parallel to the rotary shuttle shaft 3, and the positioning post is embedded in the arc-shaped groove 10.

[0046] Reference Figure 10 Specifically, a limiting seat 9 is fixedly connected to the rotating seat 6. The limiting seat 9 has a strip groove 9a that is perpendicular to the rotary shaft 3. The limiting structure 8 includes a bolt fixed to the machine base 1. The bolt passes through the strip groove 9a, and the limiting seat 9 can move relative to the bolt when the rotating seat 6 swings up and down.

[0047] The moving blade 5 can be driven by a motor. Specifically, a motor is installed on the base 1, and the output shaft of the motor is parallel to the rotary hook shaft 3 and fixedly connected to a first connecting rod. The first connecting rod is hinged to the tool holder of the moving blade 5 through a second connecting rod. The driving method using a motor and connecting rod is low in cost and can ensure the swing accuracy of the moving blade.

[0048] During thread cutting, the moving blade 5 first swings upward to below the needle plate 4. The needle, carrying the thread, passes downward through the hook groove 5a on the moving blade 5. Then, the needle moves upward. When the needle moves upward to above the needle plate 4, the moving blade 5, carrying the thread in the hook groove 5a, swings downward towards the pressure plate 2, so that the pressure plate 2 can press against the upper edge of the hook groove 5a of the moving blade 5 to clamp the thread end. At this time, the pushing part 5b on the moving blade 5 abuts against the abutting part 6a on the rotating seat 6. Then, the moving blade 5 continues to swing downward. The pushing part 5b on the moving blade 5 overcomes the elastic force of the elastic element 7 and pushes the abutting part 6a to drive the rotating seat 6 to swing downward synchronously around the rotary hook axis 3. Even if the pressure plate 2 can always press against the upper edge of the hook groove 5a of the moving knife 5 to clamp the thread end, the pressure plate 2 and the moving knife 5 swing downward synchronously, which can drive the thread located at the needle hole 4a to move along the thread cutting groove 4b to the vicinity of the thread cutting blade 4b1 and make the thread taut. Then, when the fabric moves forward, it can move forward synchronously with the taut thread and be cut directly at the thread cutting blade 4b1, thereby realizing thread cutting at the needle plate 4. After the thread cutting is completed, the moving knife 5 swings upward to reset, and then the rotating seat 6 swings upward to reset under the action of the elastic element 7 (the pressure plate 2 resets synchronously with the rotating seat 6). That is, the thread cutting is driven by a single driving element.

[0049] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A needle plate thread cutting mechanism for a sewing machine, the sewing machine comprising a machine base (1) and a thread pressing plate (2), a rotary hook shaft (3), and a needle plate (4) having a needle drop hole (4a) respectively disposed on the machine base (1), the needle plate thread cutting mechanism comprising a movable blade (5) fitted outside the rotary hook shaft (3) and capable of swinging up and down around the rotary hook shaft (3), the movable blade (5) having a thread hook groove (5a), characterized in that, The pressure plate (2) can press against the upper edge of the hook groove (5a). The needle plate cutting mechanism also includes a cutting groove (4b) opened on the needle plate (4). The cutting groove (4b) is opened towards the pressure plate (2) and is located between the needle hole (4a) and the pressure plate (2). One end of the cutting groove (4b) is connected to the needle hole (4a), and the other end of the cutting groove (4b) has a cutting blade (4b1) on the groove wall.

2. The needle plate thread cutting mechanism of a sewing machine according to claim 1, characterized in that, The shearing groove (4b) is in the shape of a "Z" or an "L".

3. The needle plate thread cutting mechanism of a sewing machine according to claim 1 or 2, characterized in that, The wire-cutting blade (4b1) is inclined from top to bottom in a direction away from the needle hole (4a).

4. The needle plate thread cutting mechanism of a sewing machine according to claim 1 or 2, characterized in that, The surface of the upper edge of the hook groove (5a) is uneven.

5. The needle plate thread cutting mechanism of a sewing machine according to claim 1 or 2, characterized in that, All bends in the wall of the shearing groove (4b) are made of rounded transition.

6. The needle plate thread cutting mechanism of a sewing machine according to claim 1 or 2, characterized in that, The base (1) includes a mounting base (11), the pressure plate (2) is strip-shaped, one end of the pressure plate (2) is fixed to the mounting base (11), and the other end of the pressure plate (2) is a free end that can press against the upper edge of the hook groove (5a).

7. The needle plate thread cutting mechanism of a sewing machine according to claim 1 or 2, characterized in that, The base (1) includes a rotating base (6), which can swing up and down around the rotary shuttle shaft (3). The pressure plate (2) is formed by bending a strip of metal. The pressure plate (2) includes a straight section (2a) parallel to the rotary shuttle shaft (3) and an arc-shaped section (2b) protruding to the side relative to the straight section (2a). The curvature of the arc-shaped section (2b) matches the curvature of the upper surface of the moving blade (5). The straight section (2a) is fixed to the rotating base (6). The end of the arc-shaped section (2b) away from the straight section (2a) is the pressure end (2b1) that abuts against the moving blade (5).

8. The needle plate thread cutting mechanism of a sewing machine according to claim 7, characterized in that, The base (1) is also provided with a limiting structure (8) for limiting the up and down swing of the rotating seat (6). An elastic element (7) is connected between the rotating seat (6) and the base (1). Under the action of the elastic element (7), the rotating seat (6) can swing upward around the shuttle shaft (3) and abut against the limiting structure (8). The moving knife (5) has a pushing part (5b), and the rotating seat (6) has a resisting part (6a). When the pressure plate (2) presses against the upper edge of the hook groove (5a), the pushing part (5b) on the moving knife (5) can overcome the elastic force of the elastic element (7) and push the resisting part (6a) to drive the rotating seat (6) to swing downward around the shuttle shaft (3) synchronously.

9. The needle plate thread cutting mechanism of a sewing machine according to claim 8, characterized in that, The rotating seat (6) has an arc-shaped groove (10) centered on the axis of the rotary shuttle shaft (3). The abutting part (6a) is the groove wall of the arc-shaped groove (10). The pushing part (5b) is a positioning post set on the tool holder of the moving knife (5) and arranged parallel to the rotary shuttle shaft (3). The positioning post is embedded in the arc-shaped groove (10).

10. The needle plate thread cutting mechanism of a sewing machine according to claim 8, characterized in that, A limiting seat (9) is fixedly connected to the rotating seat (6). The limiting seat (9) has a strip groove (9a) that is perpendicular to the rotary shaft (3). The limiting structure (8) includes a bolt fixed to the machine base (1). The bolt passes through the strip groove (9a), and the limiting seat (9) can move relative to the bolt when the rotating seat (6) swings up and down.

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