Bird nest preventing thread trimming mechanism of sewing machine

Abstract

The utility model belongs to the technical field of sewing machines. The thread trimming mechanism solves the problem that in the prior art, a thread trimming head of a thread trimming mechanism is long, and nest-shaped disordered thread knots are likely to be generated. The anti-nest thread trimming mechanism of the sewing machine comprises a driving cutter, an auxiliary cutter and an elastic piece, the driving cutter and the auxiliary cutter are arranged on the outer side of a rotating shuttle shaft in a sleeving mode and can swing up and down around the rotating shuttle shaft, and the elastic piece is connected between a machine base and the auxiliary cutter. The machine base is further provided with a limiting structure used for limiting upward swinging of the auxiliary cutter, the auxiliary cutter can swing upwards around the rotating shuttle shaft under the action of the elastic piece and abut against the limiting structure, the driving cutter is provided with a pushing part, the auxiliary cutter is provided with an abutting part, and after the driving cutter swings downwards till the cutting edge of the driving cutter makes contact with the cutting edge of the auxiliary cutter, the pushing part is pressed against the abutting part. The pushing part on the driving cutter can overcome the elasticity of the elastic piece and push the abutting part to drive the auxiliary cutter to synchronously swing downwards around the rotating shuttle shaft. The thread trimming mechanism has the advantage that the thread trimming mechanism can achieve the thread trimming effect that the thread end of the trimmed thread is shorter.

Description

Technical Field

[0001] This utility model belongs to the field of sewing machine technology and relates to a thread-cutting mechanism for preventing bird nests in sewing machines. Background Technology

[0002] The thread-cutting mechanism is an important component of a sewing machine, 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 a sewing machine (application number: 202211259726.8). The thread-cutting mechanism includes an active 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 includes a thread-separating hook fixedly disposed with the active blade. The thread-separating hook has a hooking tip, which is distributed on the inner circumference of the active 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 active 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 aforementioned thread-cutting mechanism has the following shortcomings: After the previous sewing is completed and the thread is cut, a certain length of top thread remains on one side of the needle, forming the starting thread. During the next sewing attempt, this starting thread easily forms a bird's nest-like pattern on the garment, affecting the overall quality of the garment. To ensure garment quality and avoid these bird's nest-like tangled threads, a second manual trimming is required after the previous sewing to achieve a shorter thread end, which needs improvement. Summary of the Invention

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

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

[0006] A thread-cutting mechanism for preventing bird nests in a sewing machine. The sewing machine includes a base and a rotary hook shaft and a drive unit respectively mounted on the base. The thread-cutting mechanism includes an active blade and an auxiliary blade respectively mounted on the outside of the rotary hook shaft and capable of swinging up and down around the rotary hook shaft. The drive unit is connected to the active blade via a transmission. The thread-cutting mechanism is characterized by further including an elastic element connected between the base and the auxiliary blade. The base is also provided with a limiting structure for restricting the upward swing of the auxiliary blade. Under the action of the elastic element, the auxiliary blade can swing upward around the rotary hook shaft and abut against the limiting structure. The active blade has a pushing part, and the auxiliary blade has a resisting part. When the active blade swings downward until its blade contacts the blade of the auxiliary blade, the pushing part on the active blade can overcome the elastic force of the elastic element and push the resisting part to drive the auxiliary blade to swing downward synchronously around the rotary hook shaft.

[0007] In actual use, when the auxiliary blade abuts against the limiting structure, the auxiliary blade is positioned as close as possible to the needle. During thread cutting, the active blade first swings upwards, and then, under the action of the elastic element, the auxiliary blade swings upwards around the rotary hook axis to a position abutting against the limiting structure (this is the thread-cutting position). Next, after the needle inserts, it moves upwards. Then, the drive unit drives the active blade to swing downwards with the thread and contact the auxiliary blade to cut the thread. The drive unit then continues to drive the active blade downwards, and a linkage structure is formed between the pushing part on the active blade and the abutting part on the auxiliary blade to carry the auxiliary blade downwards. The blades swing downwards together, thus avoiding interference between the active blade and the auxiliary blade in normal sewing operations. This allows a single drive unit to drive the thread cutting. Furthermore, during thread cutting, the auxiliary blade swings upwards under the action of the elastic element, ensuring that its contact point with the limiting structure is consistent each time. This guarantees that the thread cutting position is the same for both the active blade and the auxiliary blade. In addition, the position of the auxiliary blade after contacting the limiting structure is set as close as possible to the needle, ensuring that the thread cutting position is also as close to the needle as possible. This allows the thread cutting mechanism to achieve a shorter thread end cutting effect.

[0008] In the aforementioned thread-cutting mechanism for preventing bird nests in a sewing machine, the auxiliary knife's blade holder 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 active knife and arranged parallel to the rotary hook shaft, with the positioning post embedded in the arc-shaped groove. This allows the active knife to better drive the auxiliary knife to swing synchronously downwards around the rotary hook shaft as it continues to swing downwards after the blades of the active knife and the auxiliary knife come into contact.

[0009] In the above-mentioned thread-cutting mechanism for preventing bird nests on a sewing machine, the limiting structure includes a limiting post connected to the machine base. The blade holder of the auxiliary knife has an inwardly recessed limiting groove, the opening of which faces the limiting post, and the limiting post abuts against the groove wall. This allows the auxiliary knife to swing upward around the rotary hook axis to the thread-cutting position more effectively under the action of the elastic element, resulting in a shorter thread end after cutting and a better bird nest prevention effect. Alternatively, the limiting structure can also adopt a limiting cooperation structure where a limiting block abuts against the blade holder of the auxiliary knife.

[0010] In the aforementioned thread-cutting mechanism for preventing bird nests in a sewing machine, the driving component is a motor. A first connecting rod is fixedly connected to the output shaft of the motor, and the first connecting rod is hinged to the blade holder of the active blade via a second connecting rod. The motor and connecting rod driving method is simple in structure, low in cost, and can ensure the swing accuracy of the active blade. Alternatively, a rotating electromagnet can also be used as the driving component.

[0011] In the aforementioned thread-cutting mechanism for preventing bird nests in a sewing machine, the elastic element is either a torsion spring or a linear spring. This allows users to choose between a torsion spring or a linear spring according to their needs, resulting in better versatility.

[0012] Compared with existing technologies, the advantages of the thread-cutting mechanism for bird nest prevention in this sewing machine are as follows: The thread-cutting mechanism utilizes a linkage structure between the active blade and the auxiliary blade, with a pushing part and a resisting part working together. Simultaneously, an elastic element and a limiting structure are installed between the machine base and the auxiliary blade. This allows a single driving element to drive the thread cutting. Furthermore, during thread cutting, the auxiliary blade swings upward under the action of the elastic element, ensuring that its contact point with the limiting structure is consistent each time. This guarantees that the thread cutting position is identical for every operation. Additionally, the auxiliary blade's contact point with the limiting structure is positioned as close to the needle as possible, further ensuring that the thread cutting position is also as close to the needle as possible, resulting in a shorter thread end. Attached Figure Description

[0013] Figure 1 This is a three-dimensional structural diagram of the thread-cutting mechanism of this sewing machine for preventing bird nests from falling.

[0014] Figure 2 This is a partial three-dimensional structural diagram of the thread-cutting mechanism for preventing bird nests on this sewing machine.

[0015] Figure 3 This is an exploded view of the thread-cutting mechanism of this sewing machine designed to prevent bird nests.

[0016] Figure 4 This is a partial three-dimensional structural diagram of the thread-cutting mechanism of this sewing machine for preventing bird nests from being used.

[0017] In the figure, 1 is the base; 2 is the rotary hook shaft; 3 is the driving component; 4 is the active blade; 4a is the pushing part; 5 is the auxiliary blade; 5a is the abutment part; 6 is the elastic component; 7 is the limiting structure; 7a is the limiting post; 7b is the limiting groove; 8 is the arc groove; 9 is the first connecting rod; and 10 is the second connecting rod. Detailed Implementation

[0018] 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.

[0019] A thread-cutting mechanism for preventing bird nests in a sewing machine, as described in the following figure. Figure 1-4 The sewing machine includes a base 1 and a rotary hook shaft 2 and a drive unit 3 respectively mounted on the base 1. The thread cutting mechanism includes an active blade 4 and an auxiliary blade 5 respectively mounted on the outside of the rotary hook shaft 2 and capable of swinging up and down around the rotary hook shaft 2. The drive unit 3 is connected to the active blade 4 via a transmission. The thread cutting mechanism also includes an elastic element 6 connected between the base 1 and the auxiliary blade 5. The base 1 is also provided with a limiting structure 7 for restricting the upward swing of the auxiliary blade 5. Under the action of the elastic element 6, the auxiliary blade 5 can swing upward around the rotary hook shaft 2 and abut against the limiting structure 7. The active blade 4 has a pushing part 4a, and the auxiliary blade 5 has a resisting part 5a. When the active blade 4 swings downward until its blade contacts the blade of the auxiliary blade 5, the pushing part 4a on the active blade 4 can overcome the elastic force of the elastic element 6 and push the resisting part 5a to drive the auxiliary blade 5 to swing downward synchronously around the rotary hook shaft 2.

[0020] Reference Figure 2 and Figure 3 Specifically, the auxiliary knife 5 has an arc-shaped groove 8 with the axis of the rotary shuttle 2 as the center on its tool holder. The abutting part 5a is the groove wall of the arc-shaped groove 8. The pushing part 4a is a positioning post set on the tool holder of the active knife 4 and arranged parallel to the rotary shuttle 2. The positioning post is embedded in the arc-shaped groove 8.

[0021] Reference Figure 4 Specifically, the limiting structure 7 includes a limiting post 7a connected to the base 1, and the tool holder of the auxiliary tool 5 has an inwardly recessed limiting groove 7b. The opening of the limiting groove 7b faces the limiting post 7a, and the limiting post 7a can abut against the groove wall of the limiting groove 7b.

[0022] Reference Figure 1 More specifically, the driving component 3 is a motor, and a first connecting rod 9 is fixedly connected to the output shaft of the motor. The first connecting rod 9 is hinged to the tool holder of the active tool 4 through a second connecting rod 10. In this embodiment, the elastic component 6 is a torsion spring or a linear spring.

[0023] The following explains the working principle of the thread-cutting mechanism for preventing bird nests on this sewing machine:

[0024] During thread cutting, the active blade 4 first swings upward, and then, under the action of the elastic element 6, the auxiliary blade 5 swings upward around the rotary hook axis 2 to the thread cutting position. At this time, the groove wall of the limiting groove 7b on the blade holder of the auxiliary blade 5 abuts against the limiting post 7a on the machine base 1, thereby limiting the further upward swing of the auxiliary blade 5. Then, after the needle goes down, it moves upward, and then the driving element 3 drives the active blade 4 to swing downward with the thread and contact the auxiliary blade 5 to cut the thread. Then, the driving element 3 continues to drive the active blade 4 to swing downward until the positioning post on the active blade 4 abuts against the groove wall of the arc-shaped groove 8 on the auxiliary blade 5. The pushing part 4a on the active blade 4 can overcome the elastic force of the elastic element 6 and push the abutting part 5a to drive the auxiliary blade 5 to rotate synchronously around the rotary hook axis 2. While the elastic element 6 remains taut and has restoring force, the motor locks the positions of the active blade 4 and the auxiliary blade 5, preventing them from interfering with normal sewing operations. This allows a single drive element 3 to drive the thread cutting. Furthermore, during thread cutting, the auxiliary blade 5 swings upward under the action of the elastic element 6, consistently contacting the limiting structure 7. This ensures that the positions of the active blade 4 and the auxiliary blade 5 are also consistent, guaranteeing that the thread cutting position is always the same. Additionally, the auxiliary blade 5 is positioned as close to the needle as possible after contacting the limiting structure 7, further ensuring that the thread cutting position is also as close to the needle as possible, resulting in a shorter thread end.

[0025] 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 thread-cutting mechanism for preventing bird nests in a sewing machine, the sewing machine comprising a base (1) and a rotary hook shaft (2) and a drive unit (3) respectively disposed on the base (1), the thread-cutting mechanism comprising an active blade (4) and an auxiliary blade (5) respectively mounted on the outside of the rotary hook shaft (2) and capable of swinging up and down around the rotary hook shaft (2), the drive unit (3) being connected to the active blade (4) via transmission, characterized in that, This wire cutting mechanism also includes an elastic element (6) connecting the base (1) and the auxiliary blade (5). The base (1) is also provided with a limiting structure (7) for limiting the upward swing of the auxiliary blade (5). Under the action of the elastic element (6), the auxiliary blade (5) can swing upward around the rotary shaft (2) and abut against the limiting structure (7). The active blade (4) has a pushing part (4a), and the auxiliary blade (5) has a resisting part (5a). When the active blade (4) swings downward until its blade contacts the blade of the auxiliary blade (5), the pushing part (4a) on the active blade (4) can overcome the elastic force of the elastic element (6) and push the resisting part (5a) to drive the auxiliary blade (5) to swing downward synchronously around the rotary shaft (2).

2. The thread-cutting mechanism for preventing bird nests in a sewing machine according to claim 1, characterized in that, The auxiliary knife (5) has an arc-shaped groove (8) centered on the axis of the rotary shuttle shaft (2) on its tool holder. The abutment part (5a) is the groove wall of the arc-shaped groove (8). The pushing part (4a) is a positioning post arranged on the tool holder of the active knife (4) and parallel to the rotary shuttle shaft (2), and the positioning post is embedded in the arc-shaped groove (8).

3. A thread-cutting mechanism for preventing bird nests in a sewing machine according to claim 1 or 2, characterized in that, The limiting structure (7) includes a limiting post (7a) connected to the base (1), and the tool holder of the auxiliary tool (5) has an inwardly recessed limiting groove (7b). The opening of the limiting groove (7b) faces the limiting post (7a), and the limiting post (7a) can abut against the groove wall of the limiting groove (7b).

4. The thread-cutting mechanism for preventing bird nests in a sewing machine according to claim 3, characterized in that, The driving component (3) is a motor, and a first connecting rod (9) is fixedly connected to the output shaft of the motor. The first connecting rod (9) is hinged to the tool holder of the active tool (4) through a second connecting rod (10).

5. A thread-cutting mechanism for preventing bird nests in a sewing machine according to claim 1 or 2, characterized in that, The elastic element (6) is a torsion spring or a linear spring.

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