Thread trimming device for a sewing machine

Abstract

The utility model belongs to the technical field of sewing machine bird nest prevention, and relates to a thread pushing and cutting device of sewing machine, which comprises a thread starting cutting knife rotatably assembled on the outer circumferential side of a rotating hook, a thread cutting knife after sewing and a reference thread cutting knife, the reference thread cutting knife is provided with a needle hole and a thread pushing groove, the thread pushing groove extends from the needle hole to the direction of the needle, the end of the thread pushing groove is connected with an inner blade, one end of the reference thread cutting knife close to the needle is also provided with an outer blade, the inner blade cooperates with the blade of the thread starting cutting knife to cut the sewing thread, and the outer blade cooperates with the blade of the thread cutting knife after sewing to cut the sewing thread. The thread pushing and cutting device of the sewing machine can reduce the residual length of the thread end and completely eliminate the bird nest phenomenon.

Description

Technical Field

[0001] This utility model belongs to the technical field of bird nest prevention for sewing machines, and relates to a thread pushing and cutting device for sewing machines. Background Technology

[0002] In industrial sewing machines, automatic thread trimming has become standard, automatically cutting the thread at the end of sewing. However, this trimming leaves a short thread end on the needle, known as the starting thread. At the start of the next sewing cycle, this starting thread end easily gets caught in the fabric, forming a tangled mess of thread—a phenomenon known in the industry as the "bird's nest"—seriously affecting the appearance and quality of the sewn product.

[0003] To eliminate bird nests, existing technologies have developed mechanisms with independent thread-cutting functions. For example, Chinese patent document CN221645269U (publication date: 2024.09.03) discloses a double-blade bird nest-reducing thread-cutting mechanism. This mechanism includes a fixed main thread-cutting blade (as a stationary blade), a movable thread-cutting blade for starting the stitch, and a movable thread-cutting blade for finishing the stitch. Its bird nest-prevention principle is as follows: during the initial stitching, the thread-cutting blade moves to below the needle, uses its hook groove to catch the thread end, and then moves the thread end to the fixed main thread-cutting blade, where the moving blade and the stationary blade engage to cut the thread end.

[0004] However, the aforementioned bird's nest structure still has defects. The cutting position is determined by the installation position of the fixed blade. In order to avoid affecting the sewing operation, the fixed blade is usually a considerable distance away from the needle, resulting in a considerable length of residual thread after cutting, which cannot completely eliminate the bird's nest phenomenon. Utility Model Content

[0005] This invention addresses the shortcomings of existing technologies by providing a thread pusher and cutter for sewing machines, which can reduce the length of residual thread ends and completely eliminate the "bird's nest" phenomenon.

[0006] To solve the above-mentioned technical problems, the objective of this utility model is achieved through the following technical solution: A thread-pushing and cutting device for a sewing machine includes a starting thread cutter, a post-sewing thread cutter, and a reference thread cutter rotatably mounted on the outer periphery of a rotary hook. The reference thread cutter has a needle hole and a thread-pushing groove. The thread-pushing groove extends from the needle hole toward the needle, and an inner blade is connected to the end of the thread-pushing groove. An outer blade is also provided at the end of the reference thread cutter near the needle. The inner blade cooperates with the blade of the starting thread cutter to cut the thread, and the outer blade cooperates with the blade of the post-sewing thread cutter to cut the thread.

[0007] In the above-mentioned thread-pushing and thread-cutting device for a sewing machine, the starting thread-cutting knife and the reference thread-cutting knife are located on the same side of the needle, and the post-sewing thread-cutting knife is located on the other side of the needle.

[0008] In the above-mentioned thread-pushing and cutting device for a sewing machine, the starting thread cutter and the post-sewing thread cutter are driven independently in both directions by a first motor, and the reference thread cutter is driven by a second motor; the independent in both directions means that when the first motor rotates in the first circumferential direction, it drives the starting thread cutter to move, and when it rotates in the second circumferential direction, it drives the post-sewing thread cutter to move.

[0009] In the above-mentioned thread pushing and cutting device for a sewing machine, preferably, both the first motor and the second motor are stepper motors.

[0010] In the above-mentioned thread pushing and cutting device for a sewing machine, the starting thread cutting knife, the post-sewing thread cutting knife, and the reference thread cutting knife are respectively fixed on the first moving knife holder, the second moving knife holder, and the third moving knife holder. The first moving knife holder, the second moving knife holder, and the third moving knife holder are rotatably mounted on the lower shaft sleeve. The first moving knife holder and the second moving knife holder are connected to the first motor, and the third moving knife holder is connected to the second motor.

[0011] In the above-mentioned thread pushing and cutting device for a sewing machine, a first drive crank is mounted on the motor shaft of the first motor, and a drive roller is provided on the first drive crank; the first moving blade holder is connected to a first moving blade connecting rod and a first moving blade shaft, and the first moving blade shaft is driven to rotate by the drive roller; the second moving blade holder is connected to a second moving blade connecting rod and a second moving blade shaft, and the second moving blade shaft is driven to rotate by the end of the first drive crank.

[0012] In the above-mentioned thread pushing and cutting device for a sewing machine, a second drive crank is mounted on the motor shaft of the second motor, and the third moving blade holder is connected to a third moving blade connecting rod and a third moving blade shaft, the third moving blade shaft being driven to rotate by the second drive crank.

[0013] In the above-mentioned thread pushing and cutting device for a sewing machine, a fixed pressure plate is also included. The pressure plate is located on the rotation path of the reference thread cutter, and its position corresponds to the end trajectory of the thread pushing groove, so as to clamp the sewing thread end pushed by the reference thread cutter.

[0014] The thread pushing and cutting device of the sewing machine described above also includes a fixed suction pipe with its opening facing the cutting area to absorb the cut thread ends.

[0015] In the aforementioned thread-pushing and cutting device for a sewing machine, the reference thread cutter switches between multiple positions: an initial position; a thread-threading position, where the needle hole is directly below the needle; a thread-hooking position, where the thread end is fed into the pressure plate, which may coincide with the initial position; and a thread-cutting position, located between the initial position and the needle, closer to the needle than the initial position to shorten the thread end. The starting-seam thread cutter switches between the initial position and the thread-cutting position; the post-seam thread cutter switches between the initial position and the thread-cutting position.

[0016] Compared with the prior art, this utility model has the following advantages: This invention provides a thread-pushing and cutting device for a sewing machine. By employing a three-moving blade configuration—a reference thread cutter, a starting thread cutter, and a post-sewing thread cutter—which can move independently, the cutting reference is transformed from a traditional fixed position to a dynamically controllable position that is closer to the needle and the fabric. This improvement further shortens the length of the residual thread after cutting, effectively preventing the formation of "bird's nest" thread clumps at the source. This invention uses a dual-drive architecture with a first motor bidirectionally driving the starting and post-sewing thread cutters, and a second motor independently driving the reference thread cutter. This achieves independent and precise control of the movement sequence of each execution unit, ensuring reliable and orderly connection between thread pushing positioning and the two coordinated cutting actions, thus improving the certainty and stability of the entire thread cutting process. Attached Figure Description

[0017] Figure 1 This is a perspective view of the present invention; Figure 2 yes Figure 1 Enlarged view of point A; Figure 3 This is a perspective view of the first motor-driven sewing cutter and the sewing cutter of this utility model; Figure 4 This is a perspective view of the first motor of this utility model; Figure 5 This is a perspective view of the second motor-driven reference wire cutter of this utility model; Figure 6 yes Figure 5 Enlarged view of point B; Reference numerals: 1. Rotary hook; 2. Starting stitch cutter; 3. Post-stitch cutter; 4. Reference cutter; 5. Needle hole; 6. Thread pusher groove; 7. Needle; 8. Inner blade; 9. Outer blade; 10. First motor; 11. Second motor; 12. First moving cutter holder; 13. Second moving cutter holder; 14. Third moving cutter holder; 15. Lower shaft bushing; 16. First drive crank; 17. Drive roller; 18. First moving cutter connecting rod; 19. First moving cutter shaft; 20. Second moving cutter connecting rod; 21. Second moving cutter shaft; 22. Second drive crank; 23. Third moving cutter connecting rod; 24. Third moving cutter shaft; 25. Pressing plate; 26. Suction pipe. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. See also: Figure 1-6 : A thread-pushing and cutting device for a sewing machine includes a starting thread cutter 2, a post-sewing thread cutter 3, and a reference thread cutter 4 rotatably mounted on the outer periphery of a rotary hook 1. The reference thread cutter 4 is provided with a needle hole 5 and a thread-pushing groove 6. The thread-pushing groove 6 extends from the needle hole 5 toward the needle 7. An inner blade 8 is connected to the end of the thread-pushing groove 6. An outer blade 9 is also provided at the end of the reference thread cutter 4 near the needle 7. The inner blade 8 cooperates with the blade of the starting thread cutter 2 to cut the sewing thread, and the outer blade 9 cooperates with the blade of the post-sewing thread cutter 3 to cut the sewing thread.

[0019] In this embodiment, the driving structure of the starting seam cutter 2 and the post-seam cutter 3 is as follows: the starting seam cutter 2 and the post-seam cutter 3 are driven independently in both directions by the first motor 10. When the first motor 10 rotates in the first circumferential direction, it drives the starting seam cutter 2 to move; when it rotates in the second circumferential direction, it drives the post-seam cutter 3 to move. Specifically, the starting seam cutter 2 and the post-seam cutter 3 are respectively fixed on the first moving blade holder 12 and the second moving blade holder 13. The first moving blade holder 12 and the second moving blade holder 13 are rotatably mounted on the lower shaft sleeve 15 and are connected to the first motor 10 for transmission.

[0020] Its transmission connection structure is as follows: a first drive crank 16 is mounted on the motor shaft of the first motor 10, and a drive roller 17 is provided on the first drive crank 16; the first moving tool holder 12 is connected to a first moving tool connecting rod 18, the first moving tool connecting rod 18 is connected to the first moving tool crank, the first moving tool crank is assembled at one end of the first moving tool shaft 19, and a first moving tool plate is fixed at the other end of the first moving tool shaft 19. The end of the first moving tool plate is provided with a hook-shaped structure that cooperates with the drive roller 17; the second moving tool holder 13 A second moving cutter connecting rod 20 is connected to a second moving cutter crank. The second moving cutter crank is mounted on one end of a second moving cutter shaft 21. The other end of the second moving cutter shaft 21 is connected to a second moving cutter plate via a small connecting rod. One end of the second moving cutter plate is sleeved on the first moving cutter shaft 19 via an independent hinge seat or bearing (the first moving cutter shaft 19 only provides a fixed hinge point, and there is no transmission relationship between the second moving cutter plate and the first moving cutter shaft 19). The other end is provided with a moving cutter roller that mates with the end of the first drive crank 16.

[0021] In this embodiment, the first moving cutter shaft 19 and the second moving cutter shaft 21 are parallel to the lower shaft and are independently and rotatably supported on the sewing machine base plate or a specific bracket by bearings or bushings. Their function is to transmit the driving force of the first motor 10 and drive the first moving cutter holder 12 and the second moving cutter holder 13 to rotate, respectively.

[0022] When the first motor 10 rotates counterclockwise, the first drive crank 16 drives the drive roller 17 to move. The roller presses into the hook-shaped structure at the end of the first moving blade plate, thereby pushing the first moving blade plate and driving the first moving blade shaft 19 to rotate. Finally, the first moving blade holder 12 and the sewing cutter 2 are driven to move through the first moving blade crank and the first moving blade connecting rod 18. When the first motor 10 rotates clockwise, the end of the first drive crank 16 contacts and pushes the moving blade roller on the second moving blade plate, causing the second moving blade plate to swing around its hinge point. The second moving blade shaft 21 is pulled to rotate through the small connecting rod, and then the second moving blade holder 13 and the sewing cutter 3 are driven to move through the second moving blade crank and the connecting rod.

[0023] In this embodiment, the driving structure of the reference dicing blade 4 is as follows: the reference dicing blade 4 is fixed on the third moving blade holder 14, the third moving blade holder 14 is rotatably mounted on the lower shaft sleeve 15, and the third moving blade holder 14 is connected to the second motor 11 via a transmission connection. The transmission connection structure is as follows: a second drive crank 22 is mounted on the motor shaft of the second motor 11; the third moving blade holder 14 is connected to a third moving blade connecting rod 23; the third moving blade connecting rod 23 is connected to the third moving blade crank; the third moving blade crank is mounted on one end of the third moving blade shaft 24; the other end of the third moving blade shaft 24 is connected to the second drive crank 22 via a blade shaft connecting rod; when the second motor 11 rotates, the second drive crank 22 drives the third moving blade shaft 24 to rotate via the blade shaft connecting rod, thereby driving the third moving blade holder 14 and the reference dicing blade 4 to move via the third moving blade crank and the third moving blade connecting rod 23. The third moving cutter shaft 24 is parallel to the lower shaft and is independently and rotatably supported on the sewing machine base plate or a specific bracket by bearings or bushings. Its function is to transmit the driving force of the second motor 11 and drive the third moving cutter holder 14 to rotate.

[0024] In this embodiment, a fixed pressure plate 25 is also included. The pressure plate 25 is located on the rotation path of the reference cutting knife 4, and its position corresponds to the end trajectory of the push groove 6, so as to clamp the suture thread end pushed by the reference cutting knife 4.

[0025] In this embodiment, a fixed suction pipe 26 is also included, with the opening of the suction pipe 26 facing the shearing area to absorb the sheared wire ends.

[0026] The specific working process of this embodiment is as follows: In the initial state, the starting thread cutter 2 and the reference thread cutter 4 are positioned on the same side of the needle 7, and the post-sewing thread cutter 3 is positioned on the other side of the needle 7, with each cutter in its initial position. Before sewing begins, the second motor 11 drives the reference thread cutter 4 to rotate, moving it to the thread-threading position. In this position, its needle hole 5 is precisely aligned with the falling trajectory of the needle 7, and the needle 7, carrying the thread, falls smoothly through the needle hole 5 of the reference thread cutter 4. After the needle 7 rises, the second motor 11 drives the reference thread cutter 4 to rotate from the thread-threading position to the hooking position, simultaneously moving the thread end away from the needle 7. When it reaches the hooking position, the thread end is clamped and fixed by the reference thread cutter 4 and the pressure plate 25. While the thread end is clamped, the sewing machine starts, the needle 7 sews several stitches, and the second motor 11 drives the reference thread cutter 4 again, rotating it from the hooking position to the cutting position and stopping it. This position is very close to the fabric. The first motor 10 rotates counterclockwise, driving the first moving blade holder 12 and the starting thread cutter 2 to rotate through the first drive crank 16-drive roller 17 mechanism, moving them to the same cutting position. The blade of the starting thread cutter 2 works in conjunction with the blade 8 inside the already positioned reference thread cutter 4 to cut the starting thread end, which has been fixed by the sewing thread, very close to the root. After cutting, the first motor 10 and the second motor 11 drive the starting thread cutter 2 and the reference thread cutter 4 back to their initial positions, respectively. The sewing machine enters a normal sewing cycle. At the end of sewing, the second motor 11 drives the reference thread cutter 4 to rotate to the thread-cutting position and stop. The first motor 10 rotates clockwise, driving the second moving blade holder 13 and the post-sewing thread cutter 3 to rotate via the end of the first drive crank 16, moving them to the thread-cutting position. The blade of the post-sewing thread cutter 3 works in conjunction with the outer blade 9 of the already positioned reference thread cutter 4 to cut the thread. Afterwards, the first motor 10 and the second motor 11 drive the post-sewing thread cutter 3 and the reference thread cutter 4 back to their initial positions, respectively. After each thread cut, the suction pipe 26 activates to remove the cut thread ends, keeping the work area clean.

[0027] The above embodiments are merely preferred embodiments of the present utility model and are not intended to limit the scope of protection of the present utility model. Therefore, all equivalent changes made to the structure, shape, and principle of the present utility model should be covered within the scope of protection of the present utility model.

Claims

1. A thread pusher and cutter device for a sewing machine, characterized in that, The device includes a rotatable thread-cutting knife (2), a post-sewing thread-cutting knife (3), and a reference thread-cutting knife (4) mounted on the outer periphery of the rotary hook (1). The reference thread-cutting knife (4) is provided with a needle hole (5) and a thread-pushing groove (6). The thread-pushing groove (6) extends from the needle hole (5) toward the needle (7). An inner blade (8) is connected to the end of the thread-pushing groove (6). An outer blade (9) is also provided at one end of the reference thread-cutting knife (4) near the needle (7). The inner blade (8) cooperates with the blade of the thread-cutting knife (2) to cut the sewing thread, and the outer blade (9) cooperates with the blade of the post-sewing thread-cutting knife (3) to cut the sewing thread.

2. The thread pusher and cutter device for a sewing machine according to claim 1, characterized in that, The starting seam cutter (2) and the post-seam cutter (3) are driven independently in both directions by the first motor (10), and the reference cutter (4) is driven by the second motor (11).

3. The thread pusher and cutter device for a sewing machine according to claim 2, characterized in that, The starting cutter (2), the post-cutting cutter (3), and the reference cutter (4) are respectively fixed on the first moving cutter holder (12), the second moving cutter holder (13), and the third moving cutter holder (14). The first moving cutter holder (12), the second moving cutter holder (13), and the third moving cutter holder (14) are rotatably mounted on the lower shaft sleeve (15). The first moving cutter holder (12) and the second moving cutter holder (13) are connected to the first motor (10) for transmission, and the third moving cutter holder (14) is connected to the second motor (11) for transmission.

4. The thread pusher and cutter device for a sewing machine according to claim 3, characterized in that, The first motor (10) has a first drive crank (16) mounted on its motor shaft, and a drive roller (17) is provided on the first drive crank (16); the first moving tool holder (12) is connected to a first moving tool connecting rod (18) and a first moving tool shaft (19), and the first moving tool shaft (19) is driven to rotate by the drive roller (17); the second moving tool holder (13) is connected to a second moving tool connecting rod (20) and a second moving tool shaft (21), and the second moving tool shaft (21) is driven to rotate by the end of the first drive crank (16).

5. The thread pusher and cutter device for a sewing machine according to claim 3, characterized in that, The second motor (11) has a second drive crank (22) mounted on its motor shaft. The third moving tool holder (14) is connected to a third moving tool connecting rod (23) and a third moving tool shaft (24). The third moving tool shaft (24) is driven to rotate by the second drive crank (22).

6. The thread pusher and cutter device for a sewing machine according to claim 1, characterized in that, It also includes a fixed pressure plate (25), which is located on the rotation path of the reference cutting knife (4) and its position corresponds to the end trajectory of the push groove (6) to hold the suture thread end pushed by the reference cutting knife (4).

7. The thread pusher and cutter device for a sewing machine according to claim 1, characterized in that, It also includes a fixed suction pipe (26), the opening of which faces the shearing area to absorb the sheared wire ends.

Images