Thread trimming structure of sewing machine

Abstract

The utility model provides a thread cutting structure of sewing machine belongs to sewing machine technical field. It solved how to avoid the problem of bird nest -like thread ball phenomenon on the sewing material. The thread cutting structure of this sewing machine, sewing machine includes the needle plate with the needle drop hole of lower shaft, the thread cutting structure includes the dynamic cutter and the thread pressing piece of the sleeve setting in the lower shaft outside and can rotate relative to the lower shaft circumference, the needle plate is located the upper of dynamic cutter and thread pressing piece, the outer wall of dynamic cutter is equipped with the thread hooking hole, the thread hooking hole one side hole wall is the inclined wall that sets up relative to the axial inclination of lower shaft, the needle drop hole is close to the edge of one side of inclined wall setting, the thread pressing piece is close to the edge of other side of inclined wall setting, the needle plate bottom is fixed with the thread cutting knife, the needle drop hole is the strip hole, one end of needle drop hole is used for the needle to wear and set, the other end of needle drop hole is towards the inclined setting of thread cutting knife head, and the head of thread cutting knife projects on the end hole wall of needle drop hole inclined setting and sets up. The thread cutting structure of this sewing machine can avoid the bird nest -like thread ball phenomenon on the sewing material.

Description

Technical Field

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

[0002] The thread-cutting structure is a very important part of a sewing machine. For example, Chinese Patent (Application No.: 202211259726.8) discloses a thread-cutting structure, a thread-cutting method, and a sewing machine. The thread-cutting structure includes a rotary hook and a thread-cutting mechanism. 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 also 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. The thread-separating receiving groove communicates with the thread-passing space.

[0003] However, in actual operation, after each sewing session, a certain length of thread end is left on the needle to ensure that the next sewing session can proceed. But it is precisely because of the presence of this thread end that when sewing begins again, the needle pulls this thread end onto the fabric, forming a bird's nest-like ball of thread, which affects the quality of the sewing. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a thread-cutting structure for sewing machines. The technical problem this invention aims to solve is: how to avoid the appearance of bird's nest-like clumps of thread on the sewing fabric.

[0005] The objective of this utility model can be achieved through the following technical solution: a thread-cutting structure for a sewing machine, the sewing machine including a lower shaft and a needle plate with a needle drop hole, the thread-cutting structure including a movable blade and a pressure plate sleeved on the lower shaft and capable of circumferential rotation relative to the lower shaft, the needle plate being located above the movable blade and the pressure plate, characterized in that a hook hole is provided on the outer wall of the movable blade, one side wall of the hook hole is an inclined wall inclined relative to the axial direction of the lower shaft, the needle drop hole is located near one edge of the inclined wall, the pressure plate is located near the other edge of the inclined wall, a thread-cutting blade is fixed at the bottom of the needle plate, the needle drop hole is a strip-shaped hole, one end of the needle drop hole is used for the needle to pass through, the other end of the needle drop hole is inclined toward the blade head of the thread-cutting blade, and the blade head of the thread-cutting blade protrudes from the inclined end wall of the needle drop hole.

[0006] The working principle of the thread-cutting structure of this sewing machine is as follows: During the initial sewing stage, the needle drives the top thread downwards. After the needle returns to its original position, the thread end is left in the hook hole on the moving blade. At this time, the drive unit in the sewing machine can drive the moving blade to rotate circumferentially towards the pressure plate along the lower shaft. During this process, as the moving blade continues to rotate, the thread end can gradually move inwards under the guidance of the inclined wall of the hook hole, and is pressed and positioned on the moving blade when it contacts the edge of the pressure plate and the hook hole. Thanks to the cooperation of the moving blade and the pressure plate, in this state, one end of the thread end is fixed to the fabric, and the other end is pressed on the moving blade. At this time, the operator controls the sewing machine to continue sewing. Because the fabric is pushed by the feed dog during the sewing process, the thread end moves relatively to a certain extent relative to the needle plate. It is worth mentioning that the needle drop hole on the needle plate in this application is a strip-shaped hole and is arranged at an angle relative to the head of the thread-cutting blade. When the thread end is compressed, its path is offset relative to the needle. Because the thread cutter protrudes from the inclined end of the needle hole on the bottom of the needle plate, the thread end closer to the fabric is in contact with the blade. During sewing, the moving fabric further pulls on the thread end, keeping it taut against the blade and ultimately cutting it off. This prevents the thread end remaining on the fabric from tangling with the thread on the needle, forming a bird's nest-like clump. Notably, the thread cutter and needle plate used in this application are separate units. Specifically, the strip-shaped thread cutter can be fixed to the lower side of the needle plate with screws, ensuring easy replacement when its sharpness decreases, effectively reducing replacement costs.

[0007] In the thread-cutting structure of the sewing machine described above, the moving blade includes a blade holder and a blade head. The blade holder is rotatably mounted outside the lower shaft, and the blade head is fixed on the blade holder. The sewing machine also includes a fixed base located below the lower shaft. A rotating shaft arranged axially along the lower shaft is rotatably connected to the fixed base. A crank and a connecting rod are hinged between the fixed base and the lower shaft. The crank is fixed to the rotating shaft, and the connecting rod is hinged to the blade holder. Specifically, this application separates the moving blade into two parts: a blade holder and a blade head. This ensures that only the blade head needs to be replaced during subsequent maintenance. Furthermore, the fixed base serves as a carrier for the rotating shaft used for transmission. During operation, the rotation of the rotating shaft drives the crank to rotate accordingly. The crank drives the connecting rod to swing, causing the connecting rod to rotate the blade holder. This allows the moving blade to rotate around the lower shaft and cooperate with the pressure plate to press the thread end of the top thread.

[0008] In the thread-cutting structure of the sewing machine described above, the pressure plate includes a pressure frame and a pressure plate. The pressure frame is rotatably sleeved outside the lower shaft, and the pressure plate is fixed on the pressure frame. A swing arm and a connecting rod are hinged between the fixed base and the lower shaft. The swing arm is rotatably connected to the fixed base, and the connecting rod is hinged to the pressure frame. The pressure frame and the cutter holder are arranged axially along the lower shaft, and the cutter holder can abut against the pressure frame along the circumference of the lower shaft and push the pressure frame to rotate synchronously. This design makes the disassembly and maintenance of the quilting plate easier and allows it to rotate circumferentially relative to the lower shaft. It's worth noting that the rotation control of the quilting plate is actually achieved by pushing it with a blade holder. The fundamental reason is that although the quilting plate and the blade work together to clamp the thread end of the top thread, it's still unavoidable that the thread end will be longer than expected. In this case, this application uses the blade holder of the moving blade in conjunction with the quilting plate's quilting frame to further pull the thread end of the top thread, thus straightening and tightening it, ensuring the effectiveness of the thread trimming and preventing excessively long thread ends left on the fabric after trimming. Furthermore, during sewing, the shuttle tip needs to hook the top thread to form a loop that interweaves with the bobbin thread to create a stitch on the fabric. This application uses the moving blade and quilting plate to move the thread end downwards, ensuring that the thread end is far from the needle hole after trimming, thus preventing the thread end from being interwoven with the fabric and affecting the sewing quality.

[0009] In the thread-cutting structure of the sewing machine described above, the outer wall of the blade holder has a connecting part one that protrudes radially outward along the lower axis, the moving blade is fixed on the connecting part one, the outer wall of the pressure frame has a connecting part two that protrudes radially outward along the lower axis, the pressure plate is fixed on the connecting part two, and the connecting part two has an abutment part that protrudes axially along the lower axis. The connecting part one can abut against the abutment part and push the pressure frame to drive the pressure plate to rotate counterclockwise synchronously with the blade holder. As a specific solution, before the pressure plate and the cutter head work together to clamp the end of the thread, the cutter holder does not contact the abutment part during this process. Therefore, the cutter holder can rotate freely without affecting the actual arrangement position of the pressure plate. However, as the pressure plate and the cutter head work together to continuously clamp the end of the thread, the cutter holder can gradually come into contact with the abutment part. Therefore, as the cutter holder continues to rotate, it can squeeze the abutment part, thereby driving the pressure plate and the pressure plate to rotate synchronously with the moving cutter, thus achieving the purpose of further tightening the end of the thread.

[0010] In the thread-cutting structure of the sewing machine described above, a transition shaft arranged axially along the lower axis is rotatably connected to the fixed base. The swing arm is fixed to the transition shaft, and a torsion spring is sleeved on the transition shaft. The torsion spring elastically acts between the fixed base and the swing arm circumferentially along the transition shaft, enabling the connecting rod two to pull the pressure plate to rotate clockwise. This arrangement ensures control of the pressure plate through the cooperation of the transition shaft, the swing arm, and the connecting rod two. Furthermore, by arranging the torsion spring, when the cutter holder rotates to its reset position, the connecting part two and the abutment part separate. The torsion spring, elastically acting between the fixed base and the swing arm circumferentially along the transition shaft, drives the swing arm to push the connecting rod two. The connecting rod two then drives the pressure plate and the pressure plate to rotate and reset around the lower axis, thereby ensuring the normal operation of the next pressure plate operation.

[0011] In the thread-cutting structure of the sewing machine described above, the outer wall of the fixed seat facing the crank has a notch, and the notch is located diagonally below the lower shaft. Under the elastic action of the torsion spring, the swing arm abuts against the side wall of the notch. This arrangement limits the swing amplitude of the swing arm by utilizing the side wall of the notch, preventing the pressure plate from rotating excessively during the rotational reset process.

[0012] Compared with existing technologies, the thread-cutting structure of this sewing machine has the following advantages:

[0013] 1. By using the moving blade and the pressing plate together, the thread end of the top thread is clamped and pulled straight onto the cutting edge of the thread cutter. On this basis, by pushing or pulling the sewing material, the force between the thread end of the top thread and the cutting edge of the moving blade is increased, so that the thread end of the top thread is cut off, preventing the thread end of the top thread and the top thread remaining on the needle from intertwining and tangling on the sewing material to form a bird's nest-like clump of thread.

[0014] 2. By coordinating the cutter head and the presser plate, the cutter head and the presser plate can further pull the top thread end to straighten it when clamping it, thereby further improving the cutting effect of the top thread end and ensuring that the length of the thread end left on the sewing material is shorter. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the thread-cutting mechanism of this sewing machine and a partial enlarged view.

[0016] Figure 2 This is a schematic diagram of the thread-cutting mechanism of this sewing machine after the needle plate has been removed.

[0017] Figure 3 This is a schematic diagram of the moving blade and the linkage mechanism that works with it.

[0018] Figure 4 This is a structural diagram of the pressure plate and its associated linkage mechanism.

[0019] Figure 5 This is a schematic diagram of the tool holder and wire pressing frame assembled on the lower shaft.

[0020] Figure 6 This is a schematic diagram of the needle plate structure.

[0021] Figure 7 This is a structural diagram of the fixed base.

[0022] In the picture,

[0023] 1. Lower shaft;

[0024] 2. Moving blade; 21. Hook hole; 211. Inclined wall; 22. Blade head; 23. Blade holder; 231. Connecting part one;

[0025] 3. Wire clamping piece; 31. Wire clamping bracket; 311. Connecting part two; 3111. Abutting part; 32. Wire clamping plate;

[0026] 4. Needle plate; 41. Needle drop hole; 42. Thread cutter;

[0027] 5. Fixed base; 51. Rotating shaft; 52. Adapter shaft; 521. Torsion spring; 53. Notch;

[0028] 6. Crank;

[0029] 7. Linkage 1;

[0030] 8. Swing arm;

[0031] 9. Connecting rod two. Detailed Implementation

[0032] 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.

[0033] like Figure 1 As shown, in the thread-cutting structure of this sewing machine, the sewing machine includes a lower shaft 1 rotatably connected in the base and arranged in the horizontal direction, and a needle plate 4 fixed on the base table. The needle plate 4 is specifically located directly above the output end of the lower shaft 1, and a fixed seat 5 fixed in the base is provided below the lower shaft 1.

[0034] Combination Figure 2 A moving blade 2 and a pressure plate 3 are rotatably sleeved on the outer side of the lower shaft 1, combined with Figure 3The moving blade 2 includes a tool holder 23 rotatably sleeved outside the lower shaft 1 and a blade head 22 screwed onto the tool holder 23. Specifically, the outer wall of the tool holder 23 has a connecting part 231 that protrudes radially along the lower shaft 1. The blade head 22 is screwed onto the connecting part 231. A rotating shaft 51 parallel to the lower shaft 1 is rotatably connected to the fixed base 5. One end of the rotating shaft 51 is connected to a motor installed in the base through a cam mechanism. A crank 6 and a connecting rod 7 are provided between the fixed base 5 and the lower shaft 1. The crank 6 is fixed to the other end of the rotating shaft 51 by screws. One end of the connecting rod 7 is hinged to the tool holder 23, and the crank 6 and the connecting rod 7 are hinged together. Thus, when the rotating shaft 51 rotates, it transmits power to the tool holder 23 in sequence through the crank 6 and the connecting rod 7, so that the tool holder 23 drives the blade head 2 to rotate along the circumference of the lower shaft 1.

[0035] Combination Figure 4 The wire pressing plate 3 includes a wire pressing frame 31 rotatably sleeved outside the lower shaft 1 and a wire pressing plate 32 screwed onto the wire pressing frame 31. Specifically, the outer wall of the wire pressing frame 31 has a connecting part 311 that protrudes radially along the lower shaft 1. The cutting head 22 is screwed onto the connecting part 311. The fixing base 5 is also rotatably connected to a transition shaft 52 that is parallel to the lower shaft 1. Furthermore, the upper side of the fixing base 5 has a protruding transition protrusion. An adapter hole is provided on the upper part along the axial direction of the lower shaft 1. The adapter shaft 52 is rotatably connected in the adapter hole. A swing arm 8 and a connecting rod 9 are provided between the fixed seat 5 and the lower shaft 1. The swing arm 8 is locked to the adapter shaft 52 by screws. One end of the connecting rod 9 is hinged to the wire pressing frame 31, and the other end is hinged to the swing arm 8. Thus, when the adapter shaft 52 rotates, it transmits power to the wire pressing frame 31 in sequence through the swing arm 8 and the connecting rod 9, so that the wire pressing frame 31 drives the wire pressing plate 32 to rotate along the circumference of the lower shaft 1.

[0036] Combination Figure 7 A torsion spring 521 is provided on the outer sleeve of the adapter shaft 52. One end of the torsion spring 521 is pressed against the side wall of the swing arm 8, and the other end is pressed against the side wall of the adapter protrusion. As the swing arm 8 rotates around the adapter shaft 52, the torsion spring 521 is deformed by force and generates the opposite reverse force, so that the swing arm 8 has the drive to swing back to reset. Secondly, a notch 53 is opened at the edge of the side wall of the fixed seat 5 facing the crank 6, which is located diagonally below the lower shaft 1. Under the elastic action of the torsion spring 521, the outer side wall of the swing arm 8 can abut against the side wall of the notch 53. The inner wall of the notch 53 is used to ensure that the reset position of the swing arm 8 is restricted, thereby ensuring that the position of the wire pressing frame 31 and the wire pressing plate 32 on the wire pressing frame 31 on the lower shaft 1 is kept in a relatively appropriate position relative to the moving knife 2.

[0037] Combination Figure 5The tool holder 23 and the wire pressing frame 31 are specifically arranged at intervals along the axial direction of the lower shaft 1. The outer wall of the connecting part 2 311 has abutting part 3111 that protrudes along the axial direction of the lower shaft 1. After the tool holder 23 rotates around the lower shaft 1 to a certain extent, the connecting part 231 can abut against the abutting part 3111.

[0038] Combination Figure 6 A strip-shaped needle drop hole 41 is provided on the needle plate 4. A long strip-shaped thread cutter 42 is fixed on the lower side of the needle plate 4. A triangular hook hole 21 is provided on the side of the moving blade 2. The hook hole 21 is specifically a right triangle, so that one side of the hook hole 21 is an inclined wall 211. The inner end of the needle drop hole 41 is inclined towards the cutting edge of the thread cutter 42, and the outer end is close to one edge of the inclined wall 211. The cutting edge of the thread cutter 42 protrudes from the inner end of the needle drop hole 41.

[0039] Working principle: The sewing begins when the needle hole 41 and the hook hole 21 are in opposite positions. The needle, carrying the thread end, goes down. With the thread end remaining in the hook hole 21, the needle moves upwards to its original position. At this time, the rotating shaft 51 rotates, and the transmission control of the crank 6 and connecting rod 7 drives the cutter head 23 to rotate counterclockwise along the lower shaft 1. That is, the moving cutter 2 rotates while the pressure plate 3 remains stationary. In this state, the thread end remaining in the hook hole 21 is guided by the inclined wall 211 of the hook hole 21, sliding from one edge to the other. This causes the thread end and the pressure plate 32 of the pressure plate 3 to move circumferentially relative to each other along the lower shaft 1. Simultaneously, during this process, the cutter head 22 of the moving cutter 2 continuously approaches the pressure plate 32 of the pressure plate 3 circumferentially relative to the lower shaft 1. Finally, when the connecting part 231 of the knife holder 23 and the connecting part 311 of the pressure plate 31 come into contact, the pressure plate 32 presses against the edge of one side wall of the inclined wall 211, thereby clamping the thread end of the top thread by the cooperation of the knife head 22 and the pressure plate 32. In this state, the thread end of the top thread passing through the needle hole 41 has changed its wiring path relative to the needle and is in contact with the knife head 22 of the thread cutter 42. At this time, the rotating shaft 51 continues to rotate, driving the moving knife 2 to continue to rotate. The knife holder 23 pushes the pressure plate 31, so that the moving knife 2 and the pressure plate 3 continue to rotate counterclockwise relative to the lower shaft 1 while keeping the thread end clamped. When the sewing material is driven to move by the feed dog, the thread end of the top thread is continuously pulled tight and is finally cut off by the thread cutter 42.

[0040] It is worth mentioning that, in the above principle, the swing arm 8 always abuts against the side wall of the notch 53 under the elastic action of the torsion spring 521, thereby ensuring the overall positioning of the pressure plate 3 on the lower shaft 1. When the moving knife 2 applies a pushing force to the pressure plate 3, the torsion spring 521 will be affected by the pushing force and will undergo torsional deformation. In this state, the swing arm 8 is pulled outward and separated from the side wall of the notch 53. At this time, the pressure plate 3 is in a state of synchronous rotation with the moving knife 2. When the rotating shaft 51 rotates to reset, the moving knife 2 no longer applies pressure to the pressure plate 3. At this time, the torsion spring 521 can undergo the opposite reset deformation and pull the swing arm 8 to swing back to reset and abut against the side wall of the notch 53 again through its elastic force, so that the pressure plate 3 rotates clockwise relative to the lower shaft 1 to reset.

[0041] 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.

[0042] Although this document frequently uses terms such as lower shaft 1, moving blade 2, hook hole 21, inclined wall 211, blade head 22, blade holder 23, connecting part one 231, pressure plate 3, pressure frame 31, connecting part two 311, abutment part 3111, pressure plate 32, needle plate 4, needle drop hole 41, thread cutter 42, fixing seat 5, rotating shaft 51, adapter shaft 52, torsion spring 521, notch 53, crank 6, connecting rod one 7, swing arm 8, and connecting rod two 9, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of this utility model; interpreting them as any additional limitation would contradict the spirit of this utility model.

Claims

1. A thread-cutting structure for a sewing machine, the sewing machine comprising a lower shaft (1) and a needle plate (4) having a needle drop hole (41), the thread-cutting structure comprising a movable blade (2) sleeved outside the lower shaft (1) and a thread presser plate (3) rotatable relative to the lower shaft (1), the needle plate (4) being located above the movable blade (2) and the thread presser plate (3), characterized in that... The outer wall of the moving knife (2) is provided with a hook hole (21). One side wall of the hook hole (21) is an inclined wall (211) that is inclined relative to the lower shaft axis. The needle drop hole (41) is located near the edge of the inclined wall (211). The thread pressing piece (3) is located near the other edge of the inclined wall (211). The bottom of the needle plate (4) is fixed with a thread cutter (42). The needle drop hole (41) is a strip hole. One end of the needle drop hole (41) is used for the needle to pass through. The other end of the needle drop hole (41) is inclined toward the head of the thread cutter (42). The head (22) of the thread cutter (42) protrudes from the inclined end wall of the needle drop hole (41).

2. The thread-cutting structure of the sewing machine according to claim 1, characterized in that, The moving knife (2) includes a knife holder (23) and a knife head (22). The knife holder (23) is rotatably sleeved outside the lower shaft (1). The knife head (22) is fixed on the knife holder (23). The sewing machine also includes a fixed seat (5) located below the lower shaft (1). A rotating shaft (51) arranged along the axial direction of the lower shaft (1) is rotatably connected in the fixed seat (5). A crank (6) and a connecting rod (7) are hinged between the fixed seat (5) and the lower shaft (1). The crank (6) is fixed on the rotating shaft (51). The connecting rod (7) is hinged to the knife holder (23).

3. The thread-cutting structure of the sewing machine according to claim 2, characterized in that, The pressure plate (3) includes a pressure frame (31) and a pressure plate (32). The pressure frame (31) is rotatably sleeved on the lower shaft (1). The pressure plate (32) is fixed on the pressure frame (31). A swing arm (8) and a connecting rod (9) are hinged between the fixed seat (5) and the lower shaft (1). The swing arm (8) is rotatably connected to the fixed seat (5). The connecting rod (9) is hinged to the pressure frame (31). The pressure frame (31) and the knife holder (23) are arranged axially along the lower shaft (1). The knife holder (23) can abut against the pressure frame (31) along the circumference of the lower shaft (1) and push the pressure frame (31) to rotate synchronously.

4. The thread-cutting structure of the sewing machine according to claim 3, characterized in that, The outer wall of the tool holder (23) has a connecting part one (231) that protrudes radially outward along the lower axis (1). The moving blade (2) is fixed on the connecting part one (231). The outer wall of the wire pressing frame (31) has a connecting part two (311) that protrudes radially outward along the lower axis (1). The wire pressing piece (3) is fixed on the connecting part two (311). The connecting part two (311) has an abutment part (3111) that protrudes axially along the lower axis (1). The connecting part one (231) can abut against the abutment part (3111) and push the wire pressing frame (31) to drive the wire pressing piece (3) to rotate counterclockwise synchronously with the tool holder (23).

5. The thread-cutting structure of the sewing machine according to claim 3 or 4, characterized in that, The fixed base (5) is rotatably connected to a transition shaft (52) arranged along the lower shaft (1). The swing arm (8) is fixed on the transition shaft (52). A torsion spring (521) is sleeved on the transition shaft (52). The torsion spring (521) acts elastically along the circumference of the transition shaft (52) between the fixed base (5) and the swing arm (8), so that the connecting rod (9) can pull the pressure frame (31) to rotate clockwise.

6. The thread-cutting structure of the sewing machine according to claim 5, characterized in that, The fixed seat (5) has a notch (53) on the outer wall of the side facing the crank (6), and the notch (53) is located obliquely below the lower shaft (1). Under the elastic action of the torsion spring (521), the swing arm (8) and the side wall of the notch (53) abut against each other.

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