Thread trimming device of sewing machine

Abstract

The invention provides a thread trimming device of a sewing machine, and belongs to the technical field of sewing machines. The thread trimming mechanism solves the problem that two driving structures are needed in an existing thread trimming mechanism. The thread trimming device of the sewing machine comprises a crank assembly, a main tool apron, an auxiliary tool apron, a driving tool, an auxiliary tool and a thread pressing piece, the crank assembly is provided with a protruding linkage part, the auxiliary tool apron is provided with a first protruding part and a second protruding part, and the thread trimming device of the sewing machine further comprises a spring. When the crank assembly drives the main cutter holder to rotate anticlockwise, the right end of the thread pressing piece can abut against the groove edge of the needle falling groove of the main cutter, the side portion of the main cutter holder can abut against the second protruding part, and the auxiliary cutter holder is driven to rotate synchronously. The thread trimming device of the sewing machine has the advantage of simple structure.

Description

Technical Field

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

[0002] Currently, during the initial stitching operation on a sewing machine, due to the instability of the initial stitch, the top thread easily intertwines and tangles with the bottom thread under the fabric under the action of the rotary hook, forming loose and messy clumps of thread of varying sizes, the so-called "bird's nest stitch." This type of stitch not only appears rough in appearance but may also affect the quality of subsequent stitches, reduce the strength of the seam, and pose a potential threat to the quality of the finished garment.

[0003] To this end, the applicant designed a thread-cutting mechanism and a sewing machine having the same, and applied for a Chinese patent with application number 202422909251.3 and publication number CN223433633U. The thread-cutting mechanism includes: a first movable blade, including a thread clamping part and a first cutting edge part; a second movable blade, disposed on one side of the first movable blade, the second movable blade including a thread-collecting groove for passing the thread through and a second cutting edge part; the second cutting edge part is located on the side of the thread-collecting groove away from the first movable blade, and the second cutting edge part is disposed facing the opening of the thread-collecting groove; the first cutting edge part is located on the side of the thread clamping part away from the second movable blade, and the first cutting edge part is disposed facing the thread clamping part; wherein, the second movable blade is movably disposed in a direction close to or away from the first movable blade, so as to move to a thread-clamping position where a clamping gap for clamping the thread is formed between the thread clamping part and the second cutting edge part, or to a thread-cutting position where the first cutting edge part and the second cutting edge part come into contact to cut the thread. The first movable blade is driven by the first driving structure through the first rotating component, and the second movable blade is driven by the second driving structure through the second rotating component.

[0004] However, the two moving blades are driven by two separate drive structures, which not only makes the structure more complex but also occupies more space. Given the limited installation space below the sewing machine table, installation is inconvenient and production costs are high. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in the prior art by proposing a thread-cutting device for a sewing machine, which solves the problem that in existing thread-cutting mechanisms, two moving blades need to move in opposite directions or in the same direction, requiring two separate drive structures to drive them.

[0006] The objective of this invention can be achieved through the following technical solutions: A thread-cutting device for a sewing machine, located below a needle plate with needle holes, includes a crank assembly for transmission connection with a drive component, a main blade holder and an auxiliary blade holder, both circular and coaxially arranged, a drive blade with a needle-dropping groove fixed on the main blade holder, an auxiliary blade fixed on the auxiliary blade holder, and a thread-pressing plate. The main blade holder is connected to the crank assembly. The drive blade and auxiliary blade are respectively located on the left and right sides of the needle hole. The thread-pressing plate is located on the left side of the needle hole and above or below the drive blade. The crank assembly has a linkage portion protruding towards the auxiliary blade holder on the left side. The auxiliary blade holder faces the main blade holder. The sewing machine has two protrusions, one and the other, which are both columnar. The thread cutting device also includes a spring acting on the auxiliary blade seat. The auxiliary blade seat can rotate clockwise around its own axis under the elastic force of the spring, and the first protrusion abuts against the lower side of the linkage. When the crank assembly drives the main blade seat to rotate clockwise, the linkage can press down on the first protrusion to push the auxiliary blade seat to rotate counterclockwise so that the active blade and the auxiliary blade move closer to each other. When the crank assembly drives the main blade seat to rotate counterclockwise, the right end of the pressure plate can abut against the groove edge of the active blade needle drop groove, and the side of the main blade seat can abut against the second protrusion and drive the auxiliary blade seat to rotate synchronously.

[0007] The thread-cutting device of this sewing machine is installed below the needle plate. The main cutter and auxiliary cutter are both ring-shaped and are fitted onto the mounting base of the rotary hook. They are coaxial with the rotary hook, so that the main cutter and auxiliary cutter can rotate around their own axis. The crank assembly can be connected to the motor drive.

[0008] By default, the sewing machine needle is positioned directly above the needle hole on the needle plate, and the needle slot of the active blade is positioned directly below the needle hole. Under the elastic force of the spring, the auxiliary blade holder rotates clockwise until the upper side of the protrusion rests against the lower side of the right end of the linkage.

[0009] When sewing begins, the needle moves downward, passing through the needle hole and the needle groove, causing the top thread to enter the needle groove. As the needle begins to rise, the top thread forms a small loop under the fabric. The tip of the rotary hook passes through the small loop and carries the top thread completely under the active blade.

[0010] When thread clamping and pulling are required, the motor drives the crank assembly to rotate the main blade holder counterclockwise, the linkage part swings upward, and the auxiliary blade holder rotates clockwise under the spring force, keeping the first protrusion against the lower side of the linkage part. The main blade holder and the auxiliary blade holder rotate in opposite directions, that is, the active blade moves to the left counterclockwise, and the pressure plate and auxiliary blade move to the right clockwise. The pressure plate approaches the needle groove of the active blade until the right end of the pressure plate abuts against the edge of the needle groove of the active blade, thus clamping the thread between the pressure plate and the active blade. At this time, the side of the main blade holder abuts against the second protrusion, which limits the auxiliary blade holder. The auxiliary blade holder no longer rotates clockwise under the spring force, but rotates counterclockwise synchronously with the active blade holder. The pressure plate and the active blade clamp the thread and pull it away from the needle hole, providing tension for the initial thread and preventing the thread from tangling and forming a bird's nest, resulting in a clean and neat stitch.

[0011] When thread cutting is required, the motor drives the crank assembly to rotate the main blade holder clockwise. The linkage part presses down as the crank assembly swings, causing the auxiliary blade holder to rotate counterclockwise via the protrusion. The active and auxiliary blades then move closer to each other towards the needle hole until they meet and cut the thread. This achieves the removal of the Bird's Nest stitching.

[0012] In the thread-cutting device of this sewing machine, a single crank assembly is driven by a drive component. In conjunction with the structure of the linkage part, spring, and protrusion one, the driving seat and the auxiliary seat are linked in opposite directions. Through the structural design of protrusion two, the driving seat and the auxiliary seat are linked in the same direction. While realizing the actions of clamping, pulling, and cutting the thread, the setting of the drive structure is reduced, which not only simplifies the structure and reduces the space occupied, but also reduces the production cost.

[0013] In the thread-cutting device of the sewing machine described above, the main blade holder has a protruding part on its left side. The active blade is fixedly connected to the protruding part, which is located above the second protrusion. When the main blade holder rotates counterclockwise, the lower side of the protruding part can abut against the second protrusion. The protruding part provides a position for the installation of the active blade and also functions in conjunction with the second protrusion to achieve linkage between the main blade holder and the auxiliary blade holder, serving two purposes, simplifying the structure, and reducing space occupation.

[0014] In the thread-cutting device of the sewing machine described above, when the needle groove of the active blade is located directly below the needle hole, there is a gap between the protrusion and the second protrusion. This gap ensures that, initially, the active blade, the auxiliary blade, and the pressure plate move in opposite directions. This not only allows the auxiliary blade to clear the space below the needle hole, avoiding interference, but also allows the pressure plate and the active blade to move relative to each other, achieving the thread-clamping action and resulting in a more stable thread-clamping effect.

[0015] In the thread-cutting device of the sewing machine described above, both protrusion one and protrusion two are located to the left of the axis of the auxiliary cutter seat, and the distance between protrusion one and the axis of the auxiliary cutter seat is greater than the distance between protrusion two and the axis of the auxiliary cutter seat. Protrusion one is farther from the axis than protrusion two, which facilitates the cooperation between protrusion one and the linkage mechanism, as well as between protrusion two and the moving cutter seat, avoiding interference and making the structure of the moving cutter seat simpler and smaller in size.

[0016] In the thread-cutting device of the sewing machine described above, the position of protrusion one is higher than the position of protrusion two. The higher position of protrusion one allows it to better abut against the linkage under the elastic force of the spring, thus achieving rapid linkage.

[0017] In the thread-cutting device of the sewing machine described above, the active blade also has a long, narrow thread-pressing groove and a long, narrow needle-dropping groove. The right ends of the needle-dropping groove and the thread-pressing groove are connected so that they together form a V-shaped groove. The active blade also has a moving blade edge, which is located on the left side of the left end of the needle-dropping groove and faces the direction of the needle-dropping groove. The interconnected thread-pressing groove and needle-dropping groove facilitate needle drop and thread placement, as well as the cooperation between the thread-pressing plate and the active blade for thread pressing.

[0018] In the thread-cutting device of the sewing machine described above, the crank assembly includes crank one and crank two. Crank one is vertically disposed on the left side of the main cutter holder, with the linkage located at the upper end of crank one. Crank two is horizontally disposed below the main cutter holder. The left end of crank two is hinged to the lower end of crank one, and the right end of crank two is hinged to the right side of the main cutter holder. By arranging crank one and crank two, the linkage for driving the auxiliary cutter holder is located on the left side, and the force-bearing position for driving the main cutter holder is located on the right side. This achieves synchronous reverse driving of the main cutter holder and the auxiliary cutter holder while avoiding interference between the driving structures.

[0019] Compared with existing technologies, in the thread cutting device of this sewing machine, a single crank assembly is driven by a drive component. In conjunction with the structure of the linkage part, spring, and protrusion one, the active seat and the auxiliary seat are linked in opposite directions. Through the structural design of protrusion two, the active seat and the auxiliary seat are linked in the same direction. While realizing the actions of clamping, pulling, and cutting the thread, the setting of the drive structure is reduced, which not only simplifies the structure and reduces the space occupied, but also reduces the production cost. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the installation of the thread-cutting device on this sewing machine.

[0021] Figure 2 This is a schematic diagram of the thread-cutting device of this sewing machine from another perspective.

[0022] Figure 3 This is a schematic diagram of the crank assembly and main blade holder working together in the thread-cutting device of this sewing machine.

[0023] Figure 4 This is a schematic diagram of the auxiliary blade holder in the thread-cutting device of this sewing machine.

[0024] Figure 5 This is a schematic diagram of the active blade in the thread-cutting device of this sewing machine.

[0025] Figure 6 This is a schematic diagram of the initial state of the thread-cutting device in this sewing machine.

[0026] Figure 7 This is a schematic diagram of the structure before the thread clamping mechanism in the thread cutting device of this sewing machine.

[0027] Figure 8 This is a schematic diagram of the thread clamping mechanism in the thread cutting device of this sewing machine.

[0028] Figure 9 This is a schematic diagram of the thread-pulling mechanism of this sewing machine after the thread has been pulled.

[0029] Figure 10 This is a schematic diagram of the thread-cutting device of this sewing machine during thread cutting.

[0030] In the diagram, 1 is the needle plate; 1a is the needle hole; 2 is the crank assembly; 2a is the crank one; 2b is the crank two; 3 is the main blade holder; 3a is the protrusion; 4 is the auxiliary blade holder; 4a is the protrusion one; 4b is the protrusion two; 5 is the driving blade; 5a is the needle drop groove; 5b is the thread pressing groove; 5c is the moving blade edge; 6 is the auxiliary driving blade; 7 is the thread pressing plate; 8 is the linkage part; and 9 is the spring. Detailed Implementation

[0031] 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.

[0032] like Figures 1-4 As shown, the thread cutting device of this sewing machine is located below the needle plate 1 with needle holes 1a, and includes a crank assembly 2 for transmission connection with the drive component, a main blade seat 3 and an auxiliary blade seat 4, both of which are circular and coaxially arranged, an active blade 5 with a needle drop groove 5a fixed on the main blade seat 3, an auxiliary blade 6 fixed on the auxiliary blade seat 4, and a thread pressing plate 7.

[0033] The crank assembly 2 includes two elongated cranks, 2a and 2b. Crank 2a is vertically positioned on the left side of the main cutter holder 3, with a horizontally positioned transmission rod connected to its upper end. This transmission rod is used to drive the output of a motor, which serves as the driving component. Crank 2b is horizontally positioned below the main cutter holder 3. The left end of crank 2b is hinged to the lower end of crank 2a, and the right end of crank 2b is hinged to the right side of the main cutter holder 3. The auxiliary cutter 6 is located on the right side below the pinhole 1a, while the active cutter 5 and the pressure plate 7 are located on the left side below the pinhole 1a. The pressure plate 7 is positioned above the active cutter 5, and its lower right end can abut against the upper side of the active cutter 5. Alternatively, the pressure plate 7 can be positioned below the active cutter 5, depending on the requirements.

[0034] Specifically, a linkage part 8 is fixedly connected to the upper end of crank 2a, and this linkage part 8 protrudes towards the auxiliary blade seat 4 located on its right side. The lower left part of the auxiliary blade seat 4 facing the main blade seat 3 has two protrusions, both columnar, namely protrusion 4a and protrusion 4b. The sewing machine's thread cutting device also includes a spring 9, the lower end of which is connected to the left side of the auxiliary blade seat 4, and the upper end of which is used to fix it to the sewing machine base plate. Under the elastic force of the spring 9, the auxiliary blade seat 4 can rotate clockwise around its own axis and cause protrusion 4a to abut against the lower side of the linkage part 8. When the crank assembly 2 drives the main blade seat 3 to rotate clockwise, the linkage part 8 can press down on protrusion 4a to push the auxiliary blade seat 4 to rotate counterclockwise so that the active blade 5 and the auxiliary blade 6 move closer to each other. The main blade holder 3 has a protruding portion 3a on its left side. The active blade 5 is fixedly connected to the protruding portion 3a. The protruding portion 3a is located above the second protrusion 4b, and when the main blade holder 3 rotates counterclockwise, the lower side of the protruding portion 3a can abut against the second protrusion 4b. In this embodiment, the position of the first protrusion 4a is higher than the position of the second protrusion 4b, and the distance between the first protrusion 4a and the axis of the auxiliary blade holder 4 is greater than the distance between the second protrusion 4b and the axis of the auxiliary blade holder 4.

[0035] like Figure 5 As shown, the active blade 5 is curved in an arc shape and has a long strip-shaped pressure groove 5b. The length direction of the pressure groove 5b is roughly set along the left and right direction. The needle drop groove 5a is long and its length direction is set at an angle to the length direction of the pressure groove 5b. The right ends of the two are connected so that the needle drop groove 5a and the pressure groove 5b together form a V-shaped groove with the opening facing left. The active blade 5 also has a moving blade edge 5c. The moving blade edge 5c is located on the left side of the left end of the needle drop groove 5a and faces the direction of the needle drop groove 5a.

[0036] The thread-cutting device of this sewing machine is installed below the needle plate 1 of the sewing machine, such as Figure 2 As shown, the main cutter holder 3 and the auxiliary cutter holder 4, which are in the shape of a ring, are respectively sleeved on the outside of the mounting base of the rotary hook and are set on the same axis as the rotary hook, so that the main cutter holder 3 and the auxiliary cutter holder 4 can rotate around their own axis. The crank 2a can be connected to the motor drive.

[0037] like Figure 6 As shown, in the default state, the sewing machine needle is located directly above the needle hole 1a of the needle plate 1, and the needle groove 5a of the active blade 5 is located directly below the needle hole 1a. The auxiliary blade holder 4 rotates clockwise under the force of the spring 9 until the upper side of the protrusion 4a abuts against the lower side of the right end of the linkage 8. At this time, the auxiliary blade 6 intersects with the active blade 5, and there is a gap between the protrusion 3a and the protrusion 4b.

[0038] When sewing begins, the needle moves downward, passing through the needle hole 1a and the needle groove 5a, causing the top thread to enter the needle groove 5a. When the needle begins to rise, the top thread forms a small loop under the fabric. The tip of the rotary hook passes through the small loop and completely carries the top thread below the active blade 5.

[0039] like Figure 7 As shown, the motor drives the crank assembly 2 to rotate the main blade holder 3 counterclockwise, the linkage part 8 swings upward, and the auxiliary blade holder 4 rotates clockwise under the elastic force of the spring 9, so that the protrusion 4a remains against the lower side of the linkage part 8. When the main blade holder 3 and the auxiliary blade holder 4 rotate in opposite directions, the active blade 5 moves to the left in the counterclockwise direction, and the pressure plate 7 and the auxiliary blade 6 move to the right in the clockwise direction. The pressure plate 7 approaches the pressure groove 5b and the needle drop groove 5a of the active blade 5, and the protrusion 3a also passes by the protrusion 4b.

[0040] like Figure 8 As shown, the pressure plate 7 and the active blade 5 move relative to each other until the right end of the pressure plate 7 abuts against the top surface of the groove edge where the pressure groove 5b and the needle drop groove 5a of the active blade 5 connect, thus clamping the wire between the lower side of the right end of the pressure plate 7 and the upper side of the active blade 5. At this time, the protrusion 3a on the side of the main blade holder 3 abuts against the second protrusion 4b, and the second protrusion 4b limits the auxiliary blade holder 4, so the auxiliary blade holder 4 no longer rotates clockwise under the elastic force of the spring 9.

[0041] like Figure 9 As shown, the crank assembly 2 continues to drive the main blade holder 3 to rotate counterclockwise. The main blade holder 3 acts on the protrusion 4b through the protrusion 3a, driving the auxiliary blade holder 4 to rotate counterclockwise synchronously. The protrusion 4a and the linkage 8 separate. Meanwhile, the pressure plate 7 and the active blade 5 clamp the top thread and pull it synchronously away from the needle hole 1a, providing tension for the initial top thread, preventing the top thread from tangling and forming a bird's nest, and achieving a clean and neat stitch.

[0042] like Figure 10As shown, when the thread needs to be cut, the motor drives the crank assembly 2 to rotate the main blade holder 3 clockwise. The linkage part 8 presses down as the crank assembly 2 swings, and drives the auxiliary blade holder 4 to rotate counterclockwise through the protrusion 4a. Then the active blade 5 and the auxiliary blade 6 move closer to each other in the direction of the needle hole 1a until the auxiliary blade 6 pushes the thread along the needle groove 5a to the blade edge 5c. The active blade 5 and the auxiliary blade 6 cooperate to cut the thread, thus removing the bird's nest stitches.

[0043] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention 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 the invention or exceeding the scope defined by the appended claims.

Claims

1. A thread-cutting device for a sewing machine, disposed below a needle plate (1) having a needle hole (1a), comprising a crank assembly (2) for transmission connection with a drive component, a main blade holder (3) and an auxiliary blade holder (4) both circular and coaxially arranged, an active blade (5) with a needle groove (5a) fixed on the main blade holder (3), an auxiliary blade (6) both fixed on the auxiliary blade holder (4), and a thread pressing plate (7), wherein the main blade holder (3) is connected to the crank assembly (2), the active blade (5) and the auxiliary blade (6) are respectively disposed on the left and right sides of the needle hole (1a), and the thread pressing plate (7) is located on the left side of the needle hole (1a), characterized in that, The crank assembly (2) has a linkage part (8) protruding towards the auxiliary cutter seat (4). The auxiliary cutter seat (4) has a protruding protrusion one (4a) and a protrusion two (4b) on the side facing the main cutter seat (3). The sewing machine's thread cutting device also includes a spring (9) acting on the auxiliary cutter seat (4). The auxiliary cutter seat (4) can rotate clockwise around its own axis under the elastic force of the spring (9) and make the protrusion one (4a) abut against the lower side of the linkage part (8). The crank assembly (2) When the main blade holder (3) rotates clockwise, the linkage part (8) can press down the protrusion one (4a) to push the auxiliary blade holder (4) to rotate counterclockwise so that the active blade (5) and the auxiliary blade (6) move closer to each other. When the crank assembly (2) drives the main blade holder (3) to rotate counterclockwise, the right end of the pressure plate (7) can abut against the groove edge of the needle groove (5a) of the active blade (5) and the side of the main blade holder (3) can abut against the protrusion two (4b) and drive the auxiliary blade holder (4) to rotate synchronously.

2. The thread-cutting device for a sewing machine according to claim 1, characterized in that, The main blade holder (3) has a protruding protrusion (3a) on the left side. The active blade (5) is fixedly connected to the protrusion (3a). The protrusion (3a) is located above the second protrusion (4b). The main blade holder (3) rotates counterclockwise. The lower side of the protrusion (3a) can abut against the second protrusion (4b).

3. The thread-cutting device for a sewing machine according to claim 2, characterized in that, When the needle groove (5a) of the active blade (5) is located directly below the needle hole (1a), there is a gap between the protrusion (3a) and the second protrusion (4b).

4. The thread-cutting device for a sewing machine according to claim 1, 2, or 3, characterized in that, Both the first protrusion (4a) and the second protrusion (4b) are located on the left side of the axis of the auxiliary knife seat (4), and the distance between the first protrusion (4a) and the axis of the auxiliary knife seat (4) is greater than the distance between the second protrusion (4b) and the axis of the auxiliary knife seat (4).

5. The thread-cutting device for a sewing machine according to claim 1, 2, or 3, characterized in that, The active blade (5) also has a long strip-shaped pressure groove (5b), and the needle drop groove (5a) is long strip-shaped. The right ends of the needle drop groove (5a) and the pressure groove (5b) are connected so that the needle drop groove (5a) and the pressure groove (5b) together form a V-shaped groove. The active blade (5) also has a moving blade edge (5c). The moving blade edge (5c) is located on the left side of the left end of the needle drop groove (5a) and the moving blade edge (5c) faces the needle drop groove (5a).

6. The thread-cutting device for a sewing machine according to claim 1, 2, or 3, characterized in that, The crank assembly (2) includes crank one (2a) and crank two (2b). Crank one (2a) is vertically disposed on the left side of the main cutter seat (3), and the linkage part (8) is located at the upper end of crank one (2a). Crank two (2b) is horizontally disposed below the main cutter seat (3). The left end of crank two (2b) is hinged to the lower end of crank one (2a), and the right end of crank two (2b) is hinged to the right side of the main cutter seat (3).

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