Bird nest prevention thread trimming mechanism for a sewing machine

Abstract

This invention discloses a bird's nest-preventing thread-cutting mechanism for a sewing machine, comprising a lower shaft front sleeve inside the sewing machine base, a lower moving blade and an upper moving blade rotatably mounted on the outside of the lower shaft front sleeve, an auxiliary moving blade and a driver for driving the movement of the auxiliary moving blade are slidably mounted inside the sewing machine base; the auxiliary moving blade is located on one side of the lower moving blade, and the blade of the auxiliary moving blade faces downwards from the needle drop point; the lower moving blade has a starting thread hole and a first thread-cutting blade distributed in a clockwise direction; when the first thread-cutting blade is below the needle drop point, the driver drives the auxiliary moving blade to move until the blade of the auxiliary moving blade engages with the first thread-cutting blade, so that when cutting the thread, the auxiliary moving blade and the lower moving blade can be driven to move below the needle drop hole to cooperate in cutting the thread end, achieving an ultra-short thread end at the starting point of the sewing and improving the sewing effect.

Description

Technical Field

[0001] This invention belongs to the field of sewing machine technology, specifically a sewing machine anti-bird nest thread-cutting mechanism. Background Technology

[0002] Utility model patent with patent number 202420219566.2 discloses a double-movable-blade thread-cutting mechanism for preventing bird nests and a sewing machine. The double-movable-blade thread-cutting mechanism for preventing bird nests includes a fixed starting sewing blade, a main moving blade and a sewing back moving blade, both movably configured on the outer periphery of the rotary hook in the sewing machine. The main moving blade is provided with a starting sewing thread-cutting blade, a thread-hooking groove, a thread-separating groove and a sewing back thread-cutting blade. The thread-hooking groove allows the needle in the sewing machine to pass through. When the main moving blade moves toward the starting sewing blade, the starting sewing thread-cutting blade can engage with the starting sewing blade to reliably prevent bird nests from being cut during the sewing process. When the main moving blade and the sewing back moving blade move toward each other, the sewing back thread-cutting blade can engage with the sewing back moving blade.

[0003] However, there are certain defects in the patent disclosure. The starting stitch cutter is fixed, and the main moving blade moves toward the starting stitch cutter. The starting stitch cutting blade can engage with the starting stitch cutter to cut the thread end. However, since the blade of the starting stitch cutter is still a certain distance away from the needle drop point, the thread end at the starting stitch end is still relatively long after cutting, which needs to be improved. Summary of the Invention

[0004] This invention addresses the technical problem that existing thread-cutting mechanisms still leave a small thread end on the fabric after cutting. It provides a bird's nest-proof thread-cutting mechanism for sewing machines, which can drive the auxiliary moving blade and the lower moving blade to move below the needle hole to cut off the thread end during thread cutting, achieving an ultra-short thread end at the start of the sewing and improving the sewing effect.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a bird nest prevention thread cutting mechanism for a sewing machine, comprising a lower shaft front sleeve inside the sewing machine base, a lower moving blade and an upper moving blade rotatably mounted on the outside of the lower shaft front sleeve, an auxiliary moving blade and a driver for driving the movement of the auxiliary moving blade are slidably mounted inside the sewing machine base; the auxiliary moving blade is located on one side of the lower moving blade, and the blade of the auxiliary moving blade faces downwards from the needle drop point; the lower moving blade has a thread-starting hole and a first thread-cutting blade distributed in a clockwise direction; when the first thread-cutting blade is located below the needle drop point, the driver drives the auxiliary moving blade to move until the blade of the auxiliary moving blade engages with the first thread-cutting blade.

[0006] To optimize the above technical solution, the present invention also includes the following improved technical solutions.

[0007] The sewing machine base is equipped with a fixed bracket, and a sliding block is slidably provided on one side of the fixed bracket. The auxiliary moving knife is fixed on the sliding block, and the sliding block is provided with an arc-shaped groove, which is slidably engaged with the screw on the fixed bracket.

[0008] The sewing machine base is provided with a drive mounting plate, and the driver is fixed to the bottom of the drive mounting plate; a first connecting plate is rotatably mounted on one side of the drive mounting plate, and a drive plate is provided at the output end of the driver. The drive plate is rotatably connected to the sliding block through the first connecting plate.

[0009] The first connecting plate has a first connecting part and a second connecting part. The first connecting part is rotatably connected to the drive plate, and the second connecting part is rotatably connected to a second connecting plate. The other end of the second connecting plate is rotatably connected to the sliding block.

[0010] The aforementioned upper moving knife is positioned opposite to the auxiliary moving knife with its blade facing downwards from the needle drop point. The upper moving knife is located outside the lower moving knife. The lower moving knife has a lead-in groove and a second cutting blade distributed on the same circumference in a counterclockwise direction. The lead-in groove is arranged obliquely and its opening communicates with the outside. When the upper moving knife and the second cutting blade move towards each other to below the needle drop point, the blade of the upper moving knife engages with the second cutting blade.

[0011] The aforementioned second thread-cutting blade, the thread-threading hole, the lead-in groove, and the first thread-cutting blade are arranged sequentially in a clockwise direction along the circumference of the lower moving blade; a first guide groove is provided between the thread-threading hole and the lead-in groove, a second guide groove is provided between the lead-in groove and the first thread-cutting blade, and a third guide groove is provided between the thread-threading hole and the second thread-cutting blade.

[0012] The first cutting blade has a first protrusion at its end that cooperates with the auxiliary moving blade to cut the thread; the second cutting blade has a second protrusion at its end that cooperates with the upper moving blade to cut the thread; the first wire groove, the second wire groove, and the third wire groove each have a first recess, a second recess, and a third recess for the needle and thread to pass through.

[0013] The sewing machine base is equipped with a thread-cutting drive motor. A first drive crank is provided on one side of the thread-cutting drive motor. A drive component is fixed to the output end of the thread-cutting drive motor. A pulley is rotatably mounted on the drive component. The first drive crank has a long groove. The pulley slides against the inner wall of the long groove. A second drive crank is provided on one side of the first drive crank. The second drive crank is rotatably connected to the lower moving blade and the upper moving blade respectively.

[0014] The aforementioned second drive crank has a first connecting end and a second connecting end. The first connecting end is rotatably connected to the lower moving cutter via a first connecting rod, and the second connecting end is rotatably connected to the upper moving cutter via a second connecting rod.

[0015] The first drive crank has a drive connecting rod, the other end of which is fixedly connected to the second drive crank; the drive connecting rod is fitted with a bushing, and the drive connecting rod is rotatably mounted in the sewing machine base through the bushing, and a return spring is fitted on the bushing.

[0016] Compared with the prior art, the anti-bird nest thread cutting mechanism of the present invention, when cutting the thread at the beginning of the stitch, rotates the first cutting blade of the lower moving blade to below the needle drop point, and the auxiliary moving blade can move relative to the first cutting blade until the blade of the auxiliary moving blade engages with the first cutting blade, thereby cutting the thread at the needle drop point, making the thread cutting position closer to the needle drop point, and the thread end at the beginning of the stitch is shorter, thus improving the sewing effect. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of this embodiment.

[0018] Figure 2 This is an exploded view of this embodiment.

[0019] Figure 3 This is a three-dimensional structural diagram of the lower moving blade.

[0020] Figure 4 This is a front view of the first stitch.

[0021] Figure 5 This is a front view of the state after the first stitch is completed.

[0022] Figure 6 This is a front view showing the state of the thread end after it has been cut.

[0023] Figure 7 It is a front view of the continuous sewing process.

[0024] Figure 8 This is a front view of the finished sewing process with the thread cut. Detailed Implementation

[0025] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0026] Figures 1 to 8 The diagram shown is a structural schematic of the present invention.

[0027] The reference numerals in the attached drawings are as follows: 1. Lower shaft front sleeve; 2. Auxiliary moving blade; 3. Lower moving blade; 3a. Threading hole; 3b. First thread cutting blade; 3c. Thread guide groove; 3d. Second thread cutting blade; 3e. First protrusion; 3f. Second protrusion; 3g. First guide groove; 3h. Second guide groove; 3i. Third guide groove; 3j. First recess; 3k. Second recess; 3m. Thread separating part; 3n. Thread suction tube; 4. Fixed bracket; 5. Sliding block; 6. Slide groove; 6a. Screw; 7. Driver; 8. Driver mounting plate; 9. First connecting plate 10, first connecting part 10a, second connecting part 10b, drive plate 11, second connecting plate 12, upper moving blade 13, lower blade holder 14, upper blade holder 15, wire cutting drive motor 16, wire cutting motor mounting bracket 17, first drive crank 18, long slot 18a, drive component 19, pulley 20, second drive crank 21, first connecting end 21a, second connecting end 21b, first connecting rod 22, second connecting rod 23, drive connecting rod 24, bushing 25, return spring 26.

[0028] like Figure 1 and Figure 2 As shown, the anti-bird nest thread-cutting mechanism of a sewing machine according to the present invention includes an auxiliary moving knife 2 slidably installed in the sewing machine base and a lower moving knife 3 rotatably installed on the outside of the lower shaft front sleeve 1. The auxiliary moving knife 2 is located outside the lower moving knife 3, and the blade of the auxiliary moving knife 2 faces downward of the needle drop point.

[0029] like Figure 3 As shown, the lower moving blade 3 has a starting thread hole 3a and a first thread cutting blade 3b distributed on the same circumference in a clockwise direction. After a few stitches are started, the first thread cutting blade 3b of the lower moving blade 3 rotates to below the needle drop point. The auxiliary moving blade 2 can move relative to the first thread cutting blade 3b until the blade of the auxiliary moving blade 2 engages with the first thread cutting blade 3b to cut the needle thread. This makes the thread cutting position closer to the needle drop point, and the thread end at the starting point of the sewing material shorter, thus improving the sewing effect.

[0030] The sewing machine base is equipped with a suction tube 4, with the opening of the suction tube 4 facing downwards from the needle drop point. The suction tube 4 can promptly pick up excess thread ends and waste after cutting.

[0031] The sewing machine base is equipped with a fixed bracket 5, and a sliding block 6 is slidably mounted on one side of the fixed bracket 5. The auxiliary moving blade 2 is fixed on the sliding block 6. The sliding block 6 has an arc-shaped groove 6a, and a screw 7 is slidably mounted in the groove 6a. The end of the screw 7 is fixed to the fixed bracket 5, and the auxiliary moving blade 2 can move along the groove 6a.

[0032] The sewing machine base is equipped with a driver 8 that drives the auxiliary moving blade 2. In this embodiment, the driver 8 is preferably a single-acting cylinder or a double-acting cylinder, but it can also be an electromagnet or a linear motor. The sewing machine base is equipped with a drive mounting plate 9, and the driver 8 is fixed to the bottom of the drive mounting plate 9. A first connecting plate 10 is rotatably mounted on one side of the drive mounting plate 9, and a drive plate 11 is provided at the output end of the driver 8. The drive plate 11 is rotatably connected to the sliding block 6 through the first connecting plate 10.

[0033] The first connecting plate 10 has a first connecting part 10a and a second connecting part 10b. The first connecting part 10a is rotatably connected to the drive plate 11, and the second connecting part 10b is rotatably connected to a second connecting plate 12. The other end of the second connecting plate 12 is rotatably connected to the sliding block 6. The output end of the driver 8 drives the auxiliary moving knife 2 to move along the slide groove 6a towards the needle drop point through the drive plate 11, the first connecting plate 10, and the second connecting plate 12.

[0034] An upper moving knife 13 is rotatably mounted on the outer side of the lower shaft front sleeve 1. The upper moving knife 13 is positioned opposite to the auxiliary moving knife 2 and its blade faces downwards from the needle drop point. The upper moving knife 13 is located outside the lower moving knife 3. The lower moving knife 3 is rotatably mounted on the outer side of the lower shaft front sleeve 1 via the lower knife holder 14. The upper moving knife 13 is rotatably mounted on the outer side of the lower shaft front sleeve 1 via the upper knife holder 15.

[0035] The lower moving blade 3 has a thread guide groove 3c and a second thread cutting blade 3d arranged on the same circumference in a counterclockwise direction. The thread guide groove 3c is arranged obliquely and its opening is connected to the outside. After sewing is completed, when the upper moving blade 13 and the second thread cutting blade 3d move towards each other to below the needle drop point, the blade of the upper moving blade 13 engages with the second thread cutting blade 3d to cut the needle thread.

[0036] The second thread-cutting blade 3d, the starting thread hole 3a, the thread guide groove 3c, and the first thread-cutting blade 3b are arranged clockwise along the circumference of the lower moving blade 3. A first guide groove 3g is located between the starting thread hole 3a and the thread guide groove 3c; a second guide groove 3h is located between the thread guide groove 3c and the first thread-cutting blade 3b; and a third guide groove 3i is located between the starting thread hole 3a and the second thread-cutting blade 3d. After sewing, the needle thread will retain a certain length as it passes through the first guide groove 3g and the third guide groove 3i along the thread guide groove 3c. After the blade of the upper moving blade 13 engages with the second thread-cutting blade 3d to cut the thread, the bottom thread end inside the rotary hook will still have some slack and will not be too short.

[0037] To increase the contact area between the blade of the auxiliary moving blade 2 and the first cutting blade 3b, the end of the first cutting blade 3b has a first protrusion 3e that cooperates with the auxiliary moving blade 2 to cut the wire, thus optimizing the wire cutting effect. To increase the contact area between the blade of the upper moving blade 13 and the second cutting blade 3d, the end of the second cutting blade 3d has a second protrusion 3f that cooperates with the upper moving blade 13 to cut the wire, thus optimizing the wire cutting effect.

[0038] The first guide groove 3g, the second guide groove 3h, and the third guide groove 3i each have a first recess 3j, a second recess 3k, and a third recess 3m for the needle and thread to pass through. The first recess 3j, the second recess 3k, and the third recess 3m have a guiding function, which facilitates the movement of the needle and thread along the corresponding trajectory.

[0039] A thread-cutting drive motor 16 is installed inside the sewing machine base, and the thread-cutting drive motor 16 is fixed inside the sewing machine base by a thread-cutting motor mounting bracket 17. A first drive crank 18 is provided on one side of the thread-cutting drive motor 16, and a drive component 19 is fixed to the output end of the thread-cutting drive motor 16. A pulley 20 is rotatably mounted on the drive component 19. The first drive crank 18 has an elongated groove 18a, and the pulley 20 slides against the inner wall of the elongated groove 18a. The thread-cutting drive motor 16 drives the pulley 20 on the drive component 19 to move along the elongated groove 18a, thereby causing the first drive crank 18 to swing.

[0040] A second drive crank 21 is provided on one side of the first drive crank 18. The second drive crank 21 is rotatably connected to the lower moving tool 3 and the upper moving tool 13, respectively. The second drive crank 21 has a first connecting end 21a and a second connecting end 21b. The first connecting end 21a is rotatably connected to the lower tool holder 14 through a first connecting rod 22, and the second connecting end 21b is rotatably connected to the upper tool holder 15 through a second connecting rod 23. The second drive crank 21 swings synchronously with the first drive crank 18, and the second drive crank 21 simultaneously drives the upper moving tool 13 and the lower moving tool 3 to rotate.

[0041] The first drive crank 18 has a drive connecting rod 24, the other end of which is fixedly connected to the second drive crank 21. A bushing 25 is fitted onto the drive connecting rod 24, allowing it to be rotatably mounted within the sewing machine base via the bushing 25. A return spring 26 is fitted onto the bushing 25. The return spring 26 can be connected in two ways: firstly, one end of the return spring 26 is connected to the sewing machine base, and the other end is connected to the second drive crank 21; secondly, one end of the return spring 26 is connected to the sewing machine base, and the other end is connected to the first drive crank 18.

[0042] When the wire-cutting drive motor 16 drives the drive component 19 to rotate clockwise, the pulley 20 moves obliquely downward relative to the long groove 18a, thereby causing the first drive crank 18 to swing clockwise, and the second drive crank 21 to swing synchronously. The second drive crank 21 drives the lower moving blade 3 and the upper moving blade 13 to move in opposite directions. When the wire-cutting drive motor 16 drives the drive component 19 to rotate counterclockwise, the pulley 20 moves obliquely upward relative to the long groove 18a, thereby causing the first drive crank 18 to swing counterclockwise, and the second drive crank 21 to swing synchronously. The second drive crank 21 drives the lower moving blade 3 and the upper moving blade 13 to move in opposite directions.

[0043] like Figure 4As shown, when starting the first stitch, the starting thread hole 3a of the lower moving knife 3 rotates clockwise to below the needle drop point, the needle passes downward through the starting thread hole 3a, the top thread loop crosses the bottom thread end in the rotary hook, and then the needle retracts upward.

[0044] like Figure 5 As shown, after the first stitch is completed, the lower moving blade 3 rotates counterclockwise toward the auxiliary moving blade 2. The top thread and bottom thread in the starting thread hole 3a move along the first recess 3j and the second recess 3k to the first thread cutting blade 3b. When the blade of the auxiliary moving blade 2 contacts the first thread cutting blade 3b, the blade of the auxiliary moving blade 2 and the first thread cutting blade 3b just clamp the thread end. Then the needle performs one or more stitches.

[0045] like Figure 6 As shown, after sewing a few stitches, the first cutting edge 3b of the lower moving blade 3 rotates clockwise to below the needle drop point. Then, the auxiliary moving blade 2 moves relative to the first cutting edge 3b until the blade of the auxiliary moving blade 2 engages with the first cutting edge 3b, thereby cutting off the thread end at the starting point. The suction tube 4 then sucks up the excess thread.

[0046] like Figure 7 As shown, the auxiliary moving blade 2 returns to its initial position, and the lower moving blade 3 rotates counterclockwise to avoid the position below the needle's drop position. Then, the needle performs subsequent sewing operations.

[0047] During the final stitch, the top thread forms a small loop below the sewing table. The upper moving blade 13 and the lower moving blade 3 move towards each other. The lower moving blade 3 rotates clockwise, and its thread-separating part 3n passes through the top thread loop. The top thread and bottom thread on the cut side enter the thread guide groove 3c. The top thread and bottom thread in the thread guide groove 3c move along the first recess 3j and the third recess 3m to the second cutting blade 3d. Figure 8 As shown, the lower moving blade 3 continues to rotate clockwise until the second cutting edge 3d moves towards the upper moving blade 13 and reaches below the needle drop point. The second cutting edge 3d engages with the blade of the upper moving blade 13, cutting the top and bottom threads.

[0048] The preferred embodiments of the present invention have been described, and various changes or modifications made by those skilled in the art will not depart from the scope of the present invention.

Claims

1. A bird nest-prevention thread-cutting mechanism for a sewing machine, comprising a lower shaft front sleeve (1) inside the sewing machine base, a lower moving blade (3) and an upper moving blade (13) rotatably mounted on the outside of the lower shaft front sleeve (1), characterized in that: An auxiliary moving blade (2) and a driver (8) for driving the movement of the auxiliary moving blade (2) are slidably installed inside the sewing machine base; the auxiliary moving blade (2) is located on one side of the lower moving blade (3), and the blade of the auxiliary moving blade (2) faces downwards from the needle drop point; the lower moving blade (3) has a starting sewing thread hole (3a) and a first thread cutting blade (3b) distributed in a clockwise direction; when the first thread cutting blade (3b) is located below the needle drop point, the driver (8) drives the auxiliary moving blade (2) to move until the blade of the auxiliary moving blade (2) engages with the first thread cutting blade (3b).

2. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 1, characterized in that: The sewing machine base is provided with a fixed bracket (5), and a sliding block (6) is slidably provided on one side of the fixed bracket (5). The auxiliary moving knife (2) is fixed on the sliding block (6). The sliding block (6) is provided with an arc-shaped groove (6a), and the groove (6a) is slidably engaged with the screw (7) on the fixed bracket (5).

3. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 2, characterized in that: The sewing machine base is provided with a drive mounting plate (9), and the driver (8) is fixed to the bottom of the drive mounting plate (9); a first connecting plate (10) is rotatably mounted on one side of the drive mounting plate (9), and a drive plate (11) is provided at the output end of the driver (8). The drive plate (11) is rotatably connected to the sliding block (6) through the first connecting plate (10).

4. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 3, characterized in that: The first connecting plate (10) has a first connecting part (10a) and a second connecting part (10b). The first connecting part (10a) is rotatably connected to the drive plate (11), and the second connecting part (10b) is rotatably connected to a second connecting plate (12). The other end of the second connecting plate (12) is rotatably connected to the sliding block (6).

5. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 4, characterized in that: The upper moving knife (13) is positioned opposite to the auxiliary moving knife (2) with its blade facing below the needle drop point. The upper moving knife (13) is located outside the lower moving knife (3). The lower moving knife (3) has a lead wire groove (3c) and a second cutting edge (3d) distributed on the same circumference in a counterclockwise direction. The lead wire groove (3c) is arranged obliquely and its opening is connected to the outside. When the upper moving knife (13) and the second cutting edge (3d) move towards each other to below the needle drop point, the blade of the upper moving knife (13) engages with the second cutting edge (3d).

6. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 5, characterized in that: The second thread-cutting blade (3d), the thread-threading hole (3a), the thread-leading groove (3c), and the first thread-cutting blade (3b) are arranged in a clockwise direction along the circumference of the lower moving blade (3); a first guide groove (3g) is provided between the thread-threading hole (3a) and the thread-leading groove (3c), a second guide groove (3h) is provided between the thread-leading groove (3c) and the first thread-cutting blade (3b), and a third guide groove (3i) is provided between the thread-threading hole (3a) and the second thread-cutting blade (3d).

7. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 6, characterized in that: The first cutting blade (3b) has a first protrusion (3e) at its end that cooperates with the auxiliary moving blade (2) to cut the thread; the second cutting blade (3d) has a second protrusion (3f) at its end that cooperates with the upper moving blade (13) to cut the thread; the first wire groove (3g), the second wire groove (3h), and the third wire groove (3i) each have a first recess (3j), a second recess (3k), and a third recess (3m) for the needle and thread to pass through.

8. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 7, characterized in that: The sewing machine base is equipped with a thread-cutting drive motor (16). A first drive crank (18) is provided on one side of the thread-cutting drive motor (16). A drive component (19) is fixed at the output end of the thread-cutting drive motor (16). A pulley (20) is rotatably mounted on the drive component (19). The first drive crank (18) is provided with a long groove (18a). The pulley (20) slides against the inner wall of the long groove (18a). A second drive crank (21) is provided on one side of the first drive crank (18). The second drive crank (21) is rotatably connected to the lower moving blade (3) and the upper moving blade (13) respectively.

9. The anti-bird nest thread-cutting mechanism for a sewing machine according to claim 8, characterized in that: The second drive crank (21) has a first connecting end (21a) and a second connecting end (21b). The first connecting end (21a) is rotatably connected to the lower moving blade (3) through a first connecting rod (22), and the second connecting end (21b) is rotatably connected to the upper moving blade (13) through a second connecting rod (23).

10. A bird-nest-proof thread-cutting mechanism for a sewing machine according to claim 9, characterized in that: The first drive crank (18) has a drive connecting rod (24), the other end of which is fixedly connected to the second drive crank (21); the drive connecting rod (24) is fitted with a bushing (25), and the drive connecting rod (24) is rotatably mounted in the sewing machine base through the bushing (25); a return spring (26) is fitted on the bushing (25).

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