An automatic upper thread breaking device for a sewing machine

Abstract

The present invention discloses an automatic upper thread breaking device for a sewing machine. The sewing machine comprises a base, a head mounting frame fixed on the base, a head mounted on the head mounting frame, a workbench mounted on the base corresponding to the lower part of the head, and a lower thread breaking device mounted on the lower surface of the workbench. The head has a sewing needle bar, and the lower thread breaking device is arranged below the needle head at the end of the needle bar. The upper thread automatic breaking device comprises: a thread sweeping mechanism, a tensioning mechanism and a thread breaking mechanism. The upper thread automatic breaking device for a sewing machine of the present invention can automatically break the thread during sewing, and can make the length of the thread head remaining on the sewing material after the thread is broken less than 1 mm, without the need for manual secondary trimming.

Description

Technical Field

[0001] The present invention relates to the technical field of sewing, and more particularly to an automatic upper thread breaking device for a sewing machine. Background Art

[0002] At present, the sewing machines on the market can realize the automatic thread breaking function. It cuts by the engagement of the cutters. At the same time, the cutter engagement time is controlled by the sensor to control the length of the thread end remaining on the sewing material after the thread breaks. Generally, the length of the residual thread end on the sewing material after the thread breaks is more than 5mm. When the cutter engagement is poor or the sensor is installed in an inappropriate position, the thread end remaining on the surface of the sewing material after the thread breaks will be longer. In order to remove the thread end, manual secondary thread cutting is required, which not only increases working time, but also wastes a lot of labor.

[0003] Therefore, how to provide a sewing machine with better effect so that the length of thread ends remaining on the sewing material after thread breakage is shorter without the need for manual secondary operation is an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0004] In view of this, the present invention provides a sewing machine which can automatically cut the thread during the sewing process and can make the length of the thread end remaining on the sewing material after the thread is cut less than 1 mm, without the need for manual secondary trimming.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] An automatic upper thread breaking device for a sewing machine, the sewing machine comprising a base, a head mounting frame fixed on the base, a head mounted on the head mounting frame, a workbench mounted on the base corresponding to the bottom of the head, and a lower thread breaking device mounted on the bottom surface of the workbench, the head having a sewing needle bar, the lower thread breaking device being arranged below the needle head at the end of the needle bar, and comprising: a thread sweeping mechanism, a tensioning mechanism and a thread breaking mechanism;

[0007] The thread sweeping mechanism includes a thread sweeping hook, a rotating shaft, a connecting rod and a first cylinder for driving the connecting rod. The first cylinder is fixedly mounted on the machine head mounting frame, and the driving end is fixedly connected to one end of the connecting rod, and the other end of the connecting rod is transmission-connected to one end of the rotating shaft. The rotating shaft is rotatably connected to the machine head mounting frame, and the flat end of the thread sweeping hook is fixedly mounted on the outer side wall of the rotating shaft and corresponds to one side of the sewing needle bar.

[0008] The tensioning mechanism includes a movable hook, a limit plate and a second cylinder for driving the movable hook. The second cylinder is fixedly mounted on the machine head mounting frame, and the driving end is fixedly connected to one end of the movable hook. One end of the limit plate is fixed on the machine head and corresponds to one side of the sewing needle rod. The hook end of the movable hook can be abutted and closed with the other end of the limit plate.

[0009] The wire breaking mechanism comprises a slide cylinder, a hot air gun and a hot air blower for providing heat energy to the hot air gun. The slide cylinder is fixed on the machine head mounting frame, and the hot air gun is fixed on the driving end of the slide cylinder.

[0010] Through the above technical scheme, it can be known that compared with the prior art, the present invention discloses a device for automatically cutting the upper thread on a sewing machine. When the sewing operation is finished, the lower thread cutting device first cuts the lower thread, and then cuts the upper thread. First, the first cylinder drives the connecting rod to move linearly, and the connecting rod drives the rotating shaft to rotate. The sweeping hook installed on the rotating shaft hooks the upper thread to a certain position. Then, the second cylinder drives the movable hook to tighten the upper thread, and the hook end abuts and closes with the limit plate to fix the position of the upper thread. Finally, the slide cylinder slides to drive the hot air gun head close to the upper thread, and the hot air gun sprays hot air with a certain temperature to melt the upper thread. By melting the upper thread with hot air, the upper thread can be directly melted from the root of the upper thread, avoiding the cutting error caused by the traditional tool bite cutting process. At the same time, when the movable hook tightens the upper thread, the lower thread connected to it is pulled into the fabric by the tension of the upper thread, and the lower thread head cannot be seen on the surface, thereby achieving the effect of removing the lower thread head while cutting the upper thread, and no manual secondary trimming is required, which saves labor and improves sewing efficiency. The automatic thread cutting device for a sewing machine of the present invention has a simple structure and is flexible to operate. It removes thread ends on the surface of sewing materials, prevents the generation of thread lumps and bird nests to a certain extent, makes sewing clean and tidy, and further optimizes sewing traces.

[0011] According to the present invention, the connecting rod and the rotating shaft are connected by a crank.

[0012] The beneficial effect of adopting the above technical solution is that the crank connection structure is simple, flexible and convenient.

[0013] According to the present invention, the tensioning mechanism also includes a limiting groove body, the limiting groove body is fixed on the machine head, the limiting plate is fixed at the lower part of the limiting groove body, the movable hook slides in the limiting groove body and the hook end of the movable hook can movably abut the other end of the limiting plate.

[0014] The beneficial effect of adopting the above technical solution is to ensure that the sliding direction of the movable hook does not deviate.

[0015] According to the present invention, the slide cylinder includes an outer frame for fixing the cylinder as a whole, a pneumatic guide rod assembly fixedly installed on the outer frame for driving the cylinder, and a moving block movably mounted on the pneumatic guide rod assembly for completing the movement of the cylinder, the outer frame is fixed on the machine head mounting frame, and the hot air gun is fixed on the moving block.

[0016] The beneficial effect of adopting the above technical solution is that the hot air gun can reciprocate with the moving block on the slide cylinder.

[0017] According to the present invention, the wire breaking mechanism also includes a slide cylinder mounting plate, which is fixed on the machine head mounting frame and is provided with adjustment holes for adjusting the position and angle of the outer frame. The outer frame is fixed to the slide cylinder mounting plate by pins passing through the adjustment holes.

[0018] The beneficial effect of adopting the above technical solution is that the position and angle of the slide cylinder can be adjusted by passing the pin through the adjustment hole on the slide cylinder mounting plate. The position adjustment can ensure that the action position of the hot air gun fixed thereon is within the sliding stroke of the slide cylinder. The angle adjustment facilitates the adjustment of the air outlet angle of the hot air gun fixed thereon, which can more effectively fuse the surface line.

[0019] According to the present invention, the wire breaking mechanism also includes a fixed block, which is fixedly mounted on the moving block. The hot air gun is inserted into the fixed block along the sliding direction of the moving block. The fixed block is provided with screws for fixing the hot air gun.

[0020] The beneficial effect of adopting the above technical solution is that the screw can adjust the extension amount of the hot air gun along the sliding direction of the moving block, and can better determine the action distance between the position of the hot air gun head and the face line.

[0021] According to the present invention, the wire breaking mechanism further includes a hose, and both ends of the hose are connected to the hot air gun and the hot air blower.

[0022] The beneficial effect of adopting the above technical solution is that the hose can be arranged conveniently without affecting the operation of the sewing machine.

[0023] According to the present invention, the bottom line breaking device includes a fixed knife, a movable knife capable of engaging with the fixed knife, and a driving device for driving the movable knife to move. The fixed knife is fixedly installed on the bottom surface of the workbench, the movable knife is rotatably installed on the bottom surface of the workbench, and the driving device is connected to the movable knife.

[0024] The beneficial effect of adopting the above technical solution is that the bottom line can be cut by the engagement of the fixed knife and the movable knife.

[0025] According to the present invention, an abutment groove is provided on one end of the limiting plate that abuts against the movable hook.

[0026] The beneficial effect of adopting the above technical solution is that when the movable hook tightens the surface thread and abuts against the limiting plate to close, the surface thread is stuck in the abutting groove, which can prevent the surface thread from sliding and causing failure to tighten.

[0027] According to the present invention, it also includes a controller, a first solenoid valve, a second solenoid valve and a third solenoid valve. The controller is electrically connected to the first solenoid valve, the second solenoid valve and the third solenoid valve. The first solenoid valve is electrically connected to the first cylinder, the second solenoid valve is electrically connected to the second cylinder, and the third solenoid valve is electrically connected to the slide cylinder.

[0028] The beneficial effect of adopting the above technical solution is that the controller can control the movement of the first cylinder, the second cylinder and the slide cylinder by controlling the first solenoid valve, the second solenoid valve and the third solenoid valve, thereby ensuring that the wire sweeping mechanism, the tensioning mechanism and the wire breaking mechanism work closely together to complete the cutting of the surface wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 The accompanying drawing is a schematic structural diagram of an upper thread automatic cutting device for a sewing machine provided by the present invention;

[0031] Figure 2 The accompanying drawing is a schematic structural diagram of an upper thread automatic cutting device for a sewing machine provided by the present invention;

[0032] Figure 3 The accompanying drawing is a schematic structural diagram of a thread-wiping mechanism of an upper thread automatic thread-breaking device for a sewing machine provided by the present invention;

[0033] Figure 4 The accompanying drawing is a schematic structural diagram of a tensioning mechanism of an upper thread automatic thread breaking device for a sewing machine provided by the present invention;

[0034] Figure 5 The accompanying drawing is a schematic diagram of the structure of a movable hook and a limiting plate of an upper thread automatic breaking device for a sewing machine provided by the present invention;

[0035] Figure 6 The accompanying drawing is a schematic structural diagram of a thread breaking mechanism of an upper thread automatic thread breaking device for a sewing machine provided by the present invention;

[0036] Figure 7 The accompanying drawing is a front view of a lower thread breaking device of an upper thread automatic breaking device for a sewing machine provided by the present invention;

[0037] Reference numerals:

[0038] 1. wire sweeping mechanism, 11. wire sweeping hook, 12. rotating shaft, 13. connecting rod, 14. first cylinder;

[0039] 2. tensioning mechanism, 21. movable hook, 22. limiting plate, 23. second cylinder, 24. limiting slot;

[0040] 3. Wire breaking mechanism, 31. Slide cylinder, 311. Outer frame, 312. Moving block, 32. Hot air gun, 33. Hot air blower, 34. Slide cylinder mounting plate, 35. Fixed block, 351. Screw, 36. Hose;

[0041] 4. Machine head mounting frame;

[0042] 5. Workbench;

[0043] 6. Bottom line breaking device, 61. Fixed knife, 62. Moving knife;

[0044] 7. Needle bar. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The embodiment of the present invention discloses an automatic upper thread breaking device for a sewing machine. Referring to the accompanying drawings, the sewing machine comprises a base, a machine head mounting frame 4 fixed on the base, a workbench 5 mounted on the base corresponding to the lower part of the machine head, and a lower thread breaking device 6 mounted on the bottom surface of the workbench 5. The machine head has a sewing needle bar 7. The lower thread breaking device 6 is arranged below the needle head at the end of the needle bar 7 and comprises: a thread sweeping mechanism 1, a tensioning mechanism 2 and a thread breaking mechanism 3.

[0047] Among them, refer to the attached Figure 3 The thread sweeping mechanism 1 includes a thread sweeping hook 11, a rotating shaft 12, a connecting rod 13 and a first cylinder 14 for driving the connecting rod 13. The first cylinder 14 drives the connecting rod 13 to move linearly, and the connecting rod 13 drives the rotating shaft 12 to rotate. The thread sweeping hook 11 installed on the rotating shaft 12 can hook the surface thread backward to a certain position;

[0048] Among them, refer to the attached Figure 4 , 5 The tensioning mechanism 2 includes a movable hook 21, a limiting plate 22 and a second cylinder 23 for driving the movable hook 21. The second cylinder 23 drives the movable hook 21 to tighten the upper thread, and the hook end abuts and closes with the limiting plate 22 to fix the position of the upper thread. When the movable hook 21 tightens the upper thread, the bottom thread connected to it is pulled into the fabric by the tension of the upper thread, and the bottom thread end cannot be seen on the surface. The limiting plate 22 restricts the movable hook 21.

[0049] Among them, refer to the attached Figure 6The wire breaking mechanism 3 includes a slide cylinder 31, a hot air gun 32 and a hot air blower 33 for providing heat energy to the hot air gun 32. The driving end of the slide cylinder 31 slides, driving the head of the hot air gun 32 installed thereon to approach the surface line. The hot air gun 32 sprays hot air with a certain temperature to melt the surface line.

[0050] Advantageously, the hot air gun 32 can also be replaced by laser, plasma high-frequency arc, ultrasonic wave, heating knife, vibrating knife, flame, etc.

[0051] According to an embodiment of the present invention, the connecting rod 13 and the rotating shaft 12 are connected by a crank, and the crank connection structure is simple, flexible and convenient.

[0052] According to one embodiment of the present invention, the tensioning mechanism 2 also includes a limiting groove body 24, the limiting groove body 24 is fixed on the machine head, the limiting plate 22 is fixed at the lower part of the limiting groove body 24, the movable hook 21 slides in the limiting groove body 24 and the hook end of the movable hook 21 can movably abut against the other end of the limiting plate 22, which can ensure that the sliding direction of the movable hook 21 does not deviate.

[0053] According to one embodiment of the present invention, the slide cylinder 31 includes an outer frame 311 for fixing the cylinder as a whole, a pneumatic guide rod assembly fixedly installed on the outer frame 311 for driving the cylinder, and a moving block 312 movably mounted on the pneumatic guide rod assembly for completing the movement of the cylinder. The outer frame 311 is fixed on the machine head mounting frame 4, the hot air gun 32 is fixed on the moving block 312, and the moving block 312 performs reciprocating motion.

[0054] According to one embodiment of the present invention, the wire breaking mechanism 3 also includes a slide cylinder mounting plate 34, which is fixed on the head mounting frame 4 and is provided with an adjustment hole for adjusting the position and angle of the outer frame 311. The outer frame 311 is fixed to the slide cylinder mounting plate 34 by passing a pin through the adjustment hole. The position and angle of the slide cylinder 31 can be adjusted by passing a pin through the adjustment hole on the slide cylinder mounting plate. The position adjustment of the slide cylinder 31 can ensure that the action position of the hot air gun 32 fixed thereon is within the sliding stroke of the slide cylinder 31. The angle adjustment facilitates the adjustment of the air outlet angle of the hot air gun 32 fixed thereon, which can more effectively melt the surface wire.

[0055] Advantageously, the thread breaking mechanism 3 further comprises a fixed block 35, the fixed block 35 is fixedly mounted on the moving block 312, the hot air gun 32 is inserted into the fixed block 35 along the sliding direction of the moving block 312, and a screw 351 for fixing the hot air gun 32 is provided on the fixed block 35. The screw 351 can adjust the extension amount of the hot air gun 32 along the sliding direction of the moving block 312, and can better determine the action distance between the position of the gun head of the hot air gun 32 and the face line.

[0056] According to one embodiment of the present invention, the thread breaking mechanism 3 further comprises a hose 36, both ends of which are connected to the hot air gun 32 and the hot air blower 33. The hose is conveniently arranged and does not affect the operation of the sewing machine.

[0057] According to one embodiment of the present invention, referring to the attached Figure 7 The bottom line cutting device 6 includes a fixed knife 61, a movable knife 62 that can engage with the fixed knife, and a driving device for driving the movable knife to move. The fixed knife 61 is fixedly installed on the bottom surface of the workbench 5, and the movable knife 62 is rotatably installed on the bottom surface of the workbench 5. The driving device is connected to the movable knife 62, and the bottom line can be cut by the engagement of the fixed knife 61 and the movable knife 62.

[0058] According to some embodiments of the present invention, an abutment groove is provided on one end of the limiting plate 22 that abuts against the movable hook 21. When the movable hook 21 tightens the surface thread and closes the limiting plate 22, the surface thread is stuck in the abutment groove, which can prevent the surface thread from sliding and failing to tighten.

[0059] According to some embodiments of the present invention, it also includes a controller, a first solenoid valve, a second solenoid valve and a third solenoid valve. The controller controls the electrical connection between the first solenoid valve, the second solenoid valve and the third solenoid valve. The first solenoid valve controls the first cylinder 14, the second solenoid valve controls the second cylinder 23, and the third solenoid valve controls the slide cylinder 31 to ensure that the wire sweeping mechanism 1, the tensioning mechanism 2 and the wire breaking mechanism 3 work closely together to complete the cutting of the surface wire.

[0060] The controller can be controlled in two ways:

[0061] Method 1: Controlled by PLC (Programmed Logic Controller). The sewing machine clamping, starting signal and the driving signal of the bottom thread breaking device are successively transmitted to the PLC through the relay. The PLC receives the signal and controls the first solenoid valve, the second solenoid valve and the third solenoid valve to operate in sequence according to a predetermined program, thereby driving the first cylinder 14, the second cylinder 23 and the slide cylinder 31 to reciprocate and complete the cutting of the upper thread.

[0062] Method 2: Control via PCB (Printed Circuit Board). After the PCB is set, the first solenoid valve, the second solenoid valve and the third solenoid valve are directly controlled to drive the first cylinder 14, the second cylinder 23 and the slide cylinder 31 to reciprocate at a specific time to complete the cutting of the upper thread.

[0063] The principle of the upper thread automatic breaking device for a sewing machine of the present invention is as follows:

[0064] When the sewing operation is finished, the movable knife of the bottom thread cutting device is driven to engage with the fixed knife to cut the bottom thread, and then the surface thread is cut. First, the first cylinder drives the connecting rod to move linearly, and the connecting rod drives the rotating shaft to rotate. The sweeping hook installed on the rotating shaft hooks the surface thread back to a certain position. Then, the second cylinder drives the movable hook to tighten the surface thread, and the hook end abuts and closes with the limit plate to fix the position of the surface thread. Finally, the sliding cylinder moving block slides, driving the hot air gun head close to the surface thread, and the hot air gun sprays hot air with a certain temperature to melt the surface thread. By melting the surface thread with hot air, the surface thread can be directly melted from the root, avoiding the cutting error caused by the traditional tool engagement and cutting process. At the same time, when the movable hook tightens the surface thread, the bottom thread connected to it is pulled into the fabric by the tension of the surface thread, and the bottom thread head cannot be seen on the surface, thereby achieving the effect of removing the bottom thread head while cutting the surface thread.

[0065] By using the automatic upper thread cutting device for a sewing machine of the present invention, the length L of the thread ends remaining on the sewing material after the thread is broken is relatively stable, and the range of L is within 1 mm, and no manual secondary trimming is required.

[0066] Table 1

[0067] frequency 1 2 3 4 5 6 7 8 9 10 L / mm 0.5 0.7 0.5 0.9 0.7 0.7 0.8 0.6 0.9 1 frequency 11 12 13 14 15 16 17 18 19 20 L / mm 0.8 0.8 0.9 0.5 0.7 0.7 0.9 0.8 0.7 0.9

[0068] The automatic upper thread breaking device for a sewing machine of the present invention can be widely used in various types of sewing equipment such as computer sewing machines, flat machines, DY machines, etc.

[0069] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0070] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An automatic upper thread breaking device for a sewing machine, the sewing machine comprising a base, a head mounting frame (4) fixed on the base, a head mounted on the head mounting frame (4), a workbench (5) mounted on the base corresponding to the lower part of the head, and a lower thread breaking device (6) mounted on the bottom surface of the workbench (5), the head having a sewing needle bar (7), the lower thread breaking device (6) being arranged below the needle head at the end of the needle bar (7), characterized in that: include: A wire sweeping mechanism (1), a tensioning mechanism (2) and a wire breaking mechanism (3); The thread sweeping mechanism (1) comprises a thread sweeping hook (11), a rotating shaft (12), a connecting rod (13) and a first cylinder (14) for driving the connecting rod (13); the first cylinder (14) is fixedly mounted on the machine head mounting frame (4), and a driving end is fixedly connected to one end of the connecting rod (13); the other end of the connecting rod (13) is transmission-connected to one end of the rotating shaft (12); the rotating shaft (12) is rotationally connected to the machine head mounting frame (4); the flat end of the thread sweeping hook (11) is fixedly mounted on the outer side wall of the rotating shaft (12) and corresponds to one side of the sewing needle bar (7); The tensioning mechanism (2) comprises a movable hook (21), a limiting plate (22), a second cylinder (23) and a limiting groove (24) for driving the movable hook (21); the second cylinder (23) is fixedly mounted on the machine head mounting frame (4), and a driving end is fixedly connected to one end of the movable hook (21); one end of the limiting plate (22) is fixed on the machine head and corresponds to one side of the sewing needle rod (7); the hook end of the movable hook (21) can be abutted and closed with the other end of the limiting plate; the limiting groove (24) is fixed on the machine head, the limiting plate (22) is fixed to the lower part of the limiting groove (24); the movable hook (21) slides in the limiting groove (24) and the hook end of the movable hook (21) can be movably abutted with the other end of the limiting plate (22); The wire breaking mechanism (3) comprises a slide cylinder (31), a hot air gun (32) and a hot air blower (33) for providing heat energy to the hot air gun (32), the slide cylinder (31) being fixed on the machine head mounting frame (4), and the hot air gun (32) being fixed on the driving end of the slide cylinder (31); The slide cylinder (31) comprises an outer frame (311) for integrally connecting and fixing the cylinder, a pneumatic guide rod assembly fixedly arranged on the outer frame (311) for driving the cylinder, and a moving block (312) movably mounted on the pneumatic guide rod assembly for completing the movement of the cylinder, wherein the outer frame (311) is fixed on the machine head mounting frame (4), and the hot air gun (32) is fixed on the moving block (312).

2. The upper thread automatic cutting device for a sewing machine according to claim 1, characterized in that: The connecting rod (13) and the rotating shaft (12) are connected by a crank.

3. The upper thread automatic cutting device for a sewing machine according to claim 1, characterized in that: The wire breaking mechanism (3) further comprises a slide cylinder mounting plate (34), wherein the slide cylinder mounting plate (34) is fixed on the machine head mounting frame (4) and is provided with an adjustment hole for adjusting the position and angle of the outer frame (311), and the outer frame (311) is fixed to the slide cylinder mounting plate (34) by means of a pin passing through the adjustment hole.

4. The upper thread automatic cutting device for a sewing machine according to claim 3, characterized in that: The wire breaking mechanism (3) further comprises a fixed block (35), wherein the fixed block (35) is fixedly mounted on the moving block (312), the hot air gun (32) is inserted into the fixed block (35) along the sliding direction of the moving block (312), and the fixed block (35) is provided with a screw (351) for fixing the hot air gun (32).

5. The upper thread automatic cutting device for a sewing machine according to claim 4, characterized in that: The wire breaking mechanism (3) further comprises a hose (36), and two ends of the hose (36) are connected to the hot air gun (32) and the hot air blower (33).

6. The upper thread automatic cutting device for a sewing machine according to claim 5, characterized in that: The bottom thread breaking device (6) comprises a fixed knife (61), a movable knife (62) capable of engaging with the fixed knife, and a driving device for driving the movable knife to move, wherein the fixed knife (61) is fixedly mounted on the bottom surface of the workbench (5), the movable knife (62) is rotatably mounted on the bottom surface of the workbench (5), and the driving device is connected to the movable knife (62).

7. The upper thread automatic cutting device for a sewing machine according to claim 6, characterized in that: An abutment groove is provided on the end of the limiting plate (22) that abuts and closes with the movable hook (21).

8. An automatic upper thread breaking device for a sewing machine according to any one of claims 1 to 7, characterized in that: It also includes a controller, a first solenoid valve, a second solenoid valve and a third solenoid valve, wherein the controller is electrically connected to the first solenoid valve, the second solenoid valve and the third solenoid valve, the first solenoid valve is electrically connected to the first cylinder (14), the second solenoid valve is electrically connected to the second cylinder (23), and the third solenoid valve is electrically connected to the slide cylinder (31).

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