Thread trimming and presser foot lifting mechanism for a sewing machine

Abstract

The application provides a thread trimming and presser foot lifting mechanism of a sewing machine, comprising a motor, a cam, a thread trimming unit and a presser foot lifting unit; the motor comprises a rotating shaft, and the cam is installed on the rotating shaft; the cam comprises a first surface and a second surface, the thread trimming unit is connected with the first surface, and the presser foot lifting unit is connected with the second surface; when the rotating shaft drives the cam to rotate in a first direction, the first surface drives the thread trimming unit to perform a thread trimming action, and the presser foot lifting unit remains in a stationary state; when the rotating shaft drives the cam to rotate in a second direction, the second surface drives the presser foot lifting unit to perform a presser foot lifting action, and the thread trimming unit remains in a stationary state. The motor and the cam realize double-surface transmission of the cam, one surface of the cam controls thread trimming, and the other surface controls presser foot lifting, one motor can realize thread trimming and presser foot lifting, the structure of the thread trimming and presser foot lifting mechanism is simpler, there are fewer components, the precision requirement of the components is lower, the thread trimming and presser foot lifting mechanism is easy to assemble, the cost is lower, and the noise during operation of the thread trimming and presser foot lifting mechanism is smaller.

Description

Technical Field

[0001] This invention relates to the field of sewing machine technology, and in particular to a thread-cutting and presser foot lifting mechanism for a sewing machine. Background Technology

[0002] Traditional sewing machines mostly use electromagnets as a power source. The automatic thread cutting mechanism and the automatic presser foot lifting mechanism each require an electromagnet for control. When automatically cutting the thread, the thread cutting mechanism is driven by the extension and retraction of one electromagnet core. When automatically lifting the presser foot, the presser foot is lifted and lowered by the extension and retraction of another electromagnet core.

[0003] However, the aforementioned automatic wire cutting mechanism and automatic presser foot lifting mechanism require a large number of parts and have high dimensional accuracy requirements for components such as the wire cutting cam, resulting in complex assembly, high cost, risk of jamming, and significant noise. Summary of the Invention

[0004] This invention provides a thread-cutting and presser foot-lifting mechanism for a sewing machine to solve the aforementioned technical problems of existing automatic thread-cutting mechanisms and automatic presser foot-lifting mechanisms.

[0005] To solve the above-mentioned technical problems, the present invention provides a thread-cutting and presser foot lifting mechanism for a sewing machine, including a motor, a cam, a thread-cutting unit, and a presser foot lifting unit;

[0006] The motor includes a rotating shaft, and the cam is mounted on the rotating shaft;

[0007] The cam includes a first surface and a second surface, the wire-cutting unit is connected to the first surface, and the pressure foot lifting unit is connected to the second surface;

[0008] When the rotating shaft drives the cam to rotate in the first direction, the first surface drives the wire cutting unit to perform the wire cutting action, and the lifting pressure foot unit remains stationary.

[0009] When the rotating shaft drives the cam to rotate in the second direction, the second surface drives the lifting foot unit to perform the lifting foot action, and the wire cutting unit remains stationary. The first direction and the second direction are opposite.

[0010] Optionally, a first track groove is provided on the first surface, the first track groove including a first arc segment, a second arc segment, a third straight segment and a fourth arc segment connected in sequence; the diameter of the first arc is greater than the diameter of the fourth arc, and the diameter of the fourth arc is greater than the diameter of the second arc;

[0011] The wire cutting unit includes an upper cutter roller, an upper cutter crank, an upper cutter crank shaft, a lower cutter roller, a lower cutter crank, and a lower cutter crank shaft; the upper cutter roller is connected to one end of the upper cutter crank and installed in the first track groove, and the other end of the upper cutter crank is fixed to one end of the upper cutter crank shaft; the lower cutter roller is connected to one end of the lower cutter crank and installed in the first track groove, and the other end of the lower cutter crank is fixed to one end of the lower cutter crank shaft; there is a gap between the upper cutter roller and the lower cutter roller;

[0012] When the upper cutter roller is within the first arc segment, the upper cutter crank remains stationary; when the upper cutter roller is within the second arc segment or the third straight segment, the upper cutter crank drives the upper cutter crank shaft to rotate.

[0013] When the lower cutter roller is within the first arc segment or the fourth arc segment, the lower cutter crank remains stationary; when the upper cutter roller is within the second arc segment or the third straight segment, the lower cutter crank drives the lower cutter crank shaft to rotate.

[0014] Optionally, the first track groove is a sinkhole.

[0015] Optionally, the wire cutting unit further includes an upper wire cutting crank, an upper blade connecting rod, an upper cutting blade holder, and an upper cutting blade connected in sequence, as well as a lower wire cutting crank, a lower blade connecting rod, a lower cutting blade holder, and a lower cutting blade connected in sequence.

[0016] One end of the upper cutter's wire-cutting crank is fixed to the other end of the upper cutter crank shaft; the upper cutter crank is used to drive the upper cutter to move closer to or away from the lower cutter.

[0017] One end of the lower cutter's wire-cutting crank is fixed to the other end of the lower cutter crank shaft; the lower cutter crank is used to drive the lower cutter to move closer to or away from the upper cutter.

[0018] Optionally, the upper tool crankshaft is hollow and cylindrical, and the lower tool crankshaft passes through the upper tool crankshaft along its axial direction.

[0019] Optionally, the presser foot lifting unit includes a presser foot lifting crank, a presser foot lifting shaft, a pull rod crank, a presser foot lifting pull rod, a presser foot rear lever, a front lever pull rod, a presser foot front lever, a presser foot lifting plate, a presser rod guide, a presser rod, and a presser foot, connected in sequence; the presser foot lifting shaft is fixed to the machine housing by a presser foot lifting shaft sleeve.

[0020] Optionally, the presser foot lifting unit further includes a presser rod bushing, the presser rod passing through the presser rod bushing, and the presser rod guide sleeve fixed to the housing.

[0021] Optionally, one end of the lifting foot shaft is provided with a return spring for resetting the lifting foot shaft.

[0022] Optionally, a drive block is provided on the second surface, one end of the lifting foot crank is fixedly mounted on the lifting foot shaft, and the other end is mounted on a bearing; when the drive block rotates along the second direction with the cam, the drive block drives the bearing to move, thereby driving the lifting foot crank to rotate.

[0023] The present invention provides a thread-cutting and presser foot lifting mechanism for a sewing machine. The mechanism uses a motor and a cam to achieve double-sided transmission of the cam. One side of the cam controls thread cutting, and the other side controls presser foot lifting. One motor can achieve both thread cutting and presser foot lifting, making the structure of the thread-cutting and presser foot lifting mechanism simpler, with fewer parts, lower precision requirements for the parts, easier assembly, lower cost, and lower noise during operation. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a thread-cutting and presser foot lifting mechanism for a sewing machine according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of the first surface of a cam provided in an embodiment of the present invention.

[0026] Figure 3 yes Figure 1 A partial schematic diagram of the upper and lower cutters driven by a motor.

[0027] Figure 4 yes Figure 3 A partial schematic diagram of the upper cutter driven by a motor.

[0028] Figure 5 yes Figure 3 A partial schematic diagram of the lower cutter driven by a motor.

[0029] Figure 6 This is a schematic diagram of the structure of the second surface of a cam provided in an embodiment of the present invention.

[0030] [The annotations in the attached figures are explained below]:

[0031] 1-Motor, 2-Cam, 3-Upper blade roller, 4-Upper blade crank, 5-Upper blade crank shaft, 6-Lower blade roller, 7-Lower blade crank, 8-Lower blade crank shaft, 9-Upper blade thread-cutting crank, 10-Upper blade connecting rod, 11-Upper cutter holder, 12-Upper cutter, 13-Lower blade thread-cutting crank, 14-Lower blade connecting rod, 15-Lower cutter holder, 16-Lower cutter, 17-Lift presser foot crank, 18-Lift 19-Pull rod crank, 20-Pull foot pull rod, 21-Pull foot rear lever, 22-Front lever pull rod, 23-Pull foot front lever, 24-Pull foot lifting plate, 25-Pull rod guide frame, 26-Pull rod, 27-Pull foot, 28-Pull foot bushing, 29-Pull rod bushing, 30-Return spring, 31-Rear lever shaft screw, 32-Threaded pin, 33-Drive block, 34-Screw;

[0032] 201 - First page, 202 - Second page;

[0033] 2011 - First track groove;

[0034] A - First circular arc segment, B - Second circular arc segment, C - Third straight line segment, D - Fourth circular arc segment. Detailed Implementation

[0035] To make the objectives, advantages, and features of the present invention clearer, the thread-cutting and presser foot lifting mechanism of a sewing machine proposed in this invention will be further described in detail below with reference to the accompanying drawings. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the explanation of the embodiments of the present invention.

[0036] In the description of this invention, the terms "first," "second," and other qualifiers are added for convenience of description and reference, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with qualifiers such as "first" and "second" may explicitly or implicitly include one or more of that feature.

[0037] like Figures 1-6 As shown, the present invention provides a thread-cutting and presser foot lifting mechanism for a sewing machine, including a motor 1, a cam 2, a thread-cutting unit, and a presser foot lifting unit; the motor 1 includes a rotating shaft, and the cam 2 is mounted on the rotating shaft; the cam 2 includes a first surface 201 and a second surface 202, the thread-cutting unit is connected to the first surface 201, and the presser foot lifting unit is connected to the second surface 202; when the rotating shaft drives the cam 2 to rotate in a first direction, the first surface 201 drives the thread-cutting unit to perform a thread-cutting action, and the presser foot lifting unit remains stationary; when the rotating shaft drives the cam 2 to rotate in a second direction, the second surface 202 drives the presser foot lifting unit to perform a presser foot lifting action, and the thread-cutting unit remains stationary, the first direction and the second direction being opposite.

[0038] The motor 1 can be a stepper motor or a servo motor; the first direction can be clockwise and the second direction can be counterclockwise; or, the first direction is counterclockwise and the second direction is clockwise.

[0039] This embodiment provides a thread-cutting and presser foot lifting mechanism for a sewing machine. The cam 2 is driven on both sides by a motor 1 and a cam 2. One side of the cam 2 controls thread cutting, and the other side controls presser foot lifting 27. One motor 1 can achieve both thread cutting and presser foot lifting 27, making the structure of the thread-cutting and presser foot lifting mechanism simpler, with fewer parts, lower precision requirements for the parts, easier assembly, lower cost, and less noise during operation.

[0040] Optional, such as Figures 1-5 As shown, a first track groove 2011 is provided on the first surface 201. The first track groove 2011 includes a first arc segment A, a second arc segment B, a third straight segment C, and a fourth arc segment D connected in sequence. The diameter of the first arc is larger than the diameter of the fourth arc, and the diameter of the fourth arc is larger than the diameter of the second arc. The wire cutting unit includes an upper cutter roller 3, an upper cutter crank 4, an upper cutter crank shaft 5, a lower cutter roller 6, a lower cutter crank 7, and a lower cutter crank shaft 8. One end of the upper cutter roller 3 is connected to the upper cutter crank 4 and installed in the first track groove 2011. The other end of the upper cutter crank 4 is fixed to one end of the upper cutter crank shaft 5. The lower cutter roller 6 is connected to the lower cutter crank 7. One end of the lower cutter crank 7 is connected to and installed in the first track groove 2011, and the other end of the lower cutter crank 7 is fixed to one end of the lower cutter crank shaft 8; there is a gap between the upper cutter roller 3 and the lower cutter roller 6; when the upper cutter roller 3 is in the first arc segment A, the upper cutter crank 4 remains stationary; when the upper cutter roller 3 is in the second arc segment B or the third straight segment C, the upper cutter crank 4 drives the upper cutter crank shaft 5 to rotate; when the lower cutter roller 6 is in the first arc segment A or the fourth arc segment D, the lower cutter crank 7 remains stationary; when the upper cutter roller 3 is in the second arc segment B or the third straight segment C, the lower cutter crank 7 drives the lower cutter crank shaft 8 to rotate.

[0041] The first track groove 2011 provided in this embodiment can control the dual-axis transmission of the upper blade crankshaft 5 and the lower blade crankshaft 8, thereby precisely controlling the upper and lower blade movements used for cutting wire, ensuring stable wire cutting and convenient adjustment. In other embodiments, a track groove can be provided on the first surface 201 of the cam 2 for the upper blade crankshaft 5 and the lower blade crankshaft 8 respectively, and the upper blade roller 3 and the lower blade roller 6 are respectively installed in the corresponding track grooves.

[0042] Optional, such as Figure 2 As shown, the first track groove 2011 is a recessed groove. The first track groove 2011 being a recessed groove means that it only penetrates the first surface 201 but not the second surface 202, which improves the strength of the cam 2. In other embodiments, the first track groove 2011 can be a through-hole groove, meaning that the first track groove 2011 penetrates both the first surface 201 and the second surface 202.

[0043] Optional, such as Figures 1-5 As shown, the wire cutting unit further includes an upper blade wire cutting crank 9, an upper blade connecting rod 10, an upper cutting blade holder 11, and an upper cutting blade 12 connected in sequence, and a lower blade wire cutting crank 13, a lower blade connecting rod 14, a lower cutting blade holder 15, and a lower cutting blade 16 connected in sequence; one end of the upper blade wire cutting crank is fixed to the other end of the upper blade crank shaft 5; the upper blade crank 4 is used to drive the upper cutting blade 12 to move closer to or away from the lower cutting blade 16; one end of the lower blade wire cutting crank is fixed to the other end of the lower blade crank shaft 8; the lower blade crank 7 is used to drive the lower cutting blade 16 to move closer to or away from the upper cutting blade 12.

[0044] The wire-cutting unit provided in this embodiment can precisely control the movement of the upper cutter 12 and the lower cutter 16 to achieve the wire-cutting action. In other embodiments, the specific components of the wire-cutting unit can be adjusted according to actual needs, thereby adjusting the distance between the upper cutter 12 and the lower cutter 16 and the cam 2.

[0045] Optional, such as Figures 3-5 As shown, the upper tool crankshaft 5 is a hollow cylinder, and the lower tool crankshaft 8 extends through the upper tool crankshaft 5 along its axial direction. This simplifies the structure of the upper tool crankshaft 5 and the lower tool crankshaft 8, reducing the space occupied by them. In other embodiments, the upper tool crankshaft 5 and the lower tool crankshaft 8 can be arranged relatively independently.

[0046] Optional, such as Figure 1 and Figure 6 As shown, the presser foot lifting unit includes a presser foot crank 17, a presser foot shaft 18, a pull rod crank 19, a presser foot pull rod 20, a presser foot rear lever 21, a front lever pull rod 22, a presser foot front lever 23, a presser foot lifting plate 24, a presser rod guide 25, a presser rod 26, and a presser foot 27 connected in sequence; the presser foot shaft 18 is fixed to the machine housing by a presser foot shaft sleeve 28.

[0047] The presser foot lifting unit provided in this embodiment enables the presser foot 27 to move up and down. In other embodiments, the specific components included in the presser foot lifting unit can be adjusted according to actual needs.

[0048] Optional, such as Figure 1 As shown, the pressure foot lifting unit also includes a pressure rod bushing 29, through which the pressure rod 26 passes, and the pressure rod guide sleeve is fixed to the housing. The pressure rod bushing 29 can improve the stability of the pressure rod 26 during its up-and-down movement. In other embodiments, the pressure rod bushing 29 may not be provided.

[0049] Optional, such as Figure 1 As shown, a return spring 30 is provided at one end of the lifting foot shaft 18 to reset the lifting foot shaft 18. The return spring 30 can restore the lifting foot shaft 18 to its initial position, facilitating control of the pressing action of the pressure foot 27. In other embodiments, the return spring 30 may not be provided, and the reset of the lifting foot shaft 18 can be achieved by the rotation of the motor 1.

[0050] Optional, such as Figure 1 and Figure 6 As shown, a drive block 33 is provided on the second surface 202. One end of the lifting foot crank 17 is fixedly mounted on the lifting foot shaft 18, and the other end is mounted on a bearing. When the drive block 33 rotates along the second direction with the cam 2, the drive block 33 drives the bearing to move, thereby driving the lifting foot crank 17 to rotate. Through the motor 1, cam 2, drive block 33, and bearing, the lifting foot crank 17 can be driven to rotate, thereby driving the presser foot 27 to move up and down. The following is in conjunction with the accompanying drawings. Figures 1-6 As shown, and taking the first direction as clockwise and the second direction as counterclockwise as an example, the working principle of the thread-cutting and presser foot lifting mechanism of the sewing machine is explained:

[0051] After the sewing machine is powered on, the controller controls motor 1 to find the zero point position. When the thread cutting begins, motor 1 rotates clockwise by a certain angle, and the motor 1 shaft drives cam 2 to rotate clockwise by a certain angle. The upper cutter crank shaft 5 can rotate around itself. The roller of the upper cutter crank shaft 5, i.e., the upper cutter roller 3, is embedded in the first track groove 2011 and is located at the first arc segment A. At this time, the upper cutter crank shaft 5 is in a stationary state. The roller of the lower cutter crank shaft 8, i.e., the lower cutter roller 6, is embedded in the first track groove 2011 and is located at the first arc segment A. One end of the lower cutter crank 7 is fixed to one end of the lower cutter crank shaft 8, and one end of the lower cutter thread cutting crank 13 is fixed to the other end of the lower cutter crank shaft 8. When cam 2 drives the lower cutter crank 7 to rotate, the lower cutter crank 7 can drive the lower cutter crank shaft 8 to rotate. The other end of the lower cutting thread cutting crank 13 is connected to one end of the lower cutting connecting rod 14 by a shaft screw. The lower cutting thread cutting crank 13 drives the lower cutting connecting rod 14 to move. The other end of the lower cutting connecting rod 14 is connected to the lower cutting blade holder 15 by a shaft screw. The lower cutting connecting rod 14 drives the lower cutting blade holder 15 to rotate around its own axis. The lower cutting blade 16 is fixed on the lower cutting blade holder 15 and can move with the lower cutting blade holder 15. When the roller of the lower blade crank 7 moves to the fourth arc segment D, the lower blade crank 7 is stationary and the lower cutter 16 stops moving. At this time, the upper blade crank shaft 5 moves to the second arc segment B, and the cam 2 drives the upper blade crank 4 to rotate. The other end of the upper blade crank shaft 5 is fixed on the upper blade thread cutting crank 9. The upper blade crank shaft 5 drives the upper blade thread cutting crank 9 to rotate. The other end of the upper blade thread cutting crank 9 is connected to one end of the upper blade connecting rod 10 through a shaft screw. The upper blade thread cutting crank 9 drives the upper blade connecting rod 10 to move. The other end of the upper blade connecting rod 10 is connected to the upper cutter holder 11 through a shaft screw. The upper cutter connecting rod 10 drives the upper cutter holder 11 to rotate around its own axis. The upper cutter 12 is fixed on the upper cutter holder 11. When the upper cutter 12 moves with the upper cutter holder 11 into the third straight segment C, the lower cutter 16 and the upper cutter 12 close and cut the thread. After the thread is cut, when motor 1 can rotate counterclockwise to the zero position, the lower cutter 16 and the upper cutter 12 open to the initial position, and the thread cutting ends.

[0052] When the presser foot is lifted, the controller controls motor 1 to rotate counterclockwise from the zero position. After rotating a certain angle, the shaft of motor 1 drives cam 2 to rotate counterclockwise by a certain angle. The presser foot lifting crank 17 is in separate contact with cam 2. Cam 2 drives the presser foot lifting crank 17 to rotate. The presser foot lifting crank 17 is fixed on the presser foot lifting shaft 18. The presser foot lifting shaft 18 passes through the presser foot shaft sleeve 28, which is fixed to the machine housing. The presser foot lifting shaft 18 can rotate around its own axis. The lifting foot crank 17 drives the lifting foot shaft 18 to rotate. The pull rod crank 19 is fixed on the lifting foot shaft 18. The lifting foot shaft 18 drives the pull rod crank 19 to rotate a certain angle. The lifting foot pull rod 20 is hinged to the pull rod crank 19. The pull rod crank 19 pulls the lifting foot pull rod 20. The other end of the lifting foot pull rod 20 is hinged to the lifting foot rear lever 21. The rear lever shaft screw 31 passes through the lifting foot rear lever 21 and is fixed to the machine housing. The lifting foot pull rod 20 pulls the lifting foot rear lever 21 to rotate a certain angle around the rear lever shaft screw 31. The other end of the rear lever 21 is hinged to the front lever 22, and the other end of the front lever 22 is hinged to the front lever 23. A threaded pin 32 passes through the front lever 23 and is fixed to the machine housing. The rear lever 21 drives the front lever 22 to move left and right. The front lever 22 pulls the front lever 23 to rotate around the threaded pin 32 by a certain angle. The other end of the front lever 23 is hinged to the presser foot lifting plate 24. The front lever 23 drives the presser foot lifting plate 24 to rise. The pressure rod guide 25 is fitted into the pressure rod 26 and tightened with screws 34. The presser foot lifting plate 24 drives the pressure rod 26 to rise. The presser foot 27 is fixed to the pressure rod 26, and the pressure rod 26 drives the presser foot 27 to rise. The aforementioned process is the process of lifting the presser foot 27. When it is necessary to lower the presser foot 27, the motor 1 rotates clockwise to the zero position, and the presser foot 27 falls back to the initial position.

[0053] In summary, the sewing machine thread-cutting and presser foot-lifting mechanism provided by the present invention achieves double-sided transmission of cam 2 through motor 1 and cam 2. One side of cam 2 controls thread cutting, and the other side controls presser foot 27 lifting. One motor 1 can realize both thread cutting and presser foot 27 lifting, making the structure of the thread-cutting and presser foot-lifting mechanism simpler, with fewer parts, lower precision requirements for parts, easy assembly, lower cost, and lower noise during operation.

[0054] The above description is only a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the present invention.

Claims

1. A thread-cutting and presser foot lifting mechanism for a sewing machine, characterized in that, Includes a motor, cam, wire-cutting unit, and presser foot lifting unit; The motor includes a rotating shaft, and the cam is mounted on the rotating shaft; The cam includes a first surface and a second surface, the wire-cutting unit is connected to the first surface, and the pressure foot lifting unit is connected to the second surface; When the rotating shaft drives the cam to rotate in the first direction, the first surface drives the wire cutting unit to perform the wire cutting action, and the lifting pressure foot unit remains stationary. When the rotating shaft drives the cam to rotate in the second direction, the second surface drives the lifting foot unit to perform the lifting foot action, and the wire cutting unit remains stationary. The first direction and the second direction are opposite. A first track groove is provided on the first surface. The first track groove includes a first arc segment, a second arc segment, a third straight segment, and a fourth arc segment connected in sequence. The diameter of the first arc segment is larger than the diameter of the fourth arc segment, and the diameter of the fourth arc segment is larger than the diameter of the second arc segment. The wire cutting unit includes an upper cutter roller, an upper cutter crank, an upper cutter crank shaft, a lower cutter roller, a lower cutter crank, and a lower cutter crank shaft; the upper cutter roller is connected to one end of the upper cutter crank and installed in the first track groove, and the other end of the upper cutter crank is fixed to one end of the upper cutter crank shaft; the lower cutter roller is connected to one end of the lower cutter crank and installed in the first track groove, and the other end of the lower cutter crank is fixed to one end of the lower cutter crank shaft; there is a gap between the upper cutter roller and the lower cutter roller; When the upper cutter roller is within the first arc segment, the upper cutter crank remains stationary; when the upper cutter roller is within the second arc segment or the third straight segment, the upper cutter crank drives the upper cutter crank shaft to rotate. When the lowering roller is within the first arc segment or the fourth arc segment, the lowering crank remains stationary; when the lowering roller is within the second arc segment or the third straight segment, the lowering crank drives the lowering crank shaft to rotate. The presser foot lifting unit includes a presser foot lifting crank, a presser foot lifting shaft, a pull rod crank, a presser foot lifting pull rod, a presser foot rear lever, a front lever pull rod, a presser foot front lever, a presser foot lifting plate, a presser rod guide, a presser rod, and a presser foot, connected in sequence; the presser foot lifting shaft is fixed to the machine housing by a presser foot lifting shaft sleeve.

2. The thread-cutting and presser foot lifting mechanism of a sewing machine as described in claim 1, characterized in that, The first track trough is a settling trough.

3. The thread-cutting and presser foot lifting mechanism of a sewing machine as described in claim 1, characterized in that, The wire cutting unit also includes an upper blade wire cutting crank, an upper blade connecting rod, an upper cutting blade holder and an upper cutting blade connected in sequence, and a lower blade wire cutting crank, a lower blade connecting rod, a lower cutting blade holder and a lower cutting blade connected in sequence. One end of the upper blade cutting crank is fixed to the other end of the upper blade crank shaft; the upper blade crank is used to drive the upper cutting blade to move closer to or away from the lower cutting blade. One end of the lower cutting blade crank is fixed to the other end of the lower cutting blade crank shaft; the lower cutting blade crank is used to drive the lower cutting blade to move closer to or away from the upper cutting blade.

4. The thread-cutting and presser foot lifting mechanism of a sewing machine as described in claim 3, characterized in that, The upper cutter crank shaft is hollow and cylindrical, and the lower cutter crank shaft passes through the upper cutter crank shaft along its axial direction.

5. The thread-cutting and presser foot lifting mechanism of a sewing machine as described in claim 1, characterized in that, The presser foot lifting unit also includes a presser rod bushing, the presser rod passes through the presser rod bushing, and the presser rod bushing is fixed to the housing.

6. The thread-cutting and presser foot lifting mechanism of a sewing machine as described in claim 1, characterized in that, One end of the lifting foot shaft is provided with a return spring for resetting the lifting foot shaft.

7. The thread-cutting and presser foot lifting mechanism of a sewing machine as described in claim 1, characterized in that, A drive block is provided on the second surface. One end of the lifting foot crank is fixedly installed on the lifting foot shaft, and the other end is installed with a bearing. When the drive block rotates along the second direction with the cam, the drive block drives the bearing to move, thereby driving the lifting foot crank to rotate.

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