A driving mechanism for thread trimming, presser foot lifting and stitch length adjustment in a sewing machine

Abstract

The utility model provides a kind of sewing machine in cutting thread, lifting presser foot and stitch length adjustment driving mechanism, belong to sewing machine technical field.It solves the problem of complex structure caused by using two motors to reduce failure.It includes first motor and second motor, cutting thread mechanism includes cutting thread shaft and the lower cutting thread crank fixed in cutting thread shaft, lifting presser foot mechanism includes driving rod, the output shaft of first motor is fixed with driving cam, the wheel edge of driving cam has idle stroke surface and cam surface, the lower end of driving rod is abutted in the wheel edge of driving cam, cutting thread mechanism further includes upper cutting thread crank and cutting thread connecting rod, upper cutting thread crank is sleeved on the output shaft of first motor and both are fixed along axial direction, the upper and lower ends of cutting thread connecting rod are respectively hinged with upper cutting thread crank and lower cutting thread crank, the side of driving cam is axially protruding and is provided with acting portion, acting portion and upper cutting thread crank are abutted along circumferential direction.It has the advantages such as structure.

Description

Technical Field

[0001] This utility model belongs to the field of sewing machine technology and relates to a drive mechanism for thread cutting, presser foot lifting and stitch length adjustment in a sewing machine. Background Technology

[0002] Sewing machines involve various operations during actual sewing, such as thread cutting, presser foot lifting, and stitch length adjustment (when the stitch length is adjusted to a negative value, the sewing machine reverses the stitch length). For example, a sewing machine with a compound adjustment mechanism disclosed in patent application number 202120171902.7 includes a frame, a thread cutting mechanism, a presser foot lifting mechanism, and a reverse stitch adjustment mechanism. The swing seat of the reverse stitch adjustment mechanism rotates around a set pin, and the angle of rotation of the swing seat around the pin determines the stitch length of the sewing machine. It also includes a drive motor, and a control cam that rotates accordingly is mounted on the output shaft of the drive motor. The presser foot lifting mechanism and the thread cutting mechanism are respectively mounted on both sides of the control cam. The output shaft drives the thread cutting mechanism, the presser foot lifting mechanism, and the reverse stitch adjustment mechanism through the control cam. However, in practice, the operation of any one of the three mechanisms requires the other two mechanisms to remain stationary. This means that using a single control cam to control the operation of these three mechanisms has very strict requirements on the rotation angle, which is prone to errors.

[0003] To address this, a sewing machine with patent application number 202220183469.3 was designed. It includes a feed shaft, a feed dog shaft, a presser foot lifting mechanism, a thread cutting mechanism, and a first motor. A linkage sleeve is fitted onto the feed shaft. One end of the linkage sleeve is fixed to a first crank, and the other end is fixed to a second crank. A lifting seat driven by the first crank is fitted onto the linkage sleeve. The front of the lifting seat drives the presser foot lifting linkage of the presser foot lifting mechanism. A thread cutting crank driven by the second crank is fixed to the thread cutting shaft of the thread cutting mechanism. A motor crank is fixed to the first motor shaft of the first motor, and a motor connecting rod connects the motor crank and the first crank. It also includes a second motor located on the same side and parallel to the first motor. A stitch length adjustment mechanism is provided on the feed shaft. The stitch length adjustment mechanism consists of an adjusting swing seat, a first connecting rod, a second connecting rod, and an adjusting link. The adjusting link is connected to the sewing machine main shaft, and the second motor is connected to the adjusting swing seat. By driving the adjusting swing seat, the adjusting link is driven, thereby adjusting the stitch length. The sewing machine uses a first motor to drive the thread cutter and presser foot lifting, and a second motor to drive the stitch length adjustment, reducing the occurrence of malfunctions.

[0004] However, the aforementioned sewing machine also has its shortcomings: the component that transmits the power of the first motor is the motor crank; the structure that drives the lifting foot linkage in the lifting foot mechanism to lift the presser foot consists of the motor crank, the motor linkage, the first crank, and the lifting seat; and the structure that drives the thread cutting crank in the thread cutting mechanism to swing consists of the motor crank, the motor linkage, the first crank, the linkage sleeve, and the second crank. Obviously, both the structure used to drive the lifting foot linkage to lift the presser foot and the structure used to drive the thread cutting crank in the thread cutting mechanism to swing are relatively complex, which makes the overall structure of the sewing machine complex as well. Utility Model Content

[0005] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in a sewing machine, thus solving the problem of structural complexity caused by using two motors to reduce malfunctions.

[0006] The objective of this utility model can be achieved through the following technical solutions:

[0007] A drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in a sewing machine. The sewing machine includes a machine body and a thread cutting mechanism, a presser foot lifting mechanism, and a stitch length adjustment mechanism, all disposed within the machine body. This drive mechanism includes a first motor and a second motor. The second motor drives the stitch length adjustment mechanism. The thread cutting mechanism includes a thread cutting shaft and a lower thread cutting crank fixed to one end of the thread cutting shaft. The presser foot lifting mechanism includes a drive rod that slides vertically within the machine body. The key feature is that a drive cam is fixed to the output shaft of the first motor. The edge of the drive cam has a free-travel surface and a cam surface. The lower end of the drive rod abuts against... The drive cam wheel edge, the wire cutting mechanism also includes an upper wire cutting crank and a wire cutting connecting rod. The upper wire cutting crank is directly or indirectly sleeved on the output shaft of the first motor and the two are fixed together along the axial direction. The upper and lower ends of the wire cutting connecting rod are respectively hinged to the upper wire cutting crank and the lower wire cutting crank. One side of the drive cam is provided with an action part protruding along the axial direction. The action part abuts against the circumferential edge of one side of the upper wire cutting crank. When the drive cam rotates, it pushes the upper wire cutting crank to swing through the action part. The space stroke surface moves along the lower end of the drive rod. When the drive cam rotates, it drives the drive rod to lift through the cam surface. The action part separates from the upper wire cutting crank along the circumferential direction.

[0008] When the sewing machine is in sewing mode, the thread trimming mechanism, presser foot lifting mechanism, and stitch length adjustment mechanism are all inactive. The drive rod rests against the cam surface near the idle travel surface, and the actuating part on the drive cam abuts against the upper thread trimming crank circumferentially. When stitch length adjustment is needed, the output shaft of the second motor rotates, driving the stitch length adjustment mechanism. During stitch length adjustment, the first motor remains inactive, keeping the thread trimming mechanism and presser foot lifting mechanism stationary. To better understand the rotation direction of the first motor's output shaft during operation, counterclockwise rotation of the drive cam is defined as the thread trimming direction, and clockwise rotation as the presser foot lifting direction. When thread trimming is needed, the output shaft of the first motor rotates counterclockwise, pushing the thread trimming crank to rotate via its actuating part. Because the upper wire-cutting crank is hinged to the upper end of the wire-cutting connecting rod, and the lower end of the wire-cutting connecting rod is hinged to the lower wire-cutting crank fixed on the wire-cutting shaft, the rotation of the upper wire-cutting crank pulls the wire-cutting connecting rod upwards. This, in turn, causes the lower wire-cutting crank to swing, thus rotating the wire-cutting shaft and performing the wire-cutting action. During wire cutting, the second motor does not operate, and the idle travel surface of the drive cam edge moves along the lower end of the decelerating rod, keeping the pressure foot lifting mechanism stationary. After wire cutting is completed, the output shaft of the first motor rotates clockwise to return to its original position. In this direction, the actuating part is in front and the upper wire-cutting crank is behind, so the drive cam cannot generate thrust on the upper wire-cutting crank through the actuating part. The wire-cutting mechanism is reset by its own return torsion spring.

[0009] When the presser foot needs to be lifted, the output shaft of the first motor rotates clockwise, causing the cam of the drive cam to move along the lower end of the drive rod, continuously pushing the drive rod upward to perform the presser foot lifting action. During this process, the actuating part and the upper shear crank continuously separate circumferentially; that is, the upper shear crank remains stationary during the presser foot lifting process, and the second motor is also not working. When the presser foot no longer needs to be lifted, the output shaft of the first motor rotates counterclockwise. During this process, the contact position between the drive rod and the edge of the drive cam continuously moves from the cam surface towards the idle stroke surface, allowing the drive rod to continuously move downward under the combined action of gravity and the return spring on the presser foot until the contact position is again on the idle stroke surface near the cam surface. At this point, the drive rod moves down to the initial position, and the presser foot returns to the pressed-down state.

[0010] This drive mechanism uses a first motor to drive the wire cutting and presser foot lifting, and a second motor to drive the needle pitch adjustment, thus reducing the failure rate. Furthermore, this drive mechanism employs a drive cam as the component for driving the wire cutting and presser foot lifting. Specifically, a cam surface is provided on the edge of the drive cam to directly engage with the drive rod to lift the presser foot. An axially arranged actuating part is provided on the side of the drive cam, which engages with an upper wire cutting crank directly or indirectly sleeved on the output shaft of the first motor to drive the wire cutting. This ensures that the structure of the presser foot lifting and the structure of the wire cutting do not interfere with each other, while also greatly simplifying the overall structure.

[0011] In the aforementioned sewing machine's drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment, a return arm is obliquely protruding upwards from one side of the thread cutting link. The side where the return arm is located corresponds to the side of the upper thread cutting crank that abuts against the working part circumferentially. The return arm is positioned close to the upper end of the thread cutting link, and a groove is formed between the return arm and the upper end of the thread cutting link. The groove is lower than the working part. The upper thread cutting crank, pushed by the drive cam, pulls the thread cutting link upwards, causing the working part to move into the groove.

[0012] Typically, wire-cutting mechanisms utilize a built-in return torsion spring for resetting. However, in practice, situations may occur where the wire cutter jams, rendering the return torsion spring insufficient to achieve resetting. To address this, this drive mechanism incorporates a return arm that protrudes obliquely upwards from one side of the wire-cutting connecting rod. This return arm corresponds to the side of the upper wire-cutting crank that circumferentially abuts against the actuating part. The return arm is positioned close to the upper end of the wire-cutting connecting rod, forming a groove between it and the upper end of the connecting rod. Initially, this groove is lower than the actuating part. As the wire-cutting connecting rod is pulled upwards to cut the wire, the groove continuously moves upwards, causing the actuating part to move into the groove. After wire cutting, the output shaft of the first motor rotates in the opposite direction, driving the drive cam to rotate. In this direction, the actuating part is in front and the upper wire-cutting crank is behind, thus preventing the drive cam from generating thrust on the upper wire-cutting crank through the actuating part. However, since the actuating part is located within the groove, as the drive cam rotates in this direction, the actuating part comes into contact with the return arm of the wire-cutting linkage. During rotation, the drive cam applies a downward thrust to the return arm through the actuating part, thereby forcibly pushing the wire-cutting linkage downward. The downward push of the wire-cutting linkage forcibly drives the wire-cutting shaft to rotate in the opposite direction, completing the forced reset. The position of the groove continuously moves downward as the wire-cutting linkage is pushed down, and the actuating part gradually slides out of the groove during this process, preventing the actuating part from jamming against the wire-cutting linkage. After the forced reset action is performed, the mechanism returns to its initial state under the action of the built-in reset torsion spring.

[0013] In the drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in the aforementioned sewing machine, the upper thread cutting crank includes a ring-shaped sleeve and a force-receiving part protruding from the outer peripheral wall of the sleeve and in the shape of an arm. The upper thread cutting crank is directly or indirectly connected to the output shaft of the first motor through the sleeve. The action part abuts against the force-receiving part, and the upper end of the thread cutting connecting rod is hinged to the force-receiving part.

[0014] By configuring the upper wire-cutting crank to include a ring-shaped sleeve portion and an arm-shaped force-receiving portion protruding from the outer periphery of the sleeve portion, the sleeve portion allows the upper wire-cutting crank to be directly or indirectly sleeved on the output shaft of the first motor, while the arm-shaped force-receiving portion allows the upper wire-cutting crank to abut against the action portion provided on the side of the drive cam in the circumferential direction, and also allows the upper wire-cutting crank to be hinged to the upper end of the wire-cutting connecting rod.

[0015] In the aforementioned sewing machine, the drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment has a cylindrical mounting part protruding from the side where the action part is located. The central hole of the drive cam passes through the mounting part, and the upper thread cutting crank is sleeved on the mounting part. A limit snap ring is provided on the mounting part, and the upper thread cutting crank is axially fixed between the side wall of the drive cam where the mounting part is located and the limit snap ring.

[0016] During assembly, the upper shearing crank is first fitted onto the cylindrical mounting part. A retaining spring is then installed on the mounting part to axially fix the upper shearing crank between the side wall of the drive cam where the mounting part is located and the retaining spring. This allows the upper shearing crank and the drive cam to be assembled into a single component. Finally, this component is fixed to the output shaft of the first motor through the center hole of the drive cam. This design makes assembly more convenient and, in particular, ensures a high degree of fit between the upper shearing crank and the drive cam.

[0017] In the drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in the aforementioned sewing machine, a roller is rotatably connected to the bottom of the drive rod via a fastener. The center line of the roller is parallel to the center line of the drive cam. The roller and the upper thread cutting crank are axially offset. The bottom of the roller extends out of the lower end of the drive rod and abuts against the edge of the drive cam wheel.

[0018] A roller is connected to the lower end of the drive rod. The centerline of the roller is parallel to the centerline of the drive cam, and the bottom of the roller abuts against the edge of the drive cam. This creates rolling friction between the roller and the drive cam when the drive cam rotates and lifts the drive rod using its cam surface. This reduces the resistance when the drive rod is lifted and minimizes wear during long-term use. Furthermore, the axial spacing between the roller and the upper shear crank ensures that there will be no interference between the drive rod and the upper shear crank, even though the upper shear crank is directly mounted on the output shaft of the first motor.

[0019] In the drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in the aforementioned sewing machine, the first motor and the second motor are both fixed to the tail of the machine body and are arranged side by side along the width direction of the machine body. A motor cover is fixedly connected to the tail of the machine body. The first motor, the second motor, and the main motor of the sewing machine are all located inside the motor cover. Heat dissipation vents are provided at the bottom and rear of the motor cover.

[0020] In sewing machines, the main motor is typically located at the rear of the machine body. However, by placing both the first and second motors at the rear of the machine body, side-by-side along the width of the machine, a single motor cover can enclose all three motors. Furthermore, ventilation openings at the bottom and rear of the motor cover ensure excellent heat dissipation, preventing overheating that could occur if all three motors were housed within a single cover.

[0021] Compared with existing technologies, the drive mechanisms for thread cutting, presser foot lifting, and stitch length adjustment in this sewing machine have the following advantages:

[0022] 1. Based on reducing the failure rate by using a first motor to drive the wire cutting and presser foot lifting, and a second motor to drive the needle pitch adjustment, a drive cam is used as the component to drive the wire cutting and presser foot lifting. The cam surface is set on the wheel edge of the drive cam to directly cooperate with the drive rod to lift the presser foot. An action part is set on the side of the drive cam along the axial direction and cooperates with the upper wire cutting crank directly or indirectly sleeved on the output shaft of the first motor to drive the wire cutting. This ensures that the structure of the presser foot lifting and the structure of the wire cutting do not interfere with each other, and at the same time, the structure is simpler because there is no need to add a linkage bushing or other components on the feeding shaft.

[0023] 2. A return arm is provided on one side of the wire cutting connecting rod, protruding obliquely upward. The side where the return arm is located corresponds to the side of the upper wire cutting crank that abuts against the action part in the circumferential direction. The return arm is located near the upper end of the wire cutting connecting rod, and a groove is formed between the return arm and the upper end of the wire cutting connecting rod. This allows the action part of the drive cam to move into the groove when cutting the wire. In this way, when the drive cam reverses after cutting the wire, it can apply a downward force to the wire cutting connecting rod through the abutment between the action part and the return arm to achieve forced return of the blade. Attached Figure Description

[0024] Figure 1 It is a 3D diagram of a sewing machine.

[0025] Figure 2 This is a three-dimensional diagram of a sewing machine from another angle.

[0026] Figure 3 This is a three-dimensional schematic diagram of the drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in this sewing machine.

[0027] Figure 4 This is a three-dimensional schematic diagram of the part of the drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in this sewing machine that is used to achieve thread cutting and presser foot lifting.

[0028] Figure 5 This is a schematic diagram showing the interaction between the drive cam and the upper shear crank.

[0029] Figure 6 This is an exploded view of the drive cam and the upper shear crank.

[0030] Figure 7 This is a schematic diagram of the interaction between the drive cam and the drive rod.

[0031] Figure 8 This is a planar schematic diagram of the driving cam, driving rod, and upper thread-cutting crank of a sewing machine during sewing.

[0032] Figure 9 This is a planar schematic diagram of the drive cam, drive rod, and upper wire-cutting crank during wire cutting.

[0033] Figure 10 This is a planar schematic diagram of the drive cam, drive rod, and upper shear crank when the presser foot is lifted.

[0034] In the diagram, 1. Machine body; 2. First motor; 3. Second motor; 4. Thread cutting shaft; 5. Thread cutting swing arm; 6. Thread cutting swing rod; 7. Thread cutting knife holder; 8. Thread cutting knife; 9. Return torsion spring; 10. Drive rod; 10a. Connecting part; 11. First swing plate; 12. Second swing plate; 13. Pull rod; 14. Connecting seat; 15. Adjusting swing seat; 16. Stitch pitch adjustment drive component; 17. Stitch pitch adjustment connecting rod; 18. Drive cam; 19 a. Free travel surface; 18b. Cam surface; 18c. Actuating part; 18d. Mounting part; 18e. Annular mounting groove; 19. Guide seat; 20. Roller; 21. Upper wire cutting crank; 21a. Sleeve part; 21b. Force-bearing part; 22. Lower wire cutting crank; 23. Wire cutting connecting rod; 23a. Return arm; 23b. Groove; 24. Limiting snap ring; 25. Motor cover; 25a. Heat dissipation vent; 26. Main motor; 27. Presser foot. Detailed Implementation

[0035] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0036] like Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, a drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in a sewing machine is disclosed. The sewing machine includes a body 1 and a thread cutting mechanism, a presser foot lifting mechanism, and a stitch length adjustment mechanism, all of which are disposed within the body 1. The drive mechanism includes a first motor 2 and a second motor 3 arranged in parallel. The first motor 2 drives the thread cutting mechanism and the presser foot lifting mechanism, and the second motor 3 drives the stitch length adjustment mechanism. In this embodiment, the first motor 2 and the second motor 3 are both fixed to the tail of the body 1 and are arranged side by side along the width direction of the body 1. A motor cover 25 is fixedly connected to the tail of the body 1. The first motor 2, the second motor 3, and the main motor 26 of the sewing machine are all located inside the motor cover 25. Heat dissipation vents 25a are provided at the bottom and rear side of the motor cover 25. The wire cutting mechanism includes a wire cutting shaft 4 disposed at the bottom of the machine body 1 along the length of the machine body 1, a wire cutting swing arm 5 fixed to one end of the wire cutting shaft 4 corresponding to the head of the machine body 1, a wire cutting swing rod 6 hinged to the wire cutting swing arm 5, a wire cutting knife holder 7 hinged to the wire cutting swing rod 6, a wire cutting knife 8 fixed on the wire cutting knife holder 7, and a return torsion spring 9 sleeved on the wire cutting shaft 4 and acting on the machine body 1 and the wire cutting swing arm 5 at both ends respectively. The presser foot lifting mechanism includes a drive rod 10 that slides vertically within the body 1, a first swing plate 11 hinged within the body 1, a second swing plate 12 hinged within the body 1, a pull rod 13 whose two ends are respectively hinged to the first swing plate 11 and the second swing plate 12, and a connecting seat 14 fixedly connected to the presser foot 27 and hinged to the second swing plate 12. The upper end of the drive rod 10 has a plate-shaped connecting part 10a protruding from its outer periphery. The first swing plate 11 is connected to the connecting part 10a. A return spring (not shown in the figure) is sleeved on the presser foot 27. The stitch length adjustment mechanism is existing technology. Its specific structure and working principle can be found in the stitch length adjustment, presser foot lifting, thread cutting and thread loosening mechanism of a sewing machine disclosed in patent application number 202323002272.9, as well as the sewing machine with patent application number 202220183469.3 and patent application number 202120171902.7 mentioned in the background art. The stitch length adjustment mechanism includes an adjustment swing seat 15 hinged to the bottom of the machine body 1. A stitch length adjustment drive 16 is fixed on the output shaft of the second motor 3. The stitch length adjustment drive 16 is a crank and a stitch length adjustment connecting rod 17 is provided between it and the adjustment swing seat 15. The two ends of the stitch length adjustment connecting rod 17 are respectively hinged to the adjustment swing seat 15 and the stitch length adjustment drive 16.

[0037] like Figure 3 , Figure 4 and Figure 7As shown, the output shaft of the first motor 2 is longer than the output shaft of the second motor 3. A drive cam 18 is fixed on the output shaft of the first motor 2, and the drive cam 18 and the needle pitch adjustment drive 16 are offset axially. The wheel edge of the drive cam 18 has a free stroke surface 18a and a cam surface 18b, and the lower end of the drive rod 10 abuts against the wheel edge of the drive cam 18. In this embodiment, a guide seat 19 is fixed inside the machine body 1, and the drive rod 10 is vertically slidably mounted on the guide seat 19. The bottom of the drive rod 10 is rotatably connected to a roller 20 by fasteners. The center line of the roller 20 is parallel to the center line of the drive cam 18, and the bottom of the roller 20 extends out of the lower end of the drive rod 10 and abuts against the wheel edge of the drive cam 18. The wire cutting mechanism also includes an upper wire cutting crank 21, a lower wire cutting crank 22, and a wire cutting connecting rod 23. The lower wire cutting crank 22 is fixed to one end of the wire cutting shaft 4 corresponding to the tail of the machine body 1. The upper wire cutting crank 21 is directly or indirectly sleeved on the output shaft of the first motor 2, and the two are fixed together axially. The upper and lower ends of the wire cutting connecting rod 23 are hinged to the upper wire cutting crank 21 and the lower wire cutting crank 22, respectively. An action part 18c is provided on one side of the drive cam 18 along the axial direction. The action part 18c is columnar and abuts against the upper wire cutting crank 21 circumferentially. When the drive cam 18 rotates and pushes the upper wire cutting crank 21 to swing through the action part 18c, the travel surface 18a moves along the lower end of the drive rod 10. When the drive cam 18 rotates and drives the drive rod 10 to lift through the cam surface 18b, the action part 18c separates from the upper wire cutting crank 21 circumferentially.

[0038] Furthermore, such as Figure 4 , Figure 5 and Figure 6As shown, a return arm 23a is obliquely protruding upward on one side of the wire-cutting connecting rod 23. The side where the return arm 23a is located corresponds to the side of the upper wire-cutting crank 21 that abuts against the action part 18c in the circumferential direction. The return arm 23a is located near the upper end of the wire-cutting connecting rod 23. A groove 23b is formed between the return arm 23a and the upper end of the wire-cutting connecting rod 23. The groove 23b is lower than the action part 18c. The hinge center of the wire-cutting connecting rod 23 and the upper wire-cutting crank 21 is lower than the action part 18c in the vertical direction. The upper wire-cutting crank 21 is pushed upward by the drive cam 18, which pulls the wire-cutting connecting rod 23 upward, causing the action part 18c to move into the groove 23b. A cylindrical mounting portion 18d protrudes from the side where the action portion 18c is located on the drive cam 18. The center hole of the drive cam 18 passes through the mounting portion 18d. The upper wire-cutting crank 21 is sleeved on the mounting portion 18d. An annular mounting groove 18e is provided on the mounting portion 18d. A limit spring 24 is provided in the annular mounting groove 18e. The upper wire-cutting crank 21 is axially fixed between one side wall of the drive cam 18 where the mounting portion 18d is located and the limit spring 24. The upper wire-cutting crank 21 includes an annular sleeve portion 21a and a force-receiving portion 21b protruding from the outer peripheral wall of the sleeve portion 21a and in the shape of an arm. The upper wire-cutting crank 21 is directly or indirectly connected to the output shaft of the first motor 2 through the sleeve portion 21a. The action portion 18c abuts against the force-receiving portion 21b, and the upper end of the wire-cutting connecting rod 23 is hinged to the force-receiving portion 21b.

[0039] When the sewing machine is in sewing mode, the thread trimming mechanism, presser foot lifting mechanism, and stitch length adjustment mechanism are all inactive. The roller 20 rests against the idle travel surface 18a near the cam surface 18b. The actuating part 18c on the drive cam 18 abuts against the upper thread trimming crank 21 circumferentially. The groove 23b is located below the hinge position of the hinge part 23b of the thread trimming connecting rod 23 and the upper thread trimming crank 21. The hinge center of the hinge part 23b and the upper thread trimming crank 21 is vertically lower than the actuating part 18c. At this time, the groove 23b is not on the trajectory of the actuating part 18c as it rotates with the drive cam 18, just as... Figure 8As shown. When the stitch length needs to be adjusted, the output shaft of the second motor 3 drives the stitch length adjustment drive 16 to rotate. The stitch length adjustment drive 16 pulls the adjustment swing seat 15 to swing through the stitch length adjustment linkage 17 to achieve stitch length adjustment. During the stitch length adjustment process, the first motor 2 does not work, keeping the thread cutting mechanism and the presser foot lifting mechanism stationary. To better understand the rotation direction of the output shaft of the first motor 2 during operation, the following description of the operation is based on the direction shown in the attached figure. When the thread needs to be cut, the output shaft of the first motor 2 rotates counterclockwise and pushes the thread cutting crank to rotate through the actuating part 18c. Since the upper cutting crank 21 is hinged to the upper end of the cutting connecting rod 23, and the lower end of the cutting connecting rod 23 is hinged to the lower cutting crank 22 fixed on the cutting shaft 4, when the upper cutting crank 21 rotates, it pulls the cutting connecting rod 23 upwards. This, in turn, causes the lower cutting crank 22 to swing. Consequently, the cutting shaft 4 rotates, causing the cutting arm 5 to swing. This, in turn, pulls the cutting blade holder 7 to swing via the cutting arm 6, thus moving the cutting blade 8 fixed on the cutting blade holder 7 to cut the thread. Just as... Figure 9 As shown, during the upward pulling of the wire-cutting linkage 23, the position of the groove 23b also continuously moves upward, causing the actuating part 18c to move into the groove 23b. During wire cutting, the second motor 3 does not work, and the idle travel surface 18a of the drive cam 18 moves along the roller 20, keeping the pressure foot lifting mechanism stationary.

[0040] After the wire cutting is completed, the output shaft of the first motor 2 rotates clockwise to return to its original position. In this direction, the actuating part 18c is in front and the wire cutting crank 21 is behind, so the drive cam 18 cannot generate a thrust on the wire cutting crank 21 through the actuating part 18c. However, since the actuating part 18c is located in the groove 23b, as the drive cam 18 rotates in this direction, the actuating part 18c abuts against the return arm 23a on the wire cutting connecting rod 23. During the rotation of the drive cam 18, a downward thrust is applied to the return arm 23a through the actuating part 18c, thereby forcibly pushing the wire cutting connecting rod 23 downward. The downward push of the wire cutting connecting rod 23 will forcibly drive the wire cutting shaft 4 to rotate in the opposite direction to complete the forced reset. The position of the groove 23b moves downward as the wire cutting connecting rod 23 is pushed downward, and the actuating part 18c gradually slides out of the groove 23b during this process, so that the actuating part 18c and the wire cutting connecting rod 23 will not be stuck together. After the forced reset action is performed, the wire cutting mechanism is reset to the initial state under the action of the reset torsion spring 9, and the upper wire cutting crank 21 is once again abutted against the action part 18c in the circumferential direction.

[0041] When the pressure foot needs to be lifted, the output shaft of the first motor 2 rotates clockwise, causing the cam surface 18b of the drive cam 18 to contact the roller 20. As the drive cam 18 continues to rotate, the cam surface 18b, through the roller 20, continuously pushes the drive rod 10 upwards, just as... Figure 10 As shown, as the drive rod 10 is pushed upward, the connection between the drive rod 10 and the first swing plate 11 moves upward. This means that the hinge point between the first swing plate 11 and the pull rod 13 moves downward. At this time, the first swing plate 11 pulls the second swing plate 12 around its hinge point with the machine body 1 through the pull rod 13, so that the second linkage plate drives the pressure foot 27 to overcome the elastic force of the return spring and lift upward. During the movement of the roller 20 along the cam surface 18b, the action part 18c and the upper wire cutting crank 21 continuously separate in the circumferential direction. That is to say, during the lifting of the pressure foot, the upper wire cutting crank 21 remains stationary, so the wire cutting blade 8 also remains stationary, and the second motor 3 does not work. When it is no longer necessary to lift the presser foot 27, the output shaft of the first motor 2 rotates counterclockwise. During this process, the contact position between the roller 20 and the edge of the drive cam 18 continuously moves from the cam surface 18b toward the idle stroke surface 18a, so that the drive rod 10 can continuously move downward under the combined action of gravity and the return spring until the contact position of the two is again at the position on the idle stroke surface 18a near the cam surface 18b. At this time, the drive rod 10 moves down to the initial position, and the presser foot 27 is back in the pressed state.

[0042] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A drive mechanism for thread cutting, presser foot lifting, and stitch length adjustment in a sewing machine, the sewing machine comprising a machine body (1) and a thread cutting mechanism, a presser foot lifting mechanism, and a stitch length adjustment mechanism all disposed within the machine body (1), the drive mechanism comprising a first motor (2) and a second motor (3), the second motor (3) driving the stitch length adjustment mechanism to work, the thread cutting mechanism comprising a thread cutting shaft (4) and a lower thread cutting crank (22) fixed to one end of the thread cutting shaft (4), the presser foot lifting mechanism comprising a drive rod (10) sliding vertically within the machine body (1), characterized in that, A drive cam (18) is fixed on the output shaft of the first motor (2). The wheel edge of the drive cam (18) has a free travel surface (18a) and a cam surface (18b). The lower end of the drive rod (10) abuts against the wheel edge of the drive cam (18). The wire cutting mechanism also includes an upper wire cutting crank (21) and a wire cutting connecting rod (23). The upper wire cutting crank (21) is directly or indirectly sleeved on the output shaft of the first motor (2) and the two are fixed together along the axial direction. The upper and lower ends of the wire cutting connecting rod (23) are respectively connected to the upper wire cutting crank (21) and the lower wire cutting crank (23). The crank (22) is hinged together. One side of the drive cam (18) is provided with an action part (18c) protruding axially. The action part (18c) abuts against one side edge of the upper shear crank (21) in the circumferential direction. When the drive cam (18) rotates and pushes the upper shear crank (21) to swing through the action part (18c), the space stroke surface (18a) moves along the lower end of the drive rod (10). When the drive cam (18) rotates and drives the drive rod (10) to lift through the cam surface (18b), the action part (18c) separates from the upper shear crank (21) in the circumferential direction.

2. A drive mechanism for thread trimming, presser foot lifting and stitch length adjustment in a sewing machine as claimed in claim 1, wherein, The wire-cutting link (23) has a return arm (23a) that protrudes obliquely upward on one side. The side where the return arm (23a) is located corresponds to the side of the upper wire-cutting crank (21) that abuts against the action part (18c) in the circumferential direction. The return arm (23a) is located near the upper end of the wire-cutting link (23). A groove (23b) is formed between the return arm (23a) and the upper end of the wire-cutting link (23). The groove (23b) is lower than the action part (18c). The upper wire-cutting crank (21) is pushed upward by the drive cam (18) to pull the wire-cutting link (23) upward, causing the action part (18c) to move into the groove (23b).

3. A drive mechanism for thread trimming, presser foot lifting and stitch length adjustment in a sewing machine as claimed in claim 2, wherein, The upper wire-cutting crank (21) includes a ring-shaped sleeve (21a) and a force-receiving part (21b) protruding from the outer peripheral wall of the sleeve (21a) and in the shape of an arm. The upper wire-cutting crank (21) is directly or indirectly connected to the output shaft of the first motor (2) through the sleeve (21a). The action part (18c) abuts against the force-receiving part (21b), and the upper end of the wire-cutting connecting rod (23) is hinged to the force-receiving part (21b).

4. A drive mechanism for thread trimming, presser foot lifting and stitch length adjustment in a sewing machine as claimed in claim 3, wherein, The drive cam (18) has a cylindrical mounting part (18d) protruding from the side where the action part (18c) is located. The center hole of the drive cam (18) passes through the mounting part (18d). The upper wire-cutting crank (21) is sleeved on the mounting part (18d). A limit snap ring (24) is provided on the mounting part (18d). The upper wire-cutting crank (21) is fixed axially between the side wall of the drive cam (18) where the mounting part (18d) is located and the limit snap ring (24).

5. A driving mechanism for thread trimming, presser foot lifting and stitch length adjustment in a sewing machine as claimed in claim 1 or 2 or 3 or 4 wherein, The bottom of the drive rod (10) is rotatably connected to a roller (20) by a fastener. The center line of the roller (20) is parallel to the center line of the drive cam (18). The roller (20) and the upper shear crank (21) are axially misaligned. The bottom of the roller (20) extends out of the lower end of the drive rod (10) and abuts against the wheel edge of the drive cam (18).

6. A driving mechanism for thread trimming, presser foot lifting and stitch length adjustment in a sewing machine as claimed in claim 1 or 2 or 3 or 4 wherein, The first motor (2) and the second motor (3) are both fixed to the tail of the machine body (1) and are arranged side by side along the width direction of the machine body (1). The tail of the machine body (1) is fixedly connected to a motor cover (25). The first motor (2), the second motor (3) and the main motor (26) of the sewing machine are all located inside the motor cover (25). The bottom and rear side of the motor cover (25) are provided with heat dissipation vents (25a).

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