Drive mechanism for thread trimming and presser foot lifting in a sewing machine

Abstract

The application provides a driving mechanism for thread trimming and presser foot lifting in a sewing machine, belonging to the technical field of sewing machines. It comprises a motor, a driving wheel fixed on the output shaft of the motor, a transmission mechanism I linked with a thread trimming shaft, and a transmission mechanism II linked with a presser foot shaft. The driving wheel is provided with a driving surface I capable of driving the transmission mechanism I, a driving surface II capable of driving the transmission mechanism II, and a free stroke surface concentric with the output shaft of the motor. The driving surface I, the driving surface II and the free stroke surface are all arranged at the edge of the driving wheel. The driving surface I and the driving surface II are both convex curved surfaces and are respectively connected to the two sides of the free stroke surface. When the transmission mechanism I is in contact with the driving surface I, the transmission mechanism II is in contact with the free stroke surface. When the transmission mechanism I is in contact with the free stroke surface, the transmission mechanism II is in contact with the driving surface II. The application has the advantages of high matching precision and high overall assembly efficiency.

Description

Technical Field

[0001] This invention belongs to the field of sewing machine technology, and relates to overlock sewing machines, and more particularly to the drive mechanism for cutting thread and lifting presser foot in overlock sewing machines. Background Technology

[0002] Overlock sewing machines, also known as hemming machines, edge-sealing machines, or sergers, are generally available with three, four, or five threads. Their main function is to prevent fraying at the seams of garments. Overlock sewing machines have a presser foot mechanism and a thread-cutting mechanism. The presser foot mechanism includes a rotating presser foot shaft and a presser foot assembly connected to one end of the shaft. When the presser foot shaft rotates, the presser foot assembly is raised. The thread-cutting mechanism includes a rotating thread-cutting shaft and a cutter fixed to one end of the shaft. When the thread-cutting shaft rotates, the cutter cuts the thread.

[0003] Traditional overlock sewing machines use two separate electromagnets to drive the thread-cutting shaft and presser foot shaft respectively, resulting in a bulky and costly overall structure. To address this, a modification to the traditional overlock sewing machine structure has been proposed, resulting in a drive mechanism and overlock sewing machine with patent application number 202022394810.3. This mechanism includes a first transmission assembly, at least a portion of which is movably configured to drive the pressing mechanism of the overlock sewing machine to perform a pressing action; a second transmission assembly, at least a portion of which is movably configured to drive the thread-cutting component of the overlock sewing machine to perform a lowering action; a first pushing component, for transmission connection with the first transmission assembly to drive the first transmission assembly to move; a second pushing component, for transmission connection with the second transmission assembly to drive the second transmission assembly to move; and a drive component (motor) with a rotatable output shaft, on which both the first and second pushing components are mounted to rotate under the drive of the drive component. This design allows the drive mechanism to control both the thread-cutting and presser foot lifting devices with a single motor, completing both actions, resulting in a simpler structure.

[0004] However, the aforementioned drive mechanism and overlock sewing machine also have shortcomings: the first pushing component is actually the first transmission cam, which is sleeved on the output shaft to drive the first transmission assembly to move. At the same time, the second pushing component is actually the second transmission cam, which is sleeved on the output shaft to drive the second transmission component to move. Both the first and second transmission cams will have some machining errors during machining (such as the coaxiality of the center hole). Furthermore, the first and second transmission cams have specific installation angles and positional relationships on the output shaft. The combination of these two factors makes it difficult to guarantee the matching accuracy of the entire drive mechanism, resulting in the need for multiple adjustments during the assembly of the whole machine. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in the prior art by proposing a drive mechanism for thread cutting and presser foot lifting in an overlock sewing machine, thereby solving the problem of low assembly efficiency caused by difficulty in ensuring fitting accuracy.

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

[0007] The drive mechanism for thread cutting and presser foot lifting in an overlock sewing machine includes a motor fixed to one side of the machine casing, a drive wheel fixed to the output shaft of the motor, a transmission mechanism one linked to the thread cutting shaft, and a transmission mechanism two linked to the presser foot shaft. The drive wheel is provided with a drive surface one capable of driving the transmission mechanism one, a drive surface two capable of driving the transmission mechanism two, and a free travel surface concentrically arranged with the output shaft of the motor. The key feature is that the drive surface one, drive surface two, and free travel surface are all located on the edge of the drive wheel. The drive surface one and drive surface two are both convex curved surfaces and are respectively connected to both sides of the free travel surface. When the transmission mechanism one is in contact with the drive surface one, the transmission mechanism two is in contact with the free travel surface. When the transmission mechanism one is in contact with the free travel surface, the transmission mechanism two is in contact with the drive surface two.

[0008] Initially, the contact position between transmission mechanism one and the drive wheel is at the junction of drive surface one and idle travel surface, and the contact position between transmission mechanism two and the drive wheel is at the junction of drive surface two and idle travel surface. When wire cutting is required, the output shaft of the motor drives the drive wheel to rotate, causing the drive surface to initially contact transmission mechanism one. As drive surface one moves on transmission mechanism one, transmission mechanism one is pushed, causing it to drive the wire cutting shaft to swing and complete the wire cutting action. During the wire cutting process, the contact position between transmission mechanism two and the drive wheel moves from the junction of drive surface two and idle travel surface to the idle travel surface. Transmission mechanism two is not subjected to force, keeping the pressure foot shaft stationary to avoid interfering with the wire cutting action.

[0009] When the presser foot needs to be lifted, the motor's output shaft rotates in the reverse direction, first moving the contact position between transmission mechanism one and the drive wheel back to the connection point between drive surface one and the idle travel surface. This also moves the contact position between transmission mechanism two and the drive wheel back to the connection point between drive surface two and the idle travel surface. Then, the motor's output shaft continues to rotate in the current direction, causing drive surface two to contact transmission mechanism two. As drive surface two moves on transmission mechanism two, it generates a pushing force, causing transmission mechanism two to drive the presser foot shaft to swing, thus completing the presser foot lifting action. During the presser foot lifting process, the contact position between transmission mechanism one and the drive wheel moves from the connection point between drive surface one and the idle travel surface to the idle travel surface. Transmission mechanism one is not subjected to any force, keeping the wire-cutting shaft stationary to avoid interfering with the presser foot lifting action.

[0010] By simultaneously setting drive surface one, drive surface two, and idle stroke surface on the edge of the drive wheel and combining them with the curvature design, this drive mechanism can complete the wire cutting action with transmission mechanism one and the lifting of the presser foot with transmission mechanism two using only one drive wheel. The machining on a single drive wheel, especially since drive surface one, drive surface two, and idle stroke surface are all located on the edge of the drive wheel, allows for excellent control of machining errors. After the drive wheel is machined, the relative angle and position between drive surface one and drive surface two are determined. This eliminates the need for two transmission cams, saving the time spent adjusting the relative angle and position between the two transmission cams during assembly. During assembly, only the positions between transmission mechanism one and the drive wheel, and the positions between transmission mechanism two and the drive wheel, need to be adjusted, greatly improving assembly efficiency.

[0011] In the aforementioned overlock sewing machine, the curvature of the thread-cutting and presser foot-lifting drive mechanism of the drive surface one and the curvature of the drive surface two gradually increase from one end connected to the idle stroke surface to the other end.

[0012] With the above settings, when the drive wheel rotates in the direction of increasing curvature of the drive surface one, it can gradually apply a pushing force to the transmission mechanism one by means of the gradual increase in curvature of the drive surface one, so that the transmission mechanism one drives the wire cutting shaft to swing to complete the wire cutting action; when the drive wheel rotates in the direction of increasing curvature of the drive surface two, it can gradually apply a pushing force to the transmission mechanism two by means of the gradual increase in curvature of the drive surface two, so that the transmission mechanism two drives the pressure foot shaft to swing to complete the pressure foot lifting action.

[0013] In the aforementioned overlock sewing machine, the drive mechanism for cutting thread and lifting presser foot has a length greater than that of drive surface one, and a length greater than that of idle travel surface one.

[0014] The rotation angle of the drive wheel required to complete the wire cutting is greater than the rotation angle of the drive wheel required to complete the lifting of the presser foot. Therefore, on the basis of setting the length of drive surface one to be greater than that of drive surface two, the length of the idle stroke surface is set to be greater than that of drive surface one. This ensures that during the process of drive surface one moving along the mating part to complete the wire cutting, the transmission mechanism two is always in contact with the idle stroke surface to keep the presser foot shaft stationary.

[0015] In the aforementioned overlock sewing machine, the drive mechanism for thread cutting and presser foot lifting is further provided with a retaining surface 1 and a retaining surface 2, both concentrically arranged with the rotation center of the drive wheel. The retaining surface 1 is connected to the drive surface 1 and the two are smoothly transitioned. The retaining surface 2 is connected to the drive surface 2 and the two are smoothly transitioned. When the transmission mechanism 1 contacts the retaining surface 1, the transmission mechanism 2 contacts the idle stroke surface. When the transmission mechanism 2 contacts the retaining surface 2, the transmission mechanism 1 contacts the idle stroke surface.

[0016] When the drive wheel rotates from contact between the drive surface one and the transmission mechanism one to contact between the holding surface one and the transmission mechanism one, since the holding surface one smoothly transitions with the drive surface one and is concentric with the rotation center of the drive wheel, it means that the wire cutting shaft is still in the wire cutting state at this time. Similarly, when the drive wheel rotates from contact between the drive surface two and the transmission mechanism two to contact between the holding surface two and the transmission mechanism two, since the holding surface two smoothly transitions with the drive surface two and is concentric with the rotation center of the drive wheel, it means that the presser foot shaft is still in the state of lifting the presser foot at this time.

[0017] Under normal conditions, for the drive wheel to remain stably in one position, the motor needs to generate a locking force. At this point, the motor does not stop, but its output shaft does not rotate. This drive mechanism uses two retaining surfaces, a first and a second, on the edge of the drive wheel. Since both retaining surfaces are concentric with the rotation center of the drive wheel, the curvature of both retaining surfaces is equal. This allows the motor to maintain the wire-cutting shaft in a wire-cutting state or the presser foot shaft in a raised presser foot state for a period of time with a relatively small locking force, thus preventing the motor from overheating. However, if the drive wheel were to stop directly at the point of maximum curvature of either drive surface one or drive surface two, the motor would require a larger locking force due to the varying curvature of either surface, leading to overheating and reduced lifespan.

[0018] In the aforementioned overlock sewing machine, the drive mechanism for thread cutting and presser foot lifting includes a bracket fixed to the machine housing at one end of the motor housing. The drive wheel is located inside the bracket, and the motor output shaft is located above the presser foot shaft and parallel to it. The first transmission mechanism includes a rotating seat hinged to the bracket. The rotation center line of the rotating seat is perpendicular to the motor output shaft and located below the motor output shaft. A mating part protrudes from the side of the rotating seat. The second transmission mechanism includes a swing arm connected to the presser foot shaft. One end of the swing arm and the mating part are both located at the edge of the drive wheel and simultaneously abut against the edge of the drive wheel. The position where the swing arm contacts the edge of the drive wheel is always higher than the position where the mating part contacts the edge of the drive wheel.

[0019] The rotating base is directly hinged to the bracket, reducing the distance between it and the drive wheel. The rotation center lines of both the pressure foot shaft and the rotating base are positioned below the motor's output shaft. A mating part protrudes from the side of the rotating base, with one end of the swing arm and the mating part located at the edge of the drive wheel. The position of the swing arm contacting the edge of the drive wheel is always higher than the position of the mating part contacting the edge of the drive wheel. This allows for a rational structural arrangement within a limited space, ensuring that the drive mechanism can complete the wire-cutting action with only one drive wheel and the pressure foot lifting action with the second transmission mechanism. Furthermore, the hinged rotating base to the bracket means that the rotating base and drive wheel are assembled integrally on the machine housing. The relative position between the rotating base's center line and the drive wheel is pre-determined, ensuring fitting accuracy and simplifying assembly, thus improving assembly efficiency. This design also broadens applicability, accommodating different machine models.

[0020] In the aforementioned overlock sewing machine, the drive mechanism for cutting thread and lifting presser foot is cylindrical. The mating part includes a mating arm that protrudes radially along the rotating seat and then bends to be approximately parallel to the drive wheel, as well as a wheel-shaped component connected to one side of the mating arm. A reset torsion spring is sleeved on the rotating seat, which acts on the rotating seat to keep the edge of the wheel-shaped component abutting against the edge of the drive wheel.

[0021] With the above configuration, the drive wheel can use the second drive surface located on the edge to complete the lifting presser foot action, and at the same time, it can use the first drive surface located on the edge to drive the rotating seat to rotate. This ensures that the drive mechanism can complete the driving of the wire cutting action and the driving of the lifting presser foot action with only one drive wheel, thereby improving the assembly efficiency of the whole machine.

[0022] In the aforementioned overlock sewing machine, the drive mechanism for cutting the thread and raising the presser foot includes a support plate one fixed to the motor housing and a plate two perpendicular to the plate one and fixed to the machine housing by several fastening screws. The rotating seat is hinged to the plate two, and the side of the rotating seat is also provided with a connecting part. The transmission mechanism one also includes a transmission rod with one end hinged to the connecting part and a swing block hinged to the other end of the transmission rod and detachably connected to the thread cutting shaft.

[0023] Once the motor is fixed to the housing, the entire transmission mechanism is also assembled onto the housing simultaneously. Only the swing block needs to be connected to the wire-cutting shaft. This setup further ensures precision and improves assembly efficiency.

[0024] In the aforementioned overlock sewing machine, in the drive mechanism for cutting the thread and lifting the presser foot, one end of the reset torsion spring abuts against the side of one of the fastening screws, and the other end of the reset torsion spring abuts against the connecting part.

[0025] Through the above settings, the fastening screws that fix plate two to the machine housing are used in a reasonable way, so that the elastic force of the reset torsion spring one sleeved on the rotating seat can act stably on the rotating seat, so as to ensure the matching accuracy between transmission mechanism one and drive wheel.

[0026] In the aforementioned overlock sewing machine, the drive mechanism for cutting thread and lifting presser foot includes a plate-shaped body connected to the presser foot shaft, an arm protruding from the upper side of the plate-shaped body, and a wheel-shaped component two connected to one side of the arm. The first wheel-shaped component and the second wheel-shaped component are approximately parallel, and the projections of the first wheel-shaped component and the second wheel-shaped component on the first plate are offset. The presser foot shaft is provided with a reset torsion spring two that acts on the swing arm to keep the edge of the second wheel-shaped component in contact with the edge of the drive wheel.

[0027] The above settings ensure that the drive wheel can use the second drive surface located at the edge to drive the lifting presser foot action, while also using the first drive surface located at the edge to drive the wire cutting action, thereby ensuring the fitting accuracy and improving the overall assembly efficiency.

[0028] In the aforementioned overlock sewing machine, the drive mechanism for cutting thread and lifting presser foot has a recessed cavity on the side of the machine housing. The motor is located inside the recessed cavity. One end of the presser foot shaft extends into the recessed cavity, and the swing arm is connected to that end of the presser foot shaft. The connecting part includes a connecting piece 1 that protrudes radially from the side of the rotating seat, a connecting piece 2 that is perpendicular to the connecting piece 1 and extends out of the recessed cavity, and a connecting piece 3 that is perpendicular to the connecting piece 2. One end of the transmission rod is hinged to the connecting piece 3.

[0029] The above design makes the entire overlock sewing machine more compact and smaller in size. At the same time, by using the connecting piece two to extend out of the cavity, it is possible to ensure that the rotating seat inside the cavity can be smoothly connected to the thread-cutting shaft outside the cavity, so that the rotating seat can drive the thread-cutting shaft to swing and perform the thread-cutting work when it rotates.

[0030] Compared with existing technologies, the drive mechanism for thread cutting and presser foot lifting in this overlock sewing machine has the following advantages:

[0031] 1. By simultaneously setting the first driving surface, the second driving surface, and the idle travel surface on the edge of the driving wheel and combining them with the curvature design, this drive mechanism can complete the wire cutting action with the first transmission mechanism and complete the pressing foot lifting action with the second transmission mechanism using only one driving wheel. The machining error can be well controlled, and the relative angle and relative position between the first driving surface and the second driving surface are determined after the driving wheel is machined. During assembly, it is only necessary to adjust the position between the first transmission mechanism and the driving wheel and the position between the second transmission mechanism and the driving wheel, which greatly improves the assembly efficiency.

[0032] 2. The rotating seat is directly hinged to the bracket used to fix the motor to the housing, so that the transmission mechanism and the drive wheel can be installed as a whole on the housing. The relative position between the center line of the rotating seat and the drive wheel has been determined in advance to ensure the fitting accuracy. This makes the assembly of the whole machine simpler, more convenient and improves the assembly efficiency. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of an overlock sewing machine.

[0034] Figure 2 This is a schematic diagram of the drive mechanism for thread cutting and presser foot lifting in this overlock sewing machine.

[0035] Figure 3 This is a schematic diagram showing the connection between the drive wheel, transmission mechanism, and wire-cutting shaft.

[0036] Figure 4 This is a schematic diagram of the connection between the transmission mechanism and the wire-cutting shaft.

[0037] Figure 5 This is a schematic diagram showing the connection between the drive wheel, transmission mechanism 2, and pressure foot shaft.

[0038] Figure 6 This is a schematic diagram of the drive wheels.

[0039] Figure 7 This is a schematic diagram showing the interaction between wheel component one, wheel component two, and the drive wheel when the wire cutting and pressing foot lifting actions are not performed.

[0040] Figure 8 This is a schematic diagram showing the interaction between wheel-shaped component one, wheel-shaped component two, and the drive wheel when performing the wire-cutting action.

[0041] Figure 9 This is a schematic diagram showing the interaction between wheel component one, wheel component two, and the drive wheel when performing the lifting and pressing foot action.

[0042] In the diagram: 1. Housing; 1a. Cavity; 2. Presser foot shaft; 3. Presser foot assembly; 4. Wire cutting shaft; 5. Cutting blade; 6. Motor; 7. Drive wheel; 7a. Free stroke surface; 7b. Drive surface one; 7c. Drive surface two; 7d. Inner recess one; 7e. Inner recess two; 7f. Holding surface one; 7g. Holding surface two; 8. Swing arm; 8a. Plate-shaped body; 8b. Arm body; 8c. Wheel-shaped part two; 9. Rotating seat; 9a. Mating part; 9a1. Mating arm; 9a2. Wheel-shaped part one; 9b. Connecting part; 9b1. Connecting piece one; 9b2. Connecting piece two; 9b3. Connecting piece three; 10. Bracket; 10a. Plate one; 10b. Plate two; 11. Fastening screw; 12. Connecting screw; 13. Return torsion spring one; 14. Transmission rod; 15. Swing block; 16. Return torsion spring two. Detailed Implementation

[0043] 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.

[0044] like Figure 1 , Figure 2 , Figure 3 , Figure 6 and Figure 7 As shown, the overlock sewing machine includes a drive mechanism for cutting thread and lifting the presser foot. The overlock sewing machine includes a machine housing 1, a presser foot shaft 2, a presser foot assembly 3 connected to one end of the presser foot shaft 2, and a thread cutting shaft 4 with a cutter 5 fixed to one end. This drive mechanism includes a motor 6 fixed to one side of the housing 1, a drive wheel 7 fixed to the output shaft of the motor 6, a transmission mechanism 1 linked to the wire cutting shaft 4, and a transmission mechanism 2 linked to the presser foot shaft 2. The edge of the drive wheel 7 is provided with a free travel surface 7a concentrically arranged with the rotation center of the drive wheel 7, and a drive surface 7b and a drive surface 7c, both of which are convex curved surfaces. The drive surface 7b and the drive surface 7c are located on both sides of the free travel surface 7a. The free travel surface 7a is a segment of arc surface. The curvature of the drive surface 7b and the curvature of the drive surface 7c gradually increase in the direction away from the free travel surface 7a. An indentation 7d is formed between the drive surface 7b and the free travel surface 7a, and an indentation 7e is formed between the drive surface 7c and the free travel surface 7a. In this embodiment, both the indentation 7d and the indentation 7e are arc-shaped indentations. Drive surface 7b engages with transmission mechanism 1, and drive surface 7c engages with transmission mechanism 2. When drive wheel 7 rotates, it drives transmission mechanism 1 via drive surface 7b, causing the wire cutting shaft 4 to swing. When drive wheel 7 rotates, it drives transmission mechanism 2 via drive surface 7c, causing the pressure foot shaft 2 to swing. The length of drive surface 7b is greater than drive surface 7c, and the length of idle surface 7a is greater than drive surface 7b. The edge of drive wheel 7 also has retaining surface 7f and retaining surface 7g, both concentrically positioned with the rotation center of drive wheel 7. Retaining surface 7f connects to drive surface 7b with a smooth transition, and retaining surface 7g connects to drive surface 7c with a smooth transition. When transmission mechanism 1 contacts retaining surface 7f, transmission mechanism 2 contacts idle surface 7a; when transmission mechanism 2 contacts retaining surface 7g, transmission mechanism 1 contacts idle surface 7a.

[0045] Furthermore, such as Figure 1 and Figure 2As shown, one end of the motor 6 housing is connected to a bracket 10 fixed to the housing 1. A cavity 1a is provided on one side of the housing 1. The motor 6 is located in the cavity 1a and the bracket 10 is fixed to the bottom wall of the cavity 1a. The drive wheel 7 is located inside the bracket 10. The output of the motor 6 is parallel to the presser foot shaft 2. The transmission mechanism 2 includes a swing arm 8 connected to the presser foot shaft 2. The transmission mechanism 1 includes a rotating seat 9 hinged to the bracket 10 and whose rotation center line is perpendicular to the output shaft of the motor 6. A mating part 9a is provided on the side of the rotating seat 9. One end of the swing arm 8 and the mating part 9a abut against the edge of the drive wheel 7. When one end of the swing arm 8 is located at the second recess 7e, the mating part 9a is located at the first recess 7d. Specifically, the bracket 10 includes a plate 10a fixed to one end of the housing of the motor 6 and a plate 10b perpendicular to the plate 10a and fixed to the bottom wall of the cavity 1a by a number of fastening screws 11. The rotating seat 9 is hinged to the plate 10b.

[0046] Furthermore, such as Figure 3 and Figure 4 As shown, the rotating seat 9 is columnar, and is hinged to the second plate 10b via a connecting screw 12 that passes through the rotating seat 9 and the second plate 10b and is threaded into the housing 1. The mating part 9a includes a mating arm 9a1 that protrudes radially along the rotating seat 9 and is then bent, and a wheel-shaped member 9a2 connected to one side of the end of the mating arm 9a1. The mating part 9a is located below the rotation center line of the drive wheel 7. A return torsion spring 13 is sleeved on the rotating seat 9 to ensure that the edge of the wheel-shaped member 9a2 always abuts against the edge of the drive wheel 7. The side of the rotating seat 9 also has a connecting part 9b. The transmission mechanism also includes a transmission rod 14 with one end hinged to the connecting part 9b and a swing block 15 that is hinged to the other end of the transmission rod 14 and detachably connected to the other end of the wire cutting shaft 4. The swing block 15 has two parallel mounting holes. One mounting hole is used to connect with the wire cutting shaft 4, and the other mounting hole is used to form a hinge with the transmission rod 14 through the hinge shaft. The swing block 15 also has a straight groove that connects the two mounting holes. The swing block 15 also has a locking hole that is connected to the straight groove (the locking hole is perpendicular to the mounting hole). When a locking screw is connected in the locking hole, the straight groove can be closed, thereby making the hole walls of the two mounting holes hug the hinge shaft and the wire cutting shaft 4 to form a fixed position. One end of the return torsion spring 13 abuts against the side of one of the fastening screws 11, and the other end of the return torsion spring 13 abuts against the connecting part 9b. The connecting part 9b includes a connecting piece 9b1 that protrudes radially from the side of the rotating seat 9, a connecting piece 9b2 that is perpendicular to the connecting piece 9b1 and extends out of the cavity 1a, and a connecting piece 9b3 that is perpendicular to the connecting piece 9b2. One end of the transmission rod 14 is hinged to the connecting piece 9b3.

[0047] Furthermore, such as Figure 1 and Figure 5As shown, one end of the presser foot shaft 2 extends into the cavity 1a and is located below the motor 6. The swing arm 8 is connected to the end of the presser foot shaft 2 that extends into the cavity 1a, i.e., the swing arm 8 is located in the cavity 1a. One end of the swing arm 8 is located at the edge of the drive wheel 7. The presser foot shaft 2 is provided with a return torsion spring 16 that ensures that one end of the swing arm 8 always abuts against the edge of the drive wheel 7. The position where one end of the swing arm 8 contacts the drive wheel 7 is always higher than the position where the mating part 9a contacts the edge of the drive wheel 7. Specifically, the swing arm 8 includes a plate-shaped body 8a connected to the presser foot shaft 2, an arm body 8b protruding from the upper side of the plate-shaped body 8a, and a wheel-shaped component 8c connected to one side of the end of the arm body 8b. One end of the return torsion spring 16 abuts against the bottom wall of the cavity 1a, and the other end of the return torsion spring 16 abuts against the lower side of the plate-shaped body 8a. The edge of the wheel-shaped component 8c always abuts against the edge of the drive wheel 7 under the elastic force of the return torsion spring 16. Wheel-shaped component 9a2 and wheel-shaped component 8c are approximately parallel to each other. The projections of wheel-shaped component 9a2 and wheel-shaped component 8c on plate 10a are offset. In this embodiment, both wheel-shaped component 9a2 and wheel-shaped component 8c are bearings.

[0048] Initial state, such as Figure 7 As shown, wheel-shaped component 9a2 is located at the recess 7d between the drive surface 7b and the idle travel surface 7a, and abuts against the drive wheel 7 under the elastic force of the return torsion spring 13. Wheel-shaped component 8c is located at the recess 7e between the drive surface 7c and the idle travel surface 7a, and abuts against the drive wheel 7 under the elastic force of the return torsion spring 16.

[0049] When wire cutting is required, the output shaft of motor 6 drives the drive wheel 7 to rotate, causing the drive surface 7b to contact the wheel-shaped member 9a2. Since the curvature of the drive surface 7b gradually increases from the end connected to the idle travel surface 7a to the other end, the movement of the drive surface 7b on the wheel-shaped member 9a2 causes the wheel-shaped member 9a2 to experience a downward pushing force. This causes the mating part 9a to be pressed downwards, causing the rotating seat 9 to rotate. The connecting part 9b then tilts upwards and, through its hinge with the transmission rod 14, pulls the transmission rod 14 upwards. The transmission rod 14 then drives the wire-cutting shaft 4 to swing, causing the cutter 5 to complete the wire-cutting action. This state is as follows: Figure 8 As shown. During the wire cutting process, the idle stroke surface 7a contacts the wheel-shaped component 8c. The wheel-shaped component 8c is not subjected to force, so the swing arm 8 remains stationary, thereby keeping the pressure foot shaft 2 stationary to avoid interfering with the wire cutting action.

[0050] When the pressure foot needs to be lifted, the output shaft of motor 6 rotates in the reverse direction, first causing the contact position between wheel-shaped part 9a2 and drive wheel 7 to return to the recess 7d between drive surface 7b and idle travel surface 7a. This causes the contact position between wheel-shaped part 8c and drive wheel 7 to return to the recess 7e between drive surface 7c and idle travel surface 7a. This state is as follows: Figure 7 As shown. Then, the output shaft of motor 6 continues to rotate in the current direction, causing the driving surface 7c to contact the wheel-shaped member 8c. Since the curvature of the driving surface 7c gradually increases from the end connected to the idle stroke surface 7a to the other end, the wheel-shaped member 8c is pushed by the movement of the driving surface 7c on the wheel-shaped member 8c. This drives the swing arm 8 to swing, thereby driving the presser foot shaft 2 to rotate. As a result, the presser foot assembly 3 gradually lifts upward during the rotation of the presser foot shaft 2. This state is as follows. Figure 9 As shown. During the lifting of the presser foot, the idle stroke surface 7a contacts the wheel-shaped part 9a2. The wheel-shaped part 9a2 is not subjected to force, so the rotating seat 9 remains stationary, thereby keeping the wire cutting shaft 4 stationary to avoid interfering with the lifting of the presser foot.

[0051] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A driving mechanism for cutting thread and lifting presser foot in a overlock machine, comprising a motor (6) fixed on one side of the machine housing (1), a driving wheel (7) fixed on the output shaft of the motor (6), a transmission mechanism I linked with the thread cutting shaft (4) and a transmission mechanism II linked with the presser foot shaft (2), the driving wheel (7) is respectively provided with a driving surface I (7b) capable of driving the transmission mechanism I to act, a driving surface II (7c) capable of driving the transmission mechanism II to act and a free stroke surface (7a) concentrically arranged with the output shaft of the motor (6), characterized in that, The driving surface one (7b), the driving surface two (7c) and the idle stroke surface (7a) are arranged at the edge of the driving wheel (7), the driving surface one (7b) and the driving surface two (7c) are both convex curved surfaces and are connected to the two sides of the idle stroke surface (7a) respectively, when the transmission mechanism one is in the position of contacting the driving surface one (7b), the transmission mechanism two is in the position of contacting the idle stroke surface (7a), when the transmission mechanism one is in the position of contacting the idle stroke surface (7a), the transmission mechanism two is in the position of contacting the driving surface two (7c), the edge of the driving wheel (7) further has a retaining surface two (7g) which is arranged concentrically with the output shaft of the motor (6), the retaining surface two (7g) is connected with the driving surface two (7c) and the two are smoothly transitioned, when the transmission mechanism two is in the position of contacting the retaining surface two (7g), the transmission mechanism one is in the position of contacting the idle stroke surface (7a).

2. The driving mechanism for cutting thread and lifting presser foot in a zigzag machine according to claim 1, wherein The curvature of the driving surface one (7b) and the curvature of the driving surface two (7c) are gradually increased along the one end connected with the idle stroke surface (7a) to the other end respectively.

3. The driving mechanism for cutting thread and lifting presser foot in overlock machine according to claim 2, characterized in that, The length of the driving surface one (7b) is greater than the length of the driving surface two (7c), and the length of the idle stroke surface (7a) is greater than the length of the driving surface one (7b).

4. The driving mechanism for thread-trimming and presser foot-lifting in a zigzag machine according to claim 3, wherein The edge of the driving wheel (7) further has a retaining surface one (7f) which is arranged concentrically with the output shaft of the motor (6), the retaining surface one (7f) is connected with the driving surface one (7b) and the two are smoothly transitioned, when the transmission mechanism one is in the position of contacting the retaining surface one (7f), the transmission mechanism two is in the position of contacting the idle stroke surface (7a).

5. The driving mechanism for thread trimming and presser foot lifting in a zigzag machine according to claim 1 or 2 or 3 or 4, characterized in that, One end of the motor (6) is connected with a support (10) which is fixed with the machine shell (1), the driving wheel (7) is located inside the support (10), the output shaft of the motor (6) is located above the presser foot shaft (2) and the two are parallel, the transmission mechanism one includes a rotating seat (9) which is hinged on the support (10), the rotating center line of the rotating seat (9) is perpendicular to the output shaft of the motor (6) and is located below the output shaft of the motor (6), the side of the rotating seat (9) is protrusively provided with a matching part (9a), the transmission mechanism two includes a swing arm (8) which is connected on the presser foot shaft (2), one end of the swing arm (8) and the matching part (9a) are both located at the edge of the driving wheel (7) and simultaneously abut against the edge of the driving wheel (7), the position of one end of the swing arm (8) contacting the edge of the driving wheel (7) is always higher than the position of the matching part (9a) contacting the edge of the driving wheel (7).

6. The driving mechanism for cutting thread and lifting presser foot in overlock machine according to claim 5, characterized in that, The rotating seat (9) is in a cylindrical shape, the matching part (9a) includes a matching arm (9a1) which is protrusively bent along the radial direction of the rotating seat (9) and is substantially parallel to the driving wheel (7), and a wheel-shaped part one (9a2) which is connected to one side of the matching arm (9a1), a reset torsional spring one (13) is sleeved on the rotating seat (9) and acts on the rotating seat (9) to make the edge of the wheel-shaped part one (9a2) always abut against the edge of the driving wheel (7).

7. The driving mechanism for the thread-trimming and presser-lifting of a lockstitch sewing machine according to claim 6, characterized in that, The support (10) comprises a first plate (10a) fixed to the housing of the motor (6) and a second plate (10b) perpendicular to the first plate (10a) and fixed to the housing (1) by means of a plurality of fastening screws (11), the rotating seat (9) being hinged to the second plate (10b), the side of the rotating seat (9) further comprising a connecting portion (9b), the first transmission mechanism further comprising a transmission rod (14) hinged at one end to the connecting portion (9b) and a swinging block (15) hinged at the other end to the transmission rod (14) and removably connected to the thread cutting shaft (4).

8. The driving mechanism for thread-trimming and presser foot-lifting in a zigzag machine according to claim 7, characterized in that, One end of the first reset torsion spring (13) abuts against the side of one of the fastening screws (11), and the other end of the first reset torsion spring (13) abuts against the connecting portion (9b).

9. The driving mechanism for thread trimming and presser foot lifting in a zigzag machine according to claim 6, wherein The swinging arm (8) comprises a sheet-shaped body (8a) connected to the presser bar (2), an arm body (8b) protruding from the upper side of the sheet-shaped body (8a), and a wheel-shaped member (8c) connected to one side of the arm body (8b), the wheel-shaped member (9a2) and the wheel-shaped member (8c) being in a substantially parallel state, and the projections of the wheel-shaped member (9a2) and the wheel-shaped member (8c) on the first plate (10a) being staggered, the presser bar (2) being provided with a second reset torsion spring (16) acting on the swinging arm (8) to keep the edge of the wheel-shaped member (8c) in contact with the edge of the driving wheel (7).

10. The driving mechanism for thread trimming and presser foot lifting in a zigzag machine according to claim 7, wherein The housing (1) is provided with a recessed cavity (1a) on the side, the motor (6) is arranged in the recessed cavity (1a), one end of the presser bar (2) extends into the recessed cavity (1a) and the swinging arm (8) is connected to the end of the presser bar (2), the connecting portion (9b) comprises a connecting sheet (9b1) protruding radially from the side of the rotating seat (9), a connecting sheet (9b2) perpendicular to the connecting sheet (9b1) and extending out of the recessed cavity (1a), and a connecting sheet (9b3) perpendicular to the connecting sheet (9b2), one end of the transmission rod (14) being hinged to the connecting sheet (9b3).

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