CN220413708U - Joint transmission structure of flat seaming machine and flat seaming machine - Google Patents

Abstract

The utility model relates to the technical field of sewing machines, in particular to a joint transmission structure with a flat sewing machine, the flat sewing machine comprises a presser foot lifting mechanism, a thread trimming mechanism, a backstitch mechanism, an execution cam, and a working curved surface arranged on the side part of the execution cam; one side of the working curved surface drives a first transmission rod piece, a first thread cutting crank and a second thread cutting crank; the other side of the working curved surface drives a second transmission rod piece, a first presser foot lifting crank and a second presser foot lifting crank; a stepping motor drives three rewinding mechanisms, a thread trimming mechanism and a presser foot lifting mechanism to realize three actions, and the changed parts on the original general three-automatic lockstitch sewing machine are fewer.

Description

Joint transmission structure of flat seaming machine and flat seaming machine

Technical Field

The utility model relates to the technical field of sewing machines, in particular to a joint transmission structure with a flat sewing machine and the flat sewing machine.

Background

ZL202110083300.0 discloses a sewing machine with a compound adjusting device, which adopts a driving motor to drive a reverse sewing mechanism, a thread trimming mechanism and a presser foot lifting mechanism, wherein the reverse sewing mechanism can adjust the needle pitch of the sewing machine; this patent has the following drawbacks:

this technical scheme needs to improve sewing machine's casing, and original back stitch mechanism, thread trimming mechanism and lift presser foot mechanism all need the adaptive change structure, leads to sewing machine's spare part reuse rate lower.

Sewing machines are a highly differentiated industry, and various types of parts of sewing machines are commercially available. Therefore, when each new technical scheme appears, whether the scheme can be rapidly brought to the market or not has a great relationship with the reuse rate of parts. The higher the reuse rate of the parts is, the lower the production cost is, the lower the later maintenance cost is, and the replacement parts can be quickly found from the market after faults occur, so that the maintenance is easy.

The applicant intends to develop a new combined transmission structure to realize a combined driving scheme that a motor drives the reverse stitching mechanism, the thread trimming mechanism and the presser foot lifting mechanism respectively, and the scheme needs higher multiplexing rate of parts.

Disclosure of Invention

The utility model aims to provide a combined transmission structure and a flat seaming machine, which have simple structures and can drive three mechanisms only by changing a crank, a connecting shaft and a connecting rod.

The aim of the utility model is realized in the following way:

a joint transmission structure of a flat sewing machine comprises

The presser foot lifting mechanism is used for lifting the presser foot of the flat sewing machine;

a thread cutting mechanism for cutting off a sewing thread of the lockstitch sewing machine;

the backstitch mechanism is used for controlling the action of a feed dog of the lockstitch sewing machine;

and also comprises

The side part of the execution cam is provided with a working curved surface, and the working curved surface comprises a first working curved surface and a second working curved surface; the first working curved surface is connected with the second working curved surface in a smooth manner; the first working curved surface is an arc surface, and the center of the arc surface is consistent with the rotation center of the execution cam; the second working curved surface is a cam surface protruding to one side;

the first transmission rod piece is rotatably arranged in the shell of the flat seaming machine; the first transmission rod piece is horizontally arranged transversely, one end of the first transmission rod piece is close to the execution cam, and the other end of the first transmission rod piece extends towards the machine head direction of the flat seaming machine;

the first thread cutting crank is arranged at one end of the first transmission rod piece, which is close to the execution cam, and is in matched transmission with the working curved surface of the execution cam;

the second wire cutting crank is arranged at one end, close to the machine head direction, of the first transmission rod piece; the second thread cutting crank drives the thread cutting mechanism;

the second transmission rod piece is sleeved on the outer side of the first transmission rod piece; the second transmission rod piece is horizontally arranged transversely, one end of the second transmission rod piece is close to the execution cam, and the other end of the second transmission rod piece extends towards the machine head direction of the flat seaming machine; two ends of the first transmission rod piece are respectively exposed out of the second transmission rod piece;

the first presser foot lifting crank is arranged at one end, close to the execution cam, of the second transmission rod piece and is in matched transmission with the working curved surface of the execution cam;

the second presser foot lifting crank is arranged at one end, close to the machine head direction, of the second transmission rod piece; the presser foot lifting crank II is used for driving the presser foot lifting mechanism;

the upper end of the reverse joint adjusting connecting rod is hinged to one side of the executing cam, and the lower end of the reverse joint adjusting connecting rod is hinged to the swing seat of the reverse joint mechanism;

an execution motor which is installed on the shell of the lockstitch sewing machine and is used for driving the execution cam.

Preferably, the rotation area of the execution cam comprises a reverse stitching area, a thread trimming area and a presser foot lifting area;

when the executing cam is positioned in the reverse stitching area, the first thread cutting crank and the first presser foot lifting crank are matched with the first working curved surface;

when the executing cam is positioned in the thread cutting area, the thread cutting crank I is matched with the second working curved surface; the first presser foot lifting crank is matched with the first working curved surface;

when the executing cam is positioned in the presser foot lifting area, the first presser foot lifting crank is matched with the second working curved surface, and the first thread cutting crank is matched with the first working curved surface.

Preferably, in the process that the executing cam enters the presser foot lifting area from the thread cutting area, after the first roller of the thread cutting crank passes through the highest angle point of the second working curved surface, the first thread cutting crank and the first presser foot lifting crank are located on the second working curved surface together, and the first thread cutting crank and the first presser foot lifting crank act continuously along the second working curved surface.

Preferably, the swinging ends of the first thread cutting crank and the first presser foot lifting crank are matched with the executing cam, the swinging ends are provided with rollers, and the surfaces of the rollers are abutted against the working curved surface of the executing cam.

Preferably, a forced reset structure is arranged between the first thread cutting crank and the executing cam;

the specific structure of the forced reset structure is as follows: a reset protrusion is arranged on one side of the first thread cutting crank; in the process of executing the thread cutting action by the thread cutting crank, the reset protrusion enters the rotating area of the executing cam; when the thread cutting mechanism is blocked by external force and cannot reset, the executing cam pushes the reset protrusion and resets the thread cutting mechanism;

or, the specific structure of the forced reset structure is as follows: a reset push rod extends from one side of the first wire cutting crank; a first pushing block is arranged on one side of the execution cam, and the first pushing block and the reset push rod are positioned on the same plane; in the process of executing the thread cutting action by the thread cutting crank, a reset push rod enters a rotating area of the first pushing block; when the wire cutting mechanism is blocked by external force and cannot reset, the executing cam pushes the reset push rod and resets the wire cutting mechanism.

Preferably, a second pushing block is further arranged on one side of the first pushing block; the first pushing block, the second pushing block and the reset push rod are all positioned on the same plane; the outer end part of the reset push rod is provided with a guide curved surface;

when the executing cam enters the presser foot lifting area from the thread cutting area, the first pushing block passes through the rotating area of the reset push rod, and when the thread cutting mechanism is blocked by external force and cannot reset, the first pushing block pushes the reset push rod and resets the thread cutting mechanism;

when the execution cam enters the presser foot lifting area from the reverse stitching area, the second pushing block passes through the rotating area of the reset push rod, and when the thread cutting mechanism is blocked by external force and cannot reset, the second pushing block pushes the reset push rod and resets the thread cutting mechanism;

the included angle between the first pushing block and the second pushing block is 130-170 degrees.

Preferably, a third roller is arranged at the swinging end of the second presser foot lifting crank;

the presser foot lifting mechanism comprises a reversing lever and a push rod, the reversing lever is hinged on a shell of the lockstitch sewing machine, and the push rod is vertically arranged in the shell and is restrained to move vertically;

one end of the reversing lever is connected with the presser foot assembly through a pull rod, and the other end of the reversing lever is hinged with the ejector rod; a lifting frame is fixedly arranged in the middle of the ejector rod, and a lifting abutting part is arranged at the lower side of the lifting frame; and the roller of the second presser foot lifting crank is abutted against the lifting abutting part and drives the lifting frame to move up and down.

Preferably, the swinging end of the second thread cutting crank is hinged with a thread cutting connecting rod, the lower end of the thread cutting connecting rod is hinged with a third thread cutting crank, the third thread cutting crank is fixedly arranged on a thread cutting shaft, and the thread cutting shaft drives the thread cutting assembly.

Preferably, the first thread cutting crank and the first presser foot lifting crank are arranged at a certain included angle;

the first roller of the first thread cutting crank is positioned at the lower side of the rotation center of the executing cam;

the roller II of the first presser foot lifting crank is positioned on the upper side of the rotation center of the execution cam;

the second transmission rod piece, the first presser foot lifting crank and the second presser foot lifting crank are welded into a whole; or the second transmission rod piece, the first presser foot lifting crank and the second presser foot lifting crank are integrally formed;

the execution motor is arranged on one side of the shell far away from the machine head; and a motor shaft of the execution motor extends towards the machine head direction, and the motor shaft extends into the middle part of the execution cam and drives the execution cam.

A lockstitch machine comprising a joint transmission structure of any preceding claim. Compared with the prior art, the utility model has the following outstanding and beneficial technical effects:

in the technical scheme, one stepping motor drives three reverse stitching mechanisms, a thread trimming mechanism and a presser foot lifting mechanism to realize three actions; the structure has fewer changed parts on the original general three-automatic lockstitch sewing machine;

the technical scheme can reuse the mature open oil pan without specially designing the closed oil pan;

according to the technical scheme, the linkage effect of three mechanisms can be realized by only changing fewer cranks, connecting shafts and connecting rods; the modification to the housing is also less, and is common to the previous assembly and functions.

Drawings

Fig. 1 is an overall schematic view of the flush joint machine of the present utility model.

Fig. 2 is a schematic illustration of the co-operating of the present utility model with the remaining mechanism.

Fig. 3 is one of schematic views of the joint transmission structure of embodiment 1.

Fig. 4 is a second schematic view of the joint transmission structure of embodiment 1.

Fig. 5 is a schematic view of the joint transmission structure of embodiment 1 cooperating with the thread cutting mechanism and the presser foot lifting mechanism.

Fig. 6 is a schematic transmission diagram of the thread cutting mechanism and the presser foot lifting mechanism of embodiment 1.

Fig. 7 is a schematic view of the joint transmission structure of embodiment 2.

Fig. 8 is a schematic view of the joint transmission structure of embodiment 2 in a first extreme position of the stitch length adjustment area.

Fig. 9 is a second extreme position schematic of the joint transmission structure of embodiment 2 in the stitch length adjustment area.

Fig. 10 is a schematic view of the joint transmission structure of embodiment 2 in a maximum wire cutting position.

Fig. 11 is a schematic view of a counter-clockwise rotation forced return wire cutting mechanism of the joint transmission structure of embodiment 2.

Fig. 12 is a schematic view of the joint transmission structure of embodiment 2 in the maximum position of the presser foot lifting.

Fig. 13 is a schematic view of the combined transmission structure clockwise rotation forced resetting thread cutting mechanism of embodiment 2.

Fig. 14 is a schematic view of the integrated molding of the presser foot lifting crank and the second transmission link of embodiment 3.

Reference numerals:

1-a housing; 11-a first transmission rod piece; 12-an execution cam; 121-a first work surface; 122-a second work surface; 13-a second transmission rod piece; 14-a first push block; 15-a second push block; 16-included angle;

2-a presser foot lifting mechanism; 21-lifting a presser foot crank I; 22-lifting a second presser foot crank; 23-a second roller; 24-reversing lever; 25-ejector rods; 26-a pull rod; 27-lifting frames; 28-lifting the abutment; 29-a roller III;

3-a wire cutting mechanism; 31-first wire cutting crank; 32-a second wire cutting crank; 33-a wire cutting crank III; 34-roller one; 35-reset protrusion; 36-resetting the push rod; 37-a guide curve; 38-cutting the spool; 39-a wire cutting connecting rod;

4-a reverse stitching mechanism; 41-swinging seat; 42-backstitch adjusting connecting rod;

5-executing a motor; 51-a motor shaft;

6-upper shaft; 7-cloth feeding shaft.

Detailed Description

The following are specific embodiments of the present utility model, and the technical solutions of the present utility model will be further described with reference to the accompanying drawings, but the present utility model is not limited to these embodiments.

Embodiment one:

a joint transmission structure of a flat sewing machine as shown in fig. 1-6 comprises

A presser foot lifting mechanism 2 for lifting a presser foot of the lockstitch sewing machine;

a thread cutting mechanism 3 for cutting off a sewing thread of the lockstitch sewing machine;

a backstitch mechanism 4 for controlling the motion of a feed dog of the lockstitch sewing machine;

and also comprises

The execution cam 12 is provided with a work curve on its side, the work curve including a first work curve 121 and a second work curve 122. The first work curved surface 121 and the second work curved surface 122 are connected smoothly, the first work curved surface 121 is an arc surface, the center of the arc surface is consistent with the rotation center of the execution cam 12, and the second work curved surface 122 is a cam surface protruding to one side.

The first transmission rod piece 11 is rotatably installed in the shell 1 of the lockstitch sewing machine, the first transmission rod piece 11 is horizontally arranged transversely, one end of the first transmission rod piece 11 is close to the executing cam 12, and the other end extends towards the machine head direction of the lockstitch sewing machine.

And the first thread cutting crank 31 is arranged at one end of the first transmission rod 11 close to the execution cam 12, and the first thread cutting crank 31 is matched with the working curved surface of the execution cam 12 to finish transmission.

And the second thread cutting crank 32 is arranged at one end, close to the machine head direction, of the first transmission rod piece 11, and the second thread cutting crank 32 is used for driving the thread cutting mechanism 3 to execute actions. The first transmission rod piece 11, the first wire cutting crank 31 and the second wire cutting crank 32 are of an integrated structure or an assembled structure; the integrated structure is formed by integrally forming three parts, and the assembled structure is formed by welding or bolting the three parts;

the second transmission rod piece 13 is sleeved outside the first transmission rod piece 11; the second transmission rod member 13 is horizontally arranged, one end of the second transmission rod member 13 is close to the executing cam 12, the other end extends towards the machine head direction of the flat knitting machine, and two ends of the first transmission rod member 11 are respectively exposed out of the second transmission rod member 13. In the implementation, the second transmission rod piece is of a shaft sleeve structure;

the first presser crank 21 is arranged at one end of the second transmission rod 13 close to the execution cam 12, and the first presser crank 21 is matched with the working curved surface of the execution cam 12 for transmission.

The second presser foot lifting crank 22 is arranged at one end of the second transmission rod piece 13 close to the machine head direction; the second presser foot lifting crank 22 is used for driving the presser foot lifting mechanism 2. And due to the arrangement of the second transmission rod piece 13, a fixed distance can be kept between the first presser foot lifting crank 21 and the second presser foot lifting crank 22, so that the first presser foot lifting crank 21 can be stably matched with the executing cam 12. The second transmission rod piece 13, the first presser foot lifting crank 21 and the second presser foot lifting crank 22 are of an integrated structure or an assembled structure;

the reverse joint adjusting link 42 has an upper end hinged to one side of the actuator cam 12 and a lower end hinged to the swing seat 41 of the reverse joint mechanism 4. When the cam 12 is rotated, the reverse joint adjusting connecting rod 42 is driven to displace, so that the reverse joint mechanism 4 is driven to work.

An execution motor 5 mounted on the housing 1 of the lockstitch sewing machine and used for driving an execution cam 12.

The upper shaft 6 is used for connecting an upper shaft motor so as to drive the puncture needle mechanism to work. And the cloth feeding shaft 7 is used for executing cloth feeding action so as to complete sewing work in cooperation with other mechanisms.

Because the presser foot lifting mechanism 2, the thread trimming mechanism 3 and the backstitch mechanism 4 in the technical scheme are all driven by the execution cam 12, the operation that only one stepping motor is used for driving three mechanisms is realized, the precision of matching among different actions is improved, the number of required components of the lockstitch sewing machine is reduced, and the production cost is reduced.

Further, the structure in this technical scheme is few in the position of changing on three automatic lockstitch sewing machine of original general pattern, consequently can use the position of current lockstitch sewing machine to upgrade and reform transform, need not to make new part, very big improvement the multiplexing rate of current part, simultaneously, this technical scheme can reuse ripe open-type food tray, need not to design closed food tray specially, also further reduced the manufacturing cost of this product.

According to the technical scheme, the linkage effect of three mechanisms can be achieved by only changing fewer cranks, connecting shafts and connecting rods. The machine shell 1 is less in change, is generally used for the previous assembly and functions, and is convenient for comprehensively upgrading and reforming the existing large-scale column-mounted lockstitch sewing machine.

As shown in fig. 1 to 6, the rotation area of the execution cam 12 includes a backstitch area, a thread cutting area, and a presser foot lifting area;

when the executing cam 12 is positioned in the reverse joint area, the first thread cutting crank 31 and the first presser foot lifting crank 21 are matched with the first working curved surface 121;

when the executing cam 12 is positioned in the thread cutting area, the thread cutting crank I31 is matched with the second working curved surface 122; the first presser foot lifting crank 21 is matched with the first working curved surface 121;

when the execution cam 12 is in the presser foot lifting region, the first presser foot lifting crank 21 is matched with the second working curved surface 122, and the first thread cutting crank 31 is matched with the first working curved surface 121.

As shown in fig. 1-6, in the process that the executing cam 12 enters the presser foot lifting area from the thread trimming area, after the roller one 34 of the thread trimming crank one 31 passes over the highest angle point of the second working curved surface 122, at this time, the thread trimming crank one 31 and the presser foot lifting crank one 21 are jointly located on the area corresponding to the second working curved surface 122, so that the thread trimming crank one 31 and the presser foot lifting crank one 21 can continuously follow the second working curved surface 122.

As shown in fig. 1-6, the swinging ends of the first thread trimming crank 31 and the first presser foot lifting crank 21 are matched with the executing cam 12, and the swinging ends of the first thread trimming crank 31 and the first presser foot lifting crank 21 are respectively provided with a roller, wherein the swinging end of the first thread trimming crank 31 is connected with a roller 34, the swinging end of the first presser foot lifting crank 21 is connected with a roller 23, and the wheel surfaces of the roller 34 and the roller 23 are abutted against the working curved surface of the executing cam 12, so that the roller 34 and the roller 23 can be driven to synchronously move when the executing cam 12 rotates.

As shown in fig. 1 to 6, a forced return structure is provided between the first wire cutting crank 31 and the execution cam 12.

In this embodiment, the specific structure of the forced reset structure is: a reset protrusion 35 is arranged on one side of the first thread cutting crank 31; in the process of executing the thread cutting action by the thread cutting crank I31, the reset protrusion 35 enters the rotating area of the executing cam 12; when the wire cutting mechanism 3 is blocked by external force and can not reset in time, the reset protrusion 35 is pushed and the wire cutting mechanism 3 is reset along with the rotation of the execution cam 12, so that the wire cutting mechanism 3 can continue to work normally.

As shown in fig. 1-6, the swinging end of the second presser foot lifting crank 22 is provided with a third roller 29.

The presser foot lifting mechanism 2 comprises a reversing lever 24 and a push rod 25, wherein the reversing lever 24 is hinged on the shell 1 of the lockstitch sewing machine, and the push rod 25 is vertically arranged in the shell 1 and is restrained to move vertically.

One end of the reversing lever 24 is connected with the presser foot assembly through a pull rod 26, and the other end of the reversing lever 24 is hinged with a push rod 25. A lifting frame 27 is fixedly arranged in the middle of the ejector rod 25, and a lifting abutting part 28 is arranged on the lower side of the lifting frame 27. The third roller 29 connected with the second presser crank 22 is abutted against the lifting abutting part 28 and drives the lifting frame 27 to move up and down.

As shown in fig. 1-6, the swinging end of the second thread cutting crank 32 is hinged with a thread cutting connecting rod 39, the lower end of the thread cutting connecting rod 39 is hinged with a third thread cutting crank 33, the third thread cutting crank 33 is fixedly arranged on a thread cutting shaft 38, and the thread cutting shaft 38 drives the thread cutting assembly to execute thread cutting action.

As shown in fig. 1 to 6, the first thread cutting crank 31 and the first presser foot lifting crank 21 are arranged at a certain included angle, so that the first roller 34 and the second roller 23 can be abutted against different positions of the executing cam 12, when the executing cam 12 rotates, the first roller 34 and the second roller 23 can move according to different paths when being pushed by the first working curved surface 121 or the second working curved surface 122, and the thread cutting mechanism 3 and the presser foot lifting mechanism 2 are driven to execute different works and are not easy to interfere with each other.

The roller one 34 of the first wire cutting crank 31 is positioned at the lower side of the rotation center of the execution cam 12;

the roller two 23 of the presser foot crank one 21 is located on the upper side of the rotation center of the execution cam 12.

The execution motor 5 is arranged on one side of the shell 1 far away from the machine head; the motor shaft of the execution motor 5 extends towards the machine head direction, and the motor shaft extends into the middle part of the execution cam 12 and drives the execution cam 12.

A flat seaming machine comprises a joint transmission structure of the flat seaming machine.

Embodiment two:

as shown in fig. 7 to 13, in the present embodiment, the specific structure of the forced reset structure is: a reset push rod 36 extends from one side of the first wire cutting crank 31. One side of the execution cam 12 is provided with a first pushing block 14, the first pushing block 14 and the reset push rod 36 are on the same plane, and when the execution cam 12 rotates, the first pushing block 14 can push the reset push rod 36 to move.

During the thread cutting operation of the first thread cutting crank 31, the reset push rod 36 enters the rotation area of the first push block 14. When the wire cutting mechanism 3 is jammed by an external force and cannot be reset, the execution cam 12 can push the reset push rod 36 and reset the wire cutting mechanism 3.

As shown in fig. 7 to 13, a second pushing block 15 is further provided on the opposite side of the execution cam 12 from the first pushing block 14, and the first pushing block 14, the second pushing block 15 and the reset pushing rod 36 are all on the same plane.

The outer end of the reset push rod 36 is provided with a guide curved surface 37, and when the first push block 14 and the second push block 15 rotate along with the execution cam 12, the first push block 14 and the second push block 15 can be released from the guide curved surface 37 and push the reset push rod 36, so that the thread cutting mechanism 3 is reset.

When the executing cam 12 enters the presser foot lifting area from the thread cutting area, the first pushing block 14 passes through the rotating area of the reset push rod 36, and when the thread cutting mechanism 3 is blocked by external force and cannot be reset, the first pushing block 14 pushes the reset push rod 36 and resets the thread cutting mechanism 3.

When the execution cam 12 enters the presser foot lifting area from the reverse stitching area, the second pushing block 15 passes through the rotating area of the reset push rod 36, and when the thread cutting mechanism 3 is blocked by external force and cannot be reset, the second pushing block 15 pushes the reset push rod 36 and resets the thread cutting mechanism 3.

An included angle 16 is formed between the positions where the first pushing block 14 and the second pushing block 15 are arranged, and the preferable angle of the included angle 16 is 130-170 degrees.

Embodiment III:

as shown in fig. 3, 4 and 14, further, the second transmission rod 13, the first presser foot lifting crank 21 and the second presser foot lifting crank 22 may be welded as a whole, or the second transmission rod 13, the first presser foot lifting crank 21 and the second presser foot lifting crank 22 may be integrally formed.

Therefore, the assembly can be conveniently carried out during the assembly, and the synchronous rotation between the first presser crank 21 and the second presser crank 22 can be better ensured, so that the accuracy during the working is improved.

The above embodiments are only preferred embodiments of the present utility model, and are not intended to limit the scope of the present utility model in this way, therefore: all equivalent changes in structure, shape and principle of the utility model should be covered in the scope of protection of the utility model.

Claims (10)

1. A joint transmission structure of a flat sewing machine comprises

A presser foot lifting mechanism (2) for lifting a presser foot of the lockstitch sewing machine;

a thread cutting mechanism (3) for cutting off a sewing thread of the lockstitch sewing machine;

a backstitch mechanism (4) for controlling the action of the feed dog of the lockstitch sewing machine;

the method is characterized in that: and also comprises

An execution cam (12) whose side is provided with a working surface including a first working surface (121) and a second working surface (122); the first working curved surface (121) and the second working curved surface (122) are connected in a smooth manner; the first working curved surface (121) is an arc surface, and the center of the arc surface is consistent with the rotation center of the executing cam (12); the second working curved surface (122) is a cam surface protruding to one side;

the first transmission rod piece (11) is rotatably arranged in the shell (1) of the flat seaming machine; the first transmission rod piece (11) is horizontally arranged transversely, one end of the first transmission rod piece (11) is close to the execution cam (12), and the other end extends towards the machine head direction of the flat seaming machine;

the first thread cutting crank (31) is arranged at one end, close to the executing cam (12), of the first transmission rod piece (11), and the first thread cutting crank (31) is matched with the working curved surface of the executing cam (12) for transmission;

a second wire cutting crank (32) which is arranged at one end of the first transmission rod piece (11) close to the machine head direction; the second thread cutting crank (32) drives the thread cutting mechanism (3); the first transmission rod piece (11), the first wire cutting crank (31) and the second wire cutting crank (32) are of an integrated structure or an assembled structure;

the second transmission rod piece (13) is sleeved outside the first transmission rod piece (11); the second transmission rod piece (13) is horizontally arranged transversely, one end of the second transmission rod piece (13) is close to the execution cam (12), and the other end extends towards the machine head direction of the flat seaming machine; two ends of the first transmission rod piece (11) are respectively exposed out of the second transmission rod piece (13);

the first presser foot lifting crank (21) is arranged at one end, close to the execution cam (12), of the second transmission rod (13), and the first presser foot lifting crank (21) is matched and transmitted with the working curved surface of the execution cam (12);

the presser foot lifting crank II (22) is arranged at one end, close to the machine head direction, of the second transmission rod piece (13); the presser foot lifting crank II (22) is used for driving the presser foot lifting mechanism (2); the second transmission rod piece (13), the first presser foot lifting crank (21) and the second presser foot lifting crank (22) are of an integrated structure or an assembled structure;

a reverse joint adjusting connecting rod (42), the upper end of which is hinged on one side of the executing cam (12), and the lower end of which is hinged on a swinging seat (41) of the reverse joint mechanism (4);

an actuator motor (5) mounted on the housing (1) of the sewing machine and adapted to drive the actuator cam (12).

2. The joint transmission structure of a lockstitch sewing machine according to claim 1, wherein: the rotating area of the executing cam (12) comprises a reverse stitching area, a thread trimming area and a presser foot lifting area;

when the executing cam (12) is positioned in the reverse stitching area, the first thread cutting crank (31) and the first presser foot lifting crank (21) are matched with the first working curved surface (121);

when the executing cam (12) is positioned in the thread cutting area, the thread cutting crank I (31) is matched with the second working curved surface (122); the first presser foot lifting crank (21) is matched with the first working curved surface (121);

when the executing cam (12) is positioned in the presser foot lifting area, the first presser foot lifting crank (21) is matched with the second working curved surface (122), and the first thread cutting crank (31) is matched with the first working curved surface (121).

3. The joint transmission structure of a lockstitch sewing machine according to claim 2, wherein: and in the process that the executing cam (12) enters the presser foot lifting area from the thread cutting area, after the roller I (34) of the thread cutting crank I (31) passes through the highest angle point of the second working curved surface (122), the thread cutting crank I (31) and the presser foot lifting crank I (21) are positioned on the second working curved surface (122) together, and the thread cutting crank I (31) and the presser foot lifting crank I (21) continuously follow the second working curved surface (122).

4. The joint transmission structure of a lockstitch sewing machine according to claim 1, wherein: the swinging ends of the first thread cutting crank (31) and the first presser foot lifting crank (21) are matched with the executing cam (12), the swinging ends are provided with rollers, and the surfaces of the rollers are abutted against the working curved surface of the executing cam (12).

5. The joint transmission structure of a lockstitch sewing machine according to claim 2, wherein: a forced reset structure is arranged between the first thread cutting crank (31) and the executing cam (12);

the specific structure of the forced reset structure is as follows: a reset protrusion (35) is arranged on one side of the first thread cutting crank (31); in the process of executing the thread cutting action by the thread cutting crank I (31), a reset protrusion (35) enters a rotating area of the executing cam (12); when the thread cutting mechanism (3) is blocked by external force and cannot reset, the executing cam (12) pushes the reset protrusion (35) and resets the thread cutting mechanism (3);

or, the specific structure of the forced reset structure is as follows: a reset push rod (36) extends from one side of the first wire cutting crank (31); a first pushing block (14) is arranged on one side of the execution cam (12), and the first pushing block (14) and the reset push rod (36) are positioned on the same plane; in the process of executing the thread cutting action by the thread cutting crank I (31), a reset push rod (36) enters a rotating area of the first pushing block (14); when the wire cutting mechanism (3) is blocked by external force and cannot reset, the executing cam (12) pushes the reset push rod (36) and resets the wire cutting mechanism (3).

6. The joint transmission structure of a lockstitch sewing machine of claim 5, wherein: a second pushing block (15) is further arranged on one side of the first pushing block (14); the first pushing block (14), the second pushing block (15) and the reset push rod (36) are all positioned on the same plane; the outer end part of the reset push rod (36) is provided with a guide curved surface (37);

when the executing cam (12) enters the presser foot lifting area from the thread cutting area, the first pushing block (14) passes through the rotating area of the reset push rod (36), and when the thread cutting mechanism (3) is blocked by external force and can not be reset, the first pushing block (14) pushes the reset push rod (36) and resets the thread cutting mechanism (3);

when the execution cam (12) enters the presser foot lifting area from the reverse stitching area, the second pushing block (15) passes through the rotating area of the reset push rod (36), and when the thread cutting mechanism (3) is blocked by external force and can not be reset, the second pushing block (15) pushes the reset push rod (36) and resets the thread cutting mechanism (3);

the included angle (16) between the first pushing block (14) and the second pushing block (15) is 130-170 degrees.

7. The joint transmission structure of a lockstitch sewing machine according to claim 1, wherein: a third roller (29) is arranged at the swinging end of the second presser foot lifting crank (22);

the presser foot lifting mechanism (2) comprises a reversing lever (24) and a push rod (25), wherein the reversing lever (24) is hinged on a shell (1) of the lockstitch sewing machine, and the push rod (25) is vertically arranged in the shell (1) and is restrained to vertically move;

one end of the reversing lever (24) is connected with the presser foot assembly through a pull rod (26), and the other end of the reversing lever (24) is hinged with the ejector rod (25); a lifting frame (27) is fixedly arranged in the middle of the ejector rod (25), and a lifting abutting part (28) is arranged at the lower side of the lifting frame (27); and a roller III (29) of the presser foot lifting crank II (22) is abutted against the lifting abutting part (28) and drives the lifting frame (27) to move up and down.

8. The joint transmission structure of a lockstitch sewing machine according to claim 1, wherein: the swinging end of the second thread cutting crank (32) is hinged with a thread cutting connecting rod (39), the lower end of the thread cutting connecting rod (39) is hinged with the third thread cutting crank (33), the third thread cutting crank (33) is fixedly arranged on a thread cutting shaft (38), and the thread cutting shaft (38) drives the thread cutting assembly.

9. The joint transmission structure of a lockstitch sewing machine according to claim 2, wherein: the first thread cutting crank (31) and the first presser foot lifting crank (21) are arranged at a certain included angle;

the roller I (34) of the thread cutting crank I (31) is positioned at the lower side of the rotation center of the executing cam (12);

a roller II (23) of the presser foot lifting crank I (21) is positioned on the upper side of the rotation center of the execution cam (12);

the execution motor (5) is arranged on one side of the shell (1) away from the machine head; the motor shaft of the execution motor (5) extends towards the machine head direction, and the motor shaft extends into the middle of the execution cam (12) and drives the execution cam (12).

10. A flush joint machine, characterized in that: a joint transmission structure comprising the lockstitch machine of any one of claims 1-9.