CN216141714U

CN216141714U - Novel presser foot lifting mechanism of sewing machine and sewing machine

Info

Publication number: CN216141714U
Application number: CN202121778481.0U
Authority: CN
Inventors: 任恩林; 蒋达淼; 周善足
Original assignee: Zhejiang Qishi Electromechanical Technology Co ltd
Current assignee: Zhejiang Qishi Electromechanical Technology Co ltd
Priority date: 2021-07-31
Filing date: 2021-07-31
Publication date: 2022-03-29
Anticipated expiration: 2031-07-31

Abstract

The utility model belongs to the technical field of sewing equipment, and particularly relates to a novel presser foot lifting mechanism of a sewing machine and the sewing machine, which comprise a presser foot lifting assembly and a stepping motor, wherein the presser foot lifting assembly is connected with a presser foot rod, and the novel presser foot lifting mechanism also comprises a presser foot lifting cam, which is fixed on a motor shaft of the stepping motor and driven by the stepping motor; the pressure foot lifting connecting rod is provided with a butting seat, and the lower end of the butting seat is butted against the wheel surface of the pressure foot lifting cam; the upper end of the pressure foot lifting connecting rod is connected with the pressure foot lifting assembly. According to the utility model, through the structure of the linkage shaft sleeve, the thread cutting action and the presser foot lifting action are realized through the forward and reverse rotation of the single stepping motor, and the first motor is arranged on one side of the sewing machine shell, so that the sewing machine does not occupy the internal volume of the sewing machine, the installation is convenient, the integral layout is simple, and the matching performance among all parts is good.

Description

Novel presser foot lifting mechanism of sewing machine and sewing machine

Technical Field

The utility model belongs to the technical field of sewing equipment, and particularly relates to a novel presser foot lifting mechanism of a sewing machine and the sewing machine.

Background

The Chinese patent application CN201910097866 discloses a thread trimming and presser foot lifting and needle sealing device of a sewing machine and the sewing machine, which comprises a power part, a thread trimming cam and a transmission assembly, wherein the power part drives the thread trimming cam and the transmission assembly to synchronously rotate, the transmission assembly drives a presser foot lifting and needle sealing driving shaft to rotate, the presser foot lifting and needle sealing driving shaft is provided with a presser foot lifting crank and a needle sealing cam, a thread trimming contour surface on the thread trimming cam can be matched with a thread trimming ball on the thread trimming driving crank, the thread trimming driving crank is driven to rotate and drives a thread trimming mechanism to execute thread trimming actions, the rotation of the presser foot lifting crank can drive the presser foot lifting mechanism to execute the presser foot lifting actions, and the needle sealing contour surface on the needle sealing cam can drive a needle distance adjusting mechanism to execute the needle distance adjusting actions.

The utility model has the following defects:

the motor sets up at sewing machine casing lower extreme, because the whole volume of motor is great, is not convenient for its installation, and can lead to sewing machine internals overall arrangement difficulty.

Disclosure of Invention

The utility model aims to provide a novel presser foot lifting mechanism of a sewing machine, which has simple layout and easy assembly and can finely adjust the height of a presser foot.

The purpose of the utility model is realized as follows:

a novel presser foot lifting mechanism of a sewing machine comprises a presser foot lifting component and a stepping motor, wherein the presser foot lifting component is connected with a presser foot rod, and the novel presser foot lifting mechanism further comprises

The pressure lifting pin cam is fixed on a motor shaft of the stepping motor and is driven by the stepping motor;

the pressure foot lifting connecting rod is provided with a butting seat, and the lower end of the butting seat is butted against the wheel surface of the pressure foot lifting cam; the upper end of the pressure foot lifting connecting rod is connected with the pressure foot lifting assembly.

Further, the upper end of the presser foot lifting connecting rod is provided with a fine adjustment assembly, which comprises

The outer end of the driving block is connected with the pressure foot lifting assembly, and a threaded hole is formed in the driving block;

the adjusting bolt is rotatably arranged in the threaded hole; the lower end of the adjusting bolt is fixedly connected with the upper end of the pressure foot lifting connecting rod.

Furthermore, a spring is sleeved on the adjusting bolt, and the upper end and the lower end of the spring are respectively abutted to the head of the adjusting bolt and the driving block.

Furthermore, two pressure foot lifting cams are arranged on a motor shaft of the stepping motor in a front-back mode respectively, and a limiting groove is formed between the two pressure foot lifting cams; the pressure foot lifting connecting rod is arranged in the limiting groove.

Furthermore, the left side and the right side of the abutting seat are respectively provided with an abutting boss extending downwards, and the two abutting bosses are respectively abutted against one side plane of the two pressure foot lifting cams.

A sewing machine comprises a feeding shaft, a feed lifting shaft and a thread cutting assembly, and is characterized by further comprising the novel presser foot lifting mechanism and

the linkage shaft sleeve is sleeved on the feeding shaft and driven by the first motor to swing; a second crank is fixed at one end of the linkage shaft sleeve;

the thread cutting crank is driven by the swinging part of the second crank; the thread cutting crank is fixed on a thread cutting shaft of the thread cutting assembly.

Furthermore, the pressure foot lifting cam and the abutting seat, and the swinging part of the second crank and the thread cutting crank can be intermittently separated;

when the presser foot lifting cam drives the abutting seat, the swinging part of the second crank is separated from the thread trimming crank;

when the swinging part of the second crank drives the thread trimming crank, the pressure foot lifting cam is separated from the abutting seat.

Further, a strip-shaped groove is formed in the thread cutting crank, and an opening is formed in one end of the strip-shaped groove;

the swinging part of the second crank slides in the strip-shaped groove and drives the thread trimming crank;

when the presser foot lifting cam drives the abutting seat, the swinging part of the second crank is separated from the thread trimming crank from the opening.

Furthermore, a first crank is fixed at the other end of the linkage shaft sleeve and connected with a driving connecting rod; a motor crank is fixed on a motor shaft of the first motor, and two ends of the driving connecting rod are respectively connected with the motor crank and the first crank.

Furthermore, one side of the motor crank is also provided with a connecting plate, an installation shaft which is axially opposite to a motor shaft of the first motor is connected with the connecting plate, and the installation shaft is provided with the presser foot lifting cam.

Compared with the prior art, the utility model has the outstanding and beneficial technical effects that:

according to the utility model, through the structure of the linkage shaft sleeve, the thread cutting action and the presser foot lifting action are realized through the forward and reverse rotation of the single stepping motor, and the first motor is arranged on one side of the sewing machine shell, so that the sewing machine does not occupy the internal volume of the sewing machine, the installation is convenient, the integral layout is simple, and the matching performance among all parts is good. Meanwhile, the intermittent separation structure between the presser foot lifting cam and the abutting seat and between the swinging part of the second crank and the thread cutting crank is used for separating the thread cutting action from the presser foot lifting action, so that the synchronous operation of the thread cutting action and the presser foot lifting action is prevented from influencing the use of the sewing machine.

The presser foot lifting assembly is also provided with a fine adjustment assembly, when the presser foot lifting cam or the abutting seat is worn for a long time, the gap between the presser foot lifting cam and the abutting seat is increased, so that the presser foot cannot be lifted to the original height, and a user can rotate the adjusting bolt downwards to enable the presser foot lifting connecting rod to move downwards to reduce the distance between the abutting block and the presser foot lifting cam, so that the lifting height difference caused by the abrasion of the presser foot lifting cam or the abutting seat is compensated.

The two pressure foot lifting cams are arranged, a limiting groove is formed between the two pressure foot lifting cams, and the left side and the right side of the abutting seat are provided with the abutting bosses extending downwards; the pressure foot lifting connecting rod is prevented from deviating to one side during working through the limiting groove and the abutting boss, so that the pressure foot lifting is influenced.

Drawings

FIG. 1 is a schematic view of the structure of the sewing machine of the present invention.

Fig. 2 is a schematic structural view of the linkage shaft sleeve.

Fig. 3 is an exploded view of the linkage sleeve.

Fig. 4 is an exploded view at the lift foot link.

Fig. 5 is an enlarged view at a in fig. 2.

The reference numerals in the figures denote the meanings:

1. a feed shaft; 2. a feed lifting shaft; 3. lifting the presser foot assembly; 31. a presser bar; 4. a thread trimming assembly; 41. a thread cutting shaft; 5. a first motor; 51. a motor shaft; 52. a motor crank; 53. a drive link; 54. connecting plates; 55. Installing a shaft; 6. a linkage shaft sleeve; 61. a first crank; 7. a second crank; 71. a swing portion; 81. lifting a presser foot cam; 82. a support seat; 83. lifting a presser foot connecting rod; 84. a drive block; 85. a threaded hole; 86. adjusting the bolt; 87. a spring; 88. a limiting groove; 89. abutting against the boss; 9. a thread cutting crank; 91. a strip-shaped groove; 92. An opening; 10. a second motor; 11. and a needle pitch adjusting component.

Detailed Description

The utility model is further described below with reference to specific examples:

a sewing machine comprises a feeding shaft 1, a feed lifting tooth shaft 2, a presser foot lifting component 3, a thread cutting component 4 and a novel presser foot lifting mechanism;

as shown in fig. 1, the feeding shaft 1 and the feed lifting rock shaft 2 are used for driving the feed lifting rock assembly to rotate in a reciprocating and circumferential manner so as to feed the feed lifting rock; the presser foot lifting assembly 3 is used for lifting a presser foot, the left end of the presser foot lifting assembly is connected with a presser foot rod 31 of the sewing machine, the presser foot rod 31 is driven by the presser foot, and the right end of the presser foot lifting assembly 3 is connected with a presser foot lifting connecting rod 83 which is longitudinally arranged; the thread trimming component 4 is arranged on one side of the feed lifting tooth component, and thread trimming is carried out by driving a moving knife in the thread trimming component 4 to move towards one side of a top knife. The tooth lifting component, the thread trimming component 4 and the presser foot lifting component 3 are all of the existing structures, and redundant description is not repeated; first motor 5 is step motor, and it sets up in the whole one side that leans on the right side of sewing machine casing, and its installation is comparatively easy, and just the inside part overall arrangement of sewing machine influences lessly.

Further, the device also comprises a linkage shaft sleeve 6 which is sleeved on the feeding shaft 1 and driven by the first motor 5 to swing; a second crank 7 is fixed at one end of the linkage shaft sleeve 6;

the thread cutting crank 9 is driven by the swinging part 71 of the second crank 7; the thread cutting crank 9 is fixed to the thread cutting spool 41 of the thread cutting assembly 4.

The presser foot lifting convex mechanism comprises a presser foot lifting cam 81, is fixed on a motor shaft 51 of the first motor 5 and is driven by the first motor 5 to swing; a pressing foot lifting and lifting cam 81 is provided with a butting seat 82 at the upper side, the lower end of the butting seat 82 butts against the wheel surface of the pressing foot lifting cam 81, a pressing foot lifting connecting rod 83 is fixed on the butting seat 82, and the upper end of the pressing foot lifting connecting rod 83 is connected with the pressing foot lifting assembly 3;

as shown in fig. 2, a first crank 61 is fixed at the other end of the linkage shaft sleeve 6, and the first crank 61 is connected with a driving connecting rod 53; a motor crank 52 is fixed on a motor shaft 51 of the first motor 5, and two ends of the driving connecting rod 53 are respectively connected with the motor crank 52 and the first crank 61. A bearing piece which enables the linkage shaft sleeve 6 to rotate on the feeding shaft 1 is arranged between the linkage shaft sleeve 6 and the feeding shaft 1, so that the linkage shaft sleeve 6 does not rotate along with the rotation of the feeding shaft 1, and the linkage shaft sleeve 6 is driven to rotate only by the first motor 5; referring to fig. 2 and 3, the first crank 61 and the second crank 7 are integrally formed or clamped on two sides of the linking shaft sleeve 6, wherein the first crank 61 is fixed on the left side of the linking shaft sleeve 6 and is arranged close to the first motor 5, and the second crank 7 is fixed on the right side of the linking shaft sleeve 6 through a clamping structure.

The sewing machine further comprises a second motor 10, wherein the second motor 10 is located on the right side of the sewing machine shell and is used for driving the needle pitch adjusting assembly 11 and driving the feeding shaft 1 to swing back and forth through the needle pitch adjusting assembly 11. The needle pitch adjusting assembly 11 is arranged on the feeding shaft 18, the needle pitch adjusting assembly 11 comprises an adjusting swing seat, a first connecting rod, a second connecting rod and an adjusting connecting rod, the adjusting swing seat, the first connecting rod, the second connecting rod and the adjusting connecting rod are sequentially connected, and the adjusting connecting rod is connected with a sewing machine main shaft; the second motor 10 is connected with the adjusting swing seat, and drives the adjusting connecting rod to adjust the needle pitch by driving the adjusting swing seat to work. According to the utility model, the needle pitch adjustment and the operation of lifting the presser foot and cutting the thread are respectively carried out through the first motor 5 and the second motor 10, and the tooth lifting action, the presser foot lifting action and the thread cutting action of the sewing machine are independently operated and do not interfere with each other through the linkage shaft sleeve 6, so that the number of parts is greatly reduced, the cost is reduced, and the assembly difficulty is reduced.

Specifically, when the thread trimming device works, the pressure lifting and pressing foot cam 81 and the abutting seat 82, and the swinging part 71 of the second crank 7 and the thread trimming crank 9 can be intermittently separated;

when the presser foot lifting cam 81 drives the presser foot seat 82, the swinging part 71 of the second crank 7 is separated from the thread trimming crank 9;

when the swinging part 71 of the second crank 7 drives the trimming crank 9, the pressure foot lifting cam 81 is separated from the abutting seat 82.

As shown in fig. 2 and 3, one end of the motor crank 52 is provided with a hoop, the hoop is integrally formed with the motor crank 52, and the motor crank 52 is fixed on the motor shaft 51 of the first motor 5 through the hoop; one side of the motor crank 52 is provided with a link plate 54 disposed axially, a mounting shaft 55 is connected to the link plate 54, the mounting shaft 55 axially faces the motor shaft 51 of the first motor 5, and the mounting shaft 55 is integrally formed with the link plate 54 and the motor crank 52, the link plate 54 supports the mounting shaft 55 on the outer side of the motor crank 52, and a space for placing the driving link 53 is formed between the motor crank 52 and the mounting shaft 55.

The mounting shaft 55 is integrally formed with the pressure raising and pressing foot cam 81, the upper side of the pressure raising and pressing foot cam 81 is provided with a resisting seat 82, the lower end of the resisting seat 82 is abutted against the wheel surface of the pressure raising and pressing foot cam 81, a pressure raising and pressing foot connecting rod 83 is fixed on the resisting seat 82, and the pressure raising and pressing foot connecting rod 83 is longitudinally arranged and is connected with the pressure raising and pressing foot assembly 3. In the utility model, the convex part on the presser foot lifting cam 81 faces the front side of the sewing machine, when the sewing machine works, the first motor 5 rotates upwards to drive the presser foot lifting cam 81 to rotate by a fixed angle, and the convex part of the presser foot lifting cam 81 moves upwards to abut against the lower part of the abutting seat 82, the abutting seat 82 is jacked by the upward rotation of the presser foot lifting cam 81, the abutting seat 82 drives the presser foot lifting connecting rod 83 to ascend, each element of the presser foot lifting assembly 3 is sequentially driven by the ascending of the presser foot lifting connecting rod 83, and finally the presser foot rod 31 is driven to ascend to complete the presser foot lifting; when the presser foot needs to be lowered, the first motor 5 rotates downwards in the reverse direction, so that the non-protruding part of the presser foot lifting cam 81 abuts below the abutting seat 82 or the presser foot lifting cam 81 is directly separated from the abutting seat 82, the abutting seat 82 is lowered, the presser foot rod 31 is lowered, and at the moment, the presser foot rod 31 loses the supporting force for lifting the presser foot rod and is lowered due to the self gravity of the presser foot rod 31, so that the presser foot is lowered.

It should be noted that, in general, the presser bar 31 is provided with an elastic member for pressing the presser foot, and the presser bar 31 is lifted up to lift the presser foot by overcoming the elastic member in the presser foot lifting operation in the sewing machine, whereas when the sewing machine does not lift the presser foot any more, the elastic member presses down the presser bar 31 and simultaneously resets the presser foot lifting assembly 3, and the presser foot lifting assembly 3 is reset to lower the presser foot lifting link 83 to a specified position. In the utility model, because the pressure raising and pressing cam 81 is abutted against the abutting seat 82, a user can adjust the position between the pressure raising and pressing cam 81 and the abutting seat 82, when the pressure raising and pressing cam 81 is not rotated to raise the pressure, the pressure raising and pressing cam 81 is separated from the abutting seat 82, and only when the pressure raising and pressing cam 81 is rotated upwards to enable the convex part on the pressure raising and pressing cam 81 to face the abutting seat 82, the pressure raising and pressing cam 81 is abutted against the abutting seat 82 to raise the pressure due to the position change of the convex part of the pressure raising and pressing cam 81.

The trimming operation in the utility model is also completed by the first motor 5, when trimming, the first motor 5 rotates downwards to drive the motor crank 52 to rotate downwards, the first crank 61 is driven to swing downwards by the driving connecting rod 53, the first crank 61 swings downwards and simultaneously drives the second crank 7 to swing downwards by the linkage shaft sleeve 6, the swing part 71 of the second crank 7 is connected with the trimming crank 9, the trimming component 4 is driven to work by the trimming crank 9, and thus the trimming component 4 is driven to work by the downward movement of the second crank 7 to trim wires.

The swinging part 71 of the second crank 7 and the trimming crank 9 can be intermittently separated by changing the structure of the trimming crank 9, specifically referring to fig. 3 and 5, a strip-shaped groove 91 is arranged on the trimming crank 9, and an opening 92 is arranged at one end of the strip-shaped groove 91; wherein, trimming crank 9 is connected with trimming subassembly 4 through the clamp form, has in clamp side integrated into one piece bar groove 91, bar groove 91 downward sloping setting to be equipped with vertical opening 92, second crank 7's swing portion 71 specifically is the cross axle that sets up at second crank 7 end, and the cross axle is located in bar groove 91, when second crank 7 downswing, through swing portion 71 promotes downwards trimming crank 9 downswing carries out the trimming, and when second crank 7 was upwards, the cross axle upwards swing is followed opening 92 breaks away from bar groove 91 to make trimming crank 9 in second crank 7 phase separation, make both no longer link.

According to the utility model, through the structure of the linkage shaft sleeve 6, the thread cutting action and the presser foot lifting action are realized through the forward and reverse rotation of the single stepping motor, and the first motor 5 is arranged on one side of the sewing machine shell, so that the sewing machine does not occupy the internal volume of the sewing machine, the installation is convenient, the integral layout is simple, and the matching performance among all parts is good. Meanwhile, the intermittent separation structure between the pressure foot lifting cam 81 and the abutting seat 82 and between the swinging part 71 of the second crank 7 and the thread cutting crank 9 realizes the separation of the thread cutting action and the pressure foot lifting action, and prevents the synchronous operation from influencing the use of the sewing machine.

Further, lift presser foot connecting rod 83 upper end and be equipped with fine setting subassembly, include:

the outer end of the driving block 84 is connected with the pressure foot lifting assembly 3, and a threaded hole 85 is formed in the driving block 84;

an adjusting bolt 86 rotatably disposed in the threaded hole 85; the lower end of the adjusting bolt 86 is fixedly connected with the upper end of the pressure foot lifting connecting rod 83.

As shown in fig. 4, the driving block 84 comprises a square connecting block, a connecting rod for connecting the presser foot lifting assembly 3 is arranged on one side of the driving block 84 facing the presser foot lifting assembly 3, and a longitudinal threaded hole 85 is formed in the center of the driving block 84; the adjusting bolt 86 is longitudinally arranged in the driving block 84, and the lower end of the adjusting bolt 86 is provided with a connecting hole which is connected with the upper end of the presser foot lifting connecting rod 83. The fine adjustment assembly is generally used for increasing the gap between the presser foot lifting cam 81 and the abutting seat 82 after the presser foot lifting cam 81 or the abutting seat 82 is worn for a long time, so that the presser foot cannot be lifted to the original height, and a user can rotate the adjusting bolt 86 downwards to enable the presser foot lifting connecting rod 83 to move downwards to reduce the distance between the abutting block and the presser foot lifting cam 81, so as to compensate the lifting height difference caused by the wear of the presser foot lifting cam 81 or the abutting seat 82.

Furthermore, a spring 87 is sleeved on the adjusting bolt 86, the spring 87 abuts between the head of the adjusting bolt 86 and the driving block 84 up and down, and the spring 87 can be used for limiting the maximum adjusting distance, namely when the adjusting bolt 86 is rotated downwards, the upward reaction force of the spring 87 can prompt a user, so that the damage of the pressure raising and pressing foot cam 81 caused by the over-adjustment of the user is prevented.

Furthermore, two pressure raising and pressing foot cams 81 are arranged on the motor shaft 51 of the first motor 5 in a front-back manner, and a limiting groove 88 is formed between the two pressure raising and pressing foot cams 81; the presser foot lifting connecting rod 83 is disposed in the limiting groove 88. Referring to fig. 1 and 4, the two pressure raising and pressing cams 81 are respectively disposed at the front and rear ends of the mounting shaft 55, and the limiting groove 88 is formed between the inner side surfaces of the pressure raising and pressing cams 81; the pressure foot lifting connecting rod 83 has a certain length, is arranged on the abutting seat 82 in a penetrating way, and is connected with the abutting seat 82; when the pressure foot lifting device works, the pressure foot lifting connecting rod 83 is located in the limiting groove 88, and the pressure foot lifting connecting rod 83 is prevented from deviating to one side when working through the limiting groove 88, so that the pressure foot lifting is influenced.

Further, the left side and the right side of the abutting seat 82 are both provided with an abutting boss 89 extending downwards. As shown in fig. 2, the distance between the two abutting bosses 89 can just accommodate the two lifting presser foot cams 81, and when the lifting presser foot cam 81 rotates upwards, the two lifting presser foot cams 81 can be embedded between the two abutting bosses 89, so that the two abutting bosses 89 abut against one side plane of the two lifting presser foot cams 81 respectively; the abutment boss 89 can further limit the pressure foot lifting connecting rod 83, and prevent the pressure foot lifting connecting rod 83 from deviating to one side during working.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, so: all equivalent changes made according to the structure, shape and principle of the utility model are covered by the protection scope of the utility model.

Claims

1. The utility model provides a sewing machine's novel presser foot mechanism of lifting, is including lifting presser foot subassembly (3) and first motor (5), lift presser foot subassembly (3) and be connected with presser bar (31), its characterized in that: also comprises

The pressure raising and pressing foot cam (81) is fixed on a motor shaft (51) of the first motor (5) and is driven by the first motor (5);

the pressure foot lifting connecting rod (83), a butting seat (82) is arranged on the pressure foot lifting connecting rod (83), and the lower end of the butting seat (82) is butted against the wheel surface of the pressure foot lifting cam (81); the upper end of the pressure foot lifting connecting rod (83) is connected with the pressure foot lifting component (3).

2. The novel presser foot lifting mechanism of a sewing machine according to claim 1, characterized in that: the upper end of the presser foot lifting connecting rod (83) is provided with a fine adjustment component, which comprises

The outer end of the driving block (84) is connected with the pressure foot lifting assembly (3), and a threaded hole (85) is formed in the driving block (84);

an adjusting bolt (86) rotatably disposed in the threaded hole (85); the lower end of the adjusting bolt (86) is fixedly connected with the upper end of the presser foot lifting connecting rod (83).

3. The novel presser foot lifting mechanism of a sewing machine according to claim 2, characterized in that: the adjusting bolt (86) is further sleeved with a spring (87), and the upper end and the lower end of the spring (87) are respectively abutted to the head of the adjusting bolt (86) and the driving block (84).

4. The novel presser foot lifting mechanism of a sewing machine according to any one of claims 1 to 3, characterized in that: the two pressure foot lifting cams (81) are respectively arranged on the motor shaft (51) of the first motor (5) in the front-back direction, and a limiting groove (88) is formed between the two pressure foot lifting cams (81); the pressure foot lifting connecting rod (83) is arranged in the limiting groove (88).

5. The novel presser foot lifting mechanism of a sewing machine according to claim 4, characterized in that: the left side and the right side of the abutting seat (82) are respectively provided with an abutting lug boss (89) extending downwards, and the two abutting lug bosses (89) are respectively abutted on one side plane of the two pressure lifting pin cams (81).

6. Sewing machine comprising a feed shaft (1), a feed lifting shaft (2) and a thread cutting assembly (4), characterized in that it further comprises a novel presser foot lifting mechanism according to any one of claims 1 to 5, and

the linkage shaft sleeve (6) is sleeved on the feeding shaft (1) and driven by the first motor (5) to swing; a second crank (7) is fixed at one end of the linkage shaft sleeve (6);

the thread cutting crank (9) is driven by a swinging part (71) of the second crank (7); the thread cutting crank (9) is fixed on a thread cutting shaft (41) of the thread cutting assembly (4).

7. The sewing machine of claim 6, wherein: intermittent separation can be realized between the pressure foot lifting cam (81) and the abutting seat (82) and between the swinging part (71) of the second crank (7) and the thread cutting crank (9);

when the presser foot lifting cam (81) drives the abutting seat (82), the swinging part (71) of the second crank (7) is separated from the thread trimming crank (9);

when the swinging part (71) of the second crank (7) drives the thread trimming crank (9), the pressure foot lifting cam (81) is separated from the abutting seat (82).

8. The sewing machine according to claim 6 or 7, characterized in that: a strip-shaped groove (91) is formed in the trimming crank (9), and an opening (92) is formed in one end of the strip-shaped groove (91);

the swinging part (71) of the second crank (7) slides in the strip-shaped groove (91) and drives the thread trimming crank (9);

when the presser foot lifting cam (81) drives the abutting seat (82), the swinging part (71) of the second crank (7) is separated from the opening (92) to form the thread cutting crank (9).

9. The sewing machine according to claim 6 or 7, characterized in that: a first crank (61) is fixed at the other end of the linkage shaft sleeve (6), and the first crank (61) is connected with a driving connecting rod (53); a motor crank (52) is fixed on a motor shaft (51) of the first motor (5), and two ends of the driving connecting rod (53) are respectively connected with the motor crank (52) and the first crank (61).

10. The sewing machine of claim 9, wherein: one side of the motor crank (52) is also provided with a connecting plate (54), a mounting shaft (55) which is axially opposite to a motor shaft (51) of the first motor (5) is connected through the connecting plate (54), and the mounting shaft (55) is provided with the pressure foot lifting cam (81).