CN214655672U - Sewing machine - Google Patents

Abstract

The invention relates to the technical field of sewing machines, in particular to a sewing machine with a motor shared by backstitch and trimming, wherein a backstitch adjusting mechanism comprises a first crank and a first connecting rod; the rotation area of the first crank can be divided into a first regulation area, a second regulation area and a third regulation area; the first regulating area, the second regulating area and the third regulating area form a continuous sector area; in the process that the first crank enters the third adjusting area from the second adjusting area, the needle pitch of the feeding swinging seat is gradually increased to the maximum needle pitch and then gradually decreased; when the thread cutting mechanism is located at a position for cutting off sewing threads, the first crank is located in the range of the third adjusting area. The invention adopts a stepping motor to drive the backstitch mechanism and the thread trimming mechanism, belongs to the initial creation of the industry, and reduces the cost of the sewing machine. In the back half of the thread cutting, the stitch length is the process of gradually reducing, and the worry that the angle of the feeding swing seat is too large and collides with other parts of the sewing machine is avoided.

Description

Sewing machine

Technical Field

The invention relates to the technical field of sewing machines, in particular to a sewing machine with a motor shared by backstitch and thread trimming.

Background

The sewing machine industry is gradually eliminating the control mode of the electromagnet and changing the control mode into a stepping motor. Compared with the driving mode of an electromagnet, the stepping motor has the advantages of low noise, good stability and the like; meanwhile, the stepping motor has high response speed and can quickly complete corresponding instructions.

Based on the fast response capability of the stepping motor and the requirement of further reducing the cost, more and more manufacturers try to drive a plurality of mechanisms by using one stepping motor; for example, in a chinese patent 202010943302.8 previously filed by the applicant, a stepping motor is used to drive a thread cutting and presser foot lifting mechanism, which has a good market effect.

Based on the above, the applicant further develops and in the application, firstly proposes a design that a stepping motor drives a backstitch mechanism and a thread trimming mechanism.

Disclosure of Invention

The invention aims to provide a sewing machine with a backstitch mechanism and a thread trimming mechanism sharing one motor, so that the cost can be reduced on the premise of ensuring the stability of a product.

The purpose of the invention is realized as follows:

a sewing machine comprises a frame, a main shaft, a feeding shaft, a thread cutting mechanism and a feeding mechanism; the feeding mechanism is arranged between the main shaft and the feeding shaft, a feeding swing seat of the feeding mechanism rotates around a set pin shaft, the rotating angle of the feeding swing seat around the pin shaft determines the needle pitch of the sewing machine,

also comprises a driving motor, a backstitch adjusting mechanism and the thread trimming mechanism are arranged on an output shaft of the driving motor,

the backstitch adjusting mechanism is used for adjusting the angle of the feeding swinging seat; the backstitch adjusting mechanism comprises a first crank and a first connecting rod; the first crank is fixed on the output shaft and rotates along with the output shaft, the outer end of the first crank is hinged with a first connecting rod, and the other end of the first connecting rod drives the feeding swing seat;

the rotation area of the first crank can be divided into a first regulation area, a second regulation area and a third regulation area; the first regulating area, the second regulating area and the third regulating area form a continuous sector area;

when the first crank swings anticlockwise to the limit position, the position of a hinge point of the first crank and the first connecting rod is recorded as the starting point of the first adjusting area;

when the feeding swinging seat swings to zero needle pitch, the position of a hinge point of the first crank and the first connecting rod is marked as an intersection point of the first adjusting area and the second adjusting area;

when the rotation center of the first crank, the hinge point of the first crank and the first connecting rod and the hinge point of the first connecting rod and the feeding swinging seat swing to form a straight line, the position of the hinge point of the first crank and the first connecting rod is marked as an intersection point of the second adjusting area and the third adjusting area;

when the first crank swings clockwise to the extreme position, the position of a hinge point of the first crank and the first connecting rod is recorded as the end point of the third adjusting area;

the first adjusting area and the second adjusting area correspond to a backstitch or a front stitch of the sewing machine; when the first crank is positioned in a first adjusting area and a second adjusting area, the backward seam adjusting mechanism is actively adjusted;

in the process that the first crank enters the third adjusting area from the second adjusting area, the needle pitch of the feeding swinging seat is gradually increased to the maximum needle pitch and then gradually decreased;

when the thread cutting mechanism is located at a position for cutting off sewing threads, the first crank is located in the range of the third adjusting area.

Preferably, when the thread trimming mechanism is at an initial position for executing thread trimming, the first crank is located within a range of ± 45 degrees of an intersection point of the second adjusting area and the third adjusting area; and in the process of cutting off the sewing thread by the thread cutting mechanism, the needle pitch of the feeding swinging seat gradually becomes smaller.

Preferably, the thread trimming mechanism comprises:

a trimming cam installed on an output shaft of the driving motor;

a third link having a guide groove; the output shaft penetrates through the guide groove and limits the third connecting rod;

the trimming cam drives the third connecting rod to move up and down along the effective stroke of the guide groove;

the lower end of the third connecting rod drives the thread cutting crank and the thread cutting shaft.

Preferably, an upward reset pushing part and a downward trimming pushing part are arranged on one side of the third connecting rod; the trimming cam is positioned between the upward reset pushing part and the downward trimming pushing part; when the output shaft rotates reversely and resets, under the condition that the reset torsion spring of the thread cutting mechanism fails, the thread cutting cam forcibly resets the thread cutting mechanism through the ascending reset pushing part, and when the rotating angle of the output shaft enters a second adjusting region, the thread cutting cam is separated from the ascending reset pushing part.

Preferably, another structure of the thread trimming mechanism includes:

the thread cutting crank is arranged on the output shaft of the driving motor and rotates along with the output shaft; the working end of the trimming crank is provided with a pushing shaft;

a third link having a guide groove; the output shaft penetrates through the guide groove and limits the third connecting rod;

and a hook part is arranged on one side of the third connecting rod, and the pushing shaft is clamped into the hook part and drives the third connecting rod to move up and down along the effective stroke of the guide groove.

Preferably, when the output shaft rotates reversely and resets, the pushing shaft forcibly resets the thread cutting mechanism through the hook part under the condition that a reset torsion spring of the thread cutting mechanism fails; when the rotation angle of the output shaft enters a second adjusting area, the shaft is pushed to be separated from the hook part.

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

1. the invention adopts a stepping motor to drive the backstitch mechanism and the thread trimming mechanism, belongs to the initial creation of the industry, and reduces the cost of the sewing machine.

2. The backstitch adjusting mechanism comprises a first crank and a first connecting rod; the first crank is fixed on the output shaft and rotates along with the output shaft, the outer end of the first crank is hinged with a first connecting rod, and the other end of the first connecting rod drives the feeding swing seat; compare in common cam mechanism, the crank mechanism that this application adopted is a lot of less than cam mechanism's cost, and the friction contact face is less moreover, and the noise is low, and high-speed be difficult to generate heat or the card dies, and the machining precision of demand is lower. In addition, based on the requirement of quick response of the sewing machine, one action should be completed within 30-70 ms, the stroke required by the cam mechanism to complete the corresponding action is much larger, and the corresponding speed is relatively slow; the crank mechanism is more sensitive in response in a small range; the inertia generated by the movement is less, the vibration is less, and the requirement of quick response is met.

3. When the thread trimming mechanism is positioned at the initial position for executing thread trimming action, the hinge point of the first crank and the first connecting rod is positioned in the range of +/-45 degrees of the intersection point of the second adjusting area and the third adjusting area; in the process that the sewing thread is to be cut off by the thread cutting mechanism, the needle pitch of the feeding swing seat gradually becomes smaller; according to the design, in the thread cutting process, no matter the starting point of the thread cutting is arranged in the second adjusting area or the third adjusting area, the position of the thread cutting mechanism is about to cut the sewing thread, the hinge point of the first crank and the first connecting rod is always located in the range of the third adjusting area, the needle pitch is gradually reduced, and the executable space of the thread cutting mechanism is increased.

4. In the process that the rotating angle of the output shaft enters a third adjusting area from a second adjusting area, the needle pitch of the feeding swinging seat is gradually increased to the maximum needle pitch and then gradually decreased; in the back half of the thread cutting, the stitch length is the process of gradually reducing, and the worry that the angle of the feeding swing seat is too large and collides with other parts of the sewing machine is avoided.

5. The trimming cam is arranged on an output shaft of the driving motor; the output shaft penetrates through the guide groove and limits the third connecting rod; the third connecting rod is driven by the trimming cam to move up and down along the effective stroke of the guide groove; the structure is simple, the limiting of the third connecting rod is completed by the output shaft, the additional limiting design is not needed, and the structure is simple, safe and reliable.

6. One side of a third connecting rod of the invention is provided with an ascending reset pushing part and a descending trimming pushing part; when the reset torsion spring of the thread cutting mechanism fails, the thread cutting cam forcibly resets the thread cutting mechanism through the upward reset pushing part, and when the corner of the output shaft enters a second adjusting region, the thread cutting cam is separated from the upward reset pushing part; the design ensures that the trimming and the backstitch can not interfere with each other, and the trimming mechanism has a forced resetting function, and is safe and reliable.

8. The trimming crank of the invention is arranged on the output shaft of the driving motor and rotates along with the output shaft; the promotion axle card of line crank goes into the portion that colludes of third connecting rod to drive the third connecting rod along the effective stroke up-and-down motion of guide way, its structure is comparatively succinct, relies on the output shaft to accomplish the spacing of third connecting rod, need not extra spacing design, and the structure is succinct, safe and reliable.

9. According to the invention, under the condition that the reset torsion spring of the thread trimming mechanism fails, the pushing shaft forcibly resets the thread trimming mechanism through the hook part; when the rotation angle of the output shaft enters a second adjusting area, the shaft is pushed to be separated from the hook part; the design ensures that the trimming and the backstitch can not interfere with each other, and the trimming mechanism has a forced resetting function, and is safe and reliable.

Drawings

Fig. 1 is a schematic view of the overall structure of the present invention.

Fig. 2 is a schematic structural diagram of the cooperation of the backstitch mechanism and the thread trimming mechanism.

Fig. 3 shows the operating range corresponding to the rotation angle of the output shaft.

FIG. 4 is a schematic view of the sewing machine at a maximum gauge for a positive seam.

FIG. 5 is a schematic view of a sewing machine at zero gauge at the intersection of a backstitch and a backstitch.

FIG. 6 is a schematic view of the sewing machine at the maximum backstitch gauge.

FIG. 7 is a schematic view of the stitch length of the sewing machine at the completion of thread cutting.

Fig. 8 is a schematic view of the operation of the trimming cam of the trimming mechanism.

Fig. 9 is one of schematic views of a thread trimming mechanism according to another embodiment.

Fig. 10 is a second schematic view of a thread trimming mechanism according to another embodiment.

Fig. 11 is a schematic view of the thread cutting spool driving thread feeding mechanism.

Reference numerals:

1-an output shaft; 2-a first crank; 3-a guide groove; 4-trimming cam; 5-a third link; 6-a shear spool; 7-a return torsion spring; 8-feeding swing seat; 9-a pin shaft; 10-a first link; 11-an uplink reset pushing part; 12-a downward thread trimming pushing part; 13-trimming swing arm; 14-trimming crank; 15-pushing the shaft; 16-hook part; 17-a wire rope assembly; 18-slack line crank; 19-a bottom support; 20-a thread trimming assembly;

100-main motor; 200-a presser foot lifting mechanism; 300-a frame; 400-a platen; 500-driving a motor; 600-a main shaft; 700-a thread trimming mechanism; 800-a feed shaft; 900-a feeding mechanism;

a1 — first regulatory region; a2 — second regulatory region; a 3-third regulatory region; a4 — non-working regulation zone;

p 1-center of rotation of first crank; p 2-the hinge point of the first crank and the first link; p 3-the hinge point of the first connecting rod and the feeding swing seat;

b 1-start of first regulatory region; b2 — the intersection of the first and second regulatory regions; b 3-the intersection of the second and third regulatory regions; b 4-end of the third regulatory region.

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

The first embodiment is as follows:

a sewing machine comprises a frame 300, a main shaft 600, a feeding shaft 800, a thread trimming mechanism 700 and a feeding mechanism 900; the feeding mechanism 900 is arranged between the main shaft 600 and the feeding shaft 800, a feeding swing seat 8 of the feeding mechanism 900 rotates around a set pin shaft 9, the rotating angle of the feeding swing seat 8 around the pin shaft determines the needle pitch of the sewing machine,

also comprises a driving motor 500, a backstitch adjusting mechanism and the thread trimming mechanism 700 are arranged on an output shaft 1 of the driving motor,

the backstitch adjusting mechanism is used for adjusting the angle of the feeding swinging seat 8; the backstitch adjusting mechanism comprises a first crank 2 and a first connecting rod 10; the first crank 2 is fixed on the output shaft 1 and rotates along with the output shaft, the outer end of the first crank 2 is hinged with a first connecting rod 10, and the other end of the first connecting rod 10 drives the feeding swinging seat 8;

the rotation area of the first crank 2 can be divided into a first regulation area A1, a second regulation area A2, a third regulation area A3 and a non-working regulation area A4; the non-working adjusting area A4 belongs to a blind area of the crank connecting rod mechanism; the first regulation area A1, the second regulation area A2 and the third regulation area A3 form a continuous sector area;

clockwise and counterclockwise as described below are based on the layout of the regions in fig. 3.

When the first crank 2 swings anticlockwise to an extreme position, the position of a hinge point p2 between the first crank and the first connecting rod is marked as a starting point b1 of the first adjusting area;

when the feeding swinging seat 8 swings to zero needle pitch, the position of a hinge point p2 between the first crank and the first connecting rod is marked as an intersection point b2 of the first adjusting area and the second adjusting area;

when the rotation center p1 of the first crank, the hinge point p2 of the first crank and the first connecting rod, and the hinge point p3 of the first connecting rod and the feeding swinging seat swing to be in a straight line, the position of the hinge point p2 of the first crank and the first connecting rod is marked as the intersection point b3 of the second adjusting area and the third adjusting area, and is also the maximum needle pitch position of one swinging direction of the feeding swinging seat 8;

when the first crank swings clockwise to the extreme position, the position of a hinge point p2 between the first crank and the first connecting rod is marked as the end point b4 of the third adjusting area;

the first regulation zone a1 and the second regulation zone a2 correspond to the backstitch or the main seam of the sewing machine; the intersection of the first adjusting area A1 and the second adjusting area A2 is a reverse sewing and forward sewing changing position, and the stitch distance of the position is zero. The larger the angle of the feeding swing seat from the zero position is, the larger the needle pitch is.

When the first crank 2 is in the first adjustment area A1 and the second adjustment area A2, the backstitch adjusting mechanism is actively adjusted. Note that, as shown in fig. 4-7, the first regulation zone a1 is a positive slit, and the second regulation zone a2 is a negative slit; on an actual sewing machine, the first adjusting area A1 can be changed into a reverse seam, and the second adjusting area A2 can be changed into a forward seam by only arranging a hinge point p3 of the first connecting rod and the feeding swing seat at one side close to the feeding shaft; the present application does not specifically limit the first and second regulation zones a1 and a2 to correspond to the backstitch or the backstitch of the sewing machine.

During the process that the first crank 2 enters the third adjusting area A3 from the second adjusting area A2, the needle pitch of the feeding swinging seat 8 is gradually increased to the maximum needle pitch and then gradually decreased;

when the thread cutting mechanism is in a position for cutting the sewing thread, the first crank 2 is positioned in the range of the third adjusting area A3.

When the thread cutting mechanism is at the initial position for executing the thread cutting action, the first crank 2 is positioned within the meeting point b3 +/-45 degrees of the second adjusting area and the third adjusting area (further, preferably, the meeting point b3 +/-20 degrees of the second adjusting area and the third adjusting area); the starting position of the thread cutting action can be arranged at the position of a junction b3 which does not pass through the second adjusting area and the third adjusting area, or can be arranged at the position of a junction b3 which exceeds the second adjusting area and the third adjusting area, but generally, the starting position is preferably arranged in the range of swinging 20 degrees towards two sides by taking the junction b3 of the second adjusting area and the third adjusting area as a center, when the second half of the thread cutting work can be achieved, the needle pitch is gradually reduced, otherwise, the feeding swinging seat 8 is easy to collide with parts such as a feeding shaft or a bedplate, and the effect that the thread cutting mechanism and the backstitch mechanism share one stepping motor cannot be achieved.

Preferably, the thread trimming mechanism 700 includes:

a trimming cam 4 mounted on the output shaft 1 of the driving motor;

a third link 5 having a guide groove 3; the output shaft 1 penetrates through the guide groove 3 and limits the third connecting rod 5; the trimming cam 4 drives the third connecting rod 5 to move up and down along the effective stroke of the guide groove 3;

the lower end of the third connecting rod 5 drives the thread cutting crank 14 and the thread cutting shaft 6. As can be seen in fig. 11, the front end of the thread cutting spool 6 extends directly below the needle board and is connected to the thread cutting assembly 20, simplifying many conventional structures (such as electromagnets, cranks, connecting rods, etc.) and significantly reducing the cost.

Preferably, one side of the third connecting rod 5 is provided with an upward resetting pushing part 11 and a downward trimming pushing part 12; the trimming cam 4 is positioned between the upper reset pushing part 11 and the lower trimming pushing part 12; under the action of the reset torsion spring 7, the third connecting rod 5 keeps the upward-lifting movement trend, and the wire cutting cam 4 resets, so that the third connecting rod 5 can automatically reset under the action of the reset torsion spring 7; when the output shaft 1 rotates reversely and resets, under the condition that the reset torsion spring 7 of the thread cutting mechanism fails, the thread cutting cam forcibly resets the thread cutting mechanism 700 through the upward reset pushing part 11, and when the corner of the output shaft 1 enters the second adjusting area a2, the thread cutting cam is separated from the upward reset pushing part.

The middle part of the thread cutting shaft 6 is provided with a thread loosening crank 18, the working end of the thread loosening crank 18 is hinged with one end of a steel cable component 17, the other end of the steel cable component 17 drives a thread loosening mechanism of the sewing machine, the steel cable component 17 is flexible and extends into the machine head from the lower part of a table plate through a rack, and the mode of connecting the steel cable component and the thread loosening mechanism belongs to the prior art and is not detailed any more. The thread loosening instruction is integrated on the thread cutting shaft, the thread loosening action is completed while the thread is cut, the thread is stored for next sewing, and the structure is further simplified. The bottom bracket 19 is used to secure the outer jacket of the lower end of the cable assembly 17 from interfering with the remaining components.

Preferably, the driving motor 500 is a stepping motor.

Preferably, the sum of the angles of the first regulation zone A1, the second regulation zone A2 and the third regulation zone A3 is 200 degrees or less.

Preferably, the sum of the angles of the first regulation zone A1, the second regulation zone A2 and the third regulation zone A3 is less than or equal to 120 degrees.

Generally, the common stitch length adjustment of the backstitch and the main stitch generally requires an interval of 40-60 degrees, and the thread trimming action also requires an interval of 50-60 degrees; within the range of 120 degrees, the actions of the backstitch mechanism and the thread trimming mechanism can be completed compactly.

Preferably, the length of the working arm of the first crank 2 is less than or equal to the length/2 of the working arm of the first connecting rod. Within the range, the rotating center p1 of the first crank, the hinge point p2 of the first crank and the first connecting rod and the hinge point p3 of the first connecting rod and the feeding swinging seat are connected in a straight line. After the ratio is exceeded, the internal structure of part of the sewing machine needs to be changed, so that the feeding swing seat can be prevented from colliding with internal parts. It should be noted that the conventional crank structure cannot be directly applied to the backstitch mechanism, the rotation center p1 of the first crank, the hinge point p2 of the first crank and the first connecting rod, and the hinge point p3 of the first connecting rod and the feeding swing seat cannot be connected in a straight line, and the feeding swing seat can touch the needle plate or the feeding shaft or other components before the theoretical maximum needle pitch is reached, so that the sewing machine in the prior art is not suitable for the backstitch mechanism to add the thread cutting function.

Compare in common cam mechanism, the crank mechanism that this application adopted is a lot of less than cam mechanism's cost, and moreover, cam mechanism must rotate great angle and just can have sufficient stroke, leads to same instruction, and cam mechanism must rotate more angles, and the wearing and tearing aggravation is unfavorable for high-speed response.

The second embodiment is basically the same as the first embodiment, and the difference is that: the thread trimming mechanism comprises: a trimming crank 14 mounted on the output shaft 1 of the driving motor and rotated therewith; the working end of the trimming crank 14 is provided with a pushing shaft 15;

a third link 5 having a guide groove 3; the output shaft 1 penetrates through the guide groove 3 and limits the third connecting rod 5;

a hook part 16 is arranged on one side of the third connecting rod 5, and the pushing shaft 15 is clamped into the hook part 16 and drives the third connecting rod 5 to move up and down along the effective stroke of the guide groove 3.

Preferably, when the output shaft 1 rotates reversely and resets, the pushing shaft 15 forcibly resets the thread cutting mechanism through the hook part 16 under the condition that the reset torsion spring 7 of the thread cutting mechanism fails; when the rotation angle of the output shaft 1 enters the second regulation area a2, the shaft 15 is pushed to disengage from the hook.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. A sewing machine comprises a frame (300), a main shaft (600), a feeding shaft (800), a thread trimming mechanism (700) and a feeding mechanism (900); the feeding mechanism (900) is arranged between the main shaft (600) and the feeding shaft (800), a feeding swing seat (8) of the feeding mechanism (900) rotates around a set pin shaft (9), the rotating angle of the feeding swing seat (8) around the pin shaft determines the needle pitch of the sewing machine,

the method is characterized in that:

also comprises a driving motor (500), an output shaft (1) of the driving motor is provided with a backstitch adjusting mechanism and the thread trimming mechanism (700),

the backstitch adjusting mechanism is used for adjusting the angle of the feeding swinging seat (8); the backstitch adjusting mechanism comprises a first crank (2) and a first connecting rod (10); the first crank (2) is fixed on the output shaft (1) and rotates along with the output shaft, the outer end of the first crank (2) is hinged with a first connecting rod (10), and the other end of the first connecting rod (10) drives the feeding swinging seat (8);

the rotation region of the first crank (2) can be divided into a first regulation zone (A1), a second regulation zone (A2) and a third regulation zone (A3); the first regulation zone (A1), the second regulation zone (A2) and the third regulation zone (A3) form a continuous sector area;

when the first crank (2) swings anticlockwise to an extreme position, the position of a hinge point (p2) of the first crank and the first connecting rod is marked as a starting point (b1) of the first adjusting area;

when the feeding swinging seat (8) swings to zero needle pitch, the position of a hinge point (p2) of the first crank and the first connecting rod is marked as an intersection point (b2) of the first adjusting area and the second adjusting area;

when the rotating center (p1) of the first crank, the hinge point (p2) of the first crank and the first connecting rod and the hinge point (p3) of the first connecting rod and the feeding swinging seat swing to be in a straight line, the position of the hinge point (p2) of the first crank and the first connecting rod is marked as the intersection point (b3) of the second adjusting area and the third adjusting area;

when the first crank swings clockwise to the extreme position, the position of a hinge point (p2) of the first crank and the first connecting rod is marked as the end point (b4) of the third adjusting area;

the first regulation zone (a1) and the second regulation zone (a2) correspond to the backstitch or the main seam of the sewing machine; the first crank (2) is in a first adjusting area (A1) and a second adjusting area (A2), and the backstitch adjusting mechanism is actively adjusted;

during the process that the first crank (2) enters a third adjusting area (A3) from a second adjusting area (A2), the needle pitch of the feeding swinging seat (8) is gradually increased to the maximum needle pitch and then gradually decreased;

when the thread cutting mechanism is in a position for cutting sewing threads, the first crank (2) is positioned in the range of the third adjusting area (A3).

2. A sewing machine according to claim 1, wherein: when the thread trimming mechanism is at the initial position for executing thread trimming action, the first crank (2) is positioned in the range of the intersection point (b3) ± 45 degrees of the second adjusting area and the third adjusting area;

the stitch length of the feeding swing seat (8) is gradually reduced in the process that the sewing thread is cut off by the thread cutting mechanism.

3. A sewing machine according to claim 2, wherein: when the thread cutting mechanism is at the initial position for executing thread cutting action, the first crank (2) is positioned in the range of the meeting point (b3) ± 20 degrees of the second adjusting area and the third adjusting area.

4. A sewing machine according to claim 1, wherein: the thread trimming mechanism (700) comprises:

the trimming cam (4) is arranged on an output shaft (1) of the driving motor;

a third link (5) having a guide groove (3); the output shaft (1) penetrates through the guide groove (3) and limits the third connecting rod (5);

the trimming cam (4) drives the third connecting rod (5) to move up and down along the effective stroke of the guide groove (3); the lower end of the third connecting rod (5) drives the thread cutting crank (14) and the thread cutting shaft (6).

5. A sewing machine according to claim 4, characterized in that: an upward reset pushing part (11) and a downward trimming pushing part (12) are arranged on one side of the third connecting rod (5); the trimming cam (4) is positioned between the ascending reset pushing part (11) and the descending trimming pushing part (12); when the output shaft (1) rotates reversely and resets, under the condition that the reset torsion spring (7) of the trimming mechanism fails, the trimming cam forcibly resets the trimming mechanism (700) through the upward reset pushing part (11), and when the corner of the output shaft (1) enters the second adjusting area (A2), the trimming cam is separated from the upward reset pushing part.

6. A sewing machine according to claim 1, wherein: the thread trimming mechanism comprises:

a trimming crank (14) mounted on the output shaft (1) of the drive motor and rotating therewith; a pushing shaft (15) is arranged at the working end of the trimming crank (14);

a third link (5) having a guide groove (3); the output shaft (1) penetrates through the guide groove (3) and limits the third connecting rod (5);

one side of the third connecting rod (5) is provided with a hook part (16), and the pushing shaft (15) is clamped into the hook part (16) and drives the third connecting rod (5) to move up and down along the effective stroke of the guide groove (3).

7. A sewing machine according to claim 6, wherein: when the output shaft (1) rotates reversely and resets, the pushing shaft (15) forcibly resets the thread cutting mechanism through the hook part (16) under the condition that the reset torsion spring (7) of the thread cutting mechanism fails; when the rotation angle of the output shaft (1) enters a second regulation area (A2), the pushing shaft (15) is separated from the hook part.

8. A sewing machine according to claim 4, characterized in that: the middle part of the thread cutting shaft (6) is provided with a thread loosening crank (18), the working end of the thread loosening crank (18) is hinged with one end of a steel cable component (17), and the other end of the steel cable component (17) drives a thread loosening mechanism of the sewing machine.

9. A sewing machine according to claim 1, wherein: the driving motor (500) is a stepping motor; the sum of the angles (a) of the first regulation zone (A1), the second regulation zone (A2) and the third regulation zone (A3) is less than or equal to 200 degrees.

10. A sewing machine according to claim 1, wherein: the length of the working arm of the first crank (2) is less than or equal to the length/2 of the working arm of the first connecting rod.

Images