CN106894175B - A sewing machine automatic thread trimming mechanism and sewing machine - Google Patents

Abstract

The invention provides an automatic trimming mechanism of a sewing machine, which comprises a lower shaft, a trimming driving cam fixed on the lower shaft, a movable knife assembly which can swing around the lower shaft and is provided with at least movable knives and movable knife rests, a crank shaft, a trimming driving assembly arranged at the end of the crank shaft, a trimming crank fixed at the other end of the crank shaft and a trimming connecting rod, wherein the trimming driving assembly is provided with a -th extension arm, the end part of the -th extension arm is connected with a roller, two ends of the trimming connecting rod are respectively hinged with the trimming crank and the movable knife rests, the distance L1 between the crank shaft and the hinging point of the trimming crank and the trimming connecting rod is not less than 2.5, the ratio of the distance L2 between the lower shaft and the hinging point of the movable knife rests and the hinging point of the trimming connecting rod and the movable knife rests is not less than 40 degrees, and the roller is matched with the trimming contact surface at the periphery of the trimming driving cam during trimming.

Description

A sewing machine automatic thread trimming mechanism and sewing machine

technical field

The invention relates to a sewing device, in particular to an automatic thread trimming mechanism and a sewing machine of a sewing machine.

Background technique

At present, sewing machines (especially lockstitch machines) are equipped with an automatic thread trimming mechanism, which is used to cut the lower thread and the upper thread at the hook after each sewing. As shown in FIG. 1, the automatic thread trimming mechanism in the existing sewing machine generally includes a rotatable lower shaft 100, a cam 200 fixed on the lower shaft 100, a thread trimming shaft 300 parallel to the lower shaft 100, and a swingable thread trimming crank The assembly 400 , the disc 500 located at one end of the thread trimming shaft 300 , the thread trimming crank 600 fixed on the other end of the thread trimming shaft 300 , the thread trimming link 700 , the movable knife rest 800 , and the movable knife 900 fixed on the movable knife rest 800 , and the fixed knife 110 fixed on the lower end surface of the sewing machine base plate, wherein the thread trimming crank assembly 400 has a first extension arm 401, a second extension arm 402 and a third extension arm 403, and the first extension arm 401 is used to cooperate with the cam , to achieve power transmission, the second extension arm 402 is used to cooperate with the cam to achieve forced reset, and the third extension arm 403 is equipped with a slider, which is used to match the circumferential groove of the disc 500 at the end of the thread trimming shaft 300 to achieve torque transmission. Therefore, the working principle of the above automatic thread trimming mechanism is as follows: as shown in Figures 1 and 2, when thread trimming is required, the lower shaft 100 drives the cam 200 to rotate synchronously, and drives the thread trimming through the matching relationship between the first extension arm 401 and the cam 200. The crank assembly 400 swings, and then drives the thread trimming shaft 300 to swing through the cooperative relationship between the third extension arm 403 and the disc 500 ; finally, the thread trimming shaft 300 is driven to drive the thread trimming crank 600 to swing synchronously, and the thread trimming crank 600 is driven by the thread trimming link 700 The movable knife rest 800 and the movable knife 900 swing to make the movable knife 900 engage with the fixed knife 110 to cut the lower thread and the upper thread, so as to realize automatic thread trimming.

In addition, when the sewing machine is working normally, the first extending arm 401 on the thread trimming crank assembly 400 needs to be away from the cam 200, so the thread trimming crank assembly 400 can reciprocate along the axial direction of the thread trimming shaft 300, so that the third extending arm 403 and the A sliding pair needs to be arranged between the discs 500 of the thread trimming shaft 300 . Therefore, in the above-mentioned automatic thread trimming mechanism of the sewing machine, the thread trimming crank assembly includes three extension arms, which are matched with the thread trimming shaft through a sliding pair, so that the overall structure of the automatic thread trimming mechanism is complex, and the machining accuracy of the parts is relatively high. The processing cost is high, and due to the large number of parts, the assembly is inconvenient and the working hours are long.

Further, in the existing automatic thread trimming mechanism shown in Figures 1 and 2, in the thread trimming actuator ABCD composed of the thread trimming crank, the thread trimming link and the moving knife frame, the rod AB (that is, the part of the thread trimmer) The ratio of the rod length between the crank) and rod CD (that is, part of the movable tool holder) is: AB/CD≈1.2, the pendulum of rod EF (that is, the third extension arm), rod AB and rod CD during the thread trimming process The angle ratio is: ΦAB:ΦCD=1:2.58:3.33. Obviously, after the swing angle of the rod EF is amplified by the thread trimming crank assembly and the thread trimmer actuator ABCD, the large-angle rotary motion of the moving knife is finally realized, thus causing automatic The drive chain of the thread trimming mechanism is redundant and the structure is complex.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an automatic thread trimming mechanism for a sewing machine, which simplifies the transmission chain, reduces the cost, and reduces the assembly time.

In order to achieve the above purpose, the present invention provides an automatic thread trimming mechanism for a sewing machine, which includes a lower shaft rotatably supported in the bottom plate of the sewing machine, a thread trimming drive cam fixed on the lower shaft, and a moving knife assembly that can swing around the lower shaft. The movable knife assembly includes at least one movable knife and a movable knife holder for installing the movable knife, and also includes a crank shaft parallel to the lower shaft, a wire trimmer drive assembly installed at one end of the crank shaft, and fixed on the other side of the crank shaft. A wire-cutting crank at one end and a wire-cutting link, the wire-cutting drive assembly has a first extension arm, the end of the first extension arm is connected with a roller, and the two ends of the wire-cutting link are respectively connected to the wire-cutting link. The crank and the movable tool rest are hinged, and the ratio of the distance L1 between the crank shaft and the hinge point of the thread trimming crank and the thread trimmer link and the distance L2 between the same lower axis and the hinge point of the movable tool rest and the thread trimmer link is different. Less than 2.5; when trimming the thread, the roller and the thread trimming contact surface on the outer periphery of the thread trimming drive cam are matched, the thread trimming drive assembly, the crank shaft and the thread trimming crank swing synchronously, and the thread trimming link moves the tool holder. The transmission angle γ is not less than 40°.

Further, the wire-cutting drive assembly has a second extension arm, the first extension arm and the second extension arm are respectively located at two ends of the wire-cutting drive assembly, and a forced reset pin is connected to the end of the second extension arm, A forced reset driving cam is fixed on the lower shaft; when the roller passes over the end of the wire trimming segment on the wire cutting contact surface, the forced reset pin is adjacent to the forced reset contact surface on the outer periphery of the forced reset driving cam.

Further, it also includes a power source, which is connected with the thread trimming drive assembly through a transmission mechanism; when the thread is trimmed, the power source moves, and the transmission mechanism drives the thread trimming drive assembly to move along the axial direction of the crankshaft, so that all The rollers are matched with the wire cutter contact surface, and the forced reset pin is located on the outer peripheral side of the forced reset contact surface.

Preferably, the power source is an electromagnet with a mandrel parallel to the lower shaft, the transmission mechanism includes a top rod and a connecting block, the end of the mandrel is fixed in the connecting block, and one end of the top rod It is fixed in the connecting block, and the other end of the ejector rod is in abutment with the end face of the thread trimming drive assembly.

Further, the wire-cutting drive assembly has a drive body portion located between the first extension arm and the second extension arm, the drive body portion is provided with a chute extending in the axial direction of the crank shaft, and the crank shaft passes through the drive body portion. It is arranged in the driving body part, and a limit pin is fixed on the crank shaft. The limit pin is located in the chute of the driving body part and can reciprocate and slide along the extending direction of the chute.

Preferably, a return spring is sleeved on the crankshaft, and a retaining ring is fixed, the retaining ring is located between the wire trimming crank and the second extension arm, and two ends of the return spring are respectively connected with the second extension arm and the second extension arm. The retaining ring abuts.

Preferably, a reset torsion spring is sleeved on the crank shaft, and both ends of the reset torsion spring are respectively abutted with the thread trimming crank and the bottom plate of the sewing machine.

Further, the wire trimming crank includes a crank part and a connecting rod part that are independent of each other, one end of the crank part is fixed with the crank shaft, the other end of the crank part is fixed with one end of the connecting rod part, and the other end of the connecting rod part is fixed. One end is hinged with the thread trimming link.

Preferably, a limit surface is provided on the lower end surface of the bottom plate of the sewing machine, and a receiving hole is formed on the end surface of the crank portion facing the limit surface, and a limit pad is built in the receiving hole, and the limit pad is opposite to the limit surface. Cooperate.

Further, it also includes a fixed knife fixed on the bottom plate of the sewing machine, and there is one movable knife and one movable knife holder; when the thread is trimmed, the movable knife and the fixed knife are engaged.

The present application also provides a sewing machine, comprising a sewing machine base plate and the above-mentioned automatic thread trimming mechanism of the sewing machine, wherein the lower shaft and the movable knife rest are rotatably installed in the sewing machine base plate.

As mentioned above, the automatic thread trimming mechanism and sewing machine of the sewing machine involved in the present invention have the following beneficial effects:

The present application simplifies the structure and transmission chain of the automatic thread trimming mechanism of the sewing machine, reduces the number of complex parts in the original mechanism, and is beneficial to reducing costs, improving assembly efficiency, and reducing assembly man-hours.

Description of drawings

FIG. 1 is a schematic structural diagram of an automatic thread trimming mechanism of a sewing machine in the prior art.

FIG. 2 is a schematic diagram of FIG. 1 .

FIG. 3 is a schematic structural diagram of the automatic thread trimming mechanism of the sewing machine in the application.

4 and 5 are schematic diagrams of the structure of the sewing machine in which the bottom plate of the sewing machine is omitted in FIG. 3 .

FIG. 6 is a schematic diagram of the connection between the thread trimming crank and the bottom plate of the sewing machine in FIG. 3 .

FIG. 7 is a schematic structural diagram of the thread trimming drive assembly in FIG. 3 .

FIG. 8 is a schematic structural diagram of the cam in FIG. 3 .

9 and 10 are schematic diagrams of the automatic thread trimming mechanism of the sewing machine in the application, wherein FIG. 9 is a thread trimming state, and FIG. 10 is a reset state.

Component label description

1 Sewing machine base plate

101 Limit surface

2 lower shaft

3 drive cam

31 Thread trimmer drive cam

32 Thread trimmer contact surface

33 Force reset drive cam

34 Force reset contact surface

35 Connectors

4 moving tool holder

5 moving knife

6 fixed knife

7 Crankshaft

8 Thread trimmer drive assembly

81 First extension arm

82 Roller

83 Second extension arm

84 Force reset pin

85 Drive body

86 Chute

87 Limit pin

88 Roller shaft

9 Trimming crank

91 Crank

92 connecting rod

10 Thread trimmer link

11 Power source

12 ejector

13 Connection block

14 Return spring

15 retaining ring

16 Return torsion spring

17 Limit pads

18 Holder

Detailed ways

The embodiments of the present invention are described below by specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. drawn in the accompanying drawings of this specification are only used to cooperate with the contents disclosed in the specification, so as to be understood and read by those who are familiar with the technology, and are not used to limit the conditions that the present invention can be implemented. Therefore, without technical substantive significance, any modification of structure, change of proportional relationship or adjustment of size should still fall within the scope disclosed in the present invention without affecting the effect that the present invention can produce and the purpose that can be achieved. within the scope of technical content. At the same time, the terms such as "up", "down", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the present invention. The practicable scope and the change or adjustment of the relative relationship thereof shall also be regarded as the practicable scope of the present invention without substantially changing the technical content.

The present application provides an automatic thread trimming mechanism for a sewing machine, which is installed in a sewing machine, especially a lockstitch machine, to cut the lower thread and the upper thread after each sewing; Defined as the front direction, the extension direction of the lower shaft 2 in the sewing machine is the left and right direction, and the end of the lower shaft 2 close to the machine head is the left end, and the end of the lower shaft 2 close to the machine tail is the right end. As shown in FIGS. 3 to 5 , the automatic thread trimming mechanism of the sewing machine includes a lower shaft 2 rotatably supported in the sewing machine base 1 , a thread trimming driving cam 31 fixed on the lower shaft 2 , a thread trimming drive cam 31 installed in the sewing machine base 1 and rotatable The movable knife assembly swinging around the lower shaft 2, the crank shaft 7 parallel to the lower shaft 2, the thread trimming drive assembly 8 installed on the right end of the crank shaft 7, the thread trimming crank 9 fixed on the left end of the crank shaft 7, and the thread trimming connection. Rod 10, the movable knife assembly includes at least one movable knife 5 and a movable knife rest 4 for installing the movable knife 5, so the number of movable knife rests 4 is equal to the number of movable knives 5, and the movable knife rest 4 It is installed in the bottom plate of the sewing machine and can swing around the lower shaft 2. The outer peripheral surface of the thread trimmer drive cam 31 is the thread trimmer contact surface 32. The right end of the thread trimmer drive assembly 8 has a first extension arm 81, which extends The end of the arm 81 away from the crank shaft 7 is connected with a roller 82 that protrudes to the left on the left end face of the first extension arm 81 . The extended axial screw is hinged, the distance between the crank shaft 7 and the hinge point of the thread trimmer crank 9 and the thread trimmer link 10 is L1, the lower shaft 2 is hinged with the movable tool rest 4 and the thread trimmer link 10 The distance between the points is L2, and the ratio L1/L2 of L1 and L2 is not less than 2.5; when trimming the thread, the roller 82 cooperates with the thread trimming contact surface 32 on the outer periphery of the thread trimming drive cam 31, and the thread trimmer drive assembly 8. The crank shaft 7 and the thread trimming crank 9 swing synchronously, and the transmission angle γ of the thread trimming link 10 to the movable tool rest 4 is not less than 40°.

Further, the sewing machine can be a single-moving knife structure or a double-moving knife structure. When the sewing machine adopts the structure of a single-acting knife, the automatic thread trimming mechanism of the sewing machine further includes a fixed knife 6 fixed on the lower end surface of the bottom surface of the sewing machine 1, the movable knife 5 is one, and the moving knife holder 4 is one; When the moving knife 5 is engaged with the fixed knife 6 . When the sewing machine adopts the structure of double moving knives, there are two moving knives 5 and two moving knife rests 4, and the two moving knives 5 are each fixed on one moving knife rest 4, for example; China with the application number of 201610473636.7 The short-thread double-cutting mechanism disclosed in the invention application specification, or the thread-cutting mechanism of the sewing machine disclosed in the Chinese invention application specification with the application number of 201610494020.8; The thread trimming crank 9 drives to swing, so there are also two thread trimming cranks 9; when trimming the thread, the two movable knives 5 are engaged. The following embodiments are described by taking the automatic thread trimming mechanism of a sewing machine with a single-acting knife structure as an example.

The principle diagram of the automatic thread trimming mechanism of the sewing machine with the single-acting knife structure is shown in Figure 9 and Figure 10. In Figure 9 or Figure 10, A corresponds to the crank shaft 7, G corresponds to the roller 82, D corresponds to the lower shaft 2, AG corresponds to the first extension arm 81 , AB corresponds to the thread trimming crank 9 , BC corresponds to the thread trimming link 10 , CDE corresponds to the moving tool rest 4 , and the thread trimming crank 9 , the thread trimming link 10 and the moving tool rest 4 are formed. The four-bar mechanism ABCD is used to perform thread trimming. Therefore, B is the hinge point between the thread trimmer crank 9 and the thread trimmer link 10, and C is the hinge point between the thread trimmer link 10 and the moving tool holder 4. Therefore, the above-mentioned The distance L1 between the crank shaft 7 and the hinge point of the thread trimmer crank 9 and the thread trimmer connecting rod 10 is the length of the rod AB in FIG. 9 or FIG. The distance L2 between the hinge points of the connecting rod 10 is the length of the rod CD in FIG. 9 or FIG. 10 , and the transmission angle γ of the above-mentioned thread trimming connecting rod 10 to the movable tool rest 4 is the rod in FIG. 9 or FIG. 10 . The transmission angle of BC to rod CD can be seen from this: in the schematic diagram of the automatic thread trimming mechanism of the sewing machine, the rod length ratio AB/CD between rod AB and rod CD is not less than 2.5, and the transmission angle of rod BC to rod CD is not less than 2.5. γ is not less than 40°, so as to optimize the parameters of the four-bar mechanism ABCD, and the large-angle swing of the rod CD can be realized through one-stage transmission, thereby simplifying the transmission chain of the automatic thread trimming mechanism of the sewing machine.

In this embodiment, the wire-cutting contact surface 32 on the outer periphery of the wire-cutting driving cam 31 includes a to-be-cut wire segment, a wire-cutting segment and a reset segment connected in sequence at the first position. During normal sewing, the thread trimmer drive assembly 8 is in the initial position. At this time, the roller 82 is not placed on the outer peripheral side of the thread trimmer drive cam 31, and there is no matching relationship with the thread trimmer contact surface 32; after sewing, the thread trimmer The drive assembly 8 moves in the direction close to the thread trimmer drive cam 31 , and drives the first extension arm 81 and the roller 82 to move in the direction close to the thread trimmer drive cam 31 synchronously, so that the roller 82 is located on the outer peripheral side of the thread trimmer drive cam 31 , and is in contact with the line segment to be trimmed on the thread trimming contact surface 32; at this time, as shown in Figures 4, 5 and 9, the lower shaft 2 drives the thread trimming drive cam 31 to rotate synchronously, and the upper trimmer is driven by the thread trimmer drive cam 31 to rotate synchronously. The line-cutting segment of the line contact surface 32 and the roller 82 cooperate with each other to drive the line-cutting drive assembly 8, the crank shaft 7 and the line-cutting crank 9 to swing synchronously, and the line-cutting crank 9 directly drives the moving tool rest 4 and The movable knife 5 swings around the lower shaft 2, and the large-angle swing of the movable knife 5 is realized through the first-level transmission, so that the movable knife 5 rotates in the direction close to the fixed knife 6 and engages with the fixed knife 6, and then the bottom thread and the The upper thread is cut to complete the automatic thread trimming. Compared with the prior art, the present application greatly simplifies the transmission chain of the automatic thread trimming mechanism of the sewing machine, simplifies the structure of the automatic thread trimming mechanism of the sewing machine, cancels the parts with complex structures in the prior art, reduces the number of complex parts in the original mechanism, and also reduces the number of complicated parts in the original mechanism. That is, the processing technology requirements of each part in the automatic thread trimming mechanism of the sewing machine are reduced, which is beneficial to reduce costs, improve assembly efficiency, reduce assembly man-hours, reduce the overall processing cost of the automatic thread trimming mechanism of the sewing machine, and thus reduce the production cost of the entire sewing machine.

The roller 82 can be in a fixed state or in a rolling state. In this embodiment, the roller 82 is preferably in a rolling state, which can reduce the gap between the roller 82 and the wire cutter contact surface 32 when they are matched. At this time, as shown in FIG. 7 , a roller shaft 88 extending left and right is fixed at the end of the first extension arm 81 of the thread trimming drive assembly 8, and the roller 82 is rotatably sleeved on the roller shaft 88 on the left side of the first extension arm 81 .

Preferably, as shown in FIG. 4 and FIG. 5 , a reset torsion spring 16 is sleeved on the crank shaft 7 , and both ends of the reset torsion spring 16 are in contact with the thread trimming crank 9 and the sewing machine base plate 1 respectively; After cutting, the roller 82 cooperates with the reset section on the wire-cutting contact surface 32, the wire-cutting crank 9 is reset under the action of the reset torsion spring 16, and the wire-cutting connecting rod 10 drives the movable knife holder 4, the movable knife 5, and the crank handle. The shaft 7 and the thread trimmer drive assembly 8 are reset.

Further, as shown in FIG. 4 , FIG. 5 , FIG. 7 , FIG. 9 and FIG. 10 , the left end of the thread trimmer drive assembly 8 has a second extension arm 83 , and the second extension arm 83 is away from the end of the crankshaft 7 . A forced reset pin 84 is connected to the upper part, and the forced reset pin 84 protrudes to the right from the right end surface of the second extension arm 83. The forced reset drive cam 33 is fixed on the lower shaft 2, and the outer peripheral surface of the forced reset drive cam 33 is The contact surface 34 is forcibly reset. During thread trimming, when the thread trimming drive assembly 8 moves toward the direction close to the thread trimming drive cam 31 , the thread trimmer drive assembly 8 will also drive the second extension arm 83 and the forced reset pin 84 to move toward the direction close to the forced reset drive cam 33 synchronously. Move in the direction so that the forced reset pin 84 is located on the outer peripheral side of the forced reset contact surface 34; when the movable knife 5 and the fixed knife 6 are engaged to cut the suture, that is, the roller 82 crosses the thread trimming segment on the thread trimming contact surface 32 The positive reset pin 84 is adjacent to the positive reset contact surface 34 at the point of connection with the reset segment. Under normal circumstances, the thread trimming crank 9, the movable knife holder 4, the movable knife 5, the crank shaft 7 and the thread trimming drive assembly 8 are automatically reset through the reset torsion spring 16 sleeved on the crank shaft 7, so the thread trimming drive assembly 8 simultaneously It also drives the second extension arm 83 and the forced reset pin 84 to reset. After reset, the gap between the forced reset pin 84 and the forced reset drive cam 33 becomes larger and is not enough for the forced reset pin 84 to be in contact with the forced reset contact surface 34. Therefore, the forced reset pin 84 does not work when the normal reset is realized by the reset torsion spring 16 . However, when the reset torsion spring 16 cannot separate the movable knife 5 from the fixed knife 6 due to wire clamping or other reasons, the movable knife rest 4, the thread trimming crank 9, the crank shaft 7, the thread trimming drive assembly 8 and the forced reset pin 84 are not reset normally. At this time, the forced reset pin 84 is still adjacent to the forced reset contact surface 34, so when the lower shaft 2 drives the forced reset drive cam 33 to rotate synchronously, the forced reset pin 84 and the forced reset contact surface 34 are matched The forced reset pin 84 and the second extension arm 83 are driven to move, so that the thread trimming drive assembly 8 is reset, thereby driving the crank shaft 7, the thread trimming crank 9, the movable knife rest 4 and the movable knife 5 to forcibly reset, and the movable knife 5 and the fixed knife are forced to reset. The 6-phase separation of the knife ensures that the next automatic thread trimming can be carried out normally.

Preferably, as shown in FIG. 8 , the thread trimming drive cam 31 and the forced reset drive cam 33 are connected through a connecting piece 35 , and the thread trimming drive cam 31 and the forced reset drive cam 33 are located on the right and left of the connecting piece 35 respectively. On the other hand, the thread trimmer drive cam 31 , the connecting piece 35 and the forced reset drive cam 33 are processed into an integral piece, which is defined as the drive cam 3 . In the driving cam 3 , the connecting piece 35 is fixed to the lower shaft 2 by a plurality of screws arranged along the radial direction of the lower shaft 2 , and then the driving cam 3 is integrally fixed to the lower shaft 2 , which is conducive to saving space and facilitating assembly.

In this embodiment, the wire-cutting drive assembly 8 can linearly reciprocate along the axial direction of the crankshaft 7 , so that the rollers 82 are matched or separated from the wire-cutting contact surface 32 , and the forced reset pin 84 is brought into contact with the forced reset Faces 34 are close or far apart. At this time, as shown in Figures 4 and 5, the automatic thread trimming mechanism of the sewing machine further includes a power source 11, which is connected to the thread trimming drive assembly 8 through a transmission mechanism; The mechanism drives the thread trimmer drive assembly 8 to move leftward along the axial direction of the crankshaft 7 , so that the rollers 82 are matched with the thread trimmer contact surface 32 , and the forced reset pin 84 is located on the outer peripheral side of the forced reset contact surface 34 . . The crank shaft 7 is also sleeved with a return spring 14, and a retaining ring 15 is fixed. The retaining ring 15 is located between the wire trimming crank 9 and the second extension arm 83. The two ends of the return spring 14 are respectively connected to the The second extension arm 83 is in contact with the retaining ring 15; after the thread trimming is completed, the power source 11 is reset, and the second extension arm 83 is moved to the right by the elastic force of the return spring 14, thereby driving the thread trimming drive assembly 8 to move to the right and reset .

Preferably, the power source 11 is an electromagnet with a mandrel parallel to the lower shaft 2 , the electromagnet is installed on the lower end surface of the sewing machine base plate 1 through a fixing frame 18 , and the transmission mechanism includes a top rod 12 and a connecting block 13 , the left end of the mandrel is fixed in the connection block 13, the right end of the ejector rod 12 is fixed in the connection block 13, and the left end of the ejector rod 12 is in contact with the right end face of the first extension arm 81 of the thread trimming drive assembly 8 . When the wire is trimmed, the electromagnet is energized, and the iron core of the electromagnet is retracted to the left in the direction close to the magnet of the electromagnet under the action of the magnetic force, so the core axis of the electromagnet extends to the left, driving the connecting block 13 and the ejector rod 12 synchronously. Move to the left, and then push the thread trimmer drive assembly 8 to move to the left. In order to realize the guidance when the thread trimmer drive assembly 8 moves left and right, and the torque transmission between the thread trimmer drive assembly 8 and the crankshaft 7, as shown in FIG. 5 and FIG. 7 , the thread trimmer drive assembly 8 has a first extension The drive body portion 85 between the arm 81 and the second extension arm 83 is provided with a chute 86 extending along the axial direction of the crankshaft 7, and the crankshaft 7 is passed through the drive body portion 85, A limiting pin 87 is fixed on the outer peripheral surface of the crankshaft 7 . The limiting pin 87 is located in the chute 86 of the driving body portion 85 and can slide back and forth along the extending direction of the chute 86 .

In order to further simplify the part structure and reduce the cost, as shown in Figures 5 and 6, the wire trimming crank 9 is decomposed into two independent parts: the first part, the crank part 91; the second part, the connecting rod part 92. One end of the crank part 91 is fixed with the crank shaft 7 , the other end of the crank part 91 and one end of the connecting rod part 92 are fixed by two screws, and assembled into a trimming crank 9 , and the other end of the connecting rod part 92 is connected with the other end of the connecting rod part 92 . The thread trimming link 10 is hinged. After the trimming crank 9 is divided into parts, the structures of the crank part 91 and the connecting rod part 92 can be simplified, and the cost of parts can be reduced. As shown in FIG. 6 , a limit surface 101 is provided on the lower end surface of the sewing machine base plate 1 , and a receiving hole is formed on the end surface of the crank portion 91 of the thread trimming crank 9 facing the limit surface 101 . A limit pad 17 made of rubber, the limit pad 17 cooperates with the limit surface 101 to limit the initial positions of the movable knife rest 4 and the movable knife 5 .

The working principle of the automatic thread trimming mechanism of the above-mentioned sewing machine is as follows: in the initial state, the electromagnet is powered off, the iron core of the electromagnet is in a state of extending to the right, the thread trimming drive assembly 8 is located on the right side of the drive cam 3, and the roller 82 and the The cutting line contact surface 32 is separated from each other, and the movable knife 5 and the fixed knife 6 are separated. When trimming the thread, the electromagnet is energized, the core shaft moves to the left, and the thread trimmer drive assembly 8 is pushed to the left by the fixed block and the ejector rod 12 against the pressure of the return spring 14, the return spring 14 is compressed, and the roller 82 is located in the thread trimmer drive. The outer peripheral side of the cam 31 is in contact with the segment to be trimmed on the thread trimming contact surface 32; the lower shaft 2 drives the driving cam 3 to rotate synchronously, so that the roller 82 cooperates with the thread trimming segment of the thread trimming contact surface 32, thereby driving the thread trimmer The drive assembly 8 swings, the thread trimmer drive assembly 8 drives the crankshaft 7 and the thread trimmer crank 9 to swing synchronously through the limit pin 87 , and the thread trimmer crank 9 transmits the power to the moving knife frame 4 through the thread trimming link 10, and finally drives the moving knife The frame 4 and the movable knife 5 swing around the lower shaft 2 toward the fixed knife 6 until the lower thread and the upper thread are cut. The lower shaft 2 drives the driving cam 3 to continue to rotate synchronously, so that the roller 82 is matched with the reset section of the thread trimming contact surface 32, and the reset torsion spring 16 makes the thread trimming crank 9, the moving knife holder 4, the moving knife 5, the crank shaft 7, The thread trimming drive assembly 8 is reset until the limiting pad 17 on the thread trimming crank 9 is firmly in contact with the limiting surface 101 on the sewing machine base plate 1 . After the thread trimming, the electromagnet is powered off, the mandrel moves to the right and resets, under the action of the elastic force of the reset spring 14, the thread trimming drive assembly 8 is reset, and the roller 82 is separated from the thread trimming contact surface 32. At this point, a thread trimming cycle is completed.

The present application also provides a sewing machine, comprising a sewing machine base 1 and the above-mentioned automatic thread trimming mechanism of the sewing machine, wherein the lower shaft 2 and the movable knife rest 4 are rotatably installed in the sewing machine base 1 .

To sum up, the present application optimizes the automatic thread trimming mechanism of the sewing machine, in particular, optimizes the design of the parameters of the screw mechanism ABCD used to perform thread trimming in the automatic thread trimming mechanism of the sewing machine, simplifies the transmission chain, and facilitates the Assembly, reducing assembly man-hours; at the same time, the application also cancels the structure of the thread trimming shaft, slider, sliding pair and other structures in the original mechanism, and adopts low-cost pin-shaft type coordination, so the complex parts in the automatic thread trimming mechanism of the sewing machine are reduced. , the production cost is greatly reduced. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

1. An automatic thread trimming mechanism of a sewing machine, comprising a lower shaft (2) rotatably supported in the bottom plate (1) of the sewing machine, a thread trimming drive cam (31) fixed on the lower shaft (2), and a thread trimming drive cam (31) that can be wound around the lower shaft ( 2) A oscillating moving knife assembly, the moving knife assembly includes at least one moving knife (5) and a moving knife holder (4) for installing the moving knife (5), characterized in that it also includes a lower moving knife (5). A crankshaft (7) with parallel shafts (2), a wire-cutting drive assembly (8) mounted on one end of the crankshaft (7), a wire-cutting crank (9) fixed on the other end of the crankshaft (7), and a wire-cutting A connecting rod (10), the wire-cutting drive assembly (8) has a first extension arm (81), the end of the first extension arm (81) is connected with a roller (82), and the wire-cutting link ( The two ends of 10) are respectively hinged with the thread trimming crank (9) and the moving tool holder (4), and the distance between the crank shaft (7) and the hinge point of the thread trimming crank (9) and the thread trimming link (10) L1. The ratio of the distance L2 between the lower shaft (2) and the hinge point of the movable tool rest (4) and the thread trimming link (10) is not less than 2.5; when trimming the thread, the roller (82) and the thread trimming The thread trimming contact surface (32) on the outer periphery of the drive cam (31) is matched, the thread trimming drive assembly (8), the crank shaft (7) and the thread trimming crank (9) swing synchronously, and the thread trimming link (10) ) The transmission angle γ of the moving tool rest (4) is not less than 40°, and the thread trimming crank (9), the thread trimming link (10) and the moving tool rest (4) constitute a four-bar mechanism for performing thread trimming A reset torsion spring (16) is sleeved on the crank shaft (7), and both ends of the reset torsion spring (16) are in contact with the thread trimming crank (9) and the sewing machine bottom plate (1) respectively, and the thread trimming crank (9) Reset under the action of the reset torsion spring (16), and the thread trimming crank (9) drives the movable tool rest (4), the movable knife (5) and the crank shaft (7) through the thread trimming link (10) ) and the thread trimmer drive assembly (8) reset normally. 2. The automatic thread trimming mechanism of a sewing machine according to claim 1, wherein the thread trimming drive assembly (8) has a second extension arm (83), a first extension arm (81) and a second extension arm ( 83) are respectively located at both ends of the thread trimming drive assembly (8), the end of the second extension arm (83) is connected with a forced reset pin (84), and the lower shaft (2) is fixed with a forced reset drive cam (33); when the roller (82) passes over the end of the thread trimming segment on the thread trimming contact surface (32), the forced reset pin (84) is adjacent to the forced reset contact surface ( 34). 3. The automatic thread trimming mechanism of a sewing machine according to claim 2, characterized in that: it further comprises a power source (11), and the power source (11) is connected with the thread trimming drive assembly (8) through a transmission mechanism; , the power source (11) acts, and drives the wire-cutting drive assembly (8) to move along the axial direction of the crankshaft (7) through the transmission mechanism, so that the roller (82) is matched with the wire-cutting contact surface (32) , and the forced reset pin (84) is positioned on the outer peripheral side of the forced reset contact surface (34). 4. The automatic thread trimming mechanism of a sewing machine according to claim 3, wherein the power source (11) is an electromagnet with a mandrel parallel to the lower shaft (2), and the transmission mechanism comprises a top rod ( 12) and a connecting block (13), the end of the mandrel is fixed in the connecting block (13), one end of the top rod (12) is fixed in the connecting block (13), and the other end of the top rod (12) is fixed in the connecting block (13). One end abuts against the end face of the thread trimmer drive assembly (8). 5. The automatic thread trimming mechanism of a sewing machine according to claim 2, wherein the thread trimming drive assembly (8) has a drive body located between the first extension arm (81) and the second extension arm (83) A sliding groove (86) extending in the axial direction of the crankshaft (7) is provided on the driving body part (85), and the crankshaft (7) is penetrated in the driving body part (85), And a limit pin (87) is fixed on the crankshaft (7), the limit pin (87) is located in the chute (86) of the driving body part (85), and can slide back and forth along the extending direction of the chute (86). shift. 6. The automatic thread trimming mechanism of a sewing machine according to claim 2, wherein a return spring (14) is sleeved on the crank shaft (7), and a retaining ring (15) is fixed, and the retaining ring ( 15) is located between the wire trimming crank (9) and the second extension arm (83), the two ends of the return spring (14) are respectively abutted with the second extension arm (83) and the retaining ring (15). 7. The automatic thread trimming mechanism of a sewing machine according to claim 1, wherein the thread trimming crank (9) comprises a crank part (91) and a connecting rod part (92) which are independent of each other, and the crank part (91) ) is fixed with the crank shaft (7), the other end of the crank part (91) is fixed with one end of the connecting rod part (92), and the other end of the connecting rod part (92) is fixed with the thread trimming connecting rod (10). ) are hinged. 8 . The automatic thread trimming mechanism of a sewing machine according to claim 7 , wherein a limit surface ( 101 ) is provided on the lower end surface of the bottom plate of the sewing machine ( 1 ), and the crank portion ( 91 ) faces the limit surface ( 8 . The end face of 101) is provided with a receiving hole, a limiting pad (17) is built in the receiving hole, and the limiting pad (17) is matched with the limiting surface (101). 9. The automatic thread trimming mechanism of a sewing machine according to claim 1, characterized in that it further comprises a fixed knife (6) fixed on the bottom plate (1) of the sewing machine, one of said movable knives (5), said movable knife rest (4) There is one; when the thread is trimmed, the movable knife (5) is engaged with the fixed knife (6). 10. A sewing machine, comprising a sewing machine bottom plate (1), characterized in that: further comprising the automatic thread trimming mechanism of the sewing machine according to any one of claims 1-9, the lower shaft (2) and the moving knife rest (4) ) are rotatably installed in the sewing machine base plate (1).

Images