阅读说明：本技术 一种缝纫机 (Sewing machine ) 是由 何明金 祝书伟 郑吉� 柯祥林 于 2019-11-14 设计创作，主要内容包括：本发明提供一种缝纫机,包括主轴、牙架、安装在牙架上的送料牙、针板、连接在主轴和牙架之间的抬牙机构、下降驱动源和下降传动组件,下降驱动源通过下降传动组件与抬牙机构中的一抬牙传动部件相连；需要剪线时,下降驱动源动作、通过下降传动组件作用于抬牙传动部件,使送料牙下移预设距离,后续主轴转动时,主轴通过抬牙机构驱动送料牙运动、且送料牙始终在针板的上表面以下,故在剪线过程中送料牙不会将缝料向上顶起,相对于现有技术而言本申请消除了送料牙从针板上侧向上冒出的高度d3,即本申请剪线后残留在缝料上的线头长度L＝剪线位置至针板下侧的距离d1+针板厚度d2,由此减短剪线后残留在缝料上的线头长度。(The invention provides a sewing machine, which comprises a main shaft, a tooth frame, a feeding tooth arranged on the tooth frame, a needle plate, a tooth lifting mechanism connected between the main shaft and the tooth frame, a descending driving source and a descending transmission assembly, wherein the descending driving source is connected with a tooth lifting transmission part in the tooth lifting mechanism through the descending transmission assembly; when thread cutting is needed, the descending driving source acts and acts on the feed lifting tooth transmission component through the descending transmission component to enable the feed lifting teeth to move downwards for a preset distance, when the subsequent main shaft rotates, the main shaft drives the feed lifting teeth to move through the feed lifting tooth mechanism, and the feed lifting teeth are always below the upper surface of the needle plate, so that the feed lifting teeth cannot lift up a sewing material in the thread cutting process, compared with the prior art, the height d3 that the feed lifting teeth protrude upwards from the upper side of the needle plate is eliminated, namely the length L of a thread head remained on the sewing material after thread cutting is equal to the distance d1+ the thickness d2 of the needle plate from the position of the thread head on the sewing material to the lower side of the needle plate, and therefore the length of the thread head remained on the sewing material.)

1. A sewing machine comprises a main shaft (10), a tooth rack (20), a feeding tooth (30) arranged on the tooth rack (20), a needle plate (40) and a tooth lifting mechanism connected between the main shaft (10) and the tooth rack (20), and is characterized in that: the tooth lifting mechanism further comprises a descending driving source (50) and a descending transmission assembly (60), wherein the descending driving source (50) is connected with a tooth lifting transmission part in the tooth lifting mechanism through the descending transmission assembly (60); when the thread cutting is needed, the descending driving source (50) acts, the descending driving component (60) acts on the feed lifting tooth transmission component, the feed lifting tooth (30) moves downwards for a preset distance, when the subsequent main shaft (10) rotates, the main shaft (10) drives the feed lifting tooth (30) to move through the feed lifting tooth mechanism, and the feed lifting tooth (30) is always below the upper surface of the needle plate (40).

2. The sewing machine of claim 1, wherein: the tooth lifting mechanism comprises a tooth lifting shaft (71) parallel to the main shaft (10), a first tooth lifting transmission assembly connected between the main shaft (10) and the tooth lifting shaft (71), and a second tooth lifting transmission assembly connected between the tooth lifting shaft (71) and the tooth frame (20), wherein the tooth lifting transmission component is a component in the first tooth lifting transmission assembly.

3. The sewing machine of claim 2, wherein: the first lifting tooth transmission assembly comprises a lifting tooth eccentric wheel (72) fixed on a main shaft (10), a lifting tooth connecting rod (73), a lifting tooth swinging seat (74) with a first fixed swinging fulcrum (O1), a first swinging plate (75), a second swinging plate (76) and a lifting tooth crank (77) fixed on a lifting tooth shaft (71), wherein one end of the lifting tooth connecting rod (73) is rotatably sleeved on the periphery of the lifting tooth eccentric wheel (72), the other end of the lifting tooth connecting rod (73), one end of the first swinging plate (75) and one end of the second swinging plate (76) are coaxially hinged, the other end of the first swinging plate (75) is hinged with the lifting tooth swinging seat (74), the other end of the second swinging plate (76) is hinged with the lifting tooth crank (77), and the lifting tooth swinging seat (74) forms the lifting tooth transmission component.

4. The sewing machine of claim 3, wherein: the descending transmission assembly (60) comprises a rotating crank (61) which is provided with a second fixed swing fulcrum (O2) and is driven to rotate by a descending driving source (50), and a roller (62) which is arranged on the rotating crank (61), wherein a boss part (741) is arranged on the lifting tooth swinging seat (74), and the roller (62) is in contact fit with the boss part (741).

5. The sewing machine of claim 4, wherein: the descending driving source (50) is provided with a telescopic driving part which stretches and retracts along the direction parallel to the feed lifting shaft (71), the descending transmission assembly (60) further comprises an ejector pin (63) fixed to the telescopic driving part, a rotating lever (64) with a third fixed swinging fulcrum (O3) and a driving connecting rod (65), the ejector pin (63) can be abutted against the rotating lever (64), and two ends of the driving connecting rod (65) are respectively hinged to the rotating lever (64) and the rotating crank (61).

6. The sewing machine of claim 5, wherein: the descending driving source (50) is an electromagnet, an air cylinder or a linear motor.

7. The sewing machine of claim 3, wherein: the lifting tooth height adjusting mechanism comprises an adjusting stud (81) in threaded connection with the sewing machine shell, a knob (82) fixed at one end of the adjusting stud (81), an adjusting crank (83) in contact fit with the other end of the adjusting stud (81) and provided with a fourth fixed swing fulcrum (O4), and an adjusting connecting rod (84), wherein two ends of the adjusting connecting rod (84) are hinged to the adjusting crank (83) and the lifting tooth swing seat (74) respectively.

8. The sewing machine of claim 2, wherein: the second tooth lifting transmission assembly comprises a sliding block (78) and a tooth lifting swing fork (79) fixed on a tooth lifting shaft (71), the sliding block (78) is hinged with the tooth frame (20), a sliding groove is formed in the tooth lifting swing fork (79), and the sliding block (78) is located in the sliding groove and is in sliding fit with the sliding groove.

Technical Field

The present invention relates to a sewing machine.

Background

The existing flush joint machine is generally provided with a thread trimming assembly; as shown in FIG. 1, the thread trimmer assembly generally includes a movable blade 100 and a stationary blade 200, the movable blade 100 and stationary blade 200 engaging to sever the suture. Further, since the flat sewing machine has specific requirements for the cutting time, the feed dog 30 is located at the highest point of the movement stroke of the flat sewing machine, and at this time, as shown in fig. 1, the feed dog 30 protrudes upward from the needle plate 40 to push up the sewing material 500 by a distance, which is the height of the feed dog 30 protruding upward from the needle plate 40. The length of the thread end remained on the sewing material 500 after the thread cutting of the thread cutting assembly is related to the distance between the thread cutting position and the sewing material 500, wherein the thread cutting position where the movable knife 100 and the fixed knife 200 are engaged is positioned below the needle plate 40, the sewing material 500 is positioned on the feeding tooth 30, and the feeding tooth 30 protrudes upwards from the tooth groove of the needle plate 40, so that the length L of the thread end remained on the sewing material 500 after the thread cutting is determined to be the distance d1 from the thread cutting position to the lower side of the needle plate 40 + the thickness d2 of the needle plate 40 + the height d3 that the feeding tooth 30 protrudes upwards from the upper side of the needle plate 40, and the length of the thread end is longer. The longer thread end does not meet the increasing sewing requirements for some customers, the thread end is often required to be trimmed again to ensure better effect, and the trimming again can increase the workload and reduce the efficiency.

Disclosure of Invention

In view of the above-described drawbacks of the prior art, an object of the present invention is to provide a sewing machine capable of reducing the length of a thread end remaining on a work material after thread cutting.

In order to achieve the aim, the invention provides a sewing machine, which comprises a main shaft, a tooth rack, a feeding tooth arranged on the tooth rack, a needle plate, a tooth lifting mechanism connected between the main shaft and the tooth rack, a descending driving source and a descending transmission assembly, wherein the descending driving source is connected with a tooth lifting transmission part in the tooth lifting mechanism through the descending transmission assembly; when the thread needs to be cut, the descending driving source acts on the feed lifting tooth transmission part through the descending transmission assembly to enable the feed lifting tooth to move downwards for a preset distance, and when the subsequent main shaft rotates, the main shaft drives the feed lifting tooth to move through the feed lifting tooth mechanism, and the feed lifting tooth is always below the upper surface of the needle plate.

Further, the tooth lifting mechanism comprises a tooth lifting shaft parallel to the main shaft, a first tooth lifting transmission component connected between the main shaft and the tooth lifting shaft, and a second tooth lifting transmission component connected between the tooth lifting shaft and the tooth frame, wherein the tooth lifting transmission component is a component in the first tooth lifting transmission component.

Furthermore, the first lifting tooth transmission assembly comprises a lifting tooth eccentric wheel fixed on the main shaft, a lifting tooth connecting rod, a lifting tooth swinging seat with a first fixed swinging fulcrum, a first swinging plate, a second swinging plate and a lifting tooth crank fixed on the lifting tooth shaft, one end of the lifting tooth connecting rod is rotatably sleeved on the periphery of the lifting tooth eccentric wheel, the other end of the lifting tooth connecting rod, one end of the first swinging plate and one end of the second swinging plate are coaxially hinged, the other end of the first swinging plate is hinged with the lifting tooth swinging seat, the other end of the second swinging plate is hinged with the lifting tooth crank, and the lifting tooth swinging seat forms the lifting tooth transmission component.

Further, the descending transmission assembly comprises a rotating crank which is provided with a second fixed swinging fulcrum and is driven to rotate by a descending driving source, and a roller which is installed on the rotating crank, wherein a boss part is arranged on the lifting tooth swinging seat, and the roller is in contact fit with the boss part.

Furthermore, the descending driving source is provided with a telescopic driving part which is telescopic along the direction parallel to the feed lifting shaft, the descending transmission assembly further comprises a top pin fixed on the telescopic driving part, a rotating lever with a third fixed swing fulcrum and a driving connecting rod, the top pin can be abutted against the rotating lever, and two ends of the driving connecting rod are respectively hinged with the rotating lever and the rotating crank.

Further, the descending driving source is an electromagnet, an air cylinder or a linear motor.

Furthermore, the sewing machine further comprises a feed lifting height adjusting mechanism, the feed lifting height adjusting mechanism comprises an adjusting stud in threaded connection with the sewing machine shell, a knob fixed at one end of the adjusting stud, an adjusting crank in contact fit with the other end of the adjusting stud and provided with a fourth fixed swing fulcrum, and an adjusting connecting rod, and two ends of the adjusting connecting rod are respectively hinged with the adjusting crank and the feed lifting swing seat.

Furthermore, the second tooth lifting transmission assembly comprises a sliding block and a tooth lifting swing fork fixed on the tooth lifting shaft, the sliding block is hinged with the tooth frame, a sliding groove is formed in the tooth lifting swing fork, and the sliding block is located in the sliding groove and in sliding fit with the sliding groove.

As described above, the sewing machine according to the present invention has the following advantageous effects:

this application is when sewing machine sewing is about to end the needs trimming, the decline driving source makes through decline drive assembly and lifts tooth drive disk assembly and keep a position angle, this position angle of lifting tooth drive disk assembly can satisfy when follow-up main shaft rotates that the pay-off tooth is below the upper surface of faller all the time, so pay-off tooth can not upwards jack-up the sewing material at trimming in-process, for prior art this application has eliminated the height d3 that the pay-off tooth upwards appears from the faller upside, the end of a thread length L that remains on the sewing material after this application trimming promptly is distance d1+ faller thickness d2 of trimming position to the faller downside, the end of a thread length that remains on the sewing material after the trimming from this reduction.

Drawings

Fig. 1 is a schematic structural view of a conventional sewing machine during thread trimming.

Fig. 2 and 3 are schematic views of the sewing machine of the present application at different viewing angles.

Fig. 4 is an enlarged view of a circle a of fig. 3.

Fig. 5 and 6 are schematic views of connection among the descent drive source, the descent transmission assembly, the lifting tooth swinging seat and the lifting tooth height adjusting mechanism in different viewing angles.

Fig. 7 is a schematic view of the connection between the descent drive source, the descent transmission assembly, and the lifting tooth swing seat in the present application.

Fig. 8 is a schematic view of the structure of the sewing machine during thread trimming in the present application.

FIG. 9 is a power transmission diagram from the main shaft to the moving blade and from the main shaft to the feeding tooth in the sewing machine of the present application.

Description of the element reference numerals

10 spindle

20 dental articulator

30 feeding tooth

40 needle board

50-down driving source

60 drop drive assembly

61 crank for rotation

62 roller

63 knock pin

64 rotating lever

65 drive link

71 lifting tooth shaft

72 eccentric cam of lifting tooth

73 lifting tooth connecting rod

74 lifting tooth swing seat

741 roller

75 first swinging plate

76 second swinging plate

77 feed lifting crank

78 slide block

79 lifting tooth swing fork

81 adjusting stud

82 knob

83 adjusting crank

84 adjusting connecting rod

85 tension spring

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

It should be understood that the structures, proportions, and dimensions shown in the drawings and described herein are for illustrative purposes only and are not intended to limit the scope of the present invention, which is defined by the claims, but rather by the claims. In addition, the terms such as "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for convenience of description only and are not intended to limit the scope of the present invention, and changes or modifications of the relative relationship thereof may be made without substantial technical changes and modifications.

The present application provides a sewing machine of the type being a flat bed sewing machine. For convenience of description, the following embodiments define the directions as follows: as shown in fig. 2, the axial direction of the main shaft 10 in the sewing machine is defined as a left-right direction, the direction of the main shaft 10 towards the head of the sewing machine is a left direction (i.e. the left side of the paper surface in the view of fig. 2), and the direction of the main shaft 10 towards the tail of the sewing machine is a right direction (i.e. the right side of the paper surface in the view of fig. 2); the moving direction of the sewing material when the sewing machine is used for sewing is defined as a front direction.

As shown in fig. 2 and 3, the present application provides a sewing machine including a main shaft 10 extending left and right, a thread frame 20, a feed dog 30 fixedly installed on the thread frame 20, a needle plate 40, a feed dog mechanism connected between the main shaft 10 and the rear end of the thread frame 20, a descending drive source 50, and a descending transmission assembly 60, wherein the descending drive source 50 is connected to a feed dog transmission member of the feed dog mechanism through the descending transmission assembly 60. When the sewing machine sews normally, the descending driving source 50 does not act, the feed lifting tooth transmission part keeps the initial position angle under the sewing process, the main motor in the sewing machine drives the main shaft 10 to rotate, the main shaft 10 drives the tooth frame 20 and the feed lifting tooth 30 to reciprocate up and down through the feed lifting tooth mechanism, and the feed lifting tooth 30 can protrude upwards from the needle plate 40 when moving to the highest point. When the sewing of the sewing machine is about to finish and thread cutting is needed, the descending driving source 50 acts and acts on the feed lifting tooth transmission part through the descending transmission assembly 60 to force the feed feeding tooth 30 to move downwards for a preset distance, and the feed lifting tooth transmission part keeps the position angle under the thread cutting process; then, the main motor drives the main shaft 10 to rotate, the main shaft 10 drives the lower shaft in the sewing machine to rotate through the transmission mechanism, the lower shaft drives the movable knife 100 to move through the thread cutting transmission assembly, the movable knife 100 is meshed with the fixed knife 200 to cut off the thread, and thread cutting is completed as shown in fig. 8. In particular, during the trimming process, the main motor drives the main shaft 10 to rotate, thereby driving the movable blade 100 to move, the main shaft 10 drives the feeding teeth 30 to reciprocate up and down through the tooth lifting mechanism, but the feeding teeth 30 are always below the upper surface of the needle plate 40 because the tooth lifting transmission part keeps the position angle in the thread cutting process, that is, even if the main shaft 10 rotates during thread cutting, the feed dog 30 does not always protrude upward from the needle plate 40, that is, the feed dog 30 does not lift up the sewing material 500 during thread cutting, the present application eliminates the height d3 of the feed dog 30 protruding upward from the upper side of the needle plate 40 compared to the prior art, that is, in the present application, the length L of the thread end remaining on the work material 500 after thread trimming is equal to the distance d1 from the thread trimming position to the lower side of the needle plate 40 + the thickness d2 of the needle plate 40, thereby reducing the length of the thread end remained on the sewing material 500 after thread trimming and realizing the thread trimming effect of the short thread end. In addition, the thread trimming mechanism having the thread trimming transmission assembly, the movable knife 100 and the fixed knife 200 in the sewing machine is an automatic thread trimming mechanism disclosed in the prior art, for example, the chinese patent application with the application number of 201710215982.X, and therefore, the description thereof is omitted here.

As shown in fig. 2 and 3, the tooth lifting mechanism includes a tooth lifting shaft 71 parallel to the main shaft 10, a first tooth lifting transmission component connected between the main shaft 10 and the tooth lifting shaft 71, and a second tooth lifting transmission component connected between the tooth lifting shaft 71 and the tooth frame 20, wherein the tooth lifting transmission component is a component of the first tooth lifting transmission component. Preferably, as shown in fig. 2 to 4, the first lifting tooth transmission assembly includes a lifting tooth eccentric wheel 72 fixed on the main shaft 10 by a screw, a lifting tooth connecting rod 73, a lifting tooth swinging seat 74 having a first fixed swinging fulcrum O1, a first swinging plate 75, a second swinging plate 76, and a lifting tooth crank 77 fixed on the lifting tooth shaft 71 by a screw, an upper end of the lifting tooth connecting rod 73 is rotatably fitted around the periphery of the lifting tooth eccentric wheel 72, a lower end of the lifting tooth connecting rod 73, a front end of the first swinging plate 75, and a front end of the second swinging plate 76 are coaxially hinged by a left-right extending connecting pin, a rear end of the first swinging plate 75 is hinged to the lifting tooth swinging seat 74 by a left-right extending connecting pin, a rear end of the second swinging plate 76 is hinged to the lifting tooth crank 77 by a left-right extending connecting pin, the lifting tooth swinging seat 74 constitutes a lifting tooth transmission member, that is, the lowering driving source acts on the lifting tooth swinging seat 74 through the lowering transmission assembly 60, the pre-driving feeding teeth 30 descend for a preset distance before trimming. The second feed lifting transmission component comprises a slide block 78 and a feed lifting swing fork 79 fixed on the feed lifting shaft 71, the slide block 78 is hinged with the tooth rack 20 through a shaft position screw extending left and right, a slide groove is formed in the feed lifting swing fork 79, and the slide block 78 is positioned in the slide groove and is in sliding fit with the slide groove.

Preferably, as shown in fig. 4, the left and right sides of the lifter swing seat 74 are rotatably mounted to a first support pin extending left and right, respectively, the first support pin is fixed to the sewing machine housing, the first support pin constitutes a first fixed swing fulcrum O1 of the lifter swing seat 74, and the lifter swing seat 74 is rotatable about the first support pin. In addition, the lifting tooth swing seat 74 is of a concave structure and is provided with two seat arm parts which are oppositely arranged left and right, two first swing plates 75 and two second swing plates 76 are arranged in the lifting tooth swing seat 74, the left side and the right side of the lower end of the lifting tooth connecting rod 73 are respectively provided with one second swing plate 76, and the first swing plate 75 is respectively arranged between the second swing plate 76 and the seat arm part of the lifting tooth swing seat 74.

Further, as shown in fig. 5 to 7, the descent drive assembly 60 includes a rotary crank 61 having a second fixed swing fulcrum O2 and driven to rotate by the descent drive source 50, and a roller 62 mounted on the rotary crank 61, and the jaw swing seat 74 is provided with a boss portion 741, and a surface of the roller 62 is in contact engagement with the boss portion 741. The rotary crank 61 is rotatably mounted to the sewing machine base plate by a second support pin extending up and down, the second support pin constituting a second fixed swing fulcrum O2 of the rotary crank 61, the rotary crank 61 being capable of rotating about the second support pin; the central axis of the roller 62 extends vertically, and the roller 62 may be fixed to the crank 61 or may be rotatably attached to the crank 61. Further, the connection structure between the descent drive source 50 and the rotating crank 61 is: as shown in fig. 5 to 7, the descent drive source 50 has a telescopic drive portion that extends and contracts in the left-right direction parallel to the feed dog shaft 71, and the descent transmission assembly 60 further includes a knock pin 63 fixed to the telescopic drive portion, a rotation lever 64 having a third fixed swing fulcrum O3, and a drive link 65, the knock pin 63 being capable of abutting against the left end of the rotation lever 64, the right end of the rotation lever 64 being hinged to the left end of the drive link 65, and the right end of the drive link 65 being hinged to the rotation crank 61 by shaft screws extending in the up-down direction. The turning lever 64 is rotatably mounted to the sewing machine base plate by an axis screw extending up and down, the axis screw constituting a third fixed swing fulcrum O3 of the turning lever 64, the turning lever 64 is substantially a strip-shaped plate arranged obliquely, and the third fixed swing fulcrum O3 of the turning lever 64 is located between the left and right ends of the turning lever 64. In addition, an axial screw of the third fixed swing fulcrum O3 constituting the rotating lever 64 is sleeved with a return torsion spring, one end of the return torsion spring is inserted into the bottom plate of the sewing machine, the other end of the return torsion spring is abutted against the rotating lever 64, and the return torsion spring is used for returning each component in the descent transmission assembly 60 when the descent drive source 50 is powered off. The rotating crank 61 is substantially L-shaped, and the second fixed swing fulcrum O2 of the rotating crank 61, the mounting point of the roller 62 and the rotating crank 61, and the hinge point of the rotating crank 61 and the driving link 65 are distributed in a triangular shape. Preferably, the descent driving source 50 is an electromagnet, a cylinder, or a linear motor; in this embodiment, the descending driving source 50 is an electromagnet, and the descending driving source 50 is fixed to the bottom plate of the sewing machine by a mounting bracket.

Further, as shown in fig. 5 and 6, the sewing machine further includes a feed lifting height adjusting mechanism, the feed lifting height adjusting mechanism includes an adjusting stud 81 screwed into the sewing machine housing and extending forward and backward, a knob 82 fixed to a rear end of the adjusting stud 81, an adjusting crank 83 in contact fit with a front end of the adjusting stud 81 and having a fourth fixed swing fulcrum O4, and an adjusting link 84, the adjusting crank 83 is rotatably mounted to the sewing machine housing through a third support pin extending left and right, the third support pin constitutes a fourth fixed swing fulcrum O4 of the adjusting crank 83, the adjusting stud 81 and the fourth fixed swing fulcrum O4 of the adjusting crank 83 are offset in the up-down direction, and an upper end of the adjusting link 84 is hinged to the adjusting crank 83, and a lower end of the adjusting link 84 is hinged to the feed lifting swing base 74 through shaft position screws extending left and right. In addition, in order to ensure the reliability of contact fit between the front end of the adjusting stud 81 and the rear end face of the adjusting crank 83, the feed lifting tooth height adjusting mechanism further comprises a tension spring 85, two ends of the tension spring 85 are respectively connected with the adjusting crank 83 and the sewing machine shell, and the tension spring 85 applies acting force to the adjusting crank 83, so that the contact between the adjusting crank 83 and the adjusting stud 81 is reliable, and the accuracy of feed lifting tooth height adjustment of the feed feeding tooth 30 is ensured; the feed dog height of the feed dog 30 refers to the distance between the upper surface of the feed dog 30 and the upper surface of the needle plate 40 when the feed dog 30 moves to the highest point in the sewing process.

The sewing machine with the structure has the following working principle:

1. when the sewing machine is normally used for sewing, the descending driving source 50 is in a power-off state, the feed lifting tooth swinging seat 74 keeps an initial position angle in a sewing process, the main shaft 10 drives the tooth frame 20 and the feed lifting tooth 30 to reciprocate up and down through the feed lifting tooth mechanism, as shown in fig. 9, when the feed lifting tooth 30 moves to the highest point, the feed lifting tooth 30 can protrude upwards from the needle plate 40, and the sewing machine has a preset feed lifting tooth height.

2. When the sewing machine needs to cut thread immediately before sewing, as shown in fig. 9, the descending driving source 50 is powered on, an iron core of the descending driving source extends rightward, the rotating lever 64 is pushed by the ejector pin 63 to rotate around the third fixed swing fulcrum O3, the rotating lever 64 enables the rotating crank 61 to rotate around the second fixed swing fulcrum O2 through the driving connecting rod 65, the lifting tooth swinging seat 74 is driven to rotate around the first fixed swing fulcrum O1 by the contact and matching between the roller 62 on the rotating crank 61 and the boss part 741 on the lifting tooth swinging seat 74, the lifting tooth swinging seat 74 drives the lifting tooth crank 77 and the lifting tooth shaft 71 to rotate for an angle through the first swinging plate 75 and the second swinging plate 76, and the feeding tooth 30 moves downwards for a preset distance; next, a thread cutting driving source which plays a role in thread cutting clutch in the thread cutting mechanism of the sewing machine acts to enable power transmission to be formed between the lower shaft and the movable knife 100, the main shaft 10 drives the lower shaft to rotate, the lower shaft drives the movable knife 100 to move, and the movable knife 100 is meshed with the fixed knife 200 to cut off a thread; in the thread cutting process, the feeding tooth 30 does not jack the sewing material 500 upwards all the time, so that the length of the thread end remained on the sewing material 500 after thread cutting is reduced. After the thread cutting is finished, the descending driving source 50 is powered off, the components in the descending transmission assembly 60 are reset through the reset torsion springs, and the lifting tooth swing seat 74 is also reset to the initial position angle.

3. The lower supply action after the sewing of the sewing machine is finished: when the sewing material 500 needs to be taken away from the needle plate 40 after the thread cutting is finished, a needle in the sewing machine is located at the highest position, the needle and the feeding tooth 30 are both driven by the main shaft 10, so that the feeding tooth 30 is correspondingly located at the highest position and protrudes upwards from the needle plate 40; in order to take the sewing material 500 away conveniently, at the moment, the descending driving source 50 is powered on, the iron core of the descending driving source extends rightward, the descending transmission assembly 60 drives the lifting tooth swinging seat 74 to rotate around the first fixed swinging fulcrum O1 by an angle, so that the feeding tooth 30 moves downwards to be below the upper surface of the needle plate 40 to execute the lower supply action, the sewing material 500 is more convenient to enter and exit, the user experience is improved, the sewing material 500 can be prevented from being scratched, and the sewing quality is ensured. After the sewing material 500 is taken and placed, the presser foot is put down, the descending driving source 50 is powered off, all the components in the descending transmission assembly 60 are reset through the reset torsion spring, and the lifting tooth swing seat 74 is also reset to the initial position angle.

4. When the feed lifting tooth height needs to be adjusted, the sewing machine is stopped, the knob 82 is rotated, the knob 82 drives the adjusting stud 81 to rotate together, the adjusting stud 81 moves forwards or backwards when rotating, the adjusting crank 83 rotates around the fourth fixed swing fulcrum O4, the feed lifting tooth swing seat 74 is driven to rotate around the first fixed swing fulcrum O1 through the adjusting connecting rod 84, the initial position angle of the feed lifting tooth swing seat 74 is changed, the swing amplitude of the spindle 10 driving the feed lifting tooth shaft 71 to swing through the first feed lifting tooth transmission assembly is changed, the swing amplitude of the feed lifting tooth shaft 71 directly determines the feed lifting tooth height of the feed lifting tooth 30, and the feed lifting tooth height of the feed lifting tooth 30 is adjusted. When the swing amplitude of the feed lifting tooth shaft 71 is reduced, the height of the feed lifting tooth 30 is reduced, the feed lifting tooth shaft is suitable for sewing thin materials, and the wrinkling phenomenon of the sewing materials 500 can be improved; when the swing amplitude of the feed lifting tooth shaft 71 is increased, the height of the feed lifting tooth 30 is increased, the feed lifting tooth shaft is suitable for sewing thick materials and sewing over stems, the feed efficiency can be effectively improved, and the feed is smoother. Particularly, according to the method, the feed dog height of the feed dog 30 is adjusted based on changing the swing amplitude of the feed dog shaft 71, the motion track of the feed dog 30 does not move up or down integrally, but only changes the amplitude in the up-down direction, but does not change the amplitude in the front-back direction, so that the needle pitch of the sewing machine is kept unchanged in the feed dog height adjusting process, the sewing quality is not affected, and the phenomenon that the feed dog 30 drags the sewing material 500 back is avoided. Therefore, the height of the feed dog 30 can be adjusted within a certain range, stepless adjustment is achieved, the needle pitch cannot be changed while the height of the feed dog is adjusted, the sewing machine can have different heights of the feed dog according to sewing materials 500 of different specifications, the sewing quality can be effectively guaranteed, the adaptability of the sewing materials 500 of the sewing machine is improved, the universality of the sewing machine is greatly improved, and the competitiveness of products is improved.

Further, as can be seen from fig. 9: the main driving sources for completing the periodic feeding motion and the thread trimming motion of the feeding tooth 30 in the sewing machine are the main shafts 10; the thread cutting driving source plays a thread cutting clutch role, no or no power transmission exists between the lower shaft and the movable cutter 100, when thread cutting is needed, electromagnets which form the thread cutting driving source can be electrified, the thread cutting driving source is powered off in other states, and the movable cutter 100 cannot move; the descending driving source 50 functions to change the position angle of the swing seat 74 of the lifting tooth, thereby realizing the automatic descending of the feeding tooth 30.

In conclusion, the present invention effectively overcomes various disadvantages of the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.