CN107237063B

CN107237063B - thread cutting device of sewing machine

Info

Publication number: CN107237063B
Application number: CN201710685449.XA
Authority: CN
Inventors: 王明敏; 其他发明人请求不公开姓名
Original assignee: Jack Sewing Machine Co Ltd
Current assignee: Jack Technology Co Ltd
Priority date: 2017-08-11
Filing date: 2017-08-11
Publication date: 2020-01-31
Anticipated expiration: 2037-08-11
Also published as: CN107237063A

Abstract

The invention provides a thread cutting device of sewing machines, which belongs to the technical field of machinery and solves the problems that the occlusal force of a movable cutter and a fixed cutter of the thread cutting device of the existing sewing machine cannot be adjusted, the clamping force of a bottom thread cannot be adjusted, and the thread cutting performance is unstable.

Description

thread cutting device of sewing machine

Technical Field

The invention belongs to the technical field of sewing machines, and relates to a thread trimming device of sewing machines.

Background

Sewing machines are machines that use or more sewing threads to form or more stitches in the fabric to interlace or stitch or more layers of fabric, and are currently used in the garment manufacturing industry in large numbers, especially in factory-sized sewing machines, and more is widely used in mass garment manufacturing enterprises.

In the existing thread shearing device of the double-needle sewing machine, a movable cutter is fixed on a movable cutter rotating shaft, a fixed cutter supporting spring is riveted on a needle plate and is installed on the needle plate together with a fixed cutter through a fixed cutter fixing screw, wherein a fixed cutter supporting plate plays a role in increasing the meshing force of the movable cutter and the fixed cutter through supporting the fixed cutter, and the movable cutter does fixed-angle rotary motion through winding the movable cutter shaft and does thread shearing motion through matching with the fixed cutter.

For example, patent application No. 200810005774.8 discloses a sewing machine with a thread cutting device, comprising a movable knife having a hook portion at a front end portion thereof and reciprocally driven along a horizontal plane so that the hook portion crosses a needle bed to form a needle hole, a fixed knife for cutting a needle thread and/or a looper thread hooked on the hook portion and transferred to a side of the needle bed on the needle bed side by a shearing action with the movable knife when the movable knife is forwardly driven, and a clamp for elastically clamping the cut thread portion between the front end portions of the movable knife, wherein a slit having a vertical width equal to or substantially equal to a thickness of the movable knife is formed at a position closer to a rear surface of the needle bed than a cutting edge of the fixed knife on a reciprocating driving moving path of the movable knife, and the slit is brought into sliding contact with a front surface and a rear surface of the movable knife at least when the movable knife is first cut by the shearing action between the movable knife and the fixed knife, thereby pressing and guiding the front end portion of the movable knife to a fixed knife side.

The existing thread cutting device of the sewing machine has the defects that 1, the occlusal force of a fixed knife and a movable knife cannot be adjusted, although the fixed knife supporting spring supports, the knife supporting spring has fixed fatigue limit and unstable elastic quality, denier of the fixed knife has no supporting force or the fixed knife is abraded to influence the thread cutting performance, 2, a bobbin thread clamping spring, namely the elastic force of a thread clamping plate, cannot be adjusted, the bobbin thread clamping spring is simply fixed on a bracket and clamps a bobbin thread after thread cutting by means of the elastic force of the bobbin thread clamping spring, so that a required stitch is continuously formed when next sewing is started, the bobbin thread clamping spring also has fixed fatigue limit and unstable elastic quality, when the bobbin thread clamping spring loses the elastic force and fails, the bobbin thread clamping spring cannot clamp the bobbin thread after thread cutting, the phenomenon of seam starting and thread falling occurs when next sewing is performed, 3, under the conditions of thick bobbin thread and thin bobbin thread, because a plurality of existing thread clamping springs cannot freely adjust angles, the bobbin thread clamping spring acts on the bobbin thread after thread cutting, the bobbin thread is not easy to adjust the bobbin thread, the bobbin thread cutting, the bobbin thread is more difficult to be fixed from the bobbin, the bobbin thread cutting needle is more easily, the bobbin thread cutting is inconvenient to be adjusted, the bobbin thread cutting needle is more easily, the bobbin thread is inconvenient to be repaired, the bobbin thread clamping force is caused by inertia, the bobbin thread clamping force is caused by the inertia, the trouble is caused by the trouble.

Disclosure of Invention

The invention aims to provide an thread trimming device of a sewing machine aiming at the problems in the prior art, and the invention aims to solve the technical problem of how to realize the adjustability of the occlusion force between a fixed knife and a movable knife and the clamping force of a bottom thread and ensure better thread trimming performance and thread clamping performance.

The object of the invention can be achieved by adopting the following technical scheme that the thread trimming device of sewing machines comprises a rotating shuttle table, and comprises a fixed cutter frame, a movable cutter and a fixed cutter, wherein the movable cutter is arranged on the rotating shuttle table, the thread trimming device is characterized in that the fixed cutter frame comprises a strip-shaped connecting part and a block-shaped mounting part for fixing the fixed cutter, the mounting part is arranged in a bending way relative to the connecting part, a strip-shaped hole is formed in the connecting part along the length direction of the connecting part, the connecting part is attached to the side wall of the rotating shuttle table and can penetrate through a fastener through the strip-shaped hole to be fixed on the rotating shuttle table, the fixed cutter is fixed on the mounting part and is positioned above the movable cutter, a bottom thread clamping component is further arranged below the movable cutter, and the movable cutter can be matched with the fixed cutter to.

This thread trimming device of sewing machine is through improving the design, the stationary knife passes through stationary knife rest leg joint on the lateral wall of rotating shuttle platform, make this thread trimming device and each faller can general, market availability is strong, and the thread trimming performance of machine need not debug again when changing the needle position, convenient production, debugging, and maintenance simultaneously, be equipped with strip hole on the stationary knife rest, the stationary knife rest passes strip hole through the fastener and fixes on rotating shuttle platform lateral wall, thereby make the height-adjustable of stationary knife rest in the upper and lower direction, namely the height-adjustable of stationary knife in the upper and lower direction, after the stationary knife wearing and tearing, can realize the regulation of occlusal force between stationary knife and the moving knife through the position about the adjustment stationary knife, make keep better occlusal force between stationary knife and the moving knife all the time, guarantee better thread trimming performance.

In foretell sewing machine's thread trimming device, strip hole two has still been seted up along connecting portion length direction on the connecting portion, the groove of stepping down has on the connecting portion, the bottom in the groove of stepping down is seted up to strip hole two, still be equipped with eccentric bolt on the connecting portion, eccentric bolt's eccentric screw passes strip hole two and wears to establish on the lateral wall of rotating shuttle platform, eccentric bolt's nut embedding step down the inslot and with the lateral wall in the groove of stepping down pastes and leans on. When the fixed knife is worn, the vertical motion amount of the fixed knife rest is controlled by adjusting the eccentric amount of the adjusting screw of the fixed knife rest, so that the occlusion amount of the fixed knife and the movable knife is controlled, and after the adjustment is completed, the fixed knife and the movable knife are locked and fixed through the fixing part, so that a good occlusion force is always kept between the fixed knife and the movable knife, and good thread cutting performance is ensured.

In the thread trimming device of the sewing machine, the side wall of the rotating shuttle table is also provided with a strip-shaped guide groove penetrating through the upper table surface and the lower table surface of the rotating shuttle table, the connecting part of the fixed knife rest can be embedded into the guide groove in a sliding manner, and the two side walls of the connecting part are respectively attached to the two groove walls of the guide groove.

In the thread trimming device of the sewing machine, the fastening piece is a fixing bolt, the rotating shuttle table is provided with a fixing threaded hole, the rod part of the fixing bolt penetrates through the strip-shaped hole to be connected into the fixing threaded hole, the head part of the fixing bolt is pressed against the edge of the strip-shaped hole , when the fixed knife is abraded, the fixing bolt is only required to be unscrewed, then the eccentric bolt is rotated, the eccentric amount of the eccentric bolt is adjusted, the up-and-down motion amount of the fixed knife rest is controlled, so that the occlusion amount of the fixed knife and the movable knife is controlled, after the adjustment is completed, the fixing bolt is screwed for fixing, the operation is convenient, a good occlusion force can be always kept between the fixed knife and the movable knife, and good thread trimming performance.

The thread trimming device of the sewing machine is characterized in that a movable knife guide frame is further fixed on the rotating shuttle table, a guide sliding groove is formed in the movable knife guide frame, a movable knife driving sliding block is connected in the guide sliding groove in a sliding mode, the movable knife is fixed on the movable knife driving sliding block, a movable knife rotating shaft is further connected on the rotating shuttle table in a rotating mode, a swinging rod is arranged at the end of the movable knife rotating shaft, a strip-shaped groove is formed in the movable knife driving sliding block and is perpendicular to the guide sliding groove, a vertically arranged driving rod is arranged on the swinging rod and extends into the strip-shaped groove and can slide in the strip-shaped groove, through the design, the thread trimming track of the thread trimming device is a linear type thread trimming track, compared with the existing rotary type thread trimming track, the thread trimming stroke is short, the adjusting method is simple, compared with the existing thread trimming device, the thread trimming device adopts a straight knife for trimming, after times of thread trimming, the amplified motion of the movable knife starts, the formed at the moment, the size of the thread loop is stable, the size of the thread loop is only in relation with the thread trimming time, the needle plate and the needle ring and the needle plate can be changed without thread trimming mechanism, the needle bar can ensure that the quality of the needle bar is changed gradually changed from the needle bar is poor.

In the thread trimming device of the sewing machine, the driving roller is further sleeved on the driving rod and can rotate relative to the driving rod, and the driving roller stretches into the strip-shaped groove and can rotate around the driving rod in the strip-shaped groove. Through the design of drive roller, the drive roller can slide along with the actuating lever in the bar inslot, and drive roller itself can rotate around the actuating lever again simultaneously to make the slip in the spout more smooth and easy, guarantee the smooth and easy nature of trimming.

In the thread trimming device of the sewing machine, the bottom thread clamping assembly comprises a bottom thread clamping spring and a supporting spring piece, a movable knife bracket is fixedly connected to the movable knife guide frame, the end of the bottom thread clamping spring is fixed to the movable knife bracket through screws, the end of the bottom thread clamping spring is elastically abutted to the movable knife, the end of the supporting spring piece is fixed to the movable knife bracket, the end of the supporting spring is elastically abutted to the lower surface of the bottom thread clamping spring, an adjusting bolt is connected to the movable knife bracket and located below the supporting spring piece and can be abutted to the lower surface of the supporting spring piece, the supporting spring piece supports the bottom thread clamping spring during working, when the elasticity of the bottom thread clamping spring is insufficient or excessive, the adjusting bolt is arranged below the supporting spring piece, the head of the adjusting bolt can abut against the lower surface of the supporting spring piece to play a supporting role, and the height of the adjusting bolt can be controlled to realize vertical control of supporting tension by rotating the adjusting bolt, so that the bottom thread clamping spring clamping force is finally adjusted, and poor seam stripping phenomenon of the bottom thread during next sewing is avoided.

In foretell sewing machine's thread trimming device, the support spring leaf includes fashioned fixed plate of body, crosses the cab apron, supports backup plate and backup pad, the fixed plate level laminating is fixed on moving the knife rest, it is formed by fixed plate bending type that makes progress to cross the cab apron, support the backup plate by crossing cab apron bending type and parallel with the fixed plate, the backup pad with support to be connected and support relatively to support and lean on the board tilt up setting, adjusting bolt is located to support the below of backup plate and supports and lean on the lower face of supporting the backup plate.

The support plate is also provided with a small boss which protrudes upwards, the small boss is positioned at the end far away from the fixed plate and is abutted against the lower surface of the bottom thread clamping spring, the upper thread is thick when sewing due to clothing process requirements, the bottom thread is thin, the small boss is designed on the clamping spring sheet, the boss is biased towards the tongue head, and under the condition that the bottom thread and the surface thread are clamped simultaneously after thread trimming, the boss can play a role similar to levers, so that the clamping direction can be freely deflected leftwards and rightwards, the thick thread and the thin thread can be clamped simultaneously, the bottom thread is clamped more firmly, the support plate is also provided with the small boss which protrudes upwards, when the bottom thread and the thick thread of the upper thread are caused, the bottom thread clamping spring is in parallel contact with the bottom surface of the movable knife, when the sewing process requires that the upper thread is thick, the bottom thread is thin, the boss on the support spring sheet is in contact with the bottom thread clamping spring, the bottom thread clamping spring is automatically adjusted in angle according to the thick thread condition of the upper thread and the bottom thread, and the clamping direction of the bottom thread is thick, the clamping force of the bottom thread can not be changed into the same, and the sewing process can be reliable.

In the thread trimming device of the sewing machine, the upper end edge of the small boss is provided with a chamfer. The upper end edge of the small boss is arranged along the chamfer, so that the degree of freedom of left and right deflection of the clamping direction is better, the thick line and the thin line can be clamped simultaneously, and the bottom line can be clamped more firmly.

Compared with the prior art, the thread trimming device of the sewing machine has the following advantages:

1. the vertical motion amount of the fixed cutter frame is controlled by adjusting the eccentric amount of the adjusting screw of the fixed cutter frame, so that the meshing amount of the fixed cutter and the movable cutter is controlled, a better meshing force is always kept between the fixed cutter and the movable cutter, and better thread cutting performance is ensured.

2. The trimming track of the trimming device is linear, and compared with the existing rotary trimming track, the trimming device has short trimming stroke and simple adjusting method.

3. The supporting spring piece supports the bottom line clamping spring during working, when the elasticity of the bottom line clamping spring is insufficient or too large, the adjusting bolt is arranged below the supporting spring piece, the head of the adjusting bolt can be abutted against the lower surface of the supporting spring piece to play a supporting role, the adjusting bolt is rotated, the height of the adjusting bolt can be controlled to control the tension of the supporting spring piece up and down, so that the line clamping force of the bottom line clamping spring is finally adjusted, and the bad phenomenon that the seam is sewed and separated from the line can be avoided when sewing next time.

4. Because of the requirement of clothing technology, the upper thread is thick and the bottom thread is thin when sewing, small bosses are designed on the clamping spring piece, the positions of the bosses are inclined to the tongue, and under the condition that the bottom thread and the surface thread are clamped simultaneously after thread trimming, the bosses can play a role similar to levers, so that the clamping direction can be freely inclined leftwards and rightwards, the thick thread and the thin thread can be clamped simultaneously, and the clamping of the bottom thread is firmer.

Drawings

Fig. 1 is a perspective view of the thread trimming device of the sewing machine.

Fig. 2 is a perspective view of the thread trimming device of the sewing machine in another directions.

Fig. 3 is a structural view of the stationary blade holder.

Fig. 4 is a structural view of an eccentric bolt.

Fig. 5 is a structural view of the lower wire trap assembly.

Fig. 6 is a structural view of the support spring piece.

Fig. 7 is a structural view of the movable blade rotating shaft.

In the figure, 1, a rotating shuttle table, 1a, a guide groove, 2, a fixed cutter frame, 2a, a connecting plate, 2a1, a strip-shaped hole , 2a2, a strip-shaped hole II, 2a3, a abdication groove, 2b, an installation part, 3, a movable cutter, 4, a fixed cutter, 5, a fastener, 6, an eccentric bolt, 6a, an eccentric screw, 6b, a nut, 7, a movable cutter guide frame, 8, a movable cutter driving block, 8a, a strip-shaped groove, 9, a movable cutter rotating shaft, 9a, a swinging rod, 9b, a driving rod, 10, a driving roller, 11, a bottom wire clamping spring, 12, a supporting spring piece, 12a, a fixing plate, 12b, a transition plate, 12c, a butting plate, 12d, a supporting plate, 12e, a small boss, 13, a movable cutter bracket and 14 are provided with an adjusting bolt.

Detailed Description

The following is a description of specific embodiments of the present invention with reference to the drawings, but the present invention is not limited to these embodiments.

As shown in fig. 1 and 2, the sewing machine includes a rotating shuttle table 1. The thread cutting device comprises a fixed cutter frame 2, a movable cutter 3, a fixed cutter 4 and a needle plate.

As shown in fig. 2 and 7, the rotating shuttle table 1 is further fixed with a movable knife guide frame 7, the movable knife guide frame 7 is provided with a guide sliding groove, a movable knife driving sliding block 8 is connected in the guide sliding groove in a sliding manner, the movable knife 3 is fixed on the movable knife driving sliding block 8, the rotating shuttle table 1 is further connected with a movable knife rotating shaft 9 in a rotating manner, an end of the movable knife rotating shaft 9 is provided with a swinging rod 9a, the movable knife driving sliding block 8 is provided with a strip-shaped groove 8a, the strip-shaped groove 8a is perpendicular to the guide sliding groove, the swinging rod 9a is provided with a vertically arranged driving rod 9b, the driving rod 9b extends into the strip-shaped groove 8a and can slide in the strip-shaped groove 8a, the fixed knife 4 and the movable knife 3 are both positioned below the needle plate, the movable knife 3 can be matched with the fixed knife 4 to realize thread trimming, through the design, the thread trimming track of the thread trimming device is linear type, the thread trimming stroke is short, the size of the thread loop is stable, the size of the thread trimming device can only pass through the needle plate when the middle part of the movable knife 3, and the thread trimming time is stable.

Specifically, still the cover is equipped with drive roller 10 on the actuating lever 9b, and drive roller 10 can rotate relative to actuating lever 9b, and drive roller 10 stretches into in the bar groove 8a and can rotate around actuating lever 9b in the bar groove 8a to make the slip in the spout more smooth and easy, guarantee the smoothness nature of trimming.

As shown in fig. 1 and 3, the stationary knife holder 2 includes an elongated connecting portion 2a and a block-shaped mounting portion 2b for fixing the stationary knife 4, the mounting portion 2b is disposed in a bending manner relative to the connecting portion 2a, a strip-shaped hole a1 and a strip-shaped hole two 2a2 are formed in the connecting portion 2a along the length direction of the connecting portion 2a, a relief groove 2a3 is formed in the connecting portion 2a, a strip-shaped hole two 2a2 is formed in the bottom of the relief groove 2a3, an eccentric bolt 6 is further disposed on the connecting portion 2a, an eccentric screw 6a of the eccentric bolt 6 penetrates through the strip-shaped hole two 2a2 and is inserted into a side wall of the rotary shuttle table 1, a nut 6b of the eccentric bolt 6 is inserted into the relief groove 2a3 and abuts against the side wall of the relief groove 2a3, a strip-shaped guide groove 1a penetrating through the rotary shuttle table 1 is further disposed on the side wall of the rotary shuttle table 1, both side walls of the connecting portion 2a of the stationary knife holder 2a can be slidably inserted into the guide groove 1a, the fastener can be adjusted when the fixed on the fixed knife holder, the fixed knife holder, the fixed knife 4, the fixed knife can be adjusted by adjusting the fixed knife, the fixed knife 4, the fixed knife holder, the fixed knife 4, the fixed knife can be adjusted by adjusting screw, the fixed knife holder, the fixed knife 4, the fixed knife holder 2a fixed knife can be adjusted by adjusting screw, the fixed knife holder, the fixed knife.

As shown in fig. 2 and 5, a bobbin thread clamping assembly is further disposed below the movable knife 3, the bobbin thread clamping assembly includes a bobbin thread clamping spring 11 and a support spring plate 12, a movable knife bracket 13 is further fixedly connected to the movable knife guide frame 7, an end of the bobbin thread clamping spring 11 is fixed to the movable knife bracket 13 through a screw, and an end of the bobbin thread clamping spring elastically abuts against the movable knife 3, end of the support spring plate 12 is fixed to the movable knife bracket 13, an end of the support spring elastically abuts against a lower surface of the bobbin thread clamping spring 11, an adjusting bolt 14 is further connected to the movable knife bracket 13, the adjusting bolt 14 is located below the support spring plate 12 and can abut against the lower surface of the support spring plate 12, the bobbin thread clamping spring 11 is supported when the bobbin thread clamping spring 12 works, when the bobbin thread clamping spring 11 is not elastic enough or too elastic, the adjusting bolt 14 is disposed below the support spring plate 12, a head of the adjusting bolt 14 can abut against the lower surface of the support spring plate 12 to support the bobbin thread clamping spring plate, and the bobbin thread clamping spring plate 14 can be prevented from being loosened when the bobbin thread clamping spring plate is not sewn.

furthermore, as shown in fig. 6, the supporting spring 12 includes a fixed plate 12a formed by body, a transition plate 12b, a support plate 12c and a supporting plate 12d, the fixed plate 12a is horizontally attached and fixed on the movable blade bracket 13, the transition plate 12b is formed by bending the fixed plate 12a upwards, the support plate 12c is formed by bending the transition plate 12b and is parallel to the fixed plate 12a, the supporting plate 12d is connected with the support plate 12c and is arranged obliquely upwards relative to the support plate 12c, the adjusting bolt 14 is located below the support plate 12c and is supported on the lower plate surface of the support plate 12c, due to the requirement of the clothing process, thick upper thread is needed during sewing, the lower thread is thin, the supporting plate 12d is further provided with a small boss 12e protruding upwards, the small boss 12e is located at the end far away from the fixed plate 12a and is supported on the lower surface of the bottom thread clamping spring 11, and the boss can play a role similar to lever fulcrums, so that the clamping direction of the thin thread can be freely inclined, the thick thread can be clamped, and the upper end of the boss can be clamped more firmly, and the boss can be clamped, so that the upper end of the thick thread can be clamped more firmly, and the boss can be.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims

The thread trimming device of 1, kind of sewing machine, sewing machine are including rotating shuttle platform (1), and this thread trimming device includes stationary knife rest (2), moves sword (3) and stationary knife (4), move sword (3) and install on rotating shuttle platform (1), its characterized in that, stationary knife rest (2) include long banding connecting portion (2a) and cubic installation department (2b) that are used for fixed stationary knife (4), installation department (2b) relative connecting portion (2a) buckle setting, strip hole 2 (2a1) have been seted up along connecting portion (2a) length direction on connecting portion (2a), connecting portion (2a) paste and lean on the lateral wall of rotating shuttle platform (1) and can pass strip hole (2a1) and fix on rotating shuttle platform (1), stationary knife (4) are fixed on installation department (2b) and are located sword (3) top, move sword (3) drive slider (9) and guide slider (9a) and guide slider (9) and the drive in the vertical sword (539) move sword (539) and the drive the sword (9), the drive the slider (9a) and the drive the sword (9) and the slider (9) and the vertical sword (9) have been connected with the guide slider (9) and the sword (9) and have the slider in the vertical sword (9a) move the sword (9a) and the sword drive slider (9) and the sword drive the sword (9 move the sword (9) and the sword drive on the lateral wall of rotating shuttle platform (9) and the slider (9) and the vertical sword (3 move the sword (9) and have the slider, the slider (9) the slider of rotating shuttle platform (3, the slider of moving the slider (9) still be connected with the slider of rotating on the slider (9) the slider of rotating on the slider of rotating shuttle platform (3) the.
2. The trimming device of the sewing machine according to claim 1, wherein a second strip-shaped hole (2a2) is further formed in the connecting portion (2a) along the length direction of the connecting portion (2a), the connecting portion (2a) is provided with a abdicating groove (2a3), the second strip-shaped hole (2a2) is formed in the bottom of the abdicating groove (2a3), the connecting portion (2a) is further provided with an eccentric bolt (6), an eccentric screw (6a) of the eccentric bolt (6) penetrates through the second strip-shaped hole (2a2) and is arranged on the side wall of the rotating shuttle table (1), and a nut (6b) of the eccentric bolt (6) is embedded into the abdicating groove (2a3) and is attached to the side wall of the abdicating groove (2a 3).
3. The thread trimming device of a sewing machine according to claim 1, wherein the side wall of the rotating shuttle table (1) is further provided with a strip-shaped guide groove (1a) penetrating through the upper and lower table surfaces of the rotating shuttle table (1), the connecting part (2a) of the stationary knife rest (2) can be slidably embedded into the guide groove (1a), and two side walls of the connecting part (2a) are respectively attached to two groove walls of the guide groove (1 a).
4. The thread trimming device of a sewing machine according to claim 1, 2 or 3, wherein the fastening member (5) is a fixing bolt, the rotating shuttle table (1) has a fixing threaded hole, the shank of the fixing bolt passes through the strip-shaped hole (2a1) and is connected in the fixing threaded hole, and the head of the fixing bolt is pressed against the edge of the strip-shaped hole (2a 1).
5. The thread trimming device of a sewing machine according to claim 1, 2 or 3, wherein the driving rod (9b) is further sleeved with a driving roller (10), the driving roller (10) can rotate relative to the driving rod (9b), and the driving roller (10) extends into the strip-shaped groove (8a) and can rotate around the driving rod (9b) in the strip-shaped groove (8 a).
6. The trimming device of the sewing machine according to claim 1, 2 or 3, wherein the bobbin thread clamping assembly comprises a bobbin thread clamping spring (11) and a supporting spring piece (12), the movable knife bracket (13) is further fixedly connected to the movable knife guide frame (7), the bobbin thread clamping spring (11) is fixed to the movable knife bracket (13) through a screw, the other end elastically abuts against the movable knife (3), the end of the supporting spring piece (12) is fixed to the movable knife bracket (13), the other end elastically abuts against the lower surface of the bobbin thread clamping spring (11), the movable knife bracket (13) is further connected with an adjusting bolt (14), and the adjusting bolt (14) is located below the supporting spring piece (12) and can abut against the lower surface of the supporting spring piece (12).
7. The thread trimming device of a sewing machine according to claim 6, wherein the supporting spring plate (12) comprises a fixed plate (12a) formed by bodies, a transition plate (12b), a support plate (12c) and a supporting plate (12d), the fixed plate (12a) is horizontally attached and fixed on the movable knife bracket (13), the transition plate (12b) is formed by bending the fixed plate (12a) upwards, the support plate (12c) is formed by bending the transition plate (12b) and is parallel to the fixed plate (12a), the supporting plate (12d) is connected with the support plate (12c) and is arranged in an upward inclined manner relative to the support plate (12c), and the adjusting bolt (14) is located below the support plate (12c) and is abutted against the lower plate surface of the support plate (12 c).
8. The thread trimming device for sewing machines according to claim 7, wherein the supporting plate (12d) further has a small projection (12e) projecting upward therefrom, the small projection (12e) being located at the end remote from the fixing plate (12a) and abutting against the lower surface of the bobbin thread tension spring (11).
9. The thread trimming device for sewing machines according to claim 8, characterized in that the upper edge of the small boss (12e) has a chamfer.