Thread trimming structure of sewing machine

Abstract

The invention provides a thread trimming structure of a sewing machine, and belongs to the technical field of sewing machines. The problems that an existing thread trimming structure is insufficient in working reliability and short in service life are solved. The thread trimming structure of the sewing machine comprises a thread pressing piece, an auxiliary cutter arranged on a machine base and a movable cutter which is located below a needle plate and can vertically swing around a rotating shuttle shaft of the sewing machine, the auxiliary cutter is provided with a thread trimming end with an auxiliary cutter edge, a thread hooking groove is formed in the movable cutter, and a movable cutter edge is formed in the upper edge of the thread hooking groove. When the movable cutter swings upwards, the thread hooking groove can directly face the needle falling hole up and down, when the movable cutter swings downwards, the cutting edge of the movable cutter can be meshed with the cutting edge of the auxiliary cutting edge, the thread pressing piece is movably connected to the upper side face of the movable cutter, and the movable cutter is further provided with a reset spring acting on the thread pressing piece. And when the auxiliary knife edge is meshed with the movable knife edge, the thread trimming end of the auxiliary knife can abut against the lower side face of the thread pressing piece. The working reliability and the service life of the thread trimming structure can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of sewing machines and relates to a thread trimming structure of a sewing machine. Background Art

[0002] A sewing machine is a device that uses one or more threads to form one or more stitches on fabric to interweave or sew two or more layers of fabric. In order to improve sewing efficiency, a thread trimming mechanism is usually provided on the sewing machine, which automatically cuts the thread, reduces thread ends in the clothes, and improves the efficiency of subsequent finishing.

[0003] In conventional sewing machine technology, the thread pressing plate is fixedly installed, such as fixing the thread pressing plate to the machine base, so that when the moving knife is close to the thread pressing plate, the moving knife and the thread pressing plate work together to press the suture. For example, a cocircular double-knife less-bird's nest thread cutting mechanism and sewing machine (application number: 202420143812.0) disclosed in a Chinese patent document includes a main thread cutter, a seam starter thread cutter and a thread pressing plate. The main thread cutter is a fixed knife, and the thread pressing plate and the main thread cutter are both arranged on the rear side of the machine needle. The seam starter thread cutter is provided with a seam starter hook groove and a seam starter blade. By rotating the seam starter thread cutter toward the main thread cutter, the seam starter blade engages with the main thread cutter, thereby cutting the suture.

[0004] The thread trimming mechanism has the following deficiencies in actual use: its thread pressing plate is fixed to the main thread cutter by screws, or is directly fixed to the bottom surface of the sewing machine base plate. During the seam start thread trimming process, when the seam start thread cutter rotates toward the main thread cutter and is not engaged, the first thread clamping part of the thread pressing plate needs to slide against the seam start blade of the seam start thread cutter, and then abut with the second thread clamping part to form a thread clamping seam for clamping the surface thread. In this process, the seam start blade of the seam start thread cutter will be worn, and after long-term use, the seam start blade will become blunt, resulting in thread trimming failure. Therefore, the thread trimming mechanism has the problems of insufficient working reliability and short service life. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems in the prior art and to propose a thread trimming structure for a sewing machine. The present invention solves the problems of insufficient working reliability and short service life of the prior thread trimming structure.

[0006] The object of the present invention can be achieved through the following technical solutions: a thread trimming structure of a sewing machine, the sewing machine comprises a machine base and a needle plate with a needle drop hole, the thread trimming structure comprises a thread pressing piece, an auxiliary knife arranged on the machine base and a movable knife located below the needle plate and capable of swinging up and down around a rotary hook shaft of the sewing machine, the auxiliary knife having a thread trimming end with an auxiliary knife edge, the movable knife having a thread hooking groove and a movable knife edge formed on the upper edge of the thread hooking groove, the thread trimming groove being able to face the needle drop hole up and down when the movable knife is swung upward, the movable knife being able to engage with the auxiliary knife edge when the movable knife is swung downward, characterized in that the thread pressing piece is movably connected to the upper side surface of the movable knife, the movable knife is also provided with a reset spring acting on the thread pressing piece, the thread pressing piece can overcome the elastic force of the reset spring under the action of an external force and move in a direction away from the auxiliary knife, and the thread trimming end of the auxiliary knife can abut against the lower side surface of the thread pressing piece when the auxiliary knife edge engages with the movable knife edge.

[0007] In this thread cutting structure, after the sewing of the first stitch is completed, the upper thread of the needle is located in the thread hook groove. At this time, the movable knife is swung downward close to the auxiliary knife until the movable knife blade and the auxiliary knife blade are engaged to cut the upper thread. At the same time, the auxiliary knife and the thread pressing piece press the remaining thread end to position the remaining thread end, avoiding the upper thread being directly brought out of the thread hole of the needle during the upward movement of the thread pick-up rod, thereby making the sewing process stable.

[0008] Since the thread pressing piece in the present thread cutting structure is not fixedly installed as in conventional technology, but is installed on the moving knife and moves with the moving knife, during the entire process of the moving knife moving close to the auxiliary knife until the two engage and cut the surface thread, the thread pressing piece will not contact the moving knife edge of the moving knife and cause wear of the moving knife edge, ensuring that the moving knife edge always remains sharp and can stably cut the surface thread, thereby improving the working reliability of the present thread cutting structure. However, since the thread pressing piece is installed on the moving knife and moves with the moving knife, it is difficult to accurately control the swing stroke of the moving knife during the swing of the moving knife toward the auxiliary knife, so it is inevitable that overshoot will occur due to excessive swing amplitude. At this time, if the thread pressing piece is fixedly connected to the moving knife, the auxiliary knife and the thread pressing piece will collide hard, causing damage to both. In view of this, the present wire trimming structure also adopts a structural design that movably connects the wire pressing piece to the upper side of the moving knife, and is provided with a reset spring, so that even if the moving knife overshoots, the moment the auxiliary knife contacts the wire pressing piece, the auxiliary knife can push the wire pressing piece to move slightly in the direction away from the auxiliary knife to form a buffer, thereby avoiding the auxiliary knife and the wire pressing piece from hard collision, thereby protecting the auxiliary knife and the wire pressing piece, extending the service life of both, and further ensuring that the wire trimming structure maintains good working reliability for a long time. When the wire trimming process is completed, after the moving knife swings upward and retreats, the wire pressing piece can be reset under the action of the reset spring, waiting for the next wire trimming work.

[0009] In the thread trimming structure of the sewing machine, the auxiliary knife is fixedly connected to the machine base. Preferably, the auxiliary knife is connected to the machine base by bolts, which makes the auxiliary knife easy to install and has low cost.

[0010] In the thread trimming structure of the sewing machine described above, the thread trimming structure also includes a knife seat that is arranged on the machine base and can swing around the hook shaft of the sewing machine, the auxiliary knife is fixedly connected to the knife seat, and the knife seat is connected to a driving source that can drive it to swing. This structure enables the driving source to drive the auxiliary knife to swing upward after the seam start thread is cut, so that the auxiliary knife and the thread pressing piece together press the surface thread to move toward the needle hole of the needle plate as close to the needle hole as possible, and cooperate with the thread take-up rod to reel the thread upward, so that the residual thread on the fabric can be as short as possible, thereby achieving a better anti-bird nest effect and improving the aesthetics of sewing.

[0011] In the actual manufacturing process, the movable knife is also fixedly connected to the knife seat. The knife seats of the movable knife and the auxiliary knife are both rotatably set on the machine seat. The rotation center line of the knife seat coincides with the axis of the rotary hook shaft of the sewing machine. The knife seats of the movable knife and the auxiliary knife are respectively connected to a driving source such as a motor, an electromagnet or a cylinder to drive the knife seat to rotate. The structure of the driving source driving the knife seat to rotate can adopt the existing technology, and this article will not describe it in detail.

[0012] In the thread trimming structure of the sewing machine described above, the thread pressing piece is in the shape of a strip, one end of the thread pressing piece is hinged on the moving knife, and the other end is the thread pressing end. The moving knife is provided with a limiting protrusion. Under the elastic action of the reset spring, the side of the thread pressing piece close to the auxiliary knife can abut against the limiting protrusion and the lower side of the thread pressing end close to the auxiliary knife is located above the moving knife edge. When the thread pressing piece is not subjected to the thrust of the auxiliary knife, the thread pressing piece can always abut against the limiting protrusion by the action of the reset spring, and the thread pressing piece is positioned so that the lower side of the thread pressing end of the thread pressing piece close to the auxiliary knife is located above the moving knife edge. In this way, when the moving knife swings toward the auxiliary knife to the thread trimming position, the thread pressing end on the auxiliary knife can smoothly abut against the lower side of the thread pressing piece, thereby stably pressing the surface thread.

[0013] In the thread trimming structure of the sewing machine described above, there is an escape gap between the lower side of the thread pressing end close to the auxiliary knife and the upper side of the moving knife, and when the moving knife swings downward, the thread pressing end of the auxiliary knife can enter the escape gap and make the upper side of the thread trimming end abut against the lower side of the thread pressing end. This structure enables the thread trimming end of the auxiliary knife to smoothly enter the escape gap and abut against the lower side of the thread pressing end of the thread pressing piece when the moving knife swings toward the auxiliary knife to the thread trimming position, which can improve the thread pressing effect, avoid the situation where the upper thread is loose due to thread pressing failure, and thus improve the working reliability of the thread trimming structure.

[0014] In the thread trimming structure of the sewing machine, the lower side of the thread pressing end close to the auxiliary knife is a push-up slope, and the push-up slope gradually approaches the upper side of the moving knife from one end close to the auxiliary knife to the other end. This structure enables the thread pressing piece to move smoothly when the auxiliary knife swings toward the needle hole, and ensures that the upper thread is always stably pressed by the auxiliary knife and the thread pressing piece during the movement, so as to cooperate with the thread take-up rod to reel the thread upward, so that the residual thread on the fabric is as short as possible, achieving a better anti-bird nest effect and improving the aesthetics of sewing.

[0015] In the thread trimming structure of the sewing machine, a mounting hole is provided on the movable knife, a connecting hole is provided at one end of the thread pressing piece, a hinge connected to the mounting hole is provided in the connecting hole, and the thread pressing piece can rotate with the hinge. The hinge can be a bolt, which passes through the connecting hole and is threadedly connected to the mounting hole, or the hinge can be a pin, which passes through the connecting hole and is riveted to the mounting hole. Of course, the structure of the hinge can also be a structure other than a bolt and a pin, as long as the hinged installation of the thread pressing piece can be achieved.

[0016] In the thread trimming structure of the sewing machine described above, the reset spring is a torsion spring sleeved on the hinge, one end of the torsion spring is fixed on the movable knife, and the other end of the torsion spring is fixed on the thread pressing plate. Alternatively, the reset spring is a tension spring arranged on the upper side of the movable knife, and the two ends of the tension spring are respectively connected to the movable knife and the thread pressing plate. The thread pressing plate can be reset by the action of the torsion spring or the tension spring, so that after the thread pressing plate is reset, the thread pressing end of the thread pressing plate is close to the lower side of the auxiliary knife and is located above the blade of the movable knife. In this way, when the movable knife swings toward the auxiliary knife to the thread trimming position, the thread pressing end on the auxiliary knife can reliably abut against the lower side of the thread pressing plate, thereby stably pressing the surface thread.

[0017] In the thread-cutting structure of the sewing machine described above, the auxiliary knife is formed by bending a strip of metal sheet, and the auxiliary knife includes a straight section vertically arranged with respect to the rotary hook shaft of the sewing machine and an arc section bent upward with respect to the straight section, the curvature of the arc section matches the curvature of the upper surface of the moving knife, the straight section is fixedly connected to the machine base, the end of the arc section away from the straight section is the thread-cutting end, and the lower edge of the end surface of the thread-cutting end forms the auxiliary knife edge. The auxiliary knife of this structure is fixedly installed, which is convenient to install and can reduce the manufacturing cost. Since the curvature of the arc section matches the curvature of the upper surface of the moving knife, it can ensure that the cutting edges of the moving knife and the auxiliary knife can be closely engaged when cutting the thread, thereby forming an effective shearing force and avoiding the situation of thread cutting failure.

[0018] In the thread cutting structure of the sewing machine described above, the auxiliary knife is formed by bending a strip of metal sheet, and the auxiliary knife includes a straight section arranged parallel to the rotary hook shaft of the sewing machine and an arc section protruding to the side relative to the straight section, the curvature of the arc section matches the curvature of the upper surface of the moving knife, one end of the straight section is fixedly connected to the knife seat, the end of the arc section away from the straight section is the thread cutting end, and the lower edge of the end surface of the thread cutting end forms the auxiliary knife edge. The auxiliary knife of this structure is installed in a swingable manner, so that the knife seat can drive the auxiliary knife to swing in the direction close to the needle drop hole, so that after the surface thread is cut, the residual thread end is short. Similarly, the auxiliary knife of this structure is also relatively simple to manufacture, which can reduce the manufacturing cost. Since the curvature of the arc section matches the curvature of the upper surface of the moving knife, it can ensure that the cutting edges of the moving knife and the auxiliary knife can be closely engaged when cutting the thread, forming an effective shearing force, thereby avoiding the situation of thread cutting failure.

[0019] In the thread trimming structure of the sewing machine described above, the thread pressing piece is slidably connected to the moving knife along the swinging direction of the moving knife. In this structure, a sliding protrusion can be provided on the lower side of the thread pressing piece, and a sliding groove can be provided on the moving knife, so that the sliding protrusion is slidably connected with the sliding groove to realize the sliding installation of the thread pressing piece. In addition, guide strips can be provided on the front and rear sides of the thread pressing piece to realize the sliding installation of the thread pressing piece. This structure can also rely on the auxiliary knife to push the thread pressing piece to move slightly in the direction away from the auxiliary knife when the moving knife overshoots, thereby forming a buffer, thereby avoiding the situation where the auxiliary knife and the thread pressing piece collide hard.

[0020] In the thread trimming structure of the sewing machine, the thread trimming end surface of the auxiliary knife has a thread pressing groove that runs through the front and rear sides of the auxiliary knife, and when the movable knife swings downward, the side of the thread pressing piece close to the auxiliary knife can be embedded in the thread pressing groove. Such a design can not only ensure a good thread pressing effect, but also limit the thread pressing piece up and down during the swinging process of the auxiliary knife pushing the thread pressing piece, so that the thread pressing piece can swing stably.

[0021] In the thread cutting structure of the above-mentioned sewing machine, a guide wire piece is also slidably connected to the upper side surface of the auxiliary knife, and one end of the guide wire piece close to the needle protrudes from the end surface of the thread cutting end and the end of the guide wire piece has a guide wire groove. Before the movable knife swings downward to cut the thread, the guide wire piece can preferably contact the surface thread and guide the surface thread to the middle of the guide groove, so that the surface thread is always in the bite point between the movable knife and the auxiliary knife, avoiding the situation of thread cutting failure. Furthermore, when the movable knife swings downward, the end of the guide wire piece close to the needle can abut against the upper side surface of the thread pressing piece, so that after the surface thread is cut, the guide wire piece cooperates with the thread pressing piece to play a thread pressing role, thereby improving the thread pressing effect.

[0022] Compared with the prior art, the thread trimming structure of the sewing machine has the following advantages:

[0023] 1. In this thread trimming structure, the thread pressing piece is not fixedly installed as in conventional technology, but is installed on the movable knife and moves with the movable knife. Therefore, during the whole process when the movable knife moves close to the auxiliary knife until the two engage and cut the upper thread, the thread pressing piece will not contact the moving knife edge of the movable knife and cause wear of the moving knife edge, ensuring that the moving knife edge always remains sharp and can stably cut the upper thread, thereby improving the working reliability of the thread trimming structure.

[0024] 2. The wire cutting structure also adopts a structural design in which the wire pressing piece is hinged to the upper side of the movable knife, and a reset spring is provided. In this way, even if the movable knife overshoots, the auxiliary knife can push the wire pressing piece to swing slightly in the direction away from the auxiliary knife at the moment when the auxiliary knife contacts the wire pressing piece, thereby forming a buffer, avoiding the auxiliary knife and the wire pressing piece from having a hard collision, thereby protecting the auxiliary knife and the wire pressing piece, extending the service life of both, and making the wire cutting structure have the advantage of long service life.

[0025] 3. This thread cutting structure can make the residual thread ends on the fabric shorter, achieve better anti-bird nest effect, and improve the aesthetics of sewing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a front view of the first embodiment of the thread trimming structure.

[0027] Figure 2 It is a schematic diagram of the three-dimensional structure of the thread trimming structure in the first embodiment when the thread pressing piece is in the reset state.

[0028] Figure 3 It is an exploded view of the movable knife, the wire pressing piece, the return spring and the hinge in the first embodiment.

[0029] Figure 4 It is a top view of the thread trimming structure in the first embodiment after the auxiliary knife top pushes the thread sheet to swing upward.

[0030] Figure 5 yes Figure 4 Sectional view of AA.

[0031] Figure 6 It is a structural schematic diagram of the wire pressing piece in the wire cutting structure.

[0032] Figure 7 It is a structural schematic diagram of the auxiliary knife in the first embodiment.

[0033] Figure 8 It is a three-dimensional structural schematic diagram of the second embodiment of the thread trimming structure.

[0034] Fig. 9 It is a structural schematic diagram of the fourth embodiment of the thread trimming structure.

[0035] Fig.10It is a three-dimensional structural schematic diagram of the fifth embodiment of the thread trimming structure.

[0036] Fig.11 This is a diagram showing the coordination relationship between the auxiliary knife and the thread pressing piece after the movable knife swings downward in the fifth embodiment of the thread trimming structure.

[0037] Fig.12 It is a three-dimensional structural schematic diagram of the sixth embodiment of the thread trimming structure.

[0038] In the figure, 1, machine base; 2, needle plate; 21, needle drop hole; 3, thread pressing piece; 31, thread pressing end; 32, push ramp; 33, connecting hole; 4, auxiliary knife; 41, straight section; 42, arc section; 421, thread cutting end; 422, auxiliary knife edge; 423, thread pressing groove; 5, moving knife; 51, thread hook groove; 52, moving knife edge; 53, mounting hole; 54, limiting protrusion; 6, knife holder; 7, avoidance gap; 8, reset spring; 9, hinge; 10, rotary shuttle; 11, machine needle; 12, guide wire piece; 121, guide wire groove; 13, knife holder seat; 14, moving knife mounting bracket. DETAILED DESCRIPTION

[0039] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0040] Embodiment 1

[0041] like Figure 1 and Figure 2 As shown, the sewing machine includes a machine base 1, a rotary hook 10 with a rotary hook 10 axis, and a needle plate 2 with a needle drop hole 21. The thread trimming structure includes a thread pressing piece 3, an auxiliary knife 4, a knife holder seat 13 fixedly arranged on the machine base 1, and an annular movable knife mounting frame 14 rotatably sleeved on the knife holder seat 13. A movable knife 5 is fixedly connected to the movable knife mounting frame 14, so that the movable knife is located below the needle plate 2 and can swing up and down around the rotary hook 10 axis. The auxiliary knife 4 has a thread trimming end 421 with an auxiliary blade edge 422. The movable knife 5 has a thread hooking groove 51 and the upper edge of the thread hooking groove 51 is formed with The movable knife edge 52, when the movable knife 5 swings upward, the wire hook groove 51 can be directly opposite to the needle drop hole 21 up and down, and when the movable knife 5 swings downward, the movable knife edge 52 can be engaged with the auxiliary knife edge 422. The wire pressing piece 3 is hinged on the upper side surface of the movable knife 5. The movable knife 5 is also provided with a reset spring 8 acting on the wire pressing piece 3. Under the action of external force, the wire pressing piece 3 can overcome the elastic force of the reset spring 8 and swing in the direction away from the auxiliary knife 4. When the auxiliary knife edge 422 is engaged with the movable knife edge 52, the wire cutting end 421 of the auxiliary knife 4 can be against the lower side surface of the wire pressing piece 3.

[0042] like Figure 2As shown, the thread trimming structure also includes a knife holder 6 disposed on a knife holder seat 13 and capable of swinging around the axis of the rotary hook 10, and the auxiliary knife 4 is fixedly connected to the knife holder 6. The rotation centerline of the knife holder 6 and the movable knife mounting frame 14 coincides with the axis of the rotary hook 10, and the knife holder 6 and the movable knife mounting frame 14 are rotated by connecting a driving source such as a motor, an electromagnet or a cylinder to the knife holder 6 and the movable knife mounting frame 14 respectively. The structure in which the driving source drives the knife holder 6 and the movable knife mounting frame 14 to rotate can adopt the existing technology, and no redundant description is made herein, and the driving source is not shown in the figure.

[0043] like Figure 3 As shown, the pressing piece 3 is in the shape of a strip, one end of the pressing piece 3 is hinged on the movable knife 5, and the other end is the pressing end 31. The movable knife 5 is provided with a limiting protrusion 54. Under the elastic action of the reset spring 8, the side of the pressing piece 3 close to the auxiliary knife 4 can abut against the limiting protrusion 54, and the lower side of the pressing end 31 close to the auxiliary knife 4 is located above the movable knife edge 52. When the pressing piece 3 is not subjected to the thrust of the auxiliary knife 4, the pressing piece 3 can always abut against the limiting protrusion 54 by the action of the reset spring 8, and the pressing piece 3 is positioned so that the lower side of the pressing end 31 of the pressing piece 3 close to the auxiliary knife 4 is located above the movable knife edge 52. In this way, when the movable knife 5 swings toward the auxiliary knife 4 to the thread cutting position, the pressing end 31 on the auxiliary knife 4 can smoothly abut against the lower side of the pressing piece 3, thereby stably pressing the surface thread.

[0044] like Figure 4 and Figure 5 As shown, there is an escape gap 7 between the lower side of the wire pressing end 31 close to the auxiliary knife 4 and the upper side of the movable knife 5. When the movable knife 5 swings downward, the wire pressing end 31 of the auxiliary knife 4 can enter the escape gap 7 and make the upper side of the wire cutting end 421 abut against the lower side of the wire pressing end 31. Figure 5 and Figure 6 As shown, the lower side surface of the wire pressing end 31 close to the auxiliary knife 4 is a push inclined surface 32, and the push inclined surface 32 gradually approaches the upper side surface of the movable knife 5 from one end close to the auxiliary knife 4 to the other end.

[0045] like Figure 3 and Figure 6 As shown, a mounting hole 53 is provided on the movable knife 5, a connecting hole 33 is provided at one end of the pressure piece 3, a hinge 9 connected to the mounting hole 53 is penetrated in the connecting hole 33, and the pressure piece 3 can rotate with the hinge 9. The hinge 9 can be a bolt, which passes through the connecting hole 33 and is threadedly connected to the mounting hole 53, or the hinge 9 can be a pin, which passes through the connecting hole 33 and is riveted to the mounting hole 53. Of course, the structure of the hinge 9 can also be a structure other than a bolt and a pin, as long as the hinged installation of the pressure piece 3 can be achieved. The hinge 9 is sleeved with a torsion spring, one end of which is fixed to the movable knife 5, and the other end of which is fixed to the pressure piece 3.

[0046] like Figure 7 As shown, the auxiliary knife 4 is formed by bending a strip of metal sheet, and the auxiliary knife 4 includes a straight section 41 arranged parallel to the axis of the rotary hook 10 and an arc section 42 protruding to the side relative to the straight section 41, the curvature of the arc section 42 matches the curvature of the upper surface of the movable knife 5, one end of the straight section 41 is fixedly connected to the knife holder 6, and the end of the arc section 42 away from the straight section 41 is a thread cutting end 421, and the lower edge of the end surface of the thread cutting end 421 forms an auxiliary knife edge 422.

[0047] The following briefly introduces the working principle of this thread trimming structure:

[0048] Before the sewing machine sews the first stitch, the movable knife 5 moves upward, so that the end of the thread hooking groove 51 away from the movable knife edge 52 moves to just below the needle 11, or, when the needle 11 moves downward when the sewing machine sews the first stitch, the movable knife 5 moves at the same time, so that the end of the thread hooking groove 51 away from the movable knife edge 52 moves to just below the needle 11.

[0049] The sewing machine performs the first stitch, and the needle 11 carries the upper thread downward through the thread hook groove 51, and then the needle 11 moves upward. When the needle 11 moves upward to above the needle plate 2, the movable knife 5 carries the thread pressing piece 3 and swings downward close to the auxiliary knife 4 until the movable knife edge 52 and the auxiliary knife edge 422 engage with each other to cut the upper thread. At the same time, the auxiliary knife 4 and the thread pressing piece 3 press down the remaining thread.

[0050] Afterwards, if Figure 4 and Figure 5 As shown, the movable knife 5 remains fixed, and the auxiliary knife 4 swings upward, so that the auxiliary knife 4 and the thread pressing piece 3 press the upper thread to move toward the needle hole 21 of the needle plate 2 as close to the needle hole 21 as possible, and cooperate with the thread take-up rod to reel the thread upward, so that the residual thread on the fabric is as short as possible, thereby achieving a better anti-bird nest effect. Figure 5 In the figure, the thicker line indicates the surface thread after it is cut.

[0051] Embodiment 2

[0052] The structure and principle of this embodiment are basically the same as those of the first embodiment, except that: Figure 8 As shown, the auxiliary knife 4 is formed by bending a strip of metal sheet, and the auxiliary knife 4 includes a straight section 41 vertically arranged with respect to the axis of the rotary hook 10 and an arc section 42 bent upward relative to the straight section 41, the curvature of the arc section 42 matches the curvature of the upper surface of the movable knife 5, the straight section 41 is fixedly connected to the machine base 1 by bolts, the end of the arc section 42 away from the straight section 41 is a thread cutting end 421, and the lower edge of the end surface of the thread cutting end 421 forms an auxiliary knife edge 422. The auxiliary knife 4 of this structure is fixedly installed, which is convenient to install and can reduce the manufacturing cost.

[0053] Embodiment 3

[0054] The structure and principle of this embodiment are basically the same as those of the first embodiment, except that the reset spring 8 is a tension spring arranged on the upper side of the movable knife 5, and the two ends of the tension spring are respectively connected to the movable knife 5 and the thread pressing piece 3. The thread pressing piece 3 can be reset by the tension spring, so that after the thread pressing piece 3 is reset, the lower side of the thread pressing end 31 of the thread pressing piece 3 close to the auxiliary knife 4 is located above the movable knife edge 52, so that when the movable knife 5 swings toward the auxiliary knife 4 to the thread cutting position, the thread pressing end 31 on the auxiliary knife 4 can reliably abut against the lower side of the thread pressing piece 3, thereby stably pressing the surface thread.

[0055] Embodiment 4

[0056] The structure and principle of this embodiment are basically the same as those of the first embodiment, except that: Fig. 9 As shown, the wire pressing piece 3 is slidably connected to the movable knife 5 along the swinging direction of the movable knife 5 .

[0057] Embodiment 5

[0058] The structure and principle of this embodiment are basically the same as those of the first embodiment, except that: Fig.10 As shown, the end surface of the thread cutting end 421 of the auxiliary knife 4 has a thread pressing groove 423 that runs through the front and rear sides of the auxiliary knife 4. Fig.11 As shown, when the movable knife 5 swings downward, the side of the wire pressing piece 3 close to the auxiliary knife 4 can be embedded in the wire pressing groove 423.

[0059] Embodiment 6

[0060] The structure and principle of this embodiment are basically the same as those of the second embodiment, except that: Fig.12 As shown, a guide wire piece 12 is also slidably connected to the upper side surface of the auxiliary knife 4, and the end of the guide wire piece 12 close to the machine needle protrudes from the end surface of the wire cutting end 421 and the end of the guide wire piece 12 has a guide wire groove 121. When the movable knife 5 swings downward, the end of the guide wire piece 12 close to the machine needle can abut against the upper side surface of the wire pressing piece 3. Furthermore, a strip groove is also provided on the guide wire piece 12, and a bolt is provided in the strip groove to fix the guide wire piece 12 to the auxiliary knife 4, so that the position of the guide wire piece 12 can be adjusted, thereby adjusting the length of the end surface of the wire cutting end 421 protruding from the end of the guide wire piece 12 close to the machine needle.

[0061] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0062] Although this article uses more terms such as 1, machine base; 2, needle plate; 21, needle drop hole; 3, thread pressing piece; 31, thread pressing end; 32, push inclined surface; 33, connecting hole; 4, auxiliary knife; 41, straight section; 42, arc section; 421, thread cutting end; 422, auxiliary knife edge; 5, moving knife; 51, hooking groove; 52, moving knife edge; 53, mounting hole; 54, limiting protrusion; 6, knife base; 7, avoidance gap; 8, reset spring; 9, hinge; 10, rotary hook; 11, machine needle, etc., it does not exclude the possibility of using other terms. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. A thread trimming structure of a sewing machine, the sewing machine comprising a machine base (1) and a needle plate (2) having a needle drop hole (21), the thread trimming structure comprising a thread pressing piece (3), an auxiliary knife (4) arranged on the machine base (1) and a movable knife (5) located below the needle plate (2) and capable of swinging up and down around a rotary hook shaft of the sewing machine, the auxiliary knife (4) having a thread trimming end (421) with an auxiliary knife edge (422), the movable knife (5) having a thread hooking groove (51) and a movable knife edge (52) formed on the upper edge of the thread hooking groove (51), the movable knife (5) being able to make the thread hooking groove (51) and the needle drop hole (21) face each other vertically when the movable knife (5) is swung upward, and the movable knife (5) being able to make its movable knife edge (52) engage with the auxiliary knife edge (422) when the movable knife (5) is swung downward, characterized in that: The wire pressing piece (3) is movably connected to the upper side of the movable knife (5), and the movable knife (5) is also provided with a return spring (8) acting on the wire pressing piece (3). Under the action of external force, the wire pressing piece (3) can overcome the elastic force of the return spring (8) and move in the direction away from the auxiliary knife (4). When the auxiliary knife edge (422) and the movable knife edge (52) are engaged, the wire cutting end (421) of the auxiliary knife (4) can abut against the wire pressing piece (3).

2. The thread trimming structure of a sewing machine according to claim 1, characterized in that: The auxiliary knife (4) is fixedly connected to the machine base (1).

3. The thread trimming structure of a sewing machine according to claim 1, characterized in that: The thread trimming structure also includes a knife seat (6) which is arranged on the machine seat (1) and can swing around the rotary hook shaft of the sewing machine. The auxiliary knife (4) is fixedly connected to the knife seat (6), and the knife seat (6) is connected to a driving source which can drive the knife seat (6) to swing.

4. The thread trimming structure of a sewing machine according to claim 1, 2 or 3, characterized in that: The wire pressing piece (3) is in the shape of a strip, one end of the wire pressing piece (3) is hinged on the movable knife (5), and the other end is a wire pressing end (31). The movable knife (5) has a limiting protrusion (54). Under the elastic force of the reset spring (8), the side edge of the wire pressing piece (3) close to the auxiliary knife (4) can abut against the limiting protrusion (54) and the lower side surface of the wire pressing end (31) close to the auxiliary knife (4) is located above the movable knife edge (52).

5. The thread trimming structure of a sewing machine according to claim 4, characterized in that: An escape gap (7) is provided between the lower side surface of the wire pressing end (31) close to the auxiliary knife (4) and the upper side surface of the movable knife (5); when the movable knife (5) swings downward, the wire pressing end (31) of the auxiliary knife (4) can enter the escape gap (7) and cause the upper side surface of the wire cutting end (421) to abut against the lower side surface of the wire pressing end (31).

6. The thread trimming structure of a sewing machine according to claim 5, characterized in that: The lower side surface of the wire pressing end (31) close to the auxiliary knife (4) is a push inclined surface (32), and the push inclined surface (32) gradually approaches the upper side surface of the movable knife (5) from one end close to the auxiliary knife (4) to the other end.

7. The thread trimming structure of a sewing machine according to claim 3, characterized in that: The auxiliary knife (4) is formed by bending a strip of metal sheet, and comprises a straight section (41) arranged parallel to the rotary hook shaft of the sewing machine and an arc section (42) protruding laterally relative to the straight section (41), the curvature of the arc section (42) matches the curvature of the upper surface of the movable knife (5), one end of the straight section (41) is fixedly connected to the knife seat (6), the end of the arc section (42) away from the straight section (41) is the thread cutting end (421), and the lower edge of the end surface of the thread cutting end (421) forms the auxiliary knife edge (422).

8. The thread trimming structure of a sewing machine according to claim 1 or 2, characterized in that: The wire pressing piece (3) is slidably connected to the movable knife (5) along the swinging direction of the movable knife (5).

9. The thread trimming structure of a sewing machine according to claim 3, characterized in that: The end surface of the thread cutting end (421) of the auxiliary knife (4) is provided with a thread pressing groove (423) which penetrates the front and rear sides of the auxiliary knife (4); when the movable knife (5) swings downward, the side of the thread pressing sheet (3) close to the auxiliary knife (4) can be embedded in the thread pressing groove (423).

10. The thread trimming structure of a sewing machine according to claim 2, characterized in that: A guide wire piece (12) is also slidably connected to the upper side of the auxiliary knife (4), and one end of the guide wire piece (12) close to the machine needle protrudes from the end surface of the thread cutting end (421) and the end of the guide wire piece (12) has a guide wire groove (121).

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