Automatic shearing mechanism for preventing bird nests

Abstract

The present application relates to a kind of automatic shearing mechanism of bird nest prevention, including seat and needle plate, the seat is provided with driving mechanism, transmission mechanism and clamping and shearing mechanism, driving mechanism drives clamping and shearing mechanism to act by transmission mechanism, seat is fixedly connected in the bottom of needle plate by the connecting portion of top setting;The clamping and shearing mechanism includes moving knife, fixed knife and blade spring, fixed knife is fixed on seat, moving knife is movably arranged on seat, moving knife front portion is provided with machine needle avoiding hole, the pressure rod of blade spring is abutted on moving knife front portion upper surface, moving knife rear portion is through transmission mechanism with driving mechanism, driving mechanism drives moving knife to move with three-stage stroke structure;The present application first clamps thread end when starting to stitch, and the excess thread end is cut after needle is stable, it plays the effect of better bird nest prevention and thread dropping prevention, and thread end clamping is executed by elastic mechanism, not by yarn fine restriction, with the characteristics of structure reasonable, stitch beautiful, good reliability, strong applicability.

Description

TECHNICAL FIELD

[0001] The present application relates to sewing machine technology, in particular to an automatic shearing mechanism for preventing bird nests. BACKGROUND

[0002] In order to prevent the top thread from falling off the needle when the needle is raised, a section of thread is often left through the needle hole. Then, the long thread is intertwined with the bottom thread or top thread to form a ball of thread, commonly known as a "bird nest". The resulting stitch is not aesthetically pleasing. To solve this problem, some people have proposed mechanisms to prevent bird nests. Most existing bird nest prevention mechanisms clamp the thread when the needle is raised and then release the thread after the needle is raised to prevent the thread from being entangled with the bottom thread or top thread. For example, the utility model with the announcement number CN215209964U discloses a dual-purpose device for preventing bird nests and thread falling and a sewing machine containing the device. The device is used to pull the thread away from the needle after the needle passes through the needle plate. The device includes an execution mechanism configured on the underside of the needle plate for driving the thread to move, a power component for driving the execution mechanism to perform the driving action of moving the thread, and an electronic control unit electrically connected to the power component for sensing the position of the needle and driving the power component to perform the driving action. The utility model can prevent the thread from being wrapped into the cloth surface by the rotating shuttle when the thread is raised, thereby achieving the effect of preventing bird nests. Moreover, the dual-purpose device for preventing bird nests and thread falling is located on the underside of the table panel. This design can reduce the possibility of accidental contact by the operator, improve safety, and also has the function of preventing thread falling.

[0003] Although the above structure solves the problem of bird nests, especially when the thread is pulled by the execution mechanism during needle raising, it solves the problems of bird nests and thread falling. However, since the thread is pulled by the execution mechanism, the remaining thread is relatively long, and a long section of thread is left for each stitch, which makes the stitch less aesthetically pleasing.

[0004] Another example is the utility model with the announcement number CN221721104U, which discloses a dual-purpose device for preventing bird nests and thread cutting and a sewing machine. The device for preventing bird nests and thread cutting includes a fixed setting stitch starting fixed knife and a main movable knife and a stitch finishing movable knife that can be movably configured on the outer peripheral side of the rotating shuttle in the sewing machine. The main movable knife is provided with a stitch starting thread cutting edge, a thread hooking groove, a thread dividing groove, and a stitch finishing thread cutting edge. The thread hooking groove allows the needle in the sewing machine to pass through. When the main movable knife moves towards the stitch starting fixed knife, the stitch starting thread cutting edge can engage with the stitch starting fixed knife to reliably achieve stitch starting bird nest prevention. When the main movable knife and the stitch finishing movable knife move towards each other, the stitch finishing thread cutting edge can engage with the stitch finishing movable knife to achieve automatic thread cutting after stitching. Moreover, the automatic thread cutting after stitching is a double movable knife structure, which can make the engagement position of the stitch finishing thread cutting edge and the stitch finishing movable knife closer to the central axis of the needle, thereby making the residual thread on the stitched material shorter after thread cutting.

[0005] The structure is mainly realized by cooperation of the stitcher and the main movable cutter, different thread cutting mechanisms have different structures, some thread cutting mechanisms do not have the main movable cutter, and the structure cannot adjust the gap between the stitcher and the main movable cutter due to different thread materials and thicknesses, so the structure has great limitations and can only be applied to specified thread thickness and specific sewing machines. SUMMARY

[0006] The automatic thread cutting mechanism for preventing bird nests is directly fixed to the bottom of the needle plate, is very convenient to modify and disassemble, can clamp the thread end when the stitch is started, cuts the excess thread end after the needle is stably lifted, well prevents bird nests and thread falling, and is not limited by thread fineness, can be improved as long as the needle plate and the space below the needle plate have space, can be applied to various sewing devices with different functions, and has the characteristics of reasonable structure, beautiful stitch, good reliability and strong applicability.

[0007] The following technical scheme is adopted to achieve the above object:

[0008] The automatic thread cutting mechanism for preventing bird nests is directly fixed to the bottom of the needle plate, is very convenient to modify and disassemble, can clamp the thread end when the stitch is started, cut the excess thread end after the needle is stably lifted, well prevent bird nests and thread falling, and are not limited by thread fineness, can be improved as long as the needle plate and the space below the needle plate have space, can be applied to various sewing devices with different functions, and have the characteristics of reasonable structure, beautiful stitch, good reliability and strong applicability.

[0007] The following technical scheme is adopted to achieve the above object:

[0008] The automatic thread cutting mechanism for preventing bird nests is directly fixed to the bottom of the needle plate, is very convenient to modify and disassemble, can clamp the thread end when the stitch is started, cut the excess thread end after the needle is stably lifted, well prevent bird nests and thread falling, and are not limited by thread fineness, can be improved as long as the needle plate and the space below the needle plate have space, can be applied to various sewing devices with different functions, and have the characteristics of reasonable structure, beautiful stitch, good reliability and strong applicability.

[0009] The connecting part is a boss protruding upward from the top of the seat body, the boss is provided with a screw hole, the needle plate is provided with a through hole at a position corresponding to the screw hole, and a screw rod is screwed at the screw hole to fix the seat body to the bottom of the needle plate.

[0010] The seat body top is provided with a guide groove, the moving cutter is contained in the guide groove, and the driving mechanism drives the moving cutter to move linearly along the guide groove; the fixed cutter is arranged on the upper surface of the moving cutter and fixed on the seat body, the blade spring body is fixed on the seat body, and the pressing rod at the front of the blade spring extends to the front side of the fixed cutter and abuts against the upper surface of the front of the moving cutter.

[0011] The pressing rod is in a U shape, one end of the U-shaped pressing rod is integrated with the blade spring body, the spring body is fixed on one side of the fixed cutter, the U-shaped pressing rod is bent to the front end of the fixed cutter, passes around the front end of the fixed cutter, is bent backward again and extends to the other side of the fixed cutter to form the U-shaped pressing rod, so that the U shape surrounds the front end and the two sides of the fixed cutter, and the U-shaped pressing rod abuts against the upper surface of the front end of the moving cutter and keeps elastic pressure on the upper surface of the moving cutter.

[0012] The driving mechanism comprises a motor, the motor is fixedly connected to the seat body, the motor is electrically connected to the electric control, the output shaft of the motor is movably connected to the rear part of the moving cutter through a crank and a connecting rod, and the electric control controls the moving stroke of the moving cutter by controlling the rotation angle of the output shaft of the motor.

[0013] The driving mechanism comprises first and second linear driving devices, the driving direction of the first linear driving device is the same as the direction of the guide groove, and the driving direction of the second linear driving device is perpendicular to the direction of the guide groove; the second linear driving device is arranged at the bottom of the seat body, a limiting sliding block is connected to the upper end of the second linear driving device, the limiting sliding block is contained in the longitudinal guide groove of the seat body, and the second linear driving device drives the limiting sliding block to move up and down in the longitudinal guide groove; the rear part of the moving cutter is connected to the first linear driving device at the rear side of the seat body through an active connection shaft, and the bottom of the active connection shaft is provided with a downwardly protruding limiting connection column; the upward movement of the limiting sliding block can block the rear movement path of the limiting connection column and limit the moving stroke of the moving cutter, and the rear side of the limiting sliding block will not block the limiting connection column when the limiting sliding block moves downward.

[0014] The driving mechanism comprises first and second linear driving devices, both groups of linear driving devices are arranged at the rear side of the seat body and have the same driving direction, and the stroke of the driving rods of the two groups of linear driving devices is superimposed and connected to the rear part of the moving cutter.

[0015] The automatic bird nest preventing and shearing mechanism is arranged as an independent module and is fixedly connected to the bottom of the needle plate, can be installed as long as the space below the needle plate allows, and only needs to be connected to the through hole corresponding to the screw hole position of the corresponding connecting part on the existing needle plate, and can be suitable for various sewing devices with different functions.

[0016] In addition, the automatic bird nest shearing mechanism is additionally provided with a blade spring, and the pressing rod of the blade spring is matched with a needle head machine needle avoiding hole, so that the thread end is pressed when the needle is lifted, and the thread is not pulled off due to pulling; after the needle is lifted stably, the thread end is cut to make the stitch more beautiful; the specific structure is reasonable, the stitch is beautiful, the reliability is good, and the applicability is strong. BRIEF DESCRIPTION OF DRAWINGS

[0017] . Figure 1 It is a structure schematic view of the sewing equipment according to the present application (one);

[0018] Figure 2 It is a structure schematic view of the sewing equipment according to the present application (two);

[0019] Figure 3 It is a cooperation schematic view of the present application and a needle plate;

[0020] Figure 4 It is an exploded structure schematic view of the present application and a needle plate;

[0021] Figure 5 It is a structure schematic view of the first embodiment of the present application;

[0022] Figure 6 It is a structure schematic view of another direction of the first embodiment of the present application;

[0023] Figure 7 It is a schematic view of part of the structure of the first embodiment of the present application;

[0024] Figure 8 It is a structure schematic view of the separation of the air suction cover plate of the first embodiment of the present application;

[0025] Figure 9 It is a structure schematic view of the seat body of the first embodiment of the present application (one);

[0026] Figure 10 It is a structure schematic view of the seat body of the first embodiment of the present application (two);

[0027] Figure 11 It is a structure schematic view of the clamping and shearing mechanism when the moving knife is in an extended state of the second embodiment of the present application;

[0028] Figure 12 It is a structure schematic view of the clamping and shearing mechanism when the moving knife is in a thread pressing state of the second embodiment of the present application;

[0029] Figure 13 It is a structure schematic view of the clamping and shearing mechanism when the moving knife is in a retracted state of the second embodiment of the present application;

[0030] Figure 14This is a schematic diagram of the bottom structure of the second embodiment of the present invention;

[0031] Figure 15 This is a schematic diagram (a) of the structure of the seat body according to the second embodiment of the present invention.

[0032] Figure 16 This is a schematic diagram (II) of the structure of the seat body according to the second embodiment of the present invention;

[0033] Figure 17 This is a schematic diagram of the drive mechanism, transmission mechanism, and clamping and shearing mechanism according to the second embodiment of the present invention. Detailed Implementation

[0034] like Figures 1-10 As shown, an automatic bird nest cutting mechanism includes a base 1 and a needle plate 2. The base 1 is provided with a drive mechanism, a transmission mechanism 4, and a clamping and cutting mechanism 5. The drive mechanism drives the clamping and cutting mechanism 5 to move through the transmission mechanism. The base 1 is fixed to the bottom of the needle plate 2 through a connecting part provided at the top. The connecting part is a boss 11 that protrudes upward from the top of the base 1. The boss 11 is provided with a screw hole. The needle plate 2 has a through hole 21 at the position corresponding to the screw hole. The screw passes through the through hole 21 and is screwed into the screw hole to fix the base 1 to the bottom of the needle plate 2.

[0035] The clamping and shearing mechanism 5 includes a movable blade 51, a fixed blade 52, and a blade spring 53. The fixed blade 52 is fixed on the base 1, and the movable blade 51 is movably mounted on the base 1. The movable blade 51 has a needle clearance hole 511 at its front. The pressure rod 531 of the blade spring 53 abuts against the upper surface of the front of the movable blade 51. The rear of the movable blade 51 is connected to the drive mechanism through the transmission mechanism 4.

[0036] The top of the base 1 is provided with a guide groove 12, the movable blade 51 is housed in the guide groove 12, and the drive mechanism drives the movable blade 51 to move linearly along the guide groove 12; the fixed blade 52 is set on the upper surface of the movable blade 51 and fixed on the base 1, the body of the blade spring 53 is fixed on the base 1, and the pressure rod 531 at the front of the blade spring 53 extends to the front side of the fixed blade 52 and abuts against the upper surface of the front of the movable blade 51.

[0037] The pressure rod 531 is U-shaped, with one end of the U-shaped pressure rod integrated with the blade spring body. The blade spring body is fixed to one side of the fixed blade 52. The U-shaped pressure rod is bent to the front end of the fixed blade 52, and then bends backward and extends to the other side of the fixed blade 52 to form the U-shaped pressure rod. This makes the U-shape surround the front end and both sides of the fixed blade 52. In this way, the U-shaped pressure rod surrounds the front end of the fixed blade 52 and will not shift. The U-shaped pressure rod uses the elasticity of the spring to abut against the upper surface of the front end of the moving blade 51 and maintains elastic pressure on the upper surface of the moving blade 51, thereby ensuring reliability and stability when gripping the wire end.

[0038] The driving mechanism has three strokes, the driving mechanism comprises a motor 3, the motor 3 is fixedly connected to the seat body 1, the motor 3 is electrically connected to the electric control, the output shaft of the motor 3 is movably connected to the rear part of the moving blade 51 through a crank 41 and a connecting rod 42, and the electric control controls the moving stroke of the moving blade 51 by controlling the rotating angle of the output shaft of the motor 3; the first stroke is that the moving blade 51 is driven from the retracted state to the stretched state, the needle avoiding hole 511 on the moving blade 51 corresponds to the position of the needle in the stretched state, the second stroke is that the moving blade 51 is retracted from the stretched state to the thread pressing state, the needle avoiding hole 511 of the moving blade is retracted to the position of the pressing rod 531 of the blade spring 53 in the thread pressing state, and the third stroke is that the thread pressing state is retracted to the retracted state, at this time, the moving blade 51 is reset, and the cutting action of the thread is completed by the cooperation of the cutting edge of the fixed blade 52 and the needle avoiding hole of the moving blade 51 when the moving blade is reset.

[0039] The working process of the present application is as follows: when the needle is raised, the electric control controls the motor 3 to drive the moving blade 51 from the retracted state to the stretched state through the crank 41 and the connecting rod 42, at this time, the needle avoiding hole 511 of the moving blade 51 just corresponds to the needle hole of the needle plate 2, the needle enters the needle avoiding hole 511 through the needle plate 2, at this time, the thread end on the needle also enters the needle avoiding hole 511, then when the needle end has not been separated from the needle avoiding hole 51 while the needle is reset and just separated from the needle avoiding hole 511, the electric control controls the motor 3 to rotate reversely by a preset angle and not to be completely reset, at this time, the moving blade 51 retracts the thread end entering the needle avoiding hole 51, the thread end is just clamped by the pressing rod 531 of the blade spring 53 and the upper surface of the blade head, the advantage is that the subsequent operation of the needle will not cause the problem of thread separation caused by the thread being pulled due to the untimely thread loosening cooperation, after the needle completes 2 to 3 needles, the electric control controls the motor 3 to be completely reset, at this time, the moving blade 51 is further retracted through the needle avoiding hole 511 along the mouth and cooperates with the fixed blade to cut the thread end, so that the remaining thread end is shorter and will not affect the beauty of the stitch due to the thread end being too long.

[0040] Considering that the thread will be cut to produce a short thread end, the present application further provides an air suction channel at the bottom of the seat body 1, the air suction opening 16 at the front end of the air suction channel corresponds to the cutting opening position of the moving blade 51 and the fixed blade 52, and the air suction channel is communicated with the air blowing device through an air pipe; the air suction channel comprises an air suction groove 14 formed in the bottom of the seat body 1, the air suction groove 14 is closed by an air suction cover plate 15 to form the air suction channel, the air suction groove 14 is provided with an air suction opening 16 at the front end corresponding to the cutting opening of the moving blade 51 and the fixed blade 52, and an air outlet 17 is formed at the rear end of the air suction groove 14, a connecting joint 18 is installed at the air outlet, and the air pipe of the connecting joint 18 is communicated with the air blowing device; the thread segment cut by the cutting is timely sucked away through the air suction channel.

[0041] The automatic bird nest preventing and shearing mechanism of the application is additionally provided with a blade spring, and the pressing rod of the blade spring is matched with the needle avoiding hole of the moving cutter head to press the thread when the needle is lifted, so that the thread will not be pulled off due to the untimely pulling of the thread when the needle is lifted; and the overlong thread can be cut after several stitches are lifted, so that the stitch is more beautiful.

[0042] In addition, the automatic bird nest preventing and shearing mechanism is provided as an independent module and is fixedly connected to the bottom of the needle plate, and can be installed as long as the space below the needle plate allows, and only a through hole corresponding to the screw hole position of the corresponding connecting part needs to be opened on the existing needle plate, so that the module can be suitable for various sewing devices with different functions, and has the characteristics of reasonable specific structure, beautiful stitch, good reliability and strong applicability.

[0043] The driving mechanism of the application can also adopt a linear driving device, and the linear driving device can be a cylinder or an electromagnet, etc. Figures 11-17 The driving mechanism of the application adopts a linear driving device, and the driving mechanism comprises a first linear driving device 6 and a second linear driving device 7, the driving direction of the first linear driving device 6 is the same as the direction of the guide groove 12, and the driving direction of the second linear driving device 7 is perpendicular to the direction of the guide groove 12; the second linear driving device 7 is arranged at the bottom of the seat body 1, the upper end of the second linear driving device 7 is connected with a limiting sliding block 71, the limiting sliding block 71 is accommodated in the longitudinal guide groove 13 of the seat body 1, and the second linear driving device 7 drives the limiting sliding block 71 to move up and down in the longitudinal guide groove 13; the rear part of the moving cutter 51 is connected with the first linear driving device 6 at the rear side of the seat body 1 through an active connection shaft 43, and the bottom of the active connection shaft 43 is provided with a limiting connection column 44 protruding downward; the upward movement of the limiting sliding block 71 can block the backward movement path of the limiting connection column 44 and limit the stroke of the backward movement of the moving cutter 51, and the downward movement of the limiting sliding block 71 will not block the movement path of the limiting connection column 44; the seat body 1 is also provided with a moving cutter stroke limiting block 19, which is located at the rear side of the guide groove 12 and is used to limit the maximum stroke of the retraction of the moving cutter 51.

[0044] Since the stroke of the linear driving device cannot be accurately controlled like a servo motor, the limiting structure is increased in the retraction stroke, such as the cooperation of the limiting sliding block 71 and the limiting connection column 44 to control the position of the moving cutter 51 and the pressing rod 531, the maximum position of the retraction is controlled by the moving cutter stroke limiting block 19, and the maximum position of the extension is controlled by the maximum stroke of the first linear driving device 6, so that the same effect as the motor control rotation angle is achieved, and the working process will not be described again.

[0045] The three-stroke of the present application can also be realized by the mutual superposition of the strokes of two groups of linear driving devices, both of which are arranged on the rear side of the seat body and have the same driving direction, and the driving rods of the two groups of linear driving devices are coaxial or have the same direction, so that the strokes are mutually superposed and connected with the rear part of the moving knife; when the driving rods of the two groups of linear driving devices are simultaneously pushed out, the moving knife is in the stretched state; only when the driving rod of one group of linear driving devices is retracted, the moving knife is in the line-pressing state; and when the driving rods of the two groups of linear driving devices are both retracted, the moving knife is in the retracted state.

[0046] The present application is not limited to the above three ways for the driving device to control the position of the moving knife, and other similar structures for realizing the switching of the three states of the moving knife also belong to the protection scope of the present application.

Claims

1. An automatic bird nest shearing mechanism, comprising a base (1) and a needle plate (2), wherein the base (1) is provided with a drive mechanism, a transmission mechanism (4) and a clamping and shearing mechanism (5), the drive mechanism driving the clamping and shearing mechanism (5) to operate through the transmission mechanism, characterized in that: The seat body (1) is fixed to the bottom of the needle plate (2) through the connecting part arranged at the top; The clamping and shearing mechanism (5) comprises a moving cutter (51), a fixed cutter (52) and a cutter spring (53), the fixed cutter (52) is fixed on the seat body (1), the moving cutter (51) is movably arranged on the seat body (1), the moving cutter (51) is provided with a needle avoiding hole (511) at the front part, the pressing rod (531) of the cutter spring (53) abuts against the upper surface of the front part of the moving cutter (51), the rear part of the moving cutter (51) is connected with the driving mechanism through the transmission mechanism (4); The seat body (1) is provided with a guide groove (12) at the top, the moving cutter (51) is accommodated in the guide groove (12), the driving mechanism drives the moving cutter (51) to move linearly along the guide groove (12); the fixed cutter (52) is arranged on the upper surface of the moving cutter (51) and is fixed on the seat body (1), the body of the cutter spring (53) is fixed on the seat body (1), the pressing rod (531) of the front part of the cutter spring (53) extends to the front side of the fixed cutter (52) and abuts against the upper surface of the front part of the moving cutter (51); the pressing rod (531) is in U shape, one end of the U-shaped pressing rod is integrated with the body of the cutter spring, the body of the cutter spring is fixed on one side of the fixed cutter (52), the U-shaped pressing rod is formed by bending the pressing rod to the front end of the fixed cutter (52), winding around the front end of the fixed cutter (52) and then bending backward and extending to the other side of the fixed cutter (52), so that the U-shaped pressing rod surrounds the front end and the two sides of the fixed cutter (52), and the part of the U-shaped pressing rod abutting against the upper surface of the front end of the moving cutter (51) keeps elastic pressure on the upper surface of the moving cutter (51); The driving mechanism has three strokes, the first stroke is that the moving cutter (51) is from the retracted state to the stretched state, the needle avoiding hole (511) on the moving cutter (51) corresponds to the position of the needle in the stretched state; the second stroke is that the moving cutter (51) is from the stretched state to the retracted state, the needle avoiding hole (511) of the moving cutter is retracted to the position of the pressing rod (531) of the cutter spring (53) in the retracted state; the third stroke is that the retracted state is retracted, at this time, the moving cutter (51) is reset, and the cutting edge of the fixed cutter (52) cooperates with the needle avoiding hole of the moving cutter (51) to complete the line shearing action when the moving cutter is reset; The bottom of the seat body (1) is further provided with an air suction channel, the air suction opening (16) at the front end of the air suction channel corresponds to the position of the shearing opening of the moving cutter (51) and the fixed cutter (52), and the air suction channel is communicated with the air suction device through an air pipe; the air suction channel comprises an air suction groove (14) arranged at the bottom of the seat body (1), the air suction groove (14) is closed by an air suction cover plate (15) to form the air suction channel, the air suction groove (14) is provided with the air suction opening (16) at the front end corresponding to the position of the shearing opening of the moving cutter (51) and the fixed cutter (52), and the rear end of the air suction groove (14) is provided with an air outlet (17), a connecting connector (18) is arranged at the air outlet, and the air pipe of the connecting connector (18) is communicated with the air blowing device.

2. An automatic shearing mechanism for preventing bird nests as defined in claim 1, characterized in that: The connecting part is a boss (11) protruding upward on the top of the seat body, the boss (11) is provided with a screw hole, the needle plate (2) is provided with a through hole (21) corresponding to the screw hole, and the screw rod is rotatably connected at the screw hole to fix the seat body (1) on the bottom of the needle plate (2).

3. An automatic shearing mechanism for preventing bird nests as defined in claim 1, wherein: The driving mechanism comprises a motor (3) fixedly connected to the seat body (1), the motor (3) is electrically connected to the electric control, and the output shaft of the motor (3) is movably connected to the rear part of the moving knife (51) through a crank (41) and a connecting rod (42), and the electric control controls the moving stroke of the moving knife (51) by controlling the rotating angle of the output shaft of the motor (3).

4. The anti-nest automatic shearing mechanism of claim 1, wherein: The driving mechanism comprises a first linear driving device (6) and a second linear driving device (7), the driving direction of the first linear driving device (6) is the same as the direction of the guide groove (12), and the driving direction of the second linear driving device (7) is perpendicular to the direction of the guide groove (12); the second linear driving device (7) is arranged at the bottom of the seat body (1), the upper end of the second linear driving device (7) is connected to a limiting sliding block (71), the limiting sliding block (71) is accommodated in the longitudinal guide groove (13) of the seat body (1), and the second linear driving device (7) drives the limiting sliding block (71) to move up and down in the longitudinal guide groove (13); the rear part of the moving knife (51) is connected to the first linear driving device (6) on the rear side of the seat body (1) through an active connection shaft (43), and the bottom of the active connection shaft (43) is provided with a limiting connection column (44) protruding downward; the limiting sliding block (71) can block the backward movement path of the limiting connection column (44) and limit the stroke of the backward movement of the moving knife (51) when the limiting sliding block (71) rises, and the limiting sliding block (71) will not block the movement path of the limiting connection column (44) when the limiting sliding block (71) descends.

5. The anti-nest automatic shearing mechanism of claim 1, wherein: The driving mechanism comprises a first linear driving device and a second linear driving device, both groups of linear driving devices are arranged on the rear side of the seat body and have the same driving direction, and the driving rod strokes of the two groups of linear driving devices are superposed and connected to the rear part of the moving knife.

6. An automatic shearing mechanism for preventing bird nests as defined in claim 4, wherein: The seat body (1) is further provided with a moving knife stroke limiting block (19) located on the rear side of the guide groove (12).

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