Bird nest prevention automatic shearing mechanism

Abstract

The invention relates to an anti-nest automatic shearing mechanism which comprises a seat body and a needle plate, the seat body is provided with a driving mechanism, a transmission mechanism and a clamping and shearing mechanism, the driving mechanism drives the clamping and shearing mechanism to act through the transmission mechanism, and the seat body is fixedly connected to the bottom of the needle plate through a connecting part arranged at the top; the clamping and shearing mechanism comprises a movable cutter, a fixed cutter and a blade spring, the fixed cutter is fixed on the seat body, the movable cutter is movably arranged on the seat body, a machine needle avoiding hole is formed in the front part of the movable cutter, a pressing rod of the blade spring is propped against the upper surface of the front part of the movable cutter, and the rear part of the movable cutter is connected with the driving mechanism through the transmission mechanism; the driving mechanism drives the movable cutter to move and has a three-section stroke structure; according to the anti-bird nest and anti-thread-off device, the thread ends are clamped at first in the sewing starting process, redundant thread ends are cut off after needle starting is stable, the good anti-bird nest and anti-thread-off effects are achieved, thread end clamping is executed through the elastic mechanism and is not limited by yarn fineness, and the anti-bird nest and anti-thread-off device has the advantages of being reasonable in structure, attractive in stitch, good in reliability and high in applicability.

Description

Technical Field

[0001] The invention relates to sewing machine technology, in particular to an automatic shearing mechanism for preventing bird nests. Background Art

[0002] In order to prevent the upper thread from falling off the needle when starting to stitch, sewing equipment often needs to leave a section of the upper thread end when passing through the needle hole. Then the longer thread end is intertwined with the bottom thread or the upper thread when starting to stitch to form a thread ball commonly known as a "bird's nest". The stitches sewn in this way are not beautiful. In order to solve this problem, some people have proposed an anti-bird's nest mechanism. Most of the existing anti-bird's nest mechanisms clamp the thread end when starting to stitch, and release the thread end after stitching to prevent the thread end from being entangled with the bottom thread or the upper thread. For example, the utility model with announcement number CN215209964U announces a dual-purpose device for preventing bird's nests and thread falling off and a sewing machine containing the device, which is used to pull the needle through the needle plate after the needle passes through the needle plate. The end of the sewing thread is away from the needle; it includes: an actuator, which is arranged on the lower side of the needle plate, for driving the end of the sewing thread to move; a power component, for driving the actuator to execute the action of driving the end of the sewing thread to move; and an electronic control unit, which is electrically connected to the power component, for sensing the position of the needle and driving the power component to execute the driving action. The utility model can prevent the thread end from being drawn into the bottom surface of the cloth by the rotary shuttle when sewing, thereby achieving the effect of preventing bird nests; and the dual-purpose anti-bird nest and anti-thread off-line device of the utility model are all located on the lower side of the table panel. This design can reduce the possibility of accidental touch by the operator, improve safety, and also has the function of preventing thread off-line.

[0003] Although the above structure solves the problem of bird's nests, especially when starting to needle, the thread end is pulled by the actuator to solve the problems of bird's nests and thread derailment, but because the thread end is pulled by the actuator and the thread end is left longer, each stitch will leave a longer thread end, and the stitch is still not beautiful enough.

[0004] The thread trimming mechanism of the present invention is a double movable knife which is arranged on the outer periphery of the rotary hook of the sewing machine, and a main movable knife which is arranged on the outer periphery of the rotary hook of the sewing machine. The main movable knife is provided with a thread trimming blade for starting seam, a thread hooking groove, a thread dividing groove and a thread trimming blade for finishing seam, and the thread hooking groove allows the needle of the sewing machine to pass through. When the main movable knife moves toward the seam starting fixed knife, the thread trimming blade for starting seam can be engaged with the seam starting fixed knife to reliably realize the bird nest prevention at seam starting. When the main movable knife and the movable knife for finishing seam move toward each other, the thread trimming blade for finishing seam can be engaged with the movable knife for finishing seam to realize automatic thread trimming after seam, and the automatic thread trimming after seam is a double movable knife structure, which can make the engaging position of the thread trimming blade for finishing seam and the movable knife for finishing seam closer to the central axis of the needle, so that the residual thread on the sewing material after thread trimming is shorter.

[0005] The above-mentioned structure is mainly realized by the cooperation of the seam starter fixed knife and the main movable knife. The thread trimming mechanism structures of different sewing machines are different. Some thread trimming mechanisms do not have a main movable knife. In addition, due to the different materials and thicknesses of the sewing machine surface threads, the above-mentioned structure cannot adjust the gap between the seam starter fixed knife and the main movable knife. Therefore, the above-mentioned structure has great limitations and can only be used for yarns of specified thickness and specific models of sewing machines. Summary of the Invention

[0006] The purpose of the present invention is to provide an anti-bird's nest automatic shearing mechanism, an independent anti-bird's nest automatic shearing mechanism is arranged below the needle plate and on one side of the thread shearing mechanism, the anti-bird's nest automatic shearing mechanism is directly fixed to the bottom of the needle plate, and is very convenient to modify and assemble and unassemble, and can first clamp the thread end when sewing, and cut off the excess thread end after the needle is stable, which plays a good role in preventing bird's nests and preventing thread derailment, and the thread end clamping is performed by an elastic mechanism, which is not restricted by the fineness of the yarn, and can be improved as long as there is space on the needle plate and below the needle plate. It can be suitable for various sewing equipment with different functions, and has the characteristics of reasonable structure, beautiful stitches, good reliability and strong applicability.

[0007] To achieve the above objectives, the following technical solutions are adopted: An anti-bird nest automatic shearing mechanism comprises a base body and a needle plate, wherein a driving mechanism, a transmission mechanism and a clamping and shearing mechanism are arranged on the base body, and the driving mechanism drives the clamping and shearing mechanism to operate through the transmission mechanism, and is characterized in that: the base body is fixedly connected to the bottom of the needle plate through a connecting portion arranged at the top; the clamping and shearing mechanism comprises a movable knife, a fixed knife and a blade spring, the fixed knife is fixed on the base body, the movable knife is movably arranged on the base body, a needle avoidance hole is provided at the front of the movable knife, a pressure rod of the blade spring abuts against the upper surface of the front of the movable knife, and a pressure rod of the blade spring abuts against the upper surface of the front of the movable knife, and a pressure rod of the blade spring abuts against the upper surface of the front of the movable knife. It is connected to the driving mechanism through the transmission mechanism, and the driving mechanism drives the movable knife to move with a three-stage stroke structure. The first stage of the stroke is from the retracted state to the extended state of the movable knife. When in the extended state, the needle avoidance hole on the movable knife corresponds to the position of the needle. The second stage of the stroke is from the extended state to the line-pressing state of the movable knife. When in the line-pressing state, the needle avoidance hole of the movable knife is recovered to the pressure rod position of the blade spring. The third stage of the stroke is from the line-pressing state to the retracted state. At this time, the movable knife is reset and when the movable knife is reset, the blade of the fixed knife cooperates with the needle avoidance hole of the movable knife to complete the thread cutting action.

[0008] The connecting part is a boss protruding upward from the top of the seat body, and a screw hole is provided on the boss. A through hole is opened at a position corresponding to the screw hole on the needle plate, and the screw passes through the through hole and is screwed into the screw hole to fix the seat body to the bottom of the needle plate.

[0009] A guide groove is provided on the top of the base body, the movable knife is accommodated in the guide groove, and the driving mechanism drives the movable knife to move linearly along the guide groove; the fixed knife is arranged on the upper surface of the movable knife and fixed on the base body, the blade spring body is fixed on the base body, and the pressure rod at the front of the blade spring extends to the front side of the fixed knife and abuts against the upper surface of the front of the movable knife.

[0010] The pressure rod is U-shaped, one end of the U-shaped pressure rod is connected to the blade spring body as a whole, the spring body is fixed to one side of the fixed knife, and the U-shaped pressure rod is bent to the front end of the fixed knife, and then bent backward from the front end of the fixed knife and extended to the other side of the fixed knife to form the U-shaped pressure rod, so that the U shape surrounds the front end and both sides of the fixed knife, and the U-shaped pressure rod abuts the upper surface of the front end of the movable knife and maintains elastic pressure on the upper surface of the movable knife.

[0011] The driving mechanism includes a motor, which is fixed to the base body and electrically connected to the electronic control. The output shaft of the motor is movably connected to the rear of the movable knife through a crank and a connecting rod. The electronic control controls the movement stroke of the movable knife by controlling the rotation angle of the motor output shaft.

[0012] The driving mechanism includes a first linear drive device and a second linear drive device. The driving direction of the first linear drive device is the same as the direction of the guide groove, and the driving direction of the second linear drive device is perpendicular to the direction of the guide groove; the second linear drive device is provided with a bottom of the seat body, and the upper end of the second linear drive device is connected to a limiting slider, and the limiting slider is accommodated in the longitudinal guide groove of the seat body. The second linear drive device drives the limiting slider to move up and down in the longitudinal guide groove; the rear part of the movable knife is connected to the first linear drive device on the rear side of the seat body through a movable connecting shaft, and a downwardly protruding limiting connecting column is provided at the bottom of the movable connecting shaft; when the limiting slider rises, it will block the backward movement path of the limiting connecting column and limit the backward movement of the movable knife. When the limiting slider descends, the rear side will not block the limiting connecting column.

[0013] The driving mechanism includes a first linear driving device and a second linear driving device. Both sets of linear driving devices are arranged on the rear side of the base body and have the same driving direction. The driving rod strokes of the two sets of linear driving devices are superimposed on each other and are connected to the rear of the movable knife.

[0014] The present invention sets the anti-bird nest automatic shearing mechanism as an independent module and fixes the module to the bottom of the needle plate. It can be installed as long as the space below the needle plate allows. And the installation only requires opening a through hole corresponding to the screw hole position of the corresponding connection part on the existing needle plate. It can be suitable for various sewing equipment with different functions.

[0015] In addition, a blade spring is added to the bird's nest prevention automatic shearing mechanism of the present invention, and the pressure rod of the blade spring is cleverly matched with the movable cutter head needle avoidance hole to press the thread end when starting the needle, so that the surface thread will not be pulled off due to the problem of thread being pulled off when starting the needle; after the needle is stabilized, the excessively long thread end can be cut to make the stitches more beautiful; the specific structure is reasonable, the stitches are beautiful, the reliability is good, and the applicability is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of the present invention on a sewing device (1); Figure 2 This is a schematic diagram of the structure of the present invention on a sewing device (II); Figure 3 This is a schematic diagram of the cooperation between the present invention and the needle plate; Figure 4 It is a schematic diagram of the exploded structure of the present invention and the needle plate; Figure 5 This is a schematic structural diagram of a first embodiment of the present invention; Figure 6 This is a structural diagram of another aspect of the first embodiment of the present invention; Figure 7 A schematic diagram of a partial structure of a first embodiment of the present invention; Figure 8 This is a structural diagram of the first embodiment of the present invention in which the air suction cover is separated; Figure 9 This is a schematic structural diagram of the seat body according to the first embodiment of the present invention (1); Figure 10 This is a structural schematic diagram of the seat body according to the first embodiment of the present invention (II); Figure 11 This is a structural schematic diagram of the clamping and shearing mechanism in the second embodiment of the present invention when the movable blade is in an extended state; Figure 12 This is a structural schematic diagram of the clamping and shearing mechanism in the movable knife pressing state according to the second embodiment of the present invention; Figure 13 This is a schematic structural diagram of the clamping and shearing mechanism in the second embodiment of the present invention when the movable blade is in the retracted state; Figure 14 This is a schematic structural diagram of the bottom of the second embodiment of the present invention; Figure 15 This is a schematic structural diagram of the seat body according to the second embodiment of the present invention (1); Figure 16 This is a structural schematic diagram of the seat body according to the second embodiment of the present invention (II); Figure 17 This is a schematic structural diagram of the driving mechanism, transmission mechanism, and clamping and shearing mechanism of the second embodiment of the present invention. DETAILED DESCRIPTION

[0017] like Figure 1-10 As shown, an anti-bird nest automatic shearing mechanism includes a base body 1 and a needle plate 2. A driving mechanism, a transmission mechanism 4 and a clamping and shearing mechanism 5 are provided on the base body 1. The driving mechanism drives the clamping and shearing mechanism 5 to operate through the transmission mechanism. The base body 1 is fixedly connected to the bottom of the needle plate 2 through a connecting part provided on the top; the connecting part is a boss 11 protruding upward from the top of the base body, and a screw hole is provided on the boss 11. A through hole 21 is opened at a position corresponding to the screw hole on the needle plate 2, and the screw passes through the through hole 21 and is screwed on the screw hole to fix the base body 1 to the bottom of the needle plate 2.

[0018] The clamping and shearing mechanism 5 includes a movable knife 51, a fixed knife 52 and a blade spring 53. The fixed knife 52 is fixed on the base body 1, and the movable knife 51 is movably arranged on the base body 1. A needle avoidance hole 511 is provided at the front of the movable knife 51. The pressure rod 531 of the blade spring 53 abuts against the upper surface of the front of the movable knife 51. The rear of the movable knife 51 is connected to the drive mechanism through the transmission mechanism 4.

[0019] A guide groove 12 is provided on the top of the base body 1, and the movable knife 51 is accommodated in the guide groove 12. The driving mechanism drives the movable knife 51 to move linearly along the guide groove 12; the fixed knife 52 is arranged on the upper surface of the movable knife 51 and fixed on the base body 1, and the main body of the blade spring 53 is fixed on the base body 1, and the pressure rod 531 at the front of the blade spring 53 extends to the front side of the fixed knife 52 and abuts against the upper surface of the front of the movable knife 51.

[0020] The pressure rod 531 is U-shaped, and one end of the U-shaped pressure rod is connected to the blade spring body. The blade spring body is fixed on one side of the fixed knife 52. The U-shaped pressure rod is bent to the front end of the fixed knife 52, and then bends backward from the front end of the fixed knife 52 and extends to the other side of the fixed knife 52 to form the U-shaped pressure rod, so that the U shape surrounds the front end and both sides of the fixed knife 52. In this way, the U-shaped pressure rod surrounds the front end of the fixed knife 52 and the pressure rod 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 movable knife 51 and maintains elastic pressure on the upper surface of the movable knife 51, thereby ensuring reliability and stability when grabbing the thread end.

[0021] The driving mechanism has three strokes, and the driving mechanism includes a motor 3, which is fixed to the base body 1. The motor 3 is electrically connected to the electronic control. The output shaft of the motor 3 is movably connected to the rear part of the movable knife 51 through the crank 41 and the connecting rod 42. The electronic control controls the movement stroke of the movable knife 51 by controlling the rotation angle of the output shaft of the motor 3; the first stroke is from the retracted state to the extended state of the movable knife 51. In the extended state, the needle avoidance hole 511 on the movable knife 51 corresponds to the position of the needle. The second stroke is from the extended state to the line-pressing state of the movable knife 51. In the line-pressing state, the movable knife needle avoidance hole 511 is recovered to the position of the pressure rod 531 of the blade spring 53. The third stroke is from the line-pressing state to the retracted state. At this time, the movable knife 51 is reset and when the movable knife is reset, the blade of the fixed knife 52 cooperates with the needle avoidance hole of the movable knife 51 to complete the thread cutting action.

[0022] The working process of the present invention is as follows: when the needle is started, the electronic control motor 3 drives the movable knife 51 from the contracted state to the extended state through the crank 41 and the connecting rod 42. At this time, the needle avoidance hole 511 of the movable knife 51 just corresponds to the needle hole of the needle plate 2. The needle passes through the needle plate 2 and enters the needle avoidance hole 511. At this time, the upper thread end on the needle also enters the needle avoidance hole 511. Then, as the needle resets and just leaves the needle avoidance hole 511 and the thread end has not yet left the needle avoidance hole 51, the electronic control motor 3 rotates in the reverse direction and is set in advance. Angle and not completely reset, at this time the movable knife 51 enters the needle avoidance hole 51 with the thread end retracted, the thread end is just clamped by the pressure rod 531 of the blade spring 53 and the upper surface of the knife head, the advantage of this is to ensure that the subsequent operation of the needle will not cause the thread to be off due to untimely loosening of the thread and the surface thread will not be pulled, after the needle completes 2 to 3 stitches, the electronic control motor 3 is completely reset, at this time the movable knife 51 further retracts and cuts the thread end through the edge of the needle avoidance hole 511 in cooperation with the fixed knife, so that the retained thread end is shorter and the beauty of the stitches will not be affected by the thread end being too long.

[0023] Taking into account that short thread ends will be generated after thread cutting, the present invention further provides an air suction channel at the bottom of the seat body 1, and the position of the air suction port 16 at the front end of the air suction channel corresponds to the shearing position of the movable knife 51 and the fixed knife 52, and the air suction channel is connected to the blowing device through an air duct; the air suction channel includes an air suction groove 14 opened at the bottom of the seat body 1, and the air suction groove 14 is closed by a air suction cover 15 to form the air suction channel, and the front end of the air suction groove 14 is provided with an air suction port 16 at the position corresponding to the shearing position of the movable knife 51 and the fixed knife 52, and an air outlet 17 is opened at the rear end of the air suction groove 14, and a connecting joint 18 is installed at the air outlet, and the air duct of the connecting joint 18 is connected to the blowing device; the line segments generated by shearing are sucked away in time through the air suction channel.

[0024] The bird's nest prevention automatic cutting mechanism of the present invention is additionally provided with a blade spring, and the pressure rod of the blade spring is cleverly matched with the movable cutter head needle avoidance hole to press the thread end when starting to stitch, so that the upper thread will not be derailed due to the loose upper thread and not being pulled in time when starting to stitch; after a few stitches are started and sewn, the excessively long thread end can be cut to make the stitches more beautiful.

[0025] In addition, the present invention sets the anti-bird's nest automatic shearing mechanism as an independent module, and fixes the module to the bottom of the needle plate. It can be installed as long as the space below the needle plate allows, and the installation only requires opening a through hole corresponding to the screw hole position of the corresponding connection part on the existing needle plate. It can be suitable for various sewing equipment with different functions; it has the characteristics of reasonable structure, beautiful stitches, good reliability and strong applicability.

[0026] The driving mechanism of the present invention can also adopt a linear driving device, which can be a cylinder or an electromagnet, etc. Figure 11-17 As shown, the driving mechanism of the present invention adopts a linear driving device, which includes 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 provided with a bottom of the seat body 1, and the upper end of the second linear driving device 7 is connected to a limiting slider 71, which is accommodated in the longitudinal guide groove 13 of the seat body 1, and the second linear driving device 7 drives the limiting slider 71 to move upward in the longitudinal guide groove 13 Downward movement; the rear part of the movable knife 51 is connected to the first linear drive device 6 on the rear side of the base body 1 through a movable connecting shaft 43, and a downwardly protruding limit connecting column 44 is provided at the bottom of the movable connecting shaft 43; the rising of the limit slider 71 will block the backward movement path of the limit connecting column 44 and limit the backward movement of the movable knife 51, and the lowering of the limit slider 71 will not block the movement path of the limit connecting column 44; the base body 1 is also provided with a movable knife travel limit block 19, which is located on the rear side of the guide groove 12 and is used to limit the maximum travel of the movable knife 51 when it retracts.

[0027] Since the stroke of the linear drive device cannot be controlled as accurately as that of a servo motor, a limiting structure is added to the retraction stroke. For example, the position of the movable knife 51 and the pressure rod 531 is controlled by cooperating with the limiting slider 71 and the limiting connecting column 44. The maximum retraction position is controlled by the movable knife stroke limit block 19, and the maximum extension position is controlled by the maximum stroke of the first linear drive device 6. The effect achieved is the same as that of the motor controlling the rotation angle, and the working process will not be repeated.

[0028] In addition, the three-stage stroke of the present invention can also be achieved by superimposing the strokes of the driving rods of two sets of linear drive devices. The two sets of linear drive devices are both arranged on the rear side of the base body and have the same driving direction. The driving rods of the two sets of linear drive devices are coaxial or in the same direction, so that the strokes are superimposed on each other and connected to the rear part of the movable knife; when the driving rods of the two sets of linear drive devices are pushed out at the same time, the movable knife is in an extended state, and when only the driving rod of one set of linear drive devices is retracted, the movable knife is in a line-pressing state; when the driving rods of both sets of linear drive devices are retracted, the movable knife is in a retracted state.

[0029] The control of the position of the movable knife by the driving device of the present invention is not limited to the above three methods. Structures that use other similar structures to achieve the switching of the three states of the movable knife all fall within the protection scope of the present invention.

Claims

1. An anti-bird nest automatic shearing mechanism, comprising a base (1) and a needle plate (2), wherein a driving mechanism, a transmission mechanism (4) and a clamping and shearing mechanism (5) are provided on the base (1), wherein the driving mechanism drives the clamping and shearing mechanism (5) to operate through the transmission mechanism, and wherein: The seat body (1) is fixedly connected to the bottom of the needle plate (2) via a connecting portion provided at the top; The clamping and shearing mechanism (5) includes a movable knife (51), a fixed knife (52) and a blade spring (53), wherein the fixed knife (52) is fixed on the base (1), and the movable knife (51) is movably arranged on the base (1). A needle avoidance hole (511) is provided at the front of the movable knife (51), and a pressure rod (531) of the blade spring (53) abuts against the upper surface of the front of the movable knife (51), and the rear of the movable knife (51) is connected to the driving mechanism through the transmission mechanism (4); The driving mechanism has three strokes. The first stroke is when the movable knife (51) moves from a retracted state to an extended state. In the extended state, the needle avoidance hole (511) on the movable knife (51) corresponds to the position of the needle. The second stroke is when the movable knife (51) retracts from the extended state to the line pressing state. In the line pressing state, the movable knife needle avoidance hole (511) retracts to the position of the pressure rod (531) of the blade spring (53). The third stroke is when the line pressing state is retracted to the retracted state. At this time, the movable knife (51) is reset and when the movable knife is reset, the blade of the fixed knife (52) cooperates with the needle avoidance hole of the movable knife (51) to complete the thread cutting action.

2. The automatic shearing mechanism for preventing bird nests according to claim 1, characterized in that: The connecting portion is a boss (11) protruding upward from the top of the seat body, and a screw hole is provided on the boss (11). A through hole (21) is provided at a position corresponding to the screw hole on the needle plate (2). The screw passes through the through hole (21) and is screwed to the screw hole to fix the seat body (1) to the bottom of the needle plate (2).

3. The bird nest prevention automatic shearing mechanism according to claim 1, characterized in that: The seat (1) is provided with a guide groove (12) on the top, the movable knife (51) is accommodated in the guide groove (12), and the driving mechanism drives the movable knife (51) to move linearly along the guide groove (12); the fixed knife (52) is provided on the upper surface of the movable knife (51) and fixed on the seat (1), the main body of the blade spring (53) is fixed on the seat (1), and the pressure rod (531) at the front of the blade spring (53) extends to the front side of the fixed knife (52) and abuts against the upper surface of the front of the movable knife (51).

4. The automatic shearing mechanism for preventing bird nests according to claim 3, characterized in that: The pressure rod (531) is U-shaped, one end of the U-shaped pressure rod is connected to the blade spring body as a whole, and the blade spring body is fixed to one side of the fixed knife (52). The U-shaped pressure rod is formed by bending the pressure rod to the front end of the fixed knife (52), and then bending backward from the front end of the fixed knife (52) and extending to the other side of the fixed knife (52). The U shape surrounds the front end and both sides of the fixed knife (52), and the U-shaped pressure rod abuts against the upper surface of the front end of the movable knife (51) and maintains elastic pressure on the upper surface of the movable knife (51).

5. The bird nest prevention automatic shearing mechanism according to claim 3, characterized in that: The driving mechanism includes a motor (3), the motor (3) is fixedly connected to the base (1), the motor (3) is electrically connected to the electric control, the output shaft of the motor (3) is movably connected to the rear of the movable knife (51) through the crank (41) and the connecting rod (42), and the electric control controls the movement stroke of the movable knife (51) by controlling the rotation angle of the output shaft of the motor (3).

6. The automatic shearing mechanism for preventing bird nests according to claim 3, characterized in that: The driving mechanism includes a first linear driving device (6) and a second linear driving device (7), wherein 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 provided with a bottom of the seat body (1), the upper end of the second linear driving device (7) is connected to a limiting slider (71), the limiting slider (71) is accommodated in the longitudinal guide groove (13) of the seat body (1), and the second linear driving device (7) is provided with a limiting slider (71) on the upper end of the second linear driving device (7). ) drives the limit slider (71) to move up and down in the longitudinal guide groove (13); the rear part of the movable knife (51) is connected to the first linear drive device (6) on the rear side of the base (1) through a movable connecting shaft (43), and a downwardly protruding limit connecting column (44) is provided at the bottom of the movable connecting shaft (43); when the limit slider (71) rises, it will block the backward movement path of the limit connecting column (44) and limit the backward movement stroke of the movable knife (51), and when the limit slider (71) falls, it will not block the movement path of the limit connecting column (44).

7. The automatic shearing mechanism for preventing bird nests according to claim 3, characterized in that: The driving mechanism includes a first linear driving device and a second linear driving device. Both sets of linear driving devices are arranged on the rear side of the base body and have the same driving direction. The driving rod strokes of the two sets of linear driving devices are superimposed on each other and connected to the rear of the movable knife.

8. The automatic shearing mechanism for preventing bird nests according to claim 6, characterized in that: The seat body (1) is further provided with a movable knife travel limit block (19), and the movable knife travel limit block (19) is located at the rear side of the guide groove (12).

9. The bird nest prevention automatic shearing mechanism according to claim 1, characterized in that: The bottom of the seat (1) is also provided with an air suction channel, the position of the air suction port (16) at the front end of the air suction channel corresponds to the position of the shearing openings of the movable knife (51) and the fixed knife (52), and the air suction channel is connected to the blowing device through an air duct.

10. The automatic shearing mechanism for preventing bird nests according to claim 9, characterized in that: The suction channel includes a suction groove (14) provided at the bottom of the seat (1), the suction groove (14) being closed by a suction cover (15) to form the suction channel, a suction port (16) being provided at the front end of the suction groove (14) at the position corresponding to the shearing opening of the movable knife (51) and the fixed knife (52), an air outlet (17) being provided at the rear end of the suction groove (14), a connecting joint (18) being installed at the air outlet, and an air duct of the connecting joint (18) being connected to the blowing device.

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