A drone for protecting agricultural and forestry plants

Abstract

This invention relates to the field of unmanned aerial vehicles (UAVs), specifically to an agricultural and forestry plant protection UAV, comprising a fuselage and a liquid storage tank disposed within the fuselage. A pumping assembly is fixedly installed within the fuselage and connected to the liquid storage tank. A spraying assembly is also provided within the fuselage, used to increase and control the spraying range of the pesticide. The spraying assembly includes a control box located at the bottom of the pumping assembly, with the bottom of the control box having an arc-shaped design. The bottom of the control box has a vertical plate and an inclined plate, and a control plate is slidably connected inside the control box. This invention, by setting up the spraying assembly, allows the pesticide to enter the control box and, under the control of the control plate, enter the vertical and inclined plates through the central and side notches, thereby being sprayed outwards through the nozzle. The inclined plate is positioned at an angle, i.e., spraying the pesticide outwards from an inclined position, thus increasing the spraying range.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) technology, and more particularly to an agricultural and forestry plant protection UAV. Background Technology

[0002] A drone is an unmanned aircraft that does not require direct pilot control and is controlled via radio remote control equipment or preset programs. It combines aviation technology, electronic technology, computer technology, and sensor technology, and is characterized by flexibility, efficiency, and safety. It is widely used in military, civilian, and commercial fields, and drones are also widely used in agricultural and forestry plant protection, such as spraying pesticides on agricultural and forestry plants to prevent forestry pests and diseases.

[0003] However, pests and diseases affecting tall trees (such as longhorn beetles, aphids, and leaf spot) are characterized by their strong concealment and rapid spread, requiring rapid and comprehensive pesticide coverage. However, most mainstream plant protection drones currently use fixed-angle nozzles. Fixed nozzles cannot dynamically adjust the spray angle and range, making it difficult to adapt to the three-dimensional structure of the tree canopy (such as height, density, and branch distribution). This results in insufficient pesticide deposition in areas such as the inner canopy and bottom due to obstruction by external branches and trunks, and limited pesticide coverage within the forest, thus affecting the overall spraying effect.

[0004] Therefore, a drone for the protection of agricultural and forestry plants is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide an unmanned aerial vehicle (UAV) for the protection of agricultural and forestry plants, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an agricultural and forestry plant protection drone, comprising a body and a liquid storage tank disposed within the body, wherein a pumping assembly is fixedly installed in the body and the pumping assembly is connected to the liquid storage tank; a spraying assembly is provided in the body, the spraying assembly being used to improve and control the spraying range of the agent, the spraying assembly including a control box disposed at the bottom end of the pumping assembly, the bottom end of the control box being arc-shaped, the bottom end of the control box being provided with a vertical plate and an inclined plate, and a control plate being slidably connected inside the control box.

[0007] Preferably, a hose is fixedly connected between the pumping assembly and the control box, a drain pipe is fixedly connected to the bottom of the control box, and the drain pipe is fixedly connected to a vertical plate and an inclined plate respectively. The vertical plate is vertically arranged at the bottom of the control box, and the inclined plate is inclinedly arranged at the bottom of the control box. Several nozzles are provided on both the vertical plate and the inclined plate.

[0008] Preferably, a bracket is fixedly installed on the control box, and an electric push rod is fixedly installed on the bracket. The output end of the electric push rod is fixedly connected to a connecting rod, and the connecting rod is slidably connected in the control box. The control panel has a central notch and a side notch.

[0009] Preferably, the control box is equipped with a moving component, which is used to drive the control box to move continuously, so that the sprayed agent enters the forest from various directions. The moving component includes a moving frame on the control box, and a rotating shaft is fixedly connected to the control box and rotatably connected to the moving frame.

[0010] Preferably, a motor is fixedly installed on the machine body, a threaded rod is fixedly connected to the output shaft of the motor, and the threaded rod is threadedly connected to the movable frame. A guide rod is fixedly connected to the machine body, and the guide rod is slidably connected to the movable frame.

[0011] Preferably, the mobile frame is equipped with an adjustment component for adjusting the spraying angle of the pesticide, so that the pesticide can enter the interior of the trees from multiple positions and angles. The adjustment component includes a baffle fixedly connected to the machine body, the baffle having an inclined surface, and a push block slidably connected to the inclined surface.

[0012] Preferably, a first push rod is fixedly connected between the push block and the movable frame, a second push rod is fixedly installed on the movable frame, and a hydraulic pipe is fixedly connected between the first push rod and the second push rod.

[0013] Preferably, a rack is fixedly connected to the output end of the second push rod, and a gear is fixedly connected to the rotating shaft, with the rack meshing with the gear.

[0014] Preferably, a slide rod is slidably connected to the movable frame, and the slide rod is fixedly connected to the rack. A limit plate is fixedly connected to the end of the slide rod, and a tension spring is fixedly connected between the limit plate and the movable frame.

[0015] The beneficial effects of this invention are: 1. This invention, by setting up a spraying assembly, enables the drone to spray pesticides. After the pesticide enters the control box, under the adjustment of the control panel, the pesticide can enter the vertical plate and the inclined plate through the central and side notches, and then be sprayed outward through the nozzle. The inclined plate is set in an inclined state, that is, spraying the pesticide outward from an inclined position, thereby increasing the spraying range and covering a larger spraying area, thus improving spraying efficiency. At the same time, the movement adjustment of the control panel can apply a sealing effect to the drain pipe on the inclined plate, so that the pesticide only enters the vertical plate through the central notch and is discharged outward. At this time, the effect of reducing the pesticide spraying range is achieved, avoiding ineffective spraying when a large area of ​​spraying is not needed.

[0016] 2. This invention utilizes a movable component to enable the drone to circulate back and forth on the guide rod during the spraying process. This circulatory movement of the movable component drives the control box to move back and forth, thereby increasing the range of motion of the control box, specifically the bottom inclined plate and the vertical plate. This increases the range of motion of the nozzle, further expanding the spraying area and thus covering a larger area of ​​agricultural and forestry vegetation, improving spraying efficiency. Furthermore, the back-and-forth spraying of the nozzle reduces missed or repeated spraying caused by the fixed flight path of the drone.

[0017] 3. This invention, by setting an adjustment component, enables the drone to spray pesticides back and forth under the action of the moving component. The movement of the moving frame drives the push block to move back and forth along the inclined surface of the baffle. Through the cooperation of the inclined surface, the push block squeezes the first push rod. Under the action of hydraulic oil as a medium, the second push rod is pushed to extend and drive the rack to move. Under the action of the tension spring, the rack moves in the opposite direction. The back and forth movement of the rack, through the cooperation of gears, enables the control box and the nozzle at the bottom to achieve the effect of back and forth rotation. During the back and forth rotation of the nozzle, the spraying angle is continuously adjusted, so that the sprayed pesticide can enter the agricultural and forestry vegetation from different positions and angles. It is convenient for the pesticide to pass through the external branches and gaps from different angles to enter the interior, so as to achieve the spraying effect inside. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of an agricultural and forestry plant protection drone according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the airframe structure of an agricultural and forestry plant protection drone according to an embodiment of the present invention; Figure 3 This invention relates to an unmanned aerial vehicle (UAV) for protecting agricultural and forestry plants. Figure 2 Enlarged structural diagram at point A in the middle; Figure 4 This is a schematic diagram of the baffle structure of an agricultural and forestry plant protection drone according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the control box structure of an agricultural and forestry plant protection drone according to an embodiment of the present invention; Figure 6 This is a cross-sectional view of the control box of an agricultural and forestry plant protection drone according to an embodiment of the present invention; Figure 7This is a schematic diagram of the mobile frame structure of an agricultural and forestry plant protection drone according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the pusher structure of an agricultural and forestry plant protection drone according to an embodiment of the present invention.

[0020] The components in the diagram are labeled as follows: 1. Body; 2. Liquid storage tank; 3. Pump assembly; 4. Control box; 5. Vertical plate; 6. Inclined plate; 7. Control panel; 8. Hoses; 9. Drain pipe; 10. Nozzle; 11. Bracket; 12. Electric push rod; 13. Connecting rod; 14. Center notch; 141. Side notch; 15. Moving frame; 16. Rotating shaft; 17. Motor; 18. Threaded rod; 19. Guide rod; 20. Baffle; 21. Inclined surface; 22. Push block; 23. First push rod; 24. Second push rod; 25. Hydraulic pipe; 26. Rack; 27. Gear; 28. Slide rod; 29. ​​Limiting plate; 30. Tension spring. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0022] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] like Figures 1 to 8As shown, a specific embodiment of the present invention provides an agricultural and forestry plant protection drone, including a body 1 and a liquid storage tank 2 disposed in the body 1. A pumping assembly 3 is fixedly installed in the body 1 and connected to the liquid storage tank 2. Both the liquid storage tank 2 and the pumping assembly 3 are existing technologies, and their specific structures are not described in detail. In conventional drones, the pumping assembly 3, such as a high-pressure pump, extracts the pesticide from the liquid storage tank 2 and delivers it to the subsequent spraying structure for spraying onto agricultural and forestry vegetation to achieve a maintenance effect. The body 1 is equipped with a spraying assembly, which is used to improve and control the spraying range of the pesticide. In conventional agricultural and forestry drones, the installed... The fixed spraying structure limits the spraying range and makes it impossible to cover large areas of agricultural and forestry vegetation. This necessitates multiple adjustments to the drone's flight position for comprehensive spraying. However, by adding a spraying component, the drone's spraying range can be increased, covering a wider area of ​​agricultural and forestry vegetation and improving spraying efficiency. At the same time, the spraying range can be controlled to avoid ineffective spraying when a large area is not needed. The spraying component includes a control box 4 located at the bottom of the pumping component 3, with the bottom of the control box 4 being arc-shaped. The bottom of the control box 4 has a vertical plate 5 and an inclined plate 6, and a control plate 7 is slidably connected inside the control box 4.

[0024] The control box 4 is equipped with a moving component, which is used to continuously move the control box 4, so that the sprayed pesticide enters the forest from various directions. When the nozzle 10 at the bottom of the control box 4 continuously sprays the pesticide outward, the moving component can continuously move the control box 4 back and forth, thereby moving the nozzle 10 continuously, so that the pesticide enters the forest from multiple positions, increasing the movement range of the nozzle 10, thereby further improving the spraying range, expanding the pesticide coverage area, and reducing the phenomenon of missed spraying or double spraying caused by the fixed flight path of the drone. The moving component is used to continuously move the control box 4, so that the sprayed pesticide enters the forest from various directions. The moving component includes a moving frame 15 set on the control box 4, and a rotating shaft 16 is fixedly connected to the control box 4, and the rotating shaft 16 is rotatably connected to the moving frame 15.

[0025] The mobile frame 15 is equipped with an adjustment component, which is used to adjust the spraying angle of the pesticide, so that the pesticide can enter the interior of the trees from multiple positions and angles. When the control box 4 moves the nozzle 10 at the bottom to spray, although it can increase the spraying range and improve the spraying efficiency and uniformity, the shapes of agricultural and forestry vegetation are diverse, and the interior is easily blocked by external branches, making it difficult for the pesticide to enter the interior of the agricultural and forestry vegetation. However, by setting the adjustment component, the nozzle 10 can continuously adjust the spraying angle while maintaining the increase of the spraying range, so that the pesticide can be sprayed out from different angles, thereby making it easier for the pesticide to enter the agricultural and forestry vegetation from different angles, and then to pass through the gaps in the external branches at different angles to enter the interior, so that the interior can achieve the spraying effect. The adjustment component includes a baffle 20 fixedly connected to the machine body 1, and a slope 21 is opened on the baffle 20. A push block 22 is slidably connected to the slope 21.

[0026] like Figure 2 , Figure 3 , Figure 5 and Figure 6As shown, specifically, a hose 8 is fixedly connected between the pumping assembly 3 and the control box 4. A drain pipe 9 is fixedly connected to the bottom of the control box 4, and the drain pipe 9 is fixedly connected to a vertical plate 5 and an inclined plate 6 respectively. The vertical plate 5 is vertically set at the bottom of the control box 4, and the inclined plate 6 is inclined at the bottom of the control box 4. Several nozzles 10 are provided on both the vertical plate 5 and the inclined plate 6. A bracket 11 is fixedly installed on the control box 4, and an electric push rod 12 is fixedly installed on the bracket 11. A connecting rod 13 is fixedly connected to the output end of the electric push rod 12, and the connecting rod 13 is slidably connected in the control box 4. The control plate 7 has an opening... With the central notch 14 and side notches 141, during operation, the pumping assembly 3 extracts the pesticide from the storage tank 2 and delivers it through the hose 8 to the control box 4 at the bottom. Once in the control box 4, the pesticide enters the drain pipe 9 at the bottom through the central notch 14 and then flows into the vertical plate 5. The pesticide in the vertical plate 5 is then sprayed outwards through the nozzles 10, thus spraying pesticides onto agricultural and forestry vegetation. At this time, only the nozzles 10 on the vertical plate 5 spray pesticides outwards. When it is necessary to expand the spraying area, the operator drives the electric push rod 1 on the support 11 through the ground control system. 2. Pull the connecting rod 13 to move it. The connecting rod 13 pulls the control plate 7 in the control box 4. As the control plate 7 moves, the side notch 141 on the control plate 7 gradually aligns with the drain pipe 9 on the inclined plate 6, so that the medicine in the control box 4 can enter the drain pipe 9 through the side notch 141 and then enter the inclined plate 6, and be sprayed outward through the nozzle 10 on the inclined plate 6. At this time, the vertical plate 5 at the bottom of the control box 4 and the inclined plates 6 on both sides can spray the medicine outward. Since the inclined plates 6 are inclined at the bottom of the control box 4, the inclined plates 6 on both sides are in an inclined position. The agent is sprayed outwards, thereby increasing the spraying range and covering a larger spraying area, thus improving spraying efficiency. When the electric push rod 12 is driven in the reverse direction, it pushes the connecting rod 13 to move, which in turn pushes the control plate 7 to move. The position of the side notch 141 moves and is misaligned with the inlet of the drain pipe 9 on the inclined plate 6 again. Thus, the control plate 7 applies a sealing effect to the drain pipe 9 on the inclined plate 6. At this time, the agent in the control box 4 cannot enter the inclined plate 6 and be discharged outwards. The agent only enters the vertical plate 5 through the middle notch 14 and is discharged outwards. This achieves the effect of reducing the spraying range of the agent.

[0027] like Figure 2 and Figure 4As shown, specifically, a motor 17 is fixedly installed on the body 1, and a threaded rod 18 is fixedly connected to the output shaft of the motor 17. The threaded rod 18 is threadedly connected to the movable frame 15. A guide rod 19 is fixedly connected to the body 1, and the guide rod 19 is slidably connected to the movable frame 15. While the agent is being sprayed outward through the nozzle 10, the motor 17 can be started by the control system to drive the threaded rod 18 to rotate. With the cooperation of the guide rod 19, the movable frame 15 gradually moves on the threaded rod 18, so that the movable frame 15 can reach the bottom of the body 1. The back-and-forth movement of the mobile frame 15 drives the control box 4 to move back and forth. This increases the range of motion of the control box 4, namely the range of motion of the bottom inclined plate 6 and the vertical plate 5. This increases the range of motion of the nozzle 10, and the area it sprays outwards further increases, thereby covering more agricultural and forestry vegetation and improving spraying efficiency. At the same time, as the mobile frame 15 moves back and forth, the nozzle 10 sprays back and forth, reducing the phenomenon of missed spraying or double spraying caused by the fixed flight path of the drone.

[0028] like Figure 2 , Figure 7 and Figure 8 As shown, specifically, a first push rod 23 is fixedly connected between the push block 22 and the movable frame 15. A second push rod 24 is fixedly installed on the movable frame 15. A hydraulic pipe 25 is fixedly connected between the first push rod 23 and the second push rod 24. A rack 26 is fixedly connected to the output end of the second push rod 24. A gear 27 is fixedly connected to the rotating shaft 16, and the rack 26 meshes with the gear 27. At the same time, during the process of the movable frame 15 driving the nozzle 10 to move back and forth to spray, the movement of the movable frame 15 drives the first push rod 23 and the push block 22 to move. The push block 22 gradually moves along the inclined surface 21 on the baffle 20, and pressure is applied to the push block 22 under the action of the inclined surface 21. After being pressured, the push block 22 gradually pushes the first push rod. 23. Pressure is applied to cause it to contract. It is worth noting that both the first push rod 23 and the second push rod 24 are filled with hydraulic oil and connected by hydraulic pipe 25. Therefore, when the first push rod 23 contracts under pressure, it squeezes the hydraulic oil inside. Using hydraulic oil as the transmission medium, the hydraulic oil enters the hydraulic pipe 25 and gradually flows into the second push rod 24. Thus, the hydraulic oil pushes the second push rod 24 to gradually extend and move. The extension and movement of the second push rod 24 can push the rack 26 to gradually move. Thus, the gradual movement of the rack 26 causes the gear 27 to gradually rotate. The rotation of the gear 27 can drive the rotating shaft 16 to rotate. The rotation of the rotating shaft 16 can drive the control box 4 to rotate. At this time, the control box 4 rotates around the axis of the rotating shaft 16.

[0029] A sliding rod 28 is slidably connected to the movable frame 15, and the sliding rod 28 is fixedly connected to the rack 26. A limit plate 29 is fixedly connected to the end of the sliding rod 28, and a tension spring 30 is fixedly connected between the limit plate 29 and the movable frame 15. During the above process, when the movement of the movable frame 15 causes the push block 22 to move along the inclined plane 21, causing the control box 4 to rotate, the movement of the rack 26 pushes the sliding rod 28 and the limit plate 29 to move. The tension spring 30 between the limit plate 29 and the movable frame 15 is stretched by the force and generates a reaction force. When the movable frame 15 moves in reverse and resets as it cyclically moves, the movable frame 15 drives the first push rod 23 and the push block 22 to move in the opposite direction. The push block 22 moves along the inclined plane 21. At this time, under the action of the inclined plane 21, the squeezing effect of the inclined plane 21 on the push block 22 gradually decreases. At this time, under the reaction force of the tension spring 30, the limit plate 29 is pulled to move in the opposite direction and reset, that is, the sliding rod 28 is pulled to move in the opposite direction and reset. The slide bar 28 pushes the rack 26 to move in the opposite direction to reset. The reverse movement of the rack 26 drives the gear 27 and the rotating shaft 16 to rotate in the opposite direction, which in turn drives the control box 4 to rotate in the opposite direction. The reverse movement of the rack 26 pushes the second push rod 24 to retract and move. The retraction of the second push rod 24 can push the internal hydraulic oil to flow into the first push rod 23. Thus, the hydraulic oil pushes the first push rod 23 to extend and move, which pushes the top push block 22 to move in the opposite direction while closely adhering to the inclined surface 21. It can be seen that when the moving frame 15 moves back and forth in a cyclical manner, the control box 4 can achieve the effect of rotating back and forth. As the control box 4 rotates back and forth continuously, the nozzle 10 at its bottom can also rotate in a cyclical manner. During the rotation, the spraying angle of the nozzle 10 is constantly adjusted, so that the sprayed agent can enter the agricultural and forestry vegetation from different positions and angles, making it easier for the agent to pass through the external branches and gaps from different angles to enter the interior, so as to achieve the spraying effect inside.

[0030] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention includes the claims being limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0031] This invention is intended to cover all such substitutions, modifications, and alterations falling within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An unmanned aerial vehicle (UAV) for protecting agricultural and forestry plants, comprising a body (1) and a liquid storage tank (2) disposed in the body (1), characterized in that, The pumping assembly (3) is fixedly installed in the body (1), and the pumping assembly (3) is connected to the liquid storage tank (2); The machine body (1) is provided with a spraying assembly. The spraying assembly is used to improve and control the spraying range of the agent. The spraying assembly includes a control box (4) located at the bottom of the pumping assembly (3). The bottom of the control box (4) is arc-shaped. The bottom of the control box (4) is provided with a vertical plate (5) and an inclined plate (6). A control plate (7) is slidably connected inside the control box (4).

2. The agricultural and forestry plant protection drone according to claim 1, characterized in that, A hose (8) is fixedly connected between the pumping assembly (3) and the control box (4). A drain pipe (9) is fixedly connected to the bottom of the control box (4). The drain pipe (9) is fixedly connected to the vertical plate (5) and the inclined plate (6) respectively. The vertical plate (5) is vertically set at the bottom of the control box (4). The inclined plate (6) is inclined at the bottom of the control box (4). Several nozzles (10) are provided on both the vertical plate (5) and the inclined plate (6).

3. The agricultural and forestry plant protection drone according to claim 1, characterized in that, A bracket (11) is fixedly installed on the control box (4), and an electric push rod (12) is fixedly installed on the bracket (11). The output end of the electric push rod (12) is fixedly connected to a connecting rod (13), and the connecting rod (13) is slidably connected in the control box (4). A central notch (14) and a side notch (141) are provided on the control board (7).

4. The agricultural and forestry plant protection drone according to claim 1, characterized in that, The control box (4) is equipped with a moving component, which is used to drive the control box (4) to move continuously, so that the sprayed agent enters the forest from all directions. The moving component includes a moving frame (15) on the control box (4), and a rotating shaft (16) is fixedly connected to the control box (4), and the rotating shaft (16) is rotatably connected to the moving frame (15).

5. The agricultural and forestry plant protection drone according to claim 4, characterized in that, A motor (17) is fixedly installed on the body (1). A threaded rod (18) is fixedly connected to the output shaft of the motor (17), and the threaded rod (18) is threadedly connected to the moving frame (15). A connecting head guide rod (19) is fixedly installed on the body (1), and the guide rod (19) is slidably connected to the moving frame (15).

6. The agricultural and forestry plant protection drone according to claim 4, characterized in that, The mobile frame (15) is provided with an adjustment component, which is used to adjust the spraying angle of the agent so that the agent can enter the interior of the trees from multiple positions and angles. The adjustment component includes a baffle (20) fixedly connected to the body (1). The baffle (20) has an inclined surface (21) and a push block (22) is slidably connected to the inclined surface (21).

7. The agricultural and forestry plant protection drone according to claim 6, characterized in that, A first push rod (23) is fixedly connected between the push block (22) and the movable frame (15), and a second push rod (24) is fixedly installed on the movable frame (15). A hydraulic pipe (25) is fixedly connected between the first push rod (23) and the second push rod (24).

8. The agricultural and forestry plant protection drone according to claim 7, characterized in that, The output end of the second push rod (24) is fixedly connected to a rack (26), and a gear (27) is fixedly connected to the rotating shaft (16), and the rack (26) meshes with the gear (27).

9. The agricultural and forestry plant protection drone according to claim 8, characterized in that, A slide rod (28) is slidably connected to the movable frame (15), and the slide rod (28) is fixedly connected to the rack (26). A limit plate (29) is fixedly connected to the end of the slide rod (28), and a tension spring (30) is fixedly connected between the limit plate (29) and the movable frame (15).

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