Agricultural soil secondary compacting device with adjustable compacting range

Abstract

The application discloses a soil secondary compacting device with adjustable compacting range for agricultural seeding, and belongs to the technical field of soil compacting, which comprises a vehicle frame, a supporting steel frame fixed on the vehicle frame, and two groups of compacting mechanisms arranged in front and back on the supporting steel frame; the compacting mechanism comprises a fixed support fixed on the supporting steel frame, a fixed compacting wheel rotatably connected to the fixed support, a plurality of moving compacting wheels arranged along the axial direction in sequence on one side of the fixed compacting wheel, and the fixed compacting wheel and the moving compacting wheels of the compacting mechanism on the front side are distributed in a staggered manner with the corresponding fixed compacting wheel and moving compacting wheels of the compacting mechanism on the rear side; a shifting mechanism for adjusting the position of the moving compacting wheels in the compacting mechanism is arranged on the fixed support, so as to adjust the distance between the fixed compacting wheel and the moving compacting wheels and the distance between two adjacent moving compacting wheels. The position of the moving compacting wheel is adjusted, so that the compacting range is quickly adjusted.

Description

Technical Field

[0001] This invention relates to the field of farmland soil compaction technology, specifically to a secondary soil compaction device for agricultural sowing with adjustable compaction range. Background Technology

[0002] Secondary soil compaction in agricultural sowing is a technique that involves compacting the soil again after sowing. This improves the contact density between the soil and seeds, reduces soil porosity, prevents water evaporation, promotes seed water absorption and germination, and thus increases the emergence rate and ensures uniform and robust seedlings. For example, a wheat sowing machine with secondary compaction and leveling functions (publication number CN210275043U) addresses the problems of inconsistent sowing depth, weak soil grip, and poor soil water retention when sowing wheat on rotary-tilled soil. The machine includes a frame, and a fertilization unit, a drive harrow, a first compaction roller, a sowing unit, and a second compaction roller, all arranged sequentially from front to back on the frame. After harvesting summer corn, the soil is rotary-tilled, fertilizer is evenly spread on the surface, the soil is broken up, and then the fertilized soil is compacted once before sowing wheat. This secondary compaction ensures consistent sowing depth and a high seedling rate. A two-stage compaction device for sowing small-grain crops, disclosed in CN106385818A, addresses the problems of difficult-to-control sowing depth and poor sowing quality in small-grain crops. It employs a two-stage compaction technique to improve sowing quality, achieve consistent sowing depth, and provide a favorable environment for seed growth. The compaction device consists of a front compaction furrowing wheel, a connecting rod support frame, a rear compaction wheel, a soil covering mechanism, an adjusting spring, a seed metering device, and a seed box. The front and rear compaction wheels are hinged to both ends of the connecting rod support frame. The soil covering mechanism is located between the front and rear compaction wheels. The connecting rod support frame is hinged to the seed metering device, which slides relative to the seed box. One end of the adjusting spring is connected to the seed box, and the other end is connected to the connecting rod support frame. The front compaction furrowing wheel uses a wedge-shaped wheel to compact and level the uneven surface before sowing. After sowing, the rear compaction wheel performs secondary compaction, creating alternating tight and loose soil conditions.A crushing and compacting device for barley seeds, disclosed in CN118614211A, includes a frame, a mesh belt conveyor, a crushing mechanism, a compacting mechanism, and a feeding mechanism. The front end of the frame is equipped with a feeding mechanism for collecting clumps of soil, and the mesh belt conveyor is also mounted on the frame for sieving the soil. The fine-particle soil sieved by the mesh belt conveyor is used for the initial covering of seeds in the seed furrow. The discharge end of the mesh belt conveyor is connected to the crushing mechanism, which breaks the clumps of soil into larger clods, which are then used for a secondary covering of the seeds in the seed furrow. The rear end of the frame is also equipped with a compacting mechanism for compacting the covering soil, which can collect clumps of soil. The seeds are collected, screened, and crushed, and then covered with a double layer of soil. The lower layer is fine-grained soil to retain moisture and warmth for the seeds, while the upper layer is large-grained soil to reduce the impact of wind and water erosion on the soil. However, the range of agricultural sowing varies depending on the actual needs. Sowing is generally done directionally along the direction of the field with a certain width. Currently, some compaction devices cannot adjust the compaction range according to the sowing range. If the compaction area is too large, it will compact the soil that has not yet been sown, which is not conducive to the subsequent seeds entering the soil layer. If the compaction area is too small, the soil compaction will be insufficient, and a second compaction of the soil layer will be required. In addition, the soil covering the surface of some farmland is unevenly distributed, and the compaction effect is poor for soil layers with obvious depressions.

[0003] To address the aforementioned issues, there is an urgent need for innovative designs based on existing agricultural soil compaction devices. Summary of the Invention

[0004] The purpose of this invention is to provide a secondary soil compaction device for agricultural sowing with adjustable compaction range, in order to solve the problems mentioned in the background art, such as some compaction devices not being able to adjust the compaction range according to the sowing range, the compaction area being too large, which will compact the soil next to which has not yet been sown, which is not conducive to the subsequent seeds entering the soil layer, and the compaction area being too small, which will lead to insufficient soil compaction, requiring secondary equipment to compact the soil layer.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a secondary soil compaction device for agricultural sowing with adjustable compaction range, comprising a frame, a supporting steel frame welded and fixed on the frame, and two sets of compaction mechanisms arranged front and rear on the supporting steel frame; each compaction mechanism includes a fixed bracket fixed on the supporting steel frame, a fixed pressure roller rotatably connected to the fixed bracket, and a plurality of movable pressure rollers arranged sequentially along the axial direction on one side of the fixed pressure roller; the compaction mechanism closer to the frame is the front compaction mechanism, the number of movable pressure rollers in the front compaction mechanism is one more than the number of movable pressure rollers in the rear compaction mechanism, and the fixed pressure rollers and movable pressure rollers of the front compaction mechanism are staggered from the corresponding fixed pressure rollers and movable pressure rollers in the rear compaction mechanism;

[0006] The fixed bracket is equipped with a displacement mechanism that adjusts the position of the movable pressure roller in the pressing mechanism, thereby adjusting the distance between the fixed pressure roller and the movable pressure roller, and between two adjacent movable pressure rollers.

[0007] Furthermore, the displacement mechanism includes a movable bracket, the movable pressure roller is rotatably mounted on the corresponding movable bracket, a sliding frame is fixed on the movable bracket, the sliding frame on the movable bracket closest to the fixed bracket is slidably connected to the fixed bracket, and the sliding frames on the other movable brackets are slidably connected to the adjacent movable brackets.

[0008] Furthermore, a rectangular rod is fixed to the end of the movable pressure roller along the axial direction, and the rectangular rod is slidably connected to the adjacent movable pressure roller or fixed pressure roller.

[0009] Furthermore, a cylindrical rod is fixedly connected to the top middle position of the fixed bracket and the movable bracket, and an upper rotating rod and a lower rotating rod arranged in a cross pattern are rotatably connected to each cylindrical rod; the upper rotating rod and the lower rotating rod are arranged in multiple groups in sequence, and the upper rotating rod of any group is rotatably connected to the end of the lower rotating rod of the adjacent group, and the lower rotating rod of any group is rotatably connected to the end of the upper rotating rod of the adjacent group.

[0010] Furthermore, an electric telescopic rod is fixedly installed on the supporting steel frame, and the output end of the electric telescopic rod has a positioning bracket. A positioning column is installed on the positioning bracket, and the positioning column is sleeved on the cylindrical rod at the top of the movable bracket near the fixed bracket.

[0011] Furthermore, the vehicle frame is equipped with a leveling mechanism for reciprocating combing of farmland soil.

[0012] Furthermore, the leveling mechanism includes a rotating shaft rotatably connected to the frame, a sleeve rod sleeved on the outside of the rotating shaft, and multiple rake frames fixedly connected at equal intervals on the sleeve rod.

[0013] Furthermore, a guide slide rod is fixedly installed on the frame, and a guide slide block is slidably installed on the guide slide rod, with the guide slide block being fixedly connected to the outer side of the sleeve rod.

[0014] Furthermore, an arc-shaped groove is provided on the outside of the rotating shaft, and a slider is slidably connected in the arc-shaped groove. The slider is fixedly installed on the inner side wall of the sleeve rod.

[0015] Furthermore, the end of the fixed pressure roller has an active curved rod arranged along the axial direction of the fixed pressure roller, a driven support rod is fixedly connected to the rotating shaft, a transmission rod is rotatably connected to the driven support rod, and the transmission rod is rotatably connected to the active curved rod.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention has two sets of compaction mechanisms on the rear side of the frame. The main structure of the compaction mechanism includes a fixed pressure roller and a movable pressure roller. The fixed pressure roller and the movable pressure roller in the two compaction mechanisms are staggered, and the soil on the surface of the farmland can be effectively compacted through secondary compaction. Furthermore, the fixed support is provided with a displacement mechanism for adjusting the distance between the fixed pressure roller and the multiple movable pressure rollers. According to the range of farmland sowing, the distance between the fixed pressure roller and the multiple movable pressure rollers is adjusted, and the movable support is controlled to move equidistantly along the axis of the fixed pressure roller, keeping the distance between adjacent fixed pressure rollers and movable pressure rollers the same, thereby adjusting the compaction range.

[0017] The electric-driven telescopic rod controls the movement of the positioning bracket. The positioning bracket pushes a movable bracket near the fixed bracket to move. At this time, the upper and lower rotating rods, which are cross-connected, rotate and adjust. Under the rotational thrust of multiple upper and lower rotating rods, multiple movable brackets move with equal displacement, thereby adjusting the distance between the fixed pressure roller and the multiple movable pressure rollers at equal intervals. Furthermore, the frame is equipped with a leveling mechanism for reciprocatingly compacting farmland soil. During the soil compaction process of the moving frame, the lower part of the rake frame contacts the protruding soil. The rake frame moves directionally with the frame, which can push and disperse the protruding soil, keeping the soil distribution relatively uniform.

[0018] When the fixed pressure roller rotates, the rotating shaft can be controlled to reciprocate at a certain angle under the transmission of the active curved rod, the driven support rod and the transmission rod. When the rotating shaft reciprocates, the sleeve rod can be controlled to move back and forth along the direction of the guide slide rod under the transmission of the arc groove and the slider. This allows the rake frame to move laterally back and forth while following the frame, thereby improving the effect of the rake frame in pushing and dispersing the soil. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the three-dimensional structure of the vehicle frame of the present invention.

[0020] Figure 2 This is a schematic diagram of the three-dimensional structure of the supporting steel frame of the present invention.

[0021] Figure 3 This is a schematic diagram of the three-dimensional structure of the fixed pressure roller of the present invention.

[0022] Figure 4 This is a schematic diagram of the cross-sectional structure of the movable pressure roller of the present invention.

[0023] Figure 5 This is a three-dimensional structural diagram of the upper and lower rotating rods of the present invention.

[0024] Figure 6 This is a schematic diagram of the three-dimensional structure of the rake frame of the present invention.

[0025] Figure 7This is a three-dimensional structural diagram of the rotating shaft of the present invention.

[0026] Figure 8 This is a three-dimensional structural diagram of the guide slide rod of the present invention.

[0027] Figure 9 This is a schematic diagram of the cross-sectional structure of the sleeve rod of the present invention.

[0028] Figure 10 This is a three-dimensional structural diagram of the transmission rod of the present invention.

[0029] In the diagram: 1. Frame; 2. Supporting steel frame; 3. Fixed bracket; 4. Fixed pressure roller; 5. Sliding frame; 6. Moving bracket; 7. Moving pressure roller; 8. Rectangular rod; 9. Rectangular groove; 10. Cylindrical rod; 11. Lower rotating rod; 12. Upper rotating rod; 13. Positioning column; 14. Electrically driven telescopic rod; 15. Positioning bracket; 16. Rotating shaft; 17. Sleeve rod; 18. Rake frame; 19. Guide slide rod; 20. Guide slide block; 21. Arc groove; 22. Slider; 23. Active curved rod; 24. Driven support rod; 25. Transmission rod. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: Please refer to Figures 1-10 This invention provides the following technical solution: a secondary soil compaction device for agricultural sowing with adjustable compaction range, comprising a vehicle frame 1 that moves across farmland, a supporting steel frame 2 welded and fixed to the vehicle frame 1, and two sets of compaction mechanisms arranged front and rear on the supporting steel frame 2. Each compaction mechanism includes a fixed support 3 fixed to the supporting steel frame 2, a fixed pressure roller 4 rotatably connected to the fixed support 3, and multiple movable pressure rollers 7 arranged along the axial direction on one side of the fixed pressure roller 4. The number of movable pressure rollers 7 in the front compaction mechanism is one more than the number of movable pressure rollers 7 in the rear compaction mechanism. Furthermore, the fixed pressure rollers 4 and movable pressure rollers 7 in the front compaction mechanism are staggered from the corresponding fixed pressure rollers 4 and movable pressure rollers 7 in the rear compaction mechanism. The fixed support 3 is provided with a displacement mechanism for adjusting the position of the movable pressure rollers 7, thereby adjusting the distance between the fixed pressure roller 4 and adjacent movable pressure rollers 7, and between two adjacent movable pressure rollers 7.

[0032] like Figure 4As shown, the shifting mechanism includes an inverted U-shaped movable support 6, with a movable pressure roller 7 rotatably mounted within the opening of the movable support 6. A sliding frame 5 is fixed to the side wall of the movable support 6. The sliding frame 5 on the leftmost movable support 6 is slidably connected to the fixed support 3, and the sliding frames 5 on the other movable supports 6 are slidably connected to adjacent movable supports 6. The end face of the movable pressure roller 7 has a rectangular rod 8 arranged along the axial direction. The fixed pressure roller 4 and the movable pressure roller 7 (except the rightmost one) have rectangular grooves 9 opened along the axial direction. The rectangular rod 8 on the rightmost movable pressure roller 7 extends into the rectangular groove 9 on the adjacent leftmost movable pressure roller 7 for slidable connection, and the rectangular rod 8 on the leftmost movable pressure roller 7 extends into the rectangular groove 9 on the fixed pressure roller 4 for slidable connection. A cylindrical rod 10 extending upwards is fixedly connected to the middle position of the top of the fixed support 3 and the movable support 6. An upper rotating rod 12 and a lower rotating rod 11, arranged vertically, are rotatably connected to the cylindrical rod 10, and the upper rotating rod 12 and the lower rotating rod 11 are arranged in an X-shape. Multiple sets of upper rotating rods 12 and lower rotating rods 11 are arranged sequentially. The upper rotating rod 12 in any set is rotatably connected to the lower rotating rod 11 in the adjacent set, and vice versa. This multi-set linkage of upper rotating rods 12 and lower rotating rods 11 creates a continuous connection. An electrically driven telescopic rod 14 is fixedly installed on the supporting steel frame 2. The output end of the electrically driven telescopic rod 14 has a positioning bracket 15, on which a positioning post 13 is installed. The positioning post 13 is fitted onto the cylindrical rod 10 at the top of the movable bracket 6 closest to the fixed bracket 3; that is, the positioning post 13 is fitted onto the cylindrical rod 10 at the top of the leftmost movable bracket 6. Depending on the sowing range, when the electrically driven telescopic rod 14 is activated, the positioning bracket 15 moves left and right, thereby driving the movable bracket 6 to move left and right, thus adjusting the distance between adjacent movable brackets 6 and between the leftmost movable bracket 6 and the fixed bracket 3. The distance between the fixed pressure roller 4 and the left-side movable pressure roller 7, as well as between two adjacent movable pressure rollers 7, is adjusted to regulate the compaction range. At this time, the upper rotating rod 12 and the lower rotating rod 11 connected to the fixed support 3 and the movable support 6 rotate crosswise. Driven by the rotation of the upper rotating rod 12 and the lower rotating rod 11, multiple movable supports 6 can be controlled to move with equal displacement. The movable support 6 drives the movable pressure rollers 7 mounted on it to move synchronously. The rectangular rod 8 on the movable pressure roller 7 passes through and connects to the rectangular groove 9 of the adjacent fixed pressure roller 4 or movable pressure roller 7. The rectangular rod 8 moves directionally within the rectangular groove 9, thus enabling rapid and stable adjustment of the compaction range of the pressing mechanism. By setting two sets of pressing mechanisms, and the pressure rollers in the two sets of pressing mechanisms are staggered along the axial direction, that is, the fixed pressure roller 4 of the rear pressing mechanism is located between the fixed pressure roller 4 of the front pressing mechanism and the adjacent movable pressure roller 7, and the movable pressure roller 7 of the rear pressing mechanism is located between two adjacent movable pressure rollers 7 of the front pressing mechanism.This allows two sets of compaction mechanisms to roll sequentially on the surface of the farmland soil, with the rolling range matching the sowing area. Furthermore, the two roller compaction operations cover a more comprehensive area, improving the effectiveness of secondary soil compaction.

[0033] Example 2: Based on Example 1, a leveling mechanism is also disclosed, the specific structure of which is as follows: A leveling mechanism for reciprocating farmland soil is provided on the frame 1. The leveling mechanism includes a rotating shaft 16 rotatably connected to the frame 1. A sleeve rod 17 is sleeved on the outside of the rotating shaft 16. Multiple rake frames 18 are fixedly connected to the sleeve rod 17 at equal intervals. A guide slide rod 19 is fixedly installed on the frame 1. A guide slide seat 20 is slidably installed on the guide slide rod 19. The guide slide seat 20 is fixedly connected to the outer side of the sleeve rod 17. An arc-shaped groove 21 is opened on the outside of the rotating shaft 16. A slider 22 is slidably connected in the arc-shaped groove 21. The slider 22 is fixed. Installed on the inner wall of the sleeve rod 17, the fixed pressure roller 4 is connected to the active curved rod 23 along the axial direction, and the driven support rod 24 is fixedly connected to the outside of the rotating shaft 16. The driven support rod 24 is rotatably connected to the transmission rod 25, and the transmission rod 25 is rotatably connected to the active curved rod 23. When the frame 1 moves on the farmland, multiple rake frames 18 are evenly spaced on the outside of the sleeve rod 17 on the frame 1. The rake frames 18 move synchronously with the frame 1 on the farmland. The rake frames 18 can contact the soil on the protruding part of the farmland surface. During the movement, they can push and disperse the soil, so that the soil distribution on the surface of the farmland is relatively uniform, thus improving the compaction effect.

[0034] As the frame 1 moves, it drives the fixed pressure roller 4 to press against the soil and roll. The fixed pressure roller 4 drives the active curved rod 23 connected to the side to rotate synchronously. At this time, the two ends of the transmission rod 25 connected between the active curved rod 23 and the driven support rod 24 rotate accordingly. The rotating transmission rod 25 can push the driven support rod 24 and the rotating shaft 16 to rotate back and forth within the range of movement angle. When the rotating shaft 16 rotates back and forth, its outer sleeve rod 17 moves along the direction of the arc groove 21 following the slider 22. Driven by the slider 22 and the arc groove 21, the sleeve rod 17 can be controlled to move back and forth along the direction of the guide slide rod 19. The sleeve rod 17 drives multiple rake frames 18 to move laterally back and forth synchronously, so that the rake frames 18 can not only move in the direction of the frame 1, but also move back and forth in the direction perpendicular to the driving direction of the frame 1. The multi-directional moving rake frames 18 can better push and disperse the soil on the surface of the farmland, making the soil distribution more uniform and easier to compact.

[0035] Depending on actual needs, a sowing mechanism can be installed between the two sets of compaction mechanisms. This allows for a first compaction by the front compaction mechanism before sowing, followed by a second compaction by the rear compaction mechanism after sowing. Alternatively, a fertilization mechanism can be installed between the two sets of compaction mechanisms, allowing fertilization after the first compaction, followed by a second compaction. Or, the fertilization mechanism can be installed on the frame in front of the front compaction mechanism, allowing for a second compaction after fertilization.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A secondary soil compaction device for agricultural sowing with adjustable compaction range, comprising a frame (1), characterized in that: A supporting steel frame (2) is welded and fixed on the frame (1). Two sets of pressing mechanisms are arranged in front and behind on the supporting steel frame (2). The pressing mechanism includes a fixed bracket (3) fixed on the supporting steel frame (2). A fixed pressure wheel (4) is rotatably connected to the fixed bracket (3). A plurality of movable pressure wheels (7) are arranged sequentially along the axial direction on one side of the fixed pressure wheel (4). The pressing mechanism closer to the frame (1) is the front pressing mechanism. The number of movable pressure wheels (7) in the front pressing mechanism is one more than the number of movable pressure wheels (7) in the rear pressing mechanism. The fixed pressure wheel (4) and movable pressure wheel (7) of the front pressing mechanism are staggered from the corresponding fixed pressure wheel (4) and movable pressure wheel (7) in the rear pressing mechanism. The fixed bracket (3) is provided with a shifting mechanism for adjusting the position of the movable pressure roller (7) of the pressing mechanism, thereby adjusting the distance between the fixed pressure roller (4) and the movable pressure roller (7), as well as between two adjacent movable pressure rollers (7); The displacement mechanism includes a movable support (6), a movable pressure roller (7) is rotatably mounted on the corresponding movable support (6), a sliding frame (5) is fixed on the movable support (6), the sliding frame (5) on the movable support (6) close to the fixed support (3) is slidably connected to the fixed support (3), and the sliding frames (5) on the other movable supports (6) are slidably connected to the adjacent movable support (6); a rectangular rod (8) is fixed at the end of the movable pressure roller (7) along the axial direction, and the rectangular rod (8) is slidably connected to the adjacent movable pressure roller (7) or fixed pressure roller (4); The frame (1) is equipped with a leveling mechanism for reciprocating farmland soil leveling; the leveling mechanism includes a rotating shaft (16) rotatably connected to the frame (1), a sleeve rod (17) is sleeved on the outside of the rotating shaft (16), and multiple rake frames (18) are fixedly connected at equal intervals on the sleeve rod (17); a guide slide rod (19) is fixedly installed on the frame (1), and a guide slide seat (20) is slidably installed on the guide slide rod (19), and the guide slide seat (20) is fixedly connected to the outer side of the sleeve rod (17); An arc-shaped groove (21) is provided on the outside of the rotating shaft (16), and a slider (22) is slidably connected in the arc-shaped groove (21). The slider (22) is fixedly installed on the inner side wall of the sleeve rod (17). The end of the fixed pressure roller (4) has an active curved rod (23) arranged along the axial direction of the fixed pressure roller (4). A driven support rod (24) is fixedly connected on the rotating shaft (16), and a transmission rod (25) is rotatably connected on the driven support rod (24). The transmission rod (25) is rotatably connected to the active curved rod (23).

2. The soil secondary compaction device for agricultural sowing with adjustable compaction range according to claim 1, characterized in that: A cylindrical rod (10) is fixedly connected to the middle of the top of the fixed bracket (3) and the movable bracket (6). Each cylindrical rod (10) is rotatably connected to an upper rotating rod (12) and a lower rotating rod (11) arranged in an intersecting manner. The upper rotating rod (12) and the lower rotating rod (11) are arranged in multiple groups in sequence. The upper rotating rod (12) of any group is rotatably connected to the end of the lower rotating rod (11) of the adjacent group, and the lower rotating rod (11) of any group is rotatably connected to the end of the upper rotating rod (12) of the adjacent group.

3. The soil secondary compaction device for agricultural sowing with adjustable compaction range according to claim 2, characterized in that: An electric drive telescopic rod (14) is fixedly installed on the supporting steel frame (2). The output end of the electric drive telescopic rod (14) has a positioning bracket (15). A positioning column (13) is installed on the positioning bracket (15). The positioning column (13) is sleeved on the cylindrical rod (10) at the top of the movable bracket (6) near the fixed bracket (3).

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