A multi-spectral camera bracket mounted on a drone

Abstract

The present application relates to the technical field of unmanned plane, and disclose a kind of unmanned plane mounting multispectral camera support, including unmanned plane body and fixed installation in unmanned plane body bottom near front side place fixed rod, the lower end of the fixed rod is fixedly installed with installation shell, and the middle part of installation shell bottom is attached with multispectral camera body, the middle part of installation shell front side is installed with protection assembly, by the mutual cooperation between push plate, vertical plate, sliding rod, reset spring B, rack plate, movable gear, threaded rod A, threaded rod B, threaded sleeve, guide plate, guide rod, L-shaped clamping plate, fixed plate, trapezoidal block, extrusion ball, connecting plate, sliding plate, flat plate, sliding rod and reset spring C these components, it can be moved forward by pressing push plate, to quickly realize the release of multispectral camera body both sides and front side clamping, convenient operation, solve the complexity of the existing need to rotate multiple bolts and disassemble.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicles (UAVs), and in particular to a bracket for mounting a multispectral camera on an UAV. Background Art

[0002] In recent years, with the popularization of small multispectral digital cameras, agricultural multispectral research has gradually evolved from single-point measurement to regional monitoring, greatly improving the efficiency of investigation. Nowadays, hyperspectral remote sensing based on satellites and other platforms has been widely used, but these technologies are not suitable in some cases. UAVs equipped with hyperspectral equipment are an indispensable supplement to satellite remote sensing. They make up for the defects of satellite optical remote sensing and ordinary aerial photography that are often blocked by clouds and cannot obtain images. At the same time, they have also become an effective inversion method for satellite remote sensing.

[0003] When using existing drone-mounted multispectral camera brackets, multiple bolt components are usually used to install and fix the multispectral camera. However, the brackets need to be screwed in and out repeatedly during assembly and disassembly, which makes disassembly cumbersome. In addition, the existing brackets have single functions and lack components to protect the multispectral camera, resulting in poor performance.

[0004] Therefore, we propose a multispectral camera bracket for UAV mounting to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a multispectral camera bracket for mounting on an unmanned aerial vehicle to solve the problems raised by the above background technology.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: a multispectral camera mounting bracket for a drone, comprising a drone body and a fixing rod fixedly mounted at the bottom of the drone body near the front side, a mounting shell fixedly mounted at the lower end of the fixing rod, the multispectral camera body being fitted in the middle of the bottom of the mounting shell, a protective assembly being mounted in the middle of the front side of the mounting shell, and a push opening being opened above the middle of the rear side of the mounting shell, the inner cavity of which is equipped with a snap-on assembly;

[0007] The clamping assembly includes a pushing plate slidably installed in the inner cavity of the pushing port and a rack plate fixedly installed on the front side of the pushing plate near the top. A movable gear is engaged with the bottom of the rack plate near the front side, and a movable rod is fixedly installed through the middle part of the movable gear. The left and right ends of the movable rod are respectively fixed with threaded rod B and threaded rod A. The opposite ends of threaded rod B and threaded rod A are respectively movably installed on the inner wall of the inner cavity of the mounting shell, and the outer sides of threaded rod A and threaded rod B are respectively threadedly installed with threaded sleeves, and the bottoms of the threaded sleeves are respectively fixedly installed with L-shaped clamping plates. The bottom of the mounting shell is provided with movable openings near the left and right sides respectively. The bottoms of the L-shaped clamping plates pass through the inner cavities of the adjacent movable openings respectively and extend to the outside of the mounting shell respectively. The top of the inner side of the L-shaped clamping plate is fitted with the bottom of the multi-spectral camera body. Two connecting plates are provided near the bottom of the inner cavity of the mounting shell, and the connecting plates are arranged on the left and right. Sliding plates are fixedly installed on the front and back sides of the connecting plates respectively. The bottoms of the sliding plates slide through and extend to the outside of the mounting shell respectively, and the inner side of the sliding plate is fitted with the outer side of the multi-spectral camera body.

[0008] Preferably, a vertical plate is provided on the front side of the push plate, and the bottom of the vertical plate is fixedly mounted on the inner wall of the inner cavity of the mounting shell, a sliding rod is installed on the vertical plate near the top for sliding through, the rear end of the sliding rod is fixedly mounted on the push plate, and a return spring B is provided on the outer side of the sliding rod, and the two ends of the return spring B are respectively fixedly mounted on the push plate and the vertical plate.

[0009] Preferably, guide plates are fixedly installed on the front sides of the threaded sleeves, and guide rods are installed on the guide plates to slide through them, and the left and right ends of the guide rods are fixedly installed on the inner walls of the inner cavity of the installation shell.

[0010] Preferably, a flat plate is fixedly installed on the opposite side of the sliding plate near the left and right sides, and a sliding rod is installed on the flat plate for sliding through. The upper ends of the sliding rods are fixedly installed on the inner wall of the inner cavity of the mounting shell, and the outer sides of the sliding rods are respectively sleeved with a return spring C, and the two ends of the return spring C are respectively fixedly installed on the inner wall of the inner cavity of the mounting shell and the adjacent flat plate.

[0011] Preferably, a fixing plate is fixedly installed on the inner side of the L-shaped clamping plate near the top, a trapezoidal block is fixedly installed on the opposite side of the fixing plate, the bottom of the trapezoidal block is fitted with an extrusion ball, and the bottom of the extrusion ball is fixedly installed on the adjacent connecting plate.

[0012] Preferably, the protective assembly includes a protective plate slidably installed in the middle of the front side of the mounting shell and an n-shaped plate arranged in the front side of the protective plate, the rear side of the n-shaped plate is fixedly installed on the mounting shell, and a positioning rod is slidably installed through the middle of the n-shaped plate, and a pulling plate is fixedly installed at the front end of the positioning rod.

[0013] Preferably, positioning grooves are respectively provided near the middle and the top of the front side of the protective plate, and the output end of the pulling plate is inserted into the inner cavity of the lower positioning groove.

[0014] Preferably, limit rods are slidably installed on the n-shaped plate near the left and right sides, and the front ends of the limit rods are fixedly installed on the pulling plates. Return springs A are respectively sleeved on the outer sides of the limit rods, and the two ends of the return springs A are respectively fixedly installed on the n-shaped plate and the pulling plate.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Through the mutual cooperation among the push plate, vertical plate, sliding rod, return spring B, rack plate, movable gear, threaded rod A, threaded rod B, threaded sleeve, guide plate, guide rod, L-shaped clamping plate, fixed plate, trapezoidal block, squeeze ball, connecting plate, sliding plate, flat plate, sliding rod and return spring C, the push plate can be pressed to move forward, thereby quickly releasing the clamping on both sides and the front side of the multispectral camera body. The operation is convenient and solves the tedious disassembly process that requires rotating multiple bolts.

[0017] 2. Through the mutual cooperation among the protective plate, positioning groove, N-shaped plate, limit rod, reset spring A, positioning rod and pulling plate, the protective plate can be driven to move downward when the multispectral camera body is not in use, thereby protecting the front camera of the multispectral camera body and also playing a role in dust prevention. The setting of the positioning rod and positioning groove is conducive to the clamping and positioning of the position of the protective plate after movement, and the use effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an overall three-dimensional diagram of the present invention;

[0019] Figure 2 A bottom perspective view of the present invention;

[0020] Figure 3 A partial structural perspective view of the mounting housing of the present invention;

[0021] Figure 4 A partial cross-sectional perspective view of an n-shaped plate of the present invention;

[0022] Figure 5 For the present invention Figure 4 Enlarged view of point A in the middle;

[0023] Figure 6 A rear side perspective view of the mounting housing of the present invention;

[0024] Figure 7 A partial structural perspective view of the threaded rod A of the present invention;

[0025] Figure 8 A partial structural perspective view of the push plate of the present invention;

[0026] Figure 9 A partially expanded perspective view of the mounting housing of the present invention;

[0027] Figure 10 For the present invention Figure 9 Enlarged view of point B in the middle.

[0028] In the figure: 1. UAV body; 2. Fixing rod; 3. Mounting shell; 4. Multispectral camera body; 5. Protective assembly; 51. Protective plate; 511. Positioning groove; 52. N-shaped plate; 521. Limiting rod; 522. Reset spring A; 53. Positioning rod; 54. Pulling plate; 6. Clamping assembly; 61. Pushing plate; 611. Vertical plate; 612. Sliding rod; 613. Reset spring B; 62. Rack plate; 63. Movable gear; 64. Threaded rod A; 65. Threaded rod B; 66. Threaded sleeve; 661. Guide plate; 662. Guide rod; 67. L-shaped clamping plate; 671. Fixing plate; 672. Trapezoidal block; 673. Squeeze ball; 68. Connecting plate; 69. Sliding plate; 691. Flat plate; 692. Sliding rod; 693. Reset spring C. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Example 1

[0031] See also Figure 1-10 A multispectral camera bracket for mounting on a drone comprises a drone body 1 and a fixing rod 2 fixedly installed at the bottom of the drone body 1 near the front side, a mounting shell 3 is fixedly installed at the lower end of the fixing rod 2, and the multispectral camera body 4 is fitted in the middle of the bottom of the mounting shell 3, a protective component 5 is installed in the middle of the front side of the mounting shell 3, and a pushing port is opened at the upper middle of the rear side of the mounting shell 3, and a clamping component 6 is installed in the inner cavity of the pushing port. The setting of the protective component 5 protects the multispectral camera body 4, and the setting of the clamping component 6 can realize the clamping and positioning of the multispectral camera body 4.

[0032] The clamping assembly 6 includes a pushing plate 61 slidably installed in the inner cavity of the pushing port and a rack plate 62 fixedly installed on the front side of the pushing plate 61 near the top. The bottom of the rack plate 62 is engaged with a movable gear 63 near the front side, and a movable rod is fixedly installed through the middle of the movable gear 63. The left and right ends of the movable rod are respectively fixed with threaded rods B65 and threaded rods A64. The opposite ends of the threaded rods B65 and A64 are respectively movably installed on the inner wall of the inner cavity of the mounting shell 3, and the outer sides of the threaded rods A64 and B65 are respectively threaded with threaded sleeves 66. The bottom of the threaded sleeves 66 are respectively fixedly installed with L-shaped clamping plates 67. The bottom of the mounting shell 3 is respectively provided with movable sleeves near the left and right sides. The bottom of the L-shaped clamping plate 67 passes through the inner cavity of the adjacent moving openings and extends to the outside of the mounting shell 3 respectively, and the top of the inner side of the L-shaped clamping plate 67 is fitted with the bottom of the multi-spectral camera body 4. Two connecting plates 68 are provided near the bottom of the inner cavity of the mounting shell 3, and the connecting plates 68 are provided on the left and right sides. The front and rear sides of the connecting plates 68 are respectively fixed with sliding plates 69. The bottom of the sliding plate 69 slides through and extends to the outside of the mounting shell 3, and the inner side of the sliding plate 69 is fitted with the outer side of the multi-spectral camera body 4, which can realize the clamping and positioning of the two sides and the front and rear sides of the multi-spectral camera body 4, and can be disassembled by pushing the pushing plate 61 forward, which is convenient to operate.

[0033] A vertical plate 611 is provided on the front side of the push plate 61, and the bottom of the vertical plate 611 is fixedly mounted on the inner wall of the inner cavity of the mounting shell 3. A sliding rod 612 is slidably installed on the vertical plate 611 near the top. The rear end of the sliding rod 612 is fixedly mounted on the push plate 61. A return spring B613 is sleeved on the outer side of the sliding rod 612. The two ends of the return spring B613 are respectively fixedly mounted on the push plate 61 and the vertical plate 611, which is beneficial to the guiding, limiting and restoration of the push plate 61 when it moves.

[0034] A guide plate 661 is fixedly installed on the front side of the threaded sleeve 66, and a guide rod 662 is installed on the guide plate 661 so as to slide through the guide plate 661. The left and right ends of the guide rod 662 are fixedly installed on the inner wall of the inner cavity of the mounting shell 3, respectively, to guide and limit the movement of the threaded sleeve 66.

[0035] A flat plate 691 is fixedly installed on the opposite side of the sliding plate 69 near the left and right sides, and a sliding rod 692 is slidably installed on the flat plate 691. The upper ends of the sliding rods 692 are fixedly installed on the inner wall of the inner cavity of the mounting shell 3, and the outer sides of the sliding rods 692 are respectively sleeved with a return spring C693. The two ends of the return spring C693 are fixedly installed on the inner wall of the inner cavity of the mounting shell 3 and the adjacent flat plate 691, which is beneficial to the movement and restoration of the sliding plate 69.

[0036] A fixing plate 671 is fixedly installed on the inner side of the L-shaped clamping plate 67 near the top, and a trapezoidal block 672 is fixedly installed on the opposite side of the fixing plate 671. The bottom of the trapezoidal block 672 is respectively fitted with an extrusion ball 673, and the bottom of the extrusion ball 673 is respectively fixedly installed on the adjacent connecting plate 68, which is conducive to driving the trapezoidal block 672 and the adjacent L-shaped clamping plate 67 to move synchronously, thereby facilitating the sliding plate 69 to move up and down.

[0037] In this embodiment: When in use, the multispectral camera body 4 can be installed first, and the push plate 61 can be pressed forward to drive the rack plate 62 to move forward, and the reset spring B613 will be squeezed at the same time. When the rack plate 62 moves forward, it will drive the movable gear 63 to rotate. When the movable gear 63 rotates, it will drive the threaded rod A64 and the threaded rod B65 to rotate synchronously through the movable rod. When the threaded rod A64 and the threaded rod B65 rotate, they will drive the threaded sleeves 66 on both sides to move in the opposite direction. When the threaded sleeves 66 move in the opposite direction, they will drive the adjacent L-shaped clamping plates 67 to move in the opposite direction. In addition, when the L-shaped clamping plates 67 move in the opposite direction, they will drive the adjacent trapezoidal The block 672 moves in the opposite direction, so that it can move away from the adjacent squeezing ball 673. In addition, the connecting plate 68 and the sliding plate 69 will move upward and recover under the action of the rebound force of the reset spring C693. At this time, the sliding plate 69 will move into the inner cavity of the mounting shell 3, and then the multi-spectral camera body 4 can be placed in the middle of the bottom of the mounting shell 3. After the placement is completed, the pushing plate 61 can be released. At this time, the L-shaped clamping plates 67 on both sides will move relative to each other, thereby supporting the bottom of the multi-spectral camera body 4. In addition, the sliding plate 69 will also move downward to block the front and rear sides of the multi-spectral camera body 4, thereby completing the clamping installation of the multi-spectral camera body 4.

[0038] Example 2

[0039] This embodiment is an improvement made on the basis of embodiment 1. For details, please refer to Figure 1-6 The protective assembly 5 includes a protective plate 51 slidably mounted at the middle of the front side of the mounting shell 3 and an n-shaped plate 52 arranged at the front side of the protective plate 51. The rear side of the n-shaped plate 52 is fixedly mounted on the mounting shell 3, and a positioning rod 53 is slidably installed through the middle of the n-shaped plate 52. A pulling plate 54 is fixedly installed at the front end of the positioning rod 53, which can adjust the position of the protective plate 51, thereby protecting the front side of the multispectral camera body 4.

[0040] Positioning slots 511 are respectively provided near the middle and the top of the front side of the protective plate 51 , and the output end of the pulling plate 54 is inserted into the inner cavity of the positioning slot 511 below, which is conducive to the positioning work.

[0041] Limit rods 521 are slidably installed on the n-shaped plate 52 near the left and right sides, and the front ends of the limit rods 521 are fixedly installed on the pulling plate 54. The outer sides of the limit rods 521 are respectively sleeved with return springs A522, and the two ends of the return springs A522 are respectively fixedly installed on the n-shaped plate 52 and the pulling plate 54, which is beneficial to the movement and rebound recovery of the pulling plate 54.

[0042] In this embodiment: when the multispectral camera body 4 is not in use, the pulling plate 54 can be pulled forward to drive the positioning rod 53 to move forward, thereby moving away from the inner cavity of the lower positioning groove 511, and at the same time stretching the return springs A522 on both sides, and then moving the protective plate 51 downward to the front side of the multispectral camera body 4 to protect it. Then, the pulled pulling plate 54 can be released to restore it under the action of the rebound force of the return spring A522, thereby inserting it into the inner cavity of the upper positioning groove 511 to position the protective plate 51.

[0043] Working principle: When in use, the multispectral camera body 4 can be installed first, and pressing the pushing plate 61 forward can drive the rack plate 62 to move forward, and at the same time, it will squeeze the reset spring B613. When the rack plate 62 moves forward, it will drive the movable gear 63 to rotate. When the movable gear 63 rotates, it will drive the threaded rod A64 and the threaded rod B65 to rotate synchronously through the movable rod. When the threaded rod A64 and the threaded rod B65 rotate, they will drive the threaded sleeves 66 on both sides to move in the opposite direction, and when the threaded sleeves 66 move in the opposite direction, they will drive the adjacent L-shaped clamping plates 67 to move in the opposite direction. In addition, when the L-shaped clamping plates 67 move in the opposite direction, they will drive the adjacent trapezoidal blocks 672 to move in the opposite direction through the adjacent fixed plates 671, so that they can move away from the adjacent squeezing balls 673. In addition, the connecting plate 68 and the sliding plate 69 will move upward and recover under the action of the rebound force of the reset spring C693. At this time, the sliding plate 69 will move to the inner cavity of the mounting shell 3, and then the multispectral camera can be mounted. The multi-spectral camera body 4 is placed in the middle of the bottom of the mounting shell 3. After the placement is completed, the pushing plate 61 can be released. At this time, the L-shaped clamping plates 67 on both sides will move relative to each other, thereby supporting the bottom of the multi-spectral camera body 4. In addition, the sliding plate 69 will also move downward to block the front and rear sides of the multi-spectral camera body 4, thereby completing the clamping installation of the multi-spectral camera body 4. When the multi-spectral camera body 4 is not in use, the pulling plate 54 can be pulled forward to drive the positioning rod 53 to move forward, thereby moving away from the inner cavity of the lower positioning groove 511, and at the same time, the return springs A522 on both sides will be stretched, and then the protective plate 51 will be moved downward to the front side of the multi-spectral camera body 4 to protect it. Then the pulled pulling plate 54 can be released and restored under the action of the rebound force of the return spring A522, thereby inserting it into the inner cavity of the upper positioning groove 511 to position the protective plate 51.

[0044] All components involved in this application can meet the needs of this application, and the model and material can be selected according to actual needs.

[0045] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0046] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multispectral camera mounting bracket for an unmanned aerial vehicle, comprising an unmanned aerial vehicle body (1) and a fixing rod (2) fixedly mounted on the bottom of the unmanned aerial vehicle body (1) near the front side, characterized in that: A mounting shell (3) is fixedly mounted on the lower end of the fixing rod (2), and a multispectral camera body (4) is attached to the middle of the bottom of the mounting shell (3), a protective component (5) is mounted on the middle of the front side of the mounting shell (3), and a push opening is opened above the middle of the rear side of the mounting shell (3), and a clamping component (6) is mounted in the inner cavity of the push opening; The clamping assembly (6) includes a push plate (61) slidably mounted in the inner cavity of the push port and a rack plate (62) fixedly mounted on the front side of the push plate (61) near the top, the bottom of the rack plate (62) near the front side is meshed with a movable gear (63), and a movable rod is fixedly installed through the middle of the movable gear (63), and the left and right ends of the movable rod are respectively fixed with a threaded rod B (65) and a threaded rod A (64), and the opposite ends of the threaded rod B (65) and the threaded rod A (64) are respectively movably mounted on the inner wall of the inner cavity of the mounting shell (3), and the outer sides of the threaded rod A (64) and the threaded rod B (65) are respectively threadedly mounted with a threaded sleeve (66), and the bottom of the threaded sleeve (66) is respectively fixedly mounted with an L-shaped clamping The connecting plate (67) is provided with a movable opening at the bottom of the mounting shell (3) near the left and right sides, and the bottom of the L-shaped clamping plate (67) passes through the inner cavity of the adjacent movable openings and extends to the outside of the mounting shell (3), and the top of the inner side of the L-shaped clamping plate (67) is fitted with the bottom of the multi-spectral camera body (4). Two connecting plates (68) are provided near the bottom of the inner cavity of the mounting shell (3), and the connecting plates (68) are arranged on the left and right. The front and rear sides of the connecting plate (68) are respectively fixedly installed with sliding plates (69). The bottom of the sliding plate (69) slides through and extends to the outside of the mounting shell (3), and the inner side of the sliding plate (69) is fitted with the outer side of the multi-spectral camera body (4).

2. The multispectral camera bracket for mounting on an unmanned aerial vehicle according to claim 1, characterized in that: A vertical plate (611) is provided on the front side of the push plate (61), and the bottom of the vertical plate (611) is fixedly mounted on the inner wall of the inner cavity of the mounting shell (3). A sliding rod (612) is slidably mounted on the vertical plate (611) near the top. The rear end of the sliding rod (612) is fixedly mounted on the push plate (61). A return spring B (613) is sleeved on the outer side of the sliding rod (612). The two ends of the return spring B (613) are respectively fixedly mounted on the push plate (61) and the vertical plate (611).

3. The multispectral camera bracket for mounting on an unmanned aerial vehicle according to claim 1, characterized in that: A guide plate (661) is fixedly mounted on the front side of the threaded sleeve (66), and a guide rod (662) is slidably mounted on the guide plate (661). The left and right ends of the guide rod (662) are fixedly mounted on the inner wall of the inner cavity of the mounting shell (3).

4. The multispectral camera bracket for mounting on an unmanned aerial vehicle according to claim 1, characterized in that: A flat plate (691) is fixedly installed on the opposite side of the sliding plate (69) near the left and right sides, and a sliding rod (692) is installed on the flat plate (691) so as to slide through the flat plate (691). The upper ends of the sliding rods (692) are fixedly installed on the inner wall of the inner cavity of the mounting shell (3), and the outer sides of the sliding rods (692) are respectively sleeved with a return spring C (693). The two ends of the return spring C (693) are respectively fixedly installed on the inner wall of the inner cavity of the mounting shell (3) and the adjacent flat plate (691).

5. The multispectral camera bracket for mounting on an unmanned aerial vehicle according to claim 1, characterized in that: A fixing plate (671) is fixedly installed on the inner side of the L-shaped clamping plate (67) near the top, and a trapezoidal block (672) is fixedly installed on the opposite side of the fixing plate (671). The bottom of the trapezoidal block (672) is respectively fitted with an extrusion ball (673), and the bottom of the extrusion ball (673) is respectively fixedly installed on the adjacent connecting plate (68).

6. The multispectral camera bracket for mounting on an unmanned aerial vehicle according to claim 1, characterized in that: The protective assembly (5) comprises a protective plate (51) slidably mounted at the middle of the front side of the mounting shell (3) and an n-shaped plate (52) arranged at the front side of the protective plate (51); the rear side of the n-shaped plate (52) is fixedly mounted on the mounting shell (3); and a positioning rod (53) is slidably mounted through the middle of the n-shaped plate (52); and a pulling plate (54) is fixedly mounted at the front end of the positioning rod (53).

7. The multispectral camera bracket for mounting on an unmanned aerial vehicle according to claim 6, characterized in that: Positioning grooves (511) are respectively provided on the front side of the protective plate (51) near the middle and the top, and the output end of the pulling plate (54) is inserted into the inner cavity of the lower positioning groove (511).

8. The multispectral camera bracket for mounting on an unmanned aerial vehicle according to claim 6, characterized in that: Limiting rods (521) are respectively installed and slidably penetrated near the left and right sides of the n-shaped plate (52), and the front ends of the limiting rods (521) are respectively fixedly installed on the pulling plate (54). The outer sides of the limiting rods (521) are respectively sleeved with return springs A (522), and the two ends of the return springs A (522) are respectively fixedly installed on the n-shaped plate (52) and the pulling plate (54).

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