A device to prevent drone from falling in mountainous areas

Abstract

The present invention discloses a device for preventing a UAV from falling in a mountainous area, which belongs to the field of UAV equipment. The device comprises a UAV body, a protective tube is arranged in the middle of the top surface of the UAV body, and a support box is plugged into one side of the protective tube; a monitoring system is arranged on the bottom surface of the inner cavity of the support box, and the monitoring system is used to monitor the acceleration of the UAV body in a specified direction for the convenience of action; an anti-fall mechanism is arranged on the bottom surface of the inner cavity of the support box and away from the monitoring system; a push component is arranged on one side wall of the anti-fall mechanism, and the top of the push component is connected to the top surface of the inner cavity of the protective tube, and the push component is used to cooperate with the monitoring system to realize the opening of the anti-fall mechanism; and slide grooves are arranged on both side walls of the support box. It can automatically open the parachute when the UAV falls, which can prevent the UAV from breaking and spontaneously igniting, and can also protect the safety of the use of the UAV.

Description

Technical Field

[0001] The present invention relates to the field of unmanned aerial vehicle equipment, and more particularly to a device for preventing unmanned aerial vehicles from falling in mountainous areas. Background Art

[0002] The application fields of unmanned aerial vehicles are constantly expanding. Both industrial drones and consumer drones have made great progress, especially small and micro unmanned aerial vehicles represented by multi-rotor unmanned aerial vehicles. They have begun to be widely used in various application fields. Mountain drones are now also beginning to be widely used. An existing patent for a new type of drone, patent application number CN202123036884.0, is used to disassemble the rotor through the installation mechanism, which is convenient for maintenance or replacement of the rotor. The operation steps are simple and convenient, which is convenient for the operator to maintain or replace the rotor. At the same time, it is convenient to reinstall the rotor without affecting the later use of the rotor.

[0003] However, when a drone encounters a malfunction or remote control failure during flight, it may cause the drone to fall. The impact force generated by the fall may cause the drone to spontaneously combust, leading to a fire. In addition, when a drone falls to a place with many people and buildings, it is easy to cause damage to people and objects. Therefore, we propose a mountain drone anti-fall device to solve the above problems. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a mountain drone anti-falling device, which can automatically open the parachute when the drone falls, thereby preventing the drone from breaking and spontaneously combusting and protecting the safety of the drone.

[0006] 2. Technical solution

[0007] To solve the above problems, the present invention adopts the following technical solutions.

[0008] A mountain drone fall prevention device comprises a drone body, a protective tube is arranged in the middle of the top surface of the drone body, and a support box is plugged into one side of the protective tube;

[0009] A monitoring system is provided on the bottom surface of the inner cavity of the support box, and the monitoring system is used to monitor the acceleration of the drone body in a specified direction for easy action. An anti-fall mechanism is provided on the bottom surface of the inner cavity of the support box and on a side away from the monitoring system. A pushing component is provided on one side wall of the anti-fall mechanism, and the top of the pushing component is connected to the top surface of the inner cavity of the protection tube. The pushing component is used to cooperate with the monitoring system to realize the opening of the anti-fall mechanism;

[0010] Both side walls of the support box are provided with sliding grooves, both side walls of the protective tube are provided with positioning screw holes, and locking studs are threadedly connected to the inner cavities of the positioning screw holes. The positioning screw holes are used for rotating the locking studs, and one end of the locking studs is plugged into the sliding grooves. The locking studs are used to cooperate with the sliding grooves to achieve the limiting effect on the support box.

[0011] Furthermore, the monitoring system includes a pallet, a programmable controller is arranged on the top surface of the pallet, and an acceleration sensor and a lithium battery are respectively arranged on the top surface of the pallet and on both sides of the programmable controller.

[0012] Furthermore, the anti-fall mechanism includes a storage box, a launch plate is provided in the middle part of the inner cavity of the storage box, a parachute is provided on the top surface of the launch plate, and the bottom end of the parachute is connected to the top surface of the launch plate, a compression spring is provided on the bottom surface of the inner cavity of the storage box and below the launch plate, a lock groove is provided in the middle part of one side of the launch plate, a lock hole is provided in the middle part of one side wall of the storage box, and a lock tongue is inserted in the inner cavity of the lock hole, and one end of the lock tongue is plugged into the lock groove, and the middle part of the bottom surface of the launch plate is connected to the bottom surface of the inner cavity of the storage box through a pulling assembly.

[0013] Furthermore, the bottom surface of the storage box is fixedly connected to the bottom surface of the inner cavity of the tray.

[0014] Furthermore, the top end of the compression spring is in contact with the bottom surface of the ejection plate, and the bottom end of the compression spring is fixedly connected to the bottom surface of the inner cavity of the storage box.

[0015] Furthermore, the pulling assembly includes a spring rope, the top end of the spring rope is fixedly connected to the bottom surface of the ejection plate through a first anti-slip ring, and the bottom end of the spring rope is fixedly connected to the bottom surface of the inner cavity of the storage box through a second anti-slip ring.

[0016] Furthermore, the pushing assembly includes an electric push rod, the output end of the electric push rod is connected to the side wall of the storage box on the anti-fall mechanism through a connecting plate, a socket is inserted in the middle of the electric push rod, a limit ring is fixedly provided on one side wall of the socket and near the bottom, and the limit ring is connected to one end of the lock tongue through a pull rope.

[0017] Furthermore, the top of the holder is connected to the top surface of the inner cavity of the protection tube.

[0018] Furthermore, a groove ring is provided at one end of the support box and located on one side of the anti-fall mechanism, and a sealing ring is provided in the inner cavity of the groove ring.

[0019] Furthermore, a rubber pad is provided on one side wall of the inner cavity of the tray and above the monitoring system, a plurality of groups of reinforcing ribs are provided on the outer surface of the protective tube, and positioning pieces are symmetrically provided on the bottom of both side walls of the protective tube.

[0020] 3. Beneficial effects

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) In this solution, when the main body of the drone falls, it will be affected by gravity and its vertical speed will have a gravity acceleration change, so that the acceleration sensor in the monitoring system can detect the fall of the object, and then the acceleration sensor can send the detection signal to the programmable controller, which can then control the operation of the electric push rod in the push component.

[0023] (2) In this solution, the electric push rod can push the storage box on the anti-fall mechanism to the specified position through the connecting plate, and then the limit ring on the card seat can provide outward pulling force to the lock tongue through the pull rope. When the storage box reaches the specified position, the lock tongue is just pulled out of the lock groove, and then the parachute can be ejected along with the ejection plate under the elastic force of the compression spring, so that the parachute can be opened easily, so that the opened parachute can be pulled by the pulling component to hold the support box, and then the drone body can be pulled under the connection of the protective tube to slow down the fall of the drone body, which can prevent the drone body from breaking and spontaneously igniting, and protect the safety of the drone body. By rotating the locking stud on the positioning screw hole, it can be inserted into the slide groove on the side wall of the support box, thereby preventing the support box from falling off the protective tube.

[0024] (3) In this solution, since the top end of the compression spring is in contact with the bottom surface of the ejection plate, and the bottom end of the compression spring is fixedly connected to the bottom surface of the inner cavity of the storage box, the compression spring can provide elastic force to the ejection plate without causing the compression spring to fly out with the ejection plate, thereby facilitating the ejection plate to fly out.

[0025] (4) In this solution, the two ends of the spring rope can be connected to the bottom of the ejection plate and the bottom of the inner cavity of the storage box respectively by pulling the first anti-slip ring and the second anti-slip ring in the assembly, thereby preventing the ejection plate from being completely separated from the storage box, and then the upward pulling force of the parachute can be transmitted to the storage box, so as to be transmitted to the drone body, thereby slowing down the fall of the drone body. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the present invention;

[0027] Figure 2 It is a schematic diagram of the protection tube and the support box structure of the present invention;

[0028] Figure 3 It is a schematic diagram of the cross-sectional structure of the protection tube and the support box of the present invention;

[0029] Figure 4 This is a schematic diagram of the inner cavity structure of the tray of the present invention;

[0030] Figure 5 It is a schematic diagram of the structure of the monitoring system of the present invention;

[0031] Figure 6 It is a schematic diagram of the structure of the driving component of the present invention;

[0032] Figure 7 It is a schematic diagram of the structure of the anti-falling mechanism of the present invention;

[0033] Figure 8 It is a schematic diagram of the cross-sectional structure of the anti-falling mechanism of the present invention;

[0034] Fig. 9 It is a schematic diagram of the structure of the pulling assembly of the present invention.

[0035] Description of the numbers in the figure:

[0036] 1. UAV body; 2. Protection tube; 3. Support box; 4. Monitoring system; 401. Support plate; 402. Acceleration sensor; 403. Programmable controller; 404. Lithium battery; 5. Push assembly; 501. Electric push rod; 502. Connecting plate; 503. Card holder; 504. Limit ring; 505. Pull rope; 6. Anti-fall mechanism; 601. Storage box; 602. Ejection plate; 603. Parachute; 604. Compression spring; 605. Lock groove; 606. Lock hole; 607. Lock tongue; 608. Pull assembly; 6081. Spring rope; 6082. First anti-slip ring; 6083. Second anti-slip ring; 7. Slide groove; 8. Positioning screw hole; 9. Locking stud; 10. Groove ring; 11. Sealing ring; 12. Rubber pad; 13. Reinforcement rib; 14. Positioning sheet. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0038] Example:

[0039] See also Figure 1-4A mountain drone fall prevention device comprises a drone body 1, a protective tube 2 is arranged in the middle of the top surface of the drone body 1, a support box 3 is plugged into one side of the protective tube 2; a monitoring system 4 is arranged on the bottom surface of the inner cavity of the support box 3, an anti-fall mechanism 6 is arranged on the bottom surface of the inner cavity of the support box 3 and on the side away from the monitoring system 4, a pushing component 5 is arranged on one side wall of the anti-fall mechanism 6, and the top of the pushing component 5 is connected to the top surface of the inner cavity of the protective tube 2; both side walls of the support box 3 are provided with sliding grooves 7, both side walls of the protective tube 2 are provided with positioning screw holes 8, and the positioning screw holes 8 are arranged on the bottom surface of the inner cavity of the support box 3. The inner cavity of the hole 8 is screwed with a locking stud 9. One end of the locking stud 9 is plugged into the slide groove 7. Through the drone body 1, the protective tube 2 can be installed and the protective tube 2 can be flexibly carried for flight. In addition, the protective tube 2 can be installed on the tray 3. When the drone body 1 falls due to a fault or remote control failure during flight, the monitoring system 4 on the tray 3 can detect the acceleration in the vertical direction of the drone body 1, that is, the speed change, thereby triggering the control pushing component 5 to run, thereby being able to push one end of the tray 3 out of the inner cavity of the tray 3, so that the anti-fall mechanism 6 is exposed to the air. When the anti-fall mechanism 6 reaches the specified position, the anti-fall device in the anti-fall mechanism 6 will be turned on, thereby being able to slow down the fall of the drone body 1, which can prevent the drone body 1 from breaking and spontaneously igniting, and protect the safety of the drone body 1. By rotating the locking stud 9 on the positioning screw hole 8, it can be plugged into the slide groove 7 on the side wall of the tray 3, thereby preventing the tray 3 from falling off the protective tube 2.

[0040] See also Figure 5 The monitoring system 4 includes a support plate 401, a programmable controller 403 is arranged on the top surface of the support plate 401, and an acceleration sensor 402 and a lithium battery 404 are arranged on the top surface of the support plate 401 and on both sides of the programmable controller 403. The programmable controller 403 and other electrical components can be installed through the support plate 401 in the monitoring system 4. When the drone body 1 falls, it will be affected by gravity and its vertical speed will have a gravity acceleration change, so that the acceleration sensor 402 in the monitoring system 4 can detect the fall of the object, and then the acceleration sensor 402 can send the detection signal to the programmable controller 403, so that the programmable controller 403 can control the operation of the pushing component 5 and push the anti-falling mechanism 6 to the specified position, so that the anti-falling mechanism 6 can be opened conveniently. The lithium battery 404 can provide power to the electrical equipment to ensure the endurance of the equipment.

[0041] See also Figure 7 , Figure 8The anti-fall mechanism 6 includes a storage box 601, a ejection plate 602 is arranged in the middle of the inner cavity of the storage box 601, a parachute 603 is arranged on the top surface of the ejection plate 602, and the bottom end of the parachute 603 is connected to the top surface of the ejection plate 602, a compression spring 604 is arranged on the bottom surface of the inner cavity of the storage box 601 and below the ejection plate 602, a lock groove 605 is arranged in the middle of one side of the ejection plate 602, a lock hole 606 is arranged in the middle of one side wall of the storage box 601, and a lock tongue 607 is inserted into the inner cavity of the lock hole 606, and the lock tongue 607 One end is plugged into the lock slot 605, and the middle part of the bottom surface of the ejection plate 602 is connected to the bottom surface of the inner cavity of the storage box 601 through a pulling component 608. When the drone body 1 falls, the anti-fall mechanism 6 can be pushed to the specified position by pushing the component 5, and then the lock tongue 607 in the anti-fall mechanism 6 can be pulled out from the lock hole 606 and the lock slot 605, and then the parachute 603 can be ejected along with the ejection plate 602 under the elastic force of the compression spring 604, so that the parachute 603 can be opened conveniently, so that the opened parachute 603 can pull the support box 3 through the pulling component 608, and then pull the drone body 1 under the connection of the protective tube 2 to prevent the drone body 1 from falling and being damaged.

[0042] See also Figure 3 , Figure 7 The bottom surface of the storage box 601 is fixedly connected to the bottom surface of the inner cavity of the tray box 3, which can prevent the storage box 601 and the tray box 3 from falling off.

[0043] See also Figure 8 The top of the compression spring 604 is in contact with the bottom surface of the ejection plate 602, and the bottom of the compression spring 604 is fixedly connected to the bottom surface of the inner cavity of the storage box 601, which can not only enable the compression spring 604 to provide elastic force to the ejection plate 602, but also prevent the compression spring 604 from flying out with the ejection plate 602, thus facilitating the ejection plate 602 to fly out.

[0044] See also Figure 8 , Fig. 9 The pulling component 608 includes a spring rope 6081, the top of which is fixedly connected to the bottom surface of the ejection plate 602 through a first anti-slip ring 6082, and the bottom of the spring rope 6081 is fixedly connected to the bottom surface of the inner cavity of the storage box 601 through a second anti-slip ring 6083. Through the first anti-slip ring 6082 and the second anti-slip ring 6083 in the pulling component 608, the two ends of the spring rope 6081 can be connected to the bottom of the ejection plate 602 and the bottom of the inner cavity of the storage box 601 respectively, thereby preventing the ejection plate 602 from being completely separated from the storage box 601, and then enabling the upward pulling force of the parachute 603 to be transmitted to the storage box 601, so as to be transmitted to the drone body 1, thereby slowing down the fall of the drone body 1.

[0045] See also Figure 4 , Figure 6 The push assembly 5 includes an electric push rod 501, the output end of which is connected to the side wall of the storage box 601 on the anti-fall mechanism 6 through a connecting plate 502, a card holder 503 is inserted in the middle of the electric push rod 501, and a limit ring 504 is fixedly arranged on one side wall of the card holder 503 and near the bottom, and the limit ring 504 is connected to one end of the lock tongue 607 through a pull rope 505. The programmable controller 403 in the monitoring system 4 can control the operation of the electric push rod 501, so that the electric push rod 501 pushes the storage box 601 on the anti-fall mechanism 6 to the specified position through the connecting plate 502, and then the limit ring 504 on the holder 503 can provide an outward pulling force to the lock tongue 607 through the pull rope 505. When the storage box 601 reaches the specified position, the lock tongue 607 is just pulled out of the lock slot 605, and then the ejection plate 602 can be released to fly out, which is convenient for the opening of the parachute 603. The electric push rod 501 can be installed and fixed through the holder 503 to ensure the stability of the electric push rod 501.

[0046] See also Figure 4 , Figure 6 The top of the holder 503 is connected to the top surface of the inner cavity of the protection tube 2, so that the holder 503 can be fixed to the protection tube 2, thereby improving the stability of the holder 503 in use.

[0047] See also Figure 4 A groove ring 10 is provided at one end of the support box 3 and at one side of the anti-fall mechanism 6, and a sealing ring 11 is provided in the inner cavity of the groove ring 10. The sealing ring 11 can be installed through the groove ring 10, thereby improving the sealing effect of the support box 3 when it is closed on the protective tube 2 and preventing dirt from entering.

[0048] See also Figure 2 , Figure 3 A rubber pad 12 is provided on one side wall of the inner cavity of the support box 3 and above the monitoring system 4. A plurality of groups of reinforcing ribs 13 are provided on the outer surface of the protective tube 2. Positioning pieces 14 are symmetrically provided on the bottom of both side walls of the protective tube 2. The rubber pad 12 can prevent one side of the support box 3 from colliding with the electric push rod 501, and the plurality of groups of reinforcing ribs 13 can enhance the structural strength of the protective tube 2. At the same time, the positioning piece 14 can install the protective tube 2 at a specified position of the drone body 1, thereby improving the installation stability of the protective tube 2.

[0049] When in use: the drone body 1 can be used to install the protective tube 2 and flexibly carry the protective tube 2 for flight, and the protective tube 2 can be installed on the support box 3. When the drone body 1 falls, it will be affected by gravity and its vertical speed will have a gravity acceleration change, so that the acceleration sensor 402 in the monitoring system 4 can detect the fall of the object, and then the acceleration sensor 402 can send the detection signal to the programmable controller 403, so that the programmable controller 403 can control the operation of the electric push rod 501 in the pushing component 5, and the electric push rod 501 can push the storage box 601 on the anti-fall mechanism 6 to the specified position through the connecting plate 502. The limit ring 504 on the card seat 503 can provide an outward pulling force to the lock tongue 607 through the pull rope 505. When the storage box 601 reaches the specified position, the lock tongue 607 is just pulled out of the lock slot 605, and then the parachute 603 can be ejected along with the ejection plate 602 under the elastic force of the compression spring 604, so that the parachute 603 can be opened conveniently, so that the opened parachute 603 can be pulled to hold the support box 3 through the pulling component 608, and then the drone body 1 can be pulled under the connection of the protective tube 2, so as to slow down the fall of the drone body 1, which can prevent the drone body 1 from breaking and spontaneously igniting, and protect the safety of the drone body 1. The locking stud 9 on 8 can be inserted into the slide groove 7 on the side wall of the tray 3, thereby preventing the tray 3 from falling off the protective tube 2. Since the top of the compression spring 604 is in contact with the bottom surface of the ejection plate 602, and the bottom of the compression spring 604 is fixedly connected to the bottom surface of the inner cavity of the storage box 601, the compression spring 604 can provide elastic force to the ejection plate 602, and the compression spring 604 will not follow the ejection plate 602 to splash out of the wind, which facilitates the ejection plate 602 to fly out. In addition, the two ends of the spring rope 6081 can be respectively connected to the bottom of the ejection plate 602 and the inner cavity of the storage box 601 by pulling the first anti-slip ring 6082 and the second anti-slip ring 6083 in the assembly 608. The bottom is connected, thereby preventing the ejection plate 602 from being completely separated from the storage box 601, and then the upward pulling force of the parachute 603 can be transmitted to the storage box 601, so as to facilitate transmission to the drone body 1, thereby slowing down the fall of the drone body 1; the sealing ring 11 can be installed through the groove ring 10, thereby improving the sealing effect when the support box 3 is closed on the protective tube 2 to prevent dirt from entering, and the rubber pad 12 can prevent one side of the support box 3 from colliding with the electric push rod 501, and multiple groups of reinforcing ribs 13 can enhance the structural strength of the protective tube 2. At the same time, the positioning piece 14 can install the protective tube 2 at a specified position of the drone body 1, thereby improving the installation stability of the protective tube 2.

[0050] The above are only preferred specific implementations of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and improved concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for preventing a UAV from falling in a mountainous area, comprising a UAV body (1), characterized in that: A protective tube (2) is provided in the middle of the top surface of the drone body (1), and a support box (3) is plugged into one side of the protective tube (2); A monitoring system (4) is arranged on the bottom surface of the inner cavity of the support box (3), and the monitoring system (4) is used to monitor the acceleration of the drone body (1) in a specified direction for convenience of action. An anti-fall mechanism (6) is arranged on the bottom surface of the inner cavity of the support box (3) and on a side away from the monitoring system (4). A pushing component (5) is arranged on one side wall of the anti-fall mechanism (6), and the top of the pushing component (5) is connected to the top surface of the inner cavity of the protective tube (2). The pushing component (5) is used to cooperate with the monitoring system (4) to realize the opening of the anti-fall mechanism (6); The two side walls of the support box (3) are provided with slide grooves (7), the two side walls of the protection tube (2) are provided with positioning screw holes (8), and the inner cavities of the positioning screw holes (8) are screwed with locking studs (9), the positioning screw holes (8) are used for rotationally installing the locking studs (9), one end of the locking studs (9) is plugged and connected to the slide grooves (7), and the locking studs (9) are used to cooperate with the slide grooves (7) to achieve the limiting effect on the support box (3); The anti-fall mechanism (6) comprises a storage box (601), a ejection plate (602) is arranged in the middle of the inner cavity of the storage box (601), a parachute (603) is arranged on the top surface of the ejection plate (602), and the bottom end of the parachute (603) is connected to the top surface of the ejection plate (602), a compression spring (604) is arranged on the bottom surface of the inner cavity of the storage box (601) and below the ejection plate (602), a locking groove (605) is arranged in the middle of one side of the ejection plate (602), a locking hole (606) is arranged in the middle of one side wall of the storage box (601), and a locking tongue (607) is inserted into the inner cavity of the locking hole (606), and one end of the locking tongue (607) is plugged and connected to the locking groove (605), and the ejection plate (601) is provided with a locking hole (606) in the middle of the inner cavity of the locking hole (606). 02) The middle part of the bottom surface is connected to the bottom surface of the inner cavity of the storage box (601) through a pulling assembly (608), the bottom surface of the storage box (601) is fixedly connected to the bottom surface of the inner cavity of the support box (3), the top end of the compression spring (604) is in contact with the bottom surface of the ejection plate (602), the bottom end of the compression spring (604) is fixedly connected to the bottom surface of the inner cavity of the storage box (601), the pulling assembly (608) includes a spring rope (6081), the top end of the spring rope (6081) is fixedly connected to the bottom surface of the ejection plate (602) through a first anti-slip ring (6082), and the bottom end of the spring rope (6081) is fixedly connected to the bottom surface of the inner cavity of the storage box (601) through a second anti-slip ring (6083); The pushing assembly (5) comprises an electric push rod (501), the output end of the electric push rod (501) being connected to the side wall of a storage box (601) on the anti-fall mechanism (6) via a connecting plate (502), a holder (503) being inserted in the middle of the electric push rod (501), a limit ring (504) being fixedly provided on one side wall of the holder (503) and close to the bottom end, and the limit ring (504) being connected to one end of a locking tongue (607) via a pull rope (505).

2. The mountain drone anti-fall device according to claim 1, characterized in that: The monitoring system (4) comprises a support plate (401), a programmable controller (403) being arranged on the top surface of the support plate (401), and an acceleration sensor (402) and a lithium battery (404) being arranged on the top surface of the support plate (401) and on both sides of the programmable controller (403).

3. The mountain drone anti-fall device according to claim 1, characterized in that: The top end of the holder (503) is connected to the top surface of the inner cavity of the protection tube (2).

4. The mountain drone anti-fall device according to claim 1, characterized in that: A groove ring (10) is provided at one end of the support box (3) and located on one side of the anti-falling mechanism (6), and a sealing ring (11) is provided in the inner cavity of the groove ring (10).

5. The mountain drone anti-fall device according to claim 1, characterized in that: A rubber pad (12) is provided on one side wall of the inner cavity of the tray (3) and above the monitoring system (4), a plurality of groups of reinforcing ribs (13) are provided on the outer surface of the protective tube (2), and positioning pieces (14) are symmetrically provided on the bottom of both side walls of the protective tube (2).

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