A high-precision two-way extension device for a battery-swapping robot

Abstract

An embodiment of the present application proposes a high-precision bidirectional extension device for a battery-exchanging robot, comprising a telescopic arm assembly, a main drive assembly and a driven assembly, wherein the telescopic arm assembly comprises a first telescopic arm, a second telescopic arm, a third telescopic arm and a positioning assembly; wherein the first telescopic arm is slidably connected to the second telescopic arm; the second telescopic arm and the third telescopic arm are slidably connected; the positioning assembly comprises a receiver arranged on the first telescopic arm and a transmitter arranged on the second telescopic arm and the third telescopic arm respectively; wherein the receiver is used to receive light waves emitted by the transmitter for measuring the moving distances of the second telescopic arm and the third telescopic arm relative to the first telescopic arm respectively; the main drive assembly is used to receive moving distance data information of the second telescopic arm and the third telescopic arm respectively relative to the first telescopic arm, and is connected to the driven assembly and drives the second telescopic arm and the third telescopic arm to slide.

Description

Technical Field

[0001] The present application relates to the technical field of battery swapping robots, and in particular to a high-precision two-way extension device for a battery swapping robot. Background Art

[0002] The existing battery packs of vehicles using new energy power systems are generally divided into fixed and replaceable types. Among them, fixed batteries are generally fixed on the vehicle; while replaceable battery packs can be removed to replace or charge the battery packs separately. After the replaced battery packs are charged, they are reinstalled on the vehicle. Battery swap robots are used to quickly replace battery packs, but the working arms of battery swap robots need to have a certain degree of precision. The existing robot arms of battery swap robots mostly use three-level forks; the precision of the three-level forks is not high, and the three-level forks cannot be extended in both directions. Summary of the invention

[0003] In response to the above-mentioned prior art and to solve at least one of the above-mentioned technical problems, an embodiment of the present application proposes a high-precision two-way extension device for a battery swap robot, which can not only realize two-way extension of the battery swap robot when replacing a battery pack, but also can timely determine the relative positions of the first telescopic arm, the second telescopic arm and the third telescopic arm through the relative positions of the receiver and the transmitter, and timely adjust the extension distances of the first telescopic arm, the second telescopic arm and the third telescopic arm; and a meter is provided on the main drive assembly, which can record the extended length and continue to work after power supply is restored to ensure accuracy; in addition, by recording the meter data, it can assist in calibrating the second telescopic arm and the third telescopic arm to improve accuracy.

[0004] The present application embodiment proposes a high-precision two-way extension device for a battery-swapping robot, which is used for replacing a battery pack of the battery-swapping robot, comprising:

[0005] A telescopic arm assembly, comprising a first telescopic arm, a second telescopic arm, a third telescopic arm and a positioning assembly; wherein the first telescopic arm is slidably connected to the second telescopic arm; the second telescopic arm is slidably connected to the third telescopic arm; the positioning assembly comprises a receiver arranged on the first telescopic arm and a transmitter respectively arranged on the second telescopic arm and the third telescopic arm; wherein the receiver is used to receive the light waves emitted by the transmitter for measuring the movement distances of the second telescopic arm and the third telescopic arm respectively relative to the first telescopic arm; and

[0006] A main drive component receives the movement distance data information of the second telescopic arm and the third telescopic arm relative to the first telescopic arm through a feedback system, and is connected to a driven component; the driven component cooperates with the main drive component to operate and drive the second telescopic arm and the third telescopic arm to slide.

[0007] In some embodiments, the main driving assembly includes a driving device and a gear belt; wherein the driving device is disposed on the first telescopic arm; and the gear belt is used to connect the driven assembly and the driving device.

[0008] In some embodiments, a tensioning device is further included, which is arranged on the first telescopic arm to provide resistance to the extension and contraction of the gear belt; wherein the gear belt sequentially passes around the driving device, the driven assembly and the tensioning device.

[0009] In some embodiments, the telescopic arm assembly also includes a guide assembly for guiding the sliding direction of the first telescopic arm, the second telescopic arm and the third telescopic arm; wherein the guide assembly includes a guide member and a guide member cooperating with the guide member; wherein the guide members are multiple and arranged on the second telescopic arm; the guide members are both arranged on the first telescopic arm and the third telescopic arm.

[0010] In some embodiments, the driven assembly includes a first driven device and a second driven device; wherein the first driven device is arranged on the second telescopic arm; the second driven device is arranged on the third telescopic arm; and the gear belt passes around the first driven device and the second driven device in sequence.

[0011] In some embodiments, the driving device includes a motor and a reducer connected to the motor; wherein the output shaft of the reducer is sleeved with a gear that meshes with the gear belt.

[0012] In some embodiments, a counter is provided on the reducer, and the counter is provided on the reducer for coordinating and controlling the extension lengths of the second telescopic arm and the third telescopic arm and recording the extension lengths.

[0013] In some embodiments, the first driven device includes a first bracket, a first rotating shaft and a first gear; wherein the first rotating shaft is rotatably set on the first bracket, and the first bracket is set on the second telescopic arm; the first gear is sleeved on the first rotating shaft and meshed with the rack set on the first telescopic arm; a gear surface meshed with the gear belt is provided on the end of the first rotating shaft away from the first gear; the second driven member device includes a second bracket, a second rotating shaft and a second gear; wherein the second rotating shaft is rotatably set on the second bracket, and the second bracket is set on the third telescopic arm; the second gear is sleeved on the second rotating shaft and meshed with the rack set on the second telescopic arm; a gear surface meshed with the gear belt is provided on the end of the second rotating shaft away from the second gear.

[0014] In some embodiments, the third telescopic arm is semi-enclosed and arranged outside the second telescopic arm; the second telescopic arm is semi-enclosed and arranged outside the first telescopic arm; the first telescopic arm includes a first side panel and a second side panel arranged relatively parallel and spaced apart; a plurality of connecting plates are spaced apart at the top of the first side panel along its length direction; the connecting plate is located between the first side panel and the second side panel.

[0015] In some embodiments, a plurality of receiving areas are provided on the receiver, wherein the plurality of receiving areas are distributed in the length direction of the first telescopic arm.

[0016] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of the structure of a high-precision two-way extension device for a battery-swapping robot provided in one embodiment of the present application;

[0019] Figure 2 for Figure 1 Schematic diagram from another perspective;

[0020] Figure 3 for Figure 1 A top view of

[0021] Description of reference numerals:

[0022] In the figure, 1, gear belt; 2, first telescopic arm; 3, second telescopic arm; 4, third telescopic arm; 5, first driven device; 6, second driven device; 7, tensioning device; 8, driving device; 81, motor; 82, reducer; 9, receiver; 10, transmitter. DETAILED DESCRIPTION

[0023] In order to make those skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not all embodiments, and are not intended to limit the scope of the present application. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work should belong to the scope of protection of the present application.

[0024] The accompanying drawings show schematic diagrams of structures according to the embodiments disclosed in the present application. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0025] Please refer to the attached Figure 1 The example shown in the figure describes the embodiment of the present application. The example of the present application proposes a high-precision two-way extension device for a battery-swapping robot for replacing battery packs of the battery-swapping robot, including a telescopic arm assembly, a main drive assembly and a driven assembly; wherein the telescopic arm assembly includes a first telescopic arm 2, a second telescopic arm 3, a third telescopic arm 4 and a positioning assembly; wherein the first telescopic arm 2 is slidably connected to the second telescopic arm 3; the second telescopic arm 3 and the third telescopic arm 4 are slidably connected; the positioning assembly includes a receiver 9 arranged on the first telescopic arm 2 and a transmitter 10 respectively arranged on the second telescopic arm 3 and the third telescopic arm 4; wherein the receiver 9 is used to receive light waves emitted by the transmitter 10 for measuring the moving distances of the second telescopic arm 3 and the third telescopic arm 4 relative to the first telescopic arm 2; the main drive assembly is connected to the driven assembly, and under the operation of the main drive assembly, the driven assembly cooperates with the main drive assembly to operate and drive the second telescopic arm 3 and the third telescopic arm 4 to slide. In addition, the moving distance data information of the second telescopic arm 3 and the third telescopic arm 4 relative to the first telescopic arm 2 can be output to the main drive component through the feedback system, wherein the feedback system is communicatively connected to the receiver 9 and the transmitter 10, and the main drive component receives the moving distance data information of the second telescopic arm 3 and the third telescopic arm 4 relative to the first telescopic arm 2 through the feedback system, thereby further driving and adjusting the moving distance of the second telescopic arm 3 and the third telescopic arm 4 relative to the first telescopic arm 2.

[0026] Specifically, this embodiment is described by taking the length direction of the first telescopic arm 2 as being consistent with the left-right direction as an example, wherein the left-right direction and the front-back direction are as follows: Figure 1 In this embodiment, the telescopic arm assembly includes a first telescopic arm 2 and a second telescopic arm 3, and a second telescopic arm 3 and a third telescopic arm 4 that are slidably arranged relative to each other; wherein the second telescopic arm 3 can slide in the left-right direction relative to the first telescopic arm 2, and similarly, the third telescopic arm 4 can slide in the left-right direction relative to the first telescopic arm 2.

[0027] For example, Figure 1As shown, the third telescopic arm 4 is semi-enclosed and arranged outside the second telescopic arm 3, and the second telescopic arm 3 is semi-enclosed and arranged outside the first telescopic arm 2, wherein the third telescopic arm 4 and the second telescopic arm 3 are both groove-shaped, and the first telescopic arm 2 is arranged inside the second telescopic arm 3. The first telescopic arm 2 includes a first side plate and a second side plate arranged in parallel and spaced relative to each other, that is, the first side plate and the second side plate are arranged in parallel relative to each other in the front-to-back direction, and there is a certain accommodation space between them. The first side plate and the second side plate can be understood as a plate-shaped structure composed of the same profile, wherein the length, thickness and width of the two are the same, that is, the left and right top surfaces of the first side plate are flush with the left and right top surfaces of the second side plate, and a plurality of connecting plates are arranged at the top of the first side plate and at the same distance in the left-right direction, wherein the connecting plate is located between the first side plate and the second side plate, and the two ends of the connecting plate are fixedly connected to the first side plate and the second side plate in the front-to-back direction, respectively, wherein the connecting plate in this embodiment is connected to the battery-swapping robot.

[0028] In order to further understand the real-time moving direction and moving distance of the second telescopic arm 3 and the third telescopic arm 4 respectively relative to the first telescopic arm 2 and timely adjust the running track and moving accuracy of the second telescopic arm 3 and the third telescopic arm 4. In this embodiment, the telescopic arm assembly also includes a positioning assembly; wherein the positioning assembly includes a receiver 9 and a transmitter 10; wherein the receiver 9 is arranged on the first telescopic arm 2; and the transmitter 10 is arranged on the second telescopic arm 3 and the third telescopic arm 4 respectively; the transmitter 10 on the second telescopic arm 3 and the third telescopic arm 4 emits light waves, and the receiver 9 on the first telescopic arm 2 can receive light waves, and the real-time moving direction and moving distance of the second telescopic arm 3 and the third telescopic arm 4 respectively relative to the first telescopic arm 2 can be known by analyzing and measuring the position of the transmitter 10 relative to the receiver 9, and the feedback system feeds back the data information to the main drive assembly, and the operation of the main drive assembly can move the second telescopic arm 3 and the third telescopic arm 4.

[0029] The high-precision two-way extension device in this embodiment is assembled on the battery-swapping robot. When the battery pack is replaced by the battery-swapping robot, not only can the second telescopic arm 3 and the third telescopic arm 4 be extended in two directions in the left and right directions relative to the first telescopic arm 2 respectively when the battery-swapping robot replaces the battery pack, but the relative positions of the first telescopic arm 2, the second telescopic arm 3 and the third telescopic arm 4 can be determined in time through the relative positions of the receiver 9 and the transmitter 10, and the extension distance and movement accuracy of the first telescopic arm 2, the second telescopic arm 3 and the third telescopic arm 4 can be adjusted in time, which solves the technical problem that most of the mechanical arms of existing battery-swapping robots use three-stage forks, among which the accuracy of the three-stage forks is not high and the three-stage forks cannot be extended in two directions.

[0030] In some embodiments, a plurality of receiving areas are arranged on the receiver 9, wherein the plurality of receiving areas are distributed in the length direction of the first telescopic arm 2, and the plurality of receiving areas are used to locate the second telescopic arm 3 and the third telescopic arm 4 after each displacement, and when the transmitter 10 passes through a receiving area of ​​a receiver 9 during movement, a tolerance positioning compensation is performed again according to the signal feedback between the transmitter 10 and the receiver 9 to ensure its overall operation accuracy. Therefore, in this embodiment, the position of the transmitter 10 on the second telescopic arm 3 and the third telescopic arm 4 is changed in real time, and the real-time moving direction and moving distance of the second telescopic arm 3 and the third telescopic arm 4 can be known by setting the transmitter 10 and the receiver 9, and their motion trajectories can be adjusted in time to ensure the moving accuracy of the first telescopic arm 2, the second telescopic arm 3 and the third telescopic arm 4.

[0031] In some embodiments, the main driving assembly includes a driving device 8 and a gear belt 1 ; wherein the driving device 8 is disposed on the first telescopic arm 2 ; and the gear belt 1 is used to connect the driven assembly and the driving device 8 .

[0032] Specifically, Figure 1 As shown, the main driving assembly includes a driving device 8 and a gear belt 1, wherein the driving device 8 is arranged on the first telescopic arm 2 and is located above the first telescopic arm 2, and the driving device 8 includes a motor 81, wherein the gear belt 1 can be wound around the output shaft of the motor 81, and the gear belt 1 is connected to the driven assembly, so that when the motor 81 is running, the driven assembly is driven to run synchronously, and the second telescopic arm 3 and the third telescopic arm 4 are driven to slide relative to the first telescopic arm 2 respectively through the driven assembly.

[0033] Preferably, the driving device 8 further comprises a reducer 82 connected to the motor 81; Figure 2 As shown, the motor 81 is arranged on the top of the reducer 82, the output shaft of the motor 81 is connected to the input shaft of the reducer 82, and a gear is sleeved on the output shaft of the reducer 82, wherein the gear on the output shaft of the reducer 82 is meshed with the gear belt 1, that is, the gear belt 1 is wound and connected between the output shaft of the reducer 82 and the driven component. In this embodiment, the setting of the reducer 82 reduces the speed of the gear belt 1 while increasing the output torque and reducing the inertia of the load.

[0034] In some embodiments, a counter is provided on the reducer 82 , wherein the counter can be understood as a meter used to measure the length of the tensioned stretch of the gear belt 1 .

[0035] In some embodiments, the high-precision bidirectional extension device also includes a tensioning device 7; wherein the tensioning device 7 is arranged on the first telescopic arm 2 to provide resistance for the extension and contraction of the gear belt 1; wherein the gear belt 1 sequentially bypasses the gear, the driven component and the tensioning device 7 mounted on the output shaft of the reducer 82. Preferably, a counter is provided on the reducer 82, wherein the counter can be understood as a meter that can assist in controlling the extension length of the second telescopic arm 3 and the third telescopic arm 4. After reaching the specified length, the meter controls the second telescopic arm 3 and the third telescopic arm 4 to stop extending; and in the event of an emergency such as an unexpected power outage, the meter can record the extended length and continue to work after power is restored to ensure accuracy; in addition, by recording the meter data, it can assist in calibrating the second telescopic arm 3 and the third telescopic arm 4 to improve accuracy.

[0036] In some embodiments, the telescopic arm assembly also includes a guide assembly for guiding the sliding direction of the first telescopic arm 2, the second telescopic arm 3 and the third telescopic arm 4; wherein the guide assembly includes a guide member and a guide member cooperating with the guide member; wherein the guide members are multiple and are arranged on the second telescopic arm 3; and guide members are provided on both the first telescopic arm 2 and the third telescopic arm 4.

[0037] Specifically, the guide assembly includes a guide member and a guide member cooperating with the guide member, wherein the guide member is multiple and is arranged on the second telescopic arm 3, and is respectively located between the second telescopic arm 3 and the first telescopic arm 2 and between the second telescopic arm 3 and the third telescopic arm 4. The first side plate and the second side plate are respectively provided with guide members on one side facing the second telescopic arm 3, and the guide member cooperates with the guide member to ensure that the first telescopic arm 2 and the second telescopic arm 3 slide left and right according to the predetermined extension and contraction direction; similarly, it can be known that the arrangement of the guide member between the third telescopic arm 4 and the second telescopic arm 3 and the guide member cooperating with the guide member will not be repeated, and their function is also to ensure that the third telescopic arm 4 and the second telescopic arm 3 slide left and right according to the predetermined extension and contraction direction.

[0038] In some embodiments, the driven assembly includes a first driven device 5 and a second driven device 6; wherein the first driven device 5 is arranged on the second telescopic arm 3; the second driven device 6 is arranged on the third telescopic arm 4; the gear belt 1 passes around the first driven device 5 and the second driven device 6 in sequence.

[0039] Specifically, in this embodiment, the driven assembly includes a first driven device 5 and a second driven device 6, and the gear belt 1 passes around the first driven device 5 and the second driven device 6 in sequence, that is, the gear belt 1 passes around the gear on the output shaft of the reducer 82, the first driven device 5, the second driven device 6 and the tensioning device 7 in sequence. Figure 1 and Figure 3 As shown, the first driven device 5 is arranged on the second telescopic arm 3 , and the second driven device 6 is arranged on the third telescopic arm 4 .

[0040] Among them, the first driven device 5 includes a first bracket, a first rotating shaft and a first gear; wherein the first rotating shaft is rotatably arranged on the first bracket, and the first bracket is arranged on the second telescopic arm 3; the first gear is sleeved on the first rotating shaft and meshed with the rack arranged on the first telescopic arm 2; a gear surface is arranged on the end of the first rotating shaft away from the first gear, and the gear surface on the first rotating shaft is used to mesh with the gear belt 1; the second driven member device includes a second bracket, a second rotating shaft and a second gear; wherein the second rotating shaft is rotatably arranged on the second bracket, and the second bracket is arranged on the third telescopic arm 4; the second gear is sleeved on the second rotating shaft and meshed with the rack arranged on the second telescopic arm 3; a gear surface is arranged on the end of the second rotating shaft away from the second gear, and the gear surface on the second rotating shaft is used to mesh with the gear belt 1.

[0041] In this embodiment, the motor 81 rotates, and the reducer 82 rotates with the rotation of the motor 81, and the rotation of the gear on the output shaft of the reducer 82 drives the gear belt 1 to rotate, and the gear belt 1 is meshed with the gear surface on the first rotating shaft, the gear surface on the second rotating shaft and the tensioning device 7. With the rotation of the gear belt 1, the first gear and the second gear on the first rotating shaft and the second rotating shaft rotate, and the first gear and the second gear are respectively meshed with the racks on the first telescopic arm 2 and the second telescopic arm 3, thereby driving the second telescopic arm 3 and the third telescopic arm 4 to slide relative to the first telescopic arm 2.

[0042] The following describes the working principle of a high-precision two-way extension device for a battery-swapping robot: the first telescopic arm 2 is fixedly mounted on the mounting frame of the battery-swapping robot body through a connecting plate, and a clamping device is arranged on the third telescopic arm 4, wherein the mounting frame can be moved up and down on the robot body, and the robot body can move laterally during operation. During the operation of the high-precision two-way extension device, the first telescopic arm 2 is fixed during operation, and the battery pack is clamped by the clamping device on the third telescopic arm 4. After the clamping device clamps the battery pack, the high-precision two-way extension device is retracted, and the robot body can control the high-precision two-way extension device to move up and down to separate the battery pack from the vehicle to be replaced.

[0043] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0044] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0045] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A high-precision two-way extension device for a battery-swapping robot, characterized in that: Used for replacing battery packs of battery-swapping robots, including A telescopic arm assembly, comprising a first telescopic arm, a second telescopic arm, a third telescopic arm, a positioning assembly and a guide assembly; wherein the first telescopic arm is slidably connected to the second telescopic arm; the second telescopic arm is slidably connected to the third telescopic arm; the positioning assembly comprises a receiver arranged on the first telescopic arm and transmitters respectively arranged on the second telescopic arm and the third telescopic arm; The receiver is provided with a plurality of receiving areas, which are distributed in the length direction of the first telescopic arm and are used to receive the light waves emitted by the transmitter for measuring the moving distances of the second telescopic arm and the third telescopic arm respectively relative to the first telescopic arm; the guide assembly is used to guide the sliding directions of the first telescopic arm, the second telescopic arm and the third telescopic arm, and comprises a guide member and a guide member matched with the guide member; the guide members are multiple and are arranged on the second telescopic arm; the guide members are arranged on both the first telescopic arm and the third telescopic arm; A main driving assembly receives the moving distance data information of the second telescopic arm and the third telescopic arm respectively relative to the first telescopic arm through a feedback system, and comprises a driving device and a gear belt; the driving device is arranged on the first telescopic arm, and comprises a motor and a reducer connected to the motor; a gear meshing with the gear belt is sleeved on the output shaft of the reducer; a counter is arranged on the reducer for coordinating and controlling the extension length of the second telescopic arm and the third telescopic arm and recording the extension length; the gear belt is used to connect the driven assembly and the driving device; the driven assembly cooperates with the main driving assembly to operate and drive the second telescopic arm and the third telescopic arm to slide; as well as A tensioning device is arranged on the first telescopic arm and is used to provide resistance to the extension and contraction of the gear belt, wherein the gear belt passes around the driving device, the driven assembly and the tensioning device in sequence.

2. The extending device according to claim 1, characterized in that: The driven assembly includes a first driven device and a second driven device; wherein the first driven device is arranged on the second telescopic arm; the second driven device is arranged on the third telescopic arm; and the gear belt passes around the first driven device and the second driven device in sequence.

3. The extending device according to claim 2, characterized in that: The first driven device includes a first bracket, a first rotating shaft and a first gear; wherein the first rotating shaft is rotatably set on the first bracket, and the first bracket is set on the second telescopic arm; the first gear is sleeved on the first rotating shaft and meshed with the rack set on the first telescopic arm; a gear surface meshed with the gear belt is provided at one end of the first rotating shaft away from the first gear; the second driven device includes a second bracket, a second rotating shaft and a second gear; wherein the second rotating shaft is rotatably set on the second bracket, and the second bracket is set on the third telescopic arm; the second gear is sleeved on the second rotating shaft and meshed with the rack set on the second telescopic arm; a gear surface meshed with the gear belt is provided at one end of the second rotating shaft away from the second gear.

4. The extending device according to claim 1, characterized in that: The third telescopic arm is semi-enclosed and arranged outside the second telescopic arm; the second telescopic arm is semi-enclosed and arranged outside the first telescopic arm; the first telescopic arm includes a first side plate and a second side plate arranged in parallel and spaced relation; a plurality of connecting plates are spaced at intervals on the top of the first side plate along its length direction; the connecting plate is located between the first side plate and the second side plate.

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