Multifunctional adjustable smoke generating device for wind tunnel

Abstract

The invention belongs to the technical field of wind tunnel visual test devices, and particularly relates to a multifunctional adjustable smoke generation device for a wind tunnel, which comprises a liquid storage device, a storage bin, a heater, a temperature sensor, a heat insulation layer, a power pipe, a shell, a multi-hole nozzle, a single-hole nozzle and an electric telescopic rod, the heaters are arranged on the two sides, close to the inlet, in the shell, the liquid storage device and the storage bin are connected with the inner sides of the heaters, the heat insulation layer is arranged on the surfaces of the heaters, and the temperature sensors are arranged on the upper surfaces of the storage bin and the liquid storage device. The power pipe is arranged on the side surfaces of the liquid storage device and the storage bin; the multi-hole nozzle is located around the shell contraction section outlet, and the single-hole nozzle is located in the center of the shell contraction section outlet. The electric telescopic rod is connected with the bottom of the shell. The smoke generating agent is high in selectivity, the generating module is simple, heating is uniform, operation is convenient, remote observation and smoke spraying height adjustment are facilitated, smoke is uniformly diffused in the space and can rapidly reach a model area, and the method can be suitable for wide wind tunnel visualization tests.

Description

Technical Field

[0001] The invention relates to the technical field of wind tunnel visualization test devices, in particular to a multifunctional and adjustable smoke generating device for a wind tunnel. Background Art

[0002] The smoke generating device introduces smoke into the wind tunnel, making the originally invisible air flow clearly visible. The smoke flows along with the airflow, forming obvious smoke trails, which help to intuitively observe and analyze the distribution of the flow field, including flow direction, speed changes, and the formation and evolution of vortices.

[0003] Current smoke generators for wind tunnel visualization testing have the following problems: ① The device structure is relatively complex and only suitable for solid or liquid smoke agents. The appropriate generator must be selected based on the characteristics and actual needs of the smoke cake and smoke liquid, resulting in high costs and uneven heating. ② Most existing smoke generators are fixed at a fixed height and cannot be remotely observed or controlled. While such devices can meet the smoke requirements of basic wind tunnel tests to a certain extent, they are not suitable for the wind tunnel test model's requirements for smoke generation at different heights and locations. Furthermore, they have difficulty capturing three-dimensional vortex structures, resulting in blind spots in complex flow observations. ③ Most existing smoke generators use a single or multiple nozzles, with hoses connecting the nozzles to change the spray direction. This results in a less fine and uniform smoke generation, making it difficult to meet the smoke generation requirements of different parts of the model. Furthermore, generators that quickly change the spray direction through a hose connection can cause pressure loss or uneven smoke concentration due to the hose length.

[0004] Chinese invention patent CN116642655A (publication date: August 25, 2023) discloses an adjustable instantaneous flow field visualization smoke generating device. The invention can realize regional monitoring of real-time flow fields within a certain range by remotely controlling the flow rate and angle of the smoke. Chinese invention patent CN113848033A (publication date: December 28, 2021) discloses a continuous smoke generating device for a small visualization wind tunnel test bench. The invention can better control the generation, flow and tracing effect of smoke, has strong controllability, and has the characteristics of small size, light weight, good continuity and strong adaptability, and has good working reliability. Although the above patents can control the smoke output of the smoke generating device to a certain extent, they do not take into account the problem of rough smoke injection, and cannot simultaneously meet the independent smoke generation of different smoke-generating agents. The adaptability is not strong, and it does not solve the problem that the wind tunnel test model needs to generate smoke at a certain height and different angles at the same time. Summary of the Invention

[0005] This application proposes a multifunctional and adjustable smoke generator for wind tunnels. This device features dual combustion chambers that independently and stably generate smoke, allowing for simultaneous heating of the smoke cake and oil. It also enables remote monitoring and adjustment of the smoke ejection height, ensuring a more uniform and smooth smoke ejection. The specific technical solution is described below:

[0006] A multifunctional and adjustable smoke generating device for a wind tunnel, comprising a liquid reservoir, a material storage bin, a heater, a temperature sensor, a thermal insulation layer, a power tube, a shell, a multi-hole nozzle, a single-hole nozzle, and an electric telescopic rod; the liquid reservoir, material storage bin, heater, temperature sensor, thermal insulation layer, and power tube are all located inside the shell; there are two heaters, which are respectively arranged on both sides of the shell near the entrance, and the liquid reservoir and material storage bin are respectively connected to the inner sides of different heaters, the thermal insulation layer is arranged on the surface of the heater, and the temperature sensor is arranged on the upper surfaces of the grain storage bin and the liquid reservoir, for detecting the heated temperature of the liquid reservoir and the material storage bin, and adjusting the smoke volume by temperature control to ensure stable smoke quality; there are two power tubes, which are respectively arranged on the sides of the liquid reservoir and the material storage bin; there are several multi-hole nozzles, which are located around the outlet of the contraction section of the shell; the single-hole nozzle is located at the center of the outlet of the contraction section of the shell; there are several electric telescopic rods, which are connected to the bottom of the shell.

[0007] Furthermore, the liquid reservoir is a fixedly connected horizontal cylinder with smoke liquid inside, a smoke liquid inlet is provided at one end, and a first cigarette outlet is provided at the other end.

[0008] Furthermore, the storage bin is a fixedly connected horizontal cylinder, which contains solid smoke agent, such as smoke cakes; one end of the storage bin is provided with a solid smoke agent inlet, and the other end is provided with a second smoke outlet.

[0009] Furthermore, the aperture of the smoke oil inlet is smaller than that of the solid smoke agent inlet.

[0010] Furthermore, the heater is provided with a heating wire, which is spiral and located on the outer surface of the liquid reservoir and the material storage bin, for uniformly heating the smoke agent.

[0011] Furthermore, the thermal insulation layer is made of ceramic fiber material, which has good thermal insulation effect, reduces internal heat loss, avoids relative interference between the liquid reservoir and the material storage bin during the heating process, and maintains the independence of the two.

[0012] Furthermore, the multi-porous nozzle is made of ceramic fiber material, is threadedly connected to the periphery of the outlet of the contraction section of the shell, and can be disassembled; the multi-porous nozzle has a plurality of small nozzle holes, which can evenly spray smoke.

[0013] Furthermore, one end of the two power tubes is connected to one side of the liquid reservoir and the material storage bin respectively, and the other end passes through the shell to connect to the external power equipment to help the smoke to be transported quickly.

[0014] Furthermore, the smoke generating part of the shell is a rectangular parallelepiped, the outlet part is in the shape of a quadrangular pyramid, an internal threaded part is provided on the inner side of the top of the quadrangular pyramid, the other end of the shell is a detachable generator cover, and a plurality of threaded holes are provided on the bottom of the shell.

[0015] Furthermore, the single-hole nozzle is made of stainless steel, and an external threaded part is provided on the outer side of one end of the single-hole nozzle. The single-hole nozzle is connected to the internal threaded part on the inner side of the shell outlet through the external threaded part, and can be disassembled.

[0016] Furthermore, a first switch valve is provided on each of the multi-hole nozzles to control the opening of each multi-hole nozzle; a second switch valve is provided on the single-hole nozzle to control the opening and closing of the single-hole nozzle.

[0017] Furthermore, several of the electric telescopic rods include three layers of sleeves, which are connected to the threaded holes at the bottom of the shell by tightening bolts and can be disassembled; the electric telescopic rods are connected to an external terminal system, receive control signals, and can realize remote control of lifting and lowering.

[0018] Compared with the existing technology, the advantages and effects of this application are as follows:

[0019] 1. The smoke generating device of the present application can simultaneously meet the heating needs of solid smoke agent and smoke oil. By setting up a liquid reservoir and a material storage bin, the solid smoke agent and smoke oil heating spaces are independent and both can generate smoke stably. It has strong applicability and saves the cost of test equipment.

[0020] 2. This application installs a porous nozzle and a straight single-hole nozzle with fine nozzle holes at the outlet of the contraction section of the shell of the smoke generating device, so that the smoke can be sprayed from the surrounding and center of the outlet to achieve more uniform dispersion of the smoke, and each nozzle is provided with a switch valve to control the switch of the nozzle and the smoke output flow rate. According to the requirements of the experiment for the model airflow trajectory and the complex flow characteristics of different positions in the wind tunnel, the device of this application is well suited for wind tunnel visualization experiments: a stable smoke column is formed in the central area to ensure a significant tracing effect, and the porous nozzles on the surrounding areas can evenly diffuse the smoke to every corner to avoid local excessive concentration or thinness. The device of this application is suitable for experiments to study boundary layer flow fields.

[0021] 3. This application connects an electric telescopic rod that can receive remote terminal control signals to the bottom of the shell. During the experiment, the electric telescopic rod can be remotely raised and lowered according to the actual smoke conditions and flow paths, which has strong applicability. This technical feature can accurately adjust the electric telescopic rod to the set height position without the need for manual operation close to the wind tunnel, further improving safety and test efficiency. At the same time, it can realize visual observation of different parts of the model. By opening the nozzles at different angles, some key airflow phenomena can be accurately observed.

[0022] 4. This application features modular assembly and disassembly, adapting to different experimental models and equipment layouts. The removable generator cover facilitates inspection and disassembly of internal components. The threaded connection between the nozzles and the telescopic rod ensures tightness and structural stability, and the ability to replace nozzles with different apertures makes it suitable for scenarios requiring the generation of varying smoke particle sizes.

[0023] 5. The smoke generating device of this application is convenient for storage and transportation, has a wide range of applications, and has high comprehensive benefits. It meets the requirements of various wind tunnel visualization tests. The material burns more fully, and the smoke can be accurately and evenly released in a controllable manner around the model, clearly showing the flow of airflow in various parts. This application can be used to conduct wind tunnel visualization tests in many fields to help researchers understand the distribution situation; for example, in aerospace, smoke can be released from different parts of the aircraft to help optimize the appearance design; in automotive engineering, the airflow flow at different positions of the car model can be observed to help reduce wind resistance; in construction engineering, the smoke flow characteristics of the building bridge in the wind environment can be observed to help evaluate and analyze the wind-induced vibration characteristics, etc.

[0024] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application so that it can be implemented in accordance with the contents of the specification, and to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following is a detailed description of the preferred embodiment of the present application in conjunction with the accompanying drawings.

[0025] Based on the detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For those skilled in the art, other drawings can also be obtained based on these drawings without inventive work. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0027] in:

[0028] Figure 1 It is a three-dimensional diagram of a multifunctional and adjustable smoke generating device for a wind tunnel provided by the present application;

[0029] Figure 2 This is a top cross-sectional view of a multifunctional and adjustable smoke generating device for a wind tunnel provided by the present application;

[0030] Figure 3 This is a diagram of the internal structure of a multifunctional and adjustable smoke generating device for a wind tunnel provided by the present application;

[0031] Figure 4 This is a connection diagram of an electric telescopic rod of a multifunctional and adjustable smoke generating device for a wind tunnel provided by the present application;

[0032] Among them: 1. Liquid reservoir; 2. Storage bin; 3. Heater; 4. Temperature sensor; 5. Thermal insulation layer; 6. Power tube; 7. Shell; 8. Multi-hole nozzle; 9. Single-hole nozzle; 10. Electric telescopic rod; 11. Oil inlet; 12. Solid smoke agent inlet; 13. Generator cover; 14. Heating wire; 15. First cigarette outlet; 16. Second cigarette outlet; 17. First switch valve; 18. Second switch valve; 19. Internal threaded part; 20. External threaded part; 21. Threaded hole; 22. Bolt; 23. Sleeve. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, 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 part of the embodiments of the present application, rather than all of the embodiments. In the following description, specific details such as specific configurations and components are provided only to help fully understand the embodiments of the present application. Therefore, it should be clear to those skilled in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, for clarity and brevity, the description of known functions and structures has been omitted in the embodiments.

[0034] It should be understood that references throughout this specification to "one embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic associated with the embodiment is included in at least one embodiment of the present application. Therefore, the appearance of "one embodiment" or "this embodiment" throughout this specification does not necessarily refer to the same embodiment. Furthermore, these particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0035] In addition, the present application may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed.

[0036] The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist at the same time. The term " / and" in this article describes another type of association object relationship, indicating that there can be two relationships. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after are in an "or" relationship.

[0037] The term "at least one" in this article is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, at least one of A and B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0038] It should also be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprises," or any other variations thereof are intended to cover non-exclusive inclusion.

[0039] Example 1

[0040] This embodiment introduces a multifunctional and adjustable smoke generating device for a wind tunnel. Figure 1 , see the top cross-sectional view Figure 2 , please refer to the internal structure diagram Figure 3 The device includes a liquid reservoir 1, a storage bin 2, a heater 3, a temperature sensor 4, a thermal insulation layer 5, a power tube 6, a shell 7, a multi-hole nozzle 8, a single-hole nozzle 9, and an electric telescopic rod 10;

[0041] Preferably, the liquid reservoir 1, storage bin 2, heater 3, temperature sensor 4, insulation layer 5, and power tube 6 are all located inside the housing 7;

[0042] Preferably, there are two heaters 3, which are respectively arranged on both sides of the inside of the shell 7 near the entrance. The liquid reservoir 1 and the storage bin 2 are respectively connected to the inner sides of different heaters 3. The thermal insulation layer 5 is arranged on the surface of the heater 3. The temperature sensor 4 is arranged on the upper surface of the grain storage bin 2 and the liquid reservoir 1, and is used to detect the heated temperature of the liquid reservoir 1 and the storage bin 2, and adjust the smoke volume by temperature control to ensure stable smoke quality.

[0043] Preferably, there are two power pipes 6, which are respectively arranged on the sides of the liquid reservoir 1 and the storage bin 2;

[0044] Preferably, there are several porous nozzles 8 located around the outlet of the contraction section of the shell 7;

[0045] Preferably, the single-hole nozzle 9 is located at the center of the outlet of the contraction section of the shell 7;

[0046] Preferably, there are several electric telescopic rods 10 connected to the bottom of the shell 7.

[0047] The technical effect achieved by this embodiment is: by arranging multi-hole nozzles and single-hole nozzles, this embodiment can make the smoke spray out from the surrounding areas and the center of the outlet, so as to achieve more uniform dispersion of the smoke. By arranging temperature sensors on the upper surfaces of the grain storage bin and the liquid storage tank, the heating temperature of the liquid storage tank and the storage bin can be detected, and the smoke volume can be adjusted by temperature control to ensure stable smoke quality.

[0048] Example 2

[0049] Based on Example 1, this example further introduces a multifunctional and adjustable smoke generating device for a wind tunnel.

[0050] Preferably, the liquid reservoir 1 is a fixedly connected horizontal cylinder filled with tobacco liquid, with a tobacco liquid inlet 11 provided at one end and a first cigarette outlet 15 provided at the other end.

[0051] Preferably, the storage bin 2 is a fixedly connected horizontal cylinder, which contains solid smoke agent, such as smoke cakes; the end of the storage bin 2 with a larger diameter is provided with a solid smoke agent inlet 12, and the other end is provided with a second smoke outlet 16.

[0052] Preferably, the diameter of the smoke oil inlet 11 is smaller than that of the solid smoke agent inlet 12 .

[0053] Preferably, the heater 3 is provided with a heating wire 14 , which is spiral-shaped and located on the outer surfaces of the liquid reservoir 1 and the material storage bin 2 , for uniformly heating the smoke-generating agent.

[0054] Preferably, the heat insulating layer 5 is made of ceramic fiber material, which has good heat insulating effect, reduces internal heat loss, avoids relative interference between the liquid reservoir 1 and the material storage bin 2 during the heating process, and maintains the independence of the two.

[0055] Preferably, the porous nozzle 8 is made of ceramic fiber material, is threadedly connected to the periphery of the outlet of the contraction section of the shell 7, and is detachable; the porous nozzle 8 has a plurality of small nozzle holes, which can evenly spray smoke.

[0056] Preferably, one end of the two power tubes 6 is connected to one side of the liquid reservoir 1 and the material storage bin 2 respectively, and the other end passes through the shell 7 to connect to the external power equipment to help the smoke to be transported quickly.

[0057] Preferably, the smoke generating part of the shell 7 is a rectangular parallelepiped, the outlet part is in the shape of a quadrangular pyramid, an internal threaded part 19 is provided on the inner side of the top of the quadrangular pyramid, the other end of the shell 7 is a detachable generator cover 13, and a plurality of threaded holes 21 are provided on the bottom of the shell 7.

[0058] Preferably, the single-hole nozzle 9 is made of stainless steel, and an outer end thereof is provided with an external threaded member 20. The single-hole nozzle 9 is connected to the internal threaded member 19 on the inner side of the outlet of the housing 7 through the external threaded member 20 and can be disassembled.

[0059] Preferably, a first switch valve 17 is provided on each of the porous nozzles 8 to control the opening of each porous nozzle 8; a second switch valve 18 is provided on the single-hole nozzle 9 to control the opening and closing of the single-hole nozzle 9.

[0060] Preferably, several of the electric telescopic rods 10 include three-layer sleeves 23, which are screwed to the threaded holes 21 at the bottom of the housing 7 by bolts 22 and can be disassembled; the electric telescopic rods 10 are connected to the external terminal system to receive control signals, and can be remotely controlled to lift and lower. For the connection diagram of the electric telescopic rod 10, please refer to Figure 4 .

[0061] The technical effects achieved by this embodiment are as follows: this embodiment can meet the requirements of simultaneous heating of solid smoke agent and smoke oil, the spaces of the two are independent and both can stably generate smoke, it has strong applicability, and saves test equipment costs; by connecting an electric telescopic rod that can receive remote terminal control signals to the bottom of the shell, the electric telescopic rod can be accurately adjusted to a set height position, without the need for manual operation close to the wind tunnel, further improving safety and test efficiency; the device of this embodiment as a whole presents modular assembly and disassembly, and can adapt to different types of experimental models and equipment layouts.

[0062] Example 3

[0063] Based on Examples 1-2, this example further introduces a method for using a multifunctional and adjustable smoke generating device for a wind tunnel:

[0064] Step S1: Open the control terminal and initialize the electric telescopic rod 10 to ensure that the device is in normal working condition;

[0065] Step S2: Adjust the electric telescopic rod 10 to the height where the airflow streamline on the surface of the model needs to be studied, and open the switch valve of the corresponding nozzle according to the location of the model to be studied and the size of the smoke particles required;

[0066] Step S3: Select the smoke agent to be burned based on actual factors such as smoke characteristics and stability required by different wind tunnels, and add it to the corresponding liquid reservoir 1 or storage bin 2;

[0067] Step S4: The heater 3 is turned on to heat the smoke generating agent. The generated smoke is powered by the power tube 6 and is quickly transported to flow out through the opened multi-hole nozzle 8 or the central single-hole nozzle 9. At the same time, the temperature sensor 4 is monitored to detect and adjust the heating temperature of the liquid reservoir 1 and the storage bin 2 in real time to adjust the flow rate of the smoke oil and smoke.

[0068] During the use of the smoke generating device, the state of the airflow streamline should be observed in real time, and the electric telescopic rod 10 should be remotely operated on the control terminal to adjust the telescopic rod to the appropriate position in time to ensure that the smoke enters the wind tunnel flow field evenly and stably to avoid the smoke being too thick or too thin to affect the visualization effect.

[0069] The above description is only a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. Any changes, modifications, substitutions, integrations and parameter changes to these embodiments within the spirit and principles of the present invention shall fall within the scope of protection of the claims of the present invention.

Claims

1. A multifunctional and adjustable smoke generating device for a wind tunnel, characterized in that: It comprises a liquid reservoir (1), a material storage bin (2), a heater (3), a temperature sensor (4), a heat insulation layer (5), a power tube (6), a shell (7), a multi-hole nozzle (8), a single-hole nozzle (9), and an electric telescopic rod (10); The liquid reservoir (1), the material storage bin (2), the heater (3), the temperature sensor (4), the heat insulation layer (5), and the power tube (6) are all located inside the housing (7); There are two heaters (3), which are respectively arranged on both sides of the housing (7) near the entrance. The liquid reservoir (1) and the storage bin (2) are respectively connected to the inner sides of different heaters (3). The heat insulation layer (5) is arranged on the surface of the heater (3). The temperature sensor (4) is arranged on the upper surface of the grain storage bin (2) and the liquid reservoir (1). There are two power pipes (6), which are respectively arranged on the sides of the liquid reservoir (1) and the storage bin (2); There are a plurality of multi-hole nozzles (8) located around the outlet of the contraction section of the shell (7); the single-hole nozzle (9) is located at the center of the outlet of the contraction section of the shell (7); There are a plurality of electric telescopic rods (10) connected to the bottom of the housing (7).

2. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 1, characterized in that: The liquid reservoir (1) is a fixedly connected horizontal cylinder, which contains tobacco liquid, is provided with a tobacco liquid inlet (11) at one end, and a first tobacco outlet (15) at the other end.

3. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 2, characterized in that: The storage bin (2) is a fixedly connected horizontal cylinder with solid smoke agent inside. One end of the storage bin (2) is provided with a solid smoke agent inlet (12), and the other end is provided with a second smoke outlet (16).

4. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 3, characterized in that: The heater (3) is provided with a heating wire (14), which is spiral-shaped and located on the outer surfaces of the liquid reservoir (1) and the material storage bin (2).

5. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 4, characterized in that: The heat insulation layer (5) and the porous nozzle (8) are both made of ceramic fiber material.

6. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 5, characterized in that: One end of the two power tubes (6) is connected to one side of the liquid reservoir (1) and the material storage bin (2), respectively, and the other end passes through the shell (7) to be connected to the external power equipment.

7. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 1, characterized in that: The smoke generating portion of the shell (7) is a rectangular parallelepiped, the outlet portion is in the shape of a quadrangular pyramid, an internal threaded member (19) is provided on the inner side of the top end of the quadrangular pyramid, the other end of the shell (7) is a detachable generator cover (13), and a plurality of threaded holes (21) are provided on the bottom of the shell (7).

8. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 7, characterized in that: The single-hole nozzle (9) is made of stainless steel, and an external threaded part (20) is provided on the outer side of one end thereof.

9. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 3, characterized in that: A first switch valve (17) is provided on each of the plurality of multi-hole nozzles (8), and a second switch valve (18) is provided on the single-hole nozzle (9).

10. The multifunctional and adjustable smoke generating device for a wind tunnel according to claim 3, characterized in that: Several of the electric telescopic rods (10) include three-layer sleeves (23) and are connected to threaded holes (21) at the bottom of the housing (7) via bolts (22). The electric telescopic rods (10) are connected to an external terminal system.

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