An elevator maintenance aid
Patent Information
- Application Number
- CN202522235342.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-09-29
- Estimated Expiration
- 2035-10-22
AI Technical Summary
[0002]在电梯运行系统中，牵引钢丝绳作为连接机箱与对重的核心传动部件，其运行状态直接决定电梯的安全稳定性与使用寿命；牵引钢丝绳长期承受机箱重力、启停冲击力及电梯井内粉尘、油污侵蚀，易出现表面磨损、油污附着、局部锈蚀等问题——若未及时有效维护，轻则导致钢丝绳摩擦系数下降、传动效率降低，重则引发钢丝绳断丝、断股，甚至造成机箱坠落等重大安全事故；因此，定期对牵引钢丝绳进行清洁、检查与维护，是电梯运维体系中不可或缺的关键环节；
[0010]与现有技术相比，本实用新型的有益效果是：本实用新型通过第二电机与丝盘、滑移块的配合，驱动滑移块沿导向槽向牵引钢丝绳移动并实现稳固夹持，便于装置自主固定在钢丝绳上，无需工人手持或弯腰扶持，提高了作业安全性，进而能够实现装置脱离人工支撑的自主定位功能；再通过第三电机与转动轮、固定环的配合，带动固定环及清洁组件绕钢丝绳圆周转动，便于清洁组件覆盖钢丝绳所有表面包括背对工人的背面、侧面，提高了清洁全面性，进而能够实现无死角清洁功能；同时通过直线电机与钢索滑轮的配合，带动装置沿钢丝绳升降，无需工人频繁移动位置，提高了维护效率，通过隔膜泵与喷头的配合，自动喷洒清洁液，无需人工手动涂抹；最终解决了工人弯腰作业易发生安全事故、钢丝绳背对工人一面清洁遗漏的问题，进一步提升了操作便捷性，整体实现了牵引钢丝绳安全、全面、高效的维护。
Smart Images
Figure CN224812020U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of elevator maintenance technology, and in particular to an auxiliary device for elevator maintenance. Background Technology
[0002] In elevator operating systems, the traction wire rope, as the core transmission component connecting the car and the counterweight, directly determines the elevator's safety, stability, and service life. The traction wire rope is constantly subjected to the weight of the car, the impact of starting and stopping, and the corrosion from dust and oil in the elevator shaft, making it prone to surface wear, oil adhesion, and localized corrosion. If not maintained promptly and effectively, this can lead to a decrease in the wire rope's friction coefficient and transmission efficiency, or even cause wire or strand breakage, and in severe cases, lead to major safety accidents such as the car falling. Therefore, regular cleaning, inspection, and maintenance of the traction wire rope is an indispensable and crucial part of the elevator operation and maintenance system. Currently, the mainstream maintenance method for elevator traction cables is still mainly manual. The specific operation typically involves: first, stopping the elevator to ensure the traction cable is unloaded; then, workers enter the elevator shaft or the top of the machine and use simple tools such as rags and brushes to wipe away oil and dust from the cable surface. Since the traction cable is often suspended above the elevator shaft or the top of the machine, workers frequently need to bend over, look up, or even lean out while cleaning. The elevator shaft is a narrow space with no stable support platform, making it slippery and prone to falls and collisions. Accidents; prolonged bending over can also lead to lumbar strain in workers, increasing occupational health risks; at the same time, the rag can only cover the area of the wire rope that the worker can reach from the front. For the side of the wire rope that is not facing the worker (such as the back or side of the wire rope when it is suspended), it is difficult for the worker to apply the rag properly. Even if they try, it is easy to miss cleaning due to obstructed vision. In addition, the use of power tools can only clean the front. Oil and dust in these uncleaned areas will continue to accumulate, accelerating the wear and aging of the wire rope and creating safety hazards. Therefore, the above problems need to be improved. Utility Model Content
[0003] The purpose of this utility model is to address the shortcomings of existing technologies by proposing an auxiliary device for elevator maintenance.
[0004] To achieve the above objectives, this utility model adopts the following technical solution: an auxiliary device for elevator maintenance, comprising a main cylindrical body, a first support ring fixedly connected to the middle of the outer wall of the main cylindrical body, two fixed frames symmetrically arranged on the top surface of the first support ring, and a sliding groove opened on the top surface of the two fixed frames. A guide rail is installed in each of the sliding grooves, and a linear motor slides opposite to each other on the two guide rails. A mounting frame is fixedly connected to the top surface of the linear motor, and a steel cable pulley is rotatably arranged on the opposite surface of the two mounting frames. A first motor with a worm gear reducer is coaxially fixedly connected to one side of one of the two steel cable pulleys and mounted on the outer wall of the mounting frame. A guide is fixedly connected to the top of the main cylindrical body. The guide disc has three guide grooves on its top surface facing the axis of the main cylinder. A limiting cylinder is fixed to the inner wall of the guide disc. Each guide groove has a sliding block facing the axis of the main cylinder. The bottom ends of the three sliding blocks are engaged with a screw spool rotatably mounted on the inner wall of the main cylinder. A bevel gear surface is coaxially fixed to the bottom end of the screw spool. A second motor with its own bevel gear is engaged on one side of the bottom surface of the bevel gear surface. An annular groove is opened at the lower end of the outer wall of the main cylinder. Three rotating wheels are rotatably mounted in the annular groove. A fixed ring is rotatably mounted on the bottom surface of the three rotating wheels. Three mounting rods are fixedly mounted in a triangular arrangement on the outer circumference of the fixed ring. A cleaning component is provided at the lower end of the opposite face of each of the three mounting rods.
[0005] Preferably, one of the three rotating wheels is coaxially fixed to a third motor installed in a fixed ring, and a battery box is provided on the outer wall of the main cylinder.
[0006] Preferably, a storage box is fixed to the lower middle part of one of the three mounting rods on opposite sides, a nozzle is connected to the top surface of the storage box, and a diaphragm pump connected to the nozzle is provided on the top surface inside the storage box.
[0007] Preferably, the cleaning component includes three positioning screws that are respectively screwed onto three mounting rods. A vertical plate is rotatably connected to one end of each positioning screw facing the axis of the main cylinder. Two cleaning brushes are symmetrically provided on one end of the vertical plate.
[0008] Preferably, two limiting posts are symmetrically arranged on both sides of the opposite surface of the vertical plate and the mounting rod, and the mounting rod has limiting insertion holes corresponding to the insertion of the limiting post body.
[0009] Preferably, a limiting cylinder is coaxially fixed to the bottom end of the main cylinder, and a limiting ring groove is opened on the outer wall of the limiting cylinder. A limiting plate extending into the limiting ring groove is fixed to the opposite surface of the three mounting rods and the limiting ring groove.
[0010] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model, through the cooperation of a second motor, a wire disc, and a sliding block, drives the sliding block to move along the guide groove towards the traction wire rope and achieves stable clamping, facilitating the device's autonomous fixation on the wire rope without requiring workers to hold it or bend over for support, thus improving operational safety and enabling the device to achieve autonomous positioning without manual support. Furthermore, through the cooperation of a third motor, a rotating wheel, and a fixed ring, the fixed ring and cleaning components rotate around the circumference of the wire rope, facilitating the cleaning components to cover all surfaces of the wire rope, including the back and sides facing away from the worker, improving the comprehensiveness of cleaning and achieving a thorough cleaning function. Simultaneously, through the cooperation of a linear motor and a steel cable pulley, the device is driven to rise and fall along the wire rope, eliminating the need for frequent worker repositioning and improving maintenance efficiency. Through the cooperation of a diaphragm pump and a nozzle, cleaning fluid is automatically sprayed, eliminating the need for manual application. Ultimately, this solves the problems of workers bending over during operation and the potential for missed cleaning of the side of the wire rope facing away from the worker, further enhancing operational convenience and achieving safe, comprehensive, and efficient maintenance of the traction wire rope. Attached Figure Description
[0011] The accompanying drawings, which are included to provide a further understanding of the present invention and form part of this application, illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the present invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a first-view schematic diagram of the overall structure proposed in this utility model; Figure 2 This is a second-view schematic diagram of the overall structure proposed in this utility model; Figure 3 This is a schematic diagram of the overall structure of the cleaning component proposed in this utility model; Figure 4 This is a partial cross-sectional view of the storage box proposed in this utility model.
[0012] The components in the diagram are numbered as follows: 1. Main cylinder; 2. Fixing frame; 3. Steel cable pulley; 4. Threaded spool; 5. Linear motor; 6. Rotating wheel; 7. Cleaning brush; 8. Positioning screw; 9. Limiting post; 10. Storage box; 11. Third motor; 12. Nozzle. Detailed Implementation
[0013] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.
[0014] Example: See Figures 1 to 4This utility model discloses an auxiliary device for elevator maintenance, comprising a main cylindrical body 1. A first support ring is fixedly connected to the middle of the outer wall of the main cylindrical body 1. Two fixed frames 2 are symmetrically arranged on the top surface of the first support ring. The top surface of the two fixed frames 2 has a sliding groove, and a guide rail is installed in each of the sliding grooves. A linear motor 5 is slidably mounted on the two guide rails. A mounting frame is fixedly connected to the top surface of the linear motor 5. A steel cable pulley 3 is rotatably arranged on the opposite surface of the two mounting frames. A first motor with a worm gear reducer is coaxially fixed to one side of one of the two steel cable pulleys 3 and mounted on the outer wall of the mounting frame. A guide plate is fixedly connected to the top of the main cylindrical body 1. The top surface of the guide plate has three guide grooves facing the axis of the main cylindrical body 1. A limit cylinder is fixedly connected to the inner wall of the guide plate. Each of the guide grooves has a guide groove facing the axis of the main cylindrical body 1. The cylinder 1 has three sliding blocks at its core. The bottom ends of these three sliding blocks are engaged with a screw spool 4 rotatably mounted on the inner wall of the main cylinder 1. A bevel gear surface is coaxially fixed to the bottom end of the screw spool 4. A second motor with its own bevel gear is engaged on one side of the bottom surface of the bevel gear surface. An annular groove is formed at the lower end of the outer wall of the main cylinder 1, within which three rotating wheels 6 rotatably rotate. A fixing ring is rotatably mounted on the bottom surface of each of the three rotating wheels 6. Three mounting rods are fixed to the outer wall of the fixing ring in a triangular arrangement. Cleaning components are provided at the lower ends of the opposing surfaces of the three mounting rods. The main cylinder 1 is made of Q345 alloy steel, which has high structural strength and strong resistance to deformation, providing a stable mounting platform for all components. The first support ring and the fixing frame 2 are made of high-strength steel, with high hardness and good wear resistance, providing stable support for the linear motor 5 and the steel cable pulley. 3; The linear motor 5 adopts the FPB30 model linear motor, which features precise positioning and stable operation. It can drive the mounting frame and the steel cable pulley 3 to precisely adjust their positions and adapt to traction steel wire ropes of different diameters; The first motor adopts the Y2-80M1-2 model motor, which is equipped with a worm gear reducer to reduce speed and increase torque, ensuring the smooth rotation of the steel cable pulley 3; The screw spool 4 and the bevel gear surface are made of high-strength alloy material, with high tooth surface hardness and high transmission accuracy. The second motor adopts the RS-555 model motor, whose built-in bevel gear cooperates with the bevel gear surface at the bottom of the screw spool 4, which can drive the sliding block to precisely clamp the traction steel wire rope; The rotating wheel 6 is made of a material with a high coefficient of friction and good shock absorption effect, which can drive the fixed ring and the cleaning component to rotate smoothly; The above contents constitute the mounting frame. The basic framework provides core structural support for subsequent functions such as position adjustment, cleaning, and maintenance. One of the three rotating wheels 6 is coaxially fixed to a third motor 11 installed in a fixed ring. A battery box is located on the outer wall of the main cylinder 1. The third motor 11 is a 39BYG model stepper motor, which features controllable speed and smooth start and stop, and can precisely drive the rotating wheel 6 to rotate. The rotating wheel 6 and the third motor 11 are coaxially fixed, and the power transmission is lossless. It can drive the fixed ring to rotate at a constant speed around the axis of the main cylinder 1, thereby achieving a thorough circumferential coverage of the traction wire rope by the cleaning component and improving the comprehensiveness of cleaning. The fixed ring is made of lightweight and high-strength material, which can reduce the load on the rotating wheel 6 and extend the service life of the third motor 11.A storage box 10 is fixed to the lower middle part of one of the three mounting rods facing each other. A nozzle 12 is connected to the top surface of the storage box 10. A diaphragm pump connected to the nozzle 12 is located inside the top surface of the storage box 10. The storage box 10 is made of polyethylene, which is chemically resistant, lightweight, and can safely store elevator-specific cleaning fluid to meet the needs of a single maintenance. The diaphragm pump is a JET400 model, characterized by stable pressure and low noise, and can accurately deliver the pressurized cleaning fluid to the nozzle 12. The nozzle 12 is made of stainless steel, providing excellent atomization and evenly spraying the cleaning fluid onto the surface of the traction steel wire rope, wetting the oil and reducing cleaning resistance. This, combined with the cleaning components, enhances the cleaning effect while preventing waste of cleaning fluid.
[0015] In this utility model, the cleaning component includes three positioning screws 8 respectively screwed onto three mounting rods. A vertical plate is rotatably connected to one end of each positioning screw 8 facing the axis of the main cylinder 1. Two cleaning brushes 7 are symmetrically arranged on one end of the vertical plate. The positioning screws 8 are made of 304 stainless steel, offering good rust resistance and high thread precision, allowing for precise adjustment of the distance between the vertical plate and the traction steel wire rope through rotation. The vertical plate is made of ABS engineering plastic, which is lightweight and has good insulation, preventing damage caused by metal-to-metal friction with the steel wire rope. The bristles of the cleaning brushes 7 are made of nylon, offering good toughness and wear resistance, effectively removing impurities from the gaps in the steel wire rope without scratching its surface. The symmetrically arranged brushes allow for simultaneous cleaning from both sides, improving cleaning efficiency. Two limiting posts 9 are symmetrically arranged on the opposite sides of the vertical plate and mounting rods, with corresponding limiting insertion holes on the mounting rods for inserting portions of the limiting posts 9. The limiting posts 9 are made of 45# steel, offering high strength and resistance to deformation. The limit pin, in conjunction with the limiting holes on the mounting rods, restricts the movement direction of the vertical plate, preventing it from shifting or tilting during cleaning and ensuring uniform contact between the cleaning brush 7 and the wire rope surface. The smooth inner wall of the limiting pin reduces frictional resistance when the limiting post 9 slides, making the vertical plate adjustment smoother and preventing wear on the limiting post 9, thus extending the component's service life. A limiting cylinder is coaxially fixed to the bottom of the main cylinder 1, and a limiting ring groove is opened on the outer wall of the limiting cylinder. Limiting plates extending into the limiting ring groove are fixed to the opposite surfaces of the three mounting rods and the limiting ring groove. Both the limiting cylinder and the limiting plates are made of Q235 steel plate, which is structurally stable and has strong impact resistance. The limiting plates extending into the limiting ring groove restrict the radial movement of the mounting rods, preventing the cleaning component from shaking or shifting during circumferential rotation and ensuring stable cleaning operations. The inner wall of the limiting ring groove is polished to reduce frictional wear when the limiting plate rotates, improve the overall operational stability of the device, and meet the safety operation requirements during elevator maintenance.
[0016] Working principle: When using this utility model, the device is pre-installed during the elevator installation stage. Specifically, during elevator installation, the traction steel wire rope on the top surface of the machine box is inserted through the opening at the top of the main cylinder 1 of the device, passes through the main cylinder 1 and the limiting cylinder, so that the device can achieve initial suspension and positioning based on the steel wire rope. The device only contacts the steel wire rope and is not directly fixed to the top surface of the machine box. During pre-installation, the three sliding blocks are adjusted to the initial open state, and the sliding blocks are far away from the axis of the main cylinder 1 to avoid squeezing the traction steel wire rope. At the same time, the steel cable pulley 3, cleaning components and other components are initially aligned with the steel wire rope, laying the foundation for subsequent maintenance operations. When no maintenance is required, the steel wire rope is then inserted and the device is moved. When maintenance of the traction wire rope is required, the elevator car must first be moved to the bottom of the elevator shaft. At this time, the traction wire rope no longer bears the weight load of the car and is in a stress-free state. It must also be kept in a normal vertical position to provide safe operating space for subsequent device adjustment and maintenance, and to ensure that the cable pulley 3 can accurately engage with the wire rope, facilitating the subsequent lifting and lowering operation of the device along the wire rope via the cable pulley 3. Then, the second motor with its own bevel gear is started. The bevel gear of the second motor meshes with the bevel gear surface at the bottom of the spool 4, driving the bevel gear surface to rotate and thus driving the spool 4 to rotate on the inner wall of the main cylinder 1. Because the bottom ends of the three sliding blocks are engaged with the spool 4 and The guide plate is embedded in the guide groove facing the axis of the main cylinder 1. The rotation of the screw disc 4 will drive the three sliding blocks to move synchronously along the guide groove towards the traction wire rope until the inner wall of the sliding block is tightly attached to the outer wall of the traction wire rope. The device and the traction wire rope are firmly locked by three-point symmetrical clamping. At this time, the device is completely fixed by the clamping of the sliding block and the wire rope, and is released from the initial suspension state. At the same time, the limiting cylinder on the inner wall of the guide plate can limit the movement of the sliding block, avoid excessive compression of the sliding block and deformation of the traction wire rope, and ensure the safety and stability of the fixing process. Then, the position is adjusted and the linear motor 5 is started. The linear motor 5 slides in opposite directions along the guide rail in the slide groove of the fixing frame 2. Linear motor 5 drives the corresponding mounting bracket to move until the distance between the steel cable pulleys 3 on the opposite surfaces of the two mounting brackets is completely matched with the diameter of the traction steel wire rope and the groove of the steel cable pulley 3 is precisely fitted with the outer wall of the steel wire rope. Then, the first motor with worm gear reducer is started. The first motor drives one of the steel cable pulleys 3 to rotate. Through the cooperation of the two steel cable pulleys 3, the traction steel wire rope is further clamped. At this time, the steel cable pulley 3 can rely on the friction with the steel wire rope to drive the device to rise and fall along the vertical steel wire rope, realizing the movement of the device in different maintenance positions. The worm gear reducer can reduce the motor speed and increase the torque to ensure that the steel cable pulley 3 rotates smoothly and avoids slippage when the device is raised and lowered.To perform a thorough cleaning of the traction wire rope circumferentially, the third motor 11, installed within the fixed ring, is activated. The third motor 11 is coaxially fixed to one of the rotating wheels 6, causing the wheel 6 to rotate. Since the three rotating wheels 6 are embedded in the annular grooves on the outer wall of the main cylinder 1 and their bottom surfaces are rotatably connected to the fixed ring, the rotation of a single rotating wheel 6 will cause the fixed ring to rotate around the axis of the main cylinder 1. This axis of the main cylinder 1 is the axis of the traction wire rope, which in turn causes the three triangularly arranged mounting rods on the outer wall of the fixed ring and the cleaning components at their lower ends to move synchronously in a circular motion, thus achieving cleaning. The cleaning component provides comprehensive coverage around the traction wire rope, while the positioning screw 8 can be rotated according to the actual diameter deviation of the traction wire rope. The positioning screw 8 is screwed onto the mounting rod. Moving the positioning screw 8 axially along the mounting rod pushes a vertical plate rotatably connected to one end towards or away from the traction wire rope until the cleaning brush 7 on the vertical plate contacts the outer wall of the wire rope and maintains appropriate pressure. The pressure should be such that the brush bristles are slightly bent and do not damage the surface of the wire rope. The limiting posts 9 on both sides of the vertical plate slide synchronously along the limiting holes on the mounting rod, restricting the direction of movement of the vertical plate; this completes the position adjustment. After the holiday, the cleaning and maintenance phase begins. As the cleaning components move circumferentially with the fixed ring, the two cleaning brushes 7 on the vertical plate continuously rub against the outer wall of the traction wire rope. The brush bristles penetrate deep into the gaps on the surface of the wire rope to remove attached dust, oil, and metal debris. Simultaneously, the device can be slowly raised and lowered along the vertical wire rope via the steel cable pulley 3 to clean the wire rope at different heights. If the surface of the traction wire rope is heavily soiled with oil, the diaphragm pump on the top surface of the storage box 10 is activated. The diaphragm pump pressurizes the elevator-specific wire rope cleaning fluid in the storage box 10 and sprays it through the connected nozzle 12. The cleaning solution is sprayed onto the surface of the wire rope to moisten the oil and reduce cleaning resistance. The spraying and brush cleaning work in tandem. Throughout the maintenance process, the limiting ring groove at the bottom of the main cylinder 1 engages with the limiting plates on the three mounting rods. The limiting plates extend into the ring groove, restricting the radial movement of the mounting rods and preventing wobbling or displacement of the cleaning components during circumferential rotation. Simultaneously, the guide groove guides the sliding block, and the engagement of the limiting post 9 with the limiting insertion hole further ensures precise movement of each component, preventing component displacement due to the device's fixed-to-the-wire-rope positioning. At this point, the device is in use.
[0017] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.
Claims
1. An auxiliary device for elevator maintenance, comprising a main cylindrical body (1), characterized in that: A first support ring is fixed to the middle of the outer wall of the main cylinder (1). Two fixed frames (2) are symmetrically arranged on the top surface of the first support ring. The top surface of the two fixed frames (2) has a sliding groove. A guide rail is installed in each of the sliding grooves. A linear motor (5) is slidably arranged on the two guide rails. A mounting frame is fixed to the top surface of the linear motor (5). A steel cable pulley (3) is rotatably arranged on the opposite surface of the two mounting frames. A first motor with a worm gear reducer is coaxially fixed to one side of one of the two steel cable pulleys (3) and is mounted on the outer wall of the mounting frame. A guide plate is fixed to the top of the main cylinder (1). The top surface of the guide plate has three grooves facing the main cylinder (1). The guide groove of the shaft is fixedly connected to the inner wall of the guide disc with a limiting cylinder. Each guide groove is provided with a sliding block facing the shaft of the main cylinder (1). The bottom ends of the three sliding blocks are engaged with a screw disc (4) rotatably set on the inner wall of the main cylinder (1). The bottom end of the screw disc (4) is coaxially fixed with a bevel gear surface. A second motor with its own bevel gear is engaged on one side of the bottom surface of the bevel gear surface. An annular groove is opened at the lower end of the outer wall of the main cylinder (1). Three rotating wheels (6) are rotatably provided in the annular groove. A fixed ring is rotatably provided on the bottom surface of the three rotating wheels (6). Three mounting rods are fixedly arranged in a triangular pattern on the outer side of the fixed ring. A cleaning component is provided at the lower end of the opposite face of the three mounting rods.
2. The auxiliary device for elevator maintenance according to claim 1, characterized in that: One of the three rotating wheels (6) is coaxially fixed to a third motor (11) installed in a fixed ring, and a battery box is provided on the outer wall of the main cylinder (1).
3. The auxiliary device for elevator maintenance according to claim 2, characterized in that: A storage box (10) is fixed to the lower end of the middle of one of the three mounting rods on opposite sides. A nozzle (12) is connected to the top surface of the storage box (10). A diaphragm pump connected to the nozzle (12) is provided on the top surface of the storage box (10).
4. The auxiliary device for elevator maintenance according to claim 3, characterized in that: The cleaning assembly includes three positioning screws (8) that are screwed onto three mounting rods respectively. One end of the positioning screw (8) facing the axis of the main cylinder (1) is rotatably connected to a vertical plate. Two cleaning brushes (7) are symmetrically provided on one end of the vertical plate.
5. The auxiliary device for elevator maintenance according to claim 4, characterized in that: Two limiting posts (9) are symmetrically provided on both sides of the opposite face of the vertical plate and the mounting rod. The mounting rod has a limiting insertion hole for the corresponding insertion part of the limiting post (9).
6. The auxiliary device for elevator maintenance according to claim 5, characterized in that: The bottom end of the main cylinder (1) is coaxially fixed to a limiting cylinder. A limiting ring groove is opened on the outer wall of the limiting cylinder. The three mounting rods are all fixed to the opposite surfaces of the limiting ring groove with limiting plates extending into the limiting ring groove.