A magnetic adsorption wall-climbing robot based on multi-degree-of-freedom flexible hinge connection

Abstract

This utility model discloses a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection, belonging to the field of wall-climbing robot technology. It includes a control component comprising a sealed protective shell, inside which a control unit, a power supply unit, and a wireless charging receiver are installed. A front support unit and a rear support unit are respectively sealed and connected to the front and rear sides of the sealed protective shell via flexible joints. Independent suspension components are provided on both sides of the front and rear support units, and waterproof drive motors are fixed to the bottom of each independent suspension component. The power input terminals of the waterproof drive motors are electrically connected to the control unit via waterproof wires, and each waterproof drive motor's power output terminal is connected to a magnetic wheel body. This utility model features adaptive adhesion to large-curvature walls to prevent detachment, stable adsorption during obstacle crossing, and high magnetic energy utilization, making it suitable for operations on complex metal walls of ships.

Description

Technical Field

[0001] This utility model relates to the field of wall-climbing robot technology, and in particular to a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection. Background Technology

[0002] Existing magnetic adsorption wall-climbing robots mostly adopt tracked or four-wheeled rigid chassis structures. This integral rigid frame has the following three major technical drawbacks in actual ship operations:

[0003] (1) Poor surface adaptability (fitting problem):

[0004] The chassis of existing robots is a rigid integral structure that cannot adapt to dynamic deformation. When the robot operates on surfaces with large curvature, such as the bow or bulbous bow, the rigid chassis cannot conform to the curvature of the hull, resulting in gaps between the magnetic adsorption unit and the steel plate surface (i.e., the "suspended" phenomenon). The effective contact area between the magnetic wheel and the hull is drastically reduced, making it extremely easy for the robot to detach.

[0005] (2) Insufficient obstacle crossing stability (weld problem):

[0006] The hull surface is generally covered with welds and rivets with a height of 3-5mm. For tracked or rigid wheeled robots, when a single pivot point contacts a protruding obstacle such as a weld, the entire chassis will be rigidly lifted due to the lack of independent suspension cushioning (lever effect). This will cause the remaining magnetic adsorption points to detach from the wall instantly, and the magnetic attraction force will drop to zero in an instant, directly causing the robot to fall into the sea.

[0007] (3) Low magnetic energy utilization and load limitation (weight problem):

[0008] To compensate for the unstable adsorption caused by the rigid structure, existing designs often resort to the passive method of blindly increasing the mass of the magnets to prevent them from falling. This approach significantly increases the robot's dead weight (self-weight), resulting in low magnetic force utilization of the system. Under the same magnetic attraction force, the robot's effective payload capacity is actually greatly reduced. Utility Model Content

[0009] The purpose of this invention is to provide a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection, which can achieve adaptive fitting and anti-fall-off operation on curved surfaces, improve wall-climbing stability, and solve the core pain points of traditional rigid wall-climbing robots.

[0010] To achieve the above objectives, this utility model provides a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection, including a control component. The control component includes a sealed protective shell, inside which a control unit and a power supply unit are installed. A wireless charging receiver electrically connected to the power supply unit is installed on the inner wall of the sealed protective shell. A front support unit and a rear support unit are respectively sealed and connected to the front and rear sides of the sealed protective shell through flexible connecting joints. Independent suspension components are provided on both sides of the front and rear support units. A waterproof drive motor is fixed to the bottom of each independent suspension component. The power input terminal of the waterproof drive motor is electrically connected to the control unit through a waterproof wire. Each power output terminal of the waterproof drive motor is connected to a magnetic wheel body.

[0011] Preferably, the flexible connecting joint includes a universal adjustment assembly, and the two ends of the universal adjustment assembly are respectively connected to a first connecting rod and a second connecting rod.

[0012] Preferably, the flexible connecting joint further includes a corrugated tube sheath covering the outside of the universal adjustment assembly, the first connecting rod, and the second connecting rod, and the inner side of the corrugated tube sheath is provided with a wire passage.

[0013] Preferably, the universal adjustment assembly is at least one of a ball joint, a universal joint, a damping spring joint, and a flexible rubber connector.

[0014] Preferably, a front laser cleaner is provided at the bottom of the front support unit, and a rear laser cleaner is provided at the bottom of the rear support unit; both the front and rear laser cleaners are electrically connected to the control unit via wires.

[0015] Preferably, both the front and rear support units have vertically downward hollow connecting rods fixed to their bottoms, and electromagnets are fixed to the bottoms of the hollow connecting rods. The electromagnets are electrically connected to the control unit through wires passing through the hollow connecting rods.

[0016] Preferably, the independent suspension assembly includes a fixing plate and a fixing rod fixed to both sides of the front and rear load-bearing units, with the fixing rod located below the fixing plate; an L-shaped connecting block is fixedly connected to the bottom of the outer side of the fixing plate, a spring rod is rotatably fixed to the L-shaped connecting block, a connecting plate is fixedly connected to the bottom of the spring rod, and one side of the connecting plate is rotatably fixed to the fixing rod via a connecting rotating rod; the waterproof drive motor is fixed to the bottom of the connecting plate.

[0017] Preferably, two sets of spring rods are symmetrically arranged on the front and rear sides of the L-shaped connecting block. The tops of the two sets of spring rods are rotatably fixed to the L-shaped connecting block, and a connecting plate is fixedly connected to the bottom of each set of spring rods. Each connecting plate is symmetrically connected to the fixed rod through a connecting rotating rod, and the waterproof drive motor is fixed to the bottom of each connecting plate.

[0018] Preferably, the magnetic wheel body includes a magnetic wheel housing, and permanent magnet units are encapsulated in a Hellbeck array arrangement near the outer edge of the magnetic wheel housing. All the permanent magnet units are configured to converge magnetic field lines on the side of the magnetic wheel body facing the working wall and shield the magnetic field on the side facing away from the working wall.

[0019] Preferably, a protective rim with a thickness of 1-2 mm is provided on the outer surface of the rim of the magnetic wheel housing.

[0020] Therefore, the beneficial effects of this utility model using the above-mentioned magnetic adsorption wall-climbing robot based on multi-degree-of-freedom flexible hinge connection are as follows:

[0021] (1) The present invention significantly reduces the phenomenon of magnetic wheel suspension that is prone to occur in rigid chassis through the connection structure of multi-degree-of-freedom flexible connection joint, maximizes the effective contact area between magnetic wheel and working wall, significantly reduces the risk of adsorption failure and robot fall off due to poor fit, and improves the reliability of complex curved surface operation.

[0022] (2) Each magnetic wheel body is equipped with an independent suspension component, which ensures the continuity and stability of the magnetic attraction force of the whole machine during obstacle crossing and solves the industry pain point that traditional rigid chassis robots are prone to falling into the sea when crossing obstacles; at the same time, it is equipped with an electrically adjustable auxiliary electromagnet, which can dynamically adjust the auxiliary attraction force according to the working scenario, further enhancing the anti-fall capability under extreme working conditions.

[0023] (3) The magnetic wheel body of this utility model adopts a Heilbeck array to arrange permanent magnet units, which can force the magnetic field lines to converge towards the working wall side and shield the magnetic field on the non-working side, thus greatly improving the single-sided magnetic attraction force compared with ordinary arrays. This design abandons the traditional passive solution of blindly increasing the mass of magnets to compensate for the attraction force. Under the same attraction force requirement, it greatly reduces the amount of permanent magnets used, reduces the robot's weight, achieves the optimal ratio of attraction force to weight, significantly improves the robot's effective load-bearing capacity, and expands the compatibility of the work equipment.

[0024] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the overall structure of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model;

[0026] Figure 2 This is a schematic diagram of the control component of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model;

[0027] Figure 3 This is a schematic diagram of a curved surface operation of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model;

[0028] Figure 4 This is a schematic diagram of the flexible connection joint of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model;

[0029] Figure 5 This is a schematic diagram of the independent suspension component of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model;

[0030] Figure 6 This is a schematic diagram of the magnetic wheel body of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model;

[0031] Figure 7 This is a schematic diagram of the bottom structure of the front bearing unit of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model;

[0032] Figure 8 This is a schematic diagram of the bottom structure of the rear support unit of an embodiment of a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to this utility model.

[0033] Figure Labels

[0034] 1. Control component; 11. Sealed protective housing; 12. Control unit; 13. Power supply unit; 14. Wireless charging receiver; 2. Flexible connecting joint; 21. Universal adjustment component; 22. First connecting rod; 23. Second connecting rod; 24. Corrugated pipe sheath; 25. Threading channel; 3. Front bearing unit; 31. Front laser cleaner; 4. Rear bearing unit; 41. Rear laser cleaner; 5. Independent suspension component; 51. Fixing plate; 52. L-shaped connecting block; 53. Spring rod; 54. Connecting plate; 55. Fixing rod; 56. Connecting rotating rod; 6. Magnetic wheel body; 61. Magnetic wheel housing; 62. Permanent magnet unit; 63. Protective wheel rim; 7. Waterproof drive motor; 8. Waterproof wire; 9. Hollow connecting rod; 10. Electromagnet. Detailed Implementation

[0035] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0036] Unless otherwise defined, the technical or scientific terms used in this utility model shall have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains. The terms "first," "second," and similar terms used in this utility model do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0037] Example 1:

[0038] like Figure 1 As shown, this utility model provides a magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection, including a control component 1, such as... Figure 2 As shown, the control component 1 includes a sealed protective housing 11. Inside the sealed protective housing 11 are a control unit 12 and a power supply unit 13. The sealed protective housing 11 effectively provides installation space and waterproofing for the internal control unit 12 and power supply unit 13, effectively preventing internal electrical components from getting damp and thus improving the robot's lifespan. A wireless charging receiver 14, electrically connected to the power supply unit 13, is installed on the inner wall of the sealed protective housing 11. This allows for wireless charging of the robot, reducing the need for charging interfaces and further improving waterproofing performance during underwater operations. The control unit 12 is equipped with a wireless signal transmission element, enabling remote control of the robot by the operator.

[0039] The front and rear sides of the sealed protective housing 11 are respectively sealed and connected to the front support unit 3 and the rear support unit 4 via flexible connecting joints 2, providing installation positions for the required equipment. Independent suspension assemblies 5 are provided on both sides of the front support unit 3 and the rear support unit 4. A waterproof drive motor 7 is fixed to the bottom of each independent suspension assembly 5. The power input terminal of the waterproof drive motor 7 is electrically connected to the control unit 12 via a waterproof wire 8. Each waterproof drive motor 7 has a magnetic wheel body 6 connected to its power output terminal.

[0040] The flexible connecting joint 2 allows the front bearing unit 3 and the rear bearing unit 4 to adaptively deflect (e.g., forming an angle of 0-15°) when the robot operates on surfaces with large curvatures such as the bow and bulbous bow. This ensures that the magnetic wheel body 6 always fits tightly against the wall along the normal direction, maximizing the effective magnetic contact area and effectively preventing detachment accidents caused by the chassis being suspended. Figure 3 As shown.

[0041] like Figure 4 As shown, the flexible connecting joint 2 includes a universal adjustment assembly 21. A first connecting rod 22 and a second connecting rod 23 are connected to both ends of the universal adjustment assembly 21, the first connecting rod 22, and the second connecting rod 23. A corrugated sleeve 24 is located outside the universal adjustment assembly 21, the first connecting rod 22, and the second connecting rod 23. A wire-passing channel 25 is provided on the inner side of the corrugated sleeve 24. The universal adjustment assembly 21 is at least one of a ball joint, a universal joint, a damping spring joint, and a flexible rubber connector. In this embodiment, the universal adjustment assembly 21 is a universal joint.

[0042] The front support unit 3 is connected to the control component 1 by means that the first connecting rod 22 and the second connecting rod 23 are rigidly connected to the front support unit 3 and the sealed protective housing 11 respectively, and are hinged by the universal adjustment component 21, which can achieve flexible directional adjustment. The corrugated sleeve 24 can provide sealing and protection for the first connecting rod 22, the universal adjustment component 21 and the second connecting rod 23. The wiring channel 25 is filled with wires. Waterproof wiring holes are opened on the front support unit 3 and the sealed protective housing 11, located inside the corrugated sleeve 24 and matching the wiring channel 25, so that the wires of the electrical devices on the front support unit 3 can be electrically connected to the control unit 12 through the wiring channel 25.

[0043] Similarly, the rear support unit 4 is connected to the control component 1 by means that the first connecting rod 22 and the second connecting rod 23 are rigidly connected to the sealed protective housing 11 and the rear support unit 4, respectively. The wires of the electrical components located on the rear support unit 4 can also be electrically connected to the control unit 12 through the corresponding wiring channels 25. In addition, waterproof wires 8 at different locations are also passed through waterproof sealing interfaces in adjacent support units and electrically connected to the control unit 12 through the corresponding wiring channels 25.

[0044] like Figure 1 and Figure 5 As shown, the independent suspension assembly 5 includes a fixing plate 51 and a fixing rod 55, both fixed on both sides of the front bearing unit 3 and the rear bearing unit 4. The fixing rod 55 is located below the fixing plate 51, so that the upper part of the entire independent suspension assembly 5 is fixed by the fixing plate 51 and the lower part of the entire independent suspension assembly 5 is fixed by the fixing rod 55, which can provide a stable fixed position for the entire independent suspension assembly 5.

[0045] An L-shaped connecting block 52 is fixedly connected to the bottom of the outer side of the fixed plate 51. Two sets of spring rods 53 are symmetrically connected to the L-shaped connecting block 52 by rotation. A connecting plate 54 is fixedly connected to the bottom of each set of spring rods 53. Each connecting plate 54 is symmetrically connected to the fixed rod 55 by a connecting rotating rod 56, so that two independent suspension components 5 are connected to each fixed plate 51 and fixed rod 55.

[0046] Since each connecting plate 54 has a waterproof drive motor 7 fixed to its bottom, and each waterproof drive motor 7 has a magnetic wheel body 6 connected to its power output end, each side of the front bearing unit 3 and the rear bearing unit 4 is connected to two magnetic wheel bodies 6, which can greatly improve the stability of the robot adhering to the surface of the ship. Moreover, by adopting the structure of the aforementioned independent suspension assembly 5, and through the rotational fixing method of the spring rod 53 and the connecting rotating rod 56, the magnetic wheel body 6 can move up and down or back and forth within a certain range under the action of the pre-tension force provided by the spring rod 53, which is beneficial for better adhesion to the wall surface during the robot's movement.

[0047] When one of the robot's magnetic wheel bodies 6 encounters a protruding obstacle such as a weld (3-5mm high) or rivet on the hull surface, the connecting rod 56 swings upward due to the ground reaction force, compressing the spring rod 53 and causing the magnetic wheel body 6 to rise independently to "swallow" the obstacle's height. During this process, the corresponding load-bearing unit remains stable and is not lifted as a whole. Because each suspension works independently, the other three wheels remain tightly attached to the flat wall surface under the action of their own elastic reset components, ensuring the continuity and stability of the robot's magnetic attraction and completely eliminating the risk of the entire robot falling off due to a single point of lifting.

[0048] To further improve the magnetic attraction effect, in this embodiment, a vertically downward hollow connecting rod 9 is fixed at the bottom of both the front bearing unit 3 and the rear bearing unit 4. An electromagnet 10 is fixed at the bottom of the hollow connecting rod 9. The fixed position of the electromagnet 10 is slightly smaller than the closest distance between the bottom of the magnetic wheel body 6 and the corresponding bearing unit, so as to avoid the hollow connecting rod 9 and the electromagnet 10 from causing obstruction during the movement, and can provide the magnetic attraction force to the maximum extent.

[0049] The electromagnet 10 passes through the corresponding bearing unit via a wire threaded inside the hollow connecting rod 9 and is electrically connected to the control unit 12 through the corresponding wiring channel 25. The control unit 12 controls the energizing state of the electromagnet 10. When the robot is in a position where it is more likely to fall, the control unit 12 can increase the power supply to the electromagnet 10, thereby increasing the adhesion force and helping the robot adhere better to the ship's hull. When the robot is in a position where it is less likely to fall, the control unit 12 can reduce the power supply to the electromagnet 10, thereby achieving energy saving.

[0050] like Figure 6 As shown, the magnetic wheel body 6 includes a magnetic wheel housing 61. Permanent magnet units 62 are encapsulated in a Hellbeck array near the outer edge of the magnetic wheel housing 61. All permanent magnet units 62 are configured to converge magnetic field lines on the side of the magnetic wheel body 6 facing the working wall, and shield the magnetic field on the side facing away from the working wall. This structure forces the magnetic field lines to converge towards the working surface (hull side), increasing the single-sided magnetic attraction force by approximately 30% compared to ordinary arrays. While providing the same attraction force, it significantly reduces the amount of permanent magnets used, lowering the robot's weight and thus significantly improving the payload capacity. Furthermore, a protective rim 63 with a thickness of 1-2 mm is provided on the outer surface of the rim of the magnetic wheel housing 61. This ensures that the magnetic wheel body 6 is in the near-field range of strongest magnetic force, avoids direct friction between the magnetic wheel body 6 and the hull paint, protects the expensive anti-corrosion coating from scratches, and also reduces wear on the magnetic wheel itself, thus extending the service life of the equipment.

[0051] In addition, such as Figure 7 and Figure 8 As shown, a front laser cleaner 31 is installed at the bottom of the front support unit 3, and a rear laser cleaner 41 is installed at the bottom of the rear support unit 4. Both the front laser cleaner 31 and the rear laser cleaner 41 are electrically connected to the control unit 12 through wires passing through the wiring channel 25 in the corresponding support unit. When it is necessary to clean or remove rust from a certain part of the hull, the front laser cleaner 31 or the rear laser cleaner 41 can be activated by the control unit 12, and the required task can be completed as the robot moves.

[0052] Therefore, this utility model adopts the above-mentioned magnetic adsorption wall-climbing robot based on multi-degree-of-freedom flexible hinge connection. Through the three-segment hinge structure of the multi-degree-of-freedom flexible hinge, it achieves adaptive fitting to large curvature walls and avoids the risk of falling off. Combined with a single-wheel independent suspension component, it ensures the stability of obstacle crossing under protruding working conditions such as weld seams. The use of Heilbeck array magnetic wheels greatly improves the utilization rate of magnetic energy, and achieves a dual improvement in robot weight reduction and effective load capacity. It systematically solves the three core technical defects of traditional rigid magnetic adsorption wall-climbing robots.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solution of this utility model, and these modifications or equivalent substitutions cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of this utility model.

Claims

1. A magnetic adsorption wall-climbing robot based on multi-degree-of-freedom flexible hinge connections, characterized in that: The system includes a control component comprising a sealed protective housing. A control unit and a power supply unit are installed inside the sealed protective housing. A wireless charging receiver electrically connected to the power supply unit is installed on the inner wall of the sealed protective housing. A front support unit and a rear support unit are respectively sealed and connected to the front and rear sides of the sealed protective housing via flexible connecting joints. Independent suspension assemblies are provided on both sides of the front and rear support units. A waterproof drive motor is fixed to the bottom of each independent suspension assembly. The power input terminal of the waterproof drive motor is electrically connected to the control unit via a waterproof wire. Each waterproof drive motor's power output terminal is connected to a magnetic wheel body.

2. The magnetic adsorption wall-climbing robot based on multi-degree-of-freedom flexible hinge connection according to claim 1, characterized in that: The flexible connecting joint includes a universal adjustment assembly, with a first connecting rod and a second connecting rod connected to each end of the universal adjustment assembly.

3. The magnetic adsorption wall-climbing robot based on multi-degree-of-freedom flexible hinge connection according to claim 2, characterized in that: The flexible connecting joint also includes a corrugated tube sheath covering the outside of the universal adjustment assembly, the first connecting rod, and the second connecting rod, and the inner side of the corrugated tube sheath is provided with a wire passage.

4. The magnetic adsorption wall-climbing robot based on multi-degree-of-freedom flexible hinge connection according to claim 2, characterized in that: The universal adjustment assembly is at least one of a ball joint, a universal joint, a damping spring joint, and a flexible rubber connector.

5. A magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to claim 1, characterized in that: A front laser cleaner is installed at the bottom of the front support unit, and a rear laser cleaner is installed at the bottom of the rear support unit; both the front and rear laser cleaners are electrically connected to the control unit via wires.

6. A magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to claim 5, characterized in that: Both the front and rear support units have vertically downward hollow connecting rods fixed to their bottoms. An electromagnet is fixed to the bottom of each hollow connecting rod, and the electromagnet is electrically connected to the control unit through a wire passing through the hollow connecting rod.

7. A magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to claim 1, characterized in that: The independent suspension assembly includes a fixing plate and a fixing rod, both fixed to both sides of the front and rear load-bearing units, with the fixing rod located below the fixing plate. An L-shaped connecting block is fixedly connected to the bottom of the outer side of the fixing plate, and a spring rod is rotatably fixed to the L-shaped connecting block. A connecting plate is fixedly connected to the bottom of the spring rod, and one side of the connecting plate is rotatably fixed to the fixing rod via a connecting rotating rod. The waterproof drive motor is fixed to the bottom of the connecting plate.

8. A magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to claim 7, characterized in that: Two sets of spring rods are symmetrically arranged on the front and rear sides of the L-shaped connecting block. The tops of the two sets of spring rods are rotatably fixed to the L-shaped connecting block, and the bottoms of the two sets of spring rods are each fixedly connected to a connecting plate. Each connecting plate is symmetrically connected to the fixed rod through a connecting rotating rod, and the bottom of each connecting plate is fixed with the waterproof drive motor.

9. A magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to claim 1, characterized in that: The magnetic wheel body includes a magnetic wheel housing. Permanent magnet units are encapsulated in a Helbeck array near the outer edge of the magnetic wheel housing. All the permanent magnet units are configured to converge magnetic field lines on the side of the magnetic wheel body facing the working wall and shield the magnetic field on the side facing away from the working wall.

10. A magnetic adsorption wall-climbing robot based on a multi-degree-of-freedom flexible hinge connection according to claim 9, characterized in that: The outer surface of the magnetic wheel housing is provided with a protective rim with a thickness of 1-2 mm.

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