Detection equipment for identifying surface damage of gearbox part of railway vehicle

Abstract

The invention belongs to the technical field of railway vehicles, and relates to detection equipment for surface damage identification of railway vehicle gearbox parts. The first mechanical arm is used for taking and placing the gearbox parts on the material storing and taking frame; the damage detection camera is used for carrying out surface damage detection on the gearbox part; and a transportation assembly. The first mechanical arm can be used for driving the mechanical arm to grab the gearbox part, the gearbox part is conveyed to the damage detection camera through the conveying assembly to be subjected to damage detection, automatic treatment of the surface damage detection process of the railway vehicle gearbox part is achieved, the detection efficiency is remarkably improved, manual intervention and personal errors are reduced, and the detection efficiency is improved. And meanwhile, through cooperation of the first mechanical arm, the second mechanical arm and the damage detection camera, the surface damage of the part can be accurately recognized and judged, the omission ratio and the false detection ratio are effectively reduced, and the reliability of the detection result is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rail vehicles and relates to a detection device for identifying surface damage of rail vehicle gearbox parts. Background Art

[0002] In modern rail transit, rail vehicle gearboxes, as core components of the vehicle's transmission system, perform crucial functions, including power transmission and speed regulation. Their operating status directly impacts train safety and efficiency. Gearbox parts are constantly exposed to complex conditions of high loads and high speeds, leaving them susceptible to surface damage such as wear, cracks, and corrosion. If these damages are not promptly detected and addressed, they can lead to transmission failure, operational malfunctions, and even accidents. Therefore, accurately identifying surface damage on gearbox parts is crucial for ensuring safe and stable train operation.

[0003] Currently, surface damage detection for rail vehicle gearbox parts primarily relies on traditional manual inspection methods, where inspectors examine the surface of parts through visual observation, tactile perception, or the use of simple tools. However, this method has many limitations: First, manual inspection is inefficient, and when dealing with a large number of parts, the inspection cycle is long, making it difficult to meet the demand for efficient inspection brought about by the rapid development of the rail transit industry. Second, inspection results are significantly influenced by subjective factors such as the inspector's experience and technical level. Different inspectors may have different judgment criteria for the same damage, reducing detection accuracy. Furthermore, manual inspection has limited ability to identify minor damage and damage to hidden areas, resulting in a high rate of missed detections. Summary of the Invention

[0004] The purpose of the present invention is to provide a detection device for identifying surface damage of rail vehicle gearbox parts, which can reduce the detection cycle, improve the detection efficiency, improve the detection accuracy and reduce the missed detection rate.

[0005] To achieve the above objectives, the present invention provides the following technical solutions: A detection device for identifying surface damage of rail vehicle gearbox parts, comprising: Storage rack, the upper part is used to store gearbox parts; The first robotic arm is used to pick up and place gearbox parts on the storage rack; Damage detection camera, used to detect surface damage on gearbox parts; The second robotic arm, whose mobile end is connected to the damage detection camera, is used to drive the damage detection camera to move around the gearbox parts; The transport assembly has a first position and a second position, and is used to transport the gearbox part to the second position after the first robotic arm places the gearbox part at the first position of the transport assembly, so as to facilitate the damage detection camera to perform surface damage detection, and after completing the surface damage detection, transport the gearbox part from the second position to the first position, and reset the gearbox part through the first robotic arm.

[0006] The present invention is also characterized in that: The movable end of the first robotic arm is provided with a robotic arm, and the movable end of the first robotic arm and the robotic arm are connected via a first rotary joint. The first rotary joint is used to drive the robotic arm to rotate to adjust the angle of the robotic arm to grab the gearbox parts.

[0007] The manipulator is a pneumatic manipulator that uses compressed air as a power source. A first pneumatic control valve is provided on the manipulator, which is used to open and cut off the compressed air to control the opening and closing of the manipulator.

[0008] The transport components include: The transport platform is arranged between the first robotic arm and the second robotic arm; A pneumatic part-fixing clamp is installed on the transport platform. The pneumatic part-fixing clamp uses compressed air as a power source. A second pneumatic control valve is provided on the pneumatic part-fixing clamp. The second pneumatic control valve is used to open and cut off the compressed air to control the opening and closing of the pneumatic part-fixing clamp, thereby clamping the gearbox parts. The pneumatic linear actuator is arranged on the transport platform and along the length direction of the transport platform. The linear actuator has a moving end, which is connected to the pneumatic part fixing clamp. The linear actuator uses compressed air as a power source. A third dynamic control valve is respectively provided at both ends of the linear actuator. The two third dynamic control valves are used to respectively open and cut off the compressed air at both ends of the linear actuator to control the moving direction of the moving end of the pneumatic linear actuator.

[0009] The storage and retrieval racks include: base; The material storage plate is tilted and arranged on the upper part of the base. The lower part of the material storage plate is hinged to the upper part of the base. A plurality of parts storage holes are evenly opened on the material storage plate. At least one adjusting rod is arranged between the material storage plate and the base, the upper end of the adjusting rod is hinged to the material storage plate, and the lower end of the adjusting rod is detachably connected to the base.

[0010] Universal wheels are located near the four corners of the base, and rotary locks are located on both sides of the base. These locks are used to lock the base in place after it stops moving. A limit switch is located on the side of the base near the first robotic arm, and a baffle is vertically installed near the limit switch. A U-shaped mobile support rod is located on the top of the base, away from the limit switch, with both ends connected to the top of the base.

[0011] The damage detection camera is a Hikvision robot machine vision CCD detection all-in-one machine.

[0012] It also includes a protective fence, and the storage and retrieval rack, gripping components, identification components and transportation components are all arranged inside the protective fence.

[0013] The detection equipment for identifying surface damage of rail vehicle gearbox parts of the present invention has the following advantages: the present invention can use the first robotic arm to drive the manipulator to grab the gearbox parts through the cooperation of the storage and retrieval rack, the first robotic arm, the damage detection camera, the second robotic arm and the transportation component, and transport the gearbox parts to the damage detection camera for damage detection through the conveying component, thereby realizing the automated processing of the surface damage detection process of rail vehicle gearbox parts, significantly improving the detection efficiency, reducing manual intervention and human errors, and improving the detection accuracy. At the same time, the coordinated cooperation of the first robotic arm, the second robotic arm and the damage detection camera can accurately identify and judge the surface damage of the parts, effectively reducing the missed detection rate and the false detection rate, and improving the reliability of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0015] Figure 2 It is a main structural schematic diagram of the present invention.

[0016] Figure 3 It is a structural diagram of the identification component in the present invention.

[0017] Figure 4 It is a structural diagram of the grabbing component in the present invention.

[0018] Figure 5 Schematic diagram of the structure of the manipulator in the present invention.

[0019] Figure 6 Schematic diagram of the structure of the transport component in the present invention.

[0020] Figure 7 A schematic structural diagram of the pneumatic part fixing clamp in the present invention.

[0021] Figure 8A schematic structural diagram of the storage and retrieval rack in the present invention.

[0022] Figure 9 A schematic structural diagram of the rotary locking member in the present invention.

[0023] Figure 10 Schematic diagram of the structure of the limit switch in the present invention.

[0024] Figure 11 A schematic structural diagram of the protective fence in the present invention.

[0025] Reference numerals: 1. Storage and retrieval rack, 1-1. Base, 1-2. Rotary locking part, 1-3. Limit switch, 1-4. Material storage plate, 1-5. Mobile support rod, 1-6. Locking lever, 1-7. Locking pin, 1-8. Locking seat, 1-9. Baffle, 1-10. Universal wheel, 1-11. Adjustment rod; 2. Grabbing assembly, 2-1. First robotic arm, 2-2. Robot, 2-3. Base, 2-5. First rotary joint, 2-6. First pneumatic control valve, 3. Identification assembly, 3-1. Second robotic arm, 3-2. Damage detection camera, 4. Transport assembly, 4-1. Transport platform, 4-2. Pneumatic part fixing gripper, 4-3. Pneumatic linear actuator, 4-4. Flexible pipe cable chain, 4-5. Second pneumatic control valve, 4-6. Third pneumatic control valve, 4-7. Second rotary joint, 5. Protective fence, 6. Electrical control box. DETAILED DESCRIPTION

[0026] The technical solutions in the present invention will be described clearly and in detail below with reference to the accompanying drawings. In the description of the embodiments of the present invention, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, such as A and / or B, which can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" refers to two or more than two. The following terms "first" and "second" are used for descriptive purposes only and cannot be understood as implying or suggesting relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0027] like Figure 1 、 Figure 2 、 Figure 3As shown, the present invention provides a detection device for identifying surface damage of rail vehicle gearbox parts, including a storage and retrieval rack 1, a first robotic arm 2-1, a damage detection camera 3-2, a second robotic arm 3-1 and a transport component 4. The upper part of the storage and retrieval rack 1 is used to store gearbox parts, the first robotic arm 2-1 is used to take and place gearbox parts on the storage and retrieval rack 1, the damage detection camera 3-2 is used to perform surface damage detection on gearbox parts, the moving end of the second robotic arm 3-1 is connected to the damage detection camera 3-2, the second robotic arm 3-1 is used to drive the damage detection camera 3-2 to move around the gearbox parts, the transport component 4 has a first position and a second position, the transport component 4 is used to transport the gearbox parts to the second position after the first robotic arm 2-1 places the gearbox parts at the first position of the transport component 4, so as to facilitate the damage detection camera 3-2 to perform surface damage detection, and after completing the surface damage detection, transport the gearbox parts from the second position to the first position, and reset the gearbox parts through the first robotic arm 2-1. The present invention cooperates with the storage and retrieval rack 1, the first robotic arm 2-1, the damage detection camera 3-2, the second robotic arm 3-1 and the transport component 4, and can use the first robotic arm 2-1 to grab the gearbox parts, and transport the gearbox parts to the damage detection camera 3-2 for damage detection through the conveying component, thereby realizing the automated processing of the surface damage detection process of the gearbox parts of rail vehicles, significantly improving the detection efficiency, reducing manual intervention and human errors, and improving the detection accuracy. At the same time, the coordinated cooperation of the first robotic arm 2-1, the second robotic arm 3-1 and the damage detection camera 3-2 can accurately identify and judge the surface damage of the parts, effectively reducing the missed detection rate and the false detection rate, and improving the reliability of the detection results.

[0028] like Figure 4 、 Figure 5 As shown, the mobile end of the first robotic arm 2-1 is provided with a robotic arm 2-2, and the mobile end of the first robotic arm 2-1 and the robotic arm 2-2 are connected via a first rotary joint 2-5. The first rotary joint 2-5 is used to drive the robotic arm 2-2 to rotate to adjust the angle of the robotic arm 2-2 to grab the gearbox parts.

[0029] like Figure 1 、 Figure 4 As shown, the fixed end of the first robotic arm 2-1 is connected to the base 2-4, and the first robotic arm 2-1, the robotic hand 2-2, the first rotary joint 2-3, and the base 2-4 together constitute the grasping assembly 2.

[0030] like Figure 1 、 Figure 3 As shown, the second robotic arm 3 - 1 and the damage detection camera 3 - 2 together constitute the recognition component 3 .

[0031] like Figure 5As shown, the manipulator 2-2 is a pneumatic manipulator. The manipulator 2-2 uses compressed air as a power source. A first pneumatic control valve 2-6 is provided on the manipulator 2-2. The first pneumatic control valve 2-6 is used to open and cut off the compressed air to control the opening and closing of the manipulator 2-2.

[0032] like Figure 6 、 Figure 7 As shown, the transport assembly 4 includes a transport platform 4-1, a pneumatic part fixing clamp 4-2 and a pneumatic linear actuator 4-3. The transport platform 4-1 is arranged between the first robotic arm 2-1 and the second robotic arm 3-1. The pneumatic part fixing clamp 4-2 is arranged on the transport platform 4-1. The pneumatic part fixing clamp 4-2 uses compressed air as a power source. A second pneumatic control valve 4-5 is provided on the pneumatic part fixing clamp 4-2. The second pneumatic control valve 4-5 is used to open and cut off the compressed air to control the opening and closing of the pneumatic part fixing clamp 4-2, thereby clamping the gearbox parts. The pneumatic linear actuator 4-3 is arranged on the transport platform Platform 4-1, a pneumatic linear actuator 4-3 is arranged along the length direction of the transport platform 4-1, the linear actuator 4-3 has a moving end, the moving end of the linear actuator 4-3 is connected to the pneumatic part fixing clamp 4-2, the linear actuator 4-3 uses compressed air as a power source, and third dynamic control valves 4-6 are respectively provided at both ends of the linear actuator 4-3. The two third dynamic control valves 4-6 are used to respectively open and cut off the compressed air at both ends of the linear actuator 4-3 to control the moving direction of the moving end of the pneumatic linear actuator 4-3, thereby driving the pneumatic part fixing clamp 4-2 to move back and forth along the length direction of the transport platform 4-1.

[0033] like Figure 6 As shown, the transport assembly 4 also includes a flexible umbilical cable chain 4-4, which is arranged along the length direction of the transport platform 4-1. One end of the flexible umbilical cable chain 4-4 is electrically connected to the second pneumatic control valve 4-5, and the other end of the flexible umbilical cable chain 4-4 is connected to the power supply assembly for supplying power to the second pneumatic control valve 4-5. At the same time, the flexible umbilical cable chain 4-4 can also move with the movement of the pneumatic part fixing clamp 4-2.

[0034] like Figure 7 As shown, the pneumatic part fixing clamp 4-2 is connected to the output end of the pneumatic linear actuator 4-3 through a second rotary joint 4-7, so that the pneumatic part fixing clamp 4-2 can be driven to rotate through the second rotary joint 4-7, and the angle of the pneumatic part fixing clamp 4-2 can be adjusted to better clamp and fix the gearbox parts.

[0035] like Figure 8As shown, the storage and retrieval rack 1 includes a base 1-1, a material storage plate 1-4 and at least one adjusting rod 1-11. The material storage plate 1-4 is tilted on the upper part of the base 1-1, and the lower part of the material storage plate 1-4 is hinged to the upper part of the base 1-1. A plurality of parts storage holes are evenly opened on the material storage plate 1-4, and different gearbox parts are stored through the plurality of parts storage holes. At least one adjusting rod 1-11 is arranged between the material storage plate 1-4 and the base 1-1. The upper end of the adjusting rod 1-11 is hinged to the material storage plate 1-4, and the lower end of the adjusting rod 1-11 is detachably connected to the base 1-1. By driving the lower end of the adjusting rod 1-11 to move on the upper part of the base 1-1, the connection position of the upper part of the base 1-1 and the lower end of the adjusting rod 1-11 is adjusted, thereby adjusting the angle of the material storage plate 1-4.

[0036] like Figure 8 、 Figure 9 、 Figure 10 As shown, universal wheels 1-10 are respectively provided at the positions near the four corners of the lower part of the base 1-1, and rotary locking members 1-2 are respectively provided at the positions near the two sides of the lower part of the base 1-1. The two rotary locking members 1-2 are used to lock the position of the base 1-1 after the base 1-1 stops moving. A limit switch 1-3 is provided on the side of the base 1-1 near the position of the first mechanical arm 2-1, and a baffle 1-9 is vertically provided on the side of the base 1-1 near the position of the limit switch 1-3. The upper part of the base 1-1 is away from the position of the limit switch 1-3. A movable support rod 1-5 is provided. The movable support rod 1-5 is U-shaped. Both ends of the movable support rod 1-5 are connected to the upper part of the base 1-1. The base 1-1 is pushed to move by the movable support rod 1-5, so that the base 1-1 moves to the specified position. When it touches the limit switch 1-3, the signal is triggered to stop, preventing the base 1-1 from moving further. As a second line of defense, even if the limit switch 1-3 fails to effectively prevent the storage and retrieval rack 1 from excessive movement, the baffle 1-9 can also act as a physical barrier to prevent it from continuing to move forward.

[0037] like Figure 9 As shown, the rotary locking member 1-2 includes a locking lever 1-6, a locking pin 1-7 and a locking seat 1-8. The locking seat 1-8 is fixed to the ground by four M12 bolts. The end of the locking lever 1-6 is precisely matched with the locking pin 1-7. After fixation, the locking lever 1-6 rotates horizontally to a vertical position, and the internal mechanical structure automatically engages to achieve reliable locking.

[0038] like Figure 11 As shown, the present invention is a detection device for identifying surface damage of rail vehicle gearbox parts, which also includes a protective fence 5. The storage and retrieval rack 1, the grabbing component 2, the identification component 3 and the transport component 4 are all arranged in the protective fence 5. The protective fence 5 provides a safe working environment for damage detection.

[0039] like Figure 11 As shown, an electrical control box 6 is provided on the side of the protective fence 5 , and the power supply component is arranged in the electrical control box 6 . The electrical control box 6 is used to supply power and perform signal control for the detection equipment.

[0040] Among them, the damage detection camera 3-2 is a Hikvision robot machine vision CCD detection all-in-one machine, the specific model is MV-SC6016C-0C-NNN color. The damage detection camera 3-2 takes images of the gearbox parts and converts them into image signals of the gearbox parts, which are then transmitted to the image processing system in the damage detection camera 3-2. The image processing system in the damage detection camera 3-2 converts the image signals of the gearbox parts into digital signals, calculates and extracts the features of the gearbox parts, and uses algorithms to analyze defects to achieve automated detection of surface damage of gearbox parts.

[0041] Working principle: When inspecting the gearbox parts of a rail vehicle for damage, the gearbox parts to be inspected are stored in the parts storage holes of the material storage plates 1-4. The first robotic arm 2-1 is started, and the first robotic arm 2-1 drives the manipulator 2-2 to extend into the center hole of the gearbox part to be inspected. The manipulator 2-2 is controlled to firmly fix the gearbox part. The first robotic arm 2-1 removes the gearbox part from the material storage plate 1-4 and places it on the opened pneumatic part fixing clamp 4-2. The pneumatic part fixing clamp 4-2 is controlled to clamp the gearbox part. The linear actuator 4-3 is then started. The moving end of the linear actuator 4-3 The pneumatic part fixing clamp 4-2 and the gearbox part on it are driven to move to the position of the identification component 3. The second robot arm 3-1 drives the damage detection camera 3-2 to move around the gearbox part to detect damage to the gearbox part. After the detection is completed, the linear actuator 4-3 is started. The linear actuator 4-3 moves in the opposite direction to drive the gearbox part back to the position of the first robot arm 2-1. The pneumatic part fixing clamp 4-2 releases the gearbox part. The first robot arm 2-1 grabs the gearbox part and puts it back on the material storage plate 1-4. It is placed in the designated row according to whether the part is qualified. Repeat the above steps to complete the damage detection of each gearbox part.

[0042] The detection equipment for identifying surface damage of rail vehicle gearbox parts of the present invention also has the following advantages: the cooperation of the first robotic arm, the robotic hand, the second robotic arm and the pneumatic part fixing clamp in the present invention can adapt to rail vehicle gearbox parts of different shapes, sizes and types, and can be expanded and upgraded in function according to actual needs, with good adaptability and scalability.

[0043] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present invention are intended to be protected by the present invention.

Claims

1. A detection device for identifying surface damage of rail vehicle gearbox parts, characterized in that: include: A storage rack (1), the upper portion of which is used to store gearbox parts; A first robotic arm (2-1) is used for taking and placing gearbox parts on the storage and retrieval rack (1); Damage detection camera (3-2), used to detect surface damage on gearbox parts; A second robotic arm (3-1), the mobile end of which is connected to the damage detection camera (3-2), and the second robotic arm (3-1) is used to drive the damage detection camera (3-2) to move around the gearbox parts; The transport assembly (4) has a first position and a second position, and is used for transporting the gearbox part to the second position after the first mechanical arm (2-1) places the gearbox part at the first position of the transport assembly (4), so as to facilitate the damage detection camera (3-2) to perform surface damage detection, and after completing the surface damage detection, transporting the gearbox part from the second position to the first position, and resetting the gearbox part via the first mechanical arm (2-1).

2. The detection device for identifying surface damage of rail vehicle gearbox parts according to claim 1, characterized in that: A manipulator (2-2) is provided at the movable end of the first manipulator arm (2-1), and the movable end of the first manipulator arm (2-1) and the manipulator (2-2) are connected via a first rotary joint (2-5). The first rotary joint (2-5) is used to drive the manipulator (2-2) to rotate so as to adjust the angle of the manipulator (2-2) to grasp the gearbox parts.

3. The detection device for identifying surface damage of a railway vehicle gearbox part according to claim 2, characterized in that: The manipulator (2-2) is a pneumatic manipulator. The manipulator (2-2) uses compressed air as a power source. A first pneumatic control valve (2-6) is provided on the manipulator (2-2). The first pneumatic control valve (2-6) is used to open and cut off the compressed air to control the opening and closing of the manipulator (2-2).

4. The detection device for identifying surface damage of a railway vehicle gearbox part according to claim 1, characterized in that: The transport component (4) comprises: A transport platform (4-1) is arranged between the first robotic arm (2-1) and the second robotic arm (3-1); A pneumatic part fixing clamp (4-2) is provided on the transport platform (4-1), the pneumatic part fixing clamp (4-2) uses compressed air as a power source, and a second pneumatic control valve (4-5) is provided on the pneumatic part fixing clamp (4-2), the second pneumatic control valve (4-5) being used to open and cut off the compressed air to control the opening and closing of the pneumatic part fixing clamp (4-2), thereby clamping the gearbox parts; A pneumatic linear actuator (4-3) is arranged on a transport platform (4-1) and along the length direction of the transport platform (4-1). The linear actuator (4-3) has a movable end, and the movable end of the linear actuator (4-3) is connected to a pneumatic part fixing clamp (4-2). The linear actuator (4-3) uses compressed air as a power source. Third dynamic control valves (4-6) are respectively provided at both ends of the linear actuator (4-3). The two third dynamic control valves (4-6) are used to respectively open and cut off the compressed air at both ends of the linear actuator (4-3) to control the moving direction of the movable end of the pneumatic linear actuator (4-3).

5. The detection device for identifying surface damage of a railway vehicle gearbox part according to claim 1, characterized in that: The storage and retrieval rack (1) comprises: Base (1-1); A material storage plate (1-4) is obliquely arranged on the upper part of the base (1-1); the lower part of the material storage plate (1-4) is hinged to the upper part of the base (1-1); and a plurality of parts storage holes are evenly opened on the material storage plate (1-4); At least one adjusting rod (1-11) is arranged between the material storage plate (1-4) and the base (1-1), the upper end of the adjusting rod (1-11) is hinged to the material storage plate (1-4), and the lower end of the adjusting rod (1-11) is detachably connected to the base (1-1).

6. The detection device for identifying surface damage of a railway vehicle gearbox part according to claim 5, characterized in that: Universal wheels (1-10) are respectively provided at positions near the four corners of the lower part of the base (1-1), and rotary locking members (1-2) are respectively provided at positions near the two sides of the lower part of the base (1-1). The two rotary locking members (1-2) are used to lock the position of the base (1-1) after the base (1-1) stops moving. A limit switch (1-3) is provided on the side of the base (1-1) near the position of the first mechanical arm (2-1). A baffle (1-9) is vertically provided on the side of the base (1-1) near the position of the limit switch (1-3). A movable support rod (1-5) is provided on the upper part of the base (1-1) away from the limit switch (1-3). The movable support rod (1-5) is U-shaped, and both ends of the movable support rod (1-5) are connected to the upper part of the base (1-1).

7. The detection device for identifying surface damage of a railway vehicle gearbox part according to claim 1, characterized in that: The damage detection camera (3-2) is a Hikvision robot machine vision CCD detection all-in-one machine.

8. The detection device for identifying surface damage of a railway vehicle gearbox part according to claim 1, characterized in that: It also includes a protective fence (5), wherein the storage and retrieval rack (1), the grabbing assembly (2), the identification assembly (3) and the transport assembly (4) are all arranged in the protective fence (5).

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