Multimodal biomimetic intelligent working robot

Abstract

This invention discloses a multimodal biomimetic intelligent work robot, including a base and an insulating shell mounted on the base. Tracked walking mechanisms capable of changing walking modes are provided on both sides of the bottom of the base. The tracked walking mechanism includes a base, with independently operable walking structures on both sides of the base. Each walking structure includes a ball seat, which is mounted on both sides of the base. A ball-head sliding sleeve is movably mounted on the ball seat and connected to a walking support. A rotary motor is mounted on one side of the walking support, used to adjust the angle of the tracked walking section, thereby changing the walking mode. The base also includes a repair mechanism that automatically switches grinding modes based on the pipe repair pattern and terrain. An adjustable welding mechanism is also provided on the insulating shell for accurately identifying the type of damage to the inner wall of the pipe. This application can automatically switch walking modes, allowing for switching between coarse and fine grinding, and can perform welding repairs on corroded, cracked, and deformed areas.

Description

Technical Field

[0001] This invention belongs to the field of pipeline maintenance technology, specifically involving a multimodal biomimetic intelligent operation robot. Background Technology

[0002] Due to the confined space and long distances inside pipelines, they are difficult for humans to access, typically requiring specialized pipeline robots for tasks such as grinding, cleaning, and inspection. Pipeline robots are a new type of robot that can move along the inside and outside of pipelines, carrying sensors and tools to perform operations both inside and outside the pipeline; they are mechatronic systems. In recent years, pipeline robots have become more flexible and common in their forms and applications, and their use in many fields is gradually being improved and developed. Pipeline robots can be categorized by their drive mechanism, including wheeled, tracked, and wall-mounted types.

[0003] For example, the invention disclosed in patent announcement number CN110185885B, a mobile robot for pipeline grinding, and the invention disclosed in patent announcement number CN112630229B, a pipeline robot for oil and gas pipelines and a method for pipeline defect detection and repair, both disclose pipeline grinding mechanisms. However, the above grinding mechanisms cannot switch grinding modes according to the maintenance status, nor can they automatically grind and avoid obstacles according to the shape of the pipeline inner wall. Their grinding accuracy and application scenarios are limited. In addition, they cannot automatically adjust their walking mode according to the shape of the pipeline interior, their passability is limited, they cannot pass through all directions, and they cannot accurately identify the type of damage to the pipeline inner wall, nor can they accurately weld cracks in the pipeline. Therefore, we propose a multimodal bionic intelligent operation robot. Summary of the Invention

[0004] The purpose of this invention is to provide a multimodal biomimetic intelligent work robot to solve the problems mentioned in the background art, such as the grinding mechanism being unable to switch grinding modes according to the maintenance status, being unable to automatically grind and avoid obstacles according to the shape of the inner wall of the pipe, having limited grinding accuracy and application scenarios, being unable to automatically adjust the walking mode according to the shape of the inside of the pipe, having limited passability and being unable to pass through all directions, and being unable to accurately identify the type of damage to the inner wall of the pipe and to accurately weld cracks inside the pipe.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a multimodal biomimetic intelligent work robot, including a base and an insulating shell disposed on the base, wherein tracked walking mechanisms capable of transforming walking modes are provided on both sides of the bottom of the base; The tracked walking mechanism includes a base, and independently operable walking structures are provided on both sides of the base. Each walking structure includes a ball seat, which is located on both sides of the base. A ball head slide is movably mounted on the ball seat and connected to a walking bracket. A rotary motor is provided on one side of the walking bracket. The rotary motor is used to adjust the angle of the track walking part, thereby changing the walking mode. The base is also equipped with a repair mechanism that automatically switches the grinding mode according to the pipe repair pattern and terrain, and the insulating shell is also equipped with an adjustable welding mechanism for accurately identifying the type of damage to the inner wall of the pipe.

[0006] Preferably, the tracked walking unit includes a track support, which is disposed on one side of the walking support and connected to the output shaft of a rotary motor. The angle of the track support can be adjusted by the rotary motor, thereby adjusting the walking pattern.

[0007] Preferably, the track support is provided with a track section, and the track support is also provided with a walking motor that drives the track section to rotate, which can control the rotation direction of the track section, thereby controlling the movement of the device.

[0008] Preferably, the track section is provided with magnetic blocks and anti-slip pads. The magnetic blocks and anti-slip pads are arranged alternately, which improves the adsorption force and anti-slip properties of the device on the inner wall of the pipe, and ensures its stability when moving in the pipe.

[0009] Preferably, the repair mechanism includes a multi-stage polishing structure and an adjustable dust collection structure; The multi-stage grinding structure includes a turntable, which is located at the bottom of a connecting seat. The connecting seat is located at the bottom of a drive disc, which is rotatably mounted inside a machine base. Coarse grinding discs are symmetrically arranged at the bottom of the turntable, and a retractable coarse grinding head is provided on one side of each coarse grinding disc. Fine grinding discs are also symmetrically arranged at the bottom of the turntable, and a fine grinding head is provided at the bottom of each fine grinding disc. This structure enables coarse and fine grinding of the inner wall of the pipe, improving grinding efficiency.

[0010] Preferably, a first electric push rod is provided inside the turntable. The first electric push rod is connected to an inner support plate, and the inner support plate is also connected to a coarse grinding head, which can raise and lower the coarse grinding head, thereby switching between coarse grinding and fine grinding modes.

[0011] Preferably, the base is further provided with a visual sensing module, and the drive plate is provided with a second electric push rod. The second electric push rod is connected to the connecting seat and can identify the protrusions or pits in the pipe, control the lifting of the turntable, and prevent the turntable from being damaged by collision.

[0012] Preferably, the adjustable dust collection structure includes a dust collection head, which is located at the center hole of the turntable and fixed to a telescopic rod. The telescopic rod is located at the bottom of the base, and the dust collection head is connected to a dust collection pipe. The dust collection pipe is connected to a dust collection fan inside the dust collection box. The dust collection box is located on the upper side of the base and can automatically adapt to the dust collection position and quickly collect the grinding dust.

[0013] Preferably, the adjustable welding mechanism includes a laser sensing module and a laser scanning probe, which are respectively mounted on a control box. The control box is located on one side of an insulating outer shell. The control box also includes a telescopic welding torch with a welding head at its end. A central processor is located inside the control box. The central processor processes the pipeline inner wall information collected by the laser sensing module and the laser scanning probe, and sends control commands to the telescopic welding torch. Through the circumferential movement of the laser sensing module and the laser scanning probe, the location, shape, and degree of pipeline corrosion, cracks, deformation, and other damage are accurately captured. The corresponding medium and supply quantity are automatically matched to achieve precise supply on demand, providing precise material support for repair operations.

[0014] Preferably, the welding head is connected to the welding medium box via a flexible pipe. The welding medium box is located on both sides of the insulating shell and is capable of conveying the welding medium.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) This application can automatically switch the walking mode according to the pipe diameter and the terrain inside the pipe wall, so as to meet the walking use of different pipe diameters and the terrain inside the pipe, and improve the passability of this device in the pipe.

[0016] (2) This application can switch between coarse grinding and fine grinding according to the grinding requirements of the inner wall of the pipe, which improves the grinding accuracy and can automatically avoid the protrusions and pits in the pipe, extend the service life and reduce the damage rate.

[0017] (3) This application can also accurately capture the location, shape and degree of damage such as pipeline corrosion, cracks and deformation, automatically match the corresponding medium and supply, and weld the corrosion, cracks and deformation locations. Attached Figure Description

[0018] Figure 1 This is a first-view structural diagram of the present invention; Figure 2 This is a schematic diagram of the second perspective structure of the present invention; Figure 3 This is a first-view structural schematic diagram of the tracked walking mechanism in this invention; Figure 4This is a second-view structural schematic diagram of the tracked walking mechanism in this invention; Figure 5 This is a schematic diagram of the tracked walking mechanism in this invention; Figure 6 This is a first-view structural diagram of the repair mechanism in this invention; Figure 7 This is a schematic diagram of the multi-stage grinding structure in this invention; Figure 8 This is a schematic diagram of the split structure of the turntable in this invention; Figure 9 This is a schematic diagram of the adjustable dust collection structure in this invention; Figure 10 This is a second-view structural diagram of the repair mechanism in this invention; Figure 11 This is a schematic diagram of the adjustable welding mechanism in this invention.

[0019] In the diagram: 1. Tracked walking mechanism; 2. Base; 3. Adjustable welding mechanism; 4. Insulating shell; 5. Welding medium box; 6. Heat dissipation vent; 7. Repair mechanism; 31. Control box; 32. Welding head; 33. Laser sensing module; 34. Laser scanning probe; 35. Telescopic welding torch; 71. Vision sensing module; 72. Multi-stage grinding structure; 73. Adjustable dust collection structure; 101. Base; 102. Ball seat; 103. Ball head sleeve; 104. Walking bracket; 105. Steering motor; 106. Rotary motor; 07. Tracked walking unit; 108. Track support; 109. Anti-slip pads; 110. Magnet block; 111. Walking motor; 721. Connecting seat; 722. Turntable; 723. Rough grinding head; 724. Rough grinding disc; 725. Fine grinding disc; 726. Fine grinding head; 727. Inner support plate; 728. First electric push rod; 729. Second electric push rod; 730. Drive plate; 731. Dust suction head; 732. Dust suction port; 733. Telescopic rod; 734. Dust suction pipe; 735. Dust collection box; 736. Exhaust port. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figures 1-5The present invention provides a technical solution: a multimodal bionic intelligent operation robot, including a base 2 and an insulating shell 4 disposed on the base 2, and a tracked walking mechanism 1 disposed on both sides of the bottom of the base 2; The tracked walking mechanism 1 includes a base 101, and independently operable walking structures are provided on both sides of the base 101. The walking structure includes a ball seat 102, which is provided on both sides of the base 101. A ball head sleeve 103 is movably provided on the ball seat 102. The ball head sleeve 103 is connected to the walking bracket 104. A rotary motor 106 is provided on one side of the walking bracket 104. The rotary motor 106 is used to adjust the angle of the track walking part 107, thereby changing the walking mode. The tracked walking unit 107 includes a track support 108, which is disposed on one side of the walking support 104 and connected to the output shaft of the rotary motor 106. The angle of the track support 108 can be adjusted by the rotary motor 106, thereby adjusting the walking pattern. The track is disposed inside the track support 108, and a walking motor 111 that drives the track to rotate is also disposed inside the track support 108, which can control the rotation direction of the track and thus control the movement of the device.

[0022] In the first walking mode, the walking pattern of the device is adjusted according to the inner diameter of the underground pipeline. If the inner diameter of the underground pipeline is large, the track support 108 can be rotated 90° by rotating motor 106, and the track support 108 can drive the track part to rotate 90°. The remaining three sets of track supports 108 are rotated 90° in sequence. At this time, the overall height of the base 2 can be adjusted. Then, the four sets of walking motors 111 are run synchronously. The four sets of walking motors 111 drive the four sets of track parts to rotate synchronously and walk.

[0023] In the second walking mode, when the inner diameter of the underground pipeline is small, the rotary motor 106 drives the track support 108 to rotate 180°, thereby unfolding the track support 108 from the walking support 104. The remaining three sets of track supports 108 are unfolded in sequence, and then the walking motor 111 is run. The walking motor 111 drives the track to rotate. Through the movement of the track, the device can move without obstacles in the underground pipeline. At the same time, when encountering mud and sand protrusions, the angle of the track support 108 can be adjusted to raise the base 2, ensuring the passability of various terrains. When the walking support 104 is moving, the ball head sleeve 103 can be universally adjusted on the ball seat 102, which can automatically adapt to the terrain inside the pipeline.

[0024] Furthermore, the track section is equipped with magnet blocks 110 and anti-slip pads 109. The magnet blocks 110 and anti-slip pads 109 are arranged alternately. When the device moves inside the pipe, the magnet blocks 110 on the track section can provide adsorption force to make the device move smoothly. At the same time, the anti-slip pads 109 provide anti-slip properties, which improves the adsorption force and anti-slip properties of the device on the inner wall of the pipe, and ensures its stability when moving inside the pipe.

[0025] Furthermore, a steering motor 105 is also provided on one side of the walking support 104, which can control the movement and steering of this device.

[0026] Please see Figures 6-8 The base 2 also includes a repair mechanism 7 at its bottom. The repair mechanism 7 comprises a multi-stage grinding structure 72 and an adjustable dust collection structure 73. The multi-stage grinding structure 72 includes a turntable 722, which is located at the bottom of a connecting seat 721. The connecting seat 721 is located at the bottom of a drive disc 730, which is rotatably mounted inside the base 2. A drive motor controlling the rotation of the drive disc 730 is also located inside the base 2. A coarse grinding disc 724 is symmetrically arranged at the bottom of the turntable 722, and an extendable... The rotary table 722 has a coarse grinding head 723 and a fine grinding disc 725 symmetrically arranged at the bottom. The fine grinding disc 725 has a fine grinding head 726 at the bottom, which can perform coarse and fine grinding on the inner wall of the pipe, improving grinding efficiency. The rotary table 722 is equipped with a first electric push rod 728, which is connected to an inner support plate 727. The inner support plate 727 is also connected to the coarse grinding head 723, which can raise and lower the coarse grinding head 723, thereby switching between coarse and fine grinding modes.

[0027] When the device moves to a damaged area of ​​the pipeline, such as cracks or holes, the first electric push rod 728 drives the inner support plate 727 downward. The inner support plate 727 drives the coarse grinding head 723 downward, removing the coarse grinding head 723 from the coarse grinding disc 724, so that the coarse grinding head 723 is in contact with the damaged area. The drive motor drives the drive disc 730 to rotate, and the drive disc 730 drives the turntable 722 to rotate through the connecting seat 721. The turntable 722 drives the coarse grinding head 723 to rotate. The coarse grinding head 723 rotates to coarsely grind impurities such as rust, metal burrs, and oxide layers around the damaged area. After coarse grinding is completed, the coarse grinding head 723 is retracted by the first electric push rod 728, and the fine grinding head 726 is brought into contact with the coarse grinding position. Then, the turntable 722 drives the fine grinding head 726 to rotate and perform fine grinding on the damaged area, providing a clean, flat, and qualified working surface for subsequent repair operations such as laser cladding and medium filling of the retractable welding gun 35.

[0028] Coarse Grinding Module: Suitable for scenarios with heavy impurities such as thick rust layer on the inner wall of pipe ≤3mm and metal burr height >1mm. The coarse grinding head 723 is made of tungsten carbide alloy with a serrated protrusion on the surface. It achieves efficient impurity removal through high-speed operation at 1200-1800rpm, with a rust removal efficiency of up to 15cm² / min, quickly opening up the "base surface channel" for repair operations.

[0029] Fine Grinding Module: This module performs fine polishing on the surface after coarse grinding. The 726 fine grinding head uses an 80-120 grit diamond-coated grinding wheel, rotating at a low speed of 500-1000 rpm to eliminate coarse grinding marks and stabilize the surface roughness at 40-80 μm. This ensures better adhesion between the subsequent alloy powder and the pipe wall, improving repair strength. Please see Figure 9 The base 101 is also equipped with a vision sensing module 71, and the drive disk 730 is equipped with a second electric push rod 729. The second electric push rod 729 is connected to the connecting seat 721 and can identify the protrusions or pits in the pipe. It can control the lifting of the turntable 722 and prevent the turntable 722 from being damaged by bumps.

[0030] Meanwhile, during the polishing process, the vision sensing module 71 detects the protrusions in the polishing area. When a protrusion is detected, the second electric push rod 729 can be retracted, and the height of the turntable 722 can be adjusted so that the turntable 722 can avoid the protrusion and prevent overload wear of the coarse polishing head 723 and the fine polishing head 726.

[0031] Please see Figure 7 , Figure 9 as well as Figure 10 The adjustable dust collection structure 73 includes a dust collection head 731, which is located at the center hole of the turntable 722 and is fixed on the telescopic rod 733. The telescopic rod 733 is located at the bottom of the base 101, and the dust collection head 731 is connected to the dust collection pipe 734. The dust collection pipe 734 is connected to the dust collection fan in the dust collection box 735. The dust collection box 735 is located on the upper side of the base 101 and can automatically adapt to the dust collection position and quickly collect the grinding dust.

[0032] During the polishing process, the telescopic rod 733 adjusts the height of the suction head 731, while the suction fan generates negative pressure, which transports metal shavings and rust powder through the suction port 732 into the suction pipe 734, and then through the suction pipe 734 into the dust collection box 735, where the negative pressure collects the metal shavings and rust powder.

[0033] Furthermore, an exhaust port 736 is provided on one side of the dust collection box 735, and a filter screen is installed inside the exhaust port 736 to ensure airflow while preventing dust from being discharged.

[0034] Please see Figure 11 An adjustable welding mechanism 3 is also provided on the insulating shell 4. The adjustable welding mechanism 3 includes a laser sensing module 33 and a laser scanning probe 34. The laser sensing module 33 and the laser scanning probe 34 are respectively mounted on the control box 31, which is located on one side of the insulating shell. The control box 31 is also equipped with a telescopic welding torch 35, with a welding head 32 at the end of the telescopic welding torch 35. A central processor is located inside the control box 31. The central processor processes the information of the inner wall of the pipeline collected by the laser sensing module 33 and the laser scanning probe 34, and sends control commands to the telescopic welding torch 35. Through the circumferential movement of the laser sensing module 33 and the laser scanning probe 34, the location, shape and degree of pipeline corrosion, cracks, deformation and other damage are accurately captured, and the corresponding medium and supply quantity are automatically matched to achieve precise supply on demand, providing precise material support for repair operations. The welding head 32 is connected to the welding medium box 5 through a flexible pipe. The welding medium box 5 is located on both sides of the insulating shell 4 and can transport the welding medium.

[0035] As the device moves, the laser scanning probe 34 moves at a constant speed in a circle along the inner wall of the pipe. Simultaneously, the laser sensing module 33 continuously emits a laser beam. The laser beam reflects off the inner wall of the pipe, and the module captures the reflected signal, calculates the round-trip time difference, and converts it into real-time distance data between the laser scanning probe 34 and the pipe wall. Simultaneously, it records the circumferential angle, axial position, and other spatial coordinates of the laser scanning probe 34, forming a three-dimensional point cloud data matrix of the pipe's inner wall. This matrix filters out environmental interference such as dust and moisture-induced noise and equipment error data, retaining only valid point clouds. The valid point clouds are then stitched and aligned to generate a complete three-dimensional model of the pipe's inner wall, eliminating scanning blind spots. This model is then compared with a preset standard pipe inner wall model to identify abnormal point cloud areas where the distance deviation exceeds a threshold. For these abnormal areas, the distribution pattern of the point cloud is analyzed: corrosion corresponds to localized... Point cloud depressions or thinning indicate cracks, which correspond to linear continuous point cloud fractures. Deformation corresponds to shape shifts in large-area point clouds. The algorithm calculates the dimensions (length, width, depth, and location coordinates, including circumferential angle and axial distance) of the abnormal area to quantify the degree of damage. The identified damage features are then verified to eliminate misjudgments such as pre-existing scratches on the pipe wall or gaps at the interface. The specific damage information is output: location coordinates, morphological classification (corrosion / crack / deformation), and quantitative parameters such as crack length and corrosion depth. Based on the identified damage morphology, the corresponding welding medium and supply quantity are automatically matched. The corresponding welding medium in the welding medium box 5 is delivered to the welding head 32. The central processor controls the operation of the telescopic welding torch 35, which adjusts the angle and position of the welding head 32 and performs welding repair on the damaged area.

[0036] Furthermore, a heat dissipation vent 6 is provided on one side of the welding medium box 5 to dissipate heat.

[0037] The central processor in this application can control the first electric push rod 728, the second electric push rod 729, the drive motor, the rotary motor 106, the vacuum fan, and the walking motor 111.

[0038] The outer insulating shell 4 is made of a robust and corrosion-resistant lightweight composite material, which has excellent impact resistance and corrosion resistance. It can protect the internal core components such as sensing, control and power in the harsh environment of underground pipelines with humid and corrosive media, ensuring stable operation. The shell adopts a streamlined and modular design, which reduces the movement resistance in the pipeline and facilitates component maintenance and functional expansion, providing a reliable structural guarantee for the long-term stable operation of the robot.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multimodal biomimetic intelligent work robot, comprising a base (2) and an insulating shell (4) disposed on the base (2), characterized in that: The base (2) is provided with tracked walking mechanisms (1) on both sides of its bottom, which can transform the walking mode. The tracked walking mechanism (1) includes a base (101), and independently operable walking structures are provided on both sides of the base (101). The walking structure includes a ball seat (102), which is provided on both sides of the base (101). A ball head sleeve (103) is movably provided on the ball seat (102). The ball head sleeve (103) is connected to the walking bracket (104). A rotary motor (106) is provided on one side of the walking bracket (104). The rotary motor (106) is used to adjust the angle of the tracked walking part (107) to change the walking mode. The base (2) is also equipped with a repair mechanism (7) that automatically switches the grinding mode according to the pipe repair pattern and terrain, and the insulating shell (4) is also equipped with an adjustable welding mechanism (3) for accurately identifying the type of damage to the inner wall of the pipe.

2. The multimodal bionic intelligent work robot according to claim 1, characterized in that: The tracked walking unit (107) includes a track support (108), which is disposed on one side of the walking support (104) and connected to the output shaft of the rotary motor (106).

3. The multimodal biomimetic intelligent work robot according to claim 2, characterized in that: The track support (108) is provided with a track section, and the track support (108) is also provided with a walking motor (111) for driving the track section to rotate.

4. The multimodal bionic intelligent work robot according to claim 3, characterized in that: The track section is provided with a magnet block (110) and an anti-slip pad (109), and the magnet block (110) and the anti-slip pad (109) are arranged alternately.

5. The multimodal bionic intelligent work robot according to claim 1, characterized in that: The repair mechanism (7) includes a multi-stage polishing structure (72) and an adjustable dust collection structure (73); The multi-stage grinding structure (72) includes a turntable (722), which is located at the bottom of a connecting seat (721). The connecting seat (721) is located at the bottom of a drive disc (730), which is rotatably located within a base (2). A coarse grinding disc (724) is symmetrically arranged at the bottom of the turntable (722). A retractable coarse grinding head (723) is arranged on one side of the coarse grinding disc (724). A fine grinding disc (725) is also symmetrically arranged at the bottom of the turntable (722), and a fine grinding head (726) is arranged at the bottom of the fine grinding disc (725).

6. The multimodal biomimetic intelligent work robot according to claim 5, characterized in that: The turntable (722) is provided with a first electric push rod (728), which is connected to the inner support plate (727). The inner support plate (727) is also connected to the coarse grinding head (723).

7. The multimodal biomimetic intelligent work robot according to claim 5, characterized in that: The base (101) is also provided with a visual sensing module (71), and the drive disk (730) is provided with a second electric push rod (729), which is connected to the connecting seat (721).

8. The multimodal bionic intelligent work robot according to claim 5, characterized in that: The adjustable vacuuming structure (73) includes a vacuum head (731), which is located at the center hole of the turntable (722) and is fixed on the telescopic rod (733). The telescopic rod (733) is located at the bottom of the base (101), and the vacuum head (731) is connected to the vacuum pipe (734). The vacuum pipe (734) is connected to the vacuum fan in the dust collection box (735), and the dust collection box (735) is located on the upper side of the base (101).

9. The multimodal bionic intelligent work robot according to claim 1, characterized in that: The adjustable welding mechanism (3) includes a laser sensing module (33) and a laser scanning probe (34). The laser sensing module (33) and the laser scanning probe (34) are respectively mounted on a control box (31). The control box (31) is mounted on one side of an insulating outer shell. The control box (31) is also equipped with a telescopic welding torch (35). The end of the telescopic welding torch (35) is equipped with a welding head (32). The control box (31) is equipped with a central processor. The central processor processes the pipe inner wall information collected by the laser sensing module (33) and the laser scanning probe (34) and sends control commands to the telescopic welding torch (35).

10. The multimodal bionic intelligent work robot according to claim 9, characterized in that: The welding head (32) is connected to the welding medium box (5) via a dust suction pipe (724), and the welding medium box (5) is disposed on both sides of the insulating shell (4).

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