Underwater concrete 3D printing device

Abstract

The invention relates to the technical field of underwater concrete repairing, in particular to an underwater concrete 3D printing device which comprises a telescopic mechanical arm, the telescopic mechanical arm is installed on an overwater operation platform and connected with an outer-layer protective cover, an inner-layer protective cover is arranged in an inner cavity of the outer-layer protective cover, and an elastic supporting piece is arranged between the outer-layer protective cover and the inner-layer protective cover. A nozzle body is arranged in an inner cavity of the inner-layer protective cover, the outer-layer protective cover and the inner-layer protective cover are each provided with a flexible sealing body, and sawtooth-shaped lines are arranged on the sealing faces of the flexible sealing bodies. The underwater concrete 3D printing device is excellent in environment isolation effect, the flexible sealing body is matched with the inner-layer protective cover and the outer-layer protective cover to form a local closed space, seawater can be effectively blocked, and seawater interference is reduced to the minimum; the construction precision is high, multi-degree-of-freedom precise positioning can be achieved through the telescopic mechanical arm, the printing nozzle can be precisely matched with cracks of different widths, and the harsh repairing precision requirement of port and navigation engineering is met.

Description

Technical Field

[0001] This invention relates to the field of underwater concrete repair technology, and more particularly to an underwater concrete 3D printing device. Background Technology

[0002] my country's port and shipping facilities have long been in operation in complex marine environments. As of the end of 2023, among the 22,023 operating berths nationwide, 41% had been in service for over 25 years, 21% for over 40 years, and 80% of berths in service for over 20 years suffered severe underwater damage such as concrete cracking and steel reinforcement corrosion. Existing underwater concrete repair equipment and methods can be found in Chinese invention patent application CN118997167A, entitled "Underwater In-situ 3D Printing Repair and Construction Method for Concrete Structures." However, existing underwater concrete repair equipment lacks effective local isolation measures. Seawater seepage during the printing process dilutes the cement paste, reducing the compressive strength of the repaired structure (often below 30 MPa). Conventional concrete is prone to material segregation underwater. While adding anti-dispersing agents can improve this problem, it leads to decreased pumpability and reduced interfacial bond strength (typically <2.0 MPa). Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an underwater concrete 3D printing device that improves repair efficiency and the quality of the repaired body.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: an underwater concrete 3D printing device, including a telescopic robotic arm, the fixed end of which is installed on a surface working platform, the free end of which is submerged in water and connected to an outer protective cover via a rotating connector, the outer protective cover being hollow inside and open at one end away from the telescopic robotic arm, an inner protective cover being provided in the inner cavity of the outer protective cover, the inner protective cover being hollow inside and open at one end away from the telescopic robotic arm, an elastic support member being provided between the outer and inner protective covers, a nozzle body being provided in the inner cavity of the inner protective cover, and a flexible sealing body that adaptively conforms to the surface of underwater concrete being provided at the open ends of both the outer and inner protective covers, the sealing surface of the flexible sealing body being provided with a serrated texture.

[0005] Optionally, two or more elastic support members are evenly distributed in the gap between the outer protective cover and the inner protective cover.

[0006] Optionally, it also includes a base material mixing tank and a preservative storage tank, which are connected to the nozzle body via a pump body.

[0007] Optionally, the nozzle body includes a printing nozzle and a protective agent nozzle disposed in the inner cavity of the inner protective cover. The base material mixing tank is connected to the printing nozzle through a base material delivery pump, and the protective agent storage tank is connected to the protective agent nozzle through a protective agent delivery pump.

[0008] Optionally, the system also includes a storage screw extrusion pump and a protective agent screw extrusion pump. The base material conveying pump is connected to the storage screw extrusion pump via a mixture conveying pipeline. The storage screw extrusion pump is connected to the printing nozzle. The protective agent conveying pump is connected to the protective agent screw extrusion pump via a protective agent conveying pipeline. The protective agent screw extrusion pump is connected to the protective agent nozzle.

[0009] Optionally, the telescopic robotic arm includes two or more telescopic arm segments that coordinate with each other, and the telescopic arm segments are connected to the outer protective cover via rotating connectors.

[0010] Optionally, the rotating connector is a universal joint.

[0011] Optionally, the free end of the telescopic robotic arm is equipped with a monitoring and identification module.

[0012] Optionally, the free end of the telescopic robotic arm is equipped with a grinding module.

[0013] Optionally, a temperature sensor is provided at the free end of the telescopic robotic arm.

[0014] The beneficial effects of this invention are as follows: This invention is applicable to the repair of defects such as cracks, spalling, and exposed rebar in underwater concrete structures such as port terminals, breakwaters, and cross-sea bridge piers, and is particularly suitable for operation scenarios with strong seawater flow and complex construction environments, such as tidal zones and splash zones. The telescopic robotic arm of the underwater concrete 3D printing device serves as the device's operating mechanism, used to move and position the outer protective cover, inner protective cover, and nozzle body underwater. The rotating connecting parts can achieve multi-degree-of-freedom adjustment to meet the repair needs of complex curved surface structures; both the outer and inner protective covers are hollow cavity structures. The inner cavity of the inner protective cover is used to install the nozzle body, and a flexible sealing body is set at the open end facing the concrete surface to be repaired. The flexible sealing body has good flexibility and wear resistance, and it can adaptively deform according to the unevenness of the concrete surface, closely fitting the structural surface to form a local closed space, preventing seawater from entering the interior of the protective cover, and creating a dry and stable local environment for the printing operation. The outer protective cover is used to block the impact of external water flow to achieve primary sealing. The elastic compression component between the outer and inner protective covers can reduce the vibration transmitted from the outer to the inner protective cover, improving printing accuracy. On the other hand, it allows the inner protective cover to adaptively press against the concrete surface. Combined with the serrated texture of the flexible sealing body, it adapts to the unevenness of the curved surface to achieve secondary sealing. The sealing success rate on uneven surfaces (Ra≤150μm) reaches 100%, solving the problem of poor fit of a single protective cover on curved surfaces and stepped damage areas. It is especially suitable for operation scenarios with strong seawater flow and complex construction environments, such as tidal zones and splash zones. The underwater concrete 3D printing device of this invention has excellent environmental isolation effect. The flexible sealing body and the inner and outer protective covers work together to form a local closed space, which can effectively block seawater and minimize seawater interference. The compressive strength of the repair body is ≥40MPa and the interfacial bonding strength is ≥2.5MPa, which is 30%-50% higher than conventional underwater repair technology. The construction accuracy is high. The telescopic robotic arm can achieve multi-degree-of-freedom precise positioning (error ±2mm), and the printing nozzle can accurately adapt to cracks of different widths. The size deviation of the repair body is controlled within ±5mm, which meets the stringent repair accuracy requirements of port and shipping engineering. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of an underwater concrete 3D printing device. Figure 2 A partial schematic diagram of an underwater concrete 3D printing device; Label Explanation: 1. Telescopic robotic arm; 11. Telescopic arm segment; 2. Outer protective cover; 21. Inner protective cover; 22. Elastic compression component; 3. Nozzle body; 31. Printing nozzle; 32. Protective agent nozzle; 4. Flexible sealing body; 5. Base material mixing tank; 51. Base material conveying pump; 52. Storage screw extrusion pump; 53. Mixed material conveying pipeline; 6. Protective agent storage tank; 61. Protective agent conveying pump; 62. Protective agent screw extrusion pump; 63. Protective agent conveying pipeline; 7. Monitoring and identification module; 8. Grinding module. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are part of this invention.

[0018] Please refer to Figures 1 to 2 As shown, an underwater concrete 3D printing device of the present invention includes a telescopic robotic arm 1. The fixed end of the telescopic robotic arm 1 is installed on a floating platform, and the free end of the telescopic robotic arm 1 is submerged in water and connected to an outer protective cover 2 via a rotating connector. The outer protective cover 2 is hollow inside and has an opening at one end away from the telescopic robotic arm 1. An inner protective cover 21 is provided in the inner cavity of the outer protective cover 2. The inner protective cover 21 is hollow inside and has an opening at one end away from the telescopic robotic arm 1. An elastic support member 22 is provided between the outer protective cover 2 and the inner protective cover 21. A nozzle body 3 is provided in the inner cavity of the inner protective cover 21. Both the open end of the outer protective cover 2 and the open end of the inner protective cover 21 are provided with a flexible sealing body 4 that adaptively conforms to the surface of the underwater concrete. The sealing surface of the flexible sealing body 4 is provided with a serrated texture.

[0019] As can be seen from the above description, the beneficial effects of the present invention include: (1) Double isolation minimizes seawater interference: the outer protective cover 2 blocks the impact of external water flow, the inner protective cover 21 and the flexible sealing body 4 form a core closed space, and the elastic compression component 22 ensures the fit and sealing. The double protection reduces the seawater infiltration rate to below 0.1%, the compressive strength of the repair body is ≥42MPa, and the interface bonding strength is ≥2.8MPa, which is more than 40% higher than conventional technology.

[0020] (2) Adaptive fit and strong adaptability to complex working conditions: The elastic compression component 22 drives the inner protective cover 21 to adapt to the undulations of the concrete surface (such as protrusions and depressions) through axial expansion and contraction. Combined with the sawtooth texture of the flexible sealing body 4, the sealing success rate on uneven surfaces (Ra≤150μm) reaches 100%, solving the problem of poor fit of a single protective cover on curved surfaces and stepped damage.

[0021] (3) Stable structure and improved printing accuracy: The setting of the elastic compression component 22 can prevent the inner protective cover 21 from shaking during the printing process and reduce the adverse effects of environmental factors on printing accuracy.

[0022] (4) Easy to maintain and extended service life: The inner protective cover 21 and the outer protective cover 2 are separate structures, which makes it easy to replace damaged parts individually. For example, when the inner protective cover 21 is worn, there is no need to replace the entire protective cover. The elastic compression component 22 is used to buffer mechanical impact, which reduces the wear rate of the flexible sealing body 4 by 50% and reduces the overall equipment maintenance cost by 30%.

[0023] As can be seen from the above description, the working principle of the present invention includes: S1. The telescopic robotic arm 1 adjusts the angle of the outer protective cover 2 by rotating the connecting piece, which drives the inner protective cover 21 to approach the concrete surface to be repaired. The flexible sealing body 4 of the inner protective cover 21 contacts the surface first. S2. The telescopic robotic arm 1 continues to advance the outer protective cover 2, the elastic compression component 22 is compressed, and the axial thrust is generated so that the flexible sealing body 4 of the inner protective cover 21 fits tightly against the concrete surface to be repaired. The serrated texture is embedded in the surface depression to form a core closed space. The flexible sealing body 4 of the outer protective cover 2 fits tightly against the surface to form an outer sealed space. S3, the nozzle body 3 sprays protective agent to replace the seawater in the inner cavity of the inner protective cover 21 and between the inner protective cover 21 and the outer protective cover 2; S4. Next, the nozzle body 3 sprays concrete base material along the preset path. The elastic compression component 22 can adaptively buffer the water flow impact to ensure the stability of the inner protective cover 21 and avoid printing deviation. S5. After the repair is completed, the telescopic robotic arm 1 retracts, the elastic compression component 22 resets, and the inner protective cover 21 separates from the concrete surface to be repaired, while the outer protective cover 2 is removed simultaneously.

[0024] Preferably, two or more elastic support members 22 are evenly distributed in the gap between the outer protective cover 2 and the inner protective cover 21.

[0025] As described above, the purpose of uniformly distributing multiple elastic support members 22 is to prevent the inner protective cover 21 from shifting under stress. The circumferential distribution of the elastic support members 22 has two advantages: First, it allows the thrust of the elastic support members 22 to be evenly distributed along the circumference of the inner protective cover 21, ensuring consistent stress across all parts of the flexible sealing body 4. Even if there are local protrusions or depressions on the concrete surface, the flexible sealing body 4 can still fit together seamlessly without any gaps, reducing seawater infiltration to below 0.1%. Multiple elastic compression members 22 can buffer water flow impact in multiple directions, while eliminating the risk of minor displacement at the seal due to vibration and other reasons. Second, underwater concrete structures often develop curved surfaces and steps due to corrosion. For complex shapes such as concave and recessed areas, a single rigid connection of the protective cover cannot be adapted. The evenly distributed elastic support members 22 can achieve self-adaptation through "independent telescopic": when one side of the inner protective cover 21 contacts the raised surface, the elastic support member 22 at the corresponding position is compressed, while the elastic support members 22 at other positions maintain their original length, causing the inner protective cover 21 to tilt slightly with the surface shape. The flexible sealing body 4 is always "fully in contact" with the concrete surface, compensating for the positioning error of the telescopic robotic arm 1, avoiding sealing failure caused by rigid contact, eliminating the need to repeatedly adjust the position of the robotic arm, and improving construction efficiency.

[0026] Preferably, it also includes a base material mixing tank 5 and a protective agent storage tank 6, which are connected to the nozzle body 3 via a pump body.

[0027] As can be seen from the above description, after the base material mixing box 5 mixes the concrete base material evenly, it is transported to the nozzle body 3. The protective agent in the protective agent storage tank 6 is transported simultaneously, providing pre-protection for the printing material, realizing a stable supply of material, and ensuring continuous and uninterrupted delivery of the protective agent.

[0028] Preferably, the nozzle body 3 includes a printing nozzle 31 and a protective agent nozzle 32 disposed in the inner cavity of the inner protective cover 2. The base material mixing tank 5 is connected to the printing nozzle 31 through the base material delivery pump 51, and the protective agent storage tank 6 is connected to the protective agent nozzle 32 through the protective agent delivery pump 61.

[0029] As can be seen from the above description, the protective agent nozzle 32 first sprays the protective agent onto the area to be repaired to form a protective film of a certain thickness (e.g., 0.5-1mm); then the printing nozzle 31 sprays the concrete base material along a preset path to cover the surface of the protective film. The protective film effectively isolates seawater from the concrete, the printing material does not segregate, and the surface flatness error of the repaired body is <3mm.

[0030] Preferably, it also includes a storage screw extrusion pump 52 and a protective agent screw extrusion pump 62. The base material conveying pump 51 is connected to the storage screw extrusion pump 52 through the mixture conveying pipeline 53. The storage screw extrusion pump 52 is connected to the printing nozzle 31. The protective agent conveying pump 61 is connected to the protective agent screw extrusion pump 62 through the protective agent conveying pipeline 63. The protective agent screw extrusion pump 62 is connected to the protective agent nozzle 32.

[0031] As can be seen from the above description, the storage screw extrusion pump 52 extrudes the concrete base material through the screw blades and controls the output (e.g., 15L / min) to avoid material blockage; the protective agent screw extrusion pump 62 precisely controls the output of the protective agent (e.g., 5L / min) to ensure uniform protective film thickness.

[0032] Preferably, the telescopic robotic arm 1 includes two or more telescopic arm segments 11 that are telescopically coordinated, and the telescopic arm segments 11 are connected to the outer protective cover 2 through a rotating connector.

[0033] As described above, the telescopic boom segment 11 is hydraulically driven to extend and retract, allowing the total length of the robotic arm to be adjusted according to the size of the surface to be repaired, thus covering the entire damaged area. The operating radius is flexibly adjustable, eliminating the need to move the waterborne work platform and adapting to repair needs at different heights.

[0034] Preferably, the rotating connector is a universal joint.

[0035] As described above, the universal joint can rotate 360° and deflect ±45°, adjusting the angle of the outer protective cover 2 to ensure that the flexible sealing body 4 can fit tightly at different positions on the surface to be repaired. The angle adjustment accuracy is ±1°, solving the fitting problem at different positions on the planar structure, and achieving a 100% sealing success rate.

[0036] Preferably, the free end of the telescopic robotic arm 1 is equipped with a monitoring and identification module 7.

[0037] As described above, the monitoring and identification module 7 identifies the peeling area and boundary; the ultrasonic transducer scans the internal structure to confirm that there are no deep cavities; the data is transmitted to the control system to generate the printing path.

[0038] Preferably, the free end of the telescopic robotic arm 1 is provided with a grinding module 8.

[0039] As described above, the grinding module 8 removes marine organisms from the surface of the peeling area (removal rate ≥95%), and the high-pressure flushing nozzle washes away the laitance and loose concrete, exposing the fresh base layer.

[0040] The overall working principle of this invention is as follows: The project plans to design a 3D printing robotic arm fixed to a dock or platform. The robotic arm is designed with a replaceable module at its front end. A monitoring and identification module 7 is installed at the location of the damaged structure to determine the type and level of structural damage. Then, the grinding module 8 is lifted and replaced to remove surface deposits, followed by replacement with a printing repair module. The printing repair module integrates a dual mixing pump and a storage pump system. The primary mixing pump at the platform end first fully mixes the basic cementitious mortar, which is then transported through the robotic arm pipeline to the secondary mixing pump in the underwater section. Here, it is mixed a second time with a quick-setting agent to form a printing mortar with rapid curvature characteristics. The mortar after secondary mixing is pumped a short distance into a template protective cover equipped with adaptive curvature by a plunger pump or diaphragm pump as a storage pump. The inner protective cover 21 is equipped with dual nozzles: one of them is connected to the platform's liquid storage tank. During operation, it first releases underwater protective agent to quickly replace the water in the inner protective cover 21 and the outer protective cover 2, creating a local protective agent environment. After the water is drained, the protective agent nozzle 32 is closed, and then the other printing nozzle 31 is opened to accurately print the printing mortar onto the damaged area. Once the mortar has hardened to the required strength, the robotic arm withdraws to complete the repair process, achieving efficient and precise repair of underwater structures.

[0041] Please refer to Figures 1 to 2 As shown, Figure 2 This is a schematic diagram of the underwater concrete 3D printing device extending underwater. Embodiment 1 of the present invention aims to overcome the shortcomings of existing underwater concrete repair equipment, such as low construction accuracy, significant seawater interference, and fragmented functions. It provides a 3D printing device that can achieve integrated "detection-pretreatment-isolation-printing" operations, adaptable to complex underwater conditions, and improves repair efficiency and the quality of the repaired body. Core components include: Telescopic robotic arm 1: Serves as the operating mechanism of the device, used to move and position components such as the outer protective cover 2 and the nozzle body 3 underwater. It is made of high-strength aluminum alloy with a surface-coated anti-corrosion coating (such as polytetrafluoroethylene), which can resist seawater corrosion and adapt to long-term underwater operation.

[0042] Outer Protective Cover 2: The exterior is a hemispherical, cylindrical, or square cavity structure (customized according to the shape of the repair area), made of lightweight, high-strength engineering plastics (such as ABS resin), with a wall thickness of 5-8mm. This ensures structural strength (able to withstand 0.5MPa seawater pressure) while reducing overall weight (a single outer protective cover 2 weighs ≤30kg), facilitating robotic arm operation. The open end of the outer protective cover 2 faces the concrete surface to be repaired, forming a partially enclosed space to reduce seawater interference with the printing process.

[0043] Inner protective cover 21: Made of lightweight, high-strength engineering plastic (such as polyetheretherketone, PEEK), it has a hemispherical hollow structure (outer diameter 280-380mm, length 350-450mm) adapted to the outer protective cover 2, with a wall thickness of 6-8mm and a weight ≤15kg. Its core function is to form a closed space for printing operations. The nozzle body 3 and a miniature camera are installed inside the cavity, and the opening end is connected to the flexible sealing body 4, directly acting on the concrete surface to be repaired. The inner wall is coated with an anti-stick coating (polytetrafluoroethylene, thickness 50-80μm) to prevent concrete materials from sticking and reduce the frequency of cleaning the inner cavity.

[0044] Elastic compression component 22: Utilizing cylindrical helical compression springs (made of 316L stainless steel, resistant to seawater corrosion), 3-4 sets are evenly arranged circumferentially between the outer protective cover 2 and the inner protective cover 21. The two ends of each spring are connected to the inner wall of the outer protective cover 2 and the outer wall of the inner protective cover 21 by welding or bolting. Its function is as follows: when the telescopic robotic arm 1 moves the outer protective cover 2 closer to the concrete surface, the inner protective cover 21 first contacts the surface through the flexible sealing body 4. As the outer protective cover 2 continues to advance, the elastic compression component 22 is compressed, generating a reverse thrust that tightly adheres the flexible sealing body 4 to the surface, adapting to surface unevenness (Ra≤150μm); buffering water flow impact and positioning errors of the telescopic robotic arm 1; avoiding damage to the flexible sealing body 4 caused by rigid contact; and extending the service life of the seal (from the current 50 operations to over 100 operations).

[0045] Nozzle body 3: Installed in the middle of the inner cavity of the inner protective cover 21, it is used to deliver printing material and protective agent. It includes printing nozzle 31 and protective agent nozzle 32, which are arranged at an angle of 30-45° to ensure that the protective agent can cover the repair area before the printing material, providing a protective interface for the printing material.

[0046] Flexible sealing body 4: Fixed to the opening edges of the outer protective cover 2 and the inner protective cover 21, it is made of elastic rubber material (such as nitrile rubber), with a thickness of 8-12mm and a Shore hardness of 45-55HA, possessing good flexibility and wear resistance. It can adaptively deform according to the unevenness of the concrete surface, closely adhering to the structural surface, preventing seawater from entering the inner cavity of the outer protective cover 2 and the inner protective cover 21, creating a dry and stable local environment for printing operations.

[0047] The base material mixing tank 5 and the protective agent storage tank 6 are both located on a floating platform (such as the dock front or engineering vessel). The base material mixing tank 5 has a volume of 1-2 m³, built-in mixing blades and a weighing sensor, and the mixing speed can be adjusted from 60-120 r / min. It is used to mix concrete base materials (a mixture of cement, fine aggregate, admixtures, and water), with a weighing accuracy of ±0.1 kg, accurately controlling the proportion of cement, fine aggregate, and admixtures to ensure the uniformity of the base cementitious mortar. The coefficient of variation of the base material mixing uniformity is <5%. The protective agent storage tank 6 has a volume of 0.5-1 m³, equipped with a concentration monitor to monitor the protective agent concentration in real time, with a detection range of 0-0.5%. It is used to store polymer underwater protective agents (such as modified polyether polyol protective agents) to prevent printing materials from directly contacting seawater. The material conveying stability is improved by 60%, with no blockage, and the protective agent dosage accuracy is ±0.1 L / min.

[0048] Pump body and conveying pipeline: The base material conveying pump 51 and the protective agent conveying pump 61 are both plunger pumps, providing conveying power for the base material and protective agent respectively; the storage screw extrusion pump 52 and the protective agent screw extrusion pump 62 can precisely control the material output, avoiding material segregation or blockage; the mixed material conveying pipeline 53 and the protective agent conveying pipeline 63 are made of wear-resistant polyurethane material with an inner diameter of 20-30mm, possessing good pressure resistance and corrosion resistance. Material conveying stability is improved by 60%, with no blockage, and the protective agent dosage accuracy is ±0.1L / min.

[0049] Monitoring and identification module 7 includes a binocular vision camera and an ultrasonic transducer, installed on the side of the free end of the telescopic robotic arm 1. It is used to collect data on apparent damage (such as crack width and spalling area) and internal defects (such as voids and steel corrosion) of underwater concrete structures, providing a basis for repair path planning. The damage identification accuracy is ±0.5mm, and the printed path plan matches the actual damage with a 99% accuracy rate.

[0050] Grinding Module 8: Includes a high-frequency vibrating blade and a high-pressure flushing nozzle, installed on the other side of the free end of the telescopic robotic arm 1. It is used to remove marine organisms (such as oysters and seaweed), laitance, and loose layers from the concrete surface, exposing a fresh base layer and improving the bond strength between the restoration and the original structure. The base layer roughness Ra=60-80μm, and the bond strength between the restoration and the original structure is improved by 30%.

[0051] The connection relationship of the above core components is as follows: the fixed end of the telescopic robotic arm 1 is installed on the water operation platform, and the free end is connected to the top of the outer protective cover 2 through a rotating connector (universal joint); the inner cavity of the inner protective cover 21 has a fixed nozzle body 3, and the edge of the opening end is bonded with a flexible sealing body 4; the outlet of the base material mixing tank 5 is connected to the storage screw extrusion pump 52 through the base material conveying pump 51 and the mixing material conveying pipeline 53, and the outlet of the storage screw extrusion pump 52 is connected to the printing nozzle 31; the outlet of the protective agent storage tank 6 is connected to the protective agent screw extrusion pump 62 through the protective agent conveying pump 61 and the protective agent conveying pipeline 63, and the outlet of the protective agent screw extrusion pump 62 is connected to the protective agent nozzle 32; the monitoring and identification module 7 and the grinding module 8 are symmetrically installed on the free end of the telescopic robotic arm 1, forming a collaborative working relationship with the protective cover as a whole.

[0052] The telescopic robotic arm 1 consists of three telescopic arm segments 11, each with a telescopic stroke of 1.2m and a maximum overall working radius of 10m. The angle of the outer protective cover 2 is adjusted via a universal joint, allowing the flexible sealing body 4 to conform to the surface to be repaired (planar structure). The universal joint is made of titanium alloy, enabling ±360° rotation and ±45° deflection, with a positioning accuracy of ±2mm and a waterproof rating of IP68. The outer protective cover 2 is hemispherical, made of ABS resin, and has a wall thickness of 6mm. The inner protective cover 21 is also hemispherical, made of polyetheretherketone (PEEK), and has a wall thickness of 7mm. The nozzle body 3 has a printing nozzle 31 with an inner diameter of 20mm and a protective agent nozzle 32 with an inner diameter of 15mm, with an included angle of 40°. This ensures that the protective agent covers the repair area before the printing material and ensures uniform spraying of the protective agent. The flexible sealing body 4 is made of nitrile rubber, 10mm thick, with a Shore hardness of 50HA. It features a serrated fit pattern to adapt to the unevenness of underwater concrete surfaces (Ra≤100μm), and a sealing pressure ≥0.2MPa, effectively preventing seawater from seeping into the outer protective cover 2 and the inner protective cover 21. In the base material mixing tank 5, the concrete base material mix ratio is cement:mineral powder:fine sand:water:water-reducing agent = 1:0.3:2.6:0.35:0.01, with a stirring speed of 80r / min and a stirring time of 10min. The protective agent storage tank 6 stores 0.15% concentration of modified polyether polyol protective agent. Pump parameters: base material delivery pump 51 pressure 0.4MPa, storage screw extrusion pump 52 speed 50r / min; protective agent delivery pump 61 pressure 0.3MPa, protective agent screw extrusion pump 62 speed 30r / min. Monitoring and Identification Module 7: Binocular vision camera with 4K resolution and 30fps frame rate; ultrasonic transducer frequency 200kHz, scanning step size 5mm. Grinding Module 8: High-frequency vibrating blade with 25kHz frequency, high-pressure flushing nozzle with 1.0MPa water pressure, combined with a rotating nozzle (300r / min) to remove surface laitance and loose concrete, ensuring the smoothness of the repaired base layer (Ra=50-100μm).

[0053] During operation, the telescopic robotic arm 1 adjusts its length via telescopic arm segments 11, moving the outer protective cover 2 to the peeling area. The universal joint adjusts the angle of the outer protective cover 2, ensuring that the flexible sealing bodies 4 at the openings of the inner and outer protective covers 21 and 2 fit tightly against the surface to be repaired, forming a double-sealed space. The nozzle body 3 completes the printing operation within the cavity. The repair process sequentially completes damage identification (15 min) → surface pretreatment (25 min) → positioning of the inner protective cover 21 (5 min) → positioning of the outer protective cover 2 (5 min) → protective agent spraying (5 min) → 3D printing (40 min), with a total operation time of 95 min. Specifically: Damage detection: The telescopic robotic arm 1 moves the monitoring and identification module 7, the binocular vision camera acquires the surface image of the crack, the ultrasonic transducer array scans the internal structure to determine the width, length and depth of the crack (depth 20-30mm), and the data is transmitted to the control system to generate the repair path.

[0054] Surface pretreatment: Switch to grinding module 8, use high-pressure flushing nozzles to remove marine organisms and laitance from the pile foundation surface, and use vibratory cutters to treat stubborn attachments. After pretreatment, the flatness of the base layer Ra=60μm, which meets the repair requirements.

[0055] Environmental isolation: The telescopic robotic arm 1 adjusts the position of the outer protective cover 2 and the inner protective cover 21 so that the flexible sealing body 4 fits the surface of the pile foundation. The serrated texture adapts to the unevenness of the curved surface, forming a double sealing space. The protective agent nozzle 32 sprays a 0.1% concentration of polymer protective agent to replace the seawater in the sealed space. The spraying stops after the concentration sensor shows that the standard (0.09%) has been met.

[0056] 3D printing repair: The base cementitious mortar mixed in the base material mixing box 5 is transported to the printing nozzle 31 by the base material conveying pump 51 and the storage screw extrusion pump 52, and printed according to the preset path with a layer thickness of 30mm and an interval of 8min between layers; during the printing process, a miniature camera observes in real time to ensure that the material does not segregate.

[0057] The compressive strength of the repair body is 42 MPa, and the interfacial bond strength is 2.8 MPa, which meets the port engineering repair standards.

[0058] Please refer to Figures 1 to 2 As shown, in Embodiment 2 of the present invention, a temperature sensor (PT100 platinum resistance thermometer, accuracy ±0.5℃) and a pressure sensor (accuracy ±0.01MPa) can be added to the free end of the telescopic robotic arm 1 to monitor the underwater operating temperature (-10-50℃) and pressure in real time, ensuring the safe operation of the equipment.

[0059] Please refer to Figures 1 to 2As shown, in Embodiment 3 of the present invention, a miniature camera (waterproof rating IP68) can be installed in the inner cavity of the inner protective cover 21 to observe the printing process in real time and facilitate remote control.

[0060] Please refer to Figures 1 to 2 As shown, in Embodiment 4 of the present invention, the base material mixing box 5 can be equipped with a heating device to control the material temperature at 20-30°C in a low-temperature environment (<5°C) to ensure the rheological properties of the material.

[0061] In summary, this invention is applicable to the repair of defects such as cracks, spalling, and exposed rebar in underwater concrete structures such as port terminals, breakwaters, and cross-sea bridge piers. It is particularly suitable for complex construction environments with high seawater flow, such as tidal zones and splash zones. The telescopic robotic arm of the underwater concrete 3D printing device serves as the device's operating mechanism, used to move and position the outer protective cover, inner protective cover, and nozzle body underwater. The outer and inner protective covers are hollow cavity structures. The inner cavity of the inner protective cover is used to install the nozzle body. Flexible sealing bodies are set at the open ends of the outer and inner protective covers facing the concrete surface to be repaired. The flexible sealing bodies have good flexibility and wear resistance, and can adaptively deform according to the unevenness of the concrete surface, closely fitting the structural surface to form a local closed space, preventing seawater from entering the inner cavity of the outer and inner protective covers, creating a dry and stable local environment for the printing operation. The underwater concrete 3D printing device of the present invention has the following advantages: (1) Integrated operation, high efficiency, integrated monitoring and identification, surface pretreatment, seawater isolation and 3D printing functions, no need for frequent switching of multiple devices, the daily effective construction time in the tidal range is increased to 6-8 hours, and the repair efficiency is 3-5 times higher than that of traditional technology; the seawater isolation effect is good, the flexible sealing body and the outer protective cover and the inner protective cover form a closed working space, combined with the pre-spraying of protective agent, which can effectively block seawater interference, so that the compressive strength of the repair body is ≥40MPa and the interface bonding strength is ≥2.5MPa, which is more than 40% higher than that of conventional underwater repair technology; (2) High construction accuracy, the telescopic robotic arm can achieve multi-degree-of-freedom precise positioning (error ±2mm), combined with the precise feeding of the spiral extrusion pump, the size deviation of the repair body is controlled within ±5mm, which meets the requirements of high underwater structure. Precision repair requirements; (3) Strong environmental adaptability, all components adopt anti-corrosion and waterproof design (protection level IP68), can work stably under temperature of -10-50℃ and seawater pressure of 0.1-1.0MPa, and are suitable for various underwater working conditions such as tidal range, splash zone, and full immersion zone; (4) Excellent environmental isolation effect, the flexible sealing body and the outer protective cover and inner protective cover work together to form a local closed space, which can effectively block seawater and minimize seawater interference. The compressive strength of the repair body is ≥40MPa and the interface bonding strength is ≥2.5MPa, which is 30%-50% higher than conventional underwater repair technology; High construction precision, the telescopic robotic arm can achieve multi-degree-of-freedom precise positioning (error ±2mm), the printing nozzle can accurately adapt to cracks of different widths, and the size deviation of the repair body is controlled within ±5mm, which meets the stringent repair precision requirements of port and shipping engineering.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. An underwater concrete 3D printing device, characterized in that, The system includes a telescopic robotic arm, with its fixed end mounted on a floating platform. The free end of the telescopic robotic arm is submerged in water and connected to an outer protective cover via a rotating connector. The outer protective cover is hollow inside and open at one end away from the telescopic robotic arm. An inner protective cover is located within the inner cavity of the outer protective cover. The inner protective cover is also hollow inside and open at one end away from the telescopic robotic arm. An elastic support is located between the outer and inner protective covers. A nozzle body is located within the inner cavity of the inner protective cover. Both the open ends of the outer and inner protective covers are equipped with flexible sealing bodies that adapt to and conform to the underwater concrete surface. The sealing surface of the flexible sealing body has a serrated texture.

2. The underwater concrete 3D printing device according to claim 1, characterized in that, Two or more elastic support members are evenly distributed in the gap between the outer protective cover and the inner protective cover.

3. The underwater concrete 3D printing device according to claim 1, characterized in that, It also includes a base material mixing tank and a protective agent storage tank, which are connected to the nozzle body via a pump body.

4. The underwater concrete 3D printing device according to claim 3, characterized in that, The nozzle body includes a printing nozzle and a protective agent nozzle set in the inner cavity of the inner protective cover. The base material mixing tank is connected to the printing nozzle through a base material delivery pump, and the protective agent storage tank is connected to the protective agent nozzle through a protective agent delivery pump.

5. The underwater concrete 3D printing device according to claim 4, characterized in that, It also includes a storage screw extrusion pump and a protective agent screw extrusion pump. The base material conveying pump is connected to the storage screw extrusion pump through the mixture conveying pipeline. The storage screw extrusion pump is connected to the printing nozzle. The protective agent conveying pump is connected to the protective agent screw extrusion pump through the protective agent conveying pipeline. The protective agent screw extrusion pump is connected to the protective agent nozzle.

6. The underwater concrete 3D printing device according to claim 1, characterized in that, The telescopic robotic arm consists of two or more telescopic arm segments that work together to extend and retract. The telescopic arm segments are connected to the outer protective cover via rotating connectors.

7. The underwater concrete 3D printing device according to claim 1, characterized in that, The rotating connector is a universal joint.

8. The underwater concrete 3D printing device according to claim 1, characterized in that, The free end of the telescopic robotic arm is equipped with a monitoring and identification module.

9. The underwater concrete 3D printing device according to claim 1, characterized in that, The free end of the telescopic robotic arm is equipped with a grinding module.

10. The underwater concrete 3D printing device according to claim 1, characterized in that, The free end of the telescopic robotic arm is equipped with a temperature sensor.

Images