In-situ laser processing head and air pressure dynamic adjustment and anti-backflow protection method thereof

Abstract

The invention discloses an in-situ laser processing head and an air pressure dynamic adjustment and anti-backflow protection method thereof, and belongs to the technical field of underwater laser processing equipment. According to the processing head, the internal air pressure is automatically adjusted along with the change of external water pressure through an air pressure balance system for communicating the pipeline with the anti-reflux device and the gas-liquid separator, and a liquid barrier is formed when the gas pipe is broken to prevent water from flowing backwards to damage the optical cavity. One path of gas enters the machining head through the anti-backflow device and the gas-liquid separator, and dynamic gas pressure compensation is achieved. When external water pressure changes or a gas circuit is broken, the device can passively respond and keep pressure balance, and it is ensured that the optical element is dry and safe. The device is compact in structure and high in corrosion resistance, does not need a complex control system, and is suitable for various underwater in-situ laser repair and additive manufacturing environments.

Description

Technical Field

[0001] This invention relates to the field of underwater laser processing equipment technology, specifically to an in-situ laser processing head and a method for dynamic air pressure adjustment and backflow prevention protection. Background Technology

[0002] With the continuous advancement of laser processing technology, the application fields of underwater laser repair are expanding. However, due to the limitations of the complex underwater processing environment, there is still a lack of dedicated laser equipment that can meet the needs of underwater repair. If the equipment is disassembled and transported to the surface for repair and manufacturing, it often takes a lot of time and is limited by transportation costs. Generally, only small parts can be disassembled and repaired. However, marine equipment such as offshore platforms, gas pipelines, and ships are difficult to disassemble and move. Therefore, there is an urgent need for relevant in-situ laser repair equipment.

[0003] When performing in-situ repairs using a conventional laser processing head submerged in water, the laser processing head, along with its optical fiber, air hoses, and other auxiliary equipment, must all be placed underwater. To cope with the complex underwater environment, the laser processing head needs to be sealed and waterproofed. However, if the laser processing head is completely sealed, during the actual in-situ processing, the pressure of the underwater environment will act on the laser processing head and subsequently on the optical cavity. The pressure difference between the underwater environment and the inside of the optical cavity will act on the optical lens, and this pressure difference will change with the processing environment. This constantly fluctuating pressure difference acting on the optical lens can lead to fatigue and breakage, affecting the precision and efficiency of laser repair manufacturing, and in severe cases, even causing safety accidents. Therefore, it is necessary to introduce gas into the laser processing head to achieve pressure balance. Furthermore, if gas is introduced into the laser processing head, the complex marine environment, such as marine life and currents, can easily cause the gas supply pipes to break, allowing water to enter the optical system, leading to equipment damage and safety accidents.

[0004] Therefore, there is an urgent need to develop a laser processing head for underwater in-situ repair and manufacturing, which can dynamically adjust the air pressure inside the lens assembly and prevent backflow when the air tube of the laser processing head ruptures. Summary of the Invention

[0005] To achieve in-situ laser repair manufacturing in deep-water environments, this invention proposes an in-situ laser processing head and a method for dynamic air pressure adjustment and backflow prevention protection.

[0006] The technical solution of the present invention is as follows: An in-situ laser processing head includes a laser processing head body, a gas-liquid separator, and an anti-backflow device. The gas-liquid separator and the anti-backflow device are located on the side of the laser processing head body. The anti-backflow device has one gas inlet and at least two gas outlets, namely gas outlet A and gas outlet B. The gas inlet is connected to a gas source. The anti-backflow device has a gas channel inside. Gas enters the gas channel through the gas inlet and is divided into two paths. One path enters the Tesla valve flow channel inside the anti-backflow device and then enters the gas-liquid separator through gas outlet B, and then enters the sealed cavity inside the laser processing head body after passing through the gas separator. The other path passes through the gas channel and enters the protective gas path of the laser processing head through gas outlet A as a protective gas.

[0007] Furthermore, the anti-backflow device is provided with at least one Tesla valve flow channel, which is n-shaped and includes two Tesla valves in opposite directions, as well as a Tesla valve connecting flow channel for connecting the two Tesla valves.

[0008] Furthermore, the gas-liquid separator includes a gas-liquid separator body, a threaded hole, a gas inlet, a gas-liquid mixing zone, a gas zone, a polytetrafluoroethylene (PTFE) film, and a film plate. The PTFE film is disposed between two layers of film plates. The gas inlet is connected to the gas-liquid mixing zone through a flow channel. The PTFE film and the film plate are located on both sides of the gas-liquid mixing zone and the gas zone, respectively. The gas zone is connected to the gas inlet on the side of the laser processing head body.

[0009] Furthermore, the gas-liquid separator has a gas inlet channel on the contact surface with the laser processing head body, and the gas flows into the interior of the laser processing head body through the gas outlet channel.

[0010] This invention also provides a method for dynamic air pressure adjustment and backflow prevention protection of an in-situ laser processing head, characterized by comprising the following steps: Step 1) Before immersing the laser processing head in water, continuously introduce protective gas and powder-carrying gas with sufficient pressure. One gas enters the laser processing head, and the other enters the sealed cavity inside the processing head body. Step 2) As the laser processing head descends and the water depth changes, the external water pressure changes dynamically, and the gas pipeline automatically compensates, so that the internal gas pressure of the processing head and the pressure below the nozzle are dynamically adjusted in sync with the external water pressure, and are always maintained higher than the ambient water pressure. Step 3) Perform repair manufacturing: The laser irradiates the substrate to form a molten pool on the substrate; the sprayed powder enters the molten pool, melts and cools to form an effective deposition, and the cladding head moves to complete the entire cladding process; Step 4) After completing the repair and manufacturing work, move the laser processing head from the deep water environment to the atmospheric environment. During this process, adjust the air pressure to be higher than the ambient pressure to avoid the impact caused by the decrease in ambient pressure.

[0011] Furthermore, in step 3), when underwater repair and manufacturing work is carried out, if the external gas pipeline ruptures, the backflowing water flows through the anti-backflow device. The Tesla valve flow channel inside the anti-backflow device generates high flow resistance to the flowing liquid, which slows down the high-speed backflowing water flow. After being slowed down, the water reaches the inside of the gas-liquid separator. The gas-liquid separator allows gas to pass through while blocking the penetration of liquid water, forming an anti-backflow barrier to ensure the dryness of the optical cavity. Promptly move the laser processing head from the deep water environment to the atmospheric environment, inspect the laser processing head and optical cavity, and replace the gas pipeline.

[0012] Invention design concept: The device utilizes a pressure balancing system that connects pipes, an anti-backflow device, and a gas-liquid separator to automatically adjust internal air pressure according to changes in external water pressure. It also forms a liquid barrier in the event of a pipe rupture, preventing water backflow and damage to the optical cavity. One gas path enters the processing head via the anti-backflow device and gas-liquid separator, achieving dynamic pressure compensation. When external water pressure changes or the gas path ruptures, the device passively responds and maintains pressure balance, ensuring the optical components remain dry and safe. This invention features a compact structure, strong corrosion resistance, and requires no complex control system, making it suitable for various underwater in-situ laser repair and additive manufacturing environments.

[0013] The beneficial effects of this invention are as follows: Compared with existing laser processing heads that rely solely on mechanical valves or single-channel gas supply, or those that use electronic devices for underwater remote control, this invention utilizes the passive flow control characteristics of the Tesla valve channel and the gas-liquid separation capability of the hydrophobic film to achieve automatic gas pressure matching and liquid blocking functions without sensors or mechanical response mechanisms. This design significantly improves the reliability and service life of the underwater processing head and can keep the optical cavity dry and the optical path stable in a marine environment.

[0014] 1) By connecting with the nozzle protective gas and the unidirectional and reverse high resistance characteristics of the Tesla valve, gas can slowly enter and maintain the synchronous change of internal gas pressure and external deep water pressure in the laser processing head, thereby achieving dynamic gas pressure regulation.

[0015] 2) The polytetrafluoroethylene microporous hydrophobic film allows gas to pass through while relying on high capillary pressure to prevent liquid water from penetrating, ensuring the dryness and safety of the mirror assembly and internal components in deep water environments.

[0016] 3) The branch channels and backflow vortex inside the Tesla valve can significantly increase the resistance to reverse water flow and slow down the seawater entry speed. The polytetrafluoroethylene film prevents seawater from entering the laser processing head body along the Tesla valve and prevents damage to the mirror assembly.

[0017] 4) The gas-liquid separator and anti-backflow device are bolted to the main body of the laser processing head, with a compact structure. The overall device is simple and reasonable, corrosion-resistant and easy to process and manufacture, and is suitable for various deep-water in-situ laser repair environments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a cross-sectional view of the main body of the laser processing head; Figure 3 This is a schematic diagram of the gas flow channel inside a laser processing head. Figure 4 A schematic diagram of the anti-backflow device structure; Figure 5 This is a cross-sectional view of the front side of the anti-backflow device; Figure 6 This is a cross-sectional view of the rear side of the anti-backflow device; Figure 7 This is a side sectional view of the anti-backflow device; Figure 8 This is a schematic diagram of a gas-liquid separator. Figure 9 This is a cross-sectional view of a gas-liquid separator; Figure 10 This is a magnified view of a portion of the gas-liquid separator; In the diagram: 1. Laser processing head body; 2. Gas-liquid separator; 3. Backflow preventer; 4. Connecting pipe; 11. Fiber optic cable; 12. Collimating and focusing lens assembly; 13. Sealing lens assembly; 14. Protective lens assembly; 15. Quick connector; 16. Sleeve; 211. Threaded hole; 212. Gas inlet; 221. Polytetrafluoroethylene microporous membrane; 231. Membrane pressure plate; 311. Gas inlet; 314. Gas outlet A; 315. Gas outlet B; 321. Tesla valve flow path; 322. Gas passage; 323. Tesla valve connecting flow path. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] like Figure 1-10 As shown, a method for dynamic air pressure regulation and backflow prevention protection and an in-situ laser processing head are disclosed. The structure mainly includes: a laser processing head body 1, a gas-liquid separator 2, an anti-backflow device 3, and a connecting pipe 4. The main body 1 of the laser processing head includes: an optical fiber 11, a collimating and focusing lens group 12, a sealing lens group 13, a protective lens group 14, a quick connector 15, and a sleeve 16. The gas-liquid separator 2 includes a threaded hole 211, a gas inlet 212, a polytetrafluoroethylene microporous membrane 221, and a membrane pressure plate 231. The backflow preventer 3 includes: gas inlet 311, gas outlet A314, gas outlet B315, Tesla valve flow channel 321, gas passage 322, and Tesla valve connecting flow channel 323. The gas-liquid separator 2 and the anti-backflow device 3 are arranged on the side of the main body 1 and are connected by threads.

[0021] The gas-liquid separator 2 is composed of a multi-layer thin-film platen and a PTFE hydrophobic membrane. The PTFE membrane has a pore size of 0.6–0.8 μm and a thickness of approximately 1 mm, allowing gas to pass through while preventing liquid permeation. In this embodiment, the gas-liquid separator 2 has two layers of membranes and three layers of platens inside.

[0022] The anti-backflow device 3 has a Tesla valve flow channel inside, which is used to attenuate the flow rate and control the direction of the gas. Its reverse low conduction characteristic can form a stable airflow during normal ventilation and provide a high resistance flow field during reverse liquid impact.

[0023] The gas is first introduced into the anti-backflow device 3. The internal flow channel of the anti-backflow device 3 divides the gas into two paths. One path enters the Tesla valve flow channel from the lower part of the anti-backflow device 3, and the other path passes through the anti-backflow device 3 into the connecting pipe 4 and is introduced into the protective gas path of the laser processing head as protective gas.

[0024] The anti-backflow device 3 has a Tesla valve flow channel with a reverse design inside. The anti-backflow device 3 has two Tesla flow channels, and the outlet pipe of the anti-backflow device is connected to the inlet of the gas-liquid separator 2. The gas entering the anti-backflow device 3 is divided into two paths, with independent deceleration channels on the left and right sides. Each deceleration channel is connected by two Tesla valves in opposite directions. Therefore, the inlet and outlet of the "Tesla valve" are both at the bottom. The gas is injected from the bottom and discharged from the bottom as well, flowing into the gas-liquid separator through the pipe. The gas-liquid separator has a slot, and the pressure plate is fixed to the outer shell through the slot.

[0025] The gas-liquid separator 2 contains a membrane pressure plate, with a polytetrafluoroethylene (PTFE) membrane between every two pressure plates. There are at least two pressure plates and at least one PTFE membrane. The gas-liquid separator 2 has a gas outlet channel connected to the laser processing head body 1, and there is at least one gas outlet channel. Figure 3 As shown, the outer shell of the laser processing head body 1 has a small gas flow channel. The outer shell of the laser processing head body 1, the anti-backflow device 3, and the gas-liquid separator 2 are all made of polyester plastic or other corrosion-resistant engineering plastics.

[0026] like Figure 1As shown: the right side is the main body of the laser processing head, and the left side is the pressure balancing device (i.e., gas-liquid separator 2 + anti-backflow device 3). The gas source is connected to the gas interface of the anti-backflow device. The main body of the laser processing head, from the protective lens upwards, needs to undergo good pressure-resistant sealing treatment. The pressure balancing device also undergoes pressure-resistant sealing treatment. There is a gas channel between the main body of the laser processing head and the pressure balancing device, and the two are connected by bolts. During laser in-situ repair manufacturing: after the gas is introduced into the protective gas interface of the laser processing head, one path of gas passes through the sleeve and the laser nozzle, finally flowing into the external environment from below the nozzle; simultaneously, another path of gas flows into the anti-backflow device, where the internal flow channel of the anti-backflow device divides the gas into two paths. One path enters the Tesla valve flow channel from the lower part of the anti-backflow device, and the other path passes through the anti-backflow device into the connecting pipe and is input into the protective gas path of the laser processing head as protective gas.

[0027] like Figure 5 As shown, the Tesla flow channel is placed in reverse, that is, opposite to the gas inflow direction. Due to the unidirectional conductivity and low reverse conductivity of the Tesla valve, the gas can slowly flow through the Tesla valve. After passing through the Tesla valve, the gas flow rate decreases, and the gas continues to flow into the gas-liquid separator. Inside the gas-liquid separator, there is a thin film plate and a polytetrafluoroethylene (PTFE) film. The PTFE film has a highly hydrophobic surface, and the micropores on the film cause surface tension, which allows gas to pass through while preventing liquid from passing through. After the gas flows through the PTFE film, it flows into the laser processing head body through the gas outlet channel. At this time, since the laser processing head body is a sealed and pressure-resistant area above the protective lens, and this area is filled with gas due to the presence of the gas flow channel, the gas achieves equilibrium with the external pressure value.

[0028] The above gas flow measures need to be implemented before in-situ repair manufacturing. As the laser processing head is submerged in water, the water pressure increases with depth. Because the gas source pressure is higher than the water pressure, gas can still be pumped out from below the nozzle. Furthermore, the pressure below the nozzle is higher than the ambient water pressure. At this point, the internal pressure of the gas pipe is balanced. The pressure flowing into the fluid reducer (the internal pressure of the laser processing head body) is equal to the gas pressure below the nozzle, both slightly higher than the ambient water pressure. Both the gas pressure below the nozzle and the internal pressure of the laser processing head body increase or decrease synchronously with the water depth, achieving dynamic pressure balance. During the continuous submersion of the laser processing head body in water, gas is continuously supplied, and gas is continuously pumped out from below the nozzle. Liquid will not flow into the nozzle or sleeve, and liquid will not contaminate the protective lens, thus not affecting the laser repair manufacturing process.

[0029] During underwater repair and manufacturing, if the gas pipeline breaks, water will flow along the gas pipe. In this case, the anti-backflow device and gas-liquid separator can prevent water from flowing into the laser processing head and affecting the lens assembly and processing. The specific principle is as follows: The water first passes through the Tesla valve channel of the anti-backflow device. The special geometry inside the Tesla channel, namely the branch channels and backflow vortices, generates strong vortices and local backflow, significantly increasing flow resistance. This slows down the water flow rate. The water accumulates outside the gas-liquid separator. At this point, the polytetrafluoroethylene (PTFE) film, due to its superhydrophobicity and the microporous structure on the film, prevents water from passing through. Simultaneously, the gas pressure inside the laser processing head is similar to the external water pressure, therefore, water cannot enter the main body of the laser processing head and the lens assembly, thus preventing it from affecting the processing.

[0030] Working principle analysis: By introducing a pressure balancing system inside the laser processing head, the internal pressure can be automatically adjusted according to changes in external water pressure, thereby maintaining the stability of the optical components and the sealed cavity. Gas is introduced into the optical cavity through pipes and flows through the gas flow channels inside the laser processing head to fill the entire cavity. During processing, the water pressure increases with water depth. Since the pressure of the gas source is higher than the water pressure, gas can still be pumped out from below the nozzle, and the pressure below the nozzle is higher than the ambient water pressure. At this time, the pressure inside the gas supply pipe is balanced, and the pressure flowing into the optical cavity (the internal pressure of the laser processing head body) is equal to the gas pressure below the nozzle, both slightly higher than the ambient water pressure. Furthermore, the gas pressure below the nozzle and the internal pressure of the laser processing head body increase or decrease synchronously with changes in water depth, achieving dynamic pressure balance.

[0031] Backflow prevention methods are divided into two types: backflow prevention and gas-liquid separation. The gas pipeline is connected to the inlet of the backflow prevention device. When the external gas path ruptures, the high-speed intruding seawater first flows through the backflow prevention device, which greatly slows down the water flow, making the water a quasi-static liquid before it enters the gas-liquid separator.

[0032] After being slowed down, the water enters the gas-liquid separator, which separates the water from the gas, completely isolating the water from the outside of the optical cavity. The protective gas remaining in the water can enter the optical cavity through the gas-liquid separator to protect the optical cavity and related components.

[0033] The above method can automatically form an anti-backflow barrier when the gas path is broken, preventing water from entering the optical cavity and ensuring equipment safety.

[0034] The anti-backflow device contains a Tesla valve flow channel. When the gas is vented in the forward direction, the Tesla valve flow channel provides low-resistance flow, allowing the gas to enter the optical cavity smoothly and achieve dynamic gas pressure compensation. However, under the action of reverse pressure, a high-resistance flow field is formed.

[0035] If the anti-backflow device is used alone, when the water pressure is too high, the water will inevitably pass through the Tesla flow channel and enter the optical cavity; the gas-liquid separator has a polytetrafluoroethylene microporous membrane inside. The polytetrafluoroethylene membrane has a highly hydrophobic surface and the micropores on the membrane cause the existence of surface tension, which allows the polytetrafluoroethylene membrane to allow gas to pass through while preventing liquid from passing through. If the gas-liquid separator is used alone, the impact flow of seawater when the gas tube ruptures is very likely to damage the microporous membrane in the gas-liquid separator, causing water to flow into the optical cavity.

[0036] Therefore, both methods need to be used in combination: gas flows through the Tesla valve channel in the anti-backflow device and the hydrophobic microporous membrane in the gas-liquid separator. The gas smoothly enters the optical cavity through the Tesla channel to achieve dynamic gas pressure compensation. When the pipeline ruptures, the high-speed water flow is greatly slowed down after passing through the Tesla channel and then enters the gas-liquid separator. The tetrafluoroethylene (PTFE) hydrophobic microporous membrane in the gas-liquid separator has liquid barrier properties to prevent the backflow of external water. When the external gas path ruptures or breaks, the system can automatically form an anti-backflow barrier by relying on the unidirectional flow control structure and hydrophobic film in the channel to prevent water from entering the optical cavity.

[0037] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also includes equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. An in-situ laser processing head, characterized in that, The device includes a laser processing head body (1), a gas-liquid separator (2), and an anti-backflow device (3). The gas-liquid separator (2) and the anti-backflow device (3) are located on the side of the laser processing head body (1). The anti-backflow device (3) has a gas inlet (311) and at least two gas outlets, namely gas outlet A (314) and gas outlet B (315). The gas inlet (311) is connected to a gas source. The anti-backflow device (3) is provided with a gas channel (322). The gas enters the gas channel (322) through the gas inlet (311) and is divided into two paths through the gas channel (322). One path enters the Tesla valve flow channel (321) inside the anti-backflow device (3) and then enters the gas-liquid separator (2) through the gas outlet B (315), and then enters the sealed cavity inside the laser processing head body (1) after passing through the gas separator (2). The other path passes through the gas channel (322) and then enters the protective gas path of the laser processing head through the gas outlet A (314) as a protective gas.

2. The in-situ laser processing head according to claim 1, characterized in that, The anti-backflow device (3) is provided with at least one Tesla valve flow channel (321). The Tesla valve flow channel (321) is n-shaped and includes two Tesla valves in opposite directions, as well as a Tesla valve connecting flow channel for connecting the two Tesla valves. When the air is ventilated, the Tesla valve flow channel (321) forms a stable airflow. When the liquid is impacted, the Tesla valve flow channel (321) provides a high-resistance flow field.

3. The in-situ laser processing head according to claim 1, characterized in that, The gas-liquid separator (2) includes a gas-liquid separator body, a threaded hole (211), a gas inlet (212), a gas-liquid mixing zone (213), a gas zone (214), a polytetrafluoroethylene film (221), and a film plate (231). The polytetrafluoroethylene film (221) is disposed between two layers of film plates (231). The gas inlet (212) is connected to the gas-liquid mixing zone (213) through a flow channel. The gas-liquid mixing zone (213) and the gas zone (214) are located on both sides of the polytetrafluoroethylene film (221) and the film plate (231). The gas zone (214) is connected to the gas inlet on the side of the laser processing head body (1).

4. The in-situ laser processing head according to claim 1, characterized in that, The gas-liquid separator (2) has a gas inlet channel (121) at the contact surface with the laser processing head body (1), and the gas flows into the interior of the laser processing head body (1) through the gas outlet channel (121).

5. A method for dynamic air pressure adjustment and backflow prevention protection of an in-situ laser processing head according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1) Before immersing the laser processing head in water, continuously supply protective gas and powder-carrying gas with sufficient pressure; one gas path enters the laser processing head, and the other path enters the sealed cavity inside the processing head body; Step 2) As the laser processing head descends and the water depth changes, the external water pressure changes dynamically, and the gas pipeline automatically compensates, so that the internal air pressure of the processing head and the pressure below the nozzle are dynamically adjusted in sync with the external water pressure, and are always maintained higher than the ambient water pressure. Step 3) Perform repair manufacturing: The laser irradiates the substrate to form a molten pool on the substrate; the sprayed powder enters the molten pool, melts and cools to form an effective deposition, and the cladding head moves to complete the entire cladding process; Step 4) After completing the repair and manufacturing work, move the laser processing head from the deep water environment to the atmospheric environment. During this process, adjust the air pressure to be higher than the ambient pressure to avoid the impact caused by the decrease in ambient pressure.

6. The method for dynamic air pressure adjustment and backflow prevention protection of the in-situ laser processing head according to claim 5, characterized in that, In step 3), when underwater repair and manufacturing work is being carried out, if the external gas pipeline ruptures, the backflowing water flows through the anti-backflow device. The Tesla valve flow channel inside the anti-backflow device generates high flow resistance to the flowing liquid, which slows down the high-speed backflowing water. After being slowed down, the water reaches the inside of the gas-liquid separator. The gas-liquid separator allows gas to pass through while blocking the penetration of liquid water, forming an anti-backflow barrier to ensure the dryness of the optical cavity. Promptly move the laser processing head from the deep water environment to the atmospheric environment, inspect the laser processing head and optical cavity, and replace the gas pipeline.

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