Plasma torch and torch

Abstract

The utility model discloses a kind of plasma spray head and spray gun, the spray head includes metal sheath, discharge assembly is arranged in the cavity in metal sheath, and its one end is also provided with nozzle;Discharge assembly includes electrode column, insulating sheath, metal cap, electrode column includes tip and root, and through hole for electrode column is provided on metal cap;Metal sheath and metal cap are grounded, to form first discharge gap between the inner side of through hole and the outer side of root, and form second discharge gap between tip and metal sheath, first discharge gap is preferential to second discharge gap and occurs electric breakdown.The above-mentioned spray head, discharge is preferentially started at electrode root, avoid random arc at electrode tip or insulating surface, significantly improve arc consistency and repeatability, weaken insulating sheath surface tangential electric field, reduce surface micro-discharge and DBD sensitivity, extend spray head life.

Description

Technical Field

[0001] This utility model relates to the field of plasma discharge technology, and in particular to a plasma nozzle and spray gun. Background Technology

[0002] Plasma jetting equipment is widely used in material surface cleaning, activation, modification, micro-welding, and localized heating. These devices typically work by applying a high voltage to compressed gas, causing the working gas to ionize inside or near the nozzle and form a plasma jet. To balance dielectric strength, heat dissipation, and mechanical protection, the nozzle often uses a metal sheath as its outer casing and houses the nozzle. High-voltage electrode posts are coaxially arranged, and insulating sheaths are often fitted to the outside of the electrodes for electrical isolation and creepage distance management. The entire unit is positioned and fixed by metal components at the front and rear ends. Power supply methods can include AC, pulse, or DC with pulsed outputs. The working gas is typically air, argon, helium, or a mixture thereof, and the gas flow forms a high-speed jet at the nozzle to stabilize the plasma channel.

[0003] In existing technologies, the location and arc initiation reliability of plasma discharge are influenced by a combination of factors, including electrode geometry, gas type and pressure-gap product (pd) characteristics, surface condition, and assembly tolerances. A typical approach involves forming a main discharge gap between the electrode tip and the metal sheath (or nozzle), utilizing the tip effect to increase the local field strength, aiming to directly break down and maintain the discharge in the nozzle region. However, this plasma discharge structure suffers from the following common problems in engineering applications: 1. The main gap is usually large and subject to airflow disturbance, resulting in a high initial breakdown threshold, which often causes abnormal arc initiation. Excessively reducing the gap or sharpening the tip to lower the arc initiation voltage will cause the nozzle orifice and electrode tip to be subjected to higher transient electrical stress, resulting in electrolytic corrosion, sputtering and thermal shock, and shortening the life.

[0004] 2. There is a risk of surface discharge (DBD / creep). Near the electrode root, there is a three-phase boundary between the electrode, insulator, and gas. If the electric field is not effectively shaped, a large tangential field strength will be generated along the ceramic end face, which can easily lead to surface micro-discharge, DBD dendritic marks, carbonization, and contamination. This is detrimental to ignition consistency and electromagnetic compatibility, and is extremely sensitive to environmental humidity and dust.

[0005] 3. When the same main gap serves both ignition and arc maintenance functions, it is often difficult to achieve both reliable ignition and stable arc maintenance. Increasing the voltage or changing the airflow to ensure ignition may lead to dual-channel discharge, arc foot wandering, or interference with downstream processes.

[0006] In general, the discharge structure inside current plasma nozzles has abnormal arc initiation problems, especially after a period of use, arc initiation becomes difficult, and DBD discharge marks are easily found on the insulating ceramic, resulting in short electrode life. Utility Model Content

[0007] The purpose of this invention is to provide a plasma nozzle and spray gun that can preferentially initiate an arc at a controlled position at the root of the electrode and facilitate the stable transfer and maintenance of the discharge channel to the nozzle area in order to solve the above-mentioned technical problems.

[0008] To achieve the above objectives, this utility model provides a plasma nozzle, which includes a metal sheath. A discharge assembly is disposed in a cavity within the metal sheath, and a nozzle communicating with the cavity is disposed at one end of the metal sheath. The discharge assembly includes an electrode post, an insulating sheath, and a metal cap. The electrode post includes a tip and a root. The tip is located inside the metal sheath near the nozzle. The insulating sheath is fitted over the outside of the root of the electrode post. The metal cap covers the end of the insulating sheath near the root of the electrode post. The metal cap has a through hole for the electrode post to pass through. The metal sheath and the metal cap are grounded, thereby forming a first discharge gap between the inner side of the through hole and the outer side of the root of the electrode post, and forming a second discharge gap between the tip of the electrode post and the metal sheath. The first discharge gap (G1) is electrically broken down preferentially over the second discharge gap (G2).

[0009] Preferably, the breakdown voltage of the first discharge gap is greater than the breakdown voltage of the second discharge gap.

[0010] Preferably, the first discharge gap is 3-6 mm.

[0011] Preferably, the second discharge gap is 2-4 mm larger than the first discharge gap.

[0012] Preferably, the inner edge of the metal cap near the root of the electrode post is chamfered.

[0013] Preferably, the chamfer diameter of the inner edge of the metal cap is 0.3-0.8 mm.

[0014] Preferably, the insulating sheath is a ceramic body.

[0015] This utility model also provides a plasma spray gun, which includes a gun body and a plasma nozzle as described above. The end of the metal sheath away from the nozzle is connected to the gun body, and an air inlet pipe communicating with the inner cavity of the insulating sheath is provided in the gun body.

[0016] Preferably, the gun body is further provided with a bearing seat, the bearing seat is provided with a bearing sleeve and a rotating shaft rotatably connected to the bearing sleeve, the rotating shaft is connected to the metal sheath, the gun body is further provided with a rotating driver that is pulsatorically connected to the rotating shaft, the rotating driver is used to drive the rotating shaft to rotate, and then drive the metal sheath and the nozzle to rotate through the rotating shaft.

[0017] Preferably, a fixed sleeve is provided inside the metal sheath, one end of the insulating sheath is disposed in the fixed sleeve, the air intake pipe is a rigid support member, one end of the air intake pipe is connected to the fixed sleeve and passes through the fixed sleeve, the rotating shaft is a hollow structure, the other end of the air intake pipe passes through the rotating shaft and is connected to the pipe head disposed on the bearing seat; a fixing ring is provided inside the insulating sheath, and the end of the electrode post opposite to the tip is disposed on the fixing ring.

[0018] Compared with existing technologies, the plasma nozzle provided by the above technical solution preferentially initiates discharge at the controlled electrode root, avoiding random arcing at the electrode tip / nozzle or insulating surface. This significantly improves arcing consistency and repeatability, requires lower initial peak voltage and arcing energy, and has a shorter arcing delay. This reduces the design difficulty and cost of high-voltage power supplies, reduces overshoot and surge, and improves energy efficiency and reliability. The metal cap is grounded and surrounds the root, concentrating the electric field in the first gap, weakening the tangential electric field on the insulating sheath surface, and reducing surface micro-discharge and DBD sensitivity. Furthermore, the initial discharge does not occur between the tip and the metal sheath, avoiding the tip from bearing maximum electrical stress and thermal shock, reducing electrolytic corrosion, sputtering, and thermal cracking, and extending nozzle life. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of the plasma nozzle in an embodiment of this utility model.

[0020] Figure 2 This is an exploded view of the plasma nozzle in an embodiment of this utility model.

[0021] Figure 3 This is a perspective view of the installation structure of the electrode column in the plasma nozzle in this embodiment of the present invention.

[0022] Figure 4 This is a three-dimensional structural diagram of the spray gun in an embodiment of this utility model.

[0023] Figure 5 for Figure 4 Side view.

[0024] Figure 6 for Figure 5 Cross-sectional view.

[0025] Figure 7This is a diagram showing the internal structure of the spray gun in an embodiment of this utility model. Detailed Implementation

[0026] To explain in detail the technical content, structural features, objectives and effects of this utility model, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0027] This embodiment discloses a plasma nozzle that ionizes introduced gas using a high-voltage electric field to obtain a plasma stream. This plasma stream is sprayed onto the surface of a target object for cleaning, activation, modification, micro-welding, and other applications.

[0028] like Figures 1 to 3 The nozzle 1 includes a metal sheath 10, a discharge assembly is disposed in the cavity inside the metal sheath 10, and a nozzle 11 communicating with the cavity is disposed at one end of the metal sheath 10.

[0029] The discharge assembly includes an electrode post 12, an insulating sleeve 13, and a metal cap 14. The electrode post 12 includes a tip 120 and a root 121. The tip 120 is located inside the metal sleeve 10 near the nozzle 11. The insulating sleeve 13 is fitted over the outside of the root 121 of the electrode post 12. The metal cap 14 covers the end of the insulating sleeve 13 near the root 121 of the electrode post 12. The metal cap 14 has a through hole 140 for the electrode post 12 to pass through.

[0030] The metal sheath 10 and the metal cap 14 are grounded, thereby forming a first discharge gap G1 between the inner side of the through hole 140 and the outer side of the root 121 of the electrode post 12. The first discharge gap G1 is defined as the shortest distance between the outer surface of the electrode post 12 and the inner wall of the through hole 140.

[0031] A second discharge gap G2 is formed between the tip 120 of the electrode post 12 and the metal sheath 10. The second discharge gap G2 is defined as the shortest distance between the tip 120 of the electrode post 12 and the metal sheath 10.

[0032] In this embodiment, the first discharge gap G1 is electrically broken down before the second discharge gap (G2).

[0033] In this embodiment, the plasma nozzle 1 employs a controllable root ignition arc-starting method, the specific principle of which is as follows: The metal cap 14 is grounded and forms a grounding cavity (or shield) around the root 121 of the electrode post 12, forming a defined ground gap, namely the first discharge gap G1, around the root 121 of the electrode post 12. The local electric field of the first discharge gap G1 is designed to satisfy the local arcing condition (i.e., the pd value or local field strength is higher than the gas breakdown threshold) under the initial high voltage, while the initial field strength of the second discharge gap G2 at the tip 120 of the electrode post 12 remains below the breakdown threshold.

[0034] The grounding of the metal cap 14 also weakens the tangential field along the surface of the insulating sheath 13 (because the grounding metal forms an equipotential surface and surrounds the ceramic end face), thereby confining most of the strong electric field to the region of the first discharge gap G1, and preventing the local excessive field strength at the tip 120 from breaking down first during the initial transient.

[0035] The physical process from initial discharge (ignition) to steady-state channel migration of electrode post 12 is as follows: When the high voltage rises to a certain threshold, gas breakdown or self-sustaining discharge occurs in the first discharge gap G1, forming a local plasma nucleus (a brief electron avalanche / differentiation discharge). Because the area near the metal cap 14 is a grounded surface, the discharge nucleus is relatively stable, controllable, and close to the root 121 of the electrode post 12.

[0036] This initial discharge can release locally charged particles (electrons, ions) and photons, and generate a low-temperature, high-electron-density region in the initial plasma channel.

[0037] Once an initial plasma cloud / conductive path is formed at the root 121, the plasma migrates toward the nozzle 11. The driving forces for this forward movement include airflow (convection), electric field gradient (from the high-voltage electrode toward the grounding sheath / nozzle 11), diffusion of electrons and ions, and changes in the plasma's own conductivity.

[0038] In the initial channel, electrons and ions enhance local conductivity and reduce resistance along the path, allowing current to extend to the nozzle 11 region at a lower voltage difference. At this time, the effective voltage drop of the second discharge gap G2 decreases or the local field strength is enhanced (plasma is a low-resistance path), allowing the discharge channel from the root 121 to the tip 120 / nozzle 11 region to extend stably and maintain an arc.

[0039] Specifically, the breakdown voltage of the first discharge gap G1 is greater than the breakdown voltage of the second discharge gap G2, so that after the first discharge gap G1 breaks down, the plasma moves towards the tip 120, and the second discharge gap G2 can be easily broken down.

[0040] Therefore, in this embodiment, the nozzle 1 achieves a stable jet plasma through the process of "preferential ignition at the root 121 → formation of plasma channel → migration of the channel to the nozzle 11 and maintenance".

[0041] Therefore, for the plasma nozzle 1 with the above structure, when high voltage is applied, the discharge preferentially starts in the root 121 region of the controlled electrode post 12, avoiding random arcing at the tip 120 of the electrode post 12 / nozzle 11 or the insulating surface, thus significantly improving ignition consistency and repeatability. Moreover, the required initial peak voltage and ignition energy are lower, and the ignition time lag is smaller, thereby reducing the design difficulty and cost of the high-voltage power supply, reducing overshoot and surge, and improving overall energy efficiency and reliability.

[0042] Furthermore, the metal cap 14 is grounded and forms a clear discharge channel around the root 121 of the electrode post 12, causing the electric field to be preferentially concentrated in the first gap, relatively weakening the tangential electric field on the surface of the insulating sheath 13, reducing the probability of surface micro-discharge and DBD, and decreasing the sensitivity to humidity, contaminants and assembly tolerances. In this embodiment, the insulating sheath 13 is preferably a ceramic body.

[0043] In addition, the initial discharge does not occur in the second gap between the tip 120 and the metal sheath 10, thus avoiding the tip 120 from being subjected to the highest electrical stress and thermal shock at the moment of ignition, reducing the risk of electrolytic corrosion, sputtering and thermal cracking of the nozzle 11 and the tip 120, and improving the stable working time and service life of the nozzle 1.

[0044] On the other hand, the first discharge gap G1 is smaller than the second discharge gap G2, thereby ensuring that the first discharge gap undergoes electrical breakdown preferentially over the second discharge gap G2. Specifically, the first discharge gap G1 is 3-6 mm, preferably 5 mm, and the second discharge gap G2 is 2-4 mm larger than the first discharge gap G1.

[0045] On the other hand, the inner edge of the metal cap 14 near the root 121 of the electrode post 12 is chamfered. Specifically, the diameter of the chamfer is 0.3-0.8 mm.

[0046] In this embodiment, the chamfering reduces electric field spikes, suppresses excessively strong local fields, shortens arc ignition time, and prevents the metal cap 14 from "hanging on the arc".

[0047] In another embodiment of this utility model, a plasma spray gun is also disclosed, such as... Figures 4 to 7 The device includes a gun body 2 and a plasma nozzle 1 as disclosed in the above embodiments. The end of the metal sheath 10 away from the nozzle 11 is connected to the gun body 2. An air inlet pipe 20 is provided inside the gun body 2, which communicates with the inner cavity of the insulating sheath 13. The air inlet pipe 20 is connected to an external air source. During operation, the air inlet pipe 20 provides a working airflow (air, argon, helium, or a mixture of gases) to the nozzle 1.

[0048] The working airflow enters the air intake pipe 20 from the external air source through the air intake interface on the gun body 2. Since the air intake pipe 20 is connected to the inner cavity of the insulating sleeve 13, the working airflow eventually enters the nozzle 1 through the insulating sleeve 13 and forms a high-speed airflow through the nozzle 11.

[0049] The airflow forms a jet at the nozzle 11, which provides a medium and cooling effect for the plasma channel, and also promotes the migration and maintenance of the formed plasma channel from the electrode root 121 toward the nozzle 11.

[0050] On the other hand, a bearing seat 21 is also provided inside the gun body 2. The bearing seat 21 is provided with a bearing sleeve 22 and a rotating shaft 23 rotatably connected to the bearing sleeve 22. The rotating shaft 23 is connected to the metal sheath 10. The gun body 2 is also provided with a rotating driver 24 that is pulsatorically connected to the rotating shaft 23. The rotating driver 24 is used to drive the rotating shaft 23 to rotate, thereby driving the metal sheath and nozzle 11 to rotate through the rotating shaft 23.

[0051] Specifically, the rotary driver 24 is connected to the rotary shaft 23 via a belt 26.

[0052] The rotating nozzle 11 can sweep the plasma jet in a ring or radial manner on the surface of the workpiece, thereby achieving uniform surface treatment (cleaning, activation, modification, etc.) of large-area or ring-shaped parts, reducing overheating or surface inhomogeneity caused by single-point overtreatment.

[0053] On the other hand, for the discharge component housed within the metal sheath 10, further improvements are made to prevent it from rotating with the metal sheath 10: Please refer again. Figures 1 to 3 and Figure 6 A fixed sleeve 15 is provided inside the metal sheath 10. One end of the insulating sheath 13 is located in the fixed sleeve 15. One end of the air intake pipe 20 is connected to the fixed sleeve 15 and passes through the fixed sleeve 15. The rotating shaft 23 is a hollow structure. The other end of the air intake pipe 20 passes through the rotating shaft 23 and is connected to the pipe head 25 located on the bearing seat 21. A fixed ring 16 is provided inside the insulating sheath 13. The end of the electrode post 12 opposite to the tip 120 is located on the fixed ring 16.

[0054] In this embodiment, the air intake pipe 20 is a rigid support component, which is connected to the fixed sleeve 15 inside the nozzle 1, and also provides support for the fixed sleeve 15. The discharge assembly is installed on the fixed sleeve 15, so that the discharge assembly does not rotate with the metal sheath 10, reducing the risk of electrical noise, wear and arcing caused by rotational contact.

[0055] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Therefore, any equivalent variations made in accordance with the scope of the present utility model application shall still fall within the scope of the present utility model.

Claims

1. A plasma nozzle, characterized in that, The device includes a metal sheath (10), a discharge assembly disposed within a cavity inside the metal sheath (10), and a nozzle (11) communicating with the cavity at one end of the metal sheath (10). The discharge assembly includes an electrode post (12), an insulating sheath (13), and a metal cap (14). The electrode post (12) includes a tip (120) and a root (121). The tip (120) is located inside the metal sheath (10) near the nozzle (11). The insulating sheath (13) is fitted over the root (121) of the electrode post (12), and the metal cap (14) covers the insulating sheath (120). At one end of the metal cap (14) near the root (121) of the electrode post (12), a through hole (140) is provided on the metal cap (14) for the electrode post (12) to pass through; the metal sheath (10) and the metal cap (14) are grounded, thereby forming a first discharge gap (G1) between the inner side of the through hole (140) and the outer side of the root (121) of the electrode post (12), and forming a second discharge gap (G2) between the tip (120) of the electrode post (12) and the metal sheath (10), and the first discharge gap (G1) is electrically broken down preferentially over the second discharge gap (G2).

2. The plasma nozzle according to claim 1, characterized in that, The breakdown voltage of the first discharge gap (G1) is greater than the breakdown voltage of the second discharge gap (G2).

3. The plasma nozzle according to claim 2, characterized in that, The first discharge gap (G1) is 3-6 mm.

4. The plasma nozzle according to claim 3, characterized in that, The second discharge gap (G2) is 2-4 mm larger than the first discharge gap (G1).

5. The plasma nozzle according to claim 1, characterized in that, The inner edge of the metal cap (14) near the root (121) of the electrode post (12) is chamfered.

6. The plasma nozzle according to claim 5, characterized in that, The inner edge of the metal cap (14) has a chamfer diameter of 0.3-0.8 mm.

7. The plasma nozzle according to claim 1, characterized in that, The insulating sheath (13) is a ceramic body.

8. A plasma spray gun, characterized in that, Includes a gun body (2) and a plasma nozzle as described in any one of claims 1 to 7, wherein the end of the metal sheath (10) away from the nozzle (11) is connected to the gun body (2), and the gun body (2) is provided with an air intake pipe (20) communicating with the inner cavity of the insulating sheath (13).

9. The plasma spray gun according to claim 8, characterized in that, The gun body (2) is also provided with a bearing seat (21), and the bearing seat (21) is provided with a bearing sleeve (22) and a rotating shaft (23) rotatably connected to the bearing sleeve (22). The rotating shaft (23) is connected to the metal sheath (10). The gun body (2) is also provided with a rotating driver (24) pulsatorically connected to the rotating shaft (23). The rotating driver (24) is used to drive the rotating shaft (23) to rotate, and then drive the metal sheath (10) and the nozzle (11) to rotate through the rotating shaft (23).

10. The plasma spray gun according to claim 9, characterized in that, A fixed sleeve (15) is provided inside the metal sheath (10). One end of the insulating sheath (13) is located in the fixed sleeve (15). The air intake pipe (20) is a rigid support. One end of the air intake pipe (20) is connected to the fixed sleeve (15) and passes through the fixed sleeve (15). The rotating shaft (23) is a hollow structure. The other end of the air intake pipe (20) passes through the rotating shaft (23) and is connected to the pipe head (25) located on the bearing seat (21). A fixed ring (16) is provided inside the insulating sheath (13). One end of the electrode post (12) opposite to the tip (120) is located on the fixed ring (16).

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