Electrostatic spraying discharge needle and spraying gun with three-dimensional cage-shaped composite conductive protective structure

Abstract

The application discloses a static spraying discharge needle with a three-dimensional cage-shaped composite conductive protective structure and a spraying gun, and belongs to the field of static spraying mechanical equipment. The outer side of the metal rod base body of the discharge needle is sequentially provided with a metal conductive protective bottom layer, a three-dimensional intercommunication cage-shaped field emission framework layer and a low-surface-energy conductive anti-adhesion surface layer, so that a three-layer integrated composite protective conductive structure is formed. Through mechanical structure improvement, the application solves the industry equipment defects of traditional spraying electrodes, such as easy oxidation and corrosion, high starting voltage of equipment and easy powder accumulation and nodulation of the tip; the three-dimensional cage-shaped hollow structure can reduce the discharge voltage and disperse the electric charge; the surface layer modification structure realizes self-cleaning and anti-adhesion; and the inner layer metal structure realizes long-acting corrosion resistance. The overall structure is suitable for automatic continuous spraying working conditions, has high assembly universality, and the stability of equipment operation and production efficiency are significantly improved.

Description

Technical Field

[0001] This invention belongs to the technical field of electrostatic spraying machinery and equipment, specifically relating to an improved electrode structure for electrostatic spraying guns, suitable for the structural design and optimization of high-voltage discharge spraying equipment in automated powder coating production lines. Background Technology

[0002] Electrostatic powder coating equipment relies on a discharge needle at the front of the spray gun to generate a high-voltage corona electric field, causing powder particles to become charged and adhere to the workpiece surface. Existing coating equipment generally uses a single solid metal rod structure for its discharge needle, which exhibits significant structural defects under long-term automated reciprocating spraying, high-speed airflow erosion, and high-voltage ionization conditions. 1. Metal tips are prone to oxidation and loss: High-voltage discharge continuously generates ozone and active oxidizing groups, which can easily corrode and oxidize the surface of ordinary metal electrodes. This leads to a decrease in the uniformity of conductivity on the electrode surface, an increase in the starting voltage of the equipment year by year, frequent occurrences of color difference and missed spraying in the coating, high frequency of electrode replacement, and high equipment maintenance costs.

[0003] 2. Traditional metal electrodes have high discharge threshold and high equipment load: The smooth metal surface has a large electron work function, and the equipment needs to maintain a high voltage of 6-8kV for a long time to stably output powder. The high voltage module works under high load for a long time, resulting in high equipment failure rate and high energy consumption.

[0004] 3. Powder and nodules easily accumulate at the electrode tip: The resin components of the sprayed powder tend to adhere to the electrode surface, gradually accumulating to form nodules, which changes the electric field distribution at the nozzle, seriously affecting the spraying quality, requiring frequent shutdowns and disassembly for cleaning, and greatly reducing the utilization rate of automated production lines.

[0005] Existing improved electrode structures generally suffer from technical shortcomings, failing to simultaneously address the three key performance characteristics of corrosion resistance, low-voltage discharge, and anti-stick self-cleaning: a single metal cladding layer only provides corrosion protection and cannot reduce discharge voltage; a single carbon layer structure exhibits poor adhesion and is prone to oxidation and detachment; conventional diamond-like carbon cladding layers have strong insulation properties, which can directly cause electrode discharge failure. Currently, the industry lacks an integrated electrode mechanical structure that is structurally stable, features multi-layered functional synergy, and is adaptable to long-term automated operating conditions.

[0006] Existing technologies can only achieve one or two of the functions of corrosion prevention, low-voltage discharge, and anti-sticking. There is no electrode mechanical structure that can simultaneously meet the requirements of three types of working conditions by relying on a three-layer radial coating + a three-dimensional hollow cage structure in the middle layer, nor has a design idea for an outer coating that does not block the conductive path been given. Summary of the Invention

[0007] To address the mechanical structural defects of existing electrostatic spraying equipment, such as the single structure of the discharge electrode, poor adaptability to working conditions, and mutual functional constraints, this invention provides a modified discharge needle with a three-dimensional cage-like composite conductive protective structure and an electrostatic spraying gun equipped with the discharge needle. Through the three-layer differentiated functional composite structure design, it simultaneously achieves electrode corrosion resistance, stable low-voltage discharge of the equipment, and tip anti-powder accumulation self-cleaning effect, thereby improving the overall stability and service life of the spraying equipment.

[0008] This invention does not involve the improvement of new conductive materials or modified material formulations. Carbon nanotubes, graphene, and fluorine-modified conductive surface layers are all mature and well-known materials in the field. The core innovation of this invention lies in the three-dimensional spatial structure design of the discharge needle with three radial layers from the inside to the outside. Multiple functions are achieved through the three-dimensional hollow structure formed by the interlacing of cage columns and cage walls.

[0009] An electrostatic spraying discharge needle with a three-dimensional cage-like composite conductive protective structure includes a metal rod substrate, wherein the metal rod substrate is a tungsten alloy or stainless steel cylindrical rod, and the metal rod substrate is divided into a rod assembly section and a tip discharge working section. The outer side of the metal rod substrate is sequentially covered and fixed with a metal conductive protective bottom layer, a three-dimensional interconnected cage-like field emission skeleton layer, and a low surface energy conductive anti-stick surface layer from the inside to the outside; the three-layer structure seamlessly covers the rod assembly section and the tip discharge section, with no exposed metal areas.

[0010] The conductive metal protective underlayer is a dense noble metal coating layer with a thickness of 0.5μm to 2μm, which is closely attached to the outer circle of the metal rod substrate to isolate the oxidizing and corrosive medium and ensure the overall conductivity uniformity of the electrode.

[0011] The three-dimensional interconnected cage-like field emission framework layer is wrapped around the outer side of the metal conductive protective bottom layer. It is formed by the interweaving of carbon nanotube framework and graphene sheets to form a three-dimensional hollow cage-like structure. The cage-like structure forms interconnected nanoscale conductive channels with a cage cavity diameter of 50nm to 200nm. This structure can form a large number of micro discharge protrusions on the electrode surface, reduce the discharge ignition voltage of the device, disperse charge accumulation, and avoid tip ablation.

[0012] The low surface energy conductive anti-adhesion surface layer covers the outside of the three-dimensional interconnected cage-like field emission framework layer, with a surface layer thickness of 100nm to 500nm. The surface layer retains a continuous conductive path by relying on the inner cage-like framework. The fluorine-modified groups on the surface layer keep the surface energy of the coating layer stably controlled in the range of 12mN / m to 20mN / m. The surface energy of conventional unmodified conductive metal coating layers is usually greater than 45mN / m. This surface layer has a significantly lower surface energy than traditional electrode coating layers. The low surface energy characteristic greatly weakens the adsorption and bonding force between the sprayed powder and the electrode surface, which can effectively inhibit powder adhesion and accumulation. With the equipment's annular blowing airflow, the electrode tip can achieve continuous self-cleaning and eliminate the problem of discharge nodule formation. The surface energy of conventional metal electrodes and ordinary conductive coatings in the industry is generally between 40 and 60 mN / m, and powders are easily adsorbed and agglomerated after contact. This solution limits the surface energy to ≤20 mN / m, which is in the low surface energy range. When the surface energy is below 20 mN / m, resin powder and pigment powder are difficult to form a stable adhesion layer on the electrode surface, and can be peeled off by slight airflow. This defines the technical boundary of the "low surface energy" of this invention.

[0013] The surface energy of the surface layer in this application is tested according to the contact angle method of GB / T 30693-2014; the cage cavity aperture refers to the equivalent nanopore size of the hollow area formed by the cage column and cage wall.

[0014] The three-dimensional interconnected cage-like field emission framework layer consists of cage pillars made of carbon nanotube bundles and cage walls made of graphene sheets that are interwoven and integrated. There are no gaps between the cage pillars and cage walls, and they are interconnected to form a continuous multi-branched conductive path. The framework layer is completely and tightly wrapped around the outside of the metal conductive protective bottom layer, and the two are in close contact to achieve conductive connection.

[0015] The outer low surface energy conductive non-stick surface layer is thinly applied to the outer surface of the cage-like skeleton. At the same time, this surface layer does not completely block the conductive path of the inner cage cavity. The coating layer is thin and breathable, and the charge can penetrate the surface layer and be continuously conducted by relying on the internal three-dimensional interconnected cage-like skeleton. It has the dual functions of conductivity and non-stick self-cleaning. It only adheres to the outer contour surface of the cage pillars and cage walls, and does not completely block the gaps in the cage cavity, keeping the cage cavity open and transparent. The charge can pass through the gaps in the surface layer and contact the cage pillars and cage walls made of carbon nanotubes and graphene materials, so that the low surface energy conductive non-stick surface layer and the inner three-dimensional interconnected cage-like field emission skeleton layer maintain conductivity.

[0016] The three-layer structure relies on the tight bonding between layers and the thin surface layer that does not block the cage cavity. It maintains conductive continuity from the metal rod substrate to the outermost surface layer. High-voltage charges can be dispersed and conducted along multiple branch conductive paths, which not only ensures the stability of electrode discharge performance, but also achieves the functions of corrosion prevention, enhanced discharge, and prevention of powder accumulation by relying on the structure of each layer.

[0017] This application only protects the modified discharge needle with a three-layer cage-like coating structure and the spray gun assembled thereon, without limiting the specific deposition or coating preparation methods of each functional layer. Existing carbon-based coating and fluorine-modified surface preparation processes can all be adapted to this structure.

[0018] Mechanical assembly structure of electrostatic spraying gun An electrostatic spray gun includes a connecting base, a high-voltage control module, a front insulating sleeve, and the aforementioned modified discharge needle; the insulating sleeve is a hollow insulating cylinder and is fixed to the front end of the connecting base, the modified discharge needle is coaxially assembled at the center of the insulating sleeve, the discharge tip extends out of the end face of the insulating sleeve, and the inner wall of the sleeve and the outer wall of the discharge needle form an annular powder conveying gap to ensure that the powder is sprayed evenly around the tip.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention solves three major mechanical defects of traditional sprayed electrodes through a three-layer integrated composite structure design: easy corrosion, high ignition voltage, and powder accumulation and nodule formation at the tip. The structure has strong synergy and its comprehensive performance far exceeds that of existing single-layer and double-layer improved structures.

[0020] 2. The three-dimensional cage-like micro-skeleton structure significantly reduces the equipment discharge voltage, reduces the workload of the high-voltage module, reduces equipment heat generation and failure probability, and significantly improves energy efficiency.

[0021] 3. The low surface energy conductive structure enables self-cleaning of the electrode tip, eliminating the need for frequent shutdowns and disassembly for cleaning, thus significantly improving the production efficiency of automated production lines.

[0022] 4. High interlayer bonding strength ensures that the layers do not separate or fall off under the conditions of high-frequency vibration and long-term scouring by high-speed airflow of the spray gun, thus significantly extending the service life of the equipment.

[0023] This invention differs from existing simple multi-layer coated electrodes. Simply stacking three planar coating layers sequentially completely seals the internal conductive channels and eliminates the microscopic discharge protrusions. The core improvement of this invention is a three-dimensional interconnected, hollowed-out cage-like spatial structure in the middle layer, forming multi-branched three-dimensional conductive pathways. This, combined with an inner layer of precious metal anti-corrosion coating and an outer layer of low-surface-energy conductive material that does not block the pathways, creates a synergistic effect of low-voltage discharge, long-term corrosion protection, and long-term anti-powder accumulation that cannot be achieved with single or double-layer planar coating structures. This is not a simple superposition of existing materials. This three-layer cage-like coating structure is specifically designed for the long-term airflow scouring and continuous high-voltage discharge conditions of electrostatic spray guns. Existing planar multi-layer coating structures cannot simultaneously meet the requirements of low-voltage discharge, long-term corrosion protection, and anti-powder accumulation in equipment. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in this embodiment, the accompanying drawings used in the embodiment will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the overall structure of the electrostatic spraying gun of the present invention, showing the overall assembly relationship of the connecting base, insulating sleeve and modified discharge needle; Figure 2 This is a three-dimensional cross-sectional view of the modified discharge needle of the present invention, which intuitively shows the coaxial stacked structure of the metal rod substrate, which is covered from the inside out with a metal conductive protective bottom layer, a three-dimensional interconnected cage-like field emission skeleton layer, and a low surface energy conductive anti-stick surface layer. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0027] The orientation shown in the accompanying drawings should not be construed as limiting the specific scope of protection of the present invention, but is only for reference and understanding of preferred embodiments. The product components shown in the drawings may be changed in position, increased in number, or simplified in structure.

[0028] The "connection" in the specification and the interconnection relationship of the components shown in the drawings can be understood as a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or a connection through an intermediate medium. Those skilled in the art can understand the connection relationship according to the specific circumstances and derive different implementation methods such as screwing, riveting, welding, snap-fitting, or embedding to suitably replace it.

[0029] The directional terms such as up, down, left, right, top, and bottom in the instruction manual and the directions shown in the attached drawings indicate that each component can directly contact or contact each other through other features; for example, "up" can mean directly above or diagonally above, or it simply means above other objects; other directions can be understood by analogy.

[0030] The materials used to manufacture solid-shaped parts as shown in the specification and drawings may be metallic, non-metallic, or other synthetic materials. The machining processes used for solid-shaped parts may include stamping, forging, casting, wire cutting, laser cutting, injection molding, CNC milling, 3D printing, machining, etc. Those skilled in the art may adapt or combine the above materials and manufacturing processes according to different processing conditions, costs, and precision requirements.

[0031] Overall structural assembly embodiment, refer to Figure 1 The electrostatic spray gun of this invention is mainly composed of a connecting base 1, a high-voltage control module, an insulating sleeve 4, and a discharge needle 5. The connecting base 1 is fixed to the end of the spraying machine to achieve coordinated machine movement. The high-voltage control module is built into the connecting base 1 and is electrically connected to the tail of the discharge needle 5, providing a stable DC high-voltage electric field for the discharge needle. The insulating sleeve 4 is integrally molded from high-strength, wear-resistant, and insulating engineering plastic and coaxially locked to the front mounting position of the connecting base 1.

[0032] The modified discharge needle 5 is coaxially inserted and limited inside the central through hole of the insulating sleeve 4. The tip of the modified discharge needle 5 extends 2mm forward from the front end face of the insulating sleeve 4, ensuring that the tip is fully exposed to the powder jet gas flow area. The inner diameter of the insulating sleeve 4 is set to 1.6mm, and the base outer diameter of the modified discharge needle 5 is 1.5mm, forming a uniform annular powder conveying gap 1-6 of 0.1mm between them. This ensures that the powder gas flow is evenly sprayed around the needle body, without powder deviation or clogging. The total thickness of the three-layer composite protective structure is in the micrometer range, which does not change the macroscopic assembly dimensions of the needle body and does not affect the original equipment assembly and fit relationship. It can directly replace the traditional standard discharge needle, making the equipment highly versatile.

[0033] Modified discharge needle layered structure gradient example The modified discharge needle 5 of this invention uses a metal rod substrate 501 as the supporting substrate. The metal rod substrate 501 is made of tungsten alloy or stainless steel solid cylindrical rod, which has high overall rigidity and is not easily deformed under high pressure conditions, making it suitable for high-frequency reciprocating spraying vibration conditions. From the inside out, the outer side of the substrate is sequentially coated with a metal conductive protective bottom layer 502, a three-dimensional interconnected cage-like field emission framework layer 503, and a low surface energy conductive anti-stick surface layer 504. This three-layer structure seamlessly covers the needle rod assembly section and the tip discharge working section, with no exposed metal areas, achieving all-round protection and functional enhancement. Three gradient structure embodiments are given below, covering all protection parameter ranges of this invention: Example 1 Lower Limit Parameters: Metal rod substrate 501, diameter 1.5mm; Metal conductive protective underlayer 502, thickness 0.5μm, dense and pinhole-free coating, meeting basic corrosion protection requirements; Three-dimensional interconnected cage-like field emission framework layer 503, average cage cavity diameter 50nm, uniformly distributed micro-protrusions forming dense electron conduction channels; Low surface energy conductive anti-stick surface layer 504, thickness 100nm, retaining a complete and continuous conductive path, possessing basic anti-sticking and discharge adaptability. This example is suitable for conventional low-frequency intermittent spraying conditions, with stable structure and controllable cost.

[0034] Example 2 Optimal Parameter Example: The metal rod substrate 501 is made of tungsten alloy with a diameter of 1.5mm; the metal conductive protective bottom layer 502 has a thickness of 0.8μm, with moderate stress and firm bonding, and will not fall off under long-term vibration; the three-dimensional interconnected cage-like field emission skeleton layer 503 has an average cage cavity diameter of 100nm, with uniform interweaving of cage columns and cage walls, resulting in optimal electric field enhancement and good charge dispersion; the low surface energy conductive anti-stick surface layer 504 has a thickness of 200nm, balancing low surface energy anti-stick performance with continuous conductivity, thus resolving the contradiction between anti-sticking and discharge. This example is suitable for a 24-hour continuous automated spraying production line and has the best overall performance.

[0035] Example 3 Upper Limit Parameters Example: Metal rod substrate 501, diameter 1.5mm; Metal conductive protective underlayer 502, thickness 2μm, providing the strongest corrosion resistance; Three-dimensional interconnected cage-like field emission framework layer 503, average cage cavity diameter 200nm, ensuring smoother conductive pathways and more significant low-voltage discharge effect; Low surface energy conductive anti-stick surface layer 504, thickness 500nm, providing excellent anti-stick and self-cleaning effects. This example is suitable for harsh spraying conditions involving high dust, high corrosion, and long-term continuous operation.

[0036] The three-dimensional interconnected cage-like field emission framework layer 503 is completely covered on the outside of the metal conductive protective bottom layer 502. It is formed by in-situ interweaving carbon nanotube bundles and graphene sheets. It relies on two known conductive materials to construct a three-dimensional hollow topological space structure that is different from traditional planar covering layers. The vertically arranged carbon nanotube bundles form cage pillars, and the horizontally extended and overlapping graphene sheets form cage walls. The cage pillars and cage walls are interconnected to form multiple interconnected cage cavities, forming a continuous and interconnected three-dimensional conductive path. At the intersection of the cage pillars and cage walls, a large number of micro discharge protrusions are naturally formed.

[0037] Carbon nanotubes and graphene are both conventional conductive materials in this field. The core improvement of this invention is not to adjust the material composition, but to change the spatial arrangement of the electrode surface coating: abandoning the industry-standard smooth and flat single-layer coating structure, a three-dimensional hollow structure is formed by interwoven cage pillars and cage walls. This spatial structure, on the one hand, reduces the electron work function by using densely distributed micro-discharge protrusions, thus reducing the start-up voltage required for device operation; on the other hand, it disperses the charge by relying on multi-branched interconnected conductive paths, avoiding the accumulation of charge at a single point on the electrode tip, and alleviating the problems of high-temperature ablation and blackening failure at the tip.

[0038] The conductive metal protective base layer 502 is a dense noble metal alloy cladding layer, optionally a thin layer of platinum-iridium alloy or ruthenium-iridium alloy. This uniform, non-porous cladding layer serves as the inner dense protective structure, effectively blocking the penetration of ozone and reactive free radicals generated by high-voltage ionization, and preventing corrosive media from directly contacting the metal rod substrate 501, thus protecting the metal rod substrate 501 from corrosion and oxidation. Simultaneously, the noble metal substrate possesses stable and continuous conductivity, ensuring uniform electric field conduction. The intermediate three-dimensional interconnected cage-like field emission framework layer 503... The porous, hollowed-out coating structure, formed by interwoven carbon nanotubes and graphene, generates numerous microscopic discharge protrusions on its surface, enhancing electric field emission efficiency. The low-surface-energy conductive and anti-stick surface layer 504 is a conductive coating layer with fluorine groups. Nano-silver conductive particles are doped within the surface layer to achieve conductivity, serving only to ensure the surface layer's own conductivity without altering the overall spatial structure of the three-layer coating. The low surface energy characteristic is achieved through numerous fluorine-modified groups on the surface, making it difficult for sprayed powder to adhere. Combined with continuous rinsing by the equipment's annular airflow, the tip is automatically cleaned, completely eliminating the problem of nodule and powder accumulation. The three-layer structure is complementary and synergistic, not simply superimposed: the metallic conductive protective bottom layer 502 is responsible for corrosion prevention and conductivity; the three-dimensional interconnected cage-like field emission framework layer 503 is responsible for enhanced discharge; and the low-surface-energy conductive and anti-stick surface layer 504 is responsible for anti-sticking and self-cleaning. This creates a comprehensive adaptability to various working conditions that existing single-layer and double-layer electrode structures cannot achieve. Furthermore, all three layers possess conductive properties without insulation barriers, ensuring stable high-voltage discharge output throughout the electrostatic spraying process.

[0039] Comparative evidence of results To fully verify the technical advantages brought about by the structural improvements of this invention, four sets of control tests were set up, with unified equipment operating conditions, unified spray powder, and unified high-voltage output environment. The four sets of control tests were conducted under the following unified operating conditions: DC high-voltage output, the same polyester spray powder, room temperature of 25℃, and constant air supply spraying environment. The test results are as follows: Comparative Example 1: Traditional bare metal discharge needle structure: stable ignition voltage 7.2kV, high equipment load and severe heat generation; after 80 hours of continuous operation, the tip is obviously oxidized and blackened, the conductivity is uneven, and a large amount of powder accumulates and forms nodules on the tip, requiring shutdown, disassembly, replacement and cleaning, resulting in low equipment uptime.

[0040] Comparative Example 2: Single metal conductive bottom layer protective structure: It has basic anti-corrosion capability and no obvious oxidation after 100 hours of continuous operation. However, the electrode surface is still a smooth metal structure, the ignition voltage is 6.8kV, there is no low-voltage discharge enhancement effect, and the surface has no anti-stick structure. Powder continues to accumulate during operation, and frequent shutdowns for cleaning are still required.

[0041] Comparative Example 3: Metal base layer + cage-like skeleton double-layer structure: It has low-voltage discharge capability and ignition voltage of 3.6kV, but there is no protective surface layer on the outside. The cage-like hollow structure is prone to powder and dust accumulation. After 120 hours of continuous operation, the dust fills the cage cavity, the electric field is disordered, the discharge is unstable, and the failure is obvious.

[0042] The optimal embodiment of this invention features a three-layer composite structure: a stable ignition voltage as low as 3.4kV, a voltage reduction of over 40% compared to traditional structures, significantly reducing the load on high-voltage modules; continuous operation for 300 hours without interruption, with no oxidation or blackening of the electrode tips, no ablation, no powder accumulation or nodules, and no delamination of the coating layer; uniform discharge and stable powder output throughout the entire process, requiring no downtime for maintenance, greatly improving the production efficiency and equipment stability of automated production lines.

[0043] Structural Adaptability Description The invention adopts a standardized replacement structure. All macroscopic assembly dimensions are fully compatible with existing commercially available electrostatic spray guns. There is no need to modify the original equipment structure such as insulating sleeves and high-voltage modules. The equipment upgrade can be completed by simply replacing this modified discharge needle 5. The modification cost is low, the applicability is wide, and it is compatible with various automated spraying production lines and fixed electrostatic spraying equipment. It has strong industrial applicability.

[0044] Those skilled in the art can implement the present invention based on this structural scheme. The following embodiments are used to fully disclose the structural effects and do not limit the scope of protection of the present invention.

[0045] Preferred embodiment: The metal rod substrate 501 is made of tungsten alloy needle with a diameter of 1.5 mm; the metal conductive protective bottom layer 502 is 0.8 μm thick; the three-dimensional interconnected cage-like field emission framework layer 503 has an average cage cavity diameter of 100 nm; and the low surface energy conductive anti-stick surface layer 504 is 200 nm thick. The three-layer structure completely covers the needle and the working tip section.

[0046] Assembly method: The inner diameter of the insulating sleeve 4 is 1.6mm, and the modified discharge needle 5 is coaxially assembled with the tip extending 2mm out of the sleeve 4 to form a uniform annular powder gap of 0.1mm, which is suitable for stable powder output of automated spraying equipment.

[0047] Performance comparison: Traditional bare needles require a starting voltage of 7.2kV and need to be replaced after 80 hours; this structure has a starting voltage as low as 3.4kV, and exhibits no oxidation, powder accumulation, or shedding for 300 consecutive hours, significantly improving equipment stability.

[0048] Working principle During operation, the high-voltage module applies a high-voltage electric field to the modified discharge needle 5. The microscopic protrusions of the three-dimensional interconnected cage-like field emission skeleton layer 503 generate an electric field enhancement effect, enabling the electrode to stably ionize air and generate charge at a relatively low voltage. The interconnected cage structure disperses the charge density, preventing localized overheating and ablation at the tip. The inner conductive metal protective layer 502 isolates the oxidizing medium, preventing corrosion failure of the metal rod substrate 501. The outer low surface energy conductive anti-stick surface layer 504 prevents the sprayed powder from adhering stably and allows it to automatically detach via airflow, enabling long-term maintenance-free continuous spraying operations.

[0049] The three-layer structure of this invention is not a simple superposition; it possesses deep interface integration and functional synergy innovation, belonging to the category of structural + material interface coupling innovation, which is different from conventional mechanical superposition. 1. Interface anchoring mechanism: Active metal sites are formed on the surface of the metal conductive protective bottom layer 502, which form a stable interface bonding structure with the carbon-based cage skeleton of the outer three-dimensional interconnected cage field emission skeleton layer 503, greatly improving the interlayer adhesion and solving the industry mechanical defects of easy detachment and delamination of carbon-based cage coating structure.

[0050] 2. Controllable conductivity differentiation mechanism: The low surface energy conductive anti-stick surface layer 504 is equipped with fluorine groups to achieve a low surface effect. The internal conductive particles ensure overall conductivity, and the inner side can be connected to the internal cage-like skeleton to form a complete and continuous conductive path structure. This overcomes industry technical bias and retains high voltage discharge capability while having low powder adhesion performance, solving the contradiction problem of insulation failure of conventional anti-stick coating layers.

[0051] 3. Enhanced field emission mechanism of cage structure: The three-dimensional interconnected cage-like field emission skeleton layer 503 with three-dimensional interconnected hollow nanostructure changes the electron emission characteristics of the electrode surface. Compared with the smooth metal surface, it significantly reduces the discharge threshold, realizes low-voltage stable discharge of equipment, and reduces the load of the whole machine.

[0052] 4. Multi-layer synergistic protection mechanism: The inner metal conductive protective bottom layer 502 blocks oxidation, the middle three-dimensional interconnected cage-like field emission skeleton layer 503 enhances discharge, and the outer low surface energy conductive anti-stick surface layer 504 is self-cleaning. The three-layer structure complements and supports each other, forming a comprehensive technical effect that cannot be achieved by a single structure.

[0053] Although the present invention has been described in detail above with reference to specific embodiments, those skilled in the art will readily understand from this disclosure that various changes or modifications can be made to the present invention without departing from the principles and spirit defined by the claims. Therefore, the detailed description of the above embodiments is for illustrative purposes only and is not intended to limit the present invention; the scope of protection of the present invention should be determined by the content of the claims.

Claims

1. An electrostatic spraying discharge needle with a three-dimensional cage-like composite conductive protective structure, comprising a metal rod substrate (501), wherein the metal rod substrate (501) is divided into a rod assembly section and a tip discharge working section, characterized in that: The metal rod substrate (501) is sequentially covered and fixed with a metal conductive protective bottom layer (502), a three-dimensional interconnected cage-like field emission skeleton layer (503), and a low surface energy conductive anti-stick surface layer (504) from the inside to the outside. The conductive metal protective underlayer (502) is a dense precious metal coating layer, which is attached to and covers the outer circle of the metal rod substrate (501); The three-dimensional interconnected cage-like field emission framework layer (503) is a three-dimensional hollowed-out cage-like spatial structure formed by the interweaving of carbon nanotubes and graphene. The cage pillars and cage walls overlap to form interconnected cage cavities and continuous multi-branch conductive paths. Discharge protrusions are generated at the junction of the cage pillars and cage walls. The low surface energy conductive anti-stick surface layer (504) covers the outside of the cage-like framework layer, and the surface layer and the inner cage-like framework maintain electrical conductivity.

2. The discharge needle according to claim 1, characterized in that: The three-dimensional interconnected cage-like field emission skeleton layer (503) forms an interconnected cage cavity and a continuous multi-branch conductive path. It relies on the micro discharge protrusions distributed at each node to reduce the discharge ignition voltage and disperses the charge accumulation through the continuous multi-branch conductive path.

3. The discharge needle according to claim 1, characterized in that: The metal rod base (501) is made of tungsten alloy or stainless steel.

4. An electrostatic spray gun, characterized in that: It includes a connecting base (1), a high-voltage control module, a front-end insulating sleeve (4), and a modified discharge needle (5) as described in any one of claims 1 to 3. The insulating sleeve (4) is fixed to the front end of the connecting base (1), and the modified discharge needle (5) is coaxially assembled at the center of the insulating sleeve (4). The tip of the modified discharge needle (5) extends out of the end face of the insulating sleeve (4), and an annular powder conveying gap is formed between the insulating sleeve (4) and the discharge needle (5).

5. The electrostatic spray gun according to claim 4, characterized in that: The inner diameter of the insulating sleeve (4) is larger than the outer diameter of the modified discharge needle (5), forming a uniform annular powder discharge gap.

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