A surface spraying device for a ligament stretcher

Abstract

The application relates to the technical field of medical instrument preparation, in particular to a surface spraying device of a ligament stretcher, which mainly solves the problems of poor surface spraying effect and easy local burning damage of the existing spraying device, and comprises a rack, a power module, a control system, a gas supply system, a powder feeding system, a heat exchange system, a plasma generating system and a spray gun. The plasma generating system comprises an anode assembly and a cathode assembly, the anode assembly comprises a first anode and a second anode, the first anode and the second anode are both composed of a plurality of segmented anode units, the anode units are isolated through an insulating layer, the plurality of anode units and the insulating layer form a ring-shaped structure, the cathode assembly comprises a first cathode and a second cathode, the spray gun comprises a primary heating assembly, a secondary heating assembly, an auxiliary heating assembly, at least three gas guide pipes, a first gas inlet pipe, at least two second gas inlet pipes, two water inlet pipes, two water outlet pipes and a spray head.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical device preparation, and in particular to a surface spraying device for a ligament stretcher. BACKGROUND

[0002] A ligament stretcher is a medical device used for rehabilitation treatment and sports training, and the surface performance thereof directly affects the use effect and safety. Traditional ligament stretchers are mostly made of metal or high polymer materials, and the surface thereof is susceptible to wear, corrosion, bacterial growth and other problems. Existing surface treatment processes such as electroplating and anodic oxidation can improve the surface performance, but have problems such as complex process, high cost and poor environmental protection, and therefore a plasma spraying device is mostly used for surface spraying, so that the surface of the ligament stretcher is covered with a coating.

[0003] A plasma spraying device is a technology that uses plasma to generate high-temperature and high-speed jets to melt and accelerate the spraying of a spraying material to the surface of a substrate. However, existing plasma generators usually adopt a single anode structure, and the anode surface is susceptible to uneven current distribution, resulting in local over-high or over-low plasma density, uneven heating of the injected spraying material, poor spraying effect, and long-term use of the anode due to local burning and failure, which requires frequent replacement. SUMMARY

[0004] Therefore, in view of the above problems, the present application provides a surface spraying device for a ligament stretcher, which mainly solves the problems of poor surface spraying effect and easy local burning damage of the existing spraying device.

[0005] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0006] A surface spraying device for a ligament stretcher, comprising a rack, a power module, a control system, a gas supply system, a powder feeding system, a heat exchange system, a plasma generating system and a spray gun;

[0007] The plasma generating system comprises an anode assembly and a cathode assembly, the anode assembly comprises a first anode and a second anode, the first anode and the second anode are both composed of a plurality of segmented anode units, each of the anode units is isolated by an insulating layer, and a plurality of the anode units and the insulating layer form a ring-shaped structure, and the cathode assembly comprises a first cathode and a second cathode;

[0008] The spray gun comprises a first heating assembly, a second heating assembly, an auxiliary heating assembly, at least three gas guide pipes, a first gas inlet pipe, at least two second gas inlet pipes, two water inlet pipes, two water outlet pipes and a spray head, the first heating assembly comprises a first shell, the first shell has a first flow channel, the first anode and the first cathode are arranged in the first flow channel, so that the first flow channel forms a first gas flow channel and a first cooling cavity which are isolated from each other, the first gas flow channel has a ring structure, the first gas inlet pipe is connected with an input end of the first gas flow channel, the second heating assembly comprises a second shell, the second shell has a second flow channel, the second anode and the second cathode are arranged in the second flow channel, so that the second flow channel forms a second gas flow channel and a second cooling cavity which are isolated from each other, each of the gas guide pipes is connected with an input end of the first gas flow channel and an output end of the second gas flow channel, each of the second gas inlet pipes is connected with a part of the gas guide pipes, the first gas inlet pipe and each of the second gas inlet pipes is connected with a gas supply system, the two water inlet pipes are connected with outlet ends of a heat exchange system and the first cooling cavity and the second cooling cavity respectively, the two water outlet pipes are connected with inlet ends of the heat exchange system and the first cooling cavity and the second cooling cavity respectively, the auxiliary heating assembly is arranged on the second gas inlet pipe, the spray head is arranged on the second shell, the spray head has a gas jet channel and a powder channel which are in communication with the second gas flow channel, and the powder channel is connected with a powder feeding system.

[0009] The power module comprises a main power supply and a plurality of sub power supplies, each of the sub power supplies is connected with each of the anode units, and the power module, the gas supply system, the powder feeding system, the heat exchange system and the plasma generating system are electrically connected with a control system.

[0010] Further, the gas supply system comprises a first gas tank, a second gas tank, a first gas pump, a second gas pump, a first switch valve, a second switch valve, a first connecting pipe and a second connecting pipe, the first gas tank is connected with the first gas inlet pipe through the first connecting pipe, the first gas pump and the first switch valve are arranged on the first connecting pipe, the second gas tank is connected with the second gas inlet pipe through the second connecting pipe, and the second gas pump and the second switch valve are arranged on the second connecting pipe.

[0011] Further, the first gas tank is filled with argon, and the second gas tank is filled with 85% to 95% argon and 5% to 15% hydrogen.

[0012] Further, an included angle between a central axis of the second gas inlet pipe and a central axis of the gas guide pipe is 30° to 70°.

[0013] Further, the spray head comprises a spray head body, the gas jet channel is distributed at the central axis of the spray head body, the powder channel comprises a main powder channel and an auxiliary powder channel, an output end of the main powder channel is connected with a middle part of the gas jet channel, and the auxiliary powder channel is connected with a middle part of the main powder channel and a middle part of the gas jet channel.

[0014] Further, the air injection channel comprises a gas guiding part and a spraying part, the diameter of the gas guiding part gradually decreases from the input end to the output end, the diameter of the input end of the gas guiding part is smaller than the diameter of the output end of the spraying part, the diameter of the spraying part gradually increases from the input end to the output end, and the ratio of the axial length of the gas guiding part to the axial length of the spraying part is 3-6:1.

[0015] Further, the output end of the main powder channel is distributed in the middle part of the gas guiding part, and the output end of the auxiliary powder channel is distributed at the joint of the gas guiding part and the spraying part.

[0016] Further, the included angle between the central axis of the main powder channel and the central axis of the air injection channel is 95-120°, and the included angle between the central axis of the auxiliary powder channel and the central axis of the air injection channel is 60-90°.

[0017] Further, the first shell comprises a first part and a second part arranged at one end of the first part, the first gas flow channel is formed between the first cathode and the first anode, and the first cooling cavity is formed between the first anode and the second part; and the second shell comprises a third part and a fourth part arranged at one end of the third part, the second gas flow channel is formed between the second cathode and the second anode, and the second cooling cavity is formed between the second anode and the fourth part.

[0018] Further, the insulating layer is alumina ceramic or polyimide.

[0019] By adopting the foregoing technical scheme, the surface spraying device of the present application has the following beneficial effects: the gas in the first gas tank enters the first gas flow channel through the first gas inlet pipe, and the electric arc is generated by electrifying the first anode and the first cathode, so that the gas forms plasma to generate high-temperature and high-speed jet flow, realizing primary heating; the high-temperature and high-speed jet flow is introduced into the second shell through the gas guide pipe, the second gas inlet pipe is connected with part of the gas guide pipe, and the auxiliary heating assembly is arranged on the second gas inlet pipe; the gas in the second gas tank is preliminarily heated in the second gas inlet pipe, and the electromagnetic field generated by the auxiliary heating assembly can affect the particle motion deviation in the jet flow; the gas entering from the second gas inlet pipe can quickly blend into the gas flow in the gas guide pipe and realize primary mixing; the gas in the plurality of gas guide pipes is mixed again when entering the second gas flow channel, and the electric arc is generated by electrifying the second anode and the second cathode, so that the gas forms plasma to generate high-temperature and high-speed jet flow, realizing secondary heating; the temperature and speed of the jet flow meet the requirements; the spraying material entering from the spray head is heated to a molten state by the jet flow and then sprayed on the surface of the ligament stretcher, so that the secondary heating can reduce the power of the first anode, the first cathode, the second anode and the second cathode in the plasma generation system, meet the temperature and speed of the jet flow, and the gas in the secondary heating can be well mixed through the arrangement of the second gas inlet pipe and the gas guide pipe and the arrangement of the auxiliary heating assembly, realize the stability of the jet flow, make the heating of the spraying material uniform, improve the spraying effect, and the first anode and the second anode are each composed of a plurality of segmented anode units, each anode unit is isolated by an insulating layer to reduce the risk of local overheating, and the separated first cooling cavity and second cooling cavity are arranged to cooperate with the heat exchange system to cool the first anode and the second anode, avoiding local burning damage and prolonging the service life of the anode by more than 50%, and the modular design facilitates maintenance and replacement of damaged units. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic diagram of an embodiment of the present application;

[0021] Figure 2 is a cross-sectional structural schematic diagram of a spray gun in an embodiment of the present application;

[0022] Figure 3 is a circuit schematic diagram of a power supply module and a plasma generation system in an embodiment of the present application;

[0023] Figure 4 is a cross-sectional structural schematic diagram of a spray head in an embodiment of the present application;

[0024] Figure 5 is a circuit module diagram of an embodiment of the present application. DETAILED DESCRIPTION

[0025] The application will be further described in conjunction with the drawings and specific embodiments.

[0026] Embodiments of the application are:

[0027] Referring to Figures 1 to 5 As shown in the drawings, a surface spraying device for ligament stretchers comprises a rack, a power module 1, a control system 2, a gas supply system 3, a powder feeding system 4, a heat exchange system 5, a plasma generating system 6 and a spray gun 7.

[0028] The gas supply system 3 comprises a first gas tank 31, a second gas tank 32, a first gas pump 33, a second gas pump 34, a first switch valve 35, a second switch valve 36, a first connecting pipe 37 and a second connecting pipe 38.

[0029] The plasma generating system 6 comprises an anode assembly and a cathode assembly, the anode assembly comprises a first anode 61 and a second anode 62, the first anode 61 and the second anode 62 are both composed of a plurality of segmented anode units 601, preferably six, each of the anode units 601 is isolated by an insulating layer 602, a plurality of the anode units 601 and the insulating layer 602 form a ring-shaped structure, the cathode assembly comprises a first cathode 63 and a second cathode 64.

[0030] The spray gun 7 includes a primary heating assembly 71, a secondary heating assembly 72, an auxiliary heating assembly 73, three air guide pipes 74, a first air inlet pipe 75, two second air inlet pipes 76, two water inlet pipes 77, two water outlet pipes 78, and a nozzle 79. The primary heating assembly 71 includes a first housing 711, which has a first flow channel. The first anode 61 and the first cathode 63 are respectively disposed within the first flow channel, forming a first gas flow channel 712 and a first cooling chamber 713 that are isolated from each other. The first gas flow channel 712 has an annular structure. The first air inlet pipe 75 is connected to the input end of the first gas flow channel 712. The first gas tank 31 is connected to the first air inlet pipe 75 via a first connecting pipe 37. The first air pump 33 and the first switching valve 35 are disposed on the first connecting pipe 37. The secondary heating assembly 72 includes a second housing 721, which has a second flow channel. The second anode 62 and the second cathode 64 are respectively disposed within the second housing 721. Within the second flow channel, a second gas flow channel 722 and a second cooling chamber 723 are formed, which are mutually isolated. Each of the gas guide pipes 74 is connected to the input end of the first gas flow channel 712 and the output end of the second gas flow channel 722. Each of the second air inlet pipes 76 is connected to a portion of the gas guide pipe 74. The second gas tank 32 is connected to the second air inlet pipe 76 through a second connecting pipe 38. The second air pump 34 and the second switching valve 36 are mounted on the second connecting pipe 38. The two water inlet pipes 77 are... The water outlet of the heat exchange system 5 is connected to the first cooling chamber 713 and the second cooling chamber 723. The two water outlet pipes 78 are respectively connected to the water inlet of the heat exchange system 5 and the first cooling chamber 713 and the second cooling chamber 723. The auxiliary heating component 73 is provided on the second air inlet pipe 76. The nozzle 79 is provided on the second housing 721. The nozzle 79 has an air jet channel 791 communicating with the second gas flow channel 722 and a powder channel 792. The powder channel 792 is connected to the powder feeding system 4.

[0031] The power module 1 includes a main power supply 11 and multiple sub-power supplies 12. Each sub-power supply 12 is connected to each anode unit 601. The power module 1, gas supply system 3, powder feeding system 4, heat exchange system 5, and plasma generation system 6 are electrically connected to the control system 2.

[0032] In this embodiment, the auxiliary heating component 73 is an electromagnetic induction component.

[0033] The surface coating device for this ligament stretcher involves a gas tank 31 where gas enters the first gas channel 712 through the first inlet pipe 75. An electric arc is generated by energizing the first anode 61 and the first cathode 63, causing the gas to form plasma and generate a high-temperature, high-speed jet, achieving primary heating. This high-temperature, high-speed jet is then guided into the second housing 721 through the guide pipe 74. The second inlet pipe 76 is connected to a portion of the guide pipe 74 and is equipped with an auxiliary heating component 73. The gas in the second gas tank 32 is initially heated within the second inlet pipe 76, and the electromagnetic field generated by the auxiliary heating component 73 influences the particle motion direction in the jet. The gas entering through the second inlet pipe 76 quickly merges into the airflow in the guide pipe 74, achieving primary mixing. The gas from multiple guide pipes 74 then enters the second gas channel 722 and mixes again. An electric arc is generated by energizing the second anode 62 and the second cathode 64, causing the gas to form plasma and generate a high-temperature, high-speed jet, achieving secondary heating. The temperature and velocity of the jet meet the requirements. The spray material entering through the nozzle 79 is then heated to a molten state and sprayed onto the surface of the ligament stretcher. This secondary heating reduces the power of the first anode 61, first cathode 63, second anode 62, and second cathode 64 in the plasma generation system 6, while meeting the jet temperature and velocity requirements. Furthermore, the arrangement of the second air inlet pipe 76 and the air guide pipe 74, along with the auxiliary heating component 73, ensures better mixing of the gases during secondary heating, achieving jet stability and uniform heating of the spray material, thus improving the spraying effect. Both the first anode 61 and the second anode 62 are composed of multiple segmented anode units 601, which are isolated from each other by an insulation layer 602, reducing the risk of local overheating. At the same time, separate first cooling chambers 713 and second cooling chambers 723 are provided in conjunction with the heat exchange system to distribute the cooling of the first anode 61 and the second anode 62, avoiding local burning damage and extending the anode life by more than 50%. The modular design facilitates maintenance and replacement of damaged units.

[0034] Furthermore, the first gas tank 31 is filled with argon, and the second gas tank 32 is filled with 85% to 95% argon and 5% to 15% hydrogen, preferably 93% argon and 7% hydrogen. Argon is an inert gas that is easily ionized and has stable chemical properties, providing a stable plasma environment. Hydrogen is a reducing gas with high thermal conductivity, which can significantly increase the temperature and jet velocity of the plasma. By mixing the two, a higher jet velocity can be generated, making the molten particles denser and reducing the porosity of the coating. Moreover, the argon is heated in the first stage, and then mixed with hydrogen for a second stage of heating, which can ensure the stability of the mixed gas and improve the safety of use.

[0035] Furthermore, the angle between the central axis of the second air intake pipe 76 and the central axis of the air guide pipe 74 is 30° to 70°, preferably 43°, to improve the gas mixing effect.

[0036] In this embodiment, the nozzle 79 includes a nozzle body 793, the air jet channel 791 is distributed along the central axis of the nozzle body 793, the powder channel 792 includes a main powder channel 101 and an auxiliary powder channel 102, the output end of the main powder channel 101 is connected to the middle of the air jet channel 791, and the auxiliary powder channel 102 connects the middle of the main powder channel 101 and the middle of the air jet channel 791. The air jet channel 791 includes an air guide section 103 and a spraying section 104. The diameter of the air guide section 103 gradually decreases from the input end to the output end, and the diameter of the input end of the air guide section 103 is smaller than the diameter of the output end of the spraying section 104. The diameter of 104 gradually increases from the input end to the output end. The ratio of the axial length of the air guide 103 to the axial length of the spraying part 104 is 3 to 6:1, preferably 5:1. The output end of the main powder channel 101 is located in the middle of the air guide 103, and the output end of the auxiliary powder channel 102 is located at the connection between the air guide 103 and the spraying part 104. The angle between the central axis of the main powder channel 101 and the central axis of the jet channel 791 is 95° to 120°, preferably 98°, and the angle between the central axis of the auxiliary powder channel 102 and the central axis of the jet channel 791 is 60° to 90°, preferably 70°.

[0037] The jet is compressed and guided by the air guide 103, which increases the flow rate and local temperature. The coating material enters the impact jet through the main powder channel 101 to achieve sufficient heating. At the same time, the auxiliary powder channel 102 compensates for the coating material in the area of ​​maximum flow rate, which can improve the smoothness of the coating material entering the air jet channel 791, thereby ensuring the uniformity of the coating material. Then, it is diffused and sprayed out through the spraying section 104 to achieve a better coating effect.

[0038] Furthermore, the first housing 711 includes a first part 201 and a second part 202 disposed at one end of the first part 201. A first gas flow channel 712 is formed between the first cathode 63 and the first anode 61, and a first cooling chamber 713 is formed between the first anode 61 and the second part 202. The second housing 721 includes a third part 203 and a fourth part 204 disposed at one end of the third part 203. A second gas flow channel 722 is formed between the second cathode 64 and the second anode 62, and a second cooling chamber 723 is formed between the second anode 62 and the fourth part 204. This increases the contact area between the first cooling chamber 713 and the second cooling chamber 723 and the first anode 61 and the second anode 62, respectively, and ensures the flowability of the first gas flow channel 712 and the second gas flow channel 722, thereby improving the cooling effect.

[0039] Furthermore, the insulating layer 602 is alumina ceramic or polyimide, preferably alumina ceramic.

[0040] In this embodiment, the spraying process includes the following steps:

[0041] 1) Surface pretreatment:

[0042] a. Use an ultrasonic cleaner with a frequency of 40 kHz and a power of 500 W to clean the ligament stretcher. The solvent is deionized water and medical grade ethanol (volume ratio 3:1). The cleaning time is 10 to 15 minutes to remove grease and particulate contaminants.

[0043] b. Use white corundum sand with a particle size of 80-120 mesh, sandblasting pressure of 0.4-0.6MPa, sandblasting angle of 80-90°, distance of 100-150 mm, and sandblasting time of 3-5 minutes to sandblast the surface of the ligament stretcher to remove the surface oxide layer and impurities, so that the surface roughness Ra reaches 2.5-3.5μm, increase the surface roughness, and improve the coating adhesion;

[0044] c. Plasma activation treatment of polymer ligament stretchers (Ar / O2 mixed gas, ratio 4:1, power 300 W, treatment time 2-3 minutes).

[0045] 2) Preparation of spray coating materials:

[0046] The coating materials include biocompatible polymers, nano-ceramic particles, and additives;

[0047] The biocompatible polymer is polyetheretherketone, accounting for 70-85%, and the degree of polymerization of the polyetheretherketone is about 104.

[0048] The nano-ceramic particles are alumina, with a particle size of 20–100 nm, accounting for 15–30% of the total.

[0049] The additive is 0.5-1% of a silane coupling agent, such as KH550.

[0050] d. Disperse the nano-ceramic particles and silane coupling agent in an ethanol solution by ultrasonication for 30 minutes (power 200 W).

[0051] e. Mix the dispersion with polyetheretherketone powder (particle size 50-80 μm) in a ball mill (200 rpm, 2 hours).

[0052] f. After drying, sieve (100-mesh sieve) to make spray powder.

[0053] 3) Spraying process: A spraying device with a spraying power of 35 kW and a spraying distance of 180 mm is used. Two types of spraying gases are used: one is argon, and the other is a mixture of argon (85%~95%) and hydrogen (5%~15%). The preferred mixture is 93% argon and 7% hydrogen. The flow rate is 45 L / min, the spraying speed is 350 mm / s, and the spraying thickness is 70 micrometers. The surface of the ligament stretcher is sprayed.

[0054] 4) Post-processing: Vacuum heat treatment furnace (vacuum degree 10⁻³ Pa), heating rate 5℃ / min to target temperature 180~200℃, hold for 1~2 hours, slowly cool to room temperature, and then mechanically polish the coating surface (sandpaper grit 800~1200 mesh) to reduce surface roughness to Ra<0.8μm and improve the feel.

[0055] 5) Quality Inspection Standards:

[0056] I. Adhesion Test

[0057] The coating adhesion was tested using the tensile method according to ASTM C633 standard and was ≥30MPa.

[0058] Abrasion resistance test

[0059] A reciprocating friction testing machine was used (load 10 N, mating material 316L stainless steel, 10 cycles). 4 (times), wear amount ≤0.02 mm³ / N·m.

[0060] Biocompatibility testing

[0061] Perform cytotoxicity assays (MTT method) according to ISO 10993, cell viability ≥90%.

[0062] Corrosion resistance test

[0063] Immersed in simulated body fluid (SBF, pH 7.4, 37℃) for 28 days, the coating showed no blistering or peeling, and the corrosion rate was <0.01mm / year.

[0064] By optimizing the spraying materials and process parameters, the wear resistance, corrosion resistance and biocompatibility of the ligament stretcher surface have been significantly improved, while also having the advantages of being environmentally friendly, efficient and low-cost.

[0065] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0066] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0067] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0068] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A surface coating device for a ligament stretcher, characterized in that: It includes a frame, power module, control system, gas supply system, powder feeding system, heat exchange system, plasma generation system, and spray gun; The gas supply system includes a first gas tank, a second gas tank, a first gas pump, a second gas pump, a first switching valve, a second switching valve, a first connecting pipe, and a second connecting pipe. The first gas tank is connected to a first inlet pipe via the first connecting pipe. The first gas pump and the first switching valve are located on the first connecting pipe. The second gas tank is connected to a second inlet pipe via the second connecting pipe. The second gas pump and the second switching valve are located on the second connecting pipe. The first gas tank is filled with argon gas, and the second gas tank is filled with 85% to 95% argon gas and 5% to 15% hydrogen gas. The plasma generating system includes an anode assembly and a cathode assembly. The anode assembly includes a first anode and a second anode. Both the first anode and the second anode are composed of multiple segmented anode units. Each anode unit is isolated from the other by an insulating layer. The multiple anode units and the insulating layer form a ring-shaped structure. The cathode assembly includes a first cathode and a second cathode. The spray gun includes a primary heating assembly, a secondary heating assembly, an auxiliary heating assembly, at least three air guide pipes, a first air inlet pipe, at least two second air inlet pipes, two water inlet pipes, two water outlet pipes, and a nozzle. The primary heating assembly includes a first housing with a first flow channel. The first anode and first cathode are respectively disposed within the first flow channel, forming a first gas flow channel and a first cooling chamber that are mutually isolated. The first gas flow channel has an annular structure. The first air inlet pipe is connected to the input end of the first gas flow channel. The secondary heating assembly includes a second housing with a second flow channel. The second anode and second cathode are respectively disposed within the second flow channel, forming a first gas flow channel and a first cooling chamber that are mutually isolated. The two channels form a second gas flow channel and a second cooling chamber that are isolated from each other. Each of the gas guide pipes is connected to the input end of the first gas flow channel and the output end of the second gas flow channel. Each of the second air inlets is connected to a portion of the gas guide pipes. The first air inlet pipe and each of the second air inlets are connected to the gas supply system. The two water inlets are connected to the water outlet of the heat exchange system and the first cooling chamber and the second cooling chamber, respectively. The two water outlet pipes are connected to the water inlet of the heat exchange system and the first cooling chamber and the second cooling chamber, respectively. The auxiliary heating component is provided on the second air inlet pipe. The nozzle is provided on the second housing. The nozzle has an air jet channel and a powder channel that communicate with the second gas flow channel. The powder channel is connected to the powder feeding system. The jet duct includes an air guide section and a spraying section. The diameter of the air guide section gradually decreases from the input end to the output end. The diameter of the input end of the air guide section is smaller than the diameter of the output end of the spraying section. The diameter of the spraying section gradually increases from the input end to the output end. The ratio of the axial length of the air guide section to the axial length of the spraying section is 3 to 6:

1. The power module includes a main power supply and multiple sub-power supplies. Each sub-power supply is connected to each anode unit. The power module, gas supply system, powder feeding system, heat exchange system, and plasma generation system are electrically connected to the control system. The surface coating process of the ligament stretcher includes the following steps: 1) Surface pretreatment: a. Use an ultrasonic cleaner with a frequency of 40 kHz and a power of 500 W to clean the ligament stretcher. The solvent is deionized water and medical grade ethanol with a volume ratio of 3:

1. The cleaning time is 10 to 15 minutes to remove grease and particulate contaminants. b. Use white corundum sand with a particle size of 80-120 mesh, sandblasting pressure of 0.4-0.6MPa, sandblasting angle of 80°-90°, distance of 100-150 mm, and sandblasting time of 3-5 minutes to sandblast the surface of the ligament stretcher to remove the surface oxide layer and impurities, so that the surface roughness Ra reaches 2.5-3.5μm, increase the surface roughness, and improve the coating adhesion; c. Plasma activation treatment of polymer ligament stretchers is performed using a mixture of Ar and O2 gas, wherein the ratio of Ar to O2 gas is 4:1, the power is 300 W, and the treatment time is 2 to 3 minutes. 2) Preparation of spray coating materials: The coating materials include biocompatible polymers, nano-ceramic particles, and additives; The biocompatible polymer is polyetheretherketone, accounting for 70-85%, and the degree of polymerization of the polyetheretherketone is 104. The nano-ceramic particles are alumina, with a particle size of 20–100 nm, accounting for 15–30% of the total. The additive is 0.5-1% of a silane coupling agent; d. Disperse the nano-ceramic particles and silane coupling agent in an ethanol solution by ultrasonication for 30 minutes at a power of 200 W; e. Mix the dispersion with polyetheretherketone powder with a particle size of 50-80 μm in a ball mill at a speed of 200 rpm for 2 hours. f. After drying, the powder is sieved through a 100-mesh sieve to produce a coating powder. 3) Spraying process: A spraying device with a spraying power of 35 kW and a spraying distance of 180 mm is used. Two types of spraying gases are used: one is argon, and the other is a mixture of 85% to 95% argon and 5% to 15% hydrogen. The flow rate is 45 L / min, the spraying speed is 350 mm / s, and the spraying thickness is 70 micrometers. The surface of the ligament stretcher is sprayed. 4) Post-processing: Vacuum heat treatment furnace with a vacuum degree of 10⁻³ Pa, heating rate of 5℃ / min to the target temperature of 180~200℃, holding at the temperature for 1~2 hours, slowly cooling to room temperature, and then mechanically polishing the coating surface with sandpaper grit of 800~1200 mesh to reduce the surface roughness to Ra<0.8μm and improve the feel.

2. The surface spraying device for the ligament stretcher according to claim 1, characterized in that: The angle between the central axis of the second air intake pipe and the central axis of the air guide pipe is 30° to 70°.

3. The surface spraying device for the ligament stretcher according to claim 1 or 2, characterized in that: The nozzle includes a nozzle body, the air jet channels are distributed along the central axis of the nozzle body, the powder channel includes a main powder channel and an auxiliary powder channel, the output end of the main powder channel is connected to the middle of the air jet channel, and the auxiliary powder channel is connected to the middle of the main powder channel and the middle of the air jet channel.

4. The surface spraying device for the ligament stretcher according to claim 3, characterized in that: The output end of the main powder channel is located in the middle of the air guiding section, and the output end of the auxiliary powder channel is located at the connection between the air guiding section and the spraying section.

5. The surface spraying device for the ligament stretcher according to claim 4, characterized in that: The angle between the central axis of the main powder channel and the central axis of the jet channel is 95° to 120°, and the angle between the central axis of the auxiliary powder channel and the central axis of the jet channel is 60° to 90°.

6. The surface spraying device for the ligament stretcher according to claim 1, characterized in that: The first housing includes a first part and a second part disposed at one end of the first part. A first gas flow channel is formed between the first cathode and the first anode, and a first cooling chamber is formed between the first anode and the second part. The second housing includes a third part and a fourth part disposed at one end of the third part. A second gas flow channel is formed between the second cathode and the second anode, and a second cooling chamber is formed between the second anode and the fourth part.

7. The surface spraying device for the ligament stretcher according to claim 1, characterized in that: The insulating layer is alumina ceramic or polyimide.

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