A drop-out fuse

Abstract

This invention relates to the field of fuses, specifically a drop-out fuse, comprising a post insulator and a fuse tube assembly. The post insulator has an inlet end and an outlet end. One end of the fuse tube assembly is connected to the inlet end via an upper moving and stationary contact assembly, and the other end is connected to the outlet end via a lower stationary contact assembly. The lower stationary contact assembly includes a lower support with a material-reducing through-hole. The material-reducing through-hole in the lower support serves two purposes: firstly, it reduces weight; secondly, it facilitates the formation of holes in the lower support, allowing for the subsequent threading of wiring harnesses and providing auxiliary connections.

Description

Technical Field

[0001] This invention relates to the field of fuses, and more specifically to a drop-out fuse. Background Technology

[0002] Drop-out fuses are a widely used short-circuit protection device in power distribution lines. They typically consist of a post insulator, a fuse tube assembly, and moving and stationary contacts at both ends of the fuse tube assembly. Their basic principle is as follows: under normal operation, the fuse wire inside the fuse tube assembly carries the line current; when an overcurrent or short-circuit fault occurs in the line, the fuse wire melts, triggering the fuse tube to drop out, forming a visible break, thereby isolating the faulty section of the line and ensuring system safety.

[0003] Existing drop-out fuses typically use a single fuse wire as both overcurrent protection and a mechanical load-bearing element. However, this single-wire solution presents a significant stress-characteristic contradiction in practical applications: on the one hand, to ensure sufficient tensile strength of the fuse wire under harsh conditions such as installation, operation, and wind vibration, and to prevent poor contact due to fatigue or loosening, thicker or higher-strength fuse wire materials are often required; on the other hand, to achieve accurate overcurrent protection characteristics, the fuse wire material must possess specific fusing current and time characteristics. If the material strength is too high, it can easily lead to excessively high fusing current and insensitive protection. If a low-strength material is selected to meet fusing accuracy, it is prone to breakage or characteristic drift due to mechanical tension during long-term operation.

[0004] This contradiction makes it difficult for a single-fuse structure to simultaneously achieve both mechanical reliability and protection precision, thus affecting the overall operational reliability of the fuse.

[0005] In existing technologies, arc-extinguishing tubes for fuses are mainly made of gas-generating materials. The high temperature of the electric arc decomposes the tube wall material to generate high-pressure gas, which cools and blows away the arc, thus extinguishing it. Traditional arc-extinguishing tubes have weak arc-extinguishing capabilities and cannot extinguish the arc simultaneously.

[0006] The lower stationary contact assembly in a fuse typically includes a lower bracket for supporting and positioning the fuse tube. In conventional designs, the lower bracket is often made of sheet metal through stamping or casting, primarily serving as structural support and conductive connection. However, this type of lower bracket has a limitation in practical applications: on the one hand, to meet mechanical strength requirements, the lower bracket often uses a large amount of material, resulting in a bulky overall structure and increased installation burden; on the other hand, during fuse assembly, the stranded wires or other auxiliary wire harnesses in the fuse assembly usually need to be fixed and limited by additional clamps or other independent components, which not only increases the number of parts but also causes inconvenience for on-site installation and maintenance due to limited assembly space.

[0007] In addition, the existing structure of the lower bracket is relatively fixed and lacks integrated design for auxiliary wiring functions, which makes the wiring harness prone to loosening and wear due to vibration or wind sway during long-term operation, posing certain safety hazards.

[0008] Therefore, in order to solve or improve at least one of the above technical problems, it is necessary to optimize the design of the existing fuse structure. Summary of the Invention

[0009] The purpose of this invention is to provide a drop-out fuse that achieves both weight reduction and auxiliary wiring without adding extra components.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A drop-out fuse includes a post insulator and a fuse tube assembly. The post insulator has an inlet end and an outlet end. One end of the fuse tube assembly is connected to the inlet end via an upper moving and stationary contact assembly, and the other end of the fuse tube assembly is connected to the outlet end via a lower stationary contact assembly. The lower stationary contact assembly includes a lower support, and the lower support has a material reduction through hole.

[0012] The fuse tube assembly includes a fuse tube, and a fuse wire unit is provided inside the fuse tube; the fuse wire unit includes a fuse wire structure and an arc-extinguishing tube sleeved on the fuse wire structure.

[0013] The fuse structure includes an upper conductive terminal, a fuse body, and a stranded wire; one end of the fuse body is connected to the upper conductive terminal, and the other end is connected to the stranded wire; the fuse body includes a first fuse and a second fuse capable of melting; the mechanical tensile strength of the first fuse is greater than that of the second fuse; the length of the first fuse is less than that of the second fuse; the upper conductive terminal is connected to the stranded wire through the first fuse and the second fuse; the first fuse is connected between the upper conductive terminal and the stranded wire in a stretched manner; the second fuse is connected between the upper conductive terminal and the stranded wire in a naturally extended manner.

[0014] The stranded wire is connected to the fuse body through a crimping sleeve; one end of the crimping sleeve is sleeved on the stranded wire, and the other end is inserted into the fuse body.

[0015] The upper conductive terminal includes a terminal post and a press-fit sleeve, with the press-fit sleeve disposed at the end of the terminal post; the fuse body is inserted into the press-fit sleeve.

[0016] The terminal post is a stepped shaft, and the terminal post includes a transition section and an assembly section. The terminal post of the assembly section is provided with knurled texture.

[0017] The second fuse is spiral or arc-shaped.

[0018] The arc-extinguishing tube includes a tube body with a through-through channel for connecting the fuse structure. The tube body includes an inner tube and an outer tube disposed outside the inner tube. The inner tube includes a first gas-generating layer, a second gas-generating layer, and a support layer arranged radially from the inside to the outside. The gas generation rate of the first gas-generating layer is greater than that of the second gas-generating layer, and the gas generation rate of the second gas-generating layer is greater than that of the support layer.

[0019] The inner wall of the inner tube is coated with an arc-extinguishing agent, and the arc-extinguishing agent is discontinuously distributed along the axial direction of the inner tube. The inner wall of the inner tube includes two coated areas located at both ends of the inner tube and one uncoated area. The uncoated area corresponds to the fuse body in the fuse structure.

[0020] The method for manufacturing the fuse structure includes the following steps:

[0021] Step 1: Identify the fuse structure components to be assembled;

[0022] Step 2: Install crimp sleeves at the ends of the stranded wires;

[0023] Step 3: Insert both ends of the fuse body into the crimping sleeve and the press-fitting sleeve respectively, and then connect the fuse body to the crimping sleeve and the press-fitting sleeve through the press-fitting process;

[0024] Step 4: After completing step 3, the assembly and manufacturing of a fuse structure is complete. If it is necessary to remake a new fuse structure, simply repeat steps 1-3 above.

[0025] The advantages of this invention are:

[0026] This invention discloses a drop-out fuse; by opening holes in the lower bracket, although the structure is simple, it can achieve multiple functions. One is to reduce weight, and another is to assist in the positioning and limiting of wire harnesses, such as the binding and limiting of the ends of stranded wires in the fuse assembly.

[0027] By setting a first fuse (high strength, short, tensioned) and a second fuse (low strength, long, relaxed) connected in parallel: the first fuse bears all mechanical tensile loads, ensuring that the fuse structure remains stable under conditions such as installation, operation, wind vibration, and thermal expansion and contraction, and avoiding loosening or breakage. The second fuse is not subject to mechanical stress under normal operating conditions, and its fusing characteristics (fusing current, fusing time) are completely determined by the material and cross-section, with no stress drift, ensuring the accuracy and consistency of overcurrent protection.

[0028] This system achieves a division of labor and coupling between mechanical and electrical functions. The first fuse (high strength, short, and tensioned) serves as the main load-bearing component, absorbing all tensile loads after installation. Because it is pre-stretched, it ensures a stable connection during long-term operation, wind vibration, or thermal expansion and contraction, preventing poor contact due to creep or loosening. The second fuse (low strength, long, and relaxed), as the main overcurrent protection component, is almost unaffected by mechanical stress under normal operating conditions. Its fusing characteristics (such as fusing current and time) do not deviate due to long-term mechanical loads, ensuring accurate and stable operation.

[0029] This avoids the "stress-characteristic" contradiction in single-fuse solutions. If a thicker or higher-strength material is selected to meet the tensile strength requirements of a traditional single fuse, it will result in a higher fusing current and less sensitive protection. If a low-strength material is selected to meet the requirements of accurate fusing, it is prone to breakage or loosening due to tensile force during installation or operation.

[0030] This invention decouples "tensile strength" and "fusing" through two parallel electrical paths, enabling the fuse to withstand high tensile forces and precisely fuse according to a preset current.

[0031] This ensures reliable fuse breaking and safe switching in the event of a fault;

[0032] The design of the first and second fuses in this invention, with parallel connection of two fuses and staged fusing, improves the reliability of arc extinguishing and interruption.

[0033] With two fuses present simultaneously, the total current carrying capacity is more stable; when they blow, the arcs form sequentially, resulting in more complete gas production, which facilitates rapid arc extinguishing by the arc-extinguishing tube inside the drop-out switch, reducing the probability of reignition and contact burnout. Simultaneously, the tension completely disappears after the fuse blows, allowing the fuse tube to reliably drop, creating a clear break point and ensuring maintenance safety.

[0034] The present invention sets the arc-extinguishing agent in a discontinuous distribution along the inner tube axis, with coating at both ends and no coating in the middle: this partitioned design allows the gas generation function and the arc-extinguishing function to perform their respective functions in space, avoiding the suppression of gas generation efficiency by the traditional fully coated structure, and also avoiding the lack of end arc control capability of the uncoated structure.

[0035] By setting up a three-layer structure with decreasing gas production rates—the first gas-producing layer, the second gas-producing layer, and the support layer—the three layers work together to make the arc extinguishing process present an ideal timing sequence of "rapid pressure build-up, continuous maintenance, and structural stability," which is especially suitable for reliable disconnection under high voltage and high current conditions.

[0036] The inner tube's support layer is made of high-strength steel paper or high-temperature resistant fiber paper, providing sufficient mechanical strength to prevent the tube from deforming or cracking under high-pressure gas impact. The outer tube is made of epoxy glass cloth wound tube or epoxy glass cloth tube, which has excellent insulation performance, high-temperature resistance and mechanical strength. After being bonded or interference-fitted with the inner tube, it forms a complementary double-layer structure, which significantly improves the overall pressure resistance, impact resistance and environmental adaptability of the arc extinguishing tube.

[0037] The arc extinguishing agent uses high thermal stability materials such as silicate, tungsten oxide, or borate, and the coating thickness is controlled between 0.1 and 0.3 mm. This ensures that enough arc-extinguishing material participates in the arc reaction, while avoiding the risk of reduced heat conduction of the pipe wall or coating peeling due to excessive coating thickness. These materials can form a dense insulating barrier at the high temperature of the arc, effectively inhibiting the reconstruction of the arc channel and improving the dielectric recovery strength. They are especially suitable for scenarios involving multiple short-circuit interruptions or reclosing.

[0038] The inner tube can be formed by layer-by-layer rolling, multi-layer impregnation, or multi-layer spraying. The process is mature and it is easy to achieve precise control of the gas-generating layer material and thickness.

[0039] Arc suppressant can be applied by segmented spraying, roller coating, or screen printing, which can achieve discontinuous coating efficiently and stably, ensuring product consistency and production efficiency, and facilitating industrial application. Attached Figure Description

[0040] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0041] Figure 1 This is a schematic diagram of the structure of the present invention.

[0042] Figure 2 This is a first-view structural schematic diagram of the first embodiment of the fuse structure of the present invention.

[0043] Figure 3 This is a second-view structural schematic diagram of the first embodiment of the fuse structure of the present invention.

[0044] Figure 4 This is a first-view structural schematic diagram of the second embodiment of the fuse structure of the present invention.

[0045] Figure 5 This is a schematic diagram of the structure of the fuse structure of the present invention when connected to the arc extinguishing tube.

[0046] Figure 6 This is a cross-sectional view of the arc-extinguishing tube of the present invention.

[0047] Figure 7 This is a cross-sectional view of the crimping sleeve in this invention.

[0048] The markings in the above figures are all:

[0049] 1-1. Fuse tube assembly. 1-2. Upper moving and stationary contact assembly. 1-3. Lower stationary contact assembly. 1-4. Post insulator. 1-11. Fuse wire structure. 1-12. Arc extinguishing tube. Detailed Implementation

[0050] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and the description of the preferred embodiments.

[0051] A drop-out fuse includes a post insulator 1-4 and a fuse tube assembly 1-1. One end of the post insulator 1-4 has an inlet terminal, and the other end has an outlet terminal. One end of the fuse tube assembly 1-1 is connected to the inlet terminal via an upper moving-stationary contact assembly 1-2, and the other end of the fuse tube assembly 1-1 is connected to the outlet terminal via a lower stationary contact assembly 1-3. The lower stationary contact assembly 1-3 includes a lower support with a material-reducing through-hole 1-31. The material-reducing through-hole 1-31 serves two purposes: firstly, it reduces weight; secondly, it facilitates the formation of holes in the lower support, allowing for the subsequent threading of wiring harnesses and providing auxiliary connections.

[0052] Furthermore, the fuse tube assembly 1-1 described in this invention includes a fuse tube, within which a fuse wire unit is provided; the fuse wire unit includes a fuse wire structure 1-11 and an arc-extinguishing tube 1-12 sleeved on the fuse wire structure 1-11; the fuse tube serves as the outer mechanical protection and mounting carrier; the fuse tube is typically made of high-strength insulating material (such as epoxy glass cloth tube) and is the outer structure of the fuse tube assembly 1-1. The arc-extinguishing tube 1-12 is mainly used for middle-layer gas generation and arc extinguishing core; the arc-extinguishing tube 1-12 is sleeved on the fuse wire structure 1-11 and is typically made of multi-layer composite gas-generating material; its main function is to generate high-pressure arc-extinguishing gas: when the fuse wire melts and generates an arc, the inner wall material of the arc-extinguishing tube 1-12 rapidly decomposes under the high temperature of the arc, generating a large amount of high-pressure gas. The gas is ejected at high speed from the tube end, strongly axially blowing the arc, causing the arc to be elongated, cooled, and ultimately extinguished.

[0053] Arc Path Confinement: Arc extinguishing tubes 1-12 confine the arc within the tube cavity, preventing the arc from spreading outward and thus preventing damage to adjacent phases or equipment.

[0054] Providing an arc-extinguishing medium: The gas produced by the decomposition of the materials in arc-extinguishing tubes 1-12 usually has good insulation properties, which can quickly restore the dielectric strength between the fracture surfaces and prevent the arc from reigniting.

[0055] The fuse structure 1-11 is mainly an overcurrent protection and mechanical tensioning unit. The fuse structure 1-11 is inserted inside the arc-extinguishing tube 1-12. The first fuse 1021 and the second fuse 1022 are connected in parallel to provide stable current carrying capacity. When an overcurrent or short-circuit fault occurs in the line, the second fuse 1022 (low strength, relaxed) melts first, followed by the first fuse 1021 (high strength, tensioned) overheating and melting, forming a clear melting sequence that triggers the fuse tube to drop.

[0056] The fuse structure 1-11 includes an upper conductive terminal 101, a fuse body 102, and a stranded wire 104. One end of the fuse body 102 is connected to the upper conductive terminal 101, and the other end is connected to the stranded wire 104. The fuse body 102 includes a first fuse 1021 and a second fuse 1022 capable of melting. The mechanical tensile strength of the first fuse 1021 is greater than that of the second fuse 1022. The length of the first fuse 1021 is less than that of the second fuse 1022. The upper conductive terminal 101 is connected to the first fuse 102. 1. The first fuse 1021 and the second fuse 1022 are connected to the stranded wire 104. The first fuse 1021 is connected between the upper conductive terminal 101 and the stranded wire 104 in a stretched manner. The second fuse 1022 is connected between the upper conductive terminal 101 and the stranded wire 104 in a naturally extended manner. In this invention, the first fuse 1021 is in a tensioned state, and the second fuse 1022 is in a relaxed state. The fuse structure 1-11 disclosed in this invention, through a dual fuse structure 1-11 with one strong and one short, one weak and one long, one tensioned and one relaxed fuse, takes into account mechanical tensile strength and achieves more accurate and reliable overcurrent / short circuit protection, while avoiding false tripping and improving the breaking success rate.

[0057] Specifically, through the above design, the present invention can achieve the following technical effects:

[0058] It realizes the division of labor and coupling of mechanical and electrical functions.

[0059] The first fuse 1021 (high strength, short, tensioned) serves as the main load-bearing component, absorbing all tensile loads after fuse installation. Because it is pre-stretched, it ensures that the entire fuse system maintains a stable connection during long-term operation, wind vibration, or thermal expansion and contraction, preventing poor contact due to creep or loosening.

[0060] The second fuse 1022 (low strength, long, relaxed) serves as the main overcurrent protection component. Under normal operating conditions, it is almost unaffected by mechanical stress, and its fusing characteristics (such as fusing current and time) will not deviate due to long-term mechanical load, ensuring the accuracy and stability of its operation.

[0061] This avoids the "stress-characteristic" contradiction inherent in single-fuse solutions;

[0062] If a traditional single fuse is made of a thicker or higher-strength material to meet tensile strength requirements, it will result in a higher fusing current and less sensitive protection. If a low-strength material is made to meet precise fusing requirements, it is prone to breakage or loosening due to tensile stress during installation or operation.

[0063] This invention decouples "tensile strength" and "fusing" through two parallel electrical paths, enabling the fuse to withstand high tensile forces and precisely fuse according to a preset current.

[0064] This ensures reliable fuse breaking and safe switching in the event of a fault;

[0065] When an overcurrent or short circuit occurs in the circuit, the second fuse 1022 (low strength) will blow first. At this time, the first fuse 1021 (high strength) remains conductive, but all the current is transferred to the first fuse 1021, causing it to overheat and blow quickly.

[0066] This "sequential fuse breaking" mechanism can generate a clear fuse breaking sequence, avoid instantaneous arcing that cannot be extinguished, ensure that the drop switch can reliably drop, form a visible break, and improve the reliability of fault isolation.

[0067] Improved impact resistance and fatigue resistance;

[0068] The first fuse 1021 is fixed by tension, similar to a pre-tightened structure, which can absorb dynamic loads caused by wind vibration, switch opening and closing vibration, or line sway, reducing impact fatigue on the second fuse 1022. This is especially suitable for harsh working conditions such as outdoor overhead lines, and can extend the service life of the overall fuse.

[0069] It simplifies installation and maintenance; during installation, only the first fuse 1021 needs to be tensioned to ensure overall mechanical strength, without the need for precise control of the stress state of the second fuse 1022, which reduces the requirements for installation process and reduces the risk of fuse failure or mechanical damage caused by improper human operation.

[0070] In summary, by using the parallel and coordinated operation of the first fuse 1021 and the second fuse 1022, this invention significantly improves the overall mechanical reliability of the fuse assembly while maintaining accurate fusing characteristics. It is particularly suitable for drop-out fuse scenarios where there are strict requirements for mechanical strength and overcurrent protection.

[0071] In this invention, it is required to control the melting time and sequence of the first fuse 1021 and the second fuse 1022, so as to precisely control the melting current and melting speed of the fuse body 102. The actual action sequence is as follows: for minor overload / small fault current, the second fuse 1022 melts first; for severe short circuit with large current, the first and second fuses 1022 melt almost simultaneously. This combination can sensitively protect against small overloads and withstand inrush current and starting impact without malfunction.

[0072] The second fuse 1022 is relaxed and not under tension. Its fusing characteristics are determined only by the current and will not be affected by tension or stress.

[0073] If both wires are taut, the thin fuse is prone to premature breakage or characteristic drift under mechanical stress.

[0074] The design of the first fuse 1021 and the second fuse 1022 in this invention, with parallel connection of two fuses and staged fusing, improves the reliability of arc extinguishing and breaking.

[0075] With two fuses present simultaneously, the total current carrying capacity is more stable; when the fuses break, they form arcs sequentially, resulting in more complete gas production, which facilitates rapid arc extinguishing by the arc-extinguishing tubes 1-12 inside the drop-out switch, reducing the probability of reignition and contact burnout. Simultaneously, the tension completely disappears after the fuse breaks, allowing the fuse tubes to reliably drop, forming a clear break point and ensuring maintenance safety.

[0076] Furthermore, in this invention, the stranded wire 104 is connected to the fuse body 102 via a crimping sleeve 103; one end of the crimping sleeve 103 is sleeved on the stranded wire 104, and the other end is inserted into the fuse body 102; one end of the crimping sleeve 103 is crimped to the stranded wire 104 to form a permanent, low-resistance mechanical and electrical connection; the other end is inserted into the fuse body 102 to facilitate connection with the fuse body 102.

[0077] In this invention, the crimp sleeve 103 serves as a connector, mainly used for the connection between the fuse body 102 and the stranded wire 104.

[0078] Meanwhile, the crimping sleeve 103 in this invention avoids the thermal impact on the fuse body 102 or stranded wire 104 when using welding. At the same time, the crimping sleeve 103 can achieve reliable contact between dissimilar metals.

[0079] In actual production, the crimping sleeve 103 can be pre-installed on the stranded wire 104. During subsequent assembly, simply insert the fuse body 102 into the sleeve and fix it in place.

[0080] Furthermore, the crimping sleeve 103 in this invention includes a crimping cylinder body, which is the main structure of the crimping sleeve 103. An assembly baffle 1033 is provided inside the crimping cylinder body 1031, blocking the channel within the crimping cylinder body 1031. This limits the insertion position of the fuse body 102 during subsequent use and facilitates the installation and positioning of the fuse body 102. In this invention, the end of the fuse body 102 can press against the assembly baffle 1033, providing a good blocking effect. Generally, the assembly baffle 1033 is located in the middle region of the crimping sleeve 1012. The assembly baffle 1033 ensures the stability and accuracy of the crimping sleeve 103's insertion position on the stranded wire 104, while also limiting the installation of the fuse body 102, ensuring the stability and accuracy of the connection between the stranded wire 104 and the fuse body 102.

[0081] Furthermore, in this invention, the upper conductive terminal 101 includes a terminal post 1011 and a press-fit sleeve 1012, with the press-fit sleeve 1012 disposed at the end of the terminal post 1011. Based on the above design, the upper conductive terminal 101 is mainly a two-section structure. The upper end is generally designed as a solid structure to ensure the structural strength of the upper conductive terminal 101, and also has a flange to ensure the stability of contact with the contacts of the drop-out fuse. The press-fit sleeve 1012 mainly serves as a connection and positioning function. In subsequent use, the fuse body 102 is inserted into the press-fit sleeve 1012; subsequently, they are connected through a press-fit process. The connection between the press-fit sleeve 1012 and the terminal post 1011 can autonomously form an internal platform, which can play a good role in axial positioning.

[0082] Furthermore, in this invention, the terminal post 1011 is a stepped shaft. The stepped shaft allows the terminal post 1011 itself to form a stepped platform. This design is mainly to facilitate the insertion and positioning of the arc-extinguishing tube 1-12 on the upper conductive terminal 101. Additionally, the terminal post 1011 in this invention includes a transition section 10111 and an assembly section 10112. The transition section 10111 has a larger outer diameter, while the assembly section 10112 has a smaller outer diameter. The connection between the two forms a stepped platform for limiting the installation of the arc-extinguishing tube 1-12. Furthermore, the terminal post 1011 of the assembly section 10112 in this invention is provided with a knurled texture 10113. This design ensures the stability of the connection between the arc-extinguishing tube 1-12 and the upper conductive terminal 101.

[0083] In this invention, the terminal body and the press-fit sleeve 1012 are an integral structure; this arrangement facilitates the production of the upper conductive terminal 101.

[0084] Furthermore, in this invention, the inner wall of the crimping sleeve 103 or / and the pressing sleeve 1012 is provided with pressing teeth 1032; the setting of pressing teeth 1032 ensures the stability of the connection between the pressing sleeve 1012 and the crimping sleeve 103 and the fuse body 102.

[0085] In this invention, the press-fit teeth 1032 include annular inner teeth 10321 and longitudinal teeth 10322; the annular inner teeth 10321 and the longitudinal teeth 10322 are arranged intersectingly; the press-fit teeth of this invention include a plurality of annular inner teeth 10321 and longitudinal teeth 10322, the plurality of annular inner teeth 10321 being spaced parallel; the longitudinal teeth 10322 being arranged perpendicular to the annular inner teeth 10321; through the plurality of longitudinal teeth 10322 and annular inner teeth 10322... The assembly of 21 forms a grid-like structure on the inner wall of the crimping sleeve 103 or the pressing sleeve 1012. This can increase the structural strength of the crimping sleeve 103 or the pressing sleeve 1012, and also increase the roughness of the inner wall of the crimping sleeve 103 or the pressing sleeve 1012. This ensures the stability of the crimping sleeve 103 or the pressing sleeve 1012 and the fuse body 102 during pressing, and reduces the risk of the fuse body 102 detaching from the crimping sleeve 103 or the pressing sleeve 1012 during stretching.

[0086] The stranded wire 104 described in this invention is a tin-plated copper stranded wire; it has good self-protection capabilities and can guarantee the service life of the stranded wire 104 to a certain extent.

[0087] In this invention, the second fuse 1022 is spiral or arc-shaped; in this invention, the second fuse 1022 is required to be connected between the upper conductive terminal 101 and the stranded wire 104 in a naturally extended manner; the second fuse 1022 is in a relaxed state; the second fuse 1022 is arranged in an arc shape, which is best achieved in production, and the length of the second fuse 1022 is required to be greater than the interval between the press sleeve 1012 and the crimping sleeve 103; specifically, the press sleeve 1012 and the crimping sleeve 103 are required to press against both ends of the second fuse 1022 respectively, and by pressing against the second fuse 1022, it causes it to bend and deform, thereby making it bend.

[0088] For the spiral shape, prefabrication is required. Generally, the second fuse 1022 is required to include a spiral middle section, with connecting sections at both ends of the spiral middle section. The connecting sections can be straight or curved. During subsequent installation and connection, the spiral middle section is located in the area between the press sleeve 1012 and the press sleeve 103, and the connecting sections at both ends are connected to the press sleeve 1012 and the press sleeve 103, respectively.

[0089] A method for manufacturing the aforementioned fuse structure 1-11 for a drop-out switch, characterized by comprising the following steps:

[0090] Step 1: Identify the fuse structure parts 1-11 to be assembled;

[0091] Step 2: Install the crimp sleeve 103 at the end of the stranded wire 104;

[0092] Step 3: The two ends of the fuse body 102 are respectively inserted into the crimping sleeve 103 and the pressing sleeve 1012, and then the fuse body 102 is connected to the crimping sleeve 103 and the pressing sleeve 1012 through the pressing process.

[0093] Step 4: After completing Step 3, the assembly and manufacturing of a fuse structure 1-11 is complete. If it is necessary to remake a new fuse structure 1-11, simply repeat Step 1-3 above.

[0094] A fuse arc-extinguishing tube 1-12 includes a tube body with a through-through channel for connecting a fuse wire structure 1-11. The tube body includes an inner tube 1-122 and an outer tube 1-121 disposed outside the inner tube 1-122. The inner wall of the inner tube 1-122 is coated with an arc-extinguishing agent 1-23. The arc-extinguishing agent 1-23 is distributed at both ends of the inner tube 1-122.

[0095] Inner tube 1-122 is used to generate high-pressure gas under the action of electric arc;

[0096] In this invention, the inner tubes 1-122 are multi-layer composite structures; in essence, they are multi-layer composite gas-generating structures.

[0097] The inner tube 1-122 includes a first gas-generating layer 1-1221, a second gas-generating layer 1-1222, and a support layer 1-1223 arranged radially from the inside to the outside. The gas generation rate of the first gas-generating layer 1-1221 is greater than that of the second gas-generating layer 1-1222, and the gas generation rate of the second gas-generating layer 1-1222 is greater than that of the support layer 1-1223. The gas generation rate of the support layer 1-1223 is lower than that of the second gas-generating layer 1-1222. The first gas-generating layer 1-1221 is used to quickly establish the arc-extinguishing gas pressure, the second gas-generating layer 1-1222 is used to maintain the gas pressure, and the support layer 1-1223 is used to improve the structural strength of the inner tube 1-122. The first gas-generating layer 1-1221 is made of low-decomposition-temperature fiber paper or modified mulberry bark paper, the second gas-generating layer 1-1222 is made of ordinary steel paper or medium-speed gas-generating fiber paper, and the support layer 1-1223 is made of high-strength steel paper or high-temperature resistant fiber paper.

[0098] The arc-extinguishing agent 1-23 is discontinuously distributed along the axial direction of the inner tube 1-122, and includes at least a coating area at both ends of the inner tube 1-122; the inner wall of the inner tube 1-122 includes at least one coating area and at least one uncoated area; the uncoated area corresponds to the fuse installation area, and the uncoated area is not coated with arc-extinguishing agent 1-23, the coating area is used to enhance the arc-extinguishing effect, and the uncoated area is used to improve the gas production efficiency.

[0099] The arc-extinguishing agent 1-23 is a silicate-based arc-extinguishing coating, a tungsten oxide coating, or a borate coating, and the thickness of the arc-extinguishing agent 1-23 in the coating area is 0.1-0.3 mm.

[0100] The outer tube 1-121 is made of epoxy glass cloth wound tube or epoxy glass cloth tube, and the outer tube 1-121 and the inner tube 1-122 are composited through an adhesive layer or interference fit.

[0101] The inner tube 1-122 is formed by layer-by-layer rolling, multi-layer impregnation and composite or multi-layer spraying. The arc extinguishing agent 1-23 is coated on the inner wall of the inner tube 1-122 by shielding segmented spraying, roller segmented coating or screen segmented printing.

[0102] The arc-extinguishing tubes 1-12 disclosed in this invention adopt a double-layer tube structure, including:

[0103] Inner tube 1-122: Multi-layer composite structure, undertaking the core functions of gas generation and arc extinguishing;

[0104] Outer tube 1-121: Single-layer high-strength structure, providing mechanical support and insulation protection;

[0105] Reliable bonding between the inner and outer layers is achieved through an adhesive layer or interference fit.

[0106] A through-hole is provided in the center of the tube for installing the fuse structure 1-11.

[0107] Inner tube 1-122 – Multi-layer gradient gas production structure; Inner tube 1-122 consists of three layers arranged radially from the inside out:

[0108] The first gas-producing layer 1-1221 is made of low-decomposition-temperature fiber paper or modified mulberry bark paper; it is used to quickly establish the pressure of the arc-extinguishing gas.

[0109] The second gas-producing layer, 1-1222, is made of ordinary steel paper or medium-speed gas-producing fiber paper and is used to maintain gas pressure and prolong the pressure duration.

[0110] The support layer 1-1223 is made of high-strength steel paper or high-temperature resistant fiber paper, which improves the structural strength of the inner tube 1-122 and prevents the tube from collapsing prematurely.

[0111] The three-layer material exhibits a decreasing gas production rate gradient along the radial direction, forming a "fast-medium-slow" gas production sequence, thereby achieving optimized control of the pressure curve.

[0112] Arc extinguishing agent 1-23 is coated on the inner wall of inner tube 1-122 in a discontinuous distribution, including at least the coating areas located at both ends of the tube body, with the coating areas and uncoated areas distributed along the axial direction.

[0113] Coated areas: Located at both ends of the inner tube 1-122, coated with arc-extinguishing agent 1-23 (silicate-based, tungsten oxide, or borate) with a thickness of 0.1–0.3 mm to enhance arc extinguishing capability; Uncoated areas: Located between the coated areas at both ends, corresponding to the fuse installation area, without arc-extinguishing agent 1-23 to maintain high gas generation efficiency of the material in this area. This structure achieves a spatial division of labor between arc extinguishing enhancement and gas generation efficiency: the two ends focus on arc extinguishing, while the middle focuses on gas generation.

[0114] The outer tube 1-121 is a structural reinforcement layer; the outer tube 1-121 is made of epoxy glass cloth wound tube or epoxy glass cloth tube, which has: high mechanical strength, can withstand electric arc impact pressure; excellent insulation performance, prevents external flashover; high temperature resistance, and the thermal expansion difference with the inner tube 1-122 is adapted through adhesive layer or interference fit.

[0115] Inner tube 1-122 forming: Through layer-by-layer rolling, multi-layer impregnation and composite or multi-layer spraying forming, the interface of the three-layer materials is ensured to be tightly bonded;

[0116] Arc suppressant 1-23 coating: precise area selective coating is achieved by using masking segmented spraying, roller segmented coating, or screen segmented printing.

[0117] Traditional single gas-generating materials suffer from slow pressure build-up or short pressure maintenance time. This solution utilizes a three-layer gradient gas-generating structure:

[0118] The first layer decomposes rapidly, generating a large amount of gas instantaneously in the early stage of the electric arc, quickly establishing the pressure required to extinguish the arc.

[0119] The second layer continuously produces gas, taking over after the first layer is consumed, maintaining the pressure platform and ensuring that the electric arc is fully stretched and cooled.

[0120] The support layer 1-1223 has the lowest gas production rate, which avoids pressure overshoot or pipe rupture in the later stage while ensuring structural integrity.

[0121] The three elements work together to form an ideal pressure sequence of "rapid pressure building - stable maintenance - prevention of collapse".

[0122] Spatial synergy between arc extinguishing and gas generation; while arc extinguishing agent 1-23 can enhance the arc extinguishing effect, it will inhibit the decomposition efficiency of the gas-generating material. This solution achieves this through segmented coating: Coated areas at both ends: the arc ignition point is usually located at both ends of the fuse, where concentrated arc extinguishing agent 1-23 can effectively inhibit arc reignition and accelerate arc extinguishing; Uncoated area in the middle: retaining the original decomposition efficiency of the gas-generating material, ensuring sufficient gas production, and avoiding insufficient gas generation due to the coverage of arc extinguishing agent 1-23.

[0123] The support layer 1-1223 is made of high-strength steel paper or high-temperature resistant fiber paper, which can maintain the shape of the tube under the high temperature of the electric arc and prevent the inner tube 1-122 from collapsing prematurely due to gas generation and ablation, thus causing the arc to fail to extinguish.

[0124] The outer epoxy glass cloth tube provides secondary structural reinforcement and also serves as an insulation barrier to prevent external breakdown of the arc-extinguishing tubes 1-12 under high-voltage conditions.

[0125] The adhesive layer or interference fit solves the risk of delamination caused by the difference in the coefficients of thermal expansion between the inner organic fiber material and the outer thermosetting material, ensuring long-term reliability.

[0126] Example 1 of arc-extinguishing tubes 1-12:

[0127] The arc-extinguishing tube 1-12 disclosed in this invention is suitable for outdoor high-voltage fuses with a rated voltage of 12kV and a rated current of 100A.

[0128] The arc-extinguishing tube 1-12 includes a cylindrical tube body with an axially penetrating through-hole at the center of the tube body. The through-hole is used to connect the fuse structure 1-11.

[0129] The tube body is composed of an inner tube 1-122 and an outer tube 1-121. The outer tube 1-121 is sleeved on the outside of the inner tube 1-122, and the two are coated with an epoxy resin adhesive layer to achieve a fixed composite.

[0130] The inner tube 1-122 has a three-layer composite structure, which is formed by rolling each layer sequentially, as detailed below:

[0131] First gas-generating layer 1-1221: Located at the innermost layer. Modified mulberry paper is used as the material. This layer is used to rapidly decompose at the moment the fuse melts, generating high-pressure gas and quickly establishing arc-extinguishing pressure.

[0132] The second gas-producing layer 1-1222 is located outside the first gas-producing layer 1-1221 and is made of ordinary steel paper. This layer continues to produce gas after the first gas-producing layer 1-1221 is ablated, maintaining the gas pressure in the arc-extinguishing chamber and ensuring that the arc is sufficiently elongated and cooled.

[0133] Support layer 1-1223: Located on the outermost layer. High-strength steel paper is used as the material. This layer mainly serves as structural support, preventing the inner tube 1-122 from collapsing prematurely during arc erosion, and also preventing the tube from bursting due to excessive gas production.

[0134] The three-layer material is formed in one step using a wet rolling process: the first gas-generating layer 1-1221, the second gas-generating layer 1-1222, and the support layer 1-1223 are stacked in sequence, then wound and pressed on a core mold, and dried and cured to form an integrated structure.

[0135] Arc-extinguishing agent 1-23 is applied; arc-extinguishing agent 1-23 is a tungsten oxide coating, applied to the inner wall of the inner tube 1-122. The coating method is segmented spraying with a masking technique.

[0136] Two annular shielding sleeves are respectively fitted onto the middle of the inner tube 1-122 to cover the fuse installation area;

[0137] Spray the unmasked areas at both ends with a coating thickness of 0.2mm;

[0138] After the spraying is completed, remove the masking cover and allow it to dry.

[0139] After coating, the inner wall of the inner tube 1-122 forms a coated area at both ends and an uncoated area in the middle. The uncoated area corresponds to the fuse installation position, and this area is not coated with arc suppressant 1-23 to maintain the original decomposition efficiency of the gas-generating material; the coated areas at both ends provide enhanced arc extinguishing capability near the arc ignition point and suppress arc reignition.

[0140] The outer tube 1-121 is made of epoxy glass cloth wound tube, with its inner diameter matching the outer diameter of the inner tube 1-122 (leaving a 0.5mm gap for the bonding layer). The outer tube 1-121 is prepared by the following process: alkali-free glass cloth is impregnated with epoxy resin, wound onto a mandrel to a predetermined thickness, and then cured.

[0141] Inner and outer layer composite: The outer surface of the inner layer tube 1-122 is uniformly coated with epoxy resin adhesive, and then the outer layer tube 1-121 is fitted onto the outside of the inner layer tube 1-122. It is held under axial pressure for 1 hour to ensure that the adhesive layer is uniformly filled, and then cured at 120℃ for 1 hour to form an integral tube body. After the composite is completed, the two ends of the tube body are chamfered, and a layer of lubricant (molybdenum disulfide coating) is applied to the inner wall of the through channel to facilitate the installation of the fuse structure 1-11.

[0142] Obviously, the specific implementation of this invention is not limited to the above-described methods. Any non-substantial improvements made using the inventive concept and technical solution of this invention are within the protection scope of this invention.

Claims

1. A drop-out fuse, comprising a post insulator and a fuse tube assembly, wherein one end of the post insulator has an inlet terminal and the other end has an outlet terminal, one end of the fuse tube assembly is connected to the inlet terminal via an upper moving and stationary contact assembly, and the other end of the fuse tube assembly is connected to the outlet terminal via a lower stationary contact assembly; characterized in that, The lower stationary contact assembly includes a lower support, on which a material reduction through hole is provided.

2. A drop-out fuse according to claim 1, characterized in that, The fuse tube assembly includes a fuse tube, and a fuse wire unit is provided inside the fuse tube; the fuse wire unit includes a fuse wire structure and an arc-extinguishing tube sleeved on the fuse wire structure.

3. A drop-out fuse according to claim 2, characterized in that, The fuse structure includes an upper conductive terminal, a fuse body, and a stranded wire; one end of the fuse body is connected to the upper conductive terminal, and the other end is connected to the stranded wire; the fuse body includes a first fuse and a second fuse capable of melting; the mechanical tensile strength of the first fuse is greater than that of the second fuse; the length of the first fuse is less than that of the second fuse; the upper conductive terminal is connected to the stranded wire through the first fuse and the second fuse; the first fuse is connected between the upper conductive terminal and the stranded wire in a stretched manner; the second fuse is connected between the upper conductive terminal and the stranded wire in a naturally extended manner.

4. A drop-out fuse according to claim 3, characterized in that, The stranded wire is connected to the fuse body through a crimping sleeve; one end of the crimping sleeve is sleeved on the stranded wire, and the other end is inserted into the fuse body.

5. A drop-out fuse according to claim 4, characterized in that, The upper conductive terminal includes a terminal post and a press-fit sleeve, with the press-fit sleeve disposed at the end of the terminal post; the fuse body is inserted into the press-fit sleeve.

6. A drop-out fuse according to claim 5, characterized in that, The terminal post is a stepped shaft, and the terminal post includes a transition section and an assembly section. The terminal post of the assembly section is provided with knurled texture.

7. A drop-out fuse according to claim 2, characterized in that, The second fuse is spiral or arc-shaped.

8. A drop-out fuse according to claim 1, characterized in that, The arc-extinguishing tube includes a tube body with a through-through channel for connecting the fuse structure. The tube body includes an inner tube and an outer tube disposed outside the inner tube. The inner tube includes a first gas-generating layer, a second gas-generating layer, and a support layer arranged radially from the inside to the outside. The gas generation rate of the first gas-generating layer is greater than that of the second gas-generating layer, and the gas generation rate of the second gas-generating layer is greater than that of the support layer.

9. A drop-out fuse according to claim 8, characterized in that, The inner wall of the inner tube is coated with an arc-extinguishing agent, and the arc-extinguishing agent is discontinuously distributed along the axial direction of the inner tube. The inner wall of the inner tube includes two coated areas located at both ends of the inner tube and one uncoated area. The uncoated area corresponds to the fuse body in the fuse structure.

10. A drop-out fuse according to claim 5, characterized in that, The method for manufacturing the fuse structure includes the following steps: Step 1: Identify the fuse structure components to be assembled; Step 2: Install crimp sleeves at the ends of the stranded wires; Step 3: Insert both ends of the fuse body into the crimping sleeve and the press-fitting sleeve respectively, and then connect the fuse body to the crimping sleeve and the press-fitting sleeve through the press-fitting process; Step 4: After completing step 3, the assembly and manufacturing of a fuse structure is complete. If it is necessary to remake a new fuse structure, simply repeat steps 1-3 above.

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