A rivet riveting type thermal trip lightning protection device and an assembling method thereof

Abstract

The application discloses a rivet riveting type thermal trip lightning protection device, which comprises an inner shell, an outer shell, a pressure-sensitive resistor, a thermal trip elastic sheet and a tripping sheet, the inner shell is internally provided with an assembling cavity, the pressure-sensitive resistor is provided with an electrode sheet, the electrode sheet is provided with a connecting lug, the pressure-sensitive resistor is arranged on one side of the inner shell, the connecting lug extends into the assembling cavity, the thermal trip elastic sheet is connected with the inner shell and extends into the assembling cavity on one side, the tripping sheet is rotatably arranged on the inner shell on one side through a rotating shaft, the tripping sheet is internally provided with a spring, the upper end of the spring abuts against the inner shell, the spring forms a downward thrust force on the tripping sheet, the thermal trip elastic sheet forms an upward thrust force on the tripping sheet, the upward thrust force of the thermal trip elastic sheet on the tripping sheet is greater than the downward thrust force of the spring on the tripping sheet, the thermal trip elastic sheet is riveted and arranged on the connecting lug of the electrode sheet through a rivet, the melting point of the rivet is 120-160 DEG C, and the inner shell is arranged in the outer shell. The application improves electrical safety, guarantees complete separation of electrodes after fault fusing, and prevents arc ignition.

Description

Technical Field

[0001] This invention belongs to the technical field of surge protection devices (SPDs / low-voltage surge protectors), specifically a riveted thermal trip surge protector and its assembly method. Background Technology

[0002] The core pressure relief element of the voltage-limiting surge protector in low-voltage power distribution systems is the zinc oxide varistor. After long-term operation, the power frequency leakage current continues to rise due to moisture and aging, which will generate a lot of heat. If there is no reliable thermal tripping mechanism, the varistor will be at a high temperature for a long time, which can easily cause safety accidents such as fire, phase-to-phase short circuit, and equipment explosion.

[0003] Currently, mature mass production solutions in the industry all use thermal release springs and varistors with tin-filled openings for soldering. This process has inherent defects in multiple dimensions, and existing alternatives cannot solve the core pain points, as follows: 1. The electrical protection performance is inconsistent, making safety management difficult. The solder joint melting threshold is affected by more than ten variables, including solder filler amount, wetting area, welding temperature, manual operation, electrode flatness, flux residue, etc. The tripping current dispersion of products of the same specification can reach ±30%; the products in batches are polarized, some products trip and the equipment loses power as soon as they get slightly hot, while some products cannot trip even when the temperature is high, which poses a major fire hazard in the power distribution.

[0004] 2. High-temperature welding damages the varistor body, shortening product lifespan. Soldering requires high-temperature wetting at temperatures above 180°C. Heat is conducted along the electrodes to the edge of the zinc oxide ceramic sheet, causing micro-cracks and grain deterioration at the ceramic sheet interface, which significantly reduces the nominal current capacity and impact withstand cycles of the surge protector. Under outdoor and photovoltaic high-temperature conditions, leakage current drift is aggravated, leading to premature product failure.

[0005] 3. The production process is lengthy, poorly adapted to automation, and has a high defect rate. The soldering process consists of four steps: opening, applying solder, constant temperature soldering, and cooling. Manual soldering is prone to producing cold solder joints, missing solder joints, and short circuits caused by solder balls. Soldering requires the consumption of solder and flux, and the investment in supporting equipment such as constant temperature soldering stations is high. The production cycle is long, and it is difficult to transform large-scale automated production lines, resulting in high rework costs.

[0006] 4. Insufficient reliability of mechanical and thermal tripping. Solder is a brittle bonding layer. Under long-term high and low temperature cycles and equipment vibration conditions, the solder joint is prone to delamination and cracking, and the contact resistance continues to drift. When the solder melts and fails, it is easy for the molten solder to be drawn into strands and stick together, and the spring cannot be completely separated from the electrode. The continuous power frequency arcing ignites the plastic shell.

[0007] 5. High cost and long cycle for product specification iteration. If the rated breaking current of thermal trip needs to be adjusted, the amount of solder, the soldering temperature and the wetting time need to be repeatedly adjusted. Each current specification needs to be re-verified and tested for reliability, resulting in a long new product development cycle.

[0008] Existing industry improvement solutions have significant shortcomings: bolt fastening and snap-fit ​​connection structures lack low-melting-point fusing functionality, making overheat protection impossible; built-in independent fuse tripping has a long heat conduction path and delayed tripping response, failing to simultaneously address the two core industry pain points of connection reliability and precise controllable tripping current. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a riveted thermal trip surge protector.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A riveted thermal trip surge arrester includes an inner shell, an outer shell, a varistor, a thermal trip spring, and a trip plate. The inner shell has an assembly cavity. An electrode plate is mounted on the varistor, and a connecting lug is provided on the electrode plate. The varistor is mounted on one side of the inner shell, and the connecting lug extends into the assembly cavity. The thermal trip spring is mounted to the inner shell, with one side extending into the assembly cavity. One side of the trip plate is rotatably mounted to the inner shell via a pivot. A spring is provided inside the trip plate, with its upper end pressing against the inner shell. The spring exerts a downward force on the trip plate, while the thermal trip spring exerts an upward force on the trip plate. The upward force of the thermal trip spring on the trip plate is greater than the downward force of the spring on the trip plate. The thermal trip spring is riveted to the connecting lug of the electrode plate via rivets. The melting point of the rivets is 120~160℃. The inner shell is mounted within the outer shell.

[0011] The assembly cavity is provided with a guide groove, and a positioning post is provided on one side of the trip plate. The positioning post is located in the guide groove, and the spring is fitted on the positioning post.

[0012] The thermal release spring is provided with a spring positioning hole, and the connecting lug is provided with an electrode through hole. The rivet passes through the electrode through hole, is inserted into the spring positioning hole, and is riveted and tightened.

[0013] The upper part of the trip piece is provided with a pressure block, which presses down on the hot trip spring, causing the hot trip spring to be tilted.

[0014] The pressure block is integrally formed on the upper part of the trip piece and is cylindrical in shape.

[0015] The inner housing has an arc-shaped clearance groove on one side of the assembly cavity, which provides space for the trip piece to rotate.

[0016] The bottom of the inner housing is equipped with lead-out electrodes.

[0017] The hot release spring is made of beryllium bronze elastic alloy by stamping.

[0018] The inner shell is provided with a partition, one side of which forms an assembly cavity, and the varistor is installed on the other side of the partition.

[0019] The present invention has the following beneficial technical effects: 1. Stable electrical performance, controllable tripping current, and significantly improved safety consistency: Using the rivet geometry as the control variable for fusing, the machining dimensional tolerance is extremely small, and there are no interfering factors such as solder amount and welding temperature. The deviation of tripping current in the same batch of products is greatly reduced. By changing the rivets of different diameters and lengths, it can match the full range of 10A to 100A breaking specifications, solving the safety defects of accidental tripping and non-tripping in batch products.

[0020] 2. No high-temperature heat damage, extending equipment lifespan: The entire process uses a room-temperature cold riveting process, completely eliminating the 180℃ high-temperature soldering process, thus avoiding hot cracking and interface deterioration at the edges of the zinc oxide ceramic sheet. Under the same impact current accelerated aging test conditions, the current-carrying durability impact number of the product of this invention is increased by more than 30%, and the long-term leakage current drift is reduced by 60%, making it suitable for photovoltaic and outdoor high-temperature and high-humidity harsh working conditions.

[0021] 3. Simplified production process, reduced costs and increased efficiency, suitable for fully automated production lines: The traditional four core processes of soldering are reduced to two processes: alignment and cold riveting, reducing the processing time per product by 50%; consumables such as solder, flux, and constant temperature soldering station are eliminated, significantly reducing material production costs; automated riveting equipment can operate continuously on an assembly line, reducing the defect rate of poor soldering, missing soldering, and short circuits of solder balls by 80%, greatly reducing manual rework costs.

[0022] 4. High mechanical strength, ensuring safe tripping and completely eliminating arcing: The double-sided rivet head clamping structure ensures a tight fit between the spring and the electrode. After 500 cycles of high and low temperatures and continuous vibration testing, the contact resistance shows no significant drift. The rivet melts and breaks uniformly, without any solder wire pulling or sticking issues. The beryllium bronze spring has stable pre-tightening force, and the electrode separation stroke is sufficient after melting, completely cutting off the power frequency fault circuit and eliminating the risk of continuous arcing, fire, and explosion.

[0023] 5. Environmentally friendly and portable: With no solder or flux volatilization at high temperatures, there are no harmful fumes in the production workshop, making the working environment more environmentally friendly; faulty modules can be disassembled and replaced individually with rivets and springs, making them more reusable and easier to maintain than integrated soldered structures, thus reducing later maintenance and replacement costs. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the assembled three-dimensional structure of the present invention; Figure 2 This is an exploded structural diagram of the present invention; Figure 3 This is a schematic diagram of the assembled parts of the present invention; Figure 4 for Figure 3 A schematic diagram of the structure after removing the trip plate.

[0025] Figure label: 1. Outer shell, 2. Inner shell, 3. Varistor, 4. Thermal trip spring, 5. Tripping piece, 6. Assembly cavity, 7. Electrode piece, 8. Connecting ear, 9. Rivet, 10. Spring, 11. Guide groove, 12. Lead-out electrode, 13. Arc-shaped clearance groove, 14. Pressure block. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] In the description of this invention, it should be understood that if terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. 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 indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a mechanical connection or an electrical connection. They can refer to a direct connection or an indirect connection through an intermediate medium, and they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0029] like Figure 1-4As shown, a riveted thermal trip surge arrester includes an inner shell 2, an outer shell 1, a varistor 3, a thermal trip spring 4, and a trip piece 5. The inner shell 2 has an assembly cavity 6. An electrode 7 is mounted on the varistor 3, and a connecting lug 8 is provided on the electrode 7. The varistor 3 is mounted on one side of the inner shell 2, and the connecting lug 8 extends into the assembly cavity 6. The thermal trip spring 4 is connected to the inner shell 2, with one side extending into the assembly cavity 6. One side of the trip piece 5 is rotatably mounted to the inner shell 2 via a pivot. A spring 10 is provided inside the trip piece 5. The upper end of spring 10 presses against the inner housing 2, exerting a downward force on the trip piece 5. The thermal trip spring 4 exerts an upward force on the trip piece 5, with the upward force of the thermal trip spring 4 being greater than the downward force of spring 10. The thermal trip spring 4 is riveted to the connecting lug 8 of the electrode piece 7 via rivet 9, thus enabling electrical conduction between the thermal trip spring 4 and the electrode piece 7 of the varistor 3. The rivet 9 has a melting point of 120~160℃ and can be made of an alloy material with a suitable melting point. The inner housing 2 is installed inside the outer housing 1. The thermal trip spring is fixed to the connecting lug, and this fixing structure is strong enough that it will not loosen due to the downward pressure of the spring. This can be achieved simply by selecting appropriate springs and rivets.

[0030] Both the inner and outer shells are made of insulating materials.

[0031] The bottom of the inner housing 2 is equipped with lead-out electrodes 12, which are usually installed at the bottom of the inner housing 2 and distributed above and below the thermal trip spring 4.

[0032] The thermal trip spring 4 is tilted, generating an upward elastic force. The spring 10 is constrained in its installation; its upper end is fixed and held in place by the inner housing 2, while its lower end presses against the trip piece 5, creating downward pressure on the trip piece. At this point, the trip piece is held upward by the thermal trip spring and cannot rotate downwards. Only when the connecting ear between the thermal trip spring and the electrode plate is no longer connected, and the thermal trip spring is no longer under the fixing force, does the trip piece rotate under the downward pressure of the spring, causing the thermal trip spring to separate from the connecting ear, meaning the thermal trip spring is no longer in contact with the electrode plate.

[0033] The assembly cavity 6 is provided with a guide groove 11, and a positioning post is provided on one side of the release piece 5. The positioning post is located in the guide groove, and the spring is fitted on the positioning post. The guide groove ensures the directional swing of the release piece.

[0034] The thermal release spring 4 has a spring positioning hole, and the connecting lug 8 has an electrode through hole. The rivet 6 passes through the electrode through hole and is inserted into the spring positioning hole. The two ends of the rivet are pressed and formed using a room temperature cold riveting process, which rigidly presses the thermal release spring and the metal electrode of the varistor together and makes them electrically connected. After cold riveting, the thermal release spring and the through hole of the metal electrode are completely coaxial and tightly fitted, with no gaps in the contact surface. The contact resistance is stable under room temperature operation, and there are no local abnormal heat points.

[0035] The trip piece 5 has a pressure block 14 on its upper part, which presses down on the hot trip spring 4, causing the hot trip spring 4 to be tilted. The pressure block 14 is integrally formed on the upper part of the trip piece 5 and is cylindrical, so it is not easy to cause damage when pressing the hot trip spring.

[0036] The inner housing 2 has an arc-shaped clearance groove 13 on one side of the assembly cavity. The arc-shaped clearance groove 13 is used to provide space for the trip piece 5 to rotate, so as to ensure that the trip piece rotates normally.

[0037] The thermal release spring is made of beryllium bronze elastic alloy and is stamped. After riveting assembly, it maintains a pre-tightening force that separates outwards. After the rivet melts, the electrode can be quickly and completely disconnected.

[0038] The inner shell is provided with a partition, one side of which forms an assembly cavity, and the varistor is installed on the other side of the partition.

[0039] The varistor, gold electrode sheet, thermal trip spring, and rivets are assembled into an integrated module core; the module core is installed into the housing to form a standard 1P pluggable surge protection module, which can be universally installed on a standard power distribution rail base.

[0040] The rivet is made of a tin-bismuth low-melting-point alloy with a melting temperature range of 120℃~160℃, matching the safety protection threshold of the varistor, thus avoiding problems such as low-temperature mismelting and high-temperature non-melting. The breaking current of the surge arrester's thermal trip spring is precisely controlled by adjusting three sets of dimensional parameters: the rivet shank diameter, the effective shank length, and the rivet head thickness. A larger rivet shank diameter results in a higher total heat absorption capacity during rivet melting, and a greater fault breaking current that the surge arrester can withstand. A shorter rivet shank length results in a shorter heat conduction path and a faster tripping response speed.

[0041] Assembly can be performed according to the following steps: S1. Material preparation and disassembly: Disassemble the outer shell of the surge protector insulation module and remove the inner shell; S2. Coaxial alignment: The positioning through hole of the thermal release spring is precisely aligned and fitted with the electrode through hole of the electrode plate of the varistor. S3. Rivet Selection and Insertion: Based on the product's target rated breaking current, retrieve the preset parameter library to match the corresponding rod diameter and rod length specifications of low melting point rivets and insert them into the coaxial through hole. S4. Room temperature cold riveting: The automated riveting machine presses the upper and lower ends of the rivet synchronously to form a pressing head, so that the spring sheet and the electrode sheet are tightly attached without gaps, achieving stable conductive fixation; no high temperature heating is required throughout the process. S5. Module packaging: The riveted integrated module core is inserted into the insulating shell, and the buckles and viewing window lens are assembled to complete the semi-finished product assembly.

[0042] S6. Parameter Calibration and Database Establishment: Conduct batch thermal tripping performance tests by replacing rivets of various specifications and sizes, and establish a standardized parameter database of rivet size and rated breaking current for rapid selection of the entire product series.

[0043] The following is an explanation using actual production examples.

[0044] Standardized basic conditions: rivet material is tin-bismuth alloy with a melting range of 120~160℃; rivet head thickness is uniformly 0.4mm; hot release spring thickness is 0.3mm beryllium bronze; cold riveting equipment is used for room temperature pressing and forming.

[0045] Example 1: 30A standard breaking current surge protector.

[0046] Tin-bismuth alloy rivets are selected, with a rivet shank diameter of 1.2mm, a shank length of 1.5mm, and a head thickness of 0.4mm; the spring is made of 0.3mm thick beryllium bronze, and the electrode through hole and the spring positioning hole φ1.2mm are coaxially aligned; it is formed by cold riveting at room temperature, and the two ends of the rivet form a pressing head.

[0047] Actual test: When the circuit fault current reaches 30A, the varistor heats up to about 140℃, the rivet melts and breaks evenly, and the thermal trip spring is driven by the trip piece to rebound and disconnect the circuit; the trip current range of 200 samples in the same batch is 28.6~31.3A, with excellent consistency.

[0048] Example 2: 60A High Breaking Current Surge Protector The rivet rod was replaced with one with a diameter of 1.8mm and a length of 1.2mm; the larger diameter rivet increases the total heat absorption of the heat melt and increases the withstand continuous fault current to 60A; the measured tripping current range is 57.2~62.5A, which meets the safety standards of the power distribution system.

[0049] Comparative example: 30A surge protector using traditional soldering process.

[0050] Products of the same specifications using a tin-filling soldering process have a tripping current range of 21~39A, with a deviation exceeding 28%; 12% of the products have poor soldering or premature tripping defects; high-temperature soldering causes the varistor to age faster, with a failure rate of 18% after 500 impact tests, which is far higher than the 3% failure rate of the riveting solution of this invention.

[0051] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A riveted thermal trip surge arrester, characterized in that, The device includes an inner housing, an outer housing, a varistor, a thermal trip spring, and a trip plate. The inner housing has an assembly cavity. An electrode plate is mounted on the varistor, and a connecting lug is provided on the electrode plate. The varistor is mounted on one side of the inner housing, and the connecting lug extends into the assembly cavity. The thermal trip spring is attached to the inner housing, with one side extending into the assembly cavity. One side of the trip plate is rotatably mounted to the inner housing via a pivot. A spring is located inside the trip plate, with its upper end pressing against the inner housing, exerting a downward force on the trip plate. The thermal trip spring exerts an upward force on the trip plate, with the upward force being greater than the downward force. The thermal trip spring is riveted to the connecting lug of the electrode plate using rivets with a melting point of 120~160℃. The inner housing is housed within the outer housing.

2. The riveted thermal trip surge arrester according to claim 1, characterized in that, The assembly cavity is provided with a guide groove, and a positioning post is provided on one side of the trip plate. The positioning post is located in the guide groove, and the spring is fitted on the positioning post.

3. The riveted thermal trip surge arrester according to claim 1, characterized in that, The thermal release spring is provided with a spring positioning hole, and the connecting lug is provided with an electrode through hole. The rivet passes through the electrode through hole, is inserted into the spring positioning hole, and is riveted and tightened.

4. The riveted thermal trip surge arrester according to claim 1, characterized in that, The upper part of the trip piece is provided with a pressure block, which presses down on the hot trip spring, causing the hot trip spring to be tilted.

5. The riveted thermal trip surge arrester according to claim 4, characterized in that, The pressure block is integrally formed on the upper part of the trip piece and is cylindrical in shape.

6. The riveted thermal trip surge arrester according to claim 1, characterized in that, The inner housing has an arc-shaped clearance groove on one side of the assembly cavity, which provides space for the trip piece to rotate.

7. The riveted thermal trip surge arrester according to claim 1, characterized in that, The bottom of the inner housing is equipped with lead-out electrodes.

8. The riveted thermal trip surge arrester according to claim 1, characterized in that, The hot release spring is made of beryllium bronze elastic alloy by stamping.

9. The riveted thermal trip surge arrester according to claim 1, characterized in that, The inner shell is provided with a partition, one side of which forms an assembly cavity, and the varistor is installed on the other side of the partition.

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