Explosion-proof microswitch

Abstract

The application discloses an explosion-proof microswitch, which comprises a shell, a knob assembly, a contact system, a first contact leg and a second contact leg, and the knob assembly comprises a button and a push rod. A first permanent magnet ring and an arc separation plate are arranged at the bottom of the button, a second permanent magnet ring is arranged at the top of the push rod, and the two permanent magnet rings are opposite to each other and have the same polarity to form a magnetic suspension gap to realize non-contact transmission. An annular concave surface of a mounting hole of the shell is matched with the arc separation plate, and an annular stepped surface is welded with a bellows to form a static seal. In the contact system, a ceramic insulating partition plate is arranged between a movable contact and a static contact, an elastic element is connected with a transmission piece in a through hole, and the movable contact indirectly contacts the static contact through the transmission piece. The explosion-proof microswitch is provided with a magnetic suspension transmission structure, a multiple sealing arc separation structure and an elastic buffer contact structure, mechanical wear and invasion of dangerous medium are avoided, contact bounce and arc erosion are reduced, explosion-proof safety, action reliability and service life are improved, the explosion-proof microswitch is suitable for high-risk scenes and meets the miniaturization requirement.

Description

Technical Field

[0001] This invention relates to the field of explosion-proof electrical equipment technology, specifically to an explosion-proof micro switch suitable for circuit switching control in flammable and explosive hazardous locations such as petrochemical plants, underground coal mines, and dusty environments. Background Technology

[0002] Microswitches, with their short travel, low actuation force, and rapid switching, are widely used in various electrical control scenarios. However, explosion-proof microswitches used in explosive atmospheres not only need to meet the operational reliability requirements of conventional microswitches, but more importantly, they must possess excellent explosion-proof performance. This ensures effective protection against the risk of explosion caused by internal arcing, preventing the intrusion of hazardous media into the switch or the spread of internal explosion energy, thus guaranteeing equipment safety and personnel safety. With the upgrading of high-end manufacturing and increasingly stringent safety regulations, explosion-proof microswitches are evolving towards miniaturization, high sensitivity, and long lifespan, placing higher demands on their explosion-proof structural design and arc control capabilities.

[0003] Currently, the explosion-proof structural design of existing explosion-proof micro switches still has many shortcomings, making it difficult to simultaneously meet the requirements of explosion-proof safety, operational reliability, and miniaturization. Firstly, traditional explosion-proof micro switches mostly use a contact-type mechanical transmission structure for their contact components, with the button and push rod directly contacting each other. This transmission method is not only prone to mechanical wear, leading to decreased switch accuracy and shortened service life, but the contact gap can also easily become a channel for hazardous media to enter. Dust, explosive gases, and other media can enter the contact chamber inside the switch through this gap, coming into contact with the electric arc generated when the contacts are switched on and off, which can easily cause an explosion, posing a serious safety hazard. Simultaneously, contact-type transmission is prone to contact bounce during operation, exacerbating arc erosion and further reducing the explosion-proof reliability and service life of the switch.

[0004] Secondly, the sealing and arc-blocking structures of existing explosion-proof microswitches are poorly designed. Most products only use a single sealing or arc-blocking measure, which is insufficient to achieve comprehensive isolation and protection. Although some products have a sealing structure, the sealing performance is poor. After long-term temperature changes, gaps easily form between the seal and the shell, leading to seal failure and inability to effectively isolate external hazardous media from the internal contact chamber. In addition, some products lack an effective arc-blocking structure. The arc generated when the contacts are switched on or off cannot be extinguished quickly. The high-temperature arc can easily ignite the intruding hazardous media, and the high-temperature and high-pressure gas generated by the arc can directly impact the shell, requiring the shell to have extremely high structural strength, which is not conducive to the miniaturization design of the switch.

[0005] Furthermore, existing explosion-proof microswitches have limited arc-extinguishing and pressure-buffering capabilities. If the arc generated during contact switching is not extinguished in time, it will continuously corrode the contacts, shortening their lifespan. Simultaneously, the high-temperature, high-pressure gas generated by the arc can easily trigger a localized explosion. Traditional switches often employ a single-chamber structure, which cannot achieve graded pressure buffering. The explosion pressure acts directly on the casing, increasing the design difficulty and manufacturing cost of the casing and making it prone to damage, leading to the spread of explosion energy. In addition, existing arc-extinguishing methods mostly use simple arc-extinguishing plate structures, resulting in low arc-extinguishing efficiency, short arc propagation paths, and difficulty in quickly cutting off the arc, failing to reduce the explosion risk at its source.

[0006] Furthermore, existing explosion-proof microswitches have flawed contact system designs. The moving and stationary contacts are in direct contact, resulting in a significant impact force at the moment of contact. This easily leads to contact bounce and arc erosion, affecting the switch's operational reliability. Moreover, the multiple arcs generated during bounce further exacerbate the danger and reduce explosion-proof performance. Additionally, some products lack adequate contact isolation measures, failing to effectively separate the arc from the external environment, further increasing the explosion risk.

[0007] In summary, current explosion-proof microswitches suffer from problems such as unreasonable transmission methods, poor sealing and arc isolation effects, insufficient arc extinguishing and pressure buffering capabilities, and severe contact bounce and arc erosion. These issues make it difficult for them to meet the explosion-proof safety, operational reliability, and service life requirements of high-risk scenarios such as petroleum, chemical, and mining industries, and also hinder the miniaturization of switches. Therefore, developing an explosion-proof microswitch that can overcome these technical deficiencies while simultaneously meeting the requirements for explosion-proof safety, operational reliability, and miniaturization has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides an explosion-proof micro switch.

[0009] The technical solution adopted in this invention is: an explosion-proof micro switch, comprising a housing, a button assembly, a contact system, a first contact pin, and a second contact pin, wherein the button assembly includes a button and a push rod. The button has a connecting rod extending from its bottom, and a first permanent magnet ring is provided at the bottom of the connecting rod. An arc-blocking plate is fixed at the bottom of the first permanent magnet ring. The outer casing is provided with mounting holes that are adapted to the push rod and the connecting rod. The inner wall of the mounting hole is provided with an annular concave surface. The annular concave surface is adapted to the shape of the arc-blocking plate and is in clearance fit with the arc-blocking plate. A second permanent magnet ring is fixed at the top of the push rod. The first permanent magnet ring and the second permanent magnet ring are opposite each other with the same pole to form a magnetic levitation gap, so that the button and the push rod form a non-contact magnetic coupling transmission. An annular stepped surface is provided on the inner wall of the mounting hole located below the annular concave surface. A bellows is welded to the bottom of the annular stepped surface. The lower end of the bellows is welded to the disc of the push rod to form a static sealing structure, which isolates the area on the mounting hole from the cavity inside the outer shell. The contact system includes a rocker arm, a movable contact disposed on the end of the rocker arm, and a stationary contact disposed on the first contact foot. A ceramic insulating partition is disposed between the movable contact and the stationary contact. A through hole is provided in the middle of the ceramic insulating partition. A transmission plate is connected to the through hole through an elastic element. When the movable contact is driven to rock up by the button assembly, it first abuts against the transmission plate and then finally contacts the stationary contact through the transmission plate.

[0010] Furthermore, the housing contains two series chambers arranged from left to right: a main contact chamber and a buffer pressure relief chamber. The main contact chamber and the buffer pressure relief chamber are separated by a ceramic partition.

[0011] Furthermore, the contact system also includes a tension spring and a transmission plate. One end of the transmission plate has an arc surface that abuts against the bottom end face of the disc, and the other end has a slot. Limiting steps are provided on both sides of the upper end of the second contact foot, and the slot is inserted below the limiting steps to connect with the second contact foot. One end of the rocker arm is provided with an arc segment, which abuts against the side of the second contact foot; One end of the tension spring is connected to the middle of the transmission plate, and the other end is connected to the middle of the rocker arm; The ceramic partition plate is provided with a through groove through which the tabs pass.

[0012] Furthermore, the bellows adopts a double-layer composite structure, with the inner layer being made of stainless steel and the outer layer being a nickel-titanium shape memory alloy wire winding reinforcement layer. The nickel-titanium shape memory alloy wire is in a relaxed state at room temperature, and when the internal temperature of the outer shell exceeds a set threshold, it undergoes phase change expansion, thereby enhancing the stiffness of the bellows to resist internal explosion pressure.

[0013] Furthermore, the axial distance of the magnetic levitation gap is 3 to 5 millimeters, and the magnetic induction intensity of the first permanent magnet ring and the second permanent magnet ring generates an axial repulsive force of 0.5 to 1.5 Newtons at the gap, so that the button remains in a stable levitation state in the release position.

[0014] Furthermore, the ceramic partition is provided with a microporous array channel, the pore diameter of which is 0.3 to 0.8 mm and the channel length is not less than 25 mm, forming a slit arc-extinguishing channel connecting the main contact cavity and the buffer pressure relief cavity.

[0015] Furthermore, the ceramic insulating partition is provided with snap-fit ​​steps on both sides, and the upper shell of the outer shell is provided with sliding grooves on both side walls. The inner wall of the sliding groove is provided with a latch that matches the snap-fit ​​steps. The ceramic insulating partition is detachably installed in the sliding groove through the cooperation of the snap-fit ​​steps and the latch. Both the upper and lower surfaces of the transmission plate are provided with circumferentially distributed elastic arc plates. The elastic arc plates protrude in the direction away from the transmission plate body to form an elastic buffer structure. When the rocker plate is rocked up, the moving contact first abuts against the elastic arc plate on one side of the transmission plate, and then drives the transmission plate to move, so that the elastic arc plate on the other side of the transmission plate is elastically pressed into contact with the stationary contact, thereby realizing circuit conduction.

[0016] Furthermore, the outer edge of the arc-blocking plate is provided with a raised flange, which is a circular ring structure. The circular concave surface is a corresponding cylindrical groove. A cylindrical explosion-proof mating surface is formed between the outer cylindrical surface of the raised flange and the inner cylindrical surface of the circular concave surface. The axial mating length of the cylindrical explosion-proof mating surface is not less than 25 mm, and the radial clearance is not greater than 0.1 mm, which meets the requirements of the IIC level explosion-proof mating surface.

[0017] Furthermore, both the first and second permanent magnet rings are axially magnetized to form an axially symmetrical magnetic field distribution; the arc-blocking plate is made of non-magnetic material, and the magnetic field strength of the magnetic levitation gap is in the range of 0.3 to 0.5 Tesla, so that the button remains in a stable levitation state in the release position. When pressed, the magnetic levitation force increases exponentially as the gap decreases, forming a progressive resistance feedback; the bellows undergoes elastic deformation when compressed, and when the external pressing force is removed, the elastic restoring force of the bellows and the magnetic levitation repulsive force work together to make the button automatically reset to the stable levitation position.

[0018] Furthermore, a bimetallic compensation ring is provided between the outer wall of the arc-blocking plate and the inner wall of the annular concave surface. The bimetallic compensation ring is made of two metals with different coefficients of thermal expansion laminated together and is fixed to the outer wall of the arc-blocking plate in a cylindrical structure. Under normal conditions, a sliding gap is maintained between the arc-blocking plate and the inner wall of the annular concave surface, allowing the arc-blocking plate to slide up and down. When a high temperature arc is generated in the main contact cavity, the bimetallic compensation ring expands and deforms outward due to heat, increasing its outer diameter and pressing against the inner wall of the annular concave surface to form an interference fit sealing structure, preventing high-temperature gas from leaking from the fit gap between the arc-blocking plate and the annular concave surface. After the temperature decreases, the bimetallic compensation ring contracts and returns to its initial state, and the arc-blocking plate resumes its sliding fit function.

[0019] The beneficial effects of this invention are: 1. Optimize the transmission structure, improve the reliability of operation and explosion-proof foundation, and extend service life: The present invention adopts a magnetic levitation gap formed by the first permanent magnet ring and the second permanent magnet ring with the same pole facing each other, so as to realize non-contact magnetic coupling transmission between the button and the push rod, replacing the traditional contact mechanical transmission, completely avoiding the wear problem caused by mechanical contact, and effectively improving the accuracy of switch operation and service life.

[0020] 2. Multiple isolation protections enhance sealing and arc-blocking effects, eliminating safety hazards: By setting an arc-blocking plate at the bottom of the connecting rod, combined with the annular concave surface of the inner wall of the mounting hole in the outer shell, the mounting hole is effectively separated, preventing hazardous media such as dust from entering the switch. It also provides excellent isolation and explosion-proof protection in the event of an internal explosion, preventing the spread of explosion energy. Simultaneously, the annular stepped surface welded to the bellows forms a static sealing structure, completely isolating the upper area of ​​the mounting hole from the contact chamber, achieving double sealing protection. This effectively prevents external explosive gases, dust, and other media from entering the contact chamber, eliminating explosion accidents caused by contact between the medium and the electric arc. The sealing performance is stable and can adapt to long-term temperature changes, avoiding seal failure.

[0021] 3. Graded buffering and efficient arc extinguishing reduce housing design requirements and facilitate miniaturization: This invention features two-stage series chambers, a main contact chamber and a buffer pressure relief chamber, separated by a ceramic partition and formed by a microporous array channel to create a slit arc extinguishing channel, achieving graded pressure management and efficient arc extinguishing. When an electric arc occurs in the main contact chamber, triggering a local explosion, the first-stage chamber absorbs the initial explosion pressure, and the high-temperature, high-pressure gas enters the second-stage chamber through the microporous array channel. The slit structure of the channel cuts and cools the electric arc, extending the arc propagation path, improving arc extinguishing efficiency, and gradually attenuating the pressure impact. This significantly reduces the requirements for the overall strength of the housing, eliminating the need for a high-strength, thick-walled housing, which is beneficial for the miniaturization of the switch. At the same time, it reduces the risk of explosion energy diffusion and improves explosion-proof safety.

[0022] 4. Optimize the contact system to reduce contact bounce and arc erosion, and improve switching reliability: A ceramic insulating partition is installed between the moving contact and the stationary contact. A transmission plate is connected to the partition through a through hole in the middle by an elastic element. When the moving contact is driven, it first abuts against the transmission plate and then contacts the stationary contact through the transmission plate, forming an elastic buffer contact structure. This structure can effectively buffer the impact force at the moment of contact between the moving contact and the stationary contact, reduce contact bounce, reduce multiple arc erosions generated during bounce, and extend the service life of the contacts. At the same time, the ceramic insulating partition can further separate the arc from the external environment, enhance the arc isolation effect, and improve the switching reliability and explosion-proof performance.

[0023] 5. Coordinated overall structure, balancing explosion-proof safety, operational reliability, and miniaturization requirements: This invention improves explosion-proof performance from multiple dimensions, including arc source suppression, hazardous medium isolation, explosion pressure buffering, and contact damage protection, through the coordinated operation of structures such as magnetic levitation transmission, arc isolation plate separation, bellows sealing, graded chamber buffering, and elastic transmission plate buffering. It also solves problems such as transmission wear, sealing failure, low arc extinguishing efficiency, and contact bounce in existing products. While ensuring high explosion-proof safety and operational reliability, it achieves a miniaturized switch design, making it widely adaptable to the needs of high-risk scenarios such as petroleum, chemical, and mining industries. It is highly practical and has broad application prospects.

[0024] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention.

[0026] Figure 2 This is a cross-sectional schematic diagram of the present invention.

[0027] Figure 3 This is an exploded view of the present invention.

[0028] Figure 4 This is a schematic diagram of the cross-section of the arc-blocking plate.

[0029] Figure 5 This is a schematic diagram of the contact system.

[0030] Figure 6 This is a schematic diagram of the structure of a ceramic insulating partition.

[0031] Figure 7 This is a schematic diagram of the upper shell structure of the outer shell.

[0032] Figure 1-7 In the middle section: 1. Outer shell; 2. First contact pin; 3. Second contact pin; 4. Button; 5. Push rod; 6. Connecting rod; 7. First permanent magnet ring; 8. Arc-blocking plate; 9. Mounting hole; 10. Annular concave surface; 11. Second permanent magnet ring; 12. Annular stepped surface; 13. Bellows; 14. Disc; 15. Tilter; 16. Moving contact; 17. Stationary contact; 18. Ceramic insulating partition; 19. Through hole; 20. Elastic element 21. Transmission plate; 22. Main contact cavity; 23. Buffer pressure relief cavity; 24. Ceramic partition; 25. Tension spring; 26. Transmission plate; 27. Arc surface; 28. Slot; 29. ​​Limiting step; 30. Arc segment; 31. Through slot; 32. Micro-pore array channel; 33. Snap-fit ​​step; 34. Slide-in long slot; 35. Bayonet; 36. Elastic arc plate; 37. Heightened flange; 38. Bimetallic compensation ring. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0035] This invention provides an explosion-proof micro switch.

[0036] In this embodiment, refer to Figure 1-7 The explosion-proof micro switch includes a housing 1, a button assembly, a contact system, a first contact 2, and a second contact 3. The button assembly includes a button 4 and a push rod 5. The button has a connecting rod 6 extending from its bottom. A first permanent magnet ring 7 is provided at the bottom of the connecting rod 6. An arc-blocking plate 8 is fixed at the bottom of the first permanent magnet ring 7. The outer shell is provided with mounting holes 9 that are adapted to the push rod and the connecting rod. The inner wall of the mounting hole 9 is provided with an annular concave surface 10. The annular concave surface 10 is adapted to the shape of the arc-blocking plate and is in clearance fit with the arc-blocking plate. A second permanent magnet ring 11 is fixed at the top of the push rod. The first permanent magnet ring and the second permanent magnet ring 11 form a magnetic levitation gap with the same pole facing each other, so that the button and the push rod form a non-contact magnetic coupling transmission. An annular stepped surface 12 is provided on the inner wall of the mounting hole located below the annular concave surface. A bellows 13 is welded to the bottom of the annular stepped surface. The lower end of the bellows 13 is welded to the disc 14 of the push rod to form a static sealing structure, which isolates the area on the mounting hole from the cavity inside the outer shell. The contact system includes a rocker arm 15, a movable contact 16 disposed on the end of the rocker arm 15, and a stationary contact 17 disposed on the first contact foot. A ceramic insulating partition 18 is disposed between the movable contact 16 and the stationary contact 17. A through hole 19 is provided in the middle of the ceramic insulating partition 18. A transmission plate 21 is connected to the through hole 19 through an elastic element 20. When the movable contact is driven to rock up by the button assembly, it first abuts against the transmission plate 21 and then finally contacts the stationary contact through the transmission plate.

[0037] In the above technical solution, a multi-layered explosion-proof protection system is constructed by optimizing the core structure of the button assembly, mounting hole, and contact system. The connecting rod extending from the bottom of the button and the push rod are opposite each other through the first and second permanent magnet rings with the same poles. The magnetic repulsion of like poles forms a magnetic levitation gap, realizing non-contact magnetic coupling transmission, which can transmit the pressing force without mechanical contact. The arc-blocking plate at the bottom of the connecting rod and the annular concave surface of the inner wall of the mounting hole are fitted with a gap to form a preliminary arc-blocking isolation structure. The annular stepped surface is welded to the bellows to form a static seal, which completely isolates the upper part of the mounting hole from the contact chamber and blocks the passage of dangerous media. In the contact system, the ceramic insulating partition separates the moving contact and the stationary contact. The elastic element in the through hole connects the transmission plate, so that when the moving contact is driven, it indirectly contacts the stationary contact through the transmission plate to form an elastic buffer contact.

[0038] Among these features, the contact-type magnetic levitation transmission completely avoids mechanical wear, improves operational accuracy and service life, eliminates contact gaps, and reduces the intrusion path of hazardous media. Furthermore, the arc-blocking plate, in conjunction with the annular concave surface, effectively blocks the entry of dust and other media, while also acting as a separator in the event of an internal explosion, preventing the spread of explosive energy. Secondly, the bellows static sealing structure provides reliable isolation, preventing external explosive gases and dust from entering the contact chamber and eliminating the risk of arc ignition of hazardous media. Finally, the elastic buffer contact structure of the contact system cushions contact impact, reducing contact bounce and arc erosion. The ceramic insulating partition separates the moving and stationary contacts into two layers, further enhancing the arc-blocking effect and improving switching reliability and explosion-proof safety.

[0039] The overall structure achieves comprehensive optimization from transmission, sealing, arc isolation to contact protection, laying the foundation for the switch's excellent explosion-proof performance while taking into account both operational reliability and service life.

[0040] Specifically, the housing contains two series chambers, a main contact chamber 22 and a buffer pressure relief chamber 23, arranged sequentially from left to right. The main contact chamber and the buffer pressure relief chamber are separated by a ceramic partition 24.

[0041] In this embodiment, two series-connected chambers, a main contact chamber and a buffer pressure relief chamber, are arranged inside the outer casing from left to right. A ceramic partition separates the two chambers, confining the electric arc and high-temperature, high-pressure gas generated by the contact system within the main contact chamber. The buffer pressure relief chamber serves as a secondary buffer space, forming a graded pressure management and arc-blocking structure. The ceramic partition itself possesses excellent high-temperature resistance, insulation, and arc-blocking properties, effectively preventing the direct diffusion of the electric arc and high-temperature gas, thus achieving physical and arc-blocking isolation between the two chambers.

[0042] The two-stage series chambers achieve graded buffering of explosion pressure. The main contact chamber absorbs the initial explosion pressure, preventing the pressure from directly impacting the outer casing, reducing the structural strength requirements of the casing, and facilitating the miniaturization of the switch. The ceramic partition effectively separates the two chambers, preventing the electric arc and high-temperature gas in the main contact chamber from directly entering the area outside the buffer pressure relief chamber, reducing the risk of explosion energy diffusion. It also provides an installation foundation for subsequent arc-extinguishing structures such as micro-pore array channels, further improving arc-extinguishing efficiency and enhancing the overall arc isolation effect, enabling the switch to adapt to higher-risk explosive environments and improving the explosion-proof rating and safety of use.

[0043] Specifically, the contact system also includes a tension spring 25 and a transmission plate 26. One end of the transmission plate 26 has an arc surface 27, which abuts against the bottom end face of the disc. The other end has a slot 28. Limiting steps 29 are provided on both sides of the upper end of the second contact. The slot is inserted below the limiting steps and connected to the second contact. One end of the rocker arm is provided with an arc segment 30, which abuts against the side of the second contact foot; One end of the tension spring is connected to the middle of the transmission plate, and the other end is connected to the middle of the rocker arm; The ceramic partition plate is provided with a through groove 31 through which the fins pass.

[0044] In this embodiment, the bottom of the push rod disc abuts against the transmission plate via an arc surface, converting the linear motion of the push rod into the oscillating motion of the transmission plate. The transmission plate is connected to the limiting step of the second contact foot via a slot, forming a lever fulcrum. A tension spring connects the middle of the transmission plate and the middle of the rocker arm, providing the rocker arm's restoring force. The arc segment at one end of the rocker arm abuts against the side of the second contact foot to form a fulcrum, and a moving contact is provided at the other end. A through groove is provided on the ceramic partition for the rocker arm to pass through, realizing the mechanical linkage between the two-stage chambers. When the button is pressed, the push rod moves down, pushing the transmission plate downward and oscillating, and the tension spring drives the rocker arm to tilt up, realizing the closure of the moving contact and the stationary contact.

[0045] The lever transmission mechanism converts the small stroke of magnetic levitation into a large swing angle of the rocker arm, improving the contact breaking capability; the tension spring provides stable contact pressure and rapid reset force; the ceramic partition through-slot design achieves the unity of explosion-proof separation and mechanical transmission; the overall structure is compact, with high transmission efficiency and fast response speed.

[0046] In addition, the design of the arc surface and the arc segment reduces mechanical wear during transmission, extends the service life of the transmission structure, reduces the resistance to movement, and improves the sensitivity of the switch operation.

[0047] Specifically, the bellows adopts a double-layer composite structure, with the inner layer being made of stainless steel and the outer layer being a nickel-titanium shape memory alloy wire winding reinforcement layer. The nickel-titanium shape memory alloy wire is in a relaxed state at room temperature, and when the internal temperature of the outer shell exceeds a set threshold, it undergoes phase change expansion, which enhances the stiffness of the bellows to resist internal explosion pressure.

[0048] In this embodiment, the bellows adopts a double-layer composite structure with an inner layer of 316L stainless steel and an outer layer of nickel-titanium shape memory alloy wire. 316L stainless steel serves as the matrix material, providing the main elastic deformation capacity and airtightness. The nickel-titanium shape memory alloy wire is in a relaxed low-temperature phase (martensitic phase) at room temperature, contributing little to the bellows stiffness. When the temperature exceeds the austenitic phase transformation completion temperature (Af, typically 60-120℃), a thermoelastic martensite-to-austenite phase transformation occurs, generating a shape recovery tendency. Due to constraint, this is converted into restoring stress, causing the winding layer to tighten, significantly enhancing the circumferential stiffness and compressive strength of the bellows.

[0049] Under normal conditions, the bellows remains flexible, without affecting normal operation and elastic reset. At high temperatures, the nickel-titanium alloy wire automatically enhances its stiffness to resist internal explosion pressure and prevent excessive deformation or rupture of the bellows. The temperature adaptive mechanism enables intelligent switching between normal flexibility and high-temperature strengthening, improving the reliability of the switch under extreme conditions. This structure requires no additional power drive, relying on temperature changes to automatically adjust stiffness. It is simple in structure, highly reliable, extends the service life of the bellows, and meets the long-term use requirements of high-risk environments.

[0050] Specifically, the axial distance of the magnetic levitation gap is 3 to 5 millimeters, and the magnetic induction intensity of the first permanent magnet ring and the second permanent magnet ring generates an axial repulsive force of 0.5 to 1.5 Newtons at the gap, so that the button remains in a stable levitation state in the release position.

[0051] In this embodiment, the first and second permanent magnet rings are axially magnetized, with their magnetic poles arranged axially to form an axisymmetric axial magnetic field. The opposite arrangement of like poles generates an axial repulsive force between the two rings, which increases exponentially as the gap decreases (following the laws of magnetic dipole interaction). By optimizing the magnetic energy product of the permanent magnet material and the ring dimensions, an axial repulsive force of 0.5-1.5N is generated within a 3-5mm magnetic levitation gap. This force balances the button's weight, ensuring the button remains stably suspended in the released position.

[0052] The 3-5mm magnetic levitation gap provides sufficient travel space for the sliding of the baffle plate and the deformation of the bellows; the 0.5-1.5N magnetic levitation force ensures the stability of the button suspension without generating excessive operating resistance; the progressively increasing magnetic resistance provides clear tactile feedback; the axially symmetrical magnetic field distribution avoids lateral forces and ensures smooth sliding.

[0053] Specifically, the ceramic partition is provided with a microporous array channel 32, the aperture of the microporous array channel 32 is 0.3 to 0.8 mm, the channel length is not less than 25 mm, forming a slit arc extinguishing channel connecting the main contact cavity and the buffer pressure relief cavity.

[0054] In this embodiment, a microporous array channel is provided on the ceramic partition separating the main contact cavity and the buffer pressure relief cavity. Multiple micropores are distributed in an array, with a single pore diameter of 0.3-0.8 mm and a total channel length of not less than 25 mm. According to the slit arc extinguishing principle, when the arc passes through the narrow channel, the channel wall generates a strong cooling and deionization effect on the arc, while the slit generates a mechanical cutting effect on the arc column, increasing the arc resistance and decreasing the current, ultimately extinguishing the arc.

[0055] The micro-orifice array achieves arc extinguishing while depressurizing. As the high-temperature and high-pressure gas passes through the micro-orifice, the pressure gradually decreases, and the arc energy is rapidly consumed. The channel length of more than 25 mm ensures sufficient arc extinguishing time. The aperture of 0.3-0.8 mm balances the arc extinguishing effect and depressurization efficiency. The array distribution reduces the risk of single-orifice blockage and improves structural reliability.

[0056] Specifically, the ceramic insulating partition is provided with snap-fit ​​steps 33 on both sides, and the upper shell of the outer shell is provided with sliding grooves 34 on both side walls. The inner wall of the sliding groove is provided with a latch 35 that matches the snap-fit ​​steps. The ceramic insulating partition is detachably installed in the sliding groove through the cooperation of the snap-fit ​​steps and the latch 35. The upper and lower surfaces of the transmission plate are provided with circumferentially distributed elastic arc plates 36. The elastic arc plates 36 protrude in the direction away from the transmission plate body to form an elastic buffer structure. When the rocker plate is rocked up, the moving contact first abuts against the elastic arc plate on one side of the transmission plate, and then drives the transmission plate to move, so that the elastic arc plate on the other side of the transmission plate is elastically pressed into contact with the stationary contact, thereby realizing circuit conduction.

[0057] In this embodiment, the ceramic insulating partition engages with the sliding groove on the upper shell of the outer casing via snap-fit ​​steps on both sides. A latch is provided on the inner wall of the sliding groove to achieve detachable snap-fit, facilitating the installation and replacement of the ceramic partition. The upper and lower surfaces of the transmission plate are provided with circumferentially distributed elastic arc plates. These elastic arc plates protrude away from the main body, forming a cantilever beam structure with elastic buffering capability. When the tilting plate tilts up, the moving contact first abuts against one side of the elastic arc plate to generate pre-pressure, driving the transmission plate to move. Then, the other side of the elastic arc plate elastically presses against the stationary contact, forming a progressive contact with double-sided elastic buffering.

[0058] The snap-fit ​​installation structure enables quick assembly and disassembly of ceramic partitions, improving maintenance convenience; the double-sided elastic arc plate structure transforms rigid contact into progressive flexible contact, effectively suppressing contact bounce and reducing the risk of arc generation and contact welding; the circumferentially distributed elastic arc plates ensure uniform contact pressure, improving the reliability of electrical connections.

[0059] Specifically, the outer edge of the arc-blocking plate is provided with a raised flange 37, which is a ring structure. The annular concave surface is a corresponding cylindrical groove. A cylindrical explosion-proof mating surface is formed between the outer cylindrical surface of the raised flange and the inner cylindrical surface of the annular concave surface. The axial mating length of the cylindrical explosion-proof mating surface is not less than 25 mm, and the radial clearance is not greater than 0.1 mm, which meets the requirements of the IIC level explosion-proof mating surface.

[0060] In this embodiment, an enhanced flange is provided on the outer edge of the arc-damping plate to form a ring structure, which mates with the cylindrical annular concave surface on the outer shell to form a cylindrical explosion-proof mating surface. According to GB / T 3836.2 standard, the minimum mating length of the IIC-class explosion-proof mating surface is 25mm, and the maximum gap is 0.1mm. The enhanced flange structure achieves sufficient axial mating length within the limited thickness of the arc-damping plate, and the cylindrical mating has self-centering characteristics, ensuring the uniformity of the mating gap.

[0061] The mating length of not less than 25mm ensures that the explosion flame is fully cooled and extinguished during propagation, meeting the IIC level explosion protection requirements; the gap of not more than 0.1mm restricts the flame propagation channel and improves the explosion-proof reliability; the self-centering fit between the heightened flange and the cylindrical concave surface simplifies the assembly process and ensures the fitting accuracy; the cylindrical structure has high structural rigidity and can withstand the impact of explosion pressure.

[0062] Specifically, both the first and second permanent magnet rings are axially magnetized to form an axially symmetrical magnetic field distribution; the arc-blocking plate is made of non-magnetic material, and the magnetic field strength of the magnetic levitation gap is in the range of 0.3 to 0.5 Tesla, so that the button remains in a stable levitated state in the release position. When pressed, the magnetic levitation force increases exponentially as the gap decreases, forming a progressive resistance feedback; the bellows undergoes elastic deformation when compressed, and when the external pressing force is removed, the elastic restoring force of the bellows and the magnetic levitation repulsive force work together to automatically reset the button to the stable levitated position.

[0063] In this embodiment, the first and second permanent magnet rings are axially magnetized, with the magnetization direction along the axial direction, forming an axisymmetric axial magnetic field distribution, thus avoiding uneven wear caused by lateral magnetic attraction. The arc-blocking plate uses non-magnetic materials such as alumina ceramic, which does not interfere with the magnetic field distribution. The magnetic field strength of the magnetic levitation gap is controlled within the range of 0.3-0.5T through the selection of permanent magnet materials and magnetic circuit design. Under this magnetic field strength, the relationship between the magnetic levitation force and the gap is within a reasonable range. The stainless steel inner layer of the bellows undergoes elastic deformation under pressure, storing elastic potential energy. When the pressure is removed, it releases elastic restoring force, which, combined with the magnetic levitation repulsive force, pushes the button to reset.

[0064] A magnetic field strength of 0.3-0.5T ensures sufficient magnetic levitation force while avoiding operational difficulties caused by excessive magnetic field strength; an axisymmetric magnetic field distribution ensures smooth sliding without wear; a non-magnetic arc-isolating plate avoids short circuits in the magnetic circuit; progressively increasing magnetic resistance provides excellent operating feel; the synergistic effect of the bellows' elastic restoring force and magnetic levitation repulsion ensures the reliability and speed of reset, avoiding the failure risk of a single reset source.

[0065] Specifically, a bimetallic compensation ring 38 is provided between the outer wall of the arc-blocking plate and the inner wall of the annular concave surface. The bimetallic compensation ring is made of two metals with different coefficients of thermal expansion laminated together and is fixed to the outer wall of the arc-blocking plate in a cylindrical structure. Under normal conditions, a sliding gap is maintained between the arc-blocking plate and the inner wall of the annular concave surface, allowing the arc-blocking plate to slide up and down. When a high temperature arc is generated in the main contact cavity, the bimetallic compensation ring expands and deforms outward due to heat, increasing its outer diameter and pressing against the inner wall of the annular concave surface to form an interference fit sealing structure, preventing high-temperature gas from leaking from the fit gap between the arc-blocking plate and the annular concave surface. After the temperature drops, the bimetallic compensation ring contracts and returns to its initial state, and the arc-blocking plate resumes its sliding fit function.

[0066] In this embodiment, the bimetallic compensation ring is laminated with two metals with different coefficients of thermal expansion (e.g., the active layer is a manganese-nickel-copper alloy with a large coefficient of expansion; the passive layer is an iron-nickel alloy with a small coefficient of expansion), and is fixed to the outer wall of the arc-damping plate in a cylindrical shape. At room temperature, the bimetallic strip remains flat or slightly convex, maintaining a sliding gap with the inner wall of the annular concave surface. When the temperature rises, due to the difference in expansion between the two metal layers, the bimetallic strip bends towards the side with the smaller coefficient of expansion, that is, expands outward, increasing the outer diameter of the cylindrical structure and pressing against the inner wall of the annular concave surface to form an interference fit seal.

[0067] Under normal conditions, the sliding gap ensures the normal up-and-down sliding of the arc-blocking plate without affecting operation; at high temperatures, it automatically expands and seals, blocking the path of high-temperature gas leakage from the mating gap, achieving temperature-adaptive intelligent protection; the metal-to-metal interference fit has high sealing reliability and high-temperature resistance; it automatically recovers after the temperature drops, can be reused, and requires no maintenance or replacement; it forms a temperature response synergy with the NiTi reinforcement layer of the bellows, jointly improving explosion-proof safety at high temperatures.

[0068] Please note to all technical personnel: Although the present invention has been described according to the specific embodiments above, the ideas of the present invention are not limited to this invention. Any modifications that utilize the ideas of the present invention will be included within the scope of protection of this patent.

Claims

1. An explosion-proof micro switch, comprising a housing, a button assembly, a contact system, a first contact pin, and a second contact pin, wherein the button assembly includes a button and a push rod, characterized in that: The button has a connecting rod extending from its bottom, and a first permanent magnet ring is provided at the bottom of the connecting rod. An arc-blocking plate is fixed at the bottom of the first permanent magnet ring. The outer casing is provided with mounting holes that are adapted to the push rod and the connecting rod. The inner wall of the mounting hole is provided with an annular concave surface. The annular concave surface is adapted to the shape of the arc-blocking plate and is in clearance fit with the arc-blocking plate. A second permanent magnet ring is fixed at the top of the push rod. The first permanent magnet ring and the second permanent magnet ring are opposite each other with the same pole to form a magnetic levitation gap, so that the button and the push rod form a non-contact magnetic coupling transmission. An annular stepped surface is provided on the inner wall of the mounting hole located below the annular concave surface. A bellows is welded to the bottom of the annular stepped surface. The lower end of the bellows is welded to the disc of the push rod to form a static sealing structure, which isolates the area on the mounting hole from the cavity inside the outer shell. The contact system includes a rocker arm, a movable contact disposed on the end of the rocker arm, and a stationary contact disposed on the first contact foot. A ceramic insulating partition is disposed between the movable contact and the stationary contact. A through hole is provided in the middle of the ceramic insulating partition. A transmission plate is connected to the through hole through an elastic element. When the movable contact is driven to rock up by the button assembly, it first abuts against the transmission plate and then finally contacts the stationary contact through the transmission plate.

2. The explosion-proof micro switch according to claim 1, characterized in that: The housing contains two series chambers arranged from left to right: a main contact chamber and a buffer pressure relief chamber. The main contact chamber and the buffer pressure relief chamber are separated by a ceramic partition.

3. The explosion-proof micro switch according to claim 2, characterized in that: The contact system also includes a tension spring and a transmission plate. One end of the transmission plate has an arc surface that abuts against the bottom end face of the disc, and the other end has a slot. Limiting steps are provided on both sides of the upper end of the second contact foot. The slot is inserted below the limiting steps and connected to the second contact foot. One end of the rocker arm is provided with an arc segment, which abuts against the side of the second contact foot; One end of the tension spring is connected to the middle of the transmission plate, and the other end is connected to the middle of the rocker arm; The ceramic partition plate is provided with a through groove through which the tabs pass.

4. The explosion-proof micro switch according to claim 1 or 2, characterized in that: The bellows adopts a double-layer composite structure. The inner layer is made of stainless steel, and the outer layer is a nickel-titanium memory alloy wire winding reinforcement layer. The nickel-titanium memory alloy wire is in a relaxed state at room temperature. When the internal temperature of the shell exceeds a set threshold, it undergoes phase change expansion to enhance the stiffness of the bellows and resist internal explosion pressure.

5. The explosion-proof micro switch according to claim 1, characterized in that: The axial distance of the magnetic levitation gap is 3 to 5 mm. The magnetic induction intensity of the first permanent magnet ring and the second permanent magnet ring generates an axial repulsive force of 0.5 to 1.5 Newtons at the gap, so that the button remains in a stable levitation state in the release position.

6. The explosion-proof micro switch according to claim 2, characterized in that: The ceramic partition plate is provided with a microporous array channel, the aperture of which is 0.3 to 0.8 mm and the channel length is not less than 25 mm, forming a slit arc extinguishing channel connecting the main contact cavity and the buffer pressure relief cavity.

7. The explosion-proof micro switch according to claim 2, characterized in that: The ceramic insulating partition is provided with snap-fit ​​steps on both sides, and the upper shell of the outer shell is provided with sliding grooves on both sides. The inner wall of the sliding groove is provided with a slot that matches the snap-fit ​​steps. The ceramic insulating partition is detachably installed in the sliding groove through the cooperation of the snap-fit ​​steps and the slots. Both the upper and lower surfaces of the transmission plate are provided with circumferentially distributed elastic arc plates. The elastic arc plates protrude in the direction away from the transmission plate body to form an elastic buffer structure. When the rocker plate is rocked up, the moving contact first abuts against the elastic arc plate on one side of the transmission plate, and then drives the transmission plate to move, so that the elastic arc plate on the other side of the transmission plate is elastically pressed into contact with the stationary contact, thereby realizing circuit conduction.

8. The explosion-proof micro switch according to claim 2, characterized in that: The outer edge of the arc-blocking plate is provided with a raised flange, which is a circular ring structure. The circular concave surface is a corresponding cylindrical groove. The outer cylindrical surface of the raised flange and the inner cylindrical surface of the circular concave surface form a cylindrical explosion-proof mating surface. The axial mating length of the cylindrical explosion-proof mating surface is not less than 25 mm, and the radial clearance is not greater than 0.1 mm, which meets the requirements of the IIC level explosion-proof mating surface.

9. The explosion-proof micro switch according to claim 1, characterized in that: Both the first and second permanent magnet rings are axially magnetized to form an axially symmetrical magnetic field distribution. The arc-blocking plate is made of non-magnetic material, and the magnetic field strength of the magnetic levitation gap is in the range of 0.3 to 0.5 Tesla, so that the button remains in a stable levitation state in the release position. When pressed, the magnetic levitation force increases exponentially as the gap decreases, forming a progressive resistance feedback. The bellows undergoes elastic deformation when compressed. When the external pressing force is removed, the elastic restoring force of the bellows and the magnetic levitation repulsive force work together to make the button automatically reset to the stable levitation position.

10. The explosion-proof micro switch according to claim 1, characterized in that: A bimetallic compensating ring is provided between the outer wall of the arc-blocking plate and the inner wall of the annular concave surface. The bimetallic compensating ring is made of two metals with different coefficients of thermal expansion and is fixed to the outer wall of the arc-blocking plate in a cylindrical structure. Under normal conditions, a sliding gap is maintained between the arc-blocking plate and the inner wall of the annular concave surface, allowing the arc-blocking plate to slide up and down. When a high temperature arc is generated in the main contact cavity, the bimetallic compensating ring expands and deforms outward due to heat, increasing its outer diameter and pressing against the inner wall of the annular concave surface to form an interference fit sealing structure, preventing high-temperature gas from leaking from the fit gap between the arc-blocking plate and the annular concave surface. After the temperature drops, the bimetallic compensating ring contracts and returns to its initial state, and the arc-blocking plate resumes its sliding fit function.

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