Explosion-proof inductance proximity switch

Abstract

The utility model discloses an explosion-proof inductance proximity switch, which belongs to the technical field of switch type sensors and comprises a front cover, a shell, a PCB (printed circuit board) and a plugging assembly. Through the mode, the front cover adopts the round plastic shell made of the impact-resistant material, the shell adopts the round high-strength metal tube shell, and the round tube has the strongest anti-pressure capability in the shells in all shapes, so that the round arrangement is beneficial to improving the capability of resisting external environment air pressure of the shell; besides, the induction surface is in clearance fit with the front cover, so that the induction surface is not affected when the outer surface of the shell is externally pressed or hit, and the high-pressure-resistant, corrosion-resistant and impact-resistant performances are high, the assembly is convenient, and the mechanism is stable.

Description

Technical Field

[0001] The utility model relates to the technical field of switch type sensors, in particular to an explosion-proof inductive proximity switch. Background Art

[0002] Inductive proximity switches, also known as eddy current proximity switches, detect the proximity of a target object by changing the inductance of a sensing coil. When the target object approaches the sensing coil, the inductance of the sensing coil changes, which in turn affects the frequency of the oscillating circuit, ultimately generating an output signal.

[0003] For example, Chinese patent CN207410319U discloses a high-frequency inductive proximity switch, including an electromagnetic head, a PCB circuit board, and a metal housing; the PCB circuit board integrates a power supply circuit, an LC oscillation circuit, an F / V conversion circuit, a signal processing circuit, and an output circuit in the form of discrete electronic components.

[0004] However, the technology has the following problems: the housing is made of metal or ordinary plastic material, which basically has only a single performance and cannot be used in environments with flammable or explosive gases, steam or dust, and its application range is limited.

[0005] Based on this, the utility model designs an explosion-proof inductive proximity switch to solve the above problems. Utility Model Content

[0006] In view of the above-mentioned shortcomings of the prior art, the utility model provides an explosion-proof inductive proximity switch.

[0007] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] An explosion-proof inductive proximity switch comprises: a front cover, a housing, a PCB board and a connector assembly; the connector assembly is used to support the PCB board and communicate with an external wire;

[0009] The front end of the front cover is in interference contact with the shell, and the front end of the shell is connected to the connector assembly;

[0010] The PCB board is installed inside the housing, and the PCB board is connected to the connector assembly;

[0011] The PCB board includes a sensing surface, which is away from the front cover and has a clearance fit with the front cover. The sensing surface is fixedly installed inside the housing.

[0012] The connector assembly is detachably connected to the housing via threads.

[0013] Furthermore, the material used for the front cover is high-impact polyamide resin, polyetheretherketone or polyimide, polyphenylene sulfide, polyetherimide or polyethersulfone, polyphenylenesulfone or polyamideimide.

[0014] Furthermore, the shell is made of corrosion-resistant stainless steel or polytetrafluoroethylene.

[0015] Furthermore, the connector assembly includes a rear cover and a connector; the rear cover and the connector are connected by interference fit, and the connector is communicatively connected to the external wire.

[0016] Furthermore, the back cover includes a front threaded cylinder, an intermediate cylinder and a rear threaded cylinder; one end of the intermediate cylinder is fixedly connected to the front threaded cylinder, the other end of the intermediate cylinder is fixedly connected to the rear threaded cylinder, and the front threaded cylinder is interference fit connected to the connector.

[0017] Furthermore, a first annular groove is provided at the junction of the rear end threaded cylinder and the middle cylinder, and a first sealing ring is embedded in the first annular groove.

[0018] Furthermore, the inner end of the front side of the shell is provided with an internal thread that matches the rear end threaded cylinder, and the rear end threaded cylinder is threadedly connected to the shell.

[0019] Furthermore, the PCB board also includes a terminal, the rear end of the terminal is interference fit connected to the front end of the sensing surface, and the front end of the terminal is fixedly connected to the rear end threaded column.

[0020] Compared to existing technologies, this utility model offers the following advantages: It addresses the limitations of existing proximity switches, such as their limited performance, limited operating environments, and inability to meet the requirements for use in environments with flammable or explosive gases, steam, or dust. First, the front cover is constructed of a circular plastic shell made of impact-resistant material, while the housing is a high-strength metal tube with a circular cross-section. Because a circular tube has the strongest compressive strength of all housing shapes, the circular design helps improve the housing's ability to withstand external pressure. Furthermore, a clearance fit is provided between the sensing surface and the front cover to prevent the sensing surface from being affected by external pressure or impact on the housing's outer surface. This utility model offers a simple structure, convenient and efficient assembly and disassembly, and is cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention.

[0022] Figure 1 This is a structural diagram of an explosion-proof inductive proximity switch of the utility model;

[0023] Figure 2 The utility model is a schematic diagram of the principle of an explosion-proof inductive proximity switch.

[0024] The numbers in the figure represent:

[0025] 1. Front cover; 2. Housing; 3. PCB board; 31. Sensing surface; 32. Terminal; 4. Connector assembly; 41. Rear cover; 42. Connector; 5. Sealing ring. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] Example 1: In some embodiments, please refer to the accompanying drawings of the specification. Figure 1-Figure 2 , an explosion-proof inductive proximity switch, comprising: a front cover 1, a housing 2, a PCB board 3 and a connector assembly 4; the connector assembly 4 is used to support the PCB board 3 and communicate with an external wire;

[0028] The front end of the front cover 1 is in interference contact with the housing 2; a glue potting process is then used to connect them to improve the sealing performance.

[0029] The front end of the housing 2 is connected to the connector assembly 4;

[0030] The front cover 1 is a circular plastic shell made of impact-resistant material, and the housing 2 is a circular corrosion-resistant metal tube shell;

[0031] The PCB board 3 is fixedly installed inside the housing 2, and the PCB board 3 is connected to the connector assembly 4;

[0032] The PCB board 3 includes a sensing surface 31, which is away from the front cover 1 and has a clearance fit with the front cover 1. The sensing surface 31 is fixedly installed inside the housing 2;

[0033] The connector assembly 4 is detachably connected to the housing 2 via threads.

[0034] This utility model addresses the limitations of existing proximity switches, such as their limited performance, limited operating environments, and inability to meet the requirements of environments with flammable or explosive gases, steam, or dust. First, the front cover 1 is constructed as a circular plastic shell made of impact-resistant material, while the housing 2 is a circular, high-strength metal tube. Because circular tubes have the strongest compressive strength of all housing shapes, the circular design helps improve the housing's ability to withstand external pressure. Furthermore, a clearance fit is provided between the sensing surface 31 and the front cover 1 to prevent the sensing surface 31 from being affected by external pressure or impact on the outer surface of the housing 2. This utility model features a simple structure, convenient and efficient assembly and disassembly, and is cost-effective.

[0035] Embodiment 2: In some embodiments, as Figure 1 As shown, as a preferred embodiment of the present invention, the material used for the front cover 1 is high-impact polyamide resin, polyetheretherketone or polyimide, polyphenylene sulfide, polyetherimide or polyethersulfone, polyphenylenesulfone or polyamideimide; improves its mechanical properties and increases the impact resistance of the front cover 1;

[0036] The material used for the shell 2 is corrosion-resistant stainless steel or polytetrafluoroethylene, which can effectively improve the corrosion resistance of the shell, further improve its mechanical properties, and enhance the pressure resistance of the shell.

[0037] Therefore, the utility model is resistant to high pressure, corrosion, and impact, and is easy to assemble and has a stable structure.

[0038] Embodiment 3: In some embodiments, as Figure 1 As shown, as a preferred embodiment of the present invention, the connector assembly 4 includes a rear cover 41 and a connector 42; the rear cover 41 and the connector 42 are connected by interference fit, and the sealing is better and more stable; the connector 42 is communicatively connected to the external wire.

[0039] The connector 42 is used for connecting an external cable.

[0040] The rear cover 41 includes a front threaded cylinder, a middle cylinder and a rear threaded cylinder;

[0041] One end of the middle cylinder is fixedly connected to the front threaded cylinder, the other end of the middle cylinder is fixedly connected to the rear threaded cylinder, and the front threaded cylinder is connected to the connector 42 by interference fit;

[0042] A first annular groove is provided at the junction of the rear end threaded cylinder and the middle cylinder, and a first sealing ring 5 is embedded in the first annular groove.

[0043] The provision of the first sealing ring 5 enhances the sealing performance of the proximity switch and further strengthens the protection of the electrical components inside the housing.

[0044] The inner end of the front side of the shell 2 is provided with an internal thread that matches the rear end threaded cylinder. The rear end threaded cylinder is threadedly connected to the shell 2, and the connection is stable and stronger, thereby improving its impact resistance.

[0045] The PCB board 3 also includes a terminal 32, the rear end of the terminal 32 is interference fit connected to the front end of the sensing surface 31, and the front end of the terminal 32 is fixedly connected to the rear end threaded cylinder, for example: the terminal 32 and the rear end threaded cylinder are connected by welding.

[0046] Embodiment 3: In some embodiments, as Figure 2 As shown, the PCB board 3 integrates the LDO voltage regulator circuit, LC oscillation circuit, F / V conversion circuit, signal processing circuit, temperature compensation circuit, output circuit and protection circuit in the form of discrete devices, and is constructed as a modular circuit. The protection circuit performs protection monitoring and control according to the output signal of the output circuit.

[0047] The LC oscillator circuit consists of a core and a coil. The core is a pot-shaped ferrite core, and the coil is wound with enameled wire. The pot-shaped core provides a built-in shielding function, confining the magnetic field to the front of the pot mouth. This eliminates the cost of dedicated shielding components.

[0048] The temperature compensation circuit includes a positive temperature coefficient thermistor. The introduction of a positive temperature coefficient temperature sensitive circuit in the temperature compensation circuit greatly enhances the stability of the proximity switch within the operating temperature range of -20℃ to 80℃, thereby effectively avoiding temperature drift and malfunction.

[0049] The various circuits on PCB board 3 are constructed with discrete components (transistors, capacitors, and resistors) as their core, integrating voltage stabilization, signal processing, temperature compensation, and protection. Flexible configuration allows for easy replacement of individual components, resulting in low maintenance costs and enhanced substitutability, effectively preventing the risk of supply shortages. The modular circuit setup significantly improves circuit production efficiency and helps achieve high output frequencies, thereby enhancing sensing sensitivity. The temperature drift compensation design is optimized for EMC and improves the proximity switch's anti-interference capability.

[0050] The output circuit has three-wire output and two-wire output. The three-wire output is used to realize switching value PNP output and NPN output, and the two-wire output is used to realize NO / NC output.

[0051] Setting up three-wire output and two-wire output in the output circuit helps to realize multiple outputs such as three-wire NPN and PNP, two-wire NO / NC, etc. as needed to meet the needs of different application scenarios, effectively expanding the application range of proximity switches.

[0052] The protection circuit includes TVS tube, ferrite beads, decoupling capacitors and voltage regulator tubes, and the protection components are shielded by a metal casing.

[0053] The metal shell helps to resist ±15KV group pulse input and ±60KV static electricity, and resist interference from electromagnetic waves of walkie-talkies.

[0054] The operating principle of a proximity switch: The inductor L in the aforementioned LC oscillator circuit is an inductor with an inductive magnetic tank as its core. When a metal object approaches sensing surface 31, eddy currents are induced within the metal object. The resulting magnetic field reacts on sensing surface 31, weakening its oscillation energy. This decreases the LC oscillation current and amplitude. This change is processed by the signal processing circuit into a varying DC signal, which is then fed into a logic XOR gate to generate a digital switching value. This signal is then amplified by a transistor and becomes the output signal.

[0055] Figure 2 The power supply voltage is 3 to 36V. The power supply is protected by a TVS diode connected to ground and filtered by a filter capacitor. A diode is connected in series with the power supply before entering the LDO step-down circuit. The diode provides reverse polarity protection, and the LDO circuit itself is characterized by voltage isolation, voltage following, and a constant current source circuit constructed using NPN / PNP transistors, along with voltage feedback. This circuit can constantly reduce the power supply voltage to VCC. The output voltage VCC is then divided by a resistor and connected to the base of the voltage feedback NPN transistor to provide voltage feedback, ensuring a constant output voltage.

[0056] The voltage converted by the LDO is provided to the LC oscillation circuit, F / V conversion circuit, and signal processing circuit.

[0057] Figure 2 The LC high-frequency oscillator circuit shown in the figure utilizes the principle of dual-triode mirror current. Together with inductor L (i.e., the solenoid) and nanofarad capacitor C, it forms an LC self-oscillator with an oscillation frequency of 400kHz. The circuit exhibits an amplitude as low as 200MV. This low amplitude and low oscillation current result in fast start-up. After the metal object being measured is removed from the solenoid, the circuit quickly starts oscillating, reestablishing the electromagnetic field. This shortened start-up time effectively increases the output frequency. It is worth noting that capacitor C in the LC circuit features an accuracy of ±0.5% and a temperature drift of no more than 20PPM / °C. This stabilizes the amplitude and frequency and reduces temperature drift.

[0058] The oscillation signal is drawn from the collector of the transistor in the LC oscillator circuit, passed to the input of the FV circuit, and then fed into the base of the NPN transistor. This transistor-based amplifier circuit amplifies the signal. The transistor collector is connected to a capacitor grounded, and RC filtering is used to convert the amplified sinusoidal signal into a DC signal. The signal voltage varies with the amplitude of the LC oscillator circuit, reflecting the strength of the oscillation circuit. The simple RC filtering method offers a reliable structure, minimal signal conversion delay, and high conversion efficiency.

[0059] Figure 2This signal processing circuit features a voltage signal, after F / V conversion, input to pin 2 of an XOR gate digital chip. The chip's other input, pin 4, can be connected to ground or VCC to achieve a NO / NO switching output. The XOR gate logically XORs the two input signals, producing a Boolean output. The circuit uses digital logic gates instead of comparators. The digital chip offers stable output and high switching speed, enabling rapid detection of signal changes and high-speed output of the comparison result.

[0060] In the output circuit, the Boolean signal is amplified by a high-power transistor and becomes a switching signal with an output current of up to 200mA and a speed of up to 1500Hz. In addition, the output mode is available in NPN / PNP, and can be divided into normally open and normally closed, which can be selected by jumper as required.

[0061] The protection circuit also offers short-circuit, overload, and reverse polarity protection. Signal processing utilizes a digital logic chip with an XOR gate. Four pins of the chip output switching signals at a frequency of 1500 Hz, connected to ground via a filter capacitor. The circuit utilizes discrete components, primarily transistors, instead of integrated circuits, resulting in lower cost and greater interchangeability, eliminating the risk of out-of-stock situations.

[0062] In summary, the proximity switch of the present invention has a simple structure, is easy to assemble, is resistant to high pressure and corrosion, has a high level of protection, and is suitable for flammable and explosive environments.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An explosion-proof inductive proximity switch, characterized in that: include: A front cover (1), a housing (2), a PCB board (3) and a connector assembly (4); the connector assembly (4) is used to support the PCB board (3) and to communicate with an external wire; The front end of the front cover (1) is in interference contact with the housing (2), and the front end of the housing (2) is connected to the connector assembly (4); The PCB board (3) is installed inside the housing (2), and the PCB board (3) is connected to the connector assembly (4); The PCB board (3) includes a sensing surface (31), the sensing surface (31) is away from the front cover (1), and has a clearance fit with the front cover (1), and the sensing surface (31) is fixedly mounted inside the housing (2); The connector assembly (4) is detachably connected to the housing (2) via threads.

2. The explosion-proof inductive proximity switch according to claim 1, characterized in that: The material used for the front cover (1) is high-impact polyamide resin, polyetheretherketone or polyimide, polyphenylene sulfide, polyetherimide or polyethersulfone, polyphenylsulfone or polyamideimide.

3. The explosion-proof inductive proximity switch according to claim 2, characterized in that: The material used for the shell (2) is corrosion-resistant stainless steel or polytetrafluoroethylene.

4. The explosion-proof inductive proximity switch according to claim 3, characterized in that: The connector assembly (4) comprises a rear cover (41) and a connector (42); the rear cover (41) and the connector (42) are connected by interference fit, and the connector (42) is communicatively connected to an external wire.

5. The explosion-proof inductive proximity switch according to claim 4, characterized in that: The rear cover (41) comprises a front threaded cylinder, an intermediate cylinder and a rear threaded cylinder; one end of the intermediate cylinder is fixedly connected to the front threaded cylinder, the other end of the intermediate cylinder is fixedly connected to the rear threaded cylinder, and the front threaded cylinder is connected to the connector (42) by interference fit.

6. The explosion-proof inductive proximity switch according to claim 5, characterized in that: A first annular groove is provided at the junction of the rear end threaded cylinder and the middle cylinder, and a first sealing ring (5) is embedded in the first annular groove.

7. The explosion-proof inductive proximity switch according to claim 6, characterized in that: The inner end of the front side of the shell (2) is provided with an internal thread matching the rear end threaded column, and the rear end threaded column is threadedly connected to the shell (2).

8. The explosion-proof inductive proximity switch according to claim 7, characterized in that: The PCB board (3) further comprises a connection terminal (32), the rear end of the connection terminal (32) is connected to the front end of the sensing surface (31) by interference fit, and the front end of the connection terminal (32) is fixedly connected to the rear end threaded cylinder.

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