A safety discharge tube

Abstract

The safety discharge tube of this invention features a short-circuit isolation strip between the inner wall of the ceramic tube and the electrodes. When the discharge tube is conducting at high temperatures during arc discharge, the molten electrode metal sputters onto the inner wall of the ceramic tube. Due to the isolation strip, the metal powder on the inner wall cannot contact the electrodes at both ends, preventing a short circuit between the two electrodes through the inner wall of the ceramic tube. This ensures that the discharge tube remains in an open-circuit state after failure, with the insulation resistance at both ends exceeding 1000 MΩ. In fields with high safety requirements, such as the railway industry, using the discharge tube of this invention ensures that the discharge tube fails in a high-resistance state, preventing short circuits in signal lines and thus improving the safety of the protected equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the lightning protection field, and particularly relates to a safe discharge tube. BACKGROUND

[0002] The discharge tube is sealed by ceramic, and is composed of two or several metal electrodes with gaps and filled with inert gas (argon or neon) inside. When the voltage applied to the two electrodes reaches the breakdown voltage of the gas in the discharge tube, the discharge tube starts to discharge and changes from high resistance state to conduction state, so that the voltage between the two electrodes does not exceed the breakdown voltage.

[0003] The working principle of the discharge tube can be simply summarized as gas discharge. When a large enough voltage is generated between the two electrodes, the gap between the electrodes is broken down by discharge, and the discharge tube changes from high resistance state to conduction state, which is similar to short circuit. When in the conduction state, the voltage between the two electrodes is relatively low, generally between 20-50V, so the discharge tube can well protect the subsequent circuit and is often used as the main component of lightning protection device.

[0004] The discharge tube can be damaged and fail due to mechanical damage, overvoltage, overcurrent and internal aging, and the failure modes are usually short circuit and open circuit. In the short circuit case, as described in the foregoing principle, the protection circuit is almost short-circuited or the protected circuit is short-circuited with the ground, so that the signal line or power line is short-circuited, the device cannot work normally, or the device on the protected line is damaged, and in serious cases, a safety accident can occur. Generally, the damage of the discharge tube cannot be predicted as the short circuit mode or the open circuit failure mode, which limits the application of the device with high safety performance requirement (such as lightning protection of railway signal device). SUMMARY

[0005] The present application provides a safe discharge tube to solve the technical problem of poor reliability of the existing discharge tube. The failure mode of the safe discharge tube is open circuit state or high resistance state, and the insulation resistance value of the two electrodes after failure is greater than 1000M ohms. The safe discharge tube is used for lightning protection of railway signal device and will not cause short circuit of the signal line.

[0006] A safe discharge tube comprises an electrode, a porcelain tube and an electron emission material. The electrode and the porcelain tube form a sealed space, the sealed space is filled with gas, the electrode is provided with a boss, the electron emission material is fixed on the boss of the electrode, the inner wall of the porcelain tube is provided with a conductive strip, and a short-circuit prevention isolation strip is arranged between the side edge of the boss of the electrode and the inner wall of the porcelain tube in the sealed space.

[0007] A step is arranged on the side of the inner wall of the porcelain tube, and the step and the electrode have a spacing to keep them from contacting each other.

[0008] A groove is arranged on the step.

[0009] The inner tube is shorter than the porcelain tube, and is fixed to the porcelain tube by a fixing device, and the two ends of the inner tube are kept apart from the two electrodes by a certain distance.

[0010] The high-temperature-resistant metal sleeve or the insulating sleeve is made of tungsten copper.

[0011] The high-temperature-resistant metal sleeve or the insulating sleeve is made of tungsten copper.

[0012] The high-temperature-resistant metal sleeve or the insulating sleeve is made of tungsten copper.

[0013] The high-temperature-resistant metal sleeve or the insulating sleeve is made of tungsten copper.

[0014] The safety discharge tube of the present application is provided with an anti-short-circuit isolation belt between the inner wall of the porcelain tube and the electrodes. When the discharge tube is in an arc discharge state at high temperature, the melted electrode metal is sputtered on the inner wall of the porcelain tube. Due to the effect of the isolation belt, the metal powder on the inner wall cannot contact the two electrodes, and the two electrodes of the discharge tube cannot be short-circuited through the inner wall of the porcelain tube, so that the discharge tube is in an open circuit state after failure, and the insulation resistance between the two ends is greater than 1000 M ohms. In some high-safety-required fields, such as the railway field, the use of the discharge tube of the present application can ensure that the discharge tube is in a high-resistance state after failure, and cannot cause short circuit of the signal line, thereby improving the safety of the protected equipment.

[0015] The present application will be further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a sectional view of a conventional discharge tube structure.

[0017] Figure 2 It is a sectional view of a safety discharge tube structure of the present application.

[0018] Figure 3 It is a sectional view of another safety discharge tube structure of the present application.

[0019] Figure 4 It is a sectional view of another safety discharge tube structure of the present application. DETAILED DESCRIPTION

[0020] As Figure 1As shown, the conventional discharge tube includes two or three electrodes, a porcelain tube, electron emission material, and a conductive strip; two electrodes and the porcelain tube form a sealed space by welding, and the sealed space is filled with gas; the electrodes are generally provided with protrusions, the protrusions of the two electrodes are separated by a certain distance, and the electron emission material is coated on the protrusions by sintering; the porcelain tube is generally a metalized ceramic insulator and is in a cylindrical shape, and a strip-shaped conductive strip extending along the inner wall in the axial direction is further arranged on the inner wall of the porcelain tube, which accelerates ionization of the discharge region through the action of the electric field, so that the discharge tube has a fast response characteristic, and the conductive strip is generally formed by 2B pencil lines, that is, so-called carbon lines.

[0021] The electrodes of the discharge tube are made of metal materials, and when the discharge tube is in an arc discharge state, the temperature is very high, and the metal of the electrode protrusion part is easy to melt and sputter on the inner wall of the porcelain tube. With the accumulation of metal powder on the inner wall, the two electrodes are connected, resulting in short circuit failure of the discharge tube.

[0022] The safety type discharge tube of the present application is provided with a short circuit prevention isolation strip between the inner wall of the porcelain tube and the electrode. When the discharge tube is in an arc discharge state at high temperature, the melted electrode metal sputters on the inner wall of the porcelain tube. Due to the action of the isolation strip, the metal powder on the inner wall cannot contact the two electrodes, and the two electrodes of the discharge tube cannot be short-circuited through the inner wall of the porcelain tube, ensuring that the discharge tube is in an open circuit state after failure, and the insulation resistance between the two ends is greater than 1000M ohms.

[0023] One embodiment of the safety type discharge tube of the present application is as shown in Figure 2 As shown, it includes two electrodes 1, a porcelain tube 2, electron emission material 3, and a conductive strip 4; a step 21 is made on the inner wall of the porcelain tube, and when the two electrodes are sealed by welding with the porcelain tube, the step 21 and the electrode 1 have a distance that keeps them from contacting each other; a groove 22 can also be arranged on the step of the porcelain tube to increase the distance between the inner wall step and the electrode 1. Through this structural arrangement, the porcelain tube 2 and the electrode 1 form a short circuit prevention isolation strip 5. When the metal on the two electrodes is melted and sputtered on the inner wall of the porcelain tube due to high temperature, even if the inner wall is full of metal powder, it will not be short-circuited through the inner wall due to the existence of the isolation strip.

[0024] As shown in Figure 3 Another embodiment of the safety type discharge tube of the present application is as shown. An inner tube 7 is arranged in the porcelain tube 2 of the discharge tube, the length of the inner tube 7 is shorter than that of the porcelain tube 2, and the inner tube 7 is fixed with the porcelain tube 2 through a fixing device 8. The two ends of the inner tube 7 and the two electrodes 1 have a distance that keeps them from contacting each other, and the conductive strip 4 is arranged on the inner wall of the inner tube 7. This structure makes the inner tube 8, the porcelain tube 2, and the electrode 1 form a short circuit prevention isolation strip 5. When the metal on the two electrodes is melted and sputtered on the inner tube 7 due to high temperature, even if the inner wall of the inner tube 7 is full of metal powder, it will not be short-circuited through the inner tube due to the existence of the isolation strip.

[0025] As Figure 4 shown in the figure, another embodiment of the safety discharge tube of the present application, a high-temperature-resistant metal sleeve or insulating sleeve 6 is arranged around the protrusion 11 of the electrode 1, covering the protrusion part of the electrode, the high-temperature-resistant metal sleeve or insulating sleeve 6 is tapered and slightly higher than the protrusion of the electrode 1. When the metal on the two electrodes is melted by high temperature and sputters outward, due to the tapered structure of the high-temperature-resistant metal sleeve or insulating sleeve 6 and the fact that it is slightly higher than the electrode protrusion, the sputtering angle of the melted metal is constrained and cannot spray onto the inner wall of the porcelain tube, but only onto the opposite electrode, that is, a short-circuit prevention isolation band 5 is formed between the high-temperature-resistant metal sleeve or insulating sleeve 6 and the inner wall of the porcelain tube. Due to the effect of the isolation band, the two electrodes will not be short-circuited through the inner wall of the porcelain tube. The high-temperature-resistant metal sleeve is made of tungsten copper.

[0026] Still another embodiment of the present application is that the surface of the protrusion of the electrode 1 is provided with a mesh-like concave-convex structure, and the electron emission material is placed in the grooves of the mesh-like concave-convex structure. The electron emission material placed in the grooves is not easy to fall off, and thus the sputtering of the electron material or metal powder outward is reduced, thereby reducing the possibility of short circuit of the two electrodes of the discharge tube.

[0027] Further, the length of the strip-shaped conductive band in the porcelain tube can be shortened, and the distance between the conductive band and the electrode is at least greater than 1 mm, and is preferably greater than 1.5 mm. The farther the distance between the conductive band and the electrode, the smaller the possibility of conduction of the two electrodes through the inner wall of the porcelain tube.

[0028] The safety discharge tube of the present application is subjected to a test of applying a power frequency current to both ends until the discharge tube fails, and the insulation resistance between the two ends is greater than 1000 OM ohms. The discharge tube is subjected to an 8 / 20 impulse current test until the discharge tube fails, and the insulation resistance between the two ends is greater than 1000 OM ohms. The discharge tube is subjected to a high-frequency pulse fast switching test until the discharge tube fails, and the insulation resistance between the two ends is greater than 1000 OM ohms. The failed discharge tube is dissected, and there is sputtered metal powder on the inner wall of the porcelain tube, but it does not cause the two electrodes to be conductive. The above tests prove that the arrangement of the short-circuit prevention isolation band in the discharge tube can make the failure mode of the discharge tube only be the open circuit mode, and not the short circuit mode.

[0029] The technical features of the above-mentioned embodiments can be combined in any manner. In order to make the description simple, not all possible combinations of the technical features in the above-mentioned embodiments are described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0030] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, as long as the short-circuit isolation measures are taken in the discharge tube to prevent the metal in the discharge tube from melting and sputtering to cause the short circuit of the discharge tube, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A safety discharge tube, comprising an electrode (1), a ceramic tube (2), and an electron emission material (3), wherein the electrode (1) and the ceramic tube (2) form a sealed space filled with gas, the electrode (1) is provided with a boss (11), the electron emission material (3) is fixed on the boss (11) of the electrode (1), and the inner wall of the ceramic tube (2) is provided with a conductive strip (4), characterized in that: A short-circuit isolation strip (5) is provided between the side of the protrusion of the electrode (1) and the inner wall of the ceramic tube (2) in the sealed space; an inner tube (7) is provided inside the ceramic tube (2), the length of the inner tube (7) is shorter than that of the ceramic tube (2), and it is fixed to the ceramic tube (2) by means of a fixing device (8). The length of the fixing device (8) is shorter than that of the inner tube (7) and is located in the middle of the outer wall of the inner tube (7). There is a distance between the two ends of the inner tube (7) and the electrodes (1) on both sides to keep them from contacting each other; a high-temperature resistant metal material sleeve or insulating sleeve (6) is provided around the protrusion (11) of the electrode (1) to cover the protrusion (11) of the electrode (1). The high-temperature resistant metal material sleeve or insulating sleeve (6) is made into a cone shape and is slightly higher than the protrusion (11) of the electrode (1).

2. The safety discharge tube according to claim 1, characterized in that: The protrusion (11) of the electrode (1) is configured as a mesh-like uneven structure, and the electron emission material (3) is placed in the groove of the mesh-like uneven structure.

3. The safety discharge tube according to claim 1, characterized in that: The distance between the conductive strip (4) and the electrode (1) is greater than 1 mm.

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