An exposure lamp

Abstract

This utility model discloses an exposure lamp, belonging to the technical field of light source equipment. The exposure lamp includes a bulb, an anode assembly, a cathode assembly, and a drive assembly. The bulb includes opposing anode and cathode ends. The anode assembly includes an electrode anode disposed within the anode end. The cathode assembly includes an electrode cathode, a cathode connector, and a cathode quartz tube. The cathode quartz tube is connected to the cathode end, the electrode cathode is disposed within the cathode end and spaced apart from the electrode anode, and the cathode connector is slidably inserted within the cathode quartz tube, with one end connected to the electrode cathode. A limiting groove is provided along the axial direction on the inner wall of the cathode quartz tube, and a limiting portion protrudes from the outer wall of the cathode connector, the limiting portion slidingly engaging within the limiting groove. The drive assembly is configured to drive the cathode connector to move relative to the cathode quartz tube. The exposure lamp has a long service life and reduces usage and labor costs.

Description

Technical Field

[0001] This utility model relates to the field of light source equipment technology, specifically to an exposure lamp. Background Technology

[0002] High-pressure exposure lamps are light source devices that generate intense light through high-pressure gas discharge. They are widely used in industrial fields such as printing plate making, PCB manufacturing, photolithography, semiconductor processing, and precision exposure. The core principle of high-pressure exposure lamps is to excite the gas (such as mercury vapor, metal halides, etc.) inside the lamp tube with a high-voltage electric field to generate high-intensity ultraviolet or visible light, featuring high brightness, stable light intensity, and adjustable spectral range.

[0003] A high-pressure exposure lamp typically includes a bulb, a cathode quartz tube, an anode quartz tube, and a cathode and anode positioned opposite each other within the bulb. The cathode and anode quartz tubes are located at opposite ends of the bulb. The cathode and cathode tungsten rod are connected, with the cathode tungsten rod located inside the cathode quartz tube. The anode and anode tungsten rod are connected, with the anode tungsten rod located inside the anode quartz tube. Both the outer surfaces of the cathode and anode quartz tubes have a metallic coating. The bulb is filled with mercury vapor and a small amount of inert gas (such as argon). The light-emitting principle of this high-pressure exposure lamp is as follows: when the cathode and anode are energized, an electric arc is generated. The high temperature generated by the arc causes mercury to evaporate from a liquid state to a gaseous state, forming mercury vapor. Under the action of a high-voltage electric field, the mercury vapor is ionized, forming plasma. Electrons collide with mercury atoms, causing electrons in the mercury atoms to jump to higher energy levels, thereby releasing photons of specific wavelengths, mainly producing ultraviolet and visible light.

[0004] However, as the usage time increases, the cathode will wear down and become shorter, leading to an increase in the distance between the cathode and anode and a weakening of the arc capability. At this point, it is necessary to increase the power to maintain the preset illuminance of the high-pressure exposure lamp, resulting in energy waste. In addition, the high-pressure exposure lamps in the existing technology have a short lifespan, requiring operators to replace them frequently, which increases the operating cost and labor cost of the high-pressure exposure lamp.

[0005] Therefore, there is an urgent need for an exposure lamp to solve the above problems. Utility Model Content

[0006] The purpose of this invention is to provide an exposure lamp with a long service life and reduced usage and labor costs.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An exposure lamp, comprising:

[0009] Bubble shells, including the relative positive and negative extremes;

[0010] The anode assembly includes an electrode anode disposed within the anode end;

[0011] A cathode assembly includes an electrode cathode, a cathode connector, and a cathode quartz tube. The cathode quartz tube is connected to the cathode end, the electrode cathode is disposed inside the cathode end and spaced apart from the electrode anode, and the cathode connector is slidably inserted into the cathode quartz tube, with one end of the cathode connector connected to the electrode cathode. A limiting groove is provided along the axial direction on the inner wall of the cathode quartz tube, and a limiting portion protrudes from the outer wall of the cathode connector, the limiting portion slidingly engaging within the limiting groove.

[0012] A drive assembly is configured to drive the cathode connector to move relative to the cathode quartz tube.

[0013] As a preferred embodiment, the exposure lamp further includes a connector, which is fixedly mounted on the mounting platform and can be grounded through a first lead wire;

[0014] The drive assembly includes a transmission sleeve and a rotary drive module. The transmission sleeve is rotatably mounted on the connecting seat, and the other end of the cathode connector is threaded into the transmission sleeve. The rotary drive module can drive the transmission sleeve to rotate.

[0015] As a preferred embodiment, the rotary drive module includes a first drive member, a drive gear, and a driven gear. The output end of the first drive member is connected to the drive gear to drive the drive gear to rotate. The driven gear is sleeved on the transmission sleeve and meshes with the drive gear.

[0016] As a preferred embodiment, the rotary drive module includes a second drive member, a rack, and a transmission gear. The output end of the second drive member is connected to the rack to drive the rack to move axially along the cathode of the electrode. The transmission gear is sleeved outside the transmission sleeve and meshes with the rack.

[0017] As a preferred embodiment, the number of limiting grooves is at least two, and the at least two limiting grooves are arranged at intervals along the circumference of the cathode quartz tube, and the cathode connector is provided with limiting parts corresponding to the limiting grooves one by one.

[0018] As a preferred embodiment, a seal is provided between the cathode connector and the cathode quartz tube.

[0019] As a preferred embodiment, the inner wall of the cathode quartz tube is provided with a receiving groove for accommodating the sealing element.

[0020] As a preferred embodiment, the cathode quartz tube is fitted with a cathode protective shell.

[0021] As a preferred embodiment, the length of the cathode electrode is 1 mm to 10 mm.

[0022] As a preferred embodiment, the end of the electrode cathode facing the electrode anode is configured in a pointed shape.

[0023] The beneficial effects of this utility model are as follows:

[0024] The exposure lamp provided by this utility model slidably mounts a cathode connector inside a cathode quartz tube. As the cathode electrode wears down over time, increasing the distance between the cathode and anode, the drive assembly moves the cathode connector closer to the anode to maintain the distance between them, thus preserving the preset illuminance of the exposure lamp. Once the cathode reaches its maximum displacement, the power is increased to maintain the preset illuminance. This design significantly extends the lifespan of the exposure lamp, reduces the frequency of lamp replacements, and consequently lowers operating and labor costs. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of this utility model and these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of the exposure lamp provided in Embodiment 1 of this utility model;

[0027] Figure 2 This is a cross-sectional schematic diagram of the cathode quartz tube and cathode connector provided in Embodiment 1 of this utility model;

[0028] Figure 3 This is a schematic diagram of the structure of the driving component provided in Embodiment 1 of this utility model;

[0029] Figure 4 This is a schematic diagram of the drive component provided in Embodiment 2 of this utility model.

[0030] Figure label:

[0031] 10. Bubble shell; 11. Positive extreme; 12. Negative extreme;

[0032] 20. Anode assembly; 21. Electrode anode; 22. Anode connector; 23. Anode quartz tube; 24. Anode protective shell;

[0033] 30. Cathode assembly; 31. Electrode cathode; 32. Cathode connector; 321. Limiting part; 33. Cathode quartz tube; 331. Limiting groove; 332. Receiving groove; 34. Cathode protective shell;

[0034] 40. Drive assembly; 41. Transmission sleeve; 42. Rotary drive module; 421. First drive component; 422. Drive gear; 423. Driven gear; 424. Second drive component; 425. Rack; 426. Transmission gear;

[0035] 50. Sealing components;

[0036] 60. Connector. Detailed Implementation

[0037] Before explaining any embodiment of the present invention in detail, it should be understood that the present invention is not limited to its application to the structural details and component arrangements set forth in the following description or shown in the above drawings.

[0038] In this invention, the terms "comprising," "including," "having," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0039] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, in this invention, the character " / " generally indicates that the preceding and following related objects have an "and / or" relationship.

[0040] In this invention, the terms "connection," "combination," "coupling," and "installation" can refer to direct connection, combination, coupling, or installation, or indirect connection, combination, coupling, or installation. For example, a direct connection refers to two parts or components being connected together without the need for an intermediary, while an indirect connection refers to two parts or components each being connected to at least one intermediary, with the connection achieved through the intermediary. Furthermore, "connection" and "coupling" are not limited to physical or mechanical connections or couplings, but can also include electrical connections or couplings.

[0041] In this invention, those skilled in the art will understand that relative terms (e.g., “about,” “approximately,” “basically,” etc.) used in conjunction with quantities or conditions are to include the value and have the meaning indicated by the context. For example, such relative terms include at least the degree of error associated with the measurement of a particular value, tolerances associated with the particular value due to manufacturing, assembly, use, etc. Such terms should also be considered as disclosing a range defined by the absolute values ​​of the two endpoints. Relative terms may refer to a certain percentage (e.g., 1%, 5%, 10% or more) of the indicated value. Numerical values ​​not using relative terms should also be disclosed as specific values ​​with tolerances. Furthermore, “basically” when expressing relative angular relationships (e.g., substantially parallel, substantially perpendicular) may refer to a certain degree (e.g., 1 degree, 5 degrees, 10 degrees or more) added to or subtracted from the indicated angle.

[0042] In this invention, those skilled in the art will understand that the function performed by a component can be performed by one component, multiple components, one part, or multiple parts. Similarly, the function performed by a part can be performed by one part, one component, or a combination of multiple parts.

[0043] In this utility model, the directional terms "upper," "lower," "left," "right," "front," and "rear" are used to describe the orientation and positional relationships shown in the accompanying drawings and should not be construed as limiting the embodiments of this utility model. Furthermore, in the context, it should be understood that when one element is mentioned as being connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected through an intermediate element. It should also be understood that directional terms such as upper side, lower side, left side, right side, front side, and rear side not only represent the direct orientation but can also be understood as the lateral orientation. For example, "below" can include directly below, lower left, lower right, lower front, and lower rear.

[0044] Example 1

[0045] Figure 1 A schematic diagram of the exposure lamp provided in this embodiment is shown. Figure 2 A cross-sectional schematic diagram of the cathode quartz tube 33 and cathode connector 32 provided in this embodiment is shown. Figures 1-2As shown, this embodiment provides an exposure lamp, which includes a bulb 10, an anode assembly 20, a cathode assembly 30, and a drive assembly 40. The bulb 10 includes opposing anode end 11 and cathode end 12. The anode assembly 20 includes an electrode anode 21 disposed within the anode end 11. The cathode assembly 30 includes an electrode cathode 31, a cathode connector 32, and a cathode quartz tube 33. The cathode quartz tube 33 is connected to the cathode end 12. The electrode cathode 31 is disposed within the cathode end 12 and spaced apart from the electrode anode 21. The cathode connector 32 is slidably inserted within the cathode quartz tube 33, and one end of the cathode connector 32 is connected to the electrode cathode 31. A limiting groove 331 is provided along the axial direction on the inner wall of the cathode quartz tube 33, and a limiting portion 321 protrudes from the outer wall of the cathode connector 32, the limiting portion 321 slidingly engaging within the limiting groove 331. The drive assembly 40 is configured to drive the cathode connector 32 to move relative to the cathode quartz tube 33.

[0046] The exposure lamp provided in this embodiment slidably mounts the cathode connector 32 inside the cathode quartz tube 33. When the cathode 31 wears down over time, causing the distance between the cathode 31 and the anode 21 to increase, the drive assembly 40 can drive the cathode connector 32 to move closer to the anode 21, thus maintaining the distance between the cathode 31 and the anode 21 and keeping the preset illuminance of the exposure lamp constant. When the cathode 31 reaches its maximum displacement, the power is increased to maintain the preset illuminance. This configuration can significantly extend the service life of the exposure lamp, reduce the frequency of lamp replacement by operators, and thus reduce the operating costs and labor costs of the exposure lamp.

[0047] Furthermore, the exposure lamp also includes a connector 60, which is fixedly mounted on the mounting platform and can be grounded through a first lead. The anode assembly 20 also includes an anode connector 22 and an anode quartz tube 23. The anode quartz tube 23 is connected to the anode end 11, and the anode connector 22 passes through the anode quartz tube 23. One end of the anode connector 22 is connected to the electrode anode 21, and the other end is connected to an external power supply through a second lead. With the above configuration, current can be conducted between the exposure lamp and the external power supply, so that an electric arc is generated after the electrode anode 21 and the electrode cathode 31 are energized.

[0048] Optionally, the end of the cathode 31 facing the anode 21 is angled. This design can enhance the local electric field strength, increase energy density, improve arc stability, reduce operating voltage, save energy, and at the same time promote electron emission and improve luminous efficiency.

[0049] Optionally, the length of the electrode cathode 31 is 1mm to 10mm. Compared with the prior art, this design increases the length of the electrode cathode 31, further extending the service life of the exposure lamp. For example, the length of the electrode cathode 31 can be 2.0mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, 4.5mm, 5.0mm, 5.5mm, 6.0mm, 6.5mm, 7.0mm, 7.5mm, 8.0mm, 8.5mm, 9.0mm, or 9.5mm. Of course, the length of the electrode cathode 31 is not limited to the above ranges; designers can adapt the length of the electrode cathode 31 by comprehensively considering the service life of the exposure lamp, installation space, and processing costs.

[0050] Figure 3 A schematic diagram of the structure of the driving component 40 provided in this embodiment is shown. Figure 3 and combined Figure 1 As shown, the drive assembly 40 includes a transmission sleeve 41 and a rotary drive module 42. The transmission sleeve 41 is rotatably mounted on the connecting seat 60, and the other end of the cathode connector 32 is threaded into the transmission sleeve 41. The rotary drive module 42 can drive the transmission sleeve 41 to rotate. That is, when the rotary drive module 42 is working, it can drive the transmission sleeve 41 to rotate, and the cathode connector 32 can move relative to itself along its own axial direction under the limiting cooperation of the limiting part 321 and the limiting groove 331, thereby approaching the electrode anode 21. It can be understood that the cooperation between the limiting groove 331 and the limiting part 321 can also limit the axial movement of the cathode connector 32, thereby preventing the cathode connector 32 from detaching from the cathode quartz tube 33.

[0051] Specifically, the rotary drive module 42 includes a first drive member 421, a drive gear 422, and a driven gear 423. The output end of the first drive member 421 is connected to the drive gear 422 to drive the drive gear 422 to rotate. The driven gear 423 is sleeved on the outside of the transmission sleeve 41 and meshes with the drive gear 422. In this embodiment, the first drive member 421 is a drive motor. When the drive motor is working, it can drive the drive gear 422 to rotate, thereby driving the driven gear 423 meshing with the drive gear 422 and the transmission sleeve 41 connected to the driven gear 423 to rotate, thereby realizing the axial movement of the cathode connector 32 and the electrode cathode 31.

[0052] Of course, in other embodiments, the driven gear 423 may not be provided. Instead, transmission teeth that can mesh with the drive gear 422 can be directly machined on the transmission sleeve 41. The drive gear 422 can directly mesh with the transmission teeth on the transmission sleeve 41, which can achieve the same effect.

[0053] like Figure 2As shown, there are at least two limiting grooves 331, which are spaced apart circumferentially along the cathode quartz tube 33. The cathode connector 32 is provided with limiting parts 321 that correspond one-to-one with the limiting grooves 331. This design can ensure the stability of the movement of the cathode connector 32 relative to the cathode quartz tube 33, and prevent it from shifting during movement, which would cause a change in the relative position between the electrode anode 21 and the electrode cathode 31.

[0054] Optionally, a sealing element 50 is provided between the cathode connector 32 and the cathode quartz tube 33 to ensure the airtightness between them and prevent mercury vapor and inert gas inside the bulb 10 from flowing out from the gap between the cathode connector 32 and the cathode quartz tube 33, thus affecting the performance of the exposure lamp. In this embodiment, a receiving groove 332 for accommodating the sealing element 50 is provided on the inner wall of the cathode quartz tube 33, thereby realizing the positioning and installation of the sealing element 50 and preventing it from shifting or falling off during use.

[0055] Continue as Figure 1 As shown, both the outer surfaces of the cathode quartz tube 33 and the anode quartz tube 23 are coated with metal. The metal coating on the outer surface of the cathode quartz tube 33 extends to the cathode end 12 of the bulb 10, and the metal coating on the outer surface of the anode quartz tube 23 extends to the anode end 11 of the bulb 10. The metal coating serves to shield light and increase strength.

[0056] When the exposure lamp is in operation, it generates intense heat, which causes the metal coating to evaporate. The resulting metal vapor floats on the surface of the metal coating. After the exposure lamp is turned off and cooled, the metal vapor condenses back onto the surface of the metal coating. To prevent loss of the metal coating after evaporation into metal vapor, in this embodiment, the cathode quartz tube 33 is fitted with a cathode protective shell 34, and the anode quartz tube 23 is fitted with an anode protective shell 24. Part or all of the metal coating on the outer surface of the cathode quartz tube 33 is located inside the cathode protective shell 34, and part or all of the metal coating on the outer surface of the anode quartz tube 23 is located inside the anode protective shell 24, thus providing wind protection and preventing loss of the metal coating.

[0057] Optionally, both the cathode protection shell 34 and the anode protection shell 24 are made of aluminum, which is beneficial for heat dissipation and can improve the heat dissipation performance of the exposure lamp. Of course, in other embodiments, the material of the cathode protection shell 34 and the anode protection shell 24 is not limited to aluminum, and designers can make adaptive selections of the materials of the cathode protection shell 34 and the anode protection shell 24 according to actual usage needs.

[0058] It should be explained that the specific structure of the bubble shell 10 and the anode assembly 20, the connection method between the anode quartz tube 23 and the bubble shell 10, the connection method between the cathode quartz tube 33 and the bubble shell 10, and the materials of the electrode cathode 31, cathode connector 32, electrode anode 21 and anode connector 22 are all existing technologies, and will not be described in detail in this embodiment.

[0059] The following is combined with Figures 1-3 The operating principle of the exposure lamp provided in this embodiment will be briefly introduced as follows:

[0060] 1) The first lead is grounded, and the second lead is connected to an external power source. When the anode 21 and cathode 31 are energized, an electric arc is generated. The high temperature generated by the electric arc causes mercury to evaporate from liquid to gas, forming mercury vapor. Under the action of a high-voltage electric field, the mercury vapor is ionized to form plasma. Electrons collide with mercury atoms, causing electrons in the mercury atoms to jump to higher energy levels, thereby releasing photons of specific wavelengths, mainly producing ultraviolet and visible light.

[0061] 2) As the usage time increases, the cathode electrode 31 is worn down and becomes shorter. At this time, the first driving member 421 is activated to drive the driving gear 422 to rotate. At the same time, the driven gear 423 meshing with the driving gear 422 and the transmission sleeve 41 connected to the driven gear 423 rotate, thereby realizing the axial movement of the cathode connector 32 and the cathode electrode 31, so that the distance between the anode electrode 21 and the cathode electrode 31 remains unchanged, so that the exposure lamp maintains the preset illuminance.

[0062] 3) When the cathode electrode 31 reaches its maximum displacement, the UV illuminance sensor on the worktable detects a decrease in the illuminance of the exposure lamp. At this time, the power control cabinet can increase the power by increasing the current, thereby maintaining the illuminance of the exposure lamp unchanged.

[0063] 4) When the power reaches its maximum, the control system will issue an alarm to remind the operator to replace the exposure lamp in time.

[0064] Example 2

[0065] This embodiment provides an exposure lamp, the specific structure of which is roughly the same as that of the exposure lamp provided in Embodiment 1, the difference being that the specific structure of the rotation drive module 42 is different.

[0066] Figure 4 A schematic diagram of the structure of the driving component 40 provided in this embodiment is shown. Figure 4 and combined Figure 1As shown, the rotary drive module 42 includes a second drive member 424, a rack 425, and a transmission gear 426. The output end of the second drive member 424 is connected to the rack 425 to drive the rack 425 to move axially along the cathode electrode 31. The transmission gear 426 is sleeved on the outside of the transmission sleeve 41 and meshes with the rack 425. In this embodiment, the second drive member 424 is an electric cylinder. When the electric cylinder is working, it can drive the rack 425 to move axially along the cathode electrode 31, thereby driving the transmission gear 426 meshing with the rack 425 and the transmission sleeve 41 connected to the transmission gear 426 to rotate, thereby realizing the axial movement of the cathode connector 32 and the cathode electrode 31.

[0067] Of course, in other embodiments, the transmission gear 426 may not be provided. Instead, transmission teeth that can mesh with the rack 425 may be directly machined on the transmission sleeve 41. The rack 425 can directly mesh with the transmission teeth on the transmission sleeve 41, which can achieve the same effect.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that the above embodiments do not limit this utility model in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of this utility model.

Claims

1. An exposure lamp characterized by comprising: include: Bubble shell (10), including the opposite positive end (11) and negative end (12); The anode assembly (20) includes an electrode anode (21) disposed within the anode end (11); A cathode assembly (30) includes an electrode cathode (31), a cathode connector (32), and a cathode quartz tube (33). The cathode quartz tube (33) is connected to the cathode end (12). The electrode cathode (31) is disposed inside the cathode end (12) and spaced apart from the electrode anode (21). The cathode connector (32) is slidably inserted into the cathode quartz tube (33), and one end of the cathode connector (32) is connected to the electrode cathode (31). A limiting groove (331) is provided along the axial direction on the inner wall of the cathode quartz tube (33), and a limiting part (321) is protruding on the outer wall of the cathode connector (32). The limiting part (321) is slidably fitted into the limiting groove (331). The drive assembly (40) is configured to drive the cathode connector (32) to move relative to the cathode quartz tube (33).

2. The exposure lamp according to claim 1, characterized by The exposure lamp also includes a connector (60), which is fixedly mounted on the mounting platform and can be grounded through the first lead wire; The drive assembly (40) includes a transmission sleeve (41) and a rotary drive module (42). The transmission sleeve (41) is rotatably mounted on the connecting seat (60). The other end of the cathode connector (32) is threaded into the transmission sleeve (41). The rotary drive module (42) can drive the transmission sleeve (41) to rotate.

3. The exposure lamp of claim 2, wherein The rotary drive module (42) includes a first drive member (421), a drive gear (422), and a driven gear (423). The output end of the first drive member (421) is connected to the drive gear (422) to drive the drive gear (422) to rotate. The driven gear (423) is sleeved on the outside of the transmission sleeve (41) and meshes with the drive gear (422).

4. The exposure lamp according to claim 2, characterized in that, The rotary drive module (42) includes a second drive member (424), a rack (425), and a transmission gear (426). The output end of the second drive member (424) is connected to the rack (425) to drive the rack (425) to move axially along the cathode (31). The transmission gear (426) is sleeved on the outside of the transmission sleeve (41) and meshes with the rack (425).

5. The exposure lamp according to claim 1, characterized in that, The number of the limiting grooves (331) is at least two, and the at least two limiting grooves (331) are arranged at intervals along the circumference of the cathode quartz tube (33). The cathode connector (32) is provided with limiting parts (321) that correspond one-to-one with the limiting grooves (331).

6. The exposure lamp according to claim 1, characterized in that, A sealing element (50) is provided between the cathode connector (32) and the cathode quartz tube (33).

7. The exposure lamp according to claim 6, characterized in that, The inner wall of the cathode quartz tube (33) is provided with a receiving groove (332) for accommodating the sealing element (50).

8. The exposure lamp according to claim 1, characterized in that, The cathode quartz tube (33) is fitted with a cathode protective shell (34).

9. The exposure lamp according to any one of claims 1 to 8, characterized in that, The length of the cathode (31) is 1 mm to 10 mm.

10. The exposure lamp according to any one of claims 1 to 8, characterized in that, The cathode (31) of the electrode is set in a pointed shape at one end facing the anode (21).

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