Adjustable dismounting tool for transformer moisture absorber glass oil cup
By designing a disassembly and assembly tool that includes a crossbeam, handle, connector, plug, and mirror, the problems of low efficiency and easy damage to the vent hole in traditional transformer desiccant glass oil cup disassembly are solved, achieving an efficient and convenient disassembly and assembly process.
Patent Information
- Application Number
- CN202522467750.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-20
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2035-11-20
AI Technical Summary
Traditionally, when disassembling the glass oil cup of a transformer desiccant, one needs to bend over to observe the location of the vent, which is inconvenient and prone to damage. It is also difficult to insert a screwdriver, resulting in difficult operation and poor disassembly and assembly quality.
Design a disassembly and assembly tool that includes a crossbeam, handle, connector, plug, and mirror. The mirror reflects the position of the vent, the plug engages with the vent, and the crossbeam is rotated by the handle to rotate the threaded pair. Combined with the adjustment structure, it can be adapted to flanges of different specifications.
It improves disassembly and assembly efficiency and quality, reduces the risk of damage to vents, enhances tool adaptability and convenience, and ensures smooth operation.
Smart Images

Figure CN224934575U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of transformer technology, specifically to an adjustable disassembly and assembly tool for the glass oil cup of a transformer desiccant. Background Technology
[0002] As a crucial component ensuring the safe operation of transformers, the transformer desiccant, through the dual action of oil seal filtration and silica gel adsorption, removes impurities and moisture from the air entering the oil conservator due to oil temperature changes, maintaining the dryness of the insulating oil. When more than 1 / 3 of the silica gel inside the desiccant becomes damp and discolored, it needs to be replaced. This process requires removing the bottom glass oil cup and its upper flange as a whole. These two components are connected to the lower flange of the desiccant via threads, and the glass oil cup and its upper flange can rotate relative to each other.
[0003] Traditional disassembly methods rely on rotating the glass oil cup, using the friction between it and the flange on the upper part of the cup to rotate the latter and complete the disassembly. However, when the friction between the two is less than the friction between the threaded parts, relative rotation occurs, hindering disassembly. In this case, maintenance personnel often use a screwdriver inserted into the vent hole of the flange on the upper part of the oil cup to assist in rotation. However, this method has obvious drawbacks: the vent hole is located on the lower surface of the flange on the upper part of the oil cup, requiring personnel to bend down and get close to the observation position, which is inconvenient; moreover, the diameter of the vent hole is small, making it difficult to insert the screwdriver and easily damaging the hole, which is both time-consuming and laborious, and affects the quality of disassembly and assembly.
[0004] In view of the shortcomings of the above-mentioned traditional disassembly methods, in order to improve the efficiency and quality of glass oil cup disassembly and assembly, and to avoid damage to the vent and connection problems caused by relative rotation of components, it is necessary to design a special tool that is convenient, highly adaptable and can assist in observation. This led to the development of the adjustable disassembly and assembly tool for the glass oil cup of this transformer desiccant. Utility Model Content
[0005] In view of this, the present invention provides an adjustable disassembly and assembly tool for the glass oil cup of a transformer desiccant, so as to solve the problem that traditional disassembly requires maintenance personnel to use a screwdriver inserted into the vent hole of the flange on the oil cup to assist in rotation.
[0006] This utility model provides an adjustable disassembly and assembly tool for a transformer desiccant glass oil cup, including a crossbeam, a handle, two connecting parts, two plugs, and a mirror. The handle is mounted on the crossbeam for driving its rotation, and a connecting part is provided at each end of the crossbeam. Each connecting part is provided with a plug, the upper end of which is used to insert into the vent hole of the flange on the glass oil cup. The mirror is mounted on the crossbeam and located below the plug.
[0007] During operation, the mirror, positioned below the plug, clearly reflects the location of the vent hole on the flange of the glass oil cup, eliminating the need for personnel to bend down and observe closely. This solves the problem of inconvenient observation of the vent hole location and facilitates quick and accurate insertion of the plug's upper end into the vent hole. After the plug is aligned with the vent hole, the operator holds the handle on the crossbeam and rotates it, causing the crossbeam to rotate. The connecting parts at both ends of the crossbeam rotate along with the crossbeam, which in turn rotates the plug on the connecting parts. The plug, through its interaction with the vent hole, drives the flange on the glass oil cup to rotate, ultimately rotating the threaded pair and completing the assembly and disassembly of the glass oil cup and its flange.
[0008] This working method makes the disassembly and assembly process more convenient, avoiding the operational difficulties caused by the inconvenience of observation with traditional tools. At the same time, the cooperation between the plug and the vent reduces the risk of damage to the vent, effectively improving the efficiency and quality of disassembly and assembly of the glass oil cup.
[0009] In one alternative embodiment, the plug is detachably connected to the connector via an adjustment structure for adjusting the lateral distance between the two plugs.
[0010] The adjustable structure allows for flexible adjustment of the lateral distance between the two plugs based on the actual spacing of the vent holes on the glass oil cup flange, thus adapting to different specifications of glass oil cup flanges. When faced with varying vent hole spacing, adjusting the lateral distance between the two plugs ensures that the upper end of the plug accurately inserts into the corresponding vent hole, guaranteeing good compatibility between the tool and different models of glass oil cup flanges. This further enhances the tool's versatility and practicality, enabling it to function effectively in various working conditions and smoothly complete the disassembly and assembly of glass oil cups.
[0011] In one alternative embodiment, the adjustment structure includes a threaded hole on the connector, a threaded hole on the plug, and a bolt passing through the two threaded holes.
[0012] The adjustment mechanism consists of threaded holes on the connector, threaded holes on the plug, and bolts passing through the two threaded holes. After determining the position of the plug relative to the connector, screw the bolts into the connector and plug in sequence to complete the plug installation. To change the distance between the two plugs, rotate the bolts in the opposite direction until they come out of the threaded holes on the plug. After determining the distance between the two plugs, screw the bolts back into the threaded holes on the plug. This further enhances the tool's adaptability to flanges on glass oil cups of different sizes, ensuring smooth disassembly and assembly operations.
[0013] In one optional embodiment, the adjustment structure further includes a through hole provided on the connector, a slide rod with one end fixed to the plug, and the other end of the slide rod passing through the through hole on the connector.
[0014] The adjustment structure also includes a through hole on the connector and a slide rod fixed at one end to the plug, with the other end of the slide rod passing through the through hole on the connector. During the adjustment of the lateral distance between the two plugs using bolts, the slide rod slides along the through hole, providing guidance for the plug's movement and ensuring that the plug maintains a stable lateral movement trajectory during spacing adjustment, preventing offset or skew. This allows the two plugs to be more accurately aligned with the vent holes on the flange of the glass oil cup. Simultaneously, the cooperation between the slide rod and the through hole enhances the connection stability between the plug and the connector, preventing the plug from shaking or loosening under load, further ensuring the smoothness of the adjustment process and the reliability of the tool during operation, and improving the tool's adaptation accuracy to vent holes of different spacings.
[0015] In one alternative embodiment, the bolt is parallel to the slide bar.
[0016] The parallel arrangement of the bolts and slide bars further optimizes the stability and adjustment precision of the adjustment structure. When adjusting the lateral distance between the two plugs, the parallel bolts and slide bars work together. The bolts fix the position of the plugs and connectors, while the slide bars guide the plugs along a direction parallel to the bolts, ensuring that the plugs slide smoothly along the preset lateral trajectory during movement, avoiding jamming or offset caused by angular deviations. This parallel structure makes the adjustment of the plug spacing smoother, accurately matching the vent holes on the flanges of glass oil cups with different spacings. It also enhances the overall rigidity of the connection between the plugs and connectors, preventing component deformation or loosening during tool rotation, ensuring a stable and efficient assembly and disassembly process.
[0017] In one alternative embodiment, the connecting member is perpendicular to the crossbeam.
[0018] The connector is positioned perpendicular to the crossbeam, allowing the plug to mate with the vent hole on the flange of the glass oil cup in a direction perpendicular to the crossbeam. This ensures that the plug can be smoothly inserted into the vent hole and fits more tightly.
[0019] In one alternative embodiment, the connecting member is connected to the crossbeam via vertical bolts.
[0020] The connecting component is connected to the crossbeam via vertical bolts. Specifically, the crossbeam has vertically threaded holes, and the connecting component also has vertically threaded holes. The vertical bolts are vertically fitted into these two threaded holes. This connection method allows the relative position between the connecting component and the crossbeam to be adjusted by rotating the vertical bolts, thereby changing the distance between the crossbeam and the bottom of the glass oil cup. This adjustment not only facilitates the unfolding of the mirror, ensuring that the mirror clearly reflects the location of the vent, but also makes it easier to adjust the distance between the handle and the glass oil cup, making it more comfortable and effortless for the operator to hold the handle, improving the convenience of operation, and thus ensuring the smooth assembly and disassembly of the glass oil cup.
[0021] In one alternative embodiment, the beam is a frame with an opening on one side, and the mirror is mounted within this frame.
[0022] In one alternative embodiment, both plugs are located on the side of the connector facing inwards from the frame, and the mirror is positioned directly below the two plugs.
[0023] Both plugs are located on the side of the connector facing inwards from the frame, and the mirror is positioned directly below the two plugs. This arrangement allows the mirror to be precisely aligned with the vent hole on the flange of the glass oil cup above the plug, ensuring that the specific location of the vent hole can be clearly observed in the mirror, thus making it easier to accurately insert the upper end of the plug into the vent hole.
[0024] In one alternative embodiment, a tapered rod is provided on the upper side of the plug.
[0025] The tapered rod on the upper side of the plug is tapered in shape, allowing for smoother insertion into the vent hole of the flange on the glass oil cup. Since the diameter of the vent hole is usually small, the tapered structure guides the plug to accurately align with the hole, reducing resistance and alignment difficulty during insertion. Attached Figure Description
[0026] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0027] Figure 1 This is a schematic diagram of the structure of an adjustable disassembly and assembly tool for a transformer desiccant glass oil cup according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the operation of an adjustable disassembly and assembly tool for a transformer desiccant glass oil cup, according to an embodiment of this utility model.
[0028] Explanation of reference numerals in the attached figures: 1. Crossbeam; 2. Handle; 3. Connecting components; 4. Plug; 5. Mirror; 6. Bolts; 7. Slide bar. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0030] As a crucial component ensuring the safe operation of transformers, the transformer desiccant, through the dual action of oil seal filtration and silica gel adsorption, removes impurities and moisture from the air entering the oil conservator due to oil temperature changes, maintaining the dryness of the insulating oil. When more than 1 / 3 of the silica gel inside the desiccant becomes damp and discolored, it needs to be replaced. This process requires removing the bottom glass oil cup and its upper flange as a whole. These two components are connected to the lower flange of the desiccant via threads, and the glass oil cup and its upper flange can rotate relative to each other.
[0031] Traditional disassembly methods rely on rotating the glass oil cup, using the friction between it and the flange on the upper part of the cup to rotate the latter and complete the disassembly. However, when the friction between the two is less than the friction between the threaded parts, relative rotation occurs, hindering disassembly. In this case, maintenance personnel often use a screwdriver inserted into the vent hole of the flange on the upper part of the oil cup to assist in rotation. However, this method has obvious drawbacks: the vent hole is located on the lower surface of the flange on the upper part of the oil cup, requiring personnel to bend down and get close to the observation position, which is inconvenient; moreover, the diameter of the vent hole is small, making it difficult to insert the screwdriver and easily damaging the hole, which is both time-consuming and laborious, and affects the quality of disassembly and assembly.
[0032] In view of the shortcomings of the above-mentioned traditional disassembly methods, in order to improve the efficiency and quality of glass oil cup disassembly and assembly, and to avoid damage to the vent and connection problems caused by relative rotation of components, it is necessary to design a special tool that is convenient, highly adaptable and can assist in observation. This led to the development of the adjustable disassembly and assembly tool for the glass oil cup of this transformer desiccant.
[0033] The following is combined with Figures 1 to 2 The following describes embodiments of the present invention.
[0034] According to an embodiment of this utility model, an adjustable disassembly and assembly tool for a transformer desiccant glass oil cup is provided, including a crossbeam 1, a handle 2, two connecting parts 3, two plugs 4, and a mirror 5. The handle 2 is mounted on the crossbeam 1 for driving its rotation, and a connecting part 3 is provided at each end of the crossbeam 1; a plug 4 is provided on each connecting part 3, and the upper end of the plug 4 is used to insert into the vent hole of the flange on the glass oil cup; the mirror 5 is mounted on the crossbeam 1 and is located below the plug 4.
[0035] During operation, taking advantage of the position of mirror 5 below plug 4, mirror 5 can clearly reflect the position of the vent hole on the flange of the glass oil cup, eliminating the need for personnel to bend down and observe closely. This solves the problem of inconvenient observation of the vent hole position and facilitates quick and accurate insertion of the upper end of plug 4 into the vent hole. After plug 4 is engaged with the vent hole, the operator holds handle 2 on the crossbeam 1 and rotates handle 2 to rotate the crossbeam 1. The connecting parts 3 at both ends of the crossbeam 1 rotate together with the crossbeam 1, thereby rotating plug 4 on the connecting parts 3. Plug 4, through its interaction with the vent hole, drives the flange on the glass oil cup to rotate, ultimately achieving the rotation of the threaded pair and completing the overall assembly and disassembly of the glass oil cup and its flange.
[0036] This working method makes the disassembly and assembly process more convenient, avoiding the operational difficulties caused by the inconvenience of observation due to traditional tools. At the same time, the cooperation between plug 4 and the vent hole reduces the risk of damage to the vent hole, effectively improving the efficiency and quality of disassembly and assembly of the glass oil cup.
[0037] In one embodiment, the plug 4 is detachably connected to the connector 3 via an adjustment structure for adjusting the lateral distance between the two plugs 4.
[0038] The adjustable structure allows the lateral distance between the two plugs 4 to be flexibly adjusted according to the actual spacing of the vent holes on the glass oil cup flange, thus adapting to different specifications of glass oil cup flanges. When faced with different vent hole spacings, adjusting the lateral distance between the two plugs 4 by operating the adjustable structure ensures that the upper end of the plug 4 is accurately inserted into the corresponding vent hole, guaranteeing good compatibility of the tool with different models of glass oil cup flanges. This further enhances the tool's versatility and practicality, allowing it to function effectively in various working conditions and smoothly complete the disassembly and assembly of glass oil cups.
[0039] Furthermore, the adjustment structure includes a threaded hole on the connector 3, a threaded hole on the plug 4, and a bolt 6 passing through the two threaded holes.
[0040] The adjustment mechanism consists of threaded holes on the connector 3, threaded holes on the plug 4, and bolts 6 passing through the two threaded holes. After determining the position of the plug 4 relative to the connector 3, the bolts 6 are screwed into the connector 3 and the plug 4 in sequence to complete the installation of the plug 4. When it is necessary to change the distance between the two plugs 4, the bolts 6 are rotated in the opposite direction until they are unscrewed from the threaded holes on the plug 4. After determining the distance between the two plugs 4, the bolts 6 are screwed into the threaded holes on the plug 4 again. This further enhances the tool's adaptability to flanges on glass oil cups of different specifications, ensuring smooth disassembly and assembly operations.
[0041] Furthermore, the adjustment structure also includes a through hole provided on the connector 3, a slide rod 7 with one end fixed to the plug 4, and the other end of the slide rod 7 passing through the through hole on the connector 3.
[0042] The adjustment structure also includes a through hole on the connector 3 and a slide rod 7 fixed at one end to the plug 4, with the other end of the slide rod 7 passing through the through hole on the connector 3. During the adjustment of the lateral distance between the two plugs 4 using the bolt 6, the slide rod 7 slides along the through hole, providing guidance for the movement of the plugs 4. This ensures that the plugs 4 maintain a stable lateral movement trajectory during spacing adjustment, preventing offset or skew, and allowing the two plugs 4 to more accurately align with the vent holes on the flange of the glass oil cup. Simultaneously, the cooperation between the slide rod 7 and the through hole enhances the connection stability between the plugs 4 and the connector 3, preventing the plugs 4 from shaking or loosening when rotated under force. This further ensures the smoothness of the adjustment process and the reliability of the tool during operation, improving the tool's adaptation accuracy to vent holes of different spacings.
[0043] Furthermore, bolt 6 and slide bar 7 are parallel to each other.
[0044] The parallel arrangement of bolt 6 and slide bar 7 further optimizes the stability and adjustment accuracy of the adjustment structure. When adjusting the lateral distance between the two plugs 4, the parallel bolt 6 and slide bar 7 work together. Bolt 6 fixes the position of plug 4 and connector 3, while slide bar 7 guides along a direction parallel to bolt 6, ensuring that plug 4 slides smoothly along the preset lateral trajectory during movement, avoiding jamming or offset caused by angular deviation between the two. This parallel structure makes the adjustment of the plug 4 spacing smoother, accurately matching the vent holes on the flange of the glass oil cup with different spacings. At the same time, it enhances the overall rigidity of the connection between plug 4 and connector 3, preventing component deformation or loosening during tool rotation, and ensuring stable and efficient assembly and disassembly processes.
[0045] In one embodiment, the connecting member 3 is perpendicular to the crossbeam 1.
[0046] The connector 3 is positioned perpendicular to the crossbeam 1, allowing the plug 4 to engage with the vent hole on the flange of the glass oil cup in a direction perpendicular to the crossbeam 1, ensuring that the plug 4 can be smoothly inserted into the vent hole and fit more tightly.
[0047] In one embodiment, the connecting member 3 is connected to the crossbeam 1 by vertical bolts. Specifically, the crossbeam 1 has vertically threaded holes, and the connecting member 3 also has vertically threaded holes, with the vertical bolts vertically assembled inside the two threaded holes.
[0048] The connecting piece 3 is connected to the crossbeam 1 by vertical bolts. Specifically, the crossbeam 1 has vertically threaded holes, and the connecting piece 3 also has vertically threaded holes. The vertical bolts are vertically fitted into these two threaded holes. This connection method allows the relative position between the connecting piece 3 and the crossbeam 1 to be adjusted by rotating the vertical bolts, thereby changing the distance between the crossbeam 1 and the bottom of the glass oil cup. This adjustment not only facilitates the unfolding of the mirror 5, ensuring that the mirror 5 can clearly reflect the position of the vent, but also makes it easier to adjust the distance between the handle 2 and the glass oil cup, making it more comfortable and effortless for the operator to hold the handle 2, improving the convenience of operation, and thus ensuring the smooth disassembly and assembly of the glass oil cup.
[0049] In one embodiment, the beam 1 is a frame with an opening on one side, and the mirror 5 is installed inside this frame.
[0050] Furthermore, both plugs 4 are located on the side of the connector 3 facing inwards from the frame, and the mirror 5 is located directly below the two plugs 4.
[0051] The crossbeam 1 is designed as a frame with an opening on one side, and the mirror 5 is installed inside the frame. This structure provides a stable mounting carrier for the mirror 5.
[0052] Both plugs 4 are located on the side of the connector 3 facing the inside of the frame, and the mirror 5 is located directly below the two plugs 4. This arrangement allows the mirror 5 to be precisely aligned with the vent hole of the flange on the glass oil cup above the plug 4, ensuring that the specific location of the vent hole can be clearly observed from the mirror 5, thus making it easier to accurately insert the upper end of the plug 4 into the vent hole.
[0053] In one embodiment, a tapered rod is provided on the upper side of the plug 4.
[0054] The tapered rod on the upper side of plug 4 is tapered in shape, allowing for smoother insertion into the vent hole of the flange on the glass oil cup. Since the diameter of the vent hole is usually small, the tapered structure guides plug 4 to accurately align with the hole, reducing resistance and alignment difficulty during insertion.
[0055] As a specific implementation method, when using the adjustable disassembly tool for the glass oil cup of the transformer desiccant, first, according to the spacing of the vent holes on the flange of the glass oil cup, adjust the lateral distance between the two plugs 4 by adjusting the structure: rotate the bolts 6 on the connector 3 and the plug 4 to move the plug 4 to a suitable position to ensure that the plug 4 can be aligned with the vent hole; at the same time, by rotating the vertical bolt between the connector 3 and the crossbeam 1, adjust the distance between the crossbeam 1 and the bottom of the glass oil cup, so that the mirror 5 can be unfolded and the handle 2 can be more suitable for gripping.
[0056] Next, the position of the vent is reflected by the mirror 5 (located directly below the two plugs 4) inside the frame of the crossbeam 1. The operator observes through the mirror 5 and accurately inserts the cone-shaped rod on the upper side of the plug 4 into the vent. The cone-shaped structure ensures tight contact without damaging the hole.
[0057] Then, the person holds and rotates the handle 2 on the crossbeam 1. The handle 2 drives the crossbeam 1 to rotate, and the perpendicular connecting parts 3 at both ends of the crossbeam 1 rotate accordingly, which in turn drives the plug 4 to rotate. The plug 4, through its interaction with the vent, drives the upper flange of the glass oil cup to rotate, causing the threaded pair between the upper flange of the glass oil cup and the lower flange of the desiccant to rotate, ultimately allowing the glass oil cup and its upper flange to be removed as a whole. Installation is performed by reversing the process. The entire process is efficient and convenient, ensuring the quality of disassembly and assembly.
[0058] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.
Claims
1. An adjustable disassembly and assembly tool for a transformer desiccant glass oil cup, characterized in that, The device includes a crossbeam (1), a handle (2), two connectors (3), two plugs (4), and a mirror (5). The handle (2) is mounted on the crossbeam (1) to drive its rotation. Each end of the crossbeam (1) is provided with a connector (3). Each connector (3) is provided with a plug (4). The upper end of the plug (4) is used to insert into the vent hole of the flange on the glass oil cup. The mirror (5) is mounted on the crossbeam (1) and is located below the plug (4).
2. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 1, characterized in that, The plug (4) is detachably connected to the connector (3) via an adjustment structure for adjusting the lateral distance between the two plugs (4).
3. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 2, characterized in that, The adjustment structure includes a threaded hole on the connector (3), a threaded hole on the plug (4), and a bolt (6) passing through the two threaded holes.
4. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 3, characterized in that, The adjustment structure also includes a through hole provided on the connector (3) and a slide rod (7) with one end fixed to the plug (4), the other end of the slide rod (7) passing through the through hole on the connector (3).
5. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 4, characterized in that, The bolt (6) is parallel to the slide bar (7).
6. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to any one of claims 1-5, characterized in that, The connecting member (3) is perpendicular to the crossbeam (1).
7. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 6, characterized in that, The connecting piece (3) is connected to the crossbeam (1) by vertical bolts.
8. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 1, characterized in that, The crossbeam (1) is a frame with an opening on one side, and the mirror (5) is installed in this frame.
9. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 8, characterized in that, Both of the plugs (4) are located on the side of the connector (3) facing the inside of the frame, and the mirror (5) is located directly below the two plugs (4).
10. The adjustable disassembly and assembly tool for the glass oil cup of the transformer desiccant according to claim 1, characterized in that, A tapered rod is provided on the upper side of the plug (4).
