Top sealing positioning structure for capacitive liquid level gauge and capacitive liquid level gauge

Abstract

The present invention discloses a top sealing positioning structure for a capacitive liquid level gauge and a capacitive liquid level gauge, wherein the top sealing positioning structure comprises a sealing positioning plug, a first sealing ring and a second sealing ring, the sealing positioning plug is provided with a first mounting column for fixing the negative tube sleeve of the capacitive liquid level gauge and a second mounting column for fixing the positive tube sleeve of the capacitive liquid level gauge, the first mounting column and the second mounting column are coaxially arranged, the outer side wall of the first mounting column is provided with a first annular groove and a first mechanical sealing structure, the outer side wall of the second mounting column is provided with a second annular groove and a second mechanical sealing structure, the first sealing ring is embedded in the first annular groove, and the second sealing ring is embedded in the second annular groove. The top sealing positioning structure disclosed by the present invention has the function of realizing the installation and positioning of the positive tube and the negative tube, meeting the concentricity requirements of the positive tube and the negative tube, realizing the double sealing of the positive tube and the negative tube, and is simple to manufacture and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of structures of capacitive liquid level gauges, and in particular to a top sealing positioning structure for a capacitive liquid level gauge and the capacitive liquid level gauge. Background Art

[0002] The capacitive liquid level gauge in the prior art includes a positive tube and a negative tube. The positive tube is inserted into the negative tube. The positive tube and the negative tube are positioned by a seal so that the positive tube and the negative tube are spaced apart. An opening is provided at the bottom of the capacitive liquid level gauge, through which a liquid medium with a height of H can be filled between the positive tube and the negative tube. The capacitance formed by the capacitive liquid level gauge will change with the change of the liquid level height H.

[0003] In order to facilitate fixation, the top sealing positioning structure and the top of the positive tube, and the top mounting flange and the top of the negative tube are generally fixedly connected by welding or extrusion. However, this is not convenient for disassembly and has high production costs. Summary of the invention

[0004] The object of the present invention is to provide a top sealing positioning structure and a liquid level sensor for a capacitive liquid level gauge, which aims to solve the technical problem that the top sealing positioning structure of the capacitive liquid level gauge in the prior art is generally fixedly connected to the top of the positive tube by welding or extrusion, which is inconvenient to disassemble, has low production efficiency and high manufacturing cost.

[0005] To achieve the above object, the solution provided by the present invention is:

[0006] The present invention provides a top sealing and positioning structure for a capacitive liquid level gauge, which is used for installing and fixing a negative tube and a positive tube of the capacitive liquid level gauge. The top sealing and positioning structure comprises a sealing and positioning plug, a first sealing ring and a second sealing ring. The sealing and positioning plug is provided with a first mounting column for fixing the negative tube sleeve and a second mounting column for fixing the positive tube sleeve. The outer diameter of the first mounting column is greater than the outer diameter of the second mounting column and the first mounting column and the second mounting column are coaxially arranged. The outer wall of the first mounting column is concavely provided with a first annular groove and convexly provided with a first mechanical sealing structure for mechanical sealing of the negative tube. The outer wall of the second mounting column is concavely provided with a second annular groove and convexly provided with a second mechanical sealing structure for mechanical sealing of the positive tube. The first sealing ring is embedded in the first annular groove, and the second sealing ring is embedded in the second annular groove.

[0007] Further, the first mechanical sealing structure is a plurality of first annular protrusions protruding from the outer wall of the first mounting column and spaced apart along the axial direction of the first mounting column; the second mechanical sealing structure is a plurality of second annular protrusions protruding from the outer wall of the second mounting column and spaced apart along the axial direction of the second mounting column.

[0008] Furthermore, the first annular groove is arranged in the middle of the first mechanical sealing structure.

[0009] Furthermore, an outer side wall of the first mounting column away from one end of the second mounting column is provided with a first limiting protrusion for axially limiting the negative electrode tube.

[0010] Furthermore, a supporting positioning column for fixing the PCB board is further provided on a side of the first mounting column away from the second mounting column.

[0011] Furthermore, the second annular groove is arranged on a side of the second mechanical sealing structure away from the first mechanical sealing structure and is spaced apart from the second mechanical sealing structure.

[0012] Furthermore, an outer side wall of the second mounting post at one end close to the first mounting post is provided with a second limiting protrusion for axially limiting the positive tube, and an outer diameter of the second limiting protrusion is smaller than an outer diameter of the first mounting post.

[0013] Furthermore, the top sealing and positioning structure also includes a contact sheet and a self-tapping screw. The sealing and positioning plug is provided with a threading hole for the electrode lead to pass through and a positioning hole connected to the threading hole. The contact sheet includes a bottom plate and side plates arranged on opposite sides of the bottom plate. The bottom plate is provided with a mounting hole. The self-tapping screw passes through the mounting hole and then taps into the positioning hole to fix the bottom plate to the bottom of the sealing and positioning plug. The two side plates are spread open to abut against the positive tube.

[0014] The present invention also provides a capacitive liquid level meter, comprising a positive tube, a negative tube and the top sealing positioning structure as described above, wherein the negative tube is sleeved outside the first mounting column and the negative tube is interference fit with the first mounting column, the positive tube is sleeved outside the second mounting column and the positive tube is interference fit with the second mounting column, and the contact sheet is partially clamped between the first mounting column and the positive tube.

[0015] Furthermore, the capacitive liquid level meter also includes a PCB board, an electrode lead and a conductive sheet, one end of the electrode lead is connected to the contact sheet, and the other end is connected to the PCB board after passing through the threading hole, one end of the conductive sheet is electrically connected to the negative electrode tube, and the other end is connected to the PCB board.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] When the top sealing positioning structure disclosed in the present invention is applied to a capacitive liquid level gauge, the first installation column and the negative electrode tube, and the second installation column and the positive electrode tube are first sealed with a sealing ring and then mechanically sealed to achieve double sealing, and the sealing effect is good;

[0018] The U-shaped contact piece and the self-tapping screw are fastened to the inner wall of the positive tube, so that the concentricity between the positive tube and the negative tube is high, the performance of the capacitive level meter is excellent, and the measurement accuracy is high;

[0019] The entire top sealing and positioning structure has a compact overall structure and a sophisticated design, which can effectively reduce the product size and is easy to install. In addition, the top sealing and positioning structure disclosed by the present invention can be manufactured by injection molding, which is simple and can effectively reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0021] Figure 1 It is a cross-sectional view of the top sealing positioning structure, the positive electrode tube and the negative electrode tube for the capacitive liquid level gauge provided by the embodiment of the present invention after being assembled;

[0022] Figure 2 is a cross-sectional view of a sealing positioning plug provided by an embodiment of the present invention;

[0023] Figure 3 is a cross-sectional view of a contact sheet provided by an embodiment of the present invention;

[0024] Figure 4 is a cross-sectional view of the top of a capacitive liquid level meter provided by an embodiment of the present invention;

[0025] Figure 5 is a top view of a negative electrode tube provided by an embodiment of the present invention;

[0026] Figure 6 It is a cross-sectional view of the bottom of the capacitive liquid level meter provided by an embodiment of the present invention.

[0027] In the figure: 10, negative electrode tube; 20, positive electrode tube; 30, sealing and positioning plug; 31, first mounting column; 311, first annular groove; 312, first mechanical sealing structure; 313, first limiting protrusion; 314, supporting and positioning column; 32, second mounting column; 321, second annular groove; 322, second mechanical sealing structure; 323, second limiting protrusion; 324, card slot; 33, threading hole; 331, first through hole; 332, second through hole; 34, positioning hole; 40, first sealing ring; 50. Second sealing ring; 60. PCB board; 70. Contact sheet; 71. Bottom plate; 711. Mounting hole; 72. Side plate; 80. Self-tapping screw; 90. Electrode lead; 100. Conductive sheet; 200. Protective cover; 210. Cavity; 220. Third through hole; 230. Top cover; 240. Flange; 250. Through hole; 260. Exhaust hole; 300. Rubber plug; 400. Positioning seat; 410. Liquid inlet hole; 500. Reinforcing rib plate; 510. Open groove; 600. Third sealing ring. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0030] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0031] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0032] See also Figures 1 to 6 As shown, an embodiment of the present invention provides a top sealing and positioning structure for a capacitive liquid level gauge, which is used for the installation and fixation of the negative tube 10 and the positive tube 20 of the capacitive liquid level gauge, wherein the positive tube 20 is inserted into the negative tube 10, and the top sealing and positioning structure includes a sealing and positioning plug 30, a first sealing ring 40 and a second sealing ring 50, and the sealing and positioning plug 30 is provided with a first mounting column 31 for the negative tube 10 to be sleeved and fixed, and a second mounting column 32 for the positive tube 20 to be sleeved and fixed, the outer diameter of the first mounting column 31 is greater than the outer diameter of the second mounting column 32, and the first mounting column 31 and the second mounting column 32 are coaxially arranged to ensure that the positive tube 20 and the negative tube 10 are also coaxially arranged, and the positive tube 20 and the negative tube 10 do not touch each other. The positive tube 20 and the negative tube 10 in this embodiment are preferably metal tubes made of aluminum material, and of course, other metal tubes that can generate capacitance after combination can also be selected.

[0033] See also Figure 1 to Figure 2 The outer wall of the first mounting column 31 is recessed with a first annular groove 311 and convexly provided with a first mechanical sealing structure 312 for mechanical sealing of the negative electrode tube 10, the outer wall of the second mounting column 32 is recessed with a second annular groove 321 and convexly provided with a second mechanical sealing structure 322 for mechanical sealing of the positive electrode tube 20, the first sealing ring 40 is embedded in the first annular groove 311, and the second sealing ring 50 is embedded in the second annular groove 321, so as to realize double sealing at the top of the positive electrode tube 20 and double sealing at the top of the negative electrode tube 10.

[0034] Preferably, the first mechanical sealing structure 312 is a plurality of first annular protrusions protruding from the outer wall of the first mounting column 31 and spaced apart along the axial direction of the first mounting column 31; the second mechanical sealing structure 322 is a plurality of second annular protrusions protruding from the outer wall of the second mounting column 32 and spaced apart along the axial direction of the second mounting column 32, and the first annular protrusion and the second annular protrusion are inverted sawtooth shapes after cross-section, and after mechanical sealing, external water, ash layers, etc. can be prevented from entering the negative electrode tube 10 or the positive electrode tube 20 from the top of the capacitive liquid level gauge.

[0035] As a preferred embodiment, the first annular groove 311 is provided in the middle of the first mechanical sealing structure 312, and the first sealing ring 40 is also mechanically sealed, so that the sealing positioning plug 30 has oil-proof, waterproof and sealing properties.

[0036] As a preferred embodiment, the outer wall of the first mounting column 31 away from one end of the second mounting column 32 is provided with a first limiting protrusion 313 for axially limiting the negative tube 10 to prevent slippage between the negative tube 10 and the sealing positioning plug 30.

[0037] As a preferred embodiment, a supporting and positioning column 314 for fixing the PCB board 60 is further provided on a side of the first mounting column 31 away from the second mounting column 32 , so as to facilitate the installation and fixation of the PCB board 60 .

[0038] In this embodiment, the second annular groove 321 is arranged on a side of the second mechanical sealing structure 322 away from the first mechanical sealing structure 312 and is spaced apart from the second mechanical sealing structure 322. Since the positive tube 20 is inside the negative tube 10, the requirements between the positive tube 20 and the sealing positioning plug 30 are reduced. Each sealing ring is preferably made of rubber material, and a double seal of mechanical gap sealing and rubber elastic sealing is adopted between the second mounting column 32 and the positive tube 20.

[0039] As a preferred embodiment, the outer wall of the second mounting column 32 at one end close to the first mounting column 31 is provided with a second limiting protrusion 323 for axially limiting the positive tube 20, and the outer diameter of the second limiting protrusion 323 is smaller than the outer diameter of the first mounting column 31 to prevent slippage between the positive tube 20 and the sealing positioning plug 30.

[0040] Please read further Figure 3The top sealing and positioning structure also includes a contact sheet 70 and a self-tapping screw 80. The sealing and positioning plug 30 is provided with a threading hole 33 for the electrode lead 90 to pass through and a positioning hole 34 connected to the threading hole 33. The positioning hole 34 extends from the bottom of the sealing and positioning plug 30 along its axial direction. The contact sheet 70 is preferably U-shaped. The contact sheet 70 includes a bottom plate 71 and side plates 72 arranged on opposite sides of the bottom plate 71. The outer side wall of the second mounting column 32 away from the first mounting column 31 is provided with a side plate 72 connected to the side plate 72. The matching card slot 324, the bottom plate 71 is provided with a mounting hole 711, and the self-tapping screw 80 passes through the mounting hole 711 and directly taps into the positioning hole 34 to fix the bottom plate 71 to the bottom of the sealing positioning plug 30. When the self-tapping screw 80 is tightened, the two side plates 72 are stretched to abut against the positive tube 20, so that the contact piece 70 is squeezed and deformed, and the friction between the sealing positioning plug 30 and the positive tube 20 is increased by deformation, so that the sealing positioning plug 30 and the positive tube 20 are in close contact, forming a good electrical connection. At the same time, in order to facilitate the deformation of the contact piece 70, the length of the card slot 324 in the axial direction of the second mounting column 32 is less than the length of the side plate 72 in the axial direction of the second mounting column 32.

[0041] In order to reduce costs, the threading hole 33 in this embodiment includes a first hole 331 and a second hole 332 set at an angle to the first hole 331. The inner diameter of the second hole 332 is larger than the inner diameter of the first hole 331 to facilitate smoother threading later. The electrode lead 90 passes through the first hole 331 and the second hole 332 in turn for electrical connection with the PCB board 60. The second hole 332 is coaxially arranged with the positioning hole 34.

[0042] Please read further Figure 4 The present invention also provides a capacitive liquid level gauge, comprising a positive tube 20, a negative tube 10 and the top sealing positioning structure as described above, wherein the negative tube 10 is sleeved outside the first mounting column 31 and the negative tube 10 and the first mounting column 31 are interference fit, the positive tube 20 is sleeved outside the second mounting column 32 and the positive tube 20 and the second mounting column 32 are interference fit, a contact sheet 70 is partially clamped between the first mounting column 31 and the positive tube 20, the positive tube 20 and the contact sheet 70 are stably mounted on the first mounting column 31, and the concentricity of the negative tube 10 and the positive tube 20 can be ensured, thereby reducing the manufacturing cost of the capacitive liquid level gauge.

[0043] The capacitive liquid level meter also includes a PCB board 60, an electrode lead 90 and a conductive sheet 100. One end of the electrode lead 90 is connected to the contact sheet 70, and the other end is connected to the PCB board 60 after passing through the mounting hole 711. One end of the conductive sheet 100 is electrically connected to the negative electrode tube 10, and the other end is connected to the PCB board 60 to achieve electrical connection between the negative electrode tube 10, the positive electrode tube 20 and the PCB board 60.

[0044] The capacitive liquid level gauge also includes a protective cover 200, which has a cavity 210 and a third through-hole 220 connected to the cavity 210. The protective cover 200 includes a top cover 230 and a flange 240 sleeved on the outside of the negative tube 10. The top cover 230 is installed on the flange 240 and enclosed with the flange 240 to form the cavity 210 and the third through-hole 220. The external circuit is electrically connected to the PCB board 60 through the third through-hole 220. The PCB board 60, the sealing positioning plug 30, the contact sheet 70, the electrode lead 90, the conductive sheet 100 and the self-tapping screw 80 are all located in the cavity 210. The protective cover 200 can effectively prevent external dust or water from entering the PCB board 60. The flange 240 is also provided with a through-hole 250 for the external screw to pass through, so as to fix the capacitive liquid level gauge on the oil tank.

[0045] Please read further Figure 5 and Figure 6 The capacitive liquid level gauge also includes a rubber plug 300 and a positioning seat 400. The rubber plug 300 is provided with a third mechanical sealing structure for mechanical sealing of the positive tube 20 and a third sealing ring 600 is provided between the rubber plug 300 and the positive tube 20, so as to realize the double sealing of the mechanical gap sealing between the bottom of the positive tube 20 and the rubber plug 300 and the elastic sealing of the rubber part, so as to prevent the liquid to be measured from entering the positive tube 20. The positioning seat 400 is connected to the positive tube 20 and the negative tube 10 at the same time to separate the bottom of the positive tube 20 and the negative tube 10. At the same time, a liquid inlet hole 410 is provided on the positioning seat 400, so that the liquid can enter between the outer wall of the positive tube 20 and the inner wall of the negative tube 10 from the liquid inlet hole 410. The capacitance value of the capacitive liquid level gauge in this embodiment is linearly related to the liquid height between the positive tube 20 and the negative tube 10.

[0046] At the same time, in order to prevent the negative electrode tube 10 from being collided, a plurality of reinforcing ribs 500 are convexly provided on the outer wall of the negative electrode tube 10, and the number of reinforcing ribs 500 is specifically four, and the protective cover 200 is covered on the outside of the reinforcing ribs 500 by injection molding. Specifically, the outer wall of the reinforcing rib 500 away from the positive electrode tube 20 is concavely provided with an opening groove 510, and the opening groove 510 runs through both ends of the reinforcing rib 500 along the axial direction, so there is a mounting opening at each end of the opening groove 510. The capacitive liquid level meter of the present invention also includes eight self-tapping screws 80, two of which pass through the conductive sheet 100 and then tap into the top mounting openings of the two opening grooves 510, so as to fix the conductive sheet 100 with the self-tapping screws 80; the other two self-tapping screws 80 directly pass through the sealing positioning plug 30 and then tap into the top mounting openings of the other two opening grooves 510, and the tensioning force of the self-tapping screws 80 is relied on to make the negative electrode tube 10 and the flange 240 more securely combined. The remaining four self-tapping screws 80 pass through the positioning seat 400 and are driven into the bottom mounting openings of each opening slot 510 , so that the negative electrode tube 10 and the positioning seat 400 are fixed more firmly.

[0047] As a preferred embodiment, an exhaust hole 260 is also provided at the upper end of the capacitive liquid level gauge. The exhaust hole 260 extends from the outer wall of the flange 240 through the reinforcing rib plate 500 to the inner wall of the negative electrode tube 10. When the liquid enters from the bottom liquid inlet hole 410 of the capacitive liquid level gauge, the gas between the positive electrode tube 20 and the negative electrode tube 10 can be discharged from the exhaust hole 260 to avoid pressure difference.

[0048] The installation steps of the capacitive liquid level gauge of the present invention are as follows: the flange 240 is injection molded on the outer side wall of the top of the negative tube 10, the first sealing ring 40 is installed in the first annular groove 311, the second sealing ring 50 is installed in the second annular groove 321, the self-tapping screw 80 passes through the contact sheet 70 and then partially taps into the positioning hole 34, at this time, do not continue to screw the self-tapping screw 80 to avoid deformation of the contact sheet 70, the positive tube 20 is sleeved on the second mounting column 32, the second mechanical sealing structure 322 is mechanically sealed by a machine, and then the self-tapping screw 80 is tightened to deform the contact sheet 70 so that the positive tube 20 and the first mounting column 322 are mechanically sealed, and then the self-tapping screw 80 is tightened to deform the contact sheet 70 so that the positive tube 20 and the first mounting column 322 are mechanically sealed. The installation between the mounting columns 31 is more secure, and then the negative tube 10 is sleeved on the second mounting column 32, and the first mechanical sealing structure 312 and the first sealing ring 40 are mechanically sealed by a machine, and then the PCB board 60, the electrode lead 90 and the conductive sheet 100 are installed and fixed in turn with four self-tapping screws 80, and then the top cover 230 is covered to achieve the top fixed seal of the capacitive liquid level gauge; the rubber plug 300 and the bottom of the positive tube 20 are mechanically sealed by a machine, and then the positioning seat 400 is installed on the bottom of the negative tube 10 through four self-tapping screws 80 and abuts against the rubber plug 300 to achieve the bottom fixed seal of the capacitive liquid level gauge.

[0049] When the top sealing positioning structure disclosed in the present invention is applied to a capacitive liquid level meter, first, the first mounting column 31 and the negative electrode tube 10, and the second mounting column 32 and the positive electrode tube 20 are first sealed with a sealing ring and then mechanically sealed to achieve double sealing, and the sealing effect is good; secondly, the U-shaped contact sheet 70 and the self-tapping screw 80 are fastened to the inner wall of the positive electrode tube 20, so that the concentricity between the positive electrode tube 20 and the negative electrode tube 10 is high, and the performance of the capacitive liquid level meter is excellent and the measurement accuracy is high; furthermore, the entire top sealing positioning structure has a compact overall structure and a sophisticated design, which can effectively reduce the product size and is easy to install. In addition, the top sealing positioning structure disclosed in the present invention can be used by injection molding to simultaneously link the mechanical and electronic parts between the flange 240, the negative electrode tube 10, the positive electrode tube 20 and the PCB board 60, which plays a highly comprehensive role. Plastic injection molding with insulating and oil-resistant properties is used to achieve rapid mass production, simple manufacturing, and can effectively reduce costs.

[0050] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A top sealing positioning structure for a capacitive liquid level gauge, used for installing and fixing the negative electrode tube and the positive electrode tube of the capacitive liquid level gauge, characterized in that: The top sealing and positioning structure comprises a sealing and positioning plug, a first sealing ring and a second sealing ring, the sealing and positioning plug is provided with a first mounting post for fixing the negative tube sleeve and a second mounting post for fixing the positive tube sleeve, the outer diameter of the first mounting post is greater than the outer diameter of the second mounting post and the first mounting post is coaxially arranged with the second mounting post, the outer side wall of the first mounting post is concavely provided with a first annular groove and convexly provided with a first mechanical sealing structure for mechanical sealing of the negative tube, the outer side wall of the second mounting post is concavely provided with a second annular groove and convexly provided with a second mechanical sealing structure for mechanical sealing of the positive tube, the first sealing ring is embedded in the first annular groove, the second sealing ring is embedded in the second annular groove, the top The sealing positioning structure also includes a contact piece and a self-tapping screw. The sealing positioning plug is provided with a threading hole for the electrode lead to pass through and a positioning hole connected to the threading hole. The contact piece includes a bottom plate and side plates arranged on opposite sides of the bottom plate. The outer wall of the second mounting column away from the first mounting column is provided with a card slot adapted to the side plate. The bottom plate is provided with a mounting hole. The self-tapping screw passes through the mounting hole and then enters the positioning hole to fix the bottom plate to the bottom of the sealing positioning plug. The two side plates are stretched open to abut against the positive tube, so that the contact piece is squeezed and deformed, and the friction between the sealing positioning plug and the positive tube is increased by deformation, so that the sealing positioning plug is in close contact with the positive tube. The axial length of the card slot in the second mounting column is less than the axial length of the side plate in the second mounting column.

2. The top sealing positioning structure according to claim 1, characterized in that: The first mechanical sealing structure is a plurality of first annular protrusions protruding from the outer wall of the first mounting column and spaced apart along the axial direction of the first mounting column; the second mechanical sealing structure is a plurality of second annular protrusions protruding from the outer wall of the second mounting column and spaced apart along the axial direction of the second mounting column.

3. The top sealing positioning structure according to claim 1, characterized in that: The first annular groove is arranged in the middle of the first mechanical sealing structure.

4. The top sealing positioning structure according to claim 1, characterized in that: An outer side wall of the first mounting column away from one end of the second mounting column is provided with a first limiting protrusion for axially limiting the negative electrode tube.

5. The top sealing positioning structure according to claim 3, characterized in that: A supporting positioning column for fixing the PCB board is also provided on a side of the first mounting column away from the second mounting column.

6. The top sealing and positioning structure according to claim 1, characterized in that: The second annular groove is arranged on a side of the second mechanical sealing structure away from the first mechanical sealing structure and is spaced apart from the second mechanical sealing structure.

7. The top sealing positioning structure according to claim 5, characterized in that: A second limiting protrusion for axially limiting the positive tube is provided on the outer side wall of the second mounting post at one end close to the first mounting post, and the outer diameter of the second limiting protrusion is smaller than the outer diameter of the first mounting post.

8. A capacitive liquid level meter, characterized in that: It includes a positive tube, a negative tube and the top sealing positioning structure as described in claim 7, the negative tube is sleeved outside the first mounting post and the negative tube and the first mounting post are interference fit, the positive tube is sleeved outside the second mounting post and the positive tube and the second mounting post are interference fit, and the contact sheet is partially clamped between the first mounting post and the positive tube.

9. The capacitive liquid level meter according to claim 8, characterized in that: The capacitive liquid level meter also includes a PCB board, an electrode lead and a conductive sheet, one end of the electrode lead is connected to the contact sheet, and the other end is connected to the PCB board after passing through the threading hole, one end of the conductive sheet is electrically connected to the negative electrode tube, and the other end is connected to the PCB board.

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