A vacuum sampler for volatile organic compounds in groundwater

Abstract

The present invention discloses a vacuum sampler for volatile organic compounds in groundwater, which relates to the technical field of groundwater sampling and comprises: a vacuum sampling assembly, wherein the vacuum sampling assembly comprises at least: a ring and a U-shaped tube that are clamped with each other, wherein a limiting ring is integrally formed inside the ring; the U-shaped tube has an exhaust seat at one end away from the ring, and the exhaust seat is connected to the vacuum generating end of the vacuum pump by an air pipe; a one-way valve assembly, which is arranged in the ring; a piston, which is sealingly and slidingly arranged in the ring and the U-shaped tube, and the upward position of the piston is limited by the limiting ring; a self-separation assembly and a pull rope connected between the one-way valve group and the piston, and when the piston moves downward, the one-way valve assembly can be released from the blocking state through the cooperation of the self-separation assembly and the pull rope, and the overall stability is high and the degree of automation is high.

Description

Technical Field

[0001] The invention relates to the technical field of groundwater sampling, in particular to a vacuum sampler for volatile organic compounds in groundwater. Background Art

[0002] Groundwater volatile organic compounds (VOCs) refer to volatile organic compounds that enter the groundwater environment due to human activities and cause deterioration of groundwater quality. The definition of VOCs varies from country to country or organization to organization, but generally includes the following characteristics:

[0003] Chemical properties: VOCs are volatile, with boiling points usually between 50°C and 260°C. The saturated vapor pressure at room temperature exceeds 133.32 Pa, and they exist in the air in the form of vapor at room temperature.

[0004] Toxicity: VOCs are migratory, persistent, and toxic, and can enter the human body through the respiratory tract, digestive tract, and skin, causing harm. Their toxicity primarily manifests as teratogenic, carcinogenic, and mutagenic effects. When concentrations reach a certain level in the body, people can experience headaches, nausea, vomiting, fatigue, and, in severe cases, convulsions and coma. They can also damage the liver, kidneys, brain, and nervous system, leading to serious consequences such as memory loss.

[0005] Types: Based on their chemical structure, volatile organic pollutants in groundwater can be further divided into eight categories: alkanes, aromatic hydrocarbons, alkenes, halogenated hydrocarbons, esters, aldehydes, ketones, and other compounds. Common organic compounds include chloroform, methyl chloride, ethyl chloride, benzene, toluene, xylene (o-, m-, and p-), ethylbenzene, and acetone.

[0006] Despite the widespread adoption of various sampling methods in the current field of groundwater sampling technology, sampling for volatile organic compounds (VOCs) remains challenging. A significant issue is the relatively low degree of automation in the sampling process, which relies primarily on manual control to start and end sampling. While this manual control approach offers a degree of flexibility, it is often limited by human factors, such as operator proficiency and reaction speed, making it difficult to achieve high-precision quantitative sampling.

[0007] Furthermore, even with the introduction of programmed control technology, simple timed sampling methods are mostly used. However, the groundwater environment is complex and changeable, and changes in external factors such as water pressure and water velocity often result in timed sampling still being unable to achieve the effect of quantitative sampling. At the same time, whether manual control or program control, a valve body needs to be set at the entrance of the sampling equipment to control the sampling flow. However, in actual use, this method is difficult to implement because the valve body occupies a large volume, and the control of the valve body usually requires additional electrical or hydraulic equipment to achieve. In addition, it is more difficult to clean such a valve body.

[0008] Therefore, it is necessary to provide a vacuum sampler for volatile organic compounds in groundwater to solve the above problems. Summary of the Invention

[0009] To solve the above problems, the present invention provides the following technical solution: a vacuum sampler for volatile organic compounds in groundwater, comprising:

[0010] A winch having a retractable end to which a retractable rope is fixed;

[0011] a base plate fixed to the free end of the retractable rope, and a vacuum pump fixed on the base plate;

[0012] a plurality of vacuum sampling components distributed below the substrate;

[0013] Wherein, the vacuum sampling assembly at least includes:

[0014] A ring and a U-shaped tube are connected to each other, wherein a limiting ring is integrally formed inside the ring; an end of the U-shaped tube away from the ring has an exhaust seat, and the exhaust seat is connected to the vacuum generating end of the vacuum pump via an air pipe;

[0015] a one-way valve assembly disposed in the ring;

[0016] a piston, which is sealingly slidably disposed in the ring and the U-shaped tube, and the upward movement position of the piston is limited by the limiting ring;

[0017] A self-separating component and a pull rope are connected between the one-way valve group and the piston. When the piston moves downward, the one-way valve group can release the blocking state through the cooperation of the self-separating component and the pull rope.

[0018] Further, preferably, the one-way valve assembly includes:

[0019] a retaining ring fixedly embedded in the interior of the ring member;

[0020] a frustoconical plug, which is slidably disposed inside the ring and is capable of sealing the retaining ring;

[0021] a first spring installed between the limiting ring and the truncated cone plug;

[0022] Wherein, the pull rope is connected to the frustum plug.

[0023] Further, preferably, the self-separating component includes:

[0024] An upper separating member having a receiving groove and a first drainage hole communicating with the receiving groove, wherein two symmetrically arranged limiting blocks are slidably arranged in the receiving groove, and a second spring is further provided between the limiting blocks and the receiving groove;

[0025] A lower separator has a T-shaped head on its top, the T-shaped head can pass over the limit block and extend into the accommodating groove, and a honeycomb block is fixedly embedded in the middle of the lower separator, and the honeycomb block is filled with expanded sponge;

[0026] Two symmetrically arranged sliding blocks are slidably arranged in the lower separation piece, the sliding blocks are connected to the honeycomb block, and the sliding blocks correspond to the limiting blocks.

[0027] Furthermore, as a preference, a second drainage hole is provided on the T-shaped head for introducing water into the honeycomb block;

[0028] The bottom of the limiting block is arc-shaped.

[0029] Furthermore, preferably, the pull rope is an elastic rope, and the length of the pull rope satisfies that: when the one-way valve assembly is in a blocked state, the pull rope is always located inside the ring in a natural state.

[0030] Furthermore, as a preference, the pull rope is a non-elastic rope, and the length of the pull rope satisfies: when the one-way valve assembly is in a blocked state, the pull rope can extend out of the ring in a natural state;

[0031] A magnetic block is embedded in the limiting ring;

[0032] The piston is made of magnetic material.

[0033] Furthermore, preferably, a filter is installed at one end of the ring away from the U-shaped tube, and the ring is connected to the base plate by a positioning frame.

[0034] Furthermore, as a preference, the outer wall of the ring is further provided with an outer stepped groove and a first clamping groove;

[0035] The inner wall of the U-shaped tube is provided with an inner stepped groove corresponding to the outer stepped groove, and the outer wall of the U-shaped tube is provided with a second clamping groove;

[0036] Two symmetrically arranged magnetic arc plates are attached to the outside of the ring and the U-shaped tube. Both magnetic arc plates have corresponding magnetic columns so that the two magnetic arc plates are magnetically attracted to each other and form a ring. The inner wall of the magnetic arc plate also has a clamping head corresponding to the first clamping slot and the second clamping slot respectively.

[0037] Compared with the prior art, the present invention provides a vacuum sampler for groundwater volatile organic compounds, which has the following beneficial effects:

[0038] In the present invention, the design of the one-way valve assembly and the self-separation assembly effectively prevents the backflow of water samples and the entry of external gas, thereby ensuring the stability and reliability of sampling. In addition, the provided piston can effectively prevent water from entering the trachea, thereby ensuring the stable operation of the vacuum pump.

[0039] In the present invention, when the vacuum pump is started and the U-shaped tube is vacuumed, a negative pressure environment is formed inside the U-shaped tube. At this time, the piston begins to move downward under the action of the negative pressure and pulls the pull rope to make the conical plug leave the retaining ring, and the groundwater enters the ring and the U-shaped tube through the one-way valve assembly. The overall control is relatively simple and efficient.

[0040] In the present invention, as the water enters the U-shaped tube, the self-separation component realizes self-separation, and the tension of the pull rope disappears. At this time, the elastic force of the first spring resets the conical plug and tightly seals the blocking ring, and the one-way valve assembly returns to the blocked state again. This process ensures the one-way flow of water samples and the stability of the sampling system, and the overall degree of automation is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 these drawings without paying any creative work.

[0042] Figure 1 This is a schematic diagram of the main structure of a vacuum sampler for volatile organic compounds in groundwater;

[0043] Figure 2 A schematic diagram of the structure of a vacuum sampling component in a vacuum sampler for volatile organic compounds in groundwater Figure 1 ;

[0044] Figure 3 The figure is a schematic diagram of the structure of a ring component in a vacuum sampler for volatile organic compounds in groundwater;

[0045] Figure 4This is a schematic diagram of the structure of a U-shaped tube in a vacuum sampler for volatile organic compounds in groundwater;

[0046] Figure 5 The figure is a schematic diagram of the structure of a magnetic arc plate used in a vacuum sampler for volatile organic compounds in groundwater;

[0047] Figure 6 for Figure 2 A schematic diagram of the enlarged structure at point A;

[0048] Figure 7 A schematic diagram of the structure of a vacuum sampling component in a vacuum sampler for volatile organic compounds in groundwater Figure 2 ;

[0049] Figure 8 for Figure 7 Schematic diagram of the enlarged structure at point B.

[0050] The reference numerals are as follows: 1. hoist; 2. retractable rope; 3. base plate; 4. vacuum pump; 5. vacuum sampling assembly; 6. air pipe;

[0051] 51. Ring; 52. U-shaped tube; 53. Magnetic arc plate; 54. One-way valve assembly; 55. Filter; 56. Positioning bracket; 57. Piston; 58. Self-separation assembly; 59. Pull rope; 510. Magnetic block;

[0052] 511, outer stepped groove; 512, first clamping groove; 513, limiting ring;

[0053] 521, inner step groove; 522, second card slot;

[0054] 531, chuck; 532, magnetic column;

[0055] 541, retaining ring; 542, truncated cone plug; 543, first spring; 544, drainage hole;

[0056] 581. Upper separating piece; 582. Lower separating piece; 583. Sliding block; 584. Honeycomb block; 585. First drainage hole; 586. Second drainage hole; 587. Limiting block; 588. Second spring. DETAILED DESCRIPTION

[0057] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned description of the drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, and this is merely a way of distinguishing the objects of the same attributes when describing them in the embodiments of the present application. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment comprising a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0058] Example 1

[0059] Please refer to Figures 1-6 In an embodiment of the present invention, a vacuum sampler for volatile organic compounds in groundwater is provided, comprising:

[0060] A hoist 1 having a retractable end to which a retractable rope 2 is fixed;

[0061] a base plate 3 fixed to the free end of the retractable rope 2, and a vacuum pump 4 fixed on the base plate 3;

[0062] A plurality of vacuum sampling components 5 distributed below the substrate 3;

[0063] Wherein, the vacuum sampling component 5 at least includes:

[0064] A ring 51 and a U-shaped tube 52 are connected to each other, wherein a limiting ring 513 is integrally formed inside the ring 51; an end of the U-shaped tube 52 away from the ring 51 has an exhaust seat, and the exhaust seat is connected to the vacuum generating end of the vacuum pump 4 via an air pipe 6;

[0065] a one-way valve assembly 54 disposed in the ring 51;

[0066] A piston 57 is sealingly and slidably disposed in the ring 51 and the U-shaped tube 52 , and the upward movement position of the piston 57 is limited by the limiting ring 513 ;

[0067] The self-separating component 58 and the pull rope 59 are connected between the one-way valve group 54 and the piston 57. When the piston 57 moves downward, the cooperation of the self-separating component 58 and the pull rope 59 can release the blocking state of the one-way valve group 54.

[0068] The implementation includes the following steps:

[0069] Step 1: Use the retractable function of the winch 1 to steadily lower the base plate 3 and the vacuum sampling assembly 5 thereunder into the groundwater. This process must ensure that the sampling assembly 5 can accurately reach the predetermined sampling depth.

[0070] Step 2: Turn on the vacuum pump 4 to evacuate the U-shaped tube 52. At this point, a negative pressure environment is formed inside the U-shaped tube 52, preparing for the subsequent sampling process.

[0071] Step 3: Under the action of negative pressure, the piston 57 begins to move downward, and drives the frustum plug 542 to move downward together. In this process, the blocking state of the one-way valve assembly 54 is released, allowing groundwater to enter the ring 51 and the U-shaped tube 52.

[0072] Step 4: After the water enters the sampling system, it is self-separated by the self-separation assembly 58. At this time, the cone plug 542 is reset under the elastic force of the first spring 543, and the one-way valve assembly 54 resumes the blocking state again, preventing the water sample from flowing back and the outside air from entering.

[0073] Step 5: After completing the above steps, the water has been successfully collected and stored in the U-shaped tube 52. At this point, the vacuum pump 4 can be turned off, and the base plate 3 and the vacuum sampling assembly 5 below it can be lifted to the ground by the winch 1 for subsequent water sample analysis.

[0074] The entire sampling process is highly automated, reducing the interference of manual operations and improving sampling accuracy and efficiency.

[0075] Through the design of the one-way valve assembly 54 and the self-separation assembly 58, the backflow of water samples and the entry of external gases are effectively prevented, thereby ensuring the stability and reliability of sampling. In addition, the provided piston 57 can effectively prevent water from entering the trachea 6, thereby ensuring the stable operation of the vacuum pump 4.

[0076] In this embodiment, the one-way valve assembly 54 includes:

[0077] A retaining ring 541 is fixedly embedded in the ring member 51;

[0078] A truncated cone plug 542 is slidably disposed inside the ring 51 and is capable of sealing the retaining ring 541 . The truncated cone plug 542 also has a drainage hole 544 .

[0079] A first spring 543 is installed between the limiting ring 513 and the truncated cone plug 542;

[0080] The pull rope 59 is connected to the truncated cone plug 542 .

[0081] During the sampling process, when vacuum pump 4 is activated and evacuates U-tube 52, a negative pressure environment is created inside the tube 52. At this point, piston 57 begins to move downward under the negative pressure, pulling on pull cord 59. The tension of pull cord 59 causes the conical plug 542 to separate from the retaining ring 541, releasing the one-way valve assembly 54 from its blocking state. Groundwater then flows through the one-way valve assembly 54 into the ring 51 and U-tube 52.

[0082] As water enters, the self-separating assembly 58 separates, and the tension of the pull cord 59 disappears. At this point, the elastic force of the first spring 543 resets the cone-shaped plug 542 and tightens the sealing ring 541, returning the one-way valve assembly 54 to its sealed state. This process ensures the one-way flow of the water sample and the stability of the sampling system.

[0083] In addition, the surface of the frustum plug 542 may be specially treated to ensure that it has good sealing performance and wear resistance.

[0084] In this embodiment, the self-separating component 58 includes:

[0085] The upper separating member 581 has a receiving groove and a first drainage hole 585 extending through the receiving groove. Two symmetrically arranged limiting blocks 587 are slidably disposed in the receiving groove. A second spring 588 is further disposed between the limiting blocks 587 and the receiving groove.

[0086] The lower separator 582 has a T-shaped head on its top, which can pass over the limit block 587 and extend into the accommodating groove. The middle part of the lower separator 582 is fixedly embedded with a honeycomb block 584 filled with expanded sponge.

[0087] Two symmetrically arranged sliders 583 are slidably arranged in the lower separation piece 582 . The sliders 583 are connected to the honeycomb block 584 , and the sliders 583 correspond to the limit blocks 587 .

[0088] When it works, it includes the following steps:

[0089] Step 1: When installing the upper separation member 581 and the lower separation member 582 , align the receiving groove of the upper separation member 581 with the T-shaped head of the lower separation member 582 and push downward.

[0090] Step 2: The T-shaped head will pass over the limiting block 587 and extend into the receiving groove. At this time, the limiting block 587 is pushed by the T-shaped head and resets under the action of the second spring 588 to form a limit for the T-shaped head.

[0091] Step 3: When water enters honeycomb block 584, the expandable sponge absorbs a certain amount of water and expands. The expanded sponge and honeycomb block 584 push slider 583, which in turn pushes stopper 587. When stopper 587 is pushed far enough, the T-shaped connector is released, and the upper and lower separators 581 and 582 disengage without manual intervention.

[0092] Step 4: After the separation assembly 58 is separated, the upper separation member 581 rises along with the pull rope 59 to prevent the water sample from flowing back.

[0093] It is worth mentioning that the self-separation component 58 uses an expansion sponge as a trigger element. When a sufficient amount of water enters the expansion sponge, the expansion sponge absorbs water and expands, pushing the slider 583 to move. This mechanism is automatic and consistent, and is not affected by the groundwater flow rate or pressure.

[0094] Furthermore, a second drainage hole 586 is provided on the T-shaped head for introducing water into the honeycomb block 584;

[0095] The bottom of the limiting block 587 is arc-shaped.

[0096] In this embodiment, the pull rope 59 is a non-elastic rope, and the length of the pull rope 59 satisfies: when the one-way valve assembly 54 is in the blocked state, the pull rope 59 can extend out of the ring member 51 in a natural state;

[0097] The limiting ring 513 is embedded with a magnetic block 510;

[0098] The piston 57 is made of magnetic material.

[0099] Then, during the stage of installing the upper separator 581 and the lower separator 582, since the length of the pull rope 59 satisfies the requirement that when the one-way valve assembly 54 is in a blocked state, the pull rope 59 can extend out of the ring 51 in a natural state, the upper separator 581 and the lower separator 582 can be clamped together on the outside of the ring 51. After that, the piston 57 is attached to the bottom of the limiting ring 513, and the magnetic block 510 is used to achieve positioning and adsorption of the piston 57. Finally, the ring 51 and the U-shaped tube 52 can be clamped together.

[0100] In this embodiment, a filter screen 55 is installed at one end of the ring member 51 away from the U-shaped tube 52 , and the ring member 51 is connected to the base plate 3 by a positioning frame 56 .

[0101] In this embodiment, the outer wall of the ring member 51 is further provided with an outer stepped groove 511 and a first clamping groove 512;

[0102] The inner wall of the U-shaped tube 52 is provided with an inner stepped groove 521 corresponding to the outer stepped groove 511 , and the outer wall of the U-shaped tube 52 is provided with a second clamping groove 522 ;

[0103] Two symmetrically arranged magnetic arc plates 53 are attached to the outside of the ring 51 and the U-shaped tube 52. The two magnetic arc plates 53 have corresponding magnetic columns 532 so that the two magnetic arc plates 53 are magnetically attracted to each other and form a ring. The inner wall of the magnetic arc plate 53 also has a clamping head 531 corresponding to the first clamping groove 512 and the second clamping groove 522 respectively.

[0104] By clamping the ring 51 and the U-shaped tube 52 together, the sample in the U-shaped tube 52 can be quickly extracted, and the self-separation component 58 can be quickly cleaned and assembled. After the ring 51 and the U-shaped tube 52 are clamped together, the two magnetic arc plates 53 can limit the axial direction of the two to ensure the clamping effect of the two.

[0105] Example 2

[0106] Please refer to Figure 7 and Figure 8 The difference from Example 1 is that the pull rope 59 is an elastic rope, and the length of the pull rope 59 satisfies that when the one-way valve assembly 54 is in a blocked state, the pull rope 59 is always located inside the ring 51 in a natural state.

[0107] Then, during the stage of installing the upper separator 581 and the lower separator 582, since the pull rope 59 is an elastic rope and the length of the pull rope 59 satisfies: when the one-way valve assembly 54 is in a blocked state, the pull rope 59 is always located inside the ring 51 in a natural state. Therefore, the pull rope 59 can be lengthened, thereby making the upper separator 581 and the lower separator 582 clamped to each other outside the ring 51. After that, the piston 57 is naturally attached to the bottom of the limit ring 513 under the pulling action of the pull rope 59, and finally the ring 51 and the U-shaped tube 52 are clamped to each other.

[0108] Compared with the solution in Example 1, this solution reduces the material requirements for the piston 57 and the installation of the magnetic block 510, but may increase the replacement frequency of the pull rope 59.

[0109] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A vacuum sampler for volatile organic compounds in groundwater, characterized in that: include: A winch (1) having a retractable end, to which a retractable rope (2) is fixed; A base plate (3) is fixed to the free end of the retractable rope (2), and a vacuum pump (4) is fixed on the base plate (3); a plurality of vacuum sampling components (5) distributed below the substrate (3); Wherein, the vacuum sampling component (5) comprises at least: A ring member (51) and a U-shaped tube (52) are mutually engaged, wherein a limiting ring (513) is integrally formed inside the ring member (51); an end of the U-shaped tube (52) away from the ring member (51) has an exhaust seat, and the exhaust seat is connected to the vacuum generating end of the vacuum pump (4) via an air pipe (6); a one-way valve assembly (54) disposed in the ring member (51); a piston (57) which is sealingly slidably disposed in the ring member (51) and the U-shaped tube (52), and the upward movement position of the piston (57) is limited by the limiting ring (513); A self-separating assembly (58) and a pull rope (59) connected between the one-way valve assembly (54) and the piston (57); when the piston (57) moves downward, the one-way valve assembly (54) can be released from its blocked state through the cooperation of the self-separating assembly (58) and the pull rope (59); Wherein, the one-way valve assembly (54) comprises: A retaining ring (541) fixedly embedded in the interior of the ring member (51); A truncated cone plug (542) is slidably disposed inside the ring member (51) and is capable of sealing the retaining ring (541); a first spring (543) installed between the limiting ring (513) and the truncated cone plug (542); Wherein, the pull rope (59) is connected to the truncated cone plug (542); The self-separating assembly (58) comprises: An upper separating member (581) has a receiving groove and a first drainage hole (585) communicating with the receiving groove, two symmetrically arranged limiting blocks (587) are slidably arranged in the receiving groove, and a second spring (588) is further arranged between the limiting blocks (587) and the receiving groove; A lower separating member (582) has a T-shaped head on its top, the T-shaped head being able to pass over the limiting block (587) and extend into the accommodating groove, and a honeycomb block (584) is fixedly embedded in the middle of the lower separating member (582), and the honeycomb block (584) is filled with an expansion sponge; Two symmetrically arranged sliders (583) are slidably arranged in the lower separation member (582), the sliders (583) are connected to the honeycomb block (584), and the sliders (583) correspond to the limit blocks (587).

2. A vacuum sampler for volatile organic compounds in groundwater according to claim 1, characterized in that: The T-shaped head is provided with a second drainage hole (586) for introducing water into the honeycomb block (584); The bottom of the limiting block (587) is arc-shaped.

3. A vacuum sampler for volatile organic compounds in groundwater according to claim 1, characterized in that: The pull rope (59) is an elastic rope, and the length of the pull rope (59) satisfies that: when the one-way valve assembly (54) is in a blocked state, the pull rope (59) is always located inside the ring member (51) in a natural state.

4. A vacuum sampler for volatile organic compounds in groundwater according to claim 1, characterized in that: The pull rope (59) is a non-elastic rope, and the length of the pull rope (59) satisfies: when the one-way valve assembly (54) is in a blocked state, the pull rope (59) can extend out of the ring member (51) in a natural state; A magnetic block (510) is embedded in the limiting ring (513); The piston (57) is made of magnetic material.

5. A vacuum sampler for volatile organic compounds in groundwater according to claim 1, characterized in that: A filter screen (55) is installed at one end of the ring member (51) away from the U-shaped tube (52), and the ring member (51) and the base plate (3) are connected by a positioning frame (56).

6. A vacuum sampler for volatile organic compounds in groundwater according to claim 1, characterized in that: The outer wall of the ring member (51) is further provided with an outer stepped groove (511) and a first clamping groove (512); An inner stepped groove (521) corresponding to the outer stepped groove (511) is formed on the inner wall of the U-shaped tube (52), and a second clamping groove (522) is formed on the outer wall of the U-shaped tube (52); Two symmetrically arranged magnetic arc plates (53) are attached to the outside of the ring member (51) and the U-shaped tube (52), and the two magnetic arc plates (53) are each provided with corresponding magnetic columns (532) so that the two magnetic arc plates (53) are magnetically attracted to each other and form a ring shape. The inner wall of the magnetic arc plate (53) is also provided with a clamping head (531) corresponding to the first clamping groove (512) and the second clamping groove (522), respectively.

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