Continuous online monitoring method for river pollutants

Abstract

The invention belongs to the technical field of water quality monitoring, and particularly relates to a continuous online monitoring method for river pollutants, which comprises unmanned ships and a background controller, a monitoring area of a river is divided into a plurality of continuous monitoring sections, the unmanned ships are deployed in the monitoring sections, and the unmanned ships cruise back and forth in the respective monitoring sections; the unmanned ship carries out sampling detection on the water body according to a set time interval, and detection data is transmitted back to the background controller; when the pollutant block mass needs to be continuously monitored, the unmanned ship is driven to carry out following monitoring after the pollutant block mass enters the monitoring section; and the unmanned ship of each monitoring section sequentially repeats the step S3 until the pollutant block mass is moved out of the monitoring area along with the water flow. According to the invention, by deploying the cruising rule of the unmanned ship, the unmanned ship can realize on-line monitoring in a defined monitoring area, and when a pollutant block mass needing to be focused appears, continuous monitoring of pollutants can be realized through mutual cooperation of the unmanned ships, and an effective basis is provided for subsequent treatment.

Description

Technical Field

[0001] This invention belongs to the field of water quality monitoring technology, specifically relating to a method for continuous online monitoring of pollutants in river channels. Background Technology

[0002] Current traditional monitoring methods for river pollutants primarily rely on fixed monitoring points and manual on-site sampling. Fixed monitoring points, limited by deployment costs and river topography, are typically only set up at key sections or areas, resulting in low density and fragmented coverage. This fails to achieve uniform coverage of the entire river, easily creating blind spots. Furthermore, fixed monitoring points cannot track and monitor key pollution clumps, hindering effective monitoring. Additionally, traditional methods often employ timed, fixed-point data collection, typically 1-2 times daily, which fails to capture instantaneous fluctuations in pollutant concentrations and sudden pollution events, leading to insufficient continuity and completeness of monitoring data. While unmanned surface vessel (USV) monitoring solutions primarily utilize in-situ sampling, offering online monitoring with high measurement frequency and good real-time performance, the water-lifting method used by USVs is prone to clogging of the sampling device's filter by suspended impurities and algae, preventing long-term monitoring and resulting in insufficient applicability and stability. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a method for continuous online monitoring of pollutants in rivers, which can monitor the distribution of pollutants in rivers online and track key polluted areas or sections, providing data support for pollution control.

[0004] The specific technical solution adopted in this invention is as follows:

[0005] A method for continuous online monitoring of river pollutants, comprising an unmanned surface vessel equipped with monitoring sensors and a back-end controller, the method comprising the following steps.

[0006] S1. Divide the river monitoring area into multiple continuous monitoring sections, deploy unmanned vessels within each monitoring section, and have the unmanned vessels travel back and forth within their respective monitoring sections;

[0007] S2. The unmanned vessel takes water samples at set time intervals and transmits the data back to the backend controller.

[0008] S3. When continuous monitoring of pollutant clumps is required, drive the unmanned vessel to follow and monitor the pollutant clumps after they enter the monitoring area;

[0009] S4. The unmanned vessels in each monitoring section repeat step S3 in sequence until the pollutant clumps are moved out of the monitoring area by the water flow.

[0010] The first unmanned vessel in the first monitoring section moves and monitors the pollutant clumps. A second unmanned vessel is set up in the second monitoring section that is connected to the first monitoring section. Before the first unmanned vessel moves to the end point of the first monitoring section, the second unmanned vessel arrives at the starting point of the second monitoring section in advance.

[0011] After the first unmanned vessel reaches the end of the first monitoring section, it immediately returns to the starting point of the first monitoring section and resumes its back-and-forth navigation. The pollutant clump enters the second monitoring section, and the second unmanned vessel moves with the pollutant clump within the second monitoring section. The unmanned vessels in subsequent monitoring sections repeat the above operation until the pollutant clump is moved out of the monitoring area by the water flow.

[0012] After the first unmanned vessel reaches the end of the first monitoring section, it crosses the end of the first monitoring section and follows the pollutant clump into the second monitoring section.

[0013] The second unmanned vessel crossed the starting point of the second monitoring section and entered the first monitoring area, and then cruised back and forth within the first monitoring area.

[0014] The unmanned surface vessels in subsequent monitoring sections repeat the above operations, moving step by step into the next level of monitoring section. The first unmanned surface vessel always follows the pollutant clump until it moves out of the monitoring area. The first unmanned surface vessel remains in the last level of monitoring section and travels back and forth.

[0015] The unmanned vessel is equipped with a measuring tank, which contains a monitoring sensor. The measuring tank is connected to a water-drawing assembly and a drain pump. The water-drawing assembly includes a water-drawing pump and a water-drawing filter rod. The water-drawing filter rod is located at the input end of the water-drawing pump. The water-drawing pump draws water samples with the help of the water-drawing filter rod and injects them into the measuring tank. After the water samples are measured by the monitoring sensor, they are discharged by the drain pump.

[0016] The unmanned vessel has a recessed receiving groove at the bottom, and the water-drawing filter rod is a rod-shaped structure hinged to the bottom of the unmanned vessel. The water-drawing filter rod has the freedom to swing out of the receiving groove.

[0017] The upper end of the water-drawing filter rod is fixedly provided with a swing shaft, and a swing gear is fixedly provided on the swing shaft. The unmanned boat is provided with a drive motor, and the output end of the drive motor meshes with the swing gear to drive the water-drawing filter rod to swing back and forth.

[0018] The water-absorbing filter rod has a hollow tubular structure, including a water-absorbing chamber and a connecting chamber located at the upper end of the water-absorbing chamber. Filter holes are provided on the side wall of the water-absorbing chamber. A purge plug is also provided inside the water-absorbing chamber. The purge plug includes a first baffle, a second baffle, and a connecting pipe located between the two. The first baffle, the second baffle, and the connecting pipe form a purge chamber. An air supply pipe is provided inside the connecting chamber. One end of the air supply pipe is connected to an air supply device, and the other end passes through a partition between the water-absorbing chamber and the connecting chamber and is connected to the connecting pipe. The air supply pipe and the through hole on the partition form a sliding limit. A lifting rack is also provided on the side wall of the air supply pipe. A lifting motor that meshes with the lifting rack is provided inside the connecting chamber. The purge plug has the freedom to reciprocate within the water-absorbing chamber by means of the lifting motor.

[0019] A water pipe is provided between the first baffle and the second baffle, and an annular cutting edge is provided below the second baffle, which abuts against the inner wall of the water intake chamber.

[0020] The bottom of the water-drawing cavity is provided with a water-drawing cap, which includes a limiting plate and a limiting plug. The limiting plate and the water-drawing cap form a limiting cavity, and the limiting plug is located inside the limiting cavity. A return spring is provided between the limiting plug and the water-drawing cap. An adapter for connecting to a water-drawing pump is provided on the side wall of the water-drawing cap. A through limiting hole is provided on the limiting plate. The limiting plug abuts against the limiting plate by means of the push of the return spring, thereby sealing the limiting hole and the adapter on the limiting plate.

[0021] Below the second baffle is an abutting rod that abuts against the limiting plug. The abutting rod pushes against the limiting plug by the movement of the purge plug. After the limiting plug moves, the limiting through hole and the adapter are connected.

[0022] The beneficial effects of this invention are:

[0023] This invention enables unmanned surface vessels (USVs) to conduct online monitoring within designated monitoring areas by adjusting their navigation rules. Furthermore, when pollutant clumps requiring close monitoring are observed, the USVs can cooperate to achieve continuous monitoring of pollutants, providing a valid basis for subsequent remediation.

[0024] This invention improves the water-drawing filter rod of existing sampling devices by using airflow reverse blowing to increase the single-cycle cruising time of unmanned vessels, reduce the number of times personnel need to clean and maintain them, and improve inspection efficiency. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process of the present invention;

[0026] Figure 2 This is a schematic diagram of an unmanned surface vessel.

[0027] Figure 3 A schematic diagram showing the upward-looking direction of the unmanned vessel;

[0028] Figure 4 This is a schematic diagram of the internal structure of the water-absorbing filter rod.

[0029] Figure 5 A schematic diagram showing the top view of the purge plug;

[0030] In the attached diagram, 1 is the water-drawing filter rod, 2 is the receiving tank, 3 is the swing shaft, 4 is the swing gear, 5 is the water-drawing chamber, 6 is the connecting chamber, 7 is the filter hole, 8 is the purge plug, 801 is the first baffle, 802 is the second baffle, 803 is the connecting pipe, 9 is the air supply pipe, 10 is the air supply device, 11 is the lifting motor, 12 is the water pipe, 13 is the cutting edge, 14 is the water-drawing cap, 15 is the limiting plate, 16 is the limiting plug, 17 is the return spring, 18 is the adapter, 19 is the limiting through hole, and 20 is the abutment rod. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0032] Specific embodiments, such as Figure 1 The present invention illustrates a method for continuous online monitoring of pollutants in river channels, comprising an unmanned vessel equipped with monitoring sensors and a back-end controller. The method includes the following steps:

[0033] S1. Divide the river monitoring area into multiple continuous monitoring sections, deploy unmanned vessels within each monitoring section, and have the unmanned vessels travel back and forth within their respective monitoring sections;

[0034] S2. The unmanned vessel takes water samples at set time intervals and transmits the data back to the backend controller.

[0035] S3. When continuous monitoring of pollutant clumps is required, drive the unmanned vessel to follow and monitor the pollutant clumps after they enter the monitoring area;

[0036] S4. The unmanned vessels in each monitoring section repeat step S3 in sequence until the pollutant clumps are moved out of the monitoring area by the water flow.

[0037] In step S3, the selected river monitoring area is divided into monitoring sections, which are numbered sequentially from upstream to downstream according to the direction of river flow. Taking the appearance of pollutant clumps upstream of a monitoring section or in the first monitoring section as an example, after the first unmanned vessel in the first monitoring section detects the pollutant clump, personnel use the back-end controller to drive the first unmanned vessel to follow the pollutant clump for monitoring. In wide river areas, the power of the first unmanned vessel can be turned off so that the hull and the pollutant clump drift together to save energy. A second unmanned vessel is set up in the second monitoring section connected to the first monitoring section. Before the first unmanned vessel moves to the end point of the first monitoring section, the second unmanned vessel arrives at the starting point of the second monitoring section in advance.

[0038] Specific Implementation Example 1,

[0039] To ensure that unmanned vessels always follow the pollutant clump and continuously monitor the concentration changes of the pollutant clump, after the first unmanned vessel reaches the end of the first monitoring section, it immediately returns to the starting point of the first monitoring section and resumes its back-and-forth navigation. The pollutant clump enters the second monitoring section, and the second unmanned vessel moves with the pollutant clump in the second monitoring section. The unmanned vessels in subsequent monitoring sections repeat the above operation until the pollutant clump is moved out of the monitoring area by the water flow.

[0040] In this embodiment, an unmanned vessel is mobilized in each monitoring section to conduct tracking and monitoring, based on the objective situation that the water flow will pass through different monitoring sections in stages. This does not affect the monitoring rhythm of each unmanned vessel, and only requires relay coordination at the junction of two monitoring sections.

[0041] Specific embodiment 2,

[0042] After the first unmanned vessel reaches the end of the first monitoring section, it crosses the end of the first monitoring section and follows the pollutant clump into the second monitoring section.

[0043] The second unmanned vessel crossed the starting point of the second monitoring section and entered the first monitoring area, and then cruised back and forth within the first monitoring area.

[0044] The unmanned surface vessels in subsequent monitoring sections repeat the above operations, moving step by step into the next level of monitoring section. The first unmanned surface vessel always follows the pollutant clump until it moves out of the monitoring area. The first unmanned surface vessel remains in the last level of monitoring section and travels back and forth.

[0045] The difference between this embodiment and Embodiment 1 is that the first unmanned vessel that first discovers the pollutant clump always moves with the pollutant clump and can continuously measure it. The lower-level unmanned vessel does not need to move precisely to the position of the upper-level unmanned vessel to carry out a relatively precise relay, or to avoid the movement path of the upper-level unmanned vessel according to the width of the river. It is only necessary to exchange the inspection area with the upper-level unmanned vessel after it enters the river. It also avoids the changes in the pollutant clump caused by the propellers of multiple unmanned vessels, which helps to obtain the objective situation of pollutant diffusion.

[0046] Specific embodiment 3,

[0047] This embodiment relates to an improvement of the water-drawing filter rod 1 on an unmanned surface vessel. The unmanned surface vessel is equipped with a measuring tank, and a monitoring sensor is installed inside the measuring tank. The measuring tank is connected to a water-drawing assembly and a drain pump. The water-drawing assembly includes a water-drawing pump and a water-drawing filter rod 1. The water-drawing filter rod 1 is installed at the input end of the water-drawing pump. The water-drawing pump draws water samples with the help of the water-drawing filter rod 1 and injects them into the measuring tank. After the water samples are measured by the monitoring sensor, they are discharged by the drain pump.

[0048] Furthermore, such as Figure 2 As shown, the unmanned vessel has a recessed receiving groove 2 at the bottom, and the water-drawing filter rod 1 is a rod-shaped structure hinged to the bottom of the unmanned vessel. The water-drawing filter rod 1 has a swinging degree of freedom to swing out of the receiving groove 2.

[0049] Furthermore, such as Figure 3 and Figure 4 As shown, a swing shaft 3 is fixedly installed on the upper end of the water-drawing filter rod 1, and a swing gear 4 is fixedly installed on the swing shaft 3. A drive motor is installed on the unmanned boat, and the output end of the drive motor meshes with the swing gear 4 to drive the water-drawing filter rod 1 to swing back and forth.

[0050] In this embodiment, the water-drawing filter rod 1 can always be suspended below the hull, or swing to the hull when needed, thereby reducing resistance and saving energy of the battery in the hull by retracting the water-drawing filter rod 1 during maneuvering.

[0051] Furthermore, such as Figure 4As shown, the water-absorbing filter rod 1 has a hollow tubular structure, including a water-absorbing chamber 5 and a connecting chamber 6 disposed at the upper end of the water-absorbing chamber 5. Filter holes 7 are provided on the side wall of the water-absorbing chamber 5. A purge plug 8 is also provided inside the water-absorbing chamber 5. The purge plug 8 includes a first baffle 801, a second baffle 802, and a connecting pipe 803 disposed between them. The first baffle 801, the second baffle 802, and the connecting pipe 803 form a purge chamber. The connecting pipe 803 is provided with a connection to the purge chamber. The air vent is provided in the connecting cavity 6, and an air supply pipe 9 is provided in the connecting cavity 6. One end of the air supply pipe 9 is connected to an air supply device 10, and the other end passes through the partition between the water intake cavity 5 and the connecting cavity 6 and is connected to the connecting pipe 803. The air supply pipe 9 and the through hole on the partition form a sliding limit. A lifting rack is also provided on the side wall of the air supply pipe 9. A lifting motor 11 that meshes with the lifting rack is provided in the connecting cavity 6. The purge plug 8 has the freedom to move back and forth in the water intake cavity 5 by means of the driving of the lifting motor 11.

[0052] The gas supply device 10 of the present invention includes a gas storage cylinder, a gas supply pump, and a solenoid valve. The gas supply pump first fills the gas storage cylinder with gas. After reaching the set gas pressure, the solenoid valve at the gas supply pump and the gas storage cylinder inlet is closed. When the gas pressure in the gas storage cylinder is lower than a preset lower limit, the gas supply pump and the corresponding solenoid valve are activated to replenish the pressure. When purging is required, the purging plug 8 is lowered by the lifting motor 11. At the same time as the purging plug 8 moves down, the solenoid valve at the gas storage cylinder outlet is opened, and gas enters the purging chamber of the purging plug 8 through the gas supply pipe 9. Since the outer side of the purging chamber is sealed by the inner wall of the water intake chamber 5, and the inner wall of the water intake chamber 5 is provided with filter holes 7, the impurities blocked in the filter holes 7 are cleared by the reverse blowing of the airflow, so that the subsequent water intake operation is smooth. This process reduces the frequency of personnel maintenance. During backflush, the propeller stops, and the backflush airflow only diffuses around the hull, improving the uniformity of pollutant mixing around the hull and making the collected water samples more representative. When drawing water for sampling, the measuring tank is first filled with water, and then the water is directly discharged to avoid interference from the original water sample in the water-drawing filter rod 1. At the same time, this water is used to rinse the measuring tank. The hull of this invention is also equipped with a buffer tank, which can be temporarily stored in the buffer tank when the measuring tank is discharged. After the measuring tank is emptied, water is drawn again to measure the water sample in the second tank. After the measurement is completed, both the measuring tank and the buffer tank are emptied. After a set time interval, the above operation is repeated to draw water for measurement.

[0053] Furthermore, such as Figure 4 As shown, a water pipe 12 is provided between the first baffle 801 and the second baffle 802, and an annular cutting edge 13 is provided below the second baffle 802, which abuts against the inner wall of the water intake cavity 5.

[0054] When algae or other organisms clog the filter holes 7 and penetrate deep into the water intake chamber 5, the invading part of the algae can be cut off by moving along the cutting edge 13, so that the subsequent backwash can open the filter holes 7, and the algae remaining in the water intake chamber 5 can be discharged during the water intake operation.

[0055] Furthermore, a water-drawing cap 14 is provided at the bottom of the water-drawing chamber 5. The water-drawing cap 14 includes a limiting plate 15 and a limiting plug 16. The limiting plate 15 and the water-drawing cap 14 form a limiting cavity. The limiting plug 16 is located inside the limiting cavity. A return spring 17 is provided between the limiting plug 16 and the water-drawing cap 14. An adapter 18 for connecting to a water pump is provided on the side wall of the water-drawing cap 14. A through limiting hole 19 is provided on the limiting plate 15. The limiting plug 16 abuts against the limiting plate 15 by means of the push of the return spring 17, sealing the limiting hole 19 and the adapter 18 on the limiting plate 15. A through hole communicating with the outside is provided on the water-drawing cap 14 below the return spring 17, so that the limiting plug 16 can move smoothly.

[0056] Below the second baffle 802, there is an abutment rod 20 that abuts against the limiting plug 16. The abutment rod 20 pushes the limiting plug 16 by the movement of the purge plug 8. After the limiting plug 16 moves, the limiting through hole 19 and the adapter 18 are connected.

[0057] After the algae are scraped off along the cutting edge 13, they temporarily accumulate in the gap between the limiting plate 15 and the second baffle 802. When the limiting plug 16 is pushed open by the abutment rod 20, the water pump is started and the water in the water intake chamber 5 is drawn out through the adapter 18. Due to the setting of the water pipe 12, the water bypasses the purging chamber and impacts the limiting plate 15, thereby generating turbulence on the limiting plate 15, causing the algae accumulated here to be lifted up. Then, it enters the adapter 18 through the limiting through hole 19 and the cavity formed by the retraction of the limiting plug 16, thus preventing the algae from accumulating in the water intake filter rod 1. This helps to increase the duration of a single inspection, reduce the frequency of maintenance, improve applicability and stability, and reduce the labor intensity of personnel.

Claims

1. A method for continuous online monitoring of pollutants in river channels, comprising an unmanned surface vessel equipped with monitoring sensors and a back-end controller, characterized in that: The method includes the following steps. S1. Divide the river monitoring area into multiple continuous monitoring sections, deploy unmanned vessels within each monitoring section, and have the unmanned vessels travel back and forth within their respective monitoring sections; S2. The unmanned vessel samples and tests the water body at set time intervals, and the test data is transmitted back to the background controller. S3. When continuous monitoring of pollutant clumps is required, drive the unmanned vessel to follow and monitor the pollutant clumps after they enter the monitoring section; S4. The unmanned vessels in each monitoring section repeat step S3 in sequence until the pollutant clumps are moved out of the monitoring area by the water flow.

2. The method for continuous online monitoring of river pollutants according to claim 1, characterized in that: The first unmanned vessel in the first monitoring section moves and monitors the pollutant clumps. A second unmanned vessel is set up in the second monitoring section that is connected to the first monitoring section. Before the first unmanned vessel moves to the end point of the first monitoring section, the second unmanned vessel arrives at the starting point of the second monitoring section in advance.

3. The method for continuous online monitoring of river pollutants according to claim 2, characterized in that: After the first unmanned vessel reaches the end of the first monitoring section, it immediately returns to the starting point of the first monitoring section and resumes its back-and-forth navigation. The pollutant clump enters the second monitoring section, and the second unmanned vessel moves with the pollutant clump within the second monitoring section. The unmanned vessels in subsequent monitoring sections repeat the above operation until the pollutant clump is moved out of the monitoring area by the water flow.

4. The method for continuous online monitoring of river pollutants according to claim 2, characterized in that: After the first unmanned vessel reaches the end of the first monitoring section, it crosses the end of the first monitoring section and follows the pollutant clump into the second monitoring section. The second unmanned vessel crossed the starting point of the second monitoring section and entered the first monitoring area, and then cruised back and forth within the first monitoring area. The unmanned surface vessels in subsequent monitoring sections repeat the above operations, moving step by step into the next level of monitoring section. The first unmanned surface vessel always follows the pollutant clump until it moves out of the monitoring area. The first unmanned surface vessel remains in the last level of monitoring section and travels back and forth.

5. The method for continuous online monitoring of river pollutants according to claim 1, characterized in that: The unmanned vessel is equipped with a measuring tank, which contains a monitoring sensor. The measuring tank is connected to a water-drawing assembly and a drain pump. The water-drawing assembly includes a water-drawing pump and a water-drawing filter rod (1). The water-drawing filter rod (1) is located at the input end of the water-drawing pump. The water-drawing pump draws water samples with the help of the water-drawing filter rod (1) and injects them into the measuring tank. After the water samples are measured by the monitoring sensor, they are discharged by the drain pump.

6. The method for continuous online monitoring of river pollutants according to claim 5, characterized in that: The unmanned vessel has a recessed receiving groove (2) at the bottom of the vessel, and the water-drawing filter rod (1) is a rod-shaped structure hinged to the bottom of the unmanned vessel. The water-drawing filter rod (1) has a swinging degree of freedom to swing out of the receiving groove (2).

7. The method for continuous online monitoring of river pollutants according to claim 6, characterized in that: The water-drawing filter rod (1) is fixedly provided with a swing shaft (3) at its upper end, and a swing gear (4) is fixedly provided on the swing shaft (3). The unmanned boat is provided with a drive motor, and the output end of the drive motor meshes with the swing gear (4) to drive the water-drawing filter rod (1) to swing back and forth.

8. The method for continuous online monitoring of river pollutants according to claim 5, characterized in that: The water-drawing filter rod (1) has a hollow tubular structure, including a water-drawing chamber (5) and a connecting chamber (6) located at the upper end of the water-drawing chamber (5). Filter holes (7) are provided on the side wall of the water-drawing chamber (5). A purge plug (8) is also provided inside the water-drawing chamber (5). The purge plug (8) includes a first baffle (801), a second baffle (802), and a connecting pipe (803) located between the two. The first baffle (801), the second baffle (802), and the connecting pipe (803) form a purge chamber. The connecting chamber (6) An air supply pipe (9) is provided inside. One end of the air supply pipe (9) is connected to an air supply device (10), and the other end passes through the partition between the water intake chamber (5) and the connecting chamber (6) and is connected to the connecting pipe (803). The air supply pipe (9) and the through hole on the partition form a sliding limit. A lifting rack is also provided on the side wall of the air supply pipe (9). A lifting motor (11) that meshes with the lifting rack is provided in the connecting chamber (6). The purge plug (8) has the freedom to move back and forth in the water intake chamber (5) by means of the driving of the lifting motor (11).

9. The method for continuous online monitoring of river pollutants according to claim 8, characterized in that: A water pipe (12) is provided between the first baffle (801) and the second baffle (802). An annular cutting edge (13) is provided below the second baffle (802), and the cutting edge (13) abuts against the inner wall of the water intake cavity (5).

10. The method for continuous online monitoring of river pollutants according to claim 9, characterized in that: The bottom of the water-drawing chamber (5) is provided with a water-drawing cap (14). The water-drawing cap (14) includes a limiting plate (15) and a limiting plug (16). The limiting plate (15) and the water-drawing cap (14) form a limiting cavity. The limiting plug (16) is located in the limiting cavity. A return spring (17) is provided between the limiting plug (16) and the water-drawing cap (14). An adapter (18) for connecting to the water-drawing pump is provided on the side wall of the water-drawing cap (14). A through limiting hole (19) is provided on the limiting plate (15). The limiting plug (16) abuts against the limiting plate (15) by means of the push of the return spring (17), sealing the limiting hole (19) and the adapter (18) on the limiting plate (15). Below the second baffle (802) is an abutting rod (20) that abuts against the limiting plug (16). The abutting rod (20) pushes against the limiting plug (16) by means of the movement of the purge plug (8). After the limiting plug (16) moves, the limiting through hole (19) and the adapter (18) are connected.

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