Low-temperature vacuum extraction system for soil or plant moisture

Abstract

The invention provides a low-temperature vacuum extraction system for soil or plant moisture, which is characterized in that a pre-cooling / heating table, a refrigeration table and a plurality of rod core type pipelines are arranged in automatic extraction equipment, placement positions corresponding to sample tubes are arranged in the rod core type pipelines, and collection test tubes are detachably arranged at the lower parts of the rod core type pipelines; a placement through hole is formed in the pre-cooling / heating table, a pre-cooling pipeline and a heating pipe are wound in the pre-cooling / heating table and correspond to the middle of the rod core type pipeline, a groove is formed in the refrigerating table, and a refrigerating pipeline is wound in the refrigerating table and corresponds to the groove; the refrigerant source is communicated with the pre-cooling pipeline and the refrigerating pipeline; a lifting platform is arranged at the upper part of the automatic extraction equipment, a vacuumizing system is arranged in the lifting platform, a floating end cover is arranged at the bottom of the lifting platform corresponding to a top port of the rod core type pipeline, and the floating end cover is communicated with the vacuumizing system; a control unit is arranged on the automatic extraction equipment and is in control connection with the vertical lifting mechanism and the heating pipe. The method has the advantages of high efficiency, low leakage rate, safety and convenience.

Description

A low-temperature vacuum extraction system for soil or plant moisture Technical Field

[0001] This invention relates to the field of soil and plant research, and in particular to a low-temperature vacuum extraction system for soil or plant moisture. Background Technology

[0002] In ecological and hydrological research, the measurement of indicators such as stable isotopes of water in soil or plants is involved. A fundamental prerequisite for accurate measurement is the complete extraction of water from the soil or plant sample. Currently, low-temperature vacuum extraction is commonly used. This involves freezing soil or plant samples collected in the field to prevent water evaporation. Then, a connecting sample tube and collection tube are constructed as the extraction tubing to completely extract the water from the sample in the sample tube to the collection tube. Since water vaporization at room temperature and pressure requires 100°C, which requires a significant amount of heat, and to increase the transfer rate of water in the extraction tube, the tubing is generally evacuated first. During the vacuuming process, the sample tube needs to be continuously frozen to prevent water loss. After vacuuming, the sample tube is continuously heated while the collection tube is continuously frozen. Under vacuum, the boiling point of water is lowered, so the water in the sample can be evaporated at around 50-80℃. Continuous heating for 60-90 minutes can completely evaporate the water in 20-30 grams of soil or plant sample. At the same time, because the temperature of the collection tube is lower, the vaporized water diffuses from the hot sample tube to the cold collection tube and is frozen solid, thus completing the collection.

[0003] Currently, there are two methods used: manual setup and automated equipment. Manually set up extraction systems typically use glass tubes, which offer good sealing. However, manual setup is cumbersome and requires significant human intervention, limiting operation to 4-5 lines at a time, resulting in very low efficiency. Furthermore, it demands highly skilled operators, requiring approximately one month of training and practice to become proficient. Existing automated extraction equipment can operate approximately 14 extraction lines simultaneously, offering improved efficiency compared to manual setup. However, the need for numerous automatic valves leads to a higher leakage rate, typically exceeding 1 Pa / s. Additionally, existing automated equipment cannot pre-cool sample tubes during the vacuum process, resulting in some evaporation and reduced accuracy. Moreover, both manual setups and existing automated equipment use liquid nitrogen cooling. While this provides excellent cooling, reaching -80 to -90 degrees Celsius, liquid nitrogen is highly volatile, posing significant safety risks and requiring replacement after only two experiments, thus increasing costs. Existing automated extraction equipment still uses a cold trap approach, where multiple collection tubes are placed in the same basin-shaped space. Cooling of the collection tubes is achieved through the surface of the cold trap and air conduction, which is prone to uneven cooling. Furthermore, the high power consumption of the cold trap makes it difficult to expand the number of extraction tubes. Finally, existing manual and automated extraction equipment cannot directly monitor the gas pressure and temperature inside the extraction tubes. Instead, they can only indirectly reflect the conditions inside the extraction tubes through the vacuum level of the vacuum equipment itself and preset heating / cooling parameters. Therefore, the monitoring data may be inaccurate. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention proposes a low-temperature vacuum extraction system for soil or plant moisture.

[0005] A low-temperature vacuum extraction system for soil or plant moisture includes a refrigerant source and an automatic extraction device. The automatic extraction device includes a pre-cooling / heating platform, a cooling platform, and multiple rod-shaped tubes. Each rod-shaped tube has a placement position corresponding to a sample tube on its inner center. A collection tube is detachably mounted on the lower part of each rod-shaped tube. The pre-cooling / heating platform has a placement through-hole corresponding to each rod-shaped tube, and a pre-cooling tube and a heating tube are wound around the center of each rod-shaped tube within the pre-cooling / heating platform. The cooling platform has a groove corresponding to the collection tube, and a cooling tube is wound around the groove inside the cooling platform. The refrigerant source is connected to both the pre-cooling tube and the cooling tube.

[0006] The upper part of the automatic extraction equipment is equipped with a lifting platform through a vertical lifting mechanism. A vacuum system is installed inside the lifting platform. A floating end cap is installed at the bottom of the lifting platform corresponding to the top port of the rod-type pipeline. The floating end cap is connected to the vacuum system.

[0007] The automatic extraction device is also equipped with a control unit, which controls the vertical lifting mechanism and the heating tube.

[0008] Based on the above, an annular plate is provided on the inner middle of the rod-shaped tube corresponding to the sample tube. The inner diameter of the annular plate is smaller than the outer diameter of the sample tube, and multiple vent holes are evenly distributed on the annular plate. A sealing end cap is threaded to the bottom of the rod-shaped tube, and a through hole is opened on the sealing end cap corresponding to the collection test tube.

[0009] Based on the above, the collection tube includes a tube body and an annular component disposed on the outside of the tube body. A first sealing structure is provided at the bottom of the rod-shaped tube corresponding to the annular component. A second sealing structure is provided at the bottom of the floating end cap corresponding to the top port of the rod-shaped tube. The first sealing structure and the second sealing structure respectively include a rubber ring and a beveled port portion. The rubber ring is respectively disposed at the angle between the outer wall of the sampling tube and the annular component and at the angle between the outer wall of the top port of the rod-shaped tube. The beveled port portion is provided at the bottom of the rod-shaped tube and the bottom of the floating end cap, and the beveled port portion is disposed corresponding to the rubber ring.

[0010] Based on the above, the floating end cap is mounted on the lifting platform by a spring, and an electromagnetic valve block is installed inside the lifting platform. The floating end cap is connected to the air inlet of the electromagnetic valve block through a hose, and the exhaust port of the electromagnetic valve block is connected to a vacuum pump. The control unit controls and connects the electromagnetic valve block and the vacuum pump.

[0011] Based on the above, the vertical lifting mechanism includes an electric push rod and a limiting mechanism. A set of electric push rods is vertically arranged on each side of the automatic extraction device, and the bottom of the lifting platform is located at the free extension / retraction end of the electric push rods. The limiting mechanism includes limiting guide posts and limiting guide sleeves. The limiting guide posts are vertically arranged at the four corners of the automatic extraction device, and the limiting guide sleeves are located at the bottom of the lifting platform and sleeved over the limiting guide posts. The control unit controls and connects to the electric push rods.

[0012] Based on the above, the automatic extraction device is also equipped with a sample refrigerator, and a placement slot is provided inside the sample refrigerator for the corresponding sample tube.

[0013] Based on the above, three of the multiple rod-core tubes are test tubes. A temperature sensor is installed in the first rod-core monitoring tube corresponding to the sample tube position. A temperature sensor is installed in the second rod-core monitoring tube corresponding to the bottom position of the collection tube. The vacuum tube of the third rod-core monitoring tube is connected to a vacuum silicon pressure gauge via a solenoid valve. Wires are threaded through the side walls of the first and second rod-core monitoring tubes, and the temperature sensors are connected to the control unit via the wires.

[0014] Based on the above, the automatic extraction device is equipped with a touch screen, and the control unit is communicatively connected to the touch screen.

[0015] Based on the above, an insulation layer is provided on the outside of the refrigeration platform.

[0016] Based on the above, the automatic extraction device is also equipped with a drying tube. One end of the drying tube is connected to the outside air through a solenoid valve, and the other end of the drying tube is connected to the main pipeline of the vacuum system through another solenoid valve.

[0017] This invention has outstanding substantive features and significant progress compared to the prior art, specifically:

[0018] (1) By setting up multiple sets of rod-core tubing, the sample tube and the collection tube are set in the same rod core. The solenoid valve block is only set at the top port of the rod-core tubing and is only used when vacuuming. There is no connecting mechanism or valve between the sample tube and the collection tube. Therefore, the number of tubing that can be operated at the same time is increased to more than 50 and the leakage rate is reduced to 0.2-0.5pa / s, which greatly improves efficiency and accuracy.

[0019] (2) By specially designing the collection tube and the sealing structure, the present invention forms a triangular groove seal that combines the advantages of positive pressure sealing and side pressure sealing, which not only improves the sealing performance but also increases the service life of the sealing rubber ring.

[0020] (3) The present invention avoids the influence of tolerance on sealing performance and equipment by setting floating end caps at the top port of the rod core type pipeline, and greatly increases the number of experimental pipelines;

[0021] (4) By setting up a sample refrigerator, the present invention facilitates the intermediate transfer of samples and collected water samples, avoiding evaporation. At the same time, the pre-cooling pipeline also avoids the evaporation of moisture in the sample tubes during the preparation stage, greatly improving the accuracy.

[0022] (5) The present invention also provides a multi-channel rod core monitoring pipeline, which facilitates direct monitoring of temperature and vacuum inside the rod core, and the monitoring data is more accurate. Attached Figure Description

[0023] Figure 1 is a schematic diagram of the structure of the present invention.

[0024] Figure 2 is a schematic diagram of the internal structure of the automatic extraction device and lifting platform of the present invention.

[0025] Figure 3 is a perspective structural diagram of the rod-core type pipeline of the present invention.

[0026] Figure 4 is a schematic diagram of the cross-sectional structure of the bottom of the rod-core type pipeline of the present invention.

[0027] Explanation of reference numerals in the attached drawings: 1. Automatic extraction device; 2. Lifting platform; 3. Sample refrigerator; 4. Touch screen; 5. Cooling platform; 6. Pre-cooling / heating platform; 7. Solenoid valve block; 8. Limiting guide sleeve; 9. Electric push rod; 10. Rod-type tubing; 11. Rubber ring; 12. Sample tube; 13. Collection tube; 14. Sealing end cap; 15. Ring-shaped piece; 16. Ring-shaped component; 17. Angled end. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] As shown in Figures 1-4, a low-temperature vacuum extraction system for soil or plant moisture includes a refrigerant source and an automatic extraction device 1. The refrigerant source provides the refrigerant medium; in this embodiment, the refrigerant medium is phenyltris(trimethylsiloxane). The refrigerant medium circulates within the pre-cooling and refrigeration pipelines, providing a low temperature of -60°C. This allows the pre-cooling pipeline to freeze the sample tubes 12 during the preparation and vacuuming stages, and the refrigeration pipeline to freeze the collection tubes 13 during the collection stage. The automatic extraction device 1 is equipped with a pre-cooling / heating platform 6, a refrigeration platform 5, and multiple core-type pipelines 10. Each core-type pipeline 10 has a hollow structure, with a placement position corresponding to the sample tube 12 on its inner center for placing the sample tube 12. In this embodiment, the inner diameter of the core-type pipeline 10 is 1-2 mm larger than the outer diameter of the sample tube 12. The lower part of the rod-shaped tube 10 is detachably equipped with a collection test tube 13. A placement through hole is provided on the pre-cooling / heating platform 6 corresponding to each rod-shaped tube 10. In practice, an annular protrusion is provided on the upper outer side of the rod-shaped tube 10. The diameter of this protrusion is larger than the diameter of the placement through hole. Therefore, after the rod-shaped tube 10 passes through the placement through hole, it is secured to the pre-cooling / heating platform 6 by the protrusion. A pre-cooling tube and a heating tube are arranged around the middle of the rod-shaped tube 10 within the pre-cooling / heating platform 6. The pre-cooling tube and heating tube are distributed vertically and are positioned around and close to the placement through hole. The inner diameter of the placement through hole is 1-2 mm larger than the outer diameter of the rod-shaped tube 10, thus facilitating heating of the rod-shaped tube 10. The rod-shaped tube 10 is made of a metal material with good thermal conductivity; in this embodiment, stainless steel is used. The cooling platform 5 has a groove corresponding to the collection tube 13, and a cooling pipe is wound around the groove inside the cooling platform 5. After the rod-shaped tube 10 is placed on the pre-cooling / heating platform 6, the bottom of the collection tube 13 below it is exactly in the groove, which facilitates the cooling pipe to cool the collection tube 13 in the groove. In this embodiment, an insulation layer is provided on the outside of the cooling platform 5 to improve the cooling and insulation effect. The upper part of the automatic extraction device 1 is provided with a lifting platform 2 through a vertical lifting mechanism. A vacuum system is provided inside the lifting platform 2. A floating end cap is provided at the bottom of the lifting platform 2 corresponding to the top port of the rod-shaped tube 10. The floating end cap is connected to the vacuum system. After the rod-shaped tube 10 is placed into the placement through hole, the lifting platform 2 descends and seals the top of the rod-shaped tube 10 through the floating end cap. The vacuum system can then perform vacuum treatment on the inside of the rod-shaped tube 10 and the sample tube 12 and collection tube 13 inside it. The automatic extraction device 1 is also equipped with a control unit, which controls the vertical lifting mechanism and the heating tube.

[0030] In practice, the automatic extraction device 1 is equipped with a touch screen 4, and the control unit is communicatively connected to the touch screen 4 for human-machine interaction. In this embodiment, the control unit is an MCU controller, and the refrigerant source is also a purchased existing device. The automatic extraction device 1 is equipped with quick-connect sockets corresponding to the pre-cooling pipeline and the refrigeration pipeline for connecting to the refrigerant source. The quick-connect sockets, the control unit, and the circuit structure of the device and other units are all applications of existing technology and are not part of the innovation of this application, so they will not be described in detail. In use, the refrigerant source is connected to the pre-cooling pipeline and the refrigeration pipeline, and the refrigerant source and the automatic extraction device 1 are connected to the mains power. Human-machine interaction is performed through the touch screen 4 to control the pre-cooling pipeline to work for pre-cooling, and at the same time, the vertical lifting mechanism is controlled to raise the lifting platform 2, take out the core tubes 10, and install the collection test tubes 13 at the bottom of the core tubes 10. Then, the core tubes 10 are placed into the placement through holes. After all the rod-shaped tubes 10 are placed into the placement through holes, the pre-cooling tubes also lower the overall temperature of the pre-cooling / heating stage 6 to the target low temperature. At this time, the sample tubes 12 are taken out from the laboratory refrigerator and placed into the rod-shaped tubes 10 respectively. The lifting stage 2 is controlled to descend and the top port of the rod-shaped tubes 10 is sealed by the floating end cap. Then, the vacuum system is started to perform a vacuum operation in the rod-shaped tubes 10. After the target vacuum level is reached, the valve of the vacuum tube is closed, the circulation of the pre-cooling tube is stopped, and the circulation of the heating tube and the cooling tube is started at the same time to heat the pre-cooling / heating stage 6 and freeze the collection tubes 13. The heat is used to heat the sample in the sample tubes 12 through the rod-shaped tubes 10. In a vacuum environment and at a relatively low temperature such as 50-80℃, the water in the sample melts and vaporizes. At this time, because the bottom temperature of the collection tubes 13 is low, the vaporized water diffuses into the collection tubes 13 and is frozen into a solid. After reaching the target experimental duration, stop heating and open the valve of the vacuum system to introduce air into the core tube 10 and restore atmospheric pressure. Then, control the vertical lifting system to raise the lifting platform 2, remove the core tube 10, and sequentially remove the collection test tube 13 for refrigeration. After removing the sample tube 12, put the core tube 10 back into the automatic extraction device 1. After all the tubes have been removed, stop the cooling circulation of the cooling pipes and lower the lifting platform 2 to complete the experiment and sampling.

[0031] Specifically, an annular plate 15 is provided on the inner middle of the rod-shaped tube 10 corresponding to the sample tube 12. The inner diameter of the annular plate 15 is smaller than the outer diameter of the sample tube 12, which facilitates the placement of the sample tube 12 on the annular plate 15. Since the inner diameter of the rod-shaped tube 10 is only 1-2 mm larger than the outer diameter of the sample tube 12, the sample tube 12 can be tilted without affecting its use. Multiple ventilation holes are evenly distributed on the annular plate 15 to ensure overall connectivity within the rod-shaped tube 10. A sealing end cap 14 is threaded to the bottom of the rod-shaped tube 10, and a through hole is provided on the sealing end cap 14 corresponding to the collection tube 13. In this embodiment, the collection tube 13 is a specially made test tube. The collection tube 13 includes a test tube body and an annular component 16 disposed on the outside of the test tube body. When in use, after removing the sealing end cap 14, the top of the collection tube 13 is placed into the bottom of the rod-type tube 10, and then the through hole of the sealing end cap 14 is fitted over the bottom of the collection tube 13 and tightened onto the rod-type tube 10, thereby completing the installation of the collection tube 13.

[0032] The bottom of the rod-shaped tube 10 is provided with a first sealing structure corresponding to the annular component 16; the bottom of the floating end cap is provided with a second sealing structure corresponding to the top port of the rod-shaped tube 10. In reality, the outer wall of the sampling tube and the annular component 16 form a right angle at their connection, and the outer side of the top port of the rod-shaped tube 10 is also provided with this angle structure. The first sealing structure and the second sealing structure respectively include a rubber ring 11 and a beveled port portion 17. The rubber ring 11 is respectively located at the angle between the outer wall of the sampling tube and the annular component 16 and at the angle between the outer wall of the top port of the rod-shaped tube 10. The bottom of the rod-shaped tube 10 and the bottom of the floating end cap are respectively provided with the beveled port portion 17, which is provided corresponding to the rubber ring 11. When the sealing end cap 14 is connected to the bottom of the rod-type pipeline 10, and when the floating end cap abuts against the top of the rod-type pipeline 10, the beveled end portion 17 presses against the rubber ring 11, thereby forming a seal. Excessive leakage will cause a decrease in vacuum, thus affecting the boiling point of water vaporization and consequently the extraction rate of water. In reality, both positive pressure seals and lateral pressure seals with the rubber ring 11 located on the sidewall are prone to wear of the rubber ring 11 due to relative movement during connection and disassembly, thereby reducing sealing performance and affecting leakage. The sealing structure in this embodiment has both positive pressure sealing and lateral pressure sealing effects, and the seal does not undergo relative displacement of the rubber ring 11 during connection and disassembly, thus ensuring good sealing performance and significantly extending the service life of the rubber ring 11. Furthermore, there are no connecting structures or valves between the sample tube 12 and the collection tube 13 within the rod-type pipeline 10, greatly improving the sealing effect. In this embodiment, 54 core tubes 10 can be used simultaneously, that is, 54 extraction operations can be performed simultaneously. However, the test leakage rate is only 0.2-0.5 Pa / s. The number of tubes is nearly 4 times higher than that of the existing automatic extraction equipment 1, but the leakage rate is reduced by more than half compared with the existing automatic extraction equipment 1. The efficiency and accuracy are greatly improved.

[0033] In reality, due to manufacturing tolerances, it is difficult to achieve a completely consistent seal across multiple points when sealing multiple points simultaneously. Therefore, this embodiment employs a floating end cap, where the floating end cap is spring-loaded onto the lifting platform 2. The spring specifications are determined based on experimental requirements to avoid rigid connection and sealing by the pressure of the lifting platform 2 with a fixed end cap, thus ensuring that the minimum resistance force during sealing is greater than the required sealing pressure. An electromagnetic valve block 7 is installed inside the lifting platform 2. The floating end cap is connected to the air inlet of the electromagnetic valve block 7 via a flexible hose, and the exhaust port of the electromagnetic valve block 7 is connected to a vacuum pump. In practice, the vacuum pump can be installed inside the lifting platform 2 or within the automatic extraction device 1. When installed within the automatic extraction device 1, it is connected to the electromagnetic valve block 7 via a flexible hose. The control unit controls the connection between the electromagnetic valve block 7 and the vacuum pump.

[0034] Preferably, the automatic extraction device 1 is further equipped with a drying tube. One end of the drying tube is connected to the outside air through a solenoid valve, and the other end is connected to the main pipeline of the vacuum system through another solenoid valve. The solenoid valves at both ends of the drying tube are controlled by a control unit. The solenoid valve at the air inlet of the drying tube is normally closed to prevent moisture from the outside air from entering and affecting the service life of the drying tube. After the moisture extraction operation is completed, although heating is stopped, there is still a certain temperature inside the core tube 10. Since the core tube 10 is in a certain vacuum state, air needs to be introduced to restore atmospheric pressure. However, the outside air may contain moisture, and some of this moisture may vaporize and enter the collection tube 13, affecting accuracy. By setting up the drying tube and opening the solenoid valves at both ends of the drying tube and the solenoid valve block 7 of the vacuum pipeline, the outside air is dried and filtered before being introduced into the core tube 10, which facilitates the restoration of atmospheric pressure inside the core tube 10 without affecting the collection of the collection tube 13.

[0035] Preferably, the automatic extraction device 1 is also equipped with a sample refrigerator 3. The sample refrigerator 3 has a placement slot corresponding to the sample tube 12. Since this embodiment involves a large number of extraction experimental tubes, and the operation requires a certain amount of time, after the sample tubes 12 are taken out of the laboratory refrigerator and before they are all placed into the core-type tubing 10 for pre-cooling, to prevent the sample moisture in the sample tubes 12 from melting, the sample tubes 12 are temporarily stored in the sample refrigerator 3. Similarly, after the extraction operation is completed, the collection tubes 13 are removed from the core-type tubing 10 and placed in the sample refrigerator 3 for temporary storage. Finally, they are all collected and stored in the large laboratory refrigerator, further improving accuracy.

[0036] In this embodiment, the vertical lifting mechanism includes electric push rods 9 and limiting mechanisms. A set of electric push rods 9 are vertically arranged on both sides of the automatic extraction device 1, and the bottom of the lifting platform 2 is located at the free extension / retraction end of the electric push rods 9. The electric push rods 9 are existing equipment and are not part of the innovation of this application, therefore they will not be described in detail. The limiting mechanism includes limiting guide posts and limiting guide sleeves 8. The limiting guide posts are vertically arranged at the four corners of the automatic extraction device 1, and the limiting guide sleeves 8 are located at the bottom of the lifting platform 2 and sleeved outside the limiting guide posts. The control unit controls the connection to the electric push rods 9, and controls the lifting and lowering of the lifting platform 2 through the extension and retraction of the electric push rods 9. The cooperation of the four limiting mechanisms is used to limit the vertical lifting and lowering of the lifting platform 2.

[0037] Preferably, this embodiment has 54 extraction lines, of which 3 are used as monitoring lines. That is, 51 lines are used for extraction experiments and 3 lines are used as real-time monitoring lines. Among these 3 lines, the first rod-core monitoring line has a temperature sensor installed at the position corresponding to the sample tube; the second rod-core monitoring line has a temperature sensor installed at the bottom position corresponding to the collection tube; and the third rod-core monitoring line's vacuum line is connected to a vacuum silicon pressure gauge via a solenoid valve. That is, the first line is used to monitor the temperature at the position corresponding to the sample tube 12, the second line is used to monitor the temperature at the bottom of the collection tube 13, and the third line is used to monitor the vacuum level in the rod-core line 10. Wires are threaded through the side walls of the first and second rod-core monitoring lines, and the temperature sensors are connected to the control unit via the wires. The position of the rod-core line 10, i.e., the rod-core monitoring line, can be set as needed, especially in a position where the heating or cooling effect is relatively weak, such as relatively close to the edge of the pre-cooling / heating platform 6 or the cooling platform 5. The difference between the rod-core monitoring tubing body and other rod-core tubing bodies lies only in that the first and second rod-core monitoring tubing bodies have wires threaded through their side walls. The internal difference is that the first and second rod-core monitoring tubing bodies do not contain sample tubes 12, but collection tubes 13 are normally installed. In this way, direct monitoring of the interior of the rod-core tubing 10 can be performed in this embodiment, resulting in more accurate monitoring data.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A low-temperature vacuum extraction system for soil or plant moisture, characterized in that: The system includes a refrigerant source and an automatic extraction device (1). The automatic extraction device (1) is equipped with a precooling / heating platform (6), a cooling platform (5), and multiple rod-shaped tubes (10). The inner middle of each rod-shaped tube (10) is provided with a placement position corresponding to a sample tube (12). A collection tube (13) is detachably provided at the lower part of each rod-shaped tube (10). The precooling / heating platform (6) has a placement through hole corresponding to each rod-shaped tube (10). The precooling / heating platform (6) is equipped with a precooling tube and a heating tube corresponding to the middle of each rod-shaped tube (10). The cooling platform (5) has a corresponding collection tube. The test tube (13) has a groove, and the cooling platform (5) has a cooling pipe wrapped around the groove; the refrigerant source is connected to the precooling pipe and the cooling pipe respectively; the upper part of the automatic extraction device (1) is provided with a lifting platform (2) through a vertical lifting mechanism, and a vacuum system is provided in the lifting platform (2); the bottom of the lifting platform (2) is provided with a floating end cap corresponding to the top port of the rod-type pipe (10), and the floating end cap is connected to the vacuum system; the automatic extraction device (1) is also provided with a control unit, and the control unit controls the vertical lifting mechanism and the heating pipe.

2. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The inner middle of the rod-core tube (10) is provided with an annular plate (15) corresponding to the sample tube (12). The inner diameter of the annular plate (15) is smaller than the outer diameter of the sample tube (12). Multiple air vents are evenly distributed on the annular plate (15). The bottom of the rod-core tube (10) is threaded with a sealing end cap (14). The sealing end cap (14) is provided with a through hole corresponding to the collection tube (13).

3. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The collection tube (13) includes a tube body and an annular component (16) disposed on the outside of the tube body. The bottom of the rod-type tube (10) is provided with a first sealing structure corresponding to the annular component (16). The bottom of the floating end cap is provided with a second sealing structure corresponding to the top port of the rod-type tube (10). The first sealing structure and the second sealing structure respectively include a rubber ring (11) and a beveled port portion (17). The rubber ring (11) is disposed at the angle between the outer wall of the sampling tube and the annular component (16) and at the angle between the outer wall of the top port of the rod-type tube (10). The bottom of the rod-type tube (10) and the bottom of the floating end cap are respectively provided with the beveled port portion (17), and the beveled port portion (17) is disposed corresponding to the rubber ring (11).

4. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The floating end cap is mounted on the lifting platform (2) by a spring. An electromagnetic valve block (7) is installed inside the lifting platform (2). The floating end cap is connected to the air inlet of the electromagnetic valve block (7) through a hose. The exhaust port of the electromagnetic valve block (7) is connected to a vacuum pump. The control unit controls and connects the electromagnetic valve block (7) and the vacuum pump.

5. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The vertical lifting mechanism includes an electric push rod (9) and a limiting mechanism. A set of electric push rods (9) are vertically arranged on both sides of the automatic extraction device (1). The bottom of the lifting platform (2) is located at the free extension end of the electric push rod (9). The limiting mechanism includes a limiting guide post and a limiting guide sleeve (8). The four corners of the automatic extraction device (1) are vertically arranged with the limiting guide post. The limiting guide sleeve (8) is located at the bottom of the lifting platform (2) and sleeved outside the limiting guide post. The control unit controls and connects to the electric push rod (9).

6. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The automatic extraction device (1) is also equipped with a sample refrigerator (3), and a placement slot is provided in the sample refrigerator (3) corresponding to the sample tube (12).

7. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: Three of the multiple rod-core tubes (10) are test tubes. A temperature sensor is installed in the first rod-core monitoring tube corresponding to the sample tube (12). A temperature sensor is installed in the second rod-core monitoring tube corresponding to the bottom of the collection tube (13). The vacuum tube of the third rod-core monitoring tube is connected to a vacuum silicon pressure gauge through a solenoid valve. Wires are threaded through the side walls of the first and second rod-core monitoring tubes, and the temperature sensors are connected to the control unit through the wires.

8. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The automatic extraction device (1) is equipped with a touch screen (4), and the control unit is communicatively connected to the touch screen (4).

9. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The cooling platform (5) is provided with an insulation layer on its outer side.

10. The low-temperature vacuum extraction system for soil or plant moisture according to claim 1, characterized in that: The automatic extraction device (1) is also equipped with a drying tube. One end of the drying tube is connected to the outside air through a solenoid valve, and the other end of the drying tube is connected to the main pipeline of the vacuum system through another solenoid valve.

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