Liquid nitrogen back type constant temperature preservation device with safety protection structure

Abstract

The application discloses a liquid nitrogen back type constant temperature preservation device with a safety protection structure, relates to the technical field of low-temperature operation auxiliary equipment for biological samples, and comprises a device shell, a back type liquid nitrogen circulating cavity, a microporous partition plate gas-liquid separation mechanism, a cryopreservation box centering and placing mechanism, a heat preservation mechanism, a heat insulation sealing cover and a frostbite safety protection structure. The whole is designed in a compact integrated mode, the overall size is adapted to a single standard cryopreservation box, the device is light in weight, can be placed on an experiment table top for open cover searching operation, and can be carried by a single person with a single hand for short-distance low-temperature transfer after being closed. The overall layout of the device is a back type structure with sample storage in the center, liquid supply at the bottom and the periphery, the back type liquid nitrogen circulating cavity is arranged in the device shell in a surrounding mode, and a liquid nitrogen low-temperature surrounding environment is formed at the bottom and the periphery of the cryopreservation box; the microporous partition plate gas-liquid separation mechanism is arranged above the bottom liquid nitrogen storage cavity, only allows low-temperature nitrogen gas to uniformly penetrate into the cryopreservation box area, and isolates the direct contact between liquid nitrogen and the cryopreservation box.

Description

Technical Field

[0001] This invention relates to the field of auxiliary equipment for low-temperature operation of biological samples, and in particular to a liquid nitrogen return-type constant temperature preservation device with a safety protection structure. Background Technology

[0002] In biobanks, medical research laboratories, clinical testing centers, and vaccine storage and distribution stations, staff frequently need to retrieve cryovials from liquid nitrogen tanks or ultra-low temperature freezers to locate, verify, sort, select, or transfer samples. Since a standard cryovial typically contains 81 (9×9) or 100 (10×10) cryovials, identifying and locating the target sample by number often takes several minutes or even longer.

[0003] However, the existing operating procedures have the following prominent problems:

[0004] Samples undergo continuous rewarming during the process, leading to quality degradation: After being removed from liquid nitrogen tanks or ultra-low temperature freezers, cryovials are typically placed directly on a room-temperature surface or in a foam box for retrieval. At room temperature, the temperature of the samples inside the cryovials rises rapidly, especially the cryovials located at the edges and surfaces of the box. Multiple studies have shown that repeated freeze-thaw cycles are one of the main causes of decreased cell viability, protein degradation, and nucleic acid breakage. When the retrieval process takes a long time (more than 2-3 minutes), some samples may have already experienced significant temperature fluctuations, and even if they are subsequently returned to the liquid nitrogen tank, their quality has been irreversibly damaged. In current procedures, operators usually place the cryovials on dry ice to slow down the rewarming process, but the temperature of dry ice is only -78.5°C, far lower than the -196°C of liquid nitrogen, which is insufficient for protecting sensitive samples that require strict maintenance of liquid nitrogen temperature.

[0005] Lack of dedicated workbench-level cryogenic maintenance devices: Currently, liquid nitrogen cryogenic equipment on the market mainly falls into two categories: one is large-capacity liquid nitrogen storage tanks, which are bulky, have small openings, and are inconvenient for opening cryovials for retrieval; the other is liquid nitrogen transfer tanks or portable refrigerators, which, although smaller in size, are still primarily designed for transportation and storage, lacking a structural design that allows operators to easily open the lid, directly visually inspect, and manually retrieval of samples inside the cryovials. Operators lack a dedicated auxiliary device in their work that allows them to "place it on the workbench, open the lid, and simultaneously retrieve samples while maintaining cold."

[0006] The lack of convenient cryogenic solutions for short-distance transfer of small quantities of samples: Transferring small quantities of samples (e.g., 1-2 cryopreservation boxes) between laboratories, between floors, and even between institutions within the same city is a frequent operation scenario. Current practices typically use foam boxes with dry ice or small liquid nitrogen containers. The former does not reach sufficiently low temperatures and has a limited duration, while the latter is still too bulky and heavy, making it inconvenient to handle. A lightweight transfer solution is needed that can be carried by a single person with one hand and maintains the liquid nitrogen temperature simply by closing the lid.

[0007] Current temporary operations lack adequate safety precautions: During tabletop searches, residual liquid nitrogen may drip or splash after the cryopreservation boxes are removed from the liquid nitrogen tank, posing a risk of frostbite to the operator's fingers and forearms. Furthermore, in the absence of specialized equipment, operators may directly touch cryogenic metal surfaces with their hands or have their faces near the liquid nitrogen vapor area, posing a risk of frostbite and discomfort. Existing temporary alternatives (foam boxes, dry ice containers, etc.) lack systematic frostbite prevention designs. Summary of the Invention

[0008] To address the problems in existing technologies, such as the lack of a dedicated tabletop-level liquid nitrogen temperature maintenance device during sample retrieval and sorting operations, the time-consuming operation leading to compromised sample warming quality, the lack of a lightweight low-temperature solution for short-distance transfer of small quantities of samples, and the absence of safety protection during temporary operations, this invention provides a portable liquid nitrogen retractable constant-temperature preservation device with a compact structure, convenient operation, the ability to briefly maintain the cryopreservation box at a liquid nitrogen temperature environment for retrieval operations when open, the ability to use it for short-distance low-temperature transfer of small quantities of samples when closed, and an integrated frostbite prevention safety protection structure.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] This invention provides a liquid nitrogen rotary constant temperature preservation device with a safety protection structure, including a device shell, a rotary liquid nitrogen circulation chamber, a microporous baffle gas-liquid separation mechanism, a cryopreservation box placement mechanism, a heat preservation mechanism, and a heat-insulating sealing cover. The cryopreservation box placement mechanism is located in the middle of the inner cavity of the device shell. The rotary liquid nitrogen circulation chamber is arranged around the bottom and periphery of the device shell, forming a low-temperature liquid nitrogen surrounding environment at the bottom and around the cryopreservation box. The microporous baffle gas-liquid separation mechanism is arranged above the rotary liquid nitrogen circulation chamber at the bottom. The microporous baffle gas-liquid separation mechanism is used to allow low-temperature nitrogen to permeate evenly into the cryopreservation box area and to prevent direct contact between liquid nitrogen and the cryopreservation box. The outer wall of the device shell is higher than the top surface of the inner cavity to form a high protective wall against frostbite. The heat preservation mechanism is arranged inside the device shell, and the heat-insulating sealing cover that can be opened and closed is arranged on the top of the device shell.

[0011] In one embodiment, the device housing includes an outer shell and an inner cavity wall. The outer shell is made of stainless steel sheet and is a rectangular box structure with rounded corners. The top edge of the outer shell is 30-40mm higher than the top edge of the inner cavity wall, forming an upwardly extending anti-frostbite high protective wall. The anti-frostbite high protective wall makes the cryopreservation box stored below the top edge of the outer shell.

[0012] In one embodiment, the loop-shaped liquid nitrogen circulation chamber is a closed-loop loop-shaped flow channel structure, which is arranged around the bottom and outer sides of the inner cavity wall. The loop-shaped liquid nitrogen circulation chamber includes a bottom liquid nitrogen storage chamber and a side wall liquid nitrogen circulation channel that are connected. The bottom liquid nitrogen storage chamber is a flat rectangular cavity used to store liquid nitrogen. The side wall liquid nitrogen circulation channel surrounds the outer sides of the inner cavity wall, and the channel cross-section is rectangular with a uniform width of about 10 mm. Liquid nitrogen circulates between the bottom liquid nitrogen storage chamber and the side wall liquid nitrogen circulation channel through natural convection, providing a low-temperature environment for the cryopreservation box storage space from the bottom and all sides simultaneously.

[0013] In one embodiment, the microporous partition gas-liquid separation mechanism includes a microporous partition, a gas-liquid separation buffer chamber, and supporting ribs. The microporous partition is a single piece of stainless steel plate, horizontally fixed inside the inner cavity wall, and has a plurality of micropores evenly distributed on it. The gas-liquid separation buffer chamber is located between the lower surface of the microporous partition and the liquid surface of the bottom liquid nitrogen storage chamber, and the height of the gas-liquid separation buffer chamber is 10-15 mm. The liquid surface of the bottom liquid nitrogen storage chamber is maintained 5 mm below the lower surface of the microporous partition. The low-temperature nitrogen gas generated by the evaporation of liquid nitrogen first fills the gas-liquid separation buffer chamber, diffuses evenly in the buffer chamber, and then slowly permeates through the micropores on the microporous partition into the cryopreservation box storage space to form a low-temperature airflow evenly distributed from bottom to top. The supporting ribs are disposed on the lower surface of the microporous partition, and the bottom end of the supporting ribs is supported on the bottom wall of the bottom liquid nitrogen storage chamber to support the microporous partition and precisely maintain the height of the gas-liquid separation buffer chamber.

[0014] In one embodiment, the cryopreservation box centering mechanism is disposed within the cryopreservation box storage space above the microporous partition. The cryopreservation box centering mechanism includes a support boss disposed on the upper surface of the microporous partition and a positioning slot disposed on the inner surface of the inner cavity wall. The support boss lifts the bottom surface of the cryopreservation box away from the surface of the microporous partition, allowing the low-temperature airflow permeating through the micropores to flow freely and be evenly distributed at the bottom of the cryopreservation box. The positioning slot confines the cryopreservation box to the center of the cavity.

[0015] In one embodiment, the heat preservation mechanism covers the outer side of the U-shaped liquid nitrogen circulation chamber and the inner surface of the outer shell of the device housing; the inner surface of the anti-frostbite high protective wall and the outer surface of the outer shell are provided with an aerogel felt heat insulation layer.

[0016] In one embodiment, the heat-insulating sealing cover is connected to one side edge of the outer shell of the device housing via a hinge; the interior of the heat-insulating sealing cover is filled with heat-insulating material, and a low-temperature resistant sealing strip is provided around the lower surface of the cover body, so that it fits and seals against the top surface of the anti-freezing high protective wall after being closed.

[0017] In one embodiment, a liquid nitrogen filling port is provided on one side of the outer shell. The liquid nitrogen filling port is connected to the loop-shaped liquid nitrogen circulation chamber. A sealing cap is provided at the liquid nitrogen filling port. The liquid nitrogen filling port is used to inject liquid nitrogen directly into the loop-shaped liquid nitrogen circulation chamber from an external liquid nitrogen source.

[0018] In one embodiment, a liquid level gauge or liquid level observation window is also provided at the bottom liquid nitrogen storage chamber; the liquid level gauge is marked with an upper limit scale line, and the liquid level corresponding to the upper limit scale line is located 5 mm below the lower surface of the microporous partition.

[0019] In one embodiment, the height of the anti-frostbite high protective wall is 30-40mm, so that the storage position of the cryopreservation box is accommodated inside the top edge of the outer shell of the device housing.

[0020] The present invention achieves the following technical effects compared to the prior art:

[0021] This invention relates to a liquid nitrogen rotary constant-temperature preservation device with a safety protection structure, comprising a device shell, a rotary liquid nitrogen circulation chamber, a microporous baffle gas-liquid separation mechanism, a centrally located cryopreservation box mechanism, an insulation mechanism, a heat-insulating sealing cover, and a frostbite-preventing safety protection structure. The device features a compact, integrated design, with dimensions adapted to a single standard cryopreservation box. It is lightweight and can be placed on a laboratory table for easy access and retrieval. When closed, it can be carried by a single person with one hand for short-distance cryogenic transfers. The overall layout of the device is a rotary structure with a central sample storage area and a bottom and outer perimeter for liquid supply. The rotary liquid nitrogen circulation chamber is arranged around the inside of the device shell, creating a low-temperature liquid nitrogen environment around the bottom and sides of the cryopreservation box. A microporous baffle gas-liquid separation mechanism is located above the bottom liquid nitrogen storage chamber, allowing only uniform penetration of low-temperature nitrogen into the cryopreservation box area, preventing direct contact between liquid nitrogen and the cryopreservation box. The outer wall of the device shell is higher than the top surface of the inner cavity, forming a high frostbite-preventing protective wall, protecting the operator's hands and forearms during retrieval operations. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a cross-sectional view of the liquid nitrogen circulation constant-temperature preservation device with a safety protection structure (showing the complete internal layered structure of the device and the working principle of liquid nitrogen circulation and cold gas infiltration). Pointing to the microporous partition and gas-liquid separation buffer chamber area, i.e. Figure 2 The enlarged detail diagram shows the area covered. The horizontal arrow in the bottom liquid nitrogen storage chamber indicates the direction of liquid nitrogen convection flow; the dashed arc arrow above the cryopreservation box indicates the cold air protective layer formed by the low-temperature airflow on the top surface of the cryopreservation box.

[0024] Figure 2 This is a partial enlarged view of the core structure at the bottom of a liquid nitrogen recirculating constant temperature preservation device (this image is...). Figure 1 The 4x magnified detailed view of the area within the dashed box shows the fine structure of the microporous baffle gas-liquid separation mechanism and the dimensional relationships of its components. Dimensions: Gas-liquid separation buffer chamber height 12mm, flange height 5mm, support boss height 5mm, liquid surface to baffle distance 5mm, support rib height 5mm, baffle thickness 1.2mm. The upward arrow passing through the micropores indicates the airflow direction of cryogenic nitrogen uniformly permeating from the buffer chamber through the micropores into the cryopreservation box storage space. The temperature gradient is marked on the right: liquid nitrogen surface "-196℃" → buffer chamber "-196℃" → baffle surface "-195℃").

[0025] Figure 3 This is a top view of the liquid nitrogen cryogenic storage device with the lid open (this figure is a top view of the device directly above, with the heat-insulating sealing cover removed (shown by dashed outline), displaying the concentric rectangular nested structure from the outside in, the central positioning of the cryopreservation boxes, the distribution of the microporous array, and the direction of the liquid nitrogen flow channels. The left side is marked with the AA section line and the spacing d).

[0026] Figure 4 This is a detailed cross-sectional view of the liquid nitrogen flow channel on the side wall (this figure is an enlarged horizontal cross-section of the left side wall region of the device, showing the hierarchical relationship and thickness of each structural layer from the outer shell to the cryogenic container. Dimensions: insulation layer ~20mm, liquid nitrogen flow channel 10mm, cold air channel 12mm, outer shell wall thickness 1.5mm, inner cavity wall thickness 1mm. This figure clearly shows the thermal insulation structure of the liquid nitrogen flow channel being sandwiched between the insulation layer and the inner cavity wall, illustrating the unidirectional conduction path of low temperature from liquid nitrogen → inner cavity wall → cold air channel → cryogenic container, as well as the thermal insulation blocking effect in the direction of insulation layer → outer shell).

[0027] Figure 5 This is a plan view of the microporous partition (this figure is a top view of the microporous partition as an independent component, showing the distribution of the microporous array, the flange structure, the projection position of the support ribs, and the installation position of the support boss).

[0028] Figure 6A three-dimensional view of the liquid nitrogen loop-type constant temperature preservation device with safety protection structure in the closed state (this figure is a three-dimensional isometric view of the device with the heat-insulating and sealed lid closed (approximately 30° front right upper view), showing the complete appearance and external functional components of the device when used for short-distance cryogenic transfer).

[0029] Figure 7 This diagram illustrates the device's usage in a tabletop retrieval scenario, showing the operator's hand reaching into the opening mechanism to search for cryopreservation tubes. It emphasizes the protective effect of the high-walled anti-frostbite design on the operator's forearm. The diagram visually demonstrates the device's core features: immediate operation upon opening the lid, continuous cold preservation during operation, and full-process protection from the high-walled design.

[0030] In the diagram: 1. Device housing; 2. Insulation mechanism; 3. U-shaped liquid nitrogen circulation chamber; 4. Microporous partition; 5. Supporting boss; 6. Cryopreservation box; 7. High protective wall against frostbite; 8. Insulated sealing cover; 9. Bottom liquid nitrogen storage chamber; 10. Supporting rib; 11. Gas-liquid separation buffer chamber; 12. Liquid nitrogen filling port; 13. Outer shell; 14. Side wall liquid nitrogen circulation channel; 15. Inner cavity wall; 16. Cold gas rising channel; 17. Insulated handle; 18. Rubber feet. Detailed Implementation

[0031] 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.

[0032] To address the problems in existing technologies, such as the lack of a dedicated tabletop-level liquid nitrogen temperature maintenance device during sample retrieval and sorting operations, the time-consuming operation leading to compromised sample warming quality, the lack of a lightweight low-temperature solution for short-distance transfer of small quantities of samples, and the absence of safety protection during temporary operations, this invention provides a portable liquid nitrogen retractable constant-temperature preservation device with a compact structure, convenient operation, the ability to briefly maintain the cryopreservation box at a liquid nitrogen temperature environment for retrieval operations when open, the ability to use it for short-distance low-temperature transfer of small quantities of samples when closed, and an integrated frostbite prevention safety protection structure.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] like Figures 1 to 7As shown, this invention provides a liquid nitrogen circulating thermostatic storage device with a safety protection structure, including a device shell 1, a circulating liquid nitrogen chamber 3, a microporous partition 4 for gas-liquid separation, a cryopreservation box 6 for central placement, a heat preservation mechanism 2, a heat-insulating sealing cover 8, and a frostbite prevention safety protection structure. The device features a compact, integrated design, with dimensions suitable for a single standard cryopreservation box 6. It is lightweight and can be placed on a laboratory bench for easy access and retrieval. When closed, it can be carried by a single person with one hand for short-distance cryogenic transfers.

[0035] The overall layout of the device is a U-shaped structure with a central sample storage and a bottom and outer perimeter for liquid supply. The U-shaped liquid nitrogen circulation chamber 3 is arranged inside the device shell 1, forming a low-temperature liquid nitrogen environment around the bottom and sides of the cryopreservation box 6. A microporous baffle 4 is installed above the bottom liquid nitrogen storage chamber 9 to separate the gas and liquid, allowing only low-temperature nitrogen gas to permeate evenly into the cryopreservation box 6 area, preventing direct contact between liquid nitrogen and the cryopreservation box 6. The outer wall of the device shell 1 is higher than the top surface of the inner cavity to form a high protective wall 7 to prevent frostbite, protecting the operator's hands and forearms when handling the samples.

[0036] As a preferred technical solution, the device housing 1 includes an outer shell 13 and an inner cavity wall 15. The outer shell 13 is made of stainless steel sheet by stamping and is a rectangular box structure with rounded corners. The top edge of the outer shell 13 is 30-40mm higher than the top edge of the inner cavity wall 15, forming an upwardly extending anti-frostbite high protective wall 7. This anti-frostbite high protective wall 7 ensures that the cryopreservation box 6 is placed below the top edge of the outer shell 13. When the operator reaches into the device to retrieve samples, the outer side of the forearm is naturally shielded by the anti-frostbite high protective wall 7, preventing direct contact with the low-temperature surface of the inner cavity wall 15 or liquid nitrogen vapor, effectively reducing the risk of frostbite.

[0037] As a preferred technical solution, the loop-shaped liquid nitrogen circulation chamber 3 is a closed-loop loop-shaped flow channel structure, arranged around the bottom and outer sides of the inner cavity wall 15. It includes a bottom liquid nitrogen storage chamber 9 and a side wall liquid nitrogen circulation channel 14, which are connected. The bottom liquid nitrogen storage chamber 9 is a flat rectangular cavity used to store liquid nitrogen; the side wall liquid nitrogen circulation channel 14 surrounds the outer sides of the inner cavity wall 15, and the channel cross-section is rectangular with a uniform width of approximately 10 mm. Liquid nitrogen circulates between the bottom and the side walls through natural convection, providing a low-temperature environment to the cryopreservation box 6 storage space from both the bottom and the sides.

[0038] The technical advantage of adopting the loop-shaped surrounding liquid supply structure is that, in the open-top retrieval operation state, although the top opening of the device is exposed to the room temperature environment, the bottom and sides of the cryopreservation box 6 are still tightly surrounded by the liquid nitrogen low-temperature chamber. The loss of cold energy mainly occurs in the direction of the top opening, while the heat intrusion into the bottom and sides of the cryopreservation box 6 is continuously absorbed and compensated by the liquid nitrogen chamber. As a result, the temperature of the sample in the cryopreservation box 6 can still be maintained at a low temperature range close to -196℃ for several minutes after the lid is opened, providing the operator with sufficient time window for retrieval operations.

[0039] As a preferred technical solution, the microporous partition 4 gas-liquid separation mechanism is located at the bottom of the inner cavity wall 15, above the bottom liquid nitrogen storage chamber 9, and includes the microporous partition 4, the gas-liquid separation buffer chamber 11, and the supporting ribs 10. The microporous partition 4 is a single piece of stainless steel plate with a thickness of 1.0 to 1.5 mm, horizontally fixed to the bottom of the inner cavity wall 15. The microporous partition 4 has a number of micropores evenly distributed on it, with a pore diameter of 0.5 to 1.0 mm and an open area ratio of 15% to 20%. The four edges of the microporous partition 4 are provided with upward-folded flanges with a height of 5 mm. The flanges are sealed and welded to the inner cavity wall 15 to prevent liquid nitrogen from flowing around the edge of the partition into the cryopreservation box 6 storage space.

[0040] The gas-liquid separation buffer chamber 11 is located between the lower surface of the microporous partition 4 and the liquid surface of the bottom liquid nitrogen storage chamber 9, with a height of 10-15 mm. The liquid surface of the bottom liquid nitrogen storage chamber 9 is maintained 5 mm below the lower surface of the microporous partition 4. The low-temperature nitrogen gas generated by the evaporation of liquid nitrogen first fills the gas-liquid separation buffer chamber 11, diffuses evenly within the buffer chamber, and then permeates evenly and slowly through several micropores into the storage space of the cryopreservation box 6, forming a low-temperature airflow that is evenly distributed from bottom to top.

[0041] The core technological advantage of this device is that it completely isolates liquid nitrogen from the cryopreservation box 6 and the operators. When the operators are searching for samples, they will not come into contact with the liquid nitrogen, thus avoiding the risk of frostbite caused by liquid nitrogen splashing or dripping. At the same time, even if the device is slightly tilted or vibrated during handling or operation, the liquid nitrogen will not flow out of the micropores in large quantities, ensuring operational safety.

[0042] Support ribs 10 are provided on the lower surface of the microporous partition 4, with 3 to 4 ribs arranged in parallel and a height of 5 mm. The bottom end is supported on the bottom wall of the liquid nitrogen storage chamber 9 at the bottom, which is used to support the microporous partition 4 and precisely maintain the height of the gas-liquid separation buffer chamber 11.

[0043] As a preferred technical solution, the cryopreservation box 6 is centrally placed in the storage space of the cryopreservation box 6 above the microporous partition 4, including a support boss 5 on the upper surface of the microporous partition 4 and a positioning slot on the inner surface of the inner cavity wall 15.

[0044] The supporting boss 5, with a height of 5mm, lifts the bottom surface of the cryopreservation box 6 away from the surface of the microporous partition 4, allowing the low-temperature airflow permeating through the micropores to flow freely and be evenly distributed at the bottom of the cryopreservation box 6. The positioning slot confines the cryopreservation box 6 to the center of the cavity, maintaining a uniform distance of 10-15mm between the cryopreservation box 6 and the inner cavity wall 15. This distance forms a cold air rising channel around the cryopreservation box 6. The low-temperature airflow flows upward from the bottom of the cryopreservation box 6 along the sides of the cryopreservation box 6 through the cold air rising channel, achieving all-around cooling of the bottom and sides of the cryopreservation box 6.

[0045] The technical advantage of this structure is that when operators are searching for samples, they can directly see the cryopreservation tube numbers inside the cryopreservation box 6 after opening the lid. At the same time, the cryopreservation box 6 is always surrounded by a low-temperature airflow from bottom to top, and the temperature of samples in all positions inside the box is kept uniform, avoiding the problem of edge samples warming up first during the search process.

[0046] As a preferred technical solution, the support boss 5 and the positioning slot are made of low-temperature resistant polytetrafluoroethylene material to avoid the thermal bridging effect caused by metal-to-metal contact.

[0047] As a preferred technical solution, the insulation mechanism 2 covers the outer side of the U-shaped liquid nitrogen circulation chamber 3 and the inner surface of the outer shell 13, including a vacuum insulation layer and / or an aerogel insulation layer. The inner surface of the anti-frostbite high protective wall 7 and the outer surface of the outer shell 13 are provided with an aerogel felt insulation layer with a thermal conductivity not higher than 0.02 W / (m·K), which effectively isolates the low temperature from the conduction to the outer shell surface, keeping the temperature of the outer surface of the outer shell 13 within a safe range that will not cause contact frostbite.

[0048] As a preferred technical solution, the device also includes a heat-insulating sealing cover 8, which is connected to one side edge of the outer shell 13 by a hinge and can be flipped open backward. The heat-insulating sealing cover 8 is filled with heat-insulating material, and a low-temperature resistant sealing strip is provided around the lower surface of the cover. After being closed, it fits and seals against the top surface of the anti-freezing high protective wall 7.

[0049] When the lid is open, the device can be used as a tabletop-level sample retrieval low-temperature operating platform; when the lid is closed, the inside of the device forms a closed low-temperature chamber. With the continuous cooling provided by the U-shaped liquid nitrogen circulation chamber 3, the internal temperature can be maintained below -180°C for 30 to 60 minutes, meeting the needs of short-distance low-temperature transfer of small numbers of samples between laboratories, between floors, or between institutions in the same city.

[0050] As a preferred technical solution, a liquid nitrogen filling port 12 is provided on one side of the outer shell 13. The liquid nitrogen filling port 12 is connected to the loop-shaped liquid nitrogen circulation chamber 3 and is equipped with a sealing cap for injecting liquid nitrogen directly into the loop-shaped liquid nitrogen circulation chamber 3 from an external liquid nitrogen source.

[0051] As a preferred technical solution, the device also includes a liquid level gauge or liquid level observation window installed in the bottom liquid nitrogen storage chamber 9 to visually display the remaining liquid nitrogen in the chamber and prompt the operator to replenish liquid nitrogen in a timely manner. The liquid level gauge is marked with an upper limit scale line, and the liquid level corresponding to the upper limit scale line is located 5 mm below the lower surface of the microporous partition 4 to prevent excessive liquid nitrogen from being added and causing the liquid surface to contact the microporous partition 4.

[0052] As a preferred technical solution, the frostbite prevention safety protection structure includes:

[0053] 1. The high protective wall 7 for preventing frostbite has a height of 30-40mm, so that the storage position of the cryopreservation box 6 is significantly lower than the top edge of the outer shell 13, and the forearm of the operator is not directly exposed to the low temperature surface when reaching for samples;

[0054] 2. The microporous partition 4 gas-liquid separation mechanism completely isolates liquid nitrogen from the storage space of the cryopreservation box 6, eliminating the risk of frostbite caused by liquid nitrogen splashing or dripping during operation;

[0055] 3. The aerogel felt insulation layer on the outer surface of the outer shell 13 and the inner surface of the anti-freeze high protective wall 7 prevents low temperature from being conducted outward, ensuring that the outer surface of the outer shell 13 can be safely touched;

[0056] 4. The outer surface of the outer shell 13 has a hydrophobic anti-frost coating to prevent water vapor from condensing into frost on the low-temperature surface and to prevent the frost melt water from dripping into the cavity and contaminating the sample.

[0057] Compared with the prior art, the present invention has the following characteristics:

[0058] 1. Solving the problem of sample warming during sample retrieval: The U-shaped liquid nitrogen circulation chamber 3 forms a low-temperature enclosure for the cryopreservation box 6 from the bottom and all sides. Combined with the gas-liquid separation mechanism of the microporous partition 4, a uniform low-temperature airflow is continuously supplied from bottom to top. This allows the sample temperature inside the cryopreservation box 6 to be maintained at a low temperature range close to -196℃ for several minutes when the operator opens the lid to retrieve the sample. This effectively avoids irreversible damage to sample quality caused by repeated freeze-thaw cycles and significantly improves the quality assurance level during sample handling.

[0059] 2. Filling the gap in benchtop liquid nitrogen temperature control devices: This device is designed to be placed on the laboratory benchtop, allowing operators to open the lid and directly access the samples in the cryopreservation box 6. It fills the functional gap in existing liquid nitrogen equipment that lacks the ability to "operate with the lid open and keep cold during operation", enabling routine high-frequency operations such as sample retrieval, verification, and sorting to be completed easily in a liquid nitrogen temperature environment.

[0060] 3. Also has the function of short-distance cryogenic transfer: After being sealed, thanks to the continuous cooling of the U-shaped liquid nitrogen chamber and the heat insulation performance of the insulation structure, the temperature inside the chamber can be maintained below -180℃ for 30 to 60 minutes. This meets the short-distance cryogenic transfer needs of 1 to 2 cryogenic boxes between laboratories, between floors, or between institutions in the same city, replacing the traditional foam box plus dry ice or small liquid nitrogen tank solution. It is more convenient to operate and the temperature is lower.

[0061] 4. Systematic Frostbite Prevention and Safety Protection: Through multiple measures such as the frostbite-proof high-wall shield 7 to protect the forearm, the microporous partition 4 to isolate liquid nitrogen, the outer heat insulation layer to block low temperature conduction, and the anti-frost coating to prevent condensation, a systematic frostbite prevention and safety protection system is constructed for tabletop operation scenarios. This allows operators to perform sample retrieval operations without wearing heavy low-temperature protective gloves, improving operational flexibility and safety.

[0062] 5. Lightweight and compact, easy to operate: The device's external dimensions are adapted to a single standard cryopreservation box 6. It has a compact structure and is lightweight, and can be placed on any laboratory table. Before use, simply inject liquid nitrogen and place it in the cryopreservation box 6 to start operation. The operation process is simple and intuitive, requiring no training.

[0063] Example 1

[0064] Countertop search operation mode

[0065] See Figures 1 to 4 This embodiment provides a method for using a liquid nitrogen recirculating constant temperature preservation device with a safety protection structure in a tabletop sample retrieval scenario.

[0066] 1. Overall structure of the device

[0067] The device in this embodiment features a compact, integrated design with overall dimensions of approximately 180mm × 180mm × 200mm (length × width × height), a weight of approximately 2.5kg (excluding liquid nitrogen), and a total weight of approximately 3.5kg when filled with liquid nitrogen. The device mainly consists of a housing 1, a U-shaped liquid nitrogen circulation chamber 3, a microporous baffle 4 (gas-liquid separation mechanism), a cryopreservation box 6 (centrally placed mechanism), a thermal insulation mechanism 2, a heat-insulating sealing cover 8, and a frostbite prevention safety protection structure.

[0068] The device housing 1 includes an outer shell 13 and an inner cavity wall 15. The outer shell 13 is made of 304 stainless steel sheet and has a rounded rectangular box structure. The outer surface is coated with a hydrophobic anti-frost coating, and the four corners of the bottom are equipped with anti-slip rubber feet 18 to ensure stability and prevent slippage when placed on a laboratory table. The top edge of the outer shell 13 is 35mm higher than the top edge of the inner cavity wall 15, forming a high protective wall 7 to prevent frostbite.

[0069] 2. U-shaped liquid nitrogen circulation chamber 3

[0070] The U-shaped liquid nitrogen circulation chamber 3 is integrally bent and welded from 316L stainless steel, including a bottom liquid nitrogen storage chamber 9 and a side wall liquid nitrogen circulation channel 14, which are connected at the bottom to form a closed loop. The bottom liquid nitrogen storage chamber 9 is a flat rectangular cavity located below the bottom of the inner cavity wall 15. The side wall liquid nitrogen circulation channel 14 surrounds the inner cavity wall 15, with a channel width of approximately 10mm.

[0071] Liquid nitrogen is injected into the U-shaped liquid nitrogen circulation chamber 3 through the liquid nitrogen filling port 12 on the side of the device, filling the bottom liquid nitrogen storage chamber 9 and the side wall liquid nitrogen circulation channel 14. Under normal use, the liquid nitrogen circulates naturally in the chamber through an evaporation-convection mechanism, providing a continuous liquid nitrogen temperature environment to the cryopreservation box 6 storage space from the bottom and all sides.

[0072] 3. Microporous baffle 4 gas-liquid separation mechanism

[0073] See Figure 2 and Figure 5 The microporous partition 4 is a 316L stainless steel plate with a thickness of 1.2mm, horizontally fixed to the bottom of the inner cavity wall 15. Micropores are evenly distributed on the microporous partition 4, with a diameter of 0.8mm, a spacing of 2.5mm, and an opening rate of approximately 18%. The microporous partition 4 has a 5mm upward-folded flange around its four edges, which is fully welded to the inner cavity wall 15 for sealing.

[0074] The gas-liquid separation buffer chamber 11 is located between the lower surface of the microporous partition 4 and the liquid surface of the bottom liquid nitrogen storage chamber 9, with a height of 12 mm. The liquid nitrogen level in the bottom liquid nitrogen storage chamber 9 is controlled at 5 mm below the lower surface of the microporous partition 4. The -196℃ nitrogen gas generated by the evaporation of liquid nitrogen fills the gas-liquid separation buffer chamber 11, diffuses evenly, and slowly permeates through the micropores into the storage space of the cryopreservation box 6, forming a uniform low-temperature airflow from bottom to top.

[0075] 103 supporting ribs are arranged in parallel on the lower surface of the microporous partition 4, with a height of 5mm, and are welded to the bottom wall of the liquid nitrogen storage chamber 9.

[0076] 4. Cryopreservation box 6-center placement mechanism

[0077] See Figure 1 and Figure 3 The upper surface of the microporous partition 4 is provided with four polytetrafluoroethylene (PTFE) support protrusions 5, each 5 mm high, which lift the bottom surface of the cryopreservation box 6 away from the surface of the microporous partition 4, allowing the low-temperature airflow to flow freely at the bottom of the cryopreservation box 6. The inner cavity wall 15 is provided with a set of PTFE positioning slots on each of its four sides, which confine the cryopreservation box 6 to the center of the cavity, with a uniform spacing of 12 mm around the perimeter, forming a cold gas rising channel 16.

[0078] When using the device, the operator removes the cryopreservation box 6 from the liquid nitrogen tank and places it directly into the cryopreservation box 6 storage space. The cryopreservation box 6 is automatically centered and positioned by the positioning slot and suspended in the air by the support boss 5. At this time, the bottom of the cryopreservation box 6 is evenly covered by the low-temperature gas flow that permeates through the micropores, and the sides are surrounded by the low-temperature environment of the liquid nitrogen circulation channel 14 on the side wall. Although the top surface is exposed to the opening direction, the low-temperature gas flow from bottom to top continuously rises and overflows, forming a low-temperature gas protective layer on the top surface of the cryopreservation box 6, effectively slowing down the warming rate of the sample at the top.

[0079] 5. Searching process

[0080] The operator stands or sits in front of the experimental table, with the apparatus placed on the tabletop. The insulated sealing cover 8 is opened and flipped backward. The cryopreservation box 6 is placed into the apparatus. Because the anti-frostbite high protective wall 7 is about 35mm higher than the top surface of the cryopreservation box 6, the operator's hands can be inserted through the top opening, and the fingertips can operate above the cryopreservation box 6 to check the cryopreservation tube labels column by column or row by row and remove the target cryopreservation tube. The outer side of the forearm is shielded by the high protective wall and does not come into contact with the low-temperature surface of the inner cavity wall 15. After the operation is completed, the cryopreservation box 6 is removed and placed back into the liquid nitrogen tank, and the insulated sealing cover 8 is closed.

[0081] Tests showed that at room temperature of 25°C, after liquid nitrogen was injected into the device and the sample was placed in cryopreservation box 6, the temperature of the sample in the center of cryopreservation box 6 remained below -190°C for 5 minutes after opening the lid and below -170°C for 10 minutes, providing operators with ample time for searching.

[0082] Example 2

[0083] Short-distance cryogenic transfer mode

[0084] See Figure 6 and Figure 7 This embodiment provides a method for using the above-mentioned device in a short-distance, low-temperature transfer scenario involving a small number of samples.

[0085] The operator injects liquid nitrogen into the device, places the cryopreservation box 6 containing the target sample inside, and closes the insulated sealing cover 8. The inside of the insulated sealing cover 8 is filled with aerogel insulation material, and the low-temperature resistant silicone sealing strip around the lower surface of the cover fits against the top surface of the anti-freezing high protective wall 7 to form a seal. The upper surface of the cover is equipped with an insulated handle 17, which the operator can hold with one hand.

[0086] When the lid is closed and sealed, a closed cryogenic chamber is formed inside the device. The cryopreservation box 6 is continuously cooled from the bottom and sides by the U-shaped liquid nitrogen circulation chamber 3, and the top is sealed and insulated by the heat-insulating cover 8. Tests showed that at room temperature of 25℃, the internal temperature remained below -190℃ for 30 minutes and below -180℃ for 60 minutes after the lid was closed, meeting the needs for low-temperature transfer of small quantities of samples between laboratories, between floors, or over short distances within the same city.

[0087] The device is compact in size and weighs about 3.5kg. It can be carried by one person with one hand or put into a handbag. It is lighter than traditional small liquid nitrogen transfer tanks (usually over 5kg) and has a lower temperature and stronger cold preservation capacity than foam box plus dry ice solution (-78.5℃).

[0088] Example 3

[0089] Safety protection effect

[0090] This embodiment illustrates the specific protective effects of each frostbite prevention safety structure of the device.

[0091] (1) Frostbite prevention high protective wall 7: The height of the high protective wall is 35mm, which is higher than the top surface of the cryopreservation box 6. When the operator puts his hand into the device, there is always a high protective wall between the outer side of the forearm and the inner cavity wall 15. The measured temperature of the outer surface of the high protective wall of the outer shell 13 is maintained above 0℃ during continuous use (due to the barrier of the aerogel heat insulation layer), and it is possible to touch it with bare hands for a short time without causing frostbite.

[0092] (2) Liquid nitrogen isolation by microporous partition 4: The device was placed at a 15° angle to simulate the tilting situation during transportation. No liquid nitrogen was observed to seep out above the microporous partition 4. Only low temperature gas overflowed evenly from the micropores, proving that the flow limiting effect of the micropores and the buffering effect of the gas-liquid separation buffer chamber 11 can effectively prevent liquid nitrogen leakage.

[0093] (3) Anti-frost coating: After continuous use for 1 hour in a room temperature environment with a relative humidity of 60%, no obvious frost appeared on the surface of the outer shell 13, while the control group (uncoated stainless steel surface) had frost within 10 minutes.

[0094] (4) Outer shell insulation layer: The measured temperature values ​​at each measuring point on the outer surface of the outer shell 13 are all higher than 0℃, and there is no risk of contact frostbite.

[0095] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A liquid nitrogen return-type constant temperature preservation device with a safety protection structure, characterized in that: The device includes a housing, a U-shaped liquid nitrogen circulation chamber, a microporous baffle gas-liquid separation mechanism, a cryopreservation box placement mechanism, a heat preservation mechanism, and a heat-insulating sealing cover. The cryopreservation box placement mechanism is located in the center of the inner cavity of the housing. The U-shaped liquid nitrogen circulation chamber is arranged around the bottom and periphery of the housing, forming a low-temperature liquid nitrogen environment around the bottom and sides of the cryopreservation box. The microporous baffle gas-liquid separation mechanism is arranged above the U-shaped liquid nitrogen circulation chamber at the bottom. The microporous baffle gas-liquid separation mechanism allows low-temperature nitrogen to permeate evenly into the cryopreservation box area and prevents direct contact between liquid nitrogen and the cryopreservation box. The outer wall of the housing is higher than the top surface of the inner cavity, forming a high protective wall against frostbite. The heat preservation mechanism is arranged inside the housing, and the heat-insulating sealing cover is arranged on the top of the housing.

2. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 1, characterized in that: The device housing includes an outer shell and an inner cavity wall. The outer shell is made of stainless steel sheet and is a rectangular box structure with rounded corners. The top edge of the outer shell is 30-40mm higher than the top edge of the inner cavity wall, forming an upward-extending anti-frostbite high protective wall. The anti-frostbite high protective wall makes the cryopreservation box placed below the top edge of the outer shell.

3. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 2, characterized in that: The loop-shaped liquid nitrogen circulation chamber is a closed-loop loop-shaped flow channel structure, which is arranged around the bottom and outer sides of the inner cavity wall. The loop-shaped liquid nitrogen circulation chamber includes a bottom liquid nitrogen storage chamber and a side wall liquid nitrogen circulation channel that are connected. The bottom liquid nitrogen storage chamber is a flat rectangular cavity used to store liquid nitrogen. The side wall liquid nitrogen circulation channel surrounds the outer sides of the inner cavity wall, and the channel cross-section is rectangular with a uniform width of about 10 mm. Liquid nitrogen circulates between the bottom liquid nitrogen storage chamber and the side wall liquid nitrogen circulation channel through natural convection, providing a low-temperature environment for the cryopreservation box storage space from the bottom and all sides.

4. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 3, characterized in that: The microporous partition gas-liquid separation mechanism includes a microporous partition, a gas-liquid separation buffer chamber, and supporting ribs. The microporous partition is a single piece of stainless steel plate, horizontally fixed inside the inner wall of the cavity. A number of micropores are evenly distributed on the microporous partition. The gas-liquid separation buffer chamber is located between the lower surface of the microporous partition and the liquid surface of the bottom liquid nitrogen storage chamber. The height of the gas-liquid separation buffer chamber is 10-15 mm. The liquid surface of the bottom liquid nitrogen storage chamber is maintained 5 mm below the lower surface of the microporous partition. The low-temperature nitrogen gas generated by the evaporation of liquid nitrogen first fills the gas-liquid separation buffer chamber. After being evenly diffused in the buffer chamber, it slowly permeates into the cryopreservation box storage space through the micropores on the microporous partition, forming a low-temperature airflow evenly distributed from bottom to top. The support rib is disposed on the lower surface of the microporous partition, and the bottom end of the support rib is supported on the bottom wall of the bottom liquid nitrogen storage chamber, which is used to support the microporous partition and precisely maintain the height of the gas-liquid separation buffer chamber.

5. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 4, characterized in that: The cryopreservation box centering mechanism is located within the cryopreservation box storage space above the microporous partition. The cryopreservation box centering mechanism includes a support boss on the upper surface of the microporous partition and a positioning slot on the inner surface of the inner cavity wall. The support boss lifts the bottom surface of the cryopreservation box away from the surface of the microporous partition, allowing the low-temperature airflow that permeates through the micropores to flow freely and be evenly distributed at the bottom of the cryopreservation box. The positioning slot confines the cryopreservation box to the center of the cavity.

6. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 1, characterized in that: The heat preservation mechanism covers the outer side of the U-shaped liquid nitrogen circulation chamber and the inner surface of the outer shell of the device housing; the inner surface of the anti-freezing high protective wall and the outer surface of the outer shell are provided with an aerogel felt heat insulation layer.

7. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 1, characterized in that: The heat-insulating sealing cover is connected to one side edge of the outer shell of the device housing via a hinge; the interior of the heat-insulating sealing cover is filled with heat-insulating material, and a low-temperature resistant sealing strip is provided around the lower surface of the cover body. After the cover is closed, it fits and seals against the top surface of the anti-freezing high protective wall.

8. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 2, characterized in that: A liquid nitrogen filling port is provided on one side of the outer shell. The liquid nitrogen filling port is connected to the loop-shaped liquid nitrogen circulation chamber. The liquid nitrogen filling port is equipped with a sealing cap. The liquid nitrogen filling port is used to inject liquid nitrogen directly into the loop-shaped liquid nitrogen circulation chamber from an external liquid nitrogen source.

9. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 4, characterized in that: It also includes a liquid level gauge or liquid level observation window set at the bottom liquid nitrogen storage chamber; the liquid level gauge is marked with an upper limit scale line, and the liquid level corresponding to the upper limit scale line is located 5 mm below the lower surface of the microporous partition.

10. The liquid nitrogen recirculating constant temperature preservation device with safety protection structure according to claim 1, characterized in that: The height of the anti-frostbite high protective wall is 30-40mm, so that the storage position of the cryopreservation box is accommodated inside the top edge of the outer shell of the device housing.

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