Liquid nitrogen filling device and liquid nitrogen filling method

Abstract

To provide a liquid nitrogen apparatus for filling liquid nitrogen in such a manner that an absorber inside a freezing container surely absorbs a predetermined amount of the liquid nitrogen.SOLUTION: A liquid nitrogen filling apparatus 11 for filling liquid nitrogen into a freezing container 2 arranged with a liquid nitrogen absorber 2a therein, comprises: a flow rate control part 14 provided in a liquid nitrogen supply pipeline 12; a filling nozzle 31; and liquid level sensors 32 for detecting height of a liquid surface inside the container. The liquid nitrogen filling apparatus perform control to: stop feeding the liquid nitrogen upon detecting, by the liquid level sensor 32, that the liquid surface has reached a predetermined first reference height H; re-start feeding the liquid nitrogen upon detecting that the liquid surface is below a predetermined second reference height L lower than the first reference height; re-stop feeding the liquid nitrogen upon re-detecting that the liquid surface is above the first reference height H; and repeat the re-start and the re-stop feeding liquid nitrogen until a predetermined time preset by timer control elapse without detecting the liquid surface lower than the predetermined second reference height L.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a liquid nitrogen filling device and a liquid nitrogen filling method, and more particularly to a liquid nitrogen filling device and a liquid nitrogen filling method for filling liquid nitrogen into various freezing containers, including freezing transport containers known as dry shippers. [Background technology]

[0002] A cryotransport container known as a dry shipper is a vacuum vessel equipped with an absorbent material that absorbs liquid nitrogen, lowering the temperature inside the container to below -150°C, enabling the transport of samples in a vapor-phase storage state. In various laboratories and cell storage rooms where this cryotransport container is used, a filling nozzle is inserted into the cryotransport container from a liquid nitrogen supply source, such as a portable liquid nitrogen container, and liquid nitrogen is filled. Typically, the container is filled with a specified amount of liquid nitrogen multiple times, left for a specified period of time, and then the liquid nitrogen inside the container is discarded to complete the process.

[0003] However, when liquid nitrogen is filled, the liquid level begins to drop immediately because it is absorbed by the absorbent material. Therefore, when filling manually, the valve must be operated to replenish liquid nitrogen each time, and when operating the valve at the start and end of filling, the flow rate of liquid nitrogen must be adjusted by adjusting the valve opening, which is an additional step. Furthermore, mist forms inside the container, making it difficult to see the liquid level, making it difficult to fill with the appropriate amount of liquid nitrogen when filling multiple times.

[0004] Therefore, a method has been proposed in which liquid nitrogen is automatically filled into a cryopreservation container while the weight of the container is being measured, and a method in which the liquid level is automatically filled while being monitored (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-52798 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of a system that automatically supplies liquid nitrogen by only determining the temperature of the gas phase region and the liquid level of the liquid phase region inside the container, as in Patent Document 1, there is a possibility that it is not possible to determine whether the internal absorbent material is able to absorb the specified amount of liquid nitrogen.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a filling device and a filling method for filling liquid nitrogen so that the absorbent material in a frozen transport container can reliably absorb a predetermined amount of liquid nitrogen. [Means for solving the problem]

[0008] In order to achieve the above object, the liquid nitrogen filling device of the present invention is a liquid nitrogen filling device for filling liquid nitrogen into a freezing container having a liquid nitrogen absorbent disposed therein, the liquid nitrogen filling device comprising: a liquid nitrogen supply pipe for supplying liquid nitrogen from a liquid nitrogen supply source to the freezing container; Liquid nitrogen supply piping and a liquid level sensor that detects the liquid level in the freezing container. When the liquid level sensor detects that the liquid level has reached a predetermined first reference height, the flow rate control unit stops the supply of liquid nitrogen. When the liquid level sensor detects that the liquid level is below a predetermined second reference height that is lower than the first reference height, the flow rate control unit resumes the supply of liquid nitrogen. When the liquid level sensor again detects that the liquid level has exceeded the first reference height, the flow rate control unit again stops the supply of liquid nitrogen. Without detecting that the liquid level is below the second reference height, the liquid nitrogen supply is repeatedly restarted and stopped until a predetermined time set by timer control has elapsed.

[0009] In addition, in the liquid nitrogen filling device of the present invention, the fluid control unit is Liquid nitrogen supply piping a small flow rate solenoid valve provided on the Liquid nitrogen supply pipingand a normal flow solenoid valve provided in a flow path branched from the small flow solenoid valve. Furthermore, when filling starts, the small flow solenoid valve is opened and the normal flow solenoid valve is closed, and when a predetermined time set by timer control has elapsed since the start of filling, the normal flow solenoid valve is opened, and when the liquid level sensor detects that the liquid level has exceeded a predetermined height, the normal flow solenoid valve is closed.

[0010] Furthermore, the liquid nitrogen filling device of the present invention may be equipped with a weighing scale for measuring the weight of the freezing container.

[0011] In addition, the liquid nitrogen filling method of the present invention is a liquid nitrogen filling method for filling a freezing container having a liquid nitrogen absorbent placed therein with liquid nitrogen, and is characterized in that when it is detected that the liquid level has reached a predetermined first reference height, the supply of liquid nitrogen is stopped, when it is detected that the liquid level is below a predetermined second reference height that is lower than the first reference height, the supply of liquid nitrogen is resumed, and when it is again detected that the liquid level has exceeded the predetermined first reference height, the supply of liquid nitrogen is stopped again by the flow control unit, and the resumption and stopping of the supply of liquid nitrogen is repeated until a predetermined time has elapsed without detecting that the liquid level is below the second reference height.

[0012] Furthermore, the liquid nitrogen filling method of the present invention is characterized in that, at the start of filling, liquid nitrogen is filled at a small flow rate that is smaller than the normal flow rate, and when a predetermined time has elapsed since the start of filling, liquid nitrogen is filled at the normal flow rate, and when it is detected that the liquid level in the freezing container has exceeded a predetermined liquid level height, liquid nitrogen is filled at the small flow rate.

[0013] In addition, in the liquid nitrogen filling method of the present invention, it is preferable that after the supply of liquid nitrogen is completed, the weight of the freezing container is measured, and if the weight is within a predetermined range, it is determined that filling is complete. [Effects of the Invention]

[0014] According to the liquid nitrogen filling device and liquid nitrogen filling method of the present invention, the liquid level is detected by a liquid level sensor and controlled by a timer, and the supply of liquid nitrogen is repeatedly restarted and stopped until the liquid level reaches a level above the target filling level.This makes it possible to automatically add more liquid nitrogen until the absorbent material in the freezing container has reliably absorbed the specified amount of liquid nitrogen.

[0015] Furthermore, by supplying liquid nitrogen only at a small flow rate at the start of filling, it is possible to prevent liquid nitrogen from splashing outside the container due to the sudden evaporation of liquid nitrogen caused by the temperature difference between the container and the liquid nitrogen at the start of filling, while at the same time ensuring a high filling speed by returning to the normal flow rate once the temperature inside the container has dropped to a certain level.

[0016] In addition, once the liquid level reaches a predetermined height, liquid nitrogen is only supplied at a small flow rate, which prevents the liquid nitrogen sprayed from the filling nozzle from coming into contact with the resin parts inside the freezing transport container or from spilling outside the container when the container is filled to a certain extent with liquid nitrogen.

[0017] Furthermore, a weighing scale is provided to measure the weight of the freezing container after a predetermined time has passed, making it possible to determine whether or not the container is completely filled. If the weight is not within the predetermined range, deterioration of the absorbent material's performance can be detected. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an explanatory diagram showing the configuration of a liquid nitrogen filling device according to an embodiment of the present invention; [Figure 2] 1 is a flowchart illustrating a liquid nitrogen filling method of the present invention. [Figure 3] FIG. 10 is an explanatory diagram showing the change in the liquid level in the frozen transport container at the start of filling. [Figure 4] FIG. 10 is an explanatory diagram showing the change in the liquid level in the frozen transport container during additional filling. [Figure 5] 10 is a flowchart illustrating weight determination using a weighing scale. DETAILED DESCRIPTION OF THE INVENTION

[0019] A liquid nitrogen filling device and a liquid nitrogen filling method according to an embodiment of the present invention will be described in detail below with reference to the drawings. Figure 1 is an explanatory diagram showing a schematic configuration of a liquid nitrogen filling device 11 according to an embodiment of the present invention.

[0020] The liquid nitrogen filling device 11 of this embodiment is a device for filling liquid nitrogen from a liquid nitrogen supply source 1 into a freezing transport container (freezing container) 2 called a dry shipper.

[0021] The frozen transport container 2 has an absorbent material 2a placed inside, and by impregnating and retaining liquid nitrogen in the absorbent material 2a, the container is maintained in a gaseous atmosphere at an extremely low temperature, allowing the stored frozen samples to be transported and preserved. A neck tube 2b is placed around the inner periphery of the opening of the container.

[0022] As shown in Figure 1, the liquid nitrogen filling device 11 is generally configured to include a liquid nitrogen supply pipe 12 connected to a liquid nitrogen supply source 1, a control device 13, a flow rate control unit 14 provided on the liquid nitrogen supply pipe 12, a filling nozzle unit 15 provided at the end of the liquid nitrogen supply pipe 12, and a weighing scale 16 for measuring the weight of the frozen transport container 2.

[0023] The liquid nitrogen supply pipe 12 is a heat-insulated pipe, and although a simple heat-insulated pipe is sufficient, a vacuum double pipe is more preferable.

[0024] The flow rate control unit 14 includes a small flow rate solenoid valve 21 provided in the liquid nitrogen supply pipe 12, and a normal flow rate solenoid valve 23 provided in a branch path 22 that branches off from the liquid nitrogen supply pipe 12 upstream of the small flow rate solenoid valve 21 and joins the liquid nitrogen supply pipe 12 downstream of the small flow rate solenoid valve 21. In this embodiment, the flow rate is 2 L / min when the small flow rate solenoid valve 21 is used, and the flow rate is about 4 L / min when the normal flow rate solenoid valve 23 is used.

[0025] The filling nozzle unit 15 consists of a filling nozzle 31 connected to the end of the liquid nitrogen supply pipe 12 via a flexible hose 30, and a liquid level sensor 32 that detects the liquid level of the liquid nitrogen in the frozen transport container 2.

[0026] The filling nozzle 31 of this embodiment is of a type that uses a gas-liquid separator, and an exhaust path 33 for the gas phase portion is provided via a flexible hose.

[0027] In this embodiment, the liquid level sensor 32 is composed of four level gauges 32a, b, c, and d so as to be able to detect four levels of liquid level. The liquid level sensor 32 is provided with a level gauge 32c for detecting a liquid level H (a first reference level according to the present invention) that corresponds to the specified amount of liquid to be filled into the frozen transport container 2, and a level gauge 32b for detecting a liquid level L (a second reference level according to the present invention) that is lower than the first reference level and corresponds to a recommended filling height. Furthermore, the liquid level sensor 32 is provided with a level gauge 32a for detecting a liquid level LL that is lower than the liquid level L, and a level gauge 32d for detecting a liquid level HH that is higher than the liquid level H. In this embodiment, for example, the liquid level HH is set to be 40 mm higher than the liquid level H, the liquid level L is set to be 20 mm lower than the liquid level H, and the liquid level LL is set to be an additional 20 mm lower.

[0028] The height of the filling nozzle unit 15 at the opening of the frozen transport container 2 can be adjusted by a height adjustment mechanism 34. In this embodiment, a liquid level gauge 32c for detecting the liquid level H is adjusted to be at the same height as the lower end of the neck tube 2b.

[0029] The control device 13 is electrically connected to each of the level gauges 32a-d of the liquid level sensor 32, and receives signals detected by each of the level gauges. The control device 13 is also electrically connected to the small flow rate solenoid valve 21 and the normal flow rate solenoid valve 23, and sends signals to each solenoid valve to control opening and closing. The control device 13 is also electrically connected to the weighing scale 16. The control device 13 also has a timer control function.

[0030] Next, the liquid nitrogen filling method of the present invention will be described with reference to the flow chart of FIG.

[0031] First, when the controller 13 is instructed to start filling, the timer at the start of filling starts, only the small flow rate solenoid valve 21 opens, and filling of liquid nitrogen begins. Note that Figure 3 shows the change in the liquid level from the start of filling.

[0032] When a predetermined time set by the filling start timer (for example, set to 120 seconds in this embodiment) has elapsed, the filling start timer stops and a signal is sent from the control device 13 to open the normal flow rate solenoid valve 23 (step S1). The liquid level is filled up to the liquid level S shown in Fig. 3. At this time, the small flow rate solenoid valve 21 may be controlled to close, or the small flow rate solenoid valve 21 may be left open and liquid nitrogen may be filled from both the liquid nitrogen supply pipe 12 and the branch path 22.

[0033] This control allows liquid nitrogen to be filled at a small flow rate at the start of filling, preventing the liquid nitrogen from scattering outside the container due to the sudden evaporation of liquid nitrogen caused by the temperature difference between the frozen transport container 2 and the liquid nitrogen at the start of filling, while ensuring a sufficient filling speed by switching to a normal flow rate (or a flow rate combining the normal flow rate and the small flow rate) after the temperature inside the container has dropped to a certain level. This control also prevents the liquid nitrogen from scattering when the liquid nitrogen passes through the liquid nitrogen supply pipe 12, flexible hose 30, and filling nozzle 31, which are at near room temperature, and then vaporizes and is forcefully sprayed from the nozzle.

[0034] Next, when the liquid level gauge 32a detects that the liquid level in the frozen transport container 2 has reached the liquid level LL, the control device 13 sends a signal to close the normal flow rate solenoid valve 23 (step S2). At this time, if the small flow rate solenoid valve 21 has been controlled to be closed, the control device 13 sends a signal to reopen the small flow rate solenoid valve 21.

[0035] In this way, by throttling the flow rate of liquid nitrogen after a certain amount of liquid nitrogen has been filled, it is possible to prevent the liquid nitrogen sprayed from the filling nozzle 31 from coming into contact with the resin part inside the frozen transport container 2 or from spilling over outside the container. In addition, since disturbance of the liquid surface can be prevented as much as possible, the accuracy of liquid level detection by the liquid level sensor 32 can be improved.

[0036] Furthermore, when the liquid level gauge 32b detects that the liquid level in the frozen transport container 2 rises and reaches the liquid level H, the small flow rate solenoid valve 21 closes and the liquid level monitoring timer starts (step S3).

[0037] When the supply of liquid nitrogen is stopped, the liquid nitrogen in the frozen transport container 2 is absorbed by the absorbent material 2a, causing the liquid level to drop. Next, the liquid level sensor 32 determines whether the liquid level in the frozen transport container 2 is below the liquid level L (step S4).

[0038] If the liquid level is below the liquid level L, it is determined that the amount of filling is still insufficient, and the small flow rate solenoid valve 21 is opened again to start additional filling. Note that Figure 4 is an explanatory diagram showing the change in the liquid level in the frozen transport container during additional filling.

[0039] Thereafter, when the level gauge 32b detects that the liquid level has reached the liquid level H again, the small flow rate solenoid valve 21 closes and the liquid level monitoring timer starts again (step S3).

[0040] Thereafter, the liquid level sensor 32 again determines whether the liquid level is below the liquid level L, and if it is below the liquid level L, the small flow rate solenoid valve 21 is opened again and filling is started. In this way, steps S3 and S4 are repeated, thereby enabling automatic additional filling.

[0041] If the liquid level sensor 32 does not detect that the liquid level is below the liquid level L (step S4) and the liquid level monitoring timer determines that a predetermined time has elapsed (step S5), the liquid level monitoring timer stops, the filling amount is determined to be sufficient, automatic filling is completed, and the filling of liquid nitrogen is terminated.

[0042] If the level gauge 32d detects that the liquid level has reached the liquid level HH during the above-mentioned filling operation, the control device 13 may issue an alarm indicating overfilling, close the small flow solenoid valve 21 and the normal flow solenoid valve 23, and stop filling of liquid nitrogen. In this way, by providing an interlock mechanism using the level gauge as a measure to prevent overfilling, it is possible to reliably prevent liquid nitrogen from spilling outside the container during filling, and not only to prevent excessive use of liquid nitrogen, but also to improve safety during filling and prevent damage to the building floor.

[0043] Furthermore, although the filling operation may be completed using the above filling method, the completion of filling may also be reliably determined using a weighing scale 16. FIG. 5 is a flowchart illustrating weight determination using a weighing scale. After automatic filling is completed, the weight of the frozen transport container 2 is measured by the weighing scale 16. If the result is within the set range of the full weight, weight determination is completed, filling is completed, and the frozen transport container 2 can be removed.

[0044] On the other hand, if the full weight is outside the set range after a predetermined time has elapsed, the control device 13 issues an abnormality alarm signal, indicating an abnormality such as insufficient liquid nitrogen absorption, which indicates deterioration of the absorbent performance in the frozen transport container, or excessive liquid nitrogen filling.

[0045] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0046] The control device 13 stores preset values ​​(mass of empty container, full weight for weight determination, liquid level height at which the specified amount is reached (first reference height)) for each model of frozen transport container from each manufacturer, and when the model of the container is input, the height adjustment mechanism 34 can automatically adjust the height of the filling nozzle unit 15. In addition, it is preferable that recommended predetermined times for the filling start timer and liquid level monitoring timer be set for each model.

[0047] Furthermore, the liquid nitrogen supply source 1 is a portable liquid nitrogen container in FIG. 1, but may also be a cold evaporator.

[0048] Furthermore, the filling nozzle is not limited to the type using a gas-liquid separator, but can take any known configuration, such as a nozzle using sintered metal or a sintered metal nozzle covered with a cylindrical cover with an open bottom end.

[0049] As for the liquid level sensor (liquid level gauge), not only a thermocouple type but also an LED type, a float type, a capacitance type or other sensor may be used, but a heater-integrated thermocouple is preferable.

[0050] In addition, in this embodiment, the flow rate control unit 14 is provided with the small flow rate solenoid valve 21 and the normal flow rate solenoid valve 23 in two paths, the liquid nitrogen supply pipe and the branch path, but it is also possible to provide a single flow rate control valve without providing a branch path, and to control the flow rate by changing the opening of the flow rate control valve.

[0051] Furthermore, in this embodiment, a case has been described in which liquid nitrogen is filled into a freezing transport container 2 for transporting and transporting samples, known as a dry shipper, as a freezing container with a liquid nitrogen absorbent placed inside. However, the present invention can be applied to various freezing containers, such as a freezing container for cryopreservation with a liquid nitrogen absorbent placed inside, as long as a liquid nitrogen absorbent is placed inside. [Explanation of symbols]

[0052] 1 Liquid nitrogen supply source, 2 Freezing transport container, 2a Absorbent material, 2b Neck tube, 11 Liquid nitrogen filling device, 12 Liquid nitrogen supply piping, 13 Control device, 14 Flow rate control section, 15 Filling nozzle unit, 16 Weight scale, 21 Small flow rate solenoid valve, 22 Branch path, 23 Normal flow rate solenoid valve, 30 Flexible hose, 31 Filling nozzle, 32 Liquid level sensor, 32a, b, c, d Liquid level gauge, 33 Exhaust path, 34 Height adjustment mechanism

Claims

1. A liquid nitrogen filling device for filling liquid nitrogen into a freezing container having a liquid nitrogen absorbent disposed therein, a liquid nitrogen supply pipe for supplying liquid nitrogen from a liquid nitrogen supply source to the freezing container; a flow rate control unit provided in the liquid nitrogen supply pipe; a liquid level sensor that detects the liquid level in the freezing container; When the liquid level sensor detects that the liquid level has reached a predetermined first reference height, the flow rate control unit stops the supply of liquid nitrogen; When it is detected that the liquid level is below a predetermined second reference height that is lower than the first reference height, the flow rate control unit resumes supplying liquid nitrogen; When the liquid level sensor detects again that the liquid level has exceeded the first reference height, the flow rate control unit stops the supply of liquid nitrogen again; A liquid nitrogen filling device characterized by being controlled so that the supply of liquid nitrogen is repeatedly restarted and stopped until a predetermined time set in advance by timer control has elapsed, without detecting that the liquid level is below the second reference height.

2. The flow rate control unit a small flow rate solenoid valve provided on the liquid nitrogen supply pipe; a normal flow rate solenoid valve provided in a flow path branched from the liquid nitrogen supply pipe; 2. The liquid nitrogen filling device according to claim 1, further comprising:

3. When filling begins, The small flow rate solenoid valve is opened and the normal flow rate solenoid valve is closed, When a predetermined time set by timer control has elapsed since the start of filling, Open the normal flow solenoid valve; When the liquid level sensor detects that the liquid level has exceeded a predetermined level, Close the normal flow solenoid valve 3. The liquid nitrogen filling device according to claim 2, wherein said liquid nitrogen filling device is controlled.

4. 4. The liquid nitrogen filling device according to claim 1, further comprising a weight scale for measuring the weight of the freezing container.

5. A liquid nitrogen filling method for filling liquid nitrogen into a freezing container having a liquid nitrogen absorbent disposed therein, comprising: When it is detected that the liquid level has reached a predetermined first reference height, the supply of liquid nitrogen is stopped, When it is detected that the liquid level is below a predetermined second reference level that is lower than the first reference level, the supply of liquid nitrogen is resumed; When it is detected again that the liquid level has exceeded the predetermined first reference height, the supply of liquid nitrogen is stopped again; A liquid nitrogen filling method characterized by repeatedly restarting and stopping the supply of liquid nitrogen until a predetermined time has elapsed without detecting that the liquid level is below the second reference height.

6. When filling begins, Start filling liquid nitrogen at a flow rate lower than the normal flow rate. When a predetermined time has passed since the start of filling, Fill with liquid nitrogen at the normal flow rate. When it is detected that the liquid level in the freezing container exceeds a predetermined liquid level, Fill with liquid nitrogen at a low flow rate 6. The method for filling liquid nitrogen according to claim 5.

7. 7. The method for filling liquid nitrogen according to claim 5, wherein the weight of the freezing container is measured after the supply of liquid nitrogen is completed, and if the weight is within a predetermined range, it is determined that filling is complete.

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