Freezing device

Abstract

The present invention makes it possible to more suitably perform cooling while reducing the consumption of a refrigerant.　In a freezing device 11 that comprises a freezing chamber 12 which uses a liquefied gas as a refrigerant and which has an exhaust port 15, a cooling plate 16, on which an object to be frozen is placed directly or indirectly, is provided on an inner bottom surface 12a of the freezing chamber 12. The cooling plate 16 is made of metal and incorporates a refrigerant flow path 16a therein, and performs a freezing process of supplying a liquid refrigerant to an inlet 16b of the refrigerant flow path 16a while discharging a gaseous refrigerant from the outlet of the refrigerant flow path 16a to fill the freezing chamber 12.

Description

freezing equipment

[0001] The present invention relates to a freezing device suitable for freezing biological materials such as cells and tissues in the fields of regenerative medicine and biotechnology.

[0002] Cells are frozen at a uniform cooling rate to prevent damage to the cells. Freezing methods include those using liquefied gases such as liquid nitrogen and those using electrically powered Stirling refrigerators. While each method has its advantages and disadvantages, Stirling refrigerators, which perform localized cooling, are characterized by their compact size and high efficiency, but have the drawback of being mechanically limited in capacity compared to those using liquid nitrogen. For this reason, they are unsuitable for freezing large amounts of biological material at once. Furthermore, they are limited in freezing speed, unable to freeze at rates exceeding the typical 1°C / min, and may not be able to freeze different types of cells.

[0003] As a freezing device that uses a liquefied gas such as liquid nitrogen as a refrigerant, a device for freezing cells is disclosed in Patent Document 1. This freezing device is configured to cool the object to be frozen by flowing a liquefied gas refrigerant through a cooling block on which the object to be frozen is placed, and also to cool the object by introducing the liquefied gas refrigerant into a cooling chamber.

[0004] With this configuration, the size can be increased and there is no limit to the cooling speed, but the refrigerant that flows into the cooling block is discharged from the refrigerant outlet path, which results in a large amount of refrigerant being consumed.

[0005] Publication No. 1-21923

[0006] A main object of the present invention is to provide a more appropriate cooling system while reducing the amount of refrigerant consumed.

[0007] To this end, the freezing device provided by this invention has the following configuration: In the freezing device, which uses liquefied gas as a refrigerant and has a freezing chamber with an exhaust port, a metal cooling plate with a refrigerant flow path is provided in the freezing chamber, and liquid refrigerant is supplied to the inlet of the refrigerant flow path, and gaseous refrigerant is discharged into the freezing chamber from the outlet of the refrigerant flow path.

[0008] In this configuration, the cooling plate, which is cooled in the freezing chamber by the liquid refrigerant supplied to the refrigerant flow path, indirectly or directly cools the object to be frozen. At the same time, the gaseous refrigerant released from the cooling plate diffuses into the freezing chamber, cooling the entire freezing chamber. In addition, the gaseous refrigerant exhausts the air inside the freezing chamber through the exhaust port, preventing condensation.

[0009] According to this invention, a liquid refrigerant is supplied to a cooling plate close to the object to be frozen and a gaseous refrigerant is released from the cooling plate, so cooling by the cooling plate and cooling by the gaseous refrigerant in the freezing chamber can be performed simultaneously. This allows for uniform cooling without unevenness. Furthermore, the refrigerant supplied to the cooling plate is not discharged but is used to cool the freezing chamber, so refrigerant consumption can be reduced while cooling the entire freezing chamber. Moreover, the air in the freezing chamber can be purged with the gaseous refrigerant, allowing for uniform cooling and more appropriate freezing. In this way, a freezing device can be provided that takes advantage of the advantages of a refrigerant such as liquid nitrogen, which has a high cooling capacity and a wide temperature control range.

[0010] 1 is a cross-sectional view showing a schematic structure of a freezing device;

[0011] An embodiment of the present invention will be described below with reference to the drawings.

[0012] Figure 1 shows a cross-sectional view of the schematic structure of a freezing device 11. This freezing device 11 is a programmable freezer suitable for freezing cells and other biological materials, and uses a cryogenic liquefied gas as a refrigerant. In other words, the amount of refrigerant supplied is adjusted by an automatic valve according to a freezing program, and freezing is carried out while controlling the cooling rate of the material to be frozen.

[0013] The freezing chamber 12, which is the space where cooling takes place, is provided within a housing 13 having a thermal insulation function, and has a single-wing door 14 for loading and unloading the material to be frozen, and an exhaust port 15 for discharging gas from the freezing chamber 12. In the illustrated example, the door 14 is located on the front of the housing 13. The exhaust port 15 is located on one of the left and right wall surfaces when looking at the door 14 from the front, and is connected to an exhaust path (not shown) that leads to the outside.

[0014] A cooling plate 16 is provided on the inner bottom surface 12a of the freezing chamber 12. The cooling plate 16 is a thick plate made of a metal material with good thermal conductivity, such as an aluminum alloy, stainless steel alloy, or copper, and has a refrigerant flow path 16a inside. The cooling plate 16 has a rectangular or square shape in plan view, with flat top and bottom surfaces. The refrigerant flow path 16a has an inlet 16b and an outlet 16c on one of the four end surfaces of the cooling plate 16. The portion between the inlet 16b and the outlet 16c meanders and widens in the planar direction to ensure uniform cooling. The inlet 16b is used to introduce liquid refrigerant, and the outlet 16c is used to discharge gaseous refrigerant that has evaporated during flow. The outlet 16c may be simply open, or may be equipped with a nozzle (not shown) for atomization. A temperature sensor 17 is provided on the upper surface of the cooling plate 16. The temperature sensor 17 can be configured as a thermocouple.

[0015] A heater plate 18 for heating the cooling plate 16 is provided below the cooling plate 16, with the entire opposing surfaces in surface contact with each other (see FIG. 2). The heater plate 18 is a thick plate made of a metal material with good thermal conductivity, similar to the cooling plate 16, and is configured with a built-in heater 18a, such as a cartridge heater.

[0016] The cooling plate 16 and the heater plate 18 may be integrally formed. That is, a cooling layer having the refrigerant flow path 16a may be formed on the upper surface of a thick metal plate in the thickness direction, and a heating layer having the heater 18a may be formed on the lower surface.

[0017] The heater plate 18 to which the cooling plate 16 is joined is supported in a raised state by a positioning plate 19 made of synthetic resin provided on the inner bottom surface 12a of the freezing chamber 12, making it less susceptible to external disturbances. When supported in this manner, the inlet 16b and outlet 16c of the cooling plate 16 are oriented on the side of the freezing chamber 12 opposite the side where the exhaust port 15 is located.

[0018] A refrigerant gas supply unit 21 that supplies gaseous refrigerant to freezing chamber 12 is provided on the inner wall of freezing chamber 12 opposite exhaust port 15, i.e., the inner surface where inlet 16b and outlet 16c face each other. Refrigerant gas supply unit 21 is composed of a nozzle that atomizes liquid refrigerant. A fan 22 is provided ahead of refrigerant gas supply unit 21, i.e., at a position corresponding to the space between refrigerant gas supply unit 21 and cooling plate 16 in a plan view. Fan 22 rotates to agitate the gas within freezing chamber 12 and send it toward exhaust port 15.

[0019] A temperature sensor 23 is also provided inside the freezing chamber 12. The temperature sensor 23 measures the temperature inside the freezing chamber 12, that is, the temperature of the atmosphere filling the freezing chamber 12, and can be configured, for example, by a thermocouple.

[0020] On the outer surface of the housing 13 opposite the surface on which the exhaust port 15 is provided, there are provided a flow path 31 for introducing refrigerant into the freezing chamber 12 and a control unit 32 for adjusting the flow rate of the refrigerant. Specifically, a liquid refrigerant supply path 34 having at one end a connection port detachably connected to a refrigerant container 33 provided outside the device and at the other end connected to an inlet 16b of the refrigerant flow path 16a of the cooling plate 16 constitutes one of the flow paths 31. A gaseous refrigerant supply path 35, which is connected to the refrigerant gas supply unit 21, branches off from the liquid refrigerant supply path 34. This gaseous refrigerant supply path 35 is another of the flow paths 31. Flow rate adjustment valves 34a and 35a are provided at the branch points of the liquid refrigerant supply path 34 and the gaseous refrigerant supply path 35, respectively. The flow rate adjustment valve 34a of the liquid refrigerant supply path 34 is referred to as the "main adjustment valve 34a," and the flow rate adjustment valve 35a of the gaseous refrigerant supply path 35 is referred to as the "sub-adjustment valve 35a." Although not shown, the flow path 31 is also provided with a safety valve and an emergency shutoff valve.

[0021] The main regulating valve 34a and the auxiliary regulating valve 35a are connected to a control unit 32, along with the heater 18a of the heater plate 18 and the motor 24 that drives the fan 22. The control unit 32 is connected to a storage unit that stores a plurality of freezing programs, along with an input device for operation and an output device for display, both of which are not shown. During the freezing process, the selected freezing program is read out and control operations in accordance with that freezing program are carried out on the main regulating valve 34a, the auxiliary regulating valve 35a, the heater 18a, and the motor 24. The temperature sensors 17 and 23 mentioned above are also connected to the control unit 32, and the temperature information input from the temperature sensors 17 and 23 is used as reference in the control operations of the control unit 32.

[0022] The freezing device 11 having such a configuration freezes the object to be frozen in the following manner.

[0023] When the cell freezing container containing the material to be frozen is a freezing tube 51, a tube rack 52 such as that shown in Figure 2 is used. The tube rack 52 is made of a solid metal block with good thermal conductivity, similar to the cooling plate 16. It is shaped like a rectangular parallelepiped, and has a plurality of holding holes 53 evenly spaced on its top surface for inserting and holding the freezing tubes 51. The tube rack 52, with the freezing tubes 51 containing the material to be frozen together with a cryopreservation medium held in the holding holes 53, is placed on the cooling plate 16 inside the freezing chamber 12.

[0024] When the desired freezing program is selected and the cooling operation is started, the control unit 32 opens the main regulating valve 34a in accordance with the freezing program to supply liquid refrigerant to the inlet 16b of the refrigerant flow path 16a of the cooling plate 16. The amount of refrigerant supplied is so small that it vaporizes before passing through the refrigerant flow path 16a, and the refrigerant gas (gaseous refrigerant) that has increased in volume due to vaporization is released from the outlet 16c of the refrigerant flow path 16a and diffuses within the freezing chamber 12.

[0025] By filling the freezing chamber 12 with gaseous refrigerant in this manner, the freezing method using the freezing device 11 executes a purging step in which the air present in the freezing chamber 12 is pushed out through the exhaust port 15. In other words, the purging step is a step in which the air in the freezing chamber 12 is purged with gaseous refrigerant prior to the freezing process or at the initial stage of the freezing process.

[0026] As the freezing process progresses by supplying refrigerant in accordance with the freezing program, the temperature of the cooling plate 16 drops, and so does the temperature of the atmosphere in the freezing chamber 12. The cooling plate 16 then indirectly cools the object to be frozen via the tube rack 52, and at the same time, the gaseous refrigerant released from the cooling plate 16 fills the freezing chamber 12, cooling the entire interior of the freezing chamber 12. During this cooling, the air in the freezing chamber 12 has already been purged, so there is no moisture in the freezing chamber 12 and frost and condensation are prevented.

[0027] During the freezing process, the temperature inside the freezing chamber 12 (ambient temperature) is higher than the temperature of the cooling plate 16 (plate temperature), and cooling proceeds at a uniform cooling rate toward the target temperature while maintaining a temperature difference within a certain range, for example, about 20°C.

[0028] During this cooling process, the control unit 32 opens and closes the main regulating valve 34a based on the detection results (plate temperature information, ambient temperature information) of the temperature sensor 17 on the cooling plate 16 and the temperature sensor 23 in the freezing chamber 12. By opening and closing the main regulating valve 34a and, if necessary, using the heater 18a to heat the air, highly accurate cooling is achieved, achieving an optimal cooling rate and cooling profile. It is preferable to use PID control for the control unit 32.

[0029] After the freezing process is completed and the object to be frozen is removed, the input device is operated to cause the control unit 32 to energize the heater 18a, whereby the cooled cooling plate 16 can be quickly returned to room temperature.

[0030] As described above, liquid refrigerant is supplied to the cooling plate 16, which is in indirect contact with the object to be frozen, for cooling, and at the same time, gaseous refrigerant is released from the cooling plate 16 to cool and freeze the inside of the freezing chamber 12, so that uniform cooling without unevenness is possible by two types of cooling. Moreover, the refrigerant supplied to the cooling plate 16 is vaporized and used to cool the inside of the freezing chamber 12 in a manner that maintains a temperature difference between the ambient temperature and the plate temperature within a certain range, so that the entire freezing chamber 12 is cooled while refrigerant consumption is minimized.

[0031] Furthermore, prior to or in the initial stages of the freezing process, the air in the freezing chamber 12 is purged with gaseous refrigerant, thereby preventing frosting and condensation and allowing the material to be cooled uniformly, thereby achieving more appropriate freezing.

[0032] A refrigerant such as liquid nitrogen has a high cooling capacity and a wide temperature control range. Furthermore, even if the cooling plate 16 is enlarged, the above-mentioned effect is not impaired, so the freezing device 11 can take advantage of the refrigerant and appropriately freeze a large amount of material at once.

[0033] As described above, the freezing device 11 is equipped with the refrigerant gas supply unit 21 and the fan 22, which can be used for purging and freezing. That is, purging is not performed using a refrigerant passed through the cooling plate 16, but rather, purging can be performed by introducing refrigerant gas from the gaseous refrigerant supply path 35 into the freezing chamber 12 and operating the fan 22 at the start of the cooling operation. It is also possible to perform forced convection cooling by operating the fan 22 during the freezing process. Of course, when performing forced convection cooling, refrigerant gas may be supplied into the freezing chamber 12 through the gaseous refrigerant supply path 35.

[0034] The above configuration is one embodiment for carrying out the present invention, and the present invention is not limited to only the above configuration, and other configurations can also be adopted.

[0035] For example, the freezing device 11 may have a structure in which the top is open, rather than having the opening and closing door 14 on the front.

[0036] The coolant may be something other than liquid nitrogen.

[0037] When the cell freezing container that contains the material to be frozen is in the shape of a bag, a protector and a holder for holding the protector are used instead of the tube rack 52 .

[0038] DESCRIPTION OF SYMBOLS 11...Freezing device 12...Freezing chamber 15...Exhaust port 16...Cooling plate 16a...Refrigerant flow path 16b...Inlet 16c...Outlet 17...Temperature sensor 18...Heater plate 21...Refrigerant gas supply unit 22...Fan 23...Temperature sensor 32...Control unit 34...Liquid refrigerant supply path 34a...Main adjustment valve (flow rate adjustment valve) 35...Gaseous refrigerant supply path 35a...Sub-adjustment valve (flow rate adjustment valve)

Claims

1. A freezing device using a liquefied gas as a refrigerant and equipped with a freezing chamber having an exhaust port, wherein a metal cooling plate equipped with a refrigerant flow path is provided in the freezing chamber, and a liquid refrigerant is supplied to the inlet of the refrigerant flow path, and a gaseous refrigerant is discharged into the freezing chamber from the outlet of the refrigerant flow path.

2. The freezing device according to claim 1, wherein a heater plate for heating said cooling plate is provided below said cooling plate.

3. A freezing device according to claim 1 or claim 2, wherein a refrigerant gas supply unit is provided for supplying gaseous refrigerant to the freezing chamber, and the freezing chamber is equipped with a fan.

4. A freezing device according to claim 1 or claim 2, wherein a flow rate adjustment valve is provided in a liquid refrigerant supply path that supplies refrigerant to the cooling plate, and a control unit is provided that compares plate temperature information input from a temperature sensor provided on the cooling plate with ambient temperature information input from a temperature sensor provided within the freezing chamber, and opens and closes the flow rate adjustment valve to perform cooling in accordance with a predetermined freezing program while maintaining the temperature difference between the two within a certain range.

5. A freezing method using a freezing device that uses liquefied gas as a refrigerant, in which the air in the freezing chamber is purged with gaseous refrigerant prior to or at the initial stage of the freezing process.

6. A freezing method according to claim 5, wherein a metal cooling plate having a built-in refrigerant flow path is provided in a freezing chamber where the freezing process is carried out, a liquid refrigerant is supplied to the inlet of said refrigerant flow path, and a gaseous refrigerant is released from the outlet of said refrigerant flow path into said freezing chamber, and cooling is carried out in accordance with a predetermined freezing program while maintaining the temperature of the atmosphere in said freezing chamber at a temperature higher than the temperature of said cooling plate by a certain range.

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