Refrigeration – Storage of solidified or liquified gas – Including cryostat
Reexamination Certificate
1999-08-02
2001-03-27
Capossela, Ronald (Department: 3744)
Refrigeration
Storage of solidified or liquified gas
Including cryostat
C062S457900
Reexamination Certificate
active
06205794
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates generally to cryogenic storage devices and, more particularly, to a cryogenic tank adapted to receive biological specimens.
II. Description of the Prior Art
There are many previously known cryogenic storage tanks which are generally cylindrical in shape and have a closed bottom and open top thus defining a cryogenic freezing chamber. A source of liquefied gaseous material, typically liquid nitrogen, is fluidly connected to the interior of the chamber through a valve system so that the liquid level with the cryogenic chamber is maintained within predetermined limits. A lid is also conventionally disposed across the open top of the cryogenic tank.
In use, frozen biological specimens, such as blood, semen or other types of biological specimens, are simply immersed in the liquid contained within the cryogenic chamber thus storing the biological materials in the desired fashion. Since the temperature of the liquefied gaseous material is extremely low, e.g. below −191° C., the viability of the biological specimens can be maintained for long periods of time.
One disadvantage of these previously known cryogenic storage devices, however, is that, since the biological specimens are immersed within the liquefied gaseous material, cross contamination between the biological specimens is possible. For example, in the event that a biological specimen leaks into the liquefied gaseous material, any impurities, diseases, viruses or the like contained within that biological specimen may thereafter be transmitted to a different biological specimen also contained within the cryogenic freezing tank by using the liquefied gaseous material within the tank as the transportation mechanism for such undesirable contaminants.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a cryogenic device which overcomes all of the above-mentioned disadvantages of the previously known devices.
In brief, the cryogenic storage device of the present invention comprises a tank having an open top and a wall which defines an interior chamber adapted to receive biological specimens. Preferably, the wall is generally cylindrical in shape and closed at its lower end.
A fluid reservoir is disposed around at least a portion of the wall on an outer surface of the wall. This reservoir is adapted to receive a liquefied gaseous material, such as liquid nitrogen. At least one, and preferably several, circumferentially spaced vents are provided on the interior of the wall so that the vents permit vapor from the liquefied gaseous material contained within the reservoir to escape the reservoir.
A source of the liquefied gaseous material, such as liquid nitrogen, is fluidly connected to the reservoir by a valve system which maintains the level of the liquefied gaseous material in the reservoir within predetermined limits. Thus, when the level of the liquefied gaseous material falls below the lower limit, the valve opens and fluidly connects the liquefied gaseous material from the source to the reservoir thus moving the liquid level in the reservoir towards its upper limit. In doing so, the liquefied gaseous material contained in the reservoir cools the interior chamber of the tank in which the biological specimens are contained.
In practice, it has been found that, while using liquefied nitrogen, the temperature of the interior chamber of the tank can be maintained below −140° C., i.e. the temperature necessary to maintain the viability of biological specimens within the tank. In practice, the actual temperature of the tank can be maintained at a temperature less than −190° C.
Since only gas, rather than liquefied gaseous material, is contained within the interior chamber of the tank, cross contamination of the biological specimens is rendered virtually impossible.
REFERENCES:
patent: 3007319 (1961-11-01), Ogden
patent: 3092974 (1963-06-01), Haumann et al.
patent: 4054037 (1977-10-01), Yoder
patent: 4578963 (1986-04-01), Sitte
patent: 4640099 (1987-02-01), Gibot
patent: 4739622 (1988-04-01), Smith
patent: 4958498 (1990-09-01), Brothers
patent: 4976112 (1990-12-01), Roberts et al.
Capossela Ronald
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
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