Cryogenic storage device

Abstract
A cryogenic storage device is disclosed having a tank with an open top and a wall which defines an interior chamber adapted to receive biological specimens. A fluid reservoir is disposed around at least a portion of the wall on an outer surface of the wall and this fluid reservoir receives a liquefied gaseous material, such as liquid nitrogen. The source of the liquid gaseous material is fluidly connected through a valve to the reservoir to maintain the level of the liquefied gaseous material between preset limits in the reservoir thus cooling the interior of the interior chamber and any biological specimens contained within the interior of the chamber.
Description




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.











BRIEF DESCRIPTION OF THE DRAWINGS




A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which:





FIG. 1

is a perspective view illustrating a preferred embodiment of the cryogenic device of the present invention; and





FIG. 2

is a longitudinal sectional view of a portion of the preferred embodiment of the present invention.











DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION




With reference first to

FIG. 1

, a preferred embodiment of the cryogenic storage device


10


of the present invention is there shown and comprises a tank


12


which is generally cylindrical in shape. The tank


12


includes an open top


14


and a closed bottom


15


.




As best shown in

FIG. 2

, the tank


12


includes an inner wall


16


which defines a generally cylindrical interior chamber


18


adapted to receive biological specimens. Such biological specimens are inserted into and removed from the chamber


18


through the open tank top


14


and are held in conventional cryogenic trays. The specimens are typically frozen prior to their insertion into the chamber


18


although, optionally, the device


10


of the present invention can both freeze and store specimens.




Still referring to

FIG. 2

, the tank


12


further includes a second wall


20


spaced outwardly from and surrounding the inner wall


16


such that a reservoir


22


is formed between the tank walls


16


and


20


. This reservoir


22


extends entirely circumferentially around the sides of the chamber


18


as well as the bottom of the chamber


18


.




Still referring to

FIG. 2

, in the preferred embodiment of the invention, a third or outer wall


24


is optionally provided around the wall


20


such that the outer wall


24


is spaced outwardly from the wall


20


around both its sides and bottom thus forming an insulation space


26


between the walls


24


and


20


. This insulation space


26


is preferably maintained in a vacuum thus thermally insulating the outer wall


24


from the reservoir


22


. Alternatively, however, the insulation space


26


can be filled with a thermal insulation.




With reference now to

FIGS. 1 and 2

, a plurality of circumferentially spaced vents


28


are provided around the inner wall


16


adjacent its open top


14


and these vents


28


prohibit excessive pressure buildup in the reservoir


22


. Each vent


28


, furthermore, includes a fluid passageway


30


(

FIG. 2

) which fluidly connects the top of the reservoir


22


to the interior chamber


18


. Furthermore, the outlet from each vent


30


is preferably directed towards the bottom of the chamber


18


so that any vapor flowing outward through the vents


28


is expelled downwardly toward the bottom of the chamber


18


. Alternatively, however, the vents


28


may exhaust exteriorly of the tank


12


.




Referring now to

FIGS. 1 and 2

, a source


32


of liquefied gaseous material, such as liquid nitrogen, is fluidly connected through a valve means


34


to a fill port


36


on the tank


12


. As best shown in

FIG. 2

, this fill port


36


is fluidly connected by a conduit


38


to the reservoir


22


adjacent its bottom.




A valve actuator


40


selectively provides an output signal to the valve means


34


to selectively open the valve means


34


whenever the fluid level in the reservoir


22


is below a predetermined amount and, likewise, to close the valve means


34


whenever the liquid level in the reservoir


22


exceeds a second and higher predetermined level. Thus, by selectively opening and closing the valve means


34


and permitting the liquefied gaseous material to flow from the source


32


and to the reservoir


22


, the valve means


34


and its valve controller


40


maintains the liquid level in the reservoir


22


between predetermined maximum and minimum amounts.




Although the controller


40


may use any conventional means to determine the liquid level within the reservoir


22


, in the preferred embodiment of the invention, the controller


40


is fluidly connected by a conduit


42


to the top of the reservoir


22


and selectively actuates the valve means


34


as a function of the barometric pressure within the reservoir


22


. This barometric pressure varies as a function of the liquid level in the reservoir


22


.




With reference to

FIG. 1

, a lid


50


is preferably disposed across the open top


14


of the tank


12


at all times except when biological specimens are introduced into or removed from the chamber


18


. This top


50


, in the conventional fashion, does not form an airtight seal between the lid


50


and the top


14


of the tank


12


. Rather, the lid


50


allows a continuous flow of vapor from the chamber


18


and exteriorly of the tank


12


.




In practice, the reservoir


22


is partially filled from the source


32


while the valve means


34


and its controller


40


periodically refill the reservoir


22


to maintain the liquid level in the reservoir


22


within predetermined threshold amounts so that the liquefied gaseous material in the reservoir


22


cools the interior chamber


18


and any biological specimens contained in the chamber


18


. Such periodic refilling is required since vapors from the liquefied gas contained in the reservoir


22


continuously exhausts through the vents


30


and preferably into the chamber


18


thus aiding in cooling not only the chamber


18


but also biological specimens contained within the chamber


18


. Furthermore, each time the reservoir


22


is partially refilled from the source


32


, the increase of liquid level in the reservoir


22


exhausts vapors through the vents


28


and preferably into the chamber


18


.




In practice, it has been found that, assuming that nitrogen is utilized as the liquefied gaseous material, the temperature within the chamber


18


can be maintained not only below −140° C., i.e. the amount required to maintain the viability of biological specimens, but can actually maintain the temperature within the chamber


18


at a temperature of less than −190° C. Furthermore, since only gases contained within the chamber


18


are utilized to cool and maintain cold the biological specimens contained with the chamber


18


, cross contamination of the biological specimens is essentially precluded.




Having described my invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.



Claims
  • 1. A cryogenic storage device comprisinga tank having an open top, a bottom and a wall which define an interior chamber adapted to receive biological specimens, a fluid reservoir disposed around an outer surface of said wall and said bottom, an upper end of said reservoir terminating at said open top of said tank, said reservoir adapted to receive a liquefied gaseous material, a source of liquefied gaseous material, means for selectively fluidly connecting said source of liquefied gaseous material to said reservoir so that liquefied gaseous material flows from said source and substantially fills said reservoir wherein thermal conduction through said wall cools said specimens in said tank chamber.
  • 2. The invention as defined in claim 1 and further comprising at least one vent fluidly connecting said reservoir to said interior chamber.
  • 3. The invention as defined in claim 1 and comprising a second wall spaced from and surrounding said first mentioned wall, said reservoir being formed between said walls.
  • 4. The invention as defined in claim 3 and comprising a third wall spaced from and surrounding said second wall and forming an annular chamber therebetween, and thermal insulation disposed in said annular chamber.
  • 5. The invention as defined in claim 4 wherein each of said walls is cylindrical in shape and closed at a bottom end, said walls being coaxial with respect to each other.
  • 6. The invention as defined in claim 1 wherein said at least one vent comprises a plurality of circumferentially spaced vents around an interior surface of said wall.
  • 7. The invention as defined in claim 1 wherein said liquid gaseous material comprises liquid nitrogen.
  • 8. The invention as defined in claim 1 and comprising a lid movable between an open and closed position, wherein in said closed position, said lid overlies and covers said open top of said tank.
  • 9. The invention as defined in claim 1 wherein said selective connecting means comprises a valve fluidly connected in series between said source and said reservoir, means for measuring the level of liquid gaseous material in said reservoir, and means for selectively opening and closing said valve to maintain the level of liquid gaseous material in said reservoir within predefined limits.
  • 10. The invention as defined in claim 9 wherein said measuring means comprises means for measuring barometric pressure in said reservoir above said level of liquid in said reservoir.
US Referenced Citations (8)
Number Name Date Kind
3007319 Ogden Nov 1961
3092974 Haumann et al. Jun 1963
4054037 Yoder Oct 1977
4578963 Sitte Apr 1986
4640099 Gibot Feb 1987
4739622 Smith Apr 1988
4958498 Brothers Sep 1990
4976112 Roberts et al. Dec 1990