Information
-
Patent Grant
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6205794
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Patent Number
6,205,794
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Date Filed
Monday, August 2, 199924 years ago
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Date Issued
Tuesday, March 27, 200123 years ago
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Inventors
-
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Examiners
Agents
- Gifford, Krass, Groh, Sprinkle, Anderson & Citkowski, P.C.
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CPC
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US Classifications
Field of Search
US
- 062 511
- 062 78
- 062 4579
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International Classifications
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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)