CRYOGENIC FREEZER

A cryogenic freezer having a housing defining an interior chamber. A first and second fan are positioned in the chamber and are spaced apart from each other. At least one motor is drivingly connected to the fans so that, upon activation of the motor, the fans circulate air through the interior chamber in the same direction.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to a cryogenic storage freezer for biological specimens.

II. Description of Related Art

There are many different situations where it is desirable to store biological specimens for long periods of time. Such biological specimens would include not only body fluids and organic matter, but also biological pharmaceutical agents.

In order to store such biological specimens, the biological specimens are placed in a storage freezer and lowered to a very low temperature, e.g. −100° Celsius or less. At such low temperatures, the biological specimens become completely frozen thus preventing deterioration of the biological specimen over time. Conventionally, liquid nitrogen is used to cool the biological specimens in the freezer, although other super-cooled liquids or gases may alternatively be used.

The previously known cryogenic freezers for storing biological specimens are relatively expensive not only to purchase but also to operate. The primary operation cost for the freezer resides in the cost of the liquid nitrogen which must be frequently introduced into the storage freezer in order to maintain the interior temperature of the storage freezer at the desired ultra-cold temperatures. Consequently, it is highly desirable to store as many biological specimens, typically contained within vials in the freezer in order to reduce the overall cost per vial of the cryogenic freezing and subsequent cost of the liquid nitrogen to maintain the biological specimens in a frozen condition.

In order to obtain viability of the biological specimens when the biological specimens are subsequently removed from the freezer and thawed for use, it is necessary to freeze the biological specimens in a predefined temperature profile and at a freezing rate defined by that profile. Consequently, it is highly desirable to obtain and maintain even cooling of the biological specimens throughout the entire contents of the cryogenic freezer regardless of whether the cryogenic freezer is only partially filled or completely filled with vials of biological specimens.

In order to create an even temperature distribution throughout the entire contents of the cryogenic freezer, not only during the cooling process, but also when the contents of the freezer are completely cooled, the previously known freezers have utilized a fan to circulate the gas from the liquid nitrogen within the interior of the freezer. However, in practice a single fan is unable to create sufficient gas flow within the interior of the cryogenic freezer, particularly when the cryogenic freezer is filled with biological specimens. When this occurs, some of the biological specimens are now frozen in accordance with the required temperature and rate profile which can adversely affect the vitality and viability of the biological specimens upon subsequent removal from the freezer and thawing.

SUMMARY OF THE PRESENT INVENTION

A cryogenic storage freezer may include a housing that defines an interior (freezing) chamber. The housing may have a rectangular, or other, shape and it may be constructed of any suitable material, such as stainless steel. A pair of grates may be positioned in the interior chamber to divide the interior chamber into a pair of end chambers and a central chamber. Trays or other carrying apparatus for biological specimen (or the like) may be positioned in the interior chamber, such as in the central chamber, and a pair of fans driven by one or more motors may be positioned in the interior chamber and spaced apart from each other (with one, e.g., being in each end chamber).

An open top may be provided in the housing to provide access to the interior chamber. The open top may also be accessed by a lid that it is hingedly connected along one side to the housing. Opening and closing of the lid to provide access to the open top may also be assisted by the use of a power actuator connected to the lid.

A tank or other source of ultra-cold liquid gas may be fluidly connected to a liquid gas input on the housing. A control(s) may also be provided to operate the fans and the introduction of liquid as into the interior chamber from the tank or other source.

By proper control the introduction of an ultra-cold liquid gas (e.g., liquid nitrogen) into the interior chamber, coupled with the activation of the motors, the temperature of the central chamber containing biological specimen may be maintained in a highly even fashion so all the specimen contained therein will be cooled and maintained according to a desired temperature profile.

With reference first toFIGS. 1-3, a preferred embodiment of the cryogenic storage freezer10of the present invention is shown. The cryogenic freezer10is generally rectangular in shape having a housing12constructed of any suitable material, such as stainless steel. The housing12defines an interior freezing chamber14(FIG. 3).

As best shown inFIG. 3, a pair of spaced apart fans16and18are positioned within the chamber14. A first motor20is drivingly connected to the first fan16to rotatably drive the fan16upon activation of the motor20. Secondly, a second motor22is drivingly connected to the second fan18so that, upon activation of the second motor22, the second motor22rotatably drives the second fan18. Each, motor20,22may be an electrically powered motor.

Although separate motors20and22are utilized to rotatably drive the fans16and18, respectively, alternatively a single motor may be drivingly connected to both fans16and18so that, upon activation of the single motor, both fans16and18are rotatably driven.

A motor control23controls both the activation and speed of the motors20and22. Furthermore, the fans16and18together with their associated motors20and22upon activation, circulate the air through the chamber14in the same direction, e.g. left to right as viewed inFIG. 3. Furthermore, this may be accomplished by either the selection of the right pitch of the two fans16and18, or the direction of rotation of the fans16and18.

A pair of grates24are preferably disposed within the housing12so that one grate24is positioned adjacent each fan16and18. Furthermore, these grates24divide the interior chamber14into two end chambers26and28, and a central chamber30in between the two grates24. Furthermore, the fans16and18are contained within the end chambers26and28, respectively. In practice, the grates24enable free gas flow through the interior chamber14of the housing12and yet isolate the fans16and18from the central chamber30for safety reasons.

With reference now toFIGS. 3 and 4, the central chamber30has an open top32. A lid34is then pivotally connected by hinges36to the housing12to allow the lid34to move between a closed position, illustrated in solid line inFIG. 4, in which the lid34overlies the open top32of the central chamber30and generally closes the open top32, and an open position, illustrated in phantom line inFIG. 4. In its open position, the lid34provides access to the central chamber30through the open top32so that trays38(FIG. 3) containing biological specimens and the like may be inserted into and removed from the central chamber30. A power actuator40(FIG. 4) is pivotally connected to the lid34. Actuation of the actuator40moves the lid34between its open and closed positions.

In practice, a tank or source42(FIG. 2) of ultra-cold liquid gas, such as liquid nitrogen, is fluidly connected to a liquid gas input44on the housing12. The control23controls not only the operation of the motors20and22, but also the introduction of liquid nitrogen from the tank42into the interior chamber14of the freezer10.

With the lid34in its open position, the tray38containing biological specimens is positioned within the central chamber30of the housing12. The lid34is then closed.

By proper control of the introduction of the liquid nitrogen gas into the interior chamber14, coupled with the activation of the motors20and22, the temperature of the entire central chamber30may be maintained in a highly even fashion so that all the specimens contained within the tray will be cooled according to the desired profile. Any conventional means, furthermore, may be used to control the input of the liquid nitrogen gas into the interior chamber14.

From the foregoing, it can be seen that the present invention provides a cryogenic storage freezer which achieves very even cooling and high precision profile cooling of all of the specimens contained within a specimen tray. 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.