FORM 2
THE PATENTS ACT, 1970
(Act 39 of 1970)
COMPLETE SPECIFICATION
(See Section 10; Rule 13)
Title: “Cryogenic liquid based variable temperature cold
storage unit and method”
Applicants: INOX India Pvt. Ltd.
Address: 9th Floor, K P Platina, Race Course, Vadodara -
390007, Gujarat, India.
Nationality: An Indian Company
The following specification describes the nature of the invention and the manner in which is it is to be performed:

FIELD OF THE PRESENT INVENTION
The present invention relates to variable temperature cold storage unit.
More particularly, the present invention relates to a cryogenic liquid based variable temperature cold storage unit that uses liquid cryogen, liquid cryogen vapor or combination of liquid cryogen & cold cryogen vapor. A variable cold storage unit that can be used for cold storage of various specimens including but not limited to vaccines, Siemen, biological samples at a temperature between -200C to -1960C.
BACKGROUND OF THE PRESENT INVENTION
Cold storage unit for storing vaccines, Siemens, Biological samples typically involve (i) A cold storage units filled with liquid cryogen and immersion of specimens in liquid cryogen (ii) A cold storage unit that consists of a liquid cryogen pool at the bottom of the inner vessel or storage chamber with specimens stored above the liquid cryogen pool. (iii) A cold storage unit that consists of cryogen vapour being passed through the storage chamber. The cold storage unit typically also feature double walled vacuum insulated construction. Such freezers provide variable storage temperatures to certain extent.
US7299641B2 of Statis foundation (US) filed on December 12th, 2005 has disclosed a cryogenic storage system for cryogenic storage using liquid refrigerant is provided. The cryogenic storage system includes first and second vacuum vessels, a vacuum source, a quantity of a liquid refrigerant, and at least one temperature control assembly. An insulating wall may be provided on an interior surface of one of the vessels. A common vacuum condition is provided in voids that are present in the wall of the first and second vessels as well as in the insulating wall. The at least one temperature control assembly includes a power supply, a temperature sensor, a heater, and a conductive element. The at least one conductive element provides a link or thermal coupling between a space defined in the first vessel and the liquid refrigerant stored in the second vessel.

US8534079B2 of Chart Inc filed on 18-03-2010 has disclosed a freezer that uses liquid cryogen as a refrigerant includes an inner vessel defining a storage chamber and an outer jacket generally surrounding the inner vessel so that an insulation space is defined there between. A heat exchanger is positioned in a top portion of the storage chamber and has an inlet in communication with a supply of the liquid cryogen refrigerant so that the liquid cryogen refrigerant selectively flows through the heat exchanger to cool the storage chamber while being vaporized. A purge line is in communication with the outlet of the heat exchanger and includes a purge outlet positioned over the exterior of the heat exchanger. A purge valve is positioned within the purge line so that the vaporized liquid cryogen from the heat exchanger is selectively directed to the exterior of the heat exchanger to reduce ice formation on the heat exchanger.
In prior art system & process following are the prime critical issues or disadvantages have been found:
A disadvantage of prior art cold storage units is that they do not offer any flexibility to end user and provide mono-functionality. One type of cold storage unit cannot be used for other modes of cold storage or change according to storage requirements different specimens.
A further disadvantage of prior art is that temperature cannot be directly controlled. In the prior art, the temperature is controlled or maintained by varying or maintaining the amount of liquid cryogen in the reservoir.
A further disadvantage of the prior art is that immersion in liquid cryogen may lead to cross contamination between different specimens stored in different containers.
OBJECTIVES OF THE PRESENT INVENTION
The principal objective of the present invention is to obviate the problems faced by the prior art technologies.

There is an objective to provide cryogenic liquid based variable temperature cold storage unit that can be used for cold storage of various specimens including but not limited to vaccines, Siemen, Biological samples.
It is an objective to provide cryogenic liquid based variable temperature cold storage unit that uses liquid cryogen, liquid cryogen vapor or combination of liquid cryogen & cold cryogen vapor.
Yet it is also an objective to provide cryogenic liquid based variable temperature cold storage unit that can be used for cold storage of various specimens at a temperature between -200C to -1960C.
It is also an objective to provide cryogenic liquid based variable temperature cold storage unit that can be used for other modes of cold storage or change according to storage requirements different specimens including but not limited to vaccines, siemen, biological samples.
One of the objectives of providing cryogenic liquid based variable temperature cold storage unit is to control temperature of the storage unit without varying or maintaining the amount of liquid cryogen in the storage chamber.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.
BRIEF DESCRIPTION OF DRAWINGS
Figure-1: Schematic embodiment of a Variable temperature cold storage
unit in the primary mode (MODE-1) of the present invention in which the
storage chamber (13) is cooled by cold vapour flowing from the top of the
storage unit.
Figure-1(A): Boarder flow diagram of Mode-1

Figure-1(B): Boarder flow diagram of Mode-1: “upon closure of Bypass valve
(08), Inlet valve (11) will open to allow the flow of cryogen or cryogen vapour
via Heat Exchanger (12)”.
Figure-1(C): Boarder flow diagram of Mode-1: “Exhaust valve (07) will
remain in open condition and allow the cryogen or cryogen vapor to flow to
atmosphere until the temperature sensor (05) measured value is equal or
lower than the specified value of temperature”.
Figure-1(D): Boarder flow diagram of Mode-1: “temperature value is
achieved and registered by temperature sensor (05), the Exhaust valve (07)
will be closed and Purge Valve (06) will open allow the flow of cryogen or
cryogen vapour in to Variable temperature cold storage unit”.
Figure-1(E): Boarder flow diagram of Mode-1: “The cryogen or cryogen
vapour cools the Storage chamber (13) and then vents out to atmosphere
via the specified space on the lid (21) of the opening”.
Figure-2: Schematic embodiment of a Variable temperature cold storage
unit in the second mode (MODE-2) of the present invention in which the
storage chamber (13) is cooled by cold vapour from the cryogen pool (25) at
the bottom of the storage chamber (13). Storage chamber (13) and Cryogen
pool (25) are partitioned by specific level platform (23).
Figure-2(A): Boarder diagram of Mode-2
Figure-2(B): Boarder diagram of Mode-2: “upon closure of Bypass valve
(08), automated valve (18) will open to allow the flow of cryogen in to the
Variable temperature cold storage unit”.
Figure-2(C): Boarder diagram of Mode-2: “evaporating vapour from the
cryogen (25) at bottom of Variable temperature cold storage unit will cool
the storage chamber (13) and then vents out to atmosphere via the specified
space on the lid (21) of the opening”.
Figure-3: Schematic embodiment of a Variable temperature cold storage
unit in the third mode (MODE-3) of the present invention in which the
storage chamber (13) is cooled as it is immersed in pool (25) up to the
specified point.

Figure-3(A): Boarder flow diagram (Mode-3)
Figure-3(B): Boarder flow diagram of Mode-3: “upon closure of Bypass valve (08), automated valve (18) will open to allow the flow of cryogen in to the Variable temperature cold storage unit”.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to a cryogenic liquid based variable temperature cold storage unit that uses liquid cryogen, liquid cryogen vapor or combination of liquid cryogen & cold cryogen vapor. A variable cold storage unit that can be used for cold storage of various specimens at a temperature between -200C to -1960C including but not limited to vaccines, Siemen, Biological samples.
The proposed cold storage unit is double walled, vacuum super insulated vessel consisting of inner vessel which acts as storage chamber, outer jacket which surrounds the inner vessel so as to create annular space between inner vessel & outer vessel. Vacuum is created in the annular space to enhance the efficiency of insulation which generally consists of combination of aluminum foil and non-conducting media generally termed as insulation.
Instruments or components are placed strategically inside the storage chamber or inner vessel to achieve efficient cooling.
Hereinafter, embodiments of the present invention are described with reference to drawings.
An embodiment of the cold storage unit of the invention is shown in general in figure-1, 2 and 3.
The cold storage unit mainly comprises of inner vessel (02), and the internal empty or hollow space of the inner vessel (02) represents the storage chamber (13). Outer jacket or vessel (01) surrounds the inner vessel (02) so as to create annular space (03) between inner vessel (02) & outer vessel

(01). Super insulation is part of the annular space (03). If the insulation is
super insulation type then it is wrapped on the outer surface of the inner
vessel (02). In alternate embodiment insulation may be replaced or
supplemented with other insulation materials known in the art and is
installed in annular space (03). Vacuum is created in the annular space
(03) to enhance the efficiency of Insulation.
Vacuum port (15) is provided anywhere on the outer vessel, which is used
to create vacuum in the annular space.
Access to the storage chamber (13) can be eccentric, co-axially, narrow or
wide known in the art. The opening is generally accompanied by the lid (21).
The storage chamber (13) can be provided with different methods of storing
specimens known is the art.
The actual cooling operations are automated as per modes to be operated,
all the embodiments of the modes i.e. mode-1, mode-2 and mode-3 have
been shown in figures:
Mode-1: Figure-1, 1(A), 1(B), 1(C), 1(D) and 1E.
Mode-2: Figure-2, 2(A), 2(B) and 2(C)
Mode-3: Figure-3, 3(A) and 3(B).
The mode of operations can be selected using controller (14). The controller (14) provides user to customize, optimize with configurations to suit the use requirements of specimen storage.
According to the first embodiment, mode-1 is disclosed. Figure-1 is a schematic embodiment in which the storage chamber (13) is cooled by cold vapour flowing from the top of the variable temperature storage chamber.
According to the first embodiment as shown in figure-1, there is provided a cryogenic liquid based variable temperature cold storage unit, the said variable temperature cold storage unit comprising: a) an inner vessel (02);

b) the internal empty space of the inner vessel (02) representing a storage chamber (13) characterized in that the outer surface of the inner vessel (02) is wrapped with super insulation;
c) an outer vessel (01) surrounding the inner vessel so as to create annular space (03) between inner vessel (02) and outer vessel (01) characterized in that the annular space (03) is covered with super insulation and filled with vacuum to enhance the efficiency of the insulation;
d) vacuum port (15) is provided on the outer vessel (01) to create vacuum in the annular space (03);
e) a heat exchanger (12) positioned in the storage chamber (13), said heat exchanger (12) having an outlet and an inlet adapted to communicate with a supply of the liquid cryogen refrigerant so that the liquid cryogen refrigerant may flow through the heat exchanger (12) to cool the storage chamber (13) while being vaporized;
f) an inlet line (17) in communication with the inlet of the heat exchanger (12) and adapted to communicate with the supply of liquid cryogen;
g) a purge valve (06) positioned within the purge line (20) so that the vaporized liquid cryogen from the heat exchanger (12) may be selectively directed to the exterior of the heat exchanger to reduce ice formation on the heat exchanger (12);
h) an exhaust line (18) in communication with the outlet of the heat
exchanger (12) and the inlet line (17); i) an exhaust valve (07) positioned within the exhaust line (18); j) a bypass line (19) in communication with the inlet line (17); k) a bypass valve (08) positioned in the bypass line (19) characterized in
that the bypass valve (08) is an automatic valve and is actuated with
a controller (14); l) an inlet temperature sensor (10) in communication with the inlet line
(17);

m) a purge gas temperature sensor (09) in communication with the purge
line (20); n) an exhaust gas temperature sensor (05) in communication with the
exhaust line (18); o) a chamber temperature sensor (04) in communication with the
storage chamber (13); p) cryogenic storage container (22) is connected to variable cold storage unit through connection (16) for the purpose of supplying liquid cryogen to variable cold storage unit; q) a controller (14) in communication with the inlet line (17), purge line (20), exhaust line (18), temperature sensors (04), (05), (09), (10), the bypass valve (08), purge valve (06) and exhaust valve (07), characterized in that for mode-1, the said controller (14) programmed to: i. open the bypass valve (08) when a temperature of gas flowing through the inlet line (17) is higher than a temperature of the storage chamber (13); ii. close the bypass valve (08) when the temperature of gas flowing through the inlet line (17) is lower than the temperature of the storage chamber (13); iii. open the purge valve (06) and close the exhaust valve (07) when a temperature of gas flowing through the purge line (20) is higher than a minimum desired temperature of the storage chamber (13); iv. close the purge valve (06) and open the exhaust valve (07) when the temperature of gas flowing through the purge line (20) is lower than the minimum desired temperature of the storage chamber (13); v. close the exhaust valve (07) when a temperature of gas flowing through the exhaust line (18) is lower than the minimum desired

temperature of the storage chamber by a predetermined amount;
and vi. close all valves when a temperature of the storage chamber (13) is
less than the minimum desired temperature. Variable temperature cold storage unit needs to be connected to Cryogenic storage container (22) which is capable to continuously supply cryogen as and when needed. Cryogenic storage container (22) can be of any capacity, pressure, single unit or multiple unit, located besides the Variable temperature cold storage unit or connected to Variable temperature cold storage unit via vacuum jacked or other means of transporting cryogens / Cryogen vapors known in prior art, supplying to single or multiple variable temperature cold storage units.
Cryogenic storage container (22) should supply cryogen at constant pressure and generally at pressure lower than 3 barg or lower to Variable temperature cold storage unit. The pressure value can be a specific set point or can be adapted to user requirements.
Cryogenic storage container (22) is connected to Variable temperature cold storage unit through connection (16) suitable for use in cryogenic service. User just needs to select the mode of operation for Variable temperature cold storage unit from controller (14). Upon selection the default values will be displayed; which can be customized as per user requirements and saved. In case of unworkable combinations of values are mentioned then error codes will be displayed.
Upon completion of setting, the controller (14) will sense the temperature of the inlet line (17) coming from Cryogenic storage container (22) via temperature sensor (10) which is installed on the Variable temperature cold storage unit.
If the line temperature value measured via temperature sensor (10) is higher than the specified or default value, then controller (14) will open the bypass valve (08) which is an automatic valve which can be actuated with a controller (14).

Bypass valve (08) will remain in open condition and allow the cryogen or cryogen vapor to flow to atmosphere until the temperature sensor (10) value is equal or lower than the specified value.
Once the required temperature value is achieved and registered by temperature sensor (10), the Bypass valve (08) will be closed.
Border flow diagram is indicated in the Figure-1(A).
User has the provision to bypass the sequence of operation per his need
and illustrated in Figure-1(A).
Either way, upon closure of Bypass valve (08), Inlet valve (11) will open to
allow the flow of cryogen or cryogen vapour via Heat Exchanger (12) as
indicated in Figure-1(B).
Temperature of the cryogen or cryogen vapour will be measured by exhaust
gas temperature sensor (05).
If the measured value is higher than specified or default value, Exhaust
valve (07) will open which is an automatic valve which can be actuated with
a controller (14).
Exhaust valve (07) will remain in open condition and allow the cryogen or
cryogen vapor to flow to atmosphere until the temperature sensor (05)
measured value is equal or lower than the specified value and is illustrated
in Figure-1(C).
Once the required temperature value is achieved and registered by
temperature sensor (05), the Exhaust valve (07) will be closed and Purge
Valve (06) will open to allow the flow of cryogen or cryogen vapour in to
Variable temperature cold storage unit as indicated in Figure-1(D).
The cryogen or cryogen vapour cools the Storage chamber (13) and then
vents out to atmosphere via the specified space on the lid of the opening as
indicated in Figure-1(E).
Temperature of the Storage chamber (13) is measured and recorded via cold
storage temperature sensor (s) (04).

Once the required temperature value is achieved in Storage chamber (13)
the valves process will be closed and system will achieve the steady state.
Only the temperature monitoring will be continued via Temperature
sensors.
The entire process will restart once temperature of the storage chamber (13)
measured via Cold storage temperature sensor (04) exceeds or higher than
the specified value or range.
During the entire process, values of variable temperature may be selected from a temperature range between -200C to -1960C which is dependent on the samples or specimen to be kept in the variable temperature cold storage unit.
According to the second embodiment, mode-2 is disclosed. Figure-2 is a
schematic embodiment in which the storage chamber (13) is cooled by cold
vapour from the cryogen pool (25) at the bottom of the storage chamber
(13).
According to the second embodiment as per figure-2, there is provided a
cryogenic liquid based variable temperature cold storage unit, the said
variable temperature cold storage unit comprising:
a) an inner vessel (02);
b) the internal empty space of the inner vessel (01) representing a storage chamber (13) characterized in that the outer surface of the inner vessel (02) is wrapped with super insulation;
c) an outer vessel (01) surrounding the inner vessel (02) so as to create annular space (03) between inner vessel (02) and outer vessel (01) characterized in that the annular space (03) is covered with super insulation and filled with vacuum to enhance the efficiency of the insulation;
d) vacuum port (15) is provided on the outer vessel (01) to create vacuum in the annular space (03);

e) an inlet line (17) in communication to the bottom of the storage chamber (13) and adapted to communicate with the supply of liquid cryogen;
f) a bypass line (19) in communication with the inlet line (17);
g) a bypass valve (08) positioned in the bypass line (19) characterized in that the bypass valve (08) is an automatic valve and is actuated with a controller (14);
h) an inlet temperature sensor (10) in communication with the inlet line
(17); i) a cold storage temperature sensor (04) in communication with the
storage chamber (13); j) cryogenic storage container (22) is connected to variable cold storage unit through the connection (16) for the purpose of supplying liquid cryogen to variable cold storage unit; k) an automated valve (18) to create cryogenic pool (25) at the bottom of the variable temperature storage chamber (13) through the passing of cryogen from cryogenic storage container (22); l) Storage chamber (13) and Cryogen pool (25) are partitioned by a specific
level platform (23); m) a controller (14) in communication with the inlet line (17) and (24), bypass line (19) and temperature sensors (19) and (04), the bypass valve (08) and Inlet valve (18), characterized in that for mode-2, the said controller programmed to:
i. open the bypass valve (08) when a temperature of gas flowing through the inlet line (17) is higher than a temperature of the storage chamber (13); ii. close the bypass valve (08) when the temperature of gas flowing through the inlet line (17) is lower than the temperature of the storage chamber (13); iii. open the automated valve (18) allowing the flow of cryogen from the bottom of the variable temperature cold storage chamber (13) and

creating cryogen pool (25) at the bottom of the variable temperature cold storage chamber (13) until the cryogen pool (25) reaches at a level (23) of the bottom of the storage chamber (13); iv. close all valves when a temperature of the storage chamber (13) is less than the minimum desired temperature.
Characterized in that evaporating vapour of the cryogen pool (25) allow to cool the variable temperature cold storage chamber (13) and vent out to atmosphere via the space provided on the lid (21) of the opening of the variable temperature cold storage unit. Variable temperature cold storage unit needs to be connected to Cryogenic storage container (22) which is capable to continuously supply cryogen as and when needed. Cryogenic storage container (22) can be of any capacity, pressure, single unit or multiple unit, located besides the Variable temperature cold storage unit or connected to Variable temperature cold storage unit via vacuum jacked or other means of transporting cryogens / Cryogen vapors known in prior art, supplying to single or multiple Variable temperature cold storage units.
Cryogenic storage container (22) should supply cryogen at constant pressure and generally at pressure lower than 3 barg or lower that to Variable temperature cold storage unit. The pressure value can be a specific set point or can be adapted to user requirements.
Cryogenic storage container (22) is connected to Variable temperature cold storage unit through connection (16) suitable for use in cryogenic service. User just needs to select the mode of operation for Variable temperature cold storage unit from controller (14). Upon selection the default values will be displayed; which can be customized as per user requirements and saved. In case of unworkable combinations of values are mentioned then error codes will be displayed.
Upon completion of setting, the controller (14) will sense the temperature of the inlet line (17) coming from Cryogenic storage container (22) via

temperature sensor (10) which is installed on the Variable temperature cold
storage unit.
If the inlet line temperature value measured via temperature sensor (10) is
higher than the specified or default value, then controller (14) will open the
bypass valve (08) which is an automatic valve which can be actuated with a
controller.
Bypass valve (08) will remain in open condition and allow the cryogen or
cryogen vapor to flow to atmosphere until the temperature sensor (10) value
is equal or lower than the specified value.
Once the required temperature value is achieved and registered by
temperature sensor (10), the Bypass valve (08) will be closed.
Border flow diagram is indicated in the Figure-2(A).
Either way, upon closure of Bypass valve (08), automated valve (18) will open to allow the flow of cryogen or cryogen vapour in to the Variable temperature cold storage unit as indicated in Figure-2(B).
The process will continue until the specified level (23) determined by
customer as per requirement (example 310 liter of volume if the container
size is 550 liter) is reached at the bottom of the Variable temperature cold
storage unit.
Evaporating vapour from the cryogen (25) at bottom of Variable temperature
cold storage unit will cool the storage chamber (13) and then vents out to
atmosphere via the specified space on the lid (21) of the opening as
indicated in Figure-2(C).
Temperature of the Storage chamber (13) is measured and recorded via cold
storage temperature sensor (s) (04).
During the entire process, values of variable temperature may be selected from a temperature range between -200C to -1960C which is dependent on the samples or specimen to be kept in the variable temperature cold storage unit.

According to the third embodiment, mode-3 is disclosed. Figure-3 is a schematic embodiment in which the storage chamber (13) is cooled as it is immersed in pool (25) up to the specified level (23) as per customer requirement for example: Customer based on the storage requirement can select the level (23) anywhere between 50% to 100% of the variable temperature storage chamber (13).
Accordingly, as shown in figure-3, a cryogenic liquid based variable temperature cold storage unit comprising:
a) an inner vessel (02);
b) the internal empty space of the inner vessel (02) representing a storage chamber (13) characterized in that the outer surface of the inner vessel (02) is wrapped with super insulation;
c) an outer vessel (01) surrounding the inner vessel (02) so as to create annular space (03) between inner vessel (02) and outer vessel (01) characterized in that the annular space (03) is covered with super insulation and filled with vacuum to enhance the efficiency of the insulation;
d) vacuum port (15) is provided on the outer vessel (01) to create vacuum in the annular space (03);
e) an inlet line (17) and (24) at the bottom of the variable temperature
storage chamber (13) for supplying of liquid cryogen to the variable temperature cold storage chamber (13);
f) a bypass line (19) in communication with the inlet line (17);
g) a bypass valve (08) positioned in the bypass line (17) characterized in that the bypass valve (08) is an automatic valve and is actuated with a controller (14);
h) an inlet temperature sensor (10) in communication with the inlet line
(17); i) a cold storage temperature sensor (04) in communication with the
storage chamber;

j) cryogenic storage container (22) is connected to variable cold storage unit through connection (16) for the purpose of supplying liquid cryogen to variable cold storage unit; k) cryogenic storage container (22) is equipped with pressure limiting device to control the pressure of cryogen being supplied to variable temperature cold storage unit; l) an automated valve (18) to create cryogenic pool (19) and immersing the variable temperature cold storage chamber (13) up to the specified point through the passing of cryogen from the inlet line (17) and (24) of the variable temperature cold storage chamber (13); m) a controller (14) in communication with the inlet line (17) and (24), exhaust line (19), temperature sensors (10) and (04), the bypass (08) and inlet valves (18), characterized in that for mode-3, the said controller programmed to:
i. open the bypass valve (08) when a temperature of gas or liquid flowing through the inlet line (17) is higher than a temperature of the storage chamber (13); ii. close the bypass valve (08) when the temperature of gas or liquid flowing through the inlet line (17) is lower than the temperature of the storage chamber (13); iii. open the automated valve (18) allowing the flow of cryogen from the bottom of the variable temperature cold storage chamber (13) and creating cryogen pool (19) in the variable temperature cold storage chamber (13) until the variable temperature cold storage chamber immerses to a specified level (23); iv. close all valves when a temperature of the storage chamber (13) is less than the minimum desired temperature. Variable temperature cold storage unit needs to be connected to Cryogenic storage container (22) which is capable to continuously supply cryogen as and when needed. Cryogenic storage container (22) can be of any capacity, pressure, single unit or multiple unit, located besides the Variable

temperature cold storage unit or connected to Variable temperature cold
storage unit via vacuum jacked or other means of transporting cryogens /
Cryogen vapors known in prior art, supplying to single or multiple variable
temperature cold storage units.
Cryogenic storage container (22) should be equipped with a pressure
limiting device that limits the pressure of cryogen being supplied to Variable
temperature cold storage unit. The pressure value can be a specific set
value or can be adjusted to user requirements. In an alternate embodiment
the pressure limiting device can be installed on the Variable temperature
cold storage unit.
Cryogenic storage container (22) is connected to Variable temperature cold
storage unit through connection (16) suitable for use in cryogenic service.
User just needs to select the mode of operation for Variable temperature
cold storage unit from controller (14). Upon selection the default values will
be displayed; which can be customized as per user requirements and saved.
In case of unworkable combinations of values are mentioned then error
codes will be displayed.
Upon completion of setting, the controller (14) will sense the temperature of
the inlet line (17) coming from Cryogenic storage container (22) via
temperature sensor (10) which is installed on the Variable temperature cold
storage unit.
If the inlet line (17) temperature value measured via temperature sensor
(10) is higher than the specified or default value, then controller (14) will
open the bypass valve (08) which is an automatic valve which can be
actuated with a controller (14).
Bypass valve (08) will remain in open condition and allow the cryogen or
cryogen vapor to flow to atmosphere until the temperature sensor (10) value
is equal or lower than the specified value.
Once the required temperature value is achieved and registered by inlet
temperature sensor (10), the Bypass valve (08) will be closed.

Border flow diagram is indicated in the Figure-3(A).
Either way, upon closure of Bypass valve (08), automated valve (18) will
open to allow the flow of cryogen or cryogen vapour in to the Variable
temperature cold storage unit as indicated in Figure-3(B).
The process will continue until the specified level is reached in the Variable
temperature cold storage unit.
In all the above embodiments the specimens are paced in the Storage chamber (13). The specimens can be stored in dry storage area (absence of liquid cryogen) and illustrated in embodiments 1 & 2. The specimens can be stored in Liquid cryogen as illustrated in embodiment 3.
Additional features can be added / considered on the this viz.., warning audio/ visual alarms, remote monitoring etc.., to enhance safety & customer conveniences.

LIST & NUMBERING OF COMPONENTS OF COLD STORAGE UNIT AS PER THE PRESENT INVENTION

No.
01 02 03 04
05
06 07 08 09
10 11 12 Part or component No.
13 14 15 16
17
18 19 20 21
22 23 24 25 Part or Component

Outer vessel

Storage chamber

Inner vessel

Controller

Annular space

Vacuum port

Cold storage temperature sensor

Connections

Exhaust gas temperature sensor

Inlet line

Purge valve

Automated valve

Exhaust valve

Exhaust line

Bypass valve

Purge line

Purge gas temperature sensor

Lid

Temperature sensor

Cryogenic storage container

Inlet valve

Plat form

Heat exchanger

Inlet line

Cryogen

WE CLAIM:
1. A cryogenic liquid based variable temperature cold storage unit comprising:
a) an inner vessel (02);
b) the internal empty space of the inner vessel (02) representing a storage chamber (13) characterized in that the outer surface of the inner vessel (02) is wrapped with super insulation;
c) an outer vessel (01) surrounding the inner vessel so as to create annular space (03) between inner vessel (02) and outer vessel (01) characterized in that the annular space (03) is covered with super insulation and filled with vacuum to enhance the efficiency of the insulation;
d) vacuum port (15) is provided on the outer vessel (01) to create vacuum in the annular space (03);
e) a heat exchanger (12) positioned in the storage chamber (13), said heat exchanger (12) having an outlet and an inlet adapted to communicate with a supply of the liquid cryogen refrigerant so that the liquid cryogen refrigerant may flow through the heat exchanger (12) to cool the storage chamber (13) while being vaporized;
f) an inlet line (17) in communication with the inlet of the heat exchanger (12) and adapted to communicate with the supply of liquid cryogen;
g) a purge valve (06) positioned within the inlet line (17) so that the vaporized liquid cryogen from the heat exchanger (12) may be selectively directed to the exterior of the heat exchanger to reduce ice formation on the heat exchanger (12);
h) an exhaust line (18) in communication with the outlet of the heat
exchanger (12) and the inlet line (17); i) an exhaust valve (07) positioned within the exhaust line (18); j) a bypass line (19) in communication with the inlet line (17);

k) a bypass valve (08) positioned in the bypass line characterized in that the bypass valve (08) is an automatic valve and is actuated with a controller (14); l) an inlet temperature sensor (10) in communication with the inlet line
(17); m) a purge gas temperature sensor (09) in communication with the purge
line (20); n) an exhaust gas temperature sensor (05) in communication with the
exhaust line (20); o) a chamber temperature sensor (04) in communication with the
storage chamber (13); p) cryogenic storage container (22) is connected to variable cold storage unit through connection (16) for the purpose of supplying liquid cryogen to variable cold storage unit; q) a controller (14) in communication with the inlet line (17), purge line (20), exhaust line (18), temperature sensors (10), (04), (05) and (09), the bypass valve (08), purge valve (06) and exhaust valve (07), characterized in that for mode-1, the said controller (14) programmed to: i. open the bypass valve (08) when a temperature of gas flowing through the inlet line (17) is higher than a temperature of the storage chamber (13); ii. close the bypass valve (08) when the temperature of gas flowing through the inlet line (17) is lower than the temperature of the storage chamber (13); iii. open the purge valve (06) and close the exhaust valve (07) when a temperature of gas flowing through the purge line (20) is greater than a minimum desired temperature of the storage chamber (13); iv. close the purge valve (06) and open the exhaust valve (07) when the temperature of gas flowing through the purge line (20) is

lower than the minimum desired temperature of the storage
chamber (13); v. close the exhaust valve (07) when a temperature of gas flowing
through the exhaust line (18) is lower than the minimum desired
temperature of the storage chamber by a predetermined amount;
and vi. close all valves when a temperature of the storage chamber (13) is
less than the minimum desired temperature.
2. The cryogenic liquid based variable temperature cold storage unit as claimed in claim-1 wherein heat exchanger is a cooling coil.
3. The cryogenic liquid based variable temperature cold storage unit as claimed in claim-1 wherein cryogen is selected from liquid nitrogen.
4. The cryogenic liquid based variable temperature cold storage unit as claimed in claim-1 wherein the temperature of the chamber is between -200C to -1960C.
5. A cryogenic liquid based variable temperature cold storage unit comprising:

a) an inner vessel (02);
b) the internal empty space of the inner vessel (012) representing a storage chamber (13) characterized in that the outer surface of the inner vessel (02) is wrapped with super insulation;

c) an outer vessel (01) surrounding the inner vessel (02) so as to create annular space (03) between inner vessel (02) and outer vessel (01) characterized in that the annular space (03) is covered with super insulation and filled with vacuum to enhance the efficiency of the insulation;
d) vacuum port (15) is provided on the outer vessel (01) to create vacuum in the annular space (03);
e) an inlet line (17) in communication to the bottom of the storage chamber (13) and adapted to communicate with the supply of liquid cryogen;

f) a bypass line (19) in communication with the inlet line (17);
g) a bypass valve (08) positioned in the bypass line (17) characterized in that the bypass valve (08) is an automatic valve and is actuated with a controller (14);
h) an inlet temperature sensor (10) in communication with the inlet line
(17); i) a cold storage temperature sensor (04) in communication with the
storage chamber (13); j) cryogenic storage container (22) is connected to variable cold storage unit through the connection (16) for the purpose of supplying liquid cryogen to variable cold storage unit; k) an automated valve (18) to create cryogenic pool (25) at the bottom of the variable temperature storage chamber (13) through the passing of cryogen from cryogenic storage container (21); l) Storage chamber (13) and Cryogen pool (25) are partitioned by a
specific level platform (23); m) a controller (14) in communication with the inlet line (17), exhaust line, temperature sensors (04) and (10), the bypass vale (08) and the inlet valve (18), characterized in that for mode-2, the said controller programmed to:
i. open the bypass valve (08) when a temperature of gas flowing through the inlet line (17) is higher than a temperature of the storage chamber (13); ii. close the bypass valve (08) when the temperature of gas flowing through the inlet line (17) is lower than the temperature of the storage chamber (13); iii. open the automated valve (18) allowing the flow of cryogen from the bottom of the variable temperature cold storage chamber (13) and creating cryogen pool (25) at the bottom of the variable temperature cold storage chamber (13) until the cryogen pool (19)

reaches at a specified level (23) of the bottom of the storage chamber (13); iv. close all valves when a temperature of the storage chamber is less than the minimum desired temperature.
Characterized in that evaporating vapour of the cryogen pool (19) allow to cool the variable temperature cold storage chamber (13) and vent out to atmosphere via the space provided on the lid of the opening of the variable temperature cold storage unit.
6. The cryogenic liquid based variable temperature cold storage unit as claimed in claim-5 wherein cryogen is selected from liquid nitrogen.
7. The cryogenic liquid based variable temperature cold storage unit as claimed in claim-5 wherein the temperature of the chamber is between -200C to -1960C.
8. A cryogenic liquid based variable temperature cold storage unit comprising:

a) an inner vessel (02);
b) the internal empty space of the inner vessel (02) representing a storage chamber (13) characterized in that the outer surface of the inner vessel (02) is wrapped with super insulation;

c) an outer vessel (01) surrounding the inner vessel (02) so as to create annular space (03) between inner vessel (02) and outer vessel (01) characterized in that the annular space (03) is covered with super insulation and filled with vacuum to enhance the efficiency of the insulation;
d) vacuum port (15) is provided on the outer vessel (01) to create vacuum in the annular space (03);
e) an inlet line (17) at the bottom of the variable temperature storage
chamber (13) for supplying of liquid cryogen to the variable temperature cold storage chamber (13);
f) a bypass line (19) in communication with the inlet line (17);

g) a bypass valve (08) positioned in the bypass line (19) characterized in that the bypass valve (08) is an automatic valve and is actuated with a controller (14); h) an inlet temperature sensor (10) in communication with the inlet line
(17); i) a cold storage temperature sensor (04) in communication with the
storage chamber; j) cryogenic storage container (22) is connected to variable cold storage unit through connection (16) for the purpose of supplying liquid cryogen to variable cold storage unit; k) cryogenic storage container (17 21) is equipped with pressure limiting device to control the pressure of cryogen being supplied to variable temperature cold storage unit; l) an automated valve (18) to create cryogenic pool (19) and immersing the variable temperature cold storage chamber (13) up to the specified level (23) through the passing of cryogen from the inlet line (17) and (24) of the variable temperature cold storage chamber (13); m) a controller (14) in communication with the inlet line (17) and (24), temperature sensors (10) and (04), the bypass valve (08) and inlet valve (18), characterized in that for mode-3, the said controller programmed to:
i. open the bypass valve (08) when a temperature of gas flowing through the inlet line (17) is higher than a temperature of the storage chamber (13); ii. close the bypass valve (08) when the temperature of gas flowing through the inlet line (17) is lower than the temperature of the storage chamber (13); iii. open the automated valve (18) allowing the flow of cryogen from the bottom of the variable temperature cold storage chamber (13) and creating cryogen pool (19) at the bottom of the variable temperature cold storage chamber (13) until the variable

temperature cold storage chamber immerses to a specified level (23) as entered in controller (14); iv. close all valves when a temperature of the storage chamber (13) is less than the minimum desired temperature.
9. The cryogenic liquid based variable temperature cold storage unit as claimed in claim-8 wherein cryogen is selected from liquid nitrogen.
10. The cryogenic liquid based variable temperature cold storage unit as claimed in claim-8 wherein the temperature of the chamber is between -200C to -1960C.