Pulsed Cryogen Freezer

This application is a continuation of and claims priority to U.S. patent application Ser. No. 18/930,874, entitled “PULSED CRYOGEN FREEZER,” which was filed on Oct. 29, 2024. U.S. application Ser. No. 18/930,874 is a continuation of and claims priority to U.S. patent application Ser. No. 17/985,559 (Now U.S. Pat. No. 12,158,295), entitled “PULSED CRYOGEN FREEZER,” which was filed on Nov. 11, 2022. The aforementioned applications are hereby incorporated by reference herein in their entirety.

This specification relates to a system, device, or apparatus for a cryogenic freezer and a method of controlling temperature within the cryogenic freezer.

Vapor phase liquid cryogen freezers have been used for several decades for long term storage of biological specimens, which are heat sensitive. These freezers store the biological samples, materials, products and the like using cryogenic liquids, such as a refrigerant. These freezers may have a reservoir of liquid cryogen, such as liquid nitrogen, in the bottom of the freezer storage chamber with the product stored above the reservoir or partly submerged within the cryogenic liquid. The freezers may be a dewar, which may feature a double-walled, vacuum insulated construction so that the storage chamber is well insulated. Such freezers may provide storage temperatures ranging from approximately −90° C. to −195° C.

The temperature in these freezers may not be directly controlled. Instead, the temperature may be controlled by maintaining the amount of cryogenic liquid in the reservoir. The temperature of the freezer storage compartment may vary depending upon the amount of liquid cryogen in the freezer. Moreover, there is a concern that submerging biological specimens in the cryogenic liquid presents a risk of cross-contamination between specimen containers. Even when the stored specimen containers are placed in the cold vapor above the cryogenic liquid reservoir, there exists a potential for the specimen or specimen container to contact or be submerged within the cryogenic liquid if the freezer is overfilled with the cryogenic liquid.

Accordingly, there is a need for a system and a method to manage and control the temperature within the freezer while preventing the specimen from becoming submerged in the liquid cryogen.

Examples described herein relate to embodiments of a freezer and a method of controlling temperature within a cryogenic freezer. The freezer includes an outer vessel and an inner vessel within the outer vessel. The inner vessel defines a storage chamber. The freezer includes a sensor that measures a temperature within the storage chamber. The freezer may include multiple sensors that measure temperatures within the storage chamber. The freezer includes a controller coupled to the first sensor. The controller pulses an amount of medium into the storage container to control the temperature within the storage container. The medium may be a liquid or gaseous cryogen refrigerant including liquid nitrogen.

In one aspect, the invention is embodied in a freezer. The freezer includes an outer vessel and an inner vessel. The inner vessel is positioned within the outer vessel. The inner vessel defines a storage chamber. The freezer includes a first sensor configured to measure a temperature within the storage chamber. The freezer includes a controller coupled to the first sensor. The controller is configured to pulse an amount of medium into the storage container to control the temperature within the storage container.

These and other embodiments may optionally include one or more of the following features. The freezer may include a turn tray. The turn tray may be positioned within the inner vessel. The turn tray may be configured to hold a number of storage areas. The first sensor may be positioned adjacent to the turn tray. The first sensor may be positioned on the turn tray. A second sensor may be positioned at a bottom of the turn tray. The second sensor may be configured to detect or measure the amount of medium within the storage chamber. The controller may be configured to pulse the amount of medium within the storage chamber further based on the detected or measured amount of medium within the storage chamber. The controller may be configured to decrease a frequency or a timing of the pulse when the detected or measured amount of medium within the storage chamber is greater than or equal to a threshold amount or when the temperature is less than a threshold temperature. To pulse the amount of medium within the storage chamber, the controller may be configured to increase the frequency or the timing of the pulse when the detected or measured amount of medium within the storage chamber is less than the threshold amount and when the temperature is greater than the threshold temperature.

The freezer may further include an outlet that is positioned at a bottom, side wall, or other location of a storage vessel to allow dispensing of medium into a sample space around a turn tray. The freezer may further include an outlet that is positioned at a bottom of the storage chamber and configured to deliver or disperse medium into the storage chamber. The outlet may be a valve, an end to a tube, or another outlet structure. The freezer may further include a medium source that is in fluid communication with the outlet and configured to provide the medium through one or more conduits and out the outlet to deliver or disperse the medium into the storage chamber. The controller may be coupled to the medium source and the outlet. To pulse the amount of medium into the storage container, the controller may be configured to adjust a position of a valve of the outlet to open, partially open, or close the valve or control the medium source to provide the medium through the outlet. The medium source may be a storage container containing a supply of the medium. The medium may be a liquid cryogen refrigerant including liquid nitrogen. The liquid nitrogen may be pressurized for transfer to the outlet.

The controller may be configured to determine a timing or a frequency of the pulsing of the amount of medium into the storage container. The controller may be configured to pulse the amount of medium into the storage container based on the timing or the frequency. The controller may be configured to determine a difference between the temperature within the storage temperature and a set point temperature. The controller may be configured to determine the timing or the frequency of the pulsing of the amount of medium into the storage container based on the difference.

In another aspect, the invention is embodied in a freezer for using liquid cryogen as a refrigerant. The freezer may include an inner vessel defining a storage chamber. The freezer may include an outer vessel surrounding the inner vessel. The outer vessel may define a vacuum-insulated space in between the outer vessel and the inner vessel. The freezer may include a temperature sensor configured to measure a temperature within the storage chamber at a determined height. The freezer may include a controller coupled to the temperature sensor. The controller is configured to pulse an amount of cryogen into the storage container to control the temperature within the storage container. The controller may be configured to pulse an amount of liquid into the storage container to control the temperature within the storage container and also limit an amount of liquid that pools and/or collects at a bottom of the storage container.

These and other embodiments may optionally include one or more of the following features. The freezer may include a turn tray positioned within the inner vessel. The turn tray may be configured to hold a number of storage areas. The temperature sensor may be positioned on or adjacent to the turn tray. The freezer may include a cryogen level sensor positioned at a bottom of the turn tray. The cryogen level sensor may be configured to detect or measure the amount of cryogen within the storage chamber. The controller may be configured to pulse the amount of cryogen within the storage chamber further based on the detected or measured amount of cryogen within the storage chamber. To pulse the amount of cryogen within the storage chamber, the controller may be configured to decrease a frequency or a timing of the pulse when the detected or measured amount of cryogen within the storage chamber is greater than or equal to a threshold amount or when the temperature is less than a threshold temperature. The controller is further configured to increase the frequency or the timing of the pulse when the detected or measured amount of cryogen within the storage chamber is less than the threshold amount or when the temperature is greater than the threshold temperature.

The freezer may further include an outlet that is positioned at a bottom of the storage chamber. The outlet may be an outlet valve. The outlet valve may be configured to deliver or disperse cryogen (e.g., liquid cryogen) into the storage chamber. The freezer may further include a cryogen source that is in fluid communication with the outlet valve and configured to provide the cryogen through one or more conduits and out the outlet valve to deliver or disperse the medium into the storage chamber. The controller may be coupled to the cryogen source and the outlet valve. To pulse the amount of cryogen into the storage container, the controller may be configured to adjust a position of the outlet valve to open, partially open, or close the outlet valve, or control the cryogen source to provide the cryogen through to the outlet valve. The cryogen source may be a storage container containing a supply of the cryogen that includes liquid nitrogen. The liquid nitrogen may be pressurized for transfer to the outlet valve.

In another aspect, the invention is embodied in a method for controlling temperature within a cryogenic freezer. The method includes measuring or detecting a temperature within a storage chamber of the cryogenic freezer by a processor and using a temperature sensor. The method includes determining whether the temperature is greater than or equal to a set-point temperature by the processor. The method includes pulsing an amount of cryogen into the storage chamber when the temperature is greater than or equal to the set-point temperature by the processor and using an outlet valve and a cryogen source.

These and other embodiments may optionally include one or more of the following features. The method may include measuring or detecting the amount of cryogen in the storage chamber by the processor and using a cryogen level sensor. The method may include pulsing the amount of cryogen into the storage chamber based on the amount of cryogen in the storage chamber by the processor and using the outlet valve and the cryogen source. Pulsing the amount of liquid within the storage chamber may include decreasing a frequency or a timing of the pulse when the detected or measured amount of cryogen within the storage chamber is greater than or equal to a threshold amount or when the temperature is less than a threshold temperature. Pulsing the amount of cryogen within the storage chamber may include increasing the frequency or the timing of the pulse when the detected or measured amount of cryogen within the storage chamber is less than the threshold amount or when the temperature is greater than the threshold temperature.

The method may include determining a difference between the temperature within the storage chamber and the set-point temperature. The method may include determining a timing or a frequency of the pulsing of the amount of cryogen into the storage chamber based on the difference. The method may include pulsing the amount of cryogen into the storage chamber based on the timing or the frequency.

Disclosed herein are systems, devices, or apparatuses for a freezer, particularly a freezer for using pulsed cryogen as a refrigerant, and a method of controlling temperature within a cryogenic freezer system. Current freezer technology uses expensive heat exchangers and complex assembly processes to address the risk of exposing material stored within the cold storage space to liquid cryogen (e.g., by submerging the samples in the cryogen). References to cryogen throughout may include liquid cryogen, gaseous cryogen, or a combination of liquid and gaseous cryogen. The pulsed cryogen freezer eliminates the need for the heat exchangers while reducing the risk of liquid nitrogen exposure. The pulsed cryogen freezer maintains the temperature within the payload area of the pulsed cryogen freezer while also controlling the level of cryogen within the payload area of the pulsed cryogen freezer so that the specimen in the payload area does not become submerged or contact the cryogen within.

Other benefits and advantages of the pulsed liquid nitrogen freezer include the capability to expand the usable storage temperature range of the pulsed liquid nitrogen freezer. For example, the usable storage temperature range may expand from −185° C. to −195° C. to −20° C. to −150° C. Moreover, the pulsed liquid nitrogen freezer may be retro-fitted to couple or connect to various different types of high efficiency liquid nitrogen-based freezers. Additionally, the pulsed liquid nitrogen freezer may be configured to be adapted to the various different types of high efficiency liquid nitrogen-based freezers so that the freezers may be applied to various applications.

is a perspective view of a cryogenic freezer. The cryogenic freezerincludes a dewar. The dewarmay be cylindrical or have an alternative shape. The dewarmay be a double-walled flask or container with a vacuum-insulated space between the walls. The dewarmay be used to hold a liquid below ambient temperatures. Temperature-sensitive materials, such as biological samples, may be stored at a low temperature inside the dewar.

The cryogenic freezermay have an access neck. The access neckmay be positioned on top of the dewarand define an access openingthrough which the inside of the dewarmay be accessed. The cryogenic freezermay have a top. The topmay include a removable plate(also called the “Dewar lid”) that covers the access opening.

The cryogenic freezermay include a housing. The housingmay be positioned on top of the dewar. A control panelmay be mounted in a front wall of the housing. The control panelmay include a touch screen and a display. The control panelmay be accessed, viewed, and/or configured. The housingmay house one or more electronic components. In some embodiments, the one or more components may include a controller, as shown infor example.

is a cross-sectional view of the cryogenic freezer. The dewarof the cryogenic freezermay include an outer walland inner wall. The outer walland/or inner wallmay be constructed of a material that includes stainless steel, aluminum alloy or other metal or non-metal that resists cryogenic temperatures. The outer wallmay surround the inner wall. The outer wallmay define an enclosed spaceinside which the inner wallis positioned. The inner wallmay define a storage chamberin which materials, such as biological samples, may be stored at a below ambient temperature, such as at cryogenic temperatures. The spacebetween the outer walland inner wallmay be evacuated of air to provide vacuum insulation. The spacemay include other types of insulation and one or more physical insert configured to reduce heat transfer through the space. In some embodiments, another form-factor and insulated enclosure or vessel may be a substitute for the vacuum insulated dewar.

The access neckon top of the dewarmay define the access openingthrough which the storage chamberof the dewarmay be accessed. The topof the cryogenic freezer may include a removable top platethat covers the access opening. The top platemay be insulated. The top plateof the topmay be opened and closed to provide access to the storage chamberthrough the access opening.

The cryogenic freezermay include one or more temperature sensorsand/or a cryogen level sensor. The temperature sensorsmay be a thermocouple device. The thermocouple device produces a temperature-dependent voltage, and the voltage may be interpreted to measure temperature. A temperature sensormay be located adjacent the top of the cylindrical shaftof the turn tray. The temperature sensormay be located at the top of the cylindrical shaftof the turn tray, which may be the warmest point within the storage chamber. The temperature sensormay measure or detect the temperature within the storage chamber, and when positioned at the top of the cylindrical shaftand/or furthest away from the cooling source, measure or detect the warmest temperature within the storage chamber. The temperature sensormay be positioned below the turn tray. The temperature sensormay be positioned adjacent the bottom of the cylindrical shaftof the turn tray. In various embodiments, the temperature sensormay be positioned at the bottom of the cylindrical shaftof the turn tray. The temperature sensormay measure or detect the temperature closest to the medium pooling or located within the bottom of the storage chamber. The temperature sensormay also be used to measure or detect an amount of medium, such as an amount of cryogen, within the storage chamber. For example, when the temperature sensorfalls below a threshold temperature, such as approximately −190° C., this may indicate that the temperature sensoris submerged within the medium, such as cryogen (e.g., liquid cryogen) or nitrogen, and thus, the payload may be in contact or submerged within the medium. This ensures that the payload is not submerged and/or does not contact the medium that may be pooling within the bottom of the storage chamber. The one or more temperature sensorsmay provide a feedback to the controllerso that the controllermay determine whether the payload within the storage chamberis in contact with or submerged within the medium, and particularly, in contact with or submerged within the liquid medium.

The cryogenic freezermay include a cryogen level sensor. The cryogen level sensormay measure or detect the level of the medium within the storage chamber. The cryogen level sensormay work in combination with the temperature sensorto detect the amount or level of medium that is pooling within the bottom of the storage chamberto determine whether the payload is in contact with or submerged within the medium. The cryogen level sensormay be coupled to the controllervia a connection tube. The connection tubemay be annular. The connection tubemay have an outleton the top.

The cryogenic freezermay include a turn tray. The turn traymay be located within the inner wall. The turn traymay hold a number of storage areas. The storage areas may store temperature-sensitive samples, such as biological materials. An actuatormay be coupled to the turn tray. The actuatormay rotate, spin, move, or otherwise position the turn tray. The turn traymay have a cylindrical shaftthat extends downward in the storage chamber. The actuatormay rotate the cylindrical shaft. In some implementations, the temperature sensormay both be located on the cylindrical shafton the turn trayor elsewhere within the storage chamber. The controllermay control the actuatorto rotate or position the turn trayto provide access to the temperature-sensitive samples stored in the different storage sections of the turn traywhen the topis opened. The turn traymay be accessed through the access openingor by removing the top. Moreover, by rotating or turning the turn tray, the cryogenic freezermay circulate the air and uniformly cool the inside of the storage chamber.

The cryogenic freezermay include an outlet. The outlet may be a valve. The outletmay be positioned at the bottom of the storage chamber. The outletmay be coupled to the controllervia a connection tube. The connection tubemay have an inleton the top. The outletmay be configured to deliver or disperse the medium, such as the cryogen, into the storage chamber. The outletmay be in fluid communication with a cryogen sourceor other medium source. The cryogen sourcemay be configured to provide a medium, such as the cryogen, through the connection tubeand deliver or disperse the cryogen or other medium into the storage chamberout of the outlet. The delivered cryogen may include liquid nitrogen. In some embodiments, the delivered cryogen may be a mixture of liquid and gas and/or other medium. The outletmay point towards the bottom of the inner wallto encourage pulsed cryogen to diffuse and vaporize, thereby reducing pooling of cryogen and enhancing convective heat transfer.

is a schematic diagram of external connections of the cryogenic freezer. The controllermay be a microprocessor or other electronic programmable device. The controllermay have input portsand output ports. The temperature sensors, the cryogen level sensor, and a cryogen inlet temperature sensormay be in communication with the controllerand coupled to the input ports. A cryogen pulse control valveand a gas bypass valvemay be controlled by the controllerand coupled to the output ports.

The temperature sensormay measure or detect a temperature inside the storage chamber. The controllermay receive the measured or detected temperature via the input port. The temperature sensormay take the temperature at or near the warmest point within the storage chamber. The temperature sensormay measure or detect a temperature inside the storage chamberclosest to the medium pooling at the bottom of the storage chamber. The controllermay receive the measured or detected temperature via the input port. The temperature sensormay take the temperature at or near a lowest point of the storage chamber. The controllermay determine a difference between the temperature and the set point temperature. The controllermay determine a timing, a frequency, and/or a length of the pulsing of the cryogen into the storage chamberbased on the difference. In some embodiments, the controllermay compare the temperature to a threshold temperature. The threshold amount may be stored in a local or external memoryor on a cloud server. The controllermay decrease the timing or the frequency of the pulse when the temperature is less than the threshold temperature. The controllermay increase the timing, the frequency, and/or the length of the pulse when the temperature is greater than the threshold temperature.

The controllermay control the pulse duration or length. The control of the pulse duration or length may be based on the desired user operating temperature and dimensions of the storage chamber. Pulse duration may be directly proportional to the dimensions of the storage chamberand inversely proportional to the desired user operating temperature. Pulse duration limits may be based on historical control and/or use data.

The memorymay be coupled to the controllerand store instructions that the controllerexecutes. The memorymay include one or more of a Random Access Memory (RAM), Read Only Memory (ROM), USB storage device or other volatile or non-volatile memory. The memorymay be a non-transitory memory or a data storage device, such as a hard disk drive, a solid-state disk drive, a hybrid disk drive, or other appropriate data storage, and may further store machine-readable instructions, which may be loaded and executed by the processor.

The temperature sensorand/or cryogen level sensormay measure or detect the amount of medium, such as cryogen, within the storage chamber. The controllermay receive the measured or detected amount of cryogen within the storage chambervia the input port. The controllermay pulse cryogen into the storage chamberbased on the measured or detected amount of cryogen within the storage chamberto prevent the filling of the cryogen to pool within the bottom of the storage chamberand contact the payload. The controllermay compare the measured or detected amount of cryogen to a threshold amount. The threshold amount may be stored in a local or external memoryor on a cloud server. The controllermay decrease a frequency, a timing and/or a length of the pulse when the measured or detected amount of cryogen within the storage chamberis greater than or equal to a threshold amount. The controllermay increase the frequency, the timing and/or the length of the pulse when the measured or detected amount of cryogen within the storage chamberis less than the threshold amount and cooling is needed to maintain the temperature below the set-point temperature.

The cryogen inlet temperature sensormay measure or detect a temperature of the cryogen at an outlet of the cryogen sourceprior to the cryogen entering the inlet. The controllermay receive the measured or detected cryogen inlet temperature via the input port. The controllermay compare the detected cryogen inlet temperature to the temperature of the storage chamber. If the cryogen inlet temperature is greater than the temperature of the storage chamber, the controllermay control the gas bypass valveto prevent cryogen in gas form that is higher in temperature than the storage chamberfrom entering the storage chamberduring a cooling cycle. Once the cryogen temperature equals the set point temperature inside the storage chamber, the controllermay control the gas bypass valveto allow cryogen into the storage chamber.

The cryogen pulse control valvemay pulse cryogen into the storage chamberto control the temperature within the storage chamber. The controllermay control the cryogen pulse control valveto open, partially open, or close. In the open state, the cryogen pulse control valvemay allow cryogen into cryogenic freezerthrough the inlet. In the partially open state, the cryogen pulse control valvemay allow less cryogen into the cryogenic freezerthrough the inletthan the open state. In the closed state, the cryogen pulse control valvemay stop the delivery cryogen into the cryogenic freezer. The controllermay pulse the cryogen by turning the one or more valves into an “ON” or “OPEN” state and then “OFF” or “CLOSED” state and cycling between the different states for different or same lengths of time.

A supply plumbing relief valvemay be situated between the cryogen sourceand the cryogen pulse control valve. The supply plumbing relief valvemay open or close to create a difference in pressure between the cryogen sourceand the cryogen pulse control valve. In the open position, the supply plumbing relief valvemay release pressure to adjust the pressure differential. In the closed position, the supply plumbing relief valvemay maintain an existing pressure. The pressure differential may allow the medium, such as cryogen, to travel from the cryogen sourceto the cryogen pulse control valve. In some embodiments, there may be a pump instead of the supply plumbing relief valveto pump the cryogen from the cryogen sourceto the cryogen pulse control valve.

The cryogen sourcemay be a tank storing the medium, such as cryogen, under pressure. The medium may be a liquid cryogen, such as liquid nitrogen. The cryogen may evaporate while being transported through the plumbing to the cryogen pulse control valve. When gaseous cryogen temperature is greater than the temperature of the storage chamber, the controllermay control the gas bypass valveto prevent the gaseous cryogen that has a higher temperature than the set-point temperature from entering the storage chamber. When the gaseous cryogen cools to a temperature equal to or less than the temperature of the storage chamber, the controllermay control the gas bypass valveto allow the gaseous cryogen or a mixture of liquid and gaseous cryogen to enter the storage chamber. Allowing gaseous cryogen or a mixture of liquid and gaseous cryogen to enter the storage chamberto cool the storage chambermay conserve cryogen and increase the overall system efficiency.

The controllermay be coupled to a network access device. The network access devicemay include a communication port or channel, such as one or more of a Dedicated Short-Range Communication (DSRC) unit, a Wi-Fi unit, a Bluetooth® unit, a radio frequency identification (RFID) tag or reader, or a cellular network unit for accessing a cellular network (such as 3G, 4G or 5G). The network access devicemay transmit data to and receive data from a remote device. The remote devicemay be a stationary or a portable computing device including a smartphone, a laptop computer, a desktop computer, a tablet computer, and/or the like. For example, the remote devicemay use the network access deviceto communicate with the cryogenic freezer, such as monitor and/or control the temperature and/or the amount of cryogen inside the storage chamber.

The controllermay be coupled to a user interface. The user interfacemay receive user input such as a threshold temperature or a threshold amount of cryogen inside the storage chamber. The user input may cause the controllerto control the pulsing frequency or timing of the cryogen.

The user interfacemay provide notifications to the user or other operator, such as when the amount of cryogen inside the storage chamberreaches or exceeds a threshold level. The user interfacemay display statistics such as the amount of cryogen inside the storage chamber, the frequency, length or the timing of pulsing cryogen into the dewar, and/or other statistics related to filling the dewarwith the cryogen. The user interfacemay also display alerts, such as the need to increase or decrease the frequency or the timing of the pulsing of the cryogen.

is a flow diagram of a processfor controlling temperature within the cryogenic freezer. One or more computers or one or more data processing apparatuses, for example, the controller, appropriately programmed, may implement the process. The various components of the cryogenic freezer, such as the temperature sensors, the cryogen level sensor, outlet valve, cryogen source, and cryogen pulse control valvemay implement the process.

The cryogenic freezermay obtain a set-point temperature and/or a threshold for an amount of medium (). The user interfacemay receive user input that indicates the set-point temperature and/or the threshold level of medium. The set-point temperature may be indicative a temperature where cryogenic freezing is insufficient or reduced to maintain the cryogenic temperature to preserve the payload within the storage chamber. The threshold level of medium may be indicative of an amount of medium within the storage chamber that would contact the payload that is stored in the storage chamber. The set-point temperature and/or the threshold level of medium may be user-inputted, pre-configured, pre-determined or otherwise obtained or determined.

The cryogenic freezermay measure or detect a temperature within the storage chamber(). The cryogenic freezermay use the temperature sensorto measure or detect the temperature within the storage chamberof the cryogenic freezer. The temperature sensormay be positioned at the top of the cylindrical shaftof the turn trayso that the temperature sensoris furthest from the medium that is pooled within the storage chamberand that cools the storage chamberand close to the topwhere ambient air may enter when the top plateof the topis opened. Thus, the temperature sensormay be exposed to and measure or detect the warmest temperature within the storage chamber. The temperature sensormay be positioned at the bottom of the cylindrical shaftto measure or detect a temperature at or near the medium that is pooling within the storage chamber. In some implementations, the controllermay calculate an average temperature among the one or more measured or detected temperatures from the one or more temperature sensors. The temperature may be measured, detected, or calculated over a period of time or time interval. The different variations of the temperature may herein be referred to as “temperature” throughout the the specification.

The cryogenic freezermay measure or detect a level or an amount of medium within the storage chamber(). The cryogenic freezermay use the cryogen level sensorand/or the temperature sensorto measure or detect the level or the amount of medium within the storage chamber. For example, the cryogenic freezermay detect when the medium contacts the cryogen level sensorto determine that the medium has exceeded a particular amount of medium within the bottom of the storage chamber. In another example, when the temperature sensorfalls below a threshold temperature, this may indicate that the temperature sensoris in contact with the medium and that the medium has reached a threshold amount in the bottom of the storage chamber. The cryogenic freezermay use the measured or detected level or the amount of medium and the temperature to control the delivery of the medium into the storage chamber, e.g., the position of one of more valves, such as the outlet valve, that allow the flow of the medium into the storage chamber.

The cryogenic freezermay determine whether the temperature is greater than or equal to a set-point temperature (). The set-point temperature is a temperature or a range of temperatures at which the user desires to maintain the temperature of the storage chamber. The temperature sensormay be located at the top of the cylindrical shaftof the turn tray. When the temperature is less than the set-point temperature, this may indicate that the temperature within the storage chamberis within a temperature range sufficient to maintain the cryogenic temperatures necessary for the payload stored within the storage chamber. The cryogenic freezermay reduce, pause or stop the delivery or pulsing of the medium to maintain the temperature within the storage chamber(). This may include reducing, pausing or stopping the delivery or pulsing of the medium into the storage chamberto allow the temperature within the storage chamberto be maintained below the set-point temperature without delivering too much medium into the storage chamber.

The cryogenic freezermay reduce, pause or stop the delivery or pulsing of the medium into the storage chamberto prevent the payload from submerging in the medium that pools within the bottom of the storage chamber. The cryogenic freezermay adjust a frequency or a timing, such as reducing a frequency or reducing a length of time, of the delivery of the medium into the storage chamber. The controllermay control the cryogen pulse control valveand/or the outlet valveto open or close at a decreased frequency or an increased time interval in between openings of the outlet valveand/or remain open for a shorter time interval. The cryogenic freezerthen continues to monitor or detect the temperature within the storage chamber().

Otherwise, when the temperature is greater than or equal to the set-point temperature, the cryogenic freezermay determine a timing and/or frequency of the delivery of the medium to provide additional cooling (). The timing of the delivery of the medium may refer to a length of time of each pulse of medium that is delivered, which is a result of one or more valves being opened and then closed, and the frequency of the delivery of the medium may refer to the number of pulses of medium that are delivered per time interval, such as per second or per hour. The initial timing and/or the initial frequency may be based on the size of the storage chamberand the set-point temperature to reach a steady-state temperature that is below the set-point temperature, which may be user-configured or calculated by the controller.further describes the processfor determining the timing and/or the frequency of the pulsing of the medium into the storage chamber. The pulsing of the medium into the storage chambermay provide cooling and/or additional cooling into the storage chamberto maintain the temperature below the set-point temperature and maintain the target temperature for the payload. In various embodiments, the target temperature is a cryogenic freezing temperature.

Once the timing and/or frequency of the pulsing of the medium into the storage chamberis determined, the cryogenic freezermay determine whether the amount or level of the medium is greater than or equal to threshold amount (). When the amount or level of the medium is greater than or equal to the threshold amount, this may indicate that that the payload in the storage chamberis in contact or submerged underneath the medium that has or is pooling at the bottom of the storage chamber. When the payload is in contact or submerged underneath the medium, the medium may contaminate the payload. And so, the cryogenic freezermay reduce, pause or stop the delivery or pulsing of the medium to maintain the temperature within the storage chamberwithout the payload contacting or submerging underneath the medium, as described above ().

Otherwise, when the amount or level of the medium is less than the threshold amount, the cryogenic freezermay pulse or continue to pulse the medium into the storage chamberto cool or provide additional cooling within the storage chamber(). The cryogenic freezermay pulse the medium into the storage chamberbased on the determined timing and/or frequency. The cryogenic freezerpulses an amount of medium into the storage chamberwhen the temperature is greater than or equal to the set-point temperature and when the amount or level of medium is less than the threshold amount. The pulsed medium may be a liquid cryogen or a mixture of gas and liquid. The controllermay control the cryogen pulse control valveto transport cryogen to the outlet valvefor the outlet valveto expel the medium. The controllermay control the outlet valveto fully open or partially open to adjust the rate of the cryogen entering into the storage chamber. For example, if the temperature is less than the set-point temperature, the outlet valvemay partially open to pulse cryogen at a slower rate. On the other hand, if the temperature is greater than or equal to the set-point temperature, the outlet valvemay more fully open the outlet valveto pulse cryogen at a faster rate.further describes the process of adjusting the amount to open or close the outlet valveto control the pulsing of the medium. Regardless, the cryogenic freezermay continue to monitor the temperature and level or amount of medium in the storage chamberto maintain the temperature within the storage chamberuntil the cryogenic freezer is deactivated ().

is a flow diagram of a processfor determining the timing and/or frequency of the pulsing of the medium into the storage chamber using the cryogenic freezer. One or more computers or one or more data processing apparatuses, for example, the controller, appropriately programmed, may implement the process. The various components of the cryogenic freezer, such as the temperature sensors, outlet valve, cryogen source, and/or cryogen pulse control valvemay implement the process.

Once the temperature within the storage chamberis determined or detected and the amount of medium is less than the threshold amount, the cryogenic freezermay determine a difference between the temperature within the storage chamberand the set-point temperature (). The difference may be a measure of the magnitude of the temperature that exceeds the target temperature range to maintain the payload within the storage chamber. The target temperature range may be a cryogenic temperature range. The difference may correlate or correspond with the amount of additional cooling that is necessary to reduce the temperature to below the set-point temperature. For example, the larger the difference, the more additional cooling that is required to cool the storage chamberto bring the temperature down below the set-point temperature.