Abstract:
An air cargo container temperature control system and method utilizing multiple refrigeration circuits and a controller that activates one or more of the refrigeration circuits in various modes to maintain temperature control. Each of the refrigeration circuits comprises a compressor, a condenser, and an evaporator all in fluid communication to form each refrigeration circuit. Additionally, heating elements are positioned in an evaporator cell for heating load space air and/or defrosting evaporator coils. The system is also provided with a battery pack having a transformer and battery chargers for charging corresponding battery cells by transforming power from an external source. The method compares a measured temperature to a set point temperature and activates one or more refrigeration circuits depending on the temperature difference.

Description:
REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/722,269 filed on Sep. 30, 2005, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to temperature control systems and, more particularly, to a temperature control system for cargo carriers and a method of operating the same.  
       SUMMARY  
       [0003]     Some embodiments of the present invention provide a temperature control system for conditioning air in a load space. The temperature control system can include a refrigeration circuit extending between a compressor, an evaporator coil, and a condenser. The temperature control system can also include a controller programmed to control operation of the temperature control system and to regulate the temperature of the load space. The controller can be programmed to operate the temperature control system in a cooling mode, a heating mode, and a defrost mode based, at least in part, on data received from one or more sensors distributed along the refrigeration circuit and/or positioned in the load space. In addition, some embodiments of the present invention include a battery and an on-board charger for recharging the battery using an external power supply.  
         [0004]     In addition, some embodiments of the invention provide a method for controlling operation of a temperature control system having a plurality of refrigeration circuits, a battery pack, and a power cord. The method can include the acts of sensing a temperature in a load space, operating the temperature control system in a heating mode or cooling mode based, at least in part, on the sensed temperature, powering the temperature control system with power from the battery, and recharging the battery with an external power source.  
         [0005]     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a front perspective view of a carrier and a temperature control system according to some embodiments of the present invention.  
         [0007]      FIG. 2  is a front perspective view of the temperature control system shown in  FIG. 1 .  
         [0008]      FIG. 3  is a top view of the temperature control system shown in  FIG. 1 .  
         [0009]      FIG. 4  is a bottom view of the temperature control system shown in  FIG. 1 .  
         [0010]      FIG. 5  is a front view of the temperature control system shown in  FIG. 1 .  
         [0011]      FIG. 6  is a rear view of the temperature control system shown in  FIG. 1 .  
         [0012]      FIG. 7  is a left side view of the temperature control system shown in  FIG. 1 .  
         [0013]      FIG. 8  is a right side view of the temperature control system shown in  FIG. 1 .  
         [0014]      FIG. 9  is an enlarged front perspective view of the temperature control system shown in  FIG. 1  with a portion cut away.  
         [0015]      FIG. 10  is a schematic illustration of the temperature control system shown in  FIG. 1 .  
         [0016]      FIG. 11  is rear perspective of the battery pack shown in  FIG. 1 .  
         [0017]      FIGS. 12A-12B  are flowcharts illustrating a method operating a temperature control system according to the present invention. 
     
    
       [0018]     Before the various embodiments of the present invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that phraseology and terminology used herein with reference to device or element orientation (such as, for example, terms like “central,” “upper,” “lower,” “front,” “rear,” and the like) are only used to simplify description of the present invention, and do not alone indicate or imply that the device or element referred to must have a particular orientation. The elements of the temperature control system referred to in the present invention can be installed and operated in any orientation desired. In addition, terms such as “first,” “second,” and “third” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance.  
         [0019]     Also, the use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.  
       DETAILED DESCRIPTION  
       [0020]      FIG. 1  illustrates a carrier  10  and a temperature control system  14  according to some embodiments of the present invention. The carrier  10  of the illustrated embodiment is a shipping container and can be mounted on a straight truck, a tractor-trailer combination, a railcar, a ship, a boat, and/or an airplane. As shown in  FIG. 1 , the carrier  10  includes an outer wall  18 , which at least partially defines a load space  22  and which at least partially supports the temperature control system  14 . The outer wall  18  includes a cargo door  24 , which provides access to the load space  22  for loading cargo into and unloading cargo from the load space  22 .  
         [0021]     As used herein, the term “load space” includes any space to be temperature and/or humidity controlled, including transport and stationary applications for the preservation of food, beverages, plants, flowers, and other perishables and maintenance of a desired atmosphere for the shipment of industrial products.  
         [0022]     In some embodiments, the temperature control system  14  can include a housing  25 , a battery pack  26 , and a storage chamber  30 . In the illustrated embodiment of  FIG. 1 , the temperature control system housing  25 , the battery pack  26 , and the storage chamber  30  are located adjacent to the load space  22  in respective upper, central, and lower portions of the carrier  10 . In other embodiments, the temperature control system housing  25 , the battery pack  26 , and the storage chamber  30  can have alternative relative orientations (e.g., horizontally or vertically in-line, or spaced throughout the carrier  10 ) and locations within the carrier  10  (e.g., the temperature control system housing  25  can be located in a lower portion of the carrier  10 , the battery pack  26  can be located in a central portion of the carrier  10 , and the storage chamber  30  can be located in a lower portion of the carrier  10 ).  
         [0023]     The temperature control system  14  of the illustrated embodiment of  FIG. 1  is operable to condition load space air and to maintain load space air temperature and/or humidity within a desired range surrounding a set point temperature T SP  (e.g., 5° C.) and/or a set point humidity H SP  (e.g., 60°).  
         [0024]     In some embodiments, the temperature control system housing  25  supports an evaporator  34  and defines an air inlet  38  and an air outlet  42 . In other embodiments, the temperature control system housing  25  can include two, three, or more air inlets  38  and/or two, three, or more air outlets  42 . During operation of the temperature control system  14  and as explained in greater detail below, one or more fans or blowers  44  draw air from the load space  22  into the evaporator  34  through the air inlet  38 , direct the load space air across evaporator coils (described below), and vent the air back into the load space  22  through the air outlet  42 . In some embodiments, load space air is also or alternately vented to the outside of the carrier  10  to vent CO 2  or other exhaust gasses from the load space  22  and to maintain the quality of the air in the load space  22 .  
         [0025]     In the illustrated embodiment of  FIGS. 1 and 9 , the temperature control system housing  25  supports a first refrigeration circuit  46 , a second refrigeration circuit  50 , and a third refrigeration circuit  54 . In other embodiments, the temperature control housing  25  can at least partially support one, two, four, or more refrigeration circuits.  
         [0026]     In some embodiments, such as the illustrated embodiment of  FIGS. 2-10 , the first refrigeration circuit  46  includes and fluidly connects a compressor  58  (e.g., a hermetic compressor), an evaporator coil  62 , and a condenser  66  located in respective upper, lower, and central portions of the temperature control system housing  25 . More particularly, in the illustrated embodiment of  FIGS. 1-10  of the present invention, the compressor  58  is positioned on one side of the temperature control system housing  25 , the condenser  66  is positioned on the other side of the temperature control system housing  25 , and the evaporator coil  62  extends through the evaporator  34 . In other embodiments, one or more of the compressor  58 , evaporator coil  62 , and condenser  66  can have alternative relative orientations (e.g., horizontally or vertically in-line or spaced throughout the housing) and locations within the housing  25  (e.g., the condenser  66  can be located in an upper portion of the housing  25 , the compressor  58  can be located in a central portion of the housing  25 , and the evaporator coil  62  can be located in a lower portion of the housing  25 ).  
         [0027]     In embodiments having a second refrigeration circuit  50 , such as the illustrated embodiment of  FIGS. 2-10 , the second refrigeration circuit  50  can include and fluidly connect a compressor  74  (e.g., a hermetic compressor), an evaporator coil  78 , and a condenser  82  located in respective upper, lower, and central portions of the temperature control system housing  25 . More particularly, in the illustrated embodiment of  FIGS. 1-10  of the present invention, the compressor  74  is positioned on one side of the temperature control system housing  25  adjacent to the compressor  58  of the first refrigeration circuit  46 , the condenser  82  is positioned on the other side of the temperature control system housing  25  adjacent to the condenser  66  of the first refrigeration circuit  46 , and the evaporator coil  62  extends through the evaporator  34  adjacent to the evaporator coil  62  of the first refrigeration circuit  46 . In other embodiments, one or more of the compressor  74 , evaporator coil  78 , and condenser  82  can have alternative relative orientations and locations within the housing  25 .  
         [0028]     In embodiments having a third refrigeration circuit  54 , such as the illustrated embodiment of  FIGS. 2-10 , the third refrigeration circuit  54  can include and fluidly connect a compressor  90  (e.g., a hermetic compressor), an evaporator coil  94 , and a condenser  98  located in respective upper, lower, and central portions of the temperature control system housing  25 . More particularly, in the illustrated embodiment of  FIGS. 2-10  of the present invention, the compressor  90  is positioned on one side of the temperature control system housing  25  adjacent to the compressor  58  of the first refrigeration circuit  46  and the compressor  74  of the second refrigeration circuit  50 , the condenser  98  is positioned on the other side of the temperature control system housing  25  adjacent to the condenser  66  of the first refrigeration circuit  46  and the condenser  82  of the second refrigeration circuit  50 , and the evaporator coil  94  extends through the evaporator  34  adjacent to the evaporator coil  62  of the first refrigeration circuit  46  and the evaporator coil  78  of the second refrigeration circuit  50 . In other embodiments, one or more of the compressor  90 , evaporator coil  94 , and condenser  98  can have alternative relative orientations and locations within the housing  25 .  
         [0029]     In the illustrated embodiment of  FIGS. 2-10 , the compressors  58 ,  74 , and  90  of the first second and third refrigeration circuits  46 ,  50 ,  54  are grouped together to define a compressor cell  106 . The condensers  66 ,  82 ,  98  of the first, second and third refrigeration circuits  46 ,  50 ,  54  are grouped together to define a condenser cell  110 . The evaporators  62 ,  78 , and  94  of the first, second and third refrigeration circuits  46 ,  50 ,  54  are grouped together and are positioned together to define an evaporator cell  114 . In the illustrated embodiment of  FIGS. 2-10 , the evaporator cell  114  is positioned in the evaporator housing  25 .  
         [0030]     In some embodiments of the present invention, the temperature control system  14  includes a controller  118  having a microprocessor  122  which controls and coordinates operation of the temperature control system  14 . In these embodiments, the controller  118  is programmed to operate the temperature control system  14  in a COOLING mode, a HEATING mode, a DEFROST mode, and a NULL mode, based at least in part upon the set point temperature T SP , the set point humidity H SP , the ambient temperature, the load space temperature, and/or the cargo in the load space  22 .  
         [0031]     The temperature control system  14  can include one or more temperature sensors  138 . In some embodiments, a temperature sensor  138  is positioned in the load space  22  to record load space temperature. In other embodiments, a temperature sensor  138  is positioned in the air inlet  38 . In still other embodiments, a temperature sensor  138  is positioned in the air outlet  42 . The temperature control system  14  can also or alternately include temperature and/or pressure sensors distributed along one or more of the first, second, and third refrigeration circuits  46 ,  50 ,  54  for sensing the temperature and/or pressure of refrigerant in one or more of the first, second, and third refrigeration circuits  46 ,  50 ,  54 . In these embodiments, data recorded by the sensors  138  is transmitted to the controller  118 .  
         [0032]     As shown in  FIGS. 2-10 , the temperature control system  14  can include one or more heating elements (e.g., heating coils, pan heaters, propane-fueled burners, and the like) positioned in the evaporator  34  for heating load space air and/or defrosting the evaporator coils  62 ,  78   94 . In other embodiments, warm refrigerant can be directed through the evaporator coils  62 ,  78 ,  94  to warm load space air, or alternatively, to defrost the evaporator coils  62 ,  78 ,  94  during operation in the DEFROST mode. In the illustrated embodiment of  FIGS. 2-10 , first and second heating elements  130 ,  134  are positioned in the evaporator  34  adjacent to the evaporator coils  62 .  78 .  94 .  
         [0033]     As mentioned above, the temperature control system  14  can include a battery pack  26 . In the illustrated embodiment of  FIGS. 1 and 11 , the battery pack  26  includes a battery housing  139  supported in an opening in the outer wall  18  adjacent to the temperature control system housing  25 .  
         [0034]     The battery pack  26  of the illustrated embodiment includes first and second battery cells  140   a ,  140   b . In other embodiments, the battery pack  26  can include one, two, four, or more battery cells  140 . Each of the battery cells  140  is operable to store an electrical charge and to power the temperature control system  14 .  
         [0035]     During normal operation of the temperature control system  14 , the battery cells  140   a ,  140   b  supply power to elements of the temperature control system  14 . In this manner, the temperature control system  14  can operate independently for extended periods of time (e.g., between about twenty and about forty hours) without requiring an external power supply. More particularly, the temperature control system  14  and the carrier  10  of the present invention can be loaded onto airplanes and other vehicles and can be moved away from external power supplies for extended periods of time.  
         [0036]     The battery pack  26  also supports a transformer  141  and first and second battery chargers  142   a ,  142   b  for charging corresponding battery cells  140   a ,  140   b . When the electrical charge in one or more of the battery cells  140   a ,  140   b  is low and/or when the temperature control system  14  and the carrier  10  are located near an external power supply (e.g., in a warehouse or on a loading dock), electrical power can be transferred from the external power supply to the battery chargers  142   a ,  142   b  to charge the battery cells  140   a ,  140   b  and to power elements of the temperature control system  14 . In some embodiments, electrical power is directed through the transformer  141 , which transforms the electrical power from the external power source into a form which can be stored by the batteries (e.g., the transformer converts the electrical power from AC to DC). In other embodiments, the transformer  141  and/or the battery chargers  142   a ,  142   b  convert power from a first voltage to a second voltage (e.g., from 24 volts to 12 volts).  
         [0037]     In some embodiments, such as the illustrated embodiment of  FIG. 1 , a power cord  143  is stored in the storage chamber  30 . In these embodiments, an operator can use the power cord  143  to electrically connect one or more of the battery chargers  142   a ,  142   b  and the transformer  141  to the external power source. In addition, in some embodiments, a number of plugs or adapters  144  are housed in the storage chamber  30 . Each of the adapters  144  has a different configuration and is engageable with a different external power source.  
         [0038]      FIGS. 12A and 12B  illustrate a method of operating a temperature control system  14  according to the present invention. More particularly,  FIGS. 12A and 12B  outline an algorithm in the form of a computer program that can be used to practice the present invention.  
         [0039]     Each time the temperature control system  14  is switched on (i.e., booted-up), the controller  1   8  initiates a startup routine. Among other things, the startup routine determines if the temperature control system  14  is operating correctly and searches for errors in the controller&#39;s programming and mechanical failures in the temperature control system  14 . If an error is detected, the controller  118  can be programmed to activate an alarm to alert an operator.  100391  Following startup, the temperature sensor(s)  138  record a temperature T and transmit temperature data to the controller  118  at act  146 . As explained above, temperature sensors  138  can be positioned throughout the load space  22  and the temperature control system  14 . Accordingly, in some embodiments of the present invention, the temperature T recorded by the sensors  138  can be the temperature of air in the load space  22 , the temperature of air entering the evaporator  34 , the temperature of air in the air inlet  38 , the temperature of air exiting the evaporator  34 , the temperature of air in the air outlet  42 , and/or the temperature of refrigerant exiting the evaporator coils  62 ,  78 ,  94  of first, second, and third refrigeration circuits  46 ,  50 ,  54 .  
         [0040]     At act  150 , the controller  118  compares the temperature T recorded by the sensor(s)  138  to the set point temperature T SP . If the temperature T is greater than the set point temperature T SP  (“NO” at act  150 ), the controller  118  is programmed to operate the temperature control system  14  in a COOLING mode (described below). Alternatively, if the temperature T is less than or equal to the set point temperature T SP  (“YES” at act  150 ), the controller  118  is programmed to move to act  154 .  
         [0041]     At act  154 , the controller  118  can be programmed to determine whether the temperature T is greater than or equal to the total of the set point temperature T SP  minus a temperature constant T 0  (e.g., between about 0.2° C. and about 0.3° C.). If the temperature T is greater than or equal to the total of the set point temperature T SP  minus the temperature constant T 0  “YES” at act  154 ), the controller  118  is programmed to return to act  146 . In some embodiments, the controller  118  can be programmed to include a delay (e.g., 2 minutes) between act  154  and act  146 . If the temperature T is less than the total of the set point temperature T SP  minus the temperature constant T 0  (“NO” at act  154 ), the controller  118  is programmed to move to act  156 .  
         [0042]     At act  156 , the controller  118  is programmed to determine whether the temperature T is less than or equal to the total of the set point temperature T SP  minus a temperature constant T 1  (e.g. between about 0.5° C. and about 0.6° C.). If the temperature T is less than or equal to the total of the set point temperature T SP  minus the temperature T 1  (“YES” at act  156 ), the controller  118  is programmed to move to act  158  and to activate the first and second heaters  130 ,  134  and the tan  44  to heat the load space air. The controller  118  then returns to act  146 . In some embodiments the controller  118  can be programmed to include a delay (e.g., 2 minutes) between act  158  and act  146 . If the temperature T is greater than the total of the set point temperature T SP  minus the temperature constant T 1  (“NO” at act  156 ), the controller  118  is programmed to move to act  162 .  
         [0043]     At act  162 , the controller  118  is programmed to determine whether the temperature T is less than or equal to the total of the set point temperature T SP  minus a temperature constant T 2  (e.g., between about 0.4° C. and about 0.5° C.). If the temperature T is less than the total of the set point temperature T SP  minus the temperature constant T 2  (“YES” at act  162 ), the controller  118  is programmed to move to act  166  and to activate the first heater  130  and the fan  44  to heat the load space air. The controller  118  then returns to act  146 . In some embodiments, the controller  118  can be programmed to include a delay (e.g., 2 minutes) between act  166  and act  146 . If the temperature T is greater than the total of the set point temperature T SP  minus the temperature constant T 2  (“NO” at act  162 ), the controller  118  is programmed to move to act  170 .  
         [0044]     At act  170 , the controller  118  is programmed to deactivate the first and second heaters  130 ,  134  and the fan  44  and to operate the temperature control system  14  in a NULL mode. In some embodiments the controller  118  is programmed to operate the temperature control system  14  in the NULL mode for a predetermined time and then to return to act  146 . In other embodiments, the controller  118  is programmed to include a delay (e.g., 2 minutes) between act  170  and act  146 .  
         [0045]     As mentioned above, the controller  118  is programmed to operate the temperature control system  14  in a COOLING mode if the temperature T is greater than the set point temperature T SP  (“NO” at act  150 ). As shown in  FIG. 12B , the controller  118  is programmed to determine whether the temperature T is greater than or equal to the sum of the set point temperature T SP  and a temperature constant T 3  (e.g., between about 1.5° C. and about 1.2° C.). If the temperature T is greater than the sum of the set point temperature T SP  and the temperature constant T 1  (“YES” at act  172 ), the controller  118  is programmed to move to act  174  and to operate compressors  58 ,  74 ,  90  of the first, second, and third refrigeration circuits  46 , 50 ,  54  at HIGH speed and operate the fan  44  to direct load space air across the evaporator coils  62 ,  78 ,  94  of the first second, and third refrigeration circuits  46 ,  50 ,  54  to cool the load space air. The controller  118  then returns to act  146 . In some embodiments, the controller  118  can be programmed to include a delay (e.g., 2 minutes) between act  174  and act  146 . If the temperature T is less than the sum of the set point temperature T SP  and the temperature constant T 3  (“NO” at act  172 ) the controller  118  is programmed to move to act  178 .  
         [0046]     At act  178 , the controller  118  is programmed to determine whether the temperature T is greater than or equal to the sum of the set point temperature T SP  and a temperature constant T 4  (e.g. between about 1.1° C. and about 1.2° C.). If the temperature T is greater than or equal to the sum of the set point temperature T SP  and the temperature constant T 4  (“YES” at act  178 ), the controller  118  is programmed to move to act  182  and to operate the compressors  58 ,  74 ,  90  of the first, second, and third refrigeration circuits  46 ,  50 ,  54  at LOW speed and to operate the fan  44  to direct load space air across the evaporator coils  62 ,  78 ,  94  of the first, second, and third refrigeration circuits  46 ,  50 ,  54  to cool the load space air. The controller  118  then returns to act  146 . In some embodiments, the controller  118  can be programmed to include a delay (e.g., 2 minutes) between act  182  and act  146 . If the temperature T is less than the sum of the set point temperature T SP  and the temperature constant T 4  (“NO” at act  178 ), the controller  118  is programmed to move to act  186 .  
         [0047]     At act  186 , the controller  118  is programmed to determine whether the temperature T is greater than or equal to the sum of the set point temperature T SP  and a temperature constant T 5  (e.g., between about 0.7° C. and 0.8° C.). If the temperature T is greater than or equal to the sum of the set point temperature T SP  and the temperature constant T 5  (“YES” at act  186 ), the controller  18  is programmed to move to act  190  and to operate the compressors  58 ,  74  of the first and second refrigeration circuits  46 ,  50  at LOW speed and operate the fan  44  to direct load space air across the first and second evaporator coils  62 ,  78  to cool the load space air. The controller  118  then returns to act  146 . In some embodiments, the controller  118  can be programmed to include a delay (e.g., 2 minutes) between act  190  and act  146 . If the temperature T is less than the sum of the set point temperature T SP  and the temperature constant T 5  (“NO” at act  186 ), the controller  118  is programmed to move to act  194 .  
         [0048]     At act  194 , the controller  118  is programmed to determine whether the temperature T is greater than or equal to the sum of the set point temperature T SP  and a temperature constant T 6  (e.g., between about 0.3° C. and about 0.4° C.). If the temperature T is greater than or equal to the sum of the set point temperature T SP  and the temperature constant T 6  (“YES” at act  194 ), the controller  118  is programmed to move to act  198  and to operate the compressor  58  of the first refrigeration circuit  46  at LOW speed and operate the fan  44  to direct load space air across the evaporator coil  62  of the first refrigeration circuit  46  to cool the load space air. The controller  118  then returns to act  146 . In some embodiments, the controller  118  can be programmed to include a delay (e.g., 2 minutes) between act  198  and act  146 . If the temperature T is less than the sum of the set point temperature T SP  and the temperature constant T 6  (“NO” at act  194 ), the controller  18  is programmed to move to act  202 .  
         [0049]     At act  202 , the controller  118  is programmed to deactivate the compressors  58 ,  74 ,  90  of the first, second, and third refrigeration circuits  46 ,  50 ,  54  and the fan  44  and to operate the temperature control system  14  in the NULL mode. In some embodiments the controller  118  is programmed to operate the temperature control system  14  in the NULL mode for a predetermined time and then to return to act  146 . In other embodiments, the controller  118  is programmed to include a delay (e.g., 2 minutes) between act  202  and act  146 .  
         [0050]     The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention.  
         [0051]     For example, while reference is made herein to a temperature control system  14  having temperature sensors  138  and to a method of operating a temperature controls system based at least in part, upon temperature data, in alternate embodiments of the present invention, the temperature control system  14  can include one or more pressure sensors and the temperature control system  14  can be controlled and/or operated using pressure data recorded by the pressure sensors.