Abstract:
A freezer for a food product, includes a housing having an internal space with a processing atmosphere for reducing a temperature of the food product; and a pressure balance apparatus in communication with the processing atmosphere to restrict atmosphere external to the freezer from reaching the internal space, the pressure balance apparatus comprising at least one sensor exposed to the processing atmosphere for generating a first signal indicating an amount of oxygen (O 2 ) sensed at the internal space, and a blower disposed to direct a pressurized flow of the processing atmosphere to the internal space responsive to the first signal. A related method is also provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present embodiments relate to apparatus and methods to exhaust cryogen from freezers, such as for example food freezers. 
         [0002]    All current cryogenic food freezing systems require trained personnel to operate and adjust the freezers. 
         [0003]    Proper balance of a cryogenic food freezing system is important, but can be difficult to maintain throughout continuous production of the food products. The term “balance” as used herein refers to an operating status wherein spent gaseous cryogen of the freezing or chilling process is exhausted or leaked from an inlet and/or an outlet of the freezer at a minimal rate in order to prevent room air (ie, atmosphere external to the freezer) from being drawn into the freezer system. When external room air is drawn into a cryogenic freezer, an additional heat load is incurred on the system resulting in an overall reduction of operating efficiency of the freezing system. 
         [0004]    There are no known automatic methods to ensure a cryogenic freezing system stays “balanced” throughout production. Ice and snow accumulation occur in the freezing system which effect the operating conditions in the freezer and the freezer balance. To ensure maximum operating efficiency, the freezer must be constantly monitored and adjusted to maintain the necessary operating balance, especially where perishable products, such as food products are processed. 
       SUMMARY OF THE INVENTION 
       [0005]    There is therefore provided a cryogenic exhaust control system which automatically balances a freezer throughout production, relieves the operator from the burden of “balancing” the freezer, and provides higher overall efficiencies for the freezing system. 
         [0006]    In general, a cryogenic exhaust control system is provided herein which automatically balances an atmosphere of a freezer, the control system including an oxygen (O 2 ) monitor at a corresponding inlet and outlet of the freezer, and a balance blower installed at an outlet, an inlet, or both the outlet and inlet of the freezer which draws cold cryogenic gas from within the freezer, pressurizes the gas and reintroduces same via a nozzle across a width of the conveyor belt at the discharge outlet of the freezer. The oxygen monitor and the balance blower coact via a controller, such that when an undesirable amount of oxygen or concentration of same is sensed at the outlet (which means room air or air external to the freezer is being drawn into the freezer at the outlet), a speed of the balance blower is decreased to provide more cryogen gas to be discharged from the outlet of the freezer, thereby inhibiting room air (air external to the freezer) from entering the outlet and into the freezer. As more gas is forced into the discharge outlet of the freezer, more gas is also expelled from the inlet which similarly prevents atmosphere external to the freezer from entering the freezer through the inlet 
         [0007]    A similar arrangement is provided at the inlet of the freezer. The oxygen monitors are used to control the balance blower. Another balance blower of construction similar to the outlet balance blower can be positioned for use at the inlet, depending upon the conditions of the freezer, the plant in which the freezer is operated, and the products being treated by the freezer. However, installation and use of the outlet balance blower is usually sufficient to impact conditions at the inlet, thereby obviating the need for the inlet balance blower, That is, when a higher oxygen concentration is sensed at the outlet, the balance blower speed decreases to allow more gas to discharge from the freezer at both the inlet and the outlet. The discharging gas prevents atmosphere external to the freezer at the outlet from gaining access to an interior of the freezer through the inlet and the outlet, The same principle applies at the freezer inlet. That is, when the oxygen sensor at the inlet senses that too much oxygen is being permitted entry through the freezer at the inlet, the balance blower speed is corresponding lowered to force the gas in the freezer through the inlet to prevent the atmosphere external to the freezer from gaining access to the freezer through the inlet. 
         [0008]    Both the inlet and the outlet are continuously monitored and the speed of the balance blower(s) adjusted, thereby maintaining the freezer atmosphere in a “balanced” condition. The system of the present embodiments can be used with many types of freezer, such as for example a spiral food freezer. 
         [0009]    There is therefore provided herein a freezer for a food product which includes a housing having an internal space with a processing atmosphere for reducing a temperature of the food product; and a pressure balance apparatus in communication with the processing atmosphere to restrict atmosphere external to the freezer from reaching the internal space, the pressure balance apparatus comprising at least one sensor exposed to the processing atmosphere for generating a first signal indicating an amount of oxygen (O 2 ) sensed at the internal space, and a blower disposed to direct a pressurized flow of the processing atmosphere to the internal space responsive to the first signal. 
         [0010]    There is also provided herein a method of balancing a processing atmosphere in an internal space of a freezer for food products, comprising sensing an amount of oxygen (O 2 ) becoming present in the processing atmosphere; generating a first signal indicating the amount of oxygen sensed; withdrawing a portion of the processing atmosphere and pressurizing said portion responsive to the first signal; and discharging the pressurized portion to the processing atmosphere for pressurizing said atmosphere and preventing additional O 2  from becoming present in said atmosphere. 
         [0011]    Additional features of the present inventive embodiments are set forth in the remaining claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding of the present invention, reference may be had to the following description of exemplary embodiments considered in connection with the accompanying drawing Figures, of which: 
           [0013]      FIG. 1  shows a side view in cross-section of a freezer having the cryogenic exhaust control system of the present embodiments; and 
           [0014]      FIG. 2  shows an enlarged cross-sectional view of a portion of the exhaust control system in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Before explaining the inventive embodiments in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, if any, since the invention is capable of other embodiments and being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. 
         [0016]    In the following description, terms such as a horizontal, upright, vertical, above, below, beneath and the like, are to be used solely for the purpose of clarity illustrating the invention and should not be taken as words of limitation. The drawings are for the purpose of illustrating the invention and are not intended to be to scale. 
         [0017]    Referring to  FIGS. 1 and 2 , a freezer  10 , such as by way of example only a food freezer, is provided with a cryogenic exhaust control apparatus (or pressure balance apparatus) shown generally at  12 . The freezer  10  may be a spiral food freezer. The apparatus  12  includes elements positioned at different locations of the freezer  10 , which elements will be described hereinafter. 
         [0018]    The freezer  10  includes an internal space  14  or chamber through which a conveyor belt  16  transits conveying products  18  such as for example food products through the internal space for chilling and/or freezing. For the sake of brevity and clarity of  FIG. 1 , only a portion of the conveyor belt  16  is shown at an inlet  20  and an outlet  22  of the freezer  10 . The inlet  20  and the outlet  22  are in communication with the internal space  14 . 
         [0019]    Liquid cryogen  24  is introduced into a pipe  26  which extends into the internal space  14  of the freezer  10 , and to a spray bar  28  having a plurality of spray nozzles  30  mounted thereto. A modulating control valve  32  is positioned in the pipe  26  to control the introduction of the liquid cryogen  24  to the spray bar  28  and the nozzles  30 . The control valve  32  can transmit and receive (transeive) a valve signal  33  which indicates its actuated position in the pipe  26 , and to have such position altered as described below. The liquid cryogen may be liquid nitrogen (LIN), carbon dioxide (CO 2 ) or cold air. Jet streams  34  of cryogen are injected into the internal space  14  from the nozzles  30 . The jet streams  34  may include LIN, solid CO 2  and gaseous cryogen. 
         [0020]    An inlet exhaust  36  is mounted for fluid communication with the inlet  20 , while an outlet exhaust  38  is mounted for fluid communication with the outlet  22 , as shown in particular in  FIG. 1 . A main exhaust  40  is arranged in fluid communication with the internal space  14  of the freezer  12 . The exhausts  36 ,  38 ,  40  provide for cryogenic gas to be vented from the inlet  20 , the outlet  22  and the internal space  14 , respectively. 
         [0021]    An inlet oxygen sensor  42  is mounted for sensing the presence or concentration of oxygen at the inlet  20 , while an outlet oxygen sensor  44  is mounted for sensing the presence or concentration of oxygen at the outlet  22 . 
         [0022]    A balance blower  46  is mounted proximate the outlet  22 , as shown with more particularity in  FIG. 2 , and in fluid communication with the outlet. The balance blower  46  can transmit and receive (transeive) a blower signal  47  to indicate its operating rpms and pressure, and to have such altered as described below. 
         [0023]    A basic operation of the apparatus and freezer embodiments is described hereinafter. A spiral freezer, by way of example only, is described with respect to  FIGS. 1 and 2  for such operation. 
         [0024]    The food products  18  are deposited on the conveyor belt  16  and transported to the internal space  14  of the freezer  10 . The inlet oxygen and outlet oxygen sensors  42 ,  44  sense an amount or concentration of oxygen at the corresponding inlet  20  and outlet  22 , respectively. The inlet exhaust  36  and the outlet exhaust  38  each capture cryogenic gas to be expelled from the internal space  14  of the freezer  10 . The modulating control valve  32  provides for an increase in liquid cryogen delivered to the spray bar  28 , which valve coasts with the central exhaust  40 . That is, as the control valve  32  opens to provide an increase in the liquid cryogen  24  through the pipe  26 , the central exhaust  40  increases its speed, i.e., its pull rate increases to pull more gas from the internal space  14  and discharge the gas from the space. Such discharge facilitates the freezer maintaining a mass balance for processing the food products at the internal space  14 . The central exhaust  40  operates to withdraw approximately 80% of spent cryogen gas from the internal space  14 . Accordingly, there is also no ingress or entry of external atmosphere into the freezer through the exhaust  40 . By way of example only, nitrogen is the cryogenic gas, and the liquid cryogen  24  being introduced is liquid nitrogen (LIN). 
         [0025]    The oxygen sensors  42 ,  44  have corresponding ports  48 ,  50 , respectively, located in an area of the internal space  14  proximate the inlet  20  and the outlet  22 , respectively, where a cryogen environment of 100% is present. The ports  48 ,  50  are positioned approximately 12-24 inches into the interior space  14  of the freezer  10 . The oxygen sensor  42  generates an oxygen concentration signal  43 , while the oxygen sensor  44  generates an oxygen concentration signal  45 . 
         [0026]    As shown with more particularity in  FIG. 2 , the outlet oxygen sensor  44  transmits a signal  45  to the controller  54  which receives same and determines whether an oxygen concentration at the outlet exceeds a predetermined amount. If the oxygen content at the outlet  22  is non-existent or does not exceed a predetermined amount, and if the inlet oxygen sensor  42  has not transmitted a sensor signal  43  indicating the oxygen level at the inlet  20  has exceeded a predetermined amount, freezer  10  will continue operating as is, i.e., operating in a balance state. If however, the outlet oxygen sensor  44  transmits the sensor signal  45  indicating that oxygen at the outlet  22  has exceeded the predetermined limit, and/or if the inlet oxygen sensor  42  transmits the sensor signal  43  to the controller  54  indicating a similar condition at the inlet  20 , the controller  54  will transmit a signal  47  to the balance below  46  to reduce rpms, i.e., reduce the pressure at the outlet  22  so that the cryogen at the internal space  14  can be exhausted to somewhat a greater extent from the outlet  22  and the inlet  20  to prevent external atmosphere from gaining access to the internal space  14 . The valve  32  and controller  54  are also in communication via a valve signal  33 . Such an arrangement permits the controller  54  to adjust an amount of cryogen introduce through the pipe  26  into the internal space  14 . 
         [0027]    In operation, the balance blower  46  withdraws the cold cryogenic gas from the internal space  14  and pressurizes the gas within the blower before reintroducing the gas by way of a nozzle  52  positioned to discharge the cryogenic gas above and across a width of a conveyor belt  16  at the outlet  22 . As shown, the nozzle  52  is somewhat angled toward the internal space  14 . The speed of the balance blower  46  is adjusted to control a volumetric flow of gas discharged from the nozzle  52 . That is, it is desirable to retain as much of the cryogen gas as possible within the internal space  14  for purposes of continuous chilling and freezing of the food product  18 . The speed of the blower  46  exhausting the pressurized cryogen gas through the nozzle  52  does just that. However, it is possible that eventually the external atmosphere will become pulled or move into the outlet  22  and to the internal space  14 , thereby warming and therefore adversely impacting the effectiveness of the freezer. The balance blower  46  will therefore be effective in balancing the cryogenic freezing occurring at the internal space  14 , and this is done by applying a pressure at the outlet  22  of the freezer. That is, as more gas is forced from the balance blower  46  through the nozzle  52  into the outlet  22 , more cryogenic gas at the internal space  14  is expelled from the inlet  20 . In both instances, air or atmosphere external to the inlet  20  and the outlet  22  is prevented from gaining entry to the internal space  14  which would compromise the chilling or freezing processes occurring at the internal space  14 . In this manner of operation, the freezer is “balanced”. Such balancing also results in any oxygen being removed or purged from the internal space  14 . 
         [0028]    The inlet and outlet oxygen sensors  42 ,  44  are used to control a speed of the balance blower  46  by transmitting signals  43 ,  45  directly to the controller  54 , which in turn transmits a blower signal  47  to the balance blower. That is, as a higher oxygen concentration is sensed at the outlet  22  by the outlet sensor  44 , a speed of the balance blower  46  is reduced in order to allow more cryogenic gas at the internal space  14  to be discharged at the outlet  22  in order to prevent atmosphere external to the freezer from entering the freezer through the outlet; and at the same time pressurizing the internal space to expel cryogenic gas from the inlet  20  to prevent external atmosphere from gaining entry to the interior space through the inlet. 
         [0029]    A similar principle applies at the inlet. That is, if the inlet oxygen sensor  42  senses an unacceptable amount of oxygen at the inlet, which means that atmosphere external to the freezer is gaining access to the internal space  14  via the inlet  20 , two (2) alternate embodiments may be employed. A first embodiment relies upon only the balance blower  46  to balance an atmosphere at the internal space  14  of the freezer  10 . Another embodiment calls for using the balance blower  46  at the outlet  22  in conjunction with another balance blower (not shown) mounted for similar operation at the inlet  20 . Accordingly, both the inlet  20  and the outlet  22  are continuously monitored for the presence of oxygen and the speed of the balance blower  46  (and an inlet balance blower if used) adjusted to maintain the “balance” of an atmosphere at the internal space  14  of the freezer  10 . 
         [0030]    The controller  54  is positioned for use to monitor concentrations of O 2  at the inlet  20  and the outlet  22 , and to adjust operation of the outlet balance blower  46  by generating a signal to this blower, and the inlet balance blower if provided, as necessary to balance the freezer. The central exhaust  40  can also be adjusted to substantially reduce if not eliminate the introduction of air into the internal space  14 . 
         [0031]    The present embodiments provide for increased efficiencies of the freezing process and the reduction in manual labor necessary for same. 
         [0032]    It will be understood that the embodiments described herein are merely exemplary, and that a person skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention described herein and provided in the appending claims. It should be understood that the embodiments described above are not only in the alternative, but can be combined.