Patent Publication Number: US-6712064-B2

Title: Cooking oven with improved heat distribution manifold system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a manifold system for directing air flow across a conveyor within a cooking oven for cooking of food products. 
     2. Description of Prior Art 
     Linear cooking ovens for cooking food typically include a conveyor or conveyor belt for conveying food to be cooked from an inlet to an outlet and through a cooking chamber. A heat source, air mover and heat exchanger are typically provided within the cooking chamber for cooking the food provided on the conveyor. 
     Existing linear cooking ovens are typically difficult to maintain and clean because of condensate, oil droplets and other fluids and particles that may accumulate in and around the heat exchanger. As a result, costly line interruptions and/or disassembly are necessary to maintain the rigid hygienic standards required for such linear cooking ovens. Cleaning and maintenance on existing linear cooking ovens often involves heat exchangers that fold or rotate into a cleaning position thereby requiring flexible hoses, connections and other components to permit ease of movement of the heat exchanger. 
     In addition, a uniform and consistent cooking environment is difficult to maintain in existing cooking ovens because of a lack of proper air flow, recirculation, heat exchange and other factors. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to provide a cooking oven that provides uniform and controllable cooking conditions within a cooking chamber and/or along a conveyor. 
     It is another object of this invention to provide a cooking oven having components that are modular. 
     It is another object of this invention to provide a cooking oven which is easily cleaned. 
     It is still another object of this invention to provide a cooking oven that separates the heat exchanger from the conveyor so that food on the conveyor is not contaminated by discharge and/or accumulations on the heat exchanger. 
     It is yet another object of this invention to provide a cooking oven that utilizes return air from the conveyor into continuous cycles of air flow through an air distribution system. 
     A linear cooking oven according to one preferred embodiment of this invention is preferably a modular oven which may have any desired number of interchangeable modules. The cooking oven preferably includes a housing having an inlet and an outlet and an enclosed chamber. A conveyor extends between the inlet and the outlet and through the chamber. 
     An air distribution system is positioned in fluid communication with the chamber and may include one or more blowers or other devices for circulating conditioned air throughout the chamber. The air distribution system is preferably positioned above the conveyor and adjacent a curved heat exchanger. The curved heat exchanger directs air from the air distribution system through the chamber and across the conveyor. The curved heat exchanger preferably includes an air inlet and an air outlet positioned in a non-linear relationship relative to the air inlet with at least a partially curved surface between air the inlet and the air outlet. 
     As a result of the described configuration of the cooking oven, the curved heat exchanger preferably directs air flow from a top portion of chamber to a lower portion of chamber and across the conveyor. One or more air manifolds are preferably connected with respect to the cooking oven so as to more precisely direct air flow from the air distribution system to the conveyor. Preferably, a plurality of air manifolds are positioned along the conveyor, preferably both above and below the conveyor. 
     Each air manifold includes a pair of sidewalls extending between a back wall and an inlet of the respective air manifold. A pair of outlet nozzles preferably extend along a length of each air manifold between the back wall and the inlet. In addition, in an alternate embodiment of this invention, an angled surface within each outlet nozzle preferably extends along a length of the air manifold. In arrangements of multiple air manifolds, each air manifold is spaced apart from each adjacent air manifold to create an air gap between sidewalls of adjacent air manifolds. Air directed through the air manifolds impinges on the food items on the conveyor where heat is drawn out into the food items. The cooled return air is then delivered through the air distribution system. Return air from the conveyor is delivered through the plurality of air gaps between the air manifolds. 
     According to one preferred embodiment of this invention, the cooking oven further includes a damper system comprising a plurality of louvers connected with respect to at least one upper manifold and at least one lower manifold. The plurality of louvers is adjustable to control the air flow between the upper manifold and the lower manifold. A manual or electronic adjustment arm may be affixed with respect to the plurality of louvers to route air flow between the upper manifold and the lower manifold. Preferably, when at least one louver in the upper manifold is opened, at least one other corresponding louver is closed in the lower manifold. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and objects of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein: 
     FIG. 1 is a side view of a cooking oven according to one preferred embodiment of this invention; 
     FIG. 2 is a top view of the cooking oven shown in FIG. 1; 
     FIG. 3 is a front view of the cooking oven shown in FIG. 1; 
     FIG. 4 is top view of a heat exchanger according to one preferred embodiment of this invention; 
     FIG. 5 is a front view of the heat exchanger shown in FIG. 4; 
     FIG. 6 is a side view of the heat exchanger shown in FIG. 4; 
     FIG. 7 is a cross-sectional view of a portion of the heat exchanger shown in FIG. 5 according to one preferred embodiment of this invention; 
     FIG. 8 is a top view of a cooking oven according to one preferred embodiment of this invention; 
     FIG. 9 is a side view of the cooking oven shown in FIG. 8; 
     FIG. 10 is a front view of the cooking oven shown in FIG. 8; 
     FIG. 11 is a side view of a manifold according to one preferred embodiment of this invention; 
     FIG. 12 is a bottom view of the manifold shown in FIG. 11; 
     FIG. 13 is a top view of the manifold shown in FIG. 11; 
     FIG. 14 is a front view of the manifold shown in FIG. 11; 
     FIG. 15 is a side perspective view of the manifold shown in FIG. 11; 
     FIG. 16 is a front perspective view of a portion of a cooking oven including a plurality of manifolds according to one preferred embodiment of this invention; 
     FIG. 17 is a side view of an upper manifold and a lower manifold according to one preferred embodiment of this invention; 
     FIG. 18 is a side perspective view of a portion of a cooking oven including a plurality of louvers according to one preferred embodiment of this invention; and 
     FIG. 19 is a front schematic view of the cooking process according to one preferred embodiment of this invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1-3 show a linear cooking oven according to one preferred embodiment of this invention. Cooking oven  10  is preferably a modular oven which may have any desired number of modules  12  joined together in an end-to-end relationship. Cooking oven  10  having three modules  12  is shown for purposes of illustration. 
     As shown, cooking oven  10  includes housing  15  having inlet  17  and outlet  19 . Housing  15  encloses chamber  30 , namely a cooking chamber. Conveyor  40 , preferably a conveyor belt or similar device known to those having ordinary skill in the art, extends between inlet  17  and outlet  19  and through chamber  30 . Conveyor  40  is preferably a pervious belt thus permitting air and liquid to flow through. 
     According to a preferred embodiment of this invention, conveyor  40  operates continuously whenever cooking oven  10  is in operation. Thus, cooking oven  10  may be referred to as a continuous oven. Uncooked food is loaded onto conveyor  40  continuously at inlet  17  and transported through one or more modules  12  in succession, and emerges cooked, at the outlet end of the oven. As the food passes through cooking oven  10 , the individual modules  12  may operate either under the same or different cooking conditions. Since each individual module  12  contains distinct components as described herein, each individual module  12  may be tuned differently to create different cooking environments and conditions. For example, one module  12  may be operated with steam only and a subsequent module  12  may be operated with a mixture of hot air or gas and steam at a higher temperature than the first module  12 . As such, according to one alternative embodiment of this invention, the first module  12  may be operated as a preheat module and a last module  12  may be operated as a cool-down module, although for greater efficiency it is preferable to preheat the food product before entering cooking oven  10  and cool down the food product after exiting cooking oven  10 . 
     Additionally, one or more modules  12  may operate with a damper system directing heated air to the upper manifold (as described below), one or more modules  12  may operate with the damper system directing heated air to the lower manifold (described below), and one or more modules  12  may operate with heated air directed to both the upper manifold and lower manifold, to provide overall optimum cooking of the food items. However, according to a preferred embodiment of this invention, each module  12  will direct heated air to the upper manifold and lower manifold equally. According to an alternative three module  12  embodiment, a first and a third module  12  will direct heated air to the upper manifold and a second module  12  will direct air to the lower manifold. 
     As shown in FIGS. 1-3, air distribution system  50  is positioned in fluid communication with chamber  30 . Air distribution system  50  preferably includes one or more fans, blowers  55  or other devices for circulating conditioned air to air manifolds which upon impinging on food items returns through air distribution system  50 . Air distribution system  50  may include a combination of forced draft air flow and induced air flow to generate proper and uniform conditions throughout cooking oven  10 . As shown in FIGS. 9 and 10, air distribution system  50  is preferably positioned above conveyor  40 . 
     As used in this specification and claims, air flow is defined as conditioned air, vapor, gas and/or fluid used to circulate through cooking oven  10 . According to one preferred embodiment of this invention, air flow comprises steam. 
     Curved heat exchanger  60 , for instance as shown in FIGS. 4-7, is preferably positioned in fluid communication with chamber  30 , as shown in FIGS. 8-10. Curved heat exchanger  60  preferably directs air from the air distribution system  50  through chamber  30  and across conveyor  40 . 
     According to one preferred embodiment of this invention, and as shown in FIGS. 4-7, curved heat exchanger  60  includes air inlet  62  and air outlet  66 . Air inlet  62  is preferably positioned in at least approximately a 90° relationship relative to air outlet  66  with at least a partially curved surface between air inlet  62  and air outlet  66 . 
     According to one preferred embodiment of this invention, a plurality of curved plates  65  are positioned between air inlet  62  and air outlet  66 . The plurality of curved plates  65  preferably extend generally parallel with respect to each other for at least a portion, if not all, of the a length of curved heat exchanger  60 . 
     As shown in cross-section in FIG. 7, curved plates  65  may include a hollow portion or channel  68  for containing and transporting a thermal fluid, such as oil. One channel  68  may adjoin each curved plate  65  as shown. The fluid passing through channels  68  serves to elevate the heat exchanger plates  65  to a desired temperature or temperature range. A wide variety of heating fluids may be passed through channels  68 , including various types of heating oils, steam or super heated steam. Alternatively, plates  65  may be heated by another means such as electrical induction. 
     According to one preferred embodiment of this invention, curved heat exchanger  60  may be cleaned by raising and/or lowering a hood and/or housing  15  to access curved heat exchanger  60 . Alternatively, and in contrary fashion to the preferred embodiment of this invention, cooking oven  10  may include an apparatus for raising and/or lowering curved heat exchanger  60  to provide easy access for cleaning, servicing, etc. 
     As a result of the described configuration of cooking oven  10 , curved heat exchanger  60  preferably directs air flow from a top portion of chamber  30  to a lower portion of chamber  30  and across conveyor  40 . As such, curved heat exchanger  60  extends vertically from air inlet  62  and horizontally from air outlet  66 . Curved heat exchanger  60  may thereby direct air flow from air inlet  62  facing an upper portion of chamber  30  and through air outlet  66  facing conveyor  40  so that air inlet  62  is positioned at approximately a right angle relative to air outlet  66 . 
     According to one preferred embodiment of this invention, curved heat exchanger  60  is positioned outside of a vertical boundary defined by edges of conveyor  40 . As a result of such a configuration, conveyor  40 , and food thereon, will not be contaminated by dripping oil, water and other contaminants. 
     A primary advantage of curved heat exchanger  60  is its ability to direct the flow of heated air to the air manifolds in a horizontal or nearly horizontal direction while simultaneously relying on gravity and air flow to facilitate cleaning between heat exchanger plates  65 . Because portions of curved heat exchanger  60  are vertical or nearly vertical, oil droplets and other contaminants which are collected between plates  65  tend to flow forward, and are discharged from the downstream end of curved heat exchanger  60  instead of accumulating between plates  65 . The useful operating time, which is the time between shutdowns of cooking oven  10  for cleaning and maintenance of the heat exchanger, is greatly increased when curved heat exchanger  60  of the invention is used, as opposed to a conventional tube and fin or other heat exchangers. Also, the curved configuration of curved plates  65  allows for a more compact fit of curved heat exchanger  60  within cooking oven  10 . 
     Curved heat exchanger  60  may be curved along the entire length of plates  65  as shown in FIG.  6 . Alternatively, curved heat exchanger  60  need not be curved along the entire length of plates  65 , so long as there is at least one curved portion or corner. For instance, curved plates  65  may have a straight portion and a curved portion, a straight portion and two curved portions, two straight portions and a curved portion, and so on. 
     Curved heat exchanger  60  may include plates  65  which are curved at an angle of 90 degrees as shown in FIG.  6 . Alternatively, depending upon the application, the total angle of curvature may range between about 20-180 degrees, suitably between about 30-150 degrees, likely between about 45-135 degrees, desirably between about 60-120 degrees. The total angle of curvature may be defined as the angular difference between plates  65  at air inlet  62  and air outlet  66  of curved heat exchanger  60 . This way, if curved heat exchanger  60  has more than one curved portion, the curvatures of the multiple portions are added together to arrive at the total angle of curvature for curved heat exchanger  60 . The radius or radii of curvature may also vary, depending on the size and shape of cooking oven  60 . 
     Depending upon the flow pattern of air within cooking oven  10 , curved heat exchanger  60  may be positioned in various parts of cooking oven for optimum performance. To facilitate self-cleaning of curved heat exchanger  60 , with the aid of gravity, air inlet  62  should be at a higher elevation than air outlet  66 , as shown in FIG. 6, for instance. 
     Generally speaking, chamber  30  preferably includes a platform in line with the air distribution system, an air mover positioned over the platform and curved heat exchanger  60  positioned adjacent to the platform and redirecting air from the air mover across the platform. According to such an embodiment, the platform may comprise conveyor  40 , cooking surface, or any other surface requiring redirected heat from an air mover and/or heat source to another location with chamber  30 . 
     More specifically, according to one preferred embodiment of this invention, curved heat exchanger  60  is positioned adjacent conveyor  40  and directs air from above conveyor  40  through chamber  30  and preferably through a damper system and/or a plurality of manifolds, as described in more detail below, whereupon such air is impinged on the food items and the cooled return air is then delivered through the air distribution system. 
     Manifold System 
     FIGS. 11-15 show various views of air manifold  80  according to one preferred embodiment of this invention. Air manifold  80  is preferably connected with respect to cooking oven  10  so as to direct air flow from air distribution system  50  to conveyor  40 . 
     According to one preferred embodiment of this invention, a plurality of air manifolds  80  are positioned along conveyor  40 , preferably above and below conveyor  40 . One or more air manifolds  80  are preferably positioned within each module  12  of cooking oven  10  thereby permitting free and compatible exchange/addition/subtraction of modules  12  within cooking oven  10 . 
     Air manifold  80  includes a pair of sidewalls  85  extending between back wall  83  and inlet  81 . A pair of outlet nozzles  90  preferably extend along a length of each air manifold  80  between back wall  83  and inlet  81 . 
     In addition, according to an additional embodiment of this invention, an angled surface  95  constitutes a floor of air manifold  80  between the outlet nozzles  90 , and extends along a length of air manifold  80 . According to one preferred embodiment of this invention, the angled surface  95  extends between the outlet nozzles  90  from inlet  81  to a lower half of back wall  83  of air manifold  80 . Angled surface  95  helps to ensure an even or uniform air pressure along the length of air manifold  80 , resulting in more uniform velocity of air ejected along the length of nozzles  90 . If angled surface  95  of air manifold  80  were horizontal instead of angular, the air pressure and velocity would be higher at locations closer to inlet  81 , and lower closer to back wall  83 . Angled surface  95  helps overcome the variable air pressure that would otherwise exist based on the distance from inlet  81 . 
     Angled surface  95  extending across outlet nozzle  90  preferably equalizes a pressure of the conditioned air across angled surface  95  thereby creating a uniform air flow out of outlet nozzle  90  and across a width of conveyor  40 . Uniform air flow is important for uniform cooking conditions within cooking oven  10 . Depending upon the application, angled surface  95  may have an angle of about 5 to 50 degrees from horizontal, suitably about 10 to 40 degrees, desirably about 15 to 30 degrees. 
     As shown in the figures, according to one preferred embodiment of this invention wherein air manifolds  80  are positioned over conveyor  40 , inlet  81  and the pair of outlet nozzles  90  of each air manifold  80  extend in the same direction. Therefore, air flow is directed upwardly into inlet  81  from air distribution system  50  and then across air manifold  80  and back downward through outlet nozzles  90  across the length of air manifold  80 . 
     Each air manifold  80  includes a rectangular space  91  resembling a three-sided box, open at the bottom (toward conveyor  40 ), between nozzles  90 . Some of the heated air which leaves nozzles  90  contacts the food items and/or conveyor  40 , then deflects upward into the space  91 , where it is carried back down by the venturi effect of the heated air leaving nozzles  90 . This recirculation of heated air helps to mix the cooking air and facilitates more uniform cooking. 
     In arrangements of multiple air manifolds  80 , such as shown in FIG. 16, each air manifold  80  is spaced apart from each adjacent air manifold  80  to create an air gap  87  between sidewalls  85  of adjacent air manifolds  80 . Return air from conveyor  40  is preferably delivered through a plurality of air gaps  87  between sidewalls  85  of adjacent air manifolds  80  in cooking oven  10 . 
     According to one preferred embodiment of this invention, each outlet nozzle  90  comprises a narrower opening than either a width of air gap  87  or a width of air manifold  80 . A relatively narrow opening of each outlet nozzle  90  results in concentrating heating and/or cooling of the food product positioned on conveyor  40 . 
     In one particular embodiment of this invention, air manifolds  80  are spaced approximately 6″ apart from each other. In such embodiment, an air manifolds  80  above conveyor  40  include outlet nozzles  90  spaced approximately 10″ apart from each other within each air manifold  80 . In yet another embodiment, air manifolds  80  are spaced approximately 8″ apart from each other and outlet nozzles  90  are spaced approximately 8″ apart from each other. Air manifolds  80  below conveyor  40  preferably include outlet nozzles  90  spaced approximately 2.5″ apart from each other within each air manifold  80 . 
     Damper System 
     According to one preferred embodiment of this invention shown in FIGS. 17 and 18, cooking oven  10  further includes a damper system comprising a plurality of louvers  70  connected with respect to upper manifold  101  and lower manifold  105 , the plurality of louvers  70  adjustable to control the air flow between the upper manifold  101  and lower manifold  105 . 
     As shown in FIG. 18, adjustment arm  75  may be additionally connected with respect to the plurality of louvers  70 . Adjustment arm  75  preferably opens at least one louver of the plurality of louvers  70  and correspondingly closes at least one other louver of the plurality of louvers  70  to control air flow between upper manifold  101  and lower manifold  105 . Adjustment arm  75  may be manually controlled or electronically controlled. 
     As best shown in FIG. 17, inlet manifold  73  is preferably connected with respect to the plurality of louvers  70  to route air flow including return air from conveyor  40  and primary air from heat exchanger  60 . Because of the described arrangement of recirculated air, this invention necessarily requires primary air from heat exchanger  60  and return air from conveyor  40 . The plurality of louvers  70  preferably extend along at least a portion of a length of the conveyor  40 . 
     As shown in FIG. 18, a first plurality of louvers  70  may be arranged in an array across upper manifold  101  and a second plurality of louvers  70  may be arranged in an array across lower manifold  105 . The first plurality of louvers  70  and the second plurality of louvers  70  may be arranged in subgroups across upper manifold  101  and lower manifold  105 , respectively. For instance, as shown in FIG. 18, subgroups of three louvers  70  may be positioned in an array across upper manifold  101  and/or lower manifold  105 . 
     As a result of the described arrangement of louvers  70 , air flow is directed and controlled through and between the plurality of louvers  70  connected with respect to upper manifold  101  and the lower manifold  105 . Preferably, when at least one louver  70  in upper manifold  101  is opened, at least one other corresponding louver  70  is closed in lower manifold  105  thereby controlling air flow between the upper manifold  101  and the lower manifold  105 . More specifically, as an array of louvers  70  is opened in upper manifold  101 , a corresponding array of louvers  70  is closed in lower manifold  105 . 
     One advantage of this arrangement is that the total heated air flow can be maintained at a constant rate in a given module  12 . The damper system directes the heated air to upper manifold  101 , lower manifold  105 , or a desired combination of both, without changing the total amount of heated air supplied for cooking. Thus, the amount of heated air can be fixed and controlled at a predetermined rate as desired to give the optimum level of overall cooking. The damper system can be used to direct air to upper and lower manifolds  101 ,  105  as desired to ensure that the cooking is substantially uniform and even. 
     While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that this invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.