Abstract:
An improved convection/impingement oven for continuously cooking food. The oven has a wire link type belt which moves through an elongated cooking chamber. Hot air is blown on the upper surface of the food to be cooked. A separately controlled hot air source is blown on the lower surface of the food. Hot air impingement units are placed along the length of the oven and the cooking vapors are not recirculated but instead pass along the elongated cooking chamber and are exhausted at the end. Preferably a color development and sealing section has upper and lower burners which heat the food and the heat from these burners also pass the entire length of the cooking chamber before being exhausted. Also preferably steam or a water spray is used to regulate the humidity and this may be regulated in several different sections of the cooking chamber.

Description:
This is a continuation Ser. No. 08/494,716 field on Jun. 26, 1995, U.S. Pat. No. 5,560,952. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The field of the invention is cooking ovens and the invention relates more particularly to ovens of the type used to commercially bake, broil or otherwise cook meats, baked goods and other foods. With the increased use of frozen dinners, the moisture content in the meat contained in a frozen dinner has become more critical. Since microwave cooking tends to heat water, it is important that sufficient water be retained in the meat so that after it is microwaved it has the desired flavor and texture. 
     Many patents have been granted on continuous cooking ovens. For instance the Straub U.S. Pat. No. 3,604,336 shows a moving belt with upper and lower burners, a center exhaust duct is provided and no provision is made for moisture control of the finished product. 
     The Szabrak et al U.S. Pat. No. 3,721,178 also uses many burners along the length of the oven. The Nerthling U.S. Pat. No. 3,823,660 utilizes a continuous moving belt with radiant heaters above and below the food to be cooked. Burners are also used and the exhaust vent is positioned along one side of the entire length of the oven. 
     The Fagerstrom et al patent shows an electrical heating device over which air is passed after which it passes through channels above and below the product to be cooked. The cooking vapors are vented at points along the oven. The Caridis et al U.S. Pat. No. 3,947,241 shows a recirculating oven wherein a flame is fed into an upper chamber and then passes in a u-shaped path into the lower chamber where the product to be cooked is located. A certain amount of cooking vapors is exhausted at both ends of the oven. 
     A charmaker is shown in the Fetzer U.S. Pat. No. 4,026,201 which uses many rings which are heated and ride on the upper surface of the food product. The Baker et al U.S. Pat. No. 4,121,509 utilizes electric heating elements and recirculated air which passes through tubes at the end of the oven and flows against the upper and lower surface of the food to be cooked. 
     The Caridis et al U.S. Pat. No. 4,167,585 is similar in structure to U.S. Pat. No. 3,947,241 and is basically a recirculation system wherein water vapor is injected into the moving stream of process vapor to control the temperature and moisture content. 
     The Benson et al U.S. Pat. No. 4,297,942 shows a branding process utilizing an oversized screen with upper and lower burners, the heat from which it is exhausted from the branding unit. The Baker U.S. Pat. No. 4,936,286 is a small continuous broiler which has three side-by-side conveyors. The Leary et al U.S. Pat. No. 4,949,629 is a continuous cooking oven which has two very separate cooking zones, both zones utilize recirculation of the cooking vapors. Lastly, the Barkhau et al U.S. Pat. No. 4,991,497 cooks food in a closed bottom tray and utilizes air high velocity impingement nozzles to accomplish the cooking. The air is recirculated. 
     Although one would think that recirculation of cooking vapor would result in an efficient unit, this is not the case. Since ovens must be constructed in a manner so that they can be easily and completely cleaned, it is not practical to place an outer layer of insulation on the oven. Therefore, the large additional surface area that is required to bring about recirculation radiates more than the amount of heat saved in recirculation. Furthermore, for some products such as pork, the recirculation process results in an undesirable pink color in the meat even though it is completely cooked. Therefore, an oven which is more efficient in the use of heat would be highly desirable. Still further, it is useful to be able to cook various different types of food products requiring a wide range of controls for heat temperature and humidity. 
     SUMMARY OF THE INVENTION 
     The present invention is for an improved convection/impingement oven for continuously cooking food. The oven is of the type having a pervious, continuous, moving belt which has an upper product supporting surface referred to as a “food supporting belt” and a return belt portion. The food supporting belt has a lower surface which permits the passage of hot air or other vapors upwardly therethrough and the passage of fat or other drippings downwardly therethrough. The food passes from a product feed end to a product discharge end through a closed elongated cooking chamber which is enclosed by a top, two sides, and a bottom. The food supporting belt and the return belt both pass through this chamber. A burner blower is supplied with outside air and feeds air to at least one burner which feeds hot air to a first manifold which is at about atmospheric pressure and has an air intake which permits atmospheric air to enter from outside the oven. A second blower then takes the atmospheric pressure hot air and increases the pressure thereof for later feeding into a low pressure hot-air manifold and from there through air impingement nozzles onto the food to be cooked. A plurality of upper air impingement nozzles are positioned above the food supporting belt and these nozzles are fed from an upper air impingement manifold which in turn is supplied from the said low pressure hot air manifold. A plurality of lower air impingement nozzles are positioned below the lower surface of the food supporting belt, and this is fed from a lower air impingement manifold which in turn is fed by the low pressure hot air manifold. Means are provided for independently controlling the flow of hot air to the upper air impingement manifold and to the lower air impingement manifold. A cooking vapor vent having an inlet positioned adjacent the product discharge of the cooking chamber comprises the only outlet for the cooking vapors. The cooking vapors move along the cooking chamber and hot air is introduced along the length of the chamber thereby causing the hot air flow, concurrently with the food-supporting surface, to move at an ever increasing rate along the cooking over. Preferably the lower hot air impingement units and the upper hot air impingement units are fed by separate burners and blowers. Also preferably a color development and sealing unit is positioned at the product feed end of the cooking chamber and upper and lower burners are played upon the food to be cooked (and preferably a branding wheel) and the heat from these two burners is passed the entire length of the cooking chamber. The color development and sealing burners are adjustable so that the direction of the flame may made from horizontal to directly downwardly. It is also preferable that a plurality of steam nozzle assemblies are positioned along the cooking chamber, preferably between the impingement units. Also, preferably the steam nozzles are separated into several discreet groups which are independently controllable so that different zones of the oven can be of different humidity and/or temperature. 
     The present invention is also for a process of cooking food comprising the steps of placing an object to be cooked on the upper surface of a perforate moving belt. Next, a color development and sealing flame is aimed so that the heat therefrom passes into the entrance of an elongated cooking chamber. Steam may next be introduced above and below the object to be cooked and hot air is impinged on the upper and lower surface with the temperature and force of the impinging stream of hot air from the upper nozzles being independently controlled from that from the lower nozzles. The object to be cooked is passed through at least one set of upper and lower air impingement nozzles and upper and lower stream nozzles and the finally cooked product is removed at the product discharge end. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the improved convection/impingement cooking oven of the present invention. 
         FIG. 2  is a cross sectional view taken along line  2 — 2  of FIG.  1 . 
         FIG. 3  is an enlarged cross sectional view of the product feed end of the oven of  FIG. 1  including the color development and sealing assembly, a steam nozzle assembly, and a hot air impingement assembly. 
         FIG. 3A  is an enlarged view taken along line  3 A of FIG.  3 . 
         FIG. 4  is a cross sectional view taken along line  4 — 4  of FIG.  3 . 
         FIG. 5  is an enlarged cross sectional view of the product discharge end of the oven of FIG.  1 . 
         FIG. 6  is a cross sectional end view showing the oven of  FIG. 1  with the hood thereof raised. 
         FIG. 7  is a front view of the control panel of the cooking unit of FIG.  1 . 
         FIG. 8  is a diagrammatic view of the control panel of FIG.  7 . 
         FIG. 9  is an enlarged plan view of the impingement console unit of FIG.  1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The improved convection/impingement oven of the present invention is shown in  FIGS. 1 and 2  and indicated by reference character  10 . Oven  10  has a product feed end  11  and a product discharge end  12 . The food to be cooked is placed on a pervious, continuous, moving belt  13  which is fabricated from a plurality of linked rods, of steel or other construction known in the art. The unit is operated from a control counsel  console  14 , and impingement console  15  contains the burners for feeding the air impingement unit. Details of the impingement console are shown in FIG.  5    9 . 
     A cross sectional view of oven  10  is shown in  FIG. 2  where it can be seen that the upper part of belt  13  moves from left to right as shown in FIG.  2  and passes through an elongated cooking chamber which is shown more clearly in  FIGS. 3 and 4 , where it is indicated by reference character  16 . As the food to be cooked passes along the forward moving portion  17  or the belt  13 , ( the forward moving portion  17  is called the “food supporting belt”) upper and lower air impingement nozzles such as those indicated in  FIG. 2  by reference characters  18  and  19  pass hot air onto the upper and lower surface of the product to be cooked. Also, steam nozzles assemblies such as indicated-in  FIG. 2  by reference characters  62 ,  70 , and  73  pass steam or water vapor into the cooking vapor  21  which forms above and below the food to be cooked. 
     The essential feature of the present invention is the ability to separately control both the temperature and volume emitted from the upper and lower air impingement nozzles in the oven. As shown in  FIG. 1 , a blower assembly  22  feeds air and fuel to a burner nozzle  25 . Burner nozzle  25 . Burner nozzle  25  forms a flame which heats the air in the interior of manifold  27 . The interior of manifold  27  is at about atmospheric pressure and draws air as needed through conduit  24  which is open to the exterior of the oven. Conduit  24  does not draw any recirculated hot air from vent  83 . Similarly, a blower assembly feeds air and fuel to a burner nozzle  26 . Burner nozzle  26  forms a flame which heats the air in manifold  28 . The hot air in manifold  28  is at about atmospheric pressure and draws air as needed through conduit  241  which also is drawn from outside the oven. The hot air at atmospheric pressure in manifold  27  is fed to a blower assembly  29  which increases its pressure to from one-half to ten psig. As blower assembly  29  requires more hot air, above that required to simply move the gasses exiting nozzle  25 , it is supplied by the air stream entering conduit  24  so it never has a negative feed pressure. Blower assembly  29  feeds the hot air into a hot air conduit  31  from which it passes into the upper hot air manifold  32  shown in  FIGS. 3 ,  5 , and  6 . Blower assembly  30  feeds hot air from manifold  28  to lower hot air conduit  33  (which is directly below conduit  31  in  FIG. 9 ) from which it passes into lower hot air manifold  34 . Both the burner assembly  22 / 23 / 25  and  25 / 26  and the blower assemblies  29  and  30  may be independently controlled so that the temperature as well as the air pressure may be set to a preferred level for the product to be cooked. 
     Turning now to  FIGS. 3 and 6 , the lower hot air manifold  34  feeds hot air into right and left hot air channels  38  and  39  which feed a lower air impingement nozzle assembly  19 . Air under a relatively low pressure (one-half to ten pounds per square inch gauge) passes outwardly through upwardly directed holes  85  (see  FIG. 3A ) in the plates of the nozzle and impinges upon the food to be cooked. Hot air also passes outwardly through holes  88  in an angled plate  87  which directs hot air both downwardly and toward vent  83  down the oven chamber. Similarly, holes in nozzle assembly  18 , fed by channels  35  and  36 , urge hot air downwardly and forwardly to impinge the food and to help urge the gas flow down the oven chamber to the vent  83 . This not only heats the food by conduction but also tends to remove any stagnant air and vapor layer which surrounds the food. Thus, the food is heated more efficiently and more quickly by the fact of the air impingement. It further carries with it the surrounding cooking vapor with its temperature and humidity so that the food is more quickly raised to the desired temperature. Since the food supporting belt  17  is largely open, the hot air passes readily through it and around all sides of the food to be cooked (which is indicated by reference character  41  in FIG.  6 ). 
     The surfaces of the cooking chamber are shown in  FIG. 6  although the hood  42  has been raised therefrom. The upper wall of the cooking chambers indicated by reference character  43  and the left side wall by  44  and the right side wall by  45 . The base portions  46  and  51  rest in the sealing lips  47  and  52  of the lower pan  61  when the hood is lowered. The hood consisting of walls  43 ,  44  and  45  are held on a cross member  53  which is, in turn, held by two vertical members  54  and  55 . Members  54  and  55  are supported by rods  56  and  57 . The hood is raised and lowered by a chain hoist  40  supported by frame  50 . Rods  56  and  57  telescope into vertical members  54  and  55  so that as hood  42  is lowered, the base  58  thereof rests upon the frame to create a dead air space  60  above the upper surface and the side walls of the cooking chamber. The lower pan of the cooking chamber is indicated by reference character  61  which provides a conventional slanted grease or other liquid removing floor. It is important that the air volume of the cooking chamber be relatively small so that only the air necessary for cooking need be heated and the outer surface of the cooking chamber be minimized to minimize radiation heat loss. Outer sides are, of course, provided along the entire length of the oven to further reduce heat loss. 
     Returning now to  FIGS. 3 and 4 , a steam nozzle assembly  62  is shown in side view in FIG.  3  and in front view of  FIG. 4. A  steam line  63  is controlled by a steam valve  64  shown in FIG.  2 . This is independently controlled from steam valves  65  and  66  which provides the operator with additional temperature and moisture control. It is, of course, understood that the term “steam” is intended to include a spray of water mist which is quickly turned to steam in the high temperatures of the cooking chamber. Returning to  FIG. 3  steam nozzle assembly  62  emits an upper stream of steam  67  and a lower stream of steam  68  through nozzles  20 . Since the product to be cooked has just passed through a high temperature color development and sealing operation, the streams of steam  67  and  68  tend to extinguish and flareup that may occur. Also, it should be noted that the streams  67  and  68  are directed toward the discharge end  12  of the oven which helps move the cooking vapor  21  concurrently with respect to the food supporting belt  17 . A separate steam line  69  supplies a steam nozzle assembly  70  which also has a pair of streams of steam  71  and  72 . Steam nozzle assembly  70  is controlled by steam valve  65  as are the other steam nozzle assemblies indicated by reference character  70  in FIG.  2 . Steam nozzle assemblies  73  shown in  FIG. 2  are controlled by steam valve  66 . 
     Turning now to the color development and sealing assembly, an upper color development and sealing burner  74  (see  FIG. 3 ) is fed with high pressure air and gas to provide a flame  75  which heats the upper surface of food  41  to be cooked. This provides coloring and sealing to the food. Similarly, a lower color development and sealing burner  76  has a flame  77  which heats the lower surface of food product  41 . The heat from both the upper and lower flames  75  and  77  heat a branding wheel  78  which is driven by a chain link belt  79  from a gear  80  which also contacts the continuous moving belt  13 . Branding wheel  78  is floating so that it will rise if necessary. Branding wheel  78  may also be permanently raised to eliminate any branding. The branding rods  81  always move at the same speed as a food supporting belt  17  to provide a neat brand on the upper surface of food product  41 . The lower side of the food product  41  is branded by the moving belt  13 , although belt  13  may be cooled so eliminate branding if desired. 
     Burners  74  and  76  may be aimed through a 90 degree arc. They may be aimed horizontally toward the cooking chamber or at any angle between horizontally to directly downwardly and upwardly respectively toward the moving belt  17 . The choice of direction depends on the amount of coloring and sealing desired and the type of food being cooked. Thus the flames  75  and/or  77  may be aimed to directly impinge the surfaces of the food to be cooked, or they may merely heat the surfaces depending on how the burners  74  and  76  are aimed. 
     An important feature of the color development and sealing assembly is the aiming of the flames  75  and  77  toward the opening of the cooking chamber and the conveying of the heat from these flames into the cooking chamber. The portion of the cooking chamber which surrounds the branding rods is in a stair stepped shape indicated by reference character  82 . The hot air is moved inwardly into the cooking chamber and not exhausted in a separate vent. The hot air carries the entire length of the cooking chamber and is not vented until it passes out of the cooking vapor vent  83  shown in  FIGS. 1 and 2 . Also the upper color development and sealing burner and the lower color development and sealing burner are independently controlled so that the proper amount of heat may be applied depending on the product being cooked. 
     The construction of the upper and lower impingement manifolds is a very important feature of the present invention.  FIG. 3a  shows the top of lower and upper air impingement manifolds  19  and  18  where it an be seen that nozzle  19  has a nozzle plate  84  with a plurality of small holes  85  which causes the air to move out in small discrete streams against the product to be cooked. There are no nozzles on the angled face  86  but there are nozzles on the angled face  87  which are indicated by reference character  88 . Similarly upper air impingement manifold  18  has a nozzle plate  89  shown in  FIG. 3  in side view which also has a plurality of holes  90 . An angled face  91  also has a plurality of holes  92  but angled face  93  has no holes. This causes the air to be urged downwardly and also at a approximately 45 degree angle in the direction of the discharge and to help move the cooking vapors  21  along the oven. It is also evident in  FIG. 3  that the upper surface  43  of cooking chamber  16  is angled upwardly as indicated by reference character  94  to accommodate the air impingement manifolds as well as the steam manifolds. This causes the internal volume of the cooking chamber to be minimized and helps to increase the velocity of the cooking vapor  21  concurrently with the food supporting belts  17 . 
     Also viewing  FIG. 2  it is evident to see that with the multiple entries of hot air and steam the volume of cooking vapors increases along the chamber so that as the food becomes more cooked, the cooking vapor  21  increases in velocity. 
     Further details of construction of the steam nozzle assembly is shown in  FIG. 4  where it can be seen that steam line  63  feeds a vertical steam line  95 . This, in turn, feeds an upper horizontal steam manifold  96  and a lower horizontal steam manifold  97 . Each of these manifolds have a plurality of individual nozzles  20  which urge the streams of steam in the direction shown for instance, in  FIG. 3  indicated by reference character  67  and  68 . 
     Another important feature of the present invention is the single pass operation where the only significant venting of cooking vapor is through cooking vapor vent  83  which includes a damper  99  and an air blower, not shown, positioned upwardly from damper  99 . Air is thus drawn upwardly through vent  83  and is exhausted and is not recirculated. 
     As the food  41  passes along the cooking chamber, it tends to draw heat out of the cooking vapors  21 . Thus, although the temperature may be as high as 1000 to 1600 degrees Fahrenheit near the product feed end of the cooking chamber it decreases along the chamber. For example, it may drop to 800, 600, 400 and 300 degrees in some instances, along the chamber so that as the food warms, the cooking temperature difference between the product and the cooking vapors  21  decreases. This characteristic optimizes the cooling operation and reduces the possibility of overcooking in a manner not possible in the typical over or a recirculating oven which remains at a relatively constant temperature. 
     Also shown in  FIG. 5  is a belt cleaning loop  100  which causes the belt to pass through a tank  101  filled with water  102 . It has been found that the belt remains relatively clean during most cooling operations. If it is desired to add non-stick coatings to the belt, they can be added to tank  102 . 
     Control panel  103  is shown in  FIGS. 7 and 8 . The cooking unit is provided with numerous means for controlling temperature, air flow, humidity, and belt speed. Appropriate monitoring units such as pressure sensing means, theremocouples and other sensors provide input to the control panel for facilitating the operation of the unit. The controls are more specifically set forth in FIG.  8 . Particular note is made of the wide variety of controls available on both the upper impingement unit and the lower impingement unit. The result is a highly versatile and yet efficient continuous convection/impingement cooking oven which is capable of placing the optimum temperature, time and humidity together with upper and lower air flow impingement on the food to be cooked so that the best possible product will result. 
     The present embodiments of this invention are thus to be considered in all respects as illustrative and not restrictive: the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.