Abstract:
A compact conveyor oven is disclosed comprising a cooking chamber, thermal heating source, conveyor means and independent top and bottom airflow within the cooking chamber wherein substantially equal pressurization of the top and bottom airflows is achieved within the compact footprint.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/906,394, filed Mar. 10, 2007, entitled COMPACT CONVEYOR OVEN. This provisional application is incorporated herein as if fully set forth. 
    
    
     BACKGROUND 
     The typical cook time for a food product such as a fresh medium size pizza through a conventional conveyor oven is approximately 7 minutes. The conveyor oven therefore reduces cooking time as compared to previous ovens such as the deck oven, and also simplifies the cooking procedure because the food product is automatically loaded into and unloaded from the cooking tunnel. 
     Conveyor ovens typically utilize a continuous open link conveyor belt to transport food products through this heated tunnel, or cooking chamber, which has openings at each end of the oven through which the conveyor belt sufficiently extends in order for the operator to start incoming food product on one end, and retrieve the finished cook product from the other. A standard impingement style conveyor oven typically employs the use of a cooking chamber approximately 70 inches (177.8 cm) long and 32 inches (81.28 cm) wide. For the foregoing reasons, there is a need for a faster cooking, more compact conveyor oven. 
     SUMMARY 
     The present invention is directed to a more compact conveyor oven that cooks food product faster than conventional conveyor ovens. According to certain versions of the invention, a first airflow delivery system comprises a first airflow circulation means that directs airflow away from the airflow circulation means and airflow directing vanes that thereafter alter the direction of the airflow in a direction back towards the airflow directing means such that substantially equal pressure is provided to a first nozzle plate for impingement of airflow through apertures of said nozzle plate upon the top surface of a food product within the compact conveyor oven; and a second airflow delivery system comprising a second airflow circulation means that directs airflow away from the second airflow circulation means and airflow directing vanes that thereafter alter the direction of the airflow in a direction back towards the airflow directing means such that substantially equal pressure is provided to a second nozzle plate for impingement of airflow through apertures of said nozzle plate upon the bottom surface of a food product within the compact conveyor oven. 
     According to certain versions of the invention an airflow deflecting vane is positioned to require airflow to be directed around said deflecting vane in order to prevent short circuiting of return airflow to the first and second airflow circulation means. 
     According to certain versions of the invention airflow deflecting vanes are positioned to direct spent airflow upwards for return to the first airflow circulation means and downwards for return to the second airflow circulation means. 
     According to certain versions of the invention a continuous top and bottom nozzle plate is positioned allowing for an economical velocity pressure system to be utilized. 
     Additional objects, features and advantages of the present invention will become readily apparent from the following detailed description of the exemplary version thereof, when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
    
    
     
       DRAWINGS 
       The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative version when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a compact conveyor oven; 
         FIG. 2  is a front view of  FIG. 1 ; 
         FIG. 3  is a right side view of  FIG. 1 ; 
         FIG. 4  is an exploded view of  FIG. 1 ; 
         FIG. 5  is a transparent top view of  FIG. 1 ; 
         FIG. 6  is a view of a section of conveyor belt of  FIG. 1 ; 
         FIG. 7  is a view of nozzle plate of  FIG. 1 ; 
         FIG. 8  is a view of gas burner system of  FIG. 1 ; 
         FIG. 9  is a perspective view detailing return air path; 
         FIG. 10  is exploded view of the gas burner of  FIG. 8 ; 
         FIG. 11  is a view of internal gas piping of  FIG. 1 ; 
         FIG. 12  illustrates the air cooling system of  FIG. 1 . 
     
    
    
     DESCRIPTION 
     With initial reference to  FIGS. 1-3  compact conveyor oven  10  includes exterior front wall  12 , exterior right side wall  14 , exterior left side wall  16 , exterior back wall  18 , exterior bottom wall  20  and exterior top wall  22 . Food products, not shown, are transported into and through cooking chamber  24  by conveyor  28 . Preferably the conveyor assembly  28  comprises a continuous loop wire mesh conveyor belt which extends through entrance opening  32  and exit opening  36 . The width of belt  28  is approximately 32 inches (81.28 cm.) and the length of belt  28  within cooking chamber  24  is approximately 40 inches (101.6 cm.). Preferably, the conveyor belt extends a sufficient distance from the entrance and exit openings of the oven to allow food products to be readily positioned on the conveyor belt for travel through the cooking chamber of the oven and removal upon exiting the oven. 
     Compact conveyor oven  10  may be supported by legs  25  and movable by rollers  27  or may sit on a shelf or table top, or be stacked one above another. 
     The compact conveyor oven is comprised of two independently controlled gas transfer systems, described herein as a top gas transfer system and a bottom gas transfer system and although the top and bottom gas transfer systems are identical, it is not required that they be identical. Described herein in detail is the top gas transfer system. The bottom system is made, functions and operates in the same manner as the top system. The term “gas” refers to any fluid mixture, including air, nitrogen and other mixtures that may be used for cooking, and applicant intends to encompass within the language and meaning any gas or gas mixture existing or developed in the future that performs the same function. Additionally, the term “airflow” refers to, and includes gas flow. 
     Top gas delivery system  40 ,  FIG. 4  delivers temperature-controlled gas to the top side of conveyor belt  28  and lower gas delivery system  42  delivers gas to the bottom side of belt  28 . Independent control of top and bottom gas transfer systems  40 ,  42  is known and further described in U.S. Pat. No. 5,717,192. 
     Top gas delivery system  40  is comprised of gas flow means  50 ,  60 ,  62 ,  FIG. 5 , and top gas transfer section  41 ,  FIG. 9 . Gas transfer section  41  is comprised of divider  200 , nozzle plate  54 , turning vanes  56 , and gas transfer section side walls  41   a - d  and top wall  41   e . Although section  41  is illustrated as tapered toward the back of oven  10 , there is no requirement for such tapering. Nozzle plate  54  is further comprised of nozzle plate sections  55 ,  57 , (divided By divider  200 ), described further herein, and nozzles  58 . The size (area) of section  57  may be larger than that of section  55  (as shown in  FIG. 5  and noted below); alternatively, sections  55  and  57  may be of equal size. 
     Variable speed blower motors and variable speed blower motor controllers may be utilized, but there is no requirement for their use and indeed the compact conveyor oven of the present invention may avoid the problems and complexity of variable speed blower motors by maintaining a constant gas flow, or alternatively, a substantially constant gas glow rate through the oven cooking chamber, gas transfer and gas delivery systems. Gas flows may be very aggressive, or less aggressive, depending upon the cooking requirements for each food product and one means to achieve gas flow modulation is by use of a gas pumping means such as a blower motor, blower wheel combination, utilizing a controller or a multi speed switch that allows for the switching of the blower motor speed in pre-determined fixed increments. 
     Connected to top blower wheel  50  is blower motor shaft  60 , which is direct drive with electric motor  62 ,  FIG. 5 . Other means may be employed for coupling blower wheel  50  to electric motor  62 , such as belt drive and the drive means is not limited to direct drive and applicant intends to encompass within the language any structure presently existing or developed in the future that performs the same function. 
     Gas is heated within combustion chamber  70 ,  FIG. 5  by a gas combustion burner assembly  80  prior to delivery to blower wheel  50 . Blower wheel  50  discharges gas into nozzle plate section  55  of gas transfer section  41  toward the front wall of oven  10 . In order to achieve the compact design of our invention, the gas flow is then re-directed by vanes  56  and thereafter flows to larger nozzle section  57 . Gas flow to larger section  57  pressurizes entire nozzle plate  54  allowing for substantially equal pressures throughout section  41 . Substantially equal pressure throughout section  41  provides for substantially equal impingement of gas flow through nozzles  58  and onto the top of food product. 
     As can be seen in  FIG. 2 , after the gas is discharged through nozzle plate  54  and into cooking chamber  24  via apertures  58  the gas impinges upon any food product upon belt  28 . Apertures  58  may be slotted, regularly formed or irregularly formed apertures and are illustrated herein as uniform nozzles,  FIG. 7 , and applicant intends to encompass within the meaning of nozzle any structure presently existing or developed in the future that performs the same function as nozzles  54  and as used herein the term “aperture” and “nozzle” have the same meaning. Apertures  58  are sized for a low pressure drop, while providing and maintaining sufficient gas velocities in the range of approximately 2000 ft/minute (609.6 meters/minute) to approximately 6000 ft/minute (1828.80 meters/minute) to properly cook the food product as described herein. In some instances, velocities below 2000 ft/minute (609.6 meters/minute) or above 6000 ft/minute (1828.80 meters/minute) may also be utilized, depending upon the particular food product to be cooked, or a particular cooking recipe that the controller is executing, and applicant does not intend to limit the invention to gas velocities within a particular range. Apertures  58  are sized such that substantially equivalent velocities of gas impinge against the top surface of belt  28 . 
     Gas discharged through apertures  58  impinge upon food product, not shown, upon conveyor belt  28  and is then drawn toward entrance and exit openings  32 ,  36  where the spent gas is deflected upward by gas deflecting vanes  100  and then travels upward along transfer section side walls  41   a ,  41   b  and  41   c ,  FIG. 9 . The gas flows traveling up walls  41   a  and  41   c  is re-directed by deflecting vanes  102  for return to heating chamber  70 ,  FIG. 5 . Deflecting vanes  102  force gas to travel in a substantially uniform manner, thereby preventing short circuiting of the gas traveling up walls  41   a ,  41   c  toward the back of oven  10 . As can be seen in  FIG. 4 , without deflecting vanes  102 , gas toward the tapered end of section  41  (back wall  41   d ) would have shorter distance to travel and therefore would make more revolutions or cycles through the oven than gas returning further away from front wall  12  of oven  10 . 
     Gas returning to heating chamber  70  may be reheated by gas combustion burner  80 ,  FIGS. 5 ,  8 ,  10 . In order to maintain the small size (footprint) of the compact conveyor oven, combustion gas burner  80  is placed between blower wheels  50 ,  52 . Placement of combustion burner  80  between blower wheels  50 , 52  sometimes requires burner  80  to be fitted with a burner tube,  103   FIG. 8 . In order to assure flame efficiency, burner tube  103  is adjusted (“tuned”) to allow a sufficient amount of make-up air to enter tube  103 . Gas combustion occurs within tube  103  and then passes through apertures  105  for delivery to oven cavity  24 . 
     Portions of compact oven  10  are cooled by cooling duct  110 ,  FIG. 12  wherein fresh air is drawn through intake opening  112  by motor  111  and distributed throughout oven  10  as required. Placement of cooling duct  110  along the back of oven wall  18  provides spacing such that oven  10  cannot be positioned directly adjacent a wall or other structure or device because cooling duct  110  forms a self spacing air path in addition to a cooling mechanism for oven  10 . In order to allow for additional footprint savings, gas plumbing pipe,  115 ,  FIG. 11  is located within back wall  18  of oven  10 . This allows one oven to be easily stacked upon another such oven. 
     As previously described, the top and bottom gas supply systems are the same configuration and function to uniformly circulate hot gas flow to the top and bottom sides of food product upon belt  28 , and return the gas to the gas heating means for re-delivery to the cooking chamber. 
     The number and placement of the apertures  58  will vary according to the particular oven that is desired. For example, a general purpose compact conveyor oven may be scaled to a baking oven by changing the number of apertures, which may be fewer in number but be larger in size, thereby allowing for a more gentle gas flow across the food product, and producing proper delicate baking of the food product. If a browning oven were desired, the apertures may be more numerous and smaller in diameter. Additionally, the operator may desire more flexibility of cooking nozzle plates  54  may be fabricated in a manner that allows for quick change-out of the plates by the operator. 
     The gas flow within the conveyor oven, as well as other functions of cooking appliance  10  are directed by a controller, not shown. The controller determines, among other things, the velocity of gas flow, which may be constant or varied, or, may be constantly varied throughout the cooking cycle. It may be desired to cook the food product on one velocity throughout the entire cooking cycle, or to vary the gas velocity depending upon conditions such as a pre-determined cooking recipes, or vary the gas velocity in response to various sensors that may be placed within the cooking zone, oven return gas paths or various other positions within the oven. The location and placement of said sensors will be determined by the particular application of the oven. Additionally, other means may be utilized wherein data is transmitted back to the controller, and thereafter the controller adjusts the cooking recipe in an appropriate manner. For example sensors (temperature, humidity, velocity, vision and gas borne chemical mixture level sensors) may be utilized to constantly monitor the cooking conditions and adjust the gas flow, and other sensors not described herein may also be utilized and the compact cooking conveyor oven may utilize sensors that are not currently commercially practical due to cost or other limitations (such as laser, non-invasive temperature sensors, IR sensors and laser to locate the sensed area and other sensors that are currently too expensive to be commercially feasible), and the oven is not limited to those discussed herein, as many sensing devices are known and utilized in and applicant intends to encompass within the language any structure presently existing or developed in the future that performs the same function. 
     Although the top gas flow system has been described in detail, the bottom gas system functions in the same manner although lower nozzle plate  59  contains channels or grooves that allow conveyor belt runners  61 ,  FIG. 6  of conveyor belt  28  to ride or glide within channels  59 , thereby enabling belt  28  to be located closer to lower nozzles  58 . Location of belt  28  closer to nozzles  58  allows for higher heat transfer rates to the bottom sides of food products upon belt  28 . Conveyor belt  28  is fitted with floating bearings  66 ,  FIG. 6  that allow for simplified maintenance and tensioning of belt  28 . 
     Although the exemplary embodiment illustrates the use of a two blower design with one blower providing the gas flow to the top of the cooking cavity and a second blower for gas flow to the bottom of the cooking cavity, one gs flow means may be utilized, or more than two gas flow means may be utilized and applicant intends to encompass within the language any structure presently existing or developed in the future that performs the same function. 
     Although one version present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. For example, various sizes of compact conveyor ovens may be made. In these cases larger or smaller component parts may be utilized, and fewer or more components may be employed. In the case where it is desirable to make a smaller conveyor oven, one gas flow acceleration means may be utilized instead of two; smaller or fewer thermal gas devices may be used. 
     To summarize, the present invention provides for a compact conveyor oven utilizing hot gas flow, supplied from combustion energy in order to achieve faster cooking of food products. The compact conveyor oven is simple and economical to manufacture, use and maintain, and is directly scalable to larger or smaller embodiments. 
     Other modifications and improvements thereon will become readily apparent. Accordingly, the spirit and scope of the present invention is to be considered broadly and limited only by the appended claims, and not by the foregoing specification. Any element in a claim that does not explicitly state “means for” performing a specific function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. §112, ¶6. In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 U.S.C. §112.