Abstract:
A continuous system for heating articles that pass through an oven cavity heated by microwave energy. A conveyor used to continuously feed items through the oven cavity contains one or more dividing mechanisms arranged along its longitudinal axis. The dividing mechanism(s) prevent at least some of the articles from touching one another while being heated. The dividing mechanism may take the form of one or more o-ring cord dividers that are wrapped around and driven by the conveyor. In an alternate embodiment, the dividing mechanism may comprise a plurality of molds defining a specific outer contour for the articles to be heated.

Description:
RELATED APPLICATION(S)  
       [0001]     This application claims the benefit of U.S. Provisional Application No.  60 / 603 , 774 , filed Aug. 23, 2004. The entire teachings of the above application(s) are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Commercial food preparation operations typically involve cooking, drying, and/or browning of items. It is often necessary to apply these processes to large quantities of food articles in the shortest possible time, and this has led to the use of continuous feed microwave ovens of several types.  
         [0003]     One such microwave oven makes use of an elongated, single mode microwave energy applicator. The single mode applicator is designed, from an electromagnetic standpoint, to be a waveguide that applies microwave energy in a shape that is optimized depending upon the shape of the product being cooked. For example, if the product being cooked is relatively square in cross-section, the applicator may itself be designed as an elongated, tapered rectangular cavity that is several feet long.  
         [0004]     Such an applicator is typically left open on both ends so that food articles to be cooked can travel on a conveyor belt that travels inside the waveguide. With food portion sizes appropriate for heating using an applicator of this design, the product entrance and exit may be constructed using well known techniques to prevent microwave leakage. For example, the entrance and exit openings can be limited in size to be something less than the propagating waveguide dimension, which in turn depends upon the wavelength of the microwave energy. Thus, for microwave applicators designed for operating in the 900 Megahertz (MHz) region, as long as openings are no more than about 6 inches or so in each dimension, energy will be contained.  
       SUMMARY OF THE INVENTION  
       [0005]     It is thus known that a continuous feed system can be provided for heating articles passing through an oven cavity with a heating source, such as a microwave energy source. However, when a conveyor belt is used to continuously feed articles through the oven cavity, the belt may be unsupported in the middle of the oven, which causes the belt to dish or become concave. Such a belt configuration causes the food articles traveling through the oven to slide toward one another, causing the articles to stick or become adhered to one another during the heating process.  
         [0006]     To solve this problem, the present invention presides one or more dividing mechanisms along a longitudinal axis of the conveyor. The dividing mechanisms keep at least some of the food articles from touching. In one embodiment, one or more O-ring cord dividers can be wrapped around and driven by the conveyor. A guiding device can be used to maintain the dividing mechanism on the belt in a desired position.  
         [0007]     In other embodiments, a mold for use with a continuous feed system is provided to form products in which a specific outer contour of the articles is desired. The mold can include cavities having any desired geometrical shape, such as circular, square, triangular, oval, etc. A guiding device can be used to maintain the mold in a desired position with respect to the conveyor.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of various embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0009]      FIG. 1  is a perspective view of a heating system in accordance with an embodiment of the invention.  
         [0010]      FIG. 2  is a perspective view of the output side of the system of  FIG. 1 .  
         [0011]      FIG. 3  is a perspective view of a heating system in accordance with another embodiment of the invention.  
         [0012]      FIG. 4  is a side view of a heating system in accordance with a further embodiment of the invention.  
         [0013]      FIG. 5  is an enlarged view of an output side of the system of  FIG. 4 .  
         [0014]      FIG. 6  is a perspective view of the output side shown in  FIG. 5 .  
         [0015]      FIG. 7  is a side view of a heating system in accordance with yet another embodiment of the invention.  
         [0016]      FIG. 8  is an enlarged view of an output side of the system of  FIG. 7 .  
         [0017]      FIG. 9  is a perspective view of the output side shown in  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     A description of preferred embodiments of the invention follows.  FIG. 1  illustrates one embodiment of a partial continuous feed heating system, designated as reference numeral  10 . For example, the heating system  10  can be used with the apparatus disclosed in U.S. Provisional Application No. 60/514,457, filed on Oct. 24, 2003, the entire teachings of which are incorporated herein by reference. Generally, articles  12  to be heated, cooked, browned, thawed, dried, or a combination thereof (i.e., processed), are carried by a conveyor belt  14  through at least one oven. As the articles  12  travel through the oven, they can be at least heated or cooked by one or more heating sources.  
         [0019]     A circularly polarized microwave signal is one in which the polarization vector of the microwave energy continually rotates. Generally, however the system will use a rectangular waveguide with linear polarization.  
         [0020]     A second heating source can include a burner or heater that provides hot air to the oven to heat the articles  12  by forced air convection. In other embodiments, the second heating source can include an infrared source or employ other suitable surface heating techniques. In further embodiments, a third heating source can be used to further process the articles  12 . The third heating source can include a steam source coupled to the oven through steam vents.  
         [0021]     Conveyor belt  14 , in one embodiment, is formed from a substantially microwave transparent material. That is, the belt  14  is formed from a material that is substantially electrically non-conductive. In one embodiment, the belt is substantially heat resistant up to about 500 degrees Fahrenheit. That is, the belt can operate in temperatures sufficient to cook the articles  12  without significant degradation. In one embodiment, the belt  14  is formed from material that does not adhere to the cooked articles  12 . For example, the belt  14  can be formed from glass fibers that can be woven. The glass fibers can also be mixed or coated with Teflon™ material or other suitable materials.  
         [0022]     Because the conveyor belt  14  is unsupported in the middle of the oven, the belt tends to dish or become concave due to gravity. When this happens, it has been found that the food articles  12  traveling through the oven tend to slide toward the middle of the conveyor belt  14  and become adhered to one another as they are processed.  
         [0023]     In one embodiment of the present invention, this problem is alleviated by one or more longitudinal dividing mechanisms  16 , such as an O-ring cord divider. The dividing mechanism(s) can be used to insure that at least some of the food articles  12  do not touch each other along two or more lanes along the longitudinal axis of the conveyor belt  14 .  
         [0024]     In a particular embodiment, the dividing mechanism(s)  16  can be formed from a material that has suitable release properties, such as Teflon™ material, so that the food articles  12  do not stick to it. The dividing mechanism(s)  16  should also be formed from a material that is chemically stable, for example, FDA approved, substantially microwave transparent, substantially electrically non-conductive, and temperature resistant, for example, able to withstand temperatures of at least 300 degrees Fahrenheit without significant degradation. In a particular embodiment, the dividing mechanism  16  is formed from silicone rubber.  
         [0025]     In this embodiment, the dividing mechanism(s)  16  can be wrapped around and driven by the conveyor belt  14 . To keep the dividing mechanism(s)  16  in position, a guiding device that can include one or more guides  18  can be positioned on an arm  20  that is pivotable with respect to table  22 . The guide  18  is movable along the arm  20  in a particular embodiment. Guide  18  includes a slot through which the dividing mechanism  16  is fed so as to maintain the dividing mechanism  16  at a desired position relative to the conveyor belt  14 . A scraper  21  ( FIG. 2 ) can be provided adjacent the output side  28  of the conveyor belt  14  to clean off the belt. The scraper  21  can include a slot through which the dividing mechanism  16  is fed to maintain the dividing mechanism  16  at a desired position relative to the conveyor belt  14 .  
         [0026]     In other embodiments, the dividing mechanism(s)  16  can be integrally formed with, or fixably attached to, the conveyor belt  14 . In yet other embodiments, the dividing mechanism(s)  16  can be provided on the top surface of the conveyor belt  14 , i.e., the dividing mechanism is stretched above the top surface of the conveyor belt  14 . The dividing mechanism(s)  16  extends vertically from the conveyor belt  14  a distance sufficient to prevent the articles  12  being heated from touching one another.  
         [0027]      FIG. 3  illustrates an embodiment in which one or more mold(s)  24  is provided for forming food articles  12  in which a specific outer contour of the articles is desired. In one embodiment, the mold  24  is a continuous belt of material having shaped cavities  26  formed within it. The cavities  26  can have any desired geometrical shape, such as circular, square, triangular, oval, etc. Certain food articles, for example, cheese, become thinner and wider when heated. When these food articles are placed in the cavities  26  prior to being heated, the outer contour of the food product is maintained by the cavity during the heating process.  
         [0028]     The mold  24  can be formed from a material that has suitable release properties, such as Teflon™ material, so that the food articles  12  do not stick or adhere to it. The material should also be chemically stable, for example, FDA approved, substantially microwave transparent, substantially electrically non-conductive, and high temperature resistant, for example, able to withstand temperatures of at least 300 degrees Fahrenheit without significant degradation. The mold  24  can be a separate element than the conveyor belt  14  so as to be removable therefrom. The mold  24  can be formed from an elastomer such that it can wrap around the conveyor belt  14  and be driven thereby. In a particular embodiment, the mold  24  can be formed from silicone rubber. In other embodiments, the mold  24  can be driven separate from the conveyor belt  14 . A guiding device, such as illustrated in  FIG. 1 , can be used to maintain the mold(s)  24  in a desired position relative to the conveyor belt  14 .  
         [0029]     In a particular embodiment, cheese is placed in the cavities  26  of the mold  24  and processed in the oven. As the water boils out of the cheese, it bubbles and puffs up and expands to form a product that is “foamy” in texture. The outer contour of the resulting product is maintained by the interior shape of the cavity  26 . Without the mold  24 , the cheese would melt and become thin and wide like a pancake.  
         [0030]      FIGS. 4-6  illustrate another embodiment of a heating system  10  in which the mold  24  extends beyond the conveyor belt  14  at the output side  28  of the system. An air knife  30  or other suitable mechanism can be used to remove the articles  12  that become adhered to the cavities  26 . In this embodiment, the articles  12  can fall onto a cross conveyor belt  32  which carries the articles to a desired location.  
         [0031]      FIGS. 7-9  illustrate a further embodiment of a heating system  10  in which the table  22  on the output side  28  of the system is extended which allows the articles  12  to cool sufficiently to become stable to increase the range of handling options. In a particular embodiment, a cooling device  34  can be used to cool the articles  12  on one or both sides of the table  22 . The articles  12  can then be deposited onto another conveyor belt  36 .  
         [0032]     In further embodiments, two or more molds  24  can be provided on the conveyor belt  14  to provide two or more lanes of food product to be simultaneously processed. In other embodiments, the cavities  26  can be integrally formed in the conveyor belt  14 , thereby obviating the necessity of having a separate mold having cavities therein.  
         [0033]     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.