Abstract:
A modular heater for a conveyor oven has a flange that is removably attachable to the conveyor oven. The flange has an interior surface and an exterior surface. A heating element is attached to the interior surface of the flange. At least one contact is attached to the exterior surface of the flange. The contact is electrically connected to the heating element.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to conveyor ovens and, more particularly to, an improved conveyor oven having modular heating elements that may be easily replaced and independently controlled to modify the cooking characteristics of the conveyor oven.  
         BACKGROUND OF THE INVENTION  
         [0002]    Many restaurants use conveyor ovens to prepare food. Conveyor ovens typically cook or heat food by forced convection. A food service professional may place food such as a pizza or a dish of lasagna, for example, on the conveyor and the food is cooked or heated as it is conveyed through heated air within the oven.  
           [0003]    Air within the oven may be heated by resistive electrical heating elements located within the oven. Often, the heating elements are located inside ductwork in the inner structure of the oven. A fan or blower may force air through the ductwork. The air is consequently heated to a desired cooking temperature as it flows over the heating elements.  
           [0004]    Typical heating elements however, are difficult to repair or replace because they are located within ductwork inside the oven. Consequently, repairs and maintenance are time-consuming and expensive. A restaurant may lose additional money because a broken oven cannot cook meals for customers.  
           [0005]    Another limitation of conventional ovens is the ability to upgrade heating elements. If newer, more efficient heating elements are developed, owners of conventional ovens may be required to have their outdated oven rebuilt at considerable cost. In some cases, an oven may not have the potential for upgrades because of space limitations or incompatible circuitry. The outdated oven may require replacement for the owner to have the desired features.  
           [0006]    Additionally, conventional ovens have only a single resistive heating element having one temperature control. Supplying this typical resistive heating element with electricity will heat oven air to one particular temperature. Some foods however, may require different temperatures to properly cook different regions of the food. Pizza, for example, may require a hotter temperature air to properly cook a crisp crust while the top of the pizza may require a cooler temperature air to avoid burning a cheese topping. An oven having only a single temperature is not capable of cooking foods according to the desires of some food service professionals. Although a rheostat may be used to control the degree to which the heating element heats the air, controlling the temperature of air within different zones of the oven is difficult or impossible using conventional ovens having only one heating element.  
           [0007]    It would, therefore, be desirable to have an improved heating element that is not difficult to replace or repair. It would also be desirable to have an improved heating element that is not difficult or impossible to upgrade. Further, it would be desirable to have an improved heating element in a conveyor oven that does not have the heating and cooking limitations of conventional conveyor ovens.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention is a modular heater for a conveyor oven that has a flange that is removably attachable to the conveyor oven. The flange has an interior surface and an exterior surface. A heating element is attached to the interior surface of the flange. At least one contact is attached to the exterior surface of the flange. The contact is electrically connected to the heating element.  
           [0009]    In one embodiment of the invention, a conveyor oven has a housing. The housing has an upper end and a lower end. A base has a first end and a second end, the first end of the base is attached to the lower end of the housing. A top has a first end and a second end, the first end of the base is attached to the upper end of the housing. The top extends generally parallel and adjacent to the base. The volume between the base and the top generally defines an oven chamber. A blower distributes air to the oven chamber and a modular heater heats the air distributed in the oven chamber.  
           [0010]    In another embodiment of the invention, a food preparation system has a conveyor oven that has a cooking chamber. A blower distributes air to the cooking chamber and a heating element module to heat the air distributed by the blower. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    For a more complete understanding of the present invention, including its features and advantages, reference is now made to the detailed description of the invention, taken in conjunction with the accompanying drawings of which:  
         [0012]    [0012]FIG. 1 is an exploded perspective view of a conveyor oven that depicts an embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is perspective view of a plenum assembly that depicts an embodiment of the present invention;  
         [0014]    [0014]FIG. 3 is a cut-away view of a plenum housing that depicts an embodiment of the present invention; and  
         [0015]    [0015]FIG. 4 is a schematic diagram that depicts an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    While the making and using of various embodiments of the present invention is discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the invention.  
         [0017]    A heating element according to one embodiment of the present invention has many useful advantages over heating elements in a typical conveyor oven. Typical conveyor ovens have a heating element that is usually difficult to access for repair and maintenance. Also, upgrading the heating element may be difficult or impossible depending on space limitations of the oven or the configuration of a particular heating element. A heating element according to one embodiment of the present invention is contained in an easily accessible modular unit. The heating element may be easily replaced or upgraded by simply plugging a new heating element module into the existing cavity. An improved heating element according to one embodiment of the present invention will be described in more detail below.  
         [0018]    As depicted in FIG. 1, an oven  10  has a housing  12 . The housing  12  may house various components of the oven  10  such as plenum housings, heating elements, blowers, a power supply, switches, motors and the like. The housing  12  may be fabricated from stainless steel or other suitable material such as aluminum or carbon fiber. The housing  12  may be formed by a brake or fabricated from multiple pieces and bolted, screwed or welded together. The housing  12  may rest directly on a countertop or table or may have adjustable feet (not shown) to compensate for uneven surfaces.  
         [0019]    A base  14  is attached to the lower portion of the housing  12 . The base  14  may be welded, bolted or screwed to the housing  12 . Similar to the housing  12 , the base  14  may also be fabricated from stainless steel, aluminum or other suitable material for the food service industry. The base  14  may impart additional stability to the oven  10  by distributing the weight of the oven  10  over a larger area. The dimensions of the base  14  will generally define the size of the oven  10 . Smaller capacity ovens  10  will usually have a smaller base  14 , whereas larger capacity ovens  10  will usually have a larger base  14 .  
         [0020]    The base  14  provides support for a conveyor  16 . The conveyor  16  may be a wire mesh that conveys food through the oven  10 . A motor within the housing  12  typically drives the conveyor  16  but the conveyor  16  may also be driven by an external drive or other drive that is housed within the conveyor  16 . Alternate methods of driving the conveyor  16  will be apparent to those having ordinary skill in the art of conveyor ovens.  
         [0021]    The base  14  may also support one or more lower plenums  18 . The lower plenums  18  deliver heated air or gasses to the lower side of a food that is cooked in the oven  10 . The lower plenums  18  may be fabricated from stainless steel, aluminum, molded plastic or other material that is suitable to channel heated air or gasses. The lower plenums  18  may simply rest on the base  14  or interlock into the base  14 , the housing  12 , or a plenum housing (described below). The lower plenums  18  may be easily removable from the oven  10  to facilitate cleaning and maintaining the oven  10 . The lower plenums  18  will be described in greater detail below.  
         [0022]    A top  20  is attached to an upper portion of the housing  12 . The top  20  may be fabricated from materials such as stainless steel, aluminum or other materials known in the art of oven manufacturing. The size of the top  20  may have dimensions similar to the dimensions of the base  14 . The volume of space between the base  14  and the top  20  generally defines a chamber  22  of the oven  10 . The size of the chamber  22  determines the size of the conveyor  16  and ultimately determines the size or amount of food that may be cooked in the oven  10  during a particular time. Different sizes of ovens  10  may be manufactured by varying the lengths and widths of the top  20  and base  14  and varying the distance between the top  20  and the base  14 .  
         [0023]    One or more baffles  30  may be removably attached to the top  20  or other portion of the oven  10  to contain and redirect heated air or gasses within the chamber  22 . The baffles  30  may help prevent heated air or gasses from escaping through the entrance or exit of the oven  10 , and thereby improve the efficiency of the oven  10  and the environment of a user. The baffles  30  may be removed from the oven  10  to facilitate cleaning the chamber  22 . One or more side covers  32  may also be removably attached to the top  20  or other portion of the oven  10 . The side covers  32  may be insulated to help protect users from injuries caused by hot surfaces on the oven  10 .  
         [0024]    The top  20  may support one or more upper plenums  24 . The upper plenums  24  deliver heated air or gasses to the upper side of food that is cooked in the oven  10 . The upper plenums  24  may also deliver heated air or gasses to the chamber  22  to thoroughly cook the entire food rather than cook only a particular region of the food, such as the top of a pizza, for example. The upper plenums  24  may be fabricated from stainless steel, aluminum, molded plastic or other material that is suitable to channel heated air or gasses. The upper plenums  24  may interlock into the top  20 , the housing  12 , or the plenum housing (described below). The upper plenums  24  may be easily removable from the oven  10  to facilitate cleaning and maintaining the oven  10 .  
         [0025]    Referring now to FIG. 2, a plenum assembly includes an upper plenum housing  40  and a lower plenum housing  42 . An upper motor  44  within the upper plenum housing  40  drives an upper blower  46 . Similarly, a lower blower motor  48  drives a lower blower  50 . Separate motors  44 ,  48  may be independently controlled to differentiate airflow between the upper plenum  24  and the lower plenum  18 . Independently controlled airflow allows a user to more precisely control the cooking process. For example, more air, at a higher temperature, may be directed to the through the lower plenum  18  to most effectively cook and crisp the crust of a pizza. During the same cooking process, less air, at a lower temperature, may be directed through the upper plenum  24  to properly heat pizza toppings and melt cheese on the pizza. If the same temperature air were directed to both upper and lower surfaces of the pizza, the crust could be undercooked or the cheese could be burned.  
         [0026]    The blowers  46 ,  50  within the housing  12  may force the heated air or gasses into the plenums  18 ,  24 . The plenums  18 ,  24  may be tapered towards their distal ends to maintain air or gas velocity along the length of the plenums  18 ,  24 . The heated air or gasses may be discharged from the plenums  18 ,  24  through a series of distribution ports  52  in the lower surface of the upper plenum  24  and the upper surface of the lower plenum  18 . The series of distribution ports  52  may be sized and arranged to deliver an appropriate volume of heated air or gasses and properly cook food within the oven  10 . Heated air or gasses from the upper plenum  24  may be directed to impinge on the upper surface of the food while heated air or gasses from the lower plenum  18  may be directed to impinge on the lower surface of the food. This directional distribution of heated air or gasses aids in cooking separate portions of foods such as the meat or cheese toppings on a pizza, for example.  
         [0027]    Turning now to FIG. 3, a cutaway view of the upper plenum housing  40  is depicted in detail. Although the upper plenum housing  40  is depicted, the lower plenum housing  42  functions in a similar manner and both upper and lower components will be discussed with reference to FIG. 3. The blowers  46 ,  50  may draw air from the oven chamber  22  as shown generally by arrow  58 . Upon starting the oven  10 , ambient air will be drawn through the entrance and exit of the oven  10  into the blowers  46 ,  50 . The air may then be distributed into the plenum housings  40 ,  42 . The plenum housings  40 ,  42  have a heating element module  54  within the air path to heat air that is moved by the blowers  46 ,  50 . The heating element module  54  may heat the air by electrical resistance, combustion, or infrared heating, for example. Other components to heat the air within the oven  10  will be apparent to those having ordinary skill in oven design.  
         [0028]    Each branch of the plenum housings  40 ,  42  may have a separate heating element module  54 . Each heating element module  54  may be independently controlled to deliver different temperature air to different regions of the chamber  22 . For example, in an oven  10  that has front and rear branches of the plenums  18 ,  24 , air to each of the branches of the plenums  18 ,  24  may be heated to a different temperature according to the cooking characteristics of a particular food. Consequently, different temperature air may be directed to different regions of the chamber  22 .  
         [0029]    Additionally, the heating element modules  54  and the speed of the blowers  46 ,  50  may be simultaneously controlled by a computer processor (not shown) to more precisely control the temperature profile of the chamber  22 . A series of thermocouples (not shown) placed within the chamber  22  may monitor the oven temperature in realtime. The computer processor may compare the information from the thermocouples to a desired temperature profile and adjust the output of the blowers  46 ,  50  and the heating element modules  54  accordingly. At any given time, individual blowers  46 ,  50  and heating element modules  54  may be controlled to operate in a range from completely off to maximum output. This ability to independently control the output of the blowers  46 ,  50  and the heating element modules  54  allows a user of the oven  10  to have complete control of the temperature profile within the chamber  22 . Other methods of controlling the temperature profile within the chamber  22  will be apparent to those having ordinary skill in control theory.  
         [0030]    After the air is forced over the heating element module  54 , the air continues to flow through the plenum housings  40 ,  42  and is delivered to the plenums  18 ,  24 . Arrows  60  generally designate this airflow from the plenum housings  40 ,  42 . The airflow may be collimated by a series of vanes  56  within the plenum housings  40 ,  42 . The vanes  56  may be thin strips of metal, plastic, or other suitable material that are spot welded, screwed, glued or otherwise fastened in the flow path of the air. The vanes  56  are designed to redirect, distribute and equalize airflow across the cross section of the plenum housings  40 ,  42  and the plenums  18 ,  24 . Collimated air is more efficiently delivered through the plenums  18 ,  24  and, consequently, into the chamber through the distribution ports  52 . As a result, the vanes  56  alter airflow characteristics to improve heat distribution within the chamber  22 .  
         [0031]    Heated air circulates within the chamber  22  and cooks or heats the food on the conveyor  16 . Because the blowers  46 ,  50  draw air from the chamber  22 , the blowers  46 ,  50  draw heated air after the oven  10  has been operating for a period of time and the heating element modules  54  impart additional heat to the air. If the heating element modules  54  and the blowers  46 ,  50  are operated at a steady rate, the temperature within the chamber  22  will eventually reach a steady state. However, varying environmental conditions such as room temperature changes and the addition of cold food products to the chamber  22  will alter the temperature profile of the chamber  22 . Independent and variably controllable heating element modules  54  may add or reduce heating to compensate for changes in a proper temperature profile. Consequently, food may be properly cooked in a consistent manner.  
         [0032]    Turning now to FIG. 4, the heating element module  54  is depicted in greater detail. The heating element module  54  has a flange  62  that may be releasably attached to the plenum housing  40 ,  42  by fasteners  64 . The fasteners  64  may be thumbscrews, wing nuts, or other removable fasteners known in the art. The heating element module  54  may also be removably attached to the plenum housing  40 ,  42  by an interference or friction-type fit or spring-loaded lug. Other methods of removably attaching the heating element module  54  to the plenum housing  40 ,  42  will be apparent to those having ordinary skill in the art of fastening components.  
         [0033]    An element  66  is attached to the inside of the flange  62 . The element  66  is positioned within the airflow path of the plenum housing  40 ,  42  to heat air that is moved by the blower  46 ,  50 . Electrical contacts  68  are attached to the outside of flange  62 . A power source (not shown) from the oven  10  is attached to the contacts  68 , which deliver heating power to the element  66 . For example, if the heating element module  54  has an electric element  66 , electricity from the power source is delivered to the contacts  68 , which resistively heats the element  66 . Heat from the element  66 , in turn, heats air that flows over the element  66 .  
         [0034]    The heating element module  54  may be easily replaced or upgraded because it is removable from the plenum housing  40 ,  42 . The heating element module  54  may be removed by simply pulling the heating element module  54  from the plenum housing  40 ,  42  if the heating element module  54  has an interference fit or by unfastening and removing the heating element module  54  if the heating element module is attached with fasteners. This easily replaceable feature is advantageous because a damaged element  66  may be quickly replaced without losing valuable time. The time that the oven  10  is out of service is reduced significantly.  
         [0035]    Additionally, the oven  10  may be upgraded if new, more efficient heating elements are developed. The new element  66  may be added to a heating element module  54 , which may be swapped for an outdated heating element module  54 . For example, a heating element module  54  may have a supplemental element  66  to impart additional heat to the oven. The upgrade is quick and easy because the heating element modules have a standard size and interface with the oven  10 . Therefore upgrades do not require expensive modifications and retrofitting to the oven  10 .  
         [0036]    Another advantage of the heating element module  54  is that different heating element modules  54  may be installed in an oven. Although the dimensions and interfaces with the oven  10  may be the same, the power output may be different for heating element modules  54 . For example, heating element modules  54  in the lower plenum housing  42  may have a higher power output to more thoroughly cook the lower portion of a food while the heating element modules  54  in the upper plenum housing  40  may have a lower power output to reduce the likelihood that the top of the food will be burned. Heating element modules  54  having different characteristics may be arranged in a variety of configurations within the oven  10  to provide great flexibility in controlling the temperature profile within the chamber  22 .  
         [0037]    Whereas the invention has been shown and described in connection with the preferred embodiment thereof, it will be understood that many modifications, substitutions and additions may be made which are within the intended broad scope of the appended claims. There has therefore been shown and described an improved heating element that accomplishes at least all of the above stated advantages.