Patent Publication Number: US-2021172597-A1

Title: Durable even heat burner for conveyor charbroiler

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application, Ser. No. 62/944,741, filed on 6 Dec. 2019. The co-pending provisional application is hereby incorporated by reference herein in its entirety and is made a part hereof, including but not limited to those portions which specifically appear hereinafter. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention generally relates to cooking appliances and assemblies and, more particularly, to conveyor cooking appliances and assemblies such as charbroilers. 
     Discussion of Related Art 
     Conveyor charbroilers are common commercial foodservice appliances used to quickly cook food item protein such as burgers or chicken, for example, in quick serve restaurants (“QSRs”). In common practice, a raw or frozen food item is placed on a conveyor that moves the food item through a heated chamber for cooking. The most common burner design uses a box-like burner with 5-7 layers of a screen material on the surface of the burner to distribute a flame, provide pressure drop and hold the flame. 
       FIG. 1  shows a side view of a standard burner assembly, generally designated by the reference numeral  110 . The burner assembly  110  includes a box burner  112  with an inlet  114  for the introduction of a fuel gas (e.g., natural gas) and oxidant (e.g., air) combustible mixture. The box burner includes a block plate  116  to assist in desired distribution of the combustible mixture. The burner  110  further includes five layers  131 ,  132 ,  133 ,  134 , and  135  of a screen material on the surface of the burner to distribute the flame, provide pressure drop and hold the flame. In such a design, the total of the five screen layers can together form a thickness of one-quarter inch or more. 
     A problem with these types of burners is attaining and maintaining an even distribution of fuel and air mixture inside five burner used to generate or produce the flame so that an even flame is formed at or on the burner surface. Current conveyor charbroilers use multiple screen burners which buckle, thereby forming gaps between the screen layers, resulting in uneven hearing and eventual failure of the burner assembly. Any unevenness in heating can result in uneven thermal expansion in the layers of the screen material to create or result in gaps between the layers. Such gaps commonly can create even greater unevenness in pressure distribution on the surface of the burner to cause or result in buckling and/or generation of severe hot spots.  FIG. 2  shows a side view of the burner shown in  FIG. 1  with gaps formed. This burner  110 ′ now has hot spots on the 5-layer screen burner surface leading to screen warping from uneven pressure and flame distribution. This leads to excessive stress on the burner screens and eventual failure. In the event of such failure, the general practice is to cut, remove and/or discard any failed layer(s) of the screen until such time that the next layer and eventually the burner itself fails and has to be replaced. Complete failure of the burner system typically occurs within a year of initial operation and can occur within months depending on factors such as how the unit is used and the frequency of the use of the unit. Removing the failed screen layers as well as the need for frequent burner replacement can result in significant down time for conveyor broilers. Moreover, as a restaurant may commonly only have only one conveyor broiler, such down time can result in significant loss of sales. 
     Thus, there is a need and a demand for improved conveyor charbroilers and associated assemblies such as, for example, exhibiting improved conveyor charbroiler durability and/or heat distribution. 
     SUMMARY OF THE INVENTION 
     The invention generally relates to a burner assembly for a charbroiler. The general object of the invention can be attained, at least in part, through a burner assembly. The burner assembly includes a burner box with an inlet for the introduction of a combustible mixture and a block plate integrated with the burner box. The block plate is configured to assist in a desired distribution of the combustible mixture. The burner assembly also includes a distribution plate overlying the block plate and a mesh surface above the distribution plate. The mesh surface includes only a single layer. The distribution plate is positioned between the block plate and the mesh surface. 
     The distribution plate includes a plurality of pores to permit desired distribution of the combustible mixture through the plurality of pores. The pores are sized small enough to avoid or prevent flashback. The distribution plate also provides a pressure drop to the burner assembly. The distribution plate evenly distributes the combustible mixture throughout the burner assembly. The distribution plate can also create an even temperature across a surface of the burner box. 
     Additionally, the mesh surface of the burner assembly holds a flame to the surface of the burner box. The mesh surface consists of a single screen. The block plate of the burner assembly is positioned on a top of the burner box. The combustible mixture used in the burner assembly preferably includes a fuel gas and an oxidant. 
     The invention also includes an improvement to a burner assembly including a burner box with an inlet for the introduction of a combustible mixture. The burner box includes a block plate to assist in desired distribution of the combustible mixture. The improvement includes a pressure distribution plate overlying the block plate and a mesh layer overlying the pressure distribution plate. The mesh layer holds a flame to a surface of the burner box. 
     The pressure distribution plate includes a plurality of pores to permit desired distribution of the combustible mixture therethrough. The pores are sized small enough to avoid or prevent flashback. 
     Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified schematic side view of a standard burner assembly; 
         FIG. 2  is a simplified schematic side view of the burner assembly shown in  FIG. 1  but now showing screen warping such as to result in uneven pressure and flame distribution; 
         FIG. 3  is a simplified schematic side view of a burner assembly in accordance with one embodiment of the present invention; 
         FIG. 4  is simplified schematic top view of the burner assembly shown in  FIG. 3 ; 
         FIG. 5  shows a pressure distribution plate in accordance with one embodiment of the invention; 
         FIG. 6  illustrates operation with an existing burner design: and 
         FIG. 7  illustrates operation with a burner designed in accordance with one embodiment of the invention. 
     
    
    
     Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale. 
     DETAILED DESCRIPTION 
     The present invention contemplates new and improved conveyor cooking appliances and assemblies such as charbroilers that utilize box burners with, having or containing a high temperature metal screen or mesh surface to provide even heat and consistent cooking results as well as a more reliable longer lasting burner. The design incorporates a block plate to distribute a fuel gas and air mixture as well as a distribution plate under the metal mesh surface. The distribution plate and the mesh surface provide a needed pressure drop for the cooking appliances. The distribution plate and the mesh surface can also evenly distribute the fuel gas and air mixture How and create a very even surface flame temperature across the whole surface of the burner without having to use multiple layers of screens. 
     As described above,  FIGS. 1 and 2  show schematics of standard burner assemblies in the prior art. The present invention is intended to remedy deficiencies in these prior art assemblies. 
       FIG. 3  shows a burner assembly  210 . The burner assembly  210  includes a box burner  212  with an inlet  214  for the introduction of a fuel gas (e.g., natural gas) and oxidant (e.g., air) combustible mixture. The box burner also includes a block plate  216  to assist in desired distribution of the combustible mixture. A pressure distribution plate  220  overlies the block plate  216 . The pressure plate  220  underlies a screen or mesh layer  230 . Preferably, the screen or mesh layer  230  is made of a single high-temperature-withstanding screen or mesh layer. Such examples of the screen or mesh layer include, but are not limited to, Iconel, Incoloy, Kanthal, and various types of steel. 
     With such a design, the single mesh layer  230  may preferably include a thickness of only 1/16″, as compared to the ¼″ thickness required for previous burner assemblies such as burner assembly  110  described in  FIGS. 1 and 2  above. It is to be understood that other thicknesses of the single mesh layer may also be used depending on a variety of factors including material of the layer and the use and type of burner assembly. The single layer of screen  230  overlying the pressure distribution plate  220  can also serve to hold a flame to the surface of the burner assembly  210  without forming gaps in the distribution of heat. Such gaps as seen in the prior art result in uneven heating. The uneven heating causes warping and the formation of gaps in mesh screens resulting in more uneven pressure distribution and flame distribution across the assembly. Therefore, the single layer of screen  230  in the claimed invention holds the flame to the burner assembly surface without forming gaps, thus overcoming the difficulties and shortcomings associated with the uneven burning and heating of previous charbroilers. 
     The pressure plate  220 , also sometimes termed a pressure distribution plate, desirably includes a plurality of openings or pores  236  to permit desired distribution of the combustible fuel-oxidant mixture. The plurality of pores  236  are sized to allow the combustible mixture to pass through the pores  236 , while the pores  236  are also sized small enough to reduce or eliminate flashback. The combination of the pressure distribution plate  220  with the small pores  236  low inside the burner  212  can distribute the combustible mixture evenly across the burner assembly  210  and also provide a drop in pressure across the mesh layer  230 . Additionally, the pressure distribution plate  220  is desirably constructed of a material durable enough to withstand operation in a combustion environment. Thus, typical suitable materials of construction may include, but are not limited to, Inconel and stainless steel, for example. 
       FIG. 4  shows a channel  232  downstream of the inlet  214  for the combustible mixture to travel through. The channel  232  is preferably centered inside the burner assembly  210  underneath the pressure plate  220 . The channel  232  includes a plurality of holes  234  for the combustible mixture to escape through. The combustible mixture enters the burner assembly  210  from the inlet  214  and goes through the channel  232 . From there, the mixture can be released from the channel  232  through the holes  234  and through the pressure distribution plate  220  before reaching the mesh layer  230 , resulting in an evenly distributed burn of the mixture. In previous designs, a combustible mixture would have been released directly to a surface of the burner. 
       FIG. 5  shows a pressure distribution plate  320  in accordance with one embodiment of the invention. The incorporation and utilization of the pressure distribution plate provides a desired drop in pressure across the burner assembly while evenly distributing gas flow and creating an even surface flame temperature across the whole surface of the burner without having to use multiple layers of screens.  FIG. 6  shows the warping that results in a burner assembly design without the even heating of the claimed invention.  FIG. 7  shows improved integrity of a burner assembly incorporated with a distribution plate and single mesh layer to evenly distribute the combustible mixture within the burner box. 
     The subject development illustratively disclosed herein suitably may be practiced in the absence of any element, part, step, component, or ingredient which is not specifically disclosed herein. 
     While in the foregoing detailed description the subject development has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the subject development 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.