Abstract:
A wire mesh burner plate for use in large, gas burners for large ovens is comprised of spaced-apart wire mesh plates. The spacing between the wire mesh plates defines an air/fuel mixture space. The fuel passes through the lower or first mesh, experiences a pressure drop, mixes with air and passes through a second wire mesh. The gas combusts after passing through the second wire mesh. The fine gauge of the mesh prevents combustion from flowing backwardly into the fuel/air mixture space. Several individual wire mesh burner plates can be flexibly attached to each other such that a very wide space can be covered. Thermal stresses are reduced by being distributed across multiple burners.

Description:
BACKGROUND 
     This invention relates to ovens. More particularly, this invention relates to a burner plate for use with a gas burner that can be used to generate infrared heat. 
     Convection ovens cook food using heated air and are slow. Microwave ovens on the other hand are very fast. They pass microwaves, usually at a wavelength of about 12 cm through food. Water, fat and other substances in the food absorb energy from the microwaves. Microwave ovens are generally used for time efficiency in both industrial applications such as restaurants and at home, rather than for cooking quality because a microwave oven cannot brown food. 
     Infrared ovens are generally faster than convection ovens because they use infrared radiation, but they are slower than microwave ovens. Of the various wavelengths of IR, short wavelength infrared is known to penetrate food more deeply than long-wavelength food and therefore cooks faster than long wavelength IR. 
     A problem with infrared ovens is the time required to heat an element to the temperature at which it will emit short wavelength IR. An energy efficient source of short-wavelength infrared that heats quickly would be an improvement over the prior art. More particularly, an oven that directs infrared onto a food being cooked from both above and below the item would be an improvement over the prior art. 
     SUMMARY 
     A burner plate for a gas-fired oven burner is provided by a parallelepiped formed from perforated stainless steel sheet and having a hollow interior. The open interior of the burner plate provides an air/fuel mixing space wherein gaseous fuel and combustion air is mixed. The gas-air mixture combusts above the wire-mesh parallel piped to heat a wire screen until it emits infrared. By loosely connecting several separate wire mesh burners together, thermal expansion and contraction is accommodated by the connections between the burners as well as the mesh material they are formed from. A very large burner plate can be provided by several individual wire mesh burners. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the front, top and side views of a mesh burner plate for a gas oven burner; 
         FIG. 2  shows a perspective view of a mesh burner plate constructed from open-faced or open-top parallelepipeds; 
         FIG. 3  shows a cut-away view of the mesh burner plate of  FIG. 2 ; 
         FIG. 4  shows a top view of a mesh burner plate constructed from several mesh burner plates of  FIG. 2 ; 
         FIG. 5  shows a cross-section of the burner plate of  FIG. 4 ; 
         FIG. 6  shows an isolated view of the connections between two individual plates of  FIG. 5 ; and 
         FIG. 7  is a view of the connection between the burner plates shown in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows the front, top and side views of a burner plate  10  for a gas oven burner (not shown). In  FIG. 1 , the front view is identified by reference letter A; the top view is identified by reference letter B and the side view is identified by reference letter C. As can be seen in  FIG. 1 , the burner plate  10  is in the shape of a parallelepiped, the mathematical definition of which is a 6-faced polyhedron, all of the faces of which are parallelograms lying in pairs of parallel planes. 
     In one embodiment, the burner plate  10  is formed from perforated  22  gauge stainless steel sheet, the holes  16  of which are so numerous, small and closely spaced such that the perforated sheet resembles a wire mesh. For clarity, the material from which the burner plate  10  is formed is referred to hereinafter as “mesh” and/or “wire mesh” but such a term includes a mesh material literally as well as perforated sheet material. 
     The holes  16  in the mesh are formed to extend completely through the mesh material to allow gases to pass through. The mesh material is of course heat tolerant because fuel gas that passes through the burner plate  10  combusts immediately after passing through the burner plate&#39;s major faces  14  and  16  with the combustion occurring adjacent to one of the major faces  14  or  16 . As stated above, the mesh in a preferred embodiment was made from stainless steel however, other heat tolerant materials into which small holes can be formed or made are also usable, examples of which include ceramic mesh, perforated ceramic sheets and ceramic-coated stainless steel. 
     The parallelepiped burner plate  10  of  FIG. 1  has first and second major faces  14  and  16 , which are the widest faces of the parallelepiped. The first and second major faces  14  and  16  are substantially rectangular and spaced apart from each other by a distance H. The major faces  14  and  16  are also considered to oppose or face each other. 
     The burner  10  has four sides  18 - 1  through  18 - 4 , each of which is orthogonal or substantially orthogonal to the opposing major faces  14  and  16  and which are also made from the mesh from which the major faces  14  and  16  are made from. The burner plate  10  has a width W and a length L. It also has a depth or height H, defined by the distance between the first and second opposing faces  14  and  16 . An open space or volume within the interior of the burner plate  10 , i.e., between the opposing major faces  14  and  16  and between the sides  18 - 1  through  18 - 4 , define the air/fuel mixture space  29 . 
     Fuel gas and combustion air  31  that passes through a first one of the major faces ( 14  or  16 ) experiences a small but non-zero pressure drop after it passes through the holes in the face ( 14  or  16 ). The gas&#39; momentum and its expansion upon passing through one of the faces ( 14  or  16 ) create turbulence in the air/fuel mixture space  29 , which causes the fuel gas and combustion air to mix. The continued delivery of fuel and combustion gas through one of the major faces ( 14  or  16 ) will cause the fuel gas and combustion gas to be forced out the other major face ( 16  or  14 ) where it is ignited and will combust so long as fuel and combustion air continue to be supplied. The hole  16  diameter and the gas flow itself prevent ignition and combustion from occurring within the air/fuel mixture space  29 . 
     As set forth above, fuel gas combustion occurs immediately adjacent to one of the major faces ( 14  or  16 ), after the fuel gas has passed through the burner plate  10 . Both of the burner plate  10  major faces  14  and  16  as well as the side walls  18  are subjected to intense heat and great temperature fluctuations whenever the burner  10  is heated. While the burner plate  10  is in the shape of a parallelepiped, those of ordinary skill in the art will recognize that the burner plate faces  14  and  16  and the four sides  18 - 1  through  18 - 4 , will not lie in precise geometric planes due in part to the heat that causes expansion and contraction and distortion as the mesh material is repeatedly heated and cooled. The faces  14  and  16  and the sides  18  are approximately planar. For purposes of this disclosure and claim construction, any reference to the faces  14  and  16  and the sides  18  as being “planar” or lying in planes, should be construed to mean that a physical embodiment will be substantially planar and will of course include some amount of bending, undulations, warping, flexing and other deviations from a pure, geometric plane. 
     In  FIG. 1 , the intersections of the major face  14  and  16  edges and the edges of the sides  18  are depicted in  FIG. 1  as lines. In other words,  FIG. 1  does not depict any seams or connections between the faces  14  and  16  and the sides  18 . 
     In one alternate embodiment, the six faces of the burner plate  10  can be extruded from a solid material so that there are no joints or seams where the faces  14  and  16  meet the sides  18 . In such an embodiment, the small diameter and regularly spaced holes that allow gas to pass through the burner  10  can be formed after the extrusion process, such as by perforation. 
     In another embodiment, a single panel of wire mesh or perforated sheet steel can be cut or stamped and folded along pre-determined fold lines, origami-like, to form a parallelepiped-shaped burner plate  10 . Open edges of the origami-like parallelepiped shape are welded or mechanically joined together. 
     In another embodiment, the six faces of the burner plates  10  can be formed from a six different pieces of planar wire mesh material or perforated sleet steel and then joined to each other at the corners form by the intersection of the major faces  14  and  16  to the sides  18 . The major faces  14  and  16  can be joined to the sides  18  by welding or an appropriate, heat tolerant adhesive. The faces  14  and  16  and the side  18  could also be riveted, bolted or screwed to small angle brackets either inside or outside the air/fuel mixture space  29 . 
     In a preferred embodiment depicted in  FIG. 2 , however, the parallelepiped-shaped burner plate  10  is assembled from two separate “open-top” or “open face” parallelepiped halves or pieces  20  and  26 , each of which is formed from the aforementioned perforated stainless steel sheet such that when the two open-top parallelepipeds are nested together, they also form a shape that also resembles a parallelepiped. 
     In  FIG. 2 , a top or “first” open-faced parallelepiped  20  is formed from a single piece of wire mesh, which is considered to include perforated sheet steel, so that the first parallelepiped  20  has a first major face  22  of mesh material and four mesh material sides  24 - 1 ,  24 - 2 ,  24 - 3  and  24 - 4 . In this embodiment, the mesh material is stainless steel, which allows the sides  24  to be formed by bending or folding until the sides  24  are orthogonal or substantially orthogonal to the first major face  22 . Importantly, the second major face of the top or “first” parallelepiped  20  is open, i.e., it is missing. Because one major face is missing from the parallelepiped, the first parallelepiped  20  is referred to as an “open-faced” or an “open-top” parallelepiped. The top or first open-faced parallelepiped nevertheless has a first width, W 1 , a first length, L 1  and a first depth or height, H 1  as shown in  FIG. 2 . 
     A bottom or “second” open-faced parallelepiped  26  is also formed from wire mesh. The second parallelepiped  26  also has a first major face  28  that is formed from the wire mesh. Like the first or top open-faced parallelepiped  20 , the second parallelepiped  26  has its second major face  30  missing or open. Four wire mesh sides  32 - 1 ,  32 - 2 ,  32 - 3  and  32 - 4  are bent or otherwise shaped to be orthogonal or substantially orthogonal to the first major face  28 . 
     Similar to the first open-top parallelepiped  20 , the second open-top parallelepiped  26  has a width, W 2 , a length, L 2 , and a depth or height H 2 , however, the dimensions of the width W 2  and the length L 2  are less than W 1  and L 1  in order to allow the second open top parallelepiped  26  to fit snugly within, i.e., nest within, the first parallelepiped  20 . 
       FIG. 3  is a cross section taken along the section lines  3 - 3  of view “B” in  FIG. 1 . As such,  FIG. 3  depicts nesting the second open-top parallelepiped  26  within the first open-top parallelepiped  20  shown in  FIG. 2 . Note that the open or missing major face of the second open-top parallelepiped  26 , is located completely within the volume enclosed by the faces of the first open-faced parallelepiped  20 . The open face of the second open-top parallelepiped is also adjacent to, or abutting, the first major face  22  of the first open-top parallelepiped  20 . Similarly, the open or missing major face of the first open-top parallelepiped  20 , abuts or is adjacent to the first major face  28  of the second open-top parallelepiped  26 . Such a configuration is referred to herein as one parallelepiped ( 26 ) being “nested” within the other parallelepiped ( 20 ). The depth or heights of the parallelepipeds  20  and  26  define an air/fuel mixture space  29  enclosed within wire mesh wherein fuel and combustion air  31  are mixed. The fuel and air  31  passes through the bottom or second parallelepiped  26 , into the air/fuel mixture space  29 , and from the air/fuel mixture space  29  through the top or first parallelepiped  20  where it is ignited and combusts. 
     In a preferred embodiment, the air/fuel mixture space  29  height H is approximately one-half inch. In alternate embodiments, however, the air/fuel mixture space  29  can be any space between about three-fifths of an inch to about one inch. 
     In all of the embodiments described above, the mesh burner plate  10  is comprised to two substantially planar and spaced-apart wire mesh plates ( 14  and  16  in  FIG. 1 ;  20  and  26  in  FIGS. 2 &amp; 3 ), which can be considered to lie in substantially horizontal and substantially parallel geometric planes. The plates have closely and regularly-spaced holes or openings  1   6  that extend completely through the constituent material so that gas  31  can flow through the holes  16  in the plates with combustion occurring just above but adjacent to one of them. 
     Depending on the orientation of the burner plate  10  an oven, i.e, whether it is mounted to project heat upwardly or downwardly, and depending on the direction of gas flow through the burner plate  10 , one of the plates ( 16  in  FIG. 1 and 26  in  FIG. 2 ) can be considered an inlet screen vis-à-vis the air/fuel mixture space  29 . The other plate (i.e.,  14  in  FIG. 1 and 20  in  FIG. 2 ) can be considered an outlet screen, against which fuel combustion takes place. 
     In a preferred embodiment, the holes  16  in both plates are the same or substantially the same size, i.e., large enough to permit a gaseous fuel/air mixture  18  to flow through them with only a small pressure drop. A pressure drop across the first or lower plate, i.e., the inlet plate, will induce or enhance turbulence and thereby induce or enhance the mixing of the fuel gas with combustion gas. 
     In an alternate embodiment, holes  16  in the inlet plate can be made larger than the holes  16  in the second or top plate to reduce or eliminate a pressure drop and to increase the volumetric flow rate of gases through the burner plate  10 . Conversely, the holes in the inlet plate can be made smaller than the holes in the outlet plate to increase the pressure drop at the inlet plate and to thereby increase turbulence through the inlet plate, increasing the mixing of fuel gas and combustion air. Larger holes in the outlet plate should the produce less turbulence through the outlet plate and should result in a combustion flame being held closer to the outlet plate as well as possibly providing a more uniform temperature. 
     As set forth above, the burner plates  10  described above are for use in a gas-fired oven, however, the area of the burner plate  10  and hence its ability to distribute heat uniformly is limited by its length and width. A much wider and/or longer gas burner and much wider heat distribution can be realized by coupling several of the burner plates  10  together, side-by-side as well as end-to-end 
       FIG. 4  is a top view of an elongated burner plate  11  comprised of several of the individual burner plates  10  depicted in  FIG. 2  connected together, side-to-side.  FIG. 5  shows a cross-section of the elongated burner plate  11  shown in  FIG. 4 .  FIG. 6  shows a depiction of the connection of two of the burner plates  10  shown in  FIG. 2 .  FIG. 7 , however, exaggerates the size differences between the open-top parallelepipeds  20  and  26  in order to more clearly show how a series of the burner plates  10  of  FIG. 2  can be readily connected to each other by simply alternating the larger and smaller open-top parallelepipeds  20  and  26  so that their sides can be interlocked. 
     In  FIG. 7 , a first large open-top parallelepiped  20 - 1  faces downwardly and nests with a first small open-top parallelepiped  26 - 1  within it. A second large open-top parallelepiped  20 - 2  lies to the right of the first open-top parallelepiped  20 - 1  facing upwardly and nests with a second, small open-top parallelepiped  26 - 2  within it. Note, however, that the “right” side  24 - 2  of the first downwardly-facing open-top parallelepiped  20 - 1  is interlocked with, i.e., hangs over, the “left” side  24 - 4  of the second, upwardly-facing large open-top parallelepiped  20 - 2 . Similarly, the “right” side of the second, upwardly-facing large open-top parallelepiped is engaged with the “left side of a third, downwardly-facing large open-top parallelepiped  20 - 3 . 
     As can be seen in  FIG. 7 , by inverting every-other large open-top parallelepiped  20 , the adjacent sides of them can be interlocked and frictionally held in place by small open-top parallelepipeds  26  that are nested into each of the large open-top parallelepipeds  20 . An extended burner plate  11  formed in this way can be constructed to provide very wide parallel plate wire mesh burner plates  11  for use in gas fired burners and ovens. 
     In an alternate embodiment, a burner plate assembly  11  is made from several of the burner plates  10  depicted in  FIGS. 1 and 2  interlocked at their narrow sides, i.e., sides identified by reference numerals  18 - 1  and  18 - 3  in  FIG. 1  and the sides identified by reference numerals  24 - 1  and  24 - 3  in  FIG. 2 . In yet another alternate embodiment, a burner plate assembly  11  is made from several burner plates  10  hooked together at both their long sides and the narrow sides to provide a long and wide burner plate assembly. When the burner plate assembly is made from burner plates of  FIG. 2  and  FIG. 3  connected along both the narrow and long sides, they are arranged in a checkerboard pattern, i.e., with every other burner plate being a large open-top parallelepiped next to a smaller open-top parallelepiped. 
     As the assembly of burner plates  10  shown in  FIGS. 4-7  are heated and cooled over time, each of the burner plates  10  will expand and contract. By using several small burners  10 , however, thermally induced stress is better absorbed by multiple burners  10  than it would be by a one large burner. 
     In order to keep gas from leaking through the burner side walls, a gasket  32  is formed from a non-combustible strap wraps around the side walls to prevents fuel gas and air from leaking through the holes  16  in the side walls. 
     In one embodiment, the holes  16  were round, and approximately 0.045 inches in diameter. The holes are aligned in “horizontal” rows (for purposes of this paragraph) with the center-to-center hole spacing between adjacent rows, i.e., a row above or below a “horizontal” row, being approximately 0.074 inches. The center-to-center hole spacing between holes in the same horizontal row is approximately 0.086 inches. The hole centers in adjacent horizontal rows are offset from each other such that a sixty degree angle is formed between a line extending horizontally through the centers of the holes in one horizontal row and a line extending through the centers of the holes in vertically adjacent rows, i.e., rows above or below a horizontal row. The center-to-center spacing of two holes adjacent to each other in adjacent vertical rows is about 0.086 inches. In an alternate embodiment, the holes  16  are either rectangular, elliptical, triangular or diamond-shaped or a combination of shapes. 
     Since the fuel/air mixture combusts above the plate  12 , a large number of openings  14  are preferred over a small number of openings in order to provide a substantially continuous blanket of combusting fuel. In a preferred embodiment, the dimensions of a single burner plate using wire mesh having the hole sizes and arrangement described above was approximately 2.05 inches by 3.75 inches with a thickness of approximately one-half inch. 
     The foregoing description provides examples of a preferred embodiment. It should not be construed as, or considered to be, limiting the scope of the invention. Rather the scope of the invention is defined by the appurtenant claims.