CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This claims the benefit of Provisional Application No. 61/053,741, filed May 16, 2008, the entire contents of which are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates generally to cooking appliances and more specifically to modular commercial cooking units with removable cooking surfaces, sometimes referred to as “hot tops.” 
       BACKGROUND 
       [0003]    The term “hot top” is often used in the art to refer to cooking appliances having a cooking surface such as a metal plate or grill over a heat source that heats the cooking surface. Traditional commercial hot tops may include a long straight tubular or rectangular burner or burners mounted symmetrically under a rectangular cast iron cooking surface. These may generally be referred to as an “even heat hot top.” Alternatively, a single round or toroidal burner may be mounted under a rectangular cast iron cooking surface generally toward the front or user side of the hot top. These types of hot tops may generally be referred to as “front fired hot tops.” The even heat hot top generally imparts evenly distributed heat to the cooking surface that may be varied by a single control, typically via a single valve. The front fired hot top provides a graduated heat pattern from front to back, with the hottest area above the center portion of the burner and with the temperature generally diminishing away from the burner center, i.e. heat is distributed in a circular pattern. There is a need for a hot top with a more variable and more finely controllable heating pattern on the cooking surface. 
       SUMMARY 
       [0004]    Briefly described, a hot top cooking unit comprises a housing with a generally open top, a front, a first side, a second side, and a rear defining and enclosing a firebox. A front ledge may be disposed along the top edge of the front projecting forwardly of the front of the housing. Similarly, side ledges may be disposed along the top edges of the sides and a rear ledge may be disposed along the top edge of the rear of the housing. A first burner and a second burner are disposed in the firebox defined by the housing and a control panel, preferably on the front of the housing, includes a first controller that controls fuel flow to the first burner and a second controller that controls fuel flow to the second burner. A cover plate defining a cooking surface, which may be a cast iron grill or plate, is removably disposed over the open top of the housing and is supported by at least two of the front ledge, the side ledges, and the rear ledge. The plate is removably disposed from its position over the heat source for cleaning or service, but cooking is always performed on the plate and never directly on the burners. The first burner and the second burner generally are disposed equal distances from the side edges and are symmetrically spaced with respect to the front and rear of the firebox. 
         [0005]    A method of operating a cooking unit includes providing a hot top cooking unit as generally described above, operating the first controller to establish the temperature setting of the first burner, and operating the second controller to establish the temperature setting of the second burner. The first temperature setting and the second temperature setting may be different. 
         [0006]    Other aspects, features, and details of the present disclosure can be more completely understood by reference to the following detailed description, taken in conjunction with the drawings and from the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]    According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to illustrate more clearly the embodiments of the disclosure. 
           [0008]      FIG. 1  is a perspective view of a hot top and plate according to a first embodiment of the disclosure. 
           [0009]      FIG. 2  is a front view of the hot top of  FIG. 1 . 
           [0010]      FIG. 3  is a top view of the hot top of  FIG. 1 . 
           [0011]      FIG. 4  is a side view of the hot top of  FIG. 1 . 
           [0012]      FIG. 5  shows three hot tops according to the disclosure arrayed in series in a range. 
       
    
    
       [0013]    Corresponding parts are designated by corresponding reference numbers throughout the drawings. 
       DETAILED DESCRIPTION  
       [0014]    For purposes of illustration and not limitation, the disclosure below describes a hot top within the context of a range. Further, references herein to “end,” “side,” “bottom,” and “top” refer to orientations or positions of elements when the hot top is oriented as if disposed in a range in an upright orientation. The terms “upper,” “lower,” “vertical,” and “horizontal,” generally refer to the location and/or orientation of an element or line with respect to a drawing figure in which it appears. 
         [0015]      FIG. 1  illustrates a hot top cooking unit  10  that includes a housing  12  with a first side  14 , a rear  16 , a second side  18 , and a front  20  that together enclose and define a firebox with a generally open top. A ledge  11  extends around the open top of the firebox and includes a first side ledge  13 , a rear ledge  15 , a second side ledge  17 , and a front ledge  19 . A cooking surface or cover plate  40 , which may, for instance, be a cast iron grill surface, is removably supportable on the ledge  11  so that the cover plate  40  overlies the open top of the firebox. A first burner  22  and a second burner  24 , each independently controlled by a respective controller  28 , are disposed at the front  20 , where a control panel  26  is defined. Control panel  26  may, for example, include a starter  30  and opening(s)  32  in a front plate  25 . The starter  30  is provided for lighting or otherwise initiating the burners  22 ,  24 , and can be, for example, a piezo-electric starter. The openings  32  are provided in front panel  25  to allow the burners to be ignited with a lighter or matches rather than starter  30  and to permit viewing of the pilot light, such as to gauge whether the pilot light is lit before supplying gas to the burners. The particular configuration of the control panel and its components may be different from that shown in  FIG. 1 , which illustrates only one example of a control panel layout. 
         [0016]    Cover plate  40 , which defines a cooking surface, is sized to be placed atop the housing  12  and to cover substantially the open top of the firebox and the burners therein. Cover  40  includes sides  42 ,  44 ,  46 , and  48  and spacers or feet  45  that engage at least two of first side ledge  13 , rear ledge  15 , second side ledge  17 , and front ledge  19 . When placed atop the housing, side  42  is disposed atop front ledge  19 , side  44  is disposed atop second side ledge  17 , side  46  is disposed atop rear ledge  15 , and side  48  is disposed atop first side ledge  13 . Cover plate  40  generally has a substantial thickness to support weight from pots, pans, and food and/or liquids or foods in such pots/pans, and can be formed of any material, but preferably is formed of cast iron. 
         [0017]    Referring again to  FIG. 1 , the first burner  22  and the second burner  24  are located generally in central or symmetrical positions relative to each side of the housing  12 . The combination of dual burners with independent controllers allows selective burn temperature settings of either or both burners to vary the temperature distribution on the cover plate  40  to create, for example, both even heat and gradually varying heat gradient patterns. The individual burner controllers allow either or both burners to be used. In a first example, both burners can be set to approximately the same temperature setting to achieve even heat across the hot plate. In a second example, only the front burner is used to achieve high heat at the front and a gradually cooling temperature gradient from the front to the back of the cover plate. In a third example, only the rear burner is used to achieve high heat at the rear of the cover plate and a gradually cooling temperature gradient from the back to the front of the cover plate. As a fourth example, both the front burner and the rear burner can be used and, by operating each controller to regulate the flow of gas, each burner can be set to produce different amounts of heat to impart a variable temperature distribution pattern to the hot plate as desired to provide virtually unlimited combinations of temperature profiles, including profiles for warming food on the cover plate  40 . 
         [0018]      FIG. 2  illustrates control array  26 , including panel  25 , knobs  28 , starter  30 , and openings  32  of hot top  10 .  FIG. 3  illustrates cover plate  40 , top  20 , control array  26 , knobs  28 , and cap  36  of the hot top and also shows gas line input  38 , which connects to a gas supply. Gas line input  38  preferably is a connector that allows quick connection/disconnection to an exterior gas supply line, though other configurations are possible and included within the scope of this disclosure.  FIG. 4  shows side  44  of cover plate  40  disposed over side  18  of frame  12 , gas input  38 , punch out  34 , and knobs  28 . 
         [0019]    As shown in  FIG. 5 , multiple hot tops according to the disclosure can be arranged in a single range to provide multiple controllable cooking surfaces. In such an arrangement, fuel such as natural gas or propane may be supplied from a single gas source into one hot top and a common gas manifold may be created by removing punch-out disc  34  in second side  18  and cap  36  (see  FIGS. 2 and 3 ) for delivery of gas from side  18  through side  12  to an adjacent hot top.  FIG. 5  shows three hot tops  10   a,    10   b,  and  10   c  installed in a range  50 . Range  50  includes a rear wall  52 , a first side  54 , a front  56 , which generally includes a door  60  that provides access to an oven cavity, and is supported on feet  58 . Each hot top has similar elements as those detailed in  FIGS. 1-4  above, such as frame  12   c  and side  18   c  shown at hot top  10   c,  with control panel  26  disposed at front plate  25  and individually control provided by controllers  28 . Each hot top  10   a,    10   b,  and  10   c  is covered with a cover plate  40   a,    40   b,  and  40   c,  respectively, which define cooking surfaces, and each cover has similar elements as detailed above, with side  44   c  of cover  40   c  shown in  FIG. 5 . 
         [0020]    According to common practice, the various features of the drawings discussed herein are not necessarily shown to scale, dimensions of the various features and elements may be expanded or reduced to illustrate more clearly the embodiments of the invention.
A modular hot top cooking unit houses two burners generally located symmetrically within a firebox of the cooking unit. Dual separate controllers independently operate each burner. A cover plate defining a cooking surface covers the firebox and overlies the two burners. The dual controls allow both burners to be operated independently to achieve even heat across the cover plate, allow only one burner to be utilized to achieve gradual heat, or allow both burners to be used at different temperatures to achieve variable heat along the cover plate.