Abstract:
A cabinet is provided. The cabinet is configured to receive and support a plurality of trays therein. The cabinet includes a housing defining an enclosure with a top, a bottom, and right and left sides disposed between the top and bottom and a plurality of shelves disposed within the enclosure and disposed between the right and left sides in a spaced relationship. One or more heaters are disposed in conjunction with each of the plurality of shelves. A cover is disposed directly below at least some of the plurality of shelves, and configured to be slidably connected with respect to the shelf for selective placement into the enclosure or removal from the shelf. A control system is in electrical communication with the one or more heaters, and is configured to operate the one or more heaters in a predetermined manner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/178,546, filed on May 15, 2009, and entitled “Warming Cart,” the entirety of which is hereby fully incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The subject disclosure relates to carts and cabinets that are configured to maintain a previously cooked food product warm during a delay time between the cooking process and serving to the customer. 
       BRIEF SUMMARY 
       [0003]    A first representative embodiment of the disclosure provides a warming cart. The cart includes a housing defining an enclosure with top, bottom, right, and left walls and a plurality of racks disposed within the housing in a vertically spaced arrangement. A plurality of heaters are disposed in conjunction with the plurality of racks, with at least one of the plurality of heaters being disposed in conjunction with each of the plurality of racks. The plurality of heaters are configured to operate on a duty cycle to maintain the racks within a specified desired temperature range. 
         [0004]    A second representative embodiment of the disclosure provides a cabinet configured to receive and support a plurality of trays therein. The cabinet includes a housing defining an enclosure with a top, a bottom, and right and left sides disposed between the top and bottom. A plurality of shelves are disposed within the enclosure and disposed between the right and left sides in a spaced relationship. One or more heaters are disposed in conjunction with each of the plurality of shelves. A cover is disposed directly below at least some of the plurality of shelves, and configured to be slidably connected with respect to the respective shelf for selective placement into the enclosure or removal from the shelf. A control system is in electrical communication with the one or more heaters and is configured to operate the one or more heaters in a predetermined manner. 
         [0005]    A third representative embodiment of the disclosure provides a cabinet configured to receive and support a plurality of trays therein. The cabinet includes a housing defining an enclosure with a top, a bottom, and right and left sides disposed between the top and bottom, the housing comprising substantially open front and back sides. A plurality of shelves are disposed within the enclosure and disposed between the right and left sides in a spaced relationship. One or more heaters are disposed in conjunction with each of the plurality of shelves. A cover is disposed directly below at least some of the plurality of shelves, and configured to be slidably connected with respect to the respective shelf for selective placement into the enclosure or removal from the shelf. A control system is in electrical communication with the one or more heaters and is configured to operate the one or more heaters in a predetermined manner. 
         [0006]    Advantages of the disclosed cabinet of use will become more apparent to those skilled in the art from the following description of embodiments that have been shown and described by way of illustration. As will be realized, other and different embodiments are contemplated, and the disclosed details are capable of modification in various respects. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of a warming cabinet showing a pan disposed therein. 
           [0008]      FIG. 2  is a front view of the warming cabinet of  FIG. 1 . 
           [0009]      FIG. 3  is a detail view of detail A of  FIG. 2 . 
           [0010]      FIG. 4  is the view of  FIG. 1  showing a cover partially removed from the warming cabinet. 
           [0011]      FIG. 5  is the view of  FIG. 1  showing the operable portions of the control system of the warming cabinet. 
           [0012]      FIG. 6  is a back view of another warming cabinet. 
           [0013]      FIG. 7  is a schematic of the control circuit used with a warming cabinet. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Turning now to  FIGS. 1-7 , a warming cart or cabinet  10  is provided. The warming cart  10  includes a body  10   a  that is defined from a top wall  11 , a bottom wall  12 , a left wall  14 , and a right wall  13  that define a warming volume  18  therein. The warming cart  10  is configured with an open front side  15  and an open back side  16  to allow one or more pans  100  to be quickly disposed within the cart  10  and the warming volume and removed from the cart  10  without operation of doors or other barriers found on conventional warming carts. As shown in  FIGS. 1 ,  2 ,  4 , and  5  the front side  15  is open to allow pans  100 , trays, pizza boxes and the like to slide through the open front side  15  and within the warming volume  18  of the cart, and as shown in  FIG. 6  the back side  16  is also open to allow pans  100  and the like to slide through the back side  16  into the warming volume  18 . The cart  10  may be a free standing unit and may be provided with castors, wheels, or the like  50  upon the bottom thereof to allow the cart  10  to be easily transported. In some embodiments, the cart  10  may be 5-6 feet tall and configured to movably rest upon the floor of the establishment, while in other embodiments, the cart  10  may be only about 1-2 feet tall and configured to rest upon a table or other elevated surface within the establishment. 
         [0015]    The warming cart  10  includes a plurality of racks  20  that are disposed in a vertical orientation with respect to each other and disposed between the right and left walls  14 ,  13  within the warming volume  18 . The racks  20  each include a shelf  21  that is fixed to the right and left sides  14 ,  13  of the body  10   a , with the top surface  22  of the shelf  21  being spaced from a bottom surface  23  of a neighboring shelf  21   a  distance to allow a conventional restaurant cooking pan  100  to be inserted therebetween ( FIG. 2 ). In some embodiments, the shelves  21  are disposed within the cart  10  with a vertical spacing just greater than the normal 2.5 inch depth of conventional restaurant warming pans  100 . In some embodiments, the shelves  21  are configured with sufficient width to accept two or more standard 12 inch wide restaurant warming pans therewithin in a side by side relationship ( FIG. 6 ), with a length of just greater than 20 inches to allow the pans to be completely received within the warming volume  18  of the cart  10  ( FIG. 1 ). In other embodiments, the cart  10  may be sized to receive a single restaurant pan on each shelf, or to receive a conventionally sized pizza box (such as an 18 inch square box) upon each shelf  21 . 
         [0016]    In some embodiments, the cart  10  may include 2, 5 ( FIG. 1 ), 10 ( FIG. 6 ), or another number of vertically spaced shelves  21  within the warming volume  18 . The shelves  21  may include one or more heaters  60  (as discussed in greater detail below) therein or therewith, such that the shelves  21  may each produce about 300 watts of heat during steady state operation. For example, in embodiments with 5 or fewer shelves, the unit may be operable with 120v 15 amp service, while in larger units with greater than 5 shelves, or greater than 300 watts per shelf, the unit may require higher 208 v service. 
         [0017]    The plurality of shelves  21  may each include a removable and slidable cover  40  that is disposed in conjunction with and below each shelf  21  (with the exception of the bottom shelf  21 , with a cover  40  also provided above the upper-most shelf). The cover  40  is configured to provide a lid to each restaurant or hotel pan  100  that is placed onto the shelf  21  within the warming volume  18  such that the heat from the food products disposed within the pan  100  (and the heat of the residual heat of the pan  100  itself) is substantially prevented from escaping due to convective heat transfer. The cover  40  additionally substantially encloses the one or more pans  100  disposed upon the shelf  21  therebelow, which maintains any moisture or water vapor within the pan  100  to prevent the warmed food disposed within the pan  100  from drying if the food is maintained in the unit for an extended period of time. An additional cover  40  may be slidably disposed at the top of the warming volume  18  to enclose a pan  100  that is disposed upon the upper-most shelf  21 . 
         [0018]    The covers  40  are disposed onto the respective shelves  21  to be removable as necessary, by sliding the cover  40  from the shelf  21  by way of a track  48  that is either disposed upon the right and left side walls  13 ,  14  ( FIG. 2 ) of the body housing  10   a  (and located proximate and below the location where each shelf  21  connects with the right and left side walls  13 ,  14 ) or a track  48  may be fixed directly to the respective shelf  21  and is disposed beneath each of the right and left sides of the shelf  21 . In some embodiments, as shown in  FIGS. 3-4 , the cover  40  may include flanges  42  or similar structures that are closely received within the track  48  to encourage stability within the track  48  and ease of sliding movement therewithin. The covers  40  are disposed to provide a spacing between the cover  40  and the shelf  21  disposed thereunder that receives a conventional restaurant cooking pan  100  therebetween, with little to no space between the upper edges of the pan  100  and the bottom surface of the cover  40 . In some embodiments, this spacing may be just greater than 2.5 inches, the depth of conventional restaurant warming pans. This arrangement allows the pans  100  to be removed, if desired, with the cover  40  installed within the cart  10  and disposed directly above a pan  100 , if desired. The cover  40  is drawn schematically in  FIGS. 2 and 5  depicting a space between the top of the cover  40  and the bottom surface  23  of the shelf  21 . In some embodiments, this space depicted in the drawings is provided between the cover  40  and the shelf  21 , while in other embodiments the top surface of the cover  40  contacts the bottom surface  23  of the shelf  21  to provide conductive heat transfer therebetween. 
         [0019]    Each of the plurality of shelves  21  include one or more heaters  60  (shown schematically in  FIGS. 2 and 3 ) that are disposed within the internal volume shelf  21 , or disposed under the shelf but in contact with the shelf  21 . In some embodiments, the shelves  21  may include two planar sheets of thin material (such as stainless steel) that form an envelope for the heater  60  to be disposed therebetween. The heater  60  is normally disposed such that the heater  60  makes surface contact with at least the upper sheet  22  forming the shelf  21  (and also the heater  60  may contact the lower sheet  23  forming the shelf  21 ) such that a percentage of the heat generated by the heaters disposed in conjunction with each shelf  21  is transferred directly to the shelf by conductive heat transfer. The remaining portion of heat generated by the heaters  60  disposed in conjunction with each shelf  21  may be transferred to the shelf  21  by radiation heat transfer. It is also contemplated that some heat may be transferred to the shelf  21  via convection due to potential air currents established within the shelf  21  due to the relative different temperatures of the air at various positions within the shelf  21  and/or forced air convection in embodiments with forced air flow within the shelf  21 . 
         [0020]    In some embodiments, the shelf  21  may include a bottom sheet  23  that is disposed below the heater  60  in each shelf  21 . This bottom sheet  23  may be in contact with the heater  60  to allow for conductive heat transfer thereto as well as receiving heat from the heater due to radiation heat transfer, and potentially convective heat transfer if the shelf  21  is configured to allow significant air flow (either due to natural convection and/or forced air convection) within the shelf  21 . The shelf  21 , and specifically the bottom sheet  23  of the shelf  21 , and the cover  40  are configured to transfer a portion of the heat generated by the one or more heaters  60  disposed within the shelf  21  to the portion of the warming volume  18  located below the shelf  21 . Accordingly, a pan  100  disposed within the cart  10  may receive heat from both the shelf  21  below the pan (by conduction and radiation), but the pan  100  and the food product located within the pan  100  may receive heat from the shelf  21  disposed above the pan  100  due to radiation. 
         [0021]    As shown in  FIG. 7 , each of the one or more heaters  60  is operated by control circuitry  200  located within the cart  10  that is configured to control the duty cycle and the heat generation capacity of the heaters  60  and therefore the temperature of the shelves  21  and ultimately the food product disposed within the warming volume  18 . In some embodiments, each shelf  21  may include one or more heaters  60  that are controlled separately from the heaters  60  that are disposed in conjunction with the remaining shelves  21 . In embodiments where the heaters  60  of different shelves  21  are controlled independently, the cart  10  would include the number of control systems  200  as different heaters to be independently controlled. In embodiments with multiple control systems  200 , each control system (such as the infinite switch  210 ) is wired in parallel (or potentially in series) with each control system  200  being energized or secured by a single On/Off switch  104 . In other embodiments, multiple On/Off switches  104  may be provided on the cart  10  to allow the user to selectively provide or secure power to different shelves  21  within the cart  10 . 
         [0022]    In other embodiments, two or more shelves  21  (normally contiguous shelves  21 ) may controlled simultaneously to form a multiple shelf heating zone that is controlled by the same control system. As shown in  FIG. 7 , the control system  200  selectively provides current to multiple heaters  60 , which may provide for multiple heated shelves  21  in the same zone. In still other embodiments, all of the shelves  21  may be controlled using the same control system  200 . 
         [0023]    The control system  200  may use a feedback control technology or it may use a non-feedback structure. In some embodiments, the heaters  60  (either individually or together to form zones of multiple shelves) may be controlled by one or more infinite switches  210  with the multiple heaters  60  being connected in parallel through breadboard type connectors  211 . In other embodiments, the multiple heaters  60  may be connected in series in a circuit with the infinite switch  210 . Infinite switches  210  include a bimetallic strip that selectively opens and closes based on the heat generated therein due to the current passing through one or more of the metals forming the strip. The infinite switch  210  is controllable by varying the orientation of the bistable, which changes the percentage of time that current is available to the heaters, and thus changes the time average output of the heaters  60 . 
         [0024]    The one or more infinite switches  210  are normally preset by the manufacturer to a setting that provides a desired steady state temperature ultimately to a food product disposed therein, wither within a pan, upon a baking sheet or the like, or within a pizza box. In embodiments with multiple heat zones, the two or more infinite switches  210  may be calibrated to establish two or more heat zones of differing temperatures within the warming volume, to allow food products that require different warming temperatures to be simultaneously disposed within the cart  10 . Alternatively, the multiple heat zones within the cart  10  may be used to allow for the gradual heat up or cool down of a food product located within a pan  100  selectively disposed within each heat zone for a specified period of time. In still other embodiments, the heaters  60  (or heat zones) are specifically calibrated to generate a uniform temperature within the entire warming volume  18  of the cart  10 . It has been experimentally determined that heaters disposed within or in conjunction with lower shelves  21  need to be energized a longer percentage of available time than heaters  60  disposed in conjunction with upper shelves  21 , due at least in part due to the natural tendency of heat to rise. Accordingly, the manufacturer (or end user) may calibrate the infinite switches  210  for lower shelves  21  (or lower heat zones) to operate more frequently than the heaters  60  in the upper shelves  21  (or heat zones) to achieve a substantially uniform temperature within the warming volume  18  at steady state. An understanding of the heat input rate to a tray  100  disposed within a respective zone and the typical ambient heat losses from a tray  100  disposed within a zone will allow for the intelligent and controlled manipulation of pans  100  as desirable. 
         [0025]    In some embodiments, the one or a plurality of infinite switches  210  may be disposed within the cart  10  in a sealed location  70  to prevent the users of the cart  10  from inadvertently altering the settings of the infinite switches  210  and therefore the heat input in each zone. The infinite switches  210  are preferably disposed with a closed volume of the cart that is accessible if desired by removing a limited number of conventional fasteners, to allow for relatively easy and convenient access if desired by a user or a technician. 
         [0026]    In other embodiments, the cart  10  may include one or more infinite switches  210  that are configured to control temperature in the desired number of heating zones within the cart  10 . The one or more infinite switches  210  are disposed (or may be controlled) by the end user of the cart  10  through knobs  110  or other operators that are disposed upon the cart  10  and accessible by the user. The knobs  110  may be calibrated to depict the expected temperature within the heating zone at steady state when a tray is disposed within the cart  10 . The cart  10  may additionally include a power available light  102 , a power on light  103 , as well as an indication of the temperature within a one or a plurality of positions within the cart, or within each heating zone, or upon each shelf. 
         [0027]    Alternatively, the cart  10  may include a feedback control system that includes one more sensors disposed in each heating zone, or within the cart  10  itself, an input device for the user to select the desired temperature at steady state within the heating zone, and a control system configured to adjust the heat output within each zone to achieve the desired temperature. In some embodiments, the controller may selectively provide or secure current to the one or more heaters  60  disposed within each zone to control the temperature of the zone. In some embodiments, the control system may include or operate in conjunction with a display that provides an indication of a temperature upon or proximate to each of the plurality of shelves  21  (or representative shelves within a specific heat zone). The control system  200  may include or communicate with an input device for the user to select a desired temperature within the specific shelf  21  or heat zone, or the user may additionally select a desired heat up rate upon a shelf or a heat zone. In some embodiments, the sensor and input device may be wired in series with the infinite switches  210  such that the sensor and input device control the percentage of time that the infinite switches operate, which provides the user with a simple and relatively inexpensive way to control the operation and temperature of the cart, and allow the user to operate the cart to achieve a consistent temperature when the ambient temperature where the cart is located may vary dramatically. 
         [0028]    While the preferred embodiments of the invention have been described, it should be understood that the invention is not so limited and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.