Abstract:
A hot and cold food holding appliance including (1) Positioning a heat transfer plate above the top of food holding pans forming the top surface of each food holding compartment. (2) Providing a heat transfer module to transfer energy to/from the food holding pans in each compartment. (3) Thermally isolating each heat transfer module from an adjacent heat transfer module. (4) Removable heat transfer partitions that can used to subdivide each food holding compartment into sections providing additional heat transfer capability along the sides of each food holding pan and blocking the flow of ambient air between the food holding pans. (5) A control system that regulates the temperature of each food holding compartment by sensing the temperature of each heat transfer module and adjusting the amount of heat energy to be transferred.

Description:
FIELD OF THE INVENTION 
     The present invention relates to food holding appliances and, more particularly, to hot and cold food holding equipment used in the restaurant and food preparation industry. 
     BACKGROUND OF THE INVENTION 
     Restaurants and food service providers must have quick access to both hot and cold foods to assemble sandwiches and meals for delivery to customers. Food is likely to be prepared in batches and stored in a food holding appliance near the point of assembly. The food must be held in a food safe environment that inhibits the growth of bacteria and also preserves the quality of the food throughout the holding time. It is important that all food components of a meal be close to the point of assembly to increase the efficiency and speed of the preparation staff. As food service restaurants increase their menu offerings the number of unique food components increases, creating demand for more flexible hot and cold food holding capacity that can be configured to give each food product a unique thermal treatment. There is a need for a flexible food holing appliance that can hold both hot and cold foods without requiring too much counter top space in the preparation area. Counter top space is highly valued in commercial restaurants and it is important to have the flexibility to hold both hot and cold food products as close to the point of use as possible. This requires the use of the vertical space above the counter top which is usually not utilized as efficiently as possible. The ability to utilize the vertical space efficiently requires a combination of hot and cold food storage that is not available in existing food holding appliances. The flexibility to change a food holding space from hot to cold will further enhance the efficiency and utility of a food holding appliance allowing the food service provider to change their menu offerings quickly using one food holding appliance instead of several different appliances. 
     Food holding appliances in use today usually arrange food pans in an array distributed across a planar surface. Hot food holding is accomplished by filling a rectangular container with hot water and suspending the food pans over the hot water, U.S. Pat. No. 4,274,391 shows this design. Cold food holding is very similar with food holding pans suspended over a rectangular box or channel that is wrapped with refrigeration coils or with forced cold air around the bottom, sides, and over the top surface of the food pans, U.S. Pat. Nos. 6,722,150 and 5,282,367. The top surface of the food pans are arranged in an array distributed over a flat surface with the top of the food pan parallel or slightly below the top surface. These food holing appliances require considerable counter top space with food holding pans arranged in horizontal rows distributed in an array across the surface. Both of these food holding appliances are typically used in salad bars and hot food serving lines for food buffet arrangements. They are also commonly used in the food preparation kitchen for holding hot and cold food prior to assembly of meals. 
     Hot and cold food holding cabinets circulate air around the pans and over the surface of the food. U.S. Pat. Nos. 4,250,955 and 6,670,585 illustrate this type of appliance. The food pans are contained within an enclosed cabinet and a means to control the humidity and temperature of the air may be provided. Access to the food is provided by a door that is opened and closed. Some types of holding cabinets can be changed from hot to cold within the same appliance by circulating hot or cold air through the cabinet. All of the food pans contained within the cabinet share the same circulated hot or cold air. Multiple food pans are supported by shelves built in to the interior of the cabinet. 
     There are other hot food holding appliances that arrange the food holding pans in an array of compartments that can be vertically and horizontally distributed. U.S. Pat. Nos. 5,947,012 and 6,541,739 illustrate this type of holding appliance. These units typically eliminate the use of water for humidification, using conductive or radiant heat to keep the food at an acceptable holding temperature. In some units the temperature of each hot holding compartment can be individually controlled. In some units the compartment is sized to fit the food pan, while others use a large rectangular compartment that can hold one or more food pans with radiant heat supplied from the top and bottom surfaces. 
     Hot and cold food holding appliances that arrange the food pans in an array along a planar surface suffer from many limitations. They use a large amount of valuable counter top space, making it difficult to hold multiple food products close to the point of assembly causing the food preparation worker to move from the assembly station to another location to access each food item. This is an inefficient use of labor that would not be necessary if multiple food products were held in a vertical array in front of the point of assembly. Workers often remove empty pans from steam heated holding units allowing the release of steam vapor which wastes energy. The water must be replaced and heated each day before food pans can be placed in to the holding unit and emptied every night to sanitized the equipment of bacteria laden food particles that have accumulated. The refrigerated units extract heat energy from the food pans by encircling them with cold walls or forcing cold air around the food pan bottom, sides, and top. It is very difficult to maintain consistent temperatures and quality. Cold air is dry and humidity can not be added because it will cause a disabling build up of frost on the evaporator coils. Dry, cold air will dry out food products and degrade the quality. Both hot and cold holding units rely on the operator to replace the food pan cover after dispensing food to keep the food quality and temperature in the range of acceptability since the exposed top surface will be affected by the restaurant kitchen environment. Due to the difficulties listed above, it is very difficult to hold hot and cold food products close to the point of assembly while maintaining acceptable quality. 
     Food holding cabinets are able to vertically integrate food holding space but suffer from a number of problems that make them inefficient and difficult to use. The food holding compartment that forms the interior of the cabinet gives each pan in the compartment the same thermal treatment by circulating hot, humidified, or cold dry air throughout the compartment. The temperature is not even, causing hot or cold spots. Every time the cabinet door is opened, the entire conditioned air content of the cabinet must be re-generated. This is a waste of energy when the cabinet contents must be repeatedly accessed to assemble food items for serving. All of the foods will share the same air within the cabinet so the transfer of flavor from one food item to another can only be stopped by adding a cover to each food pan. This cover must be removed and replaced each time the food pan is accessed for serving. Since the cabinet environment gives all of the food pans the same thermal treatment, separate cabinet compartments must be used for hot and cold food products. Holding cabinets require expensive fans, motors, and humidity generation systems to function making them expensive to purchase, maintain, and repair. 
     Food holding appliances that arrange food holding pans in an array of compartments eliminate some of the problems listed above but can not be used to hold a combination of hot and cold foods in one appliance. Cold food must be held in one of the other food holding units described above. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention a novel apparatus is disclosed that provides both hot and cold holding for food products in one food holding appliance. In preferred embodiments the improvements include one or more of the following: 
     (1) Positioning a heat transfer module containing a heat transfer plate above the top of one or more food holding pans forming the top surface of each food holding compartment. 
     (2) Providing a heat transfer module to transfer both cold or hot heat energy to the food holding pans in each compartment. 
     (3) Thermally isolating each heat transfer module form an adjacent heat transfer module to provide independent temperature control of hot or cold food holding compartments in one food holding appliance. 
     (4) Removable heat transfer partitions that can used to subdivide each food holding compartment in to sections providing additional heat transfer capability along the sides of each food holding pan and blocking the flow of ambient air between the food holding pans. 
     (5) A control system that regulates the temperature of each hot or cold food holding compartments by sensing the temperature of each heat transfer module and adjusting the amount of heat energy to be added or removed. 
     It is therefore an object of the invention to provide a food holding appliance that will hold both hot and cold foods in one appliance in thermally isolated compartments that have independent control of the food holding temperature. 
     It is another object of the invention to make efficient use of counter top space by providing one or more food holding compartments arranged in a vertical array minimizing the need for counter top space. 
     It is another object of the invention to provide food holding compartments that can be subdivided with heat transfer partitions that block ambient air flow and improve heat transfer along the sides of each food holding pan. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which: 
         FIG. 1  is a front perspective view of a food holding appliance; 
         FIG. 2  is a front perspective exploded view of a food holding appliance; 
         FIG. 3  is a front elevation view of a food holding appliance; 
         FIG. 4  is a perspective view of a heat transfer module; 
         FIG. 5  is a perspective view of a heat transfer plate casting with internal fluid passage tubes; 
         FIG. 6  is a perspective view of a heat transfer plate with fluid passage tubes fastened to the surface; 
         FIG. 7  is a perspective view of a removable heat transfer partition and removable heat transfer partition assembly; 
         FIG. 8  is a partial perspective view of an assembly of removable heat transfer partitions and heat transfer partition guide slots; 
         FIG. 9  is a control schematic view of a multiple evaporator refrigeration control system; 
         FIG. 10  is a control schematic view of an oil heat control system; 
         FIG. 11  is a perspective view of a heat transfer plate with heat transfer fluid passage and heat element; and 
         FIG. 12  is a control schematic view of an electric heat control circuit. 
     
    
    
     For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the Figures. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a front perspective view of a food holding appliance shown in which a food holding pan  14  is removably arranged in a food holding compartment  28 . 
       FIG. 2  is an exploded perspective view of a food holding appliance with the refrigeration compressor  24 , heat transfer fluid passage manifold  22 , heat transfer fluid passage  30 , and fluid control valve  48  exposed. 
       FIG. 3  is a front elevation view of a food holding appliance with the food holding pan  14  removed to expose the food holding compartment  28 , removable heat transfer partition assembly  46 , removable heat transfer partition  26 , and heat transfer partition guide  34 . 
       FIG. 4  is a perspective view of a heat transfer module  10 . 
       FIG. 5  is a perspective view of a heat transfer plate  12  with internal heat transfer fluid passage  30  tubes. 
       FIG. 6  is a perspective view of a heat transfer plate  12  with heat transfer fluid passage  30  tubes fastened to the surface. 
       FIG. 7  is a perspective view of a removable heat transfer partition  26  and a removable heat transfer partition assembly  46 . 
       FIG. 8  is a partial perspective view of a removable heat transfer partition assembly  46  and heat transfer partition guide  34  slot. 
       FIG. 9  is a control schematic view of the multiple evaporator refrigeration control system  44 . 
       FIG. 10  is a control schematic view of the oil heat control system  52 . 
       FIG. 11  is a perspective view of a heat transfer plate  12  with a heat transfer fluid passage  30  and heat element  54  combined in to one assembly. 
       FIG. 12  is a control schematic view of an electric heat control system  56 . 
     In Operation 
     Two different food holding pan  14  sizes are shown to illustrate the flexibility of placement and size of the food holding pan  14  in the food holding compartment  28 . The upper and lower horizontal boundary of the food holding compartment  28  is defined by the location of the heat transfer module  10  and the vertical boundary of the food holding compartment  28  is defined by the support structure  18 . Each food holding compartment  28  can be further divided by a removable heat transfer partition  26  and a removable heat transfer partition assembly  46  in any quantity necessary to accommodate one or more food holding pan  14 . It is understood that the food holding compartment  28  can be sized to hold a food holding pan  14  of any height, width, depth, or quantity by adapting the geometry and quantity of the heat transfer module  10 , support structure  18 , removable heat transfer partition  26 , and removable heat transfer partition assembly  46  to receive a food holding pan  14  of different capacity. Multiple food holding compartment  28  are defined by vertically arranging multiple heat transfer module  10  within the support structure  18 . An access panel with air flow passages  16  and solid access panel  20  are fastened or removably supported on the support structure  18  to limit access to the electrical and mechanical components while providing suitable air flow for the heat transfer processes. The support structure  18 , access panel with air flow passages  16 , and access panel  20  are made from a suitable corrosion resistant metal but other materials not limited to plastic or painted metal would be suitable for this purpose. The food holding pan  14  will usually be metal or plastic from a commercially available source such as Cambro Manufacturing Company part #16CW and #36CW as shown in  FIG. 1 . The food holding pan  14  can be made from any material suitable for the purpose of storage, containing, transporting, and holding food products. A temperature control  50  is shown mounted in the support structure  18 . One temperature control  50  is assigned and mounted in close proximity to each food holding compartment  28 . The temperature control  50  allows each food holding compartment  28  to be set for a different temperature. The operator will insert a food holding pan  14  in to the food holding compartment  28  and select the holding temperature by activating the temperature control  50  that is associated with the food holding compartment  28 . Multiple food holding compartment  28  can be arranged in each food holding appliance allowing the operator to hold the food in each food holding compartment  28  at a different temperature. One food holding compartment  28  can be controlled to keep food refrigerated from 32 to 41 degrees Fahrenheit while the adjacent food holding compartment  28  can be controlled to keep food hot from 145 to 212 degrees Fahrenheit. Another food holding compartment  28  can be controlled to keep food frozen at −10 to 31 degrees Fahrenheit. 
     The refrigeration compressor  24  and condenser assembly is shown mounted to the support structure  18 . The refrigeration compressor  24  and condenser is enclosed on the top by an access panel  20  and on the sides by one or more access panel with air flow passages  16  that direct the flow of air through the condenser compartment formed by these panels. The access panel with air flow passages  16  is removable to allow adjustment of the refrigeration control system  44 . The size and number of air flow passages in each access panel with air flow passages  16  can be adjusted to match the air flow requirements of the refrigeration compressor  24  and condenser. The refrigeration compressor  24  is sized to adequately transfer the correct amount of heat from each heat transfer module  10 . The heat transfer rate for each heat transfer module  10  is calculated by consideration of the food product heat load, desired food holding temperature range, expected heat loss to the environment, and the average environment ambient temperature. The heat transfer fluid passage  30 , heat transfer fluid passage manifold  22 , and fluid control valve  48  distribute the heat transfer fluid to each heat transfer module  10 . The fluid control valve  48  receives a signal from the refrigeration control system  44  and temperature control  50  to change state from closed to open, allowing heat transfer fluid to flow, or open to closed, blocking the flow of heat transfer fluid. This regulates the temperature of the heat transfer module  10  and the amount of heat energy exchanged with the food holding pan  14 . 
     The food holding compartment  28  can be divided in to smaller compartments by the addition of a removable heat transfer partition assembly  46  or removable heat transfer partition  26  by sliding them in to the heat transfer partition guide  34 . The food holding compartment  28  can be accessed for insertion or removal of a food holding pan  14  from both sides of the food holding appliance giving the operator flexibility in the management of the food holding pan  14 . The engagement of the removable heat transfer partition assembly  46  and removable heat transfer partition  26  through the heat transfer partition guide  34  produces heat conduction from the heat transfer surface  32  to these components providing additional heat transfer capacity to the sides of the food holding pan  14 . These components are made from aluminum but any heat conductive material could be used. The removable heat transfer partition assembly  46 , and removable heat transfer partition  26  could be made from an insulating material to reduce heat transfer to the food holding pan  14  sides. These components also serve to block the flow of convection air between one food holding pan  14  and another. 
     One or more heat transfer modules can be combined with the support structure  18  to define one or more food holding compartments. The heat transfer module  10  contains at least one heat transfer plate  12  that has a heat transfer fluid passage  30  for the circulation of hot or cold heat transfer fluid. The heat transfer fluid passage  30  guides the heat transfer fluid through the heat transfer plate  12  causing a difference in temperature between the heat transfer surface  32  and the food holding compartment  28  and food holding pan  14 . The heat transfer fluid passage  30  guides heat transfer fluid through the heat transfer plate  12  and provides a discharge back to the device that either cools or heats the heat transfer fluid. The heat transfer fluid passage  30  can be located in the heat transfer plate  12  to guide the cold or hot heat transfer fluid through the heat transfer plate  12  in a manner that produces uniform temperature across the heat transfer plate  12  and heat transfer surface  32  or guided in a manner to produce unequal temperatures across the heat transfer surface  32  to compensate for heat energy loss from the ends of the food holding compartment  28  and food holding pan  14  that are exposed to the ambient room temperature. The heat transfer plate  12  is made out of aluminum but any material with heat conductive properties could be used. The bottom surface of the heat transfer plate  12  provides a heat transfer surface  32  that is exposed to the food holding compartment  28  and food holding pan  14 . The heat transfer module housing  38  provides structural support and a means for locating the heat transfer plate  12  and an insulation space  36  for limiting heat transfer to adjacent heat transfer modules. The insulation space  36  could be from 0 inches to 3 inches which is determined by the amount of heat transfer allowed from the heat transfer module  10  to an adjacent heat transfer module  10  and the thermal resistance of the insulating material chosen. The top surface of the heat transfer module  10  provides a support surface for the bottom of a food holding pan  14  if there is an adjacent heat transfer module  10  located above it. The heat transfer module housing  38  is made from a corrosion resistant metal but could be made from any other material such as plastic suitable for the application. One or more heat transfer partition guide  34  slots are provided on the heat transfer surface  32  for the addition or removal of removable heat transfer partition assembly  46  units or removable heat transfer partition  26  units. 
     The heat transfer fluid passage  30  is cast in to the heat transfer plate  12  to provide intimate contact between the heat transfer fluid passage  30  and the heat transfer plate  12  providing efficient heat transfer to the heat transfer surface  32 . The heat transfer fluid passage  30  is shown with an inlet for hot or cold heat transfer fluid and a discharge outlet to direct the heat transfer fluid back to the refrigeration compressor  24  for cold heat transfer fluids or heat source for hot heat transfer fluids. One or more heat transfer partition guide  34  slots are cast in to or milled on the heat transfer surface  32  for the addition or removal of removable heat transfer partition assembly  46  units or removable heat transfer partition  26  units. The heat transfer fluid passage  30  is made from copper tube but could be any other material that has heat conductive, temperature, and pressure properties suitable for the application. 
     The heat transfer fluid passage  30  can be mounted to the surface of the heat transfer plate  12  with multiple mounting bracket  40  units that are mechanically fastened in place by screws or other fastening means. The mounting bracket  40  forces intimate contact between the heat transfer plate  12  and the heat transfer fluid passage  30 . The efficiency of this contact can be further enhanced by the application of heat conductive paste along the point of contact between the heat transfer fluid passage  30  and the heat transfer plate  12 . The heat transfer fluid passage  30  can be removed and replaced by another heat transfer fluid passage  30  with a different geometric lay out that directs the heat transfer fluid to selected regions of the heat transfer plate  12 . The arrangement shown in  FIG. 6  directs the incoming heat transfer fluid to the outer edges of the heat transfer plate  12  first, providing greater heat transfer to the outer edges than the interior of the heat transfer plate  12 . It is understood that this geometric configuration of the heat transfer fluid passage  30  can be changed to direct the incoming heat transfer fluid to any region of the heat transfer plate  12  and the discharge fluid will be a different temperature than the incoming fluid. A single heat transfer fluid passage  30  is shown in  FIG. 6  but it is understood that multiple heat transfer fluid passage  30  units can be fastened to the heat transfer plate  12  to either equalize the heat transfer surface  32  temperature or direct more heat transfer fluid to one region as opposed to another to compensate for the heat transfer load of the food holding pan  14  or heat transfer to the environment through the exposed ends of the food holding pans. 
     The geometry of each partition is shaped to follow the contour of a food holding pan  14 . This shape can be adjusted to increase or decrease the heat transfer rate to the food holding pan  14  or block the flow of convective heat transfer caused by air flowing between the food holding pan  14 . The partitions have a key like feature at the top that allow them to be inserted in to the heat transfer partition guide  34  slot when needed. A combination of two removable heat transfer partition  26  units can be welded together to form one removable heat transfer partition assembly  46 . The removable heat transfer partition  26  and removable heat transfer partition assembly  46  are made from aluminum but could be made from any material with good or poor heat conductive properties depending on the rate of heat transfer desired through the partitions. 
     The partitions are shown fully and partially engaged in the heat transfer partition guide  34  slots to illustrate that the partitions are removable and can be inserted as required to divide the food holding compartment  28  in to smaller compartments. The top of each removable heat transfer partition assembly  46  has a key like geometry that matches the geometry of the heat transfer partition guide  34 . This feature allows the removable heat transfer partition assembly  46  to be removed or inserted at any time it is needed. 
     The refrigeration compressor  24  delivers hot, compressed gas to the condenser which removes heat until the gas condenses in to a liquid. This liquid is carried through the heat transfer fluid passage  30  and heat transfer fluid passage manifold  22  to each heat transfer module  10 . The flow of heat transfer fluid is controlled by the fluid control valve  48  which receives a signal from the temperature control  50 . The heat transfer fluid passes through the heat transfer fluid passages within the heat transfer plate  12  exchanging heat energy with the food holding pan  14  cooling the food products contained within. This heat energy is adsorbed by the heat transfer fluid and it changes state from a liquid to a gas which is directed back to the compressor through the heat transfer fluid passage  30 . 
     The pump delivers heated oil to the heat transfer fluid passage  30  and heat transfer fluid passage manifold  22 , which distributes the heated oil to each heat transfer module  10 . A fluid control valve  48  receives a signal from the temperature control  50  that opens or closes each fluid control valve  48  to regulate the flow of heated oil and the temperature of the heat transfer plate  12  and heat transfer surface  32  exchanging heat energy with the food holding pan  14  heating the food products contained within. This heat energy is released from the heated oil and the cooled oil is returned to the oil heater to be heated again. 
     The heat transfer fluid passage  30  is cast in to the heat transfer plate  12  with a heat element  54  fastened to the top surface with multiple mounting bracket  40  components. The heat element  54  can be activated by the temperature control  50  to begin a defrost cycle that will melt any ice that has accumulated on the surface of the heat transfer plate  12 . The heat element  54  can also be used to heat the heat transfer plate  12  for holding food hot from 145 to 212 degrees Fahrenheit when the refrigeration system has been disabled by the temperature control  50 . 
     There is one electric heat element  54  on each heat transfer plate  12  that provides heat energy when the temperature control  50  calls for an increase in temperature. Relay R 1  disables the refrigeration system when the electric heat element  54  is on to avoid heat and cold energy from being applied at the same time. Each electric heat element  54  is controlled by a relay CR 1  and high limit thermostat. The temperature control  50  can be programmed to automatically change the temperature of the heat transfer plate  12  over time, allowing the operator to insert pans of cold food, activate the temperature control  50 , and hold the food cold for a predetermined time then automatically change the temperature after a predetermined time. 
     Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention. 
     Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.