FIELD OF THE INVENTION  
         [0001]    This invention relates to a self-service food display for the presentation of food items, for example, a salad bar.  
         BACKGROUND OF THE INVENTION  
         [0002]    Self-service food displays that present food items to diners need to maintain the food items at an appropriate serving temperature. Thus, the self-service display needs to maintain a cool environment for the case of salad items or other items that need refrigeration. One type of prior art self-service food display provides a cool environment by disposing the food items in containers on a layer of ice. This has the disadvantages of too much cooling, i.e., freezing, and of disposal of melted water.  
           [0003]    Another type of refrigerated display counter is shown in U.S. Pat. No. 4,592,209. This display counter has a tray upon which the food is displayed. A cooling air stream is circulated over the food in a direction generally parallel to the tray via a ductwork that extends along the front, under and back sides of the tray. A glass window is provided at the customer or front side of the display case. This display counter has the disadvantage that the diner must lift the glass window to pick up a food item. Also, the display counter is subject to non-uniform temperatures across the length of the salad bar due to heat transfer leakage  
           [0004]    Refrigerated food display cases for food shopping applications typically have a tank in which the food is disposed. A food shopper must reach down into the tank to get a food item. A cooled air stream is circulated over the top of the tank and through a ductwork that extends along the front, under and back sides of the tank. A blower mechanism and a refrigerated evaporator are usually disposed in the ductwork. Refrigerated food display cases of this type are disclosed in U.S. Pat. Nos. 2,967,404, 3,543,532, 4,106,305, 4,295,340 and 4,329,852.  
           [0005]    Thus, there is a need for a self-service display that maintains a uniform temperature for the displayed food items.  
           [0006]    There is also a need for a method of maintaining a uniform temperature for the displayed food items  
         SUMMARY OF THE INVENTION  
         [0007]    A self-service food display according to the present invention includes food tray that is supported by a support structure. A ductwork is positioned with respect to the food tray to provide a cooling air stream over and under the food tray. The ductwork includes a plurality of ports arranged to distribute first volumes of the cooling air stream over and under one or more intermediate sections of the food tray to maintain a substantially uniform temperature thereof. The arrangement of ports is also such as to distribute second volumes of the cooling air stream over and under opposed end sections of the food tray. Each of the second volumes is larger than any of the first volumes so as to minimize heat transfer to ambient.  
           [0008]    According to another aspect of the self-service food display of the invention, the first and second volumes of the cooling air stream flow are substantially parallel to the food tray. The ports are further positioned to distribute third volumes and fourth volumes of the cooling air stream at an angle to an upper surface of the intermediate and opposed end sections. Each of said fourth volumes is larger than any of said third volumes so as to minimize heat transfer to ambient.  
           [0009]    According to another aspect of the self-service food display of the invention, the plurality of ports is further positioned to distribute the cooling air stream in the form of air curtains extending above three sides of the food tray.  
           [0010]    An alternate embodiment of the self-service food display of the present invention includes a support structure having a base, a back and a top. A food tray having a front end, a back end and opposed side ends is supported by the support structure so as to be exposed to ambient on the front end and the opposed side ends. A ductwork extends beneath the food tray, up the back and across the top of the support structure. A plurality of air curtain ports is arranged in the ductwork for the formation of a front air curtain and one or more opposed side air curtains. At least one of the air curtain ports is disposed along a front of the top. At least a second one of the air curtain ports is disposed along one of opposed sides of the top. At least a third one of the air curtain ports is disposed along the front end and the opposed side ends of the tray.  
           [0011]    According to another aspect of the alternate embodiment, the ductwork is in fluid communication with a passageway directly under the tray so as to provide a first airflow path for the cool air stream to cool the underside of the tray. According to still another aspect of the alternate embodiment, a plurality of ports is disposed in fluid communication with the ductwork in a location to provide a second airflow path substantially parallel to and across an upper surface of the tray.  
           [0012]    According to a further aspect of the alternate embodiment, an array of ports is disposed at a location in the ductwork to provide a uniform distribution of air flow in a third path that is incident to an upper surface of the food tray at an acute angle to provide a uniform temperature throughout the third path in the vicinity of the tray.  
           [0013]    According to a still further aspect of the alternate embodiment, the food tray has two opposed side sections and one or more intermediate sections. A first volume of the cool air stream is uniformly distributed under the intermediate sections and larger volumes of the cool air stream are distributed under any of the opposed sections that are exposed to ambient to minimize heat transfer.  
           [0014]    The method of the present invention cools a food tray of a self-service food display. The food tray has a pair of opposed end sections and one or more intermediate sections. The method provides a cooling air stream. The cooling air stream is flowed over and under the intermediate sections in a manner to provide a substantially uniform temperature in the vicinity of the food tray. The cooling air stream is also flowed over and under the opposed end sections in a manner to minimize heat transfer to ambient.  
           [0015]    According to an aspect of the method of the invention, also flows the cooling air stream in a manner to provide an air curtain that extends above three sides of the food tray. According to another aspect of the method, the cooling air stream is also flowed at an acute angle to an upper surface of the food tray in a manner that provides uniform volumes of the cooling air stream to the intermediate sections. This flow also provides higher volumes of the cooling air stream to the opposed end sections to minimize heat transfer to ambient. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure and:  
         [0017]    [0017]FIG. 1 is a front view of the self-service display of the present invention;  
         [0018]    [0018]FIG. 2 is a top view of FIG. 1;  
         [0019]    [0019]FIG. 3 is an enlarged view taken along line  3 - 3  of FIG. 1;  
         [0020]    [0020]FIG. 4 is a view taken along line  4 - 4  of FIG. 3;  
         [0021]    [0021]FIG. 5 is a perspective view of the food tray assembly of the self-service display of FIG. 1;  
         [0022]    [0022]FIG. 5A is a view taken along line  5 A- 5 A of FIG. 3;  
         [0023]    [0023]FIG. 6 is a perspective view of the blower assembly of the self-service food display of FIG. 1;  
         [0024]    [0024]FIG. 7 is a plan view of an overhead air passageway of the self-service food display of FIG. 1; and  
         [0025]    FIGS.  8 - 10  are perspective views of FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    Referring to FIGS. 1 and 2, a self-service food display  20  includes a pair of display stands  22  and  24  that are integrally connected with one another. It will be apparent to those skilled in the art that only one stand  22  or  24  may be used or that more than two stands may be used, depending on the needs of the food purveying establishment. A side counter  26  extends outwardly from stand  22 . A similar side counter (not shown) may be provided for display stand  24  or the left most display stand in self-service display  20 . Self-service display  20  also includes a top panel  28  that extends along its length. Top panel  28  may be a single panel as shown or may comprised separate top panels for each display stand  22  or  24 .  
         [0027]    Display stand  22  includes a base  30  and a back  32 , which extends upwardly from base  30 . A mirror  34  is disposed on back  30  and a transparent shield  36  is disposed in hinged relationship to top  28 . Shield  36  may be clear glass or plastic. Display stand  24  includes a base  40  and a back  42 , which extends upwardly from base  40 . A mirror  44  is disposed on back  40  and a transparent shield  46  is disposed in hinged relationship to top  28 .  
         [0028]    A plurality of lights  50  is disposed just below top panel  28  to provide lighting for the self-service display  20 . A plurality of legs  52  are attached to bases  30  and  40  and side counter  26 .  
         [0029]    Referring to FIGS. 3 and 4, display stand  30  further includes a box frame  60 . Box frame  60  has a front side  62 , a right side  64 , a left side  66  and a bottom  68 . Right and left sides  64  and  66  and bottom  68  are attached to back  32  by any suitable means, such as brackets (not shown). A box  70  has a bottom  72  and a front  74  formed of an integral L-shaped member, but could be separate pieces that are joined together. Box  70  is positioned in the upper part of base  30  and supported to box frame  60  by one or more brackets  76  and to back  32  by any suitable means, such as brackets (not shown).  
         [0030]    A plurality of food items  78  are located on a food tray assembly  80 , which is disposed above box  70 . Food tray assembly  80  is dimensioned and positioned to form a gap  82  with front side  62 , right side  64  and left side  66  of box frame  60 . Food tray assembly  80  has a front panel  84  that rests on a top  71  of box  70 . A bracket  86  also supports food tray assembly  80 . Bracket  86  extends upwardly from bottom  72  of box  70 . Bracket  86  has a first end  88  attached to bottom  72  and a second end  90  attached to a bottom surface of food tray assembly  80 .  
         [0031]    Self-service food display  20  includes passageways  92 ,  94  and  96  that form ductwork for circulating an air stream to maintain food items  78  cooled. Box  70 , back  32  and the bottom of food tray assembly  80  form passageway  92 . A plurality of fans  132  and an evaporator coil  99  are disposed in passageway  92 . Evaporator coil  99  is cooled by a refrigerant that is circulated therethrough by means not shown. Passageway  94  is formed by back  32  and the back of mirror  34 , which is held in spaced relation to back  32  by a plurality of spacers  95 . Passageway  96  is mounted to top  28  and/or back  32 . Fans  132  operate to circulate an air stream in a path that includes passageways  92 ,  94  and  96  as shown by arrows  97 . The circulating air stream is cooled by evaporator coil  99 .  
         [0032]    Referring to FIGS. 3 and 5, food tray assembly  80  includes a top  100 , a bottom  114 , front panel  84 , a back splash  102 , a side  110  and a back  138  (FIG. 6). Food tray assembly  80  is apportioned into separate cooling plate sections  102 A- 102 E. Cooling plate section  102 A includes a back splash  104 A, a top  106 A, a front  84 A and a bottom  112 A. Cooling plate sections  102 B- 102 D are substantially the same. For example, cooling plate section  102 C has a back splash  104 C, a top  106 C, a front  84 C and a bottom  112 C. A plurality of partitions  115 ,  116 ,  118 ,  120 ,  122  and  123  extend upwardly from bottom  114  to form a separate under tray air duct in each cooling plate section  102 A- 102 E. Fronts  84 A- 84 E each include apertures for the passage of cooling air. For example, fronts  84 A and  84 C have apertures  124 A and  124 C, respectively. Side  110  of cooling plate section  102 A includes an aperture  126  for the passage of air.  
         [0033]    Partitions  115 ,  116 ,  118 ,  120 ,  122  and  123  are attached to the underside of tray  100  by any suitable means, such as spot welding. As shown in FIG. 3, bottom  114  is positioned so that there is a front separation  107  between bottom  114  and front panel  84  and a back separation  109  between bottom  114  and back  32 . Front separator  107  allows airflow through apertures  124 A- 124 E and  126  to passageway  92 .  
         [0034]    Referring to FIGS. 3, 5 and  5 A, end partition  115  is positioned a short distance from side  110  to allow airflow through aperture  126  into passageway  92 .  
         [0035]    Back splashes  104 A- 104 E have disposed therein a plurality of apertures  128 A- 128 E, respectively. Apertures  128   a - 128 E are in fluid communication with the circulating air stream to divert a portion thereof in an airflow across the top of food tray assembly  80  to gap  82  where it enters passageway  92 . Aperture  128 A in end cooling plate  102 A is larger than the apertures in the cooling sections intermediate the opposite end of self-service food display  20 . This assures a greater or larger volume of cool airflow at the ends of self-service food display  20  to minimize heat transfer from ambient. The airflow across the top of food tray assembly  80  is shown in FIG. 8 as leaving passageway  94  via apertures  128 A- 128 E, flowing across cooling plates  102 A- 102 E, entering passageway  92  via front apertures  124 A- 124 E to passageway  94 . The higher volume airflow across end cooling plate  102 A is depicted by the more concentrated arrows  170 .  
         [0036]    Referring to FIGS. 3 and 6, a blower assembly  130  includes bracket  86  to which fans  132  are mounted. Bracket  86  includes a plurality of apertures  134 . Fans  132  are mounted on one side of the bracket  86  in registry with apertures  134 . A plurality of filter covers are mounted in registry with apertures  134 . Bracket  138  includes a vertical portion  138  that forms a back of food tray assembly  80  between bottom assembly  114  and top assembly  100 . A plurality of apertures  140 A- 140 E are disposed in vertical portion  138 .  
         [0037]    Referring to FIGS. 3, 5 and  6 , a plurality of under tray ducts are provided for cooling plates  102 A- 102 E by bottom  114  and vertical portion  138 . For example, cooling plate  102 A has an under tray duct  142 A formed by bottom  114 , partitions  115  and  116  and vertical portion  138 . Under tray duct  142 A is in fluid communication with the circulating air stream via front separation  107 , back separation  109  and apertures  140 A. Apertures  140 A are greater in number than the apertures of the cooling plates intermediate the two ends of self-service food display  20 . For example, cooling plate  102 A has two apertures  140 B vis-a-vis five apertures  140 A for cooling plate  102 A. This distribution of apertures allows extra cooling by the circulating air stream to compensate for heat loss at the ends of self-service food display  20 . The airflow through the under tray ducts is shown in FIG. 9 by the dashed arrows in a path that includes apertures  140 A- 140 E, front separation  107 , back separation  109  and passageway  92 . The more concentrated arrows  177  depict the higher volume airflow in duct  142 A.  
         [0038]    Referring to FIG. 3, shield  32  is mounted to top panel  28  and/or to passageway  96 . A pivot  152  is mounted to allow shield  36  to rotate upward from the position shown to allow easy access to place food on food tray assembly  80  or to clean self-service food display  20 . Passageway  96  includes an elongated air nozzle  154  that includes an array of tubes  156  arranged to form the circulating air stream into a plurality of air jets that collectively form an air curtain between nozzle  154  and apertures  124 A- 124 E to passageways  92 ,  94  and  96  as shown in FIG. 9.  
         [0039]    Referring to FIGS. 3 and 7, passageway  96  includes a bottom  158  in which an array of intermediate apertures  160  is disposed between a pair of end apertures  161 . A plurality of baffles  162  guide air to end apertures  161  and intermediate apertures  160 . End apertures  161  are larger than intermediate apertures  160  so as to provide a larger volume of air along the ends of self-service food display  20  so as to form a side air curtain to minimize heat transfer from ambient. Airflow in the side air curtain is drawn into passageway  92  via aperture  126  (FIG. 5). This side curtain airflow is shown in FIG. 10 by the side arrows  176  that flow downwardly from passageway  96 .  
         [0040]    Passageway  96  is in fluid communication with the circulating air stream via apertures  159  located in a rear wall  166  thereof. Thus, a portion of the circulating air stream is diverted into passageway  96  and distributed via apertures  159  and  60  in an airflow that is directed downwardly on food items  78 , as shown by dotted arrows  164  at an acute angle to tray  100 . This airflow merges with the airflow that flows from apertures  128 A- 128 E to apertures  124 A- 124 E.  
         [0041]    It will be apparent to those skilled in the art that the side air curtains and/or larger air volumes over and under tray  100  can be omitted for any end section that is not exposed to ambient.  
         [0042]    The present invention having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.
A self-service food display in which a food tray that is supported by a support structure is cooled by an air stream that passes over and under the tray. The tray has opposed end sections and one or more intermediate sections. The air stream is uniformly distributed over the intermediate sections to substantially maintain the same temperature in the vicinity thereof. The air stream is distributed to the opposed end sections in higher volumes to minimize heat transfer with ambient. The air stream also forms an air curtain that extends above three sides of the food tray. Additionally, the air stream is distributed at an angle to an upper surface of the food tray in a manner that provides higher volumes to the opposed end sections to minimize heat transfer.