Abstract:
The present invention provides a roll-in kitchen unit having an outer housing and a trolley that fits substantially within. The trolley provides a cast frame coupled to a scaling plate for sealing the trolley within the outer housing. In one embodiment, the cast frame is reinforced with inner and outer ribs to minimize deflection of the cast frame and bring the sealing plate into alignment with the corresponding gasket of the outer housing door.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Background of the Invention 
     The present invention relates to trolleys for holding food to be easily rolled into and out of food holding cabinets, and in particular, to a trolley with reinforced supports for reducing air leakage and heat and humidity losses when the trolley is positioned in the holding cabinet. 
     Food holding cabinets providing storage, refrigeration and/or heating are commonly used by bakeries and food service establishments that prepare large quantities of food in advance to chill or heat food for temporary storage or last-minute finishing. These units aid in high-volume operations to increase an operation&#39;s efficiency and speed of service. 
     Instead of built-in shelving, food holding cabinets may employ a trolley that supports the food on multiple shelves which may be rolled into or out of the food holding cabinet so that the food holding cabinet may be quickly loaded or unloaded. Ideally, the trolley is sized to take full advantage of the volume of the food holding unit and so has outer dimensions closely approximating the interior dimensions of the food holding cabinet. The trolley may have a U-shaped carriage allowing its wheels to sit underneath the floor of the food holding cabinet when the trolley is installed in the food holding cabinet and allowing the door of the food holding cabinet to close. When the door of the food holding cabinet is closed, a sealing plate of the trolley may interface with a corresponding gasket of the door to seal the cabinet and its contents therein. 
     SUMMARY OF THE INVENTION 
     The present inventors have recognized that even small amounts of deflection of the trolley, due to varying loads of food products placed on the its multiple shelves, may result in angulation of the trolley&#39;s sealing plate making it difficult for a proper seal to be created when the trolley is installed within the food holding cabinet. This is particularly true when the seal requires the trolley&#39;s sealing plate to be substantially parallel to the corresponding gasket on the food holding cabinet door, and any unevenness of the ground exacerbates the misalignment of the trolley with the cabinet walls. 
     Accordingly, the present invention provides a trolley with a reinforced support frame, which prevents angulation of the sealing plate, bringing the sealing plate into alignment with a corresponding gasket of the food holding cabinet door. 
     In one embodiment, the present invention may be a roll-in trolley for use with a food preparation cabinet having an enclosure providing walls defining a cavity for receiving food through a front opening of the food preparation cabinet, the front opening coverable by a door. The roll-in trolley may include a food rack providing a plurality of lateral supports arranged in a column and adapted for receiving food trays along a lateral direction to rest on the lateral supports; a cantilever frame having lateral supports supporting the food rack thereon; a removable horizontally extending roller frame fitting beneath the enclosure of the oven as moved on rollers extending downwardly from the roller frame; a support frame communicating between a front end of the horizontally extending roller frame and a front end of the cantilever frame so that the roller frame may support the food rack within the enclosure when the roller frame is beneath the enclosure; and a vertically extending sealing plate positioned at an upper end of the support frame and extending over at least a portion of the front opening when the food support rack is installed in the enclosure. The support frame may have a greater unit stiffness than the lateral supports of the cantilever frame so that bending of the cantilever tube frame under weight of the food rack is substantially isolated from the vertically extending sealing plate. 
     It is thus a feature of at least one embodiment of the invention to attach the sealing plate to a support frame having increased stiffness so that a deflection of the cantilevered frame is not translated to the sealing plate. 
     The cross-sectional area of the support frame is greater than the cross-sectional area of the lateral supports of the cantilever frame. 
     It is thus a feature of at least one embodiment of the invention to increase the stiffness of the cantilevered frame by coupling it to a curved support frame with increased lateral and transverse strength. 
     The support frame consists of multiple vertical elements attaching to corresponding lateral supports and where each vertical element has a cross-sectional area greater than its corresponding lateral support. 
     It is thus a feature of at least one embodiment of the invention to increase the stiffness in both a horizontal and vertical direction to prevent deflecting or bending of the vertical elements and deflection of the lateral supports. 
     The support frame is a casting and the lateral supports of the cantilever tube assembly are tubes. The support frame may be cast stainless steel. 
     It is thus a feature of at least one embodiment of the invention to strengthen the support frames by using cast frames attached to the hollow tubes of preexisting trolley frames. 
     The support frame includes at least one rib extending along at least one of an inner and outer perimeter of the support frame to provide additional mass to the support frame. 
     It is thus a feature of at least one embodiment of the invention to increase the stiffness of the support frame by increasing the thickness using ribs providing additional mass and cross sectional area to the frame. 
     The at least one of the rib has a greater cross sectional area at a mid-point of the vertical element than at peripheral edges of the vertical element. 
     It is thus a feature of at least one embodiment of the invention to reinforce areas of expected weakness such as near a mid-point of the vertical element when force is applied to the ends. 
     The support frame provides a vertical element connected at upper and lower ends to upper and lower horizontal elements wherein the connection of the elements is curved. 
     It is thus a feature of at least one embodiment of the invention to use a unitary frame with reinforced curves to prevent bending between the upper and lower horizontal supports and the vertical support. 
     Opposite ends of the support frame are inserted into hollowed ends of lateral supports. Opposite ends of the support frame provide plugs having a smaller cross section than a cross section of the support frame. 
     It is thus a feature of at least one embodiment of the invention to allow the support frame to be adaptable with preexisting trolley frames. 
     The support frame has a generally round cross section. 
     It is thus a feature of at least one embodiment of the invention to provide ease of casting. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified perspective view of the roll-in kitchen unit of the present invention showing an oven housing having a retractable sealing plate and a door closeable over a front opening, and a trolley having its own sealing plate and installable within the oven housing; 
         FIG. 2  is a left side cross sectional view of a prior art trolley shown installed within the outer housing and the sealing plate misaligned from a gasket of the front door with deflection of a cantilevered element; 
         FIG. 3  is a left side cross sectional view of the trolley of the present invention shown installed within the housing and the sealing plate aligned with the gasket of the front door to create a proper seal; 
         FIG. 4  is a perspective view of the reinforced cast frame being inserted within hollowed tubes of the cantilevered element; 
         FIG. 5  is a fragmentary side elevation view of an upper end of the reinforced support frame showing the sealing plate welded to the reinforced support frame and having a protruded tab to assist with alignment; and 
         FIGS. 6A-6D  are fragmentary side elevation views of the lower end of the oven housing showing the retractable sealing plate moved from a stowed position beneath the oven housing to an installed position extending over an opening of the oven housing to seal the housing when the door is closed over the front opening and the trolley is removed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The Prior Art 
     Referring to  FIG. 2 , a roll-in trolley  212  of the prior art provides tray racks  246  supported below by a cantilevered frame  257  having lateral cantilever supports  252  supporting the racks  246  thereon. The lateral cantilever supports  252  extend parallel to lateral supports  254  of a roller frame extending therebelow and connected therebetween by vertical frames  256 . The tubes forming the cantilevered frame  257  have a rectangular cross-section and the cross sectional area is constant throughout the frame  257 . Mounted to the lateral cantilever supports  252  is a sealing plate  270 , which extends perpendicular to the lateral cantilever supports  252  so that it extends vertically when the lateral cantilever supports  252  are horizontal. 
     When the trolley  212  carries food on its shelving, the distal end of the racks  246  may be weighted down to deflect the lateral cantilever supports  252 , for example, 20-30 mm from a horizontal position. For example, in the exaggerated depiction shown in  FIG. 2 , the lateral cantilever supports  252  are shown to be sloping downward by an angle θ 1  with respect to horizontal. The deflections of the lateral cantilever supports  252  translate to the sealing plate  270  attached thereto. As a result, angulation of the sealing plate  270  is created consistent with the angulation of the lateral cantilever supports  252 . Moreover, the vertical frames  256  may bow outward causing the lateral cantilever supports  252  to deflect further. For example, in the exaggerated depiction of  FIG. 2 , the sealing plate  270  is angled by an angle θ 2  with respect to vertical. The angulation of the sealing plate  270  causes the face seal between the sealing plate  270  and corresponding sweep gasket  278  of the cabinet door  224  to become misaligned causing air or moisture to leak from the food holding cabinet  210 . 
     THE PRESENT INVENTION 
     Referring now to  FIG. 1 , a trolley system according to one embodiment of the present invention may provide a food holding cabinet  10  accepting a trolley  12  in a lateral insertion direction. The food holding cabinet  10  has a plurality of walls defining a generally rectangular volume or cavity including a vertically extending back sidewall  14  joined on its left and right edges by transversely opposed vertically extending left  16  and right  18  side walls extending laterally forward from the back sidewall  14 . A top wall  20  and bottom wall  22  are joined to the upper and lower edges of the back sidewall  14  and side walls  16 ,  18 , respectively, to define a ceiling and floor of the enclosable volume  34 . It is understood that the food holding cabinet  10  refers to any food preparation cabinet including but not limited to holding ovens, cooking ovens, and chillers. 
     The volume  34  may be accessed through a door  24  closeable over a front opening  26  and which seals the interior of the volume  34  when the door  24  is in a closed position. The door  24  may be connected by a hinge  28  attached to, for example, a vertical edge of the left sidewall  16 . The door  24  has a substantially planar outer surface  25  opposite an inner surface  27  interfacing with the front opening  26 . A lower portion  74  of the inner surface  27  of the door  24  may be recessed to provide a generally rectangular space or depression set back from a generally rectangular upper portion  76  of the inner surface  27  so that the trolley  12  may be installed within the food holding cabinet  10  without interfering with the door  24  closure. An upper, left and right edge of the upper portion  76  of the door  24  may have a door gasket  30  or other sealing material for sealing the connection between the door  24  and the walls  16 ,  18 ,  20  of the volume  34 . A sweep gasket  78  may be installed on the inner surface  27  of the lower edge of the upper portion  76  for sealing the connection between the door  24  and the trolley  12  when the trolley  12  is installed within the food holding cabinet  10  as will be described in further detail herein. The door gasket  30  and sweep gasket  78  are configured to seal the trolley  12  shelving within the volume  34  when the door  24  is closed as will be described in further detail herein. 
     The left and right side walls  16 ,  18  and back sidewall  14  of the volume  34  may incorporate an inner electrical coil  32 , which provides heat or cooling to the volume  34 . A water source such as a water jet or boiler (not shown) may also provide water to the volume  34 , for example, for optional steam cooking. The left and right sidewalls  16 ,  18 , back sidewall  14 , top and bottom walls  20 ,  22  may further incorporate an insulating material so as to retain heat or cooling air within the volume  34  and to prevent heat or cooling air from escaping. It is understood that the kitchen unit may have the required electrical circuitry and connections to properly power the unit and control the internal temperature, as is currently understood in the art. 
     The food holding cabinet  10  may be supported on the ground by a number of supporting feet  36  disposed below the volume  34  and extending down from the bottom wall  22  to control and provide vertical elevation to the volume  34 . According to one embodiment of the present invention, the supporting feet  36  are adjustable and positioned at each of the four corners of the exterior surface of the bottom wall  22  of the volume  34 . The supporting feet  36  are defined by a generally circular spreader  29  making contact with the ground and connected to an adjustable column  40  extending upward therefrom. The circular spreader  29  provides an expanded contact surface to spread out the weight supported thereon to prevent gouging of the floor. The adjustable column  40  is in one embodiment, an externally threaded rod that is adjustable by rotation within a corresponding internally threaded sleeve (not shown) fixed with respect to the walls of the food holding cabinet  10  for lengthening and shortening its length and thus changing its height with respect to the ground. 
     It will be understood that the adjustable support feet  36  may be separately lengthened or shortened such that the vertical height of the four corners of the food holding cabinet  10  is independently adjusted with respect to the floor in order to level the food holding cabinet  10 , that is, to orient its walls vertically. This serves the intended purpose of providing leveling to the food holding cabinet  10  on uneven surfaces. In addition, the adjustable support feet  36  provide vertical separation between the bottom wall  22  of the food holding cabinet  10  and the floor such that there is a free passage of air and water therebetween the feet  36  to facilitate in cleaning and remove the food holding cabinet  10  from potential source of contamination. 
     Still referring to  FIG. 1 , the trolley  12  may be substantially received into the food holding cabinet  10  and encloseable therein. An upper portion  42  of the trolley  12  holding the food to be processed is received within the enclosable volume  34  while a bottom portion  44  of the trolley  12  having a cantilevered support  122 , support structure  124 , and roller frame  126  with trolley wheels  80  remains outside and below the food holding cabinet  10  to eliminate contamination. 
     In one embodiment, the trolley  12  has two vertically extending ladder racks  46 ,  48  to its left and right respectively which extend upward along and parallel to the left and right oven sidewall  16 ,  18  when installed within the volume  34 . The height and lateral depth of the ladder racks  46 ,  48  are commensurate with a height and depth of the left and right oven sidewall  16 ,  18 . The ladder racks  46 ,  48  may be provided by vertical side rails  58  at front and rear corners of the left and right oven sidewall  16 ,  18  respectively joined by a plurality of laterally extending, horizontal shelf supports  50  therebetween. Cooking shelves (not shown) may be positioned directly onto the shelf supports  50  when installed onto the supports  50  in a lateral direction. 
     The cooking shelves are able to support pans or trays of food of conventional shape and size. It is contemplated that the cooking shelves may be installed in a number of different configurations so that different pan and tray heights may be held. The cooking shelves are easily installed and uninstalled for cleaning and maintenance. Alternatively, the supports  50  may hold the food pans or trays directly by accepting the lip or handle of the pan or tray thereon without the use of shelving. 
     The left ladder rack  46  and right ladder rack  48  are supported below by a cantilevered support  122  having lateral cantilever shelf beams  52 ,  53  supporting the ladder racks  46 ,  48  thereon. The left ladder rack  46  is supported at its lower edges by the upper surface of a left lateral shelf beam  52  and the right ladder rack  48  is supported at its lower edges by the upper surface of right lateral shelf beam  53 . The lateral cantilever shelf beams  52 ,  53  extend above and parallel to left and right lateral roller supports  54 ,  55  of a rectangular roller frame  126 , the latter being a generally rectangular frame having wheels  80  in each of its corners. The rectangular roller frame  126  extends below the shelf beams  52  and  53  and is connected at its lateral front end to the lateral front ends of the shelf beams  52  and  53  by a support structure  124  constructed of upward extensions  56 ,  57 . The upward extensions  56 ,  57  may be connected at a front lateral end by a horizontal transverse connecting bar  72  extending between the left upward extension  56  and right upward extension  57 . A rear end of the ladder racks  46 ,  48  may be attached to the rear lateral end of lateral cantilever shelf beams  52 ,  53  and a front end of the ladder racks  46 ,  48  may be attached to the upward extensions  56 ,  57 . 
     The lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55  may be constructed of hollow tubes having a generally rectangular cross sectional profile and constant cross sectional area. The tubes may be constructed of a metal, such as stainless steel. A front end  98  of the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55  provide openings  99  having a generally rectangular cross section allowing insertion of mating plugs  96  of the upward extensions  56 ,  57  therein as will be described. 
     Referring also to  FIG. 4 , the upward extensions  56 ,  57  have a generally U shape defined by upper  59  and lower  63  horizontal portions connected to a vertical body portion  61  by upper  118  and lower  120  junction portions respectively. The upper  118  and lower  120  junction portions provide curved connections between right angle ends such that the upper  59  and lower  63  horizontal portions extend substantially perpendicular to the vertical body portion  61 . In this respect, the ladder racks  46 ,  48  are attached to the upper horizontal portion  59  of the upward extensions  56 ,  57  with the vertical portion  61  of the upward extensions  56 ,  57  extending in front of the ladder racks  46 ,  48 . 
     The upward extensions  56 ,  57  provide plugs  96  extending outwardly from the distal ends of the upper  59  and lower  63  horizontal portions for attachment to the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55 , respectively. The plugs  96  are sized to fit within the openings  99  formed within the front ends  98  of the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55 . The plugs  96  are shaped to match the shape of the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55  thus allowing the insertion of the plugs  96  into the openings  99  of the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55 . For example, the plugs  96  may have a rectangular cross section sized slightly smaller than the rectangular openings  99  so as to be inserted therein. The plugs  96  may be friction fitted within the openings  99  or spot welded to otherwise secure the plugs  96  to the front ends  98 . The plugs  96  may be approximately 1-2 inches in length to extend a distance within the openings  99 . It is understood that the plugs  96  may have a different cross sectional shape from the rest of the upward extensions  56 ,  57  so as to allow the upward extensions  56 ,  57  to be attached to tubes or trolley supports of a different shape or size from the upward extensions  56 ,  57 . 
     Referring to  FIGS. 4 and 5 , the upward extensions  56 ,  57  may be cast metal having a generally non-rectangular solid cross section with a laterally frontward (outwardly) extending outer rib  104  and laterally rearwardly (inwardly) extending inner rib  100  on each of the upper  59  and lower  63  horizontal portions and vertical body portion  61  to provide additional stiffness at areas of expected deflection. Momentarily ignoring the outer rib  104  and inner rib  100 , the cross-sectional area of material of the vertical body  61  is generally greater than the cross-sectional area of material of the connecting lateral roller supports  54  and  55  and the cantilevered shelf beams  52  and  53  to provide a greater unit stiffness in the upward extensions  56  and  57 . The lateral cross-sectional width of the vertical body  61  and the lateral/vertical cross-sectional extent of the upper  118  and lower portion  120  is further increased by the outer rib  104  and inner rib  100 . The inner rib  100  may increase in transverse thickness at the vertical body portion  61  thinning at the upper  59  and lower  63  horizontal portions. Likewise the transverse width of the inner rib  100  may also vary within the upper  59  and lower  63  horizontal portions and vertical body portion  61 , respectively, being laterally thickest at the vertical body portion  61 . This thickening is intended to increase the cross sectional area at a midpoint of the vertical body portion  61  without further increasing its lateral width. The inner rib  100  may also increase in transverse thickness at the inner curve of the upper  118  and lower  120  junctions. It is understood that the thickening of the upper  59  and lower  63  horizontal portions and vertical body portion  61  may also be applied by the outer rib  104  similar to the inner rib  100  in a similar manner. 
     Referring to  FIGS. 1 and 5 , a vertically and transversely extending sealing plate  70  may be positioned at an upper end of the vertical body portion  61  and attached to the upper horizontal portion  59 . The sealing plate  70  may be a rectangular piece of metal, such as stainless steel sized to cover a lower front opening of the food holding cabinet  10 . In this respect, the transverse width of the sealing plate  70  generally corresponds to or may be slightly wider than a width between the left and right oven sidewall  16 ,  18  of the cabinet  10  defining the front opening  26 . The height of the sealing plate  70  may correspond with or be slightly greater than the distance between the bottom wall  22  of volume  34  and the sweep gasket  78  of the door  24  so that the sealing plate  70  may interface with the bottom wall  22  on a bottom end and the sweep gasket  78  on an upper end. The sealing plate  70  is secured to the upper horizontal portion  59  of the upward extensions  56 ,  57  but may also or alternatively be secured to the lower horizontal portion  63 . The sealing plate  70  is oriented generally perpendicular to the upper horizontal portion  59  and may abut the inner surface  102  of the vertical body portion  61 . The sealing plate  70  may be welded or otherwise secured to the upward extensions  56 ,  57  for example, by extending the upper horizontal portions  59  through hole openings  114  of the sealing plate  70  having a diameter which corresponds to the diameter of the upper horizontal portions  59  and then welding the upward extensions  56 ,  57  to the sealing plate  70  proximate to the openings  114 . 
     The upward extensions  56 ,  57  may provide a positioning tab  110  extending from the inner surface  102  of the vertical body portion  61  to assist in installing the sealing plate  70  at the desired angle with respect to the vertical body portion  61 , for example, securing the sealing plate  70  parallel to the vertical body portion  61  and perpendicular to the upper horizontal portion  59 . The positioning tab  110  may be a generally rectangular protuberance resembling a plateau having a flat locating surface  111  abutting the sealing plate  70  to provide a desired angle of the sealing plate  70 . The flat locating surface  111  may also include a button  112  corresponding to an opening  116  of the sealing plate  70  for fitting therein to confirm proper alignment of the sealing plate  70  with respect to the vertical body portion  61 . The button  112  may be press fitted into the hole opening  116  of the sealing plate  70  or may be spot welded to secure the sealing plate  70  to the positioning tab  110 . 
     Referring again to  FIG. 1 , the trolley  12  is supported beneath by a roller frame  126  carrying a number of trolley wheels  80  attached to the lateral roller supports  54 ,  55  of the roller frame  126  and lower horizontal portions  63  of the upward extensions  56 ,  57 , respectively, and disposed at the respective corners of the trolley  12 . The trolley wheels  80  may be attached to casters, which provide 360-degree swivel or pivoting of the wheel about a vertical axis perpendicular to the axis of rotation of the wheel. When the trolley  12  is installed within the volume  34 , the roller frame  126  and trolley wheels  80  remain outside of the volume  34  so as to prevent dirt and debris from entering the volume  34 . 
     Referring to  FIGS. 1 and 3 , a horizontally extending space or gap  64  exists between the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55 , respectively, between which the bottom wall  22  of the food holding cabinet  10  may be received. The gap  64  is confined by the vertical limitations provided by the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55  and by the horizontal limitations provided by the sealing plate  70 . The gap  64  is sized to receive a front lateral edge of the bottom wall  22  of the volume  34 . When the trolley  12  is installed within the volume  34 , the gap  64  receives the bottom wall  22  to a depth substantially similar to the depth of the bottom wall  22 . The sealing plate  70  at the front end of the trolley  12  prohibits further entry of the trolley  12  into the volume  34 . 
     When the trolley  12  is installed within the volume  34 , the ladder racks  46 ,  48  and the lateral cantilever shelf beams  52 ,  53  are disposed within the interior of the volume  34 . The horizontal transverse connecting bar  72  and the upward extensions  56 ,  57  remain partially outside the volume  34  but the sealing plate  70  abuts the sweep gasket  78  of the inner surface  27  of the door  24  to allow the door to sealingly close thereover. In this respect, the sweep gasket  78  of the upper portion  76  of the door  24  which extends across a width of the door  24  contacts the sealing plate  70  of the trolley  12 , which also extends across a width of the door  24 , to create a face seal between the door  24  and the sealing plate  70 . When the trolley  12  is installed within the volume  34 , the lateral roller supports  54 ,  55  are located beneath the bottom wall  22  of volume  34 . 
     Referring to  FIG. 3 , in operation, when the shelving of the trolley  12  carries food, the distal end of the ladder racks  46 ,  48  remains substantially horizontal. In this respect, the upward extensions  56 ,  57  increase the stiffness of the lateral cantilever shelf beams  52 ,  53  and lateral roller supports  54 ,  55  so that the sealing plate is isolated from deflection. Moreover, the upper  59  and lower  63  horizontal portions of the upward extensions  56 ,  57  remain substantially horizontal and vertical body portions  61  of the upward extensions  56 ,  57  remain substantially vertical, thus allowing the sealing plate  70  to remain substantially vertical and allowing the sealing plate  70  to face seal with the substantially vertical sweep gasket  78  of the door  24  in a desired manner. The sweep gasket  78  may have an increased width and height to more easily interface with the sealing plate  70 . 
     Referring to  FIGS. 1 and 6 , the food holding cabinet  10  may be optionally installed with a retractable sealing plate  86  to seal the cabinet  10  when the trolley  12  in not installed therein. Left and right guide rails  66  may be positioned beneath the food holding cabinet  10  and attached below the volume  34  to extend horizontally along the length of the left and right oven sidewall  16 ,  18 . The left and right guide rails  66  provide an inwardly extending ledge  84  of the guide rails  66 . A retractable sealing plate  86  is connected to extender bars  90  coupling the sealing plate  86  to a swivel base  82  having wheels  38  that are receivable onto the ledge  84  of the guide rails  66  so as to allow the swivel base  82  and sealing plate  86  to slide from beneath the food holding cabinet  10  to a position in front of the food holding cabinet  10 . 
     Referring still to  FIG. 6 , the swivel base  82  allows for the progressive movement of the retractable sealing plate  86  as the retractable sealing plate  86  is extended from beneath the food holding cabinet  10 , to an extension in front of the food holding cabinet  10 , and finally pivoted upward over the front opening of the volume  34 . As seen in  FIG. 6A , when the retractable sealing plate  86  is in a retracted position, the swivel base  82  and extender bars  90  are stored beneath the food holding cabinet  10  with the sealing plate  86  substantially stowed beneath the food holding cabinet  10  with the exception of, optionally, a lip  88  of the sealing plate  86  extending in front of the cabinet  10  to assist in gripping the plate  86 . As seen in  FIG. 6B , as the plate  86  is pulled outward from beneath the food holding cabinet  10 , the wheels  38  glide along the ledge  84  of the guide rails  66  of the left and right sides of the volume  34  until the swivel base  82  clears the bottom wall  22  of the volume  34 . Referring to  FIG. 6C , when the sealing plate  86  is fully extended, the wheel  38  of the swivel base  82  allows the swivel base to pivot upward to lift the sealing plate  86  upward toward the volume  34  opening. An upper ridge of the guide rails  66  may prevent the wheels  38  from being removed from the ledge  84 . In this position, the extender bars  90  may elevate the sealing plate  86  so that a lower end of the sealing plate  86  contacts the bottom wall  22  and an upper end of the sealing plate  86  extends over the volume opening as seen in  FIG. 1 . Referring to  FIG. 6D , when the door  24  of the food holding cabinet  10  is closed over the volume  34 , the upper end of the sealing plate  86  face seals with the sweep gasket  78  of the door  24  to seal the connection between the bottom wall  22  and the door  24  when the trolley  12  is not installed therein. 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     References to “a controller” and “a processor” should be understood to include one or more microprocessors that can communicate in a stand-alone and/or a distributed environment(s), and can thus be configured to communicate via wired or wireless communications with other processors, where such one or more processor can be configured to operate on one or more processor-controlled devices that can be similar or different devices. Furthermore, references to memory, unless otherwise specified, can include one or more processor-readable and accessible memory elements and/or components that can be internal to the processor-controlled device, external to the processor-controlled device, and can be accessed via a wired or wireless network. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. All of the publications described herein, including patents and non-patent publications, are hereby incorporated herein by reference in their entireties.