Patent Publication Number: US-11390308-B2

Title: Automated dish drop

Description:
BACKGROUND 
     Field of the Invention 
     This invention relates to carts and other systems for handling dishes. 
     Background of the Invention 
     Many restaurants serve patrons on reusable plates, bowls, silverware, and other serving dishes. Although this reduces the environmental impact of single-use plastic products, cleaning the dishes is a labor intensive process. 
     What is needed is an improved approach for handling dishes for use in restaurants and other food-service applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through use of the accompanying drawings, in which: 
         FIG. 1  is an isometric view of a cart in accordance with an embodiment of the present invention; 
         FIG. 2  is an isometric view of a dish cart including an alternative upper frame in accordance with an embodiment of the present invention; 
         FIG. 3  is an isometric view of a dish cart base for use with the upper frame of  FIG. 2  in accordance with an embodiment of the present invention; 
         FIG. 4  is an isometric view of a rack cart in accordance with an embodiment of the present invention; 
         FIG. 5  is an isometric view of an alternative embodiment of a dish cart in accordance with an embodiment of the present invention; 
         FIG. 6  is a partial isometric view of the dish cart of  FIG. 5 ; 
         FIG. 7  is an exploded view of an adjustable upper frame for a dish cart in accordance with an embodiment of the present invention; 
         FIG. 8  is an assembled isometric view of the dish cart of  FIG. 7 ; 
         FIGS. 9A to 9C  are partial isometric views of the dish cart of  FIG. 7 ; 
         FIGS. 10A and 10B  are cross-sectional views of the dish cart of  FIG. 7 ; 
         FIGS. 11A and 11B  are top views showing an example usage of the dish cart of  FIG. 7 ; 
         FIGS. 12A and 12B  are side views showing the example usage of the dish cart of  FIG. 7 ; 
         FIG. 13  is an isometric view of a set of dish drop stations with corresponding dish carts in accordance with an embodiment of the present invention; 
         FIG. 14  is a front isometric view of the dish drop station of  FIG. 13 ; 
         FIG. 15  is a schematic diagram illustrating usage of a dish drop station in accordance with an embodiment of the present invention; 
         FIG. 16  is an isometric view of a set dish drop stations according to an alternative embodiment of the present invention; 
         FIG. 17  is an isometric view of a dish drop station having a lid in accordance with an embodiment of the present invention; 
         FIG. 18  is an isometric view of the dish drop station of  FIG. 18  having the lid open; 
         FIG. 19  is a top view of the dish drop station of  FIG. 18 ; 
         FIG. 20  is a side view of a dish drop station showing various positions of a lift arm in accordance with an embodiment of the present invention; 
         FIGS. 21A and 21B  are side views of a dish drop station and dish cart showing a manner of usage thereof in accordance with an embodiment of the present invention; 
         FIGS. 22 and 23  are front views of a lift mechanism for a dish drop station in accordance with an embodiment of the present invention; 
         FIG. 24  is an isometric view of a cart lock mechanism of a dish drop station in accordance with an embodiment of the present invention; 
         FIG. 25  is an isometric view of the cart lock mechanism of  FIG. 24  showing the cart lock mechanism in an open state in accordance with an embodiment of the present invention; 
         FIG. 26  is an isometric view of the cart lock mechanism of  FIG. 24  showing the cart lock mechanism in a locked state in accordance with an embodiment of the present invention; 
         FIGS. 27A to 27D  are side views showing a method of operation of the cart lock mechanism of  FIG. 24  in accordance with an embodiment of the present invention; 
         FIGS. 28A to 28C  are isometric views illustrating operation of an alternative embodiment of a cart lock mechanism in accordance with an embodiment of the present invention; 
         FIG. 29  is a side view illustrating an inductive sensor and magnetic detent in accordance with an embodiment of the present invention; and 
         FIG. 30  is a schematic block diagram of a control system for a dish drop station in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a cart  10  may be understood with respect to a longitudinal direction  12   a , vertical direction  12   b , and horizontal direction  12   c  that are all mutually perpendicular to each other. 
     The cart  10  includes a handle  14  and a base  16 . The handle  14  includes vertical bars  18  that extend upwardly from the base  16  in the vertical direction  12   b , though they may also be angled such that they extend outwardly from a point of attachment to the base in one or both of the longitudinal and horizontal directions  12   a ,  12   c . A horizontal bar  20  secures to tops of the vertical bars  18  and is preferably at a convenient height to be grasped and pushed by a user. In the illustrated embodiment, the bars  18 ,  20  are one monolithic tube bent into the illustrated shape. 
     The base  16  may include a frame composed of frame members  22   a ,  22   b ,  22   c ,  22   d  such that each frame member has the long dimension thereof substantially (within 5 degrees) parallel to one side of a quadrilateral shape, such as a square or rectangle. For example, frame members  22   a  and  22   c  are offset from one another along the longitudinal direction  12   a  and have the long dimension thereof oriented substantially parallel to the horizontal direction  12   c . Likewise, frame members  22   b  and  22   d  are offset from one another along the horizontal direction  12   c  and have the long dimension thereof oriented substantially parallel to the longitudinal direction  12   a.    
     As shown, the frame member  22   a  at a front of the base  16  is bent or cutaway at a middle portion thereof such that an upper surface of a middle portion of frame member  22   a  is below upper surfaces of the other frame members  22   a ,  22   b ,  22   c . As discussed below, this bent or cutaway middle portion enables insertion of a lift arm for supporting dishes or racks stacked onto the cart  10  according to the approach described herein. 
     In the illustrated embodiment, corner piece  24   a  is secured to frame member  22   a  and  22   b , corner piece  24   b  is secured to frame members  22   b  and  22   c , corner piece  24   c  is secured to frame members  22   c  and  22   d , and corner piece  34   d  is secured to frame members  22   d  and  22   a . In some embodiments, the corner pieces  24   a - 24   d  for part of the frame such that the frame members  22   a - 22   d  are secured to one another exclusively due to their securement to the corner pieces  24   a - 24   d . The corner pieces  24   a - 24   d  define upper surfaces that are substantially parallel to the longitudinal and horizontal directions  12   a ,  12   c.    
     The corner pieces  24   a - 24   d  may define structures for securing a top plate or other platform to the base  16  for supporting stacked items such as dishes, dish racks, or other stackable items. In the illustrated embodiment, the structures are posts  26  that may insert within corresponding openings in a platform placed over the base  16 . The posts  26  may include openings for receiving fasteners for securing the platform to the base  16 . In other embodiments, the corner pieces  24   a - 24   d  include openings for receiving fasteners and the posts  26  are omitted. 
     In the illustrated embodiment, the base  16  further includes a lower frame  28  secured to the frame members  22   a - 22   d . The lower frame  28  may define rails configured to removably support a drip pan positioned under the frame formed by frame members  22   a - 22   d.    
     Wheels  30   a - 30   d  may secure to the corner pieces  24   c - 24   d . Fourth wheel (see, e.g., wheel  30   a  in  FIG. 6 ) secures to corner piece  24   a  in a like manner. In the illustrated embodiment, the wheels  30  may be caster wheels that are able to swivel about an axis substantially parallel to the vertical direction  12   b  relative to the structure to which they are mounted in addition to rolling along a horizontal support surface. In the illustrated embodiment, wheels  30   d  and the wheel secured to corner piece  24   a  (see  30   a  in  FIG. 6 ) are fixed such that their axes of rotation are substantially parallel to the horizontal direction  12   c . In contrast, wheels  30   b  and  30   c  are swivel-mounted to the corner pieces  24   b ,  24   c . In the illustrated embodiment, wheels  30   b ,  30   c  further include locks  32  that may be selectively engaged by a user to hinder rotation of the wheels  30   b ,  30   c . In other embodiments, locks  32  are additionally or alternatively coupled to the wheels  30   a ,  30   d . In still other embodiments, wheels  30   a ,  30   d  include locks  32  and have a fixed orientation whereas the wheels  30   b ,  30   c  are free to swivel and lack locks  32   
     In some embodiments, bumpers  34  made of plastic, rubber, or other resilient material are mounted to the corner pieces  24   a - 24   d , e.g. the outward facing two sides of the corner pieces  24   a - 24   d  in order to reduce damage caused by impacts. 
     Referring to  FIGS. 2 and 3 , in some embodiments a cart  10  may be augmented with additional structures to function as a dish cart. In  FIGS. 2 and 3 , the dish cart  10  includes a handle  14  having the illustrated configuration, including four vertical posts  40   a - 40   d  that extend upwardly from the base  16  substantially parallel to the vertical direction  12   b . The posts  40   a - 40   d  may be arranged in a quadrilateral shape, i.e. such that central axes of the posts  40   a - 40   d  are positioned on corners of a quadrilateral shape such as a square or rectangle. In some embodiments, the posts  40   a - 40   d  are at corners of a parallelogram to facilitate proper alignment of the top and bottom. In some embodiments, only three posts are used, rather than 4. 
     The handle  14  may further include one or more bars  42   a - 42   c  that extend substantially parallel to either the longitudinal direction  12   a  or the horizontal direction  12   c . For example, in the illustrated embodiment, bar  42   a  and is secured to vertical posts  40   a  and  40   b  and has the long dimension thereof substantially parallel to the longitudinal direction  12   a . Likewise, bar  42   c  has its long dimension substantially parallel to the longitudinal direction is secured to vertical posts  40   c  and  40   d . The bar  42   b  is connected to the bars  42   a  and  42   c  and provides a handle at a convenient height for pushing the cart  10 . In the illustrated embodiment the posts  40   a - 40   d  and bars  42   a - 42   c  are all embodied as hollow tubes made of a sufficiently strong material such as steel or aluminum. In the illustrated embodiment, bars  42   a - 42   c  and vertical posts  40   a ,  40   d  are made of a one tube bent in the illustrated shape. 
     In the embodiment of  FIGS. 2 and 3 , the handle  14  secures to the base  16  by means of tubes  44   a - 44   d  that fit over corresponding posts  46   a - 46   d  secured to the base  16 . In some embodiments, no further fastening is used, i.e. the weight of the handle  14  and the length of the tubes  44   a - 44   d  and posts  46   a - 46   d  is relied upon to prevent accidental removal. Posts  46   a - 46   d  may secure to the base  16  using the posts  26  or in place of the posts  46   a - 46   d.    
     In the embodiment of  FIGS. 2 and 3 , rails  48   a - 48   d  secure to some or all of the posts  40   a - 40   d  and extend radially inwardly to a common central point such that there is a radial extent  50  of each rail  48   a - 48   d . The radial extent  50  of the rails  48   a - 48   d  is chosen to define the diameter of items that will fit stacked on the base among the rails  48   a - 48   d . For example, a cart  10  may come with multiple sets of rails, each set including four rails  48   a - 48   d  that have extents  50  defining a diameter when secured to the posts  40   a - 40   d , the diameter defined by each set being different. In this manner, by installing different sets of rails, the cart may be configured to stack different sizes of dishes, e.g., dinner plates, salad plates, dessert plates, bowls, etc. 
     In the illustrated embodiment, each rail  48   a - 48   d  mounts to its corresponding post  40   a - 40   d  by means of fasteners  52 , such as screws, bolts, or other type of fastening means. The rails  48   a - 48   d  preferably define countersunk apertures for receiving such fasteners  52  in such that heads of screws or bolts do not contact stacked items on the cart  10 . 
     In the illustrated embodiment, the posts  40   a - 40   d  and tubes  44   a - 44   d  are fastened to a plate  54 , such as by means of welding, screws, bolts, or other fastening means. For example, the plate  54  may be made of the same material (steel, aluminum) as the posts  40   a - 40   d  and the tubes  44   a - 44   d . The plate  54  may define apertures aligned with channels defined by the tubes  44   a - 44   d  such that the posts  46   a - 46   d  may pass through the plate  54  to insert within the tubes  44   a - 44   d.    
     In some embodiments, a pad  56  secures to the plate  54  to provide a softer support surface for dishes stacked on the base  16 . For example, the pad  56  may be embodied as a circular plastic piece fastened to the plate  54  by means of screw, adhesive, clips, or some other fastening means. As is apparent in  FIG. 2 , the pad  56  defines various openings  58 . The plate  56  defines corresponding openings aligned with the openings  58 . The openings  58  may be lobe openings  58  having a size configured to allow a multi-lobed lift paddle to pass through the pad  56  and plate  54 , as will be discussed in greater detail below. The pad  56  may further define a slot  60  aligned with a corresponding slot  62  in the plate  54  for permitting through passage of a lift arm secured to the lift paddle. As is apparent in  FIG. 2 , the slot  60  extends completely to the edge of the pad  56  and the slot  62  in the plate  54  extends completely to the front edge of the plate  54 . The slot  62  extends to the edge of the plate  54  and may be positioned over the frame member  22   a  that includes the bent or cutaway portion for receiving the lift paddle and lift arm. In particular, a gap may be defined between the bottom surface of the plate  54  and the bent or cutaway portion of the frame member  22   a  for receiving the lift paddle and lift arm. 
     In some embodiments, the pad  56  further defines grooves  64  extending radially inward to the openings  58  and/or slot  60 . In this manner, material and fluid from dishes stacked in the cart is guided to the openings  58  and/or slot  60 . 
     Referring specifically to  FIG. 3 , in some embodiments, the base  16  includes a lower plate  66  mounted to the frame members  22   a - 22   d  and/or corner pieces  24   a - 24   d  or used in place of the frame members  22   a - 22   d  and corner pieces  24   a - 24   d . The posts  46   a - 46   d  may be welded or otherwise fastened to the lower plate  66 . As is apparent, an inner portion of the lower plate  66  defines an indentation or depression  68  that extends to the front edge of the base  16  over the frame member  22   a  such that the lift paddle and lift arm may insert between the indentation  68  and plate  54  and subsequently be lifted up through the slots  60 ,  62  and lobe openings  58  as described in greater detail below. The lift paddle and lift arm may likewise pass down through the slots  60 ,  62  and lobe openings  58  and the lift paddle and the lift arm may be withdrawn from the gap between the plate  54  and indentation  68  as is also described in greater detail below. 
     Note that in the illustrated embodiment, the base  16  further defines apertures  72  in frame member  22   c  for receiving a handle  14  having the form shown in  FIG. 1 . In other embodiments, such apertures  72  may be omitted. 
       FIG. 4  illustrates a rack cart  80  that may be modified relative to the cart  10  of  FIG. 1  to function as a rack cart as described below. In other instances, the cart  10  of  FIG. 1  may be used as a rack cart without further modification. In the embodiment of  FIG. 4 , a plate  82  may be mounted to the frame members  22   a - 22   d  and/or corner pieces  24   a - 24   c . The plate  82  includes lobe openings  84  sized to permit passage therethrough of the lobes of a lift paddle. A slot  86  likewise extends from the front edge of the plate over the frame member  22   a  and connects to the lobe openings  84  such that the lift paddle and lift arm may pass through the lobe openings  84  and slot  86 . 
     In the illustrated embodiment, corner projections  88   a - 88   d  are located at the corners of the plate  82 , which is quadrilateral in shape but for rounding at the corners, with sides of the quadrilateral shape being parallel to one of the longitudinal direction  12   a  and the horizontal direction  12   c . Each corner projections  88   a - 88   d  extend from one rounded corner of the quadrilateral shape and partially along two adjoining sides of the quadrilateral shape and likewise extend upwardly along the vertical direction  12   b . The corner projections  88   a - 88   d  are sized to fit within corresponding recesses in a dish rack according to any shape known in the art such that the rack cart  80  is enabled to securely stack dish racks, glass racks, trays, or other types of racks known in the food service industry. 
       FIGS. 5 and 6  illustrate an alternative embodiment of a dish cart  10 . In particular, in the illustrated embodiment, the top plate  54  is fastened to the corner pieces  24   a - 24   d  by means of bolts  90 , such as by securing to the posts  26  on the corner pieces  24   a - 24   d  or openings for receiving the bolts  90  formed on another portion of the base  16 . 
       FIG. 5  further illustrates an alternative approach for securing the rails  48   a - 48   d  to the posts  40   a - 40   d . In particular, each post may have one or more flanges  92  secured thereto and extending radially inwardly into the cart  10 . The rails  48   a - 48   d  may then secure to these flanges  92  by means of bolts, screws, or some other fastening means. As for the embodiment of  FIGS. 2 and 3 , different sets of rails  48   a - 48   d  may secure to the flanges  92  in order to adjust the size of dishes that will fit among the rails  48   a - 48   d.    
     In the embodiment of  FIG. 5 , a screen  94 , which may be a solid or perforated piece of material, such as metal or plastic, secures to the posts  40   b ,  40   c  such that the screen is secured to the cart  10  opposite the front edge of the cart  10 . Accordingly, the screen  94  may block scattering of material out of the back of the cart  10  during use. The screen may be detachable and may be one of multiple screens having multiple colors such that the color of the screen attached to a cart indicates the contents of the cart, e.g., size of dishes loaded or able to be loaded into cart or a state of the dishes in the cart (clean or dirty) 
     In the embodiment of  FIG. 5 , metal lugs  96  secure to one or both of the posts  40   a ,  40   d  such that the metal lugs extend forwardly from the posts  40   a - 40   d  outwardly from the front of the cart  10  and substantially parallel to the longitudinal direction  12   a . The metal lugs  96  may further have a face substantially parallel to the vertical and horizontal directions  12   b ,  12   c . As discussed below with respect to  FIG. 29 , the metal lugs may facilitate securement of the cart by a magnetic detent. 
     Referring specifically to  FIG. 6 , the lower plate  66  may have various configurations. In the illustrated embodiment, the indentation  68  or depression in the lower plate  66  defines various slits  98  to facilitate drainage, such as slits oriented substantially parallel to the horizontal direction  12   c.    
     Note further that in some embodiments where the handle  14 , such as the posts  40   a - 40   d  and horizontal bars  42   a - 42   c  are secured (e.g., welded) to the top plate  54 , the top plate  54  may function as the frame for the base  16  such that frame members  22   a - 22   d  are omitted and the corner pieces  24   a - 24   d  with the wheels  30   a - 30   d  secure only to the plate  54 . Alternatively or additionally, the lower plate  66  may secure to the corner pieces  24   a - 24   d , such as interposed between the upper plate  54  and the corner pieces  24   a - 24   d.    
     As for other embodiments, the upper plate  54  of  FIG. 6  includes lobe openings  58  for receiving a lift paddle and a slot  62  extending completely to the front edge of the top plate  54 . Various configurations for a lift paddle are possible, such as a three lobe design or a four lobe design. In the embodiment of  FIG. 6 , a four lobe design is used that has four-fold symmetry, each lobe being rotated 90 degrees relative to an adjacent lobe. Accordingly, only three lobe openings  58  are used with the fourth lobe being aligned with the slot  62  and passing therethrough along with the lift arm to which the lift paddle is secured. 
     In other embodiments, such as shown in  FIG. 4 , the lift paddle has three lobes with three-fold symmetry such that each arm is rotated 120 degrees relative to the other lobes. As shown in  FIG. 4 , one lobe opening  84  is oriented parallel to the slot  86 . The three-lobe design may also be used for the carts  10  of  FIGS. 1-3, 5, and 6  as well. 
     The embodiment of  FIGS. 5 and 6  and any of the embodiments of  FIGS. 1-4  may further include structures for locking the cart  10  into a dish drop station as discussed in greater detail below. In the illustrated embodiment, the upper plate  54  includes apertures  100  for receiving a cart lock, the aperture  100  being positioned over the gap defined by the upper plate  54  and the lower plate  66  and being located closer to the front edge  100  than any other edge of the plate  54 . Corresponding apertures  100  may be positioned at the front edge of the base of any of the embodiments of  FIGS. 1-4  as well. In some embodiments, only a single aperture  100  is used. 
     In some embodiments, the plate  504  includes an indentation  102 , such as for providing clearance for a drive mechanism of a lift arm according to the embodiments of dish drop stations described below. 
     Dish carts according to the embodiments disclosed herein may further include structures such as hooks and receptacles for hooks that enable dish carts to be hooked to one another to facilitate transportation by a single person as a group. 
     Referring to  FIG. 7 , a cart  10  may be embodied as a dish cart including an adjustment assembly  110 . For example, the adjustment assembly  110  may be used to modify the dish cart  10  to stack dishes of different sizes. Accordingly, the adjustment assembly  110  may take the place of differently sized sets of rails  48   a - 48   d . The adjustment assembly  110  may be used to adapt cart  10  such as that shown in  FIG. 1  that lacks the vertical posts  40   a - 40   d . Alternatively, the vertical posts  40   a - 40   d  of a cart  10  as shown in  FIGS. 2-3 and 5-6  may provide room for the adjustment assembly  110 . 
     The adjustment assembly  110  may include a plurality of vanes  112   a - 112   c  that are rotatable about axes substantially parallel to the vertical direction  12   b . In this manner, the area within the vanes  112   a - 112   c  that is not obstructed by the vanes  112   a - 112   c  may be varied in order to accommodate dishes of different sizes. 
     In the illustrated embodiment, each vane  112   a - 112   c  may include a first rod  114  that is rotatably pinned to the base  16  and a second rod  116  that is coupled to the other rods  116  such that rotation of one vane  112   a - 112   c  about its rod  114  will cause the other rods  112   a - 112   c  to rotate about their corresponding rods  114 . 
     The vanes  112   a - 112   c  may further include a third rod  118  at an inner edge of the vane  112   a - 112   c  in order to provide rigidity to the vanes  112   a - 112   c . In the illustrated embodiment, the vanes  112   a - 112   c  each include a first sleeve  120  receiving the first rod  114 , a second sleeve  122  receiving the second rod  116 , and a third sleeve  124  receiving the third rod  118 . 
     The vanes  112   a - 112   c  may further include a web  126  extending between the first sleeve  120  and the second sleeve  122  and a web  128  extending between the first sleeve  120  and the third sleeve  124 . As is apparent in  FIG. 7 , the sleeves  120 - 124  and the webs  126 ,  128  may be monolithically formed with one another such as by co-molding or extrusion as a single member. As is also apparent in  FIG. 7 , the sleeves  120 - 124  and the webs  126 ,  128  have a substantially (within 2 mm) constant cross section along the vertical direction  12   b  in the illustrated embodiment. 
     In use, the web  128  extends inwardly with the amount by which it extends inwardly varying as the vanes  112   a - 112   c  are rotated. The presence of the third rod  118  resists bending of the inner edge of the web  128 . As is apparent, the web  128  is curved such that a concave inner surface of the web  128  faces toward a center of the base when the web  128  is pivoted outwardly to accommodate large dishes, the web  128  will not interfere with dishes stacked among the vanes  112   a - 112   c . In some embodiments, the web  128  does not contact dishes at any of its possible orientations. Instead, dishes are only contacted by the sleeve  124  in which the rod  118  is inserted. 
     In the illustrated embodiment, the first rods  114  insert within apertures  130  formed in the top plate  54 . For example, the apertures  130  may be distributed at 120 degree intervals about a point on the plate  54  such that one aperture  130  is substantially (within 1 cm) aligned with a center of the slot  62  along the horizontal direction  12   c  but positioned closer to the rear edge than to the front edge of the base  16  such the slot  62  does not intersect this aperture  130 . 
     As is apparent in  FIG. 7  each rod  114  protrude both above and below the webs  126 ,  128  of the vane  112   a - 112   c  in which it is located. In some embodiments, the portions of the rod  114  protruding above and below the webs  126 ,  128  are a single rod whereas in other embodiments they are separate rods. 
     In the illustrated embodiment, the second rod  116  protrudes only below the webs  126 ,  128  and may extend along the entire extent of the second sleeve  122  or only partially through the sleeve  122 . 
     The third rod  118  may either not protrude from the third sleeve  124 , protrude both above and below the third sleeve  124 , or protrude only one of above and below the third sleeve  124 . In the illustrated embodiments, portions of the third rod  118  that protrude above or below the third sleeve  124  are covered with caps made of a material that is softer than the metal (e.g., steel) of which the rods  114 - 118  may be formed. For example, the caps may be made of a resilient polymer or rubber to avoid damaging dishes placed among the vanes  112   a - 112   c . The caps may likewise prevent insertion of the third rod  118  into the apertures intended to receive the first or third rod. 
     Note further that the first rod  114  extends below the first sleeve  120  a greater extent than second third  116  extends below the second sleeve  122  in the illustrated embodiment. In this manner, when the first rod  114  of a vane  112   a - 112   c  is inserted in an aperture  130 , the downward protruding portion of the second rod  116  will remain above the bottom plate  54  and the pad  56  such that it does not hinder pivoting of the vane  112   a - 112   c.    
     Referring to  FIG. 8 , while still referring to  FIG. 7 , the vanes  112   a - 112   b  may engage partial circular members  132 ,  134 . Each of the partial circular members is a partial ring with the gap in the ring facing the front edge of the base  16 . In this manner, passage of the lift arm through the gap is permitted. 
     In the illustrated embodiment, the upper partial circular member  132  is pivotally mounted to the handle  14 , such as to a horizontal rod  136  extending between the vertical bars  18  of the handle  14 . This may facilitate disassembly of the adjustment assembly for cleaning. 
     The lower partial circular member  134  rests on the top plate  54  and may be positioned outside of the outer perimeter of the pad  56 . The upper partial circular member  132  may include apertures  138  and the lower partial circular member  134  may include apertures  140 . The apertures  140  may be positioned aligned with one another and with the apertures  130  in the plate  54  such that the first rod  114  of each vane  112   a - 112   c  inserts within one of the apertures  130 , one of the apertures  138 , and one of the apertures  140  when positioned substantially parallel to the vertical direction  12   b.    
     As is apparent in  FIG. 8 , the apertures  140  are slots such that the first rod  114  is permitted to both slide and rotate within the slots. In some embodiments, the apertures  140  is omitted and the inner diameter of the lower partial circular member  134  is made sufficiently large that it does not interfere with insertion of the first rods  114  into the apertures  130 . In contrast, the apertures  138  in the upper partial circular member  132  may permit rotation but not significant (e.g., larger than 2 mm) of translational movement. 
     The lower partial circular member  134  may further define apertures  142  that receive the second rods  116  of the vanes  112   a - 112   c . In the illustrated embodiment, the apertures  142  are notches that extend partially radialy inwardly across the radial extent of the lower partial circular member  134 , e.g. inwardly from an outer circumference of the lower partial circular member  134  partially across the lower partial circular member  134  toward a center of curvature defined by the lower partial circular member. 
     The apertures  142  permit rotation of the second rods  116  but do not permit significant translational movement. In this manner, when the lower partial circular member  134  is rotated, all of the second rods  116  rotate with it about the first rods  116  in the apertures  130  thereby resulting in simultaneous movement of the vanes  112   a - 112   c  subject to flexing and any non-significant translational movement relative to the lower partial circular member  134  coupling the vanes  112   a - 112   c  to one another. 
     In some embodiments, the upper partial circular member  132  may define two notches  144  (only one being visible in  FIGS. 7 and 8 ) protruding partially radially outwardly from the inner diameter of the member  132  and partially across the radial extent of the member  132 . The notches  144  are positioned to receive the protruding ends of the third rods  118  when the vanes  112   a - 112   b  are pivoted such that two of the third rods  118  contact the member  132 . In this manner, the size of dishes that may be positioned among the vanes  112   a - 112   c  is slightly increased. Note that the third rod  118  of vane  112   c  may extend into the gap in the upper partial circular member  132  such that a third notch  144  is not needed to achieve this benefit. 
       FIG. 7  further shows a drip pan  146 . The drip pan  146  may mount to the base, such as below the lower plate  66  in order to catch material that drips down through the plates  54 ,  66 . The drip pan  146  may mount to the lower plate  66  by means of rails supporting edges of the drip pan  146 , clips, or other removable fastening means. 
       FIGS. 9A to 9C  illustrate the process of adjusting the adjustment assembly  110 . In the illustrated embodiment, the lower partial circular member  134  includes a plurality of edge notches  148 . In the illustrated embodiment, the notches  148  are formed on the top and outer edge of the lower partial circular member  134  and include two sets of notches  148 . 
     The notches  148  may engage one or more lock arms  150  that are pivotally mounted to the base  16 , such as to the lower plate  54 , frame member  22   c , or other component of the base  16 . The lock arms  150  may be spring loaded such that they are biased into engagement with the notches  148 . A step arm  152  may be secured to the lock arms  150  such that pressing downwardly on the step arm  152  will result in the lock arms  150  pivoting out of engagement with the notches  148 . 
     In use, a user presses (e.g., steps) on the step arm  152  to disengage the lock arms  150  with the vanes  112   a - 112   c  in a first orientation as shown in  FIG. 9A . The user then rotates the vanes  112   a - 112   c  to a different orientation as shown in  FIG. 9B . The user then releases the step arm  152 , which permits the lock arms  150  to engage with a different pair of notches  148  corresponding to the current position of the vanes  112   a - 112   c  as shown in  FIG. 9C . In the illustrated embodiment, each set of notches  148 —includes three notches  148  such that the vanes  112   a - 112   c  may be locked in three different positions. 
       FIGS. 10A and 10B  provide further illustration of the adjustment of the vanes  112   a - 112   c .  FIG. 10A  illustrates the locking arms  150  in a first pair of notches  148  and the third rods  118  positioned as shown such that a first diameter D 1  of dishes will fit among the vanes  112   a - 112   c .  FIG. 10B  illustrates the locking arms  150  in a second set of notches  148  due to rotation of the lower partial circular member  134  and the third rods  118  positioned further inward as a result of the adjustment such that only dishes smaller than a second diameter D 2 , that is smaller than the first diameter D 1 , will fit among the vanes  112   a - 112   c.    
     In particular, the innermost points of the vanes  112   a - 112   c  may be substantially equidistant (e.g., equidistance being within 2 cm from being equal distances) from a first point, e.g. a center of the plate  56  due to their coupling by the partial circular members  132 ,  134 . This equal distance may then be varied by rotating the vanes  112   a - 112   c  using the lower partial circular member  134 . Note further that in some embodiments, the vanes  112   a - 112   c  are limited such that they cannot obstruct the first point, e.g., the center of the plate  56 . This may be achieved by sizing of the openings  140  that limit how much the lower partial circular member  134  may rotate. In some embodiments, the vanes  112   a - 112   c  are limited such that they cannot obstruct movement of the lift arm and lift paddle along the length of the vanes  112   a - 112   c.    
       FIGS. 11A and 11B  and corresponding  FIGS. 12A and 12B  illustrate an example use of the adjustment assembly  110 . In the illustrated embodiment, an interior  160  of a dish drop, such as a dish drop described according to the embodiments below, includes a block  162 , flange, or other structure that is positioned to engage the lower partial circular member  134 . A hook  164  or other structure is positioned to urge the step arm  152  downward when the base  16  is urged into the interior  160 . 
     In particular, as shown in  FIGS. 11A and 12A , the base  16  may be urged into the interior  160 . The block  162  then contacts the lower partial circular member  134  as the hook  164  engages the step arm  164  and urges it downwardly, disengaging the lock arms  150  from the notches  148  and permitting the block  162  to rotate the lower partial circular member  134 , as shown in  FIGS. 11B and 12B . The block  162  then maintains the lower partial circular member  134  in this orientation. Removal of the base  16  from the interior  16  may be resisted by a cart lock engaging the aperture  100 , such as a cart lock according to any of the embodiments described below with respect to  FIGS. 24-28C . 
       FIGS. 11A-12B  illustrate just one example of how the adjustment assembly  110  may be adjusted. In other embodiments, a knob or handle is secured to one of the rods  114 ,  116 ,  118  of one of the vanes and can be rotated by a user to adjust the adjustment assembly  110 . The knob may be removable to permit disassembly. For example, the knob may removably secure to a portion of a rod  114 ,  116 ,  118  protruding above the upper partial circular member  132 . In some embodiments, there is one and only one knob secured to one of the rods  114 ,  116 ,  118 . 
     Referring to  FIG. 13 , a dish drop  170  may include one or more dish drop stations  172   a - 172   d  that are each sized and configured to receive a cart  10  according to any of the foregoing embodiments. In the illustrated configuration, the dish carts  10  are according to the embodiment of  FIGS. 7 through 10B . 
     The dish drop  170  may include a single top wall  174  for all of the stations  172   a - 172   d  or separate top walls  174  for each station  172   a - 172   d . The top wall  714  over each station  172   a - 172   d  includes an opening  176  for receiving dishes that stack within dish carts  10  positioned within the stations  172   a - 172   d . In some embodiments, each station  172   a - 172   d  includes a collar  178  that protrudes upwardly from the top wall  174  and partially or completely surrounds the opening  176  of the station  172   a - 172   d . The collar  178  may house electronics such as an antenna for transmitting a state of the station  172   a - 172   d , sensors for detecting a height of items stacked in the station  172   a - 172   d , or other components. Accordingly, the collar  178  may be formed of plastic or other polymer that permits transmitted signals to pass therethrough. 
     In the illustrated embodiment, each station  172   a - 172   d  includes a button  180  placed on the top wall  174  for each station  172   a - 172   d  or positioned elsewhere, such as an inner wall  192  (facing away from the viewer in  FIG. 13 ). The button  180  may be a mechanical button, touch screen interface, switch, or any other type of structure able to receive user interaction. As discussed below, the button  180  may instruct a controller to lower a lift arm and lift paddle to an unlock position such that cart  10  at the station  172   a - 172   d  may be removed. 
       FIG. 14  illustrates an individual dish drop station  172   a - 172   d . As is apparent, the station  172   a - 172   d  may include side walls  182  or a side frame  182  having guides  184  mounted thereto. The guides  184  facilitate insertion of the cart  10  into the station  172   a - 172   d . At an entrance of the dish drop station  172   a - 172   d , the guides  184  may be flared, such as by means of a bevel  186  or chamfer that urges the cart  10  into alignment with the guides  184  in cases where it is slightly misaligned as shown in  FIG. 15 . 
       FIG. 14  further shows the lift arm  188  and lift paddle  190  that operate in conjunction with features of the cart  10  intended for cooperation with the lift arm  188  and lift paddle  190  as described above. The lift arm  188  protrudes from an inner wall  192  of the station  172   a - 172   d  and moves along the inner wall  192  substantially parallel the vertical direction  12   b . The inner wall  192  may define a slit  194  substantially parallel to the vertical direction  12   b  along which the arm  188  moves and through which the arm  188  protrudes. The edges of the slit  194  may be lined with a flexible material such that the flexible material substantially completely (e.g., 90 percent) covers the slit  194  but deforms to permit movement of the arm  188  as it passes along the flexible material. 
     In the illustrated embodiment, the lift paddle  190  has three lobes  196 . However, a lift paddle  190  with four lobes may be used with a cart  10  configured to cooperate therewith as described above. 
       FIG. 14  further illustrates a cart lock  198  that may engage the aperture  100  in the plate  54  of a dish cart  10  according to the embodiments disclosed above. As noted above, there may be two apertures  100  in some embodiments of the dish cart  10 . Accordingly, some embodiments of the stations  172   a - 172   d  may further include two cart locks  198 . Functioning of the cart locks  198  and different embodiments thereof are described in greater detail below. 
     In the illustrated embodiment, the collar  178  includes stack height sensors  200   a ,  200   b . In other embodiments, these sensors  200   a ,  200   b  may be incorporated into the opening  176 . The stack height sensors  200   a ,  200   b  may be offset from one another in the vertical direction  12   b . For example, stack height sensor  200   a  may be an upper height sensor and sensor  200   b  may be a lower height sensor that is positioned slightly below sensor  200   a  in the vertical direction  12   b  (e.g., on the order of 3 to 15 mm or 0.5 to 2 times a thickness of a dish stacked using the station  172   a - 172   b ). 
     In operation, a controller drives an actuator coupled to the lift arm  188  according to outputs of the sensors  200   a ,  200   b . For example: 
     (A) If sensor  200   b  is obstructed and sensor  200   a  is not, do nothing; 
     (B) If both sensors  200   a ,  200   b  are obstructed, lower the lift arm  188  until sensor  200   a  is not obstructed but sensor  200   b  is obstructed; and 
     (C) If both sensors  200   a ,  200   b  are not obstructed, raise the lift arm  188  until sensor  200   a  is not obstructed but sensor  200   b  is obstructed. 
     Case (B) occurs when items are being added to a dish cart  10  at the station  172   a - 172   d , which may occur when collecting dirty dishes or loading a dish cart  10  with clean dishes. For example, a dish drop station  172   a - 172   d  may be placed next to a dish washing machine for loading of clean dishes from the dish washing machine into carts  10 . 
     Case (C) occurs when items are being removed from a dish cart  10  at the station, which may occur when removing dirty dishes for cleaning or when removing clean dishes for serving food on them. For example, a dish drop station  172   a - 172   d  may be placed next to a conveyor belt such that a worker may remove dishes from the dish drop station  172   a - 172   d  and place them on the conveyor belt for subsequent processing such as rinsing and loading into dish racks. 
     In another example, the cart  10  may be substituted with a rack cart  80 . Accordingly, a rack cart station may have the structures of a dish drop station  172   a - 172   d  sized to receive dish racks and the top plate  174  and collar  178  may be omitted such that racks may be placed on a rack cart. However, stack height sensors  200   a ,  200   b  may be retained, such as mounted to the side walls  182  or inner wall  194 . Accordingly, in case C, racks may be removed from the rack cart station for filling with dishes while the lift arm  188  is raised such that the lower stack height sensor  200   b  becomes obstructed and the upper stack height sensor  200   a  becomes/stays unobstructed. For example, a rack cart station and a dish drop station  172   a - 172   d  may be used simultaneously according to case C: dishes are removed from the dish drop station  172   a - 172   d , rinsed, and loaded into dish racks. As dish racks are filled, new dish racks are retrieved from the rack cart station. Loaded dish racks may then be loaded into a dish washer. Loaded dish racks may be placed on a conveyor belt feeding through the dish washer. 
     The sensors  200   a ,  200   b  may be embodied as break beam sensors, optical (e.g., camera) sensors, or any other sensor for detecting presence or absence of an item within a region around the sensor. The sensors  200   a ,  200   b  may further be embodied as distance sensors that can sense a distance to a dish positioned in front of the sensors  200   a ,  200   b . In this manner, the sensors  200   a ,  200   b  can detect both whether an object is detecting it but also whether it is in fact a dish. For example, an appropriately sized dish would have an edge closer to the sensor  200   a  than another object, such as flatware or other object. A controller may therefore detect non-dishes or dishes that are too small and rejection them, e.g. refuse to lower the list arm  188  when a non-dish or a dish that is too small as determined according to the output of the distance sensors  200   a - 200   b  is detected. 
       FIG. 16  illustrates alternative embodiments for some of the features of a dish drop  170 . In the illustrated embodiment, the sidewalls  182  of each dish drop station  172   a - 172   d  include two pairs of guides  184  that are offset from one another along the vertical direction to facilitate insertion of carts into the dish drop stations  172   a - 172   d . The lift paddle  190  may have the four-lobe design as discussed above. However, the three-lobe design may also be used. 
     The dish drop stations  172   a - 172   d  may each include a front housing  208  positioned in front of the inner wall  192 , such that the inner wall  192  is positioned between the side walls  182  and the front housing  208 . The front housing  208  may house a drive motor for driving the lift arm  188  and electronic circuits forming the controller for controlling operation of the dish drop station  172   a - 172   d . The front housing  208 , and possibly the sidewalls  182 , of adjacent dish drop stations  172   a - 172   d  may be fastene, e.g. bolted, to one another. Sealant or seals may be placed between the front housings  208  of adjacent dish drop stations  172   a - 172   d  to prevent entry of contaminants into the front housings  208 . 
     In some embodiments, an emergency stop button  210  is mounted to a side of the front housing  208  of one of the drop stations  172   a - 172   d , e.g. one of the drop stations on the ends of the series of drop stations  172   a - 172   d , the rightmost dish drop station  172   d  in the illustrated embodiment. A restart button  212  may also be mounted to the side of the front housing  208  of one of the drop stations  172   a ,  172   d  on the ends. The restart button  212  may be coupled to the controller and, when pressed, may instruct the controller to restart operation of the drop stations  172   a - 172   d  following pressing of the emergency stop button  210 . In the illustrated example, this is the same station  172   d  to which the emergency stop button  210  is mounted. 
     One or more wires  214  may couple the emergency stop button  210  to the controllers of the dish drop stations  172   a - 172   d  for invoking an emergency stop of all of the dish drop stations  172   a - 172   d . Likewise, one or more wires  216  may couple the reset button  212  to the controllers of the dish drop stations  172   a - 172   d  for invoking resetting the dish drop stations  172   a - 172   d  following pushing of the emergency stop button  210 . 
     In the illustrated embodiment, one of the dish drop stations  172   a - 172   d  includes a power supply  218  that may be embodied as an adaptor or other interface to an electrical outlet. The power supply  218  may also be a rechargeable battery. In the illustrated embodiment, the power supply  218  is positioned in the dish drop station  172   a  that is on an opposite end of the series of dish drop stations  172   a - 172   d  from the dish drop station  172   d  to which the emergency stop button  210  and the power button  212  are mounted. 
     The lines  214 ,  216  may therefore include lines coupling power to the dish drop stations  172   a - 172   d  from the power supply  218  and lines coupling control signals to the dish drop stations  172   a - 172   d  from the buttons  210 ,  212 . 
     In the illustrated embodiment, each side of the rear housing (left and right in the illustrated example, i.e., substantially parallel to the vertical and longitudinal directions  12   a ,  12   b ) includes an opening. The openings on the exposed sides of the housing  208  of the dish drop stations  172   a  and  172   d  on the ends are closed by a cover  220  secured over the opening. The emergency stop button  210  and power button  212  may be mounted on this cover  220 . The cover  220  on the left side of dish drop station  172   a  is present but not visible in the illustrated example. The cover  220  on the left side may be identical but may lack the emergency stop button  210  and power button  212 . For example, an electrical plug for interfacing with the power supply  218  may be accessible through the cover  220  on the dish drop station  172   a , such as by means of an electrical cord protruding through the cover  220  and coupled to the power supply  218 . 
     The intermediate dish drop stations  172   b - 172   c  that are not on the ends may lack covers  220 . Likewise, inner facing surfaces of the end drop stations  172   a ,  172   d  may lack covers  220  (the left side of station  172   d  and the right side of station  172   a  in the illustrated example). This may facilitate routing of the lines  214 ,  216  through the stations  172   a - 172   d . Accordingly, the stations  172   a - 172   d  may provide conduits or passages through the front housing  208  to facilitate this routing. 
     The embodiment of  FIG. 16  illustrates an alternative embodiment for the collar  178  that includes a rectangular shape with a semicircular cutout around the openings  176 . The collar  178  near its rear edge defines a pivot  224  or hinge  224  to which a lid may attach and rotate about an axis substantially parallel to the horizontal direction  12   c . A motor may be incorporated into the collar  178  for automatically opening and closing the lid. A sensor may be incorporated into the collar  178  for sensing the position of the lid as positioned by a human operator, e.g. opening and closing of the list. For example, upon closing, the controller may receive an output from the position sensor indicating closing and, in response, invoke lowering of the lift arm  188  to the unlock position. Upon opening, the controller may receive an output from the position sensor indicating opening and, in response, invoke raising of the lift arm  188  until the lower stack height sensor  200   b  is obstructed and the upper stack height sensor  200   b  is not obstructed. 
     The embodiment of  FIG. 16  further illustrates beams  222  emitted by the sensors  200   a ,  200   b . As shown the beams  222  overlap the opening  176  of the dish station  172   a - 172   d  in a plane parallel to the longitudinal and horizontal directions  12   a ,  12   c . The beams  222  of the sensors  200   a ,  200   b  are offset from one another in the vertical direction  12   b  such that each sensor  200   a ,  200   b  senses obstruction at a different vertical position. As known in the art, a break beam sensor includes a transmitter that emits the beam  222  directed at a receiver that receives the beam  222  when there is no obstruction. Obstruction is therefore detected when the receiver produces an output indicating that the beam is no longer detected. Accordingly, where the sensors  200   a ,  200   b  are embodied as break beam sensors, the transmitter and receiver for each sensor  200   a ,  200   b  may be mounted within the collar  178  such that the transmitter and receiver for the upper stack height sensor  200   a  are at a higher vertical position along vertical direction  12   b  than the transmitter and receiver for the lower stack height sensor  200   b . As noted above, the sensors  200   a ,  200   b  may be distance sensors. The sensors  200   a ,  200   b  may therefore be used to estimate a diameter of a dish positioned adjacent the sensor  200   a ,  200   b.    
       FIGS. 17 and 18  illustrate a dish drop stations  172   a - 172   d  having a lid  230  rotatably mounted to the pivot  224 . The pivot  224  may be a dampened hinge in order to reduce damage to the lid and avoid sudden closing and opening. As shown, the lid  230  may hang over the rear side of the station  172   a - 172   d  when open. The lid  230  may define openings  232  to facilitate gripping and lifting by a user. In the illustrated embodiment, the distal end and lateral edges of the lid  230  may have sides  234   a - 234   c  extending downwardly therefrom and resting on the top plate  174  when the lid is closed. In such embodiments, the openings  232  may be defined in one or more of the sides  234   a - 24   c , such as in the sides  234   a  and  234   c  in the illustrated embodiment. Various other embodiments of a lid  230  may be used. For example, the lid may be slidably attached to the collar  178  or top plate  174 . 
     The lid  230  may define an indentation  236  for receiving additional dinner ware stacked on it when it is closed, e.g. a circular indentation having a flat bottom sized to receive plate that will also fit through the collar  178 , the indentation having a depth of between 1 and 2 cm below the portion of the lid  230  surrounding the indentation. 
     The controller may be coupled to a motor  238  controlling actuation of the lid  230 . The controller may also be coupled to a sensor  240  that senses a state of the lid  230 , e.g. whether the lid  230  is closed. A sensor  240  may be used that senses an angular position of the lid  230 . 
     In some embodiments, the controller may be programmed to cause the motor  238  to close the lid  230  in response to the lift arm  188  reaching the full position when receiving dishes. The controller may be programmed to cause the motor  238  to close the lid  230  in response to the lift arm  188  reaching the top position when dispensing dishes. The controller may be programmed to refrain from lifting the lift arm  188  in response to detecting that the lid sensor  346  indicates that the lid is closed. The controller may be programmed to generate an alert if the lid sensor  240  does not indicate that the lid has closed after the controller has invoked closing of the lid  230  by the motor  238 . In some embodiments, the controller may be programmed to lower the lift arm  188  to the home position or the unlock position in response to sensing that the lid  230  has been closed according to the lid sensor  240 . 
     Referring to  FIG. 19 , in many cases, a restaurant will use dishes of various sizes at the same time. Dish carts  10  may be configured to accommodate these different sizes. The dish drop stations  172   a - 172   d  may likewise be configured to accommodate differently sized dishes.  FIG. 19  illustrates a dish drop station  172   a  with a ring  240   a  positioned within the opening  176 , the ring  240   a  having a first inner diameter. A dish drop station,  172   b  in this example, includes a differently sized ring  240   a  positioned in its opening  176 , the ring  240   b  having a second inner diameter that is less than the first inner diameter. In this manner, users are prevented from putting dishes in the station  172   b  that are too large. The rings  240   b  may rest in the openings  176 , e.g., by defining flanges that rest on the top plate  174  and prevent the rings  240   a ,  240   b  from passing completely through the openings  176 . 
     The rings  240   a ,  240   b  may be used in conjunction with the block  162  of  FIGS. 11A to 12B . In particular, a ring  240   a ,  240   b  and block  162  of a dish drop station  172   a - 172   d  may be selected that correspond to one another such that the block  162  adjusts the adjustment assembly  110  of carts  10  positioned in the dish drop station  172   a - 172   d  such that the vans  112   a - 112   c  are positioned to receive dishes sized to fit through the selected ring  240   a ,  240   b  and are not positioned to receive dishes (i.e., define an unobstructed space among the vanes  112   a - 112   c  that is too small to receive dishes) that are too large to fit through the selected ring  240   a ,  240   b.    
     The rings  240   a ,  240   b  may also be used in cooperation with dish carts  10  incorporating rails  48  sized to receive dishes passing through a ring  240   a ,  240   b  matching the dish diameter that will fit among the rails  48  as described below with respect to  FIGS. 2 and 5 . 
       FIG. 19  further illustrates the configuration of the sensors  200   a ,  200   b . In particular, each break beam sensor  200   a ,  200   b  includes both a transmitter and a receiver that are co-located and mounted in the collar  178  over the opening  176 . Light  222  from the transmitter of a sensor  200   a ,  200   b  that is reflected back to the receiver of the sensor  200   a ,  200   b  indicates obstruction and may further be used to measure a distance to the object that reflected the light. 
     Referring to  FIG. 20 , in use the lift arm  188  may operate among predefined positions as controlled by the controller of the dish drop station  172   a - 172   d . In particular, the arm may begin at a home position (“Home” in  FIG. 20 ) in which the lift arm  188  and lift paddle  190  are positioned below the top plate  54  of a cart  10  positioned in the dish drop station  172   a - 172   d . Specifically, in the home position the lift arm  188  and paddle  190  are positioned in a gap below the top plate  54  and above any front frame member  22   a  or bottom plate  66 . In this manner, in the home position, the cart  10  may be inserted into the dish drop station  172   a - 172   d  without the lift arm  188  and lift paddle  190  interfering with the insertion. Likewise, in the home position, any dishes loaded onto the lift paddle  190  will be deposited on the pad  56  and will likewise not interfere with insertion of the lift arm  188  and lift paddle  190 . As discussed below with respect to  FIGS. 24 through 28C , in the home position, a cart will be able to latch itself into the dish drop station  172   a - 172   d  without requiring movement of the lift arm  188 . 
     The controller may further position the lift arm  188  in an unlock position (“Unlock” in  FIG. 20 ). The unlock position is slightly (e.g., 1-3 cm) below the home position and results in the lift arm  188  engaging the cart lock  198  such that the cart lock  198  disengages from the dish cart  10 . Example cart locks  198  are described below. 
     In some embodiments, a controller will permit automated lowering of the lift arm  188  and lift paddle  190  according to outputs of the sensors  200   a ,  200   b  until the lift arm reaches a full position (“Full” in  FIG. 20 ). Upon sensing movement of the lift arm  188  to this position, the controller will stop lowering the lift arm  188  in response to obstruction of the upper stack height sensor  200   a . For example, the controller may move the lift arm  188  to the home position or the unlock position. 
     The controller may likewise sense arrival of the lift arm  188  at a top position (“Top in  FIG. 20 ). Upon sensing arrival at the top position, the controller no longer raises the lift arm  188  in response to detecting that the lower stack height sensor  200   b  is not obstructed. 
     In some embodiments, the lid  230  may be actuated by an actuator, e.g. an electric motor. Accordingly, the controller may be programmed to cause the actuator to close the lid  230  upon detecting arrival of the lift arm  188  at the top position or the full position. 
     Upon reaching the full position or the top position, the controller may lower the lift arm  188  to the home position and refrain from taking further action until an instruction is received. For example, the controller may be programmed to wait until an instruction is received to lower the lift arm  188  to the unlock position, such as detecting pressing of the button  180 , receiving a wireless control signal, detecting closing of the lid  230 , or some other control input. 
     Sensing position of the lift arm  188  may be accomplished using any sensing technology known in the art, such as limit switches mounted in the dish drop station  172   a - 172   d  that are triggered by the lift arm  188  when located at the designated location (e.g., the full position and top position), break beam sensors mounted in the dish drop station  172   a - 172   d  that detect obstruction by the lift arm  188  when at the designated location. Sensing of the positon of the lift arm  188  may also be performed using encoders such as hall encoders or optical encoders 
       FIGS. 21A and 21B  illustrate use of a dish drop station  172   a - 172   d  in combination with a dish cart  10 . As shown in  FIG. 21A , a loaded or unloaded cart (unloaded in the illustrated example) is positioned within the dish drop station  172   a - 172   d  with its front edge facing the inner wall  192  and such that the lift arm  188  inserts below the top plate  154 , such as in a gap between the front frame member  22   a  and the lower plate  66 . Positioning of the cart  10  may be accomplished by rolling the cart into the dish drop station  172   a - 172   d  along the longitudinal direction  12   a . The lift arm  188  is positioned in the home position or the unlock position during insertion. 
     The controller may then invoke raising of the lift arm  188  and lift paddle  190  through the lobe openings  58  in the pad  56  and plate  54  and through the slots  60 ,  62 . When the cart  10  is loaded with dishes  250 , the lift arm  188  will rise until the lower stack height sensor  200   b  is obstructed and the upper stack height sensor  200   a  is not obstructed preparatory to removing dishes  250  from the cart  10  for serving food or for washing. The controller will then raise the lift arm  188  when the lower stack height sensor  200   b  is not obstructed until either the lower stack height sensor  200   b  is obstructed or the lift arm  188  reaches the top position. 
     When the cart  10  is empty, the lift arm  188  will rise to the top position preparatory to receiving clean or dirty dishes  250 . The controller will then lower the lift arm  188  when the upper stack height sensor  200   a  is obstructed until the upper stack height sensor  200   a  is not obstructed or the lift arm  188  reaches the full position. 
     Referring to  FIGS. 22 and 23 , raising and lower of the lift arm  188  may be performed using the illustrated drive mechanism that is housed within the front housing  208 . The illustrated drive mechanism is exemplary only. Any translational actuator known in the art may be used for raising and lower the lift arm  188 . In a like manner, any position sensing technology known in the art may be used to sense the position of the lift arm  188  or to detect when the lift arm  188  is at a predetermined position (e.g., the top, full, and unlock positions). 
     In the illustrated embodiment, one or more rails  260  guide sliding of one or sliders  262  mounted to the rails  260  along the vertical direction  12   b . In the illustrated embodiment, the sliders  262  clamp onto the rails  260 . Alternatively, the rail  260  may be replaced with a vertically oriented slot into which slider&#39;s  262  insert. 
     One or both of the sliders  262  is fastened to a chain  264  looped around a lower sprocket  266   a  and an upper sprocket  266   b . The upper or lower sprocket  266   a ,  266   b  may be driven by a motor  268  that is controlled by the controller. The cart lock  198  is mounted adjacent the rails  260  and engages the aperture  100  on a dish cart  10  in order to hinder removal of a cart until the lift arm  188  is in the unlock position. Various embodiments of the cart lock  198  are described below. The cart lock  198  may be located near the bottom of the travel of the lift arm  188 , such that the cart lock  198  is unlocked when the sliders  262  are slightly above (e.g., 1-3 cm) a top of the lower sprocket  266   a.    
     As noted above, position sensors may sense when the lift arm  188  is positioned at the top, full, or unlock positions. For example, sensors  270   a ,  270   b ,  270   c , and  270   d  may be positioned to sense when the lift arm is at positions corresponding to the unlock, home, full, and top position, respectively as shown. The sensors  270   a - 270   d  may be mechanical buttons or switches positioned such that they actuated by sliders  262  or lift arm  188  as it travels along the rails  260 . Alternatively, the sensors  270   a - 270   d  may be break beam sensors that are obstructed by the lift arm  188  or other structure (e.g. the sliders  262 ) coupled to the lift arm  188  as it moves to the position of the break beam sensor. 
     In other embodiments, the motor  268  is a stepper motor such or a DC (direct current) motor with an integrated absolute encoder such that its movement is known and may be used to infer the position of the lift arm  188  and whether it is at any of the top, full, and unlock positions. In still other embodiments, rotation of a sprocket  266   a ,  266   b  or the motor  268  itself is measured and used to infer the position of the lift arm  188  and whether it is at any of the top, full, unlock, and home positions. 
     Referring to  FIG. 24 , some embodiments the sliders  262  include four sliders, two on each rail  260 . The sliders  262  may fasten to a plate  278  to which the lift arm  188  is fastened, such as by means of welds, bolts, or other fastening means. 
       FIG. 24  further illustrates an example embodiment of a cart lock  198 . 
     The cart lock  198  may interface with a pressing tab  280  that is coupled to the lift arm  188 , i.e. moves vertically in unison with the lift arm  188 . In the illustrated embodiment, the pressing tab  280  is fastened to one of the sliders  262  and protrudes outwardly from the slider  262  in the horizontal direction  12   c . In the illustrated embodiment, a lower surface of the pressing tab  280  is flat and substantially parallel to the longitudinal and horizontal directions  12   a ,  12   c.    
     The cart lock  198  may define a pivot  282  and a lever  284  that is rotatable about the pivot  282 . The pivot  282  may be fixed relative to the housing  208 , such as by fastening to the inner wall  192  of the dish station  172   a - 172   d . The lever  284  protrudes on either side of the pivot  282  such that a first end of the pivot engages the pressing tab  280  when the lift arm  188  is lowered to the unlock position. A second end of the pivot is positioned having the pivot  282  positioned between the first end and the second end. The second end engages a lifting rod  286  such that when the first end is urged downwardly by the pressing tab  280 , the second end lifts the lifting rod  286 . 
     In the illustrated embodiment, the lifting rod  286  passes through a housing  288  having a return spring  290  positioned therein and encircling the lifting rod  286 . A spring stop  292  secures to the lifting rod  286  within the housing  288  and is fixed relative to the rod  286  such that the spring  290  engages the spring stop  292  and urges the rod  286  downwardly toward a bottom wall  294  of the housing. The bottom wall  294  of the housing may limit movement of the spring stop  292  when the spring stop is pressed against the bottom wall  294  of the housing. The spring  290  likewise engages a top wall  296  of the housing, which may be removable to facilitate installation of the spring  290 . 
     The lifting rod  286  extends outwardly form the top wall  296  and secures to an arm  300  protruding outwardly from the lifting rod  286 , which includes protruding outwardly in a plane substantially parallel to the longitudinal and horizontal directions  12   a ,  12   c . A locking post  302  secures to the arm  300  and protrudes downwardly therefrom offset from the lifting rod  286 . 
     As shown in  FIG. 25 , when the lifting arm  188  and pressing tab  280  are lowered to the unlock position, the lever  284  presses upwardly on the lifting rod  286  and presses the spring stop  292  against the spring  290 . This also raises the arm  300  and the locking post  302 . As shown in  FIG. 26 , as the lifting arm  188  and pressing tab  280  are raised and pressure on the lever  284  is released, the spring  290  urges the spring stop  292  downwardly along with the lifting rod  286 , thereby lowering the arm  300  and locking post  302 . 
       FIGS. 27A to 27D  illustrate interaction of the cart lock  198  with a cart  10 , specifically the top plate  54  and aperture  100  of a cart  10 . Note that some carts include two apertures  100  such that a dish drop station  172   a - 172   d  may include two cart locks  198  as described herein. 
     Referring specifically to  FIG. 27A , a user inserts a cart  10  into the dish drop station  172   a - 172   d  such that the top plate  54  engages the locking post  300 . In the example of  FIG. 27A , the arm  298  and  300  are lowered due to the lift arm  188  being above the unlock position, e.g., the home position. In the illustrated embodiment, the locking post  302  is provided with a beveled leading edge  304  that engages a beveled leading edge  306  of the plate  54  such that the locking post  302 , arm  300 , and lifting post  286  are urged upwardly against the restoring force of the spring  190 , as shown in  FIG. 27B . The cart  10  is pushed further inward such that the locking post  302  is urged to the location of the aperture  100  as shown in  FIG. 27C . Upon reaching the opening  100 , the locking post  100  is urged into the opening  100  due to the restoring force of the spring  190 . 
     In another use case, the lift arm  188  is lowered to the unlock position thereby raising the arm  300  to the position shown in  FIG. 27C . The cart  10  is then inserted such that the aperture  100  is positioned below the locking post  302 . The arm  188  is then lifted from the unlock position, which permits the spring  190  to urge the locking post  302  into the opening  100 . Removal is the opposite of insertion—the lift arm  188  is lowered to the unlock position, causing the arm  300  and locking post  302  to rise, thereby disengaging from the aperture  100  and permitting removal of the cart  10 . 
       FIGS. 28A to 28C  illustrate an alternative embodiment of a cart lock  198 . In this embodiment, an arm  310  is pivotally mounted to the front housing  208 , such as to a pivot  312 , such that the arm  310  is rotatable about an axis substantially parallel to the horizontal direction  12   c . The arm  310  defines a lock surface  314  that faces toward a front of the dish drop station  172   a - 172   d , i.e. faces away from a dish cart  10  positioned in the dish drop station  172   a - 172   d . Specifically, the lock surface  34  faces such that the lock surface may engage the opening  100  and resist removal of the dish cart  10 . 
     The arm  310  may further define a sloped or beveled surface  316  that slopes downwardly with distance toward the front of the dish drop station  172   a - 172   d . The sloped surface  316  may facilitate guiding the arm  310  over the front edge of the plate  54  when inserting a cart within the dish drop station  172   a - 172   d.    
     A hanging arm  318  is suspended from the arm  310  from a pivot  320  about which the hanging arm  318  is rotatable. The pivot  320  defines an axis of rotation that is substantially parallel to the horizontal direction  12   c . The pivot  312  is located on the arm  310  between the pivot  320  and the lock surface  314  such that a downward force on the hanging arm  318  results in rising of the lock surface  314 . The hanging arm  318  defines a pressing surface  322  that protrudes outwardly from the arm  318 . The pressing surface  322  may define a surface that for at least one position around the pivot  320  is substantially-parallel to the longitudinal and horizontal directions  12   a ,  12   c.    
     In use, when the lift arm  188  is moved to the unlock positon (see  FIG. 28C ), the lift arm  188  rests on the pressing surface  322 , thereby urging the locking surface  314  upward and ready to receive a dish cart  10 . When, the lift arm  188  is raised, the locking surface  314  pivots downward into the opening  100 . This may be facilitated by gravity. In particular, the pivot  320  may be closer to pivot  312  such that the weight of the arm  310  on the opposite side of the pivot  312  is sufficient to overcome the weight of the hanging arm  318 . In other embodiments, the arm  310  may be spring loaded such that it is urged into the position shown in  FIG. 28B  in the absence of force on the pressing surface  322 . 
     Referring to  FIG. 29 , in some embodiments, a dish drop station  172   a - 172   d  may include additional or alternative means for retaining a dish cart  10 . For example, one or more ferromagnetic lugs  96  may secure to one or both front vertical posts  40   a ,  40   b  of a dish cart  10 , such as according to the embodiment of  FIG. 5 . One or two magnetic detents  330  may mount to the inner wall  192  of the dish drop station  172   a - 172   d  and be positioned to engage the one or two lugs  96  when the cart is positioned in the dish drop station  172   a - 172   d , i.e. exert a certain amount of pull on the lug  96 , such as a force at least 3 to 20 Newtons when the cart  10  is pushed to its inwardmost position within the dish drop station  172   a - 172   d.    
     In some embodiments, the controller of the dish drop station  172   a - 172   d  may be coupled to a cart present sensor  332  that detects whether a cart  10  is positioned within the dish drop station  172   a - 172   d . For example, the cart present sensor  332  may be an inductive sensor that can detect the metal vertical posts  40   a  or  40   b  of a cart or other metal portion of the cart  10 . In particular, the sensor  332  may be an inductive sensor positioned within a plastic housing (e.g., non-inductive, non-glass filled) yet able to sense metal positioned proximate the sensor  332  outside of the housing. Other types of sensors  332  may be used, such as a break beam sensor that is obstructed by the cart  10 , a mechanical button or switch actuated when the cart  10  is inserted into the dish drop station  172   a - 172   d , or some other type of sensor. 
     In some embodiments, if the controller receives an output from the sensor  332  that indicates that no cart  10  is present, the controller may be programmed to wait for a delay period followed by moving the lift arm  188  and paddle  190  to the home position if not already at the home position. In other embodiments, the controller prevents all movement of the lift arm  188  when no cart  10  is sensed as being present 
     If the cart present sensor produces an output indicating a transition to a cart  10  being present, the controller may be programmed to raise the lift arm  188  from the home position until one of the following is true: (a) the lower stack height sensor  200   b  is obstructed while the stack height sensor  200   a  remains unobstructed (the cart  10  was loaded with dishes) or (b) the lift arm  188  reaches the full position (the cart  10  was empty and ready to be loaded). 
     Referring to  FIG. 30 , references to a controller hereinabove may be performed by a controller  340  performed to perform those functions. The controller  340  may be embodied as a general purpose computer or a dedicated circuit programmed to perform the functions ascribed to the controller hereinabove. In particular, the controller  340  may control supply of power from the power supply  218  supplied to the lift motor  268  according to outputs received from some or all of the on/off switch  180 , upper and lower stack height sensors  200   a ,  200   b , the emergency stop button  210 , reset button  212 , the unlock position sensor  270   a , the home position sensor  270   b , the full position sensor  270   c , the top position sensor  270   d , and the cart present sensor  332 . 
     In addition, the controller  340  may be coupled to a transceiver  342 , such as a WI-FI transceiver, BLUETOOTH transceiver, or other type of wireless transceiver. As noted above, the antenna for the transceiver  342  may be mounted within the plastic collar  178 . The controller  340  may be programmed to receive instructions through the transceiver  342  from a central controller or to transmits its state to a central controller. For example, the controller  340  may transmit a notification when the lift arm  188  reaching the full position, indicating that a cart  10  full of dirty dishes needs to be removed and replaced with an empty cart. The controller  340  may transmit a notification when the lift arm  188  reaches the top position, indicating that a cart  10  is empty of dishes and needs to be replaced with a cart  10  full of clean dishes. The controller  340  may transmit other information, such as a rate of rise or fall of the lift arm  188 , which may be used to estimate when it will be empty or full, respectively, enabling preemptive preparation of a full or empty cart, respectively. 
     The controller  340  may transmit a notification in response to detection of a malfunction, such as sticking of the lift arm  188 , which may be detected by the lift arm failing to move to a desired position (top, full, unlock) in response to the controller  340  instructing the motor  268  to move the lift arm  188  to the desired position. 
     The controller may transmit a notification upon detecting interaction with the button  180 , e.g., a notification indicating that human attention at the dish cart station  172   a - 172   d  is required. For example, a user may push button  180  to indicate that a cart has been filled or empty and another empty or full cart, respectively, is needed. 
     While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the disclosure. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. The foregoing description has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. Further, it should be noted that any or all of the aforementioned alternate implementations may be used in any combination desired to form additional hybrid implementations of the disclosure.