Abstract:
A system includes trays of a plurality of different widths and an unloading system for unloading cartons from the trays. The trays ( 20; 20′; 20 ″) each comprise a base ( 22 ) and a pair of end walls ( 30 ) extending upward from the base. The unloading system ( 200; 200 ′) comprises a plurality of fingers ( 202 A- 202 I). Each of the end walls comprise a plurality of vertical slots ( 40 ) open to an upper edge of the end wall. The fingers are positioned and dimensioned to pass through the slots of the trays as the trays are delivered by the tray delivery conveyor to lift contents of the trays. The fingers are positioned so that some fingers pass through the slots of each of the different widths, but others pass only through slots of wider said widths.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Benefit is claimed of U.S. Patent Application Ser. No. 61/054,936, filed May 21, 2008, and entitled “APPARATUS AND METHOD FOR REMOVING CARTONS FROM LOAD BEARING TRAYS”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the automated handling of cartons in warehouses and distribution centers and, more particularly, to the automated removal of the cartons from load bearing trays. 
     BACKGROUND OF THE INVENTION 
     Current industry practice to remove cartons automatically from trays utilizes one of two types of designs. The first design involves stopping the tray, lifting the carton up on fingers and raking the carton off the fingers. This design requires the tray to come to a stop thereby limiting the potential throughput rate. In this design, a single tray removal device can have the ability to process multiple tray sizes but imposes certain limitations to the number of sizes of trays that can be processed by a single tray removal device. It also at times imposes additional limitations on the orientation of trays with regard to the side or dimension of the tray that first approaches the tray removal device. 
     A second design is characterized by previous attempts to utilize a continuous process involving a “scraping” type device to lift the carton up and onto a powered belt. This design requires a grid of raised platforms on the bottom of the tray. The platforms form an elevated surface upon which the carton can rest. The fingers of the scraping device reach between the platforms and under the elevated carton. As the tray moves on the powered belt, the back lip of the tray drives the carton up the inclined scraper surface formed by the assembly of fingers and onto a powered belt. This design requires significantly increased vertical height in the tray design, resulting in the tray itself occupying a significant amount of space in the storage facility. It also requires the use of relatively uniform size cartons to allow the back edge of the tray to drive the carton far enough up the inclined surface to engage the powered takeaway conveyor. This design also is limited in that each tray removal device can process only one size tray thus requiring multiple devices as a means to process multiple tray sizes. 
     The cartons handled by automated systems can vary in size, therefore it is a goal of carton removal systems to provide and use trays that are of a size that will contain the carton but are no larger than necessary to do so. To the degree that the tray is larger than the carton, some space in the storage facility may be wasted. In these applications a wide variety of carton sizes are used. In order to maximize the utilization of the storage volume, multiple tray sizes are required. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, there is provided an apparatus and method for removing cartons from load bearing trays as the trays move continuously on a generally planar conveyor surface. 
     The sizes of trays may be chosen to accommodate most efficiently the sizes of the individual cartons. The carton removal apparatus can act on the trays and their contents without regard to the size of the tray and without regard to the fore and aft orientation of the trays such that either end of the tray may approach the carton removal apparatus first. 
     The tray provides a means for the apparatus to insert a multiplicity of acutely sloping wedges/fingers into generally vertical slots in the leading edge side of the advancing tray, the slots extending upward through the top edge of the tray side wall and downward to join with recessed grooves in the bottom surface of the tray. The wedges are positioned such that they insert between the bottom surface of the carton and the tray surface on which the carton rests, thereby lifting the front edge of the advancing carton onto the upper surfaces of the wedges. 
     In an exemplary embodiment, the planar upper surface of each wedge joins with, is aligned with, and is continued by, a moving conveyor belt of generally the same width as the upper surface of the individual wedge. The forward motion of the tray pushes the carton onto the upper surface of the wedges to a point at which the bottom surface of the carton comes in contact with the multiplicity of moving conveyor belts which then support the carton and move it forward, generally independent of the motion of the tray. The carton is supported by and transported by the multiplicity of conveyor belts and is thus separated from the tray. The carton, now removed from the tray, continues its motion onto a conveyor surface that adjoins the conveyor belts of the carton removal apparatus. 
     Another aspect of the invention involves a system having a plurality of trays, each comprising a base and a pair of end walls extending upward from the base. The system includes a tray unloading system. The trays are of a plurality of different widths. The tray unloading system comprises a plurality of fingers. Each of the end walls comprises a plurality of vertical slots open to an upper edge of the end wall. The fingers are positioned in dimension to pass through the slots of the trays as the trays are delivered to lift contents of the trays. The fingers are positioned so that some fingers pass through the slots of each of the different tray widths but others pass only through slots of wider said tray widths. 
     In various implementations, the fingers may be positioned at an essentially non-constant spacing effective to accommodate the different widths. The fingers may be laterally asymmetrically positioned. The non-constant spacing may comprise: a first group at a non-constant first on-center pitch; and a plurality of additional fingers separated from the first group by one or more gaps. The plurality of additional fingers may comprise a single intermediate finger separated from the first group by a first gap at an on-center dimension other than a multiple of said first on-center pitch and at least two more fingers separated from the intermediate finger by a second gap at an on-center dimension other than a multiple of said first on-center pitch. The first group may consist of five fingers. The at least two additional fingers may consist of said two additional fingers at said first on-center pitch. 
     The fingers each may comprise a tip member and a conveyor and may be positioned to guide the contents to a tray content removal conveyor. The finger conveyors may be powered in common by a motor. 
     Further aspects involve the method for operating such a system. A tray delivery conveyor is driven to move the trays downstream to the transfer system. At least some of the fingers are passed through the slots of the trays as the trays are delivered by a tray delivery conveyor. The passing includes passing the tip members through a leading one of the end walls of each tray and passing the tip members into grooves in the base of each tray and below the contents, a wedging action of the tip members providing an initial said lift of the contents of the trays. The contents are passed along the fingers to the finger conveyors. The finger conveyors are driven to transfer the contents to a tray content removal conveyor. The tray content removal conveyor is driven to further transport the contents. A trailing one of the end walls may push the contents up the tip portions or notches in a tray base may do so. The fingers may pass inside-to-outside through the trailing end wall. There may be a plurality of different widths of the trays. A partially different group of the fingers may pass through the slots respectively of the trays of different widths. 
     The different tray widths may include at least first, second, and third widths. The fingers may be positioned at a spacing effective to accommodate the different widths as firsts of the first side walls of the trays pass in a predetermined alignment with a first edge of the conveyor so that: the first width is accommodated by a first terminal group of the fingers passing through associated ones of the slots with the second side wall passing through a first gap between the first terminal group and a remainder of the fingers; the second width is accommodated by the first terminal group of the fingers and at least one of the remainder passing through associated ones of the slots with the second side wall passing through a second gap between the at least one of the remainder and remaining fingers of the remainder; and the third width is accommodated by the first terminal group of the fingers and at least two of the remainder passing through associated ones of the slots. 
     Further aspects of the invention involve trays. Each tray comprises a base and a pair of end walls extending upward from the base. The base includes an upper surface having a plurality of interspersed longitudinal grooves and ridges. Each of the end walls comprises a plurality of vertical slots open to an upper edge of the end wall and respectively aligned with an associated said groove. There may be at least two distinct lateral sizes of the slots and grooves. In various implementations, the tray may be a nineteen inch wide tray having exactly seven said slots and grooves or the tray may be a twenty-six inch wide tray having exactly ten said slots and grooves. The tray may have exactly seven said slots, a central group of three of the slots having larger slot width than the two terminal pairs of two slots or the tray may have exactly ten said slots and grooves, two terminal groups of three slots having slot width less than the respective adjacent slots separating the two terminal groups from a central pair of slots. 
     Such a system may have one or more of the following advantages.
         One advantage is the ability to remove the carton from the tray while the tray remains in motion, thereby removing a greater number of cartons in a specific period of time.   Another advantage is the ability to use a greater variety of tray sizes than previous systems, each tray being chosen to fit most closely the carton that is placed on it, thereby making more efficient use of space within the storage facility.   Another advantage is the reduction in the thickness, or vertical height, of the bottom surface of the tray, such that the tray occupies a minimum of space beyond that which is required to contain the carton, thus making more storage space within the storage facility available for storage of cartons.   Another advantage is the ability to handle multiple trays sizes in a single apparatus, thereby possibly reducing the number of devices required.   Another advantage is an improved method of stacking empty trays on each other whereby the space required within the storage facility for the storage of empty trays is reduced.   Another advantage is a process for automatic, unattended removal of cartons from a plurality of predetermined tray sizes, wherein the movement of the trays is continuous and without interruption, by a single carton removal apparatus.       

     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of a first (relatively small) tray. 
         FIG. 2  is a top view of the tray of  FIG. 1 . 
         FIG. 3  is a bottom view of the tray of  FIG. 1 . 
         FIG. 4  is a side view of the tray of  FIG. 1 . 
         FIG. 5  is an end view of the tray of  FIG. 1 . 
         FIG. 6  is a vertical longitudinal sectional view of the tray of  FIG. 1 , taken along line  6 - 6  of  FIG. 2 . 
         FIG. 7  is a view of a second (intermediate) tray. 
         FIG. 8  is a top view of the tray of  FIG. 7 . 
         FIG. 9  is a view of a third (relatively large) tray. 
         FIG. 10  is a top view of the tray of  FIG. 9 . 
         FIG. 11  is a composite view superimposing end views of the first, second, and third trays, in alignment with fingers of a detraying apparatus. 
         FIG. 12  is a view of a conveyor system including a detraying apparatus. 
         FIG. 13  is a top view of a defraying apparatus. 
         FIG. 14  is a front view of the apparatus of  FIG. 13 . 
         FIG. 15  is a side view of the apparatus of  FIG. 13 . 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     One embodiment of a tray  20  is shown in  FIG. 1 . The tray has a base  22  and circumscribing wall structure  24  extending from a junction  25  with perimeter of the base to an upper rim  26 . The wall structure includes two sloping, continuous and generally vertical sides (side walls)  28  and two generally vertical slotted ends (end walls)  30 . The sides  28  and ends  30  extend to upper edges formed as portions of the rim  26 . The base  22  has an underside or bottom  32  ( FIGS. 3&amp;4 ) which forms a tray bottom and has an upper surface or top side  34  ( FIG. 5 ) which may support one or more cartons  36  contained within the wall structure. 
     The base has upwardly-open channels or grooves  38  ( FIG. 2 ) which run from end to end, joining each end  30  at the base of a slot  40 . The grooves  38  separate and are interspersed with ridges or lands  42 . The base has upwardly-open transverse notches  44  passing from side to side along each of the ridges. The exemplary notches  44  are shallower than the grooves  38 . The exemplary wall structure  24  has an inboard face/surface  50  and an outboard face/surface  52  each with respective portions along the sides  28  and ends  30  to form inboard and outboard surfaces thereof. The exemplary trays are of substantially rectangular planform having an overall width W 1  and an overall length L 1 . Additionally, the tray has an interior width W 2  and length L 2  (measured as associated widths and lengths of the largest rectangular carton which may be supported on the upper surface of the base). An exemplary overall/exterior tray height is shown as H 1  from the underside of the base to the upper rim  26 . An exemplary base thickness/height is H 2 , leaving an interior depth/height of H 3  equals H 1  minus H 2 . For reference, a longitudinal vertical medial plane is shown as  500  and a transverse vertical medial plane is shown as  502 . The sides and ends of the tray slope outward slightly so that when trays are stacked on each other, the space required for storage of trays is kept needed. The outboard surface  52  is stepped ( FIG. 4 ) with an upwardly divergent angled lower portion  55 , a vertical upper portion  56 , and an intermediate wedge  57  joining the upper and lower portions. When stacked, the trays nest with the intermediate portion  57  contacting or closely facing the upper rim  26  of the wall of the tray immediately below. 
     The slots  40  extend along/through the end walls  30  and are open to/at the upper edges of the end walls. The slots separate interspersed intact portions  60  of the end walls. The slots  40  and their associated grooves  38  are positioned and dimensioned to accommodate fingers (discussed below) of a defraying system for removing cartons. The exemplary slots/grooves each have a characteristic width W 3 . The slots/grooves separate intact end wall portions  60  and ridges  42  having a width W 4 . An on-center spacing S 1  of the slots/grooves is measured as half of the respective width W 3  of each two adjacent such slots/grooves plus the width W 4  of the intervening intact end portions/ridges. Similarly, an on-center spacing S 2  of the intact end portions/ridges is half of the respective widths W 4  of two adjacent such end portions/ridges plus the width W 3  of the intervening slot/groove. As is discussed further below, the widths W 3  and W 4  and spacings S 1  and S 2  can vary for the different slots/grooves and intact end wall portions/ridges. In the exemplary tray, respective left and right terminal portions  64  of the intact end walls (of associated corner portions  66  of the wall structure) have widths W 5  which are greater than W 4 . This allows for relatively robust corner portions. This robustness may provide one or more of: lateral support of the side walls; vertical strength for stacking; longitudinal strength for retaining tray contents; and surface area for bar codes/labels/other indicia. 
     It is desirable to provide operation with multiple sizes of trays. Different tray lengths may readily be accommodated. However, accommodating different tray width creates problems. The exemplary tray  20  has five grooves/slots. If a larger tray were to merely be a laterally extended version (having more slots of the same width and spacing), there would be problems accommodating both trays. Specifically, if the detraying machine had fingers positioned to engage the slots of the larger tray, those fingers would interfere with one of the corner portions  66  of the smaller tray. Accordingly, as is discussed in further detail below, the basic tray of  FIG. 1  can form one part of a system where a more complicated arrangement of defraying machine fingers are provided along with a more complicated distribution of slots in larger trays. An example is described below wherein the tray of  FIG. 1  is the smallest of three exemplary sizes (more particularly, widths) of tray. 
       FIGS. 7&amp;8  show an exemplary intermediate/medium size tray  20 ′ and  FIGS. 9&amp;10  show an exemplary large tray  20 ″ in the three-width system. As is discussed further below, each of the trays is of generally similar construction with similar relatively wide corner portions but with different groove/slot distribution. The variation in groove/slot distribution may best be visualized by first looking at the finger distribution of the detraying machine. 
     Exemplary exterior dimensions L 1  and W 1  of the tray  20  are nineteen inches (48 cm) and fourteen inches (36 cm) and inside dimensions L 2  and W 2  are seventeen inches and twelve inches. For the medium tray  20 ′ these are: twenty-six inches (66 cm); nineteen inches; twenty-four inches (61 cm); and seventeen inches. For the large tray  20 ″ these are: forty-one inches (104 cm); twenty-six inches; thirty-nine inches (99 cm); and twenty-four inches. These interior dimensions are as measured at the interior base of the side walls. Each of the three sizes has overall height H 1  of an exemplary three inches (8 cm). The base height H 2  of each size tray is an exemplary 0.75 inch (2 cm), and interior depth H 3  of an exemplary 2.25 inches (6 cm). These different sizes are similar in form but vary from each other, in addition to overall size, in the number and distribution of slots and the corresponding grooves. As is discussed further below, each tray has mirror image symmetry across the planes  500  and  502 . Thus, each tray can be processed with either end leading. 
     The device is not limited to the use of only three sizes of trays and alternative embodiments could have more or fewer tray sizes and could use sizes different from those of the exemplary embodiment. The exemplary trays are made of plastic (e.g., a single-piece unitary polypropylene molding) of sufficient strength to bear the load of the cartons but alternative embodiments could be made of different plastics, metal or other materials. 
       FIG. 11  shows an end view of three sizes of trays  20 ,  20 ′, and  20 ″, and the relationship the slots in each size tray bear to the vertical slots of the other size trays and to fingers of a detraying machine  200 . 
     As is discussed further below, the detraying machine forms a portion of a transfer system for transferring cartons from the trays. The fingers are positioned to pass partially through the associated tray slots and grooves to remove (detray) the cartons from the trays. The exemplary machine  200  has nine fingers labeled  202 A- 202 I. These nine fingers are configured for use with an exemplary four-tray system including a fourth tray (not shown) even wider than the tray  20 ″. The first eight fingers  202 A- 202 H, alone, facilitate use of the three-tray system. In the exemplary system  200 , the trays pass along a conveyor system with a first side  28  in a predetermined lateral registry with the system  200  (e.g., against a first side  204  of a conveyor carrying the trays and their cartons). As the small tray  20  passes through the system, a first terminal group (i.e., starting from one side of the array of fingers)  202 A- 202 E of an exemplary five of the fingers passes through respective slots/grooves (for purpose of reference, the slots  40  being subreferenced  40 A- 40 E but the grooves  38  not being individually referenced). Each of the fingers is shown having a width W 10 . An on-center spacing S 10  is also shown between adjacent fingers (and subreferenced S 10A -S 10H  for the respective pairs of fingers). A gap width between fingers is shown as W 11 . As is discussed further below, the spacing or pitch S 10  for the group of fingers  202 A- 202 E may be constant or close thereto.  FIG. 11  shows respective inter-finger gaps  210 A- 210 H. The width W 11  of the gap  210 E is substantially larger than the width of the gaps  210 A- 210 D within the first group of fingers  202 A- 202 E. This gap is effective to accommodate the second side wall and associated corners of the small tray  20 . This gap width may be more than twice the width of the gaps  210 A- 210 D. As is discussed further below, the gap  210 E may represent approximately the loss of a single finger from an array of constant spacing. However, the spacers may be further modified to improve coverage and feeding. For example, in the Table below, two examples are given one with exactly constant spacing of the first five fingers and the other with a slightly increased spacing between the third and fourth and a correspondingly slightly decreased spacing between the fourth and fifth. This may improve feeding consistency when the various sizes of trays are considered. 
     For removing cartons from the intermediate/medium tray  20 ′, the first group of fingers  202 A- 202 E are used along with the next finger  202 F. These respectively pass through slots  40 ′A- 40 ′E and  40 ′G (and their associated grooves) of the tray  20 ′. No finger passes through the penultimate slot  40 ′F. The slot  40 ′F exists for side-to-side symmetry (so that it would be in the position of slot  40 ′B if the tray is reversed). This symmetry allows trays to be used in either of two orientations. When passing the medium tray, its second side wall and associated corner portions pass through the gap  210 F. Thus, the gap  210 F may be of similar dimension to the gap  210 E. 
     Similarly, for removing cartons from the large tray  20 ″, the first group of fingers  202 A- 202 E are also used along with the next finger  202 F and the next two fingers  202 G and  202 H. These respectively pass through slots  40 ′A- 40 ′E,  40 ′G,  40 ′I, and  40 ′J (and their associated grooves) of the tray  20 ″. No finger passes through the slots  40 ′F and  40 ′H. These slots  40 ′F and  40 ′H exist, as noted above, for side-to-side symmetry (so that they would be in the positions of slots  40 ′E and  40 ′C if the tray is reversed as in a mirror image across the plane  500 ). When passing the large tray, its second side wall and associated corner portions pass through the gap  210 H. Thus, the gap  210 H (if a finger  202 I is present) may be of similar dimension to the gaps  210 E and  210 F. 
     Exemplary slot and/or groove width may be measured at a given particular height or heights or as an average (e.g., a mean, a median, or a mode). This width is shown as essentially constant along the grooves and essentially constant along a lower/proximal portion of the intact wall portions (e.g., to about the level of the base upper surface). Thus, the intact wall portions&#39; widths may similarly be measured. Exemplary slots diverge upwardly/distally. Accordingly, the exemplary intact wall portions converge upwardly/distally along upper/distal portions thereof. Exemplary finger spacing and slot width are shown in Table 1 where widths are measured along the lower/proximal portions. Example 1 repeats dimensions from the drawings of the priority application. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Dimensions in inches 
               
             
          
           
               
                   
                 Dimension 
                 Ex. 1 
                 Ex. 2 
               
               
                   
                   
               
             
          
           
               
                   
                 S 10A   
                 2.25 
                 2.25 
               
               
                   
                 S 10B   
                 2.25 
                 2.25 
               
               
                   
                 S 10C   
                 2.25 
                 2.38 
               
               
                   
                 S 10D   
                 2.25 
                 2.12 
               
               
                   
                 S 10E   
                 4.9 
                 4.9 
               
               
                   
                 S 10F   
                 4.75 
                 4.75 
               
               
                   
                 S 10G   
                 2.25 
                 2.25 
               
               
                   
                 S 10H   
                 — 
                 4.24 
               
               
                   
                 W 1   
                 14.1 
                 14.1 
               
               
                   
                 W′ 1   
                 19.0 
                 19.0 
               
               
                   
                 W″ 1   
                 26.0 
                 26.0 
               
               
                   
                 W 3A-F   
                 1.25 
                 1.24 
               
               
                   
                 W′ 3A,B,F,G   
                   
                 1.24 
               
               
                   
                 W′ 3C-E   
                   
                 1.64 
               
               
                   
                 W″ 3A-C,E,F,H-J   
                   
                 1.24 
               
               
                   
                 W″ 3D&amp;G   
                   
                 1.49 
               
               
                   
                 W 4   
                 1.0 
                 1.08 
               
               
                   
                 W 5   
                 1.92 
                 1.93 
               
               
                   
                   
               
             
          
         
       
     
       FIGS. 12-15  show an exemplary eight-fingered machine  200 ′ as part of a system including a tray delivery conveyor  240  and a tray content (carton) removal conveyor  242 . Each finger is shown including an associated wedge-like tip  244 . These tips  244  are sized to be a close but non-interfering fit in the grooves in the base of the approaching tray. The bottom surface  246  of each wedge/tip is oriented such that it is generally parallel to the upper (transport) surface of the conveyor  240  transporting the tray and is positioned a sufficient distance above conveyor  240  for the base of the tray along the grooves to pass below the wedge. The upper surface  246  of each wedge/tip slopes at an angle acute enough that the wedge can slip between the moving tray and the bottom surface of the carton carried by the tray, and is positioned to insert into the cavity formed by the groove in the base of the tray below the carton. Exemplary wedges/tips are arranged parallel to each other so that their upper surfaces combine to form a ramp up which the carton can be pushed by the movement of tray. The exemplary fingers each also have a conveyor belt  252  for transferring the cartons to the conveyor  242 . Each finger may also include a strut  258  ( FIG. 15 ) supporting the wedge and at least partially supporting the associated conveyor  252 . A platform  260  may replace or span the struts at a height sufficiently above the conveyor  240  to allow the trays to pass below a leading edge  262  of the platform. The exemplary wedges have sufficient length so that the movement of the tray will drive the cartons up the wedges until the bottom surface of a leading portion of the carton comes into engagement with some or all of the conveyor belts  252 . 
     A small carton may be pushed forward and up the ramp (formed by the wedges/tips) primarily by friction between the bottom of the carton and the tray. The notches  44  in the ridges in the tray bottom are provided to supplement this friction and the rear/trailing end wall of the tray acts as a positive stop should the carton slide on the tray and not be captured by the notches. For a relatively large carton (e.g., one that longitudinally fills the tray) the engagement may merely be with the rear/trailing end wall. As the carton is pushed far enough onto conveyor belts  252  by the motion of tray, a point is reached wherein the friction between belts and the bottom surface of carton is sufficient for the carton to be moved by belts without regard to the motion of the tray and the carton is pulled away from the tray. This may offer a benefit over prior systems by placing the point at which control of the carton passes from the tray to the carton removal apparatus earlier in the removal process. Extending the belts  252  through the slots  40  reaching below the top of the end wall of the tray and into the interior space of the tray may facilitate this. 
       FIG. 13  shows that each strut member  258  extending from a common drive shaft  270  at the carton output end to an idler pulley  272  ( FIG. 15 ) at the intake end where the wedge/tip is attached. Each strut holds its wedge/tip in position and additionally provides support for its belt as the assembly of belts supports the weight of the carton. A motor  274  and its connection with shaft  27  may be standard items typically used in conveyors. 
     Trays arrive at the apparatus on the conveyor  240 . This conveyor is an item that is presently available from one or more sources and is of the type that, as it conveys the tray, also moves the tray to the right relative to the direction of travel so that the tray is in contact with the side wall  204  of the conveyor when it arrives at the tray unloading machine. This ensures a predictable positioning of the tray as it approaches the unloading machine, thus aligning the slots in the end of the tray with the wedges so that the wedges can enter the slots. 
     The assembly of conveyor belts  252  is powered by the motor  274  acting through the shaft  220  such that the belts move in the same direction as the conveyor mechanism  240  and they move at a speed that is generally equal to or greater than that of the conveyor  240 . Trays containing cartons arrive at the unloading machine on conveyor  240 . After a carton is removed from a tray, the unloading machine moves the carton onto the conveyor  242 . Empty trays continue on the conveyor  240 . The exemplary conveyor  240  is generally horizontal and conveyor  242  is on an incline leading up and away from the unloading machine. Alternative embodiments could vary such that the conveyor  240  slopes downward into the unloading machine with the conveyor  242  being generally level, or could also be such that both conveyors are on an incline or both are horizontal. 
     In use, the tray unloading machine operates in an unattended fashion and enables the following process. Trays containing cartons approach the apparatus on a conveyor. Each tray may be one of multiple predetermined sizes and the carton carried by the tray can vary in size and weight. Additionally, either end of the tray can approach the apparatus first. Without interrupting the continuous motion of the carton, the apparatus removes the carton from the tray, allowing the now empty tray to continue in motion and it moves the carton onto a separate conveyor for continued processing. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, when applied to different existing warehouse environments (e.g., conveyor systems, etc) details of such environments will influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.